Stable Composition Research Articles

Valence state effect of Cu on photocatalytic CO2 reduction

Copper (Cu) is extensively employed in photocatalytic CO2 reduction reactions for the production of high-value products. The valence state of transition metals plays a pivotal role in influencing the catalytic process. However, due to the complex valence state changes of Cu in the CO2 reduction reaction, research on its valence state effect is lacking. The current work is to prepare a series of TiO2/CuX with stable Cu valence composition using different copper halides (CuX and CuX2, X = Br or Cl) as precursors. The results show that the CuBr2 loading leads to Cu+/Cu2+ mixed cocatalyst and exhibits the highest activity for CO2 photoreduction. The CH4 evolution rate of the TiO2/CuBr2 catalyst is as high as 100.59 μmol h−1 g−1, which is 6.6 times that of pristine TiO2. The CH4 selectivity reaches 77%. The enhanced catalytic activity and selectivity can be ascribed to the efficient surface adsorption, activation, excellent carrier separation, and transfer of Cu+/Cu2+ mixed cocatalyst. Our findings provide a reference for designing highly active Cu-based photocatalysts.

Polymer-Grade Bio-Monomers from Oleochemicals by Combining Homogeneous Catalysis and Selective Product Crystallization in an Integrated Process

The homogeneously catalyzed methoxycarbonylation of bio-based methyl 10-undecenoate (C11-DME) produces linear 1,12-dimethyl dodecanedioate (l-C12-DME). Subsequent selective product crystallization from the reaction mixture with downstream filtration and washing allows for the generation of the bio-monomer in polymer grade quality (>99.9%). This effective purification enables its direct use, e.g., for bio-based polyamides, without further purification. It separates the expensive homogeneous catalyst dissolved in the liquid phase in its active state for efficient catalyst recycling. We present the complex interactions of process parameters regarding reaction and crystallization-based purification in an integrated catalyst recycling process. Furthermore, we demonstrate that purification of l-C12-DME with >99.9% purity over multiple consecutive recycling runs is possible. However, as the crystallization is highly sensitive towards changing concentrations of by-products and particularly unreacted substrates, this high purity is only achieved by maintaining a stable composition in the reaction mixture using a newly developed system for precise conversion control in the reaction step.

A dirty job: dishwasher wastewater reuse and upcycle through an ad hoc engineered microbial consortium

In the framework of regenerative circular economy and Sustainable Development Goals #6, water demand and wastewater production are a crucial environmental issue. To cope with this, a system called Zero Mile has been conceived to reuse/upcycle the dishwasher wastewater in both fertilisation of a vertical garden (for home plant production at zero mile) and the subsequent dishwasher rinsing cycle. The core of the Zero Mile system is a biofilter constituted by an ad hoc engineered microbial consortium, based on the mutualistic relationship between autotrophic and heterotrophic microbial partners, that makes the biodegradative process sustainable over time. Two semi-batch tests were performed to evaluate the capability and the efficiency of the microbial consortium to operate in conditions mimicking the Zero Mile system: consortia were challenged in two dishwasher wastewater volumes (50 and 500 mL), with a replenishing rate of 4 days for ¼ of the dishwasher wastewater volume. The results of these tests showed that the consortium thrives well in dishwasher wastewater over time and can survive with the volume and rates of replenishments. Next Generation Sequencing showed that the microbial consortium maintains a stable taxonomic composition, and chemical analyses demonstrated a very high bioremediation efficiency (total nitrogen and phosphorus removal). Aiming to contribute to the circular economy approach, the consortium ‘treated’ dishwasher wastewater was useful for plant fertilisation, as demonstrated by pigment content and quality indices (total phenols and flavonoids, soluble solids) measured in the lettuce plants grown in the Zero Mile demonstrator and watered with consortium reclaimed dishwasher wastewater.

