Boundary between the thermal and statistical polarization regimes in a nuclear spin ensemble

As the number of spins in an ensemble is reduced, the statistical uctuations in its polarization eventually exceed the mean thermal polarization. This transition has now been surpassed in a number of recent nuclear magnetic resonance experiments, which achieve nanometer-scale detection volumes. Here, we measure nanometer- scale ensembles of nuclear spins in a KPF6 sample using magnetic resonance force microscopy. In particular, we investigate the transition between regimes dominated by thermal and statistical nuclear polarization. The ratio between the two types of polarization provides a measure of the number of spins in the detected ensemble

Graffiti removal from granite cladding by abrasive water-jet

This study focuses on the assessment of a graffiti removal system based on abrasive water-jet technology (AWJ). Spray paints were applied on samples of an important Italian granite commercially-named as “Rosa Limbara”. This granite has been used worldwide as dimension stone for paving and cladding. Two different commercial abrasives have been added in the high-pressure water-jet in order to clean the granite saw-plane surfaces from graffiti. After a check by the naked eye, different criteria have been chosen for assessing the effectiveness of the cleaning process: the similarity in roughness (Ra, Rz, and Rmax) between the original surface and the one resulted after cleaning, the total colour difference (ΔE) and the depth of material removed by the AWJ action. The tests showed that excellent cleaning results can be achieved with both abrasives by correctly combining the operational parameters of the technology (i.e., water pressure, spacing between passes, stand-off distance, travel speed and abrasive flow-rate) without giving any damage to the stone material. The two abrasives showed good results in total colour difference although one of them gave better results in both roughness difference and material removal. Economic considerations on paint removal with AWJ technology are also offered

Nonlinear motion and mechanical mixing in as-grown GaAs nanowires

We report nonlinear behavior in the motion of driven nanowire cantilevers. The nonlinearity can be described by the Duffing equation and is used to demonstrate mechanical mixing of two distinct excitation frequencies. Furthermore, we demonstrate that the nonlinearity can be used to amplify a signal at a frequency close to the mechanical resonance of the nanowire oscillator. Up to 26 dB of amplitude gain are demonstrated in this way

On the impact of the Migdal effect in reactor CEν\nuNS experiments

The search for coherent elastic neutrino nucleus scattering (CE$\nu$NS) using reactor antineutrinos represents a formidable experimental challenge, recently boosted by the observation of such a process at the Dresden-II reactor site using a germanium detector. This observation relies on an unexpected enhancement at low energies of the measured quenching factor with respect to the theoretical Lindhard model prediction, which implies an extra observable ionization signal produced after the nuclear recoil. A possible explanation for this additional contribution could be provided by the so-called Migdal effect, which however has never been observed. Here, we study in detail the impact of the Migdal contribution to the standard CE$\nu$NS signal calculated with the Lindhard quenching factor, finding that the former is completely negligible for observed energies below $\sim 0.3\,\mathrm{keV}$ where the signal is detectable, and thus unable to provide any contribution to CE$\nu$NS searches in this energy regime. To this purpose, we compare different formalisms used to describe the Migdal effect that intriguingly show a perfect agreement, making our findings robust.Comment: 5 pages, 2 figure

Contractile reserve in systemic sclerosis patients as a major predictor of global cardiac impairment and exercise tolerance

Several studies have evidenced high prevalence of myocardial systolic and diastolic dysfunction among patients with systemic sclerosis (SSc). Exercise echocardiography has shown a diagnostic and prognostic role in identifying early left ventricular (LV) dysfunction in several myocardial pathological settings. The aim of our study was to evaluate early signs of LV impairment under exercise and their correlation to patient's exercise tolerance. Forty-five patients (age 60.4 ± 10.3 years) with SSc and 20 age and sex comparable controls were enrolled in the study. All patients underwent clinical evaluation, 2D echocardiography associated with Tissue Doppler and speckle tracking to evaluate LV deformation indexes, and an exercise echocardiography to evaluate left ventricle contractile reserve (LVCR) and exercise pulmonary pressures. Finally, a 6-minute walking test (6MWT) to evaluate exercise tolerance was also performed. Compared to controls, SSc patients showed an impaired diastolic function (E/E' 10.9 ± 3.7 vs 8.36 ± 2.01; p < 0.01) associated with larger left atrial dimensions (LAVI 28.4 ± 8.7 vs 19.3 ± 4.6 mL/m2; p < 0.01). During exercise echocardiography, a reduced global longitudinal strain at peak exercise (S-GLS) was highlighted compared to controls (15.7 ± 3.6 vs 18.2 ± 2.2; p = 0.001). A S-GLS cutoff <18 %, identified by ROC analysis, identified SSc patients with a reduced diastolic function, exercise tolerance at the 6MWT and higher pulmonary pressures. Our data show that in SSc patients a reduced LVCR characterizes the patients with a more extensive cardiovascular impairment in terms of LV diastolic function, pulmonary pressures and exercise tolerance. These data underline the importance of exercise echocardiography for the preclinical screening of the LV impairment in this population