Rheological, physicochemical, and microstructural properties of asphalt binder modified by fumed silica nanoparticles

Warm mix asphalt (WMA) is gaining increased attention in the asphalt paving industry as an eco-friendly and sustainable technology. WMA technologies are favorable in producing asphalt mixtures at temperatures 20–60 °C lower in comparison to conventional hot mix asphalt. This saves non-renewable fossil fuels, reduces energy consumption, and minimizes vapors and greenhouse gas emissions in the production, placement and conservation processes of asphalt mixtures. At the same time, this temperature reduction must not reduce the performance of asphalt pavements in-field. Low aging resistance, high moisture susceptibility, and low durability are generally seen as substantial drawbacks of WMA, which can lead to inferior pavement performance, and increased maintenance costs. This is partly due to the fact that low production temperature may increase the amount of water molecules trapped in the asphalt mixture. As a potential remedy, here we use fumed silica nanoparticles (FSN) have shown excellent potential in enhancing moisture and aging susceptibility of asphalt binders. In this study, asphalt binder modification by means of FSN was investigated, considering the effects of short-term and long-term aging on the rheological, thermal, and microstructural binder properties. This research paves the way for optimizing WMA by nanoparticles to present enhanced green asphalt technology

Pedestrians\u27 mental satisfaction\u27s relationship with physical characteristics on sidewalks using analytical hierarchy process: case study of Tehran, Iran

The aim of the current study is an examination of the relationship between the existing physical characteristics of sidewalks in Tehran, Iran, and pedestrians\u27 mental satisfaction. In order to successfully achieve this, physical and mental sidewalk characteristics were determined via expert elicitation and pedestrian investigations. Subsequently, 40 photographs of sidewalks located in Tehran were selected from all taken images, based upon photographic techniques; these were used to elicit data from 514 respondents via formally developed questionnaires. An analytical hierarchy process (AHP) was employed to analyze collated data. Results indicate that mental satisfaction is directly correlated with observed physical condition of sidewalks. It is concluded that sensitivity analyses such as those used in this study may be suitable for future optimization of sidewalk construction and maintenance; the presented approach may represent an appropriate model for increasing pedestrians\u27 satisfaction and is thus potentially of use to urban and peri-urban planners

Failure behavior of functionally graded roller compacted concrete pavement under mode I and III fracture

Today, the idea of functionally graded material (FGM), which refers to using different materials in multiple layers to improve overall system performance, is commonly used in various engineering sciences. The present study investigates the fracture behavior (modes I and III) of the functionally graded concrete pavement (FGCP) when the bottom layer is RCC (roller compacted concrete) and the top one is ordinary PCC (Portland cement concrete) or FPCC (fibrous Portland cement concrete). Results have shown that the FGC specimens’ flexural strength is similar to that of the full-depth ones and adding polypropylene fibers does not improve it; the main fiber effect is related to the specimens’ post-cracking behavior. While adding fibers highly improves the mode I fracture energy, its effect on mode III fracture toughness is negligible. The pull-off test results have also shown that more than 2 h time lag in pouring two layers will result cold joints between two layers

Role of histone modification and DNA methylation in signaling pathways involved in diabetic retinopathy

Retinopathy, characterized by an alteration of the retinal microvasculature, is a common complication of diabetes mellitus. These changes can cause increased permeability and alter endothelial cell proliferation, edema, and abnormal neovascularization and eventually result in blindness. The pathogenesis of diabetic retinopathy (DR) is complicated, involving many factors/mediators such as genetic susceptibility, microRNAs, and cytokines. One of the factors involved in DR pathogenesis is epigenetic changes that can have a key role in the regulation of gene expression; these include microRNAs, histone modifications, and methylation of DNA. The main epigenetic modifications are DNA methylation and posttranslational modifications of the histones. Generally, the studies on epigenetics can provide new opportunities to investigate the molecular basis of diseases with complicated pathogenesis, including DR, and provide essential insights into the potential design of strategies for its treatment. The aim of this study is an investigation of DR pathogenesis and epigenetic modifications that involve in DR development. © 2018 Wiley Periodicals, Inc