Thermal expansion and polarization of (1-x)PNNxPT solid solutions

The paper presents the results of detailed studies of the thermal expansion of (1-x)PbNi1/3Nb2/3O3-xPbTiO3 solid solutions with x¼0- 0.8. The anomalous and lattice contributions to deformation and the thermal expansion coefficient are analyzed and the mean square polarization Pd is determined. The results obtained are discussed within the framework of the thermodynamic theory and the Landau 2-4-6 coefficients for solid solutions are estimate

Investigation of the thermal expansion and heat capacity of the CaCu3Ti4O12 ceramics

The thermal expansion of the CaCu3Ti4O12 ceramics has been measured over a wide temperature range 120–1200 K. The high quality of the samples under study has been confirmed by good agreement of the results of measurements of the heat capacity in the range 2–300 K and in the vicinity of the phase transition of magnetic nature at 25 K with the data for the single crystal. No anomalies in the thermal expansion that can be associated with the phase transition at 726–732 K assumed by other investigators have been found. The influence exerted on the thermal expansion by the heat treatment of the sample in a helium atmosphere and in air has been investigated

Radioactive decays at limits of nuclear stability

The last decades brought an impressive progress in synthesizing and studying properties of nuclides located very far from the beta stability line. Among the most fundamental properties of such exotic nuclides, usually established first, is the half-life, possible radioactive decay modes, and their relative probabilities. When approaching limits of nuclear stability, new decay modes set in. First, beta decays become accompanied by emission of nucleons from highly excited states of daughter nuclei. Second, when the nucleon separation energy becomes negative, nucleons start to be emitted from the ground state. Here, we present a review of the decay modes occurring close to the limits of stability. The experimental methods used to produce, identify and detect new species and their radiation are discussed. The current theoretical understanding of these decay processes is overviewed. The theoretical description of the most recently discovered and most complex radioactive process - the two-proton radioactivity - is discussed in more detail.Comment: Review, 68 pages, 39 figure

Population dynamics and range shifts of moose (Alces alces) during the Late Quaternary

Aim: Late Quaternary climate oscillations had major impacts on species distributions and abundances across the northern Holarctic. While many large mammals in this region went extinct towards the end of the Quaternary, some species survived and flourished. Here, we examine population dynamics and range shifts of one of the most widely distributed of these, the moose (Alces alces). Location: Northern Holarctic. Taxon: Moose (A. alces). Methods: We collected samples of modern and ancient moose from across their present and former range. We assessed their phylogeographical relations using part of the mitochondrial DNA in conjunction with radiocarbon dating to investigate the history of A. alces during the last glacial. Results: This species has a relatively shallow history, with the most recent common ancestor estimated at ca. 150–50 kyr. Ancient samples corroborate that its region of greatest diversity is in east Asia, supporting proposals that this is the region of origin of all extant moose. Both eastern and western haplogroups occur in the Ural Mountains during the last glacial period, implying a broader contact zone than previously proposed. It seems that this species went extinct over much of its northern range during the last glacial maximum (LGM) and recolonized the region with climate warming beginning around 15,000 yr bp. The post-LGM expansion included a movement from northeast Siberia to North America via Beringia, although the northeast Siberian source population is not the one currently occupying that area. Main conclusions: Moose are a relatively recently evolved species but have had a dynamic history. As a large-bodied subarctic browsing species, they were seemingly confined to refugia during full-glacial periods and expanded their range northwards when the boreal forest returned after the LGM. The main modern phylogeographical division is ancient, though its boundary has not remained constant. Moose population expansion into America was roughly synchronous with human and red deer expansion. © 2020 The Authors. Journal of Biogeography published by John Wiley & Sons LtdWe warmly thank the following museums, curators and people for access to samples: the late Andrei Sher, Severtsov Institute, Moscow; Andy Currant, Natural History Museum, London; Alfred Gardner, Smithsonian, Washington DC; R. Dale Guthrie, University of Alaska, Fairbanks; John de Vos, National Museum of Natural History (Naturalis), Leiden; Eileen Westwig, American Museum of Natural History, NY; Fyodor Shidlovsky, Ice-Age Museum, Moscow; Tong Haowen, Institute of Vertebrate Palaeontology and Paleoanthropology, Beijing; Mammoth Museum, Yakutsk; Geological Museum, Yakutsk; Paleontological Institute, Moscow; Royal Alberta Museum, Edmonton; Zoological Institute, Saint Petersburg; Museum of the Institute of Plant and Animal Ecology, Ekaterinburg. We thank our Yukon First Nation research partners for their continued support for our work on the ice age fossils of Yukon Territory. We are grateful to the placer gold mining community and the Tr'ond?k Hw?ch'in First Nation for their continued support and partnership with our research in the Klondike goldfields region; and the Vuntut Gwitchin First Nation for their collaboration with research in the Old Crow region. We would also like to thank Shai Meiri for help in drawing the map and useful discussion, Tony Stuart for access to radiocarbon dates, and Iris van Pijlen for laboratory assistance. This research was funded by NERC grant NE/G00269X/1 through the European Union FP7 ERA-NET program BiodivERsA. Funding for AMS dating was provided through NERC/AHRC/ORAU Grant NF/2008/2/15

