Optimal Regime Research Articles

Precommercial Thinning but Not Commercial Thinning Increases the Merchantable and Large Sawlog Volume Production of Lodgepole Pine on Fair Sites

Abstract The effect of thinning on stand structure and volume production is well studied. However, the effect of combinations of precommercial (PCT) and commercial thinning (CT) on the production of different log grades and differential growth responses is less understood, although it is crucial for forest managers to choose an optimal management regime. Starting with actual operational field data from a lodgepole pine (Pinus contorta var.latifolia) PCT trial on fair quality sites (site index: 16–18 m at 50 years), we used an individual tree growth model to forecast development over the entire rotation. We found thinning changed the structure (density, quadratic mean diameter) of the stands but not the total volume production. However, in terms of merchantable volume and large sawlog volume, stands with only PCT provided the largest volume, more than either CT or a combination of PCT and CT, or the unthinned control. Moreover, our study findings also showed that, by doing only PCT, stands reached maximum merchantable or large sawlog mean annual increment earlier than other thinned or unthinned stands. This indicates that PCT might shorten the rotation length and contribute to an enhanced supply of timber. Study Implications: The effect of commercial thinning (CT) on stand structure and volume production is well studied. However, the effect of combinations of precommercial (PCT) and commercial thinning (CT) on the production of different log grades and differential growth responses is less studied, although it is crucial for forest managers to choose a management option. Starting with actual operational field data from a lodgepole pine (Pinus contorta var.latifolia) PCT trial in a fair-quality site (site index [SI]: 16–18), we used an individual tree growth model to develop the stands over the entire rotation. We found thinning changed the structure (density, quadratic mean diameter) of the stands but not the total volume production. However, in terms of merchantable volume and large sawlog volume, stands with only PCT provided the largest volume, more than either CT or a combination of PCT and CT, or the unthinned control. Moreover, our study findings also showed that, by doing only PCT, stands reached maximum merchantable or large sawlog MAI earlier than other thinned or unthinned stands. This indicates that PCT might shorten the rotation length and contribute to the continuous supply of timber production.

Евапотранспирация на средноранни домати в зависимост от приложения поливен режим

The aim of the present study is to determine the values of the seasonal evapotranspiration (ET) of mid-early tomatoes when applying an optimal and deficit irrigation regime and to determine the water use efficiency (WUE). A field experiment was conducted with mid-early tomatoes, variety “Nikolina F1”, in the period 2017-2018 on the territory of the Educational and experimental field at the Agricultural University - Plovdiv. The experiment was carried out in 4 repetitions by the method of long plots. The following options were tested: 1) optimal irrigation at pre-irrigation humidity 85% of FC, valid for the 0-50 cm layer; 2) irrigation with 75% of the irrigation rate compared to var.1; 3) irrigation with 50% of the irrigation rate compared to option 1. The plants are planted on a flat bed in a two-row strip according to the scheme 90+50x50 cm. Irrigation was carried out by means of a drip system with built-in drip generators with a distance between them of 25 cm and a flow rate of 2 l/h. The total values of evapotranspiration have been established, and with optimal irrigation, it is an average of 512 mm. When implementing 75% of the optimal irrigation rate, ET is 428 mm (83.6% of the maximum), and when applying ½ rate, it decreases on average by 30.3% and is 356.5 mm. The course of the average day-night evapotranspiration was established, and depending on the nature of the year, with optimal irrigation, the maximum values are in the range of 5.6 - 6.7 mm per day.

A Biotechnical System for Increasing the Effectiveness of the Pre-Sowing Pulsed Laser Irradiation of Seeds to Increase Sunflower Yield

In this study, we investigated the use of the pre-sowing electrophysical stimulation of seeds, particularly focusing on optimizing technological regimes for enhancing seed quality. The aim of this study was to improve sunflower seed germination utilizing laser optical radiation. The methods explored involved the pre-sowing stimulation of oilseeds and analyzing the key mechanisms affecting germination. Through our experimental research, we sought to identify the most effective laser irradiation parameters, ensuring the maximum seed quality improvement with minimal energy use. Using seeds of the first reproduction, we employed artificial aging to simulate a reduced seed quality and determined optimal irradiation regimes. Standard methods were followed to assess seed quality before and after irradiation, with 6–7 days of further exposure. Seed germination was carried out under controlled light and temperature conditions using the “on paper” method with paper napkins. A full factorial experiment was performed and key parameters for laser irradiation were determined, confirming that the pre-sowing laser pulse treatment significantly improved seed quality. In this research, we developed a biotechnical system for processing seeds and propose a method to adjust irradiation parameters based on the initial seed quality. The system effectively enhanced germination and crop yield, offering a reliable solution for improving sunflower seed productivity through laser treatment.

