Environmental Scanning Electron Microscopy Research Articles

Effect of Dimethyl Sulfoxide Primer on Microtensile Bond Strength and Micromorphological Pattern of HEMA-free Universal Adhesive to Dry/Wet Dentin After Thermomechanical Aging.

To evaluate the effect of dimethyl sulfoxide (DMSO) primer on microtensile bond strength (μTBS) and the micromorphological pattern of a hydroxyethyl methacrylate (HEMA)-free universal adhesive (UA) applied on wet/dry dentin in etch and rinse (E&R) mode before/after thermomechanical aging. For the μTBS test, the mid-coronal dentin of 80 human mandibular first molars was exposed and etched with 35% phosphoric acid. Teeth were randomly divided into two equal groups: dry and wet dentin (n = 40). Then, each group was subdivided according to dentin pretreatment by DMSO before UA (Gluma Bond Universal, Heraeus Kulzer, Hanau, Germany) application into unpretreated and 10% DMSO/water (OT Primer S100, OT Oy Dent, Turku, Finland) pretreated (n = 20). Resin composite blocks were built up using a specially designed Teflon mold. In every subgroup, both the μTBS test and failure analysis by stereomicroscope were evaluated immediately after 24 h and after thermomechanical aging (n = 10). The data were statistically analyzed using a three-way analysis of variance (ANOVA) (p = 0.05). For the micromorphological pattern, 16 maxillary first premolars were distributed as mentioned in the μTBS test, prepared, and buccolingually sectioned. The dentin-resin interface was examined using an environmental scanning electron microscope (ESEM) (n = 2). Three-way ANOVA revealed that the main effects and interactions between dentin wetness, dentin pretreatment, and evaluation time (thermomechanical aging) were not significant for µTBS (p> 0.05). Adhesive failure was the predominant type in all immediate and delayed specimens. Longer and more prominent resin tags were observed at dentin-resin interfaces after DMSO application. Neither the initial dentin wetness condition, dentin pretreatment, nor thermomechanical aging could affect the dentin bond strength. No correlation was found between the bond strength and the micromorphology findings. Key words:Wet/dry dentin bonding, Microtensile bond strength, Micromorphology, Universal adhesive, Dimethyl sulfoxide, Thermomechanical aging.

A comprehensive review of synthesis kinetics and formation mechanism of geopolymers.

Geopolymers are synthesized by alkali or acid activation of aluminosilicate materials. This paper critically reviews the synthesis kinetics and formation mechanism of geopolymers. A variety of mechanistic tools such as Environmental Scanning Electron Microscopy (ESEM) and in situ Energy Dispersive X-ray diffractometry (EDXRD), in situ Isothermal Conduction Calorimetry (ICC), in situ Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), 1H low-field Nuclear Magnetic Resonance (NMR) and Isothermal Conduction Calorimetry (ISC), and others and phenomenological models such as the John-Mehl-Avrami-Kolmogorov (JMAK) model, modified Jandar model, and exponential and Knudson linear dispersion models were used to study the geopolymerization kinetics and many mechanisms were proposed for the synthesis of geopolymers. The mechanistic tools and phenomenological models provided new insights about geopolymerization kinetics and formation mechanisms but each of the techniques used possesses some limitations. These limitations need to be removed and new methods or techniques must be developed to overcome these challenges and get more detailed information about all types of geopolymers. The formation mechanism consists of three to four stages such as dissolution of raw materials, polymerization of silica and alumina, condensation, and reorganization. The Si/Al ratio above the Si/Al ratio of reactants is more suitable and it increases the rate or degree of reaction and produces a higher compressive strength geopolymer. The Na/Al ratio of 1, water-to-solid (W/S) ratio of 0.30-0.45, a temperature in the range of 30 °C to 85 °C, and a curing time of 24 hours are the best for the synthesis of geopolymers. The growing demand for geopolymers in various fields requires the development of new advanced techniques for further understanding of kinetics and mechanisms for tailoring the properties of geopolymers for specific applications.

