Intermediate Precursor Research Articles

A year-round observation of δ13C of dicarboxylic acids and related compounds in fine aerosols: Implications from Central European background site

Isotopic analysis of specific compounds in aerosols can be a useful tool when studying atmospheric processes. Here, we present the results of stable carbon isotope ratio (δ13C) measurements performed on a one-year set (n = 96, Sep. 2013–Aug. 2014) of dicarboxylic acids and related compounds in PM1 at a rural Central European background site, Košetice (Czech Republic).The most 13C enriched acid was oxalic (C2, annual average = −16.6 ± 5.0‰) followed by malonic (C3, avg. = −19.9 ± 6.6‰) and succinic (C4, avg. = −21.3 ± 4.6‰) acids. Thus, δ13C values decreased with an increase in carbon numbers. Azelaic acid (C9, avg. = −27.2 ± 3.6‰) was found to be the least 13C enriched.A comparison of δ13C of dicarboxylic acids from other background sites, especially in Asia, shows similar values to those from the European site. This comparison also showed that C2 is more 13C enriched at background sites than at urban ones. In general, we did not observe significant seasonal differences in δ13C values of dicarboxylic acids at the Central European station. We observed statistically significant differences (p value < 0.05) between winter and summer δ13C values solely for C4, glyoxylic acid (ωC2), glutaric acid (C5) and suberic acid (C8).The only significant correlations between δ13C of C2 and δ13C of C3 were found in spring and summer, suggesting that the oxidation of C3 to C2 is significant in these months with a strong contribution from biogenic aerosols. The strongest season-independent annual correlation was observed in δ13C values between C2 and C4, the two dominant dicarboxylic acids. Therefore, C4 appears to be the main intermediate precursor of C2 throughout the whole year.

Role of depositional environment on clay coat distribution in deeply buried turbidite sandstones: Insights from the Agat field, Norwegian North Sea

The preservation of reservoir quality in deeply buried sandstones largely depends on the presence of grain-coating clays that can inhibit quartz overgrowth and cementation. These grain-coating clays are the focus of today's hydrocarbon exploration as they enable new oil and gas discoveries in sedimentary basins. However, the origin and distribution of these clays in turbidites are poorly documented in scientific literature. Our study addresses this knowledge gap by investigating the mechanisms and parameters governing the clay coat development in turbidite sandstones, with a focus on the Agat Formation (Fm) in the Norwegian North Sea. Petrographic observations, scanning electron microscopy, and X-ray diffraction analyses were used to identify the origin of clay minerals and their distribution, as well as to understand the diagenetic evolution of the sandstone and its impact on reservoir quality. Based on the sedimentary facies description, the Agat Fm comprises four principal members deposited in various depositional environments, ranging from distal lobe fringe to amalgamated proximal lobes and weakly confined channels. Chlorite and kaolinite are the main authigenic clay minerals in these sandstones, associated with a variable amount of inherited detrital clays consisting in Fe-bearing kaolinite and mixed-layer minerals composed of illite and hydroxyl-interlayered clay minerals formed in acidic soil environments. Well-developed chlorite coats are associated with the highest reservoir quality (φ > 10%), while discontinuous chlorite coats are linked to extensive quartz cementation and poor reservoir quality (φ < 5%). Samples with abundant pore-filling chlorite also exhibit poor reservoir quality (φ < 7%). Proximal lobe deposits and weakly confined channels show well-developed chlorite coats, whereas discontinuous chlorite coats are mainly found in proximal lobe deposits associated with high velocity escaping fluids during dewatering. Pore-filling chlorites are typically present in distal lobe fringes and levee deposits. Chlorite in the Agat Fm is mainly derived from the replacement of inherited detrital clays via an intermediate berthierine precursor forming during early diagenesis. The dissolution of Fe-rich grains such as biotite and ferric detrital clays under reducing conditions governed the kinetics of berthierine/chlorite growth. The late diagenesis is characterized by extensive feldspar dissolution in a closed diagenetic system, leading to the precipitation of kaolinite and quartz cement. The presence of chlorite coatings around detrital grains preserved the porosity from extensive quartz cementation during deep burial, highlighting the role of chlorite in maintaining the quality of deeply buried turbidite reservoirs.