Bayesian Empirical Likelihood Regression for Semiparametric Estimation of Optimal Dynamic Treatment Regimes.

We propose a semiparametric approach to Bayesian modeling of dynamic treatment regimes that is built on a Bayesian likelihood-based regression estimation framework. Methods based on this framework exhibit a probabilistic coherence property that leads to accurate estimation of the optimal dynamic treatment regime. Unlike most Bayesian estimation methods, our proposed method avoids strong distributional assumptions for the intermediate and final outcomes by utilizing empirical likelihoods. Our proposed method allows for either linear, or more flexible forms of mean functions for the stagewise outcomes. A variational Bayes approximation is used for computation to avoid common pitfalls associated with Markov Chain Monte Carlo approaches coupled with empirical likelihood. Through simulations and analysis of the STAR*D sequential randomized trial data, our proposed method demonstrates superior accuracy over Q-learning and parametric Bayesian likelihood-based regression estimation, particularly when the parametric assumptions of regression error distributions may be potentially violated.

Optimal Water and Nitrogen Regimes Increased Fruit Yield and Water Use Efficiency by Improving Root Characteristics of Drip-Fertigated Greenhouse Tomato (Solanum lycopersicum L.)

The growth of root system directly affects the absorption and utilization of soil water and nitrogen, and understanding the responses of root characteristics to water and nitrogen regimes is thus crucial for optimizing water and nitrogen management. The root characteristics of each soil layer, i.e., root length, root surface area, and root volume, as well as fruit yield and water use efficiency of greenhouse tomato under drip fertigation in response to different irrigation levels and nitrogen rates were explored in northwest China. There were four irrigation levels, i.e., 50% ETC (W1), 75% ETC (W2), 100% ETC (W3), and 125% ETC (W4), where ETC is the crop evapotranspiration, and four nitrogen rates, i.e., 0 kg ha−1 (N1), 150 kg ha−1 (N2), 250 kg ha−1 (N3), and 350 kg ha−1 (N4). The results showed that reasonable irrigation and nitrogen regimes (W3N3) significantly increased fruit yield by 31.64% and root length, root surface area, and root volume by 45.03%, 61.24%, and 148.21% compare to W3N1, respectively. The promoting effect of increasing irrigation level on root characteristics increased with soil depth and had the greatest increases in root volume by 27.07%, 123.43%, and 211.47% for the 0–10, 10–20, and 20–30 cm soil layers, respectively. In addition, reducing irrigation level significantly increased the percentages of roots in the top soil by 29.71%, 26.77%, and 18.53% for root length, root surface area, and root volume, respectively. The reasonable nitrogen rate (N3) significantly increased fruit yield by 41.11%, water use efficiency by 34.42%, and root length, root surface area, and root volume by 40.42%, 41.44%, and 112.76%, respectively. The over-application of nitrogen (N4) reduced root characteristics of all soil layers, fruit yield, and water use efficiency. The promoting effect of increasing nitrogen rate on root length of each soil layer decreased with soil depth, by 71.01%, 48.96%, and 15.71% for 0–10, 10–20, and 20–30 cm soil layers, respectively. Irrigation level was the main factor dominating the root growth of each soil layer. The correlation analysis showed that fruit yield had significantly positive correlations with root characteristics in all soil layers, while water use efficiency had significantly positive correlations with the percentages of root length and root surface area in the 0–10 cm soil layer. In conclusion, rational water and nitrogen regimes achieved better fruit yield by promoting root growth of greenhouse tomato, and the water use efficiency of greenhouse tomato was improved by increasing the root percentage in the topsoil layer to alleviate the adverse effects under water stress conditions. This study reveals how irrigation volume and nitrogen application can enhance tomato yield and water use efficiency by regulating root characteristics and vertical root distribution, providing support for understanding the response of root systems to changes in soil water and nitrogen conditions.

