Moderate Conditions Research Articles

Uncovering mechanism of excessive copper ion-activated depressed-sphalerite under moderate alkaline conditions: A combined experimental and DFT investigation

Currently, extensive research exists on the activation mechanisms of sphalerite, yet there is a notable absence of studies on the mechanisms behind the activation of depressed sphalerite. This paper investigates the mechanism through which moderate or excessive copper ions activate depressed sphalerite under conditions (pH 9–10) of moderate alkalinity, employing a comprehensive approach that includes pure mineral flotation experiments, contact angle measurements, FESEM-EDS, XPS, and density functional theory simulations.The results from pure mineral flotation experiments reveal that, at a copper ion concentration of 1 × 10−4 mol/L, sphalerite, previously depressed by zinc sulfate, is activated by copper ions, achieving a recovery rate of 91.46 % with butyl xanthate as the collector. However, when more cooper ions are added, the recovery of sphalerite decreases. Contact angle measurements and FESEM-EDS data indicate that under conditions of moderate alkalinity, zinc sulfate undergoes hydrolysis to form hydrophilic colloidal substances (hydroxylated zinc) that adhere to the surface of sphalerite, rendering it hydrophilic and thereby depressed. Following the introduction of copper ions, a dense striated material forms on the surface of sphalerite previously inhibited by zinc sulfate, enhancing its hydrophobicity, but if more copper ions were added, the hydrophobicity of activated sphalerite will be weakened. XPS findings further suggest that activated sphalerite by copper is capable of forming polysulfides, which then act on the sphalerite. DFT simulations verify that under moderate alkalinity conditions, copper ions first undergo a hydroxylation reaction in the solution before adsorbing or precipitating on the mineral surface as hydroxylated substances, which subsequently interact with sulfur on the surface of sphalerite. The analysis of the density of states indicates that following the addition of butyl xanthate, the strongest 3p orbital electron peak of the sulfur atom bound to butyl xanthate and the strongest 3d orbital electron peak of zinc are at distinct energy levels, suggesting that the overlap of the electronic density of states is minimal, indicating a weak and unstable interaction between the sulfur and zinc atoms bonded with butyl xanthate. Conversely, the strongest 3p orbital electron peak of the sulfur atom bonded with butyl xanthate overlaps with the strongest 3d orbital electron peak of copper and is positioned near the Fermi level, signifying a strong reactivity and more stable interaction between the sulfur and copper atoms.

Unveiling degradation mechanisms of anode-free Li-metal batteries

Anode-free Li-metal batteries (AFLMBs), in which Li+ ions from the cathode are deposited on a Cu substrate and the deposited Li-metal serves as the anode, exhibit higher energy density compared to Li-metal batteries (LMBs). However, achieving stable cycle performance, even at moderate operating conditions, is difficult and has so far hindered their practical uses. In AFLMBs, the homogeneity of solid electrolyte interphase (SEI), initially created by electrolyte reduction on Cu substrate, is not maintained during Li-metal deposition, leading to uncontrolled electrolyte decomposition. The SEI is therefore not conserved, and uneven Li deposition morphology is induced on the Cu substrate and the eventual instability of SEI leads to the overall degradation of AFLMBs. Here, we report on the failure mechanisms of AFLMBs through a comparative study with LMBs using 3 M lithium bis(fluorosulfonyl)imide (LiFSI) dissolved in N,N-dimethylsulfamoyl fluoride. Our investigation reveals that the SEI inhomogeneity in AFLMBs makes Li+ transport through SEI sluggish and non-uniform, triggering local compositional changes of the initially formed SEI on the Cu substrate and unwanted consumption of FSI– anion from the electrolyte. This work provides clear understanding to the interfacial engineering and important roles of Li-metal on the Cu substrate in AFLMBs, promising the creation of stable SEI, reversible electrochemical reaction of Li-metal, and interfacial stability of the cathode in LMBs.

Microfacies of the San Juan Formation (lower Darriwilian) in the Rio Francia section, Central Precordillera, Argentina.