Engineering acetyl-CoA metabolism to enhance stress tolerance of yeast by regulating membrane functionality

Zygosaccharomyces rouxii has excellent fermentation performance and good tolerance to osmotic stress. Acetyl-CoA is a crucial intermediate precursor in the central carbon metabolic pathway of yeast. This study investigated the effect of engineering acetyl-CoA metabolism on the membrane functionality and stress tolerance of yeast. Firstly, exogenous supplementation of acetyl-CoA improved the biomass and the ability of unsaturated fatty acid synthesis of Z. rouxii under salt stress. Q-PCR results suggested that the gene ACSS (coding acetyl-CoA synthetase) was significantly up-expressed. Subsequently, the gene ACSS from Z. rouxii was transformed and heterologously expressed in S. cerevisiae. The recombinant cells exhibited better multiple stress (salt, acid, heat, and cold) tolerance, higher fatty acid contents, membrane integrity, and fluidity. Our findings may provide a suitable means to enhance the stress tolerance and fermentation efficiency of yeast under harsh fermentation environments.

Tailoring the microstructure and solid electrolyte interface of hard carbon to realize high-initial-coulombic-efficiency and high-rate sodium storage

As the most promising anode material for sodium-ion batteries (SIBs), hard carbon still suffers the drawbacks of low initial Coulombic efficiency (ICE) and poor rate performance, which restrict its practical application. How to tailor-design its microstructure and solid electrolyte interface (SEI) is crucial to address these challenges. Herein, a novel hard carbon material was fabricated by pyrolyzing the intermediate carbon precursor with crosslinked network structure generated through the interaction between phenolic resin and lignin. Its microstructure, consisting of the defect sites and interlayer distance, has been tailored and optimized through adjusting the carbonizing conditions. By employing ether electrolytes, the generated thinner SEI film endows the hard carbon electrode with lower interface impedance and faster Na+ transport kinetics. Benefiting from the tailored microstructure and SEI film, the obtained hard carbon material shows a higher ICE of 87%, a remarkable reversible capacity of 338 mA h g−1 after 500 cycles and superior rate performance of 268 mA h g−1 at 1C over 200 cycles (205 mA h g−1 at 6 C), much higher than the recently reported work. This work provides an effective strategy to develop the hard carbon anode with high ICE and high-rate sodium storage for practical SIBs.

The ventricular-subventricular, subgranular and subcallosal zones: three niches of neural stem cells in the postnatal brain

In the postnatal brain, three regions show high mitotic activity. These brain areas are neurogenic niches, and each niche harbors a microenvironment favorable for the proliferation and differentiation of neural stem cells. These multipotential cells maintain the capacity to self-renew and generate intermediate precursors that will differentiate into neuronal and glial lineages (astrocytes and oligodendrocytes). The most well-studied niches are the ventricular-subventricular zone (V-SVZ) of the lateral ventricles, the subgranular zone (SGZ) of the dentate gyrus in the hippocampus, and the subcallosal zone (SCZ), located in the limit between the corpus callosum and the hippocampal formation. The discovery of these three neurogenic niches has gained much interest in the field because they may be a therapeutic alternative in neural regeneration and neurodegenerative disorders. In this review, we describe in brief all these regions and explain their potential impact on solving some neurological conditions.

