1,196 research outputs found
Static and dynamic measures of human brain connectivity predict complementary aspects of human cognitive performance
In cognitive network neuroscience, the connectivity and community structure
of the brain network is related to cognition. Much of this research has focused
on two measures of connectivity - modularity and flexibility - which frequently
have been examined in isolation. By using resting state fMRI data from 52 young
adults, we investigate the relationship between modularity, flexibility and
performance on cognitive tasks. We show that flexibility and modularity are
highly negatively correlated. However, we also demonstrate that flexibility and
modularity make unique contributions to explain task performance, with
modularity predicting performance for simple tasks and flexibility predicting
performance on complex tasks that require cognitive control and executive
functioning. The theory and results presented here allow for stronger links
between measures of brain network connectivity and cognitive processes.Comment: 37 pages; 7 figure
Brain Modularity Mediates the Relation between Task Complexity and Performance
Recent work in cognitive neuroscience has focused on analyzing the brain as a
network, rather than as a collection of independent regions. Prior studies
taking this approach have found that individual differences in the degree of
modularity of the brain network relate to performance on cognitive tasks.
However, inconsistent results concerning the direction of this relationship
have been obtained, with some tasks showing better performance as modularity
increases and other tasks showing worse performance. A recent theoretical model
(Chen & Deem, 2015) suggests that these inconsistencies may be explained on the
grounds that high-modularity networks favor performance on simple tasks whereas
low-modularity networks favor performance on more complex tasks. The current
study tests these predictions by relating modularity from resting-state fMRI to
performance on a set of simple and complex behavioral tasks. Complex and simple
tasks were defined on the basis of whether they did or did not draw on
executive attention. Consistent with predictions, we found a negative
correlation between individuals' modularity and their performance on a
composite measure combining scores from the complex tasks but a positive
correlation with performance on a composite measure combining scores from the
simple tasks. These results and theory presented here provide a framework for
linking measures of whole brain organization from network neuroscience to
cognitive processing.Comment: 47 pages; 4 figure
A SUSY SU(5)xT' Unified Model of Flavour with large \theta_{13}
We present a SUSY SU(5)xT' unified flavour model with type I see-saw
mechanism of neutrino mass generation, which predicts the reactor neutrino
angle to be \theta_{13} = 0.14 close to the recent results from the Daya Bay
and RENO experiments. The model predicts also values of the solar and
atmospheric neutrino mixing angles, which are compatible with the existing
data. The T' breaking leads to tri-bimaximal mixing in the neutrino sector,
which is perturbed by sizeable corrections from the charged lepton sector. The
model exhibits geometrical CP violation, where all complex phases have their
origin from the complex Clebsch-Gordan coefficients of T'. The values of the
Dirac and Majorana CP violating phases are predicted. For the Dirac phase in
the standard parametrisation of the neutrino mixing matrix we get a value close
to 90 degrees \delta = \pi/2 - 0.45 \theta^c = 84.3 degrees, \theta^c being the
Cabibbo angle. The neutrino mass spectrum can be with normal ordering (2 cases)
or inverted ordering. In each case the values of the three light neutrino
masses are predicted with relatively small uncertainties, which allows to get
also unambiguous predictions for the neutrino-less double beta decay effective
Majorana mass.Comment: 31 pages, 7 figures; typos corrected, a few clarifying comments
added; version to be published in Phys. Rev.
Maintaining carbon stocks in extractive reserves in Brazilian Amazonia
Extractive reserves in the Amazon Forest maintain carbon stocks out of the atmosphere, thereby avoiding greenhouse-gas emissions that provoke global warming. This and other environmental services, such as recycling water and maintaining biodiversity, provide major reasons for creating these reserves and for according them priority in government programs. The importance of reducing carbon emissions from deforestation has been the principal motivation for international funding, which has been key to creating and supporting extractive reserves, notably in the cases of Germany through the PPG7 program and Norway through the Amazon Fund. Estimating the amount of carbon in these reserves and the losses that have occurred from deforestation is essential as an input to making decisions that affect current and potential future extractive reserves. By 2014, there were 47 federal extractive reserves in Brazil’s Legal Amazonia region, of which 45 were in the Amazonian Tropical Forest Biome and 26 extractive reserves belonged to states, all of which were in the Amazonia Biome. This study provides data for each of the 73 extractive reserves in Legal Amazonia, based on biomass information by forest type calculated from RadamBrasil survey data, and deforestation from PRODES monitoring by LANDSAT or equivalent satellites (30-m resolution). The stocks represent carbon in the “pre-modern” biomass, that is, the biomass present in approximately 1970, or before substantial deforestation or logging activity in the region. The carbon losses reflect only deforestation, not degradation of forest by logging and/or fire. The total area of extractive reserves in Legal Amazonia amounted to 126,709 km2, of which 4301 km2 (3.4%) had been cleared by 2014. Those extractive reserves had a remaining carbon stock in forest vegetation (above and below-ground) of 2.1 billion tons. The carbon lost to deforestation totaled 74.9 million tons. Avoiding further carbon loss to both deforestation and degradation needs to be a high priority for the extractivists, as it is the value of the forest’s environmental services that has the greatest potential for providing a means of support that is increasing in value and is inherently sustainable
