Dimethyl Phthalate Degradation by UV/H2O2: Combination of Experimental Methods and Quantum Chemical Calculation          下载免费PDF全文

Er‐Deng Du  Xin‐Xin Feng  Ying‐Qing Guo  Ming‐Guo Peng  Hong‐Qi Feng  Juan‐Lin Wang  Shuo Zhang 《洁净——土壤、空气、水》2015,43(6):811-821

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青藏高原东北侧冰雹微物理过程模拟研究   总被引：31，自引：15，他引：16  

康凤琴  张强  渠永兴  冀兰芝  郭学良 《高原气象》2004,23(6):735-742

以青藏高原东北侧及毗邻地区诱发冰雹灾害的东移短小切变线天气过程为研究背景,采用中国科学院大气物理研究所三维冰雹云分档模式,用MM5V3中尺度气象模式提供冰雹云模拟研究所需的环境大气状况,模拟研究了冰雹形成和增长的微物理过程。结果表明：模式再现了当时冰雹、大风及暴雨的实况;中尺度水分和动力条件是冰雹形成和增长的重要因素,它们决定了冰雹云的强度和冰雹的大小;冰雹形成和增长过程中的微物理过程决定了冰雹云的消亡,冰雹在空中形成的潜热释放延长了降雹的时间;云中冰雹发生、增长的主要区域和云内上升气流配合良好,是防雹消雹的主要范围。  相似文献   

Unveiling the chemistry of hot protostellar cores with ALMA     

M. Guélin  N. Brouillet  J. Cernicharo  F. Combes  A. Wooten 《Astrophysics and Space Science》2008,313(1-3):45-51

High angular resolution mm-wave observations of the Orion-KL region, made with the IRAM Plateau de Bure interferometer (PdBI), reveal the presence of several cores of size 10³ AU, which have distinct spectral signatures. Complex molecules such as ethanol, vinyl cyanide and dimethyl ether show different distributions and their relative abundance varies from core to core by orders of magnitude. The molecular column densities derived in the cores also differ widely from the beam-averaged column densities observed with large single-dish telescopes. Obviously, the predictions of hot core chemistry models must be checked against high resolution observations. ALMA, which allies sensitivity and high angular resolution, will be a key instrument for this type of studies. The PdBI observations were part of a search for interstellar glycine, also carried out with the IRAM 30-m telescope and the Green Bank Telescope. We derive a 3σ upper limit on the column density of glycine of 1×10¹⁵ cm⁻² per 2″×3″ beam in the Orion Hot Core and Compact Ridge. Based on observations made with the IRAM PdB Interferometer, the IRAM 30-m telescope and the NRAO Green-Bank telescope. IRAM is supported by CNRS, MPG and IGN.  相似文献   

Ejecta from impacts at 0.2-2.3 m/s in low gravity     

Joshua E. Colwell  Stein Sture  Dan Durda  Tyler Goudie  Daniel J. Ashcom  Thomas Keohane  Michael Lupton 《Icarus》2008,195(2):908-917

Collisions between planetary ring particles and in some protoplanetary disk environments occur at speeds below 10 m/s. The particles involved in these low-velocity collisions have negligible gravity and may be made of or coated with smaller dust grains and aggregates. We undertook microgravity impact experiments to better understand the dissipation of energy and production of ejecta in these collisions. Here we report the results of impact experiments of solid projectiles into beds of granular material at impact velocities from 0.2 to 2.3 m/s performed under near-weightless conditions on the NASA KC-135 Weightless Wonder V. Impactors of various densities and radii of 1 and 2 cm were launched into targets of quartz sand, JSC-1 lunar regolith simulant, and JSC-Mars-1 martian regolith simulant. Most impacts were at normal or near-normal incidence angles, though some impacts were at oblique angles. Oblique impacts led to much higher ejection velocities and ejecta masses than normal impacts. For normal incidence impacts, characteristic ejecta velocities increase with impactor kinetic energy, KE, as approximately KE^0.5. Ejecta masses could not be measured accurately due to the nature of the experiment, but qualitatively also increased with impactor kinetic energy. Some experiments were near the threshold velocity of 0.2 m/s identified in previous microgravity impact experiments as the minimum velocity needed to produce ejecta [Colwell, J.E., 2003. Icarus 164, 188-196], and the experimental scatter is large at these low speeds in the airplane experiment. A more precise exploration of the transition from low-ejecta-mass impacts to high-ejecta-mass impacts requires a longer and smoother period of reduced gravity. Coefficient of restitution measurements are not possible due to the varying acceleration of the airplane throughout the experiment.  相似文献   