A differentiation roadmap of murine placentation at single-cell resolution

The placenta is one of the most important yet least understood organs. Due to the limitations of conventional research approaches, we are still far from a comprehensive understanding of mouse placentation, especially regarding the differentiation of trophoblast lineages at the early developmental stage. To decipher cell compositions and developmental processes, we systematically profile the single-cell transcriptomes of trophoblast cells from extraembryonic tissues (embryonic day 7.5 (E7.5) and E8.5) and placentae (E9.5–E14.5) at one-day intervals. We identify distinct trophoblast cell types during mouse placentation, including unreported progenitor cells and intermediate precursor cells. An updated differentiation roadmap of mouse trophoblast lineages is presented following systematic transcriptome analyses. Based on transcriptomic regulatory network inference, we specify transcription factors responsible for the regulation of dynamic developmental processes during lineage diversification. We map lineage differentiation trajectories and find that sinusoid trophoblast giant cells arise from the subpopulation of ectoplacental cone cells. We provide a comprehensive single-cell data resource to shed light on future mechanistic studies of the gene regulatory networks governing hemochorial placentation.

New Preparative Approach to Purer Technetium-99 Samples-Tetramethylammonium Pertechnetate: Deep Understanding and Application of Crystal Structure, Solubility, and Its Conversion to Technetium Zero Valent Matrix.

99Tc is one of the predominant fission products of 235U and an important component of nuclear industry wastes. The long half-life and specific activity of 99Tc (212,000 y, 0.63 GBq g-1) makes Tc a hazardous material. Two principal ways were proposed for its disposal, namely, long-term storage and transmutation. Conversion to metal-like technetium matrices is highly desirable for both cases and for the second one the reasonably high Tc purity was important too. Tetramethylammonium pertechnetate (TMAP) was proposed here as a prospective precursor for matrix manufacture. It provided with very high decontamination factors from actinides (that is imperative for transmutation) by means of recrystallisation and it was based on the precise data on TMAP solubility and thermodynamics accomplished in the temperature range of 3-68 °C. The structure of solid pertechnetates were re-estimated with precise X-ray structure solution and compared to its Re and Cl analogues and tetrabutylammonium analogue as well. Differential thermal and evolved gas analysis in a flow of Ar-5% H2 gas mixture showed that the major products of thermolysis were pure metallic technetium in solid matrix, trimethylammonium, carbon dioxide, and water in gas phase. High decontamination factors have been achieved when TMAP was used as an intermediate precursor for Tc.

Olig1/2-Expressing Intermediate Lineage Progenitors Are Predisposed to PTEN/p53-Loss-Induced Gliomagenesis and Harbor Specific Therapeutic Vulnerabilities.

Multiple progenitor-state mutagenesis reveal that Olig1/2-expressing intermediate precursors are highly susceptible to PTEN/p53-loss-mediated transformation and impart differential drug sensitivity, indicating tumor-initiating cell states and genetic drivers dictate glioma phenotypes and drug responses. See related commentary by Zamler and Hu, p. 807.

Semisynthetic Amides of Amphotericin B and Nystatin A1: A Comparative Study of In Vitro Activity/Toxicity Ratio in Relation to Selectivity to Ergosterol Membranes.

Polyene antifungal amphotericin B (AmB) has been used for over 60 years, and remains a valuable clinical treatment for systemic mycoses, due to its broad antifungal activity and low rate of emerging resistance. There is no consensus on how exactly it kills fungal cells but it is certain that AmB and the closely-related nystatin (Nys) can form pores in membranes and have a higher affinity towards ergosterol than cholesterol. Notably, the high nephro- and hemolytic toxicity of polyenes and their low solubility in water have led to efforts to improve their properties. We present the synthesis of new amphotericin and nystatin amides and a comparative study of the effects of identical modifications of AmB and Nys on the relationship between their structure and properties. Generally, increases in the activity/toxicity ratio were in good agreement with increasing ratios of selective permeabilization of ergosterol- vs. cholesterol-containing membranes. We also show that the introduced modifications had an effect on the sensitivity of mutant yeast strains with alterations in ergosterol biosynthesis to the studied polyenes, suggesting a varying affinity towards intermediate ergosterol precursors. Three new water-soluble nystatin derivatives showed a prominent improvement in safety and were selected as promising candidates for drug development.

