Experimental investigation on strengthening of Zea mays root fibres for biodegradable composite materials using potassium permanganate treatment.

Humans are the only species who generate waste materials that cannot be broken down by natural processes. The ideal solution to this waste problem would be to employ only compostable materials. Biodegradable materials play a key role in creating a safer and greener world. Biodegradability is the gift that keeps on giving, in the sense of creating an Earth worth living. The future is thus best served by green energy, sustainability, and renewable resources. To realize such goals, waste should be considered as a valuable resource. In this context, Zea mays (Zm) root fibres, which are normally considered as agricultural waste, can be used as reinforcing substances in polymer matrices to produce structural composite materials. Before being used in composites, such fibres must be analysed for their physical properties. Chemical treatments can be employed to improve the structural quality of fibres, and the changes due to such modification can be analysed. Therefore, the current work examines the effect of permanganate treatment on the surface properties of Zm fibres. The raw and potassium permanganate-treated samples were assayed for various properties. Physical analysis of the fibre samples yielded details concerning the physical aspects of the fibres. The thermal conductivity and moisture absorption behaviour of the samples were analysed. Chemical analysis was employed to characterize the composition of both treated and untreated samples. p-XRD was employed to examine the crystalline nature of the Zm fibres. Numerous functional groups present in each sample were analysed by FTIR. Thermogravimetric analysis was used to determine the thermal stability of Zm fibres. Elemental analysis (CHNS and EDS) was used to determine the elemental concentrations of both raw and treated samples. The surface alterations of Zm fibres brought on by treatment were described using SEM analysis. The characteristics of Zm roots and the changes in quality due to treatment were reviewed, and there were noticeable effects due to the treatment. Both samples would have applications in various fields, and each could be used as a potential reinforcing material in the production of efficient bio-composites.

Comparative study of eco-friendly wire mesh configurations to enhance sustainability in reinforced concrete structures.

Recent and past studies mainly focus on reducing the dead weight of structure; therefore, they considered lightweight aggregate concrete (LWAC) which reduces the dead weight but also affects the strength parameters. Therefore, the current study aims to use varied steel wire meshes to investigate the effects of LWAC on mechanical properties. Three types of steel wire mesh are used such as hexagonal (chicken), welded square, and expanded metal mesh, in various layers and orientations in LWAC. Numerous mechanical characteristics were examined, including energy absorption (EA), compressive strength (CS), and flexural strength (FS). A total of ninety prisms and thirty-three cubes were made. For the FS test, forty-five 100 × 100 × 500 mm prism samples were poured, thirty-three 150 × 150 × 150 mm cube samples were made, and forty-five 400 × 300 × 75 mm EA specimens were costed for fourteen days of curing. The experimental findings demonstrate that the FS was enhanced by adding additional forces that spread the forces over the section. One layer of chicken, welded, and expanded metal mesh enhances the FS by 52.96%, 23.76%, and 22.2%, respectively. In comparison to the remaining layers, the FS in a single-layer hexagonal wire mesh has the maximum strength, 29.49 MPa. The hexagonal wire mesh with a single layer had the greatest CS, measuring 36.56 MPa. When all three types of meshes are combined, the CS does not vary in this way and is estimated to be 29.79 MPa. In the combination of three layers, the chicken and expanded wire mesh had the most energy recorded prior to final failure, which was 1425.6 and 1108.7 J, whereas it was found the highest 752.3 J for welded square wire mesh. The energy absorption for the first layer with hexagonal wire mesh increased by 82.81% prior to the crack and by 88.34% prior to the ultimate failure. Overall, it was determined and suggested that hexagonal wire mesh works better than expanded and welded wire meshes.

Thermal Conductivity in Concrete Samples with Natural and Synthetic Fibers.