Influence of oxygen content on selective laser melting leading to the formation of spheroidization in additive manufacturing technology.

Selective laser melting (SLM) additive manufacturing technology with different oxygen contents leads to the appearance of spherical solids of different sizes on the surface of the part, which affects the mechanical properties of the part, surface roughness, etc. In this study, the SLM molding technique was applied using three different 316L metal powders with different oxygen contents. The spheroidization properties and morphology of the samples were observed using a Quanta 200 environmental scanning electron microscope (ESEM), and the samples were observed microscopically and subjected to EDX spectroscopy using metallographic microscopy, and the mechanical properties were investigated. The results of the study showed that when using gas atomized powders, no spheroidization occurred when the oxygen content of the powders was 5.44 ± 0.01% in all cases, whereas using water atomized powders produced spherical structures with larger dimensions. This observation was closely related to the shape and particle size of the powder. When 316L metal powder with an oxygen content of 4.52 ± 0.01% was used for molding, small spherical structures appeared on the surface of the samples. When metal powder with an oxygen content of 5.44 ± 0.01% was used for the molding, larger spherical structures appeared on the surface of the samples. When the powder with an oxygen content of 5.90 ± 0.01% was used for the molding, more small spherical structures and some large spherical structures appeared on the surface of the samples. This suggests that higher oxygen levels may inhibit the occurrence of spheroidization. EDX spectroscopic analysis revealed that the white matter on the surface of the samples without spheroidization was mainly composed of Fe and Cr, whereas the white matter on the surface of the large-sized spherical structures was mainly composed of Si and Mn, which may be related to the oxygenophilicity of the various substances.

Preparation of Co–CaCO3 catalysts for improved hydrogen production from sodium borohydride

Ca1-xCoxCO3 nanoparticle catalysts (x = 0.0, 0.1, 0.2 and 0.3 %) were prepared by the sol-gel method. The samples were characterized using various techniques such as X-ray diffraction (XRD), attenuated total reflectance spectroscopy (ATR), environmental scanning electron microscopy (ESEM), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) surface area analysis. The XRD peaks of Ca1-xCoxCO3 displayed a significant level of conformity with the rhombohedral calcite structure. The average crystal size of Ca1-xCoxCO3 nanoparticles was found to be 14 nm. The ESEM micrographs of Ca1-xCoxCO3 showed rhombic calcite shapes. The most prominent peaks in the XPS spectra of Ca1-xCoxCO3 are the Ca 2p, C 1s, Co 2p and O 1s peaks. The sample Ca1-xCoxCO3 has the highest surface area (58.27 m2/g) and large pore size (20.25 Å). The rates of hydrogen production for CaCO3, Ca0.9Co0.1CO3, Ca0.8Co0.2CO3 and Ca0.7Co0.3CO3 were 5204, 4381, 6666 and 6136 mL/g.min. The Ca0.8Co0.2CO3 catalyst revealed an activation energy for hydrogen catalytic reaction of 34.56 kJ/mol. The recyclability tests of Ca1-xCoxCO3 catalysts showed a reduction of efficiency by 7 % over 5 reaction cycles. Accordingly, the prepared Ca1-xCoxCO3 catalysts are promising for improved hydrogen production systems. This research contributes to advancements in hydrogen production technology.

Biological properties of stem cells from the apical papilla exposed to lipopolysaccharides: An in vitro study

