Detectors For Space Science     

Mark Clampin  David Lumb  Marco Sirianni  Edward Smith 《Experimental Astronomy》2005,19(1-3):45-67

The design of detector systems for flight applications requires the consideration of a number of issues unique to space instrumentation. Flight detectors must endure hostile radiation environments and thermal extremes. Paramount importance is given to reliability since inflight replacement is at best difficult and usually impossible. Flight detectors are also significant cost and design drivers since they often determine key requirements for flight instruments such as volume, mass, power consumption, heat dissipation and communications budgets. In this paper we describe the primary concerns in developing flight detector systems, and review the challenges posed by future NASA and ESA space science missions for detector development.  相似文献   

Inverse compton emission of gamma rays near the pulsar surface     

Marco Morini 《Astrophysics and Space Science》1981,79(1):203-211

The physical conditions near pulsar surface that might give rise to gamma ray emission from Crab and Vela pulsars are not yet well understood. Here I suggest that, in the context of the vacuum discharge mechanism proposed by Ruderman and Sutherland (1975), gamma rays are produced by inverse Compton scattering of secondary electrons with the thermal radiation of the star surface as well as for curvature and synchrotron radiation. It is found that inverse Compton scattering is relevant if the neutron star surface temperature is greater than 10⁶K or if the polar cap temperature is of the order of 5×10⁶K. Inverse Compton scattering in anisotropic photon fields and Klein-Nishina regime is here carefully considered.  相似文献   

On the expansion of supernova shells     

Carla Maceroni  Marco Salvati  Franco Pacini 《Astrophysics and Space Science》1974,28(1):205-212

We have investigated a simple model for the effects of a central pulsar on the expansion of supernova shells. Some numerical results relevant to the Crab Nebula are also reported.  相似文献   

Feeding Monsters – A Study of Active Galaxies     

Melanie Krips  Andreas Eckart  Roberto Neri  Joerg-Uwe Pott  Jens Zuther  Julia Scharwächter  Thomas Bertram 《Astrophysics and Space Science》2005,295(1-2):95-100

We present new interferometric observations of the molecular gas distribution and kinematics in the nuclei of different active galaxies at high angular resolution and high sensitivity carried out with the IRAM Plateau de Bure interferometer (PdBI). The observations cover galaxies in a redshift range of 0.03–1.4. We have so far observed five different active galaxies: NGC3718, NGC1068, HE1029–1831, 3C48 and Q0957+561. The first two objects belong to the NUGA (NUclei of GAlaxies) project – an international collaboration mainly between Spain, France and Germany – containing about 30 Seyfert and LINER galaxies. Both are at the same distance of 14Mpc and show a warped gas and dust disk. The new mosaic map of NGC3718 corrected for short-spacing effects with IRAM 30 m observations well demonstrates the existence of the warped gas disk with several secondary maxima in the projected gas distribution caused by orbit crowding effects. Based on these new data we have improved recent simulations of the warped disk in NGC3718. HE1029–1831 and 3C48 are nearby QSOs. HE1029–1831 is taken out of the Cologne nearby QSO sample. The maps of the integrated CO(1–0) and CO(2–1) emission clearly show that the molecular gas is mostly related to the central bulge with a non-negligible fraction distributed along the bar known from optical observations. Our new CO data of 3C48 unveil new information about the kinematics of its molecular gas complementing and improving further studies based on previous infrared observations and detailed multi-particle simulations. Finally, new measurements of the CO(1–0) line in Q0957+561 – a highly-red-shifted, gravitationally lensed quasar – will be presented as a link to earlier evolutionary stages of active galaxies and their hosts.  相似文献   

Survivorship of coral juveniles in a fish farm environment   总被引：1，自引：0，他引：1  

Villanueva RD  Yap HT  Montaño MN 《Marine pollution bulletin》2005,51(5-7):580-589

Intensive fish farming is an emerging coastal activity that can potentially enhance sedimentation and promote eutrophication in fringing coral reefs. Here, we investigate the effect of fish farm effluent on the juvenile survivorship of the reef-building coral Seriatopora caliendrum. One-month old juvenile corals (on terracotta tiles) were deployed in fish farm and reference (reef) sites in Bolinao, the Philippines at a depth of 2m. After forty days, no survivor was recovered in the fish farm, while survivorship was low (11%) in the reference site, with the survivors' growth rate at 3.3polypsmo(-1) or 1.3mm(2)mo(-1). The fish farm deployed tiles were covered with muddy sediment and were colonized by barnacles, whereas those in the reference site were overgrown by a short stand of filamentous macroalgae. Environmental monitoring revealed higher nutrient levels (ammonia and phosphate), sedimentation rate, and organic matter flux, as well as diminished water transparency and dissolved oxygen levels in the fish farm compared to the reference site. Hence, intensive fish farming offers a suite of physical, chemical and biological modifications of the coastal marine environment which have a detrimental effect on the survivorship of coral juveniles.  相似文献   

