Study Of Fine Structure Research Articles

Stable electrochemical properties of trace titanium doping layered P3-type K0.5Mn0.92Ti0.08O2 cathode material for potassium ion batteries

The wide application of potassium ion batteries (PIBs) urgently requires the development of ideal cathode materials with low cost, good reaction kinetics and structural stability. Here, a titanium-doped K0.5Mn0.92Ti0.08O2 cathode material for potassium ion batteries is developed by doping modification strategy using a high-temperature solid-state method. The structure and performance structure-activity relationship of binary K0.5Mn1-xTixO2 cathode materials doped with non-electrochemically active element Ti4+ are studied experimentally and theoretically. With the introduction of Ti4+, when the doping amount is <10 mol%, the doped solid solution is hexagonal P3 phase, and the transition metal layer spacing increases. The non-equivalent doping affects the relative content of Mn3+/Mn4+, smoothes the redox peak in the electrochemical process, reduces the doping formation energy, and improves the structural stability. The ex-situ XRD fine structure study of the electrochemical process shows that the structural change of the material during the discharge process is suppressed after doping. The best Ti-doped cathode material K0.5Mn0.92Ti0.08O2 has an initial discharge capacity of 126.9 mAh·g−1 at a current density of 20 mA·g−1, and the capacity retention rate is 53.7 % after 100 cycles. This work provides a feasible strategy for the construction of stable electrode materials for PIBs.

Molecular dynamics study of the interface fine structure and mechanical properties of Ni@SWCNT/Cu nanocrystalline composite materials

The use of carbon nanotubes (CNTs) as reinforcing phase in copper-based composites has been extensively studied. However, controlling the synthesis interface structure and explaining the nanoscale interface bonding mechanism through experimental methods still poses challenges. In this study, a model of single-walled carbon nanotube nanocrystalline copper composite was established based on molecular dynamics (MD) simulations to investigate the effects of grain boundaries and dislocations on the composite material. It was found that the addition of nickel atoms improved the interface bonding between carbon nanotubes and the copper matrix, reducing vacancies at the interface. Ni@SWCNT/Cu exhibited better mechanical properties. Structural changes and defect evolution during deformation were studied. The ultimate tensile strength of SWCNT/Cu and Ni@SWCNT/Cu composites increased by 62.29 % and 68.78 % respectively compared to nanocrystalline copper, while the Young's modulus increased by 25.91 % and 32.48 % respectively; moreover, the Young's modulus of these two composites increased by 45.24 % and 49.42 % respectively. Ni@SWCNT/Cu had the lowest wear rate and friction coefficient, with a minimum wear rate of 0.0055 and a minimum friction coefficient of 0.67, demonstrating better wear resistance. The effects of different friction speeds and depths of indentation on the friction performance of the composite materials were also investigated.

The Behavior of the Intercalant AlCl4 Anion during the Formation of Graphite Intercalation Compound: An X‐ray Absorption Fine Structure Study

This work aims to study the insertion of anion in the crystalline structure of oriented pyrolytic graphite (PG) at the point of view of the anion itself. The electronic and atomic structures of the anion at different intercalation stages are studied. In particular double‐edge (bicolor) X‐ray absorption spectroscopy at the Al and Cl K‐edges is carried out, highlighting a contraction of the anion bonding at the highest intercalation degree obtained electrochemically (stage 3), while the electronic population changes for both the edges upon cycle.

Effect of Protonation on the Molecular Structure of Adenosine 5'-Triphosphate: A Combined Theoretical and Near Edge X-ray Absorption Fine Structure Study.

The present work combines the near edge X-ray absorption mass spectrometry of a protonated adenosine 5'-triphosphate (ATP) molecule isolated in an ion trap with (time-dependent) density functional theory calculations. Our study unravels the effect of protonation on the ATP structure and its spectral properties, providing structure-property relationships at atomistic resolution for protonated ATP (ATPH) isolated in the gas-phase conditions. On the other hand, the present C and N K-edge X-ray absorption spectra of isolated ATPH appear closely like those previously reported for solvated ATP at low pH. Therefore, the present work should be relevant for further investigation and modeling of structure-function properties of protonated adenine and ATP in complex biological environments.

