Excitation Range Research Articles

Nonlinear sound absorption of Helmholtz resonators with serrated necks under high-amplitude sound wave excitation

This paper focuses on the design and sound absorption analysis of Helmholtz resonators with serrated necks inspired by the leading edges of owl wings. Numerical models for predicting the sound absorption and the flow field of the resonators are established by a finite element method based on nonlinear acoustic wave equations. The thermal conduction and vortex energy dissipation of resonators with straight and serrated necks are evaluated. The effects of the geometrical parameters including the neck diameter, the serration height, and the serration pitch on the sound absorption behaviors of the resonator are discussed. It is found that for a lower-intensity acoustic excitation, the serration leads to periodic oscillations of the fluid in the resonator neck, and increases the acoustic resistance of the resonator. For a high-intensity sound excitation, the distributions of the velocity and vorticity in the resonator neck show that the serrated structure can produce more vorticities, which is beneficial for acoustic energy dissipation. The resistance of the resonators grows significantly and the reactance decreases slightly with an increase in intensity of the sound excitation. Sound absorption coefficients of resonators fabricated by three-dimensional (3D) printing are tested in an impedance tube for a large range of sound pressure excitations. The computed results of the sound absorption coefficients are in good agreement with the experimental data, and the superior sound absorption performance of the resonator with a serrated neck is confirmed.

Generation of Reporter-Expressing New World Arenaviruses: A Systematic Comparison.

Replication-competent reporter-expressing viruses are crucial tools in molecular virology with applications that range from antiviral screening to live-cell imaging of protein spatiotemporal dynamics. However, there is currently little information available regarding viable strategies to develop reporter-expressing arenaviruses. To address this, we used Tacaribe virus (TCRV), an apathogenic BSL2 arenavirus, to assess the feasibility of different reporter expression approaches. We first generated trisegmented TCRV viruses with either the glycoprotein (GP) or nucleoprotein (NP) replaced by a reporter (GFP, mCherry, or nanoluciferase). These viruses were all viable, but showed marked differences in brightness and attenuation. Next, we generated terminal fusions with each of the TCRV proteins (i.e., NP, GP, polymerase (L), matrix protein (Z)) either with or without a T2A self-cleavage site. We tested both the function of the reporter-fused proteins alone, and the viability of corresponding recombinant TCRVs. We successfully rescued viruses with both direct and cleavable reporter fusions at the C-terminus of Z, as well as cleavable N-terminal fusions with NP. These viruses all displayed detectable reporter activity, but were also moderately attenuated. Finally, reporter proteins were inserted into a flexible hinge region within L. These viruses were also viable and showed moderate attenuation; however, reporter expression was only detectable for the luminescent virus. These strategies provide an exciting range of new tools for research into the molecular biology of TCRV that can likely also be adapted to other arenaviruses.

Assessment of the Quality Losses of Cantaloupe Fruit during Transportation

Fruit quality is a crucial factor in affecting shelf-life and purchase choice for customers. Protecting the quality of cantaloupe fruits in the chain from harvest to marketing is a very important process. The objective of this study was to investigate the dynamic characteristics of cantaloupe fruit during excitation, to investigate the effect of vibration strength on the mechanical characteristics of cantaloupe fruit, and to show the effects of this strength on the mechanical damage of cantaloupe. Experiments were performed to measure the dynamic behavior of cantaloupe fruit during transportation and to evaluate the dynamic behavior of the packaging and the damage to the cantaloupes due to transient vibration during transportation. The results show that using the paper pulp tray packing method reduces cantaloupe damage and improves their quality during harvest and post-harvest processes. The range of resonance frequencies is important for the transporting of cantaloupes; a higher starting resonance is an indication of a stiffer cantaloupe bottom, and the paper pulp tray shifts the resonance frequency when compared to volume packing methods. Another interesting observation in this study is that a fruit with a high internal damping capacity is not as injured by exciting vibrations as a fruit with a low damping capacity, even if its natural frequency falls within the range of excitation.

Structural Optimization of Combine Harvester Plate–Shell Undergoing Multi-Source Excitation

As a multi-source vibration machine, the complex vibration of the combine harvester has caused many effects on various components. In this paper, the dynamic response of the plate and shell on the combine harvester is studied, and the influence of various factors on the vibration of the plate and shell is determined. The structure of the plate and shell is optimized, and the scheme of structural optimization that replaces the finite element model with the surrogate model is developed. The structure is designed with Latin hypercube design (LHD), the model of response surface is generated based on the Kriging model, and then the parameters are optimized by a multi-objective genetic algorithm (MOGA). It is realized that the first-order natural frequency of the plate is increased by 14.6% under the same mass, avoiding the resonance range of the main excitation of the machine. At the same time, its dynamic response under the multi-point force is also greatly decreased by 62.4%.

