Titanium alloy material (TC4) samples were treated with nitriding technique. The dynamic friction and wear behavior of the modified layer were examined on a reciprocating sliding rig in artificial saliva. Microhardness, depth profile and wear mechanisms were investigated by means of MVK-H12, TALYSURF6, XPS and microscopy. The results demonstrate that after being treated with nitriding technique the titanium alloy material (TC4) has better tribological behavior and up-graded wear resistance. The wear mechanism involves adhesion.
Adsorption ; Biocompatible Materials ; Dental Alloys ; chemistry ; Dental Materials ; Dental Prosthesis ; Electricity ; Friction ; Humans ; Materials Testing ; Surface Properties ; Titanium ; chemistry

Objective:To explore the occurrence and influencing factors of post-burn psychological stress disorder in preschool children.Methods:This study was a multi-center cross-sectional survey. From January 2022 to February 2023, 85 preschool children (aged 1 to 6 years) with burns admitted to the Affiliated Hospital of North Sichuan Medical College, Nanchong Central Hospital, Suining Central Hospital, Guang'an People's Hospital, and Guangyuan Central Hospital who met the inclusion criteria were selected as respondents. A self-made general information questionnaire was used to investigate the children's general data including gender, age group, residential area, main caregiver and their education level, and family type, as well as the injury condition including cause of injury and burn severity. The Child Stress Disorders Checklist was used to investigate the occurrence of psychological stress disorder in children at 3 days to 1 month after injury, and the incidence rate was calculated. The children were classified according to their general data and injury condition, and the occurrence of psychological stress disorder in children at 3 days to 1 month after injury was recorded, and the influencing factors for post-burn psychological stress disorder in preschool children were screened.Results:A total of 85 questionnaires were distributed and 85 valid questionnaires were recovered, with an effective recovery rate of 100%. Among the children, there were 45 boys and 40 girls, with most children aged 1 to 3 years. There were slightly more children in rural areas than in cities. About half of the children were mainly cared for by their parents and grandparents, respectively, and the education level of the main caregivers was mainly high school/technical secondary school. The family type was mainly core family and extended family. The main cause of injury was hydrothermal scald, and the severity of burns was mainly moderate. The incidence rate of psychological stress disorder in this group of children at 3 days to 1 month after injury was 34.12% (29/85). There were statistically significant differences in the occurrence of psychological stress disorder in children with different age groups, causes of injuries, and burn severity at 3 days to 1 month after injury (with χ2 values??of 9.18, 7.80, and 25.47, respectively, P<0.05); there were no statistically significant differences in the occurrence of psychological stress disorder in children with different genders, residential area, main caregivers, main caregivers' education levels, or family types at 3 days to 1 month after injury ( P>0.05). Multivariate logistic regression analysis showed that age group and burn severity were independent influencing factors for the occurrence of psychological stress disorder in preschool children after burns (with odds ratios of 8.21 and 33.99, respectively, and 95% confidence intervals of 1.57-43.04 and 5.55-207.93, respectively, P<0.05), the older the child and the more severe the burn, the higher the possibility of the occurrence of psychological stress disorder. Conclusions:The incidence rate of psychological stress disorder is high in preschool children after burns. Age group and burn severity are independent influencing factors for the occurrence of post-burn psychological stress disorder in this type of children.

Objective To understand the types, proportions, and radiation dose levels of pediatric cardiac interventional procedures. Methods A retrospective analysis was conducted using the basic information and radiation dose data from all cases of pediatric cardiac interventional procedures performed at two tertiary medical institutions in Beijing from July 2023 to August 2024. The data included air kerma-area product, reference point air kerma, and fluoroscopy time. Descriptive statistical analysis was conducted to evaluate the basic information and dosimetric indicators of the procedures. Non-parametric tests were employed to examine the differences between variables, and Spearman’s correlation coefficient was utilized to investigate the relationships among various factors. All cases were categorized into the diagnostic group and the therapeutic group. In the diagnostic group, the majority of procedures involved catheter examinations and angiography for identifying the type of disease. In the therapeutic group, the primary procedures included patent ductus arteriosus, atrial septal defect, ventricular septal defect, patent foramen ovale, pulmonary stenosis, radiofrequency catheter ablation, major aortopulmonary collateral arteries, complex congenital heart diseases, and other interventional procedures. Results The survey comprised 1008 cardiac interventional procedures involving 476 males and 532 females. The ages of the participants ranged from 0 to 15 years and the body weights from 4.5 to 105 kg. Among these participants, 92 and 916 were classified in the diagnostic and therapeutic groups, respectively. The proportions of interventional procedures were in the order of atrial septal defect (36.9%), radiofrequency catheter ablation (22.3%), patent ductus arteriosus (15.1%), complex congenital heart disease (4.8%), patent foramen ovale (3.1%), pulmonary stenosis (3.1%), ventricular septal defect (2.2%), other procedures (2.0%), and major aortopulmonary collateral arteries (1.5%). The radiation doses of different interventional procedures were statistically different (P < 0.05), with air kerma-area product ranging from 0.02 to 658.4 Gy·cm², reference point air kerma from 0.1 to 2524 mGy, and fluoroscopy time from 0.2 to 62 min. Conclusion In pediatric cardiac interventional procedures, there is considerable variability in radiation doses for the same type of procedure. Additionally, radiation doses for identical procedures vary between different medical institutions, and a few cases carry a risk of deterministic effects.