UV photolysis of quinoline in interstellar ice analogs     

Jamie E. ELSILA  Matthew R. HAMMOND  Max P. BERNSTEIN  Scott A. SANDFORD  Richard N. ZARE 《Meteoritics & planetary science》2006,41(5):785-796

Abstract— The polycyclic aromatic nitrogen heterocycle (PANH) quinoline (C₉H₇N) was frozen at 20 K in interstellar ice analogs containing either pure water or water mixed with methanol or methane and exposed to ultraviolet (UV) radiation. Upon warming, the photolysis products were analyzed by high‐performance liquid chromatography and nanoscale liquid chromatography‐electrospray ionization mass spectrometry. A suite of hydroxyquinolines, which were formed by the addition of oxygen atoms to quinoline, was observed as the primary product in all the ices. Quinoline N oxide was not formed, but five hydroxyquinoline isomers were produced with no clear dominance of one isomer. Reduction products, formed by hydrogen atom addition, were also created. Ices created at 20 K with H₂O: quinoline ratios of 10:1 to 100:1 showed similar product distributions to those at 122 K, with no apparent temperature or concentration dependence. Increasing the UV dose led to a decrease in overall yield, indicating that quinoline and its products may be photo‐destroyed. Methylquinolines were formed upon photolysis of the methanol‐ and methane‐containing ices. In addition, possible methoxyquinolines or quinoline methylene alcohols were formed in the methanol‐containing ice, while methylhydroxyquinolines were created in the methane‐containing ice. This work indicates that oxidation of PANHs could occur in icy extraterrestrial environments and suggests that a search for such compounds in carbonaceous meteorites could illuminate the possible link between interstellar ice chemistry and meteoritic organics. Given the importance of oxidized and alkylated PANHs to biochemistry, the formation and delivery of such molecules to the early Earth may have played a role in the origin and evolution of life.  相似文献   

Europa's atmosphere, gas tori, and magnetospheric implications     

William H. Smyth  Max L. Marconi 《Icarus》2006,181(2):510-526

A two-dimensional kinetic model calculation for the water group species (H₂O, H₂, O₂, OH, O, H) in Europa's atmosphere is undertaken to determine its basic compositional structure, gas escape rates, and velocity distribution information to initialize neutral cloud model calculations for the most important gas tori. The dominant atmospheric species is O₂ at low altitudes and H₂ at higher altitudes with average day-night column densities of 4.5×¹⁰¹⁴ and 7.7×¹⁰¹³ cm⁻², respectively. H₂ forms the most important gas torus with an escape rate of ∼2×¹⁰²⁷ s⁻¹ followed by O with an escape rate of ∼5×¹⁰²⁶ s⁻¹, created primarily as exothermic O products from O₂ dissociation by magnetospheric electrons. The circumplanetary distributions of H₂ and O are highly peaked about the satellite location and asymmetrically distributed near Europa's orbit about Jupiter, have substantial forward clouds extending radially inward to Io's orbit, and have spatially integrated cloud populations of 4.2×¹⁰³³ molecules for H₂ and 4.0×¹⁰³² atoms for O that are larger than their corresponding populations in Europa's local atmosphere by a factor of ∼200 and ∼1000, respectively. The cloud population for H₂ is a factor of ∼3 times larger than that for the combined cloud population of Io's O and S neutral clouds and provides the dominant neutral population beyond the so-called ramp region at 7.4-7.8 RJ in the plasma torus. The calculated brightness of Europa's O cloud on the sky plane is very dim at the sub-Rayleigh level. The H₂ and O tori provide a new source of europagenic molecular and atomic pickup ions for the thermal plasma and introduce a neutral barrier in which new plasma sinks are created for the cooler iogenic plasma as it is transported radially outward and in which new sinks are created to alter the population and pitch angle distribution of the energetic plasma as it is transported radially inward. The europagenic instantaneous pickup ion rates are peaked at Europa's orbit, dominate the iogenic pickup ion rates beyond the ramp region, and introduce new secondary plasma source peaks in the solution of the plasma transport problem. The H₂ torus is identified as the unknown Europa gas torus that creates both the observed loss of energetic H⁺ ions at Europa's orbit and the corresponding measured ENA production rate for H.  相似文献   

Ultraviolet photolysis of anthracene in H2O interstellar ice analogs: Potential connection to meteoritic organics     