Magnetic order and exchange coupling in the frustrated diamond-lattice antiferromagnet MnSc2Se4

We report the magnetic properties of $A$-site spinel compound MnSc$_2$Se$_4$. The macroscopic magnetic measurements uncovers successive magnetic transitions at $T_{\rm{N1}}$= 2.04 K, followed by two further transitions at $T_{\rm{N2}}$=1.8 K and $T_{\rm{N3}}$=1.6 K. Neutron powder diffraction reveals that both, $T_{\rm{N2}} < T < T_{\rm{N1}}$ and $T <T_{\rm{N3}}$, orders are associated with the propagation vector $k$=(3/4 3/4 0), while the magnetic structures are collinear amplitude modulated and helical, respectively. Using neutron powder spectroscopy we demonstrated the effect of substitution of S by Se on the magnetic exchange. The energy range of the spin-wave excitations is supressed due to the chemical pressure of the $X$- ion in MnSc$_2X_4$ ($X$=S, Se) spinels.

Exploiting internal resonances in nonlinear structures with cyclic symmetry as a mean of passive vibration control

The purpose of this paper is to study how internal resonances can be used to mitigate the vibration of cyclically symmetric systems exhibiting geometrical nonlinear effects. The method of multiple scales is employed to derive specific conditions that allow such energy transfers. This novelty is confirmed through numerical investigations, and an application to decrease the vibration of the system is proposed. A simplified yet realistic blade model with geometrical nonlinearities is considered. It includes pre-twist, pre-bending and warping, and is duplicated to create a full bladed rotor with cyclically symmetric properties. As the model of the whole structure may become enlarged, it is further reduced via the normal form approach. The harmonic balance method is then employed to obtain periodic solutions, localize bifurcation points and then follow bifurcated branches. These numerical solutions are used in complement with the aforementioned theoretical conditions to investigate the energy transfer properties of the mechanical system. Through these simulations, an effective range of amplitude excitation is defined to obtain internal resonances leading to an overall vibration mitigation of the system.

Designing of biomass-derived carbon quantum dots@polyvinyl alcohol film with excellent fluorescent performance and pH-responsiveness for intelligent detection

Carbon quantum dots (CQDs) have attracted extensive attentions because of their unique luminescent properties and promising prospects in intelligent sensing and detection. However, the increasing environmental pollution caused by chemical substances for synthesizing illuminants limits their expansion in practical applications. Herein, we employed a facile and green synthesis strategy to extract biomass-derived CQDs from natural lignocellulose. The obtained CQD nanoparticles not only showed excellent fluorescent performance, but also posed desirable environmental-friendly characteristic. Moreover, to relieve the fluorescence quenching induced by CQDs aggregation, the well-dispersed CQDs@polyvinyl alcohol (CQDs@PVA) composite film with strong hydrogen-bond interaction was successfully fabricated. The resultant film exhibited high transparency (transmittance of 88%), excellent mechanical flexibility (tensile strength of 39.7 MPa and elongation at break of 453%), and exceptional fluorescence performance. The high concentrated emitting centered in 502 nm emission wavelength was realized in a wide excitation range of 350 ∼ 420 nm with high-stability turquoise fluorescence. More impressively, this fluorescent film demonstrated a sensitive pH-responsiveness, i.e., the fluorescent intensity varied upon pH stimulation. As a proof-of-concept, an intelligent pH-detector based on this fluorescent film was rationally designed for real-time sensing and detection of pH variation in human sweat during movement processing. From fundamental materials to desired applications, this study not only enriches the synthetic strategy of illuminants in an environment-friendly manner, but also paves the way for further applications in wearable, real-time health monitoring.

Unveiling spin-flip processes in a neutral quantum dot using an anisotropic photonic structure

We introduce a method to investigate excitonic spin flips in a neutral quantum dot (QD) that is driven nonresonantly. By inserting the QD in an anisotropic photonic structure, one creates an imbalance between the radiative decay rates of the two bright excitons. Direct spin flips between the bright excitons as well as indirect ones (via a dark exciton) mix the level populations and profoundly affect the degree of linear polarization of the excitonic emission. Measuring this quantity under continuous wave optical excitation yields the spin-flip rate over a broad range of excitation powers. Additional time-resolved experiments allow disentangling the contributions of bright-bright and dark-bright spin flips in the low-excitation regime. After providing theoretical background, we demonstrate the method on a self-assembled InAs QD embedded in a GaAs photonic wire featuring an elliptical cross section. For low-excitation power and at $T=5\phantom{\rule{0.28em}{0ex}}\mathrm{K}$, bright-bright spin flips are much slower than dark-bright spin flips, which, in turn, remain much slower than the radiative decays. Upon increasing the temperature, we observe a superlinear increase in the bright-bright spin-flip rate which completely reverses the rate hierarchy above $T=50\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. Moreover, polarization measurements reveal a dramatic increase in the spin-flip rate with the pumping power. Our findings are relevant to spontaneous emission control by anisotropic photonic structures and to the spectral coherence of QD-based quantum light sources.

