Dynamics of trophic structure for the epipelagic community in the western Bering Sea

Changes of quantitative composition and trophic structure of the nekton community in the western Bering Sea are considered for the last decades and role of pacific salmons in dynamics of trophic flows is evaluated in dependence on their abundance using the ecosystem model Ecopath. Two models are developed that describe trophic structure of the community in two cases: 1) low biomass of salmons and high biomass of walleye pollock (in 1980s, the year 1986 is analyzed as an example) and 2) decreased pollock biomass and increasing salmon biomass (in 2000s, the year 2006 as an example). Besides, a hypothetical situation is modeled with the salmon biomass multiplied by 1.5 relative to its level in 2006. Significant decrease of pollock abundance between 1980s and 2000s caused twofold reduction of total food consumption by nekton species; the heightened consumption by salmons and squids in the 2000s compensated only a small part of this reduction. However, the tenfold increase of salmons biomass changed their main diets with lowering of the prey trophic level from amphipods and squids to euphausiids, copepods, and pteropods. Now the salmons are the only numerous predator group of the fourth trophic level in the upper pelagic layer of offshore waters in the western Bering Sea. Due to their high trophic plasticity, they can feed by wide range of prey belonged to 2-3rd trophic levels that supplies them by a large amount of food. Even in the modeled case of increasing of the salmons biomass in 1.5 times relative to the level of 2000s, the current level of forage resources is able to support their populations. There is concluded that carrying capacity of the western Bering Sea is excessively sufficient for pacific salmons in periods of their high abundance

Active integrated antennas and arrays with field-effect transistors

Electromagnetic wave generation processes in the hybrid log-periodic microstripe antenna on the dielectric substrate integrated with field-effect transistor are experimentally studied in the frequency range of 6─20 GHz. The possibility of synchronization and power combining in the array consisting of antenna-coupled oscillators placed on the common dielectric substrate is investigated. It is shown that the considerable increasing the generation efficiency and power combining can be obtained by using the external synchronization signal or quasi-optical design of the array

Relaxation of residual stresses in surface-hardened rotating prismatic elements of structures under creep conditions

A method for solving boundary problems of relaxation of residual stresses in a rotating surface-hardened prismatic specimen under high-temperature creep conditions has been developed. The problem models the stress-strain state of a surface-hardened prismatic rod with one end fixed to an infinitely rigid disk rotating at a constant angular velocity. In the first stage, we solve the problem of reconstructing fields of residual stresses and plastic deformations after the hardening procedure, which play the role of the initial stress-strain state, is solved. In the second stage, we address  the problem of relaxation of residual stresses under creep conditions is addressed. A detailed study of the influence of angular velocity on the intensity of residual stress relaxation in different sections along the axial coordinate is carried out for a $10{\times}10{\times}150$ mm prismatic specimen made of EP742 alloy at a temperature of 650$^\circ$C, following ultrasonic mechanical hardening of one of its faces. The analysis of the calculation results revealed that for angular velocities ranging from 1500 rpm to 2500 rpm, a non-trivial effect is observed. The relaxation of residual stresses in more stressed sections experiencing axial tensile stresses due to rotation occurs less intensively than in the “tail” section, where the axial load is zero. The obtained results from this study can be useful in assessing the effectiveness of surface-hardened rotating components under high-temperature creep conditions

Online chemical modeling environment (OCHEM): web platform for data storage, model development and publishing of chemical information

The Online Chemical Modeling Environment is a web-based platform that aims to automate and simplify the typical steps required for QSAR modeling. The platform consists of two major subsystems: the database of experimental measurements and the modeling framework. A user-contributed database contains a set of tools for easy input, search and modification of thousands of records. The OCHEM database is based on the wiki principle and focuses primarily on the quality and verifiability of the data. The database is tightly integrated with the modeling framework, which supports all the steps required to create a predictive model: data search, calculation and selection of a vast variety of molecular descriptors, application of machine learning methods, validation, analysis of the model and assessment of the applicability domain. As compared to other similar systems, OCHEM is not intended to re-implement the existing tools or models but rather to invite the original authors to contribute their results, make them publicly available, share them with other users and to become members of the growing research community. Our intention is to make OCHEM a widely used platform to perform the QSPR/QSAR studies online and share it with other users on the Web. The ultimate goal of OCHEM is collecting all possible chemoinformatics tools within one simple, reliable and user-friendly resource. The OCHEM is free for web users and it is available online at http://www.ochem.eu

A Review of Pink Salmon in the Pacific, Arctic, and Atlantic Oceans

The Northern Hemisphere Pink Salmon Expert Group Meeting was held on October 2–3, 2022 in Vancouver, Canada, immediately preceding the International Year of the Salmon (IYS) Synthesis Symposium. The rapid expansion of pink salmon was the theme for the meeting, and experts came together to discuss the current state of knowledge for pink salmon. Specific topics of focus included the range expansion into the Atlantic and Arctic oceans, trends in distribution and abundance, research and monitoring approaches, potential inter-specific interactions, mitigation efforts, and plans for future collaborations. The outcomes of the meeting were presented at the IYS Synthesis Symposium and are further disseminated through this NPAFC Technical Report. The Executive Summary section of this report provides a brief background, a condensed overview of each topic, and concludes with overarching takeaway messages that are intended to guide future collaborations.publishedVersio