Dynamics of the fcc-to-bcc phase transition in single-crystalline PdCu alloy nanoparticles

Two most common crystal structures in metals and metal alloys are body-centered cubic (bcc) and face-centered cubic (fcc) structures. The phase transitions between these structures play an important role in the production of durable and functional metal alloys. Despite their technological significance, the details of such phase transitions are largely unknown because of the challenges associated with probing these processes. Here, we describe the nanoscopic details of an fcc-to-bcc phase transition in PdCu alloy nanoparticles (NPs) using in situ heating transmission electron microscopy. Our observations reveal that the bcc phase always nucleates from the edge of the fcc NP, and then propagates across the NP by forming a distinct few-atoms-wide coherent bcc–fcc interface. Notably, this interface acts as an intermediate precursor phase for the nucleation of a bcc phase. These insights into the fcc-to-bcc phase transition are important for understanding solid − solid phase transitions in general and can help to tailor the functional properties of metals and their alloys.

Dissecting Trypanosoma brucei RRP44 function in the maturation of segmented ribosomal RNA using a regulated genetic complementation system

Trypanosoma brucei belongs to a group of protozoans presenting fragmented large subunit rRNA. Its LSU rRNA equivalent to the 25S/28S rRNA of other eukaryotes is split into six fragments, requiring additional processing for removal of the extra spacer sequences. We have used a genetic complementation strategy to further investigate the T. brucei RRP44 nuclease in pre-rRNA maturation. TbRRP44 contains both a PIN and a RNB domain whose homologues are found in association with the exosome complex. We found that the exonucleolytic activity of the RNB domain as well as the physical presence of the PIN domain are essential for TbRRP44 function, while a catalytic site mutation in the PIN domain has no detectable effect on cell growth. A new endonucleolytic cleavage site in ITS1 was identified. In addition to the 5.8S rRNA 3'-end maturation, TbRRP44 is required for degradation of the excised 5'-ETS and for removal of part of ITS1 during maturation of the 18S rRNA 3'-end. TbRRP44 deficiency leads to accumulation of many LSU intermediate precursors, most of them not detected in control cells. TbRRP44 is also required for U3 snoRNA and spliced leader processing, indicating that TbRRP44 may have a wide role in RNA processing in T. brucei.

Fungicide-inspired precursors of π-allylpalladium intermediates for palladium-catalyzed decarboxylative cycloadditions.

Inspired by a fungicide, we designed 5-vinyloxazolidine-2,4-diones as new precursors of π-allylpalladium zwitterionic intermediates and developed palladium-catalyzed asymmetric (5 + 3) cycloaddition with azomethine imines and (3 + 2) cycloaddition with 1,1-dicyanoalkenes. Both reactions proceeded smoothly under mild reaction conditions to produce various chiral heterocyclic compounds in high yields with excellent enantioselectivities. These results revealed that 5-vinyloxazolidine-2,4-diones were a type of suitable precursor for palladium catalysis and will find extensive applications in Pd-catalyzed reactions such as cycloaddition and allylic alkylation.

Bicyclic N-dihalocyclopropylamide derivatives as precursors of nitrogen-containing fused polycyclic systems.

Examples of carbon-carbon bond-forming cyclisation reactions, involving allyl cations generated by the thermal ring-opening of halocyclopropanes, have been scarcely reported. In this contribution, we are describing the results of a study conducted with N-dihalocyclopropylamide substrates, designed as precursors of cyclic iminium intermediates that were aimed at participating in intramolecular reactions with electron-rich aromatic groups. Competitive side-reactions were identified, and access to the desired polycyclic products was carefully evaluated. The results were found to be strongly dependent on the substitution pattern of the nucleophilic aromatic moieties, as well as on the sizes of the rings of the target products. In spite of the rather moderate yields generally obtained, this approach represents a particularly short and inexpensive route to various interesting nitrogen-containing polycyclic systems, namely benzoindolizidine, benzoquinolizidine, piperidinobenzoazepane and azepanoisoquinoline compounds.

