Highly Enriched Research Articles

Mercury from Icelandic geothermal activity: High enrichments in soils, low emissions to the atmosphere

Geothermal activity is a natural source of mercury (Hg) to surface environments, but its contributions as part of the larger geogenic flux to the global Hg budget are poorly understood, in part due to large geographic gaps in emissions data where no measurements have been made. In this study we report the results of a field campaign over 2021 and 2022 on the highly active volcanic island country of Iceland. Six geothermal sites across the country were investigated for soil gaseous elemental mercury (GEM) and total Hg (THg) concentrations through a series of measurements made across the diffuse degassing surface. At 10 cm depth, soil GEM concentrations were often hundreds and in some cases thousands of times higher than ambient surface air concentrations. Geothermal soils were also highly enriched in THg due to the sorption of hydrothermal Hg on the characteristically fine, thermally-altered clays and silts. Soil “hotspots” displayed THg concentrations exceeding 100 µg g−1 comparable to levels in areas heavily contaminated by anthropogenic activity and in Hg-rich mineral soils. Strong correlations were observed between soil GEM, THg and soil temperature, and intensive measurements made at small spatial scales (∼1 m2) demonstrated the representativeness of individual sampling points. By adapting an active sampling gradient method for determining soil–air gas fluxes, we estimate an Icelandic geothermal GEM flux of 1.8 kg a−1 and a total Icelandic GEM flux, including non-geothermal areas, of ∼18 kg a−1. This work shows that Icelandic geothermal activity can generate high GEM and THg concentrations in the local soil environment, but its contribution to global Hg cycling appears to be minor.

P003 Metabolic Reprogramming in Intestinal Fibrosis: Integrating Metabolomics, Single-Cell Transcriptomics and Isotope Tracing

Abstract Background This study aims to systematically elucidate the metabolic landscape of intestinal fibrosis in Crohn's disease, revealing the key reprogrammed metabolic pathways in the fibrotic microenvironment. Methods We collected normal and fibrosis tissues from 122 Crohn's disease patients undergoing surgery for fibrosis-induced intestinal obstruction, and established DSS/TNBS-induced murine intestinal fibrosis model. To measure metabolites level in normal and fibrotic tissues, untargeted metabolomics was performed. C13-labeled glutamine was used for metabolic tracing to delineate metabolic fluxes in vitro and in vivo. We performed integration analysis by merging metabolomics and metabolic tracing data with established single-cell transcriptomic profiles. Isolation and further validation of human intestinal stromal cells were carried out, and gene expression was assessed using qRT-PCR and immunofluorescence. Results Significant metabolic heterogeneity was observed between normal and fibrotic tissues, with differential metabolites enriched in glucose and amino acid metabolism. Notably, intermediates of glycolysis were significantly increased, while tricarboxylic acid (TCA) cycle intermediates were decreased in fibrotic regions (p<0.05). Amino acids were broadly downregulated in fibrosis, whereas glutamate and glutamine were highly enriched (p<0.05). Mechanistic insights into these changes were provided by isotope tracing, revealing enhanced glycolysis and weakened TCA flux attributed to transition from TCA intermediate α-KG to glutamate. Moreover, catabolism of glutamine to glutamate was enhanced. Glutamate from above pathways converted to proline, which is the ingredient of extracellular matrix (ECM). Single-cell transcriptomic analysis indicated a high enrichment of genes related to glutamine metabolism in stromal cells, with significant upregulation of enzymes such as GLS (Glutaminase) and PYCR1 (Pyrroline-5-carboxylate Reductase 1) involved in glutamine and proline synthesis. Immunofluorescence and qRT-PCR confirmed the upregulation of GLS and PYCR1. Further experiments using primary stromal cells and murine models demonstrated that inhibiting GLS activity reduced ECM synthesis, alleviating intestinal fibrosis. Conclusion In intestinal fibrosis, glycolysis and glutamine catabolism enhanced. Stromal cells utilized the reprogrammed metabolic pathway to synthesize glutamate, thereby promoting pathological ECM anabolism. Targeting the key enzyme GLS represent a potential therapeutic strategy for intestinal fibrosis.

