Local Spectrum Research Articles

Mapping Heterogeneity of Pristine and Aged Li- and N-Mnhcf Cathode by Synchrotron-Based Energy-Dependent Full Field Transmission X-ray Microscopy.

Manganese hexacyanoferrate is a promising cathode material for lithium and sodium ion batteries, however, it suffers of capacity fading during the cycling process. To access the structural and functional characteristics at the nanometer scale, fresh and cycled electrodes are extracted and investigated by transmission soft X-ray microscopy, which allows chemical characterization with spatial resolution from position-dependent x-ray spectra at the Mn L-, Fe L- and N K-edges. Furthermore, soft X-rays prove to show superior sensitivity toward Fe, compare to hard X-rays. Inhomogeneities within the samples are identified, increasing in the aged electrodes, more dramatically in the Li-ion system, which explains the poorer cycle life as Li-ion cathode material. Local spectra, revealing different oxidation states over the sample with strong correlation between the Fe L-edge, Mn L-edge, and N K-edge, imply a coupling between redox centers and an electron delocalization over the host framework.

Modulation of Cosmic-Ray Antiprotons in the Heliosphere: Simulations for a Solar Cycle

The precision measurements of galactic cosmic-ray protons from the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics and the Alpha Magnetic Spectrometer are reproduced using a well-established three-dimensional numerical model for the period 2006 July–2019 November. The resulting modulation parameters are applied to simulate the modulation for cosmic antiprotons over the same period, which includes the times of minimum modulation before and after 2009, the maximum modulation from 2012 to 2015, including the reversal of the Sun’s magnetic field polarity, and the approach to new minimum modulation in 2020. Apart from their local interstellar spectra, the modulation of protons and antiprotons differ in their charge sign and consequent drift pattern. The lowest proton flux was in 2014 February–March, but the lowest simulated antiproton flux is found to have been in 2015 March–April. These simulated fluxes are used to predict the proton-to-antiproton ratios as a function of rigidity. The trends in these ratios contribute to clarifying, to a large extent, the phenomenon of charge-sign dependence of heliospheric modulation during vastly different phases of the solar activity cycle. This is reiterated and emphasized by displaying so-called hysteresis loops. It is also illustrated how the values of the parallel and perpendicular mean free paths, as well as the drift scale, vary with rigidity over this extensive period. The drift scale is found to be at its lowest level during the polarity reversal period, while the lowest level of the mean free paths is found to be in 2015 March–April.

Early Visual Deprivation Impairs Functional Development of the Visual Ventral Stream.

To probe the dynamic alternations of neural networks in real-time visual processing after visual deprivation (VD) removal. A prospective cross-sectional study was conducted. Twenty children with a history of early binocular VD caused by congenital cataracts and 20 matched typically developing (TD) children were enrolled. The event-related potential (ERP) data were obtained via high-density electroencephalography. ERP data were analyzed based on three components (P1, N170, and P2), three test conditions (objects, human faces, and Chinese characters), and peak time and region of interest (ROI) chosen on a grand average head map collapsed from the averaged waveform of each group. Source localization and alpha power spectrum density were applied to define the functional pattern of brain areas and evaluate the attention function. The VD group showed significantly lower P1 amplitudes than the TD group under all conditions in peak ROIs, which were situated in the left occipito-temporal region. For both VD and TD groups, there were strong N170 effects in the character and human face conditions in the component's peak ROIs. Furthermore, source mapping indicated that the VD group generally showed significantly lower activation in the visual cortex and ventral stream, whereas the beyond network areas (mostly frontal areas) intensively participated in functional compensation in the VD group. The VD group showed significant poststimulus alpha desynchronization in object recognition. Our research described the mechanisms of visual networks after early binocular VD removal. Our findings may provide a new basis for the poor visual recovery after early binocular VD removal and offer clues for visual recovery strategies.

