In-situ temperatures and thermal properties of the East Siberian Arctic shelf sediments: Key input for understanding the dynamics of subsea permafrost

Significant reserves of methane (CH4) are held in the Arctic shelf, but the release of CH4 to the overlying ocean and, subsequently, to the atmosphere has been believed to be restricted by impermeable subsea permafrost, which has sealed the upper sediment layers for thousands of years. Our studies demonstrate progressive degradation of subsea permafrost which controls the scales of CH4 release from the sediment into the water-atmospheric system. Thus, new knowledge about the thermal state of subsea permafrost is crucial for better understanding of the permafrost -hydrate system and associated CH4 release from the East Siberian Arctic Shelf (ESAS) – the broadest and shallowest shelf in the World Ocean, which contains about 80% of subsea permafrost and giant pools of hydrates. Meanwhile, the ESAS, still presents large knowledge gaps in many aspects, especially with respect to subsea permafrost distribution and physical properties of bottom sediments. New field data show that the ESAS has an unfrozen (ice-free) upper sediment layer, which in-situ temperature is −1.0 to −1.8 °C and 0.6оС above the freezing point. On one hand, these cold temperature patterns may be related to the presence of subsea permafrost, which currently primarily occurs in the part of the ESAS that is shallower than 100 m, while ice-bearing sediments may also exist locally under deeper water in the Laptev Sea. On the other hand, the negative bottom sediment temperatures of −1.8 °C measured on the Laptev Sea continental slope sediments underlying water columns as deep as down to 330 m may result from dissociation of gas hydrates or possibly from dense water cascading down from the shelf. In contrast, data collected on recent expeditions in the northern Laptev shelf, zones of warmer bottom temperatures are coinciding with methane seeps, likely induced by seismic and tectonic activity in the area. These warm temperatures are not seen in the East Siberian Sea area, not even in areas of methane seeps, yet with little seismic activity. The thermal conductivity and heat capacity of bottom sediments recorded in the database of thermal parameters for the ESAS areas mainly depend on their lithification degree (density or porosity), moisture content, and particle size distribution. The thermal conductivity and heat capacity average about 1.0 W/(m·K) and 2900 kJ/(m3·K), with ±20% and ±10% variance, respectively, in all sampled Arctic sediments to a sub-bottom interval of 0–0.5 m

Serial processing in scotopic vision: from upshift to the scotopic band

It has been known for decades that haplorrhine primates and other non-mammalian foveate vertebrates explore visual scenes by making fast eye movements that allow them to shift the image of an object of interest into the fovea. High spatial resolution accommodated by the fovea can be used to scrutinize the object of interest during a period of steady foveal fixation of the object’s image, interrupted only briefly by different types of miniature eye movements, too small to jeopardize the image position within the confines of the fovea. In this dissertation I address a peculiar aspect of the object fixation of macaque monkeys observed under conditions of full darkness. Macaque monkeys exhibit an upward shift of gaze (for short, ‘upshift’) when asked to fixate a tiny fixation spot in an otherwise dark environment. Given the advantages of foveal vision, the upshift that moves the fovea away from the object of interest, the fixation point, must appear paradoxical. The upshift was first described by Snodderly (1987) in rhesus monkeys and rediscovered and investigated in detail by Barash et al. (1998) who studied it in cynomolgus macaques. Barash et al. (1998) demonstrated that the upshift depended solely on the background luminance and not on the contrast between target and background. Barash and coworkers could also show that the upshift increased with training on the fixation and typically started within seconds after turning the background from bright to dark. The view that the upshift was a hitherto undescribed illumination-dependent fixation offset not related to known features of the systems controlling saccades and fixation, was put into a question by Goffart et al. (2006). This group claimed that the upshift is nothing but a luminance dependent disbalance of the saccadic system for the vertical. However, based on this hypothesis, the upshift should be abolished soon after the onset of fixation. To critically test this hypothesis, we carried out a first study in which we trained rhesus monkeys to fixate small targets on the screen. The monkeys fixated a target in two conditions: with bright or dark background. We investigated the time course of the difference between fixation in darkness and fixation in bright conditions that is the actual upshift. We showed that dark-background-dependent upshift persisted during at least during two seconds of fixation. Additionally, the size of the upshift depended on fixation location: fixation in the lower visual field resulted in larger upshifts whereas fixation in the upper visual field demonstrated smaller upshifts. These results clearly indicated that the upshift cannot merely be a consequence of a dysbalanced saccadic system causing hypermetric upward and hypometric downward saccades as both should be corrected within a few milliseconds, ultimately establishing foveal fixation. Anecdotal observations seemed to suggest that the upshift might differ between monkeys. In an attempt to consolidate this impression and, moreover, to identify a cause explaining eventual differences, we embarked on study of a very large sample of 14 monkeys from two species. We tested the monkeys in the same task that we had used in the preceding study. The results were very clear: all monkeys in our sample had upshift and the monkeys lacked systematic horizontal deviation during fixation in darkness. However, the monkeys tested exhibited substantial differences as to the size of the upshift. The monkeys in our large sample differed by the level of ‘habituation’: dark habituated (monkeys that had been previously trained in tasks in full darkness with small bright stimuli) and bright-habituated (monkeys that had been trained in tasks with large bright stimuli without control for full darkness of experimental setup). We showed that the size of the upshift largely reflects the extent to which a monkey is habituated to work in the dark. Dark habituated monkeys with mostly belonged to 2 the group with higher upshift whereas bright habituated monkeys were very likely to demonstrate lower upshift. Species differences (cynomolgus vs. rhesus macaques) were not found. In seeking to explain the upshift, we resorted to the geometry of the rod and cone densities, which constitute a hard bound for the resolution of the percept. Cones peak in the fovea; extrafoveally, cone density decreases as eccentricity increases. Rods are absent in the foveola. On going dorsally from the foveola, rod density increases, until reaching a peak in a location called dorsal rod peak, or rod hotspot (Packer et al., 1989; Wickler and Rakic, 1990; Wickler et al., 1990). We therefore started with the hypothesis that if any retinal location replaces the fovea in scotopic vision, it would be the rod hotspot. We therefore expected that the vertical component of the line of gaze would be distributed bimodally, one mode reflecting the fovea and the other the rod hotspot. However, the results did not corroborate this hypothesis. Upshift height varied a lot, from monkey to monkey, from condition to condition, even within session. Eventually we were led to an alternative hypothesis, that of a scotopic band. We now suggest that at any epoch during scotopic vision there might be a scotopic center, located dorsally to the fovea. The scotopic center replaces the fovea. During fixations, target images are projected on the scotopic center, not on the fovea. Saccadic trajectories show that saccades shift the target’s image directly to the scotopic center. Therefore, not all saccades foveate. Scotopic saccades do not foveate. The relative weight of the scotopic center in the evolution of saccades remains open. In any case, scotopic saccades come with their own sensorimotor transformations, as do scotopic fixations. Scotopic center is only the beginning of the scotopic analogy for high-acuity vision. Unlike the close, tight fovea of photopic vision, the scotopic center moves along a line extending dorsally from immediately dorsal to the fovea. We call this the scotopic band. The presence of the band makes scotopic sensorimotor transformations more complex than photopic because they rely on a parameter – the scotopic band setting, the current location of the scotopic center on the band. Scotopic band is set primarily according to the ambient light, reflected in the laboratory as background luminance. Increasing luminance results in lower upshift, or, equivalently, more ventral setting. However, other factors heavily influence the scotopic setting too. To mention but 2: habituation to darkness increases the upshift, that is, makes the setting more dorsal; and so do also threshold task conditions. Thus, we suggest that ultimately, the scotopic band setting reflects the statistics of the scene and the monkey’s task. The computational needs change gradually, and so do the anatomy (and physiology). Therefore, scotopic band setting is not limited to the two endpoints but occupy the points in between