In this contribution, we describe and interpret the microfacies of the upper levels of the San Juan Formation in the Río Francia section of the Central Precordillera, Argentina, for the first time. Several studies in this section identified the Lenodus antivariabilis, Lenodus variabilis, Lenodus crassus, and Lenodus pseudoplanus zones, thereby limiting this stratigraphic interval to the early Darriwilian age. Five microfacies were recognized: M1 burrowed bioclastic wackestone, M2 bioclastic mudstone-wackestone, M3 intrabioclastic grainstone, M4 crinoidal wackestone-packstone, and M5 bioclastic wackestone-packstone. These microfacies indicate a shallow subtidal inner platform environment with variations in hydrodynamic energy ranging from low to moderate conditions below the fair-weather wave base level. The vertical arrangement of these sub-environments suggests a gradual transgressive setting during the lower Darriwilian for the carbonate beds of the San Juan Formation. The Baños de Talacasto, Ancha Creek, and Don Braulio sections are correlated with the section studied in this work, where conodont zones were documented, and microfacies analyses revealed shallow subtidal environments with low-energy conditions and occasional high-energy episodes. Differences in redox conditions were observed between the Don Braulio section (anoxic) and the Río Francia section (well-oxygenated), interpreted as the result of a rapid sea-level rise, though diachronic across the platform. Microfacies analysis, combined with precise conodont biostratigraphy, provides a powerful tool for reconstructing the Middle Ordovician carbonate platform.

Oliguria caused by dehydration in combat trauma (case series)

Background. A combat gunshot wound is significantly different from a civilian trauma. It is characterized by the prevalence of penetrating injuries, which increases the volume of blood loss at the pre-hospital stage, and the destruction of large masses of muscle tissue (rhabdomyolysis), which leads to acute kidney injury. Moreover, combat trauma occurs in conditions of chronic background stress as a result of severe emotional and physical strain, uncomfortable weather conditions, and deprivation of sleep, drinking and food. So, such a phenomenon as voluntary dehydration is common among soldiers in combat conditions. In wounded, oliguria is often considered a result of acute kidney injury, but it can also be a symptom of severe dehydration. The purpose of our work was to analyze three clinical cases of oliguria caused by dehydration in wounded with combat trauma to better understand the severity of the condition of such victims and to improve medical aid for them. Materials and methods. The article describes three cases of men aged 35, 50 and 44 years with combat gunshot wounds to the extremities, who were admitted to the tertiary care hospital on the second day after the injury with oliguria (0.18–0.19 ml/kg/hr) and high creatinine (333 to 457 μmol/L). Results. All three patients were conscious, breathing spontaneously, had stable hemodynamics, and moderate anemia after pre-hospital blood transfusions. Focused ultrasound study revealed hyperdynamic left ventricle and small inferior vena cava with complete inspiratory collapse, which suggested hypovolemia. Upon further investigation of the medical history, patients admitted not drinking any liquid for one to two days prior to injury. Tissue hydrophilicity test was conducted which showed severe dehydration in all three cases. Infusion volume was calculated using P.I. Shelestiuk nomogram (modified by O.V. Kravets et al.) and amounted to 60 ml/kg of balanced crystalloid solutions. Upon starting rehydration, diuresis was restored within two hours and amounted to 0.7–2.1 ml/kg/h in all three patients. Creatinine levels normalized in 2–4 days. Patients were transferred to another hospital in a moderate condition in 4–5 days. Conclusions. Oliguria is a frequent complication of combat gunshot injury. Although it is most often associated with acute kidney injury from rhabdomyolysis, it should also be considered that in a combat environment, soldiers’ access to water may be limited and the injury may be accompanied by dehydration. In the cases presented, the differential diagnosis of the causes of oliguria in the wounded made it possible to detect signs of severe dehydration, abstain from the inappropriate use of saluretics, quickly compensate for the fluid deficit, and to avoid the development of kidney damage and the need for renal replacement therapy.

