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Abstract In this work, a new strategy was proposed to improve the foamability of poly(aryl ether ketone) (PAEK) based on novel long-chain branched PAEK (LCB-PAEK). To improve the resin melt strength, the amorphous LCB-PAEK was fabricated via a simple ternary copolymerization of phenolphthalein, 4,4′-difluorobenzophenone, and 1,1,1-tris(4-hydroxyphenyl)ethane. To regulate the extent of reaction and avoid crosslinking, 4-fluorobenzophenone was introduced as the end-capping reagent. The presence of long-chain branches were proved by gel permeation chromatography and rheological characteristics, including storage modulus and tensile viscosity. Afterwards, the prepared LCB-PAEK samples were foamed using supercritical carbon dioxide (ScCO 2) as the blowing agent. The influence of branching content on foaming results was investigated in detail, and significant improvement in foamability was observed. By regulating the foaming parameters, the highest expansion ratio of 27.5 was achieved, which was almost ninefold higher than that of linear PAEK. In addition, the good mechanical properties indicated the promising applications of LCB-PAEK foams as high-performance structural foam. Graphical abstract Novel long-chain branched poly(aryl ether ketone) significantly improved the foamability of PAEK. Image 102347 Highlights • Novel long-chain branched PAEK was designed and synthesized for high-expanded PAEK foam. • Expansion ratio of 27.5 is the highest one for PAEK foams reported so far. • Low density PAEK foams with certain mechanical properties were firstly reported. • This work Provide a strategy for design other high-performance foams, such PES, PAR, with high-expansion ratio. [ABSTRACT FROM AUTHOR]

The 57Fe 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. However, the best numerical agreement is obtained with the B1WC hybrid functional. Extension of the calculations to 350 GPa, a pressure corresponding to the Earth's inner core, predicted the IS range of 0.00 to −0.85 mm/s, covering the span from Fe(0) to Fe(VI) compounds measured at ambient pressure. The calculations also reproduced the pressure trend from polymorphs of prototypical iron oxide minerals, FeO and Fe2O3. Analysis of the electronic structure shows a strong donation of electrons from oxygen to iron at high pressure. The assignment of formal oxidation to the Fe atom becomes ambiguous under this condition. [ABSTRACT FROM AUTHOR]

A new synchrotron radiation experimental capability of coupling nuclear resonant inelastic X-ray scattering with the cryogenically cooled high-pressure diamond anvil cell technique is presented. The new technique permits measurements of phonon density of states at low temperature and high pressure simultaneously, and can be applied to studies of phonon contribution to pressure- and temperature-induced magnetic, superconducting and metal-insulator transitions in resonant isotope-bearing materials. In this report, a pnictide sample, EuFe2As2, is used as an example to demonstrate this new capability at beamline 3-ID of the Advanced Photon Source, Argonne National Laboratory. A detailed description of the technical development is given. The Fe-specific phonon density of states and magnetism from the Fe sublattice in Eu57Fe2As2 at high pressure and low temperature were derived by using this new capability. [ABSTRACT FROM AUTHOR]

New aspects of synchrotron Mössbauer microscopy are presented. A 5 µm spatial resolution is achieved, and sub-micrometer resolution is envisioned. Two distinct and unique methods, synchrotron Mössbauer imaging and nuclear resonant incoherent X-ray imaging, are used to resolve spatial distribution of species that are chemically and magnetically distinct from one another. Proof-of-principle experiments were performed on enriched 57Fe phantoms, and on samples with natural isotopic abundance, such as meteorites. [ABSTRACT FROM AUTHOR]

Abstract: Experiments on uniaxial and triaxial rock mechanics and rock acoustic emissions have been conducted for research on the impact of rock anisotropy on the development of the fractures of different directions by taking as an example the ultra-low-permeability sandstone reservoir in the Upper Triassic Yanchang Formation within the Ordos Basin. The experimental results prove the existence of anisotropy of the rock mechanical property in the different directions on the plane, which is the chief reason for the production of impacts on the development of different assemblages of fractures in the geological periods. The rock anisotropy usually restricts the development of one assemblage of conjugate shear fractures. The fractures in the Yanchang Formation within the Ordos Basin are mainly shear fractures that formed under two tectonic actions. Theoretically, here, four assemblages of shear fractures should have developed, but due to the effect of a strong rock anisotropy, in each period one assemblage of fractures chiefly developed. Thus, two assemblages of fractures are usually developed in every part at present. [Copyright &y& Elsevier]

We introduce the combination of nuclear resonant inelastic X-ray scattering and synchrotron Mössbauer spectroscopy with the laser-heated diamond anvil cell technique for studying magnetic, elastic, thermodynamic, and vibrational properties of materials under high pressures and high temperatures. An Nd:YLF laser, operating in continuous donut mode (TEM 01 ), has been used to heat samples inside a diamond anvil cell from both sides. Temperatures of the laser-heated sample are measured by means of spectral radiometry and by the detailed balance principle of the energy spectra. The temperature measured by the detailed balance principle is in very good agreement with values determined from the thermal radiation spectra fitted to the Planck radiation function up to 1700 K. Nuclear resonant scattering on 57 Fe-containing materials (i.e., Fe, FeO, Fe 2 O 3 ) has been studied up to 2500 K and 100 GPa. A detailed description of the laser-heating optics, temperature determination, the X-ray monochromatization, and the X-ray focusing optics is given in this article. [ABSTRACT FROM AUTHOR]

C-Nitroso compounds (RNO, R = alkyl and aryl) are byproducts of drug metabolism and bind to heme proteins, and their heme-RNO adducts are isoelectronic to ferrous nitroxyl (NO−/HNO) complexes. Importantly, heme-HNO compounds are key intermediates in the reduction of NO to N2O and nitrite to ammonium in the nitrogen cycle. Ferrous heme-RNO complexes act as stable analogs of these species, potentially allowing for the investigation of the vibrational and electronic properties of unstable heme-HNO intermediates. In this paper, a series of six-coordinate ferrous heme-RNO complexes (where R = iPr and Ph) were prepared using the TPP2− and 3,5-Me-BAFP2− co-ligands, and tetrahydrofuran, pyridine, and 1-methylimidazole as the axial ligands (bound trans to RNO). These complexes were characterized using different spectroscopic methods and X-ray crystallography. The complex [Fe(TPP)(THF)(iPrNO)] was further utilized for nuclear resonance vibrational spectroscopy (NRVS), allowing for the detailed assignment of the Fe–N(R)O vibrations of a heme-RNO complex for the first time. The vibrational properties of these species were then correlated with those of their HNO analogs, using DFT calculations. Our studies support previous findings that RNO ligands in ferrous heme complexes do not elicit a significant trans effect. In addition, the complexes are air-stable, and do not show any reactivity of their RNO ligands towards NO. So although ferrous heme-RNO complexes are suitable structural and electronic models for their HNO analogs, they are unsuitable to model the reactivity of heme-HNO complexes. We further investigated the reaction of our heme-RNO complexes with different Lewis acids. Here, [Fe(TPP)(THF)(iPrNO)] was found to be unreactive towards Lewis acids. In contrast, [Fe(3,5-Me-BAFP)(iPrNO)2] is reactive towards all of the Lewis acids investigated here, but in most cases the iron center is simply oxidized, resulting in the loss of the iPrNO ligand. In the case of the Lewis acid B2(pin)2, the reduced product [Fe(3,5-Me-BAFP)(iPrNH2)(iPrNO)] was identified by X-ray crystallography. [ABSTRACT FROM AUTHOR]

