Ultraviolet irradiation of naphthalene in H2O ice: Implications for meteorites and biogenesis     

Max P. BERNSTEIN  Jason P. DWORKIN  Scott A. SANDFORD  Louis J. ALLAMANDOLA 《Meteoritics & planetary science》2001,36(3):351-358

Abstract— The polycyclic aromatic hydrocarbon (PAH) naphthalene was exposed to ultraviolet radiation in H₂O ice under astrophysical conditions, and the products were analyzed using infrared spectroscopy and high‐performance liquid chromatography. As we found in our earlier studies on the photoprocessing of coronene in H₂O ice, aromatic alcohols and ketones (quinones) were formed. The regiochemistry of the reactions is described and leads to specific predictions of the relative abundances of various oxidized naphthalenes that should exist in meteorites if interstellar ice photochemistry influenced their aromatic inventory. Since oxidized PAHs are present in carbon‐rich meteorites and interplanetary dust particles (IDPs), and ubiquitous in and fundamental to biochemistry, the delivery of such extraterrestrial molecules to the early Earth may have played a role in the origin and evolution of life.  相似文献   

Urban Planning in Hong Kong and Integration with the Pearl River Delta: A Historical Account of Local Development     

Louis?Augustin-JeanEmail author 《GeoJournal》2005,62(1-2):1-13

This paper shows the importance that urban planning plays in the development of Hong Kong. This leads to a reassessment of the role of the government, which is the sole proprietor of the land, in the economy – while it acknowledges the importance of market forces. The first part shows how, since 1945, Hong Kong authorities have been obliged to intervene more in urban planning and local development, despite their liberal ideology. The second part focuses on the interaction between government action and market forces, and their influence in this development. The third part deals with the question of the economic integration between Hong Kong and the Pearl River Delta (PRD) after China started its economics reforms in 1978. The deconcentration of Hong Kong industries to China was mainly due to market forces, but provided a new role for the government. This role is analyzed through its transportation policy – the domain with the most visible governmental intervention before and after 1997. It indicates the preference of the government to develop the territory rather than better integration with the PRD, because of the internal economic problems that may emerge from this integration. Nevertheless, for political and economic reasons, this integration is also seen as necessary. The future of Hong Kong’s economy lies in the answers the authorities will give to this dilemma.  相似文献   

Biological and Temporal Variations of Trace Element Concentrations in the Moss Species Scleropodium purum (Hedw.) Limpr.     

Sebastien Leblond  Sandrine Gombert  Jean Louis Colin  Remi Losno  Catherine Rausch De Traubenberg 《Journal of Atmospheric Chemistry》2004,49(1-3):95-110

Over a period of one year, the moss Scleropodium purum was sampled every two weeks in a French rural area to determine the levels of Li, Na, Al, Si, P, Ca, V, Mn, Fe, Zn, Ba, Hg, and Pb. The element distribution in the moss shoot was studied throughout the year. An apical bioconcentration was discovered for Na, P, Ca, Mn, and Zn, whereas higher levels were found in the basal fraction for Li, Al, Si, V, Fe, Ba, Hg, and Pb. A significant variation of element concentrations was observed during the sampling period. In the apical part Li, Al, Si, V, Fe, Ba, and Hg show maximum levels in the summer and minimum in the autumn. The same pattern was found with Ca and Mn in the whole plant, whereas Na showed opposite fluctuations.  相似文献   

Generalization of two-dimensional discontinuous deformation analysis for forward modelling     

Gen-hua Shi  Richard E. Goodman 《国际地质力学数值与分析法杂志》1989,13(4):359-380

This paper provides the theoretical basis for a forward numerical model of rock block systems. This method was developed to compute stress, strain, sliding and opening of rock blocks; rigid body movement and deformation occur simultaneously. Input data consist of block geometry, loading forces, the deformability constants E and v, and the restraint or boundary conditions of the block system. Output data give the movements, deformations, stresses and strains of each block, and the sliding and detachment or rejoining of blocks. The forces acting on each block, from external loading or contact with other blocks, satisfy the equilibrium equations. Equilibrium is also achieved between external forces and the block stresses. Furthermore, this analysis fulfills constraints of no tension between blocks and no penetration of one block into another. To acheive equilibrium and satisfy these constraints, simultaneous equations are solved repeatdly with partial changes of the coefficients each time the contact constraints are chosen.  相似文献   

