The gamma strength function and level density of 1^{-} states in ^{96}Mo have been extracted from a high-resolution study of the (pover →, pover →^{'}) reaction at 295 MeV and extreme forward angles. ...By comparison with compound nucleus γ decay experiments, this allows a test of the generalized Brink-Axel hypothesis in the energy region of the pygmy dipole resonance. The Brink-Axel hypothesis is commonly assumed in astrophysical reaction network calculations and states that the gamma strength function in nuclei is independent of the structure of the initial and final state. The present results validate the Brink-Axel hypothesis for ^{96}Mo and provide independent confirmation of the methods used to separate gamma strength function and level density in γ decay experiments.
The double-gamma (γγ)-decay of a quantum system in an excited state is a fundamental second-order process of quantum electrodynamics. In contrast to the well-known single-gamma (γ)-decay, the ...γγ-decay is characterized by the simultaneous emission of two γ quanta, each with a continuous energy spectrum. In nuclear physics, this exotic decay mode has only been observed for transitions between states with spin-parity quantum numbers J(π) = 0(+) (refs 1-3). Single-gamma decays-the main experimental obstacle to observing the γγ-decay-are strictly forbidden for these 0(+) → 0(+) transitions. Here we report the observation of the γγ-decay of an excited nuclear state (J(π) = 11/2(-)) that is directly competing with an allowed γ-decay (to ground state J(π) = 3/2(+)). The branching ratio of the competitive γγ-decay of the 11/2(-) isomer of (137)Ba to the ground state relative to its single γ-decay was determined to be (2.05 ± 0.37) × 10(-6). From the measured angular correlation and the shape of the energy spectra of the individual γ-rays, the contributing combinations of multipolarities of the γ radiation were determined. Transition matrix elements calculated using the quasiparticle-phonon model reproduce our measurements well. The γγ-decay rate gives access to so far unexplored important nuclear structure information, such as the generalized (off-diagonal) nuclear electric polarizabilities and magnetic susceptibilities.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
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Micromammalian fauna and palynological spectra have been studied in two cave-type localities of the Iordanskogo Ravine in the Northern Urals (Pechora-Ilych Nature Reserve): the Studyony canopy and ...the Filin niche. The cave sedimentation conditions have been reconstructed on the basis of the paleofauna and palynological data. The fossil small mammal assemblages and the spore–pollen spectra are indicative of the spread of shrubby swampy tundra with forest islands in the Upper Pechora region at the end of the Middle Valdai (Byzovaya Interstadial, MIS 3) and tundra-steppe landscapes under the progressive climate drying during the Last Glacial Maximum. During the Late Glacial, tundra-like shrubs prevailed, and the climate was much colder than the recent one. The rodent fauna was dominated by tundra and tundra-steppe species. In the Early Holocene, the climate warming lowered the role of xerophytic shrubs, replaced by birch–spruce–pine forests. In the rodent fauna, the proportion of tundra and tundra-steppe species decreased by more than a factor of three. During the Late Holocene, dark coniferous forests with fir and Siberian pine became widespread. Rodent associations acquired a typical taiga appearance: the forest inhabitants accounted for more than half of all remains (60–80%), while the tundra species were absent.
The mineralogy of olivine veins from the Itkul hyperbasite massif, Southern Urals, has been studied. These veins are composed of forsterite with minor talc, magnetite, and magnesite. Itkul olivine, ...which was first described in 1847 as a new mineral—glinkite—is forsterite with a fayalite content of 16.5%. It has been established that the metasomatic olivinites of these veins were formed due to recrystallization of host serpentinite under the influence of a nearby granite intrusion. It is suggested that, because of the visual similarity of Itkul forsterite with Ural demantoid, the latter were for a long time called “chrysolites” or “Ural chrysolites.”
We studied reparative effect of platelet-filled biological matrixes in the treatment of mice with wounds equivalent to deep burn. The wound coatings were based on decellularized dermal matrix without ...platelets (control), with native platelets, and with platelets stabilized with 2.5 μM nanosilver. In 3 days, the epithelial layer and derma were absent in all groups and extensive scab was formed. Dermal matrix with platelets simulated intensive migration of macrophages and fibroblasts to the wound bottom; in the control group, this migration was absent. In 14 days, granulation tissue appeared in the wound bottom in animals of all groups; in the experimental groups, the number of vessels was 2-4-fold higher than in the control, though the number of inflammatory cells in experimental groups remained high. On day 21, the scab on the most of the wound area was absent in all animals of the experimental groups and epithelialization and hair growth were pronounced, comparing to control. Nevertheless, in experiment dermal layer was not already completed, inflammation reaction remained.
