Electronic Structure Density Research Articles

Efficient persulfate non-radical activation of electron-rich copper active sites induced by oxygen on graphitic carbon nitride

Peroxymonosulfate (PMS) non-radical reactions possess high catalytic activity for specific pollutants under complex water environments. However, the synthesis of high-performance catalysts and the discussion of non-radical reaction mechanisms are still unsatisfactory. Here, a novel and efficient non-radical catalyst (O-CuCN) was successfully assembled using the scheme of Copper (Cu) and oxygen (O) co-doping. The O element with great electronegativity induces graphite carbon nitride (g-C3N4) to act as a medium to change the phase properties and electron density distribution of g-C3N4, and provides a support for the targeting of Cu. Cu is introduced into g-C3N4 as an active site in the phase structure, and an electron-rich center with the Cu site is formed, which forms a metastable intermediate after the adsorption of PMS by Cu as the active site. The new catalyst O-CuCN has outstanding activity in the PMS system, and its degradation rate for bisphenol A (BPA) is increased by more than 20 times compared to that of g-C3N4, and it has excellent environmental tolerance and stability. This work demonstrates that the formation of metastable intermediates and the initiation of effective non-radical reactions can be achieved by constructing differentiated electron density structures.

Structure of the reproductive system of the sexual generation of the endemic Arctic species Acyrthosiphon svalbardicum and its temperate counterpart Acyrthosiphon pisum (Hemiptera, Aphididae).

The Arctic aphids live briefly and must breed quickly to survive. Shortened life cycle, with only two generations: the stem mother and sexuales-oviparous females and males is an adaptation for optimal use of the short breeding period, which lasts from late July to the end of August. Using Acyrthosiphon svalbardicum, an endemic High Arctic aphid species, we describe the structure of the reproductive system of sexual morphs and compare with its temperate counterparts, in particular the model organism the pea aphid Acyrthosiphon pisum. Generally, the histological composition and ultrastructure of reproductive system of sexuales of A. svalbardicum is broadly similar to the reproductive systems described already in other species of aphids. The unique characters include in both oviparous females and males an enormous layer of the fat body, adhering to the structures of the internal reproductive system. The greatly enlarged accessory glands of males accumulate a heterogenous secretion composed of irregularly organized bunches of spicule-like structures of high electron density embedded in fine and coarse granular material. This material, unknown among temperate counterparts of A. svalbardicum, during mating is transported from the accessory glands of the male to its ejaculatory duct, where it is mixed with the ejaculate, and then is transferred to the spermatheca of the oviparous female.

Electron Density Structure of the Local Galactic Disk

Abstract Pulsar dispersion measures (DMs) have been used to model the electron density of the interstellar medium (ISM) in the Galactic disk as a plane-parallel medium, despite significant scatter in the DM-distance distribution and strong evidence for inhomogeneities in the ISM. We use a sample of pulsars with independent distance measurements to evaluate a model of the local ISM in the thick disk of the Galaxy that incorporates turbulent fluctuations, clumps, and voids in the electron density. The latter two components are required because about one-third of the lines of sight are discrepant from a strictly plane-parallel model. A likelihood analysis for smooth components of the model yields a scale height kpc and a mid-plane density n 0 = 0.015 ± 0.001 cm−3. The scatter in the DM-distance distribution is dominated by clumps and voids but receives significant contributions from a broad spectrum of density fluctuations, such as a Kolmogorov spectrum. The model is used to identify lines of sight with outlier values of DM. Three of these pulsars, J1614−2230, J1623−0908, and J1643−1224, lie behind known H ii regions, and the electron density model is combined with Hα intensity data to constrain the filling factors and other substructure properties of the H ii regions (Sh 2–7 and Sh 2–27). Several pulsars also exhibit enhanced DM fluctuations that are likely caused by an intersection of their lines of sight with the superbubble GSH 238+00+09.

