Radiation thermal processes in Cr13Mo2NbVB steel - the material of the fuel assembly shell in reactor BN-350 under mechanical tests

Regularities of changes of structural-phase state and mechanical properties of steel 13Mo2NbVB - the material of the fuel assembly shell in reactor BN-350 after various mechanical tests at 350°C are experimentally studied. The formation of microprecipitations FeMo, enriched or depleted with molybdenum was found in the short-time mechanical tests, which is the cause of thermal hardening of irradiated Cr13Mo2NbVB steel and its destruction by the ductile-brittle mechanism. On the basis of long-time creep tests it was shown that the material of the spent fuel assembly shell has sufficient resource for long-time storage in the temperature and force conditions simulating long-time storage of spent nuclear fuel

Ремоделирование против реимплантации в хирургии корня аорты: сравнительные результаты и факторы риска аортальной недостаточности

Highlights. The main approaches to the aortic root valve-sparing surgery of are reimplantation and remodeling;The literature review demonstrates either the relative identity of the reimplantation and remodeling clinical outcomes, or the advantage of reimplantation in relation to long-term results.Abstract. In recent decades, valve-sparring methods of aortic root replacement, including reimplantation and remodeling, as well as their modifications, have been developed and put into widespread practice. The effectiveness and durability of these two approaches is the subject of discussions in the modern cardiac surgery community. The global experience in performing remodeling and reimplantation procedures allows  for a comprehensive literature review to compare the results of these approaches.  The presented review is devoted to the comparison of surgical aspects and clinical outcomes of reimplantation and remodeling techniques, the analysis of the feasibility of restoring the physiological architectonics of the aortic root in valve-sparring operations using Valsalva grafts, as well as the assessment of risk factors for residual aortic insufficiency after such interventions. The search strategy included the analysis of international (PubMed, Scopus, Embase) databases for the following keywords: “reimplantation versus remodeling for aortic root valve-sparring procedures”, “David procedure versus Yacoub procedure”, “Valsalva graft for aortic root valve-sparring procedures”, “Valve-sparing aortic root repair with an anatomically shaped sinus prosthesis”. Literature analysis demonstrates either the relative identity of early and long-term results of reimplantation and remodeling procedures, or the advantage of reimplantation in terms of freedom from late mortality and residual aortic insufficiency. Preservation of the physiology of the aortic root by implantation of Valsalva grafts or remodeling provides better hemodynamics and reduces stress on the leaflets, however, these postulates run counter to the data of clinical studies analyzing postoperative outcomes and demonstrating the lack of advantages of Valsalva grafts over linear prostheses in terms of freedom from aortic valve surgery. Residual postoperative regurgitation of a mild degree, a decrease in the effective height below 9 mm and additional interventions on the leaflets are reliable factors of significant aortic insufficiency in the long-term period after valve-sparring operations on the aortic root.Основные положения. Основными методами клапаносохраняющей хирургии корня аорты являются реимплантация и ремоделирование.Анализ литературы демонстрирует либо относительную идентичность клинических исходов реимплантации и ремоделирования, либо преимущество реимплантации в отношении отдаленных результатов.Резюме. В последние десятилетия разработаны и внедрены в широкую практику клапаносохраняющие методики протезирования корня аорты, включая реимплантацию и ремоделирование, а также их модификации. Эффективность   и долговечность этих двух подходов служит предметом бурных обсуждений в современном кардиохирургическом сообществе. Накопленный за три десятилетия глобальный опыт выполнения процедур ремоделирования и реимплантации позволяет провести всесторонний обзор результатов этих подходов. Представленный обзор литературы посвящен сравнению хирургических аспектов и клинических исходов методик реимплантации и ремоделирования, анализу целесообразности восстановления физиологической архитектоники корня аорты при клапаносберегающих операциях с использованием Вальсальва-графтов, а также оценке факторов риска резидуальной аортальной недостаточности после таких вмешательств. Стратегия поиска включила анализ международных баз данных (PubMed, Scopus, Embase) по следующим ключевым словам: reimplantation versus remodeling for aortic root valve-sparring procedures, David procedure versus Yacoub procedure, Valsalva graft for aortic root valve-sparring procedures, Valve-sparing aortic root repair with an anatomically shaped sinus prosthesis. Анализ литературы демонстрирует либо относительную идентичность ранних и отдаленных результатов реимплантации и ремоделирования, либо преимущество реимплантации в отношении свободы от поздней летальности и резидуальной аортальной недостаточности. Сохранение физиологичности корня аорты путем имплантации Вальсальва-графтов или ремоделирования обеспечивает лучшую гемодинамику и снижает напряжение на створки, однако эти постулаты идут вразрез с данными клинических исследований, посвященных анализу послеоперационных исходов и демонстрирующих отсутствие преимущества Вальсальва-графтов над линейными протезами в отношении свободы от реопераций на аортальном клапане. Остаточная послеоперационная регургитация легкой степени, эффективная высота ниже 9 мм и дополнительные вмешательства на створках являются достоверными факторами значимой аортальной недостаточности в отдаленном периоде после клапаносохраняющих операций на корне аорты

