Numerical Schemes for Multivalued Backward Stochastic Differential Systems

We define some approximation schemes for different kinds of generalized backward stochastic differential systems, considered in the Markovian framework. We propose a mixed approximation scheme for a decoupled system of forward reflected SDE and backward stochastic variational inequality. We use an Euler scheme type, combined with Yosida approximation techniques.Comment: 13 page

Dispersion and collapse in stochastic velocity fields on a cylinder

The dynamics of fluid particles on cylindrical manifolds is investigated. The velocity field is obtained by generalizing the isotropic Kraichnan ensemble, and is therefore Gaussian and decorrelated in time. The degree of compressibility is such that when the radius of the cylinder tends to infinity the fluid particles separate in an explosive way. Nevertheless, when the radius is finite the transition probability of the two-particle separation converges to an invariant measure. This behavior is due to the large-scale compressibility generated by the compactification of one dimension of the space

Spatial distribution of Δ14CO2 across Eurasia:measurements from the TROICA-8 expedition

Because fossil fuel derived CO2 is the only source of atmospheric CO2 that is devoid of 14C, atmospheric measurements of Δ14CO2 can be used to constrain fossil fuel emission estimates at local and regional scales. However, at the continental scale, uncertainties in atmospheric transport and other sources of variability in Δ14CO2 may influence the fossil fuel detection capability. We present a set of Δ14CO2 observations from the train-based TROICA-8 expedition across Eurasia in March–April 2004. Local perturbations in Δ14CO2 are caused by easily identifiable sources from nuclear reactors and localized pollution events. The remaining data show an increase in Δ14CO2 from Western Russia (40° E) to Eastern Siberia (120° E), consistent with depletion in 14CO2 caused by fossil fuel CO2 emissions in heavily populated Europe, and gradual dispersion of the fossil fuel plume across Northern Asia. Other trace gas species which may be correlated with fossil fuel CO2 emissions, including carbon monoxide, sulphur hexafluoride, and perchloroethylene, were also measured and the results compared with the Δ14CO2 measurements. The sulphur hexafluoride longitudinal gradient is not significant relative to the measurement uncertainty. Carbon monoxide and perchloroethylene show large-scale trends of enriched values in Western Russia and decreasing values in Eastern Siberia, consistent with fossil fuel emissions, but exhibit significant spatial variability, especially near their primary sources in Western Russia. The clean air Δ14CO2 observations are compared with simulated spatial gradients from the TM5 atmospheric transport model. We show that the change in Δ14CO2 across the TROICA transect is due almost entirely to emissions of fossil fuel CO2, but that the magnitude of this Δ14CO2 gradient is relatively insensitive to modest uncertainties in the fossil fuel flux. In contrast, the Δ14CO2 gradient is more sensitive to the modeled representation of vertical mixing, suggesting that Δ14CO2 may be a useful tracer for training mixing in atmospheric transport models

Patterns in random walks and Brownian motion

We ask if it is possible to find some particular continuous paths of unit length in linear Brownian motion. Beginning with a discrete version of the problem, we derive the asymptotics of the expected waiting time for several interesting patterns. These suggest corresponding results on the existence/non-existence of continuous paths embedded in Brownian motion. With further effort we are able to prove some of these existence and non-existence results by various stochastic analysis arguments. A list of open problems is presented.Comment: 31 pages, 4 figures. This paper is published at http://link.springer.com/chapter/10.1007/978-3-319-18585-9_

Uncertainty analysis using Bayesian Model Averaging: a case study of input variables to energy models and inference to associated uncertainties of energy scenarios

Background Energy models are used to illustrate, calculate and evaluate energy futures under given assumptions. The results of energy models are energy scenarios representing uncertain energy futures. Methods The discussed approach for uncertainty quantification and evaluation is based on Bayesian Model Averaging for input variables to quantitative energy models. If the premise is accepted that the energy model results cannot be less uncertain than the input to energy models, the proposed approach provides a lower bound of associated uncertainty. The evaluation of model-based energy scenario uncertainty in terms of input variable uncertainty departing from a probabilistic assessment is discussed. Results The result is an explicit uncertainty quantification for input variables of energy models based on well-established measure and probability theory. The quantification of uncertainty helps assessing the predictive potential of energy scenarios used and allows an evaluation of possible consequences as promoted by energy scenarios in a highly uncertain economic, environmental, political and social target system. Conclusions If societal decisions are vested in computed model results, it is meaningful to accompany these with an uncertainty assessment. Bayesian Model Averaging (BMA) for input variables of energy models could add to the currently limited tools for uncertainty assessment of model-based energy scenarios

Pan-Eurasian Experiment (PEEX): Towards a holistic understanding of the feedbacks and interactions in the land-Atmosphere-ocean-society continuum in the northern Eurasian region