ObjectiveThe aim of this study was to analyze the effect of lipopolysaccharides (LPS) on the biological properties of stem cells from the apical papilla (SCAPs), such as viability, adhesion to dentin, odontoblast-like differentiation, mineralization, and release of immunomodulatory cytokines. DesignSCAPs were isolated from immature teeth of three donors (10 to 15 years old) and cultured in mineralizing media with or without 1 μg/mL lipopolysaccharide (LPS). Cells were seeded and cultured under standardized conditions; viability was assessed by MTT assay on days 1, 3, 5, and 7; adhesion to dentin was analyzed using an environmental scanning electron microscope after 2 days; the expression of odontogenic and mineralization genes (DSPP, DMP-1, OCN, Col1A1) was evaluated through qPCR after 14 days, mineralization was evaluated with alizarin red staining after 21 days; and the release of immunomodulatory cytokines (IL-6 and IL-10) was measured by ELISA after 1 and 7 days. The Kruskal-Wallis test was performed to detect the effect of LPS on SCAPs, followed by the Dunn-Sidak test. ResultsLPS presence in the culture media affected SCAPs viability on day 5 and increased IL-6 secretion by day 7, however, SCAPs retained the adhesion to dentin and mineralization capacities, as well as the differentiation capacity into a mineralizing phenotype. ConclusionIn conclusion, within the limitations of this in vitro study, and under the inflammatory microenvironment simulated in this study, stem cells from the apical papilla were found with retained adhesion capacity to dentin, differentiation into a mineralizing phenotype, mineralization, and release of IL-10.

Effect of Surface Roughness of Pistia Leaves Inspired Surfaces on Oil Contact Angle and Coefficient of Friction under Lubricated Condition

Biomimetics field is getting more interest in engineering purposes. The plant surface roughness existing in nature such as in leaves can be mimicked into artificial technologies. Basically, the surface structures have micro and nano scales in nature and possess properties of interest. Pistia leaves for example have intrinsic of tribology application which have rarely explored. In this study, a preliminary work on 3 types of Pistia leaves inspired surface-based polymer have been conducted to look at effect of surface roughness towards contact angle (CA) measurements and coefficient of friction (COF) under lubricated condition. The surface characteristics were also examined using Variable Pressure Scanning Electron Microscope (VP-SEM). Two different oils namely palm oil and palm oil + TiO2 were tested on the Pistia leaves inspired surface to measure the CA and COF. It was found that both types of palm oils had distinct CA values and COF towards surface roughness of the Pistia inspired surfaces. A maximum difference of CA and COF were recorded in CA and COF values. The different nanocomposite of Pistia leaves inspired surface were found to affect for both parameters CA and COF under lubricated condition.

In operando study of gypsum crystal growth through in-cell environmental SEM

Thanks to their setting ability, hydraulic binder materials (e.g., cements, plasters) are used for a wide variety of applications (e.g., construction, medical). The setting reaction occurs through a dissolution–precipitation mechanism during which initial particles dissolve releasing ionic species from which new crystals precipitate. The development of such a microstructure governs the final properties of the material and are thus of uttermost interest.In this paper, the in operando study of the precipitation of gypsum crystals from the dissolution of bassanite particles using a specific cell for scanning electron microscope (SEM) observation is presented. Image analysis based on segmentation enabled to give quantitative results on the growth of crystals at global and local scales. Single crystal facets are indexed based on crystallography and literature results, which enables the quantification of crystal growth rates for the indexed crystallographic planes. Different growth regimes are identified; they are attributed to the transition from unfavored to the most favored crystal facets known for gypsum. The {111} and {110} planes were the fastest growing planes, whereas the {120} and {010} planes were the most stable and grew slowly.

Effect of TiO2@CaCO3 Waterborne Primer on the Coloring Performance of Inkjet-Printed Wood Product Coatings