Precise Single-Cell Transcriptomic Mapping of Leukemia Cell States Reveals Unconventional Lineage Priming in Acute Myeloid Leukemia

Initial disease classification within acute leukemia relies on identifying morphological and immunophenotypic features of hematopoietic differentiation retained by leukemic blasts. While existing approaches can classify leukemic cells into broad lineages, they lack precision in discerning between specific cell states, particularly at the level of immature blasts. Single-cell (sc) RNA-sequencing (RNA-seq) provides thousands of new markers to enable precise determination of leukemia cell state and provides an opportunity to refine our classification of acute leukemia. To extend our ability to identify leukemia cell states by scRNA-seq, we developed a comprehensive reference map of human bone marrow hematopoiesis. Specifically, we integrated three unsorted bone marrow datasets and three CD34+ hematopoietic stem and progenitor (HSPC) purified datasets to ensure balanced representation of early HSPCs and terminally differentiated immune cells. This culminated in a curated atlas of 263,159 high-quality sc transcriptomes, representing 55 cellular states spanning 45 healthy donors (Fig 1A). We validated our cell state annotations to ensure concordance between transcriptional states and functional populations through reference mapping of bulk and sc transcriptomes from purified HSPC subsets. For example, mapping of scRNA-seq profiles from Lin-CD34+38-45RA-90+49f+ long-term (LT) HSCs revealed 91% concordance between transcriptional HSC and functional LT-HSC. We next performed scRNA-seq profiling on 12 AML patient samples harbouring either myelodysplasia-related genetic features or classical alterations involving NPM1 or KMT2A. By mapping leukemia cells onto our reference atlas, we identified pronounced involvement of early erythroid-like blasts in a subset of AML samples. To further investigate unconventional lineage priming in AML, we processed and mapped scRNA-seq profiles from eleven studies comprising 166 additional AML samples and 9 mixed phenotype acute leukemia (MPAL) samples (Fig 1B). After quality control and exclusion of mature lymphoid cells, we performed composition analysis utilizing 600,570 leukemia cells mapped to 38 cell states to identify patterns of variation among leukemia cell states. Immature leukemia cells map to a range of cellular states spanning HSC/MPP-like, LMPP-like, MLP-like, GMP-like, MEP-like, and EarlyEry-like, among others. Notably, we identified a subset of AMLs with high MLP-like enrichment that co-cluster with MPALs as well as a subset with high EarlyEry-like involvement that co-cluster with acute erythroid leukemias (AEL), thus highlighting the biological continuum between these diseases. We next identified marker genes from each leukemia cell state and trained sparse regression models to estimate their relative abundance within bulk RNA-seq cohorts. Through bulk analysis, we confirmed that MPAL is highly enriched for MLP-like cells compared to AML (p=2.5e-12) and that M6 AELs are highly enriched for EarlyEry-like cells compared to M0-M5 AMLs (p=0.00067). Among 864 AML patients, we found that high MLP-like abundance was associated with NUP98-NSD1 fusions (p=0.0011) and RUNX1 mutations (p=8.0e-10) while high EarlyEry-like abundance was associated with Complex Cytogenetics (p=8e-15) and TP53 mutations (p=2.3e-25). Cellular states of immature leukemic cells captured inter-patient heterogeneity within 136 AEL samples, wherein high EarlyEry-like abundance was associated with TP53 mutations (p=3.6e-9) and Poor cytogenetic risk (p=1.1e-9) while high GMP-like abundance was associated with KMT2A alterations (p=0.00046) and Good/Intermediate risk (p=0.00032). Finally, through integration of sc transcriptomics and targeted DNA profiling, we found examples of genetic subclones impacting the cellular hierarchies of individual patients through induction of early differentiation blocks, skewing of lineage output from myeloid to erythroid, or potentiation of transcriptional self-renewal programs within mature myeloid cells. Together, our high-resolution mapping approach highlights the cellular state continuum between acute leukemias and enumerates the impact of genetic drivers on leukemia cell hierarchies. Precise definitions of cellular states, coupled with the presence or absence of genetic alterations, may help to refine future disease classification, prognostication, and therapy development.

Simultaneous treatment of epichlorohydrin wastewater and polyhydroxyalkanoate recovery by halophilic aerobic granular sludge highly enriched by Halomonas sp.

