542 research outputs found
Mode II fracture energy in the adhesive bonding of dissimilar substrates: carbon fibre composite to aluminium joints
The end-notched flexure (ENF) test calculates the value of mode II fracture energy in adhesive
bonding between the substrates of same nature. Traditional methods of calculating
fracture energy in the ENF test are not suitable in cases where the thickness of the adhesive
is non-negligible compared with adherent thicknesses. To address this issue, a specific
methodology for calculating mode II fracture energy has been proposed in this paper. To
illustrate the applicability of the proposed method, the fracture energy was calculated by
the ENF test for adhesive bonds between aluminium and a composite material, which considered
two different types of adhesive (epoxy and polyurethane) and various surface treatments.
The proposed calculation model provides higher values of fracture energy than
those obtained from the simplified models that consider the adhesive thickness to be zero,
supporting the conclusion that the calculation of mode II fracture energy for adhesives with
non-negligible thickness relative to their adherents should be based on mathematical models,
such as the method proposed in this paper, that incorporate the influence of this thickness
Mesoscopic structure conditions the emergence of cooperation on social networks
We study the evolutionary Prisoner's Dilemma on two social networks obtained
from actual relational data. We find very different cooperation levels on each
of them that can not be easily understood in terms of global statistical
properties of both networks. We claim that the result can be understood at the
mesoscopic scale, by studying the community structure of the networks. We
explain the dependence of the cooperation level on the temptation parameter in
terms of the internal structure of the communities and their interconnections.
We then test our results on community-structured, specifically designed
artificial networks, finding perfect agreement with the observations in the
real networks. Our results support the conclusion that studies of evolutionary
games on model networks and their interpretation in terms of global properties
may not be sufficient to study specific, real social systems. In addition, the
community perspective may be helpful to interpret the origin and behavior of
existing networks as well as to design structures that show resilient
cooperative behavior.Comment: Largely improved version, includes an artificial network model that
fully confirms the explanation of the results in terms of inter- and
intra-community structur
Mesoscopic organization reveals the constraints governing C. elegans nervous system
One of the biggest challenges in biology is to understand how activity at the
cellular level of neurons, as a result of their mutual interactions, leads to
the observed behavior of an organism responding to a variety of environmental
stimuli. Investigating the intermediate or mesoscopic level of organization in
the nervous system is a vital step towards understanding how the integration of
micro-level dynamics results in macro-level functioning. In this paper, we have
considered the somatic nervous system of the nematode Caenorhabditis elegans,
for which the entire neuronal connectivity diagram is known. We focus on the
organization of the system into modules, i.e., neuronal groups having
relatively higher connection density compared to that of the overall network.
We show that this mesoscopic feature cannot be explained exclusively in terms
of considerations, such as optimizing for resource constraints (viz., total
wiring cost) and communication efficiency (i.e., network path length).
Comparison with other complex networks designed for efficient transport (of
signals or resources) implies that neuronal networks form a distinct class.