NEWSdm Collaboration

Direct Dark Matter searches are nowadays one of the most fervid research topics with many experimental efforts devoted to the search for nuclear recoils induced by the scattering of Weakly Interactive Massive Particles (WIMPs). Detectors able to reconstruct the direction of the nucleus recoiling against the scattering WIMP are opening a new frontier to possibly extend Dark Matter searches beyond the neutrino background. Exploiting directionality would also prove the galactic origin of Dark Matter with an unambiguous signal-to-background separation. Indeed, the angular distribution of recoiled nuclei is centered around the direction of the Cygnus constellation, while the background distribution is expected to be isotropic. Current directional experiments are based on gas TPC whose sensitivity is limited by the small achievable detector mass. In this paper we present the discovery potential of a directional experiment based on the use of a solid target made of newly developed nuclear emulsions and of optical read-out systems reaching unprecedented nanometric resolution

Directional Sensitivity of the NEWSdm Experiment to Cosmic Ray Boosted Dark Matter

We present a study of a directional search for Dark Matter boosted forward when scattered by cosmic-ray nuclei, using a module of the NEWSdm experiment. The boosted Dark Matter flux at the edge of the Earth's atmosphere is expected to be pointing to the Galactic Center, with a flux 15 to 20 times larger than in the transverse direction. The module of the NEWSdm experiment consists of a 10 kg stack of Nano Imaging Trackers, i.e.~newly developed nuclear emulsions with AgBr crystal sizes down to a few tens of nanometers. The module is installed on an equatorial telescope. The relatively long recoil tracks induced by boosted Dark Matter, combined with the nanometric granularity of the emulsion, result in an extremely low background. This makes an installation at the INFN Gran Sasso laboratory, both on the surface and underground, viable. A comparison between the two locations is made. The angular distribution of nuclear recoils induced by boosted Dark Matter in the emulsion films at the surface laboratory is expected to show an excess with a factor of 3.5 in the direction of the Galactic Center. This excess allows for a Dark Matter search with directional sensitivity. The surface laboratory configuration prevents the deterioration of the signal in the rock overburden and it emerges as the most powerful approach for a directional observation of boosted Dark Matter with high sensitivity. We show that, with this approach, a 10 kg module of the NEWSdm experiment exposed for one year at the Gran Sasso surface laboratory can probe Dark Matter masses between 1 keV/c$^2$ and 1 GeV/c$^2$ and cross-section values down to $10^{-30}$~cm$^2$ with a directional sensitive search.Comment: 15 pages, 14 figures, updated references, clarified discussion in intro section. Submitted to JCA

NMR study of magnetic structure and hyperfine interactions in the binary helimagnet FeP

We report a detailed study of the ground state helical magnetic structure in monophosphide FeP by means of ${}^{31}$P NMR spectroscopy. We show that the zero-field NMR spectrum of the polycrystalline sample provides strong evidence of an anisotropic distribution of local magnetic fields at the P site with substantially lower anharmonicity than that found at the Fe site by M\"{o}ssbauer spectroscopy. From field-sweep ${}^{31}$P NMR spectra we conclude that a continuous spin-reorientation transition occurs in an external magnetic field range of 4 - 7 T, which is also confirmed by specific-heat measurements. We observe two pairs of magnetically inequivalent phosphorus positions resulting in a pronounced four-peak structure of the single crystal ${}^{31}$P NMR spectra characteristic of an incommensurate helimagnetic ground state. We revealed a spatial redistribution of local fields at the P sites caused by Fe spin-reorientation transition in high fields and developed an effective approach to account for it. We demonstrate that all observed ${}^{31}$P spectra can be treated within a model of an isotropic helix of Fe magnetic moments in the ($ab$)-plane with a phase shift of 36$^{\circ}$ and 176$^{\circ}$ between Fe1-Fe3 (Fe2-Fe4) and Fe1-Fe2 (Fe3-Fe4) sites, respectively, in accordance with the neutron scattering data.Comment: 12 pages, 11 figure