Fe nuclear resonance vibrational spectroscopic studies of tetranuclear iron clusters bearing terminal iron(iii)-oxido/hydroxido moieties.

Fe nuclear resonance vibrational spectroscopy (NRVS) has been applied to study a series of tetranuclear iron ([Fe]) clusters based on a multidentate ligand platform (L) anchored by a 1,3,5-triarylbenzene linker and pyrazolate or (butylamino)pyrazolate ligand (PzNH Bu). These clusters bear a terminal Fe(iii)-O/OH moiety at the apical position and three additional iron centers forming the basal positions. The three basal irons are connected with the apical iron center a μ-oxido ligand.

Multicaloric Cryocooling Using Heavy Rare-Earth Free La(Fe,Si)-Based Compounds.

The transition toward a carbon-neutral society based on renewable energies goes hand in hand with the availability of energy-efficient technologies. Magnetocaloric cooling is a very promising refrigeration technology to fulfill this role regarding cryogenic gas liquefaction. However, the current reliance on highly resource critical, heavy rare-earth-based compounds as magnetocaloric material makes global usage unsustainable.

Robust magnetism and crystal structure in Dirac semimetal EuMnBiunder high pressure.

Dirac materials offer exciting opportunities to explore low-energy carrier dynamics and novel physical phenomena, especially their interaction with magnetism. In this context, this work focuses on studies of pressure control on the magnetic state of EuMnBi, a representative magnetic Dirac semimetal, through time-domain synchrotron Mössbauer spectroscopy inEu. Contrary to the previous report that the antiferromagnetic order is suppressed by pressure above 4 GPa, we have observed robust magnetic order up to 33.

Strong enhancement of magnetic ordering temperature and structural/valence transitions in EuPdS under high pressure.

We present a comprehensive study of the inhomogeneous mixed-valence compound, EuPdS, by electrical transport, X-ray diffraction, time-domain Eu synchrotron Mössbauer spectroscopy, and X-ray absorption spectroscopy measurements under high pressure. Electrical transport measurements show that the antiferromagnetic ordering temperature, , increases rapidly from 2.8 K at ambient pressure to 23.

Melting and defect transitions in FeO up to pressures of Earth's core-mantle boundary.

The high-pressure melting curve of FeO controls key aspects of Earth's deep interior and the evolution of rocky planets more broadly. However, existing melting studies on wüstite were conducted across a limited pressure range and exhibit substantial disagreement. Here we use an in-situ dual-technique approach that combines a suite of >1000 x-ray diffraction and synchrotron Mössbauer measurements to report the melting curve for FeO wüstite to pressures of Earth's lowermost mantle.

Reactive high-spin iron(IV)-oxo sites through dioxygen activation in a metal-organic framework.

In nature, nonheme iron enzymes use dioxygen to generate high-spin iron(IV)=O species for a variety of oxygenation reactions. Although synthetic chemists have long sought to mimic this reactivity, the enzyme-like activation of O to form high-spin iron(IV) = O species remains an unrealized goal. Here, we report a metal-organic framework featuring iron(II) sites with a local structure similar to that in α-ketoglutarate-dependent dioxygenases.

A novel integrated time-resolved array avalanche photodiode detection system for nuclear resonant scattering measurements.

The nuclear resonant scattering (NRS) experiment requires photon-counting detectors with high time resolution, short dead time, large dynamic range, low noise, and large detection area. An 8-channel avalanche photodiode (APD) array detector system with high integrity, flexibility, and reliability has been developed to adapt to the demands of NRS experiments. The detector system mainly consists of four key parts: (i) an array-APD sensor, (ii) 8-channel integrated fast preamplifiers, (iii) the time-to-digital converter readout electronics, and (iv) a data acquisition system and EPICS support software.

Spin polarization assisted facile C-H activation by an = 1 iron(iv)-bisimido complex: a comprehensive spectroscopic and theoretical investigation.

High valent iron terminal imido species (Fe[double bond, length as m-dash]NR) have been shown to be key reactive intermediates in C-H functionalization. However, the detailed structure-reactivity relationship in Fe[double bond, length as m-dash]NR species derived from studies of structurally well-characterized high-valent Fe[double bond, length as m-dash]NR complexes are still scarce, and the impact of imido N-substituents (electron-donating electron-withdrawing) on their electronic structures and reactivities has not been thoroughly explored. In this study, we report spectroscopic and computational studies on a rare = 1 iron(iv)-bisimido complex featuring trifluoromethyl groups on the imido N-substituents, [(IPr)Fe(NC(CF)Ph)] (2), and two closely related = 0 congeners bearing alkyl and aryl substituents, [(IPr)Fe(NC(CMe)Ph)] (3) and [(IPr)Fe(NDipp)] (1), respectively.

