Monitoring of optical properties of deep waters of Lake Baikal in 2021-2022

We present the results of the two-year (2021-2022) monitoring of absorption and scattering lengths of light with wavelength 400-620 nm within the effective volume of the deep underwater neutrino telescope Baikal-GVD, which were measured by a device Baikal-5D No.2. The Baikal-5D No.2. was installed during the 2021 winter expedition at a depth of 1180 m. The absorption and scattering lengths were measured every week in 9 spectral points. The device Baikal-5D No.2 also has the ability to measure detailed scattering and absorption spectra. The data obtained make it possible to estimate the range of changes in the absorption and scattering lengths over a sufficiently long period of time and to investigate the relationship between the processes of changes in absorption and scattering. An analysis was made of changes in absorption and scattering spectra for the period 2021-2022

Large neutrino telescope Baikal-GVD: recent status

The Baikal-GVD is a deep-underwater neutrino telescope being constructed in Lake Baikal. After the winter 2023 deployment campaign the detector consists of 3456 optical modules installed on 96 vertical strings. The status of the detector and progress in data analysis are discussed in present report. The Baikal-GVD data collected in 2018-2022 indicate the presence of cosmic neutrino flux in high-energy cascade events consistent with observations by the IceCube neutrino telescope. Analysis of track-like events results in identification of first high-energy muon neutrino candidates. These and other results from 2018-2022 data samples are reviewed in this report

Search for directional associations between Baikal Gigaton Volume Detector neutrino-induced cascades and high-energy astrophysical sources

Baikal-GVD has recently published its first measurement of the diffuse astrophysical neutrino flux, performed using high-energy cascade-like events. We further explore the Baikal-GVD cascade dataset collected in 2018-2022, with the aim to identify possible associations between the Baikal-GVD neutrinos and known astrophysical sources. We leverage the relatively high angular resolution of the Baikal-GVD neutrino telescope (2-3 deg.), made possible by the use of liquid water as the detection medium, enabling the study of astrophysical point sources even with cascade events. We estimate the telescope's sensitivity in the cascade channel for high-energy astrophysical sources and refine our analysis prescriptions using Monte-Carlo simulations. We primarily focus on cascades with energies exceeding 100 TeV, which we employ to search for correlation with radio-bright blazars. Although the currently limited neutrino sample size provides no statistically significant effects, our analysis suggests a number of possible associations with both extragalactic and Galactic sources. Specifically, we present an analysis of an observed triplet of neutrino candidate events in the Galactic plane, focusing on its potential connection with certain Galactic sources, and discuss the coincidence of cascades with several bright and flaring blazars.Comment: 10 pages, 3 figure

Studies of the ambient light of deep Baikal waters with Baikal-GVD

The Baikal-GVD neutrino detector is a deep-underwater neutrino telescope under construction and recently after the winter 2023 deployment it consists of 3456 optical modules attached on 96 vertical strings. This 3-dimensional array of photo-sensors allows to observe ambient light in the vicinity of the Baikal-GVD telescope that is associated mostly with water luminescence. Results on time and space variations of the luminescent activity are reviewed based on data collected in 2018-2022

Global quantitative synthesis of ecosystem functioning across climatic zones and ecosystem types

International audienceAim Providing a quantitative overview of ecosystem functioning in a three-dimensional space defined by ecosystem stocks, fluxes and rates, across major ecosystem types and climatic zones.Location Global.Time period 1966-2019.Major taxa studied Ecosystem-level measurements (all organism types).Methods We conducted a global quantitative synthesis of a wide range of ecosystem variables related to carbon stocks and fluxes. We gathered a total of 4,479 values from 1,223 individual sites (unique geographical coordinates) reported in the literature (604 studies), covering ecosystem variables including biomass and detritus stocks, gross primary production, ecosystem respiration, detritus decomposition and carbon uptake rates, across eight major aquatic and terrestrial ecosystem types and five broad climatic zones (arctic, boreal, temperate, arid and tropical). We analysed the relationships among variables emerging from the comparisons of stocks, fluxes and rates across ecosystem types and climates.Results Within our three-dimensional functioning space, average ecosystems align along a gradient from fast rates-low fluxes and stocks (freshwater and pelagic marine ecosystems) to low rates-high fluxes and stocks (forests), a gradient that we hypothesize results mainly from variation in primary producer characteristics. Moreover, fluxes and rates decrease from warm to colder climates, consistent with the metabolic theory of ecology. However, the strength of climatic effects differs among variables and ecosystem types, resulting, for instance, in opposing effects on net ecosystem production between terrestrial and freshwater ecosystems (positive versus negative effects).Main conclusions This large-scale synthesis provides a first quantified cross-ecosystem and cross-climate comparison of multivariate ecosystem functioning. This gives a basis for a mechanistic understanding of the interdependency of different aspects of ecosystem functioning and their sensitivity to global change. To anticipate responses to change at the ecosystem level, further work should investigate potential feedbacks between ecosystem variables at finer scales, which involves site-level quantifications of multivariate functioning and theoretical developments

Atomic and magnetic structures, disorder effects, and unconventional superexchange interactions in A(2)MnGaO(5+delta) (A = Sr, Ca) oxides of layered brownmillerite-type structure

Crystal and magnetic structures of complex manganese oxides Sr2GaMnO5+delta (deltasimilar or equal to0.01,0.52) and Ca2GaMnO5+delta (deltasimilar or equal to0.05) were studied by neutron powder diffraction (ND) and muSR technique in the temperature range 2-300 K. The crystal structures contain single MnO2 layers separated by three nonmagnetic cation-oxygen layers. The principal difference between the deltasimilar or equal to0 and deltasimilar or equal to0.5 compounds is the Mn valence: Mn3+ or Mn4+, and the structure of the (GaO1+delta) buffer layer, which is formed by tetrahedra or partially filled octahedra, respectively. The magnetic moments of the manganese ions are coupled antiferromagnetically in the MnO2 plane, but antiferromagnetically (G type) or ferromagnetically (C type) between the planes for the reduced and oxidized compositions, respectively. The transition from the G- to C-type magnetic structure by oxygen doping is explained by strong diagonal 180degrees superexchange antiferromagnetic interaction between Mn4+-ions in the adjacent layers through additional oxygen atoms in the GaO buffer layer. The magnetic moments in Sr-based samples are appreciably reduced in comparison with the spin- only values of the corresponding Mn ion. By using complementary information on local magnetic field distribution from muSR we show that the reduced magnetic moments seen by ND are caused by the presence of locally flipped Mn spins and a short-ranged (40 Angstrom) antiferromagnetic phase. The magnetic disorder can be caused by the disorder observed in the oxygen positions of the GaO1+delta layer, because the coupling between the MnO2 layers is mediated by the geometry of the superexchange path through these oxygen atoms