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Strategies to Stabilize Inductively Heating Fe Nanoparticles for Catalyzing the CO<sub>2</sub> Conversion to Syngas via Reverse Water Gas Shift
No full textFe-based solid materials are studied here as self-heating catalysts that can convert CO2 into CO via a reverse water-gas shift (RWGS), a key reaction for carbon utilization. We describe the scalable synthesis of Fe nanoparticles capable to be inductively heated to 500-800 °C while catalytically active in RWGS. For iron species to develop a dual function as heaters and catalysts, the formation of nonferromagnetic Fe phases under reaction conditions must be avoided. Such phases lead to rapid cooldown of the reactor and the deactivation of the catalyst. Here, the stabilization of the self-heating RWGS catalysts was achieved by adjusting the nanoparticle properties via mesoporous supports, the addition of Co as a promoter, and redox pretreatments. Through extensive operando and in situ characterization, we show the dynamics of self-heating catalytic nanoparticles under reactive atmospheres, as those verified during RWGS reaction and pave the way for other applications in energy-intensive catalytic processes
The very faint X-ray transient Swift J174610-290018 at the Galactic center
No full textContext. Very faint X-ray transients (VFXTs) are a class of X-ray binary systems that exhibit occasional outbursts with peak X-ray luminosities (L-X less than or similar to 10(36) erg s(-1)) much lower than those of typical X-ray transients. On 22 February 2024, during its daily Galactic center monitoring, Swift-XRT detected a VFXT 7 arcmin from Sgr A*, dubbing it Swift J174610-290018. Aims. We aim to characterize the outburst that occurred in 2024 and a second, distinct outburst in 2025 to understand the nature and accretion flow properties of this new VFXT. Methods. Swift-XRT light curves were used to constrain the duration of the two events. We carried out X-ray spectral analysis, exploiting XMM-Newton and NuSTAR data. We used Chandra and XMM-Newton observations from the last 25 years to constrain the quiescent luminosity of the source and to compare the two most recent outbursts with previous detections of the source. Results. During the 2024 outburst, which lasted about 50 days, the source reached a luminosity in the 2-10 keV band (L2-10) of similar or equal to 1.2 x 10(35) erg s(-1) (assuming it is located at the Galactic center, i.e., at a distance of 8.2 kpc). The 2025 outburst is shorter (about 5 days) and reached L2-10 similar or equal to 9 x 10(34) erg s(-1). The spectral features of the source include an excess at 6.5-7 keV, which can be associated either with a single reflection line or with the ionized Fe XXV and XXVI lines. The same source was identified in both the XMM-Newton and Chandra catalogs of point sources (known as 4XMM J174610.7-290020 and 2CXO J174610.7-290019). During previous detections the source displayed luminosity levels ranging from L2-10 similar or equal to 2 x 10(32) to L2-10 similar or equal to 3 x 10(33) erg s(-1) between 2000 and 2010. Moreover, it exhibited a potential type I X-ray burst in 2004. Conclusions. The analysis of the outbursts and the potential type I burst strongly suggests that the VFXT Swift J174610-290018 is a neutron star low-mass X-ray binary. The source can be described as being an accretion disk corona source (as has been recently proposed by an XRISM/Xtend analysis). This scenario explains the overall low luminosity of this transient and the peculiar iron lines in the spectrum
High-Resolution Infrared Spectroscopy and ASAP Analysis of Cyclopentadiene: The Vibrational Modes below 860 cm-1 and the ν21 Mode at 961 cm-1
No full textThe spectroscopic fingerprints of vibrationally excited states of astronomical molecules are interesting for multiple reasons. They are excellent temperature probes of the corresponding astronomical regions and are thought to be the origin of many unknown lines in astronomical survey spectra. Rovibrational spectra provide accurate vibrational energies and can guide subsequent pure rotational studies. The Automated Spectral Assignment Procedure (ASAP) greatly simplifies the rovibrational analysis when the rotational spectrum of either the upper or lower vibrational state is known with a high degree of accuracy (e.g., from a rotational analysis). Here, we present a new implementation of ASAP for the analysis of cyclopentadiene, a cyclic pure hydrocarbon that has already been detected astronomically toward the cold core of the Taurus Molecular Cloud. Using the synchrotron radiation extracted by the AILES beamline of the SOLEIL facility, we recorded mid- and far-infrared high-resolution spectra of cyclopentadiene. We analyzed the rovibrational spectrum of the nu 21 fundamental (961 cm-1) with ASAP and used ASAP2 to determine the vibrational energies of the eight vibrational modes below 860 cm-1. ASAP2 is an extension of ASAP for rovibrational bands where the rotational structures of the lower and upper states are known with high accuracy, leaving only the vibrational band center to be determined. The presented rovibrational fingerprints agree with the results from pure rotational spectroscopy, demonstrating the efficiency and reliability of our new ASAP implementation
Residual Chemical Shift Anisotropies in the Structure Determination of Small Molecules
No full textThe determination of the relative and absolute configuration of natural compounds is a very challenging task. Among other anisotropic NMR parameters, residual chemical shift anisotropy (RCSA) induced by anisotropic media is an invaluable tool to determine relative configurations of natural and synthetic organic molecules in solution. This review introduces various RCSA-based methodologies for the structural elucidation of natural products. The current availability of alignment media in organic solvents for RCSA measurements is also discussed as are applications of RCSAs for structural analysis of various natural products
Trends in Biochemical Sciences
No full textNitrogenases are the only enzymes that reduce dinitrogen to ammonia, a reaction essential for all life on Earth.Recent work demonstrates that nitrogen fixation?like (Nfl) enzymes have extensive functions beyond nitrogen fixation, including reducing C=C double bonds of tetrapyrroles and breaking C?S bonds to support bacterial sulfur scavenging.All nitrogenase-like enzymes consist of a reductase component containing an [Fe4S4]-cluster, and a catalytic component containing diverse metalloclusters.The catalytic components of the nitrogenase-like enzymes contain simpler FeS-clusters than nitrogenases, including [Fe4S4]-clusters and nitrogenase cluster precursors
The evolution of gene regulation in mammalian cerebellum development
No full textGene regulatory changes are considered major drivers of evolutionary innovations, including the cerebellum’s expansion during human evolution, yet they remain largely unexplored. In this study, we combined single-nucleus measurements of gene expression and chromatin accessibility from six mammals (human, bonobo, macaque, marmoset, mouse, and opossum) to uncover conserved and diverged regulatory networks in cerebellum development. We identified core regulators of cell identity and developed sequence-based models that revealed conserved regulatory codes. By predicting chromatin accessibility across 240 mammalian species, we reconstructed the evolutionary histories of human cis-regulatory elements, identifying sets associated with positive selection and gene expression changes, including the recent gain of THRB expression in cerebellar progenitor cells. Collectively, our work reveals the shared and mammalian lineage-specific regulatory programs governing cerebellum development