A lamellar-ordered poly[bi(3,4-ethylenedioxythiophene)-alt-thienyl] for efficient tuning of thermopower without degenerated conductivity

Modulating the structural order of conjugated polymers has emerged as a significant approach to enhance the organic thermoelectric performance. Among these materials, poly(3,4-ethylenedioxythiophene) is considered a promising candidate due to its high conductivity. However, its low thermopower remains a major obstacle to further improve its performance as an organic thermoelectric material. To address this issue, a series of thiophene derivatives with high rigidity and containing dioxyethylene groups were synthesized, and polymer films were prepared through a simple and mild in-situ polymerization method. The polymer molecule containing a thiophene block, named poly[bi(3,4-ethylenedioxy)-alt-thienyl] , exhibits significant self-rigidification due to non-covalent interactions between oxygen and sulfur atoms, resulting in highly ordered assembly. By adding thiophene and thieno[3,2-b]thiophene structures to the intermediate precursor bi(3,4-ethylenedioxy), the 3,4-ethylenedioxy content in the polymer molecule is altered, leading to an almost four-fold increase in the thermopower of the thin film polymer and achieving a maximum thermopower of around 26 μV·K-1. Although poly[bi(3,4-ethylenedioxy)-alt-thienyl] shows a significant increase in thermopower compared to poly[bi(3,4-ethylenedioxy)], the thin film conductivity exhibits a nearly imperceptible decreasing trend due to its highly ordered microstructure. This work highlights the potential to control the aggregation state of polymer molecules and achieve an approximate decoupling between the conductivity and thermopower of thermoelectric materials by rationally designing polymer molecules.

Molecular dynamics simulations of reactive neutral chemistry in an argon‐methane plasma

AbstractMolecular dynamics simulations are performed to study the reactions in the volume of a low‐pressure methane plasma diluted in argon. In the first step, a 1D fluid model is used to determine the initial molar fractions of initial species. The obtained composition thus becomes the input for the reactive molecular dynamics simulations. The study is carried out at 300, 400, 500, and 1000 K. Increasing the temperature increases the range of different molecules formed. The time evolution of C2H and CH3 and the different reaction pathways leading to larger molecules show that C2H is the main precursor and CH3 is the main intermediate precursor for the formation of large molecules.

Hydrogen Production and Carbon Capture by Gas-Phase Methane Pyrolysis: A Feasibility Study.

Using natural gas and sustainable biogas as feed, high-temperature pyrolysis represents a potential technology for large-scale hydrogen production and simultaneous carbon capture. Further utilization of solid carbon accruing during the process (i. e., in battery industry or for metallurgy) increases the process's economic chances. This study demonstrated the feasibility of gas-phase methane pyrolysis for hydrogen production and carbon capture in an electrically heated high-temperature reactor operated between 1200 and 1600 °C under industrially relevant conditions. While hydrogen addition controlled methane conversion and suppressed the formation of undesired byproducts, an increasing residence time decreased the amount of byproducts and benefited high hydrogen yields. A temperature of 1400 °C ensured almost full methane conversion, moderate byproduct formation, and high hydrogen yield. A reaction flow analysis of the gas-phase kinetics revealed acetylene, ethylene, and benzene as the main intermediate products and precursors of carbon formation.