A facile one-step microwave-assisted synthesis of bismuth oxytelluride nanosheets for optoelectronic and dielectric application: An experimental & computational approach

In the recent developments of research on various 2D materials, a new type of semiconducting material, bismuth oxychalcogenides (Bi2O2X, X = S, Se, Te), has gained tremendous attention among the scientific community. Compared to other Bi2O2X, Bi2O2Te has not acquired significant attention due to the difficulty of synthesizing stable composition. Here in this report, we have used "microwave-assisted synthesis method" to prepare bismuth oxytelluride samples with varying synthesis conditions. A few sharp and well-defined diffraction peaks were observed from crystallographic studies, along with several binary phases. Nanosheet-like morphology was observed for different as-prepared samples. The elemental mapping confirms the presence of Bi, O, and Te in the synthesized samples. In the UV-Vis absorption spectra, a redshift with the variation of synthesis conditions was observed, suggesting the presence of more acceptor states. The calculated bandgap energies display the wide bandgap nature of the samples. A broad photoluminescence emission spectrum with peaks centered around orange-red regions was observed for individual nanosheet cases, making them useful for various optoelectronic applications. The temperature and frequency-dependent dielectric measurements were carried out for the possible application in energy storage. The obtained conductivity of the samples is suitable for different electrical applications. The computational analysis using the DFT method was carried out to provide some necessary information about the structure and physical properties of the prepared materials.

Obtaining Multicomponent Coatings of a Stable Composition for Electromagnetic Radiation Screens

The formation processes of coatings of Cu–Ni and Ag–Cu systems with a stable elemental composition by the method of electron-beam evaporation are considered. It is shown that in the zone of action of the electron beam on the ingot placed in the crucible at the total vapor pressure of the alloy elements Σp above the pressure under the cap of the installation, the melt boils, and in the outer zone adjacent to the melt zone, the process of sublimation of the hard alloy occurs. The microrelief and elemental composition of the surface layer of the Cu–Ni alloy ingot in the zones of evaporation and sublimation, as well as the elemental composition of the coatings deposited in this case, have been studied. It is shown that the most acceptable way to obtain coatings of the Cu–Ni system with a stable elemental composition is the simultaneous electron-beam evaporation of copper and nickel from two crucibles. The azeotropic composition of the alloy of the Ag–Cu system was calculated and experimentally verified. The research results are used in the manufacture of multilayered screens of electromagnetic radiation.

Screening of Perovskites as Oxygen Evolution Reaction Catalysts in Alkaline Environment Tested Under Industrially Relevant Conditions