Europium-151 and iron-57 nuclear resonant vibrational spectroscopy of naturally abundant KEu(III)Fe(II)(CN) and Eu(III)Fe(III)(CN) complexes.

We have performed and analyzed the first combined Eu and Fe nuclear resonant vibrational spectroscopy (NRVS) for naturally abundant KEu(III)[Fe(II)(CN)] and Eu(III)[Fe(III)(CN)] complexes. Comparison of the observed Eu Fe NRVS spectroscopic features confirms that Eu(III) in both KEu(III)[Fe(II)(CN)] and Eu(III)[Fe(III)(CN)] occupies a position outside the [Fe(CN)] core and coordinates to the N atoms of the CN ions, whereas Fe(III) or Fe(II) occupies the site inside the [Fe(CN)] core and coordinates to the C atoms of the CN ions. In addition to the spectroscopic interest, the results from this study provide invaluable insights for the design and evaluation of the nanoparticles of such complexes as potential cellular contrast agents for their use in magnetic resonance imaging.

QoS based enhanced lossless contention MAC protocol for ultraviolet network.

Ultraviolet (UV) communication, with its excellent characteristics of non-line-of-sight propagation, high confidentiality, and flexible networking, has gradually gained traction in the field of research. The UV media access control (MAC) protocol is relatively lacking at present, and the UV lossless contention MAC (UVLLC-MAC) protocol designed by our team earlier is limited by the predictability of communication network topology; hence, it is not applicable to multinode and multi-data networks. In order to be applicable to multinode network and satisfy the quality of service (QoS) for various data, an enhanced UVLLC-MAC (eUVLLC-MAC) protocol is proposed based on the binary exponential backoff (BEB) and UVLLC protocols.

What Is the Right Level of Activation of a High-Spin {FeNO} Complex to Enable Direct N-N Coupling? Mechanistic Insight into Flavodiiron NO Reductases.

Flavodiiron nitric oxide reductases (FNORs), found in pathogenic bacteria, are capable of reducing nitric oxide (NO) to nitrous oxide (NO) to detoxify NO released by the human immune system. Previously, we reported the first FNOR model system that mediates direct NO reduction (Dong, H. T.

High-throughput nuclear resonance time domain interferometry using annular slits.

Nuclear resonance time domain interferometry (NR-TDI) is used to study the slow dynamics of liquids (that do not require Mössbauer isotopes) at atomic and molecular length scales. Here the TDI method of using a stationary two-line magnetized Fe foil as a source and a stationary single-line stainless steel foil analyzer is employed. The new technique of adding an annular slit in front of a single silicon avalanche photodiode detector enables a wide range of momentum transfers (1 to 100 nm by varying the distance between the annular slits and sample) with a high count rate of up to 160 Hz with a Δq resolution of ±1.

BER improvement in SPAD-based photon-counting optical communication system by using automatic attenuation control technique.

In order to overcome the saturation of a single-photon avalanche diode (SPAD)-based receiver and keep the output counts at optimum level automatically, a new, to the best of our knowledge, scheme using the automatic attenuation control (AAC) technique is proposed. In the scheme, an AAC module is applied to attenuate excess incident photons. Furthermore, on the foundation of the bit error rate (BER) model of a photon-counting optical communication system, a reliable and efficient AAC algorithm is developed to compute the optimal attenuation factor.

Fe Mössbauer isomer shift of pure iron and iron oxides at high pressure-An experimental and theoretical study.

The Fe isomer shift (IS) of pure iron has been measured up to 100 GPa using synchrotron Mössbauer spectroscopy in the time domain. Apart from the expected discontinuity due to the α → ε structural and spin transitions, the IS decreases monotonically with increasing pressure. The absolute shifts were reproduced without semi-empirical calibrations by periodic density functional calculations employing extensive localized basis sets with several common density functionals.

Exploring the Limits of Dative Boratrane Bonding: Iron as a Strong Lewis Base in Low-Valent Non-Heme Iron-Nitrosyl Complexes.

