Broad Resonance Research Articles

Specific and high-affinity adsorption of volatile organic compounds on titanium dioxide surface.

The interaction between metal oxides and volatile organic compounds (VOCs) from the ambient atmosphere plays an important role in environmental and catalytic applications. Previous scanning probe microscopy and x-ray spectroscopy studies revealed surprisingly that the TiO2 [rutile (110)] surface selectively adsorbed atmospheric carboxylic acids, which typically exist in only parts-per-billion concentrations. In this work, we used in situ sum-frequency vibrational spectroscopy to study the interaction between rutile (110) and typical VOC molecules, including formic acid, acetic acid, and formaldehyde. Spectra from all three adsorbed molecules on rutile (110) were similar to the rutile surface spectrum in the ambient atmosphere, showing a broad resonance near 2950cm-1 that can be attributed to the bridging bidentate adsorption of corresponding compounds. In contrast, on a fused silica surface, a molecular monodentate adsorption configuration was observed for all the molecules, with aliphatic carbons appearing to be the dominant adventitious species.

Two-Stage Recruitment Design to Reduce Magnetic Resonance Imaging Screening Cost for a Theoretical Clinical Trial of White Matter Hyperintensity Progression.

White matter hyperintensities (WMH) and their progression are associated with risk of dementia and stroke, so are an important target for clinical trials. The cost of broad magnetic resonance imaging (MRI) screening to identify eligible individuals, however, limits the feasibility of designing clinical trials targeting WMH. A low-cost retinal or clinical screening measure before MRI could reduce recruitment costs versus an MRI-only screening design in a hypothetical clinical trial. Data from the Atherosclerosis Risk in Communities study with valid retinal and WMH measurements (N=1311) were used. To identify a population at greater likelihood of significant WMH on MRI and thus reduce the number of screening MRIs required, we evaluated 3 theoretical prescreening measures: (1) retinal, (2) clinical, (3) combined clinical-retinal. Given a target sample for clinical trials (N=646), we calculated screening sample sizes based on the proportion within the population having an elevated score for each prescreening measure (separately) multiplied by the proportion of significant WMH among those with that prescreening feature. Recruitment costs were calculated using estimated retinal and MRI cost estimates. Compared with the estimated cost of MRI-only screening (>$4.24 million, requiring MRI on 6526 participants), prescreening for a high clinical score resulted in total cost of $2.47 million, with an initial screening group of 52 778 participants, with MRI in 3801. A high clinical-retinal score cutoff resulted in costs of $2.9 million while requiring 13 572 participants, with 3801 completing MRI. A 2-stage design with low-cost prescreening measures is a promising approach, resulting in reduced theoretical recruitment costs compared with an MRI-only design.

Optical spectra of silver clusters and nanoparticles from 4 to 923 atoms from the TDDFT+U method

The localized surface-plasmon resonances of coinage-metal clusters and nanoparticles enable many applications, the conception and necessary optimization of which require precise theoretical description and understanding. However, for the size range from few-atom clusters through nanoparticles of a few nanometers, where quantum effects and atomistic structure play a significant role, none of the methods employed previously has been able to provide high-quality spectra for all sizes. The main problem is the description of the filled shells of d electrons which influence the optical response decisively. We show that the DFT+U method, employed with real-time time-dependent density-functional theory calculations (RT-TDDFT), provides spectra in good agreement with experiment for silver clusters ranging from 4 to 923 atoms, the latter representing a nanoparticle of 3 nm. Both the electron-hole-type discrete spectra of the smallest clusters and the broad plasmon resonances of the larger sizes are obtained. All calculations use the value of the effective U parameter that provides good results in bulk silver. The agreement with experiment for all sizes shows that the U parameter is surprisingly transferable. Our results open the pathway for calculations of many practically relevant systems including clusters coupled to bio-molecules or to other nano-objects.