Optical properties and energy transfer of Tm3+ single-doped and Tm3+-Tb3+ co-doped transparent glass-ceramics containing NaGd(MoO4)2 single phase

Tm3+ single-doped and Tm3+-Tb3+ co-doped SiO2–B2O3–Na2O–ZnO–MoO3-Gd2O3 glasses were successfully prepared by the melt-quenching process. X-ray diffraction and transmittance measurements were used to determine that the optimal heat treatment regime consisted of crystallization at 620 °C for 5 h and transparent glass-ceramics containing the NaGd(MoO4)2 single phase were obtained. The characterization results by SEM confirmed that the size of the crystals precipitated in the glass matrix was on the nanometer level. The effects of different contents of Tm2O3 on the luminescent properties of glass-ceramics in this system were explored. The results showed that the emission peak at 453 nm (1D2→3F4) had the highest intensity when Tm2O3 was doped with 0.5 mol% under the wavelength at 359 nm excitation. In addition, with the gradual increase of Tb2O3 contents, the luminescence colour of the Tm2O3–Tb2O3 co-doped glass-ceramics gradually shifted from blue to green. This indicates its potential application in blue-green light display technologies and various other areas. The experimental results of the water resistance stability of the samples show that the co-doped glass-ceramic still has good luminescence stability after being immersed in water, which provides further favourable support for its application.

The optimal spatially-dependent control measures to effectively and economically eliminate emerging infectious diseases.

Non-pharmaceutical interventions (NPIs) are effective in mitigating infections during the early stages of an infectious disease outbreak. However, these measures incur significant economic and livelihood costs. To address this, we developed an optimal control framework aimed at identifying strategies that minimize such costs while ensuring full control of a cross-regional outbreak of emerging infectious diseases. Our approach uses a spatial SEIR model with interventions for the epidemic process, and incorporates population flow in a gravity model dependent on gross domestic product (GDP) and geographical distance. We applied this framework to identify an optimal control strategy for the COVID-19 outbreak caused by the Delta variant in Xi'an City, Shaanxi, China, between December 2021 and January 2022. The model was parameterized by fitting it to daily case data from each district of Xi'an City. Our findings indicate that an increase in the basic reproduction number, the latent period or the infectious period leads to a prolonged outbreak and a larger final size. This indicates that diseases with greater transmissibility are more challenging and costly to control, and so it is important for governments to quickly identify cases and implement control strategies. Indeed, the optimal control strategy we identified suggests that more costly control measures should be implemented as soon as they are deemed necessary. Our results demonstrate that optimal control regimes exhibit spatial, economic, and population heterogeneity. More populated and economically developed regions require a robust regular surveillance mechanism to ensure timely detection and control of imported infections. Regions with higher GDP tend to experience larger-scale epidemics and, consequently, require higher control costs. Notably, our proposed optimal strategy significantly reduced costs compared to the actual expenditures for the Xi'an outbreak.

Forbs from seasonal managed wetlands boost plankton production more than emergent graminoids by supplying novel labile detritus

Abstract Opportunities to enhance ecosystem functions exist in human‐dominated working landscapes, but understanding of key drivers is often lacking in these novel environments. In Suisun Marsh, California, USA, impounded managed wetlands designed to promote waterfowl incidentally support higher plankton densities—a key resource for imperilled pelagic fishes—than adjacent tidal habitats. Managed wetland operations could produce plankton at critical periods for fish and the aquatic food‐web more broadly, but drivers of plankton production in managed wetlands are poorly understood. We proposed that decaying vegetation resulting from controlled flooding in managed wetlands is important for stimulating plankton blooms, but that the effect varies by plant species and functional type. We conducted a mesocosm experiment to test the effects of different inundated plants on plankton production, including three forb species, three emergent graminoid species and a control treatment without added plant material. Forbs promoted larger phytoplankton blooms and higher zooplankton production—by an order of magnitude—than both emergent graminoids and the control treatment. Emergent graminoids supported larger phytoplankton blooms, but not higher zooplankton production, than the control treatment. Phytoplankton blooms exhibited pulse dynamics in all treatments, with densities increasing initially and crashing by the end of the experiment. Phytoplankton blooms in forb and emergent treatments lasted similar durations, counter to the expectation that emergent graminoids would support diminished production over a relatively prolonged period. Among zooplankton taxa, Daphnia magna and rotifers were strongly associated with all three forbs species while the nonnative cyclopoid copepod Limnothoina tetraspina were associated with cattails (Typha domingensis) and the control. Forbs temporarily depleted dissolved oxygen concentrations during the first week of the experiment, suggesting a tradeoff by which decaying forbs boost plankton production at risk of initial hypoxia. Our results suggest that seasonal drying and flooding operations in managed wetlands are likely to enhance plankton production because dry periods promote forb growth and subsequent flooding introduces labile forb material to the aquatic food web. Results also suggest that seasonal managed‐wetlands act as novel floodplain‐analogues, by which flood pulses drive productivity. Further research is needed to quantify production benefits and tradeoffs to the aquatic ecosystem at the landscape scale and to identify optimal management regimes that will help conserve imperilled species.

