Coevolutionary immune system dynamics driving pathogen speciation

We introduce and analyze a within-host dynamical model of the coevolution between rapidly mutating pathogens and the adaptive immune response. Pathogen mutation and a homeostatic constraint on lymphocytes both play a role in allowing the development of chronic infection, rather than quick pathogen clearance. The dynamics of these chronic infections display emergent structure, including branching patterns corresponding to asexual pathogen speciation, which is fundamentally driven by the coevolutionary interaction. Over time, continued branching creates an increasingly fragile immune system, and leads to the eventual catastrophic loss of immune control.Comment: main article: 16 pages, 5 figures; supporting information: 3 page

Point discharge pulse measurements in atmospheric electricity

Previous methods for estimating the charge transferred to earth by point discharge are reviewed. It is concluded that point discharge on trees may well make a large contribution to this transfer of charge but that no reliable method of measurement has previously been duvised. A laboratory study of the pulsed nature of the point discharge currents produced at metal points and natural points has been made. It is concluded from these measurements that the amplitude and repetition frequency of these current pulses can be used to give the total discharge current. A new method for measuring point discharge currents in trees has now been developed and the apparatus successfully calibrated. This takes the form of a capacitative electrode, attached to a branch at the top of a tree, which detects pulses of point discharge current in the tree. The electrode is connected to an electronic pulse detector which gives a measure of the point discharge current in the tree. Measurements of point discharge currents have been made in two trees over a period of three months in a plantation of conifers in Weardale. The potential gradient and the point discharge current through a metal point were measured outside the plantation over a period of eleven months. The charge transferred to earth by point discharge on one tree in three months was found to be 4.3 x 10(^-4)C whereas for the metal point in the same period the charge transferred was 72 x 10(^-4)C. It is concluded that this difference is a result of the higher potential gradients necessary to initiate point discharge on the tree compared with those for the metal point. The point discharge measurements for two trees, one on the edge and one inside the plantation, are compared and found to be of similar magnitudes. The charge per unit area transferred to earth by point discharge on all the trees in the plantation is estimated to be 270 C km(^-2) yr(^-1)

Geochemistry of the Dome Mine Ankerite Veins: Insights into the Multi-Stage Enrichment of a World-Class Orogenic Gold Deposit

The Dome Mine in the world-class Timmins camp has produced over 16 Moz of gold during its 108 year production history. This gold endowment is the result of multistage enrichment of which the first stage is a set of ankerite veins that extend over 5,400 m in strike and 1,500 m vertically. A deposit wide geochemical study of the Dome ankerite veins was undertaken to characterize their genesis, geochemistry, and role in the deposit mineralization history. Samples and mapping from new and historic mine workings, bulk rock geochemistry, and stable isotope geochemistry were used to constrain the depositional context of the ankerite veins as forming syntectonically from auriferous metamorphic fluids, and provide insights into geochemical controls on vein formation. The δ18O values for dolomite from the ankerite veins show a trend of increasing δ18OVSMOW values from 10.8 to 14.9‰ downdip of the ankerite veins and to the northwest away from the Dome Fault Deformation Zone (DFDZ), which is likely a long-lived fluid conduit. Gold is intimately related to pyrite mineralization with contributions from multiple sources. This was investigated by a suite of high-resolution geochemical techniques including synchrotron-radiation X-ray fluorescence (SR-XRF). Three stages of pyrite growth were identified, each with a distinct gold and trace element fingerprint. These stages of pyrite growth and gold endowment are related to deposit wide fluid events. The application of high-resolution synchrotron techniques to ore deposit studies was developed and evaluated on a number of different types of auriferous samples from across the Timmins gold camp. These applications address the present challenges of today’s global minerals industry by quickly and effectively answering key questions regarding deposit formation and informing exploration strategies and extractive geometallury. This body of work addresses several key questions in the field of orogenic gold regarding fluid sources and key components of multi-stage deposit formation. It reveals the integral role of early carbonate veining and alteration at the Dome mine and that the ore system was fertile for a period of over 20 Ma with variability in gold tenor, trace element contents and redox throughout the deposit history

Optimal vaccination in a stochastic epidemic model of two non-interacting populations

Developing robust, quantitative methods to optimize resource allocations in response to epidemics has the potential to save lives and minimize health care costs. In this paper, we develop and apply a computationally efficient algorithm that enables us to calculate the complete probability distribution for the final epidemic size in a stochastic Susceptible-Infected-Recovered (SIR) model. Based on these results, we determine the optimal allocations of a limited quantity of vaccine between two non-interacting populations. We compare the stochastic solution to results obtained for the traditional, deterministic SIR model. For intermediate quantities of vaccine, the deterministic model is a poor estimate of the optimal strategy for the more realistic, stochastic case.Comment: 21 pages, 7 figure

