Proposed Model of the Giant Thermal Hall Effect in Two-Dimensional Superconductors: An Extension to the Superconducting Fluctuation Regime.

We extend the thermodynamic approach for the description of the thermal Hall effect in two-dimensional superconductors above the critical temperature, where fluctuation Cooper pairs contribute to the conductivity, as well as in disordered normal metals where the particle-particle channel is important. We express the Hall heat conductivity in terms of the product of temperature derivatives of the chemical potential and of the magnetization of the system. Based on this general expression, we derive the analytical formalism that qualitatively reproduces the superlinear increase of the thermal Hall conductivity with the decrease of temperature observed in a large variety of experimentally studied systems [Grissonnanche et al., Nature (London) 571, 376 (2019)NATUAS0028-083610.1038/s41586-019-1375-0]. We also predict a nonmonotonic behavior of the thermal Hall conductivity in the regime of quantum fluctuations, in the vicinity of the second critical field and at very low temperatures.

The Nernst effect in Corbino geometry.

We study the manifestation of the Nernst effect in the Corbino disk subjected to the normal external magnetic field and to the radial temperature gradient. The Corbino geometry offers a precious opportunity for the direct measurement of the magnetization currents that are masked by kinetic contributions to the Nernst current in the conventional geometry. The magnetization currents, also referred to as the edge currents, are independent on the conductivity of the sample which is why they can be conveniently described within the thermodynamic approach. They can be related to the Landau thermodynamic potential for an infinite system. We demonstrate that the observable manifestation of this, purely thermodynamic, Nernst effect consists in the strong oscillations of the magnetic field measured in the center of the disk as a function of the external field. The oscillations depend on the temperature difference at the edges of the disk. Dirac fermions and 2D electrons with a parabolic spectrum are characterized by oscillations of different phase and frequency. We predict qualitatively different power dependencies of the magnitude of the Nernst signal on the chemical potential for normal and Dirac carriers.

Entropy spikes as a signature of Lifshitz transitions in the Dirac materials.

We demonstrate theoretically that the characteristic feature of a 2D system undergoing N consequent Lifshitz topological transitions is the occurrence of spikes of entropy per particle s of a magnitude ±ln2/(J - 1/2) with 2 ≤ J ≤ N at low temperatures. We derive a general expression for s as a function of chemical potential, temperature and gap magnitude for the gapped Dirac materials. Inside the smallest gap, the dependence of s on the chemical potential exhibits a dip-and-peak structure in the temperature vicinity of the Dirac point. The spikes of the entropy per particles can be considered as a signature of the Dirac materials. These distinctive characteristics of gapped Dirac materials can be detected in transport experiments where the temperature is modulated in gated structures.

Effect of boundary conditions on the character of ambipolar diffusion in electrolytes.

We discuss the details of ambipolar relaxation of the electric field in liquid asymmetric electrolytes to its stationary value. It is demonstrated that the account for finite boundary conditions modifies the existing concepts of this diffusion process. In particular, we succeeded to suggest a qualitatively correct explanation of the observed distribution of the electric fields over the bulk of the cuvette and its nonmonotonic behavior in measurements on the finite-size cuvette. We analyze the conditions of such an anomaly at the intermediate stages of the relaxation process.

[Event-related synchronization/desynhronization during processing of target, no target and unknown visually presented words].

The aim of this investigation is to study neurophysiologic mechanisms of processing of relevant words and unknown words. Event-related synchronization/desynchronization during categorization of three types of stimuli (known targets, known no targets and unknown words) was examined. The main difference between known targets and unknown stimuli was revealed in the thetal and theta2 bands at the early stage after stimuli onset (150-300 ms) and in the delta band (400-700 ms). In the late time window at about 800-1500 ms thetal ERS in response to the target stimuli was smaller than to other stimuli, but theta2 and alpha ERD in response to the target stimuli was larger than to known nontarget words.

Scale invariance and universality in a cold gas of indirect excitons.

We address, theoretically, the puzzling similarity observed in the thermodynamic behavior of independent clouds of cold dipolar excitons in coupled semiconductor quantum wells. We argue that the condensation of self-trapped exciton gas starts at the same critical temperature in all traps due to the specific scaling rule. As a consequence of the reduced dimensionality of the system, the scaling parameters appear to be insensitive to disorder.

