Investigation of effect of electrode polarity on electrochemistry and magnetohydrodynamics using tertiary current distribution in electroslag remelting process

Transport phenomena including the electromagnetic, concentration of ions, flow, and thermal fields in the electroslag remelting (ESR) process made of slag, electrode, air, mold, and melt pool are computed considering tertiary current distribution. Nernst–Planck equations are solved in the bulk of slag, and faradaic reactions are regarded at the metal–slag interface. Aiming at exploring electrochemical effects on the behavior of the ESR process, the calculated field structures are compared with those obtained using the classical ohmic approach, namely, primary current distribution whereby variations in concentrations of ions and faradaic reactions are ignored. Also, the influence of the earth magnetic field on magnetohydrodynamics in the melt pool and slag is considered. The impact of the polarity of electrode, whether positive, also known as direct current reverse polarity (DCRP), or negative, as known as direct current straight polarity (DCSP), on the transport of oxygen to the ingot of ESR is investigated. The obtained modeling results enabled us to explain the experimental observation of higher oxygen content in DCSP than that of DCRP operated ESR process.

Essential elements of radical pair magnetosensitivity in Drosophila

Many animals use the Earth magnetic field (geoMF) for navigation. The favored mechanism for magnetosensitivity involves a blue-light (BL) activated electron transfer reaction between flavin adenine dinucleotide (FAD) and a chain of tryptophan (Trp) residues within the photoreceptor protein, CRYPTOCHROME (CRY). The spin-state of the resultant radical pair (RP) and hence the concentration of CRY in its active state is influenced by the geoMF. The canonical CRY-centric radical pair mechanism (RPM) does not, however, explain many physiological and behavioural observations. Here, using electrophysiology and behavioural analyses, we assay magnetic field (MF) responses at single neuron and organismal level. We show that the 52 C-terminal (CT) amino acids of CRY, which are missing the FAD binding domain and the Trp chain, are sufficient to facilitate magnetoreception. We also show that increasing intracellular FAD potentiates both BL-induced and MF-dependent effects on the activity mediated by the CT. Additionally, high levels of FAD alone are sufficient to cause BL neuronal sensitivity and, remarkably, potentiation of this response in the co-presence of a MF. These unexpected results reveal the essential components of a primary magnetoreceptor in flies, providing strong evidence that non-canonical (i.e., non-CRY-dependent) RPs can elicit MF responses in cells.

On the UPMSat-2 Attitude Determination and Control Subsystem’s magnetometers integration

In the present work, a method for magnetometer calibration through least squares fitting is presented. This method has been applied over the magnetometer’s data set obtained during the integration tests of the Attitude Determination and Control Subsystem (ADCS) of UPMSat-2. The UPMSat-2 mission is a 50-kg satellite designed and manufactured by the Technical University of Madrid (Universidad Politécnica de Madrid), and finally launched in September 2020. The satellite has three fluxgate magnetometers (one of them experimental) whose calibration is critical to obtain correct measurements to be used by the ADCS. Among several mathematical methods suitable to obtain the calibration parameters, an ordinary least squares fitting algorithm is selected as a first step of the calibration process. The surface estimated is an ellipsoid, surface represented by the magnetometer’s measures of the Earth magnetic field in a point of the space. The calibration elements of the magnetometers are related to the coefficients of the estimated ellipsoid.

GEOMAGNETIC CHANGES AS A RISK FACTOR CAUSING OXIDATIVE STRESS IN HUMAN ERYTHROCYTES

At present impacts exerted by heliogeophysic factors on different living organisms are being examined more and more intensely. Over the last decade, it has been detected that meteorological factors play an important role in formation of adap- tation mechanisms in living systems. Sun and earth interaction is also known to directly influence rheological properties of human blood, both in a healthy body and in case there are chronic non-communicable diseases. Given that, impacts exerted by “cosmic weather” on living organisms, people in particular, are a stimulus to perform profound studies on reactions oc- curring as a response to effects produced by solar and geomagnetic activity, first of all, solar flares and magnetic storms. At present the most widely used approach to determining influences exerted by the Earth magnetic field on biologi- cal systems involves searching for correlations between different parameters of living organisms functioning and geo- magnetic indexes. Our research goal was to assess dependence between enzymatic activity of antioxidant protection system, exemplified by superoxide dismutase (SOD) and catalase, and geomagnetic field disturbances. The research focused on examining blood samples taken from conditionally healthy volunteers living in Nizhniy Nov- gorod region. SOD and catalase activity were determined in blood erythrocytes with spectrophotometry. Geomagnetic dis- turbances force was determined as per planetary Kp-index value. The research established a statistically significant correlation between SOD and catalase activity and a value of geo- magnetic field disturbance; this correlation allows making an indirect assumption that geomagnetic conditions directly in- fluence superoxide radical production in a body. Therefore, a change in superoxide radical production is a way for the geomagnetic field to influence living organisms. Activation of free radical oxidation can make for both occurrence and more intense clinical course of several diseases (espe- cially cardiovascular and neuropsychic ones). So, in future it is advisable to assess reactivity of antioxidant protection sys- tem as a response to geomagnetic fluctuations in case there are pathologic changes in a body.