Calcium carbonate (CaCO3) is a widely used inorganic filling pigment used in coatings, and it is known for its nontoxicity, odorlessness, and environmental friendliness. The application of CaCO3 as a filler can effectively reduce raw material costs, and optimization of the filler formula enhances the coating film performance. In this study, oak planks were prepared as substrates for water-based inkjet printing. Three composite water-based primers with different TiO2-to-CaCO3 ratios and a polyurethane resin primer were used to prepare the substrate for the printing surface. The properties of the water-based primer coating and the water-based inkjet printing coating were characterized and analyzed via Fourier-transform infrared spectroscopy, video-based contact angle analysis, and environmental scanning electron microscopy. The aim was to investigate the effects of the composite waterborne primer coatings on the ink absorption and coloring properties of the interface between wood substrates and waterborne inkjet coatings. Sample WDCC-3#, with a TiO2-to-CaCO3 ratio of 15:35, exhibited the most comprehensive characteristics. The wood surface coated with 15 g/m2 of the polyurethane resin primer and 15 g/m2 of WDCC-3# exhibited a 5.8° contact angle of the water-based ink, first-grade adhesion, 4 H hardness, 70.52 whiteness value, and a roughness of ~2.33. The surface of the printed water-based inkjet-coated substrate was uniform and smooth, featuring rounded and transparent edges of the water-based ink droplets and a small CMYK color difference value. Therefore, the composite waterborne primer, incorporating TiO2 and CaCO3 in specific ratios, can be effectively combined with waterborne polyurethane primer coatings. This combination significantly improves the interfacial compatibility between the oak surface and waterborne inkjet coatings, leading to enhanced ink absorption on the oak plank surface during printing. This results in a high degree of color reproduction and clearer printed images. Overall, this study provides valuable insights for the development of primer programs for the industrial application of waterborne digital inkjet technology on wood products.

Impact of secondary ice in a frozen NaCl freeze-concentrated solution on the extent of methylene blue aggregation

Freezing and lyophilization have been utilized for decades to stabilize pharmaceutical and food products. Freezing a solution that contains dissolved salt and/or organic matter produces pure primary ice crystal grains separated by freeze-concentrated solutions (FCS). The microscopic size of the primary ice crystals depends on the cooling conditions and the concentration of the solutes. It is generally accepted that primary ice crystals size influences the rate of sublimation and also can impact physico-chemical behaviour of the species in the FCS. This article, however, presents a case where the secondary ice formed inside the FCS plays a critical role. We microscoped the structures of ice-cast FCS with an environmental scanning electron microscope and applied the aggregation-sensitive spectroscopic probe methylene blue to determine how the microstructure affects the molecular arrangement. We show that slow cooling at −50 °C produces large salt crystals with a small specific surface, resulting in a high degree of molecular aggregation within the FCS. In contrast, fast liquid nitrogen cooling yields an ultrafine structure of salt crystals having a large specific surface area and, therefore, inducing smaller aggregation. The study highlights a critical role of secondary ice in solute aggregation and introduces methylene blue as a molecular probe to investigate freezing behaviour of aqueous systems with crystalline solute.

Size and shape analysis of micro- to nano-particles of quartz powders using advanced electron microscopy and laser diffraction methods

The paper deals with particle analysis and the evaluation of the shape and size distribution of micro- to nano-sized quartz particles as a key parameter for the evaluation of quality in many industrial fields, particularly for high-purity applications. Samples are analyzed by laser diffraction, the most commonly used method for determining the size of the particles; for precise measurement with the possibility of high-resolution imaging of particles, scanning electron microscopy was applied. For morphological and size analysis of electrically non-conductive micro- to nano-particles under environmentally compatible conditions of elevated gas pressure and humidity, environmental scanning electron microscopy was selected as the most suitable. Moreover, the high-end methods of focused ion beam scanning electron microscopy and serial block-face scanning electron microscopy enabled the analysis of particles in the epoxy resin volume including spatial imaging. The application of image post-processing as an important part of the electron microscopy workflow is also discussed.

