Activator Concentration Research Articles

Investigation of the Effects of Some Plant Activators Against Verticillium Wilt (Verticillium dahliae Kleb.) on Cotton

Wilt disease caused by Verticillium dahliae Kleb. is one of the stress factors affecting yield and fiber quality traits in cotton cultivation. Plant activators provide resistance by stimulating genes that activate the resistance mechanism in the plant. The aim of this study is to determine the effect of plant activators such as auxiGRO, Green Miracle, Maxicrop, ProAct Plus, and Sojall Vitanal against Verticillium wilt under both in vitro and in vivo conditions. Firstly, the effect of various concentrations of plant activators (0, 1, 5, 25, 100, 250, and 500 ppm) on mycelial growth of two fungal isolates of V. dahliae (PHCVd3-non-defoliating pathotype and PHCVd47-defoliating pathotype) in potato dextrose agar (PDA) media was investigated in vitro. The effect of plant activators on V. dahliae was determined in tolerant cotton plants (cv Carmen) and susceptible cotton plants (cv Acala SJ2) in two different ways seed coating and foliar application in vivo. In vitro experiments were carried out with three replicates, and in vivo experiments were with five replicates depending on a completely randomized plot design. 500 ppm dose of all plant activators inhibited the mycelial growth of both isolates by approximately 90%. The lowest disease index (DI) against PHCVd3 was determined as 1.43 in the tolerant cv Carmen with seed coating of auxiGRO. The lowest DI against PHCVd47 was found in Sojall Vitanal and ProAct Plus at 2.09 and 2.12, respectively. The lowest DI against both isolates was found as 1.42 and 2.18 in cv Carmen by foliar application of ProAct Plus, respectively. Plant activators did not show any inhibitory effect on disease severity against both isolates in cv Acala SJ2. The combination of tolerant cultivar + plant activators can be suggested against Verticillium wilt disease as an alternative control.

Atık Mısır Koçanının Jeopolimer Harçta Agrega Olarak Kullanımı

This research aims to investigate the effects of waste corn cob aggregate on the properties of volcanic tuff-based geopolymer mortar. Nevşehir Pozzolan, which is produced as waste during the stone-cutting process, was used as an aluminosilicate source. The effect of alkali activator type, concentration, activator ratio, and sand-to-corn cob ratio on the properties was experimentally investigated. Study results revealed that waste Nevşehir Pozzolan was a suitable aluminosilicate for the production of geopolymer mortar. The optimum activator type, concentration, and activator ratios were sodium hydroxide with sodium silicate, 10 M, and 2.0, respectively, because they ensured the highest mechanical properties. Waste corn cob aggregate could be used instead of natural sand, and geopolymer mortar with various corn cob contents can meet the performance requirements of conventional wall materials.

Mix Design of Fly Ash and GGBS based Geopolymer Concrete activated with Water Glass

Geopolymer Concrete (GPC) has emerged as an alternative to cement concrete due to its reduced carbon footprint and excellent mechanical properties. However, not much emphasis is made on the development of mix designs using industrial waste. The current study focuses on the mix-design considerations for GPC using fly ash and Ground Granulated Blast Furnace Slag (GGBS). The mix design of GPC involves in selecting materials to produce the desired strength. In this investigation, Water Glass (WG) is used as an activator for the activation of the polymerization reaction. The mix design of GPC is the optimization of a group of various parameters, such as the activator to binder ratio, aggregate to binder ratio, coarse aggregate to fine aggregate ratio, activator concentration, and amount of binder content. The activator to binder ratio affects workability and strength, while the activator concentration influences the polymerization reaction and final strength development. The selection of suitable aggregates plays a vital role in achieving a dense and durable GPC matrix. The mix design for GPC requires a holistic approach that considers the selection of appropriate binders, activators, and aggregates. Proper optimization of these factors can result in excellent strength and durability of the GPC and a reduced carbon footprint. Further research is needed to explore alternative binders, evaluate long-term performance, and establish standardized mix design guidelines for the widespread adoption of GPC in construction.