One crucial property of concrete, particularly in construction, is its thermal conductivity, which impacts heat transfer through conduction. For example, reducing the thermal conductivity of concrete can lead to energy savings in buildings. Various techniques exist for measuring the thermal conductivity of materials, but there is limited discussion in the literature about suitable methods for concrete. In this study, the transient line source method is employed to evaluate the thermal conductivity of concrete samples with natural and synthetic fibers after 7 and 28 days of curing. The results indicate that concrete with hemp fiber generally exhibits higher thermal conductivity values, increasing by 48% after 28 days of curing, while synthetic fibers have a minimal effect. In conclusion, this research opens the door to using natural alternatives like hemp fiber to improve concrete's thermal properties, providing alternatives for thermo-active foundations and geothermal energy piles which require high thermal conductivities.

Experimental investigation on the physical, microstructural, and mechanical properties of hemp limecrete.

This paper investigates the hemp limecrete mechanical and microstructural performance of a new sustainable and environmental friendly building material. Several studies have investigated the hemp limecrete focusing on the non-structural applications. The newly developed hemp limecrete consists of high mechanical and microstructural properties. The specimens were prepared with varying lengths and proportions of hemp fibers with lime and tested for compressive strength, flexural strength, thermal conductivity and microstructural analysis like SEM and EDS. The study found that the optimal fiber content for making mortars was between 2 and 4%. This conclusion was reached after analyzing the influence of fiber length and ratio on the properties of the mortars. The dry unit weight decreased when the fiber content was higher than 4%. In terms of strength, the study found that the flexural strength of the hemp limecrete improved with an increase in fiber ratio, but the compressive strength decreased. However, with 2% hemp fiber, compressive strengths of 3.48 MPa and above were obtained. The study also highlighted the good thermal insulation properties and dimensional stability of hemp limecrete. These findings have important implications for the use of hemp limecrete as a sustainable building material. The results suggest that hemp limecrete has the potential to be a viable alternative to conventional concrete in specific applications, particularly in areas where environmental sustainability is a priority.

Examining the physico-chemical, structural and thermo-mechanical properties of naturally occurring Acacia pennata fibres treated with KMnO4.

Natural fiber is a viable and possible option when looking for a material with high specific strength and high specific modulus that is lightweight, affordable, biodegradable, recyclable, and eco-friendly to reinforce polymer composites. There are many methods in which natural fibres can be incorporated into composite materials. The purpose of this research was to evaluate the physico-chemical, structural, thermal, and mechanical properties of Acacia pennata fibres (APFs). Scanning electron microscopy was used to determine the AP fibers' diameter and surface shape. The crystallinity index (64.47%) was discovered by XRD. The irregular arrangement and rough surface are seen in SEM photos. The findings demonstrated that fiber has high levels of cellulose (55.4%), hemicellulose (13.3%), and low levels of lignin (17.75%), which were determined through chemical analysis and validated by Fourier Transform Infrared Spectroscopy (FTIR). By using FTIR, the functional groups of the isolated AP fibers were examined, and TG analysis was used to look into the thermal degrading behaviour of the fibers treated with potassium permanganate (KMnO4) Due to their low density (520 kg/m3) and high cellulose content (55.4%), they have excellent bonding qualities. Additionally, tensile tests were used for mechanical characterisation to assess their tensile strength (685 MPa) and elongation.

Microstructure and Water Retention Kinetics in Autogenous Cured Self-Compacting Concrete Blends Using Super Absorbent Polymer.

This research aimed to determine how a super absorbent polymer affects the microstructural characteristics and water retention kinetics of a new composite made by substituting granite pulver (GP) and fly ash (FA) for cement. Understanding the mechanics of water movement is crucial for comprehending the effectiveness of autogenous curing. Several experiments were conducted to analyze the water mitigation kinetics of super absorbent polymer (SAP) in the hydrating cement paste of autogenous cured self-compacting concrete (GP-ACSSC) mixtures. In the first hours following casting, water sorptivity, water retention, and hydration tests were carried out. The effects of various concentrations of SAP and GP, which was utilized as an alternative cement for the production of sustainable concrete that leads to reduction in carbon footprint, on the autogenous cured self-compacting concrete with reference to the abovementioned properties were explored. The investigation showed that releasing the curing water at a young age, even around the beginning of hydration, allowed homogenous and almost immediate distribution of water across the full cured paste volume, which improved the water retention kinetics. Compared to the control mixtures, the addition of SAP up to 0.6% and the substitution of cement with GP up to 15% had favorable impacts on all water kinetics parameters.