Comparative Study on the Response of Hyssop (Hyssopus officinalis L.), Salvia (Salvia officinalis L.), and Oregano (Origanum vulgare L.) to Drought Stress Under Foliar Application of Selenium

Drought is one of the most important abiotic factors limiting plant productivity. Although the aromatic plants of the Lamiaceae family often grow in arid regions, drought tolerance varies greatly among the different species of this family. The effect of induced drought stress can be reduced by the application of selenium. The current study aims to compare the growth and biochemical responses of three species of the Lamiaceae family (hyssop, salvia, and oregano) to drought stress and the possibility of reducing the effect of stress in these plants by foliar treatment with selenium. Drought stress reduced the fresh and dry biomass of hyssop (by 35% and 15%), salvia (by 45% and 41%), and oregano (by 51% and 32%). Se treatment did not affect the growth of plants under drought stress, but it improved relative water content in hyssop and salvia under moderate drought conditions. A reduction in the content of chlorophyll a and chlorophyll b (in hyssop and salvia). In addition, an increase in the content of hydrogen peroxide (in oregano and salvia), malondialdehyde, and proline in plants cultivated under drought conditions was observed. Se treatment led to reduced levels of hydrogen peroxide and malondialdehyde, along with an increase in chlorophyll a content (in hyssop and oregano) and proline content. The response of the antioxidant system depended on the plant species. Hyssop exhibited a significant increase in glutathione peroxidase, superoxide dismutase, and peroxidase activities. Oregano showed enhanced catalase activity. Salvia experienced a sharp increase in ascorbic acid content. Se treatment stimulated the accumulation of phenolic compounds and increased glutathione peroxidase activity in all studied species.

Assessing the impact of a large multi-purpose reservoir on flood control under moderate and extreme flood conditions

ABSTRACT This study offers a detailed examination of the Eupen dam’s role in flood mitigation in Belgium’s Vesdre valley, analysing 18 moderate and extreme flood events from 1995-2022. Notable aspects of the methodology include adjustments for an ungauged sub-basin and a mass-balance approach to compute the unknown outflow data from the inflow time-series and reservoir level data. These 18 events evidence the dam’s performance hitherto, with respect to peak discharge attenuation (9-91%), peak delay (0-68 hours), outflow volume reduction (2-94%), as well as discharge reductions associated with various return periods (38-51%), given its multipurpose objectives. The research details how the dam’s effectiveness varies with operational decisions and antecedent reservoir conditions, marking a departure from conventional studies that tend to generalise data across multiple dams and events. By focusing on individual events, the study provides insights into the nuanced interplay between dam operations and flood management, demonstrating the benefits and limitations of multi-purpose reservoirs in flood control.

Ecological success of extreme halophiles subjected to recurrent osmotic disturbances is primarily driven by congeneric species replacement.

To understand how extreme halophiles respond to recurrent disturbances, we challenged the communities thriving in salt-saturated (~36% salts) ~230L brine mesocosms to repeated dilutions down to 13% (D13 mesocosm) or 20% (D20 mesocosm) salts each time mesocosms reached salt saturation due to evaporation (for 10 and 17cycles, respectively) over 813days. Depending on the magnitude of dilution, the most prevalent species, Haloquadratum walsbyi and Salinibacter ruber, either increased in dominance by replacing less competitive populations (for D20, moderate stress conditions), or severely decreased in abundance and were eventually replaced by other congeneric species better adapted to the higher osmotic stress (for D13, strong stress conditions). Congeneric species replacement was commonly observed within additional abundant genera in response to changes in environmental or biological conditions (e.g. phage predation) within the same system and under a controlled perturbation of a relevant environmental parameter. Therefore, a genus is an ecologically important level of diversity organization, not just a taxonomic rank, that persists in the environment based on congeneric species replacement due to relatively high functional overlap (gene sharing), with important consequences for the success of the lineage, and similar to the success of a species via strain-replacement. Further, our results showed that successful species were typically accompanied by the emergence of their own viral cohorts, whose intra-cohort diversity appeared to strongly covary with, and likely drive, the intra-host diversity. Collectively, our results show that brine communities are ecologically resilient and continuously adapting to changing environments by transitioning to alternative stable states.

