Stability features of steady-state solutions for a diode with electron and ion counter-streams

Stability features of steady-state solutions for a diode with counter-streaming electron and ion flows are studied. For this purpose, the time-dependent problem for an exponential potential perturbation with complex frequency is considered. By linearization of the Poisson equation and electron and ion densities integrodifferential equation for the potential perturbation amplitude is derived. In the case of uniform unperturbed potential distribution an explicit solution of this equation is obtained. Eigen modes of the perturbation are studied. The limiting value of the diode length above which steady state solutions in question are unstable is found. The obtained analytical Eigen modes coincide with the result of numerical simulation of the potential perturbation evolution.

Microalgae Growth Inhibition-Based Reservoirs Water Quality Assessment to Identify Ecotoxicological Risks

This work intended to assess the adaptability of bioassay with Raphidocelis subcapitata to be used as a complement to the water quality assessment parameters of reservoirs imposed by the European Water Framework Directive (WFD). Thus, water samples of Portuguese reservoirs (Miranda, Pocinho, Aguieira, and Alqueva) were analyzed in three sampling periods (spring and autumn 2019, and spring 2020). A physical and chemical report of waters was also performed. R. subcapitata assay proved to be sensitive, indicating the presence of a potential perturbation that was not always associated with chemical analysis performed. In general, in the spring samplings, the water samples showed more disturbances to R. subcapitata, which in some situations may be associated with the higher content of nutrients and metals. Microalgae assay can be an effective complementary tool to indicate the ecotoxicological potential since they responded quickly to all sample components of water samples, in a wide-ranging variety of water conditions (different sites in several reservoirs). High similarities between the final ecotoxicological and the ecological potentials, according to the WFD parameters, were detected. The ecotoxicological approach based on our results allowed to confirm that bioassays with R. subcapitata are suitable and sensible to detect perturbations.

Airborne particulate matters induce thrombopoiesis from megakaryocytes through regulating mitochondrial oxidative phosphorylation

Background Although airborne fine particulate matter (PM) pollution has been demonstrated as an independent risk factor for pulmonary and cardiovascular diseases, their currently-available toxicological data is still far from sufficient to explain the cause-and-effect. Platelets can regulate a variety of physiological and pathological processes, and the epidemiological study has indicated a positive association between PM exposure and the increased number of circulative platelets. As one of the target organs for PM pollution, the lung has been found to be involved in the storage of platelet progenitor cells (i.e. megakaryocytes) and thrombopoiesis. Whether PM exposure influences thrombopoiesis or not is thus explored in the present study by investigating the differentiation of megakaryocytes upon PM treatment. Results The results showed that PM exposure promoted the thrombopoiesis in an exposure concentration-dependent manner. PM exposure induced the megakaryocytic maturation and development by causing cell morphological changes, occurrence of DNA ploidy, and alteration in the expressions of biomarkers for platelet formation. The proteomics assay demonstrated that the main metabolic pathway regulating PM-incurred alteration of megakaryocytic maturation and thrombopoiesis was the mitochondrial oxidative phosphorylation (OXPHOS) process. Furthermore, airborne PM sample promoted-thrombopoiesis from megakaryocytes was related to particle size, but independent of sampling filters. Conclusion The findings for the first time unveil the potential perturbation of haze exposure in thrombopoiesis from megakaryocytes by regulating mitochondrial OXPHOS. The substantial evidence on haze particle-incurred hematotoxicity obtained herein provided new insights for assessing the hazardous health risks from PM pollution.

Allostasis Machines: a model for understanding internal states and technological environments

In the present paper we will approach enactivism from the perspective of internal regulation: while the environment shapes the organism, it is also true that organisms have complex internal states with regulatory machinery with a set of continuous phenotype-environment interactions. The aim of the present paper is to provide a visual means to analyze these interactions in individuals and computational agents alike. An essential component of our approach is the representation of continuous internal states through the usage of the single continuous indicator we call an Allostasis Machine (AM). Consequently, we consider potential perturbation regimes for both naturalistic and virtual environments: within the naturalistic cases, it is possible to observe the effects of perturbations in isolation, or as overlapping, multiplicative events. In virtual cases, we can observe perturbations as the outcome of both realistic and fantastical environments. To conclude, we discuss how AMs can be utilized to improve our understanding of both the theoretical basis of embodied interaction and the dynamic regulation of complex psychophysiological states.