Optimizing Oxalic Acid Application Regime to Maximize Sunflower Remediation Efficacy in Cd-Contaminated Soils

The exogenous application of oxalic acid is a potential approach to amplifying phytoremediation performance on Cd-contaminated soils. However, few studies explore the optimal oxalic acid application regime from a perspective of coupling different concentrations and timings to maximize Cd removal rate. Given this, a pot experiment was conducted using oil sunflower (Helianthus annuus L.) as the test plant. Oxalic acid was added to the pots at concentrations of 1, 2, 3, 4, 5, and 6 mmol/kg at 20, 30, 40, and 50 days after emergence. A control (CK) without exogenous oxalic acid was also included. We examined the discrepancies in various soil Cd forms, sunflower height, plant non-protein thiol (NPT) levels, and soil Cd remediation efficiency under different oxalic acid application regimes. The results showed that applying oxalic acid at a concentration of 4 mmol/kg reduced the proportion of Fe-Mn oxide Cd and organic Cd compared to the control (CK), while increased the proportion of available Cd. The optimal application time is 30 or 40 days after emergence. The addition of exogenous oxalic acid promoted the growth of sunflowers, with the greatest increase in plant height observed when 4 mmol/kg oxalic acid was applied at 30 days after emergence. Exogenous oxalic acid enhanced the absorption of Cd by sunflower roots, with the total Cd accumulation in roots, stems, and leaves being higher than in the control (CK). When 4 mmol/kg oxalic acid was applied at 30 days after emergence, the total Cd accumulation in roots, stems, and leaves was highest. Under different application times and concentration levels of oxalic acid, Cd accumulation was highest in roots, followed by leaves, with stems showing the lowest accumulation. The NPT content in each part is as follows: root > stem > leaf. Applying 5 mmol/kg oxalic acid after 30 days of sunflower emergence resulted in relatively higher total NPT content in roots, stems, and leaves compared to the control (CK). The TOPSIS model was used for comprehensive evaluation, which showed that 4 mmol/kg oxalic acid application at 30 days after emergence could be used as the optimal oxalic acid application regime for phytoremediation. These findings indicate that the addition of oxalic acid effectively promoted the absorption of Cd by sunflower and increased the efficiency of Cd removal from the rhizosphere soil, with the optimal removal of soil Cd achieved by applying oxalic acid at a concentration of 4 mmol/kg 30 days after the emergence of oilseed sunflower seedlings.

Study of the jellyfish Rhizostoma pulmo hydrolysis and characterization of the obtained product

