Resolution Spectra Research Articles

High-Resolution NMR of the Hydrogenation Reaction with Parahydrogen in an Inhomogeneous Magnetic Field.

Nuclear magnetic resonance is extremely attractive for operando studies of chemical reactors. However, the heterogeneous catalyst particles placed inside an NMR probe greatly affect the uniformity of the magnetic field. This problem is especially acute when studying heterogeneous hydrogenation processes using parahydrogen. Despite the increased sensitivity due to hyperpolarization, under conditions of a strong heterogeneity of the magnetic field, the antiphase nature of the NMR signals leads to a partial or even a complete loss of spectroscopic information due to significant NMR signal broadening. The use of intramolecular multiple-quantum coherences in 2D NMR allows one to circumvent this problem. We used the COSY pulse sequence to acquire 2D NMR spectra of the reaction mixture upon propene hydrogenation with parahydrogen. The selection of double-quantum coherences in the resulting 2D NMR spectrum allowed us to obtain a highly resolved NMR spectrum under conditions of severe inhomogeneity of the magnetic field caused by the presence of catalyst granules.

Bioguided Identification of Polymethoxyflavones as Novel Vascular CaV1.2 Channel Blockers from Citrus Peel.

The huge amount of citrus peel produced worldwide represents an economic burden for society. However, this agricultural by-product is a rich source of natural molecules, potentially endowed with interesting pharmacological activities. In this regard, we decided to investigate if the polymethoxyflavones contained in citrus peel waste could be exploited as novel vasorelaxant agents. A hydroalcoholic blond orange (Citrus sinensis) peel extract, obtained by ultrasonication, was partitioned in dichloromethane. Column chromatography allowed for the isolation of four polymethoxyflavones, namely, scutellarein tetramethyl ether, nobiletin, tangeretin, and sinensetin, identified by nuclear magnetic resonance (NMR) spectroscopy and UPLC-HRMS/MS and confirmed by multivariate curve resolution of NMR fractional spectra. The four molecules showed interesting in vitro vasorelaxant activity, at least, in part, due to the blockade of smooth muscle CaV1.2 channels. Molecular modeling and docking analysis elucidated the binding mode of the polymethoxyflavones at the homology model of the rat CaV1.2c subunit and provided the structural basis to rationalise the highest activity of scutellarein tetramethyl ether in the set and the dramatic effect of the additional methoxy group occurring in nobiletin and sinensetin. In conclusion, citrus peel can be considered a freely available, valuable source of vasoactive compounds worthy of pharmaceutical and/or nutraceutical exploitation.

Improved numerical modeling of photovoltaic double skin façades with spectral considerations: Methods and investigations

Photovoltaic double skin façades are crucial tools for mitigating the escalating energy consumption in buildings. However, current simulation studies often neglect the variation in solar spectra and focus on only limited operational modes, resulting in incomplete and less accurate modeling. In response to these limitations, this study proposes an improved numerical model incorporating temporal spectral variations and non-uniform surface temperatures, which comprehensively encompasses all operational modes of photovoltaic double skin facades. Real-time solar spectra are acquired using specialized software and remote sensing data, while the transportation and conversion of radiation energy will be solely solved at individual wavelength steps, providing the model with spectrum resolution. Built on the fundamental principles of optics, thermodynamics, and hydromechanics, the proposed two-dimensional numerical model consistently demonstrates desirable accuracy across various airflow paths and mechanical ventilation conditions. Based on the proposed model, the feasibility of the previously proposed parameter-based control strategy is proved, which offers potential energy savings of 25.9–341.6 MJ compared to the radical strategy and 67.5–170.7 MJ compared to the conservative strategy. The photovoltaic efficiency drop due to spectral mismatch is also quantified as about 15–35 %. These results highlight the potential of the proposed model as an efficient tool for future research.