Samantha F. M. ASHBOURN  Jamie E. ELSILA  Jason P. DWORKIN  Max P. BERNSTEIN  Scott A. SANDFORD  Louis J. ALLAMANDOLA 《Meteoritics & planetary science》2007,42(12):2035-2041

Abstract— The polycyclic aromatic hydrocarbon (PAH) anthracene was oxidized by exposure to ultraviolet (UV) radiation in H₂O ice under simulated astrophysical conditions, forming several anthracene ketones (9‐anthrone, 1,4‐anthraquinone, and 9,10‐anthraquinone) and alcohols (1‐anthrol and 2‐anthrol). Two of the ketones produced have been detected in the Murchison meteorite but, to our knowledge, there has been no search for the alcohols or other oxidized anthracenes in meteorites. These results seem consistent with the possibility that interstellar ice photochemistry could have influenced the inventory of aromatics in meteorites. Since quinones are also fundamental to biochemistry, their formation in space and delivery to planets is relevant to studies relating to the habitability of planets and the evolution of life.  相似文献   

Late Ordovician glacial pavements revisited: a reappraisal of the origin of striated surfaces     

Max Deynoux  Jean-François Ghienne 《地学学报》2004,16(3):95-101

The recognition of ice‐related unconformities is of prime importance when dealing with the sequential architecture of pre‐Pleistocene glacial successions. Late Ordovician striated surfaces strikingly preserved in North Gondwana were long considered as abrasion surfaces at the sole of a grounded glacier overriding unlithified sediments, or having resulted from the scouring action of drifting icebergs. Field observations from Mauritania and Libya show that these striated surfaces require an alternative interpretation, which can be applied to similar surfaces described elsewhere, such as in Permo‐Carboniferous or Neoproterozoic glacial sequences. A new model is proposed that involves superimposed concurrent décollement planes within a subglacial brittle shear zone in unlithified sand beds. Shear zones in subglacial sediments are well known in Quaternary deposits but, to date, it has not been demonstrated that they may form striated surfaces occurring at continent scale with orientations consistent with palaeo ice‐flow reconstructions based on larger‐scale indicators.  相似文献   

The idea of a “World Directory of Geographical Archives”     

Max Linke 《GeoJournal》1992,26(2):222-222

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Alternative climate data sources for distributed hydrological modelling on a daily time step   总被引：1，自引：0，他引：1  

Ashraf El‐Sadek  Max Bleiweiss  Manoj Shukla  Steve Guldan  Alexander Fernald 《水文研究》2011,25(10):1542-1557

Two major criteria in choosing climate data for use in hydrological modelling are the period of record of the data set and the proximity of the collection platform(s) to the basin under study. Conventional data sets are derived from weather stations; however, in many cases there are no weather stations sufficiently close to a basin to be representative of climate conditions in that basin. In addition, it is often the case either that the period of record for the weather station(s) does not cover the period of the proposed simulation or that there are gaps in the data. Therefore, the objectives of this study are to investigate alternative climate data sources for use in hydrological modelling and to develop a protocol for creating hydrological data sets that are spatially and temporally harmonized. The methods we used for constructing daily, spatially distributed, climatic data sets of precipitation, maximum and minimum temperature, wind speed, solar radiation, potential evapotranspiration, and relative humidity are described. The model used in this study was the Soil and Water Assessment Tool implemented on the Mimbres River Basin located in southwestern New Mexico, USA, for the period 2003–2006. Our hydrological simulations showed that two events in January and February 2005 were missed, while an event in August 2006 was well simulated. We have also investigated the usefulness of several other precipitation data sets and compared the simulation results. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Mapping seismic risk: the current crisis     

Max Wyss  Philippe Rosset 《Natural Hazards》2013,68(1):49-52

The seismic risks to which populations are exposed should be estimated reliably for mitigation and preparation of response to disastrous earthquakes. Three parameters need to be known: Population numbers, properties of the built environment, and the seismic hazard. If we focus on large cities, we can say that at least one of these is known satisfactorily, namely the population, but not the other two. In the developing world, the numbers of buildings in a city are known only approximately, their distribution into building types (resistance to shaking) has to be assumed, and the distribution of types throughout the city is unknown. Recent verification of the world seismic hazard map has shown that it is grossly misleading: Instrumental measurements of accelerations due to six earthquakes were about three times larger, on average, than the maximum likely accelerations shown on the map; the macroseismic intensities reported for the last 60 earthquakes with M ≥ 7.5 were all significantly larger than expected, based on the hazard map (by 2.3 intensity units for the 12 deadliest earthquakes); and calculations of losses of life based on the hazard map underestimate the losses sustained in the 12 recent earthquakes with more than 1,000 fatalities by two to three orders of magnitude. This means that the seismic risk in most of the approximately 1,000 large cities at risk in the developing world is unknown. To remedy this intolerable situation, models for the built environment in cities need to be constructed, using cost-effective analyses of satellite images, and worst case scenario estimates of the losses in case of the nearest maximum credible earthquake.  相似文献   