Dark Exciton in 2D Hybrid Halide Perovskite Films Revealed by Magneto‐Photoluminescence at High Magnetic Field

AbstractA comprehensive study of the exciton fine structure (EFS) is presented in 2D‐phenethylammonium lead iodide films using magnetic field‐induced polarization of photoluminescence (PL) in both Faraday and Voigt configurations at fields up to 25 Tesla. Three exciton bands are identified in the PL spectrum associated with bound, dark, and bright excitons, respectively. Under a high magnetic field in Faraday/Voigt configuration, large field‐induced circular/linear polarization is observed in the PL band related to the dark exciton, which is magnetically activated. Furthermore, it is found that the dark exciton has an anomalous field‐induced circular polarization, which cannot be explained by the classical Boltzmann distribution of spin‐polarized species. These findings are well explained by an effective mass model that includes exchange terms unique to the monoclinic symmetry as a perturbation of the EFS in the approximate tetragonal symmetry. It is also confirmed that the field‐induced linear polarization is sensitive to the monoclinic exchange term, whereas the field‐induced circular polarization is immune to such term.

X-ray Absorption Fine Structural Study of Atomic Structures and Chemical States of Dopants in 4H-SiC(0001)

The atomic structures and chemical states of active and inactive dopant sites in n-type and p-type 4H-SiC(0001) substrates have been investigated by X-ray absorption near edge structure (XANES) and photoelectron spectroscopy (PES). In N atom-doped n-type 4H-SiC(0001), the PES results indicated that a N–C species was formed near the surface. XANES simulations showed that SiNx and N–C species were attributed to active and inactive dopant states, respectively. Angle-resolved XANES measurements showed that the N–C species acted as an inactive dopant site in N-doped 4H-SiC(0001). In Al-doped p-type 4H-SiC, PES analysis revealed that a single chemical state was present at the Al-doped 4H-SiC. The simulated XANES spectra showed that the Si site in 4H-SiC(0001) was replaced by an Al dopant atom, which was the active dopant site. Furthermore, relaxation of the local structure around the Al dopant in Al-doped 4H-SiC(0001) was observed due to bond stretching.

Zeeman spectroscopy of tellurium

The Zeeman structure of eight lines of 130Te covering the spectral range 640–990 nm was investigated. LandȨ gJ factors for seven levels were determined for the first time. Furthermore, we have performed the fine structure studies using abinitio multiconfiguration Dirac-Hartree-Fock calculations for levels of the ground 5p4 and excited 5p36s, 5p35d, 5p36p, 5p38s, 5p38d and 5p39d configurations. The results of the calculations were compared with available experimental data.

Mathematical modeling of experiments on the interaction of a high-power ultraviolet laser pulse with condensed targets

Objectives. The paper aimed to review and analyze the results of works devoted to numerical modeling of experiments on the interaction of high-power ultraviolet (UV) laser pulses with condensed targets. The experiments were carried out at GARPUN, the powerful KrF-laser facility at the P.N. Lebedev Physical Institute of the Russian Academy of Sciences (Moscow). The relevance of the research is related to the use of excimer UV lasers as a driver for a thermonuclear reactor. Physical aspects of laser-plasma interaction, including those related to the possibility of using two-sided cone target in a fission-fusion reactor, are discussed.Methods. The research is based on physico-mathematical models, including Euler and Lagrange.Results. The mathematical modeling of three types of natural experiments is presented: (1) burning through different thicknesses of Al foils by high-power UV laser; (2) studying hydrodynamic instability development at the UV laser acceleration of thin polymer films and features of turbulent zone formation; (3) interaction of high-power UV laser pulses with two-layer targets (Al + Plexiglas) and study of fine structures. Numerical modeling showed that a hybrid reactor with UV laser driver can use targets in the form of two-sided counter cones.Conclusions. Physico-mathematical models are developed along with 2D codes in Lagrangian and Eulerian coordinates as confirmed in the results of natural experiments. The models can be used to describe the physics of high-power UV laser pulses interacting with various targets and forecast the results of reactor-scale experiments.

