A Coplanar Waveguide Resonator Technique for the Characterization of Iron-Based Superconductors

We present in detail a coplanar waveguide resonator (CPWR) method for the characterization of superconducting single crystals. It exploits the region of a CPWR where the rf magnetic field is quite homogeneous, by coupling a sample to it. Measurements are performed with and without the crystal, allowing a cavity perturbation approach. From the modifications in the resonance frequency and quality factor of the system it is possible to extract the London penetration depth and its anisotropy, quasiparticle conductivity, surface impedance and, when a coexisting magnetic phase is present, even bulk complex susceptibility

The role of block shape and slenderness in the preliminary estimation of rockfall propagation

Among the wide range of variables that influence the falling process of blocks during a rockfall event, the shape of the block often plays a crucial role. Spherical-like blocks typically reach longer runout distances while elongated and plate volumes stop earlier. Nevertheless, with reference to runout modelling and hazard analyses, the shape of the block was disregarded for very long time until the last two decades when more rigorous rockfall models were developed. Nowadays fully 3D rigid body models and particle-based ones can take into account different and complex aspects related to block geometry and size (e.g. shape, change of shape, slenderness, fragmentation, etc.) when in site-specific applications are addressed. On the other hand, when the rockfall analysis is extended over large areas, simplified runout models can be used for preliminary, quick analyses, aimed at highlighting the most critical zones of the area. In this case, the variables that influence the rockfall process should be included in the analysis in equivalent terms. Among these simplified models, the Cone Method allows to reduce the runout phase to an equivalent sliding motion of the block along an inclined plane. The inclination of this plane with respect to the horizontal plane (i.e. the energy angle ) can be related to both block and slope properties of the real rockfall case. The authors of this paper developed a methodology for the estimation of the energy angle as a function of the condition of the site under analysis (characteristics of the blocks and the slope), to be used for preliminary forecasting analyses at medium-small scales. To this aim, a series of parametric analyses have been carried out to quantify the role of each variable on the energy angle. In this paper, the role of block shape and slenderness (i.e. the ratio between the height and the width of the rock block) is analysed via several propagation analyses carried out on simplified synthetic slopes by using the fully 3D RAMMS::ROCKFALL model. The results were finally statistically treated in terms of energy angles in order to take into account the variability of rockfall trajectories and provide a contribution for the estimation of the parameters within preliminary analyses based on the Cone Method

k-Anonymity on Graphs using the Szemerédi Regularity Lemma

Graph anonymisation aims at reducing the ability of an attacker to identify the nodes of a graph by obfuscating its structural information. In k-anonymity, this means making each node indistinguishable from at least other k-1 nodes. Simply stripping the nodes of a graph of their identifying label is insufficient, as with enough structural knowledge an attacker can still recover the nodes identities. We propose an algorithm to enforce k-anonymity based on the Szemerédi regularity lemma. Given a graph, we start by computing a regular partition of its nodes. The Szemerédi regularity lemma ensures that such a partition exists and that the edges between the sets of nodes behave quasi-randomly. With this partition to hand, we anonymize the graph by randomizing the edges within each set, obtaining a graph that is structurally similar to the original one yet the nodes within each set are structurally indistinguishable. Unlike other k-anonymisation methods, our approach does not consider a single type of attack, but instead it aims to prevent any structure-based de-anonymisation attempt. We test our framework on a wide range of real-world networks and we compare it against another simple yet widely used k-anonymisation technique demonstrating the effectiveness of our approach

Characterization of the behavior of a turbine rotor steel by inverse analysis on the small punch test

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Comprehensive Eliashberg analysis of microwave conductivity and penetration depth of K-, Co-, and P-substituted BaFe2As2

