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Saturday, 1 April 2017

INFECTION SPREAD AND VIRUS RELEASE IN VITRO IN CELL POPULATIONS AS A SYSTEM WITH PERCOLATION

Author
Juan G. Diaz Ochoa (diaz@mpi-magdeburg.mpg.de)
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International Journal of Modern Physics C (IJMPC), 2011, vol. 22, issue 03, pages 249-262
Abstract: The comprehension of the innate immune system of cell populations is not only of interest to understand systems in vivo but also in vitro, for example, in the control of the release of viral particles for the production of vaccines. In this report I introduce a model, based on dynamical networks, that simulates the cell signaling responsible for this innate immune response and its effect on the infection spread and virus production. The central motivation is to represent a cell population that is constantly mixed in a bio-reactor where there is a cell-to-cell signaling of cytokines (which are proteins responsible for the activation of the antiviral response inside the cell). Such signaling allows the definition of clusters of linked immune cells. Additionally, depending on the density of links, it is possible to identify critical threshold parameters associated to a percolation phase transition. I show that the control of this antiviral response is equivalent to a percolation process.
Keywords: Cell-to-cell signaling; virus spread in vitro; percolation; systems biology; 82.39.Rt; 87.18.Gh; 64.60.ah; 87.18.Vf; 05.50.+ (search for similar items in EconPapers)
Date: 2011
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Wood gasification integrated with fuel cells

Author
D.r McIlveen-Wright, B.c Williams and J.t McMullan
Renewable Energy, 2000, vol. 19, issue 1, pages 223-228

Abstract: Techno-economic assessments of systems which integrate biomass gasification with fuel cell modules (molten carbonate or phosphoric acid) for electricity generation are presented. The wood-fired Phosphoric Acid Fuel Cell was found to be suitable where high heat/electricity values were required, but had low electrical efficiency. Electrical efficiencies of 13–17% are typical for these systems, as are Break-even Electricity Selling Prices (BESPs) of 10–20 p/kWh and specific investments of around £3000–£7500/kWe. This technology is unlikely to be considered for further development as an electricity generation system.
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Utilization of wood biomass char in a direct carbon fuel cell (DCFC) system

Author
Seong Yool Ahn, Seong Yong Eom, Young Hoon Rhie, Yon Mo Sung, Cheor Eon Moon, Gyung Min Choi and Duck Jool Kim
Applied Energy, 2013, vol. 105, issue C, pages 207-216

Abstract: Wood biomass char was used in a direct carbon fuel cell (DCFC) as an alternative fuel. This has many advantages because the DCFC is a high-efficiency system and wood biomass is a carbon-free and regenerative material. Several analytical techniques were employed to analyze the characteristics of three fuels, their effects on the cell’s performance, and the electrochemical reactions between the fuels and the electrolyte in the system. The morphological and textural characteristics of biomass char were similar to those of two types of coal used as fuels for a DCFC system in spite of the char’s significantly lower carbon content. A practical evaluation of the fuels used in the DCFC system was conducted, and when using the biomass char, the maximum power density was 60–70% that of the corresponding value for coal under the same conditions. The performance of the biomass char fuel was improved by stirring. The possibility of its practical application was also discussed.
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A cell-centered approach to developmental biology

Author
Roeland M.H. Merks and James A. Glazier
Physica A: Statistical Mechanics and its Applications, 2005, vol. 352, issue 1, pages 113-130
Abstract: Explaining embryonic development of multicellular organisms requires insight into complex interactions between genetic regulation and physical, generic mechanisms at multiple scales. As more physicists move into developmental biology, we need to be aware of the “cultural” differences between the two fields, whose concepts of “explanations” and “models” traditionally differ: biologists aiming to identify genetic pathways and expression patterns, physicists tending to look for generic underlying principles.
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The wood from the trees: The use of timber in construction