Spectral theory of first-order systems: From crystals to Dirac operators

Let [Formula: see text] be a constant coefficient first-order partial differential system, where the matrices [Formula: see text] are Hermitian. It is assumed that the homogeneous part is strongly propagative. In the non-homogeneous case it is assumed that the operator is isotropic. The spectral theory of such systems and their potential perturbations is expounded, and a Limiting Absorption Principle is obtained up to thresholds. Special attention is given to a detailed study of the Dirac and Maxwell operators. The estimates of the spectral derivative near the thresholds are based on detailed trace estimates on the slowness surfaces. Two applications of these estimates are presented: • Global spacetime estimates of the associated evolution unitary groups, that are also commonly viewed as decay estimates. In particular, the Dirac and Maxwell systems are explicitly treated. • The finiteness of the eigenvalues (in the spectral gap) of the perturbed Dirac operator is studied, under suitable decay assumptions on the potential perturbation.

Towards a Computational Ecotoxicity Assay

Thousands of anthropogenic chemicals are released into the environment each year, posing potential hazards to human and environmental health. Toxic chemicals may cause a variety of adverse health effects, triggering immediate symptoms or delayed effects over longer periods of time. It is thus crucial to develop methods that can rapidly screen and predict the toxicity of chemicals, to limit the potential harmful impacts of chemical pollutants. Computational methods are being increasingly used in toxicity predictions. Here, the method of molecular docking is assessed for screening potential toxicity of a variety of xenobiotic compounds, including pesticides, pharmaceuticals, pollutants and toxins deriving from the chemical industry. The method predicts the binding energy of the pollutants to a set of carefully selected receptors, under the assumption that toxicity in many cases is related to interference with biochemical pathways. The strength of the applied method lies in its rapid generation of interaction maps between potential toxins and the targeted enzymes, which could quickly yield molecularlevel information and insight into potential perturbation pathways, aiding in the prioritisation of chemicals for further tests. Two scoring functions are compared, Autodock Vina and the machine-learning scoring function RF-Score-VS. The results are promising, though hampered by the accuracy of the scoring functions. The strengths and weaknesses of the docking protocol are discussed, as well as future directions for improving the accuracy for the purpose of toxicity predictions.<br>

Towards a Computational Ecotoxicity Assay

Thousands of anthropogenic chemicals are released into the environment each year, posing potential hazards to human and environmental health. Toxic chemicals may cause a variety of adverse health effects, triggering immediate symptoms or delayed effects over longer periods of time. It is thus crucial to develop methods that can rapidly screen and predict the toxicity of chemicals, to limit the potential harmful impacts of chemical pollutants. Computational methods are being increasingly used in toxicity predictions. Here, the method of molecular docking is assessed for screening potential toxicity of a variety of xenobiotic compounds, including pesticides, pharmaceuticals, pollutants and toxins deriving from the chemical industry. The method predicts the binding energy of the pollutants to a set of carefully selected receptors, under the assumption that toxicity in many cases is related to interference with biochemical pathways. The strength of the applied method lies in its rapid generation of interaction maps between potential toxins and the targeted enzymes, which could quickly yield molecularlevel information and insight into potential perturbation pathways, aiding in the prioritisation of chemicals for further tests. Two scoring functions are compared, Autodock Vina and the machine-learning scoring function RF-Score-VS. The results are promising, though hampered by the accuracy of the scoring functions. The strengths and weaknesses of the docking protocol are discussed, as well as future directions for improving the accuracy for the purpose of toxicity predictions.<br>

Realistic modeling of ephaptic fields in the human brain

Several decades of research suggest that weak electric fields may influence neural processing, including those induced by neuronal activity and recently proposed as substrate for a potential new cellular communication system, i.e., ephaptic transmission. Here we aim to map ephaptic activity in the human brain and explore its trajectory during aging by characterizing the macroscopic electric field generated by cortical dipoles using realistic finite element modeling. We find that modeled endogenous field magnitudes are comparable to those in measurements of weak but functionally relevant endogenous fields and to those generated by noninvasive transcranial brain stimulation, therefore possibly able to modulate neuronal activity. Then, to evaluate the role of self-generated ephaptic fields in the human cortex, we adapt an interaction approximation that considers the relative orientation of neuron and field to derive the membrane potential perturbation in pyramidal cells. Building on this, we define a simplified metric (EMOD1) that weights dipole coupling as a function of distance and relative orientation between emitter and receiver and evaluate it in a sample of 401 realistic human brain models from subjects aged 16-83. Results reveal that ephaptic modulation follows gyrification patterns in the human brain, and significantly decreases with age, with higher involvement of sensorimotor regions and medial brain structures. By providing the means for fast and direct interaction between neurons, ephaptic modulation likely contributes to the complexity of human function for cognition and behavior, and its modification across the lifespan and in response to pathology.