Developing Geopolymer Concrete by Using Ferronickel Slag and Ground-Granulated Blast-Furnace Slag

Geopolymer concrete is gaining recognition as an environmentally friendly alternative to traditional cement-based materials, offering potential solutions for reducing the carbon emissions of the construction industry. This study aims to develop GGBFS–FNS geopolymers utilising ferronickel slag (FNS) and ground-granulated blast-furnace slag (GGBFS). Ground FNS (GFNS) is a potential candidate for replacing fly ash in geopolymers. This research aims to develop for the first time a GGBFS–FNS alkali-activated concrete. Numerous trials were conducted including different GGBFS–FNS blend percentages, several chemical admixtures and varying activator concentrations to develop the optimal binder mix composition. The effects of different chemical admixtures on the properties of geopolymer pastes, mortars, and concretes were investigated. The study evaluated setting time, compressive strength, shrinkage, and physical and durability properties. The results indicate that conventional admixtures have limited impact on the setting time, while increasing the water/solid ratio and decreasing the GGBFS content could extend the initial and final setting times. The presence of FNS aggregate could improve the compressive strength of geopolymer mortars. The water absorber admixture was highly effective in reducing shrinkage and increasing chloride diffusion resistance. The geopolymer mix containing 50 wt.% GFNS and 50 wt.% GGBFS with the presence of the water absorber admixture presented high chloride diffusion resistance, non-reactivity to the alkali–silica reaction and high sulphate resistance. Overall, the GGBFS–FNS geopolymers exhibited promising potential for engineering applications as an environmentally friendly material, particularly in aggressive environments.

SYNTHESIS AND STUDY OF THE OPTICAL AND SPECTRAL-LUMINESCENT PROPERTIES OF LuAG:Ce CERAMICS

In this study, LuAG:Ce ceramic powders with compositions of Lu2.98Ce0.02Al5O12 and Lu2.93Ce0.07Al5O12 were synthesized using chemical precipitation. Luminescent ceramic samples were then produced from these powders by vacuum sintering green bodies in the temperature range of 1600 – 1800 ?C. The study aimed to investigate the effect of cerium concentration and vacuum sintering temperature on the optical properties of LuAG:Ce ceramics. The spectral luminescence properties of the LuAG:Ce ceramic samples were analyzed. Results showed that the luminescence intensity was dependent on the activator concentration and vacuum sintering temperature. Additionally, a shift in the maxima of the luminescence spectral bands of the LuAG:Ce ceramics was observed when varying the vacuum sintering temperature within the 1600 – 1800 ?C range.

Evaluation of the Relationship between Aromatase/Sirtuin1 Interaction and miRNA Expression in Human Neuroblastoma Cells.

Changes in activation/inhibition of Sirtuin-1 (SIRT1) and aromatase play an important role in a plethora of diseases. MicroRNAs (miRNAs) modulate multiple molecular pathways and affect a substantial number of physiological and pathological processes. The aim of this study was to investigate any possible interaction between aromatase and SIRT1 in SH-SY5Y cells and to see how there is a connection between this interaction and miRNA expression, if there is an interaction. In this study, cells were incubated in serum-deprived media for 6, 12, and 24 h. Aromatase and SIRT1 expressions were evaluated by Western blot. The IC50 concentration of SIRT1 activator (SRT1720), SIRT1 inhibitor (EX527), and aromatase inhibitors (letrozole and fadrozole) was determined by the XTT method. Then, CYP19A1 and SIRT1 levels were evaluated in the presence of SIRT1 siRNA or IC50 values for each activator/inhibitor. Finally, CYP19A1, SIRT1 expression and miRNA target gene were assessed with bioinformatic approaches. Aromatase and SIRT1 protein levels were significantly elevated in the cells incubated at 24 h in serum-deprived media (p ≤ 0.05). SIRT1 also positively regulated CYP19A1 in SH-SY5Y cells in media with/without FBS. Serum deprivation depending on time course caused changes in the oxidant/ antioxidant system. While oxidative stress index tended to decrease in the absence of FBS at 24 h compared to the control, it showed a significant decrease at 48 h in a serum-deprived manner (p ≤ 0.001). As a result of bioinformatics analysis, we determined 3 miRNAs that could potentially regulate SIRT1 and CYP19A1. hsa-miR-27a-3p and hsa-miR-181a-5p correlated in terms of their expressions at 24 h compared to 12 h, and there was a significant decrease in the expression of these miRNAs. On the contrary, the expression of hsa-miR-30c-5p significantly increased at 24 h compared to 12 h. Considering the results, a direct link between aromatase and SIRT1 was observed in human neuroblastoma cells. The identification of key miRNAs, hsa-miR-27a-3p, hsa-miR-30c-5p, and hsa-miR-181a-5p targeting both aromatase and SIRT1, provides an approach with novel insights on neurology-associated diseases.