Assessment of microplastics production from waste plastics-modified asphalt pavement

Post-consumer recycled plastics (PCRP) have been increasingly utilized in asphalt pavement applications as the world moves towards a circular economy. However, it is unknown whether microplastics (MPs) could be generated in significant amounts during the subsequent pavement life cycle. This study developed methods to detect and quantify the potential microplastic generation from asphalt pavement materials containing PCRP (specifically, linear low-density polyethylene) using the Hamburg wheel-tracking test and a water permeability test. MPs were quantified by Nile Red staining followed by fluorescence microscope imaging. Environmental scanning electron microscopy (ESEM) and energy dispersive spectroscopy (EDS) were further conducted to characterize the nanoscale morphology of the embedded PCRP. The results showed that the generated MPs could reside at water/air interface, in bulk water, or with asphalt binder and aggregates in the sediment; and their amounts varied depending on the polyethylene dosage and type. The potential environmental impact of MP production from PCRP-modified asphalt pavement needs to be examined under the context of MP particle releases from other emission sources, notably, the tire wear particle generation when rubber tires meet the road. Our assessment indicated that while there was a potential of MPs release from the PCRP-modified asphalt, the up-scaled level of their release from a pavement was estimated to be about three orders of magnitude less than the tire wear rubber particles.

A comprehensive study from the micro- to the nanometric scale: Evaluation of chilling injury in tomato fruit (Solanum lycopersicum)

Tomato fruit is susceptible to chilling injury (CI) during its postharvest handling at low temperature. The symptoms caused by this physiological disorder have been commonly evaluated by visual inspection at a macro-observation scale on fruit surface; however, the structure at deeper scales is also affected by CI. This work aimed to propose a descriptive model of the CI development in tomato tissue under the micro-scale, micro-nano-scale and nano-scale approaches using fractal analysis. For that, quality and fractal parameters were determined. In this sense, light microscopy, Environmental Scanning Electron Microscopy (ESEM) and Atomic Force Microscopy (AFM) were applied to analyse micro-, micro-nano- and nano-scales, respectively. Results showed that the morphology of tomato tissue at the micro-scale level was properly described by the multifractal behaviour. Also, generalised fractal dimension (Dq=0) and texture fractal dimension (FD) of CI-damaged pericarp and cuticle were higher (1.659, 1.601 and 1.746, respectively) in comparison to non-chilled samples (1.606, 1.578 and 1.644, respectively); however, FD was unsuitable to detect morphological changes at the nano-scale. On the other hand, lacunarity represented an appropriate fractal parameter to detect CI symptoms at the nano-scale due to differences observed between damaged and regular ripe tissue (0.044 and 0.025, respectively). The proposed multi-scale approach could improve the understanding of CI as a complex disorder to the development of novel techniques to avoid this postharvest issue at different observation scales.

Carbon fiber–polyetheretherketone-reinforced PVA composites for bone graft applications

Poly(vinyl alcohol) (PVA) is a synthetic, bioinert, semicrystalline, biodegradable, non-toxic and thermoplastic polymer extensively used in the field of biomedical engineering. The weak mechanical properties of PVA, such as low strength and Young’s modulus, limit its application as a bone implant. However, PVA can be reinforced with a suitable material to improve its mechanical properties. Carbon fiber (CF)–polyetheretherketone (PEEK) is a superior thermoplastic synthetic biomaterial with good tensile strength, stiffness, wear properties and X-ray translucence. In this study, CF–PEEK-reinforced PVA composites were prepared by varying the CF–PEEK concentration (0, 0.25, 0.50, 0.75, 1.00, 2.00 and 3.00% w/v) in the PVA matrix (10% w/v) using the solvent-casting method. The physical, chemical, biological and mechanical properties of the prepared PVA–CF–PEEK composites were studied. The environmental scanning electron microscopy micrographs showed agglomeration of CF–PEEK at higher concentrations – that is, 1, 2 and 3% w/v. With the inclusion of CF–PEEK in PVA, the contact angle of the composites was found to increase. The increased hydrophobicity of the samples resulted in reduced swelling and degradation rate. In the hemolysis study, the percentage hemolysis values were found to be <5%, revealing the hemocompatible nature of the developed composites. An increase in in vitro protein adsorption was observed, and cell viability studies showcased the biocompatible nature of the prepared composite samples. Thus, the developed CF–PEEK–PVA polymer composites present great potential for bone graft applications.

