Observation of an incoherent thermally activated proton hopping process in calix-[4]-arene by means of anelastic spectroscopy

The anelastic spectrum of calix[4]arene was measured at two different vibrational frequencies. Three thermally activated peaks were detected. The lowest temperature peak can be described considering a continous distribution function of activation energies for the relaxation. This anelastic peak can be ascribed to a thermally activated hopping process of H atoms of the OH groups, corresponding to a flip-flop of the OH bond. From the results of the present study, it seems that anelastic spectroscopy is a good experimental technique to study atomic motion inside molecules at a mesoscopic (few molecules) level.Comment: 5 pages, 4 figures, submitted to Phys. Rev.

Anelastic relaxation process of polaronic origin in La{2-x}Sr{x}CuO{4}: interaction between the charge stripes and pinning centers

The evolution of an anelastic relaxation process occurring around 80 K in La{2-x}Sr{x}CuO{4} at a measuring frequency of ~1 kHz has been followed from x = 0.0075 to the overdoped region, x = 0.2, where it disappears. The dependence of the peak intensity on doping is consistent with a polaronic mechanism, identified with the disordered charge stripes overcoming pinning centers. A marked decrease of the peak amplitude occurs at x > 0.045, the same doping range where a change of the stripe order from parallel to diagonal with respect to the Cu-O bonds has been observed by neutron diffraction. Both the energy barrier and peak amplitude also exhibit a rise near x = 1/8.Comment: 5 pages, 4 figure

Observation of the cluster spin-glass phase in La_{2-x}Sr_{x}CuO_{4} by anelastic spectroscopy

An increase of the acoustic absorption is found in La_{2-x}Sr_{x}CuO_{4} (x = 0.019, 0.03 and 0.06) close to the temperatures at which freezing of the spin fluctuations in antiferromagnetic-correlated clusters is expected to occur. The acoustic absorption is attributed to changes of the sizes of the quasi-frozen clusters induced by the vibration stress through magnetoelastic coupling.Comment: LaTeX, 2 PostScript figures, submitted to Phys. Rev.

Positive impact of mindfulness meditation on mental health of female teachers during the COVID-19 outbreak in Italy

The Covid-19 pandemic and subsequent public health measures were shown to impact negatively on people\u2019s mental health. In particular, women were reported to be at higher risk than men of developing symptoms of stress/anxiety/depression, and resilience was considered a key factor for positive mental health outcomes. In the present study, a sample of Italian female teachers (n = 66, age: 51.5 \ub1 7.9 years) was assessed with self-report instruments one month before and one month after the start of the Covid-19 lockdown: mindfulness skills, empathy, personality profiles, interoceptive awareness, psychological well-being, emotional distress and burnout levels were measured. Meanwhile, they received an 8-week Mindfulness-Oriented Meditation (MOM) course, through two group meetings and six individual video-lessons. Based on baseline personality profiles, analyses of variance were performed in a low-resilience (LR, n = 32) and a high-resilience (HR, n = 26) group. The LR and HR groups differed at baseline in most of the self-report measures. Pre\u2013post MOM significant improvements were found in both groups in anxiety, depression, affective empathy, emotional exhaustion, psychological well-being, interoceptive awareness, character traits and mindfulness levels. Improvements in depression and psychological well-being were higher in the LR vs. HR group. We conclude that mindfulness-based training can effectively mitigate the psychological negative consequences of the Covid-19 outbreak, helping in particular to restore well-being in the most vulnerable individuals

Dynamics of Mn3+ in off-stoichiometric LiMn1.5Ni0.5O4

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Comparative study of the phase transition of Li1+xMn2-xO4 by anelastic spectroscopy and differential scanning calorimetry

Li1+xMn2xO4 is one of the most promising candidates as high performance cathode for lithium ion batteries. The stoichiometric compound is known to undergo a phase transition around room temperature, which has been widely studied and attributed either to Jahn–Teller effect or to charge ordering. For the applications it is important to suppress this phase transition, which lowers the electrochemical performances of the material. DSC measurements, which have been largely used in the literature to study the occurrence of the transformation, can detect a phase transition accompanied by latent heat only for x < 0.04. This fact has been generally accepted as a proof that the transformation is suppressed by doping. However, by using a technique extremely sensitive to rearrangements of atoms in the lattice, such as anelastic spectroscopy, we show that the phase transition persists up to x = 0.08, is shifted to lower temperatures, and changes its nature from first to higher order. The implications for the mechanism driving the transition and the similarities and differences with doped Fe3O4, which is the prototype of charge order transitions, are discussed

External gap progression after cyclic fatigue of adhesive overlays and crowns made with high translucency zirconia or lithium silicate

Objectives: To evaluate three-dimensional external gap progression after chewing simulation of high translucency zirconia (HTZ) and zirconia-reinforced lithium silicate (ZLS) applied on endodontically treated teeth with different preparation designs. Materials and Method: Endodontically treated molars were prepared with low-retentive (adhesive overlay) and high-retentive (full crown) designs above cementum-enamel junction and restored with HTZ and ZLS. Micro-computed tomography analysis was assessed before and after chewing simulation to evaluate three-dimensionally the external gap progression. Results were statistically analyzed with two-way ANOVA and post-hoc Tukey test. Results: High-retentive preparation design had a significantly inferior gap progression compared to the overlay preparation (p &lt; 0.01); ZLS exhibited a significant inferior gap progression compared to HTZ (p &lt; 0.01). Conclusions: High-retentive preparations restored with ZLS seem to better perform in maintaining the sealing of the external margin after cyclic fatigue. Clinical significance: The clinician should pay attention to the proper combination of preparation designs and ceramic material selection for an endodontically treated molar restoration. HTZ seems to perform worse than lithium silicate in terms of marginal sealing, still showing lacks in resistance to cyclic fatigue when adhesive preparations are performed

An EXAFS study of RuSr2GdCu2O8: evidence of magnetoelastic coupling

The EXAFS spectrum of two samples of RuSr2GdCu2O8 prepared by means of slightly different procedures was measured in the temperature range from 10 up to 300 K on the K-edge of Cu. Both the basal and the apical Cu–O distances are not influenced by the magnetic and the superconducting transitions. Moreover the temperature dependence of the Debye–Waller factors of the R(Cu–Obasal) distance for both samples is in agreement with the Debye model for thermal disorder. On the contrary, r2(Cu–Oapical) shows a clear peak around the magnetic transition. This effect is attributed to magnetoelastic couplin