Helical edge states in silicene and germanene nanorings in perpendicular magnetic field

Due to nonzero intrinsic spin-orbit interaction in buckled honeycomb crystal structures, silicene and germanene exhibit interesting topological properties, and are therefore candidates for the realization of the quantum spin Hall effect. We employ the Kane-Mele model to investigate the electron states in hexagonal silicene and germanene nanorings having either zigzag or armchair edges in the presence of a perpendicular magnetic field. We present results for the energy spectra as function of magnetic field, the electron density of the spin-up and spin-down states in the ring plane, and the calculation of the probability current density. The quantum spin Hall phase is found at the edges between the nontrivial topological phase in silicene and germanene and vacuum. We demonstrate that the helical edge states in zigzag silicene and germanene nanorings can be qualitatively well understood by means of classical magnetic moments. However, this is not the case for comparable-sized armchair nanorings, where the eigenfunctions spread throughout the ring. Finally, we note that the energy spectra of silicene and germanene nanorings are similar and that the differences between the two are mainly related to the difference in magnitude of the spin-orbit coupling.Comment: 17 pages, 10 figure

Heart rate variability before and after cycle exercise in relation to different body positions

The purpose of this study was to assess the effect of three different body positions on HRV measures following short-term submaximal exercise. Thirty young healthy males performed submaximal cycling for five minutes on three different occasions. Measures of HRV were obtained from 5-min R to R wave intervals before the exercise (baseline) and during the last five minutes of a 15 min recovery (post-exercise) in three different body positions (seated, supine, supine with elevated legs). Measures of the mean RR normal-to-normal intervals (RRNN), the standard deviation of normal-to-normal intervals (SDNN), the root mean square of successive differences (RMSSD) and the low-frequency (LF) and the high-frequency (HF) spectral power were analyzed. Post-exercise RRNN, RMSSD were significantly higher in the two supine positions (p 0.05). Post-exercise time domain measures of HRV (RRNN, SDNN, RMSSD) were significantly lower compared with baseline values (p < 0.01) regardless body position. Post-exercise ln LF and ln HF in all three positions remained significantly reduced during recovery compared to baseline values (p < 0.01). The present study suggests that 15 minutes following short-term submaximal exercise most of the time and frequency domain HRV measures have not returned to pre-exercise values. Modifications in autonomic cardiac regulation induced by body posture present at rest remained after exercise, but the post-exercise differences among the three positions did not resemble the ones established at res

Sinteza i karakterizacija kompleksa cink(II), kadmijum(II), platina(II),i paladijum(II) sa kalijum-3-ditiokarboksi-3-aza-5-aminopentanoatom

Complexes of zinc(lI), cadmium(II). platinum(lI) and palladium(II) with a new poly-dentate dithiocarbamate ligand, 3-dithiocarboxy-3-aza-5-aminopentanoate (daap(-)), of the type M(daap)(2).nH(2)O (M = Zn(II), Cd(II), n = 2, or M = Pt(II) Pd(II) n = 0). have been prepared and characterized by elemental analysis. IR and UV/VIS spectroscopy, as well as magnetic measurements. The spectra of the complexes suggest a bidentate coordination of the daap- ligand to the metal ions via the sulfur atoms of the deprotonated dithiocarbamato group. The fact that under the same experimental conditions its S-methyl ester does not form complexes could be taken as proof of the suggested coordination mode.Reakcijom između cink(II), kadmijum(II), platina(II) i paladijum(II)-soli i kalijum- 3-ditiokarboksi-3-aza-5-aminopentanoata dobijeni su dogovarajući kompleksi tipa M(daap)2.nH2O. Izolovani kompleksi su okarakterisani elementarnom analizom, IR i UV/VIS spektroskopijom kao i merenjem magnetnih susceptibiliteta. Spektri kompleksa sugerišu bidentatnu koordinaciju daap liganda sa navedenim metalnim jonima preko atoma sumpora deprotonovane ditiokarbamato grupe. Kao dokaz navedenog načina koordinacije može poslužiti činjenica da pri istim eksperimentalnim uslovima S-metil estar liganda ne daje komplekse

A highly stable atomic vector magnetometer based on free spin precession

We present a magnetometer based on optically pumped Cs atoms that measures the magnitude and direction of a 1 $\mu$T magnetic field. Multiple circularly polarized laser beams were used to probe the free spin precession of the Cs atoms. The design was optimized for long-time stability and achieves a scalar resolution better than 300 fT for integration times ranging from 80 ms to 1000 s. The best scalar resolution of less than 80 fT was reached with integration times of 1.6 to 6 s. We were able to measure the magnetic field direction with a resolution better than 10 $\mu$rad for integration times from 10 s up to 2000 s