531 research outputs found
Paleo-Balkan and Slavic Contributions to the Genetic Pool of Moldavians
Moldova has a rich historical and cultural heritage, which may be reflected in the current genetic makeup of its population.
To date, no comprehensive studies exist about the population genetic structure of modern Moldavians. To bridge this gap
with respect to paternal lineages, we analyzed 37 binary and 17 multiallelic (STRs) polymorphisms on the non-recombining
portion of the Y chromosome in 125 Moldavian males. In addition, 53 Ukrainians from eastern Moldova and 54 Romanians
from the neighboring eastern Romania were typed using the same set of markers. In Moldavians, 19 Y chromosome
haplogroups were identified, the most common being I-M423 (20.8%), R-M17* (17.6%), R-M458 (12.8%), E-v13 (8.8%), RM269*
and R-M412* (both 7.2%). In Romanians, 14 haplogroups were found including I-M423 (40.7%), R-M17* (16.7%), RM405
(7.4%), E-v13 and R-M412* (both 5.6%). In Ukrainians, 13 haplogroups were identified including R-M17 (34.0%), I-M423
(20.8%), R-M269* (9.4%), N-M178, R-M458 and R-M73 (each 5.7%). Our results show that a significant majority of the
Moldavian paternal gene pool belongs to eastern/central European and Balkan/eastern Mediterranean Y lineages.
Phylogenetic and AMOVA analyses based on Y-STR loci also revealed that Moldavians are close to both eastern/central
European and Balkan-Carpathian populations. The data correlate well with historical accounts and geographical location of
the region and thus allow to hypothesize that extant Moldavian paternal genetic lineages arose from extensive recent
admixture between genetically autochthonous populations of the Balkan-Carpathian zone and neighboring Slavic group
Magnetic fields in galaxies: I. Radio disks in local late-type galaxies
We develop an analytical model to follow the cosmological evolution of
magnetic fields in disk galaxies. Our assumption is that fields are amplified
from a small seed field via magnetohydrodynamical (MHD) turbulence. We further
assume that this process is fast compared to other relevant timescales, and
occurs principally in the cold disk gas. We follow the turbulent energy density
using the Shabala & Alexander (2009) galaxy formation and evolution model.
Three processes are important to the turbulent energy budget: infall of cool
gas onto the disk and supernova feedback increase the turbulence; while star
formation removes gas and hence turbulent energy from the cold gas. Finally, we
assume that field energy is continuously transferred from the incoherent random
field into an ordered field by differential galactic rotation. Model
predictions are compared with observations of local late type galaxies by Fitt
& Alexander (1993) and Shabala et al. (2008). The model reproduces observed
magnetic field strengths and luminosities in low and intermediate-mass
galaxies. These quantities are overpredicted in the most massive hosts,
suggesting that inclusion of gas ejection by powerful AGNs is necessary in
order to quench gas cooling and reconcile the predicted and observed magnetic
field strengths.Comment: 10 pages, 8 figures; MNRAS in pres
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Hydrogen Bonding Between Ions of Like Charge in Ionic Liquids Characterized by NMR Deuteron Quadrupole Coupling Constants—Comparison with Salt Bridges and Molecular Systems
We present deuteron quadrupole coupling constants (DQCC) for hydroxyl-functionalized ionic liquids (ILs) in the crystalline or glassy states characterizing two types of hydrogen bonding: The regular Coulomb-enhanced hydrogen bonds between cation and anion (c–a), and the unusual hydrogen bonds between cation and cation (c–c), which are present despite repulsive Coulomb forces. We measure these sensitive probes of hydrogen bonding by means of solid-state NMR spectroscopy. The DQCCs of (c–a) ion pairs and (c–c) H-bonds are compared to those of salt bridges in supramolecular complexes and those present in molecular liquids. At low temperatures, the (c–c) species successfully compete with the (c–a) ion pairs and dominate the cluster populations. Equilibrium constants obtained from molecular-dynamics (MD) simulations show van't Hoff behavior with small transition enthalpies between the differently H-bonded species. We show that cationic-cluster formation prevents these ILs from crystallizing. With cooling, the (c–c) hydrogen bonds persist, resulting in supercooling and glass formation. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA
High-Temperature Quantum Tunneling and Hydrogen Bonding Rearrangements Characterize the Solid-Solid Phase Transitions in a Phosphonium-Based Protic Ionic Liquid
We report the complex phase behavior of the glass
forming protic ionic liquid (PIL) d3-octylphosphonium
bis(trifluoromethylsulfonyl)imide [C8H17PD3][NTf2] by means of
solid-state NMR spectroscopy. Combined line shape and spin
relaxation studies of the deuterons in the PD3 group of the
octylphosphonium cation allow to map and correlate the
phase behavior for a broad temperature range from 71 K to
343 K. In the solid PIL at 71 K, we observed a static state,
characterized by the first deuteron quadrupole coupling
constant reported for PD3 deuterons. A transition enthalpy of
about 12 kJmol 1 from the static to the mobile state with
increasing temperature suggests the breaking of a weak,
charge-enhanced hydrogen bond between cation and anion.