The Hayabusa2 mission sampled Ryugu, an asteroid that did not suffer extensive thermal metamorphism, and returned rocks to the Earth with no significant air exposure. It therefore offers a unique opportunity to study the redox state of carbonaceous Cb‐type asteroids and evaluate the overall redox state of the most primitive rocks of the solar system. An analytical framework was developed to investigate the iron mineralogy and valence state in extraterrestrial material at the micron scale by combining x‐ray diffraction, conventional Mössbauer (MS), and nuclear forward scattering (NFS) spectroscopies. An array of standard minerals was analyzed and cross‐calibrated between MS and NFS. Then, MS and NFS spectra on three Ryugu grains were collected at the bulk and the micron scales. In Ryugu samples, iron is essentially accommodated in magnetite, clay minerals (serpentine–smectite), and sulfides. Only a single set of Mössbauer parameters was necessary to account for the entire variability observed in MS and NFS spectra, at all spatial scales investigated. These parameters therefore make up a fully consistent iron mineralogical model for the Ryugu samples. As far as MS and NFS spectroscopies are concerned, Ryugu grains are overall similar to each other and share most of their mineralogical features with CI‐type chondrites. In detail however, no ferrihydrite is found in Ryugu particles even at the very sensitive scale of Mössbauer spectroscopy. The typical Fe3+/Fetot of clay minerals is much lower than typical redox ratios measured in CI chondrites (Fe3+/Fetot = 85%–90%). Furthermore, magnetite from Ryugu is stoichiometric with no significant maghemite component, whereas up to 12% of maghemite was previously identified in the Orgueil's so‐called magnetite. These differences suggest that most CI meteorites suffered terrestrial alteration and that the preterrestrial composition of these carbon‐rich samples was less oxidized than previously measured. However, it is not clear yet whether or not the parent bodies of CI chondrites were as reduced as Ryugu. Finally, the high spatial resolution of NFS allows to disentangle the redox state and the crystal chemistry of iron accommodated in serpentine and smectite. The most likely polytype of serpentine is lizardite, containing <35% of Fe3+, a fraction of which being tetrahedrally coordinated. Smectite is more oxidized (Fe3+/Fetot > 65%) and mainly contains octahedral ferric iron. This finding implies that these clays formed from highly alkaline fluids and the spatial variability highlighted here may suggest a temporal evolution or a spatial variability of the nature of this fluid. [ABSTRACT FROM AUTHOR]

Describes a protein from Xenopus laevis ovaries that inhibits the catalytic activity of purified DNA topoisomerase I from wheat germ. Identification and purification of DNA topoisomerase I inhibitor; Effects of divalent cations; Reversibility of inhibition of DNA topoisomerase I by the purified inhibitor; Species specificity of the inhibitor.

Gallstones were classified in to 5 types (pure cholesterol stone, mixed cholesterol stone, calcium bilirubinate stone, black pigment stone and combination stone). In subgroup of gallstones, the proportion of black pigments stone was increased (34.0% to 45.5%), but that of calcium bilirubinate stone was decreased (20.7% to 5.3%). On the aspect of patients'area, calcium bilirubinate stone decreased in both urban and rural area, black pigment stone was increased in both urban and rural area. [Extracted from the article]

Basaltic volcanism on the Moon produced low- and high-Ti mare basalt suites that are also distinct with respect to their iron, titanium, and magnesium isotopic compositions. Here, the equilibrium fractionation of Fe and Ti isotopes between ilmenite and melt was experimentally investigated in order to evaluate the role of ilmenite in generating the isotopic compositional variability among the lunar mare basalts. Ilmenite crystallization experiments were conducted using two bulk compositions: an ilmenite-saturated basaltic andesite and an ilmenite-saturated Apollo 14 black glass, and the Fe and Ti isotopic compositions of the experimental ilmenites and glass (quenched melt) were analyzed using solution MC-ICPMS after hand-picking. Additionally, Nuclear Resonant Inelastic X-ray Scattering (NRIXS) measurements on synthetic ilmenite were conducted and compared to previous NRIXS measurements on synthetic lunar glasses in order to derive temperature-dependent equilibrium ilmenite-melt Fe isotopic fractionations. Experimentally determined ilmenite-melt fractionations were then incorporated into a lunar magma ocean crystallization model that tracks the major element and isotopic compositional evolution of lunar magma ocean cumulates and residual liquid. There is good agreement between the Fe equilibrium isotopic fractionation measured by NRIXS and the laboratory equilibration experiments, and we find that the isotopic fractionation is sensitive to ilmenite compositional differences (0 vs. 10% Fe3+). Further, the light Ti isotopic composition of ilmenite relative to the melt (Δ 49 Ti = ilmenite-melt − 0.09 ± 0.03 ‰ at 1100 ∘C) is consistent with the higher coordination of Ti in ilmenite relative to melts and results of previous studies. The modeled Ti isotopic compositions for lunar magma ocean cumulates display Ti isotopic variability sufficient to explain the low- and high-Ti mare basalt sources. However, the difference in Fe isotopic composition between the low- and high-Ti mare basalts cannot be attributed solely to ilmenite fractionation. Instead, Fe isotopic fractionation by additional products of lunar magma ocean crystallization, such as clinopyroxene, is required to generate the inferred Fe and Mg isotopic variability in the lunar mantle. Alternatively, the Fe and Mg isotopic compositions of the lunar mare basalts may indicate Fe-Mg interdiffusion has occurred in the Ti-rich component of the mare basalt source regions via reaction between ilmenite cumulates and the olivine- and pyroxene-rich lunar mantle. [ABSTRACT FROM AUTHOR]

A versatile environmental chamber at the Beijing Synchrotron Radiation Laboratory (BSRL) is described. This facility has been used for in situ x-ray topographic studies of the structural imperfection in the solids. As an example the investigating result of the domain boundaries and their evolution with temperature in KNbO[sub 3] crystal is given. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of "paddle-shaped" benzhydrylidenefluorene (BDF)-based PI aerogels have been successfully developed. • PI aerogels exhibit ultra-low shrinkage and superior excellent thermostability. • PI aerogels show outstanding thermal insulation (54.3 mW m−1 K−1 at 200 °C). Polyimide (PI) aerogels are widely employed as thermal insulating materials in the aerospace and transportation industry in extreme environments. However, there is a lack of research that focused on the development of novel monomers for the preparation of high-performance PI aerogels. In this study, we proposed a "rigid-soft" strategy to design structurally unconventional diamine compounds. These compounds effectively enhance the rigidity of the PI chain, leading to improved thermostability, while still maintaining flexibility and moderate mechanical properties. Accordingly, two brand-new monomers (BDFD and BDFA) incorporating a twisted "paddle-shaped" benzhydrylidenefluorene (BDF)-based diamine were successfully developed. These monomers consisted of a flexible diphenylmethylene moiety coupled to a rigid fluorene building block. Leveraging these distinctive characteristics, two series of PI aerogels were prepared and exhibited exceptional performance, including a low shrinkage rate, high surface area, and uniform pore size. Notably, the PI-D1 aerogel, composed entirely of BDFD, demonstrated the highest surface area of 674.8 m2 s−1. With a molar ratio of 1/3 for BDFA/ODA, PI-A4 demonstrated the ability to achieve high-performance thermal insulation (54.3 mW m−1 K−1 at 200 °C) with excellent thermostability (T d 5% > 580 °C, T g > 299 °C) and satisfactory dimensional stability (shrinkage at 7.7 %), thanks to its smaller pore size (∼24 nm) and well-balanced rigid and flexible structure property. This research provides an effective method for creating high-performance PI aerogels with an exceptionally low shrinkage rate, which makes them appropriate for thermal management materials that require superior thermal insulation properties. [ABSTRACT FROM AUTHOR]