Impact of Different Plant Spacing Arrangements on the Profitability and Productivity of Blackgram Cultivars [Vigna mungo (L.) Hepper

Evaluation of blackgram cultivars (Vigna mungo (L.) Hepper) under various plant spacings was the title of a field study carried out at the Department of Agronomy, College of Agriculture, Badnapur. The experimental field had good drainage and was leveled. The soil was clay loam in texture, low in available nitrogen, medium in available phosphorus, very high in accessible potassium and alkaline in reactivity. The blackgram crop was able to develop and mature normally due to the moderate environmental conditions. Twelve treatment combinations were possible with the three different kinds and four different spacings used in the Factorial Split plot Design layout of the experiment. Each experimental unit included three repetitions, measuring 5.4 m × 5.0 m in the gross plot and 4.5 m x 4.6 m in the net plot. On July 14, 2015, three varieties-BDU-1, TAU-1 and AKU-15 were sown. The dibbling method was used to sow the seeds, with four distinct spacings of 30 cm x 10 cm, 30 cm x 20 cm, and 45 cm x 10 cm. The RDF was used prior to seeding. Plant preservation measures and cultural practices were implemented in accordance with recommendations. A number of pods per plant, number of seeds per pod, pod length, pod weight per plant, seed yield per plant, test weight (1000 seed weight g), harvest index, gross monetary returns (Rs ha-1), net monetary returns (Rs ha-1), and Benefit: Cost (B: C) ratio are among the characteristics and economics that indicate that BDU-1 (V1) produced a significantly higher yield among the different blackgram varieties. Variety x spacing interaction effects were shown to be non-significant.

Cerium Oxide Nanoparticles (CeO2 NPs) Enhance Salt Tolerance in Spearmint (Mentha spicata L.) by Boosting the Antioxidant System and Increasing Essential Oil Composition

Salinity represents a considerable environmental risk, exerting deleterious effects on horticultural crops. Nanotechnology has recently emerged as a promising avenue for enhancing plant tolerance to abiotic stress. Among nanoparticles, cerium oxide nanoparticles (CeO2 NPs) have been demonstrated to mitigate certain stress effects, including salinity. In the present study, the impact of CeO2 NPs (0, 25, and 100 mg L−1) on various morphological traits, photosynthetic pigments, biochemical parameters, and the essential oil profile of spearmint plants under moderate (50 mM NaCl) and severe (100 mM NaCl) salinity stress conditions was examined. As expected, salinity reduced morphological parameters, including plant height, number of leaves, fresh and dry weight of leaves and shoots, as well as photosynthetic pigments, in comparison to control. Conversely, it led to an increase in the content of proline, total phenols, malondialdehyde (MDA), hydrogen peroxide (H2O2), and antioxidant enzyme activities. In terms of CeO2 NP applications, they improved the salinity tolerance of spearmint plants by increasing chlorophyll and carotenoid content, enhancing antioxidant enzyme activities, and lowering MDA and H2O2 levels. However, CeO2 NPs at 100 mg L−1 had adverse effects on certain physiological parameters, highlighting the need for careful consideration of the applied concentration of CeO2 NPs. Considering the response of essential oil compounds, combination of salinity stress and CeO2 treatments led to an increase in the concentrations of L-menthone, pulegone, and 1,8-cineole, which are the predominant compounds in spearmint essential oil. In summary, foliar application of CeO2 NPs strengthened the resilience of spearmint plants against salinity stress, offering new insights into the potential use of CeO2 NP treatments to enhance crop stress tolerance.

Moderation of the Electronic Structure of Phosphamides to Execute the Catalytic Appel Reaction Bypassing Phosphine.