Experimental Study on the Mechanical Properties and Microstructures of Cenosphere Concrete.

The most valuable components of coal fly ash are cenospheres. Cenospheres are hollow spherical particles produced during the coal-burning processes. As a result of their excellent characteristics, such as high workability, high heat resistance, low bulk density, and high strength, cenospheres can be used in the manufacturing of lightweight cement concrete. The research efforts and outcomes are to produce long-lasting cement-based lightweight concrete (LWC) composites with good mechanical properties. The novelty of this investigation is to determine the cement concrete strength when silica fume (SF) and cenospheres (CS) were used as a replacement for cement. Throughout the experiments, a consistent substitution of 12% silica fume was incorporated into cement mass. Silica is used as a micro filler and pozzolanic reactant to strengthen concrete. The concrete mixtures were tested to ensure they met the requirements of the lightweight concrete in terms of their mechanical, physical, and durability qualities. According to the findings, lightweight concrete standards were met, and environmental sustainability was improved with the use of these mix proportions. Concrete specimen's self-weight decreases by 35% with 30% cenosphere as a replacement. The micrograph shows the lack of portlandite is filled by mullite and other alumino silicates from the cenosphere. In order to achieve sustainability in concrete manufacturing, these mixtures can be suggested for the making of structural LWC that makes use of a large volume of industrial waste while conserving cement and natural resources.

Evaluating the inhibitory activity of ferrocenyl Schiff bases derivatives on 5-lipoxygenase: Computational and biological studies.

In the search for new 5-LOX inhibitors, two ferrocenyl Schiff base complexes functionalized with catechol ((ƞ5-(E)-C5H4-NCH-3,4-benzodiol)Fe(ƞ5-C5H5) (3a)) and vanillin ((ƞ5-(E)-C5H4-NCH-3-methoxy-4-phenol)Fe(ƞ5-C5H5) (3b)) were obtained. Complexes 3a and 3b were biologically evaluated as 5-LOX inhibitors showed potent inhibition compared to their organic analogs (2a and 2b) and known commercial inhibitors, with IC50 = 0.17 ± 0.05 µM for (3a) and 0.73 ± 0.06 µM for (3b) demonstrated a highly inhibitory and potent effect against 5-LOX due to the incorporation of the ferrocenyl fragment. Molecular dynamic studies showed a preferential orientation of the ferrocenyl fragment toward the non-heme iron of 5-LOX, which, together with electrochemical and in-vitro studies, allowed us to propose a competitive redox deactivation mechanism mediated by water, where Fe(III)-enzyme can be reduced by the ferrocenyl fragment. An Epa/IC50 relationship was observed, and the stability of the Schiff bases was evaluated by SWV in the biological medium, observing that the hydrolysis does not affect the high potency of the complexes, making them interesting alternatives for pharmacological applications.

Biodegradable Green Composites: Effects of Potassium Permanganate (KMnO4) Treatment on Thermal, Mechanical, and Morphological Behavior of Butea Parviflora (BP) Fibers.