A new probe of axion-like particles: CMB polarization distortions due to cluster magnetic fields

We propose using the upcoming Cosmic Microwave Background (CMB) ground based experiments to detect the signal of ALPs (Axion like particles) interacting with magnetic fields in galaxy clusters. The conversion between CMB photons and ALPs in the presence of the cluster magnetic field can cause a polarized spectral distortion in the CMB around a galaxy cluster. The strength of the signal depends upon the redshift of the galaxy cluster and will exhibit a distinctive spatial profile around it depending upon the structure of electron density and magnetic field. This distortion produces a different shape from the other known spectral distortions like y-type and μ-type and hence are separable from the multi-frequency CMB observation. The spectrum is close to Kinematic Sunyaev-Zeldovich (kSZ) signal but can be separated from it using the polarization information. For the future ground-based CMB experiments such as Simons Observatory and CMB-S4, we estimate the measurability of this signal in the presence of foreground contamination, instrument noise and CMB anisotropies. This new avenue can probe the photon-ALP coupling over the ALP mass range from 10−13 eV to 10−12 eV with two orders of magnitude better accuracy from CMB-S4 than the current existing bounds.

Correlative x-ray phase-contrast tomography and histology of human brain tissue affected by Alzheimer’s disease

Alzheimer’s disease (AD) is a neurodegenerative disorder which is characterized by increasing dementia. It is accompanied by the development of extracellular β-amyloid plaques and neurofibrillary tangles in the gray matter of the brain. Histology is the gold standard for the visualization of this pathology, but also has intrinsic shortcomings. Fully three-dimensional analysis and quantitative metrics of alterations in the tissue structure require a complementary approach. In this work we use x-ray phase-contrast tomography to obtain three-dimensional reconstructions of human hippocampal tissue affected by AD. Due to intrinsic electron density differences, tissue components and structures such as the granule cells of the dentate gyrus, blood vessels, or mineralized plaques can be identified and segmented in large volumes. Based on correlative histology, protein (tau, β-amyloid) and elemental content (iron, calcium) can be attributed to certain morphological features occurring in the entire volume. In the vicinity of senile plaques, an accumulation of microglia in combination with a loss of neuronal cells can be observed.

ОПРЕДЕЛЕНИЕ ХАРАКТЕРИСТИК ИНЧ-ВОЛН, НАИБОЛЕЕ СИЛЬНО РЕАГИРУЮЩИХ НА НЕЗНАЧИТЕЛЬНЫЕ ИЗМЕНЕНИЯ ЭЛЕКТРОННОЙ ПЛОТНОСТИ ИОНОСФЕРЫ В ОБЛАСТИ ВЫСОКИХ ШИРОТ

In this paper, we use numerical experiment methods to address the problem of determining characteristics of ILF (0.3–3 kHz) electromagnetic waves recorded in the surface layer and providing the maximum amount of information about the Earth–ionosphere waveguide. We have analyzed the effect of the horizontal spatial structure of electron density of the Earth–ionosphere waveguide on propagation of electromagnetic waves. We have identified characteristics that allow us to record them by instrumental methods in conditions of weakly disturbed ionosphere. The density profiles used in numerical experiments have been obtained from data acquired by the Partial Reflection Radar at the Polar Geophysical Institute, located at the radiophysical observatory Tumanny in the Murmansk Region (69.0° N, 35.7° E), and by the IRI2016 model during the March 15, 2013 solar flare and the subsequent magnetic storm on March 17, 2013. The electromagnetic signal propagation model used in this work is the adaptation of gas-hydrodynamic methods to electrodynamic applications. The model is based on the scheme of upwind approximation of spatial derivatives (Godunov’s method with correction of streams). We also use splitting by spatial directions and physical processes. Signal field attenuation due to conductivity and its rotation due to Hall conductivity of the medium are considered in separate splitting steps by analytical formulas.