A set of structurally analogous, albeit electronically distinct, phosphamides (1aa-10aa) is prepared, and the effect of the electronic amendment due to p-substitution has been tested for the conversion of alcohols to halides via the Appel reaction. The -OMe-substituted diphosphamide (8aa) remains the most active, providing ∼96% conversion of alcohols to halides with a TON of 11 in moderate reaction conditions with a large substrate scope. Halide formation follows a pseudo-first-order rate with a constant rate (kobs) of 7.13 × 10-5 s-1. Temp-dependent kinetics and Eyring analyses reveal the activation parameters ΔH‡ of 28.95 (±1.6) kcal mol-1, ΔS‡ of -70.02 (±0.4) cal K-1 mol-1, and ΔG‡298 of 49.81 (±1.2) kcal mol-1. The deuterium labeling study highlights the O-H dissociation of the alcohol as the rate-determining step, while the Hammett analysis with p-substituted benzyl alcohols indicates a positive charge accumulation at the phosphorus center during the Appel reaction. The HOMO-LUMO energy and NPA analyses show that p-OMe substitutions in 8aa make the "P═O" bond more ionic and corresponding aminophosphine is nucleophilic, which are favorable for the Appel reaction. In situ detection of the Appel salt, [R3PX]CX3 and alkoxy phosphonium cation [R3POR]X, validates the reaction pathway mediated by the phosphamides.

A Review of Therapeutic and Medicinal Uses of Fenugreek (Trigonella foenum-graceum L.)

Current lifestyle and excessive use of synthetic fertilizers in agriculture field promote an unhealthy lifestyle that urges the researchers looking for a healthy and beneficial diet. Numerous crop plants have nutritional, functional, nutraceutical, and therapeutic properties. Fenugreek (Trigonella foenum gracium) is a popular crop known for these qualities and is beneficial in the human diet. It is an annual plant from the Leguminosae family that is commonly grown in the Mediterranean and Asian countries. It is mostly grown for its spices, though it can also be used for food (feed) and medicinal (antioxidant, antibacterial, anti-inflammatory, and hypoglycemic properties). Fenugreek is famous for its versatile uses, grown under moderate conditions (drought and salinity), white flowering herb, and self-pollinated plant. Fenugreek composition consists of various nutrients like vitamins, minerals, proteins, lipids, fibre, amino acids, and bioactive compounds that are used for medicinal purposes. Due to higher fibre content fenugreek is called a food stabilizer and emulsifying agent for changing food texture. Fenugreek has numerous health benefits, including the ability to lower blood sugar, heart problems, menstrual cramps, anti-cancer, reduce inflammation, and support healthy skin and hair. This review highlights the nutritional value of fenugreek with various health and medicinal benefits. Despite its multiple advantages, this review paper also discussed health problems associated with the usage of fenugreek, such as allergies and possible adverse effects linked with fenugreek use.

Reducing Stoichiometric Excess of Base to Catalytic Amount: Revisiting Staudinger Reaction for -lactam Synthesis

Background: -lactams have been primarily utilized as a leading class of effective antibiotics. They have been found to show activity against various diseases, prompting the scientific community to prioritise innovative protocols for their synthesis. The general and well-known synthetic strategy involves the classical Staudinger reaction exhibiting [2+2] cycloaddition reaction. However, the protocol utilizes stoichiometric excess of base for efficient product formation. Objective: A smarter and more acceptable approach for the synthesis of -lactams would be to reduce the excess base to a catalytic amount, furnishing a catalytic version of the Staudinger reaction. The modified version can eliminate the hazards arising out of excess use of the base, ultimately promoting the environmentally benign approach. Methods: With this hypothesis, a base-catalyzed approach in dimethyl formamide (DMF) towards the synthesis of -lactam via Staudinger reaction has been endorsed under moderate reaction conditions. Results: The scope of the substrates was explored with both electron-withdrawing and electronreleasing substitutions in the formation of -lactam. The reduction of the base amount from stoichiometric to catalytic amount was justified by the involvement of DMF in generating the basic condition for the reaction. Conclusion: It was hypothesized that the decomposition of DMF under the base-catalysed reaction condition can generate dimethylamine, which produces the required basic environment. conclusion: A base-catalysed approach in dimethyl formamide (DMF) towards the synthesis of β-lactam via Staudinger reaction has been endorsed under moderate reaction conditions. The substrates scope was explored with both electron withdrawing and electron releasing substitutions in the formation of β-lactam. The reduction of base amount from stoichiometric to catalytic was justified by the involvement of DMF in generating the basic condition for the reaction. It was hypothesized that the decomposition of DMF under the base catalysed reaction condition can generate dimethylamine which produces the required basic environment.

