ABSTRACT
OBJECTIVE: To study the efficacy of helmet-assisted non-invasive ventilation and conventional ventilation in the treatment of acute respiratory failure (ARF). MATERIALS AND METHODS: Cochrane Library, PubMed, Embase and CNKI databases were searched for randomized controlled trials and case-control trials of helmet-assisted noninvasive ventilation in the treatment of ARF. The outcome measures included respiratory rate, intubation rate, complication rate, mortality rate and arterial blood gas analysis of the commonly used indicators (PaCO2/ PaO2 / pH). The results of the included studies' odds ratio (OR) and its 95% confidential interval (CI) were analyzed using Stata software. RESULTS: The results of the analysis showed that the in-hospital mortality, intubation rate and complication rate were all significantly decreased with the p-value less than 0.05, which was statistically significant. CONCLUSIONS: Helmet-assisted noninvasive ventilation can significantly reduce hospital mortality, intubation rate and complication rate, improving the survival rate and prognosis of patients with ARF.
Subject(s)
Head Protective Devices , Noninvasive Ventilation/instrumentation , Noninvasive Ventilation/methods , Respiratory Insufficiency/therapy , Humans , Respiratory Distress Syndrome/therapyABSTRACT
A series of oxygen deficient LuFe(2)O(4-δ) materials have been prepared under a controlled oxygen partial-pressure atmosphere. Measurements of magnetization reveal that the increase of oxygen deficiencies could evidently depress the ferrimagnetic phase transition temperature (T(N)). In additional to the well-known charge ordering within the (11(-)0) crystal plane, a visible structural modulation with q = (0,1/4.2,7/8) commonly appears on the (100) plane in the oxygen deficient samples. An aberration-corrected transmission electron microscopy study on the oxygen deficient samples demonstrates the presence of oxygen vacancies and local structural distortion. The atomic structural features in correlation with the structural modulation, distortion of the FeO(5) polyhedron and the (001) twinning domains have been also examined.
ABSTRACT
The magnetoelectric coupling and polar nanodomains in the charge-ordered Fe2OBO3 have been extensively studied from room temperature down to 100 K. In situ TEM investigations demonstrate that the charge-ordering transition characterized by an incommensurate modulation could evidently result in remarkable polar nanodomains at low temperatures. This kind of nanodomain could play a critical role in triggering a high dielectric constant and notable dielectric dispersion as observed in Fe2OBO3. Moreover, measurements of the magnetoelectric coupling under electrical field demonstrate the existence of giant electrically induced changes in magnetization around the magnetic transition.
ABSTRACT
The SrFe(2)As(2 - x)P(x) (0.0 ≤ x ≤ 1.0) and CaFe(2)As(2 - y)P(y) (0.0 ≤ y ≤ 0.3) materials were prepared by a solid-state reaction method. X-ray diffraction measurements indicate that the single-phase samples can be successfully obtained for SrFe(2)As(2 - x)P(x) (0.0 ≤ x ≤ 0.8) and CaFe(2)As(2 - y)P(y) (0.0 ≤ y ≤ 0.3). Visible contraction of the lattice parameters is determined due to the relatively smaller radius of P ions in comparison with that of As. The spin-density-wave (SDW) instability associated with the tetragonal to orthorhombic phase transition is suppressed noticeably in both systems following the increase in P content. The highest superconducting transitions are observed at about 27 K in SrFe(2)As(1.3)P(0.7) and at about 13 K in CaFe(2)As(1.925)P(0.075), respectively. Structural analysis suggests that lattice contraction could notably affect the superconductivity in these materials.
ABSTRACT
The charge/orbital ordering (COO) of the layered mixed-valence manganites (La,Sr)(n+1)Mn(n)O(3n+1) (n = 1 and 2) is examined by first-principles calculations and discussed in comparison with the La(0.5)Ca(0.5)MnO(3) perovskite phase ([Formula: see text]). The results demonstrated that the layered structural features could yield not only visibly weak coupling between Mn-O layers but also various features in the orbital ordering associated with different types of local structural distortions. In both La(0.5)Sr(1.5)MnO(4) (n = 1) and LaSr(2)Mn(2)O(7) (n = 2) phases, the orbital ordering can be chiefly assigned to the d(x(2)-y(2)) orbital, in contrast with the zigzag-type d(z(2)) orbital ordering in the [Formula: see text] perovskite phase. Our theoretical analysis shows that a variety of essential factors, including the local structural distortions of the MnO(6) octahedra, the on-site Coulomb interaction, and magnetic interaction, have to be properly considered in order to achieve acceptable COO ground states for the layered variants in (La,Sr)(n+1)Mn(n)O(3n+1).
ABSTRACT
The structural and physical properties of the recently discovered electronic ferroelectric materials LuFe(2)O(4) and Lu(2)Fe(3)O(7) have been investigated for Mg substitution of Fe. X-ray diffraction data demonstrate that the lattice parameters in both systems change progressively with increasing Mg content, with a smaller unit cell volume on replacing Fe(2+) by Mg(2+). X-ray absorption near-edge spectroscopy experiments at the Fe K-edge show that the average Fe oxidation state is slightly increased along with Mg doping in Lu(2)Fe(3)O(7) materials, consistent with isomorphous replacement of Fe(2+) by Mg(2+). Measurements of dielectric properties demonstrate that Mg doping could have an effect on the electron hopping energy between Fe(2+) and Fe(3+) ions. Transmission electron microscopy and magnetization analysis reveal that Mg doping in LuFe(2)O(4) has a much greater influence than in Lu(2)Fe(3)O(7) on both the charge ordering and the low-temperature magnetic properties.
