Search results for " sky"
showing 10 items of 52 documents
Scaling laws in the distribution of galaxies
2004
Research done during the previous century established our Standard Cosmological Model. There are many details still to be filled in, but few would seriously doubt the basic premise. Past surveys have revealed that the large-scale distribution of galaxies in the Universe is far from random: it is highly structured over a vast range of scales. To describe cosmic structures, we need to build mathematically quantifiable descriptions of structure. Identifying where scaling laws apply and the nature of those scaling laws is an important part of understanding which physical mechanisms have been responsible for the organization of clusters, superclusters of galaxies and the voids between them. Find…
Influence of Multiple Scattering of the Intensity and Polarization of Diffuse Sky Radiation
1964
A physical explanation of the intensity and polarization of diffusion skylight in the plane of the sun’s vertical is attempted by an approximation method which takes into account the effects of multiple scattering. Various model atmospheres are considered. The scattered radiation field is assumed to be composed of (1) the scattered radiation due to the molecular atmosphere resulting from all orders of scattering; (2) the scattered radiation due to the turbid atmosphere including primary scattering only; and (3) the scattered radiation due to the turbid atmosphere resulting from secondary and higher-order scattering. The contribution due to the first term can be computed from the tables appl…
Una linea che taglia il cielo. Carlo Scarpa a Palermo
2018
La tesi principale di questo scritto prende spunto da una la lezione itinerante dal titolo: Uno sguardo sulle mani. Carlo Scarpa a palazzo Abatellis passando dallo Steri. Questa ha fornito l’opportunità di far emergere un monito non scontato, da tenere non solo in mente, nel rapporto fra la realtà delle mani e i manufatti architettonici realizzati da Carlo Scarpa a Palermo. In senso oggettivo è un rimando agli spazi che generano di volta in volta l’idea di una strategia dei percorsi? Come cambia lo spazio di relazione in una logica dell’interconnessione? Il saggio cerca una possibile risposta a queste domande e ragionando sulla strategia dei percorsi studiati da Scarpa nei due interventi re…
Vicarious calibration of MERIS over dark waters in the near infrared
2005
Abstract We propose to evaluate the calibration of MERIS (MEdium Resolution Imaging Spectrometer) over dark waters in the near infrared. We work with 5 months of data, from July to November 2003, over five world sites: Venice and Lampedusa in Italy, El Arenosillo in Spain, MOBY/Lanai and CalCOFI/San Nicolas in the United States. The sites are all equipped with a CIMEL station that forms part of the AERONET network. The basic idea is to associate CIMEL sky radiance measurements with MERIS level-1b data in a twin geometry which corresponds to the same scattering angle. This vicarious calibration relies on an accurate description of the atmospheric scattering based on the CIMEL measurements. A…
Direct assessment of the sensitivity drift of SQM sensors installed outdoors
2021
Long-term monitoring of the evolution of the artificial night sky brightness is a key tool for developing science-informed public policies and assessing the efficacy of light pollution mitigation measures. Detecting the underlying artificial brightness trend is a challenging task, since the typical night sky brightness signal shows a large variability with characteristic time scales ranging from seconds to years. In order to effectively isolate the weak signature of the effect of interest, determining the potential long term drifts of the radiance sensing systems is crucial. If these drifts can be adequately characterized, the raw measurements could be easily corrected for them and transfor…
The starry sky, a territorial commons?
2021
International audience; Flagstaff, Arizona, United States, April 15, 1958: the city council adopts the ordinance n°440 which aims at “preventing a rapid deterioration of the visibility of the starry sky”. This regulation results from the mobilization of the Lowell Observatory astronomers against certain public lighting devices. Through this political act, the elected officials place their city at the epicenter of an emergent international movement: the ‘Dark-sky movement’. The first replica of this movement is felt in 1972 in Tucson, Arizona. From a discomfort perceived by astronomers from the Lowell and Kitt Peak observatories, the idea of ‘light pollution’ emerges and begins to spread thr…
Spectral calibration of hyperspectral imagery using atmospheric absorption features
2006
One of the initial steps in the preprocessing of remote sensing data is the atmospheric correction of the at-sensor radiance images, i.e., radiances recorded at the sensor aperture. Apart from the accuracy in the estimation of the concentrations of the main atmospheric species, the retrieved surface reflectance is also influenced by the spectral calibration of the sensor, especially in those wavelengths mostly affected by gaseous absorptions. In particular, errors in the surface reflectance appear when a systematic shift in the nominal channel positions occurs. A method to assess the spectral calibration of hyperspectral imaging spectrometers from the acquired imagery is presented in this p…
Parental Teaching of Reading and Spelling Across the Transition From Kindergarten to Grade 1
2021
We investigated the longitudinal links between parental teaching of reading and spelling and children’s word reading and spelling skills. Data of 244 Lithuanian parent–child dyads were analyzed, who were followed across three time points: end of kindergarten (T1; Mage = 6.88; 116 girls), beginning of Grade 1 (T2), and end of Grade 1 (T3). The children’s word reading and spelling skills were tested, and the parents answered questionnaires on the frequency with which they taught their children reading and spelling. Overall, the results showed that the parents were responsive to their children’s skill levels across the domains of reading and spelling and across time (i.e., the transition from …
B–T phase diagram of Pd/Fe/Ir(111) computed with parallel tempering Monte Carlo
2017
We use an atomistic spin model derived from density functional theory calculations for the ultra-thin film Pd/Fe/Ir(111) to show that temperature induces coexisting non-zero skyrmion and antiskyrmion densities. We apply the parallel tempering Monte Carlo method in order to reliably compute thermodynamical quantities and the B-T phase diagram in the presence of frustrated exchange interactions. We evaluate the critical temperatures using the topological susceptibility. We show that the critical temperatures depend on the magnetic field in contrast to previous work. In total, we identify five phases: spin spiral, skyrmion lattice, ferromagnetic phase, intermediate region with finite topologic…
Unveiling the environment and faint features of the isolated galaxy CIG 96 with deep optical and HI observations
2018
Context. Asymmetries in atomic hydrogen (HI) in galaxies are often caused by the interaction with close companions, making isolated galaxies an ideal framework to study secular evolution. The AMIGA project has demonstrated that isolated galaxies show the lowest level of asymmetry in their HI integrated profiles compared to even field galaxies, yet some present significant asymmetries. CIG 96 (NGC 864) is a representative case reaching a 16% level. Aims. Our aim is to investigate the HI asymmetries of the spiral galaxy CIG 96 and what processes have triggered the star-forming regions observed in the XUV pseudo-ring. Methods. We performed deep optical observations at CAHA1.23m, CAHA2.2m and V…