New limits on nucleon decays into invisible channels with the BOREXINO Counting Test Facility

The results of background measurements with the second version of the BOREXINO Counting Test Facility (CTF-II), installed in the Gran Sasso Underground Laboratory, were used to obtain limits on the instability of nucleons, bounded in nuclei, for decays into invisible channels ($inv$): disappearance, decays to neutrinos, etc. The approach consisted of a search for decays of unstable nuclides resulting from $N$ and $NN$ decays of parents $^{12}$C, $^{13}$C and $^{16}$O nuclei in the liquid scintillator and the water shield of the CTF. Due to the extremely low background and the large mass (4.2 ton) of the CTF detector, the most stringent (or competitive) up-to-date experimental bounds have been established: $\tau(n \to inv) > 1.8 \cdot 10^{25}$ y, $\tau(p \to inv) > 1.1 \cdot 10^{26}$ y, $\tau(nn \to inv) > 4.9 \cdot 10^{25}$ y and $\tau(pp \to inv) > 5.0 \cdot 10^{25}$ y, all at 90% C.L.Comment: 22 pages, 3 figures,submitted to Phys.Lett.

An ancient bison from the mouth of the Rauchua River (Chukotka, Russia)

An incomplete carcass of an extinct bison, Bison ex gr. priscus, was discovered in 2012 in the mouth of the Rauchua River (69°30'N, 166°49'E), Chukotka. The carcass included the rump with two hind limbs, ribs, and large flap of hide from the abdomen and sides, several vertebrae, bones of the forelimbs and anterior autopodia, stomach with its contents, and wool. The limb bones are relatively gracile, which is unusual in bison, and a SEM study of the hair microstructure suggests higher insulating capacity than in extant members of the genus. Additionally, mitochondrial DNA analyses indicate that the Rauchua bison belonged to a distinct and previously unidentified lineage of steppe bison. Two radiocarbon dates suggest a Holocene age for the bison: a traditional 14C date provided an estimate of 8030±70 14C yr BP (SPb-743) and an AMS radiocarbon date provided an age of 9497±92 14C yr BP (AA101271). These dates make this the youngest known bison from Chukotka. Analysis of stomach contents revealed a diet of herbaceous plants (meadow grasses and sedges) and shrubs, suggesting that the early Holocene vegetation near the mouth of the Rauchua River was similar to that of the present day: tundra-associated vegetation with undersized plants

Thermal expansion and polarization of (1-x)PNN-xPT solid solutions

The paper presents the results of detailed studies of the thermal expansion of (1-x)PbNi1/3Nb2/3O3-xPbTiO3 solid solutions with x = 0-0.8. The anomalous and lattice contributions to deformation and the thermal expansion coefficient are analyzed and the mean square polarization Pd is determined. The results obtained are discussed within the framework of the thermodynamic theory and the Landau 2-4-6 coefficients for solid solutions are estimated

Perovskite-like fluorides and oxyfluorides : phase transitions and caloric effects

An analysis of the effect that chemical and hydrostatic pressures have on the thermodynamic properties of perovskite like fluorine–oxygen compounds A2A'MeOxF6–x has revealed that materials under going order–disorder transitions and having significant external pressure compliance have the highest caloric efficiency. Some of the fluorides and oxyfluorides under study can be considered promising solid coolants