In recent years the research in catalyst development for the Oxygen Evolution Reaction (OER) in alkaline media has focused on finding the catalytically most active materials. Furthermore, catalysts are usually tested in an RDE setup at room temperature in 0.1 or 1 M concentrated KOH solution, which is far from industrial application conditions, where commonly temperatures between 70-100 ⁰C and highly concentrated electrolyte (6-10 M KOH) are used [1]. This is problematic as the material response is very different at higher temperatures and concentration of electrolyte. The expected thermally activated OER performance is often accompanied by severe degradation, observed already after short-term operation at industrially relevant conditions [2]. Eventually this results in severe loss in performance. For example, Pascuzzi et al. reported fast electrode degradation at industrial operating conditions (75 ⁰C; 10 M KOH and 100 mA/cm2) due to the breakdown of the platelet-like morphology of NiFeOxHy layered double hydroxide (LDH) [3].While the long-term durability of NiFeOxHy LDH remains questionable, with conflicting findings suggesting a rather complex interplay between structure-composition-operating conditions and activity-stability, perovskites offer an interesting alternative as they can accommodate a broad range of elements on both the A- and B-site, allowing for tuning the material properties. Perovskite catalysts have in some cases shown good activity and stability, one good example is PrBa0.5Sr0.5FexCo2-xO5+ 𝛿, which showed an overpotential of 290 mV at 10 mA/cm2 and stable operation for 2000 h in 1 M KOH [4]. However, in most cases critical raw materials (CRM) are involved in high performance perovskite catalysts. Furthermore, the stability of the host perovskite remains a challenge under industrial OER conditions even for rather stable perovskite compositions. For instance, Adolphsen et al. observed the formation of secondary phases in La, Ni and Fe based perovskites at 100 ⁰C when immersed in 31 wt.% KOH electrolyte [5].In this study the performance and stability of different perovskite materials, including some of the most prominent OER perovskite catalyst materials from the literature, are explored at room temperature and at industrial operating conditions. Our tests of the most prominent catalyst materials show low stability and strong signs of decomposition at industrial operating conditions.[1] Zeng, K., & Zhang, D. (2010). Recent progress in alkaline water electrolysis for hydrogen production and applications. Progress in Energy and Combustion Science, 36(3), 307–326. https://doi.org/10.1016/j.pecs.2009.11.002[2] Lohmann-Richters, F. P., Renz, S., Lehnert, W., Müller, M., & Carmo, M. (2021). Review—Challenges and Opportunities for Increased Current Density in Alkaline Electrolysis by Increasing the Operating Temperature. Journal of The Electrochemical Society, 168(11), 114501. https://doi.org/10.1149/1945-7111/ac34cc[3] Etzi Coller Pascuzzi, M., Man, A. J. W., Goryachev, A., Hofmann, J. P., & Hensen, E. J. M. (2020). Investigation of the stability of NiFe-(oxy)hydroxide anodes in alkaline water electrolysis under industrially relevant conditions. Catalysis Science and Technology, 10(16), 5593–5601. https://doi.org/10.1039/d0cy01179g[4] Jo, H., Yang, Y., Seong, A., Jeong, D., Kim, J., Joo, S. H., Kim, Y. J., Zhang, L., Liu, Z., Wang, J. Q., Kwak, S. K., & Kim, G. (2022). Promotion of the oxygen evolution reaction: Via the reconstructed active phase of perovskite oxide. Journal of Materials Chemistry A, 10(5), 2271–2279. https://doi.org/10.1039/d1ta08445c[5] Adolphsen, J. Q., Sudireddy, B. R., Gil, V., & Chatzichristodoulou, C. (2018). Oxygen Evolution Activity and Chemical Stability of Ni and Fe Based Perovskites in Alkaline Media. Journal of The Electrochemical Society, 165(10), F827–F835. https://doi.org/10.1149/2.0911810jes

Effects of Oxygen Flows and Annealing Temperatures on Optical, Electrical, and Structural Properties of Co-Sputtered In2O3-Ga2O3-Zn Thin Films

This study investigated the effects of oxygen (O2) flow rates and annealing temperatures on optical, electrical, and structural properties of indium–gallium–zinc oxide (IGZO) film on glass substrates fabricated by using a co-sputtering system with two radio-frequency (RF) (In2O3 and Ga2O3) and one direct current (DC) (Zn) magnetron. The average transmittance and optical energy gap increased significantly when the oxygen flow rate was increased from 1 sccm to 3 sccm. An increased O2 flow during co-sputtering IGZO films caused the crystallinity of the InGaZn7O10 phase to increase, yielding a smoother and more uniform granular structure. The carrier mobility rose and the carrier concentration decreased with increasing O2 flow. The results of X-ray photoelectron spectra (XPS) analyses explained the impacts of the O2 flow rates and annealing temperatures on optical and electrical properties of the co-sputtered IGZO films. The optimum process conditions of the co-sputtered In2O3-Ga2O3-Zn films were revealed as an O2 flow rate of 3 sccm and an annealing temperature at 300 °C, which showed the largest average transmittance of 82.48%, a larger optical bandgap of 3.21 eV, and a larger carrier mobility of 7.01 cm2 V−1s−1. XPS results at various annealing temperatures indicated that the co-sputtered IGZO films with an O2 flow rate of 3 sccm have more stable chemical compositions among different annealing temperatures.