[EEG coherence analysis in depressive disorders and its possible use in clinical practice: a literature review].

Recent reviews and meta-analyses of clinical data have revealed that there is a clear need in objective biomarkers of mental disorders and, in particular, of depression. There is a lot of evidence that EEG coherence can be an important marker of depressive disorders, and can predict response to different antidepressants. The most consistent finding is a decrease of frontal interhemispheric EEG coherence which is observed for most disorders related to depression. Methodological issues are discussed with a particular emphasis on use of statistical classifiers and on coupling EEG coherence with other methods of EEG analysis.

Seebeck effect in electrolytes.

We study Seebeck effect in liquid electrolytes, starting from its simple neutral analog--thermodiffusion (so-called Ludwig-Soret or Soret effect). It is observed that when two or more subsystems of mobile particles are subjected to the temperature gradient, various types of them respond to it differently. In the case when these fractions, with different mobility parameters (Soret coefficients), are oppositely charged (a case typical for electrolytes), the nonhomogeneous internal electric field is generated. The latter field prevents these fractions from space separation and determines the intensity of the appearing Seebeck effect.

[Perception of consonant and dissonant chords: changes in the power of the EEG evoked activity].

Human perception of dissonant and consonant chords was studied by analyzing brain evoked activity. It was found that the perception of dissonant chords was accompanied by activation of the right frontal lobe, which controls negative emotions. Consonant chords activated the left frontal region, which controls positive emotions.

Giant Nernst effect due to fluctuating cooper pairs in superconductors.

A theory of the fluctuation-induced Nernst effect is developed for a two-dimensional superconductor in a perpendicular magnetic field. First, we derive a simple phenomenological formula for the Nernst coefficient, which naturally explains the giant Nernst signal due to fluctuating Cooper pairs. The latter signal is shown to be large even far from the transition and may exceed by orders of magnitude the Fermi liquid terms. We also present a complete microscopic calculation of the Nernst coefficient for arbitrary magnetic fields and temperatures, which is based on the Matsubara-Kubo formalism. It is shown that the magnitude and the behavior of the Nernst signal observed experimentally in disordered superconducting films can be well understood on the basis of superconducting fluctuation theory.

Fluctuation spectroscopy of granularity in superconducting structures.

We suggest to use "fluctuation spectroscopy" as a method to detect granularity in a disordered metal close to a superconducting transition. We show that with lowering temperature T the resistance R(T) of a system of relatively large grains initially grows due to the fluctuation suppression of the one-electron tunneling but decreases with further lowering T due to the coherent charge transfer of the fluctuation Cooper pairs. Under certain conditions, such a maximum in R(T) turns out to be sensitive to weak magnetic fields due to a novel Maki-Thompson-type mechanism.

Macroscopic quantum tunneling in "small" Josephson junctions in a magnetic field.

We study the phenomenon of macroscopic quantum tunneling (MQT) in small Josephson junctions (JJ) with an externally applied magnetic field. The latter results in the appearance of the Fraunhofer type modulation of the current density along the barrier. The problem of MQT for a pointlike JJ is reduced to the motion of the quantum particle in the washboard potential. In the case of a finite size JJ under consideration, this problem corresponds to a MQT in a potential which itself, besides the phase, depends on space variables. The general expression for the crossover temperature T0 between thermally activated and macroscopic quantum tunneling regimes and the escaping time tau(esc) have been calculated.

Effects of alexithymia on the activity of the anterior and posterior areas of the cortex of the right hemisphere in positive and negative emotional activation.

The aim of the present work was to assess the effects of alexithymia (a psychoemotional disorder associated with difficulties in identifying and describing personal feelings) on regional activity in the cerebral cortex during positive and negative emotional activation in a non-clinical set of subjects. EEG (62-channel) recordings were made during presentation of special emotional video clips to alexithymics (17 subjects) and controls (27 subjects). Alexithymia was found to influence EEG activity in the theta-2, alpha-1, and alpha-2 ranges; alexithymics showed greater reactivity in the anterior and/or posterior areas of the cortex of the right hemisphere in all frequency ranges during watching of both positive and negative clips. The similarity of the responses of alexithymics in conditions of positive and negative emotional activation identifies the increase in emotional reactivity, independent of the sign of the incoming emotional information, as non-specific. This phenomenon may provide evidence of the need for recruiting additional cognitive resources for identifying emotional feelings in relation to the impairments of the symbolic perception of emotional information seen in alexithymics observed here.

