796 research outputs found
The Inner Halo of M87: A First Direct View of the Red-Giant Population
An unusually deep (V,I) imaging dataset for the Virgo supergiant M87 with the
Hubble Space Telescope ACS successfully resolves its brightest red-giant stars,
reaching M_I(lim) = -2.5. After assessing the photometric completeness and
biasses, we use this material to estimate the metallicity distribution for the
inner halo of M87, finding that the distribution is very broad and likely to
peak near [m/H] ~ -0.4 and perhaps higher. The shape of the MDF strongly
resembles that of the inner halo for the nearby giant E galaxy NGC 5128. As a
byproduct of our study, we also obtain a preliminary measurement of the
distance to M87 with the TRGB (red-giant branch tip) method; the result is
(m-M)_0 = 31.12 +- 0.14 (d = 16.7 +- 0.9 Mpc). Averaging this result with three
other recent techniques give a weighted mean d(M87) = (16.4 +- 0.5) Mpc.Comment: In press for Astronomy and Astrophysic
Six Dimensions of Expertise: A More Comprehensive Definition of Cognitive Expertise For Team Coordination
Looking at expertise from the vantage point of many knowledge domains allows the observations and resulting definitions to be useful across a broad range of subject areas. A stable set of definitions that work on a higher, more comprehensive level than the current literature offers is needed for an integrated description of expertise. A cohesive cross-domain definition and explanation of expertise can be used to optimise group interactions. Since group performance incorporates additional components of expertise that are not present in individual performance situations, these additional components must be examined in order to see a full picture of the successful utilisation of expertise in a group setting. This expanded expertise definition will allow group dynamics to be better understood and will help break down the expertise components required to have successful group interactions
Extension of non-minimal derivative coupling theory and Hawking radiation in black-hole spacetime
We study the greybody factor and Hawking radiation with a non-minimal
derivative coupling between the scalar field and the curvature in the
background of the slowly rotating Kerr-Newman black hole.
Our results show that both the absorption probability and luminosity of
Hawking radiation of the scalar field increase with the coupling.
Moreover, we also find that for the weak coupling , the
absorption probability and luminosity of Hawking radiation decrease when the
black hole's Hawking temperature decreases; while for stronger coupling
, the absorption probability and luminosity of Hawking radiation
increase on the contrary when the black hole's Hawking temperature decreases.
This feature is similar to the Hawking radiation in a -dimensional static
spherically-symmetric black hole surrounded by quintessence \cite{chensong}.Comment: 17 pages, 6 figures, 1 table, Title changed, Appendix changed,
accepted by JHE
Awe and Wonder in Scientific Practice: Implications for the Relationship Between Science and Religion
This paper examines the role of awe and wonder in scientific practice.
Drawing on evidence from psychological research and the writings of scientists and science communicators, I argue that awe and wonder play a crucial role in scientific discovery. They focus our attention on the natural world, encourage open-mindedness, diminish the self (particularly feelings of self-importance), help to accord value to the objects that are being studied, and provide a mode of understanding in the absence of full knowledge. I will flesh out implications of the role of awe and wonder in scientific discovery for debates on the relationship between science and religion. Abraham Heschel argued that awe and wonder are religious emotions because they reduce our feelings of self-importance, and thereby help to cultivate the proper reverent attitude towards God. Yet metaphysical naturalists such as Richard Dawkins insist that awe and wonder need not lead to any theistic commitments for scientists. The awe some scientists experience can be regarded as a form of non-theistic spirituality, which is neither a reductive naturalism nor theism. I will attempt to resolve the tension between these views by identifying some common ground
Application of time-dependent density functional theory to optical activity
As part of a general study of the time-dependent local density approximation
(TDLDA), we here report calculations of optical activity of chiral molecules.
The theory automatically satisfies sum rules and the Kramers-Kronig relation
between circular dichroism and optical rotatory power. We find that the theory
describes the measured circular dichroism of the lowest states in methyloxirane
with an accuracy of about a factor of two. In the chiral fullerene C_76 the
TDLDA provides a consistent description of the optical absorption spectrum, the
circular dichroism spectrum, and the optical rotatory power, except for an
overall shift of the theoretical spectrum.Comment: 17 pages and 13 PostScript figure
Self-bias and the emotionality of foreign languages
Article first published online: June 13, 2018Foreign language contexts impose a relative psychological and emotional distance in bilinguals. In our previous studies, we demonstrated that the use of a foreign language changes the strength of the seemingly automatic emotional responses in the self-paradigm, showing a robust asymmetry in the self-bias effect in a native and a foreign language context. Namely, larger effects were found in the native language, suggesting an emotional blunting in the foreign language context. In the present study, we investigated the source of these effects by directly comparing whether they stem from a language’s foreignness versus its non-nativeness. We employed the same self-paradigm (a simple perceptual matching task of associating simple geometric shapes with the labels “you,” “friend,” and “other”), testing unbalanced Spanish–Basque–English trilinguals. We applied the paradigm to three language contexts: native, non-native but contextually present (i.e., non-native local), and non-native foreign. Results showed a smaller self-bias only in the foreign language pointing to the foreign-language-induced psychological/emotional distance as the necessary prerequisite for foreign language effects. Furthermore, we explored whether perceived emotional distance towards foreign languages in Spanish–English bilinguals modulates foreign language effects. Results suggest that none of the different indices of emotional distance towards the foreign language obtained via questionnaires modulated the self-biases in the foreign language contexts. Our results further elucidate the deeply rooted and automatic nature of foreign-language-driven differential emotional processing.This research has been partially funded by grants PSI2015-65689-P and SEV-2015-0490 from the Spanish Government, AThEME-613465 from the European Union, and a 2016 BBVA Foundation Grant for Researchers and Cultural Creators awarded to the last author (J.A.D.)