Ovipositor of bitterling fishes (Cyprinidae, Acheilognathinae): fine structure from a functional perspective

The study presents fine structure data on the ovipositor of four bitterling species (Rhodeus ocellatus, Rhodeus amarus, Paratanakia himantegus and Acheilognathus barbatulus). In A. barbatulus and P. himantegus, ovipositor structure has never been studied. Novel data on the structure of the ovipositor were collected using two complementary methods, light- and transmission electron microscopy. The new findings relate to the covering and lining epithelia, basal laminae, cell junctions and supporting/connective tissue layer. All examined fish shared the same basic ovipositor structure and the newly reported details, regardless of their species affiliation. Evaluation of structure modifications related to the passage of eggs through the ovipositor revealed a range of transitional tissue changes, corroborating their presumable role inferred from the study of fine structure.

Decay spectroscopy of Os171,172 and Ir171,172,174

We report on a study of the α-decay fine structure and the associated Eα−Eγ correlations in the decays of Os171,172 and Ir171,172,174. In total, 13 new α-decay energy lines have been resolved, and three new γ-ray transitions have been observed following the new decay branches to Re168 and W167. The weak α-decay branch from the bandhead of the νi13/2 band in Os171 observed in this work highlights an unusual competition between α, β, and electromagnetic decays from this isomeric state. The nucleus Os171 is therefore one of few nuclei observed to exhibit three different decay modes from the same excited state. The nuclei of interest were produced in Mo92(Kr83,xpyn) fusion-evaporation reactions at the Accelerator Laboratory of the University of Jyväskylä, Finland. The fusion products were selected using the gas-filled ion separator RITU and their decays were characterized using an array of detectors for charged particles and electromagnetic radiation known as GREAT. Prompt γ-ray transitions were detected and correlated with the decays using the JUROGAM II germanium detector array surrounding the target position. Results obtained from total Routhian surface (TRS) calculations suggest that α-decay fine structure and the associated hindrance factors may be a sensitive probe of even relatively small shape changes between the final states in the daughter nucleus.5 MoreReceived 13 October 2022Accepted 11 January 2023DOI:https://doi.org/10.1103/PhysRevC.107.014308Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by Bibsam.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAlpha decayLow & intermediate energy heavy-ion reactionsNuclear structure & decaysProperties150 ≤ A ≤ 189Nuclear Physics

Resonant Laser Ionization and Fine-Structure Study of Silver in an Ablation Plume

We report on a laser photo-ionization study of silver in relation to the Selective Production of Exotic Species (SPES) project at INFN-LNL in the off-line laser laboratory. In this study, two dye lasers and an ablation laser operating at 10 Hz are used alongside a time-of-flight mass spectrometer (TOF-MS). Isotopic separation of the natural, stable isotopes 107Ag and 109Ag was clearly observed in the TOF signal. Resonant photo-ionization of silver was achieved with the use of the scheme 4d105s 2S1/2→ 4d105p 2P3/2o→ 4d106d 2D3/2 with transition wavelengths of 328.163 nm and 421.402 nm, respectively. Doppler-suppressed spectroscopy of these transition lines was performed in an ablation plume. Doppler broadening with collinear injection of excitation lasers and the effect of the linewidths of the excitation lasers were investigated. The fine-structure splitting of the level 4d106d 2D (J = 5/2 and J = 3/2) was confirmed to be 186 ± 2 pm, corresponding to 314 ± 3 GHz.

Comparison of magnetic anisotropy and structural properties in chemically ordered CoPt and FePt nanoparticles

The intrinsic magnetic properties of nanoparticles (NPs) can be accurately determined using highly dispersed NPs in a matrix. In this paper, we study chemically ordered CoPt and FePt NPs with a diameter of 3 nm embedded in an amorphous carbon matrix. Although both alloys exhibit almost the same magnetic and crystallographic properties in the bulk materials, they are completely different as NPs. We show that their magnetic anisotropy differs greatly. To understand the origin of such a difference, a fine crystallographic structure study has been performed using extended x-ray absorption fine structure. In that respect, the atomic relaxations appear to be different in both nanoalloys. Ab initio calculations of the atomic relaxation shed light on these experimental results, showing that the wide distance distribution in Co sublattice should strongly alter the magnetic anisotropy of CoPt NPs.