The treatment of epichlorohydrin (ECH) wastewater exists chances for achieving cleaner production. This study initially employed moderately halophilic aerobic granular sludge (HAGS) to treat ECH wastewater, and the resulting HAGS was utilized to recover polyhydroxyalkanoate (PHA). During the acclimation process of HAGS, the chemical oxygen demand removal efficiency stabilized at 70 %. Moreover, due to the high enrichment of Halomonas sp. (relative abundance of 86 ± 0.50 %), the maximum PHA content of wasted HAGS was 52.67 wt% in the fermentation process. Simultaneously, the utilization of nuclear magnetic resonance spectroscopy (1H and 13C spectra) and fourier transform infrared spectroscopy for the structural analysis of polymers revealed that polyhydroxybutyrate was the predominant substance extracted from HAGS. In this study, the innovative use of highly enriched HAGS for treating ECH wastewater and simultaneously recovering PHA not only enables the efficient biological treatment of ECH wastewater but also realizes resource recovery of ECH wastewater.

High enrichment of heavy metals in fine particulate matter through dust aerosol generation

Abstract. Dust is a major source of atmospheric aerosols. Its chemical composition is often assumed to be similar to the parent soil. However, this assumption has not been rigorously verified. Here, we generated dust aerosols from soils to determine if there is particle-size-dependent selectivity of heavy metals in the dust generation. Mn, Cd, Pb and other heavy metals were found to be highly enriched in fine-dust (PM2.5) aerosols, which can be up to ∼ 6.5-fold. To calculate the contributions of dust to atmospheric heavy metals, regional air quality models usually use the dust chemical profiles from the U.S. Environmental Protection Agency's (EPA) SPECIATE database, which does not capture the correct size-dependent selectivity of heavy metals in dust aerosols. Our air quality modeling for China demonstrates that the calculated contribution of fine-dust aerosols to atmospheric heavy metals, as well as their cancer risks, could have significant errors without using proper dust profiles.

The microRNomes of Chinese hamster ovary (CHO) cells and their extracellular vesicles, and how they respond to osmotic and ammonia stress.

A new area of focus in Chinese hamster ovary (CHO) biotechnology is the role of small (exosomes) and large (microvesicles or microparticles) extracellular vesicles (EVs). CHO cells in culture exchange large quantities of proteins and RNA through these EVs, yet the content and role of these EVs remain elusive. MicroRNAs (miRs or miRNA) are central to adaptive responses to stress and more broadly to changes in culture conditions. Given that EVs are highly enriched in miRs, and that EVs release large quantities of miRs both in vivo and in vitro, EVs and their miR content likely play an important role in adaptive responses. Here we report the miRNA landscape of CHO cells and their EVs under normal culture conditions and under ammonia and osmotic stress. We show that both cells and EVs are highly enriched in five miRs (among over 600 miRs) that make up about half of their total miR content, and that these highly enriched miRs differ significantly between normal and stress culture conditions. Notable is the high enrichment in miR-92a and miR-23a under normal culture conditions, in contrast to the high enrichment in let-7 family miRs (let-7c, let-7b, and let-7a) under both stress conditions. The latter suggests a preserved stress-responsive function of the let-7 miR family, one of the most highly preserved miR families across species, where among other functions, let-7 miRs regulate core oncogenes, which, depending on the biological context, may tip the balance between cell cycle arrest and apoptosis. While the expected-based on their profound enrichment-important role of these highly enriched miRs remains to be dissected, our data and analysis constitute an important resource for exploring the role of miRs in cell adaptation as well as for synthetic applications.

High enrichment and near real-time quantification of airborne viruses using a wet-paper-based electrochemical immunosensor under an electrostatic field.

Conventional airborne virus measurement usually requires appreciable sampling and detection times. Viral aerosols should also be collected or prepared in a liquid medium whose volume typically ranges from milliliters to tens of milliliters; hence, many sampling and detection steps need to be taken with the unit horizontal or immobile. Moreover, viral aerosols need to be sufficiently enriched, which makes real-time monitoring difficult. Herein, we present a near real-time enrichment and quantification system of airborne viruses that consists of a wet-paper-based electrochemical immunosensor with a gel electrolyte and a modified electrostatic particle concentrator. A small amount of phosphate-buffered saline flowed on the electrode, which resulted in sensor electrodes that are barely wet (covered in a thin buffer film measuring several micrometers) to ensure antigen-antibody interaction and the removal of non-target particles on the electrode surface. This system ensures that airborne viruses are highly enriched on the working electrode of the immunosensor, and it is possible to measure the MS2 virus particle concentrations every 10min for 60min stably and selectively against non-target airborne viruses and bacteria at horizontal and tilted measurement configurations. This system thus has the potential to be used in the real-time mobile monitoring of airborne microorganisms.