Phytoplankton community structure in Tunda Island waters, Banten Indonesia as a bioindicator to measure water quality

Mining of sea sand in the water area of Tunda Island can result in changes in the quality of the aquatic environment. Phytoplankton may indicate changes due to their rapid reaction to external influences in water. This study aims to determine the water quality condition in Tunda Island waters using phytoplankton communities. The sample collection included 20 observation stations in Tunda Island waters, Banten province. The analyzed water samples had parameters of depth, temperature, pH, dissolved oxygen, total dissolved solids, salinity, nitrates, and phytoplankton communities. The results obtained by several quality water parameters still meet the quality standards except for nitrates. The composition of phytoplankton consists of 3 classes: Cyanophyceae, Bacillariophyceae, and Dinophyceae. Eight phytoplankton genera of the Bacillariophyceae class dominated during observation: Bacteriastrum sp., Chaetoceros sp., Hemiaulus sp., Lauderia sp., Nitzschia sp., Rhizosolenia sp., Skeletonema sp., Thalassiosira sp., and Thalassiotrix sp. The phytoplankton biological index describes the phytoplankton diversity index as moderate diversity, phytoplankton evenness is classified as unstable communities, and phytoplankton dominance is at a moderate condition. Variations within a phytoplankton group can reflect seasonal dynamics and the impact of changes in the aquatic environment.

Evaluating the spatiotemporal patterns of drought characteristics in a semi‐arid region of Limpopo Province, South Africa

Drought is a complex phenomenon resulting from below-average rainfall and is characterized by frequency, duration, and severity, occurring at a regional scale with dire consequences, especially in semiarid environments. This study used the Reconnaissance Drought Index (RDI) to assess drought severity in two district municipalities in Limpopo Province. Rainfall and air temperature data from 12 stations covering 1970–2020 were obtained from the Agricultural Research Council. The calculation of RDI relies on the monthly accumulation ratio of total rainfall to potential evapotranspiration (PET). For this study, PET was estimated using the Hargreaves and Samani temperature-based approach. The RDI results showed a high spatial–temporal variation in drought characteristics over the study area. All stations experienced extreme drought conditions in different years, with the maximum drought severity (-3.40) occurring from 2002–2003 in the western parts of the study area, indicating extreme drought. Furthermore, the results revealed continuous drought conditions over various periods, including severe droughts between 1995 and 1998 and between 2014 and 2016, with the severity varying between mild and moderate drought conditions. The results reveal notable but nonuniform drought patterns as the climate evolves, with potential implications for water availability and livelihoods. The study's findings underscore the significance of adopting multidimensional approaches to drought assessment that encompass meteorological and hydrological factors to inform strategies for adaptive water management and policy formulation in the face of a changing climate.

A micro-scale look into pedestrian thermophysiological comfort in an urban environment

Different spatial scales enable the analysis of thermophysiological conditions of pedestrians in an urban environment. A higher resolution hotspot analysis was conceived using GIS technology in some areas of Lisbon with different morphological conditions. Eleven hotspots were found across six study areas, located in high to moderate urban density conditions and in different types of urban spaces. So, six hotspots were found in avenues (high urban density conditions), three in streets, and two in general open spaces (moderate urban density conditions). These spaces are characterized by being busy areas with high anthropogenic influence, with high-absorbing and reflective materials, and with very poor green infrastructure. Environmental conditions, namely, radiation, mean radiant temperature, and air temperature, were the main cause of hotspot existence, and the main propellers for UTCI intensification. The urban density variable was also found to be important, especially in avenues and open spaces. In these areas, the adjusted component for environmental and urban density conditions can increase 0.60 to 1.35 °C in open spaces and 0.30 to 0.60 °C in avenues, each time there is a one-unit increase in the component. Trees, either in the street or in parks, have generally been found to decrease the UTCI.