Modeling the Atmospheric Ionization Rate During a Geomagnetic Reversal

AbstractThe Matuyama‐Brunhes reversal of Earth's magnetic dipole field took place 0.78 Ma ago, and detailed temporally resolved paleomagnetic data are available for this period. A geomagnetic reversal is expected to impact the cosmic ray flux, which in turn affects atmospheric ionization rates. To assess the magnitude of this effect, three preexisting models are used in tandem to yield 3D time series of the atmospheric ionization rates for the entire globe during the reversal. Specifically the time variable paleomagnetic field data is input into a particle trajectory calculator to produce geomagnetic cutoff rigidity maps for the entire globe. This is combined with an empirical model of the local interstellar cosmic ray spectrum and ionization yield functions based on Monte Carlo atmospheric particle simulations to produce novel time variable 3D atmospheric ionization rates during the reversal. As the dipole field weakens, the atmospheric ionization increases at low latitudes. The increase is ca. 25% at the surface and up to a factor of 5 in the upper atmosphere. Globally, ionization rates increase around 13% at the surface and up to a factor of 2 in the upper atmosphere, whereas polar regions are largely unaffected. Finally, the change in ionization due to the solar 11‐year cycle is greatly affected by the reversal. The relative change in atmospheric ionization between solar‐minimum and solar‐maximum varies between 2 and two orders of magnitude.

Penguatan Kapasitas Keorganisasian pada Ikatan Remaja Masjid Al-Mukminin Kelurahan Binawidya Kota Pekanbaru

The realization of faithful, pious, and noble youth is part of the youth development goals in Law 40 of 2009 concerning youth. The Mosque Youth Association (IRMA) Al-Mukminin, Bina Widya Village, Pekanbaru City can become a pioneer and a local scale spectrum to optimize the role of youth through activities to prosper the mosque as part of an effort to realize these youth development goals. Moving on from this, community service to increase the organizational capacity of IRMA Al-Mukminin was carried out. The purpose of the activity is to strengthen the understanding and organizational capacity of IRMA Al-Mukminin. The service method uses a transformative approach through the stages to know, identify problems, develop plans, take action, and build awareness in a sustainable manner. The results of community service activities were in the form of an increase in the organizational capacity of the Al-Mukminin Mosque Youth Association (IRMA) in Binawidya Village, Pekanbaru City.

X-ray photodesorption of complex organic molecules in protoplanetary disks

Context. X-rays emitted from pre-main-sequence stars at the center of protoplanetary disks can induce nonthermal desorption from interstellar ices populating the cold regions of the disk. This process, known as X-ray photodesorption, needs to be quantified for complex organic molecules (COMs), including acetonitrile CH3CN, which has been detected in several disks. Aims. The purpose of this work is to experimentally estimate the X-ray photodesorption yields of neutral species from pure CH3CN ices and from interstellar ice analogs for which CH3CN is mixed either in a CO-dominated ice or in a H2O-dominated ice. Methods. The ices, grown in an ultrahigh vacuum chamber, were irradiated at 15 K by soft X-rays from synchrotron light (SOLEIL synchrotron) in the N K edge region (395–420 eV) and in the O K edge region (530–555 eV). X-ray photodesorption was probed in the gas phase via quadrupole mass spectrometry by monitoring the changes in the mass signals due to the X-ray irradiation of the ices. X-ray photodesorption yields were derived from the mass signals and were extrapolated to higher X-ray energies in order to provide astrophysical yields adapted to astrochemical models. Results. X-ray photodesorption of the intact CH3CN is detected from pure CH3CN ices and from mixed 13CO:CH3CN ices, with an experimental yield of about 5 × 10−4 molecules photon−1 at 560 eV. When mixed in H2O-dominated ices, X-ray photodesorption of the intact CH3CN at 560 eV is below its detection limit, which is 10−4 molecules photon−1. Yields associated with the desorption of HCN, CH4, and CH3 are also provided. The derived astrophysical yields significantly depend on the local conditions expected in protoplanetary disks, that is, on the ice composition and on the local X-ray irradiation spectrum. They vary from ~10−4 to ~10−6 molecules photon−1 for the X-ray photodesorption of intact CH3CN from CO-dominated ices. Only upper limits varying from ~5 × 10−5 to ~5 × 10−7 molecules photon−1 could be derived for the X-ray photodesorption of intact CH3CN from H2O-dominated ices. Conclusions. X-ray photodesorption of intact CH3CN from interstellar ices might in part explain the abundances of CH3CN observed in protoplanetary disks. The desorption efficiency is expected to vary with the local physical conditions, hence with the disk region considered.