Author
Michael H. Ramage, Henry Burridge, Marta Busse-Wicher, George Fereday, Thomas Reynolds, Darshil U. Shah, Guanglu Wu, Li Yu, Patrick Fleming, Danielle Densley-Tingley, Julian Allwood, Paul Dupree, P.F. Linden and Oren Scherman
Renewable and Sustainable Energy Reviews, 2017, vol. 68, issue P1, pages 333-359

Abstract: Trees, and their derivative products, have been used by societies around the world for thousands of years. Contemporary construction of tall buildings from timber, in whole or in part, suggests a growing interest in the potential for building with wood at a scale not previously attainable. As wood is the only significant building material that is grown, we have a natural inclination that building in wood is good for the environment. But under what conditions is this really the case? The environmental benefits of using timber are not straightforward; although it is a natural product, a large amount of energy is used to dry and process it. Much of this can come from the biomass of the tree itself, but that requires investment in plant, which is not always possible in an industry that is widely distributed among many small producers. And what should we build with wood? Are skyscrapers in timber a good use of this natural resource, or are there other aspects of civil and structural engineering, or large-scale infrastructure, that would be a better use of wood? Here, we consider a holistic picture ranging in scale from the science of the cell wall to the engineering and global policies that could maximise forestry and timber construction as a boon to both people and the planet.
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Determinants of success and intensity of livestock feed technologies use in Ethiopia: Evidence from a positive deviance perspective

Author
Mulugeta Yitayih Birhanu, Anteneh Girma and Ranjitha Puskur
Technological Forecasting and Social Change, 2017, vol. 115, issue C, pages 15-2
Abstract: This study explores factors associated with success and intensity of livestock feed technologies use among positive deviants in feed technology adoption in Ethiopia. We used a nation-wide dataset of over 603 farm households, which surveyed pockets of successes in using improved livestock feed technologies. Heckman two-stage estimation procedures were used to identify factors associated with success and intensity of livestock feed technology use simultaneously. Results from the first stage of selection equation show that households socioeconomic and institutional factors such as education status of the head, herd size, exercise in feed technology utilization, cooperative membership, distance to district center, and diverse use of technologies have significant effect on success in livestock feed technologies adoption. The second stage demonstrates that intensity of household collaboration or network, membership in livestock related cooperatives, training, access to livestock feed technologies with packages, diverse use of technologies, engagement in livestock enterprises, livestock management system, willingness to invest more in feed technologies, and agro-ecologies significantly influence the intensity of feed technologies use. These results suggest that success and intensified use of improved feed technologies demand different entry strategies for risk factors, enablers, and behaviors, which may differ from the classic agricultural technologies transfer system. These include availability of appropriate biophysical and resource environments, functional linkages between different actors, access to inputs and social capital, and enabling institutional support system. Moreover, this study shows that when there is limited adoption, few pockets of success in improved technologies use, positive deviant approach would be more informative to understand the underlying factors and principles for success and intensified use of technologies than the most commonly reported conventional adoption rate studies.
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Context, drivers, and future potential for wood-frame multi-story construction in Europe

Author
Ragnar Jonsson and Tomas Nord
Technological Forecasting and Social Change, 2015, vol. 99, issue C, pages 181-196

Abstract: Compared to many manufacturing industries, there have been few major improvements over the past few decades in the productivity, profitability, or the environmental impact of construction. However, driven by institutional changes, promotion campaigns, and technological development in the 1990s, novel industrial wood-frame multi-story construction (WMC) practices have been emerging in some European countries. The aim of the study is to explore the WMC market potential in Europe by combining two complementary approaches: Top-down scenario analysis and bottom-up innovation diffusion analysis. The results show that the WMC diffusion is heavily dependent on the regulatory framework and the structure of the construction industry. The risk-averse nature of the construction value chain resisting the uptake of new practices appears to be a more significant hindrance for the future market potential of WMC, compared to the possible competition from alternative construction practices. It would require both increasing competition within the WMC sector and increasing co-operation between wood product suppliers and the construction sector to attract investments, to reduce costs, and to make the WMC practices more credible throughout the construction value chain.
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Anisotropic nonlinear response of periodic square or cubic composites