Indian traditional rice variety "Gathuwan" suppresses T-cell-mediated immune responses via activation of ERK/Nrf2/HO-1 signalling pathway.

The impact of food on immune functions has been recognized for centuries and is now being increasingly explored for therapeutic applications. Rice, in addition to being the staple food in most developing countries, exhibits diverse complexities of phytochemicals among its wide germplasm repertoire, which supports its development as a functional food. In the present study, we have explored the immunomodulatory properties of Gathuwan rice, a local rice variety grown in Chhattisgarh, India, and traditionally used for the treatment of rheumatism. Methanolic Gathuwan Brown Rice Extract (BRE) inhibits T-cell activation and proliferation and cytokine secretion (IL-2, IL-4, IL-6 and IFN-γ) without inducing cell death. BRE exhibits radical scavenging activity in a cell-free system and decreases intracellular reactive oxygen species (ROS) and glutathione levels in lymphocytes. BRE induces nuclear translocation of the immune-regulatory transcription factor Nrf2 via activation of ERK and p-38 MAP kinase and up-regulates the expression of Nrf2-dependent genes (SOD, CAT, HO-1, GPx and TrxR) in lymphocytes. BRE treatment had no effect on cytokine secretion by lymphocytes from Nrf2 knockout mice, confirming the role of Nrf2 in the immunosuppressive effects of BRE. Feeding of Gathuwan brown rice to mice had no effect on the basal haematological parameters, but lymphocytes isolated from these mice were hypo-responsive to mitogenic stimuli. Treatment of allografts with BRE significantly prevented graft-versus-host disease (GVHD)-associated mortality and morbidity in mice. Metabolic pathway enrichment analysis of ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) data revealed a high enrichment ratio of amino acid and vitamin B metabolism pathways, and among metabolite sets, pyridoxamines, phytosphingosines, hydroxybenzaldehydes, hydroxycinnamic acids and indoles were highly enriched bioactive components. In conclusion, Gathuwan BRE suppresses T-cell-mediated immune responses by altering the cellular redox balance and activating the Nrf2 signalling pathway.

Runx2 regulates chromatin accessibility to direct the osteoblast program at neonatal stages.

SUMMARYThe transcriptional regulator Runx2 (runt-related transcription factor 2) has essential but distinct roles in osteoblasts and chondrocytes in skeletal development. However, Runx2-mediated regulatory mechanisms underlying the distinctive programming of osteoblasts and chondrocytes are not well understood. Here, we perform an integrative analysis to investigate Runx2-DNA binding and chromatin accessibility ex vivo using neonatal osteoblasts and chondrocytes. We find that Runx2 engages with cell-type-distinct chromatin-accessible regions, potentially interacting with different combinations of transcriptional regulators, forming cell-type-specific hotspots, and potentiating chromatin accessibility. Genetic analysis and direct cellular reprogramming studies suggest that Runx2 is essential for establishment of chromatin accessibility in osteoblasts. Functional enhancer studies identify an Sp7 distal enhancer driven by Runx2-dependent binding and osteoblast-specific chromatin accessibility, contributing to normal osteoblast differentiation. Our findings provide a framework for understanding the regulatory landscape encompassing Runx2-mediated and cell-type-distinct enhancer networks that underlie the specification of osteoblasts.

Predicted Functional Shifts Due to Type of Soil Microbiome and Watering of Two Wild Plants in Western Region of Saudi Arabia