Advancements in electrohydraulic fatigue testing: Innovations in variable resonance frequency control and comprehensive characterization

This study addresses the challenge in electro-hydraulic fatigue testing machines where increasing excitation frequency leads to reduced output load amplitude, making it difficult to optimize both frequency and amplitude simultaneously. A new approach is introduced with the variable resonance fatigue testing machine controlled with 2D excitation valves. This technique involves adjusting the system’s intrinsic frequency by altering its mass, aligning the excitation frequency with the intrinsic frequency, and leveraging resonance energy to enhance excitation amplitude for broad-range resonance near the resonance point. The relationship between the system’s intrinsic frequency, the equivalent mass of the upper connector, and the upper fixture is explored, yielding analytical solutions. Experimental research validates these simulations, in the resonance condition, the fatigue testing machine energy efficiency can reach 94 %, to further verify the fatigue testing machine in the resonance condition to realize the High energy efficiency. Demonstrating that the system’s intrinsic frequency decreases with increasing mass, allowing for a broad frequency resonance between 200 and 300 Hz. Operating in a broadband resonance region, the output load force is increased by 60 %–95 % and the system flow is reduced by 20 %–30 %. This mass-adjustment technique effectively alters the system’s intrinsic frequency, expanding the electro-hydraulic fatigue testing machine’s application scope.

Solid-state vitrification of LiPO3 through mechanical milling

A novel glass state of LiPO3 was obtained in powders produced by mechanical planetary ball milling of the crystal phase, in a direct room temperature solid-state process. X-ray diffraction shows that the amorphization develops through the compression along the [2 0 2] direction. This new material shows the calorimetric signatures of the glass state (glass transition and crystallization), and is produced in an excited state relaxing the excess of enthalpy through an exothermic event below the glass transition, akin to bulk glasses produced by hyperquenching of their melts. 31P nuclear magnetic resonance (NMR) reveals the progressive amorphization of the particles: the collapse of the resonances from P crystallographic sites and the appearance of broad resonances from amorphous domains. The nature of this glass is different from those obtained through melt-quench of bulk samples. The glass transition (Tg = 303 °C) and crystallization (Tc = 350 °C) temperatures are lower than in the melt-quenched glass (Tg = 330 °C, Tc = 379 °C). Also, 31P NMR shows a broader distribution of environments around Q2 phosphates, and higher populations of Q1 and Q3, suggesting differences in middle-range order. The amorphization can be fully reversed by recrystallization of the powders at 333 °C.

Sponge-shaped Au nanoparticles: a stand-alone metallic photocatalyst for driving the light-induced CO2 reduction reaction

Coinage metal nanoparticles (NPs) enable plasmonic catalysis by generating hot carriers that drive chemical reactions. Making NPs porous enhances the adsorption of reactant molecules. We present a dewetting and dealloying strategy to fabricate porous gold nanoparticles (Au-Sponge) and compare their CO2 photoreduction activity with respect to the conventional gold nanoisland (Au-Island) morphology. Porous gold nanoparticles exhibit an unusually broad and red-shifted plasmon resonance which is in agreement with the results of finite difference time domain (FDTD) simulations. The key insight of this work is that the multi-step reduction of CO2 driven by short-lived hot carriers generated by the d → s interband transition proceeds extremely quickly as evidenced by the generation of methane. A 3.8-fold enhancement in the photocatalytic performance is observed for the Au-Sponge in comparison to the Au-Island. Electrochemical cyclic voltammetry measurements confirm the 2.5-fold increase in the surface area and roughness factor of the Au-Sponge sample due to its porous nature. Our results indicate that the product yield is limited by the amount of surface adsorbates i.e. reactant-limited. Isotope-labeled mass spectrometry using 13CO2 was used to confirm that the reaction product (13CH4) originated from CO2 photoreduction. We present the plasmon-mediated photocatalytic transformation of 4-aminothiophenol (PATP) into p,p'-dimercaptoazobenzene (DMAB) using Au-Sponge and Au-Island samples.

Structural, morphological, and magnetic characterizations of (Fe0.25Mn0.75)2O3 nanocrystals: A comprehensive stoichiometric determination

