Thermal barrier coatings on polymer materials

Polyimide matrix composite (PIMC) has been widely used to replace metallic parts due to its low density and high strength. It is considered as an effective approach to improve thermal oxidation resistance, operation temperature and lifetime of PIMC by depositing a protection coating. The objective of the research was to fabricate a series of thermal barrier coatings (TBCs) on PIMC by a combined sol-gel/sealing treatment process and air plasma spraying (APS). By optimizing the experimental parameters, thermal shock resistance, thermal oxidation resistance and thermal ablation resistance of PIMC could be improved significantly. The ZrO2 sol was prepared by sol-gel process and the effects of the different organic additions on phase structure, crystallite size and crystal growth behavior of the ZrO2 nanocrystallite were investigated. The addition of HAc and DMF were beneficial to decrease the crystallite size and alter the activation energy for crystal growth, further inducing the crystallization of ZrO2 nanocrystallite at low temperature (300ºC) and the stability of tetragonal ZrO2 at 600ºC. Based on the optimized parameters of the sol preparation, the ZrO2/phosphates duplex coating was fabricated on PIMC via a combined sol-gel and sealing treatment process. The sealing mechanism of the phosphates in the duplex coating was primarily attributed to the adhesive binding of the phosphates and the chemical bonding between the sealant and the coating. It was demonstrated that the duplex coating exhibited excellent thermal shock resistance and no apparent delamination or spallation occurred. Relatively, the duplex coating with the thickness of 150 μm provided excellent thermal oxidation and thermal ablation resistance for the polymer substrate. However, the presence of cracks and delamination in the coatings provided the channels for oxygen diffusion, causing the final failure of the protection coating. Figure 4 – TBCs on CFPI The Zn/YSZ and Al/YSZ coating systems were successfully deposited on PIMC by APS. Metals with comparatively low melting point as the bond coats (Cu, Al, Zn) were beneficial to increase thermal shock resistance of the coating systems. In comparison with the Al/YSZ coating system, the Zn/YSZ coating exhibited the better thermal shock resistance, which was ascribable to the lower residual stress in the Zn layer after deposition and the lower thermal stress induced during thermal shock test. For these coatings, the increase in surface toughness of the substrate as well as the decrease in thickness of metal layer favored the improvement of thermal shock resistance of the coatings. With the temperature increases, thermal shock lifetime of the coatings decreased disastrously. However, the difference was that the slight increase of the thickness of YSZ layer favored the increase in thermal shock resistance of the Al/YSZ coatings, while for the Zn/YSZ coating systems the increase in the thickness of YSZ layer made thermal shock resistance weaken. Owing to the protection of Zn/YSZ and Al/YSZ coating systems, the time for 5 wt% weight loss of the sample was prolonged from 16 h to 50 h when oxidation at 400ºC; as the oxidation temperature increased to 450ºC, the time for 5wt% weight loss was extended from 5 h to 13 h. By depositing different coatings, the anti-ablation property of PIMC was significantly improved. During property testing, the formation of cracks and delamination in the coating and the occurrence of the spallation led to the failure of the coating systems, which was mainly due to the residual stress during the deposition process, thermal stress induced by the mismatch in thermal expansion coefficient and further oxidation of the substrate. Please click Additional Files below to see the full abstract

Correlation between porosity, amorphous phase and CMAS corrosion behaviour of LaMgAl11O19 thermal barrier coatings

Calcium-magnesium-alumino-silicate (CMAS) attack is one of the significant failure mechanisms of thermal barrier coatings (TBCs), which can facilitate TBC’s degradation at elevated temperatures. To clarify the correlation between the porosity, CMAS corrosion behaviour, lanthanum magnesium hexaluminate (LaMgAl11O19, LMA) TBCs were prepared by atmospheric plasma spraying (APS) and then heat-treated at 1173K and 1523K, respectively. For comparison, LMA tablets were prepared by mechanical and cold isostatic pressing. CMAS attack at 1523K was carried out both for LMA tablets and LMA coatings. Their microstructure, phase composition, and crystallization behavior after CMAS attack were investigated using scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), X-ray diffraction as well as differential scanning calorimetry (DSC). The results indicated that CMAS attack was arrested for LMA tablets due to the formation of a dense crystalline layer induced by the chemical interactions between LMA and CMAS glass, while the as-sprayed LMA coatings were completely penetrated by molten CMAS due to the presence of amorphous phase and connected pores. Although the isothermal heat-treatment promoted a crystallization of LMA coatings, much vertical cracks formed during heat-treatment. The heat-treated LMA coatings suffered a severer CMAS attack than the as-sprayed one, since the vertical cracks inevitably provided efficient infiltration paths for molten CMAS