Single-Mode Emission in InP Microdisks on Si Using Au Antenna.

An important building block for on-chip photonic applications is a scaled emitter. Whispering gallery mode cavities based on III–Vs on Si allow for small device footprints and lasing with low thresholds. However, multimodal emission and wavelength stability over a wider range of temperature can be challenging. Here, we explore the use of Au nanorod antennae on InP whispering gallery mode lasers on Si for single-mode emission. We show that by proper choice of the antenna size and positioning, we can suppress the side modes of a cavity and achieve single-mode emission over a wide excitation range. We establish emission trends by varying the size of the antenna and show that the far-field radiation pattern differs significantly for devices with and without antenna. Furthermore, the antenna-induced single-mode emission is dominant from room temperature (300 K) down to 200 K, whereas the cavity without an antenna is multimodal and its dominant emission wavelength is highly temperature-dependent.

Living with the spiral: a duoethnographic perspective

AbstractThe authors of this article met on a Master of Arts (MA) music education course a month before the Swanwick Tillman Sequence of Musical Development was published. The course was a portal to an exciting range of literature, with the Swanwick Tillman spiral providing a long-term source of discussion and reflection as our careers have diverged and converged over the intervening years. This paper takes the form of a duoethnographic conversation in which we summarise and reflect on that ongoing synergistic discussion, showing the influence the spiral has had within our particular situations.

An Instantaneous Recombination Rate Method for the Analysis of Interband Recombination Processes in ZnO Crystals.

Time-resolved photoluminescence (TRPL) analysis is often performed to assess the qualitative features of semiconductor crystals using predetermined functions (e.g., double- or multi-exponentials) to fit the decays of PL intensity. However, in many cases—including the notable case of interband PL in direct gap semiconductors—this approach just provides phenomenological parameters and not fundamental physical quantities. In the present work, we highlight that within a properly chosen range of laser excitation, the TRPL of zinc oxide (ZnO) bulk crystals can be described with excellent precision with second-order kinetics for the total recombination rate. We show that this allows us to define an original method for data analysis, based on evaluating the “instantaneous” recombination rate that drives the initial slope of the decay curves, acquired as a function of the excitation laser fluence. The method is used to fit experimental data, determining useful information on fundamental quantities that appear in the second-order recombination rate, namely the PL (unimolecular) lifetime, the bimolecular recombination coefficient, the non-radiative lifetime and the equilibrium free-carrier concentration. Results reasonably close to those typically obtained in direct gap semiconductors are extracted. The method may represent a useful tool for gaining insight into the recombination processes of a charge carrier in ZnO, and for obtaining quantitative information on ZnO excitonic dynamics.

Endogenous modulation of delta phase by expectation–A replication of Stefanics et al., 2010

The human brain efficiently extracts the temporal statistics of sensory environments and automatically generates expectations about future events. An influential Hypothesis holds that these expectations can find their implementation in neural oscillations, notably in the delta band (.5–3 Hz). Rhythmic fluctuations of cortical excitement are thought to align and match up in phase to the temporal structure of the sensory environment. This alignment is thought to result in the more excitable phase range of neural oscillations to overlap with the predicted onset of sensory events which in turn results in more efficient processing of sensory input, especially so in audition. An unresolved issue concerns whether such phase-aligned rhythmic brain activity is driven exclusively by the exogenous temporal structure of the input, or whether it also reflects phase re-alignment due to endogenous expectations based on stimulus probability and task relevance. In a seminal study, Stefanics et al. (2010) presented stimuli in a rhythmic stream and observed that delta phase consistency across trials was modulated by endogenous target onset expectations: delta phase consistency was higher prior to more probable (strongly expected) compared to less probable (weakly expected) target onsets. The present study replicates Experiment II of the original study, most importantly the modulation of delta phase consistency by endogenous expectations, and underlines a direct relationship between phase locking and behaviour. Our additional analyses locate the sources of the delta phase-alignment to motor, pre-motor, parietal, and temporal areas, and provide evidence for an ongoing delta oscillation, in line with the interpretation of oscillatory phase alignment rather than a transient evoked response. Importantly, this work shows that the phase of delta oscillations can be modulated by top-down control, and hence qualifies as a potential mechanism for the neural implementation of (rhythmic) temporal predictions.