ВЛИЯНИЕ ПАРАМЕТРА ß СОЛНЕЧНОГО ВЕТРА НА СТАТИСТИЧЕСКИЕ ХАРАКТЕРИСТИКИ Ap-ИНДЕКСА В ЦИКЛЕ СОЛНЕЧНОЙ АКТИВНОСТИ

In this paper, we use numerical experiment methods to address the problem of determining characteristics of ULF (0.3–3 kHz) electromagnetic waves recorded in the surface layer and providing the maximum amount of information about the Earth–ionosphere waveguide. We have analyzed the effect of the horizontal spatial structure of electron density of the Earth–ionosphere waveguide on propagation of electromagnetic waves. We have identified characteristics that allow us to record them by instrumental methods in conditions of weakly disturbed ionosphere. The density profiles used in numerical experiments have been obtained from data acquired by the Partial Reflection Radar at the Polar Geophysical Institute, located at the radiophysical observatory Tumanny in the Murmansk Region (69.0° N, 35.7° E), and by the IRI2016 model during the March 15, 2013 solar flare and the subsequent magnetic storm on March 17, 2013. The electromagnetic signal propagation model used in this work is the adaptation of gas-hydrodynamic methods to electrodynamic applications. The model is based on the scheme of upwind approximation of spatial derivatives (Godunov’s method with correction of streams). We also use splitting by spatial directions and physical processes. Signal field attenuation due to conductivity and its rotation due to Hall conductivity of the medium are considered in separate splitting steps by analytical formulas.

DETERMINATION OF ELF WAVE CHARACTERISTICS MOST STRONGLY REACTING TO MINOR CHANGES OF IONOSPHERIC ELECTRON DENSITY IN A HIGH-LATITUDE REGION

In this paper, we use numerical experiment methods to address the problem of determining characteristics of ELF (0.3–3 kHz) electromagnetic waves recorded in the surface layer and providing the maximum amount of information about the Earth–ionosphere waveguide. We have analyzed the effect of the horizontal spatial structure of electron density of the Earth–ionosphere waveguide on propagation of electromagnetic waves. We have identified characteristics that allow us to record them by instrumental methods in conditions of weakly disturbed ionosphere. The density profiles used in numerical experiments have been obtained from data acquired by the Partial Reflection Radar at the Polar Geophysical Institute, located at the radiophysical observatory Tumanny in the Murmansk Region (69.0° N, 35.7° E), and by the IRI2016 model during the March 15, 2013 solar flare and the subsequent magnetic storm on March 17, 2013. The electromagnetic signal propagation model used in this work is the adaptation of gas-hydrodynamic methods to electrodynamic applications. The model is based on the scheme of upwind approximation of spatial derivatives (Godunov’s method with correction of streams). We also use splitting by spatial directions and physical processes. Signal field attenuation due to conductivity and its rotation due to Hall conductivity of the medium are considered in separate splitting steps by analytical formulas.

Research on small-scale structures of ice particle density and electron density in the mesopause region

Abstract. The formation of ice particle density irregularities with a meter scale in the mesopause region is explored in this paper by developing a growth and motion model of ice particles based on the motion equation of a variable mass object. The growth of particles by water vapor adsorption and the action of gravity and the neutral drag force on particles are considered in the model. The evolution of the radius, velocity, and number density of ice particles is then investigated by solving the growth and motion model numerically. For certain nucleus radii, it is found that the velocity of particles can be reversed at a particular height, leading to a local gathering of particles near the boundary layer, which then forms small-scale ice particle density structures. The spatial scale of the density structures can be affected by vertical wind speed, water vapor density, and altitude, and it remains stable as long as these environmental parameters do not change. The influence of the stable small-scale structures on electron and ion density is further calculated by a charging model, which considers the production, loss, and transport of electrons and ions, along with dynamic particle charging processes. Results show that the electron density is anti-correlated to the charged ice particle density and ion density for particles with radii of 11 nm or less due to plasma attachment by particles and plasma diffusion. This finding is in accordance with most rocket observations. The small-scale electron density structures created by small-scale ice particle density irregularities can produce the polar mesosphere summer echo (PMSE) phenomenon.

Coordination bonding in dicopper and dichromium tetrakis(μ-acetato)-diaqua complexes: Nature, strength, length, and topology.