Dysprosium(III)-containing single-molecule magnets (SMMs) show blocking of the molecular magnetization and hysteresis effects in one molecule. They belong to the class of the best performing SMMs at present. Here, we present first results of 161Dy-Nuclear Resonance Vibrational Spectroscopy (NRVS) experiments on the dysprosium(III) complex [Dy(H2dapp)(NO3)2](NO3) with H2dapp being 2,6-bis((E)-1-(2-(pyridine-2-yl)-hydrazineylidene)ethyl)pyridine. For the 161Dy-NRVS experiments a compact novel He flow cryostat was used at the Advanced Photon Source, Argonne National Laboratories, which enables low temperature NRVS experiments in helium vapour circumventing the often-observed difference between sensor read and "real" sample temperature in mostly used LHe and/or closed cycle cryostats with the NRVS sample being in vacuum. To explore the vibrational modes of the molecule simulations based on first density functional theory (DFT) calculations are presented. [ABSTRACT FROM AUTHOR]

The tight oil sandstone reservoir of the Upper Triassic Yanchang Formation is one of the main targets for hydrocarbon exploration in the Ordos Basin, China. Sandstones of the Upper Triassic Yanchang Formation within lacustrine deep-water gravity-flow deposits are characterized by ultralow porosity, ultralow permeability, and complex diagenetic alterations and sedimentary lithofacies. However, the diagenetic alterations and their controls on the reservoir quality of the Chang 6 tight sandstones remain poorly understood. This study integrated a variety of techniques, such as casting thin section analysis, scanning electron microscopy (SEM), back-scattered electron imagery (BSE), X-ray diffraction (XRD), cathodoluminescence (CL) microscopy, and fluid inclusion, to investigate the lithofacies, diagenetic history, and diagenetic intensity, and also evaluate their controls on reservoir quality. The research results indicated that the Chang 6 sandstones exhibit variable intensity of diagenetic alterations among the various lithofacies, which leads to variable reservoir quality. Mechanical compaction was the most important factor reducing primary porosity. Sandstones of the Ss lithofacies (siltstone to very fine-grained sandstones with graded bedding or ripple laminations) showed the highest loss of primary porosity. Carbonate cements were commonly present in sandstones of the Sc (fine-grained and cross-bedded sandstones) and Sm (fine-grained and massive sandstones) lithofacies near the sandstone–mudstone bounding surface. Sandstones with more authigenic illite rims were able to resist compaction to some extent and were favorable to the preservation of porosity; however, abundant pore-filling illite aggregates commonly bridged pore throats, causing a significant reduction in reservoir quality. Feldspar dissolution porosity leads to a slight enhancement in reservoir quality. Intergranular pores and feldspar dissolution pores are most abundant in the sandstones away from the sandstone–mudstone bounding surface of the Sc lithofacies, resulting in the best reservoir quality, which is followed by sandstones of the Sm lithofacies. Ultimately, four evolution patterns of diagenetic alterations that formed best, moderate, or poor reservoir quality were summarized by linking diagenetic alterations to lithofacies. The research results are conducive to the evaluation of reservoir quality and to understanding the genetic mechanisms of tight sandstones, so they should facilitate hydrocarbon exploration and production in similar lacustrine deep-water gravity-flow reservoirs. • Mechanical compaction is the most important factor reducing primary porosity. • Illite rims can resist compaction and favor the preservation of porosity. • Feldspar dissolution porosity of less than 4% slightly enhanced reservoir quality. • Diagenetic intensity varies with lithofacies, causing variable reservoir quality. [ABSTRACT FROM AUTHOR]

Rare Earth Elements (REEs) are commonly utilized in Earth and environmental sciences to study a variety of geological processes due to their distinct patterns and radioactive-radiogenic decay systems (147Sm-143Nd, 146Sm-142Nd, 138La-138Ce). Advances in analytical techniques now enable the use of REE stable isotopic fractionations to clarify lingering ambiguities in REE systematics. In this study, we employed Nuclear Resonant Inelastic X-ray Scattering (NRIXS) to study the phonon density of states of 151Eu and 161Dy in several pure compounds, as well as in synthetic basalt and andesite glasses, and rhyolite glasses produced under various redox conditions, to determine equilibrium isotopic fractionation factors for the REEs. We additionally utilized Density Functional Theory with a Hubbard U correction (DFT+U) to calculate these factors. Our findings indicate that the directionally averaged mean force constant of Dy3+ is ∼270 N/m across various compounds, while those of Eu2+ and Eu3+ are ∼83 and 214 N/m, respectively, in geologically relevant glasses and other pure compounds. These force constants were then used to estimate those of all REEs using scaling arguments. The results suggest that equilibrium isotopic fractionation should be limited for REEs in igneous rocks, allowing for the interpretation of REE isotopic fractionation in these rocks and minerals as a result of kinetic effects. This could facilitate understanding the role of diffusion in igneous rocks and ore formation. Additionally, our results imply that significant Eu isotopic fractionation could exist in hydrothermal fluids, which could aid in understanding the formation of ore deposits and REE cycling in the oceans. [ABSTRACT FROM AUTHOR]

The transport of hydrogen into Earth's deep interior may have an impact on lower mantle dynamics as well as on the seismic signature of subducted material. Due to the stability of the hydrous phases δ‐AlOOH (delta phase), MgSiO2(OH)2 (phase H), and ε‐FeOOH at high temperatures and pressures, their solid solutions may transport significant amounts of hydrogen as deep as the core‐mantle boundary. We have constrained the equation of state, including the effects of a spin crossover in the Fe3+ atoms, of (Al, Fe)‐phase H: Al0.84Fe3+0.07Mg0.02Si0.06OOH, using powder X‐ray diffraction measurements to 125 GPa, supported by synchrotron Mössbauer spectroscopy measurements on (Al, Fe)‐phase H and δ‐(Al, Fe)OOH. The changes in spin state of Fe3+ in (Al, Fe)‐phase H results in a significant decrease in bulk sound velocity and occurs over a different pressure range (48–62 GPa) compared with δ‐(Al, Fe)OOH (32–40 GPa). Changes in axial compressibilities indicate a decrease in the compressibility of hydrogen bonds in (Al, Fe)‐phase H near 30 GPa, which may be associated with hydrogen bond symmetrization. The formation of (Al, Fe)‐phase H in subducted oceanic crust may contribute to scattering of seismic waves in the mid‐lower mantle (∼1,100–1,550 km). Accumulation of 1–4 wt.% (Al, Fe)‐phase H could reproduce some of the seismic signatures of large, low seismic‐velocity provinces. Our results suggest that changes in the electronic structure of phases in the (δ‐AlOOH)‐(MgSiO2(OH)2)‐(ε‐FeOOH) solid solution are sensitive to composition and that the presence of these phases in subducted oceanic crust could be seismically detectable throughout the lower mantle. Plain Language Summary: Hydrogen can be transported into the interior of the Earth by phases which contain hydrogen in their crystal structure. Interpretation of measured seismic velocities relies on understanding the elastic properties of minerals, including their equation of state. In this study, we use X‐ray diffraction and Mössbauer spectroscopy to constrain the equation of state for a particular hydrous phase known as (Al, Fe)‐phase H and understand pressure‐induced related effects due to changes in the electronic structure of Fe atoms. Our results imply that only a small amount of this phase needs to be transported to the deep mantle to reproduce observed seismic velocities at the edges of large structures known as low seismic‐velocity provinces. The presence of (Al, Fe)‐phase H in subducted oceanic crust may also contribute to the scattering of seismic waves in shallower regions of Earth's interior. Key Points: The equation of state of (Al, Fe)‐phase H (Al0.84Fe3+0.07Mg0.02Si0.06OOH) is constrained by powder X‐ray diffraction to 125 GPaThe equation of state and synchrotron Mössbauer spectroscopy measurements reveal a spin crossover of Fe3+ in (Al, Fe)‐phase H (48–63 GPa)Accumulation of 1–4 wt. % (Al, Fe)‐phase H may explain seismic velocities at edges of large, low seismic velocity provinces [ABSTRACT FROM AUTHOR]