[Alexithymia impact on EEG activity of anterior and posterior regions of the right hemisphere while experiencing positive and negative emotions].

The present study was aimed to assess the influence of alexithymia (an emotional disorder associated with difficulties in identification and describing personal feelings) on regional activity while experiencing positive or negative emotional activation. The 62-channels EEG was recorded in non-alexithymic (n = 27) and alexithymic (n = 17) subjects viewing emotional film clips. Effects of alexithymia were found in the upper theta, low and upper alpha frequency bands; for all the bands the alexithymics exhibited greater reactivity of the right hemisphere, suggesting enhanced avoidance motivational tendencies, negative effect and autonomic arousal. The present phenomenon suggests engagement of additional cognitive resources in identification of emotional feelings. Such a 'cognitive effort' can be a result of impaired referential links and deficit of symbolic processing of emotions.

Effect of vortex-antivortex fluctuations on the heat capacity of a type-II superconducting film.

The small size vortex-antivortex pairs proliferation in a type-II superconducting film is considered below T(c). The corresponding contribution to the free energy is calculated. It is shown that these fluctuations give the main temperature dependent contribution to the heat capacity of the superconducting film in the sufficiently large interval of temperatures below the transition point.

Analysis of evoked EEG synchronization and desynchronization in conditions of emotional activation in humans: temporal and topographic characteristics.

Studies in 20 healthy right-handed subjects analyzed evoked EEG synchronization and desynchronization in the delta, theta1, theta2, alpha1, alpha2, beta1, beta2, beta3, and gamma ranges in response to sequential presentation of stimuli from the International Affective Picture System (IAPS) with low, medium, and high emotional activation impact. Each signal presentation was accompanied by subjective scaling of the extent of its emotional impact. EEG traces were recorded in 62 channels as signals were presented. These experiments showed that the degree of emotional impact of the signal was significantly associated with increases in evoked synchronization in the delta, theta1, theta2, beta1, beta3, and gamma ranges and with the effects of combined changes in evoked synchronization and desynchronization in the alpha2 frequency range. The interhemisphere distribution of evoked changes in power provided evidence that not only the posterior areas of the right hemisphere were involved in analyzing the emotional significance of images, as indicated by changes in evoked theta1 and theta2 synchronization and alpha2 desynchronization, but also the anterior areas of the left hemisphere, as indicated by changes in evoked theta2 synchronization. From the standpoint of affective chronometry, the earliest discrimination of the emotional content of stimuli, regardless of the sign of the emotion, occurred in the lower theta range and was seen at 0-600 msec after the start of stimulus presentation. This process was delayed 600-1000 msec in the theta2, alpha2, and gamma ranges.

[Event-related synchronization and desynchronization of EEG during appraisal of threatening and pleasant visual stimuli in high anxious subjects]. / Analiz vyzvannoi sinkhronizatsii i desinkhronizatsii EEG pri vospriiatii ugrozhaiushchei i polozhitel'noi émotsional'noi informatsii: vliianie faktora lichnostnoi trevozhnosti.

The 62-channel EEG was recorded while low (LA, n = 18) and high (HA, n = 18) trait-anxious subjects viewed sequentially presented neutral, threatening and pleasant IAPS stimuli. Event-related desynchronization (ERD) and synchronization (ERS) were studied in the delta, theta1, theta2, alpha1, alpha2, beta1, beta2, beta3, and gamma frequency bands. Between-group differences, related to stimulus emotionality, were linked to theta1 and theta2 bands. In the low theta at prefrontal sites in the test period of 100-700 ms after stimulus onset HA exhibited relative predominance of the left hemisphere in response to both threatening and pleasant stimuli, whereas LA yielded larger right than left hemisphere activity in response to all the three stimulus categories. In the upper theta band between group differences were associated with posterior cortical regions and the test period of 0-1000 ms after stimulus onset: HA exhibited the largest ERS to threatening, whereas LA prompted the largest ERS to pleasant stimuli. Finally, according to the ERD data, in the alpha1 band HA participants in comparison with LA revealed enhanced left hemisphere activation in response to all the stimulus categories. It is suggested that as it is indexed by theta-ERS relative predominance of the left hemisphere at prefrontal sites along with the largest bilateral activity of posterior cortical regions (i.e., enhanced higher order visual processing) to threatening stimuli could form the basis for general bias towards threatening information in HA at the very early stages of emotional processing.

