3,090 research outputs found
Tumor Uptake Studies of S-Adenosyl-L-[methyl-11C]Methionine and L-[methyl-11C]Methionine
開始ページ、終了ページ: 冊子体のページ付
Touch-screen-guided task reveals a prosocial choice tendency by chimpanzees (Pan troglodytes)
Humans help others even without direct benefit for themselves. However, the nature of altruistic (i.e., only the other benefits) and prosocial (i.e., self and other both benefit) behaviors in our closest living relative, the chimpanzee, remains controversial. To address this further, we developed a touch-screen-guided task that allowed us to increase the number of trials for a thorough test of chimpanzees' prosocial and altruistic tendencies. Mother-offspring dyads were tested in the same compartment; one was the actor while the other was the recipient. In Experiment 1, the actor chose among three options: prosocial, selfish (only the actor benefited) and altruistic. To better understand the nature of the chimpanzees' choices and to improve experimental control, we conducted two additional experiments. Experiment 2 consisted of two-option choices interspersed with three-option choices, and in Experiment 3 the two-option choice were blocked across all trials. The results of Experiment 1 clearly showed that chimpanzees acted prosocially in the touch-screen-guided task, choosing the prosocial option on an average of 79% of choices. Five out of the six chimpanzees showed the preference to act prosocially against chance level. The preference for the prosocial option persisted when conditions were changed in Experiments 2 and 3. When only selfish and altruistic options were available in Experiments 2 and 3, chimpanzees preferred the selfish option. These results suggest that (1) most individuals understood the nature of the task and modified their behavior according to the available options, (2) five out of the six chimpanzees chose to act prosocially when they had the option to, and (3) offspring counterbalanced between altruistic and selfish, when given those two options perhaps to avoid suffering repercussions from the mother.Ministry of Education, Science, Sports and Culture, Japan [24000001]; Japan Society for the Promotion of Science (JSPS); [16H06283]; [22700270
Discovery of the Central Excess Brightness in Hard X-rays in the Cluster of Galaxies Abell 1795
Using the X-ray data from \ASCA, spectral and spatial properties of the
intra-cluster medium (ICM) of the cD cluster Abell 1795 are studied, up to a
radial distance of ( kpc). The ICM
temperature and abundance are spatially rather constant, although the cool
emission component is reconfirmed in the central region. The azimuthally-
averaged radial X-ray surface brightness profiles are very similar between soft
(0.7--3 keV) and hard (3--10 keV) energy bands, and neither can be fitted with
a single- model due to a strong data excess within of the
cluster center. In contrast, double- models can successfully reproduce
the overall brightness profiles both in the soft and hard energy bands, as well
as that derived with the \ROSAT PSPC. Properties of the central excess
brightness are very similar over the 0.2--10 keV energy range spanned by \ROSAT
and \ASCA. Thus, the excess X-ray emission from the core region of this cluster
is confirmed for the first time in hard X-rays above 3 keV. This indicates that
the shape of the gravitational potential becomes deeper than the King-type one
towards the cluster center. Radial profiles of the total gravitating matter,
calculated using the double- model, reveal an excess mass of within kpc of the cluster
center. This suggests a hierarchy in the gravitational potential corresponding
to the cD galaxy and the entire cluster.Comment: 27 pages, 8 figures; to appear ApJ 500 (June 20, 1998
The Structure of the X-Ray Emitting Gas in the Hydra-A Cluster of Galaxies
The temperature and abundance structure in the intracluster medium (ICM) of
the Hydra-A cluster of galaxies is studied with ASCA and ROSAT. The effect of
the large extended outskirts in the point-spread function of the X-Ray
Telescope on ASCA is included in this analysis. In the X-ray brightness
profile, the strong central excess above a single beta-model, identified in the
Einstein and ROSAT data, is also found in the harder energy band (>4keV). A
simultaneous fit of five annular spectra taken with the GIS instrument shows a
radial distribution of the temperature and metal abundance. A significant
central enhancement in the abundance distribution is found, while the
temperature profile suggests that the ICM is approximately isothermal with the
temperature of ~3.5keV. The ROSAT PSPC spectrum in the central 1'.5 region
indicates a significantly lower temperature than the GIS result. A joint
analysis of the GIS and PSPC data reveals that the spectra can be described by
a two temperature model as well as by a cooling flow model. In both cases, the
hot phase gas with the temperature of ~3.5keV occupies more than 90% of the
total emission measure within 1'.5 from the cluster center. The estimated mass
of the cooler (0.5-0.7keV) component is ~2-6 x 10^9 M_solar, which is
comparable to the mass of hot halos seen in non-cD ellipticals. The cooling
flow model gives the mass deposition rate of 60+-30 M_solar/yr, an order of
magnitude lower than the previous estimation.Comment: 27 pages, 14 figures, AAS LATEX macros v4.0, to appear in The
Astrophysical Journa
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