Preoperative Aspirin Use and Outcomes in Cardiac Surgery Patients

BackgroundThe effects of preoperative aspirin use on outcomes of cardiac surgery patients remain uncertain. This study was aimed to evaluate the effect of preoperative aspirin use on major outcomes in cardiac surgery patients.MethodsAn observational cohort study was performed on consecutive patients (n = 4256) undergoing cardiac surgery in 2 tertiary hospitals. Of all patients, 2868 patients met the inclusion criteria and were divided into 2 groups: those taking (n = 1923) or not taking (n = 945) aspirin within 5 days preceding surgery.ResultsPatients in the aspirin group presented significantly more with comorbidities including hypertension, diabetes, peripheral arterial disease, previous myocardial infarction, angina, cerebrovascular disease, older age, and male gender. With propensity scores adjusted and multivariate logistic regression, however, the results of this study showed that preoperative aspirin therapy (vs nonaspirin) significantly reduced the risk of 30-day mortality (3.5% vs 6.5%, OR: 0.611, 95% CI: 0.391-0.956, P = 0.031), postoperative renal failure (3.7% vs 7.1%, OR: 0.384, 95% CI: 0.254-0.579, P < 0.001), dialysis required (1.9% vs 3.6%, OR: 0.441, 95% CI: 0.254-0.579, P < 0.001), intensive care unit stay (mean 107.2 vs 136.1 h, P < 0.001) and a composite outcome-major adverse cardiocerebral events (8.7% vs 10.8%, OR: 0.662, 95% CI:: 0.482-0.909, P = 0.011) in the patients undergoing cardiac surgery. However, readmissions did not show a significant difference between the 2 groups (14.5% vs 12.8%, P = 0.944).ConclusionsPreoperative aspirin therapy is associated with a significant decrease in the risk of major cardiocerebral complications, renal failure, intensive care unit stay and 30-day mortality but does not increase the risk of readmissions in patients undergoing cardiac surgery

Normal-weight central obesity: implications for diabetes mellitus

BackgroundCurrent guidelines for obesity prevention and control focus on body mass index (BMI) and rarely address central obesity. Few studies have been conducted on the association between normal-weight central obesity and the risk of diabetes mellitus (DM).Methods26,825 participants from the National Health and Nutrition Examination Survey (NHANES) were included in our study. A weighted multivariate logistic regression model was used to analyze the relationship between different obesity patterns and the risk of DM.ResultsOur results suggest that normal-weight central obesity is associated with an increased risk of DM (OR: 2.37, 95% CI: 1.75–3.23) compared with normal-weight participants without central obesity. When stratified by sex, men with normal-weight central obesity, obesity and central obesity were found to have a similar risk of DM (OR: 3.83, 95% CI: 2.10–5.97; OR: 4.20, 95% CI: 3.48–5.08, respectively) and a higher risk than all other types of obesity, including men who were overweight with no central obesity (OR: 1.21, 95% CI: 0.96–1.51) and obese with no central obesity (OR: 0.53, 95% CI: 0.30–0.91).ConclusionOur results highlight the need for more attention in people with central obesity, even if they have a normal BMI

Effects of Preoperative Aspirin on Cardiocerebral and Renal Complications in Non-Emergent Cardiac Surgery Patients: A Sub-Group and Cohort Study