Rutile-phase Sn-Ti Mixed Oxides as Acid Catalysts for the Condensation of C2-C3 Oxygenated Compounds in Water.

The design of new cost-effective and water-resistant acid catalysts is crucial for valorizingaqueous side-streams to increase the efficiency and competitiveness of bio-refineries in a sustainable way. In this work, Sn-Ti mixed oxides are prepared via a green and scalable co-precipitation method. This synthesis procedure allows obtaining homogeneous rutile-phase Sn-Ti mixed oxides with enhanced textural properties and a higher amount of Lewis acid sites. More importantly, the catalytic behavior of these Sn-Ti mixed oxides is investigated by using an aqueous mixture of C2-C3 representative oxygenated compounds, closer to real industrial conditions and differing from usual individual probe molecules studies performed even in the absence of water. Catalytic experiments combined and correlated with spectroscopic measurements (i.e., XRD, TEM, FT-IR with pyridine adsorption-desorption and N2 adsorption) are performed to better understand the properties of different Sn-Ti catalysts. These materials show promising results in the condensation of light oxygenated compounds present in aqueous fractions. Homogeneous and robust rutile-phase structures with inherent hydrophobic characteristics turn these Sn-Ti materials into active and highly resistant catalysts capable to transform these low-value oxygenated compounds into a mixture of hydrocarbons and aromatics useful for blending with automotive fuels, especially under complex acidic aqueous environments and moderate process conditions.

Modified Biochar Materials From Eucalyptus globulus Wood as Efficient CO2 Adsorbents and Recyclable Catalysts

AbstractHighly porous carbon materials derived from renewable resources constitute a promising and sustainable strategy regarding the enhancement of CO2 capture technologies. In this work, the valorization of Eucalyptus globulus wood, a forest invasive species present in European forests, is performed through its transformation in biochar. The deposition of nitrogen and different metals (aluminum, copper and chromium) onto biochar is performed, using the magnetron sputtering as a pioneering technique, to produce coated biochar nanoparticles with improved properties. The resultant modified biochar particles maintain a highly porous structure and present a remarkable CO2 adsorption capacity (up to 4.80 mmol g−1 for N@BC), which is attributed to the synergy of their large total surface area (527 m2 g−1) and microporosity (pore diameter = 21 Å), with a high content of nitrogen and oxygen heteroatom moieties (40.4% N, 11.4% O). Their application as heterogeneous bifunctional catalysts in CO2 cycloaddition to epichlorohydrin is performed, in the absence of any solvent or co‐catalyst, under moderate conditions (20 bar CO2, 120 °C), leading to good conversions (up to 58% conversion) and excellent selectivity for cyclic carbonates. Cu‐coated biochar is shown to be more stable than non‐modified material, being recycled and reused along 4 consecutive runs without loss of catalytic activity or selectivity.

Increasing Vitamin K2 Synthesis in Bacillus subtilis by Controlling the Expression of MenD and Stabilizing MenA.