Homonukleare Super‐Resolution NMR‐Spektroskopie

AbstractIn homonuklearen 1H NMR ‐Spektren wie dem [1H,1H]‐NOESY‐Spektrum (Nuclear Overhauser Enhancement Spectroscopy), einem historischen Eckpfeiler der biomolekularen NMR‐Strukturbiologie, treten innerhalb eines Quadrats von etwa 100 ppm2 hunderte bis tausende von Kreuzpeaks auf, was zu einer starken Signalüberlappung führt. Die spektrale Auflösung ist daher ein limitierender Faktor für die eindeutige Zuordnung der chemischen Verschiebung und die Interpretation der Daten für die Dynamik und Strukturaufklärung. Die Aufnahme der Spektren bei höheren Magnetfeldern, z. B. bei einer 1.2 GHz 1H‐Frequenz, hilft, die spektrale Überlagerung zu verringern, da die Auflösung proportional zur Magnetfeldstärke skaliert. Hier zeigen wir, dass die Linienbreiten von Kreuzpeaks in [1H,1H]‐NOESY‐ und [1H,1H]‐TOCSY‐Spektren durch Super‐Resolution Spektroskopie in jeder Dimension um einen Faktor 2 bis 3 weiter reduziert werden können. In der indirekten Dimension wird eine zusammengesetzte, exponentiell‐kosinus‐gewichtete Anzahl von Scans entlang der Zeitinkremente gemessen und durch eine Windowfunction digital geglättet, während in der direkten Dimension ein Produkt aus Exponential‐ und Kosinusfunktion alsApodisierungsfunktion angewendet wird. Darüber hinaus wird eine Zeitersparnis bei der Messung durch Reduced‐Acquired Super‐ Resolution (RASR) eingeführt. Die Anwendung auf das 20 kDa Protein KRAS zeigt, dass hochaufgelöste NMR‐Spektren, die sich für eine automatisierte Analyse eignen, in weniger als 3 Stunden aufgenommen werden können. Die Methode eröffnet einen Weg zur automatisierten Zuordnung chemischer Verschiebungen, Dynamik und Strukturbestimmung von unmarkierten kleinen und mittelgroßen Proteinen innerhalb von 24 Stunden.

Homonuclear Super-Resolution NMR Spectroscopy.

In homonuclear 1H NMR (nuclear magnetic resonance) spectra such as [1H,1H]-NOESY (Nuclear Overhauser Enhancement spectroscopy), which is a historic cornerstone spectrum for biomolecular NMR structural biology, hundreds to thousands of cross peaks are present within a square of approximately 100 ppm2 leading to a lot of signal overlap. Spectral resolution is thus a limiting factor for unambiguous chemical shift assignment and data interpretation for dynamics and structure elucidation. Acquiring the spectra at higher magnetic fields such as at a 1.2 GHz 1H frequency helps to reduce spectral crowding, since resolution scales proportionally to the magnetic field strength. Here, we show that the linewidths of cross peaks in [1H,1H]-NOESY and [1H,1H]-TOCSY spectra can be further reduced by a factor of 2-3 in each dimension by super-resolution spectroscopy. In the indirect dimension a composite exponential-cosine weighted number of scans along the time increments are recorded and digitally smoothened by a window function, while in the direct dimension an exponential-cosine window function is applied. Furthermore, measurement time saving by reduced-acquisition super-resolution (RASR) is introduced. Application to the 20 kDa protein KRAS shows that highly resolved NMR spectra suitable for automated analysis can be acquired within less than 3 hours. The method opens an avenue towards automated chemical shift assignment, dynamics and structure determination of unlabeled small and medium size proteins within 24 hours.

