9,306 research outputs found
A simulation model of temperature transitory on rocks having different thermal inertia. Analysis of the theoretical capacity of rock discrimination by remote sensing data
The possibility of identifying ground surface material by measuring the surface temperature at two different and significant times of the day was investigated for the case of hypothetical island whose rocky surface contained no vegetation and consisted of dolomite, clay, and granite. The thermal dynamics of the soil surface during a day in which atmospheric conditions were average for a latitude of about 40 deg to 50 deg were numerically simulated. The line of separation between zones of different materials was delineated by the range of temperature variation. Results show that the difference between maximum and minimum value of the temperature of ground surface during the day is linked to the thermal inertia value of the material of which the rock is formed
Photometric and spectroscopic study of the intermediate age open cluster NGC 3960
We present CCD UBVI photometry and high-resolution spectroscopy of the
intermediate age open cluster NGC 3960. The colour - magnitude diagrams (CMDs)
derived from the photometric data and interpreted with the synthetic CMD method
allow us to estimate the cluster parameters. We derive: age = 0.9 or 0.6 Gyr
(depending on whether or not overshooting from convective regions is included
in the adopted stellar models), distance (m-M)0 = 11.6 +/- 0.1, reddening
E(B-V) = 0.29 +/- 0.02, differential reddening Delta E(B-V) = 0.05 and
approximate metallicity between solar and half of solar. We obtained high
resolution spectra of three clump stars, and derived an average [Fe/H] = -0.12
(rms 0.04 dex), in very good agreement with the photometric determination. We
also obtained abundances of alpha-elements, Fe-peak elements, and of Ba. The
reddenings toward individual stars derived from the spectroscopic temperatures
and the Alonso et al. calibrations give further support to the existence of
significative variations across the cluster.Comment: Accepted for publication on MNRAS; fig. 3, 4, 5, 6 at degraded
resolutio
Photometric and spectroscopic study of the intermediate-age open cluster NGC 2355
In this paper we analyse the evolutionary status and properties of the old
open cluster NGC 2355, located in the Galactic anticentre direction, as a part
of the long term programme BOCCE. NGC 2355 was observed with LBC@LBT using the
Bessel , , and filters. The cluster parameters have been obtained
using the synthetic colour-magnitude diagram (CMD) method, as done in other
papers of this series. Additional spectroscopic observations with FIES@NOT of
three giant stars were used to determine the chemical properties of the
cluster. Our analysis shows that NGC 2355 has metallicity slightly less than
solar, with [Fe/H] dex, age between 0.8 and 1 Gyr, reddening
in the range 0.14 and 0.19 mag, and distance modulus of about 11 mag.
We also investigated the abundances of O, Na, Al, , iron-peak, and
neutron capture elements, showing that NGC 2355 falls within the abundance
distribution of similar clusters (same age and metallicity). The Galactocentric
distance of NGC~2355 places it at the border between two regimes of metallicity
distribution; this makes it an important cluster for the study of the chemical
properties and evolution of the disc.Comment: 20 pages, 11 figures, Accepted on MNRA
Many-body effective mass enhancement in a two-dimensional electron liquid
Motivated by a large number of recent magnetotransport studies we have
revisited the problem of the microscopic calculation of the quasiparticle
effective mass in a paramagnetic two-dimensional (2D) electron liquid (EL). Our
systematic study is based on a generalized approximation which makes use
of the many-body local fields and takes advantage of the results of the most
recent QMC calculations of the static charge- and spin-response of the 2D EL.
We report extensive calculations for the many-body effective mass enhancement
over a broad range of electron densities. In this respect we critically examine
the relative merits of the on-shell approximation, commonly used in
weak-coupling situations, {\it versus} the actual self-consistent solution of
the Dyson equation. We show that already for and higher, a
solution of the Dyson equation proves here necessary in order to obtain a well
behaved effective mass. Finally we also show that our theoretical results for a
quasi-2D EL, free of any adjustable fitting parameters, are in good qualitative
agreement with some recent measurements in a GaAs/AlGaAs heterostructure.Comment: 12 pages, 3 figures, CMT28 Conference Proceedings, work related to
cond-mat/041226
Heat Capacity Mapping Mission (HCMM) program: Study of geological structure of Sicily and other Italian areas
The usefulness of thermal inertia mapping in discriminating geolithological units was investigated using Sardinia and the Gulf of Orosei as test sites. Software designed for LANDSAT data were modified and improved for HCMM tapes. A first attempt was made to compare the geological cross section, the topography, the IR radiance, and the thermal inertia along selected profiles of the test site. Thermal inertia profiles appear smoothed in comparison with the thermal radiance. The lowest apparent thermal inertia (ATI) was found on granitic and basaltic outcrops where their image is of sufficient extent, while ATI is higher on carbonatic and dolomitic or moist deposits. Almost every fault is marked by a jump of ATI, the interval being sometimes of the order of one pixel. This seems to demonstrate the ability of ATI to detect contacts or tectonically disturbed zones with a good resolution. It seems more difficult to measure the differences in ATI between homogeneous materials having different lithology. Ground surveys conducted and a simulation model of diurnal temperatures of rocks having different thermal inertia are discussed
The monkey's perspective
The sequencing of the genome of a female rhesus macaque (Macaca mulatta) of Indian origin will provide us with biomedical and evolutionary insights into both humans and Old World monkeys
Multi-Epoch HST Observations of IZw18: Characterization of Variable Stars at Ultra-Low Metallicities
Variable stars have been identified for the first time in the very metal-poor
Blue Compact dwarf galaxy IZw18, using deep multi-band (F606W,
F814W)time-series photometry obtained with the Advanced Camera for Surveys
(ACS) on board the Hubble Space Telescope (HST). We detected 34 candidate
variable stars in the galaxy. We classify three of them as Classical Cepheids,
with periods of 8.71, 125.0 and 130.3 days, respectively, and other two as long
period variables with periodicities longer than a hundred days. These are the
lowest metallicity Classical Cepheids known so far, thus providing the
opportunity to explore and fit models of stellar pulsation fo Classical
Cepheids at previously inaccessible metallicities. The period distribution of
the confirmed Cepheids is markedly different from what is seen in other nearby
galaxies, which is likely related to the star bursting nature of IZw18. By
applying to the 8.71 days Cepheid theoretical Wesenheit (V,I) relations based
on new pulsation models of Classical Cepheids specifically computed for the
extremely low metallicity of this galaxy (Z=0.0004, Y=0.24), we estimate the
distance modulus of IZw18 to be mu_0= 31.4pm0.2 D=19.0^{+1.8}_{-1.7}Mpc) for
canonical models of Classical Cepheids, and of 31.2pm0.2 mag
(D=17.4^{+1.6}_{-1.6}Mpc) using over luminous models. The theoretical modeling
of the star's light curves provides mu_0=31.4pm0.1 mag, D=19.0^{+0.9}_{-0.9}
Mpc, in good agreement with the results from the theoretical Wesenheit
relations. These pulsation distances bracket the distance of 18.2pm1.5Mpc
inferred by Aloisi et al. (2007) using the galaxy's Red Giant Branch Tip.Comment: 13 Pages, 6 Figures, accepted, Ap
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