Average Bit Error Rate (BER), outage probability and average channel capacity expressions of a Modulating Retro-Reflector (MRR) optical communication system based on an Airy beam under weak turbulence are derived. The effects of propagation distance, width parameter and exponential truncation factor of the Airy beam itself on the communication performance of the system are discussed. Meanwhile, the performance of the system based on the Gaussian beam is compared with the same turbulence condition and propagation distance. The simulation results show that under the same conditions, the system based on the Airy beam shows a lower outage probability, average BER and larger average channel capacity compared to the system based on the Gaussian beam. Moreover, the advantages of the Airy beam are more significant as the average signal-to-noise ratio (SNR) increases. [ABSTRACT FROM AUTHOR]

We have performed and analyzed the first combined 151Eu and 57Fe nuclear resonant vibrational spectroscopy (NRVS) for naturally abundant KEu(III)[Fe(II)(CN)6] and Eu(III)[Fe(III)(CN)6] complexes. Comparison of the observed 151Eu vs.57Fe NRVS spectroscopic features confirms that Eu(III) in both KEu(III)[Fe(II)(CN)6] and Eu(III)[Fe(III)(CN)6] occupies a position outside the [Fe(CN)6] core and coordinates to the N atoms of the CN− ions, whereas Fe(III) or Fe(II) occupies the site inside the [Fe(CN)6]4− 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. The combined 151Eu and 57Fe NRVS measurements are also among the first few explorations of bi-isotopic NRVS experiments. [ABSTRACT FROM AUTHOR]

As an element ubiquitous in the Solar system, the isotopic composition of iron exhibits rich variations in different planetary reservoirs. Such variations reflect the diverse range of differentiation and evolution processes experienced by their parent bodies. A key in deciphering iron isotope variations among planetary samples is to understand how iron isotopes fractionate during core formation. Here we report new Nuclear Resonant Inelastic X‐ray Scattering experiments on silicate glasses of bulk silicate Earth compositions to measure their force constants at high pressures of up to 30 GPa. The force constant results are subsequently used to constrain iron isotope fractionation during core formation on terrestrial planets. Using a model that integrates temperature, pressure, core composition, and redox state of the silicate mantle, we show that core formation might lead to an isotopically light mantle for small planetary bodies but a heavy one for Earth‐sized terrestrial planets. Plain Language Summary: Planetary formation and differentiation are fundamental processes that physically and chemically shaped terrestrial planets. As a major element ubiquitous in terrestrial planets, the isotopic ratios of Fe are found to vary among different planetary reservoirs, reflecting the formation and differentiation processes that occurred on their parent bodies. Deciphering the information behind these variations require experimental and theoretical constraints on how the isotopic ratios of Fe evolve during different planetary processes. Here, we present a systematic model on how Fe isotopes behave during planetary core formation based on high pressure experiments. We show that Fe isotope fractionation between the mantle and core of terrestrial bodies depends strongly on the planet size. Key Points: We constrained the Fe isotope fractionation factor for the silicate mantle up to 30 GPa using a bulk silicate Earth compositionWe present a holistic Fe isotope fractionation model for core formation considering pressure, temperature, composition, and redox stateOur model shows that core formation can cause the mantle of small planetary bodies to be light in Fe isotopes, but heavy for that of Earth [ABSTRACT FROM AUTHOR]

The melting points of fcc - and hcp -structured Fe 0.9 Ni 0.1 and Fe are measured up to 125 GPa using laser heated diamond anvil cells, synchrotron Mössbauer spectroscopy, and a recently developed fast temperature readout spectrometer. The onset of melting is detected by a characteristic drop in the time-integrated synchrotron Mössbauer signal which is sensitive to atomic motion. The thermal pressure experienced by the samples is constrained by X-ray diffraction measurements under high pressures and temperatures. The obtained best-fit melting curves of fcc -structured Fe and Fe 0.9 Ni 0.1 fall within the wide region bounded by previous studies. We are able to derive the γ – ϵ –l triple point of Fe and the quasi triple point of Fe 0.9 Ni 0.1 to be 110 ± 5 GPa , 3345 ± 120 K and 116 ± 5 GPa , 3260 ± 120 K , respectively. The measured melting temperatures of Fe at similar pressure are slightly higher than those of Fe 0.9 Ni 0.1 while their one sigma uncertainties overlap. Using previously measured phonon density of states of hcp -Fe, we calculate melting curves of hcp -structured Fe and Fe 0.9 Ni 0.1 using our (quasi) triple points as anchors. The extrapolated Fe 0.9 Ni 0.1 melting curve provides an estimate for the upper bound of Earth's inner core–outer core boundary temperature of 5500 ± 200 K . The temperature within the liquid outer core is then approximated with an adiabatic model, which constrains the upper bound of the temperature at the core side of the core–mantle boundary to be 4000 ± 200 K . We discuss a potential melting point depression caused by light elements and the implications of the presented core–mantle boundary temperature bounds on phase relations in the lowermost part of the mantle. [ABSTRACT FROM AUTHOR]

The paper discusses the atmospheric turbulence effect on modulating retro-reflector (MRR) optical communication systems with theoretical analysis and experimental verification. The transmission model is proposed by the phase screen method. Based on this model, the scintillation indices (SI) are calculated, and the aperture averaging effect of the MRR terminal is analyzed. Furthermore, a test bed with 506 m transmission link is established. In the experiment, the SI values of the MRR link and the direct link are obtained and compared. Experimental data agree well with the numerical simulation results and verify the theoretical model. The theoretical results are useful for analyzing the influence of turbulence on MRR systems. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV) optical communication presents several advantages, such as non-line-of-sight propagation, high confidentiality, reliability, and the absence of precise alignment requirements. UV optical communication networks find application in various scenarios in complex electromagnetic environments. In this study, we propose a UV collaborative networking method based on a neighbor discovery algorithm (UVCN–NDA), which establishes neighbor tables within nodes and selects the shortest transmission path between the nodes for frame transmission. During data transmission, nodes dynamically adjust the transmission time of each bit to enhance throughput and use the distance information in the neighbor table for path selection. This strategy prevents ineffective data forwarding and subsequently reduces network power consumption. Simulation results demonstrate that the neighbor discovery algorithm implemented in this protocol exhibits higher efficiency in neighbor discovery and lower message load than existing algorithms. Furthermore, when compared to UV networks based on bit–simultaneous–transmission, the UVCN–NDA–based UV networks achieve an approximate 86.2% reduction in average power consumption and approximately 52% increase in throughput, thereby providing a considerable performance advantage. Finally, the conducted network experiments prove the shortest path selection capability of UVCN–NDA. The main innovations and work of this paper are shown below: • A novel neighbor discovery algorithm (NDA) is proposed. The algorithm takes full advantage of the special relaying method of the bit simultaneous transmission (BST) protocol, and can create a neighbor table in a node that stores information about the shortest distance of all nodes from itself. • A new UV collaborative networking method based on NDA (UVCN–NDA) is proposed. Herein, the node adjusts the transmission time of each bit during data transmission based on its distance to the destination node to improve throughput. The nodes implement path selection when transmitting data based on the distance information in the neighbor table, which prevents ineffective data forwarding and reduces network power consumption. • The proposed neighbor discovery algorithm and networking method are simulated and analyzed. • A networking experiment was performed using our designed terminals, and the experimental results prove the shortest path selection capability of proposed protocol. [ABSTRACT FROM AUTHOR]

