The influence of radiation on confinement properties of nuclear waste glasses

Self-irradiation can affect durability of glasses used to immobilize high-level nuclear waste (HLW). The stability of glasses can also be indirectly affected by the radiolytic changes in contact water leading to decrease in its pH although this is unlikely to occur for disposal systems where the interaction of groundwater with glass is delayed to times when radiation dose rates are decreased to levels insignificant to cause such effects. Besides, interaction of the water influenced by radiation with other repository protective elements (container and bentonite) will suppress the radiolytic changes. Literature analysis shows practical absence or very weak effect of self-irradiation on structure and characteristics of borosilicate glasses with typical content of nuclear waste. Data for aluminophosphate glass used in Russia have showed that, after γ-irradiation with a dose of 6.2·107 Gy, the leaching rates of elements were decreased approximately twice relatively to pristine samples

Hadron multiplicity in e+e- events induced by top quark pairs at the ILC energy

The average charged hadron multiplicity in the $e^+e^-$ events with the primary $t\bar{t}$-pair at the collision energy 500 GeV, as well as the average multiplicity of charged hadrons from the top quark are calculated in QCD to be $86.7 \pm 1.11$ and $41.0 \pm 0.54$, respectively.Comment: 24 pages, 12 figures, journal version, to be published in PMC Physics

Introduction of Large-Fruited Strawberry Varieties on the Territory of the Novosibirsk Region in the Conditions of Western Siberia

Background: For the Novosibirsk region, the need for planting material suitable for growing varieties is very high. The relatively easy technology of growing strawberries allows obtaining high yields not only for those who grow them but also on an industrial scale. Strawberry fruits contain a huge number of useful elements, including vitamins, which are necessary for the human body. The study aimed to determine the influence of the maturity group on the yield of introduced varieties of large-fruited garden strawberries.Methods: Records and observations were carried out from May 2019 to September 2020 at the collection site of the biological polygon of the Federal State Budgetary Research Institution Siberian Physical and Technical Institute in the Novosibirsk Region.Results: During the years of the study, the weather conditions of the spring period developed successfully for the growth and development of strawberries. Thus, on average, over the years of the study, high yields were shown of different maturity groups.Conclusion: The obtained yield indicators obtained were not inferior to previously zoned and local varieties, which shows that planting can be carried out both in traditional soil and in soilless culture. Thus, the quality and quantity of fruits does not change with the physicochemical properties or methods of cultivation but depends on the age of the plant and the seasonal crop cycle

Resource Queuing System with Preemptive Priority for Performance Analysis of 5G NR Systems

One of the ways to enable smooth coexistence of ultra reliable low latency communication (URRLC) and enhances mobile broadband (eMBB) services at the air interface of perspective 5G New Radio (NR) technology is to utilize preemptive priority service. In this paper, we provide approximate analysis of the queuing system with random resource requirements, two types of customers and preemptive priority service procedure. The distinctive feature of the systems – the random resource requirements – allows to capture the essentials of 5G NR radio interface but inherently increases the complexity of analysis. We present the main performance metrics of interest including session drop probability and system resource utilization as well as assess their accuracy by comparing with computer simulations. The developed model is not inherently limited to URLLC and eMBB coexistence and can be utilized in performance evaluation of 5G NR systems with priority-based service discipline at the air interface, e.g., in context of network slicing. Among other conclusions we explicitly show that both session drop and interruption probabilities of low priority traffic heavily depend not only on the intensity of high priority traffic but on stochastic characteristics of the resource request distribution.acceptedVersionPeer reviewe

The effect of fission-energy Xe ion irradiation on dissolution of UO2_2 thin films

The aim of this work was to study the effect of fission fragment damage on the dissolution of UO$_2$ thin films in water. For this purpose, thin films of UO$_2$ on LSAT (Al$_{10}$La$_3$O$_{51}$Sr$_{14}$Ta$_7$) substrates were produced and irradiated by 92 MeV $^{129}$Xe$^{23+}$ ions to a fluence of 4.8 × 10$^{15}$ ions/cm$^2$ to simulate the fission damage and induce chemical mixing that occur within nuclear fuels. The dissolution experiment was conducted under a nitrogen atmosphere (200–900 O$_2$ ppm in N$_2$ ) to study the effect of the induced irradiation damage and mixing on the dissolution of the UO$_2$ matrix. The irradiated samples showed a decrease in the amount of dissolved uranium, as compared to the corresponding unirradiated samples. This was ascribed to the irradiation-induced chemical mixing of the UO$_2$ films with the substrate elements, which resulted in stabilisation of the UO$_2$ matrix and increased its aqueous durability. Secondary phases were also observed on the surface of the UO$_2$ films after the dissolution experiment.The irradiation experiment was performed at the Grand Accelelerateur National d’Ions Lourds (GANIL) Caen, France, and supported by the French Network EMIR. AFM, SEM and EDX experiments were performed with support of M.V.Lomonosov Moscow State University Program of Development. A.J. Popel acknowledges funding from the UK EPSRC (grant EP/I036400/1) and Radioactive Waste Management Ltd (formerly the Radioactive Waste Management Directorate of the UK Nuclear Decommissioning Authority, contract NPO004411A-EPS02), a maintenance grant from the Russian Foundation for Basic Research (projects 13-03-90916) and CSAR bursary