Generalised Geometrical CP Violation in a T\u27 Lepton Flavour Model
We analyse the interplay of generalised CP transformations and the non-Abelian discrete group T ′ and use the semi-direct product G f = T ′ ⋊ H CP , as family symmetry acting in the lepton sector. The family symmetry is shown to be spontaneously broken in a geometrical manner. In the resulting flavour model, naturally small Majorana neutrino masses for the light active neutrinos are obtained through the type I see-saw mechanism. The known masses of the charged leptons, lepton mixing angles and the two neutrino mass squared differences are reproduced by the model with a good accuracy. The model allows for two neutrino mass spectra with normal ordering (NO) and one with inverted ordering (IO). For each of the three spectra the absolute scale of neutrino masses is predicted with relatively small uncertainty. The value of the Dirac CP violation (CPV) phase δ in the lepton mixing matrix is predicted to be δ = π/ 2 or 3 π/ 2. Thus, the CP violating effects in neutrino oscillations are predicted to be maximal (given the values of the neutrino mixing angles) and experimentally observable. We present also predictions for the sum of the neutrino masses, for the Majorana CPV phases and for the effective Majorana mass in neutrinoless double beta decay. The predictions of the model can be tested in a variety of ongoing and future planned neutrino experiments
Spectral Evolution and Radial Dust Transport in the Prototype Young Eruptive System EX Lup
EX Lup is the prototype of a class of pre-main sequence eruptive stars
defined by their repetitive outbursts lasting several months. In 2008
January-September EX Lup underwent its historically largest outburst,
brightening by about 4 magnitudes in visual light. In previous studies we
discovered on-going silicate crystal formation in the inner disk during the
outburst, but also noticed that the measured crystallinity fraction started
decreasing after the source returned to the quiescent phase. Here we present
new observations of the 10 m silicate feature, obtained with the MIDI and
VISIR instruments at Paranal Observatory. The observations demonstrate that
within five years practically all crystalline forsterite disappeared from the
surface of the inner disk. We reconstruct this process by presenting a series
of parametric axisymmetric radiative transfer models of an expanding dust cloud
that transports the crystals from the terrestrial zone to outer disk regions
where comets are supposed to form. Possibly the early Sun also experienced
similar flare-ups, and the forming planetesimals might have incorporated
crystalline silicate material produced by such outbursts. Finally, we discuss
how far the location of the dust cloud could be constrained by future JWST
observations.Comment: 12 pages, 4 figures, accepted for publication in Ap
Enabling Aqueous Processing of Ni‐Rich Layered Oxide Cathode Materials by Addition of Lithium Sulfate
Aqueous processing of Ni-rich layered oxide cathode materials is a promising approach to simultaneously decrease electrode manufacturing costs, while bringing environmental benefits by substituting the state-of-the-art (often toxic and costly) organic processing solvents. However, an aqueous environment remains challenging due to the high reactivity of Ni-rich layered oxides towards moisture, leading to lithium leaching and Al current collector corrosion because of the resulting high pH value of the aqueous electrode paste. Herein, a facile method was developed to enable aqueous processing of LiNi0.8Co0.1Mn0.1O2 (NCM811) by the addition of lithium sulfate (Li2SO4) during electrode paste dispersion. The aqueously processed electrodes retained 80 % of their initial capacity after 400 cycles in NCM811||graphite full cells, while electrodes processed without the addition of Li2SO4 reached 80 % of their capacity after only 200 cycles. Furthermore, with regard to electrochemical performance, aqueously processed electrodes using carbon-coated Al current collector outperformed reference electrodes based on state-of-the-art production processes involving N-methyl-2-pyrrolidone as processing solvent and fluorinated binders. The positive impact on cycle life by the addition of Li2SO4 stemmed from a formed sulfate coating as well as different surface species, protecting the NCM811 surface against degradation. Results reported herein open a new avenue for the processing of Ni-rich NCM electrodes using more sustainable aqueous routes.European Union
http://dx.doi.org/10.13039/501100000780European Union's Horizon 2020 research and innovation programPeer Reviewe
Search-Based Evolution of XML Schemas
The use of schemas makes an XML-based application more reliable, since they contribute to avoid failures by defining the specific format for the data that the application manipulates. In practice, when an application evolves, new requirements for the data may be established, raising the need of schema evolution. In some cases the generation of a schema is necessary, if such schema does not exist. To reduce maintenance and reengineering costs, automatic evolution of schemas is very desirable. However, there are no algorithms to satisfactorily solve the problem. To help in this task, this paper introduces a search-based approach that explores the correspondence between schemas and context-free grammars. The approach is supported by a tool, named EXS. Our tool implements algorithms of grammatical inference based on LL(1) Parsing. If a grammar (that corresponds to a schema) is given and a new word (XML document) is provided, the EXS system infers the new grammar that: i) continues to generate the same words as before and ii) generates the new word, by modifying the original grammar. If no initial grammar is available, EXS is also capable of generating a grammar from scratch from a set of samples
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