4,489 research outputs found
Hypernetworks: Multidimensional relationships in multilevel systems
Networks provide a powerful way of modelling the dynamics
of complex systems. Going beyond binary relations, embracing n-ary relations in network science can generalise many structures. This starts with hypergraphs and their Galois structures. Simplicial complexes generalise hypergraphs by adding orientation. Their multidimensional q-connectivity structure generalises connectivity in networks. Hypersimplices generalise simplices by making the relational structure explicit in the notation. This gives a new way of representing multilevel systems and their dynamics, leading to a new fragment-recombine operator to model the complex dynamics of interacting multilevel systems
Reduction and related phenomena in the New Red Sandstone of south-west England
This report gives an account of the geological setting of reduction features in New Red
Sandstone sediments from the area around Exmouth and Budleigh Salterton in south-west
England, along with a review of the state of research and investigation into these phenomena.
The abundance and significance of the commonest reduction phenomena (green spherical spots)
are assessed, together with geochemical and mineralogical data from recent investigations on
nodule material. The lack of identifiable fossil material within the Aylesbeare Mudstone suggests
that the hypothesis that the formation of reduction spots and nodules is dependent upon the
presence of organic matter is neither adequate nor appropriate for the occurrences in this area.
Earlier investigations had identified in some of the nodules, carbon-containing substances, the
origin of which was not clear; the possible relationship of this material to the formation of the
reduction features is considered
A revolution for the at-risk
The case for investment in early intervention for neurodevelopmental disorders
Gray Whales (Eschrichtius robustus) in the Western Chukchi and East Siberian Seas
During joint Soviet-American shipboard surveys in autumn 1979 and 1980, numerous sightings of gray whales (Eschrichtius robustus) were made in the western Chukchi and East Siberian seas. Gray whales were observed well offshore in ice-free water in 1979, but near the Chukotka coast in 1980. During the 1980 survey, gray whales were observed further west than previously recorded, with three animals seen at 174 08 E longitude, well into the East Siberian Sea. Based on indirect evidence of gray whale behavior and typical prey organisms identified in bottom samples, we assume gray whales are feeding in the western Chukchi Sea during summer and fall. Movement of these animals further west into the East Siberian Sea may occur regularly when ice conditions permit, but it may also be a response to increasing population size over the past several decades, and gray whales may be reoccupying habitat unused during periods of low population caused by commercial whaling.Key words: gray whale, Eschrichtius robustus, cetacean, Chukchi Sea, East Siberian SeaMots clés: baleine grise de Californie, Eschrichtius robustus, cétacé, mer Tchouktche, mer de Sibérie Oriental
Brain adaptation and alternative developmental trajectories
Resilience and adaptation in the face of early genetic or environmental risk has become a major interest in child psychiatry over recent years. However, we still remain far from an understanding of how developing human brains as a whole adapt to the diffuse and widespread atypical synaptic function that may be characteristic of some common developmental disorders. The first part of this paper discusses four types of whole-brain adaptation in the face of early risk: redundancy, reorganization, niche construction, and adjustment of developmental rate. The second part of the paper applies these adaptation processes specifically to autism. We speculate that key features of autism may be the end result of processes of early brain adaptation, rather than the direct consequences of ongoing neural pathology
Annual research review: Infant development, autism, and ADHD – early pathways to emerging disorders
- Background: Autism spectrum disorders (ASD) and attention deficit hyperactivity disorder (ADHD) are two of the most common neurodevelopmental disorders, with a high degree of co-occurrence.
- Methods: Prospective longitudinal studies of infants who later meet criteria for ASD or ADHD offer the opportunity to determine whether the two disorders share developmental pathways.
- Results: Prospective studies of younger siblings of children with autism have revealed a range of infant behavioral and neural markers associated with later diagnosis of ASD. Research on infants with later ADHD is less developed, but emerging evidence reveals a number of relations between infant measures and later symptoms of inattention and hyperactivity.
- Conclusions: We review this literature, highlighting points of convergence and divergence in the early pathways to ASD and ADHD
Sex differences in the association between infant markers and later autistic traits
BACKGROUND: Although it is well established that the prevalence of autism spectrum disorder (ASD) is higher in males than females, there is relatively little understanding of the underlying mechanisms and their developmental time course. Sex-specific protective or risk factors have often been invoked to explain these differences, but such factors are yet to be identified.