A Review of Pink Salmon in the Pacific, Arctic, and Atlantic Oceans

The Northern Hemisphere Pink Salmon Expert Group Meeting was held on October 2–3, 2022 in Vancouver, Canada, immediately preceding the International Year of the Salmon (IYS) Synthesis Symposium. The rapid expansion of pink salmon was the theme for the meeting, and experts came together to discuss the current state of knowledge for pink salmon. Specific topics of focus included the range expansion into the Atlantic and Arctic oceans, trends in distribution and abundance, research and monitoring approaches, potential inter-specific interactions, mitigation efforts, and plans for future collaborations. The outcomes of the meeting were presented at the IYS Synthesis Symposium and are further disseminated through this NPAFC Technical Report. The Executive Summary section of this report provides a brief background, a condensed overview of each topic, and concludes with overarching takeaway messages that are intended to guide future collaborations.publishedVersio

Abundance Dynamics of Pink Salmon, Oncorhynchus gorbuscha, as a Structured Process Determined by Many Factors

Despite the fact that pink salmon is a fish species with a short-cycle life span, its stock abundance dynamics exhibit features typical of common pelagic fish species with an average life-cycle duration. Interchanging periods of high and low pink salmon abundance levels relate to positive and negative stock abundance trends inherent for major regional groups, Asian and American parts of aggregate stocks, and for pink salmon species as a whole (Radchenko et al. 2007). This feature of pink salmon abundance dynamics is determined by structural organization of the species and its populations. Major regional groups of pink salmon are divided into temporally isolated even- and odd-year populations. The life cycle of pink salmon can be conditionally divided into two periods: freshwater (including spawning, embryonic, and downstream migration phases) and marine (including inshore, marine waters in marginal seas, and oceanic phases). The phases repeat in reverse order until fish return from the sea and reach their spawning grounds. Most stocks, in turn, are separated by paired seasonal races with distinct morphological characteristics and spawning areas within river basins. Fig. 1. Pattern of pink salmon migrations during the life-cycle phases of aggregate stocks of the Sea of Okhotsk. Selected life-cycle phases are indicated by Roman numerals. For the purposes of assessing factors affecting mortality, abundance, and biomass losses on the basis of the pink salmon life cycle, I used typical data from an aggregated stock of Sea of Okhotsk pink salmon as an example (Fig. 1). The average abundance dynamics are based on data for 22 pink salmon generations spawning in 1989 to 2010 (Table 1). Average numbers and biomass estimates were calculated based on survey data, fishery statistics, and published literature. Table 1. Abundance dynamics of an average pink salmon generation throughout the different life-cycle phases using the aggregate stocks of the Sea of Okhotsk. Data are shown for generations of fish spawning in the years 1989-2008

Residual stresses relaxation in surface-hardened half-space under creep conditions

We developed the method for solving the problem of residual stresses relaxation in surface-hardened layer of half-space under creep conditions. At the first stage we made the reconstruction of stress-strain state in half-space after plastic surface hardening procedure based on partial information about distribution for one residual stress tensor component experimentally detected. At the second stage using a numerical method we solve the problem of relaxation of self-balanced residual stresses under creep conditions. To solve this problem we introduce the following Cartesian system: x0y plane is aligned with hardened surface of half-space and 0z axis is directed to the depth of hardened layer. We also introduce the hypotheses of plane sections parallel to x0z and y0z planes. Detailed analysis of the problem has been done. Comparison of the calculated data with the corresponding test data was made for plane specimens (rectangular parallelepipeds) made of EP742 alloy during T=650°C after the ultrasonic hardening with four hardening modes. We use half-space to model these specimens because penetration's depth of residual stresses is less than specimen general size in two digit exponent. There is enough correspondence of experimental and calculated data. It is shown that there is a decay (in modulus) of pressing residual stresses under creep in 1.4–1.6 times

Diversity of AMPA Receptor Ligands: Chemotypes, Binding Modes, Mechanisms of Action, and Therapeutic Effects

L-Glutamic acid is the main excitatory neurotransmitter in the central nervous system (CNS). Its associated receptors localized on neuronal and non-neuronal cells mediate rapid excitatory synaptic transmission in the CNS and regulate a wide range of processes in the brain, spinal cord, retina, and peripheral nervous system. In particular, the glutamate receptors selective to α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) also play an important role in numerous neurological disorders and attract close attention as targets for the creation of new classes of drugs for the treatment or substantial correction of a number of serious neurodegenerative and neuropsychiatric diseases. For this reason, the search for various types of AMPA receptor ligands and studies of their properties are attracting considerable attention both in academic institutions and in pharmaceutical companies around the world. This review focuses mainly on the advances in this area published since 2017. Particular attention is paid to the structural diversity of new chemotypes of agonists, competitive AMPA receptor antagonists, positive and negative allosteric modulators, transmembrane AMPA regulatory protein (TARP) dependent allosteric modulators, ion channel blockers as well as their binding sites. This review also presents the studies of the mechanisms of action of AMPA receptor ligands that mediate their therapeutic effects