Optimasi Sudut Baji, Kecepatan Pemakanan & Rpm Terhadap Kekasaran Permukaan Material SCM 440 Dengan Metode Respon Surface (RSM)

The development of manufacturing technology has developed so rapidly. In this study, SCM 440 steel material was used, which is an alloy steel of chromium molybdenum. This steel has the advantages of stable composition,low harmful elements,high steel purity. Surface roughness is important, surface roughness is defined as the irregularity of surface configuration in an object resulting from a finishing process. This study aims to determine the influence of process variables on the surface roughness rate of SCM 440 material by varying the total cutting angles of 700,750 and 800 then variations in feeding speed of 0.08mm, 0.09mm, and 0.10mm and spindle speed or RPM, namely 160,220, and 280 puts / min in the RSM method. The Rspon Surface method is a set of mathematical and statistical techniques that are useful for analyzing problems where several independent variables affect the response variable and determine the optimal value of the process variable. From the results of the study, the value of the Second order yˆ = + 0.092224 X1² + 0.208515 X2² - 0.03661 X3² was obtained. With stationary point value X0 = ( total Cut angle ) = - 0.382409, X0 = (feeding) = 0.161715, X0 = (RPM) = 0.578250. and found the optimal values of Wedge Angle (78.212), Feeding Speed (0.095 mm) and RPM (278.29 put/min). Then it can be analyzed the optimal value that is different from the value of the RSM method framework and if the values are the same then the research fails.

Molecular bioinformatic and functional analysis of Enolase4 gene during siphonal autotomy and regeneration of razor clam Solen grandis

For the razor clam Solen grandis, siphonal autotomy and regeneration is a necessary means of facing external stress, which is accompanied by a large amount of energy consumption. To explore the function of the ENO4 gene in the siphonal autotomy and regeneration of S. grandis, the full-length cDNA of the ENO4 in S. grandis was cloned and characterized. The full-length cDNA of SgENO4 was 2,773 base pairs (bp), with an 1,851 bp coding sequence (CDS) encoding 616 amino acids. ​Bioinformatic analysis revealed a slightly lower codon usage bias and a relatively stable nucleotide composition in the SgENO4 sequence. Three conserved motifs were found from the SgENO4 sequence. These conserved motifs vary in length from 14 to 27 amino acids. Moreover, in the siphonal pre-autotomy of razor clams, expression level of the SgENO4 gene was significantly higher in the hepatopancreas and siphonal base than other tissues (P < 0.05). However, the expression of the SgENO4 gene in the siphonal base decreased significantly in the siphonal post-autotomy 7 hours and gradually recovered as the regeneration process continued. ​Linear correlation analysis showed that there was a significant linear correlation between specific weight of siphon and relative expression levels of SgENO4 (R2 = 0.826). RNA interference (RNAi) result showed that the specific weight (the proportion of siphonal weight to body weight) is significantly lower than other groups on the seventh day (P < 0.05), suggesting that interfering with the expression of the SgENO4 gene could inhibit the siphonal regeneration of S. grandis. These results further demonstrate that SgENO4 is a conserved sequence and that it plays a crucial role in the siphonal autotomy and regeneration of S. grandis, advancing further understanding in exploring molecular mechanisms in the siphonal autotomy and regeneration.