This study emphasizes the importance of utilizing biodegradable material Butea parviflora (BP) fiber for sustainable solutions. BP fiber offers numerous ecological benefits, such as being lightweight, biodegradable, and affordable to recycle. The study examines the effects of potassium permanganate (KMnO4) treatment on BP fiber and analyzes its physical and chemical behavior using various methods, including X-ray Diffraction (XRD) analysis, tensile testing, thermogravimetric analysis, thermal conductivity, Scanning Electron Microscopy (SEM), and Fourier Transform Infrared spectroscopic (FTIR) analysis. The results demonstrate that BP fiber possesses low density (1.40 g/cc) and high cellulose content (59.4%), which fosters compatibility between the matrix and resin. XRD analysis indicates a high crystallinity index (83.47%) and crystallite size (6.4 nm), showcasing exceptional crystalline behavior. Treated fibers exhibit improved tensile strength (198 MPa) and Young's modulus (4.40 GPa) compared to untreated fibers (tensile strength-92 MPa, tensile modulus-2.16 GPa). The Tg-DTA thermograms reveal the fiber's thermal resistance up to 240 °C with a kinetic activation energy between 62.80-63.46 KJ/mol. Additionally, the lowered thermal conductivity (K) from Lee's disc experiment suggests that BP fiber could be used in insulation applications. SEM photographic results display effective surface roughness for composite making, and FTIR studies reveal vibrational variations of cellulosic functional groups, which correlates with increased cellulosic behavior. Overall, the study affirms the potential of BP fiber as a reinforcing material for composite-making while emphasizing the importance of utilizing biodegradable materials for sustainability.

Mechanical Behaviour and Impact of Various Fibres Embedded with Eggshell Powder Epoxy Resin Biocomposite.

Natural fiber composites are becoming an alternate material to synthetic fiber composites, and the use of eggshell bio-filler has been explored in polymer composites as environmental protection. Jute, coir, and sisal fibers were utilized in this research to make composites out of natural fibers. Polymer composites were made using epoxy resin with different amounts of eggshell powder (ESP) as fillers (2%, 4%, 6%, 8%, and 10% of weight). The mechanical and biodegradability properties of the synthesized composites were investigated. The testing results showed that composites with an optimum percentage of 6% ESP as filler improved mechanical characteristics significantly in all three fiber composites. Among the three fibers, coir fiber with 6% ESP added showed a substantial increase in tensile, flexural, impact, and hardness strength properties by 34.64%, 48.50%, 33.33%, and 35.03%, respectively. In addition, the percentage weight loss of coir fiber composites at 9 weeks is noteworthy in terms of biodegradability testing. As a result, epoxy composites containing eggshell fillers could be employed in applications requiring better tensile, flexural, impact, and hardness strength.

A Study on Mechanical and Microstructural Characteristics of Concrete Using Recycled Aggregate.

The objective of this paper is to provide a comprehensive study about the performance of concrete using mixed coarse recycled aggregate (MCRA) as an alternative for natural aggregate (NA) at replacement levels of 0, 30, 60, and 100%, which can greatly reduce the environmental pollution by incorporating the construction and demolition wastes in the reproduction of concrete. The focus of this study was to use the raw MCRA that was directly obtained from a recycling plant and not further processed. Initially, MCRA was studied to ascertain if its property meets the recommended Indian standards for natural aggregates. Using the slump test, the workability of freshly prepared concrete with a characteristic strength of 30 MPa was assessed. Additionally, the mechanical performance of concrete was assessed on the specimens prepared in the different forms: cubes, cylinders, and beams. Moreover, Scanning Electron Microscopy (SEM) with EDAX, XRD, and FTIR were used to study the microstructural behavior of selected optimum and control mixes at 7 and 28 days of curing. The studies revealed that a higher MCRA content improved the workability of concrete and 30% replacement of MCRA improved the compressive strength by 11.01, 6.98, 6.19, and 14.24% at 7, 28, 56, and 90 days respectively. At the same time, the 30% replacement of the MCRA mix showed an improved split tensile and flexural strength by 2.92 and 6.26%, respectively. The microstructural analysis showed that the optimum mixture had a more condensed microstructure. Therefore, 30% replacement of MCRA can be incorporated in the characteristic strength of concrete of 30 MPa. In particular, MCRA incorporation had a positive influence similar to conventional concrete on the physical, mechanical, and microstructural properties, which can increase the utilization of all kinds of directly obtained construction and demolition wastes to increase the circular economy in the construction sector.

Aquagenic keratoderma.

