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In the case of low Reynolds number, the structure of the spirally corrugated tube will make the solid particles in the fluid be affected by the centrifugal force, and be more evenly distributed in the fluid to achieve anti-fouling effect. Therefore, it can be used in heat exchangers with serious fouling problems to improve heat exchange efficiency. In this paper, the first stage low-temperature superheater in the grate furnace is selected as application equipment. The local resistance coefficient, local Nusselt number and local heat flux are analyzed, the thermal-hydraulic characteristics of different sample points are evaluated. Combinatorial method of central composite design and Latin hypercube design is used to select four representative sample points, and effect of the corrugation pitch ratio and depth ratio on the convective heat transfer intensity, fluid resistance and fluid work consumption of the steam side is studied. The research results show that as the corrugation depth increases, the local heat transfer coefficient in the circumferential direction increases, and more heat is transferred from the flue gas to the steam, but the pump power consumed in the flow process has also increased. Due to the existence of spiral structure, the local heat flux density of the wall is symmetrically distributed in the circumferential direction, which represents that the temperature gradient increases, and the heat flow is improved.

Abstract Background To investigate the risk factors of pancreatitis after endoscopic retrograde cholangiopancreatography (ERCP) in patients with biliary tract diseases. Methods We retrospectively analyzed the clinical data of 480 patients who underwent ERCP for biliary tract diseases at the Affiliated Zhongshan Hospital of Dalian University from October 2011 to October 2016. The patients were divided into a study group (n = 75, with PEP) and a control group (n = 405, without PEP) based on whether they developed post-ERCP pancreatitis (PEP), and their clinical baseline data and intraoperative conditions were retrieved and compared. Then, factors associated with PEP were analyzed using logistic regression model, based on which a nomogram prediction model was constructed. The receiver operating characteristic (ROC) curve and calibration curve were used to evaluate the performance of the prediction model. Results Significant differences in age, sex, history of pancreatitis, history of choledocholithiasis, pancreatic duct imaging, pancreatic sphincterotomy, difficult cannulation, multiple cannulation attempts and juxtapapillary duodenal diverticula were observed between the two groups. Multivariate logistic regression analysis showed that age less than 60 years (OR, 0.477; 95% CI, 0.26–0.855), female sex (OR, 2.162; 95% CI, 1.220–3.831), history of pancreatitis (OR, 2.567; 95% CI, 1.218–5.410), history of choledocholithiasis (OR, 2.062; 95% CI, 1.162–3.658), pancreatic sphincterotomy (OR, 2.387; 95% CI, 1.298–4.390), pancreatic duct imaging (OR, 4.429; 95% CI, 1.481–13.242), multiple cannulation attempts (OR, 2.327; 95% CI, 1.205–4.493), difficult cannulation (OR, 2.421; 95% CI, 1.143–5.128), and JPD (OR, 2.002; 95% CI, 1.125–3.564) were independent risk factors for PEP. The nomogram for predicting the occurrence of PEP demonstrated an area under the ROC curve (AUC) of 0.787, and the calibration curves of the model showed good consistency between the predicted and actual probability of PEP. Conclusion Our results showed that age less than 60 years, female sex, history of pancreatitis, history of choledocholithiasis, pancreatic sphincterotomy, pancreatic duct imaging, multiple cannulation attempts, difficult cannulation and juxtapapillary duodenal diverticula were independent risk factors for PEP. In addition, the established nomogram demonstrated promising clinical efficacy in predicting PEP risk in patients who underwent ERCP for biliary tract diseases.