Geometry optimization, energetics, electronic structure, and topology of electron density of dicopper (I) and dichromium (II) tetrakis(μ-acetato)-diaqua complexes are studied focusing on the metal-metal interactions. The performance of broken symmetry (BS) single-determinant ab initio (Hartree-Fock, Møller-Plesset perturbation theory to the second and third orders, coupled clusters singles and doubles) and density functional theory (BLYP, B3LYP, B3LYP-D3, B2PLYP, MPW2PLYP) methods is compared to multideterminant ab initio (CASSCF, NEVPT2) methods as well as to the multipole model of charge density from a single-crystal X-ray diffraction experiment (Herich et al., Acta Cryst. 2018, B74, 681-692). In vacuo DFT geometry optimizations (improper axial water ligand orientation) are compared against the periodic ones. The singlet state is found to be energetically preferred. J coupling of (I) becomes underestimated for all ab initio methods used, when compared to experiment. It is concluded that the strength of the direct M─M interactions correlates closely with the J coupling magnitude at a given level of theory. The double potential well character of (II) and of the dehydrated form of (II) are considered with respect to the Cr─Cr distance. The physical effective bond order of the metal-metal interaction is small (below 0.1 e) in (I) and moderate (0.4 e) in (II). The CASSCF results overestimate the electron density of the metal-metal bond critical point by 20% and 50% in (I) and (II), respectively, when compared to the multipole model. © 2019 Wiley Periodicals, Inc.

Nickel oxide nanoparticles on the surface of the gallium arsenide nanocluster structure

This paper describes how the efficiency of the active element of a solar cell of gallium arsenide (GaAs) is increased by nickel oxide nanoparticles. The simulated structure of a semiconductor GaAs compound with a diamond-like lattice shows how the intersphere space grid is generated based on the face-centered cubic lattice motif. A theoretically determined optimal concentration of nanoparticles on the surface and the corresponding values of the experimental data are shown. Studies of the electronic structure on small GaAs clusters at n = 18 correspond to a minimum value of –19·238 eV and a maximum value of –5·606 eV for the state n = 0, –2·99 eV and 20·232 eV for the state n = 1, –0·693 eV and –0·03 eV for the state n = 2, –0·16 eV and –2·646 × 10–4 eV for the state n = 3, respectively. Peaks in the spectra sequentially observed within these limits coincide with the maximum value of the wave vector. Spectral variations, depending on the size of the interspheric space and the number of ion cores, correlate well with changes in densities. The electron density structure of GaAs has a complex structure. The maximum probability of finding is concentrated near four Ga ions. When approaching the center, the electron density changes in a wave-like fashion with a small maximum in the center. The results of the calculations show that gallium atoms in clusters with a higher binding energy, as a rule, are located on the surface or in the places of atomic edges, since the atoms of the faces are less consistent. Arsenic atoms are located in the center, surrounded by gallium atoms.

EFEK GELOMBANG TSUNAMI ACEH 2004 PADA GANGGUAN IONOSFER BERGERAK SKALA MENENGAH DARI PENGAMATAN JARINGAN GPS SUMATRA

Medium Scale Travelling Ionospheric Disturbance (MSTID), thought to be manifestation of atmospheric gravity wave (AGW) in the ionospheric altitude that propagates horizontally and effects on in the electron density structure of ionosphere. These atmospheric gravity waves sourced from lower atmospheric activities such as typhoons, volcanic eruptions and tsunamis. Wave energy by its coupling induction process can travel to the ionosphere region. It has been understood that the TID's wave structure have an impact on the propagation of radio waves in the ionosphere so that it will affect the performance of navigation satellite-based positioning measurements. Based on Aceh tsunami in December 2004, this study aimed to investigation of the induction of atmospheric gravity waves in the ionosphere using total electron content (TEC) data from the Sumatra GPS network (Sumatra GPS Array, SUGAR). The detection technique of TEC changes due to AGW induction with a filter to separate medium scale disturbance at the ionospheric pierce point at an altitude of 350 km (IPP, Ionospheric Pierce Point). The results show the horizontal wavelength of a medium-scale TID around 180 ± 12 Km with a velocities of around 376 ± 9 ms-1. Based on two-dimensional map, the TID moves to the southeast.