Novel thorium borides and their hardness and superconductivity under pressure: Ab initio calculations

With the motivation of searching for new superconductors with better hardness in the Th–B system, we have performed ab initio evolutionary searches for all the stable compounds in this binary system in the pressure range of 0–200 GPa. From our enthalpy of formation calculations, it is found that only ThB4 (Space group No. P4/mbm), ThB6 (Space group No. Pm3¯m), and ThB12 (Space group No. Fm3¯m) compositions are preferred at zero pressure, in accordance with the experimental reports. Under pressure, our calculations predict the thermodynamically stable compositions, ThB (Space group No. R3¯m), Th3B4 (Space group No. R3¯m), ThB2 (Space group No. Amm2), and ThB8 (Space group No. R3¯m) at 54, 19, 35, and 51 GPa, respectively. Furthermore, although the thermodynamical stability of these compounds is predicted to be at high pressures, the possibility of occurrence at 0 GPa due to metastability still exists. The detailed calculations and analysis of the electronic structure and mechanical and thermal properties have been carried out on these materials using the ab initio tool. The P4/mbm phase of ThB4 and the Fm3¯m phase of ThB12 exhibit high hardness of 30.5 and 35.2 GPa under ambient conditions, which is comparable the hard material, B4C. On the other hand, among all the thorium borides, ThB2 shows a high electron–phonon coupling constant of 0.804 and is predicted to have Tc around 12.72 K. In addition, it has been found that the predicted high-pressure compositions, Th3B4 and ThB, display superconductive behavior under pressure. Additionally, various thermophysical quantities such as lattice thermal conductivity, bulk modulus, thermal expansion coefficient, specific heat capacity, and Gibbs free energy under ambient conditions have been determined from these calculations.

Dissolved organic nitrogen cycling revealed at the molecular level in the Bohai and Yellow Sea

Marginal seas play a crucial role in the cycling of dissolved organic nitrogen (DON) between the terrestrial and marine environments. However, very few studies have considered the molecular transformation of DON in marginal seas, leaving the DON molecular modifications in its cycling largely unknown. Therefore, this study examined DON cycling in the Bohai Sea and Yellow Sea, two semi-closed marginal seas in northern China, using stable isotopes (δ15N and δ13C), optical characteristics, and molecular compositions. Compared to the Yellow Sea, the Bohai Sea had a weaker exchange with the open ocean, resulting in higher concentrations, lower δ15N, and more recalcitrant properties in DON. The DON cycling showed significant differences inside and outside the Yellow Sea Cold Water (YSCW). Degradation was the major sink of DON in the YSCW, during which more highly unsaturated compounds and carboxyl-rich alicyclic molecules were produced. Nitrogen atoms were found to be removed from the molecules with more N atoms to those with fewer ones during the DON degradation. This study discovered the molecular modifications in DON cycling and highlighted the intrinsic mechanisms in the cycling of DON in marginal seas.

EFFECT OF EXTRUSION ON PROBIOTIC FEED ADDITIVE

Today, in Ukraine, the issue of producing high-quality and safe livestock products is solved by the introduction of intensive technologies that involve the use of various feed additives, including vitamins, probiotics, prebiotics, macro- and microelements. In recent years, the development of feed additives using live cultures of microorganisms, so-called probiotic products, has attracted much attention of scientists. The strategy in the creation of these products is aimed, first of all, at ensuring the physiological needs of the animal body in biologically active substances. The addition of probiotic supplements to feed increases the bioavailability of nutrients, health, immunity, performance and conservation of animals. Probiotic feed additive EnzActive is a special product on the market of feed additives, the addition of which to feed is aimed at reducing, and in the future, the complete elimination of the use of antibiotics in animal feeding. The article examines the mechanism of action of active fodder yeast on the body of farm animals and proves that the use of active fodder yeast in animal feeding helps reduce the cost of feed due to better assimilation by the animal's body and reduction of morbidity among animals. Methods of introduction of active fodder yeast into the technological process of compound feed production are analyzed. On the basis of theoretical and experimental data, a structural scheme for the extrusion of grain raw materials with active fodder yeast is proposed, which involves preliminary mixing with crushed grain raw materials to obtain a highly homogeneous and stable composition. The physical properties of the feed additive, which includes corn grain and active feed yeast EnzActive, were experimentally determined, which indicate that, compared to the loose, extruded feed additive, it has the following advantages: the mass fraction of moisture decreases by 24.4%, the natural slope angle increases by 11, 6%, the flowability decreases by 48.2%, and the volumetric weight decreases by 24%. When extruding corn grain with active fodder yeast, the degree of starch dextrinization is 59%, and the extrudate expansion index is 2.3. Microbiological indicators were determined, which indicate that the number of yeast cells in extruded grain with active feed yeast EnzActive was only 6% compared to the number of yeast cells in untreated corn grain with active feed yeast.