BACKGROUND: Aquagenic keratoderma is triggered in the palms and soles after contact with water, and is characterized by the appearance of translucent papules forming macerated plaques. It may be associated with medications and diseases such as cystic fibrosis, atopy, and malnutrition, or be idiopathic. CASE REPORT: We describe the case of a 17-year-old female patient with chronic functional abdominal pain. She presented with a 2-month history of "wrinkling" of palms after contact with water. After stimulation with water, palmar hyperlinearity and whitish, translucent papules forming macerated-looking plaques with a central depression were observed. Dermoscopically, we observed whitish and anfractive structures with coral appearance and microdroplets of water. In the histological study, we observed continuous hyperkeratosis and acrosyringium dilation from the middle dermis to the stratum corneum. With the clinical presentation and histological findings, aquagenic keratoderma was diagnosed, and treatment was started with partial improvement. CONCLUSIONS: Aquagenic keratoderma is an underdiagnosed entity. Despite its indolent course, it could be considered as a marker of a systemic disease such as cystic fibrosis. Since the discussion about the terminology of the disease has arisen, we considered adjusting to a descriptive nomenclature, proposing the term whitish macerated aquagenic plaques of the acrosyringium. It is necessary to continue reporting these cases to understand the disease better and offer adequate management and comprehensive follow-up to the patients.

INTRODUCCIÓN: La queratodermia acuagénica se desencadena tras el contacto de las palmas de las manos y las plantas de los pies con el agua. Se caracteriza por la aparición de pápulas translúcidas que forman placas de aspecto macerado. Puede asociarse con el consumo de ciertos medicamentos y con afecciones como la fibrosis quística, la atopia y la desnutrición, o ser idiopática. CASO CLÍNICO: Se describe el caso de una paciente de 17 años con dolor abdominal crónico funcional. Presentó una dermatosis de 2 meses de evolución que afectaba las palmas con «arrugamiento¼ después del contacto con el agua. Tras el estímulo con el agua, se observaron hiperlinealidad palmar y pápulas blanquecinas y translúcidas que formaban placas de aspecto macerado con una depresión central. Dermatoscópicamente se observaron estructuras blanquecinas anfractuosas de apariencia coraliforme y microgotas de agua. En el estudio histológico se observaron hiperqueratosis continua y dilatación del acrosiringio desde la dermis media hasta el estrato córneo. Con el cuadro clínico y los hallazgos histológicos, se confirmó el diagnóstico de queratodermia acuagénica y se inició el tratamiento, con el que se observó una mejoría parcial. CONCLUSIONES: La queratodermia acuagénica es una afección subdiagnosticada y poco reportada. A pesar de cursar de forma indolente, puede considerarse como un marcador de enfermedad sistémica como la fibrosis quística. Ya que existe discusión sobre la nomenclatura de la enfermedad, consideramos ajustarnos a una nomenclatura descriptiva, como «placas blanquecinas y maceradas acuagénicas del acrosiringio¼. Es necesario continuar reportando estos casos para comprender mejor la enfermedad, ofrecer un manejo adecuado y dar seguimiento integral a los pacientes.

Destructive and Non-Destructive Testing of the Performance of Copper Slag Fiber-Reinforced Concrete.