Investigating the highest melting temperature materials : a laser melting study of the TaC-HfC system

TaC, HfC and their solid solutions are promising candidate materials for thermal protection structures in hypersonic vehicles because of their very high melting temperatures (\u3e4000 K) among other properties.  The melting temperatures of slightly hypostoichiometric TaC, HfC and three solid solution compositions (Ta1−xHfxC, with x = 0.8, 0.5 and 0.2) have long been identified as the highest known. In the current  research, they were reassessed, for the first time in the last fifty years, using a laser heating technique.  They were found to melt in the range of 4041–4232 K, with HfC having the highest and TaC the lowest.  Spectral radiance of the hot samples was measured in situ, showing that the optical emissivity of these compounds plays a fundamental role in their heat balance. Independently, the results show that the melting point for HfC0.98, (4232 ± 84) K, is the highest recorded for any compound studied until now

Discovery of optical flickering from the symbiotic star EF Aquilae

We report optical charge-coupled device (CCD) photometry of the recently identified symbiotic star EF Aquilae (EF Aql). Our observations in the Johnson V and B bands clearly show the presence of stochastic light variations with an amplitude of about 0.2 mag on a time scale of minutes. The observations point toward a white dwarf (WD) as the hot component in the system. It is the 11th object among more than 200 symbiotic stars known with detected optical flickering. Estimates of the mass accretion rate onto the WD and the mass loss rate in the wind of the Mira secondary star lead to the conclusion that less than 1% of the wind is captured by the WD. Eight further candidates for the detection of flickering in similar systems are suggested

Strong interface-induced spin-orbit coupling in graphene on WS2

Interfacial interactions allow the electronic properties of graphene to be modified, as recently demonstrated by the appearance of satellite Dirac cones in the band structure of graphene on hexagonal boron nitride (hBN) substrates. Ongoing research strives to explore interfacial interactions in a broader class of materials in order to engineer targeted electronic properties. Here we show that at an interface with a tungsten disulfide (WS2) substrate, the strength of the spin-orbit interaction (SOI) in graphene is very strongly enhanced. The induced SOI leads to a pronounced low-temperature weak anti-localization (WAL) effect, from which we determine the spin-relaxation time. We find that spin-relaxation time in graphene is two-to-three orders of magnitude smaller on WS2 than on SiO2 or hBN, and that it is comparable to the intervalley scattering time. To interpret our findings we have performed first-principle electronic structure calculations, which both confirm that carriers in graphene-on-WS2 experience a strong SOI and allow us to extract a spin-dependent low-energy effective Hamiltonian. Our analysis further shows that the use of WS2 substrates opens a possible new route to access topological states of matter in graphene-based systems.Comment: Originally submitted version in compliance with editorial guidelines. Final version with expanded discussion of the relation between theory and experiments to be published in Nature Communication

Azimuthal anisotropy and correlations at large transverse momenta in p+pp+p and Au+Au collisions at sNN\sqrt{s_{_{NN}}}= 200 GeV

Results on high transverse momentum charged particle emission with respect to the reaction plane are presented for Au+Au collisions at $\sqrt{s_{_{NN}}}$= 200 GeV. Two- and four-particle correlations results are presented as well as a comparison of azimuthal correlations in Au+Au collisions to those in $p+p$ at the same energy. Elliptic anisotropy, $v_2$, is found to reach its maximum at $p_t \sim 3$ GeV/c, then decrease slowly and remain significant up to $p_t\approx 7$ -- 10 GeV/c. Stronger suppression is found in the back-to-back high-$p_t$ particle correlations for particles emitted out-of-plane compared to those emitted in-plane. The centrality dependence of $v_2$ at intermediate $p_t$ is compared to simple models based on jet quenching.Comment: 4 figures. Published version as PRL 93, 252301 (2004