[Analysis of elicited EEG synchronization and desynchronization in emotional activation: temporal and topographic characteristics]. / Analiz vyzvannoi sinkhronizatsii i desinkhronizatsii EEG pri émotsional'noi aktivatsii u cheloveka: vremennye i topograficheskie kharakteristiki.

Event-related synchronization (ERS) and desynchronization (ERD) in delta, theta1, theta2, alpha1, alpha2, beta1, beta2, beta3, and gamma were measured in 20 healthy right-handed subjects in response to IAPS stimuli with low, moderate, and high arousal reactions. The 62-channel EEG was simultaneously recorded while subjects viewed sequentially presented pictures and subjectively rated them after each presentation. The results show that emotionally loaded stimuli induced higher ERS in the delta, theta1, theta2, beta1, beta3, and gamma bands along with combined ERD and ERS effects in alpha2 band. As to hemispheric asymmetries, the effects of emotional arousal were restricted not only to right parietal (theta1 and theta2 ERS, alpha2 ERD) but also to left frontal (theta2 ERS) regions. In terms of affective chronometry, lower theta was the first to catch the affective salience of incoming stimuli (time window 0-600 ms after the stimulus input). For theta2, alpha2, and gamma bands this process was delayed to 600-1000 ms.

Disruption of early event-related theta synchronization of human EEG in alexithymics viewing affective pictures.

The 62-channel EEG was recorded while control non-alexithymic (n=21) and alexithymic (n=20) participants viewed sequentially presented neutral, pleasant and unpleasant pictures and subjectively rated them after each presentation. The event-related synchronization (ERS) to these stimuli was assessed in the theta-1 (4-6 Hz) and theta-2 (6-8 Hz) frequency bands. The obtained findings indicate that alexithymia influences perception of only emotional stimuli. Over anterior cortical regions alexithymia vs. control individuals in response to both pleasant and unpleasant stimuli manifested decreased left hemisphere ERS in the early test period of 0-200 ms along with enhanced ERS in response to negative vs. positive and neutral stimuli in the right hemisphere at 200-600 ms after stimulus onset. The findings provide the first EEG evidence that alexithymia construct, associated with a cognitive deficit in initial evaluation of emotion, is indexed by disrupted early frontal synchronization in the upper theta band that can be best interpreted to reflect disregulation during appraisal of emotional stimuli.

[Effect of alexithymia on the event-related theta-synchronization of human EEG during reception of emotional visual stimuli]. / Vliianie aleksitimii na vyzvannuiu sinkhronizatsiiu teta-ritmov EEG cheloveka pri vospriiatii émotsional'nykh zritel'nykh stimulov.

The 62-channel EEG was recorded while control non-alexithymic (n = 21) and alexithymic (n = 20) participants viewed sequentially presented neutral, pleasant and unpleasant pictures and subjectively rated them after each presentation. The event-related synchronization (ERS) to these stimuli was assessed in the theta-1 (4-6 Hr) and theta-2 (6-8 Hz) frequency bands. The obtained findings indicate that alexithymia influences perception of only emotional stimuli. In the upper theta over anterior cortical regions alexithymia vs control individuals in response to both pleasant and unpleasant stimuli manifested decreased left hemisphere ERS in the early test period of 0-200 ms along with enhanced ERS in response to negative vs positive and neutral stimuli in the right hemisphere at 200-600 ms after stimulus onset. The findings provide the first EEG evidence that alexithymia construct, associated with a cognitive deficit in initial evaluation of emotion, is indexed by disrupted early frontal synchronization in the upper theta band that can be best interpreted to reflect disregulation during appraisal of emotional stimuli.