Analysis of liquid–vapor mixed migration mechanism in unsaturated soil based on the effect of temperature on soil microstructure

Moisture migration in unsaturated soils is a result of the interaction between temperature and soil microstructure. In order to reveal the mechanism of moisture increase of subgrade soils under diurnal cycle conditions, a series of macro and microscopic tests were carried out on the unsaturated silty clay and sand soil, including liquid–vapor mixed migration tests simulating a one-dimensional subgrade, environmental scanning electron microscope (ESEM), and matrix suction test. Then, the soil microstructure in microscopic images was investigated using the particle (pores) and cracks analysis system (PACS). Next, the relationship between the thermal effects of the soil–water characteristic curve (SWCC) and changes in soil microstructure was analyzed. Finally, the change mechanism of liquid–vapor mixed migration based on the change in soil microstructural under thermal effects was analyzed. The results showed under the diurnal cycle, both the silty clay and sand soil columns appeared in the phenomenon of a “diurnal cycle of water vapor migration”, which led to moisture accumulation at the top of the soil layer. In silty clay soil column, moisture was primarily driven by water vapor pressure and migrated upwards. Additionally, moisture redistribution led to changes in soil microstructure, which in turn influenced the process of moisture migration. The moisture content in the upper soil layer increased making both inter-aggregate and intra-aggregate pores decrease. The moisture content in the lower soil later decreased, leading to the water-holding capacity of the lower soil layer to increase. So, the moisture migration gradually decreased at night. In the sand soil column, moisture migration was mainly driven by gravity potential and migrated downwards. Moisture redistribution made inter-aggregate pore and matrix suction of the upper soil layer increase, leading to an increase in moisture migration at night.

Sulfur Free Crosslinking of EPDM Composites via Silane Grafting and Silica Incorporation.

This study aims at evaluating and developing an environmental-friendly and sulfur-free cured ethylene propylene diene monomer (EPDM) composites. Silane grafted EPDM (SiEPDM) composites incorporated with silica is prepared via a solvent-free, one-step reactive mixing process. The silane grafting and silica filler bonding are characterized using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The mechanical properties of the developed composites are examined. The fracture morphology is observed using an environmental scanning electron microscopy. The rheology and thermomechanical properties are evaluated by using a rotational rheometer and dynamic mechanical analyzer. Notably, a robust bonding between silica and the grafted silane is established, yielding a crosslinking network within the composite structure. This phenomenon is substantiated by the observed gel efficiency and rheology behavior. Consequently, a pronounced augmentation of up to 75% in tensile strength and 29% in tear strength are observed in the optimized SiEPDM-silica composites, distinguishing them from their EPDM-silica counterparts. The introduction of paraffin oil contributes to enhanced processability; however, it is concomitant with a reduction in gel efficiency and associated mechanical properties. Furthermore, subsequent UV weathering test unveils that the SiEPDM-silica composites exhibit the highest levels of residual tensile strength and modulus, indicative of their exceptional UV stability.

Effect of calcium sulphate dihydrate on dust adhesion on photovoltaic panel surfaces under condensation

The components of dust accumulation on PV panel surfaces under three different scenarios were analyzed, the adhesion strength between dust and PV panels under condensation conditions was measured, the microstructure of the adhesion interfaces, using metallographic microscopy and environmental scanning electron microscopy, was observed, the main factors of dust-PV panel adhesion were investigated, and the adhesion mechanism was explored. The results showed that calcium sulfate dihydrate (CSD) was the main soluble component in most PV panel dusts. It significantly increased the adhesion strength of the dust to the PV panels under the effect of condensation. The kinetic friction coefficients of the dust adhered samples after 150 condensation cycles increased by approximately 100% and 170% when the CSD content increased from 0 to 2.8% and 5.53%, respectively. This was attributed to the recrystallization of the CSD into blocky and rod-shaped particles. The blocky CSD particles wrapped and cemented other particles while promoting adhesion through a larger contact area with the PV panel surface and formation of hydrogen bonds. A rod-shaped CSD was interlaced to enhance agglomeration and increase friction at the adhesion interface to improve the adhesion. Moreover, CSD caused the decrease of power generation of PV panels. For 150 condensation cycles and the same cleaning conditions, dust sample with 2.88% CSD resulted in a power generation reduction of about 2.37% compared to that of dust sample without CSD. It was recommended that a hydrophobic or super hydrophobic surface was used on PV panels to reduce the residence time and contact area of water on the surface to inhibit the recrystallizing of CSD on PV panels.

