The Allometry of Host-Pathogen Interactions

Understanding the mechanisms that control rates of disease progression in humans and other species is an important area of research relevant to epidemiology and to translating studies in small laboratory animals to humans. Body size and metabolic rate influence a great number of biological rates and times. We hypothesize that body size and metabolic rate affect rates of pathogenesis, specifically the times between infection and first symptoms or death.We conducted a literature search to find estimates of the time from infection to first symptoms (t(S)) and to death (t(D)) for five pathogens infecting a variety of bird and mammal hosts. A broad sampling of diseases (1 bacterial, 1 prion, 3 viruses) indicates that pathogenesis is controlled by the scaling of host metabolism. We find that the time for symptoms to appear is a constant fraction of time to death in all but one disease. Our findings also predict that many population-level attributes of disease dynamics are likely to be expressed as dimensionless quantities that are independent of host body size.Our results show that much variability in host pathogenesis can be described by simple power functions consistent with the scaling of host metabolic rate. Assessing how disease progression is controlled by geometric relationships will be important for future research. To our knowledge this is the first study to report the allometric scaling of host/pathogen interactions

Biomarker and Geochemical Assay Validation in Mars Analog Sites: Lessons from the FELDSPAR (Field Exploration and Life Detection Sampling for Planetary Analog Research) Project

Missions looking for signs of life on other worlds can often only take a few samples once they arrive. Making sense of these "few and far between" observations is easier if we know what a "normal" level of variation for that kind of planet is. Recent eruption sites in Iceland are good places to learn about this, because they have very little life present and the same types of rocks as many places on Mars. We have visited several of these sites in Iceland and tested many different kinds of measurements: the energy available for life, the amount of DNA (an important biological molecule) present, the relative amounts of different kinds of micro-organisms, and the specific minerals that make up the rocks and ground. In addition to recommendations for future expeditions, we have also shown that using early on-site measurements to choose later on-site sample sites is very helpful in reducing the number of sample sites needed

Appendix A. Bibliography of published ecological studies reviewed to produce Fig. 1.

Bibliography of published ecological studies reviewed to produce Fig. 1

Is there scope to do better? Clinical communication with adolescents and young adults with cancer-A scoping review.

Publication status: PublishedFunder: UCLH CharityINTRODUCTION: How to communicate effectively with adolescent and young adults with cancer (AYACs) is a research priority. In a UK-wide survey of young people with cancer's research priorities, communication was a striking cross-cutting theme. It is increasingly recognised that AYACs have experiences and communication needs that differ significantly from those of younger children and older adults. The purpose of this review is to explore the features of effective clinical communication with AYACs. METHODS: A literature search was undertaken to identify and map the available evidence using a broad scope to get an overview of the pertinent literature, identify knowledge gaps and clarify concepts. The searches yielded 5825 records, generating 4040 unique articles. These were screened and 71 full articles were read by four researchers with disagreements resolved by discussion leaving 29 included articles. Narrative synthesis was undertaken in relation to each of the research questions. RESULTS: Three key themes were identified: being an adolescent/young adult, supporters, and healthcare professionals (HCPs). AYACs need to feel that HCPs understand their unique perspective. They want to be involved, this changes over time and in different contexts. Supporters are a central tenet, are most often parents and undertake several roles which are not always universally supportive. HCPs enable involvement of AYACs, and this needs to be actively promoted. AYACs preference for their level of involvement requires continual assessment. The three themes are interlinked and exist within the wider scope of the triadic encounter and cancer experience. CONCLUSION: Supporters, most often parents were a key feature across the data and were seemingly paradoxical in nature. Triadic communication, the presence of a third person, is a central tenet of communication with AYACs and we propose a conceptual model to represent the nuances, components, and facets of this complex communication

Characterizing ecohydrological and biogeochemical connectivity across multiple scales: a new conceptual framework

ABSTRACT The connectivity of ecohydrological and biogeochemical processes across time and space is a critical determinant of ecosystem structure and function. However, characterizing cross-scale connectivity is a challenge due to the lack of theories and modelling approaches that are applicable at multiple scales and due to our rudimentary understanding of the magnitude and dynamics of such connectivity. In this article, we present a conceptual framework for upscaling quantitative models of ecohydrological and biogeochemical processes using electrical circuit analogies and the Thévenin's theorem. Any process with a feasible linear electrical circuit analogy can be represented in larger scale models as a simplified Thévenin equivalent. The Thévenin equivalent behaves identically to the original circuit, so the mechanistic features of the model are maintained at larger scales. We present three case applications: water transport, carbon transport, and nitrogen transport. These examples show that Thévenin's theorem could be a useful tool for upscaling models of interconnected ecohydrological and biogeochemical systems. It is also possible to investigate how disruptions in micro-scale connectivity can affect macro-scale processes. The utility of the Thévenin's theorem in environmental sciences is somewhat limited, because not all processes can be represented as linear electrical circuits. However, where it is applicable, it provides an inherently scalable and quantitative framework for describing ecohydrological connectivity

Understanding ecohydrological connectivity in savannas: a system dynamics modelling approach

Ecohydrological connectivity is a system level property that results from the linkages in the networks of water transport through ecosystems, by which feedbacks and other emergent system behaviours may be generated. We created a system dynamics model that represents primary ecohydrological networks to examine how connectivity between ecosystem components impacts ecosystem processes. Here, we focused on the savanna ecosystems, although the analyses may be expanded to other ecosystem types in the future. To create the model, a set of differential equations representing ecohydrological processes was programmed into the dynamic solver Vensim. Stocks of water storage (e.g. atmospheric and soil moisture) were linked by flows [e.g. precipitation and evapotranspiration (ET)] that were in turn dynamically controlled by the amount of water stored. Precipitation was forced stochastically, and soil moisture and potential ET controlled actual ET. The model produced extended, probabilistic time series of stocks and flows, including precipitation, soil moisture, runoff, transpiration, and groundwater recharge. It was used to describe the behaviour of several previously studied savanna ecosystems in North America and Africa. The model successfully reproduced seasonal patterns of soil moisture dynamics and ET at the California site. It also demonstrated more complex, system level behaviours, such as multiyear persistence of drought and synergistic or antagonistic responses to disconnection of system components. Future improvements to the model will focus on capturing other important aspects of long-term system behaviour, such as changes in physiology or phenology, and spatial heterogeneity, such as the patchwork nature of savannas. Copyright (C) 2011 John Wiley & Sons, Ltd.Keywords: Soil moisture dynamics, Evapotranspiration, Resilience, System dynamics, Feedbacks, Cross-scale interactions, DisturbanceKeywords: Soil moisture dynamics, Evapotranspiration, Resilience, System dynamics, Feedbacks, Cross-scale interactions, Disturbanc