Neutrinoless double-electron capture Blaum, K.; Eliseev, S.; Danevich, F. A. ...
Reviews of modern physics,
12/2020, Letnik:
92, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Double-beta processes play a key role in the exploration of neutrino and weak interaction properties, and in the searches for effects beyond the standard model. During the last half century many ...attempts were undertaken to search for double-beta decay with emission of two electrons, especially for its neutrinoless mode 0 ν 2 β − , the latter having still not been observed. Double-electron capture (2EC) was not yet in focus because of its in general lower transition probability. However, the rate of neutrinoless double-electron capture 0 ν 2 EC can experience a resonance enhancement by many orders of magnitude when the initial and final states are energetically degenerate. In the resonant case, the sensitivity of the 0 ν 2 EC process can approach the sensitivity of the 0 ν 2 β − decay in the search for the Majorana mass of neutrinos, right-handed currents, and other new physics. An overview of the main experimental and theoretical results obtained during the last decade in this field is presented. The experimental part outlines search results of 2EC processes and measurements of the decay energies for possible resonant 0 ν 2 EC transitions. An unprecedented precision in the determination of decay energies with Penning traps has allowed one to refine the values of the degeneracy parameter for all previously known near-resonant decays and has reduced the rather large uncertainties in the estimate of the 0 ν 2 EC half-lives. The theoretical part contains an updated analysis of the electron shell effects and an overview of the nuclear-structure models, in which the nuclear matrix elements of the 0 ν 2 EC decays are calculated. One can conclude that the decay probability of 0 ν 2 EC can experience a significant enhancement in several nuclides.
A novel obligately anaerobic, mesophilic, organotrophic bacterium, strain P3M-1T, was isolated from a microbial mat formed in a wooden bath filled with hot water emerging from a 2775 m-deep well in ...the Tomsk region of western Siberia, Russia. Cells of strain P3M-1T were rod-shaped, 0.3–0.7 µm in width and formed multicellullar filaments that reached up to 400 µm in length. Strain P3M-1T grew optimally at 42–45 °C, pH 7.5–8.0, and with 0.1% (w/v) NaCl. Under optimal conditions, the doubling time was 6 h. The isolate was able to ferment a variety of proteinaceous substrates and sugars, including microcrystalline cellulose. Acetate, ethanol and H2 were the main products of glucose fermentation. The genomic DNA G+C content was 55 mol%. 16S rRNA gene sequence-based phylogenetic analyses showed that strain P3M-1T was a member of the class Anaerolinea, with 92.8 % sequence similarity to Levilinea saccharolytica KIBI-1T. Based on phylogenetic analysis and physiological properties, strain P3M-1T represents a novel species in a new genus, for which the name Ornatilinea apprima gen. nov., sp. nov. is proposed; the type strain of O. apprima is P3M-1T ( = DSM 23815T = VKM B-2669T).
Abstract
In this work demostrates a unique method for determining the absolute value of the friction force of a nanoobject on the surface of a cell membrane using atomic force microscopy. The ...tribological properties of membranes of adult human buccal epithelium cells in the presence of a protective adsorption buffer layer of ~ 100 nm on their surface were studied using atomic force microscopy in the contact scanning mode. Local mapping of the tribological characteristics of the surface was carried out, viz. friction
F
L
=
F
L
(x, y)
and adhesion
F
adh
=
F
adh
(x, y)
forces were measured. Studies of the friction force
F
fr
on the membrane surface at the nanolevel showed that its value varies discretely with an interval equal to
l
LF
≈ 100 nm. It was shown that such discreteness is determined by the interval
l
LF
of the action of adhesive forces
F
adh
and indicates the fractal nature of the functional dependence of the friction force on the coordinate
F
fr
=
F
fr
(x)
. Thus, for nano-objects with dimensions ≤
l
LF
, the absolute value of
F
fr
decreases according to a power law with an increase in the size of the object, which contradicts the similar dependence of the friction force for macro-objects in the global approximation.