BACKGROUND AND OBJECTIVE: Postoperative cardiocerebral and renal complications are a major threat for patients undergoing cardiac surgery. This study was aimed to examine the effect of preoperative aspirin use on patients undergoing cardiac surgery. METHODS: An observational cohort study was performed on consecutive patients (n = 1879) receiving cardiac surgery at this institution. The patients excluded from the study were those with preoperative anticoagulants, unknown aspirin use, or underwent emergent cardiac surgery. Outcome events included were 30-day mortality, renal failure, readmission and a composite outcome - major adverse cardiocerebral events (MACE) that include permanent or transient stroke, coma, perioperative myocardial infarction (MI), heart block and cardiac arrest. RESULTS: Of all patients, 1145 patients met the inclusion criteria and were divided into two groups: those taking (n = 858) or not taking (n = 287) aspirin within 5 days preceding surgery. Patients with aspirin presented significantly more with history of hypertension, diabetes, peripheral arterial disease, previous MI, angina and older age. With propensity scores adjusted and multivariate logistic regression, however, this study showed that preoperative aspirin therapy (vs. no aspirin) significantly reduced the risk of MACE (8.4% vs. 12.5%, odds ratio [OR] 0.585, 95% CI 0.355-0.964, P = 0.035), postoperative renal failure (2.6% vs. 5.2%, OR 0.438, CI 0.203-0.945, P = 0.035) and dialysis required (0.8% vs. 3.1%, OR 0.230, CI 0.071-0.742, P = 0.014), but did not significantly reduce 30-day mortality (4.1% vs. 5.8%, OR 0.744, CI 0.376-1.472, P = 0.396) nor it increased readmissions in the patients undergoing cardiac surgery. CONCLUSIONS: Preoperative aspirin therapy is associated with a significant decrease in the risk of MACE and renal failure and did not increase readmissions in patients undergoing non-emergent cardiac surgery

2021 Taxonomic update of phylum Negarnaviricota (Riboviria: Orthornavirae), including the large orders Bunyavirales and Mononegavirales.

Correction to: 2021 Taxonomic update of phylum Negarnaviricota (Riboviria: Orthornavirae), including the large orders Bunyavirales and Mononegavirales. Archives of Virology (2021) 166:3567–3579. https://doi.org/10.1007/s00705-021-05266-wIn March 2021, following the annual International Committee on Taxonomy of Viruses (ICTV) ratification vote on newly proposed taxa, the phylum Negarnaviricota was amended and emended. The phylum was expanded by four families (Aliusviridae, Crepuscuviridae, Myriaviridae, and Natareviridae), three subfamilies (Alpharhabdovirinae, Betarhabdovirinae, and Gammarhabdovirinae), 42 genera, and 200 species. Thirty-nine species were renamed and/or moved and seven species were abolished. This article presents the updated taxonomy of Negarnaviricota as now accepted by the ICTV.This work was supported in part through Laulima Government Solutions, LLC prime contract with the US National Institute of Allergy and Infectious Diseases (NIAID) under Contract No. HHSN272201800013C. J.H.K. performed this work as an employee of Tunnell Government Services (TGS), a subcontractor of Laulima Government Solutions, LLC under Contract No. HHSN272201800013C. This work was also supported in part with federal funds from the National Cancer Institute (NCI), National Institutes of Health (NIH), under Contract No. 75N91019D00024, Task Order No. 75N91019F00130 to I.C., who was supported by the Clinical Monitoring Research Program Directorate, Frederick National Lab for Cancer Research. This work was also funded in part by Contract No. HSHQDC-15-C-00064 awarded by DHS S&T for the management and operation of The National Biodefense Analysis and Countermeasures Center, a federally funded research and development center operated by the Battelle National Biodefense Institute (V.W.); and NIH contract HHSN272201000040I/HHSN27200004/D04 and grant R24AI120942 (N.V., R.B.T.). S.S. acknowledges partial support from the Special Research Initiative of Mississippi Agricultural and Forestry Experiment Station (MAFES), Mississippi State University, and the National Institute of Food and Agriculture, US Department of Agriculture, Hatch Project 1021494. Part of this work was supported by the Francis Crick Institute which receives its core funding from Cancer Research UK (FC001030), the UK Medical Research Council (FC001030), and the Wellcome Trust (FC001030).S

2021 Taxonomic update of phylum Negarnaviricota (Riboviria: Orthornavirae), including the large orders Bunyavirales and Mononegavirales.

In March 2021, following the annual International Committee on Taxonomy of Viruses (ICTV) ratification vote on newly proposed taxa, the phylum Negarnaviricota was amended and emended. The phylum was expanded by four families (Aliusviridae, Crepuscuviridae, Myriaviridae, and Natareviridae), three subfamilies (Alpharhabdovirinae, Betarhabdovirinae, and Gammarhabdovirinae), 42 genera, and 200 species. Thirty-nine species were renamed and/or moved and seven species were abolished. This article presents the updated taxonomy of Negarnaviricota as now accepted by the ICTV

Demographic and clinical characteristics.

<p>Values are n (%) for categorical variables and mean±SD for continuous variables.</p

Univariate Logistic Regression Analysis for Risk Factor Associated with Postoperative Cardiocerebral Events.

<p>Values are n (%) for categorical variables and mean±SD for continuous variables.</p