8,197 research outputs found
Analysis of the Very Inner Milky Way Dark Matter Distribution and Gamma-Ray Signals
We analyze the possibility that the HESS gamma-ray source at the Galactic
Center could be explained as the secondary flux produced by annihilation of TeV
Dark Matter (TeVDM) particles with locally enhanced density, in a region
spatially compatible with the HESS observations themselves. We study the inner
100 pc considering (i) the extrapolation of several density profiles from
state-of-the-art N-body + Hydrodynamics simulations of Milky Way-like galaxies,
(ii) the DM spike induced by the black hole, and (iii) the DM particles
scattering off by bulge stars. We show that in some cases the DM spike may
provide the enhancement in the flux required to explain the cut-off in the HESS
J1745-290 gamma-ray spectra as TeVDM. In other cases, it may helps to describe
the spatial tail reported by HESS II at angular scales < 0.54 degrees towards
Sgr A.Comment: 6 pages, 3 figures, 1 table. Accepted for publication in Physical
Review D - Rapid Communication
Anisotropic superconducting properties of aligned MgB2 crystallites
Samples of aligned MgB2 crystallites have been prepared, allowing for the
first time the direct identification of an upper critical field anisotropy
Hc2^{ab}/Hc2^{c}= xi_{ab}/xi_{c} ~ 1.73; with xi_{o,ab} ~ 70 A, xi_{o,c} ~ 40
A, and a mass anisotropy ratio m_{ab}/m_{c} ~ 0.3. A ferromagnetic background
signal was identified, possibly related to the raw materials purity.Comment: 4 pages, 4 figures; Revised version to appear in Phys. Rev. Let
Business and Information Technology Alignment Measurement -- a recent Literature Review
Since technology has been involved in the business context, Business and
Information Technology Alignment (BITA) has been one of the main concerns of IT
and Business executives and directors due to its importance to overall company
performance, especially today in the age of digital transformation. Several
models and frameworks have been developed for BITA implementation and for
measuring their level of success, each one with a different approach to this
desired state. The BITA measurement is one of the main decision-making tools in
the strategic domain of companies. In general, the classical-internal alignment
is the most measured domain and the external environment evolution alignment is
the least measured. This literature review aims to characterize and analyze
current research on BITA measurement with a comprehensive view of the works
published over the last 15 years to identify potential gaps and future areas of
research in the field.Comment: 12 pages, Preprint version, BIS 2018 International Workshops, Berlin,
Germany, July 18 to 20, 2018, Revised Paper
Irreversible magnetization under rotating fields and lock-in effect on ErBa_2Cu_3O_7 single crystal with columnar defects
We have measured the irreversible magnetization M_i of an ErBa_2Cu_3O_7
single crystal with columnar defects (CD), using a technique based on sample
rotation under a fixed magnetic field H. This method is valid for samples whose
magnetization vector remains perpendicular to the sample surface over a wide
angle range - which is the case for platelets and thin films - and presents
several advantages over measurements of M_L(H) loops at fixed angles. The
resulting M_i(\Theta) curves for several temperatures show a peak in the CD
direction at high fields. At lower fields, a very well defined plateau
indicative of the vortex lock-in to the CD develops. The H dependence of the
lock-in angle \phi_L follows the H^{-1} theoretical prediction, while the
temperature dependence is in agreement with entropic smearing effects
corresponding to short range vortex-defects interactions.Comment: 7 pages, 6 figures, to be published in Phys. Rev.
A model to assess customer alignment through customer experience concepts
Business and Information Technology Alignment (BITA) has been one of the main
concerns of IT and Business executives and directors due to its importance to
overall company performance, especially today in the age of digital
transformation. For BITA has been developed several models which in general has
focused in the implementation of alignment strategies for the internal
operation of the organizations and in the measurement of this internal
alignment, but, there is still a big gap in measurement models of the alignment
with the external environment of the organizations. In this paper is presented
the design and application of a maturity measurement model for BITA with the
customers, where the customers are actors of the external environment of the
companies. The proposed model involves evaluation criteria and business
practices which the companies ideally do for improve the relationship with
their customers.Comment: 12 pages, Preprint version, BIS 2019 International Workshops,
Seville, Spain, June 26 to 28, 2019, Revised Paper
BVRI Surface Photometry of Isolated Spiral Galaxies
A release of multicolor broad band (BVRI) photometry for a subsample of 44
isolated spirals drawn from the Catalogue of Isolated Galaxies (CIG) is
presented. Total magnitudes and colors at various circular apertures, as well
as some global structural/morphological parameters are estimated. Morphology is
reevaluated through optical and sharp/filtered R band images, (B-I) color index
maps, and archive near-IR JHK images from the Two-Micron Survey. The CAS
structural parameters (Concentration, Asymmetry, and Clumpiness) were
calculated from the images in each one of the bands. The fraction of galaxies
with well identified optical/near-IR bars (SB) is 63%, while a 17% more shows
evidence of weak or suspected bars (SAB). The sample average value of the
maximum bar ellipticity is 0.4. Half of the galaxies in the sample shows rings.
We identify two candidates for isolated galaxies with disturbed morphology. The
structural CAS parameters change with the observed band, and the tendencies
they follow with the morphological type and global color are more evident in
the redder bands. In any band, the major difference between our isolated
spirals and a sample of interacting spirals is revealed in the A-S plane. A
deep and uniformly observed sample of isolated galaxies is intended for various
purposes including (i) comparative studies of environmental effects, (ii)
confronting model predictions of galaxy evolution and (iii) evaluating the
change of galaxy properties with redshift.Comment: 44 pages, 9 figures and 7 tables included. To appear in The
Astronomical Journal. For the 43 appendix figures 4.1-4.43 see
http://www.astroscu.unam.mx/~avila/Figs4.1_4.43.tar.gz (7.2 Mb tar.gz file
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