This report aims to investigate in depth FeMnO3, a material of interest due to its fascinating magnetic and multiferroic properties and its many applications in fields including lithium-ion batteries, microwave devices, and catalysis. However, understanding the precise stoichiometry of the material is crucial for a better comprehension of its physical properties. A cheap, simple, and repeatable sol-gel process was used to fabricate the FeMnO3 nanocrystals. Comprehensive multi-technique characterization of the as-fabricated FeMnO3 indicates that the main phase (94 wt%) is Fe0.5Mn1.5O3, although hematite appears as the minority phase (6 wt%). Magnetic characterization shows core-shell spin-glass like behavior, as well as paramagnetic-ferrimagnetic transitions and a Griffiths phase regime. EPR measurements revealed a strong and broad resonance line across the temperature range of 4.3 K–300 K, primarily influenced by the majority phase. The g-value decreases monotonically from 2.93 at 50 K to 2.18 at 300 K. There is a notable change in the resonance field and linewidth between 40 and 50 K, attributed to surface spin glass behavior. The EPR data below 50 K are in line with the core-shell model of (Fe0.25Mn0.75)2O3 nanoparticles. Below 50 K, the shell's spin system undergoes a transition from paramagnetic to spin-glass-like, with a critical temperature around 43 K. Above 50 K, the superparamagnetic minority phase significantly affects the temperature dependence of the resonance linewidth. These results hold particular importance as they advance our understanding of the intricate magnetic interactions present in FeMnO3. For the best possible use of this material platform in new technologies, such insights are essential.

Spin dynamics investigation and structural analysis of ambient scalable Sr2+ doped zirconium ferrite nanoparticles synthesized by low temperature auto combustion route

Microwave spin resonance behaviour of Sr2+ doped Zirconium ferrite Zr1-xSrxFe2O4; (0 ≤ x ≥ 0.20) nanoparticles synthesized by auto combustion route has been investigated by electron paramagnetic resonance (EPR) which show a broad ferromagnetic resonance signal with a superimposed hump signal which is attributed to ferrite Fe3+ ions and oxygen vacancies which is in agreement with XRD and XPS. EPR shows low spin concentration and smaller relaxation time for Zr0.80Sr0.20Fe2O4 which can be used for hyperthermia and for use as a MRI contrast agent. EDS and XPS confirms the presence of Zr, Sr, Fe, O, and C and HRTEM images confirm growth along (220) and (311) with an interatomic distance of 0.3327 nm and 0.2622 nm respectively, thus, authenticating the formation of spinel structure in agreement with FTIR studies. The magnetic behaviour (M − H loop) shows high saturation magnetization and higher value of effective magnetocrystalline anisotropy (Keff) for Zr0.80Sr0.20Fe2O4.

The stabilized supralinear network accounts for the contrast dependence of visual cortical gamma oscillations.

When stimulated, neural populations in the visual cortex exhibit fast rhythmic activity with frequencies in the gamma band (30-80 Hz). The gamma rhythm manifests as a broad resonance peak in the power-spectrum of recorded local field potentials, which exhibits various stimulus dependencies. In particular, in macaque primary visual cortex (V1), the gamma peak frequency increases with increasing stimulus contrast. Moreover, this contrast dependence is local: when contrast varies smoothly over visual space, the gamma peak frequency in each cortical column is controlled by the local contrast in that column's receptive field. No parsimonious mechanistic explanation for these contrast dependencies of V1 gamma oscillations has been proposed. The stabilized supralinear network (SSN) is a mechanistic model of cortical circuits that has accounted for a range of visual cortical response nonlinearities and contextual modulations, as well as their contrast dependence. Here, we begin by showing that a reduced SSN model without retinotopy robustly captures the contrast dependence of gamma peak frequency, and provides a mechanistic explanation for this effect based on the observed non-saturating and supralinear input-output function of V1 neurons. Given this result, the local dependence on contrast can trivially be captured in a retinotopic SSN which however lacks horizontal synaptic connections between its cortical columns. However, long-range horizontal connections in V1 are in fact strong, and underlie contextual modulation effects such as surround suppression. We thus explored whether a retinotopically organized SSN model of V1 with strong excitatory horizontal connections can exhibit both surround suppression and the local contrast dependence of gamma peak frequency. We found that retinotopic SSNs can account for both effects, but only when the horizontal excitatory projections are composed of two components with different patterns of spatial fall-off with distance: a short-range component that only targets the source column, combined with a long-range component that targets columns neighboring the source column. We thus make a specific qualitative prediction for the spatial structure of horizontal connections in macaque V1, consistent with the columnar structure of cortex.