Nondestructive imaging of small size voids at Akrotiri archaeological site, Thera Island, Greece, by seismic inversion techniques     

Filippos I. Louis  Roger A. Clark  Ioannis F. Louis  Costas C. Makropoulos   《Journal of Applied Geophysics》2005,57(4):306-326

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Réponse au commentaire de Brahim Akdim et Ramón Julia sur la note Datation par la méthode U/Th d'un travertin quaternaire du Sud-Est marocain : implications paléoclimatiques pendant le Pléistocène moyen et supérieur [C. R. Geoscience 335 (2003) 469–478]     

Larbi Boudad  Lahcen Kabiri  Samer Farkh  Christophe Falguères  Louis Rousseau  Jacques Beauchamp  Élisabeth Nicot  Guillaume Cairanne 《Comptes Rendus Geoscience》2006,338(8):583

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Calibration of the MDCO dust collector and of four versions of the inverted frisbee dust deposition sampler   总被引：2，自引：0，他引：2  

Mamadou Sow  Dirk Goossens  Jean Louis Rajot 《Geomorphology》2006,82(3-4):360-375

Wind tunnel experiments were conducted to determine the efficiency of sediment samplers designed to measure the deposition of aeolian dust. Efficiency was ascertained relative to a water surface, which was considered the best alternative for simulating a perfectly absorbent surface. Two types of samplers were studied: the Marble Dust Collector (MDCO) and the inverted frisbee sampler. Four versions of the latter catcher were tested: an empty frisbee, an empty frisbee surrounded by an aerodynamic flow deflector ring, a frisbee filled with glass marbles, and a frisbee filled with glass marbles and surrounded by a flow deflector ring. Efficiency was ascertained for five wind velocities (range: 1–5 m s^− 1) and eight grain size classes (range: 10–89 μm). The efficiency of dust deposition catchers diminishes rapidly as the wind speed increases. It also diminishes as the particles caught become coarser. Adding a flow deflector ring to a catcher substantially improves the catcher's efficiency, by up to 100% in some cases. The addition of glass marbles to a catcher, on the other hand, does not seem to increase the efficiency, at least not at wind velocities inferior to the deflation threshold. For higher velocities the marbles protect the settled particles from resuspension, keeping them in the catcher. The following five parameters determine the accumulation of aeolian dust in a catcher: the horizontal dust flux, the weight of the particles, atmospheric turbulence, resuspension, and the dust shadow effect created by the catcher. The final accumulation flux depends on the combination of these parameters. The catchers tested in this study belong to the best catchers currently in use in earth science and have been the subject of various aerodynamic studies to improve their efficiency. Nevertheless the catching efficiency remains low, in the order of 20–40% for wind speeds above 2 m s^− 1. Other catchers suffer from the same low efficiencies. There is, thus, evidence to believe that dust deposition rates published in the aeolian literature and obtained by collecting the sediment in a catcher largely underestimate the true deposition. The errors are considerable, of the order of 100% and more. A reconsideration of the literature data on aeolian dust deposition measured by catchers is, therefore, required.  相似文献   

The GREGOR Fabry‐Pérot Interferometer     

K.G. Puschmann  C. Denker  F. Kneer  N. Al Erdogan  H. Balthasar  S.M. Bauer  C. Beck  N. Bello Gonzlez  M. Collados  T. Hahn  J. Hirzberger  A. Hofmann  R.E. Louis  H. Nicklas  O. Okunev  V. Martínez Pillet  E. Popow  T. Seelemann  R. Volkmer  A.D. Wittmann  M. Woche 《Astronomische Nachrichten》2012,333(9):880-893

The GREGOR Fabry‐Pérot Interferometer (GFPI) is one of three first‐light instruments of the German 1.5‐meter GREGOR solar telescope at the Observatorio del Teide, Tenerife, Spain. The GFPI uses two tunable etalons in collimated mounting. Thanks to its large‐format, high‐cadence CCD detectors with sophisticated computer hard‐ and software it is capable of scanning spectral lines with a cadence that is sufficient to capture the dynamic evolution of the solar atmosphere. The field‐of‐view (FOV) of 50″×38″is well suited for quiet Sun and sunspot observations. However, in the vector spectropolarimetric mode the FOV reduces to 25″×38″. The spectral coverage in the spectroscopic mode extends from 530–860 nm with a theoretical spectral resolution of R ≈250 000, whereas in the vector spectropolarimetric mode the wavelength range is at present limited to 580–660 nm. The combination of fast narrow‐band imaging and post‐factum image restoration has the potential for discovery science concerning the dynamic Sun and its magnetic field at spatial scales down to ∼50 km on the solar surface (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