Physicochemical and cytological properties of silicon-doping octacalcium phosphate

• Si was successfully doped in the metastable OCP crystals by a precipitation method. • Si doping led to the contraction of OCP structure with smaller lattice parameters. • Si doping preferred forming a cluster-like hierarchical structure of OCP crystals. • Si-OCP notably promoted the proliferation and osteogenic differentiation of BMSCs. • Si-OCPs enhanced the responses of BMSCs by ionic release and mineral deposits. Silicon was successfully doped into an intermediate precursor of biological apatite, octacalcium phosphate (OCP), accompanied with a lattice contraction. Si-doped OCP significantly enhanced the proliferation and osteogenic capacities of bone marrow mesenchymal stem cells by the synergistical effect of bioactive ions release and mineral deposits, providing a potential bone substitute.

Intermediate-phase engineering via dimethylammonium cation additive for stable perovskite solar cells.

Achieving the long-term stability of perovskite solar cells is arguably the most important challenge required to enable widespread commercialization. Understanding the perovskite crystallization process and its direct impact on device stability is critical to achieving this goal. The commonly employed dimethyl-formamide/dimethyl-sulfoxide solvent preparation method results in a poor crystal quality and microstructure of the polycrystalline perovskite films. In this work, we introduce a high-temperature dimethyl-sulfoxide-free processing method that utilizes dimethylammonium chloride as an additive to control the perovskite intermediate precursor phases. By controlling the crystallization sequence, we tune the grain size, texturing, orientation (corner-up versus face-up) and crystallinity of the formamidinium (FA)/caesium (FA)yCs1-yPb(IxBr1-x)3 perovskite system. A population of encapsulated devices showed improved operational stability, with a median T80 lifetime (the time over which the device power conversion efficiency decreases to 80% of its initial value) for the steady-state power conversion efficiency of 1,190 hours, and a champion device showed a T80 of 1,410 hours, under simulated sunlight at 65 °C in air, under open-circuit conditions. This work highlights the importance of material quality in achieving the long-term operational stability of perovskite optoelectronic devices.

Microwave-assisted controllable synthesis of 2D and 1D Eu3+-Y2O3 micro/nanoparticles and their photoluminescence properties

Rare earth elements doped yttria is a group of important functional materials used in various applications. In this work, Eu3+-Y2O3 particles with different morphology including nanoplates, porous nanoplates, quasi-triangular microprisms, hexagonal microprisms, microcylinders and nanorods have been synthesized by a facile two-step method without using any template or surfactant. The mixture of Eu(NO3)3, Y(NO3)3 and NaOH solution were irritated by microwave for 10 ​min to form the intermediate hybrid precursors, and the final Eu3+-Y2O3 were obtained by calcining the intermediate powder at 600 ​°C for 3 ​h. The morphologies, microstructure, crystal phase and composition of the samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermal analysis (TG–DSC) in detail. The results show that the shapes can be controlled effectively from two dimension (2D) to one dimension (1D), and the size can be adjusted from microscale to nanoscale by changing the ratio of OH−/Re3+ only. The photoluminescence (PL) intensity and decay time of the particles vary significantly with the morphologies.

Concave Engineering of Hollow Carbon Spheres toward Advanced Anode Material for Sodium/Potassium‐Ion Batteries

AbstractConcave carbon spheres have attracted enormous interest due to their unique physicochemical properties. However, the precise synthetic methodology is still scarce, because it is a great challenge to control the dynamic and nonselective deformation process of the intermediate precursor. Herein, a series of hollow carbon spheres with tunable concavity are prepared by a facile and efficient polymerization‐buckling strategy. Both the concave degree and concave density of these hollow carbon spheres can be precisely regulated. Finite element analysis indicates the unique concave morphology can relieve the stress accumulation during the cycling process, endowing concave hollow carbon spheres with superior potassium and sodium storage performance. As the anode for potassium‐ion batteries, stable capacity of 104.9 mAh g−1 can be achieved at 4 A g−1 after 1350 cycles. For sodium‐ion batteries, reversible capacity of 116.4 mAh g−1 after 2700 cycles can be enabled at 2 A g−1. This work may open a new avenue for the design of concave hollow carbon materials and promote their practical application in energy storage field.