Evaluation of Norm-Constrained Capon Method on Improving Doppler Peak Localization of Antenna-Arrayed High-Frequency Coastal Radar

Abstract Antenna-arrayed high-frequency coastal radar is widely used to monitor the ocean and obtain metocean parameters such as sea surface current, sea wave height, and surface wind. However, the accuracy of these parameters can be significantly influenced by the spectral width and Doppler velocity of the sea echo signals across azimuthal directions, and insufficient spectrum resolution increases uncertainties in the estimates of spectral width and Doppler velocity. To address this, we demonstrate an alternative approach to beamforming by utilizing the norm-constrained Capon (NC-Capon) method to enhance the Doppler spectral resolution and improve the localization accuracy of the spectral peaks. The efficacy of the NC-Capon method is exemplified through an application to a coastal radar dataset collected from 16 receiving channels, operated at a central frequency of 27.75 MHz. A comparative investigation of the NC-Capon beamforming method with the conventional Fourier beamforming method showed that the widths of the spectral peaks at different range cells and azimuthal angles are noticeably improved at lower signal-to-noise ratio (SNR) conditions. Given this, the NC-Capon beamforming method exhibits more robustness to noise and could effectively enhance the concentration of the radar sea echo signals in the Doppler frequency spectrum, thereby reducing the uncertainties of the spectral width and Doppler/radial velocity of the first-order sea echoes. These characteristics are substantiated by the comparative analysis of spectral parameters between the two beamforming methods across various ranges, beamforming angles, and SNR levels. Finally, the computed radial velocities are benchmarked against in situ measurements obtained from a bottom-mounted acoustic current profiler to confirm the validity of the NC-Capon method. Significance Statement We have recently implemented a high-frequency coastal radar equipped with an antenna array to monitor metocean variables within the offshore waters adjacent to Taichung Harbor in Taiwan. Our study focuses on enhancing the Doppler spectral resolution of radar sea echoes by employing an adaptive beamforming technique known as the norm-constrained Capon method. In comparison with the traditional linear beamforming approach, the norm-constrained Capon method demonstrates superior noise resilience. We anticipate that the norm-constrained Capon method holds promise as a dependable approach for refining the accuracy of metocean parameters obtained from antenna-arrayed high-frequency coastal radar systems.

Advanced Frequency Analysis of Signals with High-Frequency Resolution

In today’s era, it is important to analyze and utilize various signals in industrial or laboratory applications. Measured signals provide critical information about the controlled system, which can be contained precisely within a narrow frequency range. Many methods and algorithms exist to process such signals in both the time and frequency domains. In particular, signal processing in the frequency domain is primary in industrial practice because dominant components within a specific narrow frequency band are sought. The discrete Fourier transformation (DFT) algorithm is the tool used in practice to find these frequency components. The DFT algorithm provides the full frequency spectrum with a higher number of calculation steps, and its spectrum frequency resolution is low. Therefore, research has focused on finding a method to achieve high-frequency spectrum resolution. An important factor in selecting the technique was that such an algorithm should be implementable on a microprocessor-based system under harsh industrial conditions. Research results showed that the DFT ZOOM method meets these requirements. The frequency zoom has many advantages but requires some modification. It is implemented in high-performance analyzers, but a thorough and detailed description of the respective algorithm is lacking in technical articles and literature. This article mathematically and theoretically describes the modified frequency zoom algorithm in detail. The steps of the frequency zoom, from creating an analytical signal through frequency shifting and decimation to the frequency analysis of the signal, are realized. The algorithm allows for the analysis of a signal with high-frequency resolution in a limited frequency band. A significant modification of DFT ZOOM is that of using the Hilbert transform to create an analytic signal. This resolves the aliasing issue caused by the overlap between fundamental and sideband spectra. Results from processing deterministic and stochastic signals using the modified DFT ZOOM are presented. The presented experimental results contribute to a more detailed frequency analysis of the signal. As part of this scientific research, the issues of frequency zoom were thoroughly addressed, solving the partial problems of this algorithm, both in theory and in the context of signal theory.

Bond Dissociation Energy of CO2 with Spectroscopic Accuracy Using State-to-State Resolved Threshold Fragment Yield Spectra.