GEOMAGNETIC CHANGES AS A RISK FACTOR CAUSING OXIDATIVE STRESS IN HUMAN ERYTHROCYTES

At present impacts exerted by heliogeophysic factors on different living organisms are being examined more and more intensely. Over the last decade, it has been detected that meteorological factors play an important role in formation of adap- tation mechanisms in living systems. Sun and earth interaction is also known to directly influence rheological properties of human blood, both in a healthy body and in case there are chronic non-communicable diseases. Given that, impacts exerted by “cosmic weather” on living organisms, people in particular, are a stimulus to perform profound studies on reactions oc- curring as a response to effects produced by solar and geomagnetic activity, first of all, solar flares and magnetic storms. At present the most widely used approach to determining influences exerted by the Earth magnetic field on biologi- cal systems involves searching for correlations between different parameters of living organisms functioning and geo- magnetic indexes. Our research goal was to assess dependence between enzymatic activity of antioxidant protection system, exemplified by superoxide dismutase (SOD) and catalase, and geomagnetic field disturbances. The research focused on examining blood samples taken from conditionally healthy volunteers living in Nizhniy Nov- gorod region. SOD and catalase activity were determined in blood erythrocytes with spectrophotometry. Geomagnetic dis- turbances force was determined as per planetary Kp-index value. The research established a statistically significant correlation between SOD and catalase activity and a value of geo- magnetic field disturbance; this correlation allows making an indirect assumption that geomagnetic conditions directly in- fluence superoxide radical production in a body. Therefore, a change in superoxide radical production is a way for the geomagnetic field to influence living organisms. Activation of free radical oxidation can make for both occurrence and more intense clinical course of several diseases (espe- cially cardiovascular and neuropsychic ones). So, in future it is advisable to assess reactivity of antioxidant protection sys- tem as a response to geomagnetic fluctuations in case there are pathologic changes in a body.

New criteria for selecting reliable Thellier-type paleointensity results from the 1960 Kilauea lava flows, Hawaii

Thellier-type paleointensity experiments associated with partial thermal remanent magnetization checks have been widely used to determine paleointensity values from volcanic and archaeological media. However, previous studies have revealed that a substantial portion of paleointensity results with positive checks for historical lava samples largely fails to predict known Earth magnetic field intensity values. To determine the fidelity of paleointensity values, conventional Thellier-type paleointensity experiments were performed on Kilauea lava flows that erupted in 1960. The positive partial thermal remanent magnetization checks for our results range from 30.28 ± 1.38 µT to 52.94 ± 1.89 µT. This strongly indicates that conventional paleointensity checks cannot guarantee the fidelity of paleointensity results, especially when the unblocking temperatures for the newly formed magnetic particles are higher than the treatment temperature. Therefore, in this study, to check for thermal alteration during heating, the temperature dependence of the hysteresis parameter measured at room temperature for the thermally treated samples was also measured. Our new results show that nearly all biased paleointensity values correspond to a ratio of the coercivity of remanence to the magnetic coercivity of > 3 and a chemical alteration index > ~ 10%, which indicates the strong effect of the domain state and thermal alteration on the fidelity of the paleointensity results. Our study provides feasible criteria to further improve the fidelity of paleointensity estimations.

A Numerical Study on the Influence of an Axial Magnetic Field (AMF) on Vacuum Arc Remelting (VAR) Process

A comprehensive numerical model is proposed to study the influence of an axial magnetic field (AMF) on the solidification behavior of a Titanium-based (Ti–6Al–4V) vacuum arc remelting (VAR) ingot. Both static and time-varying AMF are examined. The proposed 2D axisymmetric swirl model includes calculating electromagnetic and thermal fields in the entire system composed of the electrode, vacuum plasma, ingot, and mold. A combination of vector potential formulation and induction equation is proposed to model the electromagnetic field accurately. Calculations of the flow in the melt pool and solidification of the ingot are also carried out. All governing equations are presented in cylindrical coordinate. The presence of a weak AMF, such as the earth magnetic field, can dramatically influence the flow pattern in the melt pool. The “Electro-vortex flow” is predicted ignoring AMF or in the presence of a time-varying AMF. However, the flow pattern is “Ekman pumping” in the presence of a static AMF. The amount of side-arcing has no influence on the pool depth in the presence of an AMF. Modeling results are validated against experiments.