The trematosaurid genus
Thoosuchus
Efremov, 1940, which is the type genus for the subfamily Thoosuchinae, is revised and its diagnosis is emended. This genus includes
T. yakovlevi
and
T. ...tuberculatus,
previously identified from the Rybinskian Regional Stage (Lower Triassic, Lower Olenekian), and the new species
T. abbasovi
sp. nov. The morphotype of the latter species is characterized by a number of apomorphic characters typical of more recent trematosaurid subfamilies: Platysteginae and Trematosaurinae (widely spaced orbits, the absence of an anteromedial projection of the postorbital, a narrowed middle ear cavity, a flattened depressor part of the lamina ascendens, and a well-developed crista posterior on the pterygoid), which is consistent with the later (Sludkian) age of the new species.
The problems arising in the construction of a model describing the temperature field distribution in the hydraulic puller–drilling stave assembly used in ultra-high pressure devices for jet-grouting ...of soils are considered. The influence of a change in the metal surface morphology on the temperature field distribution when using a certain type of processing of contact surfaces of the parts of devices for jet-grouting of soils is described. A solid-state model of the drilling stave region and the temperature field distribution in the elements of the hydraulic drilling stave, which occurs during its operation and is calculated by the finite element method are presented. The factors that significantly affect the heat balance of the structural unit considered are also discussed.
Separation technique of rhenium radioisotopes from a deuteron-irradiated tungsten target of natural isotopic composition has been developed. The irradiated tungsten powder was dissolved in a mixture ...of H
2
O
2
and NaOH, the solution was passed through a column filled with an extraction chromatographic sorbent TEVA Resin. Rhenium was eluted with 4 M nitric acid. The separation procedure takes approximately 3 h, the radiochemical yield of rhenium is more than 97%.
Assume that a polygon is composed of equal rectangles. We find all quadratic irrationalities
for which the polygon under study can be cut into similar rectangles with aspect ratio
.
New data on the taxonomic composition and comparison of the tetrapod assemblage from the Upper Sukhorechenskaya Subformation of the Buzuluk Depression of the East European Platform, previously ...described as “
Selenocara–Syrtosuchus
fauna,” are provided. This assemblage is dated Late Induan (Dienerian) and characterizes a new stage in recovery of East European tetrapod community after the Late Permian extinction, which is intermediate between the
Tupilakosaurus
and
Benthosuchus
faunas. Beyond Eastern Europe, a similar amphibian association is known from the
Anodontophora fassaensis
Zone (upper part of the Wordie Creek Formation) of eastern Greenland.
Approaches are developed to the separation and identification of eleven β-amino alcohols, markers of nitrogen-containing toxic chemicals (V-gases, nitrogen mustards and BZ), as trimethyl-(TMS) and
...tert
-butyldiphenylsilyl derivatives by gas chromatography with mass spectrometry detection. The conditions for the joint silylation of β-amino alcohols with reagents 1,1,1,3,3,3-hexamethyldisilazane (HMDS),
N,O
-bis(trimethylsilyl)trifluoroacetamide (BSTFA), and
tert
-butyldiphenylchlorosilane (TBDPS) are optimized. The TBDPS reagent for the derivatization of β-amino alcohols is proposed for the first time. It is shown that the optimum temperature for ensuring the derivatization of a mixture of all β-amino alcohols with HMDS is 40°C and reaction time is 15 min; with BSTFA, 60°C and 30 min; and with TBDPS, 80°C and 45 min. At that, in the case of HMDS, it is necessary to introduce an activating additive of 0.02% iodine, and for TBDPS,
N
-methylimidazole in a ratio of 1 : 2. The reactivity of β-amino alcohols with respect to silylating agents decreases in the series of
N,N
-dialkylaminoethanols:
N
-alkyldiethanolamines—triethanolamine—3‑quinuclidinol. The structural isomers of methylpropyl- and methylisopropylethanolamine can be separated only as TBDPS-derivatives on a stationary phase of medium polarity (VF-1701 MS). The limits of detection for β-aminoalcohols as TMS derivatives lie in the range of 0.05–0.5 μg/mL, and for TBDPS derivatives, 0.2–0.8 μg/mL. The results obtained ensure the reliable identification of β-amino alcohols in a mixture at concentrations of >1 μg/mL.
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