Biofouling reduction of EPDM by radiation‐assisted modification for water environment applications

AbstractEthylene propylene diene elastomer (EPDM) harbors diverse microbiota that form biofilms. Such biofilms may contaminate water and can increase drag force impacting the hydrodynamic performance of a ship, once it is used as fenders. Here, the EPDM surface is modified by radiation‐assisted grafting to prevent biofilm formation. Three different monomers, namely, methacrylic acid (MAA), isodecyl methacrylate (IDM), and lauryl methacrylate (LMA), are grafted on EPDM. The modified surfaces are characterized by Fourier transform infrared (FTIR) spectroscopy, surface wettability, mechanical and dynamic mechanical properties (DMA), and scanning electron microscopy (SEM). The modified surfaces are subjected to biofouling by prominent biofilm adherents, that is, Pseudomonas aeruginosa and Klebsiella pneumoniae. The standard plate count and resazurin fluorescence assays are performed to observe the microbial load on these surfaces. The MAA‐grafted EPDM, which is hydrophilic in nature, shows a considerable decrease in bacterial adhesion compared to pure EPDM, but for IDM and LMA‐grafted EPDM, it is the opposite. The deterioration of the surface with bacteria by environmental scanning electron microscopy (ESEM) supports the findings. The tensile property of the modified EPDM is observed to be within satisfactory limits. After such modification, the EPDM is expected to expand its application.

Synthesis and Characterization of Novel pH-Responsive Aminated Alginate Derivatives Hydrogels for Tissue Engineering and Drug Delivery.

The aims of this study are to synthesize new derivatives of sodium alginate that improve the inherent properties, such as hydrogel strengthening, and create environmental sensitivity, such as pH sensitivity, for use in drug delivery. Today, hydrogels, due to outstanding properties such as biodegradability, biocompatibility, mechanical properties, and response to stimuli properties, are widely used as harmless biomaterials in various fields in drug delivery, wound dressing, and tissue engineering. Stimulus-sensitive polymers significantly respond to slight changes in their environment. Different types of stimuli are used to influence the properties of polymers, the most important of which are temperature and pH because these are two vital factors in the human body; hence, temperature-sensitive and pHsensitive hydrogels have been extensively studied. The ability to absorb water and swell the hydrogel is due to hydrophilic chains in the hydrogel network, and water absorption by hydrogel can be controlled by response to the stimuli. Since hydrogels mimic human tissue, the ability to retain water in them is essential. As a result, it is considered in many biomedical drug delivery systems. Stimulusresponsive swelling can control diffusion out of and into the hydrogel network, which allows temporal and spatial control of drug release. When a drug is loaded onto a biodegradable and stimulisensitive hydrogel, the drug delivery system has the added advantage of sustained release of the drug, which reduces side effects. In this study, two different hydrocarbons, [1,3-diaminopropane (DAP)] as a short-chain hydrocarbon, and [1,7-diaminoheptane (DAH)] as a long-chain hydrocarbon were grafted onto three types ofsodium alginate (SA), through amide bond linkages. The hydrogel copolymer matrices were compared with sodium alginate (SA) beads. The graft copolymers were characterized using FTIR, 1HNMR, XRD spectroscopy, elemental analysis (CHNS) and thermal analysis (TGA, DTA and DSC). An environmental scanning electron microscope (ESEM) was used to investigate the surface morphology of hydrogels. Effects of variables such as the length of hydrocarbon chains cross-linked to alginate, temperature, pH, and cross-linkers on the properties of hydrogels investigated in the temperature range of 2-70 ˚C and two different pH values (4.4 and 7.4). The results showed that when the hydrocarbon chain length of diamines decreases, the extent of cross-linking and strength of the hydrogels are increased. Other results suggest that the hydrogels obtained from high-viscosity alginate derivatives had positive pH sensitivity. Hydrogels prepared in this study demonstrated good mechanical and swelling ratios that are necessary for wound dressing. DAP-g-SA and DAH-g-SA pH-sensitive hydrogels were successfully synthesized through amide bond linkages. The new synthesis derivatives showed lower swelling levels at low pH (4.4). In contrast, their swelling levels at higher pH (7.4) were significantly enhanced. Higher swelling degree could be obtained at high pH. pH-responsive hydrogels are especially useful for various biological applications due to their unique feature of controlled swelling, biodegradability, biocompatibility, and fluid retention in their network structures. pH-responsive hydrogels, as intelligent systems, can be used in controlled-release drug delivery systems such as insulin delivery.

