Finite-size scaling analysis of the distributions of pseudo-critical temperatures in spin glasses

Using the results of large scale numerical simulations we study the probability distribution of the pseudo critical temperature for the three-dimensional Edwards-Anderson Ising spin glass and for the fully connected Sherrington-Kirkpatrick model. We find that the behavior of our data is nicely described by straightforward finite-size scaling relations.Comment: 23 pages, 9 figures. Version accepted for publication in J. Stat. Mec

Cycle-based Cluster Variational Method for Direct and Inverse Inference

We elaborate on the idea that loop corrections to belief propagation could be dealt with in a systematic way on pairwise Markov random fields, by using the elements of a cycle basis to define region in a generalized belief propagation setting. The region graph is specified in such a way as to avoid dual loops as much as possible, by discarding redundant Lagrange multipliers, in order to facilitate the convergence, while avoiding instabilities associated to minimal factor graph construction. We end up with a two-level algorithm, where a belief propagation algorithm is run alternatively at the level of each cycle and at the inter-region level. The inverse problem of finding the couplings of a Markov random field from empirical covariances can be addressed region wise. It turns out that this can be done efficiently in particular in the Ising context, where fixed point equations can be derived along with a one-parameter log likelihood function to minimize. Numerical experiments confirm the effectiveness of these considerations both for the direct and inverse MRF inference.Comment: 47 pages, 16 figure

Router-level community structure of the Internet Autonomous Systems

The Internet is composed of routing devices connected between them and organized into independent administrative entities: the Autonomous Systems. The existence of different types of Autonomous Systems (like large connectivity providers, Internet Service Providers or universities) together with geographical and economical constraints, turns the Internet into a complex modular and hierarchical network. This organization is reflected in many properties of the Internet topology, like its high degree of clustering and its robustness. In this work, we study the modular structure of the Internet router-level graph in order to assess to what extent the Autonomous Systems satisfy some of the known notions of community structure. We show that the modular structure of the Internet is much richer than what can be captured by the current community detection methods, which are severely affected by resolution limits and by the heterogeneity of the Autonomous Systems. Here we overcome this issue by using a multiresolution detection algorithm combined with a small sample of nodes. We also discuss recent work on community structure in the light of our results

Modelling home care organisations from an operations management perspective

Home Care (HC) service consists of providing care to patients in their homes. During the last decade, the HC service industry experienced significant growth in many European countries. This growth stems from several factors, such as governmental pressure to reduce healthcare costs, demographic changes related to population ageing, social changes, an increase in the number of patients that suffer from chronic illnesses, and the development of new home-based services and technologies. This study proposes a framework that will enable HC service providers to better understand HC operations and their management. The study identifies the main processes and decisions that relate to the field of HC operations management. Hence, an IDEF0 (Integrated Definition for Function Modelling) activity-based model describes the most relevant clinical, logistical and organisational processes associated with HC operations. A hierarchical framework for operations management decisions is also proposed. This analysis is derived from data that was collected by nine HC service providers, which are located in France and Italy, and focuses on the manner in which operations are run, as well as associated constraints, inputs and outputs. The most challenging research areas in the field of HC operations management are also discussed

A community perspective on the concept of marine holobionts: Current status, challenges, and future directions

Host-microbe interactions play crucial roles in marine ecosystems. However, we still have very little understanding of the mechanisms that govern these relationships, the evolutionary processes that shape them, and their ecological consequences. The holobiont concept is a renewed paradigm in biology that can help to describe and understand these complex systems. It posits that a host and its associated microbiota with which it interacts, form a holobiont, and have to be studied together as a coherent biological and functional unit to understand its biology, ecology, and evolution. Here we discuss critical concepts and opportunities in marine holobiont research and identify key challenges in the field. We highlight the potential economic, sociological, and environmental impacts of the holobiont concept in marine biological, evolutionary, and environmental sciences. Given the connectivity and the unexplored biodiversity specific to marine ecosystems, a deeper understanding of such complex systems requires further technological and conceptual advances, e.g., the development of controlled experimental model systems for holobionts from all major lineages and the modeling of (info)chemical-mediated interactions between organisms. Here we propose that one significant challenge is to bridge cross-disciplinary research on tractable model systems in order to address key ecological and evolutionary questions. This first step is crucial to decipher the main drivers of the dynamics and evolution of holobionts and to account for the holobiont concept in applied areas, such as the conservation, management, and exploitation of marine ecosystems and resources, where practical solutions to predict and mitigate the impact of human activities are more important than ever