Demonstrating the absence of metal ion contamination in operando PEM fuel cells utilizing unmodified stainless steel bipolar plates

Using stainless steel as material for bipolar plates (BPPs) in proton exchange membrane fuel cells (PEMFCs) carries a perceived risk of corrosion and subsequent metal ion contamination of the membrane electrode assembly (MEA). However, assessments in literature on this hazard to PEMFC systems have been based on ex-situ corrosion studies, where general assumptions made on the BPP environment might not be a correct simulation of real on-site conditions. In this contribution, uncoated BPPs from stainless steel grades 304 L, 316 L and 904 L were subjected to in-situ hybrid endurance/stress testing to simulate realistic conditions in operating fuel cell systems and re-evaluate the need of additional corrosion protection. A post analysis of the plates showed no signs of surface dissolution on any of the tested samples and the concentration of iron in the MEA averaged 7 to 10 ppm for uncoated samples and 7 to 11 ppm for coated and graphitic reference tests, displaying a negligible amount of trace metals compared to critical thresholds found in literature. Contact resistance values were stable for all samples and observable changes in cell performance and voltage degradation was confirmed to be unrelated to the presence of uncoated bipolar plates. The combined effects of decoupling of bipolar plate surface potentials from electrode potentials and operational control of stable gas flow compositions to sustain stainless steel surface passivation, were identified as explanation for the experimentally observed corrosion resistance of uncoated stainless steel plates in PEMFCs.

Applications of DNA tetrahedron nanostructure in cancer diagnosis and anticancer drugs delivery

Abstract DNA nanostructures constructed under the guidance of DNA nanotechnology have developed rapidly for the last two decades, standing at the forefront in the biomedical field. Among them, DNA tetrahedron nanostructure (DTN) has emerged as one of the most representative DNA nanostructures. DTN was easily formed by one-step annealing of four single-stranded DNA. Due to its unique advantages such as simple and stable structural composition, high synthesis efficiency, uniform nanometer size, high programmability, and good biocompatibility, DTN has been widely used in biological detection, biological imaging, drug delivery, and other fields, and shows a great potential. Especially in the detection of cancer-related biomarkers and the delivery of anticancer drugs, nano-platforms based on DTN has achieved great success. In this review, we focus on the applications of DTN in cancer diagnosis and therapy, as well as the challenges and prospects.

Distribution, assembly, and interactions of soil microorganisms in the bright coniferous forest area of China's cold temperate zone

The bright coniferous forest area in the cold temperate zone of China is a terrestrial ecosystem primarily dominated by low mountain Larix gmelinii trees. Limited information is available regarding the assembly mechanisms and interactions of microbial communities in the soil in this region. This study employed high-throughput techniques to obtain DNA from myxomycetes, bacteria, and fungi in the soil, evaluated their diversity in conjunction with environmental factors, associated them with the assembly process, and explored the potential interaction relationships between these microorganisms. The findings of our study showed that environmental factors had a more significant influence on the α and β diversity of bacteria compared to myxomycetes and fungi. Microbial communities were influenced by environmental selection and geographical diffusion, although environmental selection appeared to have a more significant impact than geographical diffusion. Our study suggested that different microorganisms exhibited unique evolutionary patterns and may have different assembly modes within phylogenetic groups. Myxomycetes and fungi exhibited a similar assembly process that was mainly influenced by stochastic dispersal limitation and drift. In contrast, bacteria's assembly process was primarily influenced by stochastic drift and deterministic homogeneous selection. The community of myxomycetes and fungi is greatly influenced by spatial distribution and random events, while bacteria have a relatively stable population composition in specific regions and may also be subject to environmental constraints. Finally, this study revealed that Humicolopsis cephalosporioides, a fungus that exclusively resided in cold environments, may play a critical role as a keystone species in maintaining molecular ecological networks and was considered a core member of the microbiome.