Concrete technology is adopted worldwide in construction due to its effectiveness, performance, and price benefits. Subsequently, it needs to be an eco-friendly, sustainable, and energy-efficient material. This is achieved by replacing or adding energy-efficient concrete materials from industries, such as ground granulated blast furnace slag, steel slag, fly ash, bottom ash, rice husk ash, etc. Likewise, copper slag is a waste material produced as molten slag from the copper industry, which can be used in concrete production. Copper slag can perform roles similar to pozzolans in the hydration process. This paper extends the comparative study of copper slag concrete with polypropylene fiber (PPF) subjected to destructive and non-destructive testing. Under destructive testing, compressive strength of concrete cubes, compressive strength of mortar cubes, splitting tensile tests on cylindrical specimens, and flexural tests on plain cement concrete were conducted and analysed. Ultrasonic pulse velocity and rebound hammer tests were performed on the samples as per IS13311-Part 1-1992 for non-destructive testing. The 100% replacement of copper slag exhibited a very high workability of 105 mm, while the addition of 0.8% PPF decreased the flowability of the concrete. Hence, the workability of concrete decreases as the fiber content increases. The density of the concrete was found to be increased in the range of 5% to 10%. Furthermore, it was found that, for all volume fractions of fiber, there was no reduction in compressive strength of up to 80% of copper slag concrete compared to control concrete. The 40% copper slag concrete was the best mix proportion for increasing compressive strength. However, for cement mortar applications, 80% copper slag is recommended. The findings of non-destructive testing show that, except for 100% copper slag, all mixes were of good quality compared to other mixes. Linear relationships were developed to predict compressive strength from UPV and rebound hammer test values. This relationship shows better prediction among dependent and independent values. It is concluded that copper slag has a pozzolanic composition, and is compatible with PPF, resulting in good mechanical characteristics.

Queratodermia acuagénica / Aquagenic keratoderma

Resumen Introducción: La queratodermia acuagénica se desencadena tras el contacto de las palmas de las manos y las plantas de los pies con el agua. Se caracteriza por la aparición de pápulas translúcidas que forman placas de aspecto macerado. Puede asociarse con el consumo de ciertos medicamentos y con afecciones como la fibrosis quística, la atopia y la desnutrición, o ser idiopática. Caso clínico: Se describe el caso de una paciente de 17 años con dolor abdominal crónico funcional. Presentó una dermatosis de 2 meses de evolución que afectaba las palmas con «arrugamiento¼ después del contacto con el agua. Tras el estímulo con el agua, se observaron hiperlinealidad palmar y pápulas blanquecinas y translúcidas que formaban placas de aspecto macerado con una depresión central. Dermatoscópicamente se observaron estructuras blanquecinas anfractuosas de apariencia coraliforme y microgotas de agua. En el estudio histológico se observaron hiperqueratosis continua y dilatación del acrosiringio desde la dermis media hasta el estrato córneo. Con el cuadro clínico y los hallazgos histológicos, se confirmó el diagnóstico de queratodermia acuagénica y se inició el tratamiento, con el que se observó una mejoría parcial. Conclusiones: La queratodermia acuagénica es una afección subdiagnosticada y poco reportada. A pesar de cursar de forma indolente, puede considerarse como un marcador de enfermedad sistémica como la fibrosis quística. Ya que existe discusión sobre la nomenclatura de la enfermedad, consideramos ajustarnos a una nomenclatura descriptiva, como «placas blanquecinas y maceradas acuagénicas del acrosiringio¼. Es necesario continuar reportando estos casos para comprender mejor la enfermedad, ofrecer un manejo adecuado y dar seguimiento integral a los pacientes.

Abstract Background: Aquagenic keratoderma is triggered in the palms and soles after contact with water, and is characterized by the appearance of translucent papules forming macerated plaques. It may be associated with medications and diseases such as cystic fibrosis, atopy, and malnutrition, or be idiopathic. Case report: We describe the case of a 17-year-old female patient with chronic functional abdominal pain. She presented with a 2-month history of "wrinkling" of palms after contact with water. After stimulation with water, palmar hyperlinearity and whitish, translucent papules forming macerated-looking plaques with a central depression were observed. Dermoscopically, we observed whitish and anfractive structures with coral appearance and microdroplets of water. In the histological study, we observed continuous hyperkeratosis and acrosyringium dilation from the middle dermis to the stratum corneum. With the clinical presentation and histological findings, aquagenic keratoderma was diagnosed, and treatment was started with partial improvement. Conclusions: Aquagenic keratoderma is an underdiagnosed entity. Despite its indolent course, it could be considered as a marker of a systemic disease such as cystic fibrosis. Since the discussion about the terminology of the disease has arisen, we considered adjusting to a descriptive nomenclature, proposing the term whitish macerated aquagenic plaques of the acrosyringium. It is necessary to continue reporting these cases to understand the disease better and offer adequate management and comprehensive follow-up to the patients.