We report on the combined experimental and theoretical analysis of the microwave-frequency electromagnetic response of BaFe2As2single crystals with different substitutions: K in the Ba site (hole doping), Co in the Fe site (electron doping), and P in the As site (isovalent substitution). Measurements using a coplanar resonator technique lead to the experimental determination of the penetration depth and microwave conductivity as a function of temperature. The whole set of data is analyzed within a self-consistent three-bands±-wave Eliashberg approach, able to account for all the main observed features in the different properties. Besides the validation of the model itself, the comparison between experiment and theory allows discussing the possible role of the Fe-As planes in defining the superconducting properties of these compounds, the relevance of coherence effects, and the presence of nodes in the superconducting order parameter

Scaling laws for ion irradiation effects in iron-based superconductors

We report on ion irradiation experiments performed on compounds belonging to the BaFe 2As 2 family, each one involving the partial substitution of an atom of the parent compound (K for Ba, Co for Fe, and P for As), with an optimal composition to maximize the superconducting critical temperature Tc. Employed ion beams were 3.5-MeV protons, 250-MeV Au ions, and 1.2-GeV Pb ions, but additional data from literature are also considered, thus covering a wide range of ions and energies. Microwave characterization based on the use of a coplanar waveguide resonator allowed us to investigate the irradiation-induced Tc degradation, as well as the increase of normal state resistivity and London penetration depth. The damage was quantified in terms of displacements per atom (dpa). From this broad and comprehensive set of experimental data, clear scaling laws emerge, valid in the range of moderate irradiation-induced disorder (dpa up to 5 × 10 - 3 were investigated). In these conditions, linear trends with dpa were found for all the modification rates, while a power law dependence on the ion energy was found for heavy-ion irradiation. All these scaling laws are reported and discussed throughout the paper

Classification of Chimney EVAR-Related Endoleaks: Insights from the PERICLES Registry

Juxtarenal aortic aneurysms (JAAs) pose significant challenges for endovascular aneurysm repair (EVAR). A short or absent infrarenal neck typically excludes standard EVAR as a viable or reasonable treatment option. In this context, the use of chimney grafts (chEVAR) is gaining in popularity and applicability. These grafts are designed to course in the aortic lumen outside the main stent-graft to maintain normal perfusion to the involved target branches. As such, they may represent a promising and less resource-intensive option for management of JAAs. However, this technical strategy is not without challenges of its own, particularly the inevitable creation of \u201cgutters\u201d that result from the interaction of the chimney graft with the main aortic stent-graft. These gutters can become a conduit for type Ia endoleak formation, hence they represent the Achilles\u2019 heel of chEVAR. Current reports point to a relatively wide-ranging incidence (0%\u201313%) of type Ia endoleaks related to chEVAR. The PERICLES Registry collected the global transatlantic experience of 13 European and US vascular centers reporting 517 patients with complex aneurysms treated with EVAR and chimney parallel grafts. Overall, 6% of PERICLES chEVAR patients had a type Ia endoleak at completion angiography, but the rate of persistent endoleaks was only 2.9% at a mean 17.1 months of follow-up. Close review of the postoperative computed tomography angiograms of these persistent endoleak patients revealed distinct types and patterns of chEVAR-related type Ia endoleaks and form the basis of a new classification proposed herein. It is hoped that these observations will lead to development of new treatment algorithms for effective management of chimney-related endoleaks and, in some cases, to prevent them from occurring in the first place

Disorder-Driven Transition from s(+/-) to s(+ +) Superconducting Order Parameter in Proton Irradiated Ba(Fe1-xRhx)(2)As-2 Single Crystals

Microwave measurements of the London penetration depth and critical temperature T c were used to show evidence of a disordered-driven transition from s ± to s + + order parameter symmetry in optimally doped Ba ( Fe 1 − x Rh x ) 2 As 2 single crystals, where disorder was induced by means of 3.5 MeV proton irradiation. Signatures of such a transition, as theoretically predicted [V. D. Efremov et al., Phys. Rev. B 84, 180512(R) (2011)], are found as a drop in the low-temperature values of the London penetration depth and a virtually disorder-independent superconducting T c . We show how these experimental observations can be described by multiband Eliashberg calculations in which the effect of disorder is accounted for in a suitable way. To this aim, an effective two-band approach is adopted, allowing us to treat disorder in a range between the Born approximation and the unitary limit