Galaxy Evolution tool: Construction and Applications     

Yeshe Fenner  Brad K. Gibson  Marco Limongi 《Astrophysics and Space Science》2002,281(1-2):537-538

  相似文献   

Microplate motions in the hotspot reference frame     

Marco Cuffaro  Donna M. Jurdy 《地学学报》2006,18(4):276-281

We have computed motions of the major plates (seven large plates and seven medium‐sized plates) and 38 microplates relative to the hotspot reference frame, and present velocities of these 52 plates. Moreover, using updated plate boundaries for the present, we have computed new geometrical factors for plates and microplates, useful for kinematic calculations and to obtain the net‐rotation of the lithosphere and plate velocities in the mean‐lithosphere reference frame. Instead of a continuum or gradational distribution of the plates by size, the plates clearly partition into three groups each having their own characteristics. For the seven large plates, rotation poles generally lie in high latitudes; the seven medium‐sized plates have rotation poles in a restricted equatorial area; the 38 small plates show the greatest scatter. Moreover subsets of the 52 plates reveal differing fractal behaviour: the large, middle and small groupings each have a characteristic fractal dimension, suggestive of microplate clustering. The highest angular velocities occur for some of the smallest plates, with the location of their rotation poles closeby. Terra Nova, 18, 276–281, 2006  相似文献   

The Need for Ultraviolet to Understand the Chemical Evolution of the Universe and Cosmology.     

Willem Wamsteker  Jason X. Prochaska  Luciana Bianchi  Dieter Reimers  Nino Panagia  Andrew C. Fabian  Claes Fransson  Boris M. Shustov  Patrick Petitjean  Phillipp Richter  Eduardo Battaner 《Astrophysics and Space Science》2006,303(1-4):69-84

We identify an important set of key areas where an advanced observational Ultraviolet capability would have major impact on studies of cosmology and Galaxy formation in the young Universe. Most of these are associated with the Universe at z < 3–4. We address the issues associated with Dark matter evidence in the local Universe and the impact of the Warm-Hot Intergalactic Medium WHIM on the local Baryon count. The motivations to make ultraviolet (UV) studies of supernovae (SNe) are reviewed and discussed in the light of the results obtained so far by means of IUE and HST observations. It appears that UV studies of SNe can, and do lead to fundamental results not only for our understanding of the SN phenomenon, such as the kinematics and the metallicity of the ejecta, but also for exciting new findings in Cosmology, such as the tantalizing evidence for “dark energy” that seems to pervade the Universe and to dominate its energetics. The need for additional and more detailed UV observations is also considered and discussed.Finally we show the enormous importance of the UV for abundance evolution in the Intergalactic Medium (IGM), and the importance of the He II studies to identify re-ionization epochs, which can only be done in the UV.  相似文献   

Long term spectral variability in the soft gamma-ray repeater SGR 1900+14     

Andrea Tiengo  Paolo Esposito  Sandro Mereghetti  Lara Sidoli  Diego Götz  Marco Feroci  Roberto Turolla  Silvia Zane  Gian Luca Israel  Luigi Stella  Peter Woods 《Astrophysics and Space Science》2007,308(1-4):33-37

We present a systematic analysis of all the BeppoSAX data of SGR1900+14. The observations spanning five years show that the source was brighter than usual on two occasions: ～20 days after the August 1998 giant flare and during the 10⁵?s long X-ray afterglow following the April 2001 intermediate flare. In the latter case, we explore the possibility of describing the observed short term spectral evolution only with a change of the temperature of the blackbody component. In the only BeppoSAX observation performed before the giant flare, the spectrum of the SGR1900+14 persistent emission was significantly harder and detected also above 10 keV with the PDS instrument. In the last BeppoSAX observation (April 2002) the flux was at least a factor 1.2 below the historical level, suggesting that the source was entering a quiescent period.  相似文献   

Organic waste impact of capture-based Atlantic bluefin tuna aquaculture at an exposed site in the Mediterranean Sea     

Luigi Vezzulli  Mariapaola Moreno  Valentina Marin  Elisabetta Pezzati  Marco Bartoli  Mauro Fabiano 《Estuarine, Coastal and Shelf Science》2008

