130 research outputs found
Self-organized evolution in socio-economic environments
We propose a general scenario to analyze social and economic changes in
modern environments. We illustrate the ideas with a model that incorporating
the main trends is simple enough to extract analytical results and, at the same
time, sufficiently complex to display a rich dynamic behavior. Our study shows
that there exists a macroscopic observable that is maximized in a regime where
the system is critical, in the sense that the distribution of events follow
power-laws. Computer simulations show that, in addition, the system always
self-organizes to achieve the optimal performance in the stationary state.Comment: 4 pages RevTeX; needs epsf.sty and rotate.sty; submitted to Phys Rev
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An atlas of line profile studies for SU UMa type cataclysmic variables
We present H-alpha line-profile analyses for the seven SU UMa type dwarf
novae AK Cnc, WX Cet, AQ Eri, VW Hyi, RZ Leo, TU Men, and HS Vir. All data sets
are treated in the same manner, applying a sequence of techniques for each
system. The basic ingredients of this sequence are the diagnostic diagram to
determine the zero point of the orbital phase, and Doppler tomography to
visualise the emission distribution. We furthermore introduce a new qualitative
way of to evaluate the Doppler fit, by comparing the line profile of the
reconstructed with the original spectrum in the form of the V/R plot. We
present the results of the analysis in the compact form of an atlas, allowing a
direct comparison of the emission distribution in our targets. Although most of
the data sets were not taken with the intention of a line-profile analysis, we
obtain significant results and are able to indicate the type of the additional
emission in these systems. Our objects should have in principle very similar
physical properties, i.e. they cover only a small range in orbital periods,
mass ratios, and mass-transfer rates. Nevertheless, we find a large variety of
phenomena both with respect to the individual systems and also within
individual data sets of the same object. This includes `canonical' additional
emission components from the secondary star and the bright spot, but also
emission from the leading side of the accretion disc.Comment: 20 pages, 25 figures, accepted for publication in A&A, figures have
been diminished in size and qualit
Draft Genome Sequence of a Multi-Metal Resistant Bacterium Pseudomonas putida ATH-43 Isolated from Greenwich Island, Antarctica
IndexaciĂłn: Web of Science; Scopus.In this report we present the first draft genome sequence of a P. putida strain isolated from the Antarctic continent. The shotgun sequencing strategy, assembly, and subsequent annotation showed that the ATH-43 strain possesses a wide spectrum of genetic determinants involved in heavy metal and antibiotic resistance, apparently to cope with extreme oxidative stress conditions. P. putida ATH-43 genome now forms part of the 65 genomes of this species registered at the NCBI database (September, 2016) and it is highly related with the endophytic strain P. putida W619, which is also resistant to several heavy metals. Further characterization of multi-metal resistant psychrotrophic bacteria such as P. putida ATH-43 will be promising to develop novel strategies for heavy metal bioremediation in low temperature environments. All genome data has been submitted to NCBI.http://journal.frontiersin.org/article/10.3389/fmicb.2016.01777/ful
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Synchronization in complex networks
Synchronization processes in populations of locally interacting elements are in the focus of intense research in physical, biological, chemical, technological and social systems. The many efforts devoted to understand synchronization phenomena in natural systems take now advantage of the recent theory of complex networks. In this review, we report the advances in the comprehension of synchronization phenomena when oscillating elements are constrained to interact in a complex network topology. We also overview the new emergent features coming out from the interplay between the structure and the function of the underlying pattern of connections. Extensive numerical work as well as analytical approaches to the problem are presented. Finally, we review several applications of synchronization in complex networks to different disciplines: biological systems and neuroscience, engineering and computer science, and economy and social sciences
The remarkable properties of the symbiotic star AE Circinus
We present new optical spectroscopy and photometry, 2MASS infrared
observations and 24 years of combined AAVSO and AFOEV photometry of the
symbiotic star candidate \ae. The long-term light curve is characterized by
outbursts lasting several years and having a slow decline of mag/day. The whole range of variability of the star in the band is
about 4 magnitudes. The periodogram of the photometric data reveals strong
signals at 342 and 171 days. The presence of the emission feature at
6830 \AA at minimum and the detection of absorption lines of a
K5 type star confirm the symbiotic classification and suggest that AE Cir is a
new member of the small group of s-type yellow symbiotic stars. We estimate a
distance of 9.4 kpc. Our spectrum taken at the high state shows a much flatter
spectral energy distribution, the disappearance of the 6830 \AA
emission feature and the weakness of the He II 4686 emission relative to the
Balmer emission lines. Our observations indicate the presence of emission line
flickering in time scales of minutes in 2001. The peculiar character of \ae is
revealed in the visibility of the secondary star at the high and low state, the
light curve resembling a dwarf nova superoutburst and the relatively short low
states. The data are hard to reconciliate with standard models for symbiotic