Tectonometamorphic history of the Gruf complex (Central Alps): exhumation of a granulite–migmatite complex with the Bergell pluton     

Andrea Galli  Benjamin Le Bayon  Max W. Schmidt  Jean-Pierre Burg  Eric Reusser 《Swiss Journal of Geoscience》2013,106(1):33-62

We describe field occurrences of sapphirine-bearing granulites, charnockites and migmatites in the Gruf complex, Central Alps and present a new geological map and a structural analysis of the entire Gruf complex for the first time. We have carried out an accurate analysis of the relationships between granulite facies metamorphism, migmatisation and deformation within the complex, in relation to the intrusion of the Bergell pluton. Granulites and charnockites display fabrics different from those defined by the regional foliation and lineation, which are, typically for migmatites, disordered on the mesoscale. On a regional scale, strike variations are also related to the structural complexity of migmatites within which no major antiform could be identified. Irregular interfingering of sub-parallel leucosome veins and back-veining along the contact between the Gruf migmatites and the Bergell tonalite are evidence for contemporaneous emplacement and crystallisation at about 740 °C and 6.5–7.5 kbar in Oligocene times (ca 30 Ma). Metamorphic conditions in the charnockites and granulites (>920 °C for 8.5–9.5 kbar) largely exceed these regional metamorphic conditions and are dated at 282–260 Ma. We propose that the ascending Bergell pluton entrained the polymetamorphic, granulitic lower crust enclosed within the peripheral migmatitic Gruf complex.  相似文献   

Dynamic Inuit Social Strategies in Changing Environments: A Long-Term Perspective     

T. Max Friesen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(2):215-225

Geografisk Tidsskrift—Danish Journal of Geography 110(2):215–225, 2010

This paper presents an overview of the International Polar Year (IPY) research programme Dynamic Inuit Social Strategies in Changing Environments: A Long-Term Perspective. For this project, research teams from six separate multi-year subprojects performed fieldwork across much of the Canadian Arctic. Fieldwork and analysis revolved around two primary processes critical to the understanding of Inuit history: first, is the migration from Alaska to the east by the earliest Inuit, known as ‘Thule’, an apparently rapid event which replaced populations of the earlier, and culturally very different Dorset tradition; second, is the transformation of Thule Inuit into their more diverse recent cultural forms, involving abandonment of some regions, combined with major changes in settlement patterns, artifact form, architecture, economy, and social organization. The ultimate goal of the project is to understand the variable roles of climate change and social structures on the culture change which can be observed during the past 800 years of Inuit history.  相似文献   

A Review of “Economic Geography: Places,Networks, and Flows”     

Max Lu 《The Professional geographer》2013,65(3):466-468

Landing a rescue helicopter in a wilderness environment, such as Yosemite National Park, requires suitable areas that are flat, devoid of tree canopy, and not within close proximity to other hazards. The objective of this study was to identify helicopter landing areas that are most likely to exist based on available geographic data using two GIScience methods. The first approach produced an expert model that was derived from predefined feature constraints based on existing knowledge of helicopter landing area requirements (weighted overlay algorithm). The second model is derived using a machine learning technique (maximum entropy algorithm, Maxent) that derives feature constraints from existing presence-only points; that is, geographic one-class data. Both models yielded similar output and successfully classified test coordinates, but Maxent was more efficient and required no user-defined weighting that is typically subject to human bias or disagreement. The pros and cons of each approach are discussed and the comparison reveals important considerations for a variety of future land suitability studies, including ecological niche modeling. The conclusion is that the two approaches complement each other. Overall, we produced an effective geographic information system product to support the identification of suitable landing areas in emergent rescue situations. To our knowledge, this is the first GIScience study focused on estimating the location of landing zones for a search-and-rescue application.  相似文献