Summer coastal rookeries and perspectives of the Baikal seal (Pusa sibirica) population in the conditions of the global warming

Based on the secondary literature, a retrospective characterization of the climate in the Baikal region, starting from the end of the Pleistocene, is given. According to satellite monitoring data, the characteristics of the ice regime of the Lake Baikal in the conditions of climate warming are presented. Moreover, we briefly discuss the impact of climate change on the ecology and biology of the Baikal seal (Pusa sibirica Gm.). Using video materials obtained online at one of the main island coastal rookeries of seals (on the island of Tonkyi, the archipelago of the Ushkany Islands, Lake Baikal) in 2011–2017, the dependence of the number of seals hauled out on the lake level and the peculiarities of the fishing regime was determined (the survey was conducted from May–June to October). A direct relationship was determined between the relative number of animals that had a moulting delay and the ice regime of a given year: the longer the floating ice in the northern part of Lake Baikal remained, the more numerous were the first approaches of seals to the studied rookery and the greater was the proportion of moulting individuals. It is reasonable to assume that the main reason for the Baikal seal to come ashore is not prolongued moulting time, but a physiological need for sunlight, which has a healing effect on the body of animals that lack solar radiation in winter. In general, climate warming has a negative impact on the state of the Baikal seal population. The available paleoclimatic reconstructions of the Holocene indicate that the population of the Baikal seal has experienced a lot of climate changes in its history. Nevertheless, if the current trends of climatic changes persist until the end of the 21st century, the ecology and biology of the seal will drastically change (up to the beginning of terrestrial reproduction), and the population will significantly decrease. However, the Baikal seal as a species would remain

Trophic effects of sponge feeding within Lake Baikal\u27s littoral zone .2. Sponge abundance, diet, feeding efficiency, and carbon flux

Endemic freshwater demosponges in the littoral zone of Lake Baikal, Russia, dominate the benthic biomass, covering 44% of the benthos. We measured in situ sponge abundance and,orating and calculated sponge-mediated Fluxes of picoplankton (plankton \u3c2 mu m) for two common species, Baikalospongia intermedia and Baikalospongia bacillifera. By means of dual-beam how cytometry, we found retention efficiencies ranging from 58 to 99% for four types of picoplankton: heterotrophic bacteria, Synechococcus-type cyanobacteria, autotrophic picoplankton with one chloroplast, and autotrophic picoplankton with two chloroplasts. By using a general model for organism-mediated fluxes, we conservatively estimate that through active suspension feeding, sponges are a sink for 1.97 g C d(-1) m(-1), mostly from procaryotic cell types. Furthermore, grazing by these extensive sponge communities can create a layer of picoplankton-depleted water overlying the benthic community in this unique lake

The signature of the first stars in atomic hydrogen at redshift 20

Dark and baryonic matter moved at different velocities in the early Universe, which strongly suppressed star formation in some regions. This was estimated to imprint a large-scale fluctuation signal of about 2 mK in the 21-cm spectral line of atomic hydrogen associated with stars at a redshift of 20, although this estimate ignored the critical contribution of gas heating due to X-rays and major enhancements of the suppression. A large velocity difference reduces the abundance of halos and requires the first stars to form in halos of about a million solar masses, substantially greater than previously expected. Here we report a simulation of the distribution of the first stars at z=20 (cosmic age of ~180 Myr), incorporating all these ingredients within a 400 Mpc box. We find that the 21-cm signature of these stars is an enhanced (10 mK) fluctuation signal on the 100-Mpc scale, characterized by a flat power spectrum with prominent baryon acoustic oscillations. The required sensitivity to see this signal is achievable with an integration time of a thousand hours with an instrument like the Murchison Wide-field Array or the Low Frequency Array but designed to operate in the range of 50-100 MHz.Comment: 27 pages, 5 figures, close (but not exact) match to accepted version. Basic results unchanged from first submitted version, but justification strengthened, title and abstract modified, and substantial Supplementary Material added. Originally first submitted for publication on Oct. 12, 201

Decoupling Inflation From the String Scale

When Inflation is embedded in a fundamental theory, such as string theory, it typically begins when the Universe is already substantially larger than the fundamental scale [such as the one defined by the string length scale]. This is naturally explained by postulating a pre-inflationary era, during which the size of the Universe grew from the fundamental scale to the initial inflationary scale. The problem then arises of maintaining the [presumed] initial spatial homogeneity throughout this era, so that, when it terminates, Inflation is able to begin in its potential-dominated state. Linde has proposed that a spacetime with compact negatively curved spatial sections can achieve this, by means of chaotic mixing. Such a compactification will however lead to a Casimir energy, which can lead to effects that defeat the purpose unless the coupling to gravity is suppressed. We estimate the value of this coupling required by the proposal, and use it to show that the pre-inflationary spacetime is stable, despite the violation of the Null Energy Condition entailed by the Casimir energy.Comment: 24 pages, 5 eps figures, references added, stylistic changes, version to appear in Classical and Quantum Gravit

Receiver design for the REACH global 21-cm signal experiment

We detail the the REACH radiometric system designed to enable measurements of the 21-cm neutral hydrogen line. Included is the radiometer architecture and end-to-end system simulations as well as a discussion of the challenges intrinsic to highly-calibratable system development. Following this, we share laboratory results based on the calculation of noise wave parameters utilising an over-constrained least squares approach demonstrating a calibration RMSE of 80 mK for five hours of integration on a custom-made source with comparable impedance to that of the antenna used in the field. This paper therefore documents the state of the calibrator and data analysis in December 2022 in Cambridge before shipping to South Africa.Comment: 30 pages, 19 figure

Understanding the Death of Massive Stars Using an Astrophysical Transients Observatory

The death of massive stars, manifested as gamma-ray bursts and core-collapse supernovae, critically influence how the universe formed and evolves. Despite their fundamental importance, our understanding of these enigmatic objects is severely limited. We have performed a concept study of an Astrophysical Transient Observatory (ATO) that will rapidly facilitate an expansion of our understanding of these objects. ATO combines a very wide-field X-ray telescope, a near-infrared telescope, a multi-mode ultraviolet instrument, and a rapidly slewing spacecraft to realize two primary goals: (1) characterize the highest-redshift massive stars and their environments, and (2) constrain the poorly understood explosion mechanism of massive stars. The goals are met by observing the first massive stars to explode as gamma-ray bursts and to probe their environments, and by observing the shock breakout of core-collapse supernovae to measure the outer envelope parameters of massive stars. Additionally, ATO will observe the shock breakout of Type Ia supernovae and their shock interaction with a companion, electromagnetic counterparts to gravitational wave sources, kilonovae, tidal disruption events, cataclysmic variables, X-ray transients, flares from exoplanet host stars, and the escape of ionizing radiation from star-forming galaxies. A description of the ATO instruments, the mission simulation, and technology readiness level is provided