Assessment of Alkali-Silica Reaction Potential in Aggregates from Iran and Australia Using Thin-Section Petrography and Expansion Testing.

The alkali-silica reaction can shorten concrete life due to expansive pressure build-up caused by reaction by-products, resulting in cracking. Understanding the role of the aggregate, as the main reactive component, is essential for understanding the underlying mechanisms of the alkali-silica reaction and thereby reducing, or even preventing, any potential damage. The present study aims to investigate the role of petrographic studies along with accelerated tests in predicting and determining the potential reactivity of aggregates, including granite, rhyodacite, limestone, and dolomite, with different geological characteristics in concrete. This study was performed under accelerated conditions in accordance with the ASTM C1260 and ASTM C1293 test methods. The extent of the alkali-silica reaction was assessed using a range of microanalysis techniques including optical microscopy, scanning electron microscopy, energy-dispersive X-ray analysis, and X-ray powder diffraction. The results showed that a calcium-rich aggregate with only a small quantity of siliceous component but with a higher porosity and water adsorption rate can lead to degradation due to the alkali-silica reaction, while dolomite aggregate, which is commonly considered a reactive aggregate, showed no considerable expansion during the conducted tests. The results also showed that rhyodacite samples, due to their glassy texture, the existence of strained quartz and quartz with undulatory extinction, as well as the presence of weathering minerals, have a higher alkali-reactivity potential than granite samples.

Evaluating the literature of therapeutic landscapes with an emphasis on the search for the dimensions of health: A systematic review.

Health geography emphasizes landscape capacity as a perspective for examining health dimensions. Much of this emphasis is on the concept of therapeutic landscapes. In the last two decades, changes in the therapeutic landscapes concerning health, as well as why and how the development of the emphasis on the dimensions of the health in the landscape in proportion to the temporal-spatial course of literature in this field can be considered. The framework of the present study is based on a systematic review of therapeutic landscapes in the geography of health in the last two decades. This systematic literature review followed the PRISMA guidelines. Searching for "Therapeutic Landscapes" term at Science Direct and PubMed, screening, 56 eligible articles were selected in the journal Social Science and Medicine, and Health and Place. The results of the systematic review, aiming to search for the health dimensions of the therapeutic landscape, and recognize main gaps, identified three main issues: scale and range of users of therapeutic landscapes, the position importance of experiences in therapeutic landscapes, therapeutic landscapes as the holistic paradigm. The results of the research show that in recent years, attention to multiple dimensions of health, especially non-physical relationships of therapeutic landscapes and multiple dimensions of health, has been considered more and more by researchers. Personal-social perceptions and experiences are also continually evolving, so the concept of therapeutic landscapes and its relationship to health is considered living and dynamic.

Characterizing concrete corrosion below sewer tidal levels at chemically dosed locations.

Unexplainable concrete softening below the water line has been observed by Sydney Water in their gravity sewer network, some of which is subjected to corrosion control methods using chemical ferrous chloride (FeCl2) dosing of the wastewater. We applied a combination of physical and chemical tools to determine the properties of the top 20 mm of concrete cores recovered from sewer pipes. These techniques consist of neutron tomographic imaging, scanning electron microscopy, hardness mapping, and pH profiling. Concrete cores were collected from roof (crown), tidal (wall) and below flow regions of gravity sewer pipes of Sydney Water's wastewater system from locations that received no treatment as well as locations dosed with FeCl2. All samples showed a degree of softening of the surface exposed to the sewerage with an associated depletion in calcium concentration and reduced pH in the same regions.

Silver nanoparticle based coatings enhance adipogenesis compared to osteogenesis in human mesenchymal stem cells through oxidative stress.

Silver nanoparticle (AgNP) based antibacterial surfaces were fabricated using plasma polymerization technology and their effects on differentiation of human bone-marrow derived mesenchymal stem cells (hMSCs) were investigated in this study. The results showed that AgNP coated surfaces do not affect the initial adhesion, spreading and proliferation of hMSCs. Furthermore, the silver coated surface promoted adipogenic differentiation of hMSCs as demonstrated by more accumulation of lipid droplets and upregulation of adipogenesis-related genes such as peroxisome proliferator activated receptor gamma (PPARγ), adipocyte determination and differentiation factor (ADD1) and CCAAT/enhancer binding protein alpha (C/EBPα). In addition, silver incorporation activated the expression of antioxidant enzymes as a consequence of the accumulation of intracellular reactive oxygen species (ROS) in adipogenic induced cells, which was correlated with the enhanced adipogenic capacity of hMSCs. ROS generation was enhanced due to silver ion release and consequently reduced osteogenesis at the early stage after 7 days of osteogenic induction as a result of reducing alkaline phosphatase (ALP) activity. However, the differentiation and mineralization capacity of osteoblasts were restored after 14 days of osteogenic induction, which indicated that adipogenesis favors intracellular ROS accumulation mediated by silver coatings compared to osteogenesis. None of the osteogenic related genes was affected by ROS mediated by AgNP dissolution. The findings in this work are instructive for the use of silver as an antibacterial agent in the areas of tissue engineering, stem cell therapies and implantable biomedical devices.

Antibacterial Plasma Polymer Films Conjugated with Phospholipid Encapsulated Silver Nanoparticles.