Developing a highly efficient multi-node media access control protocol tailored for ultraviolet (UV) networks poses a significant challenge. While our team's UV random-access collaborative networking protocol, utilizing time-division multiple access (UVCN-TDMA), has been instrumental, its scalability is hindered by the number of network nodes. To address this limitation and facilitate large-scale UV node networking, this study advances the UVCN protocol by introducing an enhanced collaborative networking protocol known as the enhanced collaborative clustering mechanism (eCOCM). This study examined the impact of network topology, various data services, and the number of cluster nodes on network performance within the proposed eCOCM framework. Additionally, a comparative analysis between the eCOCM protocol and conventional clustering systems was conducted. The findings demonstrate notable enhancements across key performance metrics including throughput, packet loss rate, delay, and channel utilization. Finally, functional experiments were conducted under two distinct network scenarios to validate the efficacy of the proposed protocol. This study addresses the immediate challenges in UV multi-node networking and offers pragmatic insights to steer its development forward. • This study proposes an enhanced collaborative networking protocol based on a clustering mechanism (eCOCM) to cope with large-scale Ultraviolet (UV) node networking. • The effects of network topology, types of data services, and number of cluster nodes on network performance under the proposed protocol were analyzed. The protocol was compared with the clustering system. The results reveal that it achieves improved throughput, packet loss rate, delay, and channel utilization performance. • Functional experiments were performed in two network scenarios. The operational status of the eCOCM protocol was analyzed in detail based on the output and input signal waveforms of the UV nodes, and the experimental results fully confirm the validity of the protocol. [ABSTRACT FROM AUTHOR]

We report a combined conventional Mössbauer and synchrotron Nuclear Resonant Inelastic X-ray Scattering (NRIXS) study of a series of basalt, andesite, dacite, and rhyolite glasses at temperatures ranging from 5 to 1223 K. These glasses were synthesized under controlled oxygen fugacities and span a wide range of Fe3+/Fe tot ratios. As expected from theory, we find that in these glasses, the inverse of the Lamb-Mössbauer factor (the recoil-free fraction) correlates linearly with the fraction of the conventional Mössbauer spectrum that can be ascribed to Fe3+. Extrapolating the linear relationships to pure Fe3+ and Fe2+ endmembers yields a ratio for the Lamb-Mössbauer factors C of Fe3+ and Fe2+ of 1.203 ± 0.017 (1σ), with no clear dependence on the chemical composition of the glass. We show that the materials studied follow the harmonic approximation up to 1223 K for olivine and 773 K for basaltic glass, allowing us to extrapolate C in temperature. The temperature-dependence of C is well approximated by the formula C = 1.203 ± 0.033 T / 300 over the temperature range 50–750 K. This calibration is used to correct previous redox ratio determinations. We investigate how chemical composition and iron redox state influence the mean force constant of iron in glasses, a key driver of Fe isotopic fractionation during magma generation and differentiation. As previously documented by Dauphas et al. (2014), we find clear correlation between bond strength and iron redox ratio that is secondarily modulated by coordination effects in more alkali-rich felsic magmas. New data on simplified glass compositions reveal that network modifiers, notably K and Na, seem to exert an important control on Fe2+ bond strengths. The refined ratio of Mössbauer factors for Fe2+ and Fe3+ is used to improve on calibrations of iron redox state in geological glasses using XANES spectroscopy. We reevaluate the Fe3+/Fe tot ratio of MORBs based on previously published XANES and Mössbauer data. 0.087 ± 0.005 [ABSTRACT FROM AUTHOR]

Isotopic fractionation has been linked to the lattice vibrations of materials through their phonon spectra. The Lamb-Mössbauer factor (fLM) has the potential to provide information about the lattice vibrations in materials. We constrain the temperature evolution of the fLM of γ- and ε-Fe at in situ high-P-T conditions between 1650 K and the melting point. We find that the vibrations of γ- and ε-Fe can be described using a quasiharmonic model with a pressure- and temperature-dependent Debye temperature computed from the measured fLM. From the Debye temperature, we derive the equilibrium isotopic fractionation β-factor of iron. Our results show that the quasiharmonic behavior of metallic iron would lower the value of lnβFe57/54 by 0.1‰ at 1600–2800 K and 50 GPa when compared to the extrapolation of room temperature nuclear resonant inelastic X‑ray scattering data. Our study suggests that anharmonicity may be more prevalent in Fe metal than in lower mantle minerals at 2800 K and 50 GPa, a relevant condition for the core formation, and the silicate mantle may be isotopically heavy in iron. [ABSTRACT FROM AUTHOR]

Objective To evaluate the requirement for protein kinase Cβ (PKCβ) in the development of lupus in mice, and to explore the potential of targeting PKCβ as a therapeutic strategy in lupus. Methods Congenic mice bearing the disease loci Sle1 or Sle1 and Sle3, which represent different stages of severity in the development of lupus, were crossed with PKCβ-deficient mice. The effect of PKCβ deficiency in lupus development was analyzed. In addition, the effects of the PKCβ-specific inhibitor enzastaurin on the survival of B cells from mice with lupus and human 9G4-positive B cells as well as the in vivo effect of enzastaurin treatment on the development of lupus in Sle mice were investigated. Results In Sle mice, PKCβ deficiency abrogated lupus-associated phenotypes, including high autoantibody levels, proteinuria, and histologic features of lupus nephritis. Significant decreases in spleen size and in the peritoneal B-1 cell population, reduced numbers of activated CD4 T cells, and normalized CD4:CD8 ratios were observed. PKCβ deficiency induced an anergic B cell phenotype and preferentially inhibited autoreactive plasma cells and autoantibodies in mice with lupus. Inhibition of PKCβ enhanced apoptosis of both B cells from Sle mice and human autoreactive B cells (9G4 positive). Treatment of Sle mice with the PKCβ-specific inhibitor enzastaurin prevented the development of lupus. Conclusion This study identifies PKCβ as a central mediator of lupus pathogenesis, suggesting that PKCβ represents a promising therapeutic target for the treatment of systemic lupus erythematosus. Moreover, the results indicate the feasibility of using a PKCβ inhibitor for the treatment of lupus. [ABSTRACT FROM AUTHOR]