The Ascraeus Mons fan-shaped deposit: Volcano-ice interactions and the climatic implications of cold-based tropical mountain glaciation     

Seth J. Kadish  Rebecca L. Parsons 《Icarus》2008,197(1):84-109

Amazonian-aged fan-shaped deposits extending to the northwest of each of the Tharsis Montes in the Tharsis region on Mars have been interpreted to have originated from mass-wasting, volcanic, tectonic and/or glacial processes. We use new data from MRO, MGS, and Odyssey to characterize these deposits. Building on recent evidence for cold-based glacial activity at Pavonis Mons and Arsia Mons, we interpret the smaller Ascraeus fan-shaped deposit to be of glacial origin. Our geomorphological assessment reveals a number of characteristics indicative of glacial growth and retreat, including: (1) a ridged facies, interpreted to be composed of drop moraines emplaced during episodic glacial advance and retreat, (2) a knobby facies, interpreted to represent vertical downwasting of the ice sheet, and (3) complex ridges showing a cusp-like structure. We also see evidence of volcano-ice interactions in the form of: (1) an arcuate inward-facing scarp, interpreted to have formed by the chilling of lava flows against the glacial margin, (2) a plateau feature, interpreted to represent a subglacial eruption, and (3) knobby facies superimposed on flat-topped flows with leveed channels, interpreted to be subglacial inflated lava flows that subsequently drained and are covered by glacial till. We discuss the formation mechanisms of these morphologies during cold-based glacial activity and concurrent volcanism. On the basis of a Mid- to Late-Amazonian age (250-380 Ma) established from crater size-frequency distribution data, we explore the climatic implications of recent glaciation at low latitudes on Mars. GCM results show that increased insolation to the poles at high obliquities (>45°) forces sublimation of polar ice, which is transported to lower latitudes and deposited on the flanks of the Tharsis Montes. We assess how local orographic effects, the mass balance of the glacier, and the position of equilibrium line altitudes, all played a role in producing the observed geomorphologies. In doing so, we outline a glacial history for the evolution of the Ascraeus Mons fan-shaped deposit and compare its initiation, growth and demise with those of Arsia Mons and Pavonis Mons.  相似文献   

Orbital and mission planning constraints for the deflection of NEOs impacting on Earth   总被引：1，自引：0，他引：1  

Andrea Carusi  Germano D'Abramo 《Icarus》2008,194(2):450-462

This paper is the third in a series. Paper 1 presented the results of numerical modeling of deflections of NEOs in route of collision with the Earth. The model was applied to a variety of dynamical cases including both asteroidal and cometary NEOs. Paper 2 introduced the concept of “distributed deflection,” i.e., the possibility to provide the ΔV necessary to deflect an object with a succession of maneuvers each of which would have been insufficient per se to obtain the desired result. In both papers no assumptions were made on the physical composition and structure of the NEO, nor on the details of the possible deflection maneuvers from the point of view of mission analysis. Moreover, ΔV-plots were computed assuming only along-track impulses (both in the positive and negative directions), because it is easy to demonstrate that in general this is energetically the most favorable configuration. Also in the present paper no assumptions were made on the physical composition and structure of the NEO, even if order of magnitude considerations are made on the physical feasibility of a deflection, in terms of the internal strength of the NEO. We present here the results of an investigation on the mission requirements necessary to deflect an object (or contribute to a succession of deflecting maneuvers) in terms of accessibility of the spacecraft terminal orbit from Earth with the current launchers.  相似文献   

Spectroscopy, morphometry, and photoclinometry of Titan's dunefields from Cassini/VIMS     