The present study aimed to predict differential enrichment of pathways and compounds in the rhizosphere microbiomes of the two wild plants (Abutilon fruticosum and Nitrosalsola vermiculata) and to predict functional shifts in microbiomes due to water. Amplicon sequencing of 16S rRNA region V3–V4 was done and gene-based microbial compositions were enrolled in PICRUSt to predict enriched pathways and compounds. The results indicated that “ABC transporters” and “Quorum sensing” pathways are among the highest enriched pathways in rhizosphere microbiomes of the two wild plants compared with those of the bulk soil microbiomes. The highest enriched compounds in soil microbiomes of the two wild plants included five proteins and three enzymes participating in one or more KEGG pathways. Six of these eight compounds showed higher predicted enrichment in rhizosphere soil microbiomes, while only one, namely phosphate transport system substrate-binding protein, showed higher enrichment in the surrounding bulk soil microbiomes. In terms of differentially enriched compounds due to watering, only the dual-specific aspartyl-tRNA (Asn)/glutamyl-tRNA (Gln) amidotransferase subunit A showed higher enrichment in rhizosphere soil of the two wild plants after 24 h of watering. Two of the highly enriched compounds namely branched-chain amino acid transport system ATP-binding protein and branched-chain amino acid transport system substrate-binding protein, are encoded by genes stimulated by the plant’s GABA that participates in conferring biotic and abiotic stresses in plants and improves the plant’s growth performance. The 3-Oxoacyl-[ACP] reductase, a member of the short-chain alcohol dehydrogenase/ reductase (SDR) superfamily, participates in fatty acids elongation cycles and contributes to plant-microbe symbiotic relationships, while enoyl-CoA hydratase has a reverse action as it participates in “Fatty acid degradation” pathway. The methyl-accepting chemotaxis protein is an environmental signal that sense “Bacterial chemotaxis” pathway to help establishing symbiosis with plant roots by recruiting/colonizing of microbial partners (symbionts) to plant rhizosphere. This information justifies the high enrichment of compounds in plant rhizosphere. The dual-specific aspartyl-tRNA (Asn)/glutamyl-tRNA (Gln) amidotransferase subunit A contributes to the plant ability to respond to watering as it participates in attaching the correct amino acid during translation to its cognate tRNA species, while hydrolyzing incorrectly attached amino acid. These two actions reduce the influence of oxidative stress in generating misfolded proteins and in reducing fidelity of translation.

Asbestos mining waste impacts on the sedimentological evolution of the Bécancour chain of lakes, southern Quebec (Canada)

More than a century (1877–2011 CE) of asbestos mining activities in the Thetford Mines region have resulted in the accumulation of gigantic mineral waste piles on the banks of the Bécancour River (southern Quebec, Canada). This river widens downstream from the mining sites to form a chain of lakes, successively: Stater Pond, Trout Lake, Lake William and Lake Joseph. A previous paleolimnological investigation revealed that waste erosion and transport strongly modified and polluted Trout Lake. However, questions remain about the extent of the mining contamination within the Bécancour River Basin and its impacts at other spatial scales. Here, we aimed to address this lack of knowledge by analyzing the sedimentological evolution of Stater Pond and lakes William, Joseph and Bécancour (upstream reference site). Radiometric dating (210Pb, 137Cs, 14C) and analyses of geochemical composition (ICP-AES/ICP-MS), computed tomography, magnetic susceptibility, loss-on-ignition and grain size were performed on sediment cores retrieved at these sites. In contrast to Lake Bécancour, yet similar to Trout Lake, we found that Stater Pond and Lake William have received high mineral matter loads since the creation of the Lake Asbestos Mine during the 1950s. Recent lake sediments at these downstream sites were highly enriched in magnesium, chromium and nickel. Comparison of their geochemical signature with that of sedimentary source materials from within the drainage basin demonstrated that they predominantly originate from mining waste erosion. Because of this issue, Stater Pond and lakes Trout and William are nowadays exposed to very high sediment accumulation rates (up to 1.4 cm yr−1; 0.6 g cm−2 yr−1) and heavy metal enrichment. Evidence for contamination was also found in Lake Joseph, indicating that wastes are transported and deposited over ≥25 km downstream from the mining sites. Our study highlights the high risks and dangers associated with asbestos pollutants in aquatic ecosystems.

Trace metals in indoor dust from a university campus in Northeast India: implication for health risk.

This study reports concentrations of trace metals and the associated health risks in settled dust of different microenvironments of a university in Northeast India. Settled dust samples were collected from the most accessible indoor locations by the students of Tezpur University, a rural-residential university of mid Brahmaputra Valley of Assam. Collected samples were digested in an aqua regia-assisted microwave digestion system and analyzed for iron (Fe), nickel (Ni), zinc (Zn), cadmium (Cd), and lead (Pb) using atomic absorption spectroscopy (AAS). The highest concentration was obtained for Fe with a mean value of 1353.51 ± 123mg/kg. Cadmium showed the lowest concentration with a mean value of 0.75 ± 0.57mg/kg. Cadmium was the highly enriched element followed by Pb, Zn, and Ni. The metals mostly fall in the "extremely high enrichment" category. The study revealed that infiltrated soil or street dust, eroding wall paints, and automotive sources were the main contributing sources of the metals. The calculated Hazard Index (HI) value, 0.39, was lower than the acceptable HI value of 1 indicating no significant non-cancer risk to the students from exposure to these heavy metals at present. The study also found no carcinogenic risk on exposure to the metals present in the indoor dust samples.