The purpose of this work is to develop technological parameters for the hydrolysis of barrel jellyfish Rhizostoma pulmo involving the use of enzymatic agents «Enzy-mix» and alcalase, available through the domestic market, as well as to investigate the amino acid and mineral composition of the resultant hydrolysate.Methods used: the process of hydrolysis has been assessed based on the changes in peptide concentrations in the hydrolysate, the content of amino nitrogen, and the degree of hydrolysis. To investigate its chemical, amino acid, and mineral composition, the standard methods were used. Novelty: the use of jellyfish for hydrolysis after its thawing and the hydrolysis procedure not involving the addition of water into the raw material subjected to hydrolysis present a novel approach.Result: the optimal regime for hydrolysis of barrel jellyfish Rh. pulmo after its thawing has been identified, which was characterized by the use of 1% alcalase at the temperature 55±2 °C and duration of 1 h. It has been shown that alcalase is more effective in terms of amino nitrogen accumulation than enzymatic agent «Enzy-mix». The values of amino nitrogen after 1 h of hydrolysis involving the use of 1% alcalase were higher than the values of the same parameter obtained during the 3-hour hydrolysis involving 1.5% «Enzy-mix» at the temperature 40±2 °C. The hydrolysate, after its concentration to the dry matter exceeding 30%, contains no less than 15.1±0.59% of protein represented by 48% of essential amino acids, out of which leucine and isoleucine prevail (15 %). Among non-essential amino acids, the most prominent was glycine (17 %). For all essential amino acids, except for valine, the amino acid score exceeds 100%. In humans, consumption of around 20 g of the hydrolysate covers the daily physiological requirement of magnesium.Practical significance: the obtained data on the amino acid profile and mineral composition of the barrel jellyfish Rh. pulmo hydrolysate provide the basis for its consideration as a promising ingredient for the functional nutrition products.

Development of high-performance piezoelectric composites for concrete construction through carbonation of calcium and magnesium-based binder

The use of cementitious piezoelectric composite enables structure monitoring of concrete construction, while its piezoelectric and mechanical performance are relatively low. This paper developed a novel high-performance piezoelectric composite through carbonation of calcium and magnesium-based binder (including Ca(OH)2 and Mg(OH)2). The influence of PZT volume, forming regime, and polarization condition on compressive strength and piezoelectric strain coefficient (d33) of the two piezoelectric composites was investigated. Results showed that the use of PZT volume from 20 % to 80 % led to a 6-fold and 3-fold greater d33 value for Ca(OH)2 and Mg(OH)2 piezoelectric composites, respectively. While, such change in PZT volume reduced the compressive strength by 50 % and 55 % for the two piezoelectric composites. This is due to the significantly increased porosity and decreased carbonation degree as indicated by microstructural analysis. The use of a higher forming pressure from 25 to 100 MPa resulted in 60 % and 105 % increases in d33 values for the two piezoelectric composites. Such improvements in compressive strength were 120 % and 135 %, respectively. The d33 values were increased by 45 % and 60 % with the polarization voltage increasing from 1.5 to 3.5 kV/mm for the two piezoelectric composites. Such increases in d33 were 64 % and 94 % when polarization duration extended from 5 to 25 min. This study determined the optimal preparation regime of the two piezoelectric composites that can ensure the best overall performance considering the trade-off among piezoelectric, mechanical, and microstructural properties of the composites. The results of this paper can facilitate the application of novel and high-performance of piezoelectric sensor in smart concrete structures.

Effect of mineral fertilizers on the yield and growth parameters of watermelon in Kazakhstan

Abstract The study aims to determine the optimal regimes of mineral fertilization for the yield of commercial watermelon fruits. The research goal is to analyze how fertilization regimes affect the growth parameters of this plant, such as weight per fruit and average fruit weight per plant. The research subjects are watermelon varieties, such as two Crimson Sweet varieties (including hybrid Producer Hollar) and Kholodok. The study involved a field survey on the territory of Zhana Tau, a farm located in the Aktobe area of the Republic of Kazakhstan. The experimental design encompassed the following fertilizer applications: Variant I – N30P40K60, Variant II – N60P60K120 and Variant III – N90P60K120. The study found that mineral fertilizers have a significant impact on the yield and growth parameters of watermelon fruits. After the application of N30P40K60, the weight per fruit was 8.13 kg for Crimson Sweet and 8.35 kg for Kholodok. The highest fruit weight indicator, 11.45 kg, was achieved when hybrid Producer Hollar was cultivated with N90P60K120. The highest yield (55.9 t/ha) was recorded when growing hybrid Producer Hollar with N90P60K120. The yield of the Crimson Sweet and Kholodok varieties, with the same level of fertilization, amounted to 49.6 t/ha and 51.2 t/ha, respectively. Correlation-regression analysis of the data on watermelon yield showed that this parameter tends to increase with the increase in the use of mineral fertilizers. Therefore, further research may focus on studying the influence of even higher levels of each macroelement and their combined effects on crop structure and fruit quality in watermelon cultivation.