In this study, we present a precise determination of the bond dissociation energy of CO2 using state-to-state resolved threshold fragment yield spectra at a photoexcitation wavelength of around 92 nm. Our findings show that the bond dissociation energy of CO2, CO2 → CO + O, is 43976.12(15) cm-1 or 526.0714(18) kJ/mol. Furthermore, by incorporating our previously measured bond dissociation energies for CO and O2, we determined the dissociation energy of CO2 into C + O2 and the CO2 atomization energy (CO2 → C + O + O) to be 92309.73(21) and 133578.92(18) cm-1 or 1104.2699(25) and 1597.9592(22) kJ/mol, respectively. Thus, the bond dissociation energies of CO2 for all channels now have uncertainties of 0.2 cm-1 or 0.002 kJ/mol. These results serve as reference points for the enthalpies of C atom and CO and CO2 molecules and provide benchmarks for high-level ab initio quantum chemistry calculations.

Single-pulse Emissions of PSRs J1611–0114 and J1617+1123

In this paper, the emissions from two pulsars, PSRs J1611−0114 and J1617+1123, were investigated using the Five-hundred-meter Aperture Spherical radio Telescope operating at a central frequency of 1250 MHz. The average pulse profile of PSR J1611−0114 shows two components, the first of which is relatively weak in intensity. The two-dimensional pulse stack exhibits an obvious nulling phenomenon, with an estimated nulling fraction of 40.1% ± 5.4%. The durations of the nulls and bursts are consistent with power-law distributions, and no periodic nulling phenomenon is found. The results from PSR J1617+1123 demonstrate that the average pulse profile is composed of four components. The peak intensity of the fourth component varies significantly, causing an unstable integrated profile. In addition, the modulation characteristics of J1611−0114 and J1617+1123 were studied by analyzing the modulation index, longitude resolved fluctuation spectrum and two-dimensional fluctuation spectrum using the software PSRSALSA. It was found that the two pulsars exhibit intensity modulation. In particular, J1611−0114 displays even–odd modulation, with the modulation period of approximately two pulses. The modulation period of J1617+1123 is relatively broad. There is an obvious subpulse drift phenomenon, and the value of P 2 is ∼0.125c/P 0, corresponding to 12 pulse longitude bins, and the drift rate (P 2/P 3) is about 0.29.

Homonuclear J-couplings and heteronuclear structural constraints

In magic angle spinning (MAS) experiments involving uniformly 13C/15N labeled proteins, 13C–13C and 13C–15N dipolar recoupling experiments are now routinely used to measure direct dipole–dipole couplings that constrain distances and torsion angles and determine molecular structures. When the distances are short (<4 Å), the direct couplings dominate the evolution of the spin system, and the 13C–13C and 13C–15N J-couplings (scalar couplings) are ignored. However, for structurally interesting >4 Å distances, the dipolar and J-couplings are generally of comparable magnitude, and the variation in J must be included in order to optimize the precision of the experiment. This problem is circumvented in cases with well resolved spectra by using frequency-selective dipolar recoupling methods where the effects of J-couplings are refocused. However, for larger molecules with more spectral crowding, the requisite pulse length to achieve selectivity becomes long and leads to unacceptable sensitivity losses during the pulse or the spectral overlap precludes selective excitation. In this paper, we address this problem with two approaches aimed at facilitating higher precision internuclear distance measurements in systems that are not fully resolved. Namely, (1) we describe an approach for high precision measurements of specific J-couplings using the in-phase anti-phase (IPAP) sequence which is integrated into a non-selective dipolar recoupling technique and (2) we utilize the measured J-couplings to implement a double quantum filter experiment capable of providing the resolution necessary for frequency selective dipolar recoupling techniques without resorting to multidimensional spectroscopy. We illustrate these methods using a 7-peptide segment from the amyloidogenic Sup-35p protein, U-13C/15N-GNNQQNY, where we have measured 25 of the 27 possible one bond 13C–13C J-couplings.

Digitally generated high-resolution mid-infrared dual-comb spectroscopy system based on electro-optic modulation.