This suggests that the principal function of the network, viz., processing of
sensory information resulting in appropriate motor response, may be playing a
vital role in determining the connection topology. Using modular spectral
analysis, we make explicit the intimate relation between function and structure
in the nervous system. This is further brought out by identifying functionally
critical neurons purely on the basis of patterns of intra- and inter-modular
connections. Our study reveals how the design of the nervous system reflects
several constraints, including its key functional role as a processor of
information.Comment: Published version, Minor modifications, 16 pages, 9 figure
Wisdom of groups promotes cooperation in evolutionary social dilemmas
Whether or not to change strategy depends not only on the personal success of
each individual, but also on the success of others. Using this as motivation,
we study the evolution of cooperation in games that describe social dilemmas,
where the propensity to adopt a different strategy depends both on individual
fitness as well as on the strategies of neighbors. Regardless of whether the
evolutionary process is governed by pairwise or group interactions, we show
that plugging into the "wisdom of groups" strongly promotes cooperative
behavior. The more the wider knowledge is taken into account the more the
evolution of defectors is impaired. We explain this by revealing a dynamically
decelerated invasion process, by means of which interfaces separating different
domains remain smooth and defectors therefore become unable to efficiently
invade cooperators. This in turn invigorates spatial reciprocity and
establishes decentralized decision making as very beneficial for resolving
social dilemmas.Comment: 8 two-column pages, 7 figures; accepted for publication in Scientific
Report
Towards Online Multiresolution Community Detection in Large-Scale Networks
The investigation of community structure in networks has aroused great interest in multiple disciplines. One of the challenges is to find local communities from a starting vertex in a network without global information about the entire network. Many existing methods tend to be accurate depending on a priori assumptions of network properties and predefined parameters. In this paper, we introduce a new quality function of local community and present a fast local expansion algorithm for uncovering communities in large-scale networks. The proposed algorithm can detect multiresolution community from a source vertex or communities covering the whole network. Experimental results show that the proposed algorithm is efficient and well-behaved in both real-world and synthetic networks
Frustrated hierarchical synchronization and emergent complexity in the human connectome network
The spontaneous emergence of coherent behavior through synchronization plays a key role in neural function, and its anomalies often lie at the basis of pathologies. Here we employ a parsimonious (mesoscopic) approach to study analytically and computationally the synchronization (Kuramoto) dynamics on the actual human-brain connectome network. We elucidate the existence of a so-far-uncovered intermediate phase, placed between the standard synchronous and asynchronous phases, i.e. between order and disorder. This novel phase stems from the hierarchical modular organization of the connectome. Where one would expect a hierarchical synchronization process, we show that the interplay between structural bottlenecks and quenched intrinsic frequency heterogeneities at many different scales, gives rise to frustrated synchronization, metastability, and chimera-like states, resulting in a very rich and complex phenomenology. We uncover the origin of the dynamic freezing behind these features by using spectral graph theory and discuss how the emerging complex synchronization patterns relate to the need for the brain to access –in a robust though flexible way– a large variety of functional attractors and dynamical repertoires without ad hoc fine-tuning to a critical pointWe acknowledge financial support from J. de Andalucía, grant P09-FQM-4682 and we thank O. Sporns for providing us access to the human connectome data
Neurocranium versus Face: A Morphometric Approach with Classical Anthropometric Variables for Characterizing Patterns of Cranial Integration in Extant Hominoids and Extinct Hominins
The relative importance of the two main cranial complexes, the neurocranium and the splanchnocranium, has been examined in the five species of extant hominoids and in a huge sample of extinct hominins using six standard craniometric variables that measure the length, width and height of each cranial module. Factor analysis and two-block partial least squares were used for establishing the major patterns of developmental and evolutionary integration between both cranial modules. The results obtained show that all extant hominoids (including the anatomically modern humans) share a conserved pattern of developmental integration, a result that agrees with previous studies. The pattern of evolutionary integration between both cranial modules in australopiths runs in parallel to developmental integration. In contrast, the pattern of evolutionary and developmental integration of the species of the genus Homo is the opposite, which is probably the consequence of distinctive selective regimes for both hominin groups.JAPC, JMJA and PP received fundings from Ministerio de Ciencia e Innovación, Gobierno de España (http://www.idi.mineco.gob.es), project CGL2011-30334, and Consejería de Economía, Innovación, Ciencia y Empleo, Junta de Andalucía, España (http://www.juntadeandalucia.es/organismos/economiainnovacioncienciayempleo.html), project P11-HUM-7248 and Research Groups RNM-146 and HUM-607
EFFICACY AND SAFETY OF BOCEPREVIR-BASED THERAPY IN HCVG1 TREATMENT-EXPERIENCED PATIENTS WITH ADVANCED FIBROSIS/CIRRHOSIS: THE ITALIAN AND SPANISH NPP EARLY ACCESS PROGRAM
Background and Aims: To maximize cost/efficay of boceprevirbased
triple therapy (BOC) in patients with HCV-related advanced
fibrosis/cirrhosis.
Methods: ITT SVR12, safety and futility rules value were evaluated
in the multicenter national Italian and Spanish early access Name-
Patient-Program which includes treatment-experienced patients
with HCVG1-related advanced fibrosis/cirrhosis (Metavir F3/4)
treated with BOC in both countries.