High-Pressure Synthesis, Synchrotron Single-Crystal XRD and Raman Spectroscopy of Synthetic K–Ba Minerals of Magnetoplumbite, Crichtonite and Hollandite Group Indicatory of Mantle Metasomatism

The paper summarizes the results of an experimental study of the formation of K–Ba high-Ti (and Cr) oxides synthesized in the chromite–rutile/ilmenite–K2CO3/BaCO3–H2O–CO2 systems at 1.8–5.0 GPa. Experiments confirm the conclusion that the formation of K–Ba high-Ti oxides characterizes the most advanced or repeated metasomatic stages in upper mantle peridotites, which lead first to the formation of simple Ti oxides and then to the formation of K–Ba high-Ti and Cr oxides. Relations between the oxides is a function of the activity of the K and Ba components in the fluid. The appearance of priderite corresponds to the highest activity of K in the mineral-forming media. Redledgeite is formed only in the Fe-poor chromite–rutile–H2O–CO2–BaCO3 system, and, in the system with ilmenite, minerals of the magnetoplumbite group preferably crystallize. A direct dependence of the Cr content in oxides on pressure is revealed. Raman spectra of K–Ba high-titanium oxides are presented. The structure of a potassium compound of a magnetoplumbite group with the chemical formula K0.90Ti5.16Cr2.94Fe2.54Mg0.87Al0.22Mn0.30O19 is studied by single-crystal X-ray diffraction using a synchrotron radiation. The obtained data can be used to specify the nomenclature of the magnetoplumbite mineral group

Electrophoretic Effects for Environmental Safety Technologies: Evacuation of Micro-Particle Conglomerations from the Surfaces

The actuality of the problem of contamination of objects by macro-molecular compounds is a growing problem today (especially given the terrible consequences of the pandemic). In fact, macromolecular complexes are mostly located on the surface layers of the surface covered with fine dust. Therefore, the development of technology for the removal of macromolecular components is actually a problem of fine (so we will call it) dust removal. This problem cannot be effectively solved by traditional mechanical removal methods alone, as contaminated objects have a rather complex, not even Euclidian, surface morphology. Therefore, it is important to develop effective technologies based on the use of properties of special configurations of external inhomogeneous electric field and removable components by means of a specially configured inhomogeneous electric field. The paper analyzes modern technologies of fine dust cleaning both mechanically and with the help of external electrical fields under the particular conditions and creation of levitation and electrophoretic motion. It has been found exact solutions of the model, which indicate in favor of the theoretical validity of decontamination technology using electric field with manipulative properties; the conditions of the most effective use of levitation-electrophoretic technology in the tasks of dust cleaning and decontamination, including decontamination of the surface-distributed macromolecular contaminants such as coronaviruses. Index Terms dust pollution dust cleaning levitation electrophoresis macromolecular pollution coronaviru

Micro-mechanical (granular) mixtures for environmental safety technologies

One of the most significant problems that belong to effective use of granular materials GM (for example, in the construction, pharmacological, chemical, agricultural and some other industries, as well as in the technologies of screening against internal radiation) is the difficulty of ensuring their maximum compaction in order to increase the efficiency of their practical application. In this way, we study of the properties of binary granular systems, the dynamics of their compaction and the impact on this process of the ratio of component sizes and partial parameters in order to provide an innovative step in the development of appropriate technologies. To this end, we propose to use the apparatus of Kirkwood-Buff theory in combination with model equations of state, like Carnahan-Starling, together with relevant phenomenological information, which obtained from direct observations. We report theoretically the fundamental possibility of increasing the degree and speed of packaging and at first describe substantiate empirical data in the full range of values of the volume (or molar) fraction