Scanning Tunneling Spectroscopy study of paramagnetic superconducting β’’-ET4[(H3O)Fe(C2O4)3]•C6H5Br crystals

Scanning tunnelling spectroscopy (STS) and microscopy (STM) were performed on the paramagnetic molecular superconductor beta''-ET4[(H3O)Fe(C2O4)(3)]C6H5Br. Under ambient pressure, this compound is located near the boundary separating superconducting and insulating phases of the phase diagram. In spite of a strongly reduced critical temperature T-c (T-c = 4.0 K at the onset, zero resistance at T-c = 0.5 K), the low temperature STS spectra taken in the superconducting regions show strong similarities with the higher T-c ET kappa-derivatives series. We exploited different models for the density of states (DOS), with conventional and unconventional order parameters to take into account the role played by possible magnetic and non-magnetic disorder in the superconducting order parameter. The values of the superconducting order parameter obtained by the fitting procedure are close to the ones obtained on more metallic and higher T-c organic crystals and far above the BCS values, suggesting an intrinsic role of disorder in the superconductivity of organic superconductors and a further confirmation of the non-conventional superconductivity in such compounds

Approximate Analytical Model for the Squeeze-Film Lubrication of the Human Ankle Joint with Synovial Fluid Filtrated by Articular Cartilage

The aim of this article is to propose an analytical approximate squeeze-film lubrication model of the human ankle joint for a quick assessment of the synovial pressure field and the load carrying due to the squeeze motion. The model starts from the theory of boosted lubrication for the human articular joints lubrication (Walker et al., Rheum Dis 27:512–520, 1968; Maroudas, Lubrication and wear in joints. Sector, London, 1969) and takes into account the fluid transport across the articular cartilage using Darcy’s equation to depict the synovial fluid motion through a porous cartilage matrix. The human ankle joint is assumed to be cylindrical enabling motion in the sagittal plane only. The proposed model is based on a modified Reynolds equation; its integration allows to obtain a quick assessment on the synovial pressure field showing a good agreement with those obtained numerically (Hlavacek, J Biomech 33:1415–1422, 2000). The analytical integration allows the closed form description of the synovial fluid film force and the calculation of the unsteady gap thickness

The distance to the Sgr dwarf spheroidal galaxy from the Red Giant Branch Tip

We derived the distance to the central region of the Sagittarius dwarf spheroidal galaxy from the Red Giant Branch Tip. The obtained distance modulus is $(m-M)_0=17.10\pm0.15$, corresponding to a heliocentric distance $D=26.30\pm1.8$ Kpc. This estimate is in good agreement with the distance obtained from RR Lyrae stars of the globular cluster M~54, located in the core of the Sgr galaxy, once the most accurate estimate of the cluster metallicity and the most recent calibration of the $M_V(RRLy) vs.[Fe/H]$ relation are adopted.Comment: 6 pages, 5 figure, Accepted for publication in MNRA

Transfer-free electrical insulation of epitaxial graphene from its metal substrate

High-quality, large-area epitaxial graphene can be grown on metal surfaces but its transport properties cannot be exploited because the electrical conduction is dominated by the substrate. Here we insulate epitaxial graphene on Ru(0001) by a step-wise intercalation of silicon and oxygen, and the eventual formation of a SiO$_2$ layer between the graphene and the metal. We follow the reaction steps by x-ray photoemission spectroscopy and demonstrate the electrical insulation using a nano-scale multipoint probe technique.Comment: Accepted for publication in Nano Letter

Measurement of the 2νββ decay half-life of 150Nd and a search for 0νββ decay processes with the full exposure from the NEMO-3 detector

We present results from a search for neutrinoless double-β (0νββ) decay using 36.6 g of the isotope 150Nd with data corresponding to a live time of 5.25 y recorded with the NEMO-3 detector. We construct a complete background model for this isotope, including a measurement of the two-neutrino double-β decay half-life of T2ν 1=2 ¼ ½9.34 0.22ðstatÞ þ0.62 −0.60 ðsystÞ × 1018 y for the ground state transition, which represents the most precise result to date for this isotope. We perform a multivariate analysis to search for 0νββ decays in order to improve the sensitivity and, in the case of observation, disentangle the possible underlying decay mechanisms. As no evidence for 0νββ decay is observed, we derive lower limits on half-lives for several mechanisms involving physics beyond the standard model. The observed lower limit, assuming light Majorana neutrino exchange mediates the decay, is T0ν 1=2 > 2.0 × 1022 y at the 90% C.L., corresponding to an upper limit on the effective neutrino mass of hmνi < 1.6–5.3 eV

Discovery of X-ray polarization angle rotation in active galaxy Mrk 421

The magnetic field conditions in astrophysical relativistic jets can be probed by multiwavelength polarimetry, which has been recently extended to X-rays. For example, one can track how the magnetic field changes in the flow of the radiating particles by observing rotations of the electric vector position angle $\Psi$. Here we report the discovery of a $\Psi_{\mathrm x}$ rotation in the X-ray band in the blazar Mrk 421 at an average flux state. Across the 5 days of Imaging X-ray Polarimetry Explorer (IXPE) observations of 4-6 and 7-9 June 2022, $\Psi_{\mathrm x}$ rotated in total by $\geq360^\circ$. Over the two respective date ranges, we find constant, within uncertainties, rotation rates ($80 \pm 9$ and $91 \pm 8 ^\circ/\rm day$) and polarization degrees ($\Pi_{\mathrm x}=10\%\pm1\%$). Simulations of a random walk of the polarization vector indicate that it is unlikely that such rotation(s) are produced by a stochastic process. The X-ray emitting site does not completely overlap the radio/infrared/optical emission sites, as no similar rotation of $\Psi$ was observed in quasi-simultaneous data at longer wavelengths. We propose that the observed rotation was caused by a helical magnetic structure in the jet, illuminated in the X-rays by a localized shock propagating along this helix. The optically emitting region likely lies in a sheath surrounding an inner spine where the X-ray radiation is released