Phytochemical Investigation and Characterization of Azadirachta Indica-Mediated Silver Nanoparticles and Their Potential as Antibacterial and Antidiabetic Agents

In this study, we report the synthesis of silver nanoparticles (AgNP’s) by reducing silver ions from a solution of silver nitrate with an aqueous extract from Azadirachta indica. Using silver ions as the catalyst, nanoparticles were formed in 8[Formula: see text]min without the use of toxic chemicals. As evidenced by UV-vis spectroscopy, a broad surface plasmon resonance spectrum at 225[Formula: see text]nm was detected, which indicates the colloidal solution of silver nanoparticles is stable and produces silver nanoparticles. As revealed by the fourier transform-infrared spectrometer (FTIR) analysis, the flower extract contained a variety of biomolecules that acted as capping and reducing agents for the synthesis of AgNPs. As determined by X-ray diffraction (XRD), silver nanoparticles displayed a crystalline structure and ranged in size from 18 to 39[Formula: see text]nm. In addition to these findings, transmission electron microscopy (TEM) images showed that the silver nanoparticles were spherical and rod-shaped, as confirmed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDAX). A variety of pathogenic bacteria, such as Klebsiella pneumoniae, Escherichia coli, Bacillus subtilis and Staphylococcus aureus, were tested against AgNP’s antibacterial properties. A significant inhibition zone was observed for Escherichia coli when AgNPs were applied at different concentrations. Silver nanoparticles were shown to have antidiabetic effects through a diphtheria assay with inhibition rates ranging from 31.09% to 83.33% for concentrations of 50–250[Formula: see text][Formula: see text]g/mL. As researchers seek natural sources of compounds with potential health benefits, silver nanoparticles were also investigated for their antioxidant properties.

Efficient Segmental Isotope Labeling of Integral Membrane Proteins for High-Resolution NMR Studies.

High-resolution structural NMR analyses of membrane proteins are challenging due to their large size, resulting in broad resonances and strong signal overlap. Among the isotope labeling methods that can remedy this situation, segmental isotope labeling is a suitable strategy to simplify NMR spectra and retain high-resolution structural information. However, protein ligation within integral membrane proteins is complicated since the hydrophobic protein fragments are insoluble, and the removal of ligation side-products is elaborate. Here, we show that a stabilized split-intein system can be used for rapid and high-yield protein trans-splicing of integral membrane proteins under denaturing conditions. This setup enables segmental isotope labeling experiments within folded protein domains for NMR studies. We show that high-quality NMR spectra of markedly reduced complexity can be obtained in detergent micelles and lipid nanodiscs. Of note, the nanodisc insertion step specifically selects for the ligated and correctly folded membrane protein and simultaneously removes ligation byproducts. Using this tailored workflow, we show that high-resolution NMR structure determination is strongly facilitated with just two segmentally isotope-labeled membrane protein samples. The presented method will be broadly applicable to structural and dynamical investigations of (membrane-) proteins and their complexes by solution and solid-state NMR but also other structural methods where segmental labeling is beneficial.

Triple-band transparency effect by multiple couplings based on toroidal dipole resonance

We explored multiple couplings properties in composite metastructure. One part is the asymmetric double rings, supporting the narrow toroidal dipole resonance, and the other component is an upright rod that excites the broad electric dipole resonance. When these two resonant modes coincide in the spectrum, dual-band plasmon induced transparency (PIT) behavior can be obtained, which is attributed to in-phase and out-of-phase couplings between the toroidal dipole and electric dipole modes. Meanwhile, the dual-band features will become a single PIT band by varying the rotation offset angle between the upper- and lower-rings. Moreover, by introducing lateral displacement of the rod with respect to the toroidal component, a triple-band PIT effect can be achieved. In particular, under a large lateral displacement, a broadband transparency window appears across a wavelength range greater than 120 nm, where the transmission exceeds 0.9. It is derived from the hybrid coupling between toroidal dipole, electric dipole and induced high-order resonance modes. The toroidal-based PIT metamaterials not only promote the understanding of toroidal dipole moment but also provide a positive reference for toroidal-based meta-devices.

