14,815 research outputs found
Chemical composition of stellar populations in Omega Centauri
We derive abundances of Fe, Na, O, and s-elements from GIRAFFE@VLT spectra
for more than 200 red giant stars in the Milky Way satellite Omega Centauri.
Our preliminary results are that: (i) we confirm that Omega Centauri exibiths
large star-to-star metallicity variations ( 1.4 dex); (ii) the
metallicity distribution reveals the presence of at least five stellar
populations with different [Fe/H]; (iii) a clear Na-O anticorrelation is
clearly observed for the metal-poor and metal-intermediate populations while
apparently the anticorrelation disappears for the most metal-rich populations.
Interestingly the Na level grows with iron.Comment: 2 pages, 2 figures. To appear in the proceedings of IAU Symp. 268
"Light elements in the Universe" (C. Charbonnel, M. Tosi, F. Primas, C.
Chiappini, eds., Cambridge Univ. Press
Disobedience and Authority
This paper presents a theory of the allocation of authority in an organization in which centralization is limited by the agent's ability to disobey the principal. We show that workers are given more authority when they are costly to replace or do not mind looking for another job, even if they have no better information than the principal. The allocation of authority thus depends on external market conditions as well as the information and agency problems emphasized in the literature. Evidence from a national survey of organizations shows that worker autonomy is related to separation costs as the theory predicts.Delegation, Authority, Separation Costs, Optimal employment contracts
Detecting planets around stars in nearby galaxies
The only way to detect planets around stars at distances of several kpc is by
(photometric or astrometric) microlensing observations. In this paper, we show
that the capability of photometric microlensing extends to the detection of
signals caused by planets around stars in nearby galaxies (e.g. M31) and that
there is no other method that can achieve this. Due to the large crowding,
microlensing experiments towards M31 can only observe the high-magnification
part of a lensing light curve. Therefore, the dominating channel for
microlensing signals by planets is in distortions near the peak of
high-magnification events as discussed by Griest and Safizadeh. We calculate
the probability to detect planetary anomalies for microlensing experiments
towards M31 and find that jupiter-like planets around stars in M31 can be
detected. Though the characterization of the planet(s) involved in this signal
will be difficult, the absence of such signals can yield strong constraints on
the abundance of jupiter-like planets.Comment: 16 LaTex Pages, including 1 Postscript Figures, submitted to A&A;
title changed, one more author added, completely revised version: central
point is detecting planet in nearby galaxies and one more technique is taken
into consideratio
Contribution of Skylab multispectral imagery to the remote sensing studies of Mount Etna volcano
There are no author-identified significant results in this report
PRRT2 gene variant in a child with dysmorphic features, congenital microcephaly, and severe epileptic seizures: genotype-phenotype correlation?
BACKGROUND: Mutations in Proline-rich Transmembrane Protein 2 (PRRT2) have been primarily associated with individuals presenting with infantile epilepsy, including benign familial infantile epilepsy, benign infantile epilepsy, and benign myoclonus of early infancy, and/or with dyskinetic paroxysms such as paroxysmal kinesigenic dyskinesia, paroxysmal non-kinesigenic dyskinesia, and exercise-induced dyskinesia. However, the clinical manifestations of this disorder vary widely. PRRT2 encodes a protein expressed in the central nervous system that is mainly localized in the pre-synaptic neurons and is involved in the modulation of synaptic neurotransmitter release. The anomalous function of this gene has been proposed to cause dysregulation of neuronal excitability and cerebral disorders. CASE PRESENTATION: We hereby report on a young child followed-up for three years who presents with a spectrum of clinical manifestations such as congenital microcephaly, dysmorphic features, severe intellectual disability, and drug-resistant epileptic encephalopathy in association with a synonymous variant in PRRT2 gene (c.501C > T; p.Thr167Ile) of unknown clinical significance variant (VUS) revealed by diagnostic exome sequencing. CONCLUSION: Several hypotheses have been advanced on the specific role that PRRT2 gene mutations play to cause the clinical features of affected patients. To our knowledge, the severe phenotype seen in this case has never been reported in association with any clinically actionable variant, as the missense substitution detected in PRRT2 gene. Intriguingly, the same mutation was reported in the healthy father: the action of modifying factors in the affected child may be hypothesized. The report of similar observations could extend the spectrum of clinical manifestations linked to this mutation
EFFECTS OF A THREE WEEK SPORT SPECIFIC PLYOMETRICS TRAINING PROGRAM ON LEG PERFORMANCE OF MALE UNIVERSITY SOCCER PLAYERS
The purpose of the study was to evaluate the effects of a plyometrics program (twice weekly) of leg performance on male university soccer players. Thirteen subjects were divided into two groups. Group 1 served as a control group and participated in normal soccer training only. Group 2 served as a plyometrics training group and participated in both regular soccer training and a plyometrics training program. Pre- and post-training data was collected from subjects on a force plate performing counter-movement jumps. After three-weeks of training, both the control group and the plyometrics group showed improved velocity of center of mass (
Deamidation at Asparagine and Glutamine As a Major Modification upon Deterioration/Aging of Proteinaceous Binders in MuralPaintings
Proteomic strategies are herein proved to be a
complementary approach to the well established amino acid
composition analysis for the characterization of the aging and
deterioration phenomena occurring to proteinaceous materials
in works-of-art. Amino acid analyses on several samples demonstrated
that proteins in the frescoes from the Camposanto
Monumentale in Pisa are deteriorated as revealed by the
decrease in Met, Lys, and Tyr content and by the presence in
all the samples of amino malonic acid as a result of Ser, Phe, and
Cys oxidation. Proteomic analysis identified deamidation at Asn
and Gln as a further major event occurred. This work paves the
way to the exploitation of proteomic strategies for the investigation
of the molecular effects of aging and deterioration in
historical objects. Results show that proteomic searches for
deamidation by liquid chromatography-tandem mass spectrometry
(LC-MS/MS) could constitute a routine analysis for paintings or any artistic and historic objects where proteins are present.
Peptides that can be used as molecular markers when casein is present were identified
Four stellar populations and extreme helium variation in the massive outer-halo globular cluster NGC 2419
Recent work revealed that both the helium variation within globular clusters
(GCs) and the relative numbers of first and second-generation stars (1G, 2G)
depend on the mass of the host cluster. Precise determination of the internal
helium variations and of the fraction of 1G stars are crucial constraints to
the formation scenarios of multiple populations (MPs). We exploit multi-band
Hubble Space Telescope photometry to investigate MPs in NGC 2419, which is one
of the most-massive and distant GCs of the Galaxy, almost isolated from its
tidal influence. We find that the 1G hosts the ~37% of the analyzed stars, and
identified three populations of 2G stars, namely 2GA, 2GB, and 2GC, which
comprise the ~20%, ~31% and ~12% of stars, respectively. We compare the
observed colors of these four populations with the colors derived from
appropriate synthetic spectra to infer the relative helium abundances. We find
that 2GA, 2GB, and 2GC stars are enhanced in helium mass fraction by deltaY
~0.01, 0.06, and 0.19 with respectto 1G stars that have primordial helium
(Y=0.246). The high He enrichment of 2GC stars is hardly reconcilable with most
of the current scenarios for MPs. Furthermore, the relatively larger fraction
of 1G stars (~37%) compared to other massive GCs is noticeable. By exploiting
literature results, we find that the fractions of 1G stars of GCs with large
perigalactic distance are typically higher than in the other GCs with similar
masses. This suggests that NGC 2419, similarly to other distant GCs, lost a
lower fraction of 1G stars.Comment: 10 pages, 8 figures, submitted to MNRAS January 22n
- …