Evaluation of modification effect of epoxy resin based on performance of asphalt mixtures

Based on the analysis of the main failures discovered in pavement on steel deck plate and the demanding service condition of the pavement on steel deck, high-temperature rutting test, low-temperature bending test and controlled stress flexural fatigue test are used to study the performance of asphalt mixtures modified by epoxy resin including high-temperature stability, low-temperature cracking-resistance, and fatigue cracking-resistance, which are served to evaluate the modification effect of epoxy resin of different contents. With the addition of epoxy resin, all the three performances are improved greatly. However, when the amount of epoxy resin added is over a certain value, the modification effect will be stable with no extra benefit detected. Finally, in terms of the properties of the three respects, 20%, 30%, 30% are given separately as the proposal adding contents.

Co-adsorption behavior of aggregated asphaltenes and silica nanoparticles at oil/water interface and its effect on emulsion stability

In petroleum industry, crude oil emulsions are commonly formed in oilfields. The asphaltenes and fine particles in crude oil may affect the stability of the emulsions by adsorbing at the water/oil interface. In this research, the effect of silica nanoparticles and asphaltenes on emulsion stability is explored first. The asphaltenes are proved to benefit emulsion stability. Unlike the asphaltenes, however, the modified silica nanoparticles may have positive or negative effect on emulsion stability, depending on the asphaltene concentration and aggregation degree in the emulsions. Further, it is confirmed by conducting interfacial experiment that the asphaltenes and particles can adsorb at the interface simultaneously and determine the properties of the interfacial layer. More in-depth experiments concerning contact angle and asphaltene adsorption amount on the particles indicate that the asphaltenes can modify the wettability of the particles. Higher concentration and lower aggregation degree of the asphaltenes can increase their adsorption amount on the surface of particles and then improve the modification effectiveness of the particles. Resultantly, the particles with good modification effectiveness can enhance the emulsion stability while the particles with poor modification effectiveness will weaken the emulsion stability.

Effects of the urban landscape on heatwave-mortality associations in Hong Kong: comparison of different heatwave definitions

Despite increased attention given to potential modifiers of temperature-mortality associations, evidence for variations between different urban landscape characteristics remains limited. It is in this context that in this paper effect modifications of multiple urban landscape characteristics are explored under different heatwave definitions for different age groups and gender in Hong Kong, China. Daily meteorological data and heatwave-related mortality counts from 2008 to 2017 were collected from the Hong Kong Census and Statistics Department, China. A case-only design was adopted, combined with logistic regression models to examine the modification effects of five urban landscape characteristics under six heatwave definitions. Stratified analyses were conducted to investigate age- and gender-specific effect modifications. It is found that individuals living in greener areas experienced lower levels of mortality during or immediately after heatwaves. In contrast, a higher building density and nighttime land surface temperature (LST) were associated with a higher heatwave-related mortality risk. Pronounced effect modifications of these urban landscape characteristics were observed under hotter and longer heatwaves, and in older adults (age ≥ 65 years) and males. The findings provide a scientific basis for policymakers and practitioners when considering measures for coping with hotter, longer, and more frequent heatwaves in the context of global climate change.

Psychosocial Stress Modifies the Acute Cardiac Health Effects of Traffic-Related Air Pollution

Previous studies have shown that exposure to black carbon(BC,a tracer of traffic-related air pollution)and psychosocial stress are both associated with adverse cardiac effects,but whether psychosocial stress could modify the cardiac effects of BC is unclear.To investigate the potential modifying effect of psychosocial stress on the associations between acute exposure to BC and typical cardiac health variables,real-time personal 24 h measurements were conducted in a repeated-measure study among adults with elevated blood pressure(high-risk group)and a panel study among normal adults(low-risk group)in China.Measured cardiac health variables included ST-segment depression events,heart rate,and heart rate variability(HRV)variables.Perceived Stress Scale,State Anxiety Inventory and Self-rating Depression Scale were used to assess the recent psychosocial stress status of the participants,and a composite stress index was established based on these scales.Generalized linear mixed-effects model was used to analyze the associations between BC exposure and cardiac health variables and potential effect modification by psychosocial stress.A total of 9724 h measurements among 97 participants in the repeated-measure study and 20224 h measurements among 87 participants in the panel study were included in the final analysis.Acute BC exposure was significantly associated with increased ST-segment depression events and heart rate and decreases in HRV in both studies.The marginal effects of acute BC exposure on most cardiac health variables generally tended to be amplified under higher vs low levels of psychosocial stress in both studies,with the composite stress index apparently modifying the associations of BC exposure with most ST-segment depression events and HRV variables.These findings suggest that psychosocial stress may increase the participants’cardiac susceptibility to BC exposure,which could be helpful for the identification of susceptible individuals in the context of traffic-related air pollution.

