Nestedness in mutualistic networks

James et al. (2012) presented simulations that apparently falsify the analytical result by Bastolla et al. (2009), who showed that nested mutualistic interactions decrease interspecific competition and increase biodiversity in model ecosystems. This contradiction, however, mainly stems from the incorrect application of formulas derived for fully connected networks to empirical, sparse networks.Comment: 2 pages, 1 figur

Sanitser, an innovative sanitary ware body, formulated with waste glass and recycled materials

Abstract In the present paper, the results of "Sanitser" Life European project are presented. The aim of this study was to reduce the firing temperature for ceramic body (from 1250 to 1170 °C). This was achieved substituting feldspar and quartz with recycled blend materials and a little percentage of flux (less than 3%); in a sanitary ware vitreous china formulation a waste glass, granitic materials and fired broken ceramic pieces were introduced. Tests performed on the Sanitser formulation showed that it has the same final physical-chemical characteristics of the industrial vitreous china (VC) body. Besides, different ceramic pieces (wash basin, bidet and WC pan) were compared with VC production. The results showed that Sanitser body can replace vitreous china in the sanitary ware production. In this project, the firing temperature of the ceramic body is reduced significantly with a supposed decrease of the CO2 emissions. In Sanitser formulation, about 43.6% of recycled materials that would end in dumps were utilized

Modelling lava flows by Cellular Nonlinear Networks (CNN): preliminary results

International audienceThe forecasting of lava flow paths is a complex problem in which temperature, rheology and flux-rate all vary with space and time. The problem is more difficult to solve when lava runs down a real topography, considering that the relations between characteristic parameters of flow are typically nonlinear. An alternative approach to this problem that does not use standard differential equation methods is Cellular Nonlinear Networks (CNNs). The CNN paradigm is a natural and flexible framework for describing locally interconnected, simple, dynamic systems that have a lattice-like structure. They consist of arrays of essentially simple, nonlinearly coupled dynamic circuits containing linear and non-linear elements able to process large amounts of information in real time. Two different approaches have been implemented in simulating some lava flows. Firstly, a typical technique of the CNNs to analyze spatio-temporal phenomena (as Autowaves) in 2-D and in 3-D has been utilized. Secondly, the CNNs have been used as solvers of partial differential equations of the Navier-Stokes treatment of Newtonian flow

Evolution of a Modular Software Network

"Evolution behaves like a tinkerer" (Francois Jacob, Science, 1977). Software systems provide a unique opportunity to understand biological processes using concepts from network theory. The Debian GNU/Linux operating system allows us to explore the evolution of a complex network in a novel way. The modular design detected during its growth is based on the reuse of existing code in order to minimize costs during programming. The increase of modularity experienced by the system over time has not counterbalanced the increase in incompatibilities between software packages within modules. This negative effect is far from being a failure of design. A random process of package installation shows that the higher the modularity the larger the fraction of packages working properly in a local computer. The decrease in the relative number of conflicts between packages from different modules avoids a failure in the functionality of one package spreading throughout the entire system. Some potential analogies with the evolutionary and ecological processes determining the structure of ecological networks of interacting species are discussed.Comment: To appear in PNA

Habitat loss and the disassembly of mutalistic networks

Recent studies have described the architecture of plant–animal mutualistic networks, but little is known on how such networks disassemble as a consequence of global change. This is a relevant question because 1) species interac- tions seem to be very susceptible to habitat loss, and 2) the loss of a critical fraction of interactions can abruptly change the topology of the entire network with potential consequences for its functioning. Here we develop a spatially explicit metacommunity model based on the structure of 30 real mutualistic networks. We find that there is a critical value of habitat destruction beyond which interactions are lost very fast. Second, there is a homogeneous distribution of the num- ber of interactions per patch when the habitat is pristine, while this becomes very skewed at the brink of extinction. This increase in skewness is discussed in the context of potential indicators of network collapse.Peer reviewe

Use of sulfated-cellulose membrane adsorbers to intensify purification of cell culturederived influenza A and B viruses

New generation of cell culture-based vaccines enables faster response to pandemic outbreaks and helps coping with the increasing demand for seasonal vaccines. Besides efficient upstream processing technologies, appropriate economic and robust downstream processing is key to consistently achieve high yields. Chromatography membranes have been extensively evaluated to capture viruses at laboratory scale, for influenza, adenovirus or virus like particles. They have shown great potential to intensify processes thanks to a high binding capacity, high flow-rate and ease of use and are now commonly used in new generation of vaccine processes. We present here Sartobind SC, a novel sulfated cellulose membrane adsorber, for the capture of Influenza. In a recent study, the binding capacity and the purification performance of two bead-based resins and Sartobind SC was compared for three influenza virus strains (H1N1, H3N2 and B) produced in MDCK suspension cells in a chemically defined medium. The dynamic binding capacity for the sulfated cellulose membrane adsorbers was consistently higher than for the resins (8 to 22-fold). Overall, recovery of virus varied between 66% and 81%. Total protein and DNA removal were\u3e74% and\u3e96%, respectively. Due to the higher operating flow rate and binding capacity, the productivity with the membrane adsorbers was on average 25-times higher than with the resins. This purification platform based on sulfated cellulose can intensify processes and therefore reduce the cost of influenza purification. This ligand is also a promising candidate for other viruses such as vaccinia, RSV, HSV or measles