Feature extraction and identification techniques for the alignment of perturbation simulations with power plant measurements

In this work, a methodology is proposed for the comparison of the measured and simulated neutron noise signals in nuclear power plants, with the simulation sets having been generated by the CORE SIM+ diffusion-based reactor noise simulator. More specifically, the method relies on the computation of the Cross-Power Spectral Density of the detector signals and the subsequent comparison with their simulated counterparts, which involves specific frequency values corresponding to the signals’ high energy content. The different simulated perturbations considered are (i) axially traveling perturbations, (ii) fuel assembly vibrations, (iii) core barrel vibrations, and finally (iv) generic “absorber of variable strength” types. The reactor core used for the current study is a German 4-loop pre-Konvoi Pressurized Water Reactor

Epitaxial growth of AgCrSe2 thin films by molecular beam epitaxy

Funding: The authors gratefully acknowledge the European Research Council (through the QUESTDO project, 714193) and The Leverhulme Trust (Grant No. RL-2016-006) for support. The MBE growth facility was funded through an EPSRC strategic equipment grant: EP/M023958/1. The research leading to this result has been supported by the project CALIPSO under Grant Agreement 312284 from the EU Seventh Framework Programme (FP7/2007-2013).AgCrSe2 exhibits remarkably high ionic conduction, an inversion symmetry-breaking structural transition, and is host to complex non-colinear magnetic orders. Despite its attractive physical and chemical properties, and its potential for technological applications, studies of this compound to date are focused almost exclusively on bulk samples. Here, we report the growth of AgCrSe2 thin films via molecular beam epitaxy. Single-orientated epitaxial growth was confirmed by X-ray diffraction, while resonant photoemission spectroscopy measurements indicate a consistent electronic structure as compared to bulk single crystals. We further demonstrate significant flexibility of the grain morphology and cation stoichiometry of this compound via control of the growth parameters, paving the way for the targeted engineering of the electronic and chemical properties of AgCrSe2 in thin-film form.Publisher PDFPeer reviewe

Mechanical Properties of Calcareous Fly Ash Stabilised Soil

Construction of any type of structure on clayey ground could be problematic due to the high swelling potential and/or low strength characteristics of the soil. This can lead to low stability or differential settlement of the ground. Many soil stabilization techniques have been proposed to prevent the uneven settlement and failure of the soil. Stabilization of soil with class C fly ash offers many advantages such as improving engineering caracteristics, being cost-effective and being environmentally friendly. Class C fly ash chemically reacts with clay which results in a more durable and stronger soil. It has been shown by various researchers that fly ash-stabilized soil is typically stiff and strong even though there is no available standard or guidelines for the use of fly ash in construction industry. This paper presents the results from a program of experimental research on stabilization of a fine-grained soil with fly ash. Laboratory experiments, including Atterberg limits, compaction, uniaxial, and consolidation tests, were conducted on samples of a clay soil with different percentages of fly ash. The results show that adding fly ash decreased the plasticity index, increased compressive strength, and decreased the swelling and compressibility index. The maximum dry density increased and optimum moisture content decreased with addition of over 5 % fly ash by dry weight of the soil.Turkish governmentEuropean Union Horizon 202

Proximity-induced ferromagnetism and chemical reactivity in few-layer VSe2 heterostructures

Among transition-metal dichalcogenides, mono and few-layers thick VSe2 has gained much recent attention following claims of intrinsic room-temperature ferromagnetism in this system, which have nonetheless proved controversial. Here, we address the magnetic and chemical properties of Fe/VSe2 heterostructure by combining element sensitive x-ray absorption spectroscopy and photoemission spectroscopy. Our x-ray magnetic circular dichroism results confirm recent findings that both native mono/few-layer and bulk VSe2 do not show intrinsic ferromagnetic ordering. Nonetheless, we find that ferromagnetism can be induced, even at room temperature, after coupling with a Fe thin film layer, with antiparallel alignment of the moment on the V with respect to Fe. We further consider the chemical reactivity at the Fe/VSe2 interface and its relation with interfacial magnetic coupling

Detection and localisation of multiple in-core perturbations with neutron noise-based self-supervised domain adaptation