Infinite-layer nickelates as Ni-eg Hund’s metals

The recent and exciting discovery of superconductivity in the hole-doped infinite-layer nickelate Nd1−δSrδNiO2 draws strong attention to correlated quantum materials. From a theoretical view point, this class of unconventional superconducting materials provides an opportunity to unveil a physics hidden in correlated quantum materials. Here we study the temperature and doping dependence of the local spectrum as well as the charge, spin and orbital susceptibilities from first principles. By using ab initio LQSGW+DMFT methodology, we show that onsite Hund’s coupling in Ni-d orbitals gives rise to multiple signatures of Hund’s metallic phase in Ni-eg orbitals. The proposed picture of the nickelates as an eg (two orbital) Hund’s metal differs from the picture of the Fe-based superconductors as a five orbital Hund’s metal as well as the picture of the cuprates as doped charge transfer insulators. Our finding uncover a new class of the Hund’s metals and has potential implications for the broad range of correlated two orbital systems away from half-filling.

Spectrum Management for Local Mobile Communication Networks

Spectrum management is a complex topic that divides stakeholders' perspectives. Recently, a major paradigm shift has taken place with the emergence of local 4G and 5G networks via local spectrum licensing models in several countries, allowing different stakeholders to establish their own mobile communication networks within specific facilities, such as a factories and ports. These local mobile communication networks can serve mobile network operators' (MNOs) end users, closed user groups, or a mix, resulting in operations under different regulatory conditions. Their emergence relies on spectrum availability in the given location, which is managed by national regulators. Local spectrum availability can be increased with spectrum sharing where two or more radio systems operate in the same band, but stakeholder views differ - some promote it while others object it. This paper analyzes the most recent spectrum management developments from the viewpoint of emerging local mobile communication networks considering the role of spectrum sharing. The analysis reveals how differently the countries have prepared for the new business opportunity arising from local mobile communication networks in their spectrum awarding decisions and quantifies current spectrum availability for establishing local 5G networks. The results show varying spectrum management approaches taken by the regulators. Especially, local spectrum licenses appear in the most recent spectrum awards. To realize a large number of local 4G/5G and future 6G networks, spectrum sharing will become critical and needs to be clearly defined and understood to mitigate currently strong stakeholders' objection.

Inverse design of plasmonic nanoantenna using generative adversarial network

The local surface plasmon resonance (LSPR) effect has been widely used in various nanophotonic applications. However, because the LSPR effect is highly sensitive to the structure and geometry, it is desirable to efficiently search viable geometries for predefined local field enhancement spectrum. Herein we present a generative adversarial network-based LSPR nanoantenna design scheme. By encoding the antenna structure information into an red-green-blue (RGB) color image, the corresponding nanoantenna structure can be inverse-designed to achieve the required enhancement spectrum of the local field. The proposed scheme can accurately offer the multiple geometry layout for the customized specific spectrum in seconds, which could be beneficial for fast design and fabrication of plasmonic nanoantenna.

Corrosion Protection Mechanism Study of Nitrite-Modified CaAl-LDH in Epoxy Coatings

In this work, nitrite and molybdate-modified CaAl layered double hydroxide(CaAl-LDH) was first synthesized, and the corrosion protection mechanism of CaAl-LDH intercalated with nitrites in epoxy coatings was investigated. Scanning electronic microscopy (SEM) and the energy dispersive spectroscopy (EDS) was used to characterize the morphology and element composition of the synthesized powder. Fourier transform infrared spectroscopy (FTIR) was used to characterize the information of chemical composition, and X-ray diffraction (XRD) was used to analyze the structure. The SEM and XRD results indicated that the LDH structure was destroyed in the molybdate modification process, and CaMoO4 precipitates were formed. Therefore, molybdates cannot be used to be loaded in CaAl-LDH interlayer space for synthesis of an active corrosion inhibition container. The nitrite release curve and the chloride concentration decreasing curve were measured to study the anion-exchange reaction by UV-Vis spectroscopy and a home-made Ag/AgCl probe, respectively. The corrosion protection effect of the CaAl-LDH loaded with nitrites towards the carbon steel was evaluated in 0.02 M NaCl solution by electrochemical impedance spectroscopy (EIS). Then the powder was added in the epoxy coating with 2% addition (weight vs. epoxy resin). The coating morphology and roughness were evaluated by SEM and laser microscopy, and the corrosion protection effect was investigated by EIS in an immersion period of 21 d. The fitted coating resistance of the sample with 2% LDH intercalated with nitrites was one order of magnitude higher than that with 2% LDH, and the latter one was two orders of magnitude higher than the blank sample. Local electrochemical impedance spectra (LEIS) was used to characterize the corrosion development process in micro-corrosion sites. The corrosion product of the scratched area after salt spray exposure was analyzed by EDS and Raman spectroscopy. The corrosion protection mechanism of the CaAl-LDH loaded with nitrites was proposed based on the above experimental results.