Damage Detection in Steel-Concrete Composite Structures by Impact Hammer Modal Testing and Experimental Validation.

Steel-concrete composite systems are an efficient alternative to mid- and high-rise building structures because of their high strength-to-weight ratio when compared to traditional concrete or steel constructive systems. Nevertheless, composite structural systems are susceptible to damage due to, for example, deficient construction processes, errors in design and detailing, steel corrosion, and the drying shrinkage of concrete. As a consequence, the overall strength of the structure may be significantly decreased. In view of the relevance of this subject, the present paper addresses the damage detection problem in a steel-concrete composite structure with an impact-hammer-based modal testing procedure. The mathematical formulation adopted in this work allows for the identification of regions where stiffness varies with respect to an initial virgin state without the need for theoretical models of the undamaged structure (such as finite element models). Since mode shape curvatures change due to the loss of stiffness at the presence of cracks, a change in curvature was adopted as a criterion to quantify stiffness reduction. A stiffness variability index based on two-dimensional mode shape curvatures is generated for several points on the structure, resulting in a damage distribution pattern. Our numerical predictions were compared with experimentally measured data in a full-scale steel-concrete composite beam subjected to bending and were successfully validated. The present damage detection strategy provides further insight into the failure mechanisms of steel-concrete composite structures, and promotes the future development of safer and more reliable infrastructures.

Feasibility of Using Shear Wave Ultrasonic Probes as Pump-Wave Sources in Concrete Microcrack Detection and Monitoring by Nonlinear Ultrasonic Coda Wave Interferometry.

This paper represents a first attempt to study the feasibility of using shear wave (SW) ultrasonic probes as pump-wave sources in concrete microcrack detection and monitoring by Nonlinear Ultrasonic Coda Wave Interferometry (NCWI). The premise behind our study is that the nonlinear elastic hysteretic behavior at microcracks may depend on their orientation with respect to the stationary wave-field induced by the pump-wave source. In this context, the use of a SW probe as a pump-wave source may induce the nonlinear elastic behavior of microcracks oriented in directions not typically detected by a conventional longitudinal pump-wave source. To date, this premise is hard to address by current experimental and numerical methods, however, the feasibility of using SW probes as a pump-wave source can be experimentally tested. This idea is the main focus of the present work. Under laboratory conditions, we exploit the high sensitivity of the CWI technique to capture the transient weakening behaviour induced by the SW pump-wave source in concrete samples subjected to loading and unloading cycles. Our results show that after reaching a load level of 40% of the ultimate stress, the material weakening increases as a consequence of microcrack proliferation, which is consistent with previous studies. Despite the lack of exhaustive experimental studies, we believe that our work is the first step in the formulation of strategies that involve an appropriate selection and placement of pump-wave sources to improve the NCWI technique. These improvements may be relevant to convert the NCWI technique into a more suitable non-destructive testing technique for the inspection of microcracking evolution in concrete structures and the assessment of their structural integrity.

A simple graphene modified electrode for the determination of antimony(III) in edible plants and beverage.

Antimony(III) is a rare electroactive specie present on Earth, whose concentration is not typically determined. The presence of high concentrations of antimony is responsible for a variety of diseases, which makes it desirable to find convenient and reliable methods for its determination. We have developed a convenient glassy carbon modified electrode with electroreduced graphene oxide GC/rGO for the first time determination of Sb(III) in commercial lettuce, celery, and beverages. The surface of the electrode was characterized by scanning electron microscopy (SEM) and cyclic voltammetry, indicating a heterogeneous and rough surface with a real area of 0.28 cm2, which is ~2.5 times the area of GC. The optimal chemical and electrochemical parameters used were: sodium acetate buffer (pH = 4.3), an accumulation potential of -1.0 V and an accumulation time of 150 s. The analytical validation was developed evaluating the linear range (10-60 µg L-1), limit of detection (2.5 µg L-1), accuracy, repetibility and reproducibility with satisfactory results (relative standard deviation (RSD) values lower than 10%). All the analyzes performed in real samples by stripping voltammetry were compared with GF-AAS, showing statistically similar values, demonstrating that GC/rGO could be effectively applied in the analysis of food samples.