Structural Confinement Induced Near‐Unity Quantum Yield for Single‐Band Ratiometric Thermometry

AbstractLuminescence quenching at high dopant concentration and temperature typically limits the brightness of luminescence materials, which remains a major obstacle in diverse technological applications, especially in the field of luminescence thermometry. In this work, a unique class of non‐concentration quenching double‐tungstate phosphors is reported that feature the near‐unity quantum yield of Tb3+ and Eu3+ emissions induced by the structural confinement effect. Mechanistic studies affirm that the activator ions can be isolated in NaYW2O8 crystal to confine the absorbed photon energy, leading to a relatively high quenching concentration of various lanthanide activators. By facilitating interionic cross‐relaxation at heavy dopant concentration, a remarkable thermal enhancement of Tb3+ emissions over 20‐fold upon the excitation of excited‐state absorption is recorded. In contrast, thermally quenched emissions are detected under the excitation of ground‐state absorption. This excitation wavelength‐dependent thermal behavior of Tb3+ emissions is harnessed for single‐band ratiometric thermometry, registering superior thermal sensitivity and resolution (Sr = 4.01% K−1, δT = 0.1 K). The advances in combating concentration and thermal quenching of luminescence materials provide exciting opportunities for flexible thermometry in real‐world sensing scenarios.

Low temperature synthesis and enhancement of blue emitting CaMgSi2O6:Eu2+ phosphor by co-doping

Near UV excitable blue emitting Eu2+ activated CaMgSi2O6 phosphor has been synthesized by urea assisted pyrolysis technique. The effects of flux (H3BO3, NH4F, NH4Br, NH4Cl, CaF2, BaF2), sintering temperature (700–1100 °C), activator concentrations and co-dopants (Zn2+, Y3+, Al3+ and Gd3+) on the photoluminescence properties of CaMgSi2O6:Eu2+ were studied systematically. Zn2+, Y3+, Al3+ and Gd3+ co-doped CaMgSi2O6:Eu2+ phosphors improved the PL intensity and also exhibited a wide excitation band in the region of 250–420 nm, and emission at 447 nm found suitable for nUV based white LED applications. The PL emission intensity of Y3+ co-doped CaMgSi2O6:Eu2+ is comparable to that of the commercial BaMgAl1O17:Eu2+ blue emitting phosphor. However, Y3+ co-doped CaMgSi2O6:Eu2+ showed a higher thermal quenching when compared with BaMgAl1O17:Eu2+. The crystalline phase formation and morphology of synthesized silicate phosphors were confirmed by powder XRD and SEM analysis.

The performance and microstructure of alkali-activated artificial aggregates prepared from municipal solid waste incineration bottom ash

In order to reduce the negative environmental impact of municipal domestic waste incineration bottom ash (MSWIBA), it is converted into lightweight aggregates by cold bonding technology. To enhance the utilization of waste materials, minimize cement consumption, and fabricate artificial aggregates with superior comprehensive performance, we designed and synthesized alkali-activated aggregates (AAAs) in this study. This study used MSWIBA and ground granulated blast furnace slag (GGBFS) as precursors for alkali-activated aggregates (AAAs), activated by a mixture of sodium hydroxide solutions and sodium silicate. The physical and mechanical properties of AAAs, including water absorption, apparent density, crushing strength and carbon-resistance, were investigated at different NaOH concentrations. In addition, the microstructure, mineral composition, aggregation, porosity and heavy metal leaching behavior of AAAs were analyzed by SEM, XRD, FTIR, TGA, MIP and ICP techniques. All AAAs exhibited a consistent particle size distribution, characterized by apparent densities spanning the range of 1633–1940 kg/m3. The leaching levels of heavy metals align with the standards established by Chinese regulations. Among the different activator concentrations tested, aggregate (M4) displayed superior single-particle crushing strength (3.90 MPa) and better carbonization resistance. It also used a lower concentration of NaOH, which enabled more cost-effective and eco-friendly production. Overall, the findings suggest that MSWIBA can be a viable precursor for producing sustainable lightweight concrete, with 4 M NaOH being the optimal activator concentration for achieving the best performance.