METHODS: We take a developmental approach, using a prospective sample of 104 infants at high and low familial risk for ASD, to characterise sex differences in infant markers known to predict emerging autism symptoms. We examine three markers previously shown to be associated with later autistic social-communication symptoms: the Autism Observation Scale for Infants (AOSI) total score, attention disengagement speed and gaze following behaviour. Our aim was to test whether sex differences were already present in these markers at 1 year of age, which would suggest sex-specific mechanisms of risk or protection.
RESULTS: While no sex differences were found in any of the three markers investigated, we found sex differences in their relationship to 3-year autism traits; all three markers significantly predicted later autism traits only in the boys.
CONCLUSIONS: Previously identified ‘early autism markers’ were associated with later autism symptoms only in boys. This suggests that there may be additional moderating risk or protective factors which remain to be identified. Our findings have important implications for prospective studies in terms of directly testing for the moderating effect of sex on emerging autistic traits
Functional Changes in Littoral Macroinvertebrate Communities in Response to Watershed-Level Anthropogenic Stress
Watershed-scale anthropogenic stressors have profound effects on aquatic communities. Although several functional traits of stream macroinvertebrates change predictably in response to land development and urbanization, little is known about macroinvertebrate functional responses in lakes. We assessed functional community structure, functional diversity (Rao’s quadratic entropy) and voltinism in macroinvertebrate communities sampled across the full gradient of anthropogenic stress in Laurentian Great Lakes coastal wetlands. Functional diversity and voltinism significantly decreased with increasing development, whereas agriculture had smaller or non-significant effects. Functional community structure was affected by watershed-scale development, as demonstrated by an ordination analysis followed by regression. Because functional community structure affects energy flow and ecosystem function, and functional diversity is known to have important implications for ecosystem resilience to further environmental change, these results highlight the necessity of finding ways to remediate or at least ameliorate these effects
Ethical dimensions of translational developmental neuroscience research in autism
Background
Since the 1990s, increasing research has been devoted to the identification of biomarkers for autism to help attain more objective diagnosis; enable early prediction of prognosis; and guide individualized intervention options. Early studies focused on the identification of genetic variants associated with autism, but more recently, research has expanded to investigate neurodevelopmental markers. While ethicists have extensively discussed issues around advances in autism genomics, much less ethical scrutiny has focused on research on early neurodevelopment and on the interventions being developed as a result.
Objectives
We summarize the current state of the science on the identification of early markers for autism and its potential clinical applications, before providing an overview of the ethical issues arising from increasing understanding of children's neurodevelopment in very early life.
Results
Advances in the understanding of brain and behavioral trajectories preceding later autism diagnosis raise ethical concerns around three themes: (a) New models for understanding autism; (b) Risks and benefits of early identification and intervention; and (c) Communication of early concerns to families. These ethical issues should be further investigated in research conducted in partnership with autistic people and their families.
Conclusions
This paper highlights the need for ethical scrutiny of early neurodevelopmental research in autism. Scrutiny requires expertise and methods from the basic sciences and bioethics, as well as constructive collaborations among autistic people, their parents, and autism researchers to anticipate early interventions that serve the community's interests and accommodate the varied experiences and preferences of people on the spectrum and their families.</p
Efficient Triangle Counting in Large Graphs via Degree-based Vertex Partitioning
The number of triangles is a computationally expensive graph statistic which
is frequently used in complex network analysis (e.g., transitivity ratio), in
various random graph models (e.g., exponential random graph model) and in
important real world applications such as spam detection, uncovering of the
hidden thematic structure of the Web and link recommendation. Counting
triangles in graphs with millions and billions of edges requires algorithms
which run fast, use small amount of space, provide accurate estimates of the
number of triangles and preferably are parallelizable.
In this paper we present an efficient triangle counting algorithm which can
be adapted to the semistreaming model. The key idea of our algorithm is to
combine the sampling algorithm of Tsourakakis et al. and the partitioning of
the set of vertices into a high degree and a low degree subset respectively as
in the Alon, Yuster and Zwick work treating each set appropriately. We obtain a
running time
and an approximation (multiplicative error), where is the number
of vertices, the number of edges and the maximum number of
triangles an edge is contained.
Furthermore, we show how this algorithm can be adapted to the semistreaming
model with space usage and a constant number of passes (three) over the graph
stream. We apply our methods in various networks with several millions of edges
and we obtain excellent results. Finally, we propose a random projection based
method for triangle counting and provide a sufficient condition to obtain an
estimate with low variance.Comment: 1) 12 pages 2) To appear in the 7th Workshop on Algorithms and Models
for the Web Graph (WAW 2010
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