The northern Eurasian regions and Arctic Ocean will very likely undergo substantial changes during the next decades. The Arctic-boreal natural environments play a crucial role in the global climate via albedo change, carbon sources and sinks as well as atmospheric aerosol production from biogenic volatile organic compounds. Furthermore, it is expected that global trade activities, demographic movement, and use of natural resources will be increasing in the Arctic regions. There is a need for a novel research approach, which not only identifies and tackles the relevant multi-disciplinary research questions, but also is able to make a holistic system analysis of the expected feedbacks. In this paper, we introduce the research agenda of the Pan-Eurasian Experiment (PEEX), a multi-scale, multi-disciplinary and international program started in 2012 (https://www.atm.helsinki.fi/peex/). PEEX sets a research approach by which large-scale research topics are investigated from a system perspective and which aims to fill the key gaps in our understanding of the feedbacks and interactions between the land-Atmosphere-Aquatic-society continuum in the northern Eurasian region. We introduce here the state of the art for the key topics in the PEEX research agenda and present the future prospects of the research, which we see relevant in this context

Synthetic Plasmodium-Like Hemozoin Activates the Immune Response: A Morphology - Function Study

Increasing evidence points to an important role for hemozoin (HZ), the malaria pigment, in the immunopathology related to this infection. However, there is no consensus as to whether HZ exerts its immunostimulatory activity in absence of other parasite or host components. Contamination of native HZ preparations and the lack of a unified protocol to produce crystals that mimic those of Plasmodium HZ (PHZ) are major technical limitants when performing functional studies with HZ. In fact, the most commonly used methods generate a heterogeneous nanocrystalline material. Thus, it is likely that such aggregates do not resemble to PHZ and differ in their inflammatory properties. To address this issue, the present study was designed to establish whether synthetic HZ (sHZ) crystals produced by different methods vary in their morphology and in their ability to activate immune responses. We report a new method of HZ synthesis (the precise aqueous acid-catalyzed method) that yields homogeneous sHZ crystals (Plasmodium-like HZ) which are very similar to PHZ in their size and physicochemical properties. Importantly, these crystals are devoid of protein and DNA contamination. Of interest, structure-function studies revealed that the size and shape of the synthetic crystals influences their ability to activate inflammatory responses (e.g. nitric oxide, chemokine and cytokine mRNA) in vitro and in vivo. In summary, our data confirm that sHZ possesses immunostimulatory properties and underline the importance of verifying by electron microscopy both the morphology and homogeneity of the synthetic crystals to ensure that they closely resemble those of the parasite. Periodic quality control experiments and unification of the method of HZ synthesis are key steps to unravel the role of HZ in malaria immunopathology

Overview: Recent advances in the understanding of the northern Eurasian environments and of the urban air quality in China – a Pan-Eurasian Experiment (PEEX) programme perspective

The Pan-Eurasian Experiment (PEEX) Science Plan, released in 2015, addressed a need for a holistic system understanding and outlined the most urgent research needs for the rapidly changing Arctic-boreal region. Air quality in China, together with the long-range transport of atmospheric pollutants, was also indicated as one of the most crucial topics of the research agenda. These two geographical regions, the northern Eurasian Arctic-boreal region and China, especially the megacities in China, were identified as a “PEEX region”. It is also important to recognize that the PEEX geographical region is an area where science-based policy actions would have significant impacts on the global climate. This paper summarizes results obtained during the last 5 years in the northern Eurasian region, together with recent observations of the air quality in the urban environments in China, in the context of the PEEX programme. The main regions of interest are the Russian Arctic, northern Eurasian boreal forests (Siberia) and peatlands, and the megacities in China. We frame our analysis against research themes introduced in the PEEX Science Plan in 2015. We summarize recent progress towards an enhanced holistic understanding of the land–atmosphere–ocean systems feedbacks. We conclude that although the scientific knowledge in these regions has increased, the new results are in many cases insufficient, and there are still gaps in our understanding of large-scale climate–Earth surface interactions and feedbacks. This arises from limitations in research infrastructures, especially the lack of coordinated, continuous and comprehensive in situ observations of the study region as well as integrative data analyses, hindering a comprehensive system analysis. The fast-changing environment and ecosystem changes driven by climate change, socio-economic activities like the China Silk Road Initiative, and the global trends like urbanization further complicate such analyses. We recognize new topics with an increasing importance in the near future, especially “the enhancing biological sequestration capacity of greenhouse gases into forests and soils to mitigate climate change” and the “socio-economic development to tackle air quality issues”

Neutrophil Paralysis in Plasmodium vivax Malaria

Plasmodium vivax is responsible for approximately 60–80% of the malaria cases in the world, and contributes to significant social and economic instability in the developing countries of Latin America and Asia. The pathogenesis of P. vivax malaria is a consequence of host derived inflammatory mediators. Hence, a better understanding of the mechanisms involved in induction of systemic inflammation during P. vivax malaria is critical for the clinical management and prevention of severe disease. The innate immune receptors recognize Plasmodium sp. and initiate a broad spectrum of host defense mechanisms that mediate resistance to infection. However, the innate immune response is the classic “two-edged sword”, and clinical malaria is associated with high levels of circulating pro-inflammatory cytokines. Our findings show that both monocytes and neutrophils are highly activated during malaria. Monocytes produced high levels of IL-1β, IL-6 and TNF-α during acute malaria. On the other hand, neutrophils were a poor source of cytokines, but displayed an enhanced phagocytic activity and superoxide production. Unexpectedly, we noticed an impaired chemotaxis of neutrophils towards an IL-8 (CXCL8) gradient. We proposed that neutrophil paralysis is in part responsible for the enhanced susceptibility to bacterial infection observed in malaria patients