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11.
A. Migliorini F. Altieri G. Piccioni A. Cardesín Moinelo E. D’Aversa B. Gondet 《Planetary and Space Science》2011,59(10):981-987
Imaging spectrometers are highly effective instruments for investigation of planetary atmospheres. They present the advantage of coupling the compositional information to the spatial distribution, allowing simultaneous study of chemistry and dynamics in the atmospheres of Venus and Mars. In this work, we summarize recent results about the O2(a1Δg) night and day glows, respectively obtained by VIRTIS/Venus Express and OMEGA/Mars Express, the imaging spectrometers currently in orbit around Venus and Mars. The case of the O2(a1Δg - X3Σg−) IR emission at 1.27 μm on the night side of Venus and the day side of Mars is analyzed, pointing out dynamical aspects of these planets, like the detection of gravity waves in their atmospheres. The monitoring of seasonal and daily airglow variations provides hints about the photochemistry on these planets. 相似文献
12.
Leech K. Crovisier J. Bockelée-Morvan D. Brooke T. Y. Hanner M. S. Altieri B. Keller H. U. Lellouch E. Lim T. 《Earth, Moon, and Planets》1997,78(1-3):81-83
Spectra of comet C/1995 O1 (Hale-Bopp) were obtained with the Infrared Space Observatory (ISO) at medium resolution with the
grating spectrometer in the photometer (PHT-S) and/or at high resolution with the short wavelength spectrometer (SWS) and
long wavelength spectrometer (LWS) in April 1996 (Crovisier et al., 1996), September–October 1996 (Crovisier et al., 1997a,
b) and December 1997, at distances from the Sun of 4.6, 2.9 and 3.9 AU, respectively. For the first time, high-resolution
spectra of a comet covering the entire 2.4 to 200 μm spectral range were obtained.
The vibrational bands of H2O, CO2 and CO are detected in emission with PHT-S. Relative production rates of 100:22:70 are derived for H2O:CO2:CO at 3 AU pre-perihelion. H2O is observed at high spectral resolution in the ν3 group of bands around 2.7 μm and the ν2 group around 6 μm with SWS, and in several rotational lines in the 100–180 μm region with LWS. The high signal-to-noise ratio
of the ν3 band observed on September–October 1996 allows accurate determinations of the water rotational temperature (28 K) and of
its ortho-to-para ratio(2.45 ± 0.10, which significantly differs from the high temperature limit and corresponds to a spin
temperature of 25 K).
Longward of 6 μm the spectrum is dominated by dust thermal continuum emission, upon which broad emission features are superimposed.
The wavelengths of the emission peaks correspond to those of Mg-rich crystalline olivine (forsterite). In the September–October
1996 spectra, emission features at 45 and 65 μm and possible absorption at 2.9–3.2 μm suggest that grains of water ice were
present at 3 AU from the Sun.
The observations made post-perihelion in late December 1997 led to the detections of H2O, CO2 and CO at 3.9 AU from the Sun (Figures 1 and 2). The production rates were ≈3.0 × 1028,3.5 × 1028 and ≈1.5 × 1029 s-1, respectively. This corresponds to H2O:CO2:CO = 100:110:500 and confirms that at such distances from the Sun, cometary activity is dominated by sublimation of CO and
CO2 rather than by H2O.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Thomas Müller Zoltán Balog Markus Nielbock Tanya Lim David Teyssier Michael Olberg Ulrich Klaas Hendrik Linz Bruno Altieri Chris Pearson George Bendo Esa Vilenius 《Experimental Astronomy》2014,37(2):253-330
Celestial standards play a major role in observational astrophysics. They are needed to characterise the performance of instruments and are paramount for photometric calibration. During the Herschel Calibration Asteroid Preparatory Programme approximately 50 asteroids have been established as far-IR/sub-mm/mm calibrators for Herschel. The selected asteroids fill the flux gap between the sub-mm/mm calibrators Mars, Uranus and Neptune, and the mid-IR bright calibration stars. All three Herschel instruments observed asteroids for various calibration purposes, including pointing tests, absolute flux calibration, relative spectral response function, observing mode validation, and cross-calibration aspects. Here we present newly established models for the four large and well characterized main-belt asteroids (1) Ceres, (2) Pallas, (4) Vesta, and (21) Lutetia which can be considered as new prime flux calibrators. The relevant object-specific properties (size, shape, spin-properties, albedo, thermal properties) are well established. The seasonal (distance to Sun, distance to observer, phase angle, aspect angle) and daily variations (rotation) are included in a new thermophysical model setup for these targets. The thermophysical model predictions agree within 5 % with the available (and independently calibrated) Herschel measurements. The four objects cover the flux regime from just below 1,000 Jy (Ceres at mid-IR N-/Q-band) down to fluxes below 0.1 Jy (Lutetia at the longest wavelengths). Based on the comparison with PACS, SPIRE and HIFI measurements and pre-Herschel experience, the validity of these new prime calibrators ranges from mid-infrared to about 700 μm, connecting nicely the absolute stellar reference system in the mid-IR with the planet-based calibration at sub-mm/mm wavelengths. 相似文献
16.
