Algorithms of causal inference for the analysis of effective connectivity among brain regions

In recent years, powerful general algorithms of causal inference have been developed. In particular, in the framework of Pearl’s causality, algorithms of inductive causation (IC and IC*) provide a procedure to determine which causal connections among nodes in a network can be inferred from empirical observations even in the presence of latent variables, indicating the limits of what can be learned without active manipulation of the system. These algorithms can in principle become important complements to established techniques such as Granger causality and Dynamic Causal Modeling (DCM) to analyze causal influences (effective connectivity) among brain regions. However, their application to dynamic processes has not been yet examined. Here we study how to apply these algorithms to time-varying signals such as electrophysiological or neuroimaging signals. We propose a new algorithm which combines the basic principles of the previous algorithms with Granger causality to obtain a representation of the causal relations suited to dynamic processes. Furthermore, we use graphical criteria to predict dynamic statistical dependencies between the signals from the causal structure. We show how some problems for causal inference from neural signals (e.g., measurement noise, hemodynamic responses, and time aggregation) can be understood in a general graphical approach. Focusing on the effect of spatial aggregation, we show that when causal inference is performed at a coarser scale than the one at which the neural sources interact, results strongly depend on the degree of integration of the neural sources aggregated in the signals, and thus characterize more the intra-areal properties than the interactions among regions. We finally discuss how the explicit consideration of latent processes contributes to understand Granger causality and DCM as well as to distinguish functional and effective connectivity

Family of fourth-order optimal classes for solving multiple-root nonlinear equations

[EN] We present a new iterative procedure for solving nonlinear equations with multiple roots with high efficiency. Starting from the arithmetic mean of Newton's and Chebysev's methods, we generate a two-step scheme using weight functions, resulting in a family of iterative methods that satisfies the Kung and Traub conjecture, yielding an optimal family for different choices of weight function. We have performed an in-depth analysis of the stability of the family members, in order to select those members with the highest stability for application in solving mathematical chemistry problems. We show the good characteristics of the selected methods by applying them on four relevant chemical problems.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This research was partially supported by Grant PGC2018-095896-B-C22, funded by MCIN/AEI/10.13039/5011000113033 by "ERDF A way of making Europe", European Union; and by the internal research project ADMIREN of Universidad Internacional de La Rioja (UNIR).Chicharro, FI.; Garrido-Saez, N.; Jerezano, JH.; Pérez-Palau, D. (2023). Family of fourth-order optimal classes for solving multiple-root nonlinear equations. Journal of Mathematical Chemistry. 61(4):736-760. https://doi.org/10.1007/s10910-022-01429-573676061

Correlation of degree of EVA crosslinking with formation and discharge of acetic acid in PV modules

Ethylene vinyl-acetate (EVA) encapsulated crystalline silicon PV modules see encapsulant related degradation such as the hydrolysis of EVA which leads to generation of acetic acid that corrodes cells and cell metallisation. The formation and discharge of acetic acid in PV modules during an extended damp-heat test are studied in this work in dependence of the EVA crosslinking degree. To achieve different degrees of EVA encapsulation, mini-modules were laminated under different curing temperatures. The thermogravimetric analysis (TGA) is used to estimate the vinyl acetate (VA) content of the EVA before and after damp-heat ageing, from which the formation of acetic acid is evaluated. The net accumulation of acetic acid within modules is evaluated by corrosion induced power losses. Results show mini-modules with highly cross-linked EVA form less acetic acid under damp-heat stresses, however, accumulated the highest amount of acetic acid leading to the most severe corrosion. Therefore, highly cross-linked EVA is not favoured in terms of long-term degradation due to DH stresses as it may trap the generated acetic acid within modul

Risk factors for visceral leishmaniasis in a new epidemic site in Amhara Region, Ethiopia

We conducted a case-control study to evaluate risk factors for visceral leishmaniasis during an epidemic in a previously unaffected district of Ethiopia. We also collected blood and bone marrow specimens from dogs in the outbreak villages. In multivariable analyses of 171 matched case-control pairs, dog ownership, sleeping under an acacia tree during the day, and habitually sleeping outside at night were associated with significantly increased risk. Specimens from 7 (3.8%) dogs were positive by immunofluorescent antibody test (IFAT) and both enzyme-linked immunosorbent assays (ELISAs), whereas Leishmania DNA was detected in 5 (2.8%) bone marrow aspirates (from 3 seropositive and 2 seronegative dogs). Insecticide-treated nets may only protect a portion of those at risk. Further research on the vectors, the role of the dog in the transmission cycle, and the effect of candidate interventions are needed to design the best strategy for control

Development of adhesive and cohesive failures in EVA-backsheet structures in environmental testing

The development of adhesive and cohesive failures at the EVA-backsheet interface under different damp-heat (DH) testing condition is investigated in this paper. The adhesive and cohesive failures are classified by the surface roughness of the peeled off backsheet strips. Different DH testing condition leads to different dominating failure modes. The adhesive failure is the main failure mode at lower testing temperature, which has been masked by the mixed failure mode at the higher testing temperatures due to the different temperature acceleration factor of the two processes. Development of accelerated environmental testing protocol requires the failure mode analysis to ensure the target failure mode or degradation mechanism is accelerated and not masked by any other processes

Water vapour transmission rate of Ethylene Vinyl Acetate (EVA): Encapsulant with different curing levels

Water vapour transmission rate of EVA sheets with different curing levels is investigated under a various temperature and relative humidity levels. The gravimetric cup method is used to measure the transmission rate. EVA samples’ thermal and structural properties are measured and results confirm that the curing level does not affect material VAc contents or crystallinity, though their degrees of crosslinking are significantly different. For the EVA studied in this work, lower degrees of crosslinking (gel content 80%. Results also show the water transmission is able to be accelerated by temperature with an activation energy of about 7.5kJ/mol

Realistic adhesion test for photovoltaic modules qualification

Adhesion requirements for photovoltaic modules to ensure reliability are often discussed but not well defined, neither in terms of tests nor actual requirements. This paper presents a new approach for realistic assessment of the adhesion strength, which shows the conventional peel test may not ensure reliability. The test presented reproduces the actual adhesion requirements for fielded modules much more closely than the commonly used peel testing. The test is conducted in-situ during standard damp-heat test at a temperature of 85°C and 85% relative humidity, with the modules installed at an angle to give an appropriate force vector perpendicular to the backsheet. This is achieved by attaching weights to the back of the tested samples which are mounted with a 45° angle on a testing rack in the environmental cabinet. With an appropriate weight holder, this could be done as part of the standard damp-heat cycle during certification and would not involve additional testing time nor significant changes in the commonly used racking. This approach will identify the weakest interface of the multilayer encapsulation system. A number of test-to-fail bespoke samples are tested to set realistic fail criteria. It is shown that the test allows discrimination between different samples and can identify unsuitable production processes