A comprehensive study of the aerodynamic characteristics of an aspect ratio of 6.25:1 inclined square prism

Inclined prismatic structures have grown in popularity in civil engineering due to increased architectural and aesthetic demands, leading to a surging need to study their aerodynamic properties. In this study, an inclined square prism was examined using wind tunnel tests and numerical simulations with an aspect ratio of 6.25:1. The Synchronous Multi-Pressure Sensing System (SMPSS) wind tunnel technique was used to evaluate the aerodynamic characteristics of the structure, including surface pressure distribution, local force spectra, force coefficient, coherence, and the Strouhal number. Moreover, the numerical Large-eddies simulation (LES) were also deployed to investigate the flow field morphology around the structure. Results show that the orientation, direction, and angle of inclination direction significantly affect the prism’s aerodynamic characteristics. Several flow field phenomena were also revealed. Forward inclination enhances the downwash flow, whereas the backward counterpart enhances the upwash flow, and transverse inclination produces a noticeable modification in the vortex morphology near the prism base. These findings can inform structural design and contaminant dispersion efforts.

The emergence of global phase coherence from local pairing in underdoped cuprates

In conventional metallic superconductors such as aluminium, the large number of weakly bounded Cooper pairs become phase-coherent as soon as they start to form. The cuprate high-temperature superconductors belong to a different category because, being doped Mott insulators, they are known to have low superfluid density and are therefore susceptible to phase fluctuations. It has been proposed that pairing and phase coherence may occur separately in cuprates, and that the measured critical temperature corresponds to the phase-coherence temperature controlled by the superfluid density. Here we examine the evolution of pairing and phase-ordering in underdoped cuprates, and find that a chequerboard plaquette pattern of charge order plays a crucial role, such that the global phase coherence is established once its spatial occupation exceeds a threshold. We make these observations via scanning tunnelling microscopy on underdoped Bi2LaxSr2 − xCuO6 + δ. We observe a smooth crossover from the Mott insulator to superconductor on small islands that have chequerboard order. Each chequerboard plaquette contains approximately two holes and exhibits a stripy internal structure that has a strong influence on the superconducting spectroscopic features. The local spectra remain qualitatively the same across the insulator-to-superconductor transition, and the quasiparticle interference becomes long-ranged. How the superconducting state emerges from a Mott insulator in cuprate superconductors is still not fully understood. Now, the spatial extent of a chequerboard charge order with internal stripes is shown to be crucial.

Probing dark matter axions using the hyperfine structure splitting of hydrogen atoms

QCD axions can be a substantial part of dark matter if their mass ma∼10−5 eV. Since the axions were created by the misalignment mechanism, their local energy spectrum density is large. Consequently, the axion-induced atomic transition rate is enhanced if the atomic energy gap matches the axion mass. The hyperfine splitting between the spin 0 singlet ground state and the spin 1 triplet state of hydrogen is 0.59×10−5 eV, which is close to the preferred mass of dark matter axions. With an energy gap adjustment by applying a weak Zeeman magnetic field, dark matter axions can induce atomic hydrogen transitions. Furthermore, because the total spins of the hydrogen triplet and singlet differ, the axion-induced transitions are detectable by a Stern–Gerlach apparatus or a sensitive magnetic field detector. A potential realization of the proposed scheme can be similar to existing hydrogen masers.