HST/ACS colour-magnitude diagrams of M31 globular clusters
With the aim of increasing the sample of M31 clusters for which a colour
magnitude diagram is available, we searched the HST archive for ACS images
containing objects included in the Revised Bologna Catalogue of M31 globular
clusters. Sixty-three such objects were found. We used the ACS images to
confirm or revise their classification and we obtained useful CMDs for 11 old
globular clusters and 6 luminous young clusters. We obtained simultaneous
estimates of the distance, reddening, and metallicity of old clusters by
comparing their observed field-decontaminated CMDs with a grid of template
clusters of the Milky Way. We estimated the age of the young clusters by
fitting with theoretical isochrones. For the old clusters, we found
metallicities in the range -0.4<=[Fe/H]<=-1.9, that generally agree with
existing spectroscopic extimates. At least four of them display a clear blue
HB, indicating ages >10 Gyr. All six candidate young clusters are found to have
ages <1Gyr. With the present work the total number of M31 GCs with reliable
optical CMD increases from 35 to 44 for the old clusters, and from 7 to 11 for
the young ones. The old clusters show similar characteristics to those of the
MW. We discuss the case of the cluster B407, with a metallicity [Fe/H] ~-0.6
and located at a large projected distance from the centre of M31 and from the
galaxy major axis. Metal-rich globulars at large galactocentric distances are
rare both in M31 and in the MW. B407, in addition, has a velocity in stark
contrast with the rotation pattern shared by the bulk of M31 clusters of
similar metallicity. This, along with other empirical evidence, supports the
hypothesis that the cluster is physically associated with a substructure in the
M31 halo that has been interpreted as the relic of a merging event.Comment: 19 pages, 14 figures, 6 tables. Accepted for publication on Astronomy
and Astrophysic
The horizontal branch morphology of M31 globular clusters. Extreme second parameter effect in outer halo clusters
We use deep, high quality colour magnitude diagrams obtained with the Hubble
Space Telescope to compute a simplified version of the Mironov index [SMI;
B/(B+R)] to parametrize the horizontal branch (HB) morphology for 23 globular
clusters in the M31 galaxy (Sample-A), all located in the outer halo at
projected distances between 10 kpc and 100 kpc. This allows us to compare them
with their Galactic counterparts, for which we estimated the SMI exactly in the
same way, in the SMI vs. [Fe/H] plane. We find that the majority of the
considered M31 clusters lie in a significantly different locus, in this plane,
with respect to Galactic clusters lying at any distance from the center of the
Milky Way. In particular they have redder HB morphologies at a given
metallicity, or, in other words, clusters with the same SMI value are ~0.4 dex
more metal rich in the Milky Way than in M31. We discuss the possible origin of
this difference and we conclude that the most likely explanation is that many
globular clusters in the outer halo of M31 formed ~1-2 Gyr later than their
counterparts in the outer halo of the Milky Way, while differences in the
cluster-to-cluster distribution of He abundance of individual stars may also
play a role. The analysis of another sample of 25 bright M31 clusters (eighteen
of them with M_V<= -9.0, Sample-B), whose SMI estimates are much more uncertain
as they are computed on shallow colour magnitude diagrams, suggests that
extended blue HB tails can be relatively frequent among the most massive M31
globular clusters, possibly hinting at the presence of multiple populations.Comment: 13 pages, pdflatex, 7 figures (9 jpg files). Accepted for publication
in Astronomy & Astrophysic
Bacteroides fragilis requires the ferrous-iron transporter FeoAB and the CobN-like proteins BtuS1 and BtuS2 for assimilation of iron released from heme
The intestinal commensal and opportunistic anaerobic pathogen Bacteroides fragilis has an essential requirement for both heme and free iron to support growth in extraintestinal infections. In the absence of free iron, B. fragilis can utilize heme as the sole source of iron. However, the mechanisms to remove iron from heme are not completely understood. In this study, we show that the inner membrane ferrous iron
transporter ∆feoAB mutant strain is no longer able to grow with heme as the sole source of iron. Genetic complementation with the feoAB gene operon completely restored growth. Our data indicate that iron is removed from heme in the periplasmic space, and the released iron is transported by the FeoAB system. Interestingly, when B. fragilis utilizes iron from heme, it releases heme-derived porphyrins by a dechelatase activity which is upregulated under low iron conditions. This is supported by the findings showing that formation of heme-derived porphyrins in the ∆feoAB mutant and the parent strain increased 30-fold and fivefold (respectively) under low iron conditions compared to iron replete conditions. Moreover, the btuS1 btuS2 doublemutant strain (lacking the predicted periplasmic, membrane anchored CobN-like proteins) also showed growth defect with heme as the sole source of iron, suggesting that BtuS1 and BtuS2 are involved in heme-iron assimilation. Though the dechelatase mechanism remains uncharacterized, assays performed in bacterial crude extracts show that BtuS1 and BtuS2 affect the regulation of the dechelatase-specific activities in an iron-dependent manner. These findings suggest that the mechanism to extract iron from heme in Bacteroides requires a group of proteins, which spans the
periplasmic space to make iron available for cellular functions
Barriers to sustainable consumption attenuated by foreign language use
The adoption of certain innovative products, such as recycled water, artificial meat and insect-based food, could help promote sustainability. However, the disgust these products elicit acts as a barrier to their consumption. Here, we show that describing such products in a foreign language attenuates the disgust these products trigger and heightens their intended as well as actual consumption
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