Jason W. Barnes  Robert H. Brown  Christophe Sotin  Sebastien Rodriguez  Ross A. Beyer  Karly Pitman  Roger Clark 《Icarus》2008,195(1):400-414

Fine-resolution (500 m/pixel) Cassini Visual and Infrared Mapping Spectrometer (VIMS) T20 observations of Titan resolve that moon's sand dunes. The spectral variability in some dune regions shows that there are sand-free interdune areas, wherein VIMS spectra reveal the exposed dune substrate. The interdunes from T20 are, variously, materials that correspond to the equatorial bright, 5-μm-bright, and dark blue spectral units. Our observations show that an enigmatic “dark red” spectral unit seen in T5 in fact represents a macroscopic mixture with 5-μm-bright material and dunes as its spectral endmembers. Looking more broadly, similar mixtures of varying amounts of dune and interdune units of varying composition can explain the spectral and albedo variability within the dark brown dune global spectral unit that is associated with dunes. The presence of interdunes indicates that Titan's dunefields are both mature and recently active. The spectrum of the dune endmember reveals the sand to be composed of less water ice than the rest of Titan; various organics are consistent with the dunes' measured reflectivity. We measure a mean dune spacing of 2.1 km, and find that the dunes are oriented on the average in an east-west direction, but angling up to 10° from parallel to the equator in specific cases. Where no interdunes are present, we determine the height of one set of dunes photoclinometrically to be between 30 and 70 m. These results pave the way for future exploration and interpretation of Titan's sand dunes.  相似文献   

The shape distribution of asteroid families: Evidence for evolution driven by small impacts     

Gyula M. Szabó  László L. Kiss 《Icarus》2008,196(1):135-143

A statistical analysis of brightness variability of asteroids reveals how their shapes evolve from elongated to rough spheroidal forms, presumably driven by impact-related phenomena. Based on the Sloan Digital Sky Survey Moving Object Catalog, we determined the shape distribution of 11,735 asteroids, with special emphasis on eight prominent asteroid families. In young families, asteroids have a wide range of shape elongations, implying fragmentation-formation. In older families we see an increasing number of rough spheroids, in agreement with the predictions of an impact-driven evolution. Old families also contain a group of moderately elongated members, which we suggest correspond to higher-density, more impact-resistant cores of former fragmented asteroids that have undergone slow shape erosion. A few percent of asteroids have very elongated shapes, and can either be young fragments or tidally reshaped bodies. Our results confirm that the majority of asteroids are gravitationally bound “rubble piles.”  相似文献   

Amino acids produced from the ultraviolet/extreme-ultraviolet irradiation of naphthalene in a H₂O+NH₃ ice mixture     

Y.-J. Chen  M. Nuevo  T.-S. Yih  W.-H. Ip  H.-S. Fung  C.-Y. Cheng  H.-R. Tsai  C.-Y. R. Wu 《Monthly notices of the Royal Astronomical Society》2008,384(2):605-610

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A deep X-ray observation of M82 with XMM–Newton     

P. Ranalli †‡  A. Comastri  L. Origlia  R. Maiolino § 《Monthly notices of the Royal Astronomical Society》2008,386(3):1464-1480

We report on the analysis of a deep (100-ks) observation of the starburst galaxy M82 with the EPIC and RGS instruments onboard the X-ray telescope XMM–Newton . The broad-band (0.5–10 keV) emission is due to at least three spectral components: (i) continuum emission from point sources; (ii) thermal plasma emission from hot gas; and (iii) charge-exchange emission from neutral metals (Mg and Si). The plasma emission has a double-peaked differential emission measure, with the peaks at ∼0.5 and ∼7 keV. Spatially resolved spectroscopy has shown that the chemical absolute abundances are not uniformly distributed in the outflow, but are larger in the outskirts and smaller close to the galaxy centre. The abundance ratios also show spatial variations. The X-ray-derived oxygen abundance is lower than that measured in the atmospheres of red supergiant stars, leading to the hypothesis that a significant fraction of oxygen ions have already cooled off and no longer emit at energies ≳0.5 keV.  相似文献