Influence of Al addition on microstructures of Cu-B alloys and Cu-ZrB2 composites

The influence of Al addition on the microstructure of Cu-B alloys and Cu-ZrB2 composites was investigated using scanning electron microscopy, X-ray diffraction and first-principles calculation. The results show that the eutectic B in Cu-B alloys can be modified by Al from coarse needles to fine fibrous structure and primary B will form in hypoeutectic Cu-B alloys. As for Cu-ZrB2 composites, Al can significantly refine and modify the morphology of ZrB2 as well as improve its distribution, which should be due to its selective adsorption on ZrB2 surfaces. The first-principles calculation results indicate that Al is preferentially adsobed on ZrB2■, then on ZrB2■, and finally on ZrB2(0001). As a result, smaller sized ZrB2 with a polyhedron-like, even nearly sphere-like morphology, can form. Due to Al addition, the hardness of Cu-ZrB2 composites is greatly enhanced, but the electrical conductivity of the composites is seriously reduced.

Microstructure and Mechanical Properties of Poly (Vinyl Chloride) Modified by Silica Fume /Acrylic Core-Shell Impact Modifier Blends

This research explored replacing acrylic core-shell impact modifier （AIM） by silica fume to toughen PVC. 100%, 75%, 50% and 25% of AIM （8 phr） were substituted by silica fume in PVC respectively, and then processed by dry blending and twin-screw extrusion. Severe silica fume agglomeration was observed by scanning electron microscope （SEM） in the PVC matrix when 8 phr pure silica fume was used and processed by screw speed of 20 rpm. Its tensile strength was thereby reduced by 38% comparing to unmodified PVC. The silica fume was successfully dispersed while the screw speed was slowed down to 10 rpm to give a stronger screw torque and a longer melt residential time in the extruder. The tensile strength was ’recovered’ to a level comparable to unmodified PVC. Impact test were performed on all formulations extruded at 10 rpm screw speed and synergetic toughening effect was found with 50% substitution and it had the impact strength that was comparable to 8 phr pure AIM toughened PVC.

Association between heat and upper urinary tract stones morbidity and medical costs: A study in the subtropical humid climate zone

Urolithiasis is a heat-specific disease.Exploring heat-related urolithiasis susceptibility subtypes,economic burden,and modifying factors could assist governments in targeting interventions to reduce the heat-related health risks of urolithiasis morbidity.We collected data on 23,492 patients with upper urinary tract stones(main subtypes of urolithiasis)from 2013 to 2017 in Nanjing,China.We adopted generalized additive quasi-Poisson models to examine the associations between daily mean temperatures and morbidity of upper urinary tract stones,while generalized additive Gaussian models were used to explore the relationships between temperatures and log-transformed medical costs.We examined the modification effects of disease subtypes(kidney and ureteral calculus),sex,and age through stratified analyses and the modif-cation effects of other meteorological factors by introducing interaction terms in the models.We found that short-term summer heat exposure has a statistically significant effect on ureteral calculus morbidity but not on kidney calculus morbidity.For ureter calculus,a 1℃ temperature increase was associated with a 4.36%(95%confidence interval[CI]:1.94%,6.83%)increase in daily hospitalization and a 5.44%(95%CI:2.71%,8.25%)increase in daily medical costs.The attributable fraction associated with heat(greater than the median value of daily mean temperature,26.8℃)was 7.85%(95%empirical confidence interval[eCI]:3.64%,11.44%)for hospitalization and 9.36%(95%eCI:4.91%,13.14%)for medical costs.The effects of heat on ureter calculus morbidity were significantly higher among the males and those with high sunshine duration than females and those with low sunshine duration.Short-term summer heat exposure was associated with increased morbidity and medical costs of ureteral calculus.Relevant government organizations should take effective intervention measures,including community health education,to reduce the health hazards and economic losses caused by heat.