In-situ shrinkage measurement of alkali-activated materials using focused ion beam combined with environmental scanning electron microscopy

Drying shrinkage of alkali-activated slag (AAS) has gained significant attention since the volumetric instability of this material can generate premature cracking and degrade the long-term durability of concrete structures. The unique shrinkage behavior of AAS originates mainly from the particular characteristics of its main hydrated products. However, few studies have even at-tempted to investigate the shrinkage behavior of hydrated products in AAS materials. This paper presented a new method of investigating drying shrinkage behavior of AAS using focused ion beam (FIB) combined with environmental scanning electron microscopy (ESEM). This innovative experimental method allowed the in-situ measurement of phase-specific shrinkage. The results showed FIB/ESEM technique can be successfully implemented to cementitious material to prepare phase-specific samples. Furthermore, object-oriented finite element method (OOF2) has been utilized to compute the shrinkage behavior of AAS concrete using a proposed multi-scale scheme. The computations can be made at multi-scales which highlight the effect of hydration products on shrinkage behaviors. OOF2 calculation at the micro-length scale predicted an increase in the shrinkage due to the well-dispersed hydration products inside the matrix. At larger scale, the decrease in the overall shrinkage is related to the extremely low shrinkage value by aggregates. The findings reveal OOF2 offers the capability to accurately measure local stress and strain distribution within heterogeneous materials, a feature notably absent in conventional numerical homogenization approaches. The importance of this benefit is highlighted particularly in the context of free-restrained shrinkage prediction, as conventional homogenization methods fail to account for stress.

Masters of mudbrick: Geoarchaeological analysis of Iron Age earthen public buildings at Ashdod‐Yam (Israel)

AbstractExcavations at Ashdod‐Yam exposed a fortification system that features a massive mudbrick wall with large earthen ramparts laid on either side. This fortified horseshoe‐shaped enclosure once surrounded what was likely a human‐made harbor and an adjacent acropolis with complex earthen architecture, constructed and active during Iron Age IIB–C (eighth–seventh centuries B.C.E.). These Iron Age public structures are at the center of the current research. In this paper, we present the geoarchaeological analyses of Ashdod‐Yam's earthen architecture. We applied a multidisciplinary methodology to new evidence for mudbrick manufacture with the goal of understanding the relationship between governing bodies and craftsmen. The analyses combine X‐ray fluorescence, loss on ignition, environmental scanning electron microscopy, and thin‐section petrography to investigate raw material procurement, manufacturing choices, and labor organization at Ashdod‐Yam during Iron IIB–C. Construction techniques and the standardization of the mudbrick recipe point to a local enterprise regarding the site's public earthen architecture. Furthermore, the degree of labor organization must have been closely observed and supervised by a central political power. Thus, it is argued here that construction and maintenance of the site was carried out by the kingdom of Ashdod, either as a part of its own local initiative or on behalf of the Neo‐Assyrian empire.