Objective To evaluate the requirement for protein kinase Cβ (PKCβ) in the development of lupus in mice, and to explore the potential of targeting PKCβ as a therapeutic strategy in lupus. Methods Congenic mice bearing the disease loci Sle1 or Sle1 and Sle3, which represent different stages of severity in the development of lupus, were crossed with PKCβ-deficient mice. The effect of PKCβ deficiency in lupus development was analyzed. In addition, the effects of the PKCβ-specific inhibitor enzastaurin on the survival of B cells from mice with lupus and human 9G4-positive B cells as well as the in vivo effect of enzastaurin treatment on the development of lupus in Sle mice were investigated. Results In Sle mice, PKCβ deficiency abrogated lupus-associated phenotypes, including high autoantibody levels, proteinuria, and histologic features of lupus nephritis. Significant decreases in spleen size and in the peritoneal B-1 cell population, reduced numbers of activated CD4 T cells, and normalized CD4:CD8 ratios were observed. PKCβ deficiency induced an anergic B cell phenotype and preferentially inhibited autoreactive plasma cells and autoantibodies in mice with lupus. Inhibition of PKCβ enhanced apoptosis of both B cells from Sle mice and human autoreactive B cells (9G4 positive). Treatment of Sle mice with the PKCβ-specific inhibitor enzastaurin prevented the development of lupus. Conclusion This study identifies PKCβ as a central mediator of lupus pathogenesis, suggesting that PKCβ represents a promising therapeutic target for the treatment of systemic lupus erythematosus. Moreover, the results indicate the feasibility of using a PKCβ inhibitor for the treatment of lupus. [ABSTRACT FROM AUTHOR]

Abstract: The global carbon cycle may involve iron carbide as a component of the Earth''s inner core. In this study, we report the first experimental measurements of phonon density of states, sound velocities, and Debye temperatures of Fe3C up to 47GPa and 1450K using the nuclear resonant inelastic X-ray scattering (NRIXS) method in a laser-heated diamond anvil cell. Within the investigated pressure and temperature range, the effect of temperature on compressional velocity v p falls within the measurement uncertainties. The shear velocity vs decreases with increasing temperature in a non-linear fashion: at ~15GPa, vs decreases by ~12% between 300K and 740K; At ~46GPa, temperature produces a ~5% reduction between 300 and 960K and a ~6% further reduction between 960K and 1370–1450K. The high-temperature vs of Fe3C deviates from Birch''s law behavior towards smaller values, potentially matching the anomalously low vs in the inner core under the relevant pressure and temperature conditions. Our results support Fe3C as a major component of the inner core. [Copyright &y& Elsevier]

In this study, collective excitations of liquid indium are studied just above the melting point at different pressures (1.7 GPa, 240 °C; 3.0 GPa, 300 °C; 4.0 GPa, 360 °C). The pressures and temperatures are achieved by the use of an externally heated diamond anvil cell. Clear evidence for the existence of propagating modes is observed from the dynamical structure factor at constant momentum transfer (Q) up to about 18 nm-1. The reason for the observed high elastic-scattering background is identified, and its effects on the determination of elastic properties such as viscosity are discussed. [ABSTRACT FROM AUTHOR]

Jeffbenite, ideally Mg3Al2Si3O12, has been identified as inclusions in super-deep diamonds originating from depths that exceed 300 km. Although Mg-end member jeffbenite has limited stability at upper-mantle conditions, iron-bearing jeffbenite may have broader P–T stability that extends to the transition zone or uppermost lower mantle, incorporating significant amounts of ferric iron. Using synchrotron-based, single-crystal X-ray diffraction (XRD) and synchrotron Mössbauer spectroscopy (SMS) at pressures up to 29 GPa, we report the crystal structure, compressibility, and likely spin transition of iron in ferromagnesian jeffbenite (Mg2.32Al0.03Fe2+1.28Fe3+1.77Si2.85O12). High-pressure structure refinements reveal that Fe3+ substitution for Si in the T2 site, which shares edges with the M2 octahedron, likely stabilizes jeffbenite at high pressure, because it increases the cation-to-cation distance between these sites. Although ferromagnesian jeffbenite does not undergo a structural phase transition below 30 GPa, SMS hyperfine parameters suggest the onset of an electronic spin transition of iron from high-spin (HS) to low-spin (LS) at around 22 GPa, which may increase its stability at high pressures. Pressure–volume data were fit to a third order Birch–Murnaghan equation of state, resulting in V0 = 816.54(9), KT0 = 181.54(1.39), and K T 0 ′ = 2.76(14). These equation of state parameters are applicable to evaluating the encapsulation pressures of super-deep diamonds. The density and bulk modulus of ferromagnesian jeffbenite are similar to or higher than pyrope–almandine, pyrope–majorite, and skiagite–majorite solid solution garnets, further suggesting that jeffbenite may be an important ferric–iron silicate in the deeper parts of the mantle transition zone and uppermost lower mantle. However, future studies on the influence of temperature and oxidation state on the stability and equations of state of iron-bearing jeffbennite are still needed to determine what role, if any, jeffbenite plays in transition-zone mineralogy. [ABSTRACT FROM AUTHOR]

Interpreting isotopic signatures documented in natural rocks requires knowledge of equilibrium isotopic fractionation factors. Here, we determine equilibrium Fe isotope fractionation factors between several common rock-forming minerals using a comparative approach involving three independent methods: (i) isotopic analyses of natural minerals from a metapelite from Mt. Moosilauke, New Hampshire, for which equilibration temperature and pressure are well constrained to be near the aluminosilicate triple point (T ≃ 500 °C, P ≃ 4 kbar), (ii) Nuclear Resonant Inelastic X-ray Scattering (NRIXS) measurements of Fe force constants of minerals, and (iii) Density Functional Theory (DFT) ab initio calculations of Fe force constants of minerals. The minerals studied for Fe isotopes include, in increasing order of their β-factors: garnet < ilmenite ≈ fayalite < biotite < tourmaline < muscovite ≈ plagioclase. Some of this ordering is affected by the presence of Fe3+ in the minerals, which tends to form stiffer bonds and be associated with heavy Fe isotope enrichments relative to Fe2+. We are, however, able to assess the magnitude of the effect of the ratio Fe3+/ΣFe on equilibrium fractionation factors, notably on the ilmenite-hematite solid solution. Equilibrium Fe isotopic fractionation factors between garnet, ilmenite, biotite, tourmaline and fayalite are determined. We also report Mg and Ti isotopic compositions of selected Moosilauke minerals that allow us to better constrain the equilibrium fractionation factors for garnet-biotite-tourmaline (Mg isotopes) and biotite-ilmenite (Ti isotopes). We show how the newly determined equilibrium fractionation factors can be used to address diverse problems in Earth and planetary sciences, notably (i) Fe and Mg isotopic fractionation during anatexis, (ii) Fe isotopic fractionation in lunar ilmenite, and (iii) Ti isotopic fractionation during fluvial transport of minerals. [ABSTRACT FROM AUTHOR]

The isotopic compositions of iron in major mantle minerals may record chemical exchange between deep-Earth reservoirs as a result of early differentiation and ongoing plate tectonics processes. Bridgmanite (Bdg), the most abundant mineral in the Earth's lower mantle, can incorporate not only Al but also Fe with different oxidation states and spin states, which in turn can influence the distribution of Fe isotopes between Bdg and ferropericlase (Fp) and between the lower mantle and the core. In this study, we combined first-principles calculations with high-pressure nuclear resonant inelastic X-ray scattering measurements to evaluate the effects of Fe site occupancy, valence, and spin states at lower-mantle conditions on the reduced Fe partition function ratio (β -factor) of Bdg. Our results show that the spin transition of octahedral-site (B-site) Fe3+ in Bdg under mid-lower-mantle conditions generates a +0.09‰ increase in its β -factor, which is the most significant effect compared to Fe site occupancy and valence. Fe2+-bearing Bdg varieties have smaller β -factors relative to Fe3+-bearing varieties, especially those containing B-site Fe3+. Our models suggest that Fe isotopic fractionation between Bdg and Fp is only significant in the lowermost mantle due to the occurrence of low-spin Fe2+ in Fp. Assuming early segregation of an iron core from a deep magma ocean, we find that neither core formation nor magma ocean crystallization would have resulted in resolvable Fe isotope fractionation. In contrast, Fe isotopic fractionation between low-spin Fe3+-bearing Bdg/Fe2+-bearing Fp and metallic iron at the core-mantle boundary may have enriched the lowermost mantle in heavy Fe isotopes by up to +0.20‰. [ABSTRACT FROM AUTHOR]