Preface

Multiply robust inference has attracted much attention recently in the context of missing response data. An estimation procedure is multiply robust, if it can incorporate information from multiple candidate models, and meanwhile the resulting estimator is consistent as long as one of the candidate models is correctly specified. This property is appealing, since it provides the user a flexible modeling strategy with better protection against model misspecification. We explore this attractive property for the regression models with a binary covariate that is missing at random. We start from a reformulation of the celebrated augmented inverse probability weighted estimating equation, and based on this reformulation, we propose a novel combination of the least squares and empirical likelihood to separately handle each of the two types of multiple candidate models,one for the missing variable regression and the other for the missingness mechanism. Due to the separation, all the working models are fused concisely and effectively. The asymptotic normality of our estimator is established through the theory of estimating function with plugged-in nuisance parameter estimates. The finite-sample performance of our procedure is illustrated both through the simulation studies and the analysis of a dementia data collected by the national Alzheimer's coordinating center.

A fusion of least squares and empirical likelihood for regression models with a missing binary covariate

Multiply robust inference has attracted much attention recently in the context of missing response data. An estimation procedure is multiply robust, if it can incorporate information from multiple candidate models, and meanwhile the resulting estimator is consistent as long as one of the candidate models is correctly specified. This property is appealing, since it provides the user a flexible modeling strategy with better protection against model misspecification. We explore this attractive property for the regression models with a binary covariate that is missing at random. We start from a reformulation of the celebrated augmented inverse probability weighted estimating equation, and based on this reformulation, we propose a novel combination of the least squares and empirical likelihood to separately handle each of the two types of multiple candidate models,one for the missing variable regression and the other for the missingness mechanism. Due to the separation, all the working models are fused concisely and effectively. The asymptotic normality of our estimator is established through the theory of estimating function with plugged-in nuisance parameter estimates. The finite-sample performance of our procedure is illustrated both through the simulation studies and the analysis of a dementia data collected by the national Alzheimer's coordinating center.

Family history of esophageal cancer modifies the association of serum lipids and malignant esophageal lesions:a nested case-control study from the"Endoscopic Screening for Esophageal Cancer in China"trial

Background:The association of lipids and cancer has varied greatly among different cancer types,lipid components and study populations.This study is aimed to investigate the association of serum lipids and the risk of malignant lesions in esophageal squamous epithelium.Methods:In the"Endoscopic Screening for Esophageal Cancer in China"(ESECC)trial,serum samples were collected and tested for total cholesterol(TC),triglycerides,low-density lipoprotein cholesterol(LDL-C),and high-density lipoprotein cholesterol at the time of subject enrollment.Cases were defined as malignant esophageal lesions identified by baseline endoscopic examination or by follow-up to May 31,2018.Controls were randomly selected using incidence density sampling in the same cohort.Conditional logistic models were applied to identify the association of serum lipids and the risk of malignant esophageal lesions.Effect modification was evaluated by testing interaction terms of the factor under assessment and these serum lipid indicators.Results:No consistent association between serum lipid levels and esophageal malignant lesions were found in a pooled analysis of 211 cases and 2101 controls.For individuals with a family history of esophageal cancer(EC),high TC,and LDL-C were associated with a significantly increased risk of having malignant lesions(odds ratio[OR]Highvs.Low TC=2.22,95%confidence interval[CI]:1.14-4.35;ORHighvs.Low LDL-C=1.93,95%CI:1.01-3.65).However,a negative association was observed in participants without an EC family history(ORHighvs.Low TC=0.69,95%CI:0.48-0.98,Pinteraction=0.002;ORHighvs.Low LDL-C=0.50,95%CI:0.34-0.76,Pinteraction<0.001).Conclusions:In this study,we found that the association of serum lipids and malignant esophageal lesions might be modified by EC family history.The stratified analysis would be crucial for population-based studies investigating the association of serum lipids and cancer.The mechanism by which a family history of EC modifies this association warrants further investigation.