18,612 research outputs found
Growth patterns and scaling laws governing AIDS epidemic in Brazilian cities
Brazil holds approximately 1/3 of population living infected with AIDS
(acquired immunodeficiency syndrome) in Central and South Americas, and it was
also the first developing country to implement a large-scale control and
intervention program against AIDS epidemic. In this scenario, we investigate
the temporal evolution and current status of the AIDS epidemic in Brazil.
Specifically, we analyze records of annual absolute frequency of cases for more
than 5000 cities for the first 33 years of the infection in Brazil. We found
that (i) the annual absolute frequencies exhibit a logistic-type growth with an
exponential regime in the first few years of the AIDS spreading; (ii) the
actual reproduction number decaying as a power law; (iii) the distribution of
the annual absolute frequencies among cities decays with a power law behavior;
(iv) the annual absolute frequencies and the number of inhabitants have an
allometric relationship; (v) the temporal evolution of the annual absolute
frequencies have different profile depending on the average annual absolute
frequencies in the cities. These findings yield a general quantitative
description of the AIDS infection dynamics in Brazil since the beginning. They
also provide clues about the effectiveness of treatment and control programs
against the infection, that has had a different impact depending on the number
of inhabitants of cities. In this framework, our results give insights into the
overall dynamics of AIDS epidemic, which may contribute to select empirically
accurate models.Comment: 12 pages, 6 figure
An ALMA study of the Orion Integral Filament : I. Evidence for narrow fibers in a massive cloud
© 2018 ESO. Reproduced with permission from Astronomy & Astrophysics. Content in the UH Research Archive is made available for personal research, educational, and non-commercial purposes only. Unless otherwise stated, all content is protected by copyright, and in the absence of an open license, permissions for further re-use should be sought from the publisher, the author, or other copyright holder.Aim. We have investigated the gas organization within the paradigmatic Integral Shape Filament (ISF) in Orion in order to decipher whether or not all filaments are bundles of fibers. Methods. We combined two new ALMA Cycle 3 mosaics with previous IRAM 30m observations to produce a high-dynamic range N 2H + (1-0) emission map of the ISF tracing its high-density material and velocity structure down to scales of 0.009 pc (or ~2000 AU). Results. From the analysis of the gas kinematics, we identify a total of 55 dense fibers in the central region of the ISF. Independently of their location in the cloud, these fibers are characterized by transonic internal motions, lengths of ~0.15 pc, and masses per unit length close to those expected in hydrostatic equilibrium. The ISF fibers are spatially organized forming a dense bundle with multiple hub-like associations likely shaped by the local gravitational potential. Within this complex network, the ISF fibers show a compact radial emission profile with a median FWHM of 0.035 pc systematically narrower than the previously proposed universal 0.1 pc filament width. Conclusions. Our ALMA observations reveal complex bundles of fibers in the ISF, suggesting strong similarities between the internal substructure of this massive filament and previously studied lower-mass objects. The fibers show identical dynamic properties in both low- and high-mass regions, and their widespread detection in nearby clouds suggests a preferred organizational mechanism of gas in which the physical fiber dimensions (width and length) are self-regulated depending on their intrinsic gas density. Combining these results with previous works in Musca, Taurus, and Perseus, we identify a systematic increase of the surface density of fibers as a function of the total mass per-unit-length in filamentary clouds. Based on this empirical correlation, we propose a unified star-formation scenario where the observed differences between low- and high-mass clouds, and the origin of clusters, emerge naturally from the initial concentration of fibers.Peer reviewedFinal Published versio
A dense micro-cluster of Class 0 protostars in NGC 2264 D-MM1
We present sensitive and high angular resolution (~1") 1.3 mm continuum
observations of the dusty core D-MM1 in the Spokes cluster in NGC 2264 using
the Submillimeter Array. A dense micro-cluster of seven Class 0 sources was
detected in a 20" x 20" region with masses between 0.4 to 1.2 solar masses and
deconvolved sizes of about 600 AU. We interpret the 1.3 mm emission as arising
from the envelopes of the Class 0 protostellar sources. The mean separation of
the 11 known sources (SMA Class 0 and previously known infrared sources) within
D-MM1 is considerably smaller than the characteristic spacing between sources
in the larger Spokes cluster and is consistent with hierarchical thermal
fragmentation of the dense molecular gas in this region.Comment: Accepted for publication in the Astrophysical Journal Letter