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 CO2 reduction (CO2RR) and to extract correlations with their catalytic activity and selectivity. The formation of a core–shell structure during CO2RR 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 0.1 M KHCO3 at −1.1 V vs. RHE, similar to that of pure Ag NPs. In contrast, a predominant selectivity towards H2 evolution is obtained in the case of the FeCu NPs, analogous to the results obtained for pure Fe NPs, although small Cu NPs have also been shown to favor H2 production. [ABSTRACT FROM AUTHOR]

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 CO2 reduction (CO2RR) and to extract correlations with their catalytic activity and selectivity. The formation of a core–shell structure during CO2RR 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 0.1 M KHCO3 at −1.1 V vs. RHE, similar to that of pure Ag NPs. In contrast, a predominant selectivity towards H2 evolution is obtained in the case of the FeCu NPs, analogous to the results obtained for pure Fe NPs, although small Cu NPs have also been shown to favor H2 production. [ABSTRACT FROM AUTHOR]

Sound velocities of hexagonal close-packed iron (hcp-Fe) weremeasured at pressures up to 73 gigapascals and at temperatures up to1700 kelvin with nuclear inelastic x-ray scattering in a laser-heateddiamond anvil cell. The compressional-wave velocities (V[sub P]) andshear-wave velocities (V[sub S]) of hcp-Fe decreased significantly withincreasing temperature under moderately high pressures. V[sub P] andV[sub S] under high pressures and temperatures thus cannot be fitted toa linear relation, Birch's law, which has been used to extrapolatemeasured sound velocities to densities of iron in Earth's interior. Thisresult means that there are more light elements in Earth's core thanhave been inferred from linear extrapolation at room temperature. [ABSTRACT FROM AUTHOR]

Synchrotron‐based nuclear resonance vibrational spectroscopy (NRVS) using the Mössbauer isotope 161Dy has been employed for the first time to study the vibrational properties of a single‐molecule magnet (SMM) incorporating DyIII, namely [Dy(Cy3PO)2(H2O)5]Br3⋅2 (Cy3PO)⋅2 H2O ⋅2 EtOH. The experimental partial phonon density of states (pDOS), which includes all vibrational modes involving a displacement of the DyIII ion, was reproduced by means of simulations using density functional theory (DFT), enabling the assignment of all intramolecular vibrational modes. This study proves that 161Dy NRVS is a powerful experimental tool with significant potential to help to clarify the role of phonons in SMMs. [ABSTRACT FROM AUTHOR]

Erstmalig wurde Synchrotron‐basierte nukleare inelastische Streuung (NIS) unter Nutzung des Mößbauer‐Isotops 161Dy für die Untersuchung der vibronischen Eigenschaften eines DyIII‐basierten Einzelmolekülmagneten, [Dy(Cy3PO)2(H2O)5]Br3⋅2 (Cy3PO)⋅2 H2O⋅2 EtOH, eingesetzt. Die experimentelle partielle Phononen‐Zustandsdichte, die alle Schwingungen mit einer Auslenkung des DyIII‐Ions enthält, wurde mit Hilfe von auf Dichtefunktionaltheorie (DFT) basierenden Simulationen reproduziert, was die Zuordnung aller intramolekularen Schwingungsmoden des Moleküls ermöglicht. Diese Studie zeigt, dass 161Dy‐NIS als eine experimentelle Methode ein hohes Potential besitzt, um zur Klärung der Rolle von Phononen in Einzelmolekülmagneten beizutragen. [ABSTRACT FROM AUTHOR]

The increase in superconducting transition temperature (TC) 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 TC 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. The phonon densities of states, which were determined previously using nuclear resonant inelastic X-ray scattering, were used to calculate the superconducting transition temperature using the Allen-Dynes-McMillan (ADMM) formalism. Both the calculated as well as the experimentally determined values of TC show an increase compared to the bulk superconducting transition temperature. The good agreement between these values indicates that phonon softening has a major influence on the superconducting transition temperature of Sn nanostructures. The influence of electron confinement effects appears to be minor in these systems. [ABSTRACT FROM AUTHOR]

The average bit error rate (BER) and outage probability of circle polarization shift keying (CPOLSK) modulation in free-space optical (FSO) system operating under exponentiated Weibull (EW) distribution are studied. The closed expression of the average BER is derived by generalized Gauss–Laguerre polynomials. The analytical results show the relationship between the average BER and average signal to noise ratio (SNR) of CPOLSK modulation with the effect of aperture averaging under different turbulence strengths and it is compared with on–off keying (OOK) modulation. The relationship between the outage probability and normalized threshold SNR of CPOLSK modulation is studied as well. All the analytical results are verified by the Monte Carlo simulation. [ABSTRACT FROM AUTHOR]

Nuclear resonance vibrational spectroscopy (NRVS) reveals the vibrational dynamics of a Mössbauer probe nucleus. Here, 57Fe NRVS measurements yield the complete spectrum of Fe vibrations in halide complexes of iron porphyrins. Iron porphine serves as a useful symmetric model for the more complex spectrum of asymmetric heme molecules that contribute to numerous essential biological processes. Quantitative comparison with the vibrational density of states (VDOS) predicted for the Fe atom by density functional theory calculations unambiguously identifies the correct sextet ground state in each case. These experimentally authenticated calculations then provide detailed normal mode descriptions for each observed vibration. All Fe-ligand vibrations are clearly identified despite the high symmetry of the Fe environment. Low frequency molecular distortions and acoustic lattice modes also contribute to the experimental signal. Correlation matrices compare vibrations between different molecules and yield a detailed picture of how heme vibrations evolve in response to (a) halide binding and (b) asymmetric placement of porphyrin side chains. The side chains strongly influence the energetics of heme doming motions that control Fe reactivity, which are easily observed in the experimental signal. [ABSTRACT FROM AUTHOR]

Afterpulsing is a critical non-ideal factor of SPAD at telecommunication wavelength, which limits its performance. In order to evaluate the effects of afterpulsing, a new bit error rate (BER) model of SPAD-based photon-counting communication system including afterpulsing is built. To verify the theoretical model, an experimental system is founded. Compared with experimental results, the new BER model is found to be in good agreement. Based on the new BER model, the error performance of photon-counting communication system is investigated. The results indicate that maintaining the afterpulsing probability (AP) of 0, 0.1 will bring 1.2 to 3-dB sensitivity benefit than AP of 0.25. Maintaining the total number of gates per bit above 20 can significantly improve the system sensitivity or background tolerance. Inhibiting the AP below 0.1 is critical for expanding the scale of SPADs array to enhance system error performance. [ABSTRACT FROM AUTHOR]

In order to detect weak signal photons from background radiation, using an array of InGaAs/InP single-photon avalanche diode (SPAD) as a detector is receiving increasing interest. Firstly, the canonical structure and operation principle of SPAD are analyzed. Then, based on the basic parameters (excess bias, operating temperature, absorption region thickness, and multiplication region thickness), the integrated SPAD model of performance parameters, which combines photon detection efficiency (PDE) and dark count rate (DCR), is built. Moreover, a scheme of utilizing SPADs array to detect weak signal photons and an accurate bit error rate (BER) model of photon-counting communication with the limitation of non-ideal factors of SPAD are studied. Then, the joint model of the integrated SPAD model and the BER model is founded. According to the joint model, the design considerations of SPAD to improve the BER in photon-counting communication are investigated. In addition, in regard to a specific photon-counting communication system, the basic parameters of SPAD can be effectively optimized through the joint model. [ABSTRACT FROM AUTHOR]