The threat of global climate change has caused concern among scientists because crop production could be severely affected by changes in key climatic variables that could compromise food security both globally and locally. Although it is true that extreme climatic events can severely impact small farmers, available data is just a gross approximation at understanding the heterogeneity of small scale agriculture ignoring the myriad of strategies that thousands of traditional farmers have used and still use to deal with climatic variability. Scientists have now realized that many small farmers cope with and even prepare for climate change, minimizing crop failure through a series of agroecological practices. Observations of agricultural performance after extreme climatic events in the last two decades have revealed that resiliency to climate disasters is closely linked to the high level of on-farm biodiversity, a typical feature of traditional farming systems.Based on this evidence, various experts have suggested that rescuing traditional management systems combined with the use of agroecologically based management strategies may represent the only viable and robust path to increase the productivity, sustainability and resilience of peasant-based agricultural production under predicted climate scenarios. In this paper we explore a number of ways in which three key traditional agroecological strategies (biodiversification, soil management and water harvesting) can be implemented in the design and management of agroecosystems allowing farmers to adopt a strategy that both increases resilience and provides economic benefits, including mitigation of global warming. 相似文献
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Katye E. Altieri Hilton Trollip Tara Caetano Alison Hughes Bruno Merven Harald Winkler 《Climate Policy》2016,16(4):S78-S91
Achieving the international 2 °C limit climate policy requires stringent reductions in GHG emissions by mid-century, with some countries simultaneously facing development-related challenges. South Africa is a middle-income developing country with high rates of unemployment and high levels of poverty, as well as an emissions-intensive economy. South Africa takes into account an assessment of what a fair contribution to reducing global emissions might be, and is committed to a ‘peak, plateau and decline' emissions trajectory with absolute emissions specified for 2025 and 2030, while noting the need to address development imperatives. This work utilizes an economy-wide computable general equilibrium model (e-SAGE) linked to an energy-system optimization model (TIMES) to explore improving development metrics within a 14 GtCO2e cumulative energy sector carbon constraint through to 2050 for South Africa. The electricity sector decarbonizes by retiring coal-fired power plants or replacing with concentrated solar power, solar photovoltaics and wind generation. Industry and tertiary-sector growth remains strong throughout the time period, with reduced energy intensity via fuel-switching and efficiency improvements. From 2010 to 2050, the model results in the unemployment rate decreasing from 25% to 12%, and the percentage of people living below the poverty line decreasing from 49% to 18%. Total energy GHG emissions were reduced by 39% and per capita emissions decreased by 62%.Policy relevanceLower poverty and inequality are goals that cannot be subordinated to lower GHG emissions. Policy documents in South Africa outline objectives such as reducing poverty and inequality with a key focus on education and employment. In its climate policy and Intended Nationally Determined Contribution (INDC), South Africa is committed to a peak, plateau and decline GHG emissions trajectory. As in many developing countries, these policy goals require major transformations in the energy system while simultaneously increasing affordable access to safe and convenient energy services for those living in energy poverty. The modelled scenario in this work focuses on employment and poverty reduction under a carbon constraint, a novel combination with results that can provide information for a holistic climate and development policy framework. This study has focused on the long term, which is important in generating clear policy signals for the necessary large-scale investments. 相似文献
18.
B. Altieri L. Metcalfe J. Blommaert D. Elbaz J.-L. Starck H. Aussel 《Experimental Astronomy》2000,10(2-3):291-303
We discuss the instrumental factors which constrain the sensitivity limits of the mid-infrared camera (ISOCAM) of ESA's Infrared Space Observatory (ISO). The observing strategy judged to be best suited to faint-source detection is described. A data analysis technique adapted to the extraction of the faintest point-sources is discussed. We report the application of these techniques to an extremely deep mid-IR observation of high redshift gravitationally lensed objects, in two filters, looking through a lensing galaxy cluster. 相似文献
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Domenico Altieri Enrico Tubaldi Marco De Angelis Edoardo Patelli Andrea Dall’Asta 《Bulletin of Earthquake Engineering》2018,16(2):963-982
Viscous dampers are widely employed for enhancing the seismic performance of structural systems, and their design is often carried out using simplified approaches to account for the uncertainty in the seismic input. This paper introduces a novel and rigorous approach that allows to explicitly consider the variability of the intensity and characteristics of the seismic input in designing the optimal viscous constant and velocity exponent of the dampers based on performance-based criteria. The optimal solution permits controlling the probability of structural failure, while minimizing the damper cost, related to the sum of the damper forces. The solution to the optimization problem is efficiently sought via the constrained optimization by linear approximation (COBYLA) method, while Subset simulation together with auxiliary response method are employed for the performance assessment at each iteration of the optimization process. A 3-storey steel moment-resisting building frame is considered to illustrate the application of the proposed design methodology and to evaluate and compare the performances that can be achieved with different damper nonlinearity levels. Comparisons are also made with the results obtained by applying simplifying approaches, often employed in design practice, as those aiming to minimize the sum of the viscous damping constant and/or considering a single hazard level for the performance assessment. 相似文献
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Polar regions on Mars are the most suitable places to observe water vapor daily variability because in any observation crossing the Pole we can observe very different local time and because the poles are considered to be the main permanent and seasonal water reservoir of the planet. We report on a daily variability of water vapor in the South Pole Region (SPR), observed by OMEGA/Mars Express during the south spring-summer period (Ls∼250°-270°) outside the CO2 ice cap, that has never been observed before by other instruments. We have been able to estimate an increase of few precipitable microns during the day. A possible scenario includes the presence of regolith, or another component that could gather water from the atmosphere, adsorbing the water into the surface during the night time and desorbing it as soon as the Sun reaches sufficient height to heat the ground. This hypothesis is even more plausible considering the presence of observed local enhancements in the morning sections associated with the illumination of the Sun and the total absence in the data for water ice. 相似文献