The highly mobile phase above 100 K exhibits an almost
disappearing activation barrier, strongly indicating quantum
tunneling. Thus, we provide first evidence of tunneling driven
mobility of the hydrogen bonded P D moieties in the glassy
state of PILs, already at surprisingly high temperatures up to
200 K. Above 250 K, the mobile phase turns from anisotropic
to isotropic motion, and indicates strong internal rotation of
the PD3 group. The analyzed line shapes and spin relaxation
times allow us to link the structural and dynamical behavior
at molecular level with the phase behavior beyond the DSC
traces
New records of Holocene polar bear and walrus (Carnivora) in the Russian Arctic
This article discusses recent finds of Holocene polar bear and walrus from the northern regions of Russia. The ulna of a polar bear was found on Vaygach Island and radiocarbon dated to 1,971 +/- 25 BP (OxA-23631). This calibrates to 430-540 AD, taking into account the marine reservoir effect. The size of the bone is similar to that of a recent Ursus maritimus. The locality of the fossil bone is within the modern species range, which developed about two millennia ago. In 2014 a walrus tusk was found on the coast of New Siberia Island and is radiocarbon dated to 5,065 +/- 35 BP (GrA-62452). This calibrates to 3,510-3,370 BC, taking into account the marine reservoir effect. Its size and morphology are identical to that of an adult male of the subspecies Odobenus rosmarus laptevi. This subspecies populates the eastern parts of the Kara Sea, the entire Laptev Sea and the western parts of the East Siberian Sea. This new discovery could mean that populations of O. rosmarus laptevi inhabited the waters near the New Siberian Islands during the Middle Holocene, and that the present-day coastline of the Siberian Arctic Islands was already formed at that time
Tailoring porosity and rotational dynamics in a series of octacarboxylate metal-organic frameworks
Modulation and precise control of porosity of metal-organic frameworks (MOFs) are of critical importance to their materials function. Here we report the first modulation of porosity for a series of isoreticular octacarboxylate MOFs, denoted MFM-180 to MFM-185, via a strategy of selective elongation of metal-organic cages. Owing to the high ligand connectivity, these MOFs show absence of network interpenetration, robust structures and permanent porosity. Interestingly, activated MFM-185a shows a record high BET surface area of 4734 m2 g-1 for an octacarboxylate MOF. These MOFs show remarkable CH4 and CO2 adsorption properties, notably with simultaneously high gravimetric and volumetric deliverable CH4 capacities of 0.24 g g-1 and 163 v/v (298 K, 5-65 bar) recorded for MFM-185a due to selective elongation of tubular cages. Dynamics of molecular rotors in deuterated MFM-180a-d16 and MFM-181a-d16 were investigated by variable-temperature 2H solid state NMR spectroscopy to reveal the reorientation mechanisms within these materials. Analysis of the flipping modes of the mobile phenyl groups on the linkers, their rotational rates and transition temperatures, paves the way to controlling and understanding the role of molecular rotors through organic linker design within porous MOF materials
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