Nonlinear dynamics of the reversed shear Alfvén eigenmode in burning plasmas

In a tokamak fusion reactor operated at steady state, the equilibrium magnetic field is likely to have reversed shear in the core region, as the noninductive bootstrap current profile generally peaks off-axis. The reversed shear Alfvén eigenmode (RSAE) as a unique branch of the shear Alfvén wave in this equilibrium, can exist with a broad spectrum in wavenumber and frequency, and be resonantly driven unstable by energetic particles (EP). After briefly discussing the RSAE linear properties in burning plasma condition, we review several key topics of the nonlinear dynamics for the RSAE through both wave-EP resonance and wave-wave coupling channels, and illustrate their potentially important role in reactor-scale fusion plasmas. By means of simplified hybrid MHD-kinetic simulations, the RSAEs are shown to have typically broad phase space resonance structure with both circulating and trapped EP, as results of weak/vanishing magnetic shear and relatively low frequency. Through the route of wave-EP nonlinearity, the dominant saturation mechanism is mainly due to the transported resonant EP radially decoupling with the localized RSAE mode structure, and the resultant EP transport generally has a convective feature. The saturated RSAEs also undergo various nonlinear couplings with other collective oscillations. Two typical routes as parametric decay and modulational instability are studied using nonlinear gyrokinetic theory, and applied to the scenario of spontaneous excitation by a finite amplitude pump RSAE. Multiple RSAEs could naturally couple and induce the spectral energy cascade into a low frequency Alfvénic mode, which may effectively transfer the EP energy to fuel ions via collisionless Landau damping. Moreover, zero frequency zonal field structure could be spontaneously excited by modulation of the pump RSAE envelope, and may also lead to saturation of the pump RSAE by both scattering into stable domain and local distortion of the continuum structure.

Spin-1 glueballs in the Witten-Sakai-Sugimoto model

We consider the vector and the pseudovector glueball in the top-down holographic model of large-Nc QCD of Witten and their decays into ordinary mesons described by the D8 brane construction due to Sakai and Sugimoto. At leading order, the relevant interactions are determined exclusively by the Chern-Simons action of the D8 branes and are thus rigidly connected to the chiral anomaly and the Wess-Zumino-Witten terms. As found in a previous study of the pseudovector glueball, which we revisit and complete, the resulting decay widths are surprisingly large, implying that both the pseudovector and the vector glueball are very broad resonances, with a conspicuous dominance of decays into a1ρ and K1(1400)K* in the case of the vector glueball. We also obtain a certain weak mixing of vector glueballs with ordinary vector mesons, but we conclude that it does not provide an explanation for the so-called ρπ puzzle in charmonium decays. Published by the American Physical Society 2024

Shallow Bound States and Hints for Broad Resonances with Quark Content b[over ¯]c[over ¯]ud in B-D[over ¯] and B^{*}-D[over ¯] Scattering from Lattice QCD.

We present the first determination of the energy dependence of the B-D[over ¯] and B^{*}-D[over ¯] isospin-0, S-wave scattering amplitudes both below and above the thresholds using lattice QCD, which allows us to investigate rigorously whether mixed bottom-charm b[over ¯]c[over ¯]ud tetraquarks exist as bound states or resonances. The scattering phase shifts are obtained using Lüscher's method from the energy spectra in two different volumes. To ensure that no relevant energy level is missed, we use large, symmetric 7×7 and 8×8 correlation matrices that include, at both source and sink, B^{(*)}-D[over ¯] scattering operators with the lowest three or four possible back-to-back momenta in addition to local b[over ¯]c[over ¯]ud operators. We fit the energy dependence of the extracted scattering phase shifts using effective-range expansions. We observe sharp peaks in the B^{(*)}-D[over ¯] scattering rates close to the thresholds, which are associated with shallow bound states, either genuine or virtual, a few MeV or less below the B^{(*)}-D[over ¯] thresholds. In addition, we find hints for resonances with masses of order 100MeV above the thresholds and decay widths of order 200MeV.

K + N Elastic Scatterings for Estimation of the In-Medium Quark Condensate with Strange Quarks

Abstract We revisit the low-energy K+N elastic scatterings in the context of the in-medium quark condensate with strange quarks. The chiral ward identity connects the in-medium quark condensate to the soft limit value of the pseudoscalar correlation function evaluated in nuclear matter. The in-medium correlation function of the pseudoscalar fields with strangeness describes in-medium kaon propagation and is obtained by kaon–nucleon scattering amplitudes in the low-density approximation. We construct the kaon–nucleon scattering amplitudes in chiral perturbation theory up to the next-to-leading order and add some terms of the next-to-next-to-leading order with the strange quark mass to improve expansion of the strange quark sector. We also consider the effect of a possible broad resonance state around Plab = 600 MeV/c for I = 0 reported in the previous study. The low-energy constants are determined by existing K+N scattering data. We obtain good reproduction of the K+p scattering amplitude by chiral perturbation theory, while the description of the KN amplitude with I = 0 is not so satisfactory due to the lack of low-energy data. Performing analytic continuation of the scattering amplitudes obtained by chiral perturbation theory to the soft limit, we estimate the in-medium strange quark condensate.

