RESUMO
The application of in situ Raman spectroscopy under multiple fields is widely recognized as an effective approach for investigating the physical mechanism of phase transitions in ferroelectrics, because it can directly provide the detailed information about the vibration evolution of various phonon modes within lattices, such as bond stretching and rotation. Based on this technique, our work aims to thoroughly probe the dynamics of phase transitions in traditional ferroelectric potassium sodium niobate [(K,Na)NbO3, KNN] under external fields, by analyzing the in situ dependence of wavenumber and intensity of phonon modes under the varying temperature and electric fields. The results indicate that different vibration modes respectively relating to the A-site ions and NbO6 octahedra in KNN exhibit distinct and abrupt distortion behavior during the orthorhombic-tetragonal and tetragonal-cubic transitions. Moreover, a certain degree of distortion can still be observed in the cubic phase above the Curie temperature. With an applied electric field, KNN presents quite different electrostriction in orthorhombic and tetragonal phases. Particularly, more than one kind of phonon mode undergoes non-linear variations under the varying electric fields, accompanied by the mutations at some fixed fields. These findings will be conducive to further understanding the phase transition mechanism in KNN from the perspective of phonon evolution. Simultaneously, it will also give crucial guidance for the design and development of KNN-based ferroelectrics as well as functional devices.
RESUMO
OBJECTIVE: The clinical value of increased levels of neutrophil gelatinase-associated lipocalin (NGAL) in patients with septic acute kidney injury (AKI) is still unclear. This study aimed to assess the link between illness severity and NGAL in patients with septic AKI. PATIENTS AND METHODS: This is a retrospective observational study that took place at the Fourth Hospital of Hebei Medical University, Shijiazhuang, China. The cohort included 365 patients who were admitted to the ICU during the 21-month period. Of them, 18 patients were diagnosed with sepsis (septic group). The average age of patients in the septic group was over 65, and 60.00% of them eventually progressed to septic AKI. Plasma NGAL (pNGAL) and urine NGAL (uNGAL) levels at defined time points were measured. AKI staging was done based on the Kidney Disease Improving Global Outcomes (KDIGO) classification. The Sequential Organ Failure Assessment (SOFA) and Acute Physiology and Chronic Health Evaluation (APACHE) II scores were determined. Patterns and associations between NGAL levels with SOFA scores and different stages of septic AKI were investigated. RESULTS: Both pNGAL and uNGAL showed a positive correlation with SOFA and proved to be reliable predictors of the same. Furthermore, the accuracy of severe sepsis (SOFA ≥ 8) was 0.67 for pNGAL and 0.66 for uNGAL. Real-time detection of pNGAL and uNGAL indicated that they were good biomarkers of severe septic AKI. Area under the receiver operating characteristic (AUROC) for pNGAL and uNGAL were 0.72 (0.69-0.85), and 0.83 (0.71-0.95), respectively. However, only patients with KDIGO 3 AKI presented significantly elevated levels of pNGAL (p < 0.05). Furthermore, the uNGAL level at each stage of septic AKI was higher than that of the non-AKI period (p < 0.01). CONCLUSIONS: In patients with septic AKI, levels of NGAL correlated with SOFA. Levels of pNGAL were good predictors of severe kidney injury and uNGAL levels could detect mild stages of AKI.
