Destruction of superconductivity in disordered materials : a dimensional crossover

The disorder-induced Superconductor-to-Insulator Transition in amorphous Nb$_{x}$Si$_{1-x}$ two-dimensional thin films is studied for different niobium compositions $x$ through a variation of the sample thickness $d$. We show that the critical thickness $d_c$, separating a superconducting regime from an insulating one, increases strongly with diminishing $x$, thus attaining values of over 100 {\AA}. The corresponding phase diagram in the $(d, x)$ plane is inferred and related to the three-dimensional situation. The two-dimensional Superconductor-to-Insulator Transition well connects with the three-dimensional Superconductor-to-Metal Transition

Myelin contrast across lamina at 7T, ex-vivo and in-vivo dataset

In this article we report the complete data obtained in-vivo for the paper: “Lines of Baillarger in vivo and ex-vivo: myelin contrast across lamina at 7T MRI and histology” (Fracasso et al., 2015) 1. Single participant data (4 participants) from the occipital lobe acquisition are reported for axial, coronal and sagittal slices; early visual area functional localization and laminar profiles are reported. Data from whole brain images are reported and described (5 participants), for axial, coronal and sagittal slices. Laminar profiles from occipital, parietal and frontal lobes are reported. The data reported in this manuscript complements the paper (Fracasso et al., 2015) 1 by providing the full set of results from the complete pool of participants, on a single-participant basis. Moreover, we provide histological images from the ex-vivo sample reported in Fracasso et al. (2015) 1

Effect of annealing on the superconducting properties of a-Nb(x)Si(1-x) thin films

a-Nb(x)Si(1-x) thin films with thicknesses down to 25 {\AA} have been structurally characterized by TEM (Transmission Electron Microscopy) measurements. As-deposited or annealed films are shown to be continuous and homogeneous in composition and thickness, up to an annealing temperature of 500{\deg}C. We have carried out low temperature transport measurements on these films close to the superconductor-to-insulator transition (SIT), and shown a qualitative difference between the effect of annealing or composition, and a reduction of the film thickness on the superconducting properties of a-NbSi. These results question the pertinence of the sheet resistance R_square as the relevant parameter to describe the SIT.Comment: 9 pages, 12 figure

AMORPHOUS PD-SI ALLOYS AND HYDRIDES PREPARED BY LOW-TEMPERATURE ION-IMPLANTATION

Ion implantation simultaneously produces compositional changes and radiation damage in the target. If the latter is not annealed, amorphization should ultimately result. Can implantation of a covalent solute into a transition metal host stabilize the damage and hence produce an amorphous alloy at lower concentrations than other techniques ? We have studied the composition-dependence of the resistivity and TCR of thin (600-800 Å) Pd films implanted at 6 K with Si ions : The results are compared to those obtained on the corresponding well-documented quench-condensed alloys, which are amorphous at Si concentrations ~.18. The resistivity of the implanted films saturates at about 90 µΩ·cm for Si concentrations above ~.18. Thus, the critical concentration for amorphization is presumably the same for the low-temperature implanted or quench-condensed Pd-Si alloy, confirming that local structure effects dominate amorphous alloy formation criteria. In a further experiment, hydrogen was implanted into the amorphous Pd-Si films (again at 6K). The resistivity increased sharply, doubling at H concentrations around 100 %. The resulting systems were superconducting ; their maximum critical temperature was 2.6 K

Assessment of Involuntary PFM Contractions in Comparison with Existing Literature and IUGA/ICS Terminology Reports.