A variety of pelagic and benthic parameters were measured at an aquaculture farm used for the fattening of Atlantic bluefin tuna (Thunnus thynnus) which is located at an exposed site (700 m from the coast, average bottom depth of 45 m and average current speed of 6 cm s⁻¹) in the Mediterranean Sea. The objective was to test whether modern off-shore tuna fattening industries can exert a sustainable organic waste impact on the receiving environment as has been reported for the offshore culture of more traditional Mediterranean species such as sparids. In the water column, the concentration of phytopigments, organic matter, heterotrophic bacteria and the taxonomic abundance of mesozooplankton (at the species level) were assessed. In the sediment, we assessed the concentration of reduced sulphur pools, phytopigments, organic matter, heterotrophic bacteria and the taxonomic abundance of meiofauna (at the taxa level) and nematodes (at the genus level). For most parameters, we found no substantial differences between farm and control sites. Deviations of farm values from control values, when they occurred, were small and did not indicate any significant impact on either the pelagic and benthic environment. Deviations were more apparent in the benthic compartment where lower redox potential values, higher bacterial production rates and a change in nematode genus composition pointed out to early changes in the sediment's metabolism. In addition, indigenous potential pathogenic bacteria showed higher concentration at the fish farm stations and were a warning of an undesirable event that may become established following aquaculture practice in oligotrophic environments. The overall data from this study provide extensive experimental evidence to support the sustainability of modern offshore farming technology in minimizing the hypertrophic-dystrophic risks associated with the rapidly-expanding tuna-fattening industry in the Mediterranean Sea.  相似文献   

A Geometric Interpretation of Integrable Motions     

Cecilia Clementi  Marco Pettini 《Celestial Mechanics and Dynamical Astronomy》2002,84(3):263-281

Integrability, one of the classic issues in galactic dynamics and in general in celestial mechanics, is here revisited in a Riemannian geometric framework, where Newtonian motions are seen as geodesics of suitable -mechanical- manifolds. The existence of constants of motion that entail integrability is associated with the existence of Killing tensor fields on the mechanical manifolds. Such tensor fields correspond to hidden symmetries of non-Noetherian kind. Explicit expressions for Killing tensor fields are given for the N = 2 Toda model, and for a modified Hénon-Heiles model, recovering the already known analytic expressions of the second conserved quantity besides energy for each model respectively.  相似文献   

First results from the H i Jodrell All Sky Survey: inclination-dependent selection effects in a 21-cm blind survey     

Robert H. Lang  Peter J. Boyce  Virginia A. Kilborn  Robert F. Minchin  Michael J. Disney  Christine A. Jordan  Marco Grossi  Diego A. Garcia  Ken C. Freeman  Steven Phillipps  Alan E. Wright 《Monthly notices of the Royal Astronomical Society》2003,342(3):738-758

  相似文献   

Iron and nickel line properties in the X-ray-reflecting region of the Circinus galaxy     

Silvano Molendi  Stefano Bianchi  Giorgio Matt 《Monthly notices of the Royal Astronomical Society》2003,343(1):L1-L4

  相似文献   

Geometry of Chaos in Models of Stellar Dynamics     

Guido Ciraolo  Marco Pettini 《Celestial Mechanics and Dynamical Astronomy》2002,83(1-4):171-190

  相似文献   

Uncertainties in limits on TeV-gravity from neutrino-induced showers     

Eun-Joo Ahn  Marco Cavagli  Angela V. Olinto 《Astroparticle Physics》2005,22(5-6):377-385

In models with TeV-scale gravity, ultrahigh energy cosmic rays can generate microscopic black holes in the collision with atmospheric and terrestrial nuclei. It has been proposed that stringent bounds on TeV-scale gravity can be obtained from the absence of neutrino cosmic ray showers mediated by black holes. However, uncertainties in the cross section of black hole formation and, most importantly, large uncertainties in the neutrino flux affects these bounds. As long as the cosmic neutrino flux remains unknown, the non-observation of neutrino induced showers implies less stringent limits than present collider limits.  相似文献