Electrostatic control of the proximity effect in the bulk of semiconductor-superconductor hybrids

The proximity effect in semiconductor-superconductor nanowires is expected to generate an induced gap in the semiconductor. The magnitude of this induced gap, together with the semiconductor properties like spin-orbit coupling and g-factor, depends on the coupling between the materials. It is predicted that this coupling can be adjusted through the use of electric fields. We study this phenomenon in InSb/Al/Pt hybrids using nonlocal spectroscopy. We show that these hybrids can be tuned such that the semiconductor and superconductor are strongly coupled. In this case, the induced gap is similar to the superconducting gap in the Al/Pt shell and closes only at high magnetic fields. In contrast, the coupling can be suppressed which leads to a strong reduction of the induced gap and critical magnetic field. At the crossover between the strong-coupling and weak-coupling regimes, we observe the closing and reopening of the induced gap in the bulk of a nanowire. Contrary to expectations, it is not accompanied by the formation of zero-bias peaks in the local conductance spectra. As a result, this cannot be attributed conclusively to the anticipated topological phase transition and we discuss possible alternative explanations.

Toxicological screening method by HPLC-DAD with local spectral library and "home-made" internal standard

A liquid-liquid extraction technique and HPLC-DAD method using a C18 column, 5μm (150x4.6mm i.d.) were developed for a toxicological drug screening. A home-made “N-acetylparoxetine” is used as internal standard. A local UV spectra library of over 130 drugs and some of their metabolites was created. This library covers the main therapeutic classes involved in intoxication cases. The developed procedure is successfully applied to different biological samples (serum, urine, gastric fluid and post mortem whole blood) and allows rapid and simultaneous detection and identification of a large number of substances and their semi-quantification in serum.

A local spectrum enhancement‐based method and its application in incipient fault diagnosis of rotating machinery

AbstractIncipient faults of gears and rolling bearings in rotating machineries are very difficult to identify using traditional envelope analysis methods. To address this challenge, this paper proposes an effective local spectrum enhancement‐based diagnostic method that can identify weak fault frequencies in the original complicated raw signals. For this purpose, a traversal frequency band segmentation technique is first proposed for dividing the raw signal into a series of subfrequency bands. Then, the proposed synthetic quantitative index is constructed for selecting the most informative local frequency band (ILFB) containing fault features from the divided subfrequency bands. Furthermore, an improved grasshopper optimization algorithm‐based stochastic resonance (SR) system is developed for enhancing weak fault features contained in the selected most ILFB with less computation cost. Finally, the enhanced weak fault frequencies are extracted from the output of the SR system using a common spectrum analysis. Two experiments on a laboratory planetary gearbox and an open bearing data set are used to verify the effectuality of the proposed method. The diagnostic results demonstrate that the proposed method can identify incipient faults of gears and bearings in an effective and accurate manner. Furthermore, the advantages of the proposed method are highlighted by comparison with other methods.

Impedance models for single and two degree of freedom linings with an improved data base and local non-linearity

Previously developed predictive models for impedance of single-degree-of-freedom and two-degree-of-freedom acoustic linings driven by a broad band acoustic source are reexamined. Two issues are addressed, the first being improvement of the conventional perforate face sheet impedance model. Data correlations based on flow bench measurements of steady flow pressure drop are reevaluated with emphasis on low flow velocity to improve the consistency of the prediction of linear resistance. In addition, for two-degree-of-freedom linings, face sheet mass reactance is modified to account for the presence of the septum. The second issue addresses the implication that for a non-linear lining, with impedance a function of the local sound pressure level, the installed performance of the lining depends on the local impedance, as opposed to impedance based on the source sound pressure level. This is investigated in the benchmarking of the impedance models by comparison of the acoustic transfer function predicted by a propagation code with the imbedded impedance model and transfer function measurements made in a grazing flow duct test facility. The propagation code is extended to make the non-linear behavior of the lining model dependent on the local acoustic spectrum, introducing an additional level of non-linearity and an iterative application of the propagation code. A principal conclusion is that with no grazing flow both the lining model and grazing flow duct transfer function measurements show a significant effect of local variation of the acoustic spectrum. With increasing grazing flow Mach number, this effect is reduced and effectively disappears at the highest Mach number. With increasing grazing flow Mach number the grazing flow contribution to face sheet resistance dominates and tends to mask the non-linear behavior of the component of resistance not related to grazing flow.