INTRODUCTION AND HYPOTHESIS Involuntary pelvic floor muscle (PFM) contractions are thought to occur during an increase in intra-abdominal pressure (IAP). Although no studies have assessed their presence in women with normal pelvic floor (PF) function, existing literature links the absence of involuntary PFM contractions to various PF dysfunctions. This study rectifies this lacuna by evaluating involuntary PFM contractions during IAP in healthy nulliparous women with no PF dysfunction, using visual observation and vaginal palpation. Results were compared with the literature and the IUGA/ICS Terminology Reports. METHODS Nulliparous (n=149) women performed three sets of three maximal coughs. Visual observation and vaginal palpation were conducted in the standing and supine positions. The women were not instructed to contract their PFMs. Occurrence rates were calculated for each assessment method and position; differences between positions were analyzed using the Chi-squared test. RESULTS Rates of occurrence of involuntary PFM contraction were low across both assessments and positions (5-17%). Significant differences were found between standing (5%) and supine (15%) positions for visual observation, but not vaginal palpation (15%, 17% respectively). Occurrence rates also differed compared with the literature and terminology reports. CONCLUSIONS Contrary to clinical expectations, rates of occurrence of involuntary PFM contraction among our cohort of nulliparous women were extremely low. Digital palpation results showed high agreement with the terminology reports, but only partial agreement was observed for the visual observation results. Our study underscores the need for more research aimed at defining normal involuntary PF functions, a review of our understanding of involuntary PFM contractions, and better standardized guidelines for involuntary PFM assessment methods

Rejection of randomly coinciding events in Li2_2100^{100}MoO4_4 scintillating bolometers using light detectors based on the Neganov-Luke effect

Random coincidences of nuclear events can be one of the main background sources in low-temperature calorimetric experiments looking for neutrinoless double-beta decay, especially in those searches based on scintillating bolometers embedding the promising double-beta candidate $^{100}$Mo, because of the relatively short half-life of the two-neutrino double-beta decay of this nucleus. We show in this work that randomly coinciding events of the two-neutrino double decay of $^{100}$Mo in enriched Li$_2$$^{100}$MoO$_4$ detectors can be effectively discriminated by pulse-shape analysis in the light channel if the scintillating bolometer is provided with a Neganov-Luke light detector, which can improve the signal-to-noise ratio by a large factor, assumed here at the level of $\sim 750$ on the basis of preliminary experimental results obtained with these devices. The achieved pile-up rejection efficiency results in a very low contribution, of the order of $\sim 6\times10^{-5}$ counts/(keV$\cdot$kg$\cdot$y), to the background counting rate in the region of interest for a large volume ($\sim 90$ cm$^3$) Li$_2$$^{100}$MoO$_4$ detector. This background level is very encouraging in view of a possible use of the Li$_2$$^{100}$MoO$_4$ solution for a bolometric tonne-scale next-generation experiment as that proposed in the CUPID project

Bi-layer Kinetic Inductance Detectors for space observations between 80-120 GHz

We have developed Lumped Element Kinetic Inductance Detectors (LEKID) sensitive in the frequency band from 80 to 120~GHz. In this work, we take advantage of the so-called proximity effect to reduce the superconducting gap of Aluminium, otherwise strongly suppressing the LEKID response for frequencies smaller than 100~GHz. We have designed, produced and optically tested various fully multiplexed arrays based on multi-layers combinations of Aluminium (Al) and Titanium (Ti). Their sensitivities have been measured using a dedicated closed-circle 100 mK dilution cryostat and a sky simulator allowing to reproduce realistic observation conditions. The spectral response has been characterised with a Martin-Puplett interferometer up to THz frequencies, and with a resolution of 3~GHz. We demonstrate that Ti-Al LEKID can reach an optical sensitivity of about $1.4$ $10^{-17}$~$W/Hz^{0.5}$ (best pixel), or $2.2$ $10^{-17}$~$W/Hz^{0.5}$ when averaged over the whole array. The optical background was set to roughly 0.4~pW per pixel, typical for future space observatories in this particular band. The performance is close to a sensitivity of twice the CMB photon noise limit at 100~GHz which drove the design of the Planck HFI instrument. This figure remains the baseline for the next generation of millimetre-wave space satellites.Comment: 7 pages, 9 figures, submitted to A&