The use of non-intrusive techniques for monitoring nuclear reactors is becoming more vital as western fleets age. As a consequence, the necessity to detect more frequently occurring operational anomalies is of upmost interest. Here, noise diagnostics — the analysis of small stationary deviations of local neutron flux around its time-averaged value — is employed aiming to unfold from detector readings the nature and location of driving perturbations. Given that in-core instrumentation of western-type light-water reactors are scarce in number of detectors, rendering formal inversion of the reactor transfer function impossible, we propose to utilise advancements in Machine Learning and Deep Learning for the task of unfolding. This work presents an approach to such a task doing so in the presence of multiple and simultaneously occurring perturbations or anomalies. A voxel-wise semantic segmentation network is proposed to determine the nature and sourcelocation of multiple and simultaneously occurring perturbations in the frequency domain. A diffusion-based core simulation tool has been employed to provide simulated training data for two reactors. Additionally, we work towards the application of the aforementioned approach to real measurements, introducing a self-supervised domain adaptation procedure to align the representation distributions of simulated and real plant measurements

Anisotropic hybridization probed by polarization dependent x-ray absorption spectroscopy in VI3 van der Waals Mott ferromagnet

Polarization dependent x-ray absorption spectroscopy was used to study the magnetic ground state and the orbital occupation in bulk-phase VI$_3$ van der Waals crystals below and above the ferromagnetic and structural transitions. X-ray natural linear dichroism and X-ray magnetic circular dichroism spectra acquired at the V $L_{2,3}$ edges are compared against multiplet cluster calculations within the frame of the ligand field theory to quantify the intra-atomic electronic interactions at play and evaluate the effects of symmetry reduction occurring in a trigonally distorted VI$_6$ unit. We observed a non zero linear dichroism proving the presence of an anisotropic charge density distribution around the V$^{3+}$ ion due to the unbalanced hybridization between the Vanadium and the ligand states. Such hybridization acts as an effective trigonal crystal field, slightly lifting the degeneracy of the $t_{2g}^2$ ground state. However, the energy splitting associated to the distortion underestimates the experimental band gap, suggesting that the insulating ground state is stabilized by Mott correlation effects rather than via a Jahn-Teller mechanism. Our results clarify the role of the distortion in VI$_3$ and establish a benchmark for the study of the spectroscopic properties of other van der Waals halides, including emerging 2D materials with mono and few-layers thickness, whose fundamental properties might be altered by reduced dimensions and interface proximity

The ClpXP protease is dispensable for degradation of unfolded proteins in <i>Staphylococcus aureus</i>

Abstract In living cells intracellular proteolysis is crucial for protein homeostasis, and ClpP proteases are conserved between eubacteria and the organelles of eukaryotic cells. In Staphylococcus aureus, ClpP associates to the substrate specificity factors, ClpX and ClpC forming two ClpP proteases, ClpXP and ClpCP. To address how individual ClpP proteases impact cell physiology, we constructed a S. aureus mutant expressing ClpX with an I265E substitution in the ClpP recognition tripeptide of ClpX. This mutant cannot degrade established ClpXP substrates confirming that the introduced amino acid substitution abolishes ClpXP activity. Phenotypic characterization of this mutant showed that ClpXP activity controls cell size and is required for growth at low temperature. Cells expressing the ClpXI265E variant, in contrast to cells lacking ClpP, are not sensitive to heat-stress and do not accumulate protein aggregates showing that ClpXP is dispensable for degradation of unfolded proteins in S. aureus. Consistent with this finding, transcriptomic profiling revealed strong induction of genes responding to protein folding stress in cells devoid of ClpP, but not in cells lacking only ClpXP. In the latter cells, highly upregulated loci include the urease operon, the pyrimidine biosynthesis operon, the betA-betB operon, and the pathogenicity island, SaPI5, while virulence genes were dramatically down-regulated

Magnetic anisotropy at the buried CoO/Fe interface

Interfaces between antiferromagnetic CoO and ferromagnetic Fe are typically characterized by the development of Fe oxides. Recently, it was shown that the use of a proper ultra-thin Co buffer layer prevents the formation of Fe oxides [Brambilla et al., Appl. Surf. Sci. 362, 374 (2016)]. In the present work, we investigate the magnetic properties of such an interface, and we find evidence for an in-plane uniaxial magnetic anisotropy, which is characterized by a multijump reversal behavior in the magnetization hysteresis loops. X-ray photoemission spectroscopy and element-sensitive hysteresis loops reveal that the occurrence of such an anisotropy is a phenomenon developing at the very interface