Combined analysis of stellar and planetary absorption lines via global forward-transit simulations

Context. Transit spectroscopy of exoplanets has led to the detection of many species whose absorption signatures trace their atmospheric structure and dynamics. Improvements in resolution and sensitivity have, however, revealed biases induced by stellar lines occulted by the transiting planet. Aims. We characterise the planet-occulted line distortions (POLDs) in absorption spectra that arise from proxies used for the occulted stellar lines and investigate the impact of stellar rotation, centre-to-limb variations, and broadband limb-darkening. Methods. We used the EVaporating Exoplanets (EVE) code to generate realistic stellar spectra during the transit of exoplanets, accounting for the 3D geometry of the system’s architecture and atmospheric transit, as well as for spectral variations over the stellar disc. The absorption spectra were calculated using approaches drawn from the literature and compared to the expected signal. Results. The POLDs from stellar rotation are dominant for moderate to fast rotating stars, reaching amplitudes comparable to atmospheric signals, but they can be mitigated by shifting the stellar line proxies to the radial velocity of the planet-occulted region. Centre-to-limb variations become dominant for slow rotators and are more easily mitigated at the stellar limb. We re-interpret the ESPRESSO data of two iconic systems and confirm that the sodium signature from HD 209458 b mainly arises from POLDs. However, we unveil a possible contribution from the planetary atmosphere that warrants further observations. For MASCARA-1 b, we did not find evidence for atmospheric sodium absorption and we can fully explain the observed signature by a POLD for super-solar stellar sodium abundance. Conclusions. We studied POLDs dependency on star and planet properties, and on the proxy used for planet-occulted lines. Distinguishing planetary absorption signatures from POLDs is challenging without access to accurate estimates of the local stellar spectrum and system orbital parameters. We propose a way to mitigate POLDs and improve atmospheric characterisation, by using simultaneous forward modelling of both the star and the planet to simulate the global observed signatures.

On Absoluteness and Stationary Condition of WMDS for Range-Based Localization

Weighted multidimensional scaling (WMDS), an algorithm extending multidimensional scaling (MDS), has been utilized in a broad spectrum of localization. However, there are still two unsolved theoretical questions. (i) The estimator provided by MDS depicts a relative placement of targets which requires further Procrustes analysis to recover the actual placement, referred to as the absolute placement. This fact produces a question: Does the estimator of WMDS is still relative? If not, what underlying mechanisms assert the absoluteness? (ii) It has been proved that WMDS attains the Cramér-Rao lower bound (CRLB) when the ranging distribution is Gaussian. Does it hold for a general distribution? If not, what restrictions on distributions are required? Motivated by such theoretical incompleteness, this paper offers an in-depth theoretical analysis on WMDS in the scheme of range-based localization. With regard to question (i), we reveal the mechanisms that assert the estimator of WMDS always represents exactly the actual locations, and prove that the absoluteness is introduced at the moment of variable separation and all the subsequent matrix equation transformations preserve the absoluteness. As for question (ii), the functional behaviors and maximum condition of CRLB are examined under a general ranging distribution. Then, via the comparison to the variance of WMDS estimator, the stationary condition on ranging distributions for WMDS to attain the CRLB is provided. Extensive simulations are performed to validate the theoretical conclusions numerically. And there exists conformity between numerical and theoretical results.

Hybrid Radio Resource Management for 6G Subnetwork Crowds

In-X subnetworks are expected to be located at the very edge of the 6G 'network of networks' and provide localized wireless connectivity for in-vehicle, in-robot, in-body communication. By nature in-X subnetworks can lead to dense crowds, calling for efficient radio resource management techniques. In this article, we introduce a hybrid radio resource management framework where the decision capabilities can either happen at a global agent operating on an umbrella 6G network, or locally at each subnetwork, depending on the quality of the backhaul link, the crowd density and the local spectrum sensing capabilities. We present a possible application of the proposed framework for the problem of radio channel selection in a dense crowd. Possible research directions leveraging the proposed framework are also described.