ABSTRACT
A gas diffusion layer represents an important element of collector and stack components used in polymer electrolyte membrane (PEM) water electrolyzers (WE). Nowadays, titanium-based gas diffusion layers (GDLs) have high stability and are frequently employed as anode GDLs, yet reliability issues emerging from passivation have limited their practical deployment. Hence, we develop an inexpensive way of producing high conductivity and corrosion resistance of Ti-based GDLs through electrochemical nitridation. The morphology and content of the nitride phase on the surface of the Ti felt GDL are efficiently regulated by adjusting reduction potential and reaction time. According to X-ray photoelectron spectroscopy studies, the modified Ti felt is coated with ammonium ions and nitrogen-incorporated oxides, namely, TiN/TiOx, on the surface. The nitride surface shows a low interfacial contact resistance (ca. 1.0 mΩ cm2 at 140 N/cm2) and excellent corrosion resistance (0.920 µA cm-2) in the simulated PEM WE environments. The electrochemical nitridation provides an economic way to introducing N layers on the surface of the Ti-based GDL with high performance, which is very promising for efficient PEM water electrolysis.
ABSTRACT
Correlation between blood inflammatory parameters and acute appendicitis (AA) remains controversial. This meta-analysis aims to evaluate whether platelet (PLT) indices including mean platelet volume (MPV), PLT count, and platelet distribution width (PDW) are associated with AA. Pubmed, Embase, and Cochrane Library databases were searched for observational studies published from inception through April 2020 by two independent investigators. Studies reporting associations between platelet indices and AA were selected for inclusion. Standardized mean difference (SMD) and 95% confidence interval (CI) were estimated for continuous outcomes using a DerSimonian-Laird random-effects model. Of 842 records identified, 17 studies with a total of 6793 subjects met our inclusion criteria. Meta-analysis indicated that compared with those in healthy controls, significant decrease in MPV levels was observed in subjects with AA (SMD - 0.34; 95% CI - 0.56 to - 0.12; P = 0.003). Subgroup analyses represented a significant reduction of MPV levels in patients aged ≥ 30 years and non-complicated/non-perforated AA. Due to the small number of studies and patients included in each subgroup, these subgroup analyses need to be interpreted with caution. However, none of the levels of PLT (SMD - 0.13; 95% CI - 0.28-0.012; P = 0.071) or PDW (SMD 0.30; 95% CI - 0.22-0.83; P = 0.257) was seen decrease or increase in subjects with AA. This meta-analysis indicates a significant decrease in MPV levels in patients with AA, which makes MPV have the potential of serving as a biomarker for AA. The associations of other PLT indices with AA need to be further examined.
Subject(s)
Appendicitis , Acute Disease , Aged , Appendicitis/surgery , Biomarkers , Humans , Mean Platelet Volume , Platelet CountABSTRACT
BACKGROUND: Bedside ultrasonography is a promising tool for identification of acute appendicitis. We assessed the accuracy and clinical value of bedside ultrasonography for diagnosis of acute appendicitis in the emergency department. METHODS: Pubmed, Embase and Cochrane Library were searched from inception to November 2018. The diagnostic accuracy of bedside ultrasonography was compared with that of surgery and/or CT scan, which was used as reference standard. Pooled summary estimates of sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) from each included study were estimated using bivariate logistic regression model. Inter-study heterogeneity was examined using I2 statistic. Meta-regression was performed to further investigate the source of heterogeneity. Deeks's funnel plot was used to test publication bias. RESULTS: Our search yielded 5394 citations, of which 27 satisfied the inclusion criteria. Bivariate analysis yielded a mean sensitivity of 90% (95% CI 82%-0.95%) and specificity of 95% (95% CI 89%-98%). The area under the receiver operating characteristic curve was 0.97 (95% CI 0.95-0.98). There was significant inter-study heterogeneity (I2â¯=â¯96%, 95% CI 94%-99%). Meta-regression analysis suggested that study region and patient sample size could attribute to the heterogeneity. Deeks's funnel plot did not indicate the existence of publication bias (Pâ¯=â¯0.15). CONCLUSION: Bedside ultrasonography, a radiation-free and noninvasive modality, provides superior diagnostic performance in the diagnosis of acute appendicitis, but its value in different abdominal emergencies warrants further development and research.