Time‐domain synchrotron Mössbauer spectroscopy (SMS) based on the Mössbauer effect of 161Dy has been used to investigate the magnetic properties of a DyIII‐based single‐molecule magnet (SMM). The magnetic hyperfine field of [Dy(Cy3PO)2(H2O)5]Br3⋅2 (Cy3PO)⋅2 H2O⋅2 EtOH is with B0=582.3(5) T significantly larger than that of the free‐ion DyIII with a 6H15/2 ground state. This difference is attributed to the influence of the coordinating ligands on the Fermi contact interaction between the s and 4f electrons of the DyIII ion. This study demonstrates that 161Dy SMS is an effective local probe of the influence of the coordinating ligands on the magnetic structure of Dy‐containing compounds. A new point of view: The magnetic hyperfine field at the 161Dy nucleus in Dy‐containing compounds can be determined by 161Dy time‐domain synchrotron Mössbauer spectroscopy. This quantity is influenced by the polarization of the s electrons at the 161Dy nucleus via metal–ligand interactions. The effect of different ligands in Dy‐containing single‐molecule magnets can now directly be explored from the viewpoint of the lanthanide ion. [ABSTRACT FROM AUTHOR]

Time‐domain synchrotron Mössbauer spectroscopy (SMS) based on the Mössbauer effect of 161Dy has been used to investigate the magnetic properties of a DyIII‐based single‐molecule magnet (SMM). The magnetic hyperfine field of [Dy(Cy3PO)2(H2O)5]Br3⋅2 (Cy3PO)⋅2 H2O⋅2 EtOH is with B0=582.3(5) T significantly larger than that of the free‐ion DyIII with a 6H15/2 ground state. This difference is attributed to the influence of the coordinating ligands on the Fermi contact interaction between the s and 4f electrons of the DyIII ion. This study demonstrates that 161Dy SMS is an effective local probe of the influence of the coordinating ligands on the magnetic structure of Dy‐containing compounds. [ABSTRACT FROM AUTHOR]

The phase and spin transitions in single-crystal monoclinic ferrosilite, FeSiO 3 , were investigated using X-ray diffraction and Mössbauer spectroscopy up to lower-mantle pressures and room temperature in a helium pressure medium. Using single-crystal X-ray diffraction, we measured the equation of state of ferrosilite up to about 43 GPa. We observed a P 2 1 / c -to- C 2/ c phase transition between 1.5 and 1.7 GPa and a phase transition from C 2/ c to a distinct P 2 1 / c structure between 30 and 34 GPa. With time-domain Mössbauer spectroscopy, we determined the hyperfine parameters of ferrous iron up to 95 GPa. The phase transitions were correlated with discontinuities in Mössbauer spectral features. We observed the onset of high-spin-to-low-spin transitions in the M1 and M2 sites at ∼37 GPa and ∼74 GPa, respectively. Understanding the electronic structure of iron in a well-characterized single crystal of ferrosilite may help interpret the behavior of iron in complex dense silicate phases. [ABSTRACT FROM AUTHOR]

Abstract Iron is the most abundant transition metal in the Earth's interior, yet considerable uncertainties remain as to why mantle-derived rocks have diverse iron isotopic compositions. In particular, the isotopic fractionation behavior of iron in the lower-mantle minerals bridgmanite and ferropericlase are largely unexplored. The reason is that it is challenging to study isotopic fractionation at the high pressures relevant to the deep mantle. Here we report in situ measurements of the mean force constants of iron bonds in these minerals pressurized in diamond anvil cells using the technique of nuclear resonant inelastic X-ray scattering (NRIXS). We find that the transition from high- to low-spin iron in ferropericlase ((Mg 0.75 Fe 0.25)O) at approximately 60 GPa drastically stiffens its iron bonds in the low-spin state. The mean force constant of iron bonds in both Fe-bearing and (Fe,Al)-bearing bridgmanite exhibits softening by 21% at approximately 40–60 GPa, which seems to be associated with changes in the iron local environment during the transition from low to high quadrupole splitting states. These results indicate that in the lower mantle, low-spin ferropericlase is enriched in heavy iron isotopes relative to bridgmanite and metallic iron by +0.15‰ and +0.12‰, respectively. Based on these results, we investigate whether terrestrial magma ocean crystallization could have fractionated iron isotopes. We conclude that this process cannot be responsible for the heavy iron isotope enrichment measured in terrestrial basalts. Highlights • Iron isotope fractionation factors in lower mantle minerals were determined. • Spin states and local site influence the high pressure iron isotopic fractionation. • Limited iron isotope fractionation between minerals and melts is found. • The magma ocean crystallization did not cause terrestrial iron isotopic variations. [ABSTRACT FROM AUTHOR]

The synchrotron radiation technique of nuclear resonant inelastic X‐ray scattering (NRIXS), also known as nuclear resonance vibrational spectroscopy or nuclear inelastic scattering, provides a wealth of information on the vibrational properties of solids. It has found applications in studies of lattice dynamics and elasticity, superconductivity, heme biochemistry, seismology, isotope geochemistry and many other fields. It involves probing the vibrational modes of solids by using the nuclear resonance of Mössbauer isotopes such as 57Fe, 83Kr, 119Sn, 151Eu and 161Dy. After data reduction, it provides the partial phonon density of states of the Mössbauer isotope that is investigated, as well as many other derived quantities such as the mean force constant of the chemical bonds and the Debye velocity. The data reduction is, however, not straightforward and involves removal of the elastic peak, normalization and Fourier–Log transformation. Furthermore, some of the quantities derived are highly sensitive to details in the baseline correction. A software package and several novel procedures to streamline and hopefully improve the reduction of the NRIXS data generated at sector 3ID of the Advanced Photon Source have been developed. The graphical user interface software is named SciPhon and runs as a Mathematica package. It is easily portable to other platforms and can be easily adapted for reducing data generated at other beamlines. Several tests and comparisons are presented that demonstrate the usefulness of this software, whose results have already been used in several publications. Here, the SciPhon software is used to reduce Kr, Sn, Eu and Dy NRIXS data, and potential implications for interpreting natural isotopic variations in those systems are discussed. [ABSTRACT FROM AUTHOR]

Abstract: A combination of nuclear resonance vibrational spectroscopy (NRVS), FTIR spectroscopy, and DFT calculations was used to observe and characterize Fe−H/D bending modes in CrHydA1 [FeFe]‐hydrogenase Cys‐to‐Ser variant C169S. Mutagenesis of cysteine to serine at position 169 changes the functional group adjacent to the H‐cluster from a ‐SH to ‐OH, thus altering the proton transfer pathway. The catalytic activity of C169S is significantly reduced compared to that of native CrHydA1, presumably owing to less efficient proton transfer to the H‐cluster. This mutation enabled effective capture of a hydride/deuteride intermediate and facilitated direct detection of the Fe−H/D normal modes. We observed a significant shift to higher frequency in an Fe−H bending mode of the C169S variant, as compared to previous findings with reconstituted native and oxadithiolate (ODT)‐substituted CrHydA1. On the basis of DFT calculations, we propose that this shift is caused by the stronger interaction of the ‐OH group of C169S with the bridgehead ‐NH‐ moiety of the active site, as compared to that of the ‐SH group of C169 in the native enzyme. [ABSTRACT FROM AUTHOR]