Quantitative differences in synthetic gut microbial inoculums do not affect the final stabilized in vitro community compositions.

In vitro studies of synthetic gut microbial communities (SGMCs) can provide valuable insights into the ecological structure and function of gut microbiota. However, the importance of the quantitative composition of an SGMC inoculum and its effect on the eventual stable in vitro microbial community has not been studied. To address this, we constructed two 114-member SGMCs differing only in their quantitative composition-one reflecting the average human fecal microbiome and another mixed in equal proportions based on cell counts. We inoculated each in an automated anaerobic multi-stage in vitro gut fermentor simulating two different colonic conditions, mimicking proximal and distal colons. We replicated this setup with two different nutrient media, periodically sampled the cultures for 27 days, and profiled their microbiome compositions using 16S rRNA gene amplicon sequencing. While nutrient medium explained 36% of the variance in microbiome composition, initial inoculum composition failed to show a statistically significant effect. Under all four conditions, paired fecal and equal SGMC inoculums converged to reach stable community compositions resembling each other. Our results have broad implications for simplifying in vitro SGMC investigations. IMPORTANCE In vitro cultivation of synthetic gut microbial communities (SGMCs) can provide valuable insights into the ecological structure and function of gut microbiota. However, it is currently not known whether the quantitative composition of the initial inoculum can influence the eventual stable in vitro community structure. Hence, using two SGMC inoculums consisting of 114 unique species mixed in either equal proportions (Eq inoculum) or resembling proportions in an average human fecal microbiome (Fec inoculum), we show that initial inoculum compositions did not influence the final stable community structure in a multi-stage in vitro gut fermentor. Under two different nutrient media and two different colon conditions (proximal and distal), both Fec and Eq communities converged to resemble each other's community structure. Our results suggest that the time-consuming preparation of SGMC inoculums may not be needed and has broad implications for in vitro SGMC studies.

Impact of Early Weaning on Development of the Swine Gut Microbiome.

Considering that pigs are naturally weaned between 12 and 18 weeks of age, the common practice in the modern swine industry of weaning as early as between two and four weeks of age increases challenges during this transition period. Indeed, young pigs with an immature gut are suddenly separated from the sow, switched from milk to a diet consisting of only solid ingredients, and subjected to a new social hierarchy from mixing multiple litters. From the perspective of host gut development, weaning under these conditions causes a regression in histological structure as well as in digestive and barrier functions. While the gut is the main center of immunity in mature animals, the underdeveloped gut of early weaned pigs has yet to contribute to this function until seven weeks of age. The gut microbiota or microbiome, an essential contributor to the health and nutrition of their animal host, undergoes dramatic alterations during this transition, and this descriptive review aims to present a microbial ecology-based perspective on these events. Indeed, as gut microbial communities are dependent on cross-feeding relationships, the change in substrate availability triggers a cascade of succession events until a stable composition is reached. During this process, the gut microbiota is unstable and prone to dysbiosis, which can devolve into a diseased state. One potential strategy to accelerate maturation of the gut microbiome would be to identify microbial species that are critical to mature swine gut microbiomes, and develop strategies to facilitate their establishment in early post-weaning microbial communities.