star outbursts.Comment: accepted for publication in MNRAS, 7 figure
Network metaâanalysis of postâexposure prophylaxis randomized clinical trials
Objectives: We performed a network metaâanalysis of PEP randomized clinical trials to evaluate the best regimen. /
Methods: After MEDLINE/Pubmed search, studies were included if: (1) were randomized, (2) comparing at least 2 PEP threeâdrug regimens and, (3) reported completion rates or discontinuation at 28 days. Five studies with 1105 PEP initiations were included and compared ritonavirâboosted lopinavir (LPV/r) vs. atazanavir (ATV) (one study), cobicistatâboosted elvitegravir (EVG/c) (one study), raltegravir (RAL) (one study) or maraviroc (MVC) (two studies). We estimated the probability of each treatment of being the best based on the evaluation of five outcomes: PEP nonâcompletion at day 28, PEP discontinuation due to adverse events, PEP switching due to any cause, lost to followâup and adverse events. /
Results: Participants were mostly men who have sex with men (n = 832, 75%) with nonâoccupational exposure to HIV (89.86%). Fourâhundred fiftyâfour (41%) participants failed to complete their PEP course for any reason. The Odds Ratio (OR) for PEP nonâcompletion at day 28 in each antiretroviral compared to LPV/r was: ATV 0.95 (95% CI 0.58â1.56; EVG/c: OR 0.65 95% CI 0.30â1.37; RAL: OR 0.68 95% CI 0.41â1.13; and MVC: OR 0.69 95% CI 0.47â1.01. In addition, the rankogram showed that EVG/c had the highest probability of being the best treatment for the lowest rates in PEP nonâcompletion at day 28, switching, lost to followâup or adverse events and MVC for PEP discontinuations due to adverse events. /
Conclusions: Our study shows the advantages of integrase inhibitors when used as PEP, particularly EVG as a SingleâTablet Regimen
A 6.3-h superhump in the cataclysmic variable TV Columbae: the longest yet seen
We present results from a two week multi-longitude photometric campaign on TV
Col held in 2001 January. The data confirm the presence of a permanent positive
superhump found in re-examination of extensive archive photometric data of TV
Col. The 6.3-h period is 15 per cent longer than the orbital period and obeys
the well known relation between superhump period excess and binary period. At
5.5-h, TV Col has an orbital period longer than any known superhumping
cataclysmic variable and, therefore, a mass ratio which might be outside the
range at which superhumps can occur according to the current theory. We suggest
several solutions for this problem.Comment: 8 pages, 1 Latex file, 7 eps figures, MNRAS, accepte
DNA Barcoding Bromeliaceae: Achievements and Pitfalls
<div><h3>Background</h3><p>DNA barcoding has been successfully established in animals as a tool for organismal identification and taxonomic clarification. Slower nucleotide substitution rates in plant genomes have made the selection of a DNA barcode for land plants a much more difficult task. The Plant Working Group of the Consortium for the Barcode of Life (CBOL) recommended the two-marker combination <em>rbcL</em>/<em>matK</em> as a pragmatic solution to a complex trade-off between universality, sequence quality, discrimination, and cost.</p> <h3>Methodology/Principal Findings</h3><p>It is expected that a system based on any one, or a small number of plastid genes will fail within certain taxonomic groups with low amounts of plastid variation, while performing well in others. We tested the effectiveness of the proposed CBOL Plant Working Group barcoding <em>markers</em> for land plants in identifying 46 bromeliad species, a group rich in endemic species from the endangered Brazilian Atlantic Rainforest. Although we obtained high quality sequences with the suggested primers, species discrimination in our data set was only 43.48%. Addition of a third marker, <em>trnHâpsbA</em>, did not show significant improvement. This species identification failure in Bromeliaceaecould also be seen in the analysis of the GenBank's <em>matK</em> data set. Bromeliaceae's sequence divergence was almost three times lower than the observed for Asteraceae and Orchidaceae. This low variation rate also resulted in poorly resolved tree topologies. Among the three Bromeliaceae subfamilies sampled, Tillandsioideae was the only one recovered as a monophyletic group with high bootstrap value (98.6%). Species paraphyly was a common feature in our sampling.</p> <h3>Conclusions/Significance</h3><p>Our results show that although DNA barcoding is an important tool for biodiversity assessment, it tends to fail in taxonomy complicated and recently diverged plant groups, such as Bromeliaceae. Additional research might be needed to develop markers capable to discriminate species in these complex botanical groups.</p> </div
Understanding different dominance patterns in western Amazonian forests
Dominance of neotropical tree communities by a few species is widely documented, but dominant trees show a variety of distributional patterns still poorly understood. Here, we used 503 forest inventory plots (93,719 individuals â„2.5âcm diameter, 2609 species) to explore the relationships between local abundance, regional frequency and spatial aggregation of dominant species in four main habitat types in western Amazonia. Although the abundance-occupancy relationship is positive for the full dataset, we found that among dominant Amazonian tree species, there is a strong negative relationship between local abundance and regional frequency and/or spatial aggregation across habitat types. Our findings suggest an ecological trade-off whereby dominant species can be locally abundant (local dominants) or regionally widespread (widespread dominants), but rarely both (oligarchs). Given the importance of dominant species as drivers of diversity and ecosystem functioning, unravelling different dominance patterns is a research priority to direct conservation efforts in Amazonian forests.Publisher PDFPeer reviewe
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