Robust dual-angle measurement in magnetization transfer spectroscopy by time-optimal control.

Magnetization transfer spectroscopy relies heavily on the robust determination of relaxation times of nuclei participating in metabolic exchange. Challenges arise due to the use of surface RF coils for transmission (high variation) and the broad resonance band of most X nuclei. These challenges are particularly pronounced when fast mapping methods, such as the dual-angle method, are employed. Consequently, in this work, we develop resonance offset and robust excitation RF pulses for 31P magnetization transfer spectroscopy at 7T through ensemble-based time-optimal control. In our approach, we introduce a cost functional for designing robust pulses, incorporating the full Bloch equations as constraints, which are solved using symmetric operator splitting techniques. The optimal control design of the RF pulses developed demonstrates improved accuracy, desired phase properties, and reduced RF power when applied to dual-angle mapping, thereby improving the precision of exchange-rate measurements, as demonstrated in a preclinical in vivo study quantifying brain creatine kinase activity.

Robust ultra-high-Q Fano resonance for topological corner and ring-cavity mode coupling in Kagome photonic systems

Corner and edge states in higher-order topological insulators provide new degrees of freedom for manipulating light propagation. Our research demonstrates that the topological waveguide coupled to the corner and edge states of the triangular cavity obtains a topological corner mode as narrow resonance and a topological ring-cavity mode as broad resonance, respectively. By adjusting the size of the dielectric column at the apex of the triangular cavity, the two modes can be coherently coupled at the same frequency position and obtain a high-Q Fano resonance. This Fano resonant has excellent robustness for unavoidable defects in the manufacturing process, paving the way for the design of high-performance lasers, switches, and other micro-nano integrated photonics devices.

Determination of crossing-symmetric ππ scattering amplitudes and the quark mass evolution of the σ constrained by lattice QCD

Lattice QCD spectra can be used to constrain partial-wave scattering amplitudes that, while satisfying unitarity, do not have to respect crossing symmetry and analyticity. This becomes a particular problem when extrapolated far from real energies, e.g. in the case of broad resonances like the σ, leading to large systematic uncertainties in the pole position. In this manuscript, we will show how dispersion relations can implement the additional constraints, using as input lattice-determined ππ partial-wave scattering amplitudes with isospin–0,1,2. We will show that only certain combinations of amplitude parametrizations satisfy all constraints, and that when we restrict to these, the σ pole position is determined with minimal systematic uncertainty. The evolution of the now well-constrained σ pole with varying light quark mass is presented, showing how it transitions from a bound-state to a broad resonance. Published by the American Physical Society 2024

Scattering characteristics of silicon nanoprisms: A theoretical investigation across monomeric to hexameric structures

Dielectric nanostructures exhibit intriguing optical properties and outstanding advantages in designing optical nanoantennas and metasurfaces compared to plasmonic nanostructures. This study employs classical electrodynamic methods to comprehensively explore the scattering characteristics of silicon triangular nanoprisms in monomer and oligomer forms. For monomeric nanoprisms, the scattering spectra reveal two distinct and prominent resonance peaks attributed to magnetic dipole (MD) and electric dipole (ED) modes. Reducing interparticle gaps within dimeric structures leads to noticeable blueshifts in MD resonance peaks with stable intensities, in contrast to the nearly constant position and significantly reduced intensities of the ED resonance peaks. A pronounced Fano-like resonance was observed upon transitioning to tetrameric and hexameric configurations, resulting from the coupling between MD and ED modes. A broad resonance peak also emerges in the long-wavelength region due to MD-to-MD coupling. The simulations conducted herein hold significant theoretical implications, advancing our comprehension of the scattering properties of dielectric nanoparticles and contributing valuable insights into fundamental nanophotonics.