Results: 402 patients (mean age 55 years; range 22–75),
316 (78.6%) G1b, 255 (63.4%) F4, 60 (30.9%) with oesophageal
varices, 137 (34.1%) relapsers, 95 (23.6%) partial and 168 (41.8%) null
responders were enrolled. Platelets count <100,000 and albumin
levels <3.5 g/dl were present in 49 (12.2%) and 22 (6.3%) patients,
respectively. 369 (91.8%) received at least 1 dose of BOC. Overall ITT
SVR12 rates and according to prior response to P/R, fibrosis stage
and TW8 HCV-RNA value to P/R/BOC are reported in the table.
At multivariate analysis, the strongest predictors of SVR12 were
TW8 HCV-RNA undetectability (RR, 30.8; 95% CI, 8.7–108.7) and
HCV-RNA detectable but <1000 IU/mL (RR, 9.1; 95% CI, 2.6–31.8)
compared to those with HCV-RNA ≥1000 IU/mL.
Two patients (0.5%) died from multi-organ failure, 13 (3.2%)
developed hepatic decompensation, 41 (10.2%) had severe anemia
(<8.5 g/dl) and 31 (7.7%) required at least one blood transfusion.
Conclusions: In treatment-experienced patients with advanced
fibrosis/cirrhosis, SVR12 attained by BOC was satisfactory. Mortality,
life-threatening adverse events and severe anemia rates were
similar to those reported in other real-practice studies. A TW8
futility rule enables a safely discontinuation of BOC in patients
who are extremely unlikely to achieve SVR, thus optimizing the
effectiveness of treatment in this difficult-to-cure population
Recommended from our members
Query Extension Suggestions for Visual Query Systems Through Ontology Projection and Indexing
Ontology-based visual query formulation is a viable alternative to textual query editors in the Semantic Web domain for extracting data from structured data sources in terms of the skills and knowledge required. A visual query system is at any moment responsible for providing the user with query extension suggestions; however, suggestions leading to empty results are often not useful. To this end, in this article, we first present an approach for projecting OWL 2 ontologies into navigation graphs to be used for query formulation and then a solution where an efficient finite index is used to calculate non-ranked approximated extension suggestions for ontology-based visual query systems using navigation graphs. The results of our experiments suggest that one can efficiently project an ontology into a navigation graph, query it for running an interactive user interface, and suggest query extensions that do not lead to dead-ends
Comparing the Invasibility of Experimental “Reefs” with Field Observations of Natural Reefs and Artificial Structures
Natural systems are increasingly being modified by the addition of artificial habitats which may facilitate invasion. Where invaders are able to disperse from artificial habitats, their impact may spread to surrounding natural communities and therefore it is important to investigate potential factors that reduce or enhance invasibility. We surveyed the distribution of non-indigenous and native invertebrates and algae between artificial habitats and natural reefs in a marine subtidal system. We also deployed sandstone plates as experimental ‘reefs’ and manipulated the orientation, starting assemblage and degree of shading. Invertebrates (non-indigenous and native) appeared to be responding to similar environmental factors (e.g. orientation) and occupied most space on artificial structures and to a lesser extent reef walls. Non-indigenous invertebrates are less successful than native invertebrates on horizontal reefs despite functional similarities. Manipulative experiments revealed that even when non-indigenous invertebrates invade vertical “reefs”, they are unlikely to gain a foothold and never exceed covers of native invertebrates (regardless of space availability). Community ecology suggests that invertebrates will dominate reef walls and algae horizontal reefs due to functional differences, however our surveys revealed that native algae dominate both vertical and horizontal reefs in shallow estuarine systems. Few non-indigenous algae were sampled in the study, however where invasive algal species are present in a system, they may present a threat to reef communities. Our findings suggest that non-indigenous species are less successful at occupying space on reef compared to artificial structures, and manipulations of biotic and abiotic conditions (primarily orientation and to a lesser extent biotic resistance) on experimental “reefs” explained a large portion of this variation, however they could not fully explain the magnitude of differences
- …