Medical device associated infections are a persistent medical problem which has not found a comprehensive solution yet. Over the last decades, there have been intense research efforts toward developing antibacterial coatings that could potentially improve medical outcomes. Silver nanoparticles have attracted a great deal of attention as a potent alternative to conventional antibiotics. Herein, we present a biologically inspired approach to synthesize phospholipid encapsulated silver nanoparticles and their surface immobilization to a functional plasma polymer interlayer to generate antibacterial coatings. The antibacterial efficacy of the coatings was evaluated against three medically relevant pathogens including the Gram-positive Staphylococcus aureus and Staphylococcus epidermidis, and the Gram-negative Pseudomonas aeruginosa. The innate immune response to the coatings was assessed in vitro using primary bone marrow derived macrophages (BMDM). Any potential cytotoxicity was studied with primary human dermal fibroblasts (HDFs). Overall, the coatings had excellent inhibition of bacterial growth. We also observed reduced expression of pro-inflammatory cytokines from BMDM which suggests a reduced inflammatory response. The combined properties of coatings developed in this study may make them a good candidate for application on medical devices such as catheters and wound dressings.

Responsive and "smart" antibacterial surfaces: common approaches and new developments (Review).

Bacterial infections are continuing to pose a significant threat to human health. Coatings with inherent antibacterial properties are becoming increasingly common as an infection preventative measure. The aim of this review is to highlight recent progress in development of "smart" and responsive antibacterial surfaces. The review describes various strategies utilized for generation of such surfaces and the specific stimuli that are used to trigger antibacterial action. It also provides a critical discussion of the advantages and drawbacks of different approaches. The review concludes with a perspective about the future of the field and outlines the challenges and obstacles that need to be overcome in order to make future advances.

Synthesis and surface immobilization of antibacterial hybrid silver-poly(l-lactide) nanoparticles.

Infections associated with medical devices are a substantial healthcare problem. Consequently, there has been increasing research and technological efforts directed toward the development of coatings that are capable of preventing bacterial colonization of the device surface. Herein, we report on novel hybrid silver loaded poly(L-lactic acid) nanoparticles (PLLA-AgNPs) with narrowly distributed sizes (17 ± 3 nm) prepared using a combination of solvent evaporation and mini-emulsion technology. These particles were then immobilized onto solid surfaces premodified with a thin layer of allylamine plasma polymer (AApp). The antibacterial efficacy of the PLLA-AgNPs nanoparticles was studied in vitro against both gram-positive (Staphylococcus epidermidis) and gram-negative (Escherichia coli) bacteria. The minimal inhibitory concentration values against Staphylococcus epidermidis and Escherichia coli were 0.610 and 1.156 µg · mL(-1), respectively. The capacity of the prepared coatings to prevent bacterial surface colonization was assessed in the presence of Staphylococcus epidermidis, which is a strong biofilm former that causes substantial problems with medical device associated infections. The level of inhibition of bacterial growth was 98%. The substrate independent nature and the high antibacterial efficacy of coatings presented in this study may offer new alternatives for antibacterial coatings for medical devices.

Substrate independent silver nanoparticle based antibacterial coatings.

Infections arising from bacterial adhesion and colonization on medical device surfaces are a significant healthcare problem. Silver based antibacterial coatings have attracted a great deal of attention as a potential solution. This paper reports on the development of a silver nanoparticles based antibacterial surface that can be applied to any type of material surface. The silver nanoparticles were surface engineered with a monolayer of 2-mercaptosuccinic acid, which facilitates the immobilization of the nanoparticles to the solid surface, and also reduces the rate of oxidation of the nanoparticles, extending the lifetime of the coatings. The coatings had excellent antibacterial efficacy against three clinically significant pathogenic bacteria i.e. Staphylococcus epidermidis, Staphylococcus aureus and Pseudomonas aeruginosa. Studies with primary human fibroblast cells showed that the coatings had no cytotoxicity in vitro. Innate immune studies in cultures of primary macrophages demonstrated that the coatings do not significantly alter the level of expression of pro-inflammatory cytokines or the adhesion and viability of these cells. Collectively, these coatings have an optimal combination of properties that make them attractive for deposition on medical device surfaces such as wound dressings, catheters and implants.

Synthesis and antibacterial properties of a hybrid of silver-potato starch nanocapsules by miniemulsion/polyaddition polymerization.

Controlled synthesis of hollow polymeric nanocapsules has attracted significant attention in a wide range of applications. This paper reports a facile method for the synthesis of hybrid starch nanocapsules decorated with silver nanoparticles using the inverse miniemulsion polyaddition technique. Silver nanoparticles are formed and embedded in the shell of the nanocapsules during the polyaddition process without using any additional reducing agents. We found that silver also acts as a lipophobe that builds up osmotic pressure in the droplets facilitating the formation of stable round shaped nanocapsules. The nanocapsules' shell thickness could be tuned from 13 to 29 nm by varying the amount of cross-linker. We investigated the minimum inhibitory concentration (MIC) of the nanocapsules against Staphylococcus epidermidis ATCC 35984 and Escherichia coli ATCC 25922 which are two bacteria of medical relevance. The silver nanoparticle decorated nanocapsules showed antibacterial properties against both bacteria at the MIC of 2.315 µg mL-1 while control nanocapsules without silver had no antibacterial activity.

Transformation of four silver/silver chloride nanoparticles during anaerobic treatment of wastewater and post-processing of sewage sludge.

The increasing use of silver (Ag) nanoparticles [containing either elemental Ag (Ag-NPs) or AgCl (AgCl-NPs)] in commercial products such as textiles will most likely result in these materials reaching wastewater treatment plants. Previous studies indicate that a conversion of Ag-NPs to Ag2S is to be expected during wastewater transport/treatment. However, the influence of surface functionality, the nature of the core structure and the effect of post-processing on Ag speciation in sewage sludge/biosolids has not been investigated. This study aims at closing these knowledge gaps using bench scale anaerobic digesters spiked with Ag nitrate, three different types of Ag-NPs, and AgCl-NPs at environmentally realistic concentrations. The results indicate that neither surface functionality nor the different compositions of the NP prevented the formation of Ag2S. Silver sulfides, unlike the sulfides of other metals present in sewage sludge, were stable over a six month period simulating composting/stockpiling.