AIM: To investigate the risk and protective factors associated with the retinal nerve fiber layer defect (RNFLD) in a Chinese adult population. METHODS: This study was a cross-sectional population-based investigation including employees and retirees of a coal mining company in Kailuan City, Hebei Province. All the study participants underwent a comprehensive systemic and ophthalmic examination. RNFLD was diagnosed on fundus photographs. Binary logistic regression was used to investigate the risk and protective factors associated with the RNFLD. RESULTS: The community-based study included 14 440 participants. There were 10 473 participants in our study, including 7120 males (68.0%) and 3353 females (32.0%). The age range was 45-108y, averaging 59.56±8.66y. Totally 568 participants had RNFLD and the prevalence rate was 5.42%. A higher prevalence of RNFLD was associated with older age [P

The accumulation of the intermediate zeaxanthin and canthaxanthin in the astaxanthin biosynthesis pathway catalyzed by β-carotene hydroxylase (crtZ) and β-carotene ketolase (crtW) decreases the content of the astaxanthin. Here, we exploited directed evolution of the fusion of crtZ and crtW for improving astaxanthin biosynthesis in Saccharomyces cerevisiae. The results demonstrated that the fusion enzyme of crtZ-crtW with 2 X GGGGS peptides linker can effectively reduce the accumulation of intermediates and improves the content of astaxanthin. Compared with the control strain, the fusion enzyme of ketase and hydroxylase reduced zeaxanthin and canthaxanthin by 7 and 14 times and increased astaxanthin by 1.6 times, respectively. Moreover, 9 variant fusion mutants with improved astaxanthin production were generated through directed evolution. Combining these dominant mutants generated a variant, L95S + I206L, which increased the astaxanthin content of 3.8 times than the control strain. The AlphaFold2 assisted structural analysis indicated that these two mutations alter the interaction between the substrate and the enzymes pocket. Our research provided an efficient idea to reduce the accumulation of the intermediate products in complex biosynthesis pathway.

Background and purpose: Urinary tract infections (UTIs) are the most common bacterial infection in young children. This study aimed to formulate nomogram plots for clinicians to predict UTIs in children aged

Corneal transplantation is the most effective clinical treatment for corneal defects, but it requires precise size of donor corneas, surgical sutures, and overcoming other technical challenges. Postoperative patients may suffer graft rejection and complications caused by sutures. Ophthalmic glues that can long-term integrate with the corneal tissue and effectively repair the focal corneal damage are highly desirable. Herein, a hybrid hydrogel consisting of porcine decellularized corneal stroma matrix (pDCSM) and methacrylated hyaluronic acid (HAMA) was developed through a non-competitive dual-crosslinking process. It can be directly filled into corneal defects with various shapes. More importantly, through formation of interpenetrating network and stable amide bonds between the hydrogel and adjacent tissue, the hydrogel manifested excellent adhesion properties to achieve suture-free repair. Meanwhile, the hybrid hydrogel not only preserved bioactive components from pDCSM, but also exhibited cornea-matching transparency, low swelling ratio, slow degradation, and enhanced mechanical properties, which was capable of withstanding superhigh intraocular pressure. The combinatorial hydrogel greatly improved the poor cell adhesion performance of HAMA, supported the viability, proliferation of corneal cells, and preservation of keratocyte phenotype. In a rabbit corneal stromal defect model, the experimental eyes treated with the hybrid hydrogel remained transparent and adhered intimately to the stroma bed with long-term retention, accelerated corneal re-epithelialization and wound healing. Giving the advantages of high bioactivity, low-cost, and good practicality, the dual-crosslinked hybrid hydrogel served effectively for long-term suture-free treatment and tissue regeneration after corneal defect.

The risk of information leakage increases when the relay technology is introduced to extend the communication range and improve the quality of communication services of cell-edge users in visible light communication (VLC) systems. To evaluate these security risks, physical layer security (PLS) performance for decode-and-forward (DF) relay-aided VLC system is investigated in this paper. Specifically, the theoretical expressions of the upper and lower bounds of the security outage probability (SOP) for the DF relay-aided VLC system under the amplitude constraint are obtained based on a stochastic geometry analysis method. Monte Carlo simulation validates the correctness of the derived theoretical expressions of the upper and lower bounds of the SOP. Moreover, simulation results show that the security outage performance of the DF relay-aided VLC system is deteriorated compared with the non-relay VLC system. Furthermore, the influences of the eavesdroppers' distribution density, the radiation radius of LED source, the radiation radius and deployment height of the relay on the SOP have been investigated. Last but not least, the optimal deployment height of the relay can be determined for achieving the optimum security outage performance. These parameters can effectively guide the design of the secure relay-aided VLC system.