Surface Nanopatterning Using the Self-Assembly of Linear Polymers on Surfaces after Solvent Evaporation

The morphology of linear polybutadiene physisorbed on freshly cleaved mica from a dilute polymer solution is investigated through atomic force microscopy. A fine-structure study shows that the monolayer morphology in air (after rapid solvent evaporation) depends strongly on the molecular weight (Mw) of the linear polymer, the adsorbed amount, and the conformation adopted by the adsorbed polymer chains under good solvent conditions. The dependence of the observed polymer structure on Mw is most significant for samples with high surface density, where the intermolecular interactions among the adsorbed polymers are important. For high surface density, the adsorbed polymers tend to aggregate and minimize unfavorable contacts with air for all of the different Mw samples, leading to an isotropic structural pattern. These structural phenomena with increasing surface density are explained on the basis of the intermolecular interactions of the adsorbed polymers under good solvent conditions, and after the abrupt solvent evaporation corresponding to poor solvent conditions. The experimental observations are further discussed using the results obtained from molecular dynamics simulations of a simple coarse-grained model.

Promoting Dinuclear-Type Catalysis in Cu1 -C3 N4 Single-Atom Catalysts.

Reducing particle size in supported metal catalysts to single-atom level isolates the active metal sites and maximizes the atomic utilization efficiency. However, the large inter-atom distance, particularly in low-loading single-atom catalyst (SAC), is not favorable for a complex reaction where two (or more) reactants have to be activated. A key question is how to control the inter-atom distances to promote dinuclear-type coactivation at the adjacent metal sites. Here, it is reported that reducing the average inter-atom distance of copper SACs supported on carbon nitride (C3 N4 ) to 0.74 ± 0.13nm allows these catalysts to exhibit a dinuclear-type catalytic mechanism in the nitrile-azide cycloaddition. Operando X-ray absorption fine structure study reveals a dynamic ligand exchange process between nitrile and azide, followed by their coactivation on dinuclear Cu SAC sites to form the tetrazole product. This work highlights that reducing the nearest-neighbor distance of SAC allows the mechanistic pathway to diversify from single-site to multisite catalysis.

Study of Fine Radio-Burst Structures (FRBS) Observed by the Mexican Array Radio Telescope (MEXART)

Study of Fine Radio-Burst Structures (FRBS) Observed by the Mexican Array Radio Telescope (MEXART)

Local structure study of the Fe ions in mixed-valence iron(II)-iron(III) metal formate frameworks

X-ray Absorption Spectroscopy (XAS) methods have been used to study the mixed-valence iron(II)-iron(III) metal–organic frameworks (MOFs) that undergo order–disorder phase transitions. In particular, this paper reports X-ray Absorption Fine Structure (XAFS) study of the electronic and local structure at the Fe K-edge (7 keV) for three mixed-valence iron(II)-iron(III) formate frameworks, namely dietylammonium ((C2H5)2NH2[FeIIIFeII(HCOO)6], DEtAFeFe), dimethylammonium ((CH3)2NH2[FeIIIFeII(HCOO)6], DMAFeFe) and N-etylmethylammonium (CH3NH2C2H5[FeIIIFeII(HCOO)6], EtMeAFeFe) analogues. DMAFeFe (DEtAFeFe) was studied at 140 K and 155 K (240 K and 250 K) in detail to obtain information on the structural changes during the phase transitions. The near-edge x-ray absorption fine structure (XANES) analysis confirms the octahedrally coordinated Fe in the studied samples and the electron transfer from divalent to trivalent iron ions. A slight variation was found in the Fe-O bond lengths and quantified the order in the bond length distribution measured by the Debye-Waller factor (σ2) around the phase transition temperature. The Fe2+/Fe3+ ions are homogeneously distributed in the order–disorder phase transition samples. The slight variation in the local structure defines the nature of the phase transition.

Lumbar Intervertebral Disc and Discovertebral Segment, Part 1: An Imaging Review of Normal Anatomy.

The intervertebral disc is designated the most important cartilaginous articulation of the vertebral column that functions to withstand compressive biomechanical forces and confer strength and flexibility to the spine. A thorough study of the complex fine structure and anatomic relationships of the intervertebral disc is essential for the characterization of the integrity of each individual structure in the discovertebral segment. This elaborate work in human cadavers explores the sophisticated internal structure of the normal intervertebral disc and the discovertebral segment, providing detailed data derived from the dissection of specimens through imaging and close anatomic-histologic correlation. Familiarity with the normal appearances and basic functional properties of the lumbar intervertebral disc and discovertebral segment is fundamental for the recognition of aberrations that may have important clinical implications in patients with low back pain. In Part I of this article, the anatomic structure and features of the discovertebral complex in adults will be described.