The development of the Space Environment Viability of Organics (SEVO) experiment aboard the Organism/Organic Exposure to Orbital Stresses (O/OREOS) satellite     

Nathan E. Bramall  Richard Quinn  Andrew Mattioda  Kathryn Bryson  Julie D. Chittenden  Amanda Cook  Cindy Taylor  Giovanni Minelli  Pascale Ehrenfreund  Antonio J. Ricco  David Squires  Orlando Santos  Charles Friedericks  David Landis  Nykola C. Jones  Farid Salama  Louis J. Allamandola  Søren V. Hoffmann 《Planetary and Space Science》2012,60(1):121-130

The Space Environment Viability of Organics (SEVO) experiment is one of two scientific payloads aboard the triple-cube satellite Organism/ORganic Exposure to Orbital Stresses (O/OREOS). O/OREOS is the first technology demonstration mission of the NASA Astrobiology Small Payloads Program. The 1-kg, 1000-cm³ SEVO cube is investigating the chemical evolution of organic materials in interstellar space and planetary environments by exposing organic molecules under controlled conditions directly to the low-Earth orbit (LEO) particle and electromagnetic radiation environment. O/OREOS was launched on November 19, 2010 into a 650-km, 72°-inclination orbit and has a nominal operational lifetime of six months. Four classes of organic compounds, namely an amino acid, a quinone, a polycyclic aromatic hydrocarbon (PAH), and a metallo-porphyrin are being studied. Initial reaction conditions were established by hermetically sealing the thin-film organic samples in self-contained micro-environments. Chemical changes in the samples caused by direct exposure to LEO radiation and by interactions with the irradiated microenvironments are monitored in situ by ultraviolet/visible/near-infrared (UV/VIS/NIR) absorption spectroscopy using a novel compact fixed-grating CCD spectrometer with the Sun as its light source. The goals of the O/OREOS mission include: (1) demonstrating key small satellite technologies that can enable future low-cost astrobiology experiments, (2) deploying a miniature UV/VIS/NIR spectrometer suitable for in-situ astrobiology and other scientific investigations, (3) testing the capability to establish a variety of experimental reaction conditions to enable the study of astrobiological processes on small satellites, and (4) measuring the chemical evolution of organic molecules in LEO under conditions that can be extrapolated to interstellar and planetary environments. In this paper, the science and technology development of the SEVO instrument payload and its measurements are described.  相似文献   

Sedimentary Environment Influences Ecosystem Response to Nutrient Enrichment     

Emily J. Douglas  Conrad A. Pilditch  Andrew M. Lohrer  Candida Savage  Louis A. Schipper  Simon F. Thrush 《Estuaries and Coasts》2018,41(7):1994-2008

As coastal catchment land use intensifies, estuaries receive increased nutrient and sediment loads, resulting in habitats that are dominated by muddy organic-rich sediments. Increased mud (i.e. silt-clay (particles <?63 μm)) content has been associated with negative effects on soft sediment biodiversity and ecosystem functioning, but the simultaneous impact of nutrient enrichment on ecosystem response is unclear. Nutrient recycling and denitrification in estuarine soft sediments represent important ecosystem functions regenerating nutrients for primary producers and regulating the ability to remove excess terrestrially derived nitrogen. To test the effect of sedimentary environment on ecosystem resilience to nutrient perturbation, we experimentally enriched sediments with slow release fertiliser across an intertidal sedimentary gradient (0–24% mud content). The enrichment successfully elevated pore water ammonium concentrations (median 36?×?control) to levels representative of enriched estuaries. Findings show that the sedimentary environment can influence ecosystem function response to nutrient stress. In particular, denitrification enzyme activity was suppressed by nutrient enrichment, but the effect was greater as sediment mud content increased. Furthermore, compared with sandy sediments, sediments with high mud content may restrict nutrient processing (release, uptake or transformation of organic nutrients by the benthos) facilitating ecosystem shifts toward eutrophication. These results show the value of investigating the impacts of stressors in different environmental settings and demonstrate that land use practices that increase the proportion of muddy habitats in estuaries may reduce denitrification which in turn may reduce ecosystem resilience to eutrophication.  相似文献