RESUMO
The crystal structure of the ambient-pressure phase of vanadyl pyrophosphate, (VO)2P2O7, has been precisely determined at 120 K from synchrotron X-ray diffraction data measured on a high-quality single crystal. The structure refinement unambiguously establishes the orthorhombic space group Pca2(1) as the true crystallographic symmetry. Moreover, it improves the accuracy of previously published atomic coordinates by one order of magnitude, and provides reliable anisotropic displacement parameters for all atoms. Along the a axis, the structure consists of infinite two-leg ladders of vanadyl cations, (VO)2+, which are separated by pyrophosphate anions, (P2O7)4-. Parallel to the c axis, the unit cell comprises two alternating crystallographically inequivalent chains of edge-sharing VO5 square pyramids bridged by PO4 double tetrahedra. No structural phase transition has been observed in the temperature range between 300 and 120 K.
RESUMO
The first generation of Auto CPAP devices caused respiratory arousal by apnoes, hypopnoeas, incomplete obstructions and pressurechanges. The new, second generation of CPAP devices which is based on forced oscillation technique will change the pressure with slower velocity and before the respiratory arousal reaction will occur (1, 9, 10). Fifty patients with severe sleep apnoea (AHI 66+/-26 /h) were treated with both, constant- CPAP (continous positive airway pressure) or Auto CPAP under polysomnographic control in a randomised order. The Auto CPAP based on forced oscillation technique reduced the number of apnoeas and hypopnoeas as did most of the other Auto CPAP systems to AHI 2.5+/-5.9 /h (p<0.05). In comparison to Auto CPAP of the first generation it also decreased the number of respiratory arousal reactions caused by apnoeas and hypopnoeas. However there is still a significant difference to number of arousal detected with constant CPAP (p<0.01). In conclusion although the new generation of Auto CPAP reduced the number of respiratory arousals compared to first generation, we did not find a therapeutical benefit for patients with severe SAS.