Divergent response of Chernozem organic matter towards short-term water stress in Poa pratensis L. rhizosphere and bulk soil in pot experiments: A spectroscopic study

Understanding and controlling rhizospheric processes under abiotic stress is one of the key challenges in addressing food security amid the climate crisis. In this work, the impact of short-term drought and overwatering on soil organic matter (SOM) of Haplic Chernozem in the rhizosphere of Poa pratensis L. and in bulk soil was investigated. The vegetation experiment was conducted in a climatic chamber at soil moisture levels of 35, 80, and 200 % of the field capacity. UV-Vis and spectrofluorometry were used to describe the water-extractable organic matter (WEOM) characteristics and fluorofores signature, and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) to describe functional group composition of SOM. Composition and properties of SOM and WEOM of Chernozem significantly change after exposure to short-term water stress. Drought does not affect the composition of rhizosphere SOM except increasing the proportion of polysaccharides, but leads to the decrease in aromaticity and increase in molecular weight of humic-like components of rhizosphere WEOM. These findings reflect Poa adaptation to water deficiency and microbial activity suppression which results in accumulation of SOM intermediate decomposition products. On the contrary, bulk WEOM wasn't affected by drought but SOM became enriched with aromatic and oxidised components. Overwatering leads to equalisation of bulk and rhizospheric SOM composition due to a decrease in the proportion of aromatic and carboxylic components of bulk SOM and the accumulation of microbial products in both bulk and rhizospheric SOM. In general, rhizospheric WEOM undergoes relatively significant changes relative to the optimum water regime under moisture deficit, and bulk WEOM — under overwatering. The findings illustrate the involvement of the both WEOM and SOM in maintaining resilience of the soil-plant system as well as the difference in watering conditions impact on SOM in rhizosphere and bulk soil. SOM spectral data can be used for assessing the state of soil systems, such as changes in microbial activity and adaptation of the soil-plant system to abiotic stress. Our findings also illustrate the differences in the organic matter transformation of the Poa pratensis rhizosphere and the bulk Chernozem depending on environmental factors.

A Bayesian pharmacokinetics integrated phase I-II design to optimize dose-schedule regimes.

The schedule of administering a drug has profound impact on the toxicity and efficacy profiles of the drug through changing its pharmacokinetics (PK). PK is an innate and indispensable component of the dose-schedule optimization. Motivated by this, we propose a Bayesian PK integrated dose-schedule finding (PKIDS) design to identify the optimal dose-schedule regime by integrating PK, toxicity, and efficacy data. Based on the causal pathway that dose and schedule affect PK, which in turn affects efficacy and toxicity, we jointly model the three endpoints by first specifying a Bayesian hierarchical model for the marginal distribution of the longitudinal dose-concentration process. Conditional on the drug concentration in plasma, we jointly model toxicity and efficacy as a function of the concentration. We quantify the risk-benefit of regimes using utility-continuously updating the estimates of PK, toxicity, and efficacy based on interim data-and make adaptive decisions to assign new patients to appropriate dose-schedule regimes via adaptive randomization. The simulation study shows that the PKIDS design has desirable operating characteristics.

Controlling coating thickness distribution for a complex geometry with the help of simulation

This paper aims to develop a proper and valid simulation model for electroplating complex geometries. Since many variables influence the quality of the deposited coating and its thickness distribution, it is challenging to conduct efficient research only through experiments. In contrast, simulation can be an efficient way to optimize the electroplating experiments. Despite its potential, simulation has seen limited commercial use in the electroplating industry due to its inherent complexity and difficulty in achieving accurate precision for intricate geometries. The present study addresses the aspects that can enhance the electroplating simulation’s accuracy, which has been typically overlooked in the literature, such as the effect of current efficiency and its dependency on the current density, the input data for the electrode kinetics, the surface topology changes, and the differences between 2 and 3D simulations. The simulation model was validated by experimental results related to the coating thickness of Ni plating on a T-joint geometry. The results showed good agreement with the experimental ones, confirming the model’s ability to precisely predict the coating thickness and distribution and promote its broader utilization in the industry. Finally, the developed model was used to determine the optimal current density regime for achieving uniform coating thickness distribution on a T-joint sample.

