The case for the multi-species ecological system, with special reference to succession and stability

Multi-species life support system based on ecological theor

Systemic hemangiomatosis with a deletion in the KRIT1 gene : an unusual manifestation of cerebral cavernous malformation

Cavernous hemangiomas are common hamartomatous vascular proliferations often seen as incidental solitary lesions. Rarely they occur as multifocal lesions, often in characteristic locations as part of a hereditary syndrome. We report a case of systemic hemangiomatosis with multifocal involvement of the CNS, spleen, liver, adrenal, and axial skeleton recognized at autopsy. Systemic hemangiomatosis involving solid organs, the central nervous system, and bone has been described in case reports, but this collection of findings is exceedingly rare. We hypothesized that the anomalies noted at autopsy in this case might represent sporadic cerebral cavernous malformation (CCM1), specifically de novo mutation of KRIT1

Validation of the ITU-R P series radio wave propagation model for millimetre wave V-Band (60GHz) line-of-sight point-to-point short distance link

Millimetre-wave communication systems have a very high potential to become mobile technology of choice for future 4G and 5G network architectures, which has led to many researchers carrying out studies regarding the effects of the atmosphere on radio propagation. There is growing interest in the use of millimetre-wave spectrum as a potential candidate for the provision of high capacity, short range, and backhaul solutions within future 5G ultra-dense network infrastructures. However, these frequencies are highly susceptible to atmospheric conditions and therefore a more detailed understanding of such behaviour is required. This research presents results from a one-year trial of a 60GHz short-range point-to-point link test between two building rooftops at the University of Salford, UK. In this research, a short-range 60GHz radio link measures power attenuations in millimetre-wave ranges with simultaneous measurement of weather parameters. The results obtained confirm a strong correlation between path-loss and the impact of rain and atmospheric gases as predicted by the ITU path-loss model but also highlight a discrepancy. Further analysis revealed that rain duration appears to be having a detrimental effect on link performance. The experimental data from this trial is presented as evidence of the potential impact of rain at 60GHz.The results also confirm the attenuation due to atmospheric gases (Oxygen absorption and water vapour) agree with the attenuation calculations from ITU recommendation for atmospheric gases. The results having considered impacts due to atmospheric gases and rain as per the ITU recommendations, there is a general residue of between 1dB and 2dB path loss throughout the month, interspersed by definite larger peaks ranging from 3dB to 9dB. The extra 3dB to 9dB of residual path loss, is unaccounted for by the ITU path-loss model. The analysis and discussion of measurement results are presented. The results also confirm that the link throughput can be maintained except in the most extreme weather conditions

Beyond connectedness: why pairwise metrics cannot capture community stability

The connectedness of species in a trophic web has long been a key structural characteristic for both theoreticians and empiricists in their understanding of community stability. In the past decades, there has been a shift from focussing on determining the number of interactions to taking into account their relative strengths. The question is: How do the strengths of the interactions determine the stability of a community? Recently, a metric has been proposed which compares the stability of observed communities in terms of the strength of three- and two-link feedback loops (cycles of interaction strengths). However, it has also been suggested that we do not need to go beyond the pairwise structure of interactions to capture stability. Here, we directly compare the performance of the feedback and pairwise metrics. Using observed food-web structures, we show that the pairwise metric does not work as a comparator of stability and is many orders of magnitude away from the actual stability values. We argue that metrics based on pairwise-strength information cannot capture the complex organization of strong and weak links in a community, which is essential for system stability

Maximum Power Efficiency and Criticality in Random Boolean Networks

Random Boolean networks are models of disordered causal systems that can occur in cells and the biosphere. These are open thermodynamic systems exhibiting a flow of energy that is dissipated at a finite rate. Life does work to acquire more energy, then uses the available energy it has gained to perform more work. It is plausible that natural selection has optimized many biological systems for power efficiency: useful power generated per unit fuel. In this letter we begin to investigate these questions for random Boolean networks using Landauer's erasure principle, which defines a minimum entropy cost for bit erasure. We show that critical Boolean networks maximize available power efficiency, which requires that the system have a finite displacement from equilibrium. Our initial results may extend to more realistic models for cells and ecosystems.Comment: 4 pages RevTeX, 1 figure in .eps format. Comments welcome, v2: minor clarifications added, conclusions unchanged. v3: paper rewritten to clarify it; conclusions unchange

A first--order irreversible thermodynamic approach to a simple energy converter

Several authors have shown that dissipative thermal cycle models based on Finite-Time Thermodynamics exhibit loop-shaped curves of power output versus efficiency, such as it occurs with actual dissipative thermal engines. Within the context of First-Order Irreversible Thermodynamics (FOIT), in this work we show that for an energy converter consisting of two coupled fluxes it is also possible to find loop-shaped curves of both power output and the so-called ecological function against efficiency. In a previous work Stucki [J.W. Stucki, Eur. J. Biochem. vol. 109, 269 (1980)] used a FOIT-approach to describe the modes of thermodynamic performance of oxidative phosphorylation involved in ATP-synthesis within mithochondrias. In that work the author did not use the mentioned loop-shaped curves and he proposed that oxidative phosphorylation operates in a steady state simultaneously at minimum entropy production and maximum efficiency, by means of a conductance matching condition between extreme states of zero and infinite conductances respectively. In the present work we show that all Stucki's results about the oxidative phosphorylation energetics can be obtained without the so-called conductance matching condition. On the other hand, we also show that the minimum entropy production state implies both null power output and efficiency and therefore this state is not fulfilled by the oxidative phosphorylation performance. Our results suggest that actual efficiency values of oxidative phosphorylation performance are better described by a mode of operation consisting in the simultaneous maximization of the so-called ecological function and the efficiency.Comment: 20 pages, 7 figures, submitted to Phys. Rev.

Evolution of avalanche conducting states in electrorheological liquids

Charge transport in electrorheological fluids is studied experimentally under strongly nonequlibrium conditions. By injecting an electrical current into a suspension of conducting nanoparticles we are able to initiate a process of self-organization which leads, in certain cases, to formation of a stable pattern which consists of continuous conducting chains of particles. The evolution of the dissipative state in such system is a complex process. It starts as an avalanche process characterized by nucleation, growth, and thermal destruction of such dissipative elements as continuous conducting chains of particles as well as electroconvective vortices. A power-law distribution of avalanche sizes and durations, observed at this stage of the evolution, indicates that the system is in a self-organized critical state. A sharp transition into an avalanche-free state with a stable pattern of conducting chains is observed when the power dissipated in the fluid reaches its maximum. We propose a simple evolution model which obeys the maximum power condition and also shows a power-law distribution of the avalanche sizes.Comment: 15 pages, 6 figure

Assessing the energy implications of replacing car trips with bicycle trips in Sheffield, UK

A wide range of evidence supports policies which encourage people to cycle more and drive less, for health and environmental reasons. However, the likely energy implications of such a modal shift have remained relatively unexplored. In this paper we generate scenarios for increasing the cycling rate in Sheffield between 2010 and 2020. This is done through the novel application of a simple model, borrowed from population ecology. The analysis suggests that pro-cycling interventions result in energy savings through reduced consumption of fuel and cars, and energy costs through increased demand for food. The cumulative impact is a net reduction in primary energy consumption, the magnitude of which depends on a number of variables which are subject to uncertainty. Based on the evidence presented and analysed in this paper, we conclude that transport policy has a number of important energy implications, some of which remain unexplored. We therefore advocate the formation of closer links between energy policy and transport policy in academia and in practice; our approach provides a simple yet flexible framework for pursuing this aim in the context of modal shift