Nonlinear Dynamic Response of HDRB and Hybrid HDRB-Friction Sliders Base Isolation Systems     

Franco?Braga  Marco?Faggella  Rosario?Gigliotti  Michelangelo?LaterzaEmail author 《Bulletin of Earthquake Engineering》2005,3(3):333-353

The isolation systems are usually made of rubber bearings that are sometimes coupled in hybrid combination with frictional devices; this is the case of an in-site experimental campaign, performed on a base isolated apartment building in Rapolla (south of Italy). Several dropout tests at initial displacements up to 17cm allowed to obtain in-site information on the true dynamic response of the isolation system (building and isolators). The tests carried out allow a comparison between the free vibration responses of a building, isolated by using a 28 HDRB isolation system only, or an HDRB-Friction Sliders Hybrid one. The paper highlights the main differences of the response in the superstructure (the structure over the isolation system) obtained by using only HDRB isolation system, or the Hybrid one (HDRB and Friction Sliders in parallel system). Analysis and comparisons of experimental data, show the influence of nonlinearities on structural higher modes amplification, especially observed by using the higher nonlinear Hybrid isolation system. Tests results confirm that, in the case of a regular superstructure, like the Rapolla building, the isolation system nonlinearities influence the structural response.  相似文献   

Photoelectric activity of the shell staro And: New observations and discussion     

Michele Bossi  Gianantonio Guerrero  Luciano Mantegazza  Marco Scardia 《Astrophysics and Space Science》1980,72(2):433-437

Photoelectric observations of the shell staro And, obtained in 1979, are presented. The star shows variations of some hundredth of magnitudes during a few hours. The trend to retake the values of the luminosity and colour indices prior to the reduction happened between JD 42,714-27, seems to continue. We also give a qualitative model which explains satisfactorily the main features observed after the 1975 shell episode.  相似文献   

Study of the variability of the Delta Scuti stars     

Michele Bossi  Gianantonio Guerrero  Luciano Mantegazza  Marco Scardia 《Astrophysics and Space Science》1981,79(2):463-468

Photoelectric observations of the suspected Delta-Scuti star HR 5492 are given. The present data do not show any light variation greater than 0.01 mag. In spite of the very small light variations, the data analysis shows the presence of two periodicities, which are statistically significant. While the longest period (1. _. ^d 296) cannot be justified with the present data, the shorter one (0. _. ^d 044) is in excellent agreement with the hypothesis of an F4V star that is radially pulsating in the fundamental mode, even if this star is well outside the cold border of the instability strip.  相似文献   

High-pressure behaviour along the jadeite NaAlSi2O6–aegirine NaFeSi2O6 solid solution up to 10 GPa     

Fabrizio Nestola  Tiziana Boffa Ballaran  Christian Liebske  Marco Bruno  Mario Tribaudino 《Physics and Chemistry of Minerals》2006,33(6):417-425

The volume variation as a function of pressure along the jadeite–aegirine solid solution was determined at room temperature up to pressures between 6.5 and 9.7 GPa by single-crystal X-ray diffraction. The unit-cell volumes collected at room pressure for the different compositions indicate a slight deviation from linearity along the join. The pressure–volume data have been fitted using a third-order Birch-Murnaghan equation of state (BM3-EoS). The bulk modulus, K _T0, varies from 134.0(7) GPa for pure jadeite to 116.1(5) GPa for pure aegirine. Its evolution with composition along the join is not linear and can be described by the following second order polynomial:

(1)

The value of the first pressure derivative K′ is close to 4 for all the samples investigated and can be used in a BM3-EoS to determine the volume variations of these pyroxenes up to 7–10 GPa. Along the join the highest compressibility among the crystallographic directions is always observed along a, however, the compression along b is the most affected by compositional changes. The strain ellipsoid analysis indicates that the major compression occurs on the (0 1 0) plane along a direction at about 145° to the c axis (from c to a). The anisotropy of the compression increases with increasing the aegirine component, as confirmed by the analysis of both the axial compressibility and the strain tensor.  相似文献   

An exotic Cretaceous kimberlite linked to metasomatized lithospheric mantle beneath the southwestern margin of the Francisco Craton,Brazil     

Luísa D.V.Carvalho  Tiago Jalowitzki  Ricardo Scholz  Guilherme O.Gonalves  Marcelo Peres Rocha  Rogério Silvestre Pereir  Cristiano Lana  Marco Paulo de Castro  Gláucia Queiroga  Reinhardt A.Fuck 《地学前缘(英文版)》2022,(1):182-203

We present major and trace element compositions of mineral concentrates comprising garnet xenocrysts,ilmenite,phlogopite,spinel,zircon,and uncommon minerals (ti...  相似文献