Characterization, factors, and fractal dimension of pore structure of fly ash-based geopolymers

Fly ash-based geopolymer is a new cementitious material with environmentally friendly characteristics. Generally, the mechanical properties of cementitious materials are influenced by their pore structure. The variation in the pore structural characteristics of the geopolymers with various influencing factors was investigated in this study. A smaller activator modulus and liquid-solid ratio lead to a finer pore structure, while higher activator concentrations also result in a finer pore structure. However, the densification of pore structure does not follow a monotonic relationship with the conserving temperature. Increasing the conserving temperature within a certain range decreases the most probable pore diameter and porosity. Nevertheless, excessive temperature increase has the opposite effect. Furthermore, the fractal dimension was introduced to characterize the pore structure comprehensively. The results show that a lower pore volume, a larger pore-specific surface area, and a smaller most probable pore diameter contribute to increasing pore surface fractal dimension. Further, compared to porosity, the microporous pore surface fractal dimension shows a better linear correlation with compressive strength.

Synthesis, optical and cathodoluminescent properties of borosilicate glass doped with Eu3+

The purpose of this work is development of glasses for radioactive materials encapsulation. Borosilicate-based glass systems “R7/T7” (B2O3-ЅіO2-Al2O3-Na2O-СaO) doped with Eu3+, with various concentrations of activator were studied. The composition of the obtained glasses was investigated using electron-probe microanalysis technique. Optical properties of glasses were investigated using the following methods – cathodoluminescence, photoluminescence and absorption spectra. The range of the optimal activator concentration was determined. Samples of borosilicate glass (B2O3-ЅіO2-Al2O3-Na2O-СaO) doped with varied content of Eu3+ were synthesized and studied using electron probe microanalysis (EPMA) and optical techniques such as cathodoluminescence (CL), photoluminescence (PL) and light absorption spectroscopy. Glass composition was related to development of nuclear waste form or encapsulation matrix with sufficient resistance to radiation damage. It was observed that electron beam irradiation suppresses intensity of glass cathodoluminescence and this process is correlated with sodium diffusion outside irradiated area at comparable interval of time.

Chloride-induced corrosion propagation of alkali-activated slag mortar with pulverized fuel ash and metakaolin replacements

Alkali-activated materials have great potential in reducing CO2 emissions in cement production industry. This study aims to investigate the corrosion propagation performance of alkali-activated slag mortars with various pulverized fuel ash (PFA) and metakaolin (MK) replacements subject to chloride-induced corrosion. The corrosion propagation performances including corrosion potential, corrosion rate and mortar electrical resistivity under wetting and drying cycles in seawater are studied. Scanning electron microscope (SEM), mercury intrusion porosimetry (MIP) and pH value measurement were conducted to analyze the effects of PFA and MK replacements on the relationship between reaction degree, pore structure, pH value and corrosion propagation performances. The results show that the MK replacement can enhance the corrosion propagation resistance of slag-based alkali-activated mortars under high activator concentration while the PFA replacement reduces the resistance to metallic corrosion of alkali-activated mortars. Mechanisms controlling the corrosion propagation are discussed.

Volcanic tuff as a raw material for alkali-activated materials

Currently, the use of geopolymers as cementitious materials is constantly evolving due to theirexcellent properties and efficiency, such as low CO2 emissions, high compressive strength, and lowpermeability. On the other hand, volcanic tuff can be used as a potential raw material for syntheticgeopolymers due to its reactivity, wide availability in nature, low extraction cost, and relatively lowenvironmental impact. This paper presents a review of recent studies on the use of volcanic tuff as a mainbinder in the manufacture of geopolymers. The results reported by the researchers concern durability andmechanical performance, as well as the factors affecting these properties, such as the effect of activatortypes, sodium hydroxide (NaOH) concentration, curing temperature, and the addition of othercementitious materials. The results clearly showed that increasing the activator concentration and curingtemperature had a significant effect on mechanical properties, as well as that the activator (Na2SiO3 +NaOH) reduced water absorption values by creating a more compact structure in all samples thanactivation by NaOH alone. Recent results suggest that volcanic tuff-based geopolymers have mechanical,physical, and durability properties similar to or better than those of ordinary Portland cement concrete,but further research is needed to make them an economically and technically efficient building material.