Wave Field Propagation in Extended Highly Anisotropic Media

AbstractThe theory propagation in the Earth's ionosphere is well established. However, with the advent of Global Navigation Satellite System measurements, new demands are being placed on satellite system performance evaluation and diagnostic measurements. Propagation simulations are essential for system performance evaluation and they provide guidelines for interpreting diagnostic measurements. This paper presents simulations of propagation in extended highly anisotropic media obtained with split‐step integration of the parabolic wave equation. This requires three‐dimensional realizations of the electron density structure. A new configuration‐space model is used to generate realizations as summations of striations, which are local to field lines with defined scales and peak densities. The scale and peak densities can be selected to generate specified power law spectral density functions. An analytic three‐dimensional expectation spectral density function provides a parameterized ionospheric structure model. The simulations results show that replacing the extended structure with an equivalent phase screen placed at the center of the structured region provides statistically equivalent realizations of observation‐plane measurements at propagation distances greater than the layer extent. The equivalence is independent of the propagation direction relative to the magnetic field direction, although there is some variation for the extreme propagation disturbances caused by field‐aligned propagation. We also investigate the interpretation of in situ and path‐integrated diagnostic measurements and two‐dimensional propagation models, which are being used to model diagnostic measurements directly.

Vertical Structure of the Ionospheric Response Following the Mw 7.9 Wenchuan Earthquake on 12 May 2008

The response of the vertical ionospheric electron density structure to the Mw 7.9 Wenchuan earthquake on 12 May 2008 was recorded by the FORMOSAT-3/COSMIC (F3/C) radio occultation (RO) precise orbit determination (POD) total electron content (TEC). The horizontal propagation characteristics of the seismo-traveling ionospheric disturbances were identified by combining ground-based Global Navigation Satellite System (GNSS) TEC data and RO TEC data. The postseismic ionospheric infrasound wavefront with wavelength of around 80 km at altitude of 150–350 km was scanned vertically by an individual RO TEC profile. A large amount of TEC profiles around the epicenter from 0000 to 1200 UT provide evidence of continental earthquake-induced vertical oscillations that lasted in the ionosphere for several hours. RO-observed vertical perturbations appear on both the southward and northward sides of the epicenter. The vertical structure of the ionospheric oscillations with wavelength ranging from 10 to 80 km increased with altitude between 230 and 650 km.

Rotating spoke instabilities in a wall-less Hall thruster: simulations

The low-frequency rotating plasma instability (spoke) in the ISCT200 thruster operating in the wall-less configuration was simulated with a 3 dimensional PIC MCC code. In the simulations an m = 1 spoke rotating with a velocity of 6.5 km s−1 in the E × B direction was observed. The rotating electron density structure in the spoke is accompanied by a strongly depleted region of the neutral gas, which clearly shows that the spoke instability is of an ionization nature, similar to the axial breathing mode oscillations. In the simulation the electron cross-field transport through the spoke core was caused by diffusion in the high-frequency (4–10 MHz), short-scale (3 mm) electric field oscillations. These short-scale oscillations play a crucial role in the thruster discharge as over 70% of the electron current to the anode originates from the spoke core. The rest of the current originates from the spoke front where the electron cross-field transport toward the anode is due to the E × B drift in the spoke macroscopic azimuthal electric field.

Electron‐pair entropic and complexity measures in atomic systems

AbstractThe two‐electron atomic densities are analyzed in both position and momentum spaces in terms of different information‐theoretic measures, such as disequilibrium, Shannon entropy, shape complexity, and its corresponding information plane. This study is conveyed throughout the Periodic Table and the obtained results are discussed in terms of varied atomic properties such as (1) atomic charge, (2) shell filling patterns, and (3) electronic correlation. A detailed discussion on how these properties modify in a particular manner the electron density structure when considering a one‐electron or a two‐electron density description is conducted.

A Configuration Space Model for Intermediate‐Scale Ionospheric Structure

AbstractStochastic ionospheric structure is characterized by spectral density functions (SDFs), which are formally the average intensity of Fourier transformations of the electron density structure. Structure elongation along magnetic field lines is typically accommodated by constraining contours of constant spatial correlation to field‐aligned ellipsoidal surfaces. Structure realizations are generated by imposing the square root of the SDF onto uncorrelated random Fourier modes. The approach has been used successfully for interpreting both in situ and remote propagation diagnostics. However, the only connection to the field‐aligned structures generated by the underlying instability mechanism is the correlation scale. This paper introduces a configuration space model that constructs realizations as summations of field‐aligned elemental striations with a prescribed scale and peak electron density. We show that by choosing the contributing scales according to a bifurcation rule and imposing a power law intensity scaling, the corresponding SDF closely approximates an inverse power law. Thus, configuration space realizations can be structured to reproduce prescribed or measured SDFs from one‐dimensional scans. Stochastic variation comes from an imposed random distribution of striation locations, which are defined by their intercept in a reference slice plane. To conform more directly to physics‐based simulations, the striations can be interpreted as voids in the background electron density. The model is designed to support propagation simulations with arbitrary propagation angles relative to the local magnetic field direction. Relations between in situ structure and diagnostic measurements as well as phase screen equivalence can be explored.