Anthropocene trajectories of high alpine vegetation on Mont-Blanc nunataks

ABSTRACT Climate warming causes dramatic glacier retreat and intense vegetation changes in alpine regions. High-elevation nunataks, that is bedrock islands protruding from glaciers with uppermost flowering plants, are no exception. Yet the consequences of climate change on nunatak vegetation remain relatively unexplored. Here, we report findings from a re-visit of historical plant surveys carried out on six nunataks situated between 2180 m a.s.l. and 3509 m a.s.l. amidst the glaciers of the Mont-Blanc range (France). We compared vegetation surveys conducted in 2020 to those made 150 years before, and performed remote sensing analyses to depict changes in vegetation productivity during recent decades. We report an increase in plant species richness for the lowest and least isolated nunataks, which contributed to a strong signal of vegetation greening over the last 35 years. This trend was due to the upward migration of competitive species, but also due to species colonization from neighboring high alpine areas into recently unglaciated microsites. We also highlight striking ecological trajectories that have been little discussed so far, such as stable vegetation composition in the highest and most isolated nunataks, an increase of plant species associated with non-permanent snow-cover and water run-off, an increase of graminoids at lower elevations, and of phanerophytes at higher elevations. We argue that high alpine vegetation changes are not driven by the sole upward migration of lowland competitive species, and that careful monitoring of ongoing ecological changes over broad elevation gradients is necessary to better understand the rapid transformation of high alpine landscapes.

Revisiting soil microbial biomass: Considering changes in composition with growth rate

Soil microbial biomass is assumed to have stable chemical composition. Various components of the biomass such as DNA, ATP, or chloroform-labile organic carbon are measured in soil and converted into total microbial biomass using experimentally derived conversion factors, which are also assumed to be constant. However, several observations suggest the opposite. The composition of soil microbial biomass is likely changing with specific growth rate as observed in pure cultures of single microbial species. In this study, we define a “sub-Microbial” model that explicitly represents changes in composition of soil microbial biomass associated with changes in specific growth rate. We calibrate the model with published data and compare its performance with the simpler Monod and Pirt models, which consider microbial biomass as a single pool with invariant chemical composition. The model explains well the variability in chloroform-labile content of microbial biomass following organic substrate additions as well as variability in ratios of different components of microbial biomass. Changes in composition of soil microbial biomass are quantitatively significant and occur over hours and days resulting in our sub-Microbial model outperforming both the Monod and Pirt models. Our results further indicate that the composition of soil microbial biomass changes consistently with growth rate across various soils. Here, we provide a methodological recommendation how to determine total soil microbial biomass and its physiological characteristics such as growth rate, turnover rate and substrate use efficiency as accurately as possible. In light of the presented results, we would like to initiate a discussion about the methodological issues associated with measurement of soil microbial biomass as these measurements are expected to inform a new generation of microbially-explicit soil biogeochemical models predicting development of terrestrial ecosystems under various scenarios.

UNIFAC residual marine fuels stability prediction from NMR and elemental analysis of SARA components

This paper focuses on the development of theoretical approaches to predict the stability of very low-sulfur residual marine fuel (VLSFO) and is based on molecular weight, CHNS-, SARA-, NMR analysis, and the UNIFAC model. The main issue of using the UNIFAC model is to determine the group composition of marine fuel components in the UNIFAC representation. According to the data obtained, we developed a method for calculating UNIFAC pseudo-components group composition for residual and distillate petroleum products. The hyperparameters used in this model were the asphaltenes’ heat of fusion and melting point. The melting point was successfully estimated using a regression formula that took into account the molecular weight and C/H ratio. The heat of fusion was calculated using the optimization method. The resulting model makes it possible to estimate the influence of the VLSFO component’s parameters on the shape and position of the metastability line in ternary systems. The reliability of the developed model was confirmed by comparing the calculated and experimental data on the example of the VLSFO sedimentation stability diagram in the system of hydrotreated diesel fuel - catalytic cracking light gasoil - visbreaking residue. Based on the developed model it is possible to predict the stability of the residual marine fuel of a given composition. The application of this model is intended to greatly simplify the development of the stable VLSFO composition that meets the requirements of ISO 8217:2017.