Physical characterization of fatty acid supplements with varying enrichments of palmitic and stearic acid by differential scanning calorimetry

Saturated fatty acid supplements commonly fed to dairy cows differ in their fatty acid (FA) profile. Some supplements with very high enrichments of palmitic acid (PA) or stearic acid (SA) have been reported to have low total-tract digestibility. Saturated FA have the potential to form crystalline structures at high purity that may affect digestibility. Differential scanning calorimetry (DSC) is a thermal technique commonly used in materials science to measure the change in heat flow as energy is absorbed or released from a sample during heating, and it was used to characterize a series of experimental and commercial fat supplements. Our hypothesis was that products with very high enrichment of either PA or SA would differ in thermal characteristics compared with those that include moderate levels of a second FA because of the formation of secondary crystalline structures, which may contribute to decreased digestibility. First, replicated runs demonstrated low variation in melting temperature (MT) and enthalpy (coefficient of variation <4%). The effect of physical form was evaluated by comparing an initial thermal cycle to a second, successive thermal cycle after samples had resolidified in the test pan. Melting temperature was slightly increased by 1.3°C by the second cycle compared with the first, but there was no change in enthalpy. Next, supplements with 98% SA, 98% PA, and an SA/PA (44%/55%) blend with undetectable levels of unsaturated FA were compared. Melting temperature of the SA/PA mixture was 61.2°C and similar to the expected MT of PA (62.9°C). However, the MT of the high-purity SA and PA were increased to 73.7°C and 67.8°C, respectively, and enthalpy increased by 12.5% compared with the SA/PA blend. An FA stock highly enriched in SA (>98%) had the highest MT, and one moderately enriched in PA (∼85%) that contained 10.1% unsaturated FA had the lowest enthalpy value of all FA supplements and experimental stocks that were characterized. Differential scanning calorimetry may be useful to screen and design supplements with improved physical properties that may be associated with digestibility.

Pollution and health risk assessment of toxic metal(loid)s in soils under different land use in sulphide mineralized areas

Toxic metal(loid) pollution in sulphide mineralized area has been increasingly concerned. In the present study, the pollution characteristics and the health risk of Hg, As, Tl and other metal(loid)s in soils under different land use, from a rural area impacted by Tl-Hg-rich sulphide mineralization, were assessed using statistical analysis, enrichment factor (EF), potential ecological risk index (RI) and health risk assessment model. The results showed that Tl, Hg and As were highly enriched in the mine area due to the historic sporadic mining activities, and Tl, Hg and Sb were enriched in the peripheral area. Hg and Tl pollution in soils of the mine area impacted by past mining activities posed high ecological risk. High contents and enrichment of Tl and Hg in forest/grass land had a greater impact on the ecological risk in the mine area; whereas Tl and Hg in the grain land and vegetable land dominated the soil ecological risk in the peripheral area. Human health risk assessment indicated that children are more sensitive and vulnerable to toxic metal(loid)s in soils than the adults. Hg, Tl and As have potential non-carcinogenic risk to local children and adults. The HQ levels for different exposure pathways of toxic metal(loid)s were in the order of ingestion > dermal contact > air inhalation for Tl and As, and dermal contract > ingestion > air inhalation for Hg. For carcinogenic risk, all the mean CR values of ingestion in the mine area were higher than 10−4, indicating seriously potential risk. The descending order of ILCR via different pathways was the same as the HQ, for which ingestion was predominant, followed by dermal and air inhalation. The findings may help provide basic knowledge and guidelines for toxic metal(loid) pollution remediation in similar sulphide mineralized areas.

X-ray structural and physical and mechanical studies of uranium-graphite fuel (IGR reactor)