We previously reported the synthesis and preliminary characterization of a unique series of low-spin (ls) {FeNO} complexes supported by an ambiphilic trisphosphineborane ligand, [Fe(TPB)(NO)]. Herein, we use advanced spectroscopic techniques and density functional theory (DFT) calculations to extract detailed information as to how the bonding changes across the redox series. We find that, in spite of the highly reduced nature of these complexes, they feature an NO ligand throughout with strong Fe-NO π-backbonding and essentially closed-shell electronic structures of their FeNO units.

Operando NRIXS and XAFS Investigation of Segregation Phenomena in Fe-Cu and Fe-Ag Nanoparticle Catalysts during CO Electroreduction.

Operando nuclear resonant inelastic X-ray scattering (NRIXS) and X-ray absorption fine-structure spectroscopy (XAFS) measurements were used to gain insight into the structure and surface composition of FeCu and FeAg nanoparticles (NPs) during the electrochemical CO reduction (CO RR) and to extract correlations with their catalytic activity and selectivity. The formation of a core-shell structure during CO RR for FeAg NPs was inferred from the analysis of the operando NRIXS data (phonon density of states, PDOS) and XAFS measurements. Electrochemical analysis of the FeAg NPs revealed a faradaic selectivity of 36 % for CO in 0.

Effects of Noncovalent Interactions on High-Spin Fe(IV)-Oxido Complexes.

High-valent nonheme Fe-oxido species are key intermediates in biological oxidation, and their properties are proposed to be influenced by the unique microenvironments present in protein active sites. Microenvironments are regulated by noncovalent interactions, such as hydrogen bonds (H-bonds) and electrostatic interactions; however, there is little quantitative information about how these interactions affect crucial properties of high valent metal-oxido complexes. To address this knowledge gap, we introduced a series of Fe-oxido complexes that have the same S = 2 spin ground state as those found in nature and then systematically probed the effects of noncovalent interactions on their electronic, structural, and vibrational properties.

The influence of phonon softening on the superconducting critical temperature of Sn nanostructures.

The increase in superconducting transition temperature (T) of Sn nanostructures in comparison to bulk, was studied. Changes in the phonon density of states (PDOS) of the weakly coupled superconductor Sn were analyzed and correlated with the increase in T measured by magnetometry. The PDOS of all nanostructured samples shows a slightly increased number of low-energy phonon modes and a strong decrease in the number of high-energy phonon modes in comparison to the bulk Sn PDOS.

Exploring the Vibrational Side of Spin-Phonon Coupling in Single-Molecule Magnets via Dy Nuclear Resonance Vibrational Spectroscopy.

Synchrotron-based nuclear resonance vibrational spectroscopy (NRVS) using the Mössbauer isotope Dy has been employed for the first time to study the vibrational properties of a single-molecule magnet (SMM) incorporating Dy , namely [Dy(Cy PO) (H O) ]Br ⋅2 (Cy PO)⋅2 H O ⋅2 EtOH. The experimental partial phonon density of states (pDOS), which includes all vibrational modes involving a displacement of the Dy ion, was reproduced by means of simulations using density functional theory (DFT), enabling the assignment of all intramolecular vibrational modes. This study proves that Dy NRVS is a powerful experimental tool with significant potential to help to clarify the role of phonons in SMMs.

Chronological changes in epidemiologic features of patients with gallstones over the last 20 years in a single large-volume Korean center.

Purpose: South Korea has a high prevalence of gallstones, the type of which could be influenced by changes in diet and socioeconomic status. Here we aimed to investigate the epidemiological characteristics and changing patterns of gallstones over the past 20 years in Korea.

Methods: A total of 5,808 patients who underwent cholecystectomy due to gallstones at Seoul National University Hospital between 1996 and 2015 were analyzed.

Publisher Correction: Proton mediated spin state transition of cobalt heme analogs.

In the original version of this Article, the four structural depictions of orbital distributions were inadvertently omitted from Figure 5. This has now been corrected in both the HTML and PDF versions of the Article.

Proton mediated spin state transition of cobalt heme analogs.

The spin state transition from low spin to high spin upon substrate addition is one of the key steps in cytochrome P450 catalysis. External perturbations such as pH and hydrogen bonding can also trigger the spin state transition of hemes through deprotonated histidine (e.g.