Decay behavior of Eu2+-Activated sulfide phosphors: The Pivotal role of unique activator sites

We present a systematic decay analysis of four sulfide phosphors, namely SrS:Eu2+, CaAl2S4:Eu2+, KGaS2:Eu2+, and NaBaAlS3:Eu2+. In SrS and NaBaAlS3, there is only one activator site, whereas KGaS2 has two, and CaAl2S4 has three. We confirm the typical concentration quenching behavior, where the decay rate increases with the Eu2+ activator concentration. The decay curve for these sulfide phosphors consists of two components. The fast decay component remains unaffected by the Eu2+ activator concentration, while the slow component exhibits the typical concentration quenching behavior. The initial sharp decline in the decay curve, which is concentration-independent, is associated with direct quenching occurring in close proximity to the excited activator before inter-activator energy transfer takes place. The subsequent concentration quenching results from active inter-activator energy transfer. An intriguing observation is termed “wavelength quenching”, where the decay rate increases as the emission probe wavelength decreases. This phenomenon is active for multi-site phosphors but inactive for single-site phosphors, which can be attributed to the active inter-activator energy transfer between distinct crystallographic sites within the host.

High-porosity alkali-activated binders based on glass and aluminium recycling industry waste

The potential as alkali-activated precursors of ceramic-stone-porcelain (CSP) and PAVAL, two residues derived from the optical separation of glass cullet and salt slag from secondary aluminium recycling, has been assessed. Alkali-activated CSP and PAVAL binders’ formulations were prepared using NaOH 4 M and 6 M as alkaline activator solutions. The effect of the Na2O/Al2O3 ratio and alkaline activator concentration was evaluated from a chemical, physical, mechanical, and environmental perspective. The results revealed the formation of secondary reaction products attributed to the formation of (C,N)-A-S-H gels. It also showed the influence of decreasing Na2O/Al2O3 ratio in the obtained binders, increasing porosity and affecting the mechanical performance. Besides, it was demonstrated that PAVAL acts as a precursor and pore-generator. Finally, the environmental characterisation showed a significant leaching concentration of heavy metal(loid)s such as As, Cr, Mo, Sb, and Se, which decreases with longer curing periods.

Optimizing the strength of geopolymer concrete incorporating waste plastic

In this work, we systematically examine several factors in an effort to maximise the strength of geopolymer concrete that includes recycled plastic. Geopolymer concrete specimens with varying amounts of plastic content, particle size distribution, alkaline activator concentration, mix design, additional materials, additives, and fibre properties were subjected to water absorption and compressive strength tests. Compressive strength was increased to 40 MPa, while water absorption was decreased to 1.5%, all as a consequence of raising the plastic content to 15%. In addition to the ideal concentration of 8 M sodium hydroxide and 3 wt% sodium silicate, the use of coarse plastic particles helped boost the material's mechanical qualities. The employment of a superplasticizer and fibre additives, in addition to the incorporation of silica fume, increased the strength and durability of geopolymer concrete. These results provide light on how to better incorporate waste plastic into the design and formulation of geopolymer concrete, a key ingredient in the development of environmentally friendly and functional building materials.