RGO Functionalized with a Highly Electronegative Keplerate-Type Polyoxometalate for High-Energy-Density Aqueous Asymmetric Supercapacitors.

Keplerate-type polyoxometalates represent a large series of high nuclear molecular clusters; for example, (NH4 )42 [MoVI 72 MoV 60 O372 (CH3 COO)30 (H2 O)72 ] ({Mo132 }) is a kind of spherical heteropoly blue with a large overall negative charge and an electron density and topological structure similar to C60 . {Mo132 } is a good bifunctional material that can be used as an electron acceptor or donor, which is advantageous to accelerate electron transmission in supercapacitors. Herein, a nanocomposite of rGO functionalized with a Keplerate-type polyoxometalate {Mo132 } was prepared by a facile chemical reduction method and used to construct supercapacitors for the first time. The electrochemical performance of the supercapacitors can be significantly improved due to the excellent redox properties, high electronegativity, and hollow porous structures of {Mo132 }, in addition to the outstanding conductivity of rGO. The {Mo132 }-rGO nanocomposite electrode exhibited an excellent gravimetric specific capacitance of 617.3 F g-1 at a current density of 5 A g-1 in 1 m Li2 SO4 electrolyte. An aqueous asymmetric supercapacitor with a voltage range of 2.1 V, with the {Mo132 }-rGO nanocomposite as the negative electrode and modified activated carbon as the positive electrode, exhibited a high energy density of 31.6 Wh kg-1 with a power density of 207.7 W kg-1 and favorable cycling stability.

Shapes of Magnetically Controlled Electron Density Structures in the Dayside Martian Ionosphere

AbstractNonhorizontal localized electron density structures associated with regions of near‐radial crustal magnetic fields are routinely detected via radar oblique echoes on the dayside of Mars with the ionospheric sounding mode of the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) radar onboard Mars Express. Previous studies mostly investigated these structures at a fixed plasma frequency and assumed that the larger apparent altitude of the structures compared to the normal surrounding ionosphere implied that they are bulges. However, the signal is subjected to dispersion when it propagates through the plasma, so interpretations based on the apparent altitude should be treated with caution. We go further by investigating the frequency dependence (i.e., the altitude dependence) of the shape of 48 density structure events, using time series of MARSIS electron density profiles corrected for signal dispersion. Four possible simplest shapes are detected in these time series, which can give oblique echoes: bulges, dips, downhill slopes, and uphill slopes. The altitude differences between the density structures and their edges are, in absolute value, larger at low frequency (high altitude) than at high frequency (low altitude), going from a few tens of kilometers to a few kilometers as frequency increases. Bulges dominate in numbers in most of the frequency range. Finally, the geographical extension of the density structures covers a wide range of crustal magnetic fields orientations, with near‐vertical fields toward their center and near‐horizontal fields toward their edges, as expected. Transport processes are suggested to be a key driver for these density structures.

Density functional theory calculations of the water interactions with ZrO2 nanoparticles Y2O3 doped

Development of a new electricity generation techniques is one of the most relevant tasks, especially nowadays under conditions of extreme growth in energy consumption. The exothermic heterogeneous electrochemical energy conversion to the electric energy through interaction of the ZrO2 based nanopowder system with atmospheric moisture is one of the ways of electric energy obtaining. The questions of conversion into the electric form of the energy of water molecules adsorption in 3 mol% Y2O3 doped ZrO2 nanopowder systems were investigated using the density functional theory calculations. The density functional theory calculations has been realized as in the Kohn-Sham formulation, where the exchange-correlation potential is approximated by a functional of the electronic density. The electronic density, total energy and band structure calculations are carried out using the all-electron, full potential, linear augmented plane wave method of the electronic density and related approximations, i.e. the local density, the generalized gradient and their hybrid approximations.