In this Letter, we propose a high-resolution dual-comb spectroscopy (DCS) in the mid-infrared (MIR) region. A broadband electro-optic frequency comb (EOFC) with a line spacing of 13 GHz is generated in the near-infrared region. The injection locking technique is employed to lock the distributed feedback (DFB) laser to each comb line of the 34 comb lines as the seed laser for the subsequent electro-optic modulation. A dual radio frequency (RF) comb source with a 50 MHz line spacing and a 13 GHz bandwidth drives a single IQ Mach-Zehnder modulator (IQ-MZM), functioning as a single-sideband (SSB) generator and producing a DCS with high spectrum flatness and resolution flexibility. The generated DCS is converted to the MIR region via a nonlinear difference frequency generation (DFG) system. A DCS with a bandwidth of 442 GHz and a resolution of 50 MHz is achieved in the 3.3 µm region, and the figure of merit reaches 2.94×106 H z 12 in a 183.6 ms measurement time.

Total and symmetry resolved entanglement spectra in some fermionic CFTs from the BCFT approach

In this work, we study the universal total and symmetry-resolved entanglement spectra for a single interval of some 2d Fermionic CFTs using the Boundary Conformal Field theory (BCFT) approach. In this approach, the partition of Hilbert space is achieved by cutting out discs around the entangling boundary points and imposing boundary conditions preserving the extended symmetry under scrutiny. The reduced density moments are then related to the BCFT partition functions and are also found to be diagonal in the symmetry charge sectors. In particular, we first study the entanglement spectra of massless Dirac fermion and modular invariant Z2-gauged Dirac fermion by considering the boundary conditions preserving either the axial or the vector U(1) symmetry. The total entanglement spectra of the modular invariant Z2-gauged Dirac fermion are shown to match with the compact boson result at the compactification radius where the Bose-Fermi duality holds, while for the massless Dirac fermion, it is found that the boundary entropy term doesn’t match with the self-dual compact boson. The symmetry-resolved entanglement is found to be the same in all cases, except for the charge spectrum which is dependent on both the symmetry and the theory. We also study the entanglement spectra of N massless Dirac fermions by considering boundary conditions preserving different chiral U(1)N symmetries. Entanglement spectra are studied for U(1)M subgroups, where M ≤ N, by imposing boundary conditions preserving different chiral symmetries. The total entanglement spectra are found to be sensitive to the representations of the U(1)M symmetry in the boundary theory among other behaviours at O(1). Similar results are also found for the Symmetry resolved entanglement entropies. The characteristic log log (ℓ/ϵ) term of the U(1) symmetry is found to be proportional to M in the symmetry-resolved entanglement spectra.

Flexible tunable microwave photonic filter with a dual ultra-narrow passband based on a dual-wavelength Brillouin laser.

This article presents a flexibly tunable microwave photonic filter (MPF) with a dual ultra-narrow passband based on a dual-wavelength and narrow linewidth Brillouin laser. The dual passband of the filter not only exhibits ultra-high frequency selectivity but also allows for flexible and simultaneous tuning of the center frequency and interval of the passbands. In the proposed scheme, the core optical processor of the MPF consists of a dual-ring Brillouin laser resonator, which is composed of a 100-meter main fiber ring cascaded with a 10-meter secondary fiber ring. A dual-tone pump is generated through carrier-suppressed dual sideband modulation and injected into the dual-ring resonator to excite two Brillouin gains, which resonate separately in the dual-ring resonant cavity to generate a dual-wavelength single longitudinal mode Brillouin laser for processing optical RF signals. By selectively amplifying the modulated sideband signal through narrow linewidth Brillouin laser gain, the ultra-narrow dual passband are ultimately demodulated. The resulting dual filtering passband exhibits unparalleled sub-kHz bandwidth and flexible tuning capability. Experimental results demonstrate that the MPF proposed in this paper achieves an ultra-narrow dual passband of 83 Hz with a maximum side-mode suppression ratio of over 28 dB. Within the testing range of vector network analysis, the maximum tuning range of the center frequency is 20 GHz, and the passband interval can be freely tuned from 2-18 GHz. These results highlight the MPF's ability to concurrently filter dual-channel signals with high precision and its significant potential application value in ultrafine microwave frequency spectrum resolution and processing fields, such as instantaneous frequency measurement and microwave photonic sensing.