Variation and asymmetry in host-symbiont dependence in a microbial symbiosis

Background Symbiosis is a major source of evolutionary innovation and, by allowing species to exploit new ecological niches, underpins the functioning of ecosystems. The transition from free-living to obligate symbiosis requires the alignment of the partners’ fitness interests and the evolution of mutual dependence. While symbiotic taxa are known to vary widely in the extent of host-symbiont dependence, rather less is known about variation within symbiotic associations. Results Using experiments with the microbial symbiosis between the protist Paramecium bursaria and the alga Chlorella, we show variation between pairings in host-symbiont dependence, encompassing facultative associations, mutual dependence and host dependence upon the symbiont. Facultative associations, that is where both the host and the symbiont were capable of free-living growth, displayed higher symbiotic growth rates and higher per host symbiont loads than those with greater degrees of dependence. Conclusions These data show that the Paramecium-Chlorella interaction exists at the boundary between facultative and obligate symbiosis, and further suggest that the host is more likely to evolve dependence than the algal symbiont

A "hair-raising" history of alopecia areata

YesA 3500‐year‐old papyrus from ancient Egypt provides a list of treatments for many diseases including “bite hair loss,” most likely alopecia areata (AA). The treatment of AA remained largely unchanged for over 1500 years. In 30 CE, Celsus described AA presenting as scalp alopecia in spots or the “windings of a snake” and suggested treatment with caustic compounds and scarification. The first “modern” description of AA came in 1813, though treatment still largely employed caustic agents. From the mid‐19th century onwards, various hypotheses of AA development were put forward including infectious microbes (1843), nerve defects (1858), physical trauma and psychological stress (1881), focal inflammation (1891), diseased teeth (1902), toxins (1912) and endocrine disorders (1913). The 1950s brought new treatment developments with the first use of corticosteroid compounds (1952), and the first suggestion that AA was an autoimmune disease (1958). Research progressively shifted towards identifying hair follicle‐specific autoantibodies (1995). The potential role of lymphocytes in AA was made implicit with immunohistological studies (1980s). However, studies confirming their functional role were not published until the development of rodent models (1990s). Genetic studies, particularly genome‐wide association studies, have now come to the forefront and open up a new era of AA investigation (2000s). Today, AA research is actively focused on genetics, the microbiome, dietary modulators, the role of atopy, immune cell types in AA pathogenesis, primary antigenic targets, mechanisms by which immune cells influence hair growth, and of course the development of new treatments based on these discoveries.Alopecia UK

16S rRNA gene metabarcoding and TEM reveals different ecological strategies within the genus Neogloboquadrina (planktonic foraminifer)