Application of multispectral radar and LANDSAT imagery to geologic mapping in death valley

Side-Looking Airborne Radar (SLAR) images, acquired by JPL and Strategic Air Command Systems, and visible and near-infrared LANDSAT imagery were applied to studies of the Quaternary alluvial and evaporite deposits in Death Valley, California. Unprocessed radar imagery revealed considerable variation in microwave backscatter, generally correlated with surface roughness. For Death Valley, LANDSAT imagery is of limited value in discriminating the Quaternary units except for alluvial units distinguishable by presence or absence of desert varnish or evaporite units whose extremely rough surfaces are strongly shadowed. In contrast, radar returns are most strongly dependent on surface roughness, a property more strongly correlated with surficial geology than is surface chemistry

The Suppression of Immune System Disorders by Passive Attrition

Exposure to infectious diseases has an unexpected benefit of inhibiting autoimmune diseases and allergies. This is one of many fundamental fitness tradeoffs associated with immune system architecture. The immune system attacks pathogens, but also may (inappropriately) attack the host. Exposure to pathogens can suppress the deleterious response, at the price of illness and the decay of immunity to previous diseases. This “hygiene hypothesis” has been associated with several possible underlying biological mechanisms. This study focuses on physiological constraints that lead to competition for survival between immune system cell types. Competition maintains a relatively constant total number of cells within each niche. The constraint implies that adding cells conferring new immunity requires loss (passive attrition) of some cells conferring previous immunities. We consider passive attrition as a mechanism to prevent the initial proliferation of autoreactive cells, thus preventing autoimmune disease. We see that this protection is a general property of homeostatic regulation and we look specifically at both the IL-15 and IL-7 regulated niches to make quantitative predictions using a mathematical model. This mathematical model yields insight into the dynamics of the “Hygiene Hypothesis,” and makes quantitative predictions for experiments testing the ability of passive attrition to suppress immune system disorders. The model also makes a prediction of an anti-correlation between prevalence of immune system disorders and passive attrition rates

Detection Methods for Lipopolysaccharides: Past and Present

Lipopolysaccharide (LPS) is the primary component of the outer membrane of Gram‐negativebacteria. LPS aids in protecting bacterial cells, and also defines the unique serogroups used to classify bacteria. Additionally, LPS is an endotoxin and the primary stimulator of innate immune cells in mammals, making it an ideal candidate for early detection of pathogens. However, the majority of methods for detection of LPS focus on detection of the endotoxic component of the molecule, lipid A. Since lipid A is largely conserved among bacterial species and serogroups, these detection approaches are highly nonspecific. Thus, the importance of identifying the O‐polysaccharide antigenic portion of LPS, which confers serogroup specificity, has received a great deal of attention in recent years. However, methods that are highly selective to the O‐antigens are typically less sensitive than those that target the endotoxin. Here we present a history and comparison of the sensitivity of these methods and their value for detecting bacteria in a variety of different sample types

The heterogeneity of public ex situ collections of microorganisms: Empirical evidence about conservation practices, industry spillovers and public goods

Access and use of biodiversity Life science research Genetic resources Institutional analysis Governance a b s t r a c t Public service (ex situ) micro-organism collections serve to secure genetic resources for unforeseen future needs, and importantly, to provide authenticated biomaterials for contemporaneous use in private and public entities and as upstream research materials. Hence, it is important to understand the functioning and strategic decisions of these providers of public good resources. 2 The existing literature tends to use case studies of individual collections. This paper uses a unique worldwide survey of microbial collections to analyse the heterogeneity among culture collections, and to empirically assess the economic and institutional conditions that contribute to this heterogeneity with respect to conservation choice and associated industry spillovers. Results suggest that in the short run publicprivate partnerships may indeed support knowledge accumulation with particularly strong public good properties. It is important to be aware of this strong tie, in order to steer also the long term conservation patrimony into one that offers not only short term usability but also resilience to future unforeseen needs e.g. of emerging crop plagues. # 2013 Elsevier Ltd. All rights reserved. 2 Here we refer to public goods in a general way as goods which are relatively costly to exclude others from using, and, whose consumption by one user does not in a significant way reduce the quantity of the good available for others to use