The linear canonical W-transform

The time-frequency spectrum of seismic data is commonly used as an attribute in the analysis and interpretation of nonstationary seismic signals. To improve the capability of the W-transform to analyze nonstationary data, we introduce the linear canonical W-transform (LCWT) by implementing an affine matrix along with scaling parameters to generate high resolution and energy-concentrated time-frequency spectra. More features of nonstationary signals can be explored in the time-linear canonical frequency domain by transforming the time-frequency plane, which makes the algorithm more applicable to seismic signals. For the completeness of the LCWT, we also develop the inverse LCWT to extend its applications. Examples of synthetic and field seismic data show that a highly resolved and energy-concentrated time-frequency spectrum can be estimated with the LCWT with negligible additional computational burden. In addition, our algorithm is promising for several seismic data processing and interpretation techniques, such as reservoir characterization and thin layer identification.

Characteristics of Gravity Waves in Opposing Phases of the QBO: A Reanalysis Perspective with ERA5

Abstract Gravity waves dispersing upward through the tropical stratosphere during opposing phases of the QBO are investigated using ERA5 data for 1979–2019. Log–log plots of two-sided zonal wavenumber–frequency spectra of vertical velocity, and cospectra representing the vertical flux of zonal momentum in the tropical lower stratosphere, exhibit distinctive gravity wave signatures across space and time scales ranging over two orders of magnitude. Spectra of the vertical flux of momentum are indicative of a strong dissipation of westward-propagating gravity waves during the easterly phase and vice versa. This selective “wind filtering” of the waves as they disperse upward imprints the vertical structure of the zonal flow on the resolved wave spectra, characteristic of (re)analysis and/or free-running models. The three-dimensional structures of the gravity waves are documented in composites of the vertical velocity field relative to grid-resolved tropospheric downwelling events at individual reference grid points along the equator. In the absence of a background zonal flow, the waves radiate outward and upward from their respective reference grid points in concentric rings. When a zonal flow is present, the rings are displaced downstream relative to the source and they are amplified upstream of the source and attenuated downstream of it, such that instead of rings, they assume the form of arcs. The log–log spectral representation of wind filtering of equatorial waves by the zonal flow in this paper can be used to diagnose the performance of high-resolution models designed to simulate the circulation of the tropical stratosphere.

Dynamics in the Intact fd Bacteriophage Revealed by Pseudo 3D REDOR-Based Magic Angle Spinning NMR.

The development of robust NMR methodologies to probe dynamics on the atomic scale is vital to elucidate the close relations between structure, motion, and function in biological systems. Here, we present an automated protocol to measure, using magic-angle spinning NMR, the effective 13C-15N dipolar coupling constants between multiple spin pairs simultaneously with high accuracy. We use the experimental dipolar coupling constants to quantify the order parameters of multiple C-N bonds in the thousands of identical copies of the coat protein in intact fd-Y21M filamentous bacteriophage virus and describe its overall dynamics on the submillisecond time scale. The method is based on combining three pseudo three-dimensional NMR experiments, where a rotational echo double resonance (REDOR) dephasing block, designed to measure internuclear distances, is combined with three complementary 13C-13C mixing schemes: dipolar-assisted rotational resonance, through-bond transfer-based double quantum/single quantum correlation, and radio frequency driven recoupling. These mixing schemes result in highly resolved carbon spectra with correlations that are created by different transfer mechanisms. We show that the helical part of the coat protein undergoes a uniform small (∼30°) amplitude motion, while the N-terminus is highly flexible. In addition, our results suggest that the reduced mobility of lysine sidechains at the C-terminus are a signature of binding to the single stranded DNA.