FEATURES FOR OPTIMISING THE PROPERTIES OF COMPOSITE MATERIALS BASED ON ACRYLIC MONOMERS

Further development of research in the field of acrylic composites is aimed at creating modifiers with specified properties that will improve the characteristics of composites in specific application conditions; developing optimal ratios of composite components to ensure the required properties; developing universal mathematical models that will predict the properties of composites depending on the composition and curing conditions; searching for new applications for acrylic composites, such as industrial and civil engineering. Among all organic compounds, acrylic compounds demonstrate the highest rate of strength gain over a wide temperature range. This is due to the low activation energy of the polymerisation process of acrylic monomers, which is triggered by special initiators. Due to this feature, acrylic composites can cure even at low temperatures and gain high strength in a short time. However, despite the obvious advantages, there are a number of questions that require further research: how does the rate of strength gain and other properties of acrylic composites change at different temperatures? How does changing the ratio of composite components (pliable, filler, initiator) affect its properties? How does the curing process of acrylic composites work at the molecular level? Determining the answers to these questions will make it possible to select the optimal ratio of components to obtain a material with the required properties, control the rate of strength gain of the composite by changing the temperature and composition, and use acrylic composites in a wider range of temperature conditions. Thus, a deep understanding of the processes that occur during the curing of acrylic composites is a prerequisite for their effective use in various industries and construction. The aim of the study is to comprehensively study the properties of composite materials based on methyl methacrylate (MMA) for the purpose of their effective use. Research objectives: determination of the optimal temperature regime to achieve maximum composite strength in the shortest possible time (1.5-2 hours). Study the effect of various fillers and other components on the strength, durability and other properties of the material. Identification of effective ways to modify MMA to increase the strength of the composite. Development of methods for controlling the rate of strength gain to ensure optimal operation. Assessment of the durability of the adhesive bond under various operating conditions. Comparison of the properties of the developed composites with existing materials. The results of the study will make it possible to develop new, more efficient composite materials for repair work that will be widely used in construction, industry and other sectors. Keywords: acrylic composites, modification, methyl methacrylate, strength, temperature, curing, repair.

Genotype by environment interaction effect and fresh root yield stability of cassava genotypes under contrasting nitrogen regimes

Nitrogen (N) is an important nutrient element needed by cassava for optimum yield and it is a vital component of nucleotides (nucleic acids), enzymes, amino acids (proteins), chlorophyll molecules and hormones, among other essential compounds required for growth and development of cassava. Nitrogen stress is a major cassava production constraint, the study aimed to examine genotype by environment interaction (GEI) effects and fresh root yield stability of 203 diverse cassava clones to identify genotypes with stable performance under low and optimum nitrogen regimes across environments using AMMI and GGE biplot analysis. Experiments were conducted using an augmented block design with three replications for two years in three locations in Nigeria. There were significant differences (p < 0.001) in the genotype’s mean performances as well as significant differences (p < 0.001) in the environment’s mean performances for all the traits measured in both nitrogen regimes. The AMMI analysis of variance showed significant effects (p < 0.001) for genotypes, environments and the interactions for fresh root yield in both nitrogen regimes. The biplot analysis showed that for fresh root yield in the optimum nitrogen regime, the principal component accounted for 81.54% of the G + GE (Genotype plus and Genotype by Environment) variation. The G + GE for fresh root yield in the low nitrogen regime accounted for a total of 71.64% of the variation. Ten genotypes were identified as the best genotypes under the optimum nitrogen regime, while eleven genotypes were the best under the low nitrogen regime. Three genotypes under optimum nitrogen regimes were high-yielding. Still, they were unstable in their fresh root yield performance across the environments and can be recommended as specifically adapted to the environments they performed best. Three other genotypes were high-yielding genotypes under low nitrogen but were highly unstable in their fresh root yield mean performance across the environments. The environments Otobi_YR1, Igbariam_YR2, and Umudike_YR1 were identified as the most discriminatory among the test environments. The environments Umudike_YR2 and Igbariam_YR1 were identified as the most representative of the test environments and can represent a mega-environment. The best 21 genotypes that performed above the grand mean for fresh root yield in both nitrogen regimes can be further evaluated on the farmer’s field for possible advancement.

