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The present results indicate that in aged women administration of 1 mg of melatonin reduces glucose tolerance and insulin sensitivity. The present data may have both physiological and clinical implications.

Among the hybrid metal-organic perovskites for photovoltaic applications FAPbI 3 (FAPI) has the best performance regarding efficiency and the worst regarding stability, even though the reports on its stability are highly contradictory. In particular, since at room temperature the cubic α phase, black and with high photovoltaic efficiency, is metastable against the yellow hexagonal δ phase, it is believed that α−FAPI spontaneously transform into δ−FAPI within a relatively short time. We performed X-ray diffraction and thermogravimetric measurements on loose powder of FAPI, and present the first complete dielectric and anelastic spectra of compacted FAPI samples under various conditions. We found that α−FAPI is perfectly stable for at least 100 days, the duration of the experiments, unless extrinsic factors induce its degradation. In our tests, degradation was detected after exposure to humidity, strongly accelerated by grain boundaries and the presence of δ phase, but it was not noticeable on the loose powder kept in air under normal laboratory illumination. These findings have strong implications on the strategies for improving the stability of FAPI without diminishing its photovoltaic efficiency through modifications of its composition. Graphical TOC Entry1 arXiv:1905.02992v1 [cond-mat.mtrl-sci] 8 May 2019Although MAPbI 3 (MAPI, MA = methylammonium CH 3 NH 3 ) is the most studied hybrid metal-organic perovskite for photovoltaic applications, 1 better performance in terms of photovoltaic efficiency are found in FAPbI 3 (FAPI, FA = formamidinium CH(NH 2 ) 2 ). This is due both to a smaller bandgap of FAPI and to the fact that the FA + ion, in spite of a smaller electric dipole with respect to MA + , has a much larger quadrupole and faster reorientation dynamics that better screen the photoexcited carriers, enhancing their lifetime. 2 FAPI also has a better stability than MAPI at high temperature but its major flaw is that the black cubic α phase, which has the high photovoltaic efficiency, is metastable at room temperature, where instead the stable phase, and the one obtained by standard chemical methods, is the yellow hexagonal δ phase. For these reasons, major efforts are directed now at trying to stabilize the cubic α phase of FAPI through partial substitutions of FA with MA, Cs, etc. or I with Br, although this approach increases the bandgap. 3,4 It has been discussed, based on neutron diffraction measurements and simulations, that the α → δ transformation is complex and occurs through various intermediate stages, requiring to overcome a free energy barrier estimated in the order of hundreds of milli-electron volt. 5 This explains why the α phase of FAPI is kinetically trapped, resulting in a large thermal hysteresis between the δ → α transition at T h δα = 350 K and the α → δ at T c δα = 290 K. 5 Actually, the barrier for the α → δ transition has not been measured, and there is complete uncertainty on the kinetics of this transition. Indeed, also the reported temperatures for the δ → α transition during heati...

The authors investigated whether testosterone levels and testosterone availability differ between older lean subjects with and without Alzheimer's disease (AD). Sex hormone binding globulin (SHBG) and estradiol levels were higher, whereas the free androgenization index (FAI) was lower, in lean subjects with AD than in lean subjects without AD. Factors involved in the increase of SHBG secretion could have an important role in the lower testosterone availability of subjects with AD.

Transvaginal ultrasonography has a better predictive ability for differentiating cystic teratoma from other ovarian masses (kappa value 0.84) than in screening for cystic teratomas (kappa value 0.69).