The pulsed graphite reactor (IGR) is one of the oldest research reactors in the world. Since 1968, graphite with impregnated uranium with an enrichment of 90% in 235 uranium has been used as a fuel for the IGR reactor. Current conditions require the end of the use of highly enriched uranium (HEU) as fuel in research reactors, as this contradicts the concept of technologies resistant to the proliferation of nuclear weapons. For this reason, for more than two decades, international measures have been taken to phase out the use of HEU in research reactors by converting these plants to low enriched uranium fuel (LEU). This determines the relevance of research.Material science studies were conducted to determine the properties of non-irradiated fuel of high enrichment, which are important for the transportation of fuel and its subsequent dilution. Research LEU fuel was conducted in order to obtain information about the properties for comparison with the properties of HEU fuel. One of the tasks is to compare the X-ray structural and physicomechanical characteristics of HEU and LEU fuel in order to make a decision on replacing fuel cells while maintaining the energy release, power and stability of the IGR reactor.The paper presents the main results of material science research, the emphasis is on the analysis of x-ray structural and strength characteristics of uranium-graphite fuel. X-ray structural characteristics were determined by x-ray diffraction. Strength characteristics were established by determining the compressive strength.Significant results were obtained on the X-ray structural and physicomechanical characteristics of the high-enrichment IGR fuel material.X-ray structural characteristics (interlayer distance, degree of graphitization, x-ray density, texturing coefficient) and physicomechanical properties (ultimate compressive and deformation strength at maximum load) HEU of the IGR reactor fuel were determined for the first time. Research is important and can be applied in the design of fuel cells of uranium-graphite reactors.

Evaluation of Present Lake Environment from Geochemistry of Bottom Sediment of Hartbeespoort Dam, North-West Province, South Africa

Present Lake Environment of Hartbeespoort Dam was evaluated from Geochemistry of bottom Sediment. Ten (10) bottom sediment samples were collected across the entire Lake. The geochemical composition of the sediment samples was determined using X-ray fluorescence (XRF); trace and major elements determined includes As, Pb, Zn, Cu, Ni, Cr, Fe 2 O 3 , TiO 2 , MnO, CaO and P 2 O 5 . The trace elements concentrations of the sediment were grouped into three zones base on their spatial distribution. The Western zone of the lake shows a remarkable enrichment in Nickel (Ni) and Chromium (Cr) and could be associated with geogenic source. However high enrichment of phosphate (P 2 O 5 ) observed in the same zone could be attributed to anthropogenic source, due to agricultural activities on the catchment of Magalies River. Moderate enrichment of As, Zn, Cu, Cr and Pb was recorded in the central zone and could be ascribed to entrapment by fine-grained organic and Fe-rich clay deposit in the central part of the lake; this was showcased by the strong positive correlation between the trace elements and Fe 2 O 3 . As, Zn, Pb and Cu were highly enriched in the South – Eastern zone and anthropogenic source could be responsible for the enrichment due to the influence of the Crocodile River. The average concentration of As, Pb, Zn, Cu, Ni and Cr in the sediment were evaluated by comparison with the upper continental crust (UCC), Shale standard (Turekian and Wedepohl, 1961) and Sediment quality guidelines (SQG); the result indicates that As, Pb, Zn, Cu and Cr in the study area were above the lowest effect level (LEL) but below the severe affect level (SEL) which shows that the impact on biota is moderate. However, Nickel (Ni) was above the severe effect level and could therefore have severe effect on the aquatic environment. Keywords: aquatic environment, Bottom Sediment, Heavy Metals, Hartbeespoort Dam, X-ray fluorescence DOI : 10.7176/JEES/9-11-10 Publication date: November 30 th 2019

A compact, ultra-high vacuum ion source for isotopically enriching and depositing 28Si thin films.

An ultrahigh vacuum (UHV) compatible Penning ion source for growing pure, highly enriched 28Si epitaxial thin films is presented. Enriched 28Si is a critical material for quantum information due to the elimination of nuclear spins. In some cases, the material must be grown by low temperature molecular beam epitaxy, e.g., scanning tunneling microscopy hydrogen lithography-based devices. Traditional high-purity physical vapor methods typically deliver a very small fraction of source material onto the target substrate, making the cost for use with highly enriched source materials very high. Thus, directed beam sources provide an efficient alternative. This UHV Penning source uses all metal or ceramic parts and a removable electromagnet to allow bake-out. The source gas is a commercial (natural isotope abundance) silane gas (SiH4), an inexpensive source material. High enrichment levels up to 99.999 87% (8.32 × 10-7 mol/mol 29Si) and high chemical purity of 99.965% are shown without postprocessing. We present and discuss the discharge properties of this new source, the ion mass spectrum when coupled to our mass filter, and the secondary ion mass spectroscopy of the grown films.

Measurement precision and accuracy of high artificial enrichment 15 N and 13 C tracer samples.