The Conversion of Sorghum (Sorghum bicolor (L.) Moench) Stem Waste into Activated Carbon by the Pyrolysis Method Using ZnCl2 Activator

<p><strong>Abstract.</strong> The use of activated carbon in Indonesia is expanding along with the increasing demand for activated carbon. Therefore, it is necessary to continue to search for raw materials and methods for producing activated carbon to produce high-quality activated carbon. Sorghum stalk (Sorghum bicolor (L.) Moench) is used as a new precursor for the formation of activated carbon by utilizing a ZnCl<sub>2</sub> activator followed by pyrolysis in a furnace with a temperature of 800°C. This study aims to determine the effect of drying and the concentration of activator agents on activated carbon production. The ZnCl<sub>2</sub> activator concentrations used were 15% and 30%. The results showed that the activated carbon obtained through the withdrawal process with a ZnCl<sub>2</sub> concentration of 30% had the highest carbon content, namely 100%. Test results with FTIR spectroscopy showed that the activated carbon samples had groups (C-H), (O-H), (C≡C), (C=O), (C=C), and (C-O). In addition, the SEM test results showed that the surface of the activated carbon formed had many pores. With the presence of activated carbon from sorghum stem waste, it is hoped that this product can reduce the contaminants contained in wastewater.</p><p><strong>Keywords: </strong></p><p><strong></strong>Activation, Activated Carbon, Waste, Pyrolysis, Sorghum, ZnCl<sub>2</sub></p>

Experimental study on the characteristics, rheological factors, and flowability of MK-GGBFS geopolymer slurry

In this study, we investigated the effects of concentration and modulus of alkaline activator, liquid–solid (L/S) ratio, and sand volume fraction on rheological properties and flowability of metakaolin (MK)–ground granulated blast furnace slag (GGBFS) geopolymer slurry (pastes and mortars). The rheological property of geopolymer slurry was consistent with the Bingham model. A decrease in the modulus and the L/S ratio, or an increase in the concentration increased the plastic viscosity of geopolymer paste. The geopolymer pastes with higher plastic viscosity exhibited a lower fluidity. The yield stress of geopolymer paste was negatively correlated with concentration, modulus, and L/S ratio. An increase in the sand volume fraction increased the plastic viscosity and yield stress of geopolymer mortar, and decreased the consistency and fluidity of that. Moreover, the correlation between rheological parameters of the geopolymer mortar and paste, and the relationship between the flowability parameters and rheological parameters of geopolymer slurry were constructed.

Effect of Activator Concentrations on the Postfire Impact Behavior of Alkali-Activated Slag Concrete

Changing concrete ingredients significantly affects its performance due to changing the type of hydration products formed. The stability of these hydration products will dominate concrete impact behavior before and after exposure to fire. Limited research had explored the role of activators, as the main ingredient of alkali-activated slag concrete (AASC), on impact performance. Hence, this study highlights the effects of activator characteristics on the impact behavior of AASC at an ambient condition (23°C) and after exposure to elevated temperatures (200°C, 400°C, and 600°C). Conventional ordinary portland cement (OPC) concrete was also tested for general performance comparison. Besides the drop weight impact test, compressive and indirect splitting tensile strength, shrinkage, ultrasonic pulse velocity and water absorption tests were conducted to evaluate AASC performance. In addition, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used to confirm and analyze findings. Results confirmed the better impact performance of AASC compared to OPC concrete. Activator concentrations showed contrary effects on AASC performance at ambient and elevated temperatures. High activation levels improved strength and impact capacity at ambient temperature, showing lower internal defects and higher hydration product formation. Conversely, lowering the activation level at elevated temperatures was preferable and resulted in a higher residual strength and impact absorption capacity. This was ascribed to the high unreacted slag particle crystallization to akermanite at higher temperatures, leading to strength gain, fewer hydration products to decompose, and high microstructure ductility that accommodated the thermal incompatibility. Hence, designing AASC while focusing only on maximizing strength can be misleading based on the targeted performance and exposure conditions.

Heat flow modeling in the alkaline activation process of fly ash

Cement production plays an important role in strengthening the infrastructure of growing countries such as Colombia. However, the production of this material has a high energy cost and contributes to the emission of large amounts of CO2. To address these environmental concerns, it is essential to explore alternative materials that can partially or completely replace traditional cement. Alkaline activated cement (AAC) has emerged as a promising candidate in this regard. Due to this, it is necessary to understand the process of alkaline activation and the variables that influence it. This research proposes a phenomenological-based semi-physical model, which predicts the performance of some variables that control alkaline activation: activator concentration (NaOH), heat flow, and degree of reaction. The model results show that with the increment of the activator concentration, the degree of reaction also increases. Furthermore, the model has an accurate response compared with the Freisleben-Hansen model. The integral square error criterion (ISE) was used in this comparison.