CB was supported on a Daphne Jackson Fellowship sponsored by Natural Environmental Research Council (www.nerc.ac.uk) and the University of Edinburgh via the Daphne Jackson Trust. Field collections were supported by the National Science Foundation (www.nsf.gov) grant number OCE-1261519 to ADR and JSF.Uncovering the complexities of trophic and metabolic interactions among microorganisms is essential for the understanding of marine biogeochemical cycling and modelling climate-driven ecosystem shifts. High-throughput DNA sequencing methods provide valuable tools for examining these complex interactions, although this remains challenging, as many microorganisms are difficult to isolate, identify and culture. We use two species of planktonic foraminifera from the climatically susceptible, palaeoceanographically important genus Neogloboquadrina, as ideal test microorganisms for the application of 16S rRNA gene metabarcoding. Neogloboquadrina dutertrei and Neogloboquadrina incompta were collected from the California Current and subjected to either 16S rRNA gene metabarcoding, fluorescence microscopy, or transmission electron microscopy (TEM) to investigate their species-specific trophic interactions and potential symbiotic associations. 53–99% of 16S rRNA gene sequences recovered from two specimens of N. dutertrei were assigned to a single operational taxonomic unit (OTU) from a chloroplast of the phylum Stramenopile. TEM observations confirmed the presence of numerous intact coccoid algae within the host cell, consistent with algal symbionts. Based on sequence data and observed ultrastructure, we taxonomically assign the putative algal symbionts to Pelagophyceae and not Chrysophyceae, as previously reported in this species. In addition, our data shows that N. dutertrei feeds on protists within particulate organic matter (POM), but not on bacteria as a major food source. In total contrast, of OTUs recovered from three N. incompta specimens, 83–95% were assigned to bacterial classes Alteromonadales and Vibrionales of the order Gammaproteobacteria. TEM demonstrates that these bacteria are a food source, not putative symbionts. Contrary to the current view that non-spinose foraminifera are predominantly herbivorous, neither N. dutertrei nor N. incompta contained significant numbers of phytoplankton OTUs. We present an alternative view of their trophic interactions and discuss these results within the context of modelling global planktonic foraminiferal abundances in response to high-latitude climate change.Publisher PDFPeer reviewe

An information system for the building industries: A communication approach based on industrial components

This paper presents the SYDOX/MATCOMP/Xi project, funded by the French Ministry of Industry. The goal of the project was to provide the construction professionals with an on-line aid for component specification and selection at different levels of the construction life cycle. This two years project started in 1997 and involved several partners. This paper describes the main features of the information system: databases, query and communication systems. SYDOX(SYstème de DOnnées compleXes) is aimed at defining and demonstrating a prototype to access information about MATerials and COMPonents used in construction, implemented on a WWW server. Though the objective is general, the work was focused on a restricted sub-section of the construction domain. We describe the domain and the scope of the project, the starting point and the lessons learnt from the development of the prototype. We also propose some important ideas on which this research is based

Diversity, Ecology and Biogeochemistry of Cyst-Forming Acantharia (Radiolaria) in the Oceans

Marine planktonic organisms that undertake active vertical migrations over their life cycle are important contributors to downward particle flux in the oceans. Acantharia, globally distributed heterotrophic protists that are unique in building skeletons of celestite (strontium sulfate), can produce reproductive cysts covered by a heavy mineral shell that sink rapidly from surface to deep waters. We combined phylogenetic and biogeochemical analyses to explore the ecological and biogeochemical significance of this reproductive strategy. Phylogenetic analysis of the 18S and 28S rRNA genes of different cyst morphotypes collected in different oceans indicated that cyst-forming Acantharia belong to three early diverging and essentially non symbiotic clades from the orders Chaunacanthida and Holacanthida. Environmental high-throughput V9 tag sequences and clone libraries of the 18S rRNA showed that the three clades are widely distributed in the Indian, Atlantic and Pacific Oceans at different latitudes, but appear prominent in regions of higher primary productivity. Moreover, sequences of cyst-forming Acantharia were distributed evenly in both the photic and mesopelagic zone, a vertical distribution that we attribute to their life cycle where flagellated swarmers are released in deep waters from sinking cysts. Bathypelagic sediment traps in the subantarctic and oligotrophic subtropical Atlantic Ocean showed that downward flux of Acantharia was only large at high-latitudes and during a phytoplankton bloom. Their contribution to the total monthly particulate organic matter flux can represent up to 3%. High organic carbon export in cold waters would be a putative nutritional source for juveniles ascending in the water column. This study improves our understanding of the life cycle and biogeochemical contribution of Acantharia, and brings new insights into a remarkable reproductive strategy in marine protists