Author
David J Bergman
Physica A: Statistical Mechanics and its Applications, 1999, vol. 270, issue 1, pages 8-14

Abstract: It is well known that the linear electrical response of periodic composites with a microstructure that has sufficiently high symmetry is isotropic. I.e., the macroscopic conductivity or permittivity of such a system, in the absence of an external magnetic field, is a scalar quantity. This is the case for cubic microstructures in three dimensional composites, and for square as well as for triangular and hexagonal or honeycomb microstructures in columnar or thin-film composites. By contrast, it turns out that the macroscopic nonlinear response, in general, is non-isotropic even in such highly symmetric composite structures. We discuss a simple square network model and show that a nonlinear conductivity can be quite anisotropic despite the high (square) symmetry of the system. We also show that a similar model of a metal/dielectric composite with square symmetry can exhibit intrinsic optical bistability that is also strongly anisotropic.
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An expected power approach for the assessment of composite endpoints and their components

Author
G. Rauch and M. Kieser
Computational Statistics & Data Analysis, 2013, vol. 60, issue C, pages 111-122
Abstract: Composite endpoints are increasingly used in clinical trials, particularly in the field of cardiology. Thereby, the overall impact of the therapeutic intervention is captured by including several events of interest in a single variable. To demonstrate the significance of an overall clinical benefit, it is sufficient to assess the test problem for the composite. However, even if a statistically significant and clinically relevant superiority is shown for the composite endpoint, there is the need to evaluate the treatment effects for the components as, for example, a strong effect in one endpoint can mask an adverse effect in another. In most clinical applications, a descriptive analysis of the individual components is performed. However, the question remains what conclusion should be drawn from a trial where the composite shows a significant effect, but some component results which are not based on confirmatory evidence point in an adverse direction. Therefore, the first aim is to define an adequate multiple test problem of the composite and its most important components. Thereby, it might suffice to show superiority with respect to the composite and non-inferiority for the components to guarantee the clinical relevance of the result, as a slightly negative effect in one component might be acceptable as long as the total effect of all components is highly positive. To calculate the power for this multiple test problem, a number of strong assumptions on the effect sizes for the composite and its components as well as on the correlations between them are required. However, knowledge on these quantities is usually very limited and thus the choice of fixed parameter assumptions is based on a low level of evidence. The second aim therefore is to provide a more flexible power definition which takes the uncertainty about parameter assumptions into account. An expected power approach is proposed using prior distributions for the involved parameters. Thereby, the choice of the prior distribution reflects the level of evidence on the parameters. The expected power is evaluated for a range of scenarios and compared to the classical power for a fixed parameter setting. The new method is illustrated with a clinical trial example.
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A composite efficiency metrics for evaluation of resource and energy utilization

Author
Siyu Yang, Qingchun Yang and Yu Qian
Energy, 2013, vol. 61, issue C, pages 455-462

Abstract: Polygeneration systems are commonly found in chemical and energy industry. These systems often involve chemical conversions and energy conversions. Studies of these systems are interdisciplinary, mainly involving fields of chemical engineering, energy engineering, environmental science, and economics. Each of these fields has developed an isolated index system different from the others. Analyses of polygeneration systems are therefore very likely to provide bias results with only the indexes from one field. This paper is motivated from this problem to develop a new composite efficiency metrics for polygeneration systems. This new metrics is based on the second law of thermodynamics, exergy theory. We introduce exergy cost for waste treatment as the energy penalty into conventional exergy efficiency. Using this new metrics could avoid the situation of spending too much energy for increasing production or paying production capacity for saving energy consumption. The composite metrics is studied on a simplified co-production process, syngas to methanol and electricity. The advantage of the new efficiency metrics is manifested by comparison with carbon element efficiency, energy efficiency, and exergy efficiency. Results show that the new metrics could give more rational analysis than the other indexes.
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Advantages and Disadvantages of Fasting for Runners

Author BY   ANDREA CESPEDES  Food is fuel, especially for serious runners who need a lot of energy. It may seem counterintuiti...