Impact Resistance of Polypropylene Fibre-Reinforced Alkali-Activated Copper Slag Concrete.

Copper slag (CS) is produced during the smelting process to separate copper from copper ore. The object of the experimental research is to find the optimum percentage of CS and PPF volume fraction when CS replaces fine aggregate, and PPF volume fraction when subjected to impact loading. Copper slag was incorporated as 20%, 40%, 60%, 80% and 100% with PPF of 0.2-0.8% with 0.2% increment. The number of blows on failure of the specimen increases as the fibre volume increases. In addition, the energy absorption of composite concrete is higher than that of ordinary concrete. Concrete with up to 40% CS and 0.6% PPF volume shows a 111.72% increase in the number of blows for failure as compared to the control specimen. The impact resistance at failure was predicted by regression analysis, and very high regression coefficients of 0.93, 0.98 and 0.98 were obtained respectively at 7-, 14- and 28-days curing. In addition to regression analysis, a two-parameter Weibull distribution analysis was used to obtain reliable data on the number of blows at first cracking and eventual failure. The energy absorption at 28-day curing period is 1485.81 Nm which is 284% higher than the control mix. Based on the findings, it can be inferred that adding CS up to 60% densifies the microstructure due to its pozzolanic activity, while polypropylene fibre acts as a micro reinforcement, increasing the number of blows.

Elucidating sensing mechanisms of a pyrene excimer-based calix[4]arene for ratiometric detection of Hg(ii) and Ag(i) and chemosensor behaviour as INHIBITION or IMPLICATION logic gates.

This article reports the synthesis and characterisation of two lower rim calix[4]arene derivatives with thiourea as spacer and pyrene or methylene-pyrene as fluorophore. Both derivatives exhibit a fluorimetric response towards Hg2+, Ag+ and Cu2+. Only methylene-pyrenyl derivative 2 allows for selective detection of Hg2+ and Ag+ by enhancement or decrease of excimer emission, respectively. The limits of detection of 2 are 8.11 nM (Hg2+) and 2.09 nM (Ag+). DFT and TD-DFT computational studies were carried out and used to identify possible binding modes that explain the observed response during fluorescence titrations. Calculations revealed the presence of different binding sites depending on the conformation of 2, which suggest a reasonable explanation for non-linear changes in fluorescence depending on the physical nature of the interaction between metal centre and conformer. INHIBITION and IMPLICATION logic gates have also been generated monitoring signal outputs at pyrene monomer (395 nm) and excimer (472 nm) emission, respectively. Thus 2 is a potential primary sensor towards Ag+ and Hg2+ able to configure two different logic gate operations.

Monitoring the Formation of Amyloid Oligomers Using Photoluminescence Anisotropy.

The formation of oligomeric soluble aggregates is related to the toxicity of amyloid peptides and proteins. In this manuscript, we report the use of a ruthenium polypyridyl complex ([Ru(bpy)2(dpqp)]2+) to track the formation of amyloid oligomers at different times using photoluminescence anisotropy. This technique is sensitive to the rotational correlation time of the molecule under study, which is consequently related to the size of the molecule. [Ru(bpy)2(dpqp)]2+ presents anisotropy values of zero when free in solution (due to its rapid rotation and long lifetime) but larger values as the size and concentration of amyloid-ß (Aß) oligomers increase. Our assays show that Aß forms oligomers immediately after the assay is started, reaching a steady state at ∼48 h. SDS-PAGE, DLS, and TEM were used to confirm and characterize the formation of oligomers. Our experiments show that the rate of formation for Aß oligomers is temperature dependent, with faster rates as the temperature of the assay is increased. The probe was also effective in monitoring the formation of α-synuclein oligomers at different times.