Adsorption of glutamic acid on clean and hydroxylated rutile TiO2(110): an XPS and NEXAFS investigation

Due to its biocompatibility, TiO2 is a relevant material for the study of bio-interfaces. Its electronic and chemical properties are influenced by defects, which mainly consist of oxygen vacancies or adsorbed OH groups and which affect, consequently, also the interaction with biological molecules. Here we report on an x-ray photoemission spectroscopy and near edge adsorption fine structure study of glutamic acid (Glu) adsorption on the rutile TiO2(110) surface, either clean or partially hydroxylated. We show that Glu anchors to the surface through a carboxylate group and that the final adsorption state is influenced by the presence of hydroxyl groups on the surface prior to Glu deposition. Indeed, molecules adsorb both in the anionic and in the zwitterionic form, the former species being favored on the hydroxylated substrate.

Fine genetic structure of Brazilian white Morada Nova hair sheep breed from semi-arid region

Due to the critical population status of the Morada Nova breed, this research aimed to carry out an additional study of fine genetic structure, using thousands of SNP markers, to support the development of ex situ and in situ conservation strategies for this breed. Blood samples were collected from seven herds located in the Northeast region of Brazil. DNA was extracted and samples were genotyped using Ovine SNP50 BeadChip. Raw genotyping data were imported and quality control filters were applied. The following measures of genetic variability were used to compare levels of heterogeneity within herds: Observed heterozygosity (HO), Expected heterozygosity (HE), Inbreeding coefficient (F) and Number of polymorphic SNPs with MAF > 0.05 (NSNP.) The pairwise fixation index (FST) and an analysis of molecular variance (AMOVA) were calculated to estimate the genetic differentiation between all pairs of herds studied. To assess the existence of significant genetic structure among the herds, a principal component analysis (PCA) was performed. The HO for populations B, E, F, and G were greater than He, and the F in all subpopulations was low (F < 0.05). Population pairs D-E (FST = 5.9%) and D-G (FST = 6.2%) showed higher values of genetic differentiation from each other, and the two closest population pairs were A-F (FST = 0.2%) and B-E (FST = 0.9%). PCA corroborates the low overall genetic divergence among the populations. The white Morada Nova subpopulations studied here have low genetic differentiation among themselves, with no differentiation by states, but have three main genetic groups. The Morada Nova breed may be a repository of alleles of economic interest for the sheep production chain. These findings may initiate other studies that will make it possible to crossbreeding between the herds by identifying the herds that are more genetically distant and increasing the genetic diversity of the population.

The genome trilogy of Anopheles stephensi, an urban malaria vector, reveals structure of a locus associated with adaptation to environmental heterogeneity

Anopheles stephensi is the most menacing malaria vector to watch for in newly urbanising parts of the world. Its fitness is reported to be a direct consequence of the vector adapting to laying eggs in over-head water tanks with street-side water puddles polluted by oil and sewage. Large frequent inversions in the genome of malaria vectors are implicated in adaptation. We report the genome assembly of a strain of An. stephensi of the type-form, collected from a construction site from Chennai (IndCh) in 2016. The genome reported here with a L50 of 4, completes the trilogy of high-resolution genomes of strains with respect to a 16.5 Mbp 2Rb genotype in An. stephensi known to be associated with adaptation to environmental heterogeneity. Unlike the reported genomes of two other strains, STE2 (2R+b/2Rb) and UCI (2Rb/2Rb), IndCh is found to be homozygous for the standard form (2R+b/2R+b). Comparative genome analysis revealed base-level details of the breakpoints and allowed extraction of 22,650 segregating SNPs for typing this inversion in populations. Whole genome sequencing of 82 individual mosquitoes from diverse geographical locations reveal that one third of both wild and laboratory populations maintain the heterozygous genotype of 2Rb. The large number of SNPs can be tailored to 1740 exonic SNPs enabling genotyping directly from transcriptome sequencing. The genome trilogy approach accelerated the study of fine structure and typing of an important inversion in An. stephensi, putting the genome resources for this understudied species on par with the extensively studied malaria vector, Anopheles gambiae. We argue that the IndCh genome is relevant for field translation work compared to those reported earlier by showing that individuals from diverse geographical locations cluster with IndCh, pointing to significant convergence resulting from travel and commerce between cities, perhaps, contributing to the survival of the fittest strain.