Quantitative analysis of the high speed and high precision waveform digital system for Jinping Neutrino Experiment

The Jinping Neutrino Experiment (JNE) aims to construct a 500-ton liquid scintillator detector for detecting and studying neutrinos. In JNE data analysis, particle energy and position reconstruction are crucial, with result accuracy closely related to the performance of the waveform digitization system. This study developed a quantitative model to explore correlations between sampling characteristics (effective number of bits and sampling rate) and detector system performance (single photoelectron charge spectrum resolution and transfer time spread). Additionally, three ADCs (Tsinghua ADC13B1G, ADI AD9695, TI ADS54J60) and MCP-PMTs were utilized to validate the model accuracy. The experimental results for the system charge spectrum resolution are in alignment with the theoretical predictions. When the ENOB of the ADC exceeds 10.66-bit and the sampling rate exceeds 1 GSPS, the system charge spectrum resolution is better than 45%, approaching the PMT inherent resolution of 44%. The transfer time spread within the system demonstrates minimal impact from the ADC sampling characteristics. These results serve as a reference for upgrading the JNE 60-channel and 4000-channel readout electronic systems. Additionally, this study can assist developers in maximizing the performance of physics experiment readout electronics systems within constrained budgets.

Transverse relaxation optimized spectroscopy of NH2 groups in glutamine and asparagine side chains of proteins.

A transverse relaxation optimized spectroscopy (TROSY) approach is described for the optimal detection of NH2 groups in asparagine and glutamine side chains of proteins. Specifically, we have developed NMR experiments for isolating the slow-relaxing 15N and 1H components of NH2 multiplets. Although even modest sensitivity gains in 2D NH2-TROSY correlation maps compared to their decoupled NH2-HSQC counterparts can be achieved only occasionally, substantial improvements in resolution of the NMR spectra are demonstrated for asparagine and glutamine NH2 sites of a buried cavity mutant, L99A, of T4 lysozyme at 5ºC. The NH2-TROSY approach is applied to CPMG relaxation dispersion measurements at the side chain NH2 positions of the L99A T4 lysozyme mutant-a model system for studies of the role of protein dynamics in ligand binding.

A Novel Time-Frequency Parameterization Method for Oscillations in Specific Frequency Bands and Its Application on OPM-MEG.

Time-frequency parameterization for oscillations in specific frequency bands reflects the dynamic changes in the brain. It is related to cognitive behavior and diseases and has received significant attention in neuroscience. However, many studies do not consider the impact of the aperiodic noise and neural activity, including their time-varying fluctuations. Some studies are limited by the low resolution of the time-frequency spectrum and parameter-solved operation. Therefore, this paper proposes super-resolution time-frequency periodic parameterization of (transient) oscillation (STPPTO). STPPTO obtains a super-resolution time-frequency spectrum with Superlet transform. Then, the time-frequency representation of oscillations is obtained by removing the aperiodic component fitted in a time-resolved way. Finally, the definition of transient events is used to parameterize oscillations. The performance of this method is validated on simulated data and its reliability is demonstrated on magnetoencephalography. We show how it can be used to explore and analyze oscillatory activity under rhythmic stimulation.

Simulated Climate of TRAPPIST-1e Using MPAS-A and Comparisons with Other GCMs

Dayside convection is one of the most important contributors to a tidally locked planet’s climate. Considering the long-standing challenge of simulating convections, we employ a convection-resolving model known as the Model for Prediction across Scales—Atmosphere and perform a series of simulations with spatial resolution ranging from 960 to 10 km. With TRAPPIST-1e, a potentially habitable exoplanet, as the target, we aim to draw a comparative analysis against the results from the TRAPPIST-1 Habitable Atmosphere Intercomparison project. Regarding the overall climate states, our simulations reaffirm the findings of the previous general circulation model (GCM). Both the extensive substellar cloud cluster and the intricate cloud street feature are successfully reproduced. The influence of varying grid resolution exhibits a remarkably marginal impact across our resolution spectrum, albeit with a slightly heightened sensitivity observed at the nightside. Major differences center around the cloud-related variables, including cloud phase (liquid and ice), amount, and height, in both the grid resolution assessments and GCM intercomparison scenarios. Furthermore, we explore the repercussions on the phase curve and transit spectrum.