Linear Invariant Systems Theory for Signal Enhancement
This paper discusses a linear time invariant (LTI) systems approach to signal enhancement via projective subspace techniques. It provides closed form expressions for the frequency response of data adaptive finite impulse response eigenfilters. An illustrative example using speech enhancement is also presented.Este artigo apresenta a aplicação da teoria de sistemas lineares invariantes no tempo (LTI) na anĂĄlise de tĂ©cnicas de sub-espaço. A resposta em frequĂȘncia dos filtros resultantes da decomposição em valores singulares Ă© obtida aplicando as propriedades dos sistemas LTI
Crafting a Systematic Literature Review on Open-Source Platforms
This working paper unveils the crafting of a systematic literature review on
open-source platforms. The high-competitive mobile devices market, where
several players such as Apple, Google, Nokia and Microsoft run a platforms- war
with constant shifts in their technological strategies, is gaining increasing
attention from scholars. It matters, then, to review previous literature on
past platforms-wars, such as the ones from the PC and game-console industries,
and assess its implications to the current mobile devices platforms-war. The
paper starts by justifying the purpose and rationale behind this literature
review on open-source platforms. The concepts of open-source software and
computer-based platforms were then discussed both individually and in unison,
in order to clarify the core-concept of 'open-source platform' that guides this
literature review. The detailed design of the employed methodological strategy
is then presented as the central part of this paper. The paper concludes with
preliminary findings organizing previous literature on open-source platforms
for the purpose of guiding future research in this area.Comment: As presented in 10th IFIP WG 2.13 International Conference on Open
Source Systems, OSS 2014, San Jos\'e, Costa Rica, May 6-9, 201
Atomic jet from SMM1 (FIRS1) in Serpens uncovers non-coeval binary companion
We report on the detection of an atomic jet associated with the protostellar
source SMM1 (FIRS1) in Serpens. The jet is revealed in [FeII] and [NeII] line
maps observed with Spitzer/IRS, and further confirmed in HiRes IRAC and MIPS
images. It is traced very close to SMM1 and peaks at ~5 arcsec" from the source
at a position angle of $\sim 125 degrees. In contrast, molecular hydrogen
emission becomes prominent at distances > 5" from the protostar and extends at
a position angle of 160 degrees. The morphological differences suggest that the
atomic emission arises from a companion source, lying in the foreground of the
envelope surrounding the embedded protostar SMM1. In addition the molecular and
atomic Spitzer maps disentangle the large scale CO (3-2) emission observed in
the region into two distinct bipolar outflows, giving further support to a
proto-binary source setup. Analysis at the peaks of the [FeII] jet show that
emission arises from warm and dense gas (T ~1000 K, n(electron) 10^5 - 10^6
cm^-3). The mass flux of the jet derived independently for the [FeII] and
[NeII] lines is 10^7 M(sun)/yr, pointing to a more evolved Class~I/II protostar
as the driving source. All existing evidence converge to the conclusion that
SMM1 is a non-coeval proto-binary source.Comment: 10 pages, 7 figures, 1 table. Accepted for publication in Astronomy
\& Astrophysic
Multiplicação de sequóia (Sequoia sempervirens L.) em meio de cultura esterelizado com hipoclorito de sódio.
O objetivo desta pesquisa foi comparar a eficiĂȘncia deste protocolo com o protocolo convencional, que utiliza a autoclavagem como mĂ©todo de esterilização, bem como analisar o comportamento de plantas de sequĂłia em meio de cultura esterilizado com hipoclorito de sĂłdio.Suplemento. Edição dos Resumos do XVI Congresso Brasileiro de Floricultura e Plantas Ornamentais; III Congresso Brasileiro de Cultura de Tecidos e Plantas; I SimpĂłsio de Plantas Ornamentais Nativas, GoiĂąnia, set. 2007
Causal Anomalies in Kaluza-Klein Gravity Theories
Causal anomalies in two Kaluza-Klein gravity theories are examined,
particularly as to whether these theories permit solutions in which the
causality principle is violated. It is found that similarly to general
relativity the field equations of the space-time-mass Kaluza-Klein (STM-KK)
gravity theory do not exclude violation of causality of G\"odel type, whereas
the induced matter Kaluza-Klein (IM-KK) gravity rules out noncausal
G\"odel-type models. The induced matter version of general relativity is shown
to be an efficient therapy for causal anomalies that occurs in a wide class of
noncausal geometries. Perfect fluid and dust G\"odel-type solutions of the
STM-KK field equations are studied. It is shown that every G\"odel-type perfect
fluid solution is isometric to the unique dust solution of the STM-KK field
equations. The question as to whether 5-D G\"odel-type non-causal geometries
induce any physically acceptable 4-D energy-momentum tensor is also addressed.Comment: 16 page. LaTex file. To appear in Int. J. Mod. Phys. A (1998
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