Abstract
Extensive experimental investigations into understanding the fine structure of giant resonances in nuclei across the periodic table have been carried out in recent years using the ...state-of-the-art K600 magnetic spectrometer of iThemba LABS, Cape Town, South Africa. Based on the established results in comparison to various theoretical calculations, it has been found that the fine structure observed in different giant resonances, namely Isoscalar Giant Quadrupole Resonance (ISGQR), Isovector Giant Dipole Resonance (IVGDR) and Isoscalar Giant Monopole Resonance (ISGMR), in light nuclei such as
40
Ca,
28
Si and
27
Al is dominated by Landau damping although signatures for the role of the spreading width are also found. In this report, characteristic energy scales extracted in light nuclei are compared with the state-of-the-art theoretical calculations, while the fine structures results obtained are compared using semblance analysis to search for possible signatures of common fragmentation patterns induced by Landau damping and coupling to 2p-2h states obtained from different giant resonances.
The radiolysis of a radiochemical extraction system based on
N,N,N',N'
-tetra-
n
-octyl diglycolamide (TODGA) dissolved (0.15–0.2 M) in a mixture of Isopar-M with
n
-decanol or
n
-nonanol has been ...studied. The alcohol content was 6 or 20 vol %. A beam of 8-MeV electrons was used for irradiation. It has been found that the predominant radiolytic transformation of TODGA is fragmentation with the major formation of
N,N
-dioctylacetamide and 2-hydroxy-
N,N
-dioctylacetamide. Products of the dissociative addition of alkoxy radicals to the carbonyl groups of TODGA were detected. The total yield of TODGA degradation in the extraction system was no higher than 0.5 μmol/J. Degradation was insensitive to the type of alcohol, but it depended on the alcohol content of the solution.
The
40
Ar/
39
Ar dating of metamorphic schists from the basement of the West Siberian Platform exposed by Lenzitskaya well no. 77 on the Taz Peninsula was performed. The samples collected at depths ...of 3503 and 3515 m yielded age dates of 251.6 ± 3.5 and 271.2 ± 3.5 Ma. The age of ~271 Ma reflects the age of metamorphism of schists, which was induced by a strong tectonomagmatic event, associated with the onset of emplacement of rift zones and outflow of basalts in the Permian–Triassic. The age of ~252 Ma coincides with the period of the most intense emplacement of submeridional rifts in the basement of the West Siberian Platform. This process was accompanied by extension and thinning of the Earth’s crust in this region, which resulted in the exhumation of rocks from the mid-crystal level. The age boundary of ~250 Ma was established in the metamorphic and intrusive complexes of western Siberia and the Urals. This age is fixed almost everywhere and is correlated with the age of formation of the Siberian Trap Province.
The effect of radiolysis and postradiation acid hydrolysis on the composition of the degradation products of tributyl phosphate (TBP, 30 wt %) in acidified Izopar-M has been studied. It has been ...found that the simultaneous presence of nitric acid and isoparaffins in the irradiated solution has a protective effect on TBP. The main radiolytic products are due to the nitration, nitroxylation, and alkylation of TBP. Upon the postradiation thermolysis, nitro derivatives and nitrates decomposed with partial regeneration of TBP. Heating above 110°C also provoked the dealkylation of radiolytic products with the formation of volatile compounds, which increased the fire and explosion hazard of using irradiated extraction mixtures.
The DANSS detector is located directly under the nuclear reactor at the Kalinin nuclear power plant. Such a position ensures about 50 m.w.e. shielding from cosmic rays in the vertical direction; as a ...result, the detector occupies an intermediate position between surface and underground detectors in the shielding from cosmic rays. The sensitive volume of the detector consisting of a 1-m
3
plastic scintillator is surrounded by the multilayer passive shielding and muon veto. The main aim of the DANSS experiment is to measure the antineutrino spectrum at various distances from the source. To this end, the detector is placed on a lifting platform in order to record data at three positions of 10.9, 11.9, and 12.9 m from the reactor core. The detector can reconstruct muon tracks passing through its sensitive volume. The pressure, temperature, and decay coefficients for muons in various regions of the zenith angle
have been determined from the muon data collected during four years using the effective generation level method.
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