Oversaturation of the Faraday cup amplifiers of isotope ratio mass spectrometers when using tracers that are highly enriched in heavier isotopes (up to 99.9%) remains a major bottleneck to obtaining high-precision measurements. The memory effect plays a key role in reducing tracer sample measurement precision and accuracy. Several sample preparation approaches are known to reduce memory effects and to improve tracer sample measurement precision. However, the potential benefits when using very high enrichment tracer samples (> +1000 mUr) have not been tested. In this study, we test how specific sample positioning for measurements and frequent use of natural isotope abundance reference materials within the sequence affects the precision and accuracy of isotopic ratio analyses when using a Flash elemental analyser coupled to a Deltaplus XP isotope ratio mass spectrometer for very high enrichment (> +22000 mUr) 15 N tracer sample measurements. Furthermore, we investigate if tracer sample dilution with natural isotope abundance materials reduces memory effects and increases measurement precision and accuracy when measurements of high-enrichment 15 N and 13 C biomass tracer samples are conducted. Frequent use of natural isotope abundance materials and specific positioning increased 15 N tracer sample precision, but it had a negative effect on the precision of quality control substances. 15 N and 13 C tracer sample dilution improved measurement precision by a maximum of ±0.9 mUr; however, a strong linear relationship between the original and the calculated φ values was found. Highly enriched 15 N tracer samples caused a maximum memory effect of 0.11%. High levels of 15 N abundance within the samples affected measurement accuracy by an average of 6.7%. We conclude that highly enriched tracer samples do not require dilution before analysis. Tracer sample precision can be improved by using a specific measurement order of expected isotope abundance and by the frequent use of natural abundance reference materials.

In Vivo Trapping of Proteins Interacting with the Chloroplast CLPC1 Chaperone: Potential Substrates and Adaptors.

The chloroplast stromal CLP protease system is essential for growth and development. It consists of a proteolytic CLP core complex that likely dynamically interacts with oligomeric rings of CLPC1, CLPC2, or CLPD AAA+ chaperones. These ATP-dependent chaperones are predicted to bind and unfold CLP protease substrates, frequently aided by adaptors (recognins), and feed them into the proteolytic CLP core for degradation. To identify new substrates and possibly also new adaptors for the chloroplast CLP protease system, we generated an in vivo CLPC1 substrate trap with a C-terminal STREPII affinity tag in Arabidopsis thaliana by mutating critical glutamate residues (E374A and E718A) in the two Walker B domains of CLPC1 required for the hydrolysis of ATP (CLPC1-TRAP). On the basis of homology to nonplant CLPB/C chaperones, it is predicted that interacting substrates are unable to be released; that is, they are trapped. When expressed in the wild type, this CLPC1-TRAP induced a dominant visible phenotype, whereas no viable mutants that express CLPC1-TRAP in the clpc1-1 null mutant could be recovered. Affinity purification of the CLPC1-TRAP resulted in a dozen proteins highly enriched compared with affinity-purified CLPC1 with a C-terminal STREPII affinity tag (CLPC1-WT). These enriched proteins likely represent CLP protease substrates or new adaptors. Several of these trapped proteins overaccumulated in clp mutants or were found as interactors for the adaptor CLPS1, supporting their functional relationship to CLP function. Importantly, the affinity purification of this CLPC1-TRAP also showed high enrichment of all CLPP, CLPR, and CLPT subunits, indicating the stabilization of the CLPC to CLP core interaction and providing direct support for their physical and functional interaction.

MSX2 Initiates and Accelerates Mesenchymal Stem/Stromal Cell Specification of hPSCs by Regulating TWIST1 and PRAME

SummaryThe gap in knowledge of the molecular mechanisms underlying differentiation of human pluripotent stem cells (hPSCs) into the mesenchymal cell lineages hinders the application of hPSCs for cell-based therapy. In this study, we identified a critical role of muscle segment homeobox 2 (MSX2) in initiating and accelerating the molecular program that leads to mesenchymal stem/stromal cell (MSC) differentiation from hPSCs. Genetic deletion of MSX2 impairs hPSC differentiation into MSCs. When aided with a cocktail of soluble molecules, MSX2 ectopic expression induces hPSCs to form nearly homogeneous and fully functional MSCs. Mechanistically, MSX2 induces hPSCs to form neural crest cells, an intermediate cell stage preceding MSCs, and further differentiation by regulating TWIST1 and PRAME. Furthermore, we found that MSX2 is also required for hPSC differentiation into MSCs through mesendoderm and trophoblast. Our findings provide novel mechanistic insights into lineage specification of hPSCs to MSCs and effective strategies for applications of stem cells for regenerative medicine.