Default Risk, Risk Premium, and Corporate Resilience: The Role of Regulatory and Stabilization Policies

This study investigates the interaction between monetary and macroprudential policy measures and evaluates whether policymakers should address financial disruptions. To achieve this goal, we developed a dynamic stochastic general equilibrium model that incorporates frictions in financial markets and financial shocks alongside traditional macroeconomic shocks. One of the main focuses of macroprudential policies is to stabilize credit cycles. We used Moroccan data to estimate the model and assess various policy actions to counter imbalances in financial markets, including adjustments to the interest rate tool. Our findings highlight the benefits of addressing financial disruptions, the extent depending on the shock characteristics. While acting on interest rates in response to financial variables may stabilize some economic factors, it has the potential to increase the volatility of others substantially. The results confirm that the use of optimal regimes can reduce default processes and ensure companies stabilize risk premiums. Implementing such regulations leads to greater opening of the companies’ capital to external financing sources. JEL Classification C11, D53, D58, E52, E58

A local audit evaluating bone health in patients with functional hypothalamic amenorrhoea secondary to an eating disorder and a review of the application of hormone therapy in this clinical setting.

It is widely known that estrogen has a fundamental role to play in skeletal homeostasis. In the most reductionist sense, the action of estrogen can be surmised as anti-resorptive. Estrogen prevents the break-down of bone. It therefore follows that estrogen deficiency states, such as the menopause and functional hypothalamic amenorrhoea (FHA), are often characterised by increased bone remodelling and disrupted skeletal homeostasis. FHA is the cessation of menstruation secondary to abnormal signalling between the hypothalamus and pituitary gland due to deficient pulsatile secretion of Gonadotrophin Releasing Hormone (GnRH). Functional hypothalamic amenorrhoea is frequently a consequence of women suffering with eating disorders. The development of FHA secondary to eating disorders is an evolutionary adaptive response to chronic metabolic energy deficiency. Fundamentally, preservation of life is biologically prioritised over dispensable physiological process such as reproduction. Consequently, the hypothalamic-pituitary-ovarian (HPO) axis fails, which disrupts menstrual function and ovulation, culminating in a state of estrogen deficiency. One of the most important and long-lasting deleterious consequences of FHA is disrupted skeletal homeostasis and bone loss. Estrogen replacement, most commonly in the form of combined hormone replacement therapy (HRT) or the combined oral contraceptive pill (COCP), is advised for women with an early menopause to prevent bone loss. Arguably, estrogen replacement should also be utilised in the context of FHA. However, the optimum estrogen regime for women with FHA remains under-researched and so management is not evidence-based.

The influence of mechanochemical activation on the rheological properties and strength development of geopolymer

To address the significant carbon emissions caused by the cement industry and its contribution to the greenhouse effect, there is an urgent need for new construction materials that can substantially reduce the use of traditional Portland cement. Alkali-activated binders, known for their excellent performance and lower carbon footprint, have emerged as a promising alternative. Despite the numerous advantages of geopolymers, their practical application is hindered by challenges in processability required for construction techniques, such as pumping, spreading, and forming. This study focuses on enhancing the rheological properties of geopolymers through mechanochemical activation and exploring the modification mechanisms involved. Slag and fly ash raw materials were processed under different ball milling conditions, specifically varying ball milling rotation speed (BR) and ball milling time (BT). The mechanical properties, workability, and rheological behavior of geopolymer specimens were evaluated to identify the optimal milling parameters affecting these properties. Detailed analysis using XRD, SEM, and heat of hydration tests elucidated the phase composition, microstructural evolution, and thermal characteristics of mechanochemically modified geopolymers, providing insights into the fundamental mechanisms of mechanochemical activation modification. The results indicate a significant correlation between ball milling parameters and the rheological properties of geopolymers. The optimal milling regime was identified as grinding at a speed of 70r/min for 50 min. This specific milling condition imparts ideal properties to the geopolymer, including moderate yield stress (34.353 Pa), low plastic viscosity (0.452 Pa s), good thixotropy, and high 28d strength (53.28 MPa), without any significant shear thickening behavior.