As an indispensable member of the family of lipid vitamins, vitamin K2 (MK-7) plays an important role in blood coagulation, cardiovascular health, and kidney health. Microbial fermentation is favored due to its high utilization rate of raw materials, simple operation, and moderate conditions. However, the biosynthesis pathway of vitamin K2 in microorganisms is highly complex, which hinders its industrial production in microbial cell factories. One of the major challenges is the stable expression and deregulation of key enzymes in the vitamin K2 biosynthesis pathway, which remains unclear and has undergone little investigation. In this study, 2-succinyl-5-enolpyruvyl-6-hydroxy-3-cyclohexene-1-carboxylic-acid synthase (MenD) and 1,4-dihydroxy-2-naphthoate polyprenyltransferase (MenA) were identified as pivotal enzymes in the biosynthesis of vitamin K2. To investigate the catalytic efficiency of MenD in the biosynthesis pathway of vitamin K2, structure-based mutation design and site-directed mutagenesis were performed. Three mutation sites were identified in MenD: A115Y, R96 M, and R323M, which improve the expression level and protein stability. Meanwhile, the MenA mutant T290M, which exhibits improved protein stability, was obtained by modifying its hydrophobic stacking structure. Finally, an engineered strain noted ZQ13 that combinatorially overexpressed MenD (A115Y) and MenA (T290M) mutants was constructed and achieved 338.37 mg/L vitamin K2 production in a 3-L fermenter.

Growth, Morphology and Respiratory Cost Responses to Salinity in the Mangrove Plant Rhizophora Stylosa Depend on Growth Temperature.

Mangrove plants, which have evolved to inhabit tidal flats, may adjust their physiological and morphological traits to optimize their growth in saline habitats. Furthermore, the confined distribution of mangroves within warm regions suggests that warm temperature is advantageous to their growth in saline environments. We analyzed growth, morphology and respiratory responses to moderate salinity and temperature in a mangrove species, Rhizophora stylosa. The growth of R. stylosa was accelerated in moderate salinity compared with its growth in fresh water. Under warm conditions, the increased growth is accompanied by increased specific leaf area (SLA) and specific root length. Low temperature resulted in a low relative growth rate due to a low leaf area ratio and small SLA, regardless of salinity. Salinity lowered the ratio of the amounts of alternative oxidase to cytochrome c oxidase in the mitochondrial respiratory chain in leaves. Salinity enhanced the leaf respiration rate for maintenance, but under warm conditions this enhancement was compensated by a low leaf respiration rate for growth. In contrast, salinity enhanced overall leaf respiration rates at low temperature. Our results indicate that under moderate saline conditions R. stylosa leaves require warm temperatures to grow with a high rate of resource acquisition without enhancing respiratory cost.

Evaluating Heat Stress Effects on Growth in Tunisian Local Kids: Enhancing Breeding Strategies for Arid Environments.

This study evaluates the impact of thermal load on the weights of Tunisian local kids using 24 models with cubic and quadratic Legendre polynomials, based on daily temperatures (Tmin, Tmax, and Tavg) on the day of weight recording and averaged over 7, 14, and 21 days before weighing. The deviance information criterion (DIC) consistently shows that cubic polynomial models offer a better fit than quadratic models, highlighting their superior accuracy in studying the effects of thermal load on kid weights. The models with the best fit utilized average or maximum temperatures over 14 or 21 days. The patterns of response were similar across the temperature variables and periods, showing a stable weight response at lower temperatures (thermoneutral region) followed by a decline as the temperatures increased. The weight loss was -125 g/°C beyond the moderate heat stress threshold (Tavg21 = 17.7 °C) and -450 g/°C beyond the severe heat stress threshold (Tavg21 = 25.3 °C) for Tavg21. The heat stress thresholds for moderate heat stress (HS1) were 8.6 °C for Tmin14, 27.4 °C for Tmax14, and 18.6 °C for Tavg14; moreover, for acute heat stress (HS2), they were 17.2 °C for Tmin14, 32.4 °C for Tmax14, and 25.5 °C for Tavg14. High variability in individual responses was observed, with differences in the slope of response ranging from 2.0 kg/°C for moderate heat stress to around 3.0 kg/°C for severe heat stress for Tavg. The correlations between the weights under different temperatures were low, indicating that rankings based on weight could change with varying heat conditions. The animals with larger weight levels generally demonstrated better heat tolerance, and those with good heat tolerance under moderate conditions were also likely to have good tolerance under severe conditions.