Para-hexaphenylene (p-6P) nanofibers grown on a silver surface for polarization-insensitive surface plasmon polariton excitation

Surface plasmon polariton excitation was demonstrated by fluorescent light from organic para-hexaphenylene (p-6P) nanofibers grown directly on a silver thin film surface. We show results of both photoluminescence lifetime measurements and angle-resolved leakage radiation spectroscopy in the excitation range 420–620 nm, which corresponds to the material photoluminescence band. The optical characteristics of randomly oriented p-6P nanofibers assembled directly on the metal surface are remarkably comparable to those of fibers grown on crystalline substrate surfaces. In addition, compared to mica-transferred fibers, the photoluminescence lifetime is longer. More importantly, they show polarization-insensitive plasmonic activity and are entirely consistent with theoretical predictions. Both analytical and numerical finite-difference time-domain simulations support the experimental data. Our findings open a new avenue for incorporating organic nanofibers into optoelectronic applications by directly depositing the p-6P material onto selected substrates. This direct deposition significantly reduces the deformation of the fiber structure and the impurity introduction, usually implied by the transfer process.

Normalized passivity control for robust tuning in real‐time hybrid tests

AbstractReal‐time hybrid testing involves the separation of a system into an experimental component and a numerically simulated substructure which are coupled and run together. The coupling between substructures is achieved using actuators and force sensors which comprise the transfer system. Close synchronization is required between substructures for reliable hybrid testing. However, actuator lag may cause tracking errors and instability in hybrid tests. Existing lag compensation schemes require identification of the coupled dynamics of the transfer system and experimental component and can be sensitive to changes in these components. Passivity control is a technique intended to maintain stability without the need for system identification or assumptions about the actuators or test specimens. Yet, the tuning of existing passivity controllers is sensitive to both the system being tested and the amplitude and frequency range excited. This paper presents a new, normalized passivity controller which behaves well across a much broader range of operating conditions once tuned for a single‐test scenario. The proposed approach uses a virtual damping element on the numerical substructure to dissipate spurious power injected by the actuator into the system, based on the ratio of net power output to mean power throughput. The scheme has been shown to result in identical performance for a linear hybrid test with a range of step excitations from 0.5 mm up to 500 mm. The proposed method can be used to improve test stability and fidelity in isolation or alongside other compensation schemes to further improve performance.

A novel violet fluorescent protein contains a unique oxidized tyrosine as the simplest chromophore ever reported in fluorescent proteins.

We describe an engineered violet fluorescent protein from the lancelet Branchiostoma floridae (bfVFP). This is the first example of a GFP-like fluorescent protein with a stable fluorescent chromophore lacking an imidazolinone ring; instead, it consists of oxidized tyrosine 68 flanked by glycine 67 and alanine 69. bfVFP contains the simplest chromophore reported in fluorescent proteins and was generated from the yellow protein lanFP10A2 by two synergetic mutations, S148H and C166I. The chromophore structure was confirmed crystallographically and by high-resolution mass spectrometry. The photophysical characteristics of bfVFP (323/430 nm, quantum yield 0.33, and Ec 14,300 M-1 cm-1 ) make it potentially useful for multicolor experiments to expand the excitation range of available FP biomarkers and Förster resonance energy transfer with blue and cyan fluorescent protein acceptors.

Energetic and radiative properties of the A-=SUP=-2-=/SUP=-Sigma-=SUP=-+-=/SUP=--X-=SUP=-2-=/SUP=- system of the OH radical: ab initio calculation and non-adiabatic simulation

A quantum-chemical model for non-adiabatic simulation of the energetic and radiative properties of the A2Sigma+-X2 system of the OH radical is presented. The electronic structure parameters (potential energy functions and electronic matrix elements of the spin-orbit and the electron-rotation interactions) are obtained by means of ab initio calculation. The reliability of the performed calculations is confirmed by comparing ab initio estimates with experimental values for the spin-orbit splitting, the -doubling parameters of the X2 state, and the γ-doubling of the A2Sigma+ state. The frequencies and Einstein coefficients for rovibronic transitions between the A2Sigma+ and X2 states are simulated in a wide range of rovibrational excitations. The obtained values are in quantitative agreement with the data available from literature. Keywords: OH radical, ab initio calculation, non-adiabatic interaction, fine structure, radiative transition probability.

Энергетические и радиационные характеристики системы A-=SUP=-2-=/SUP=-Sigma-=SUP=-+-=/SUP=--X-=SUP=-2-=/SUP=- радикала OH: неэмпирические расчеты и неадиабатическое моделирование

A quantum-chemical model for non-adiabatic simulation of the energetic and radiative properties of the A2Σ+ − X2Π system of the OH radical is presented. The model parameters (potential energy functions and electronic matrix elements of the spin-orbit and the electron-rotation interactions) are obtained by means of ab initio calculation. The reliability of the performed calculations is confirmed by comparing ab initio estimates with experimental values for the spin-orbit splitting, the Λ-doubling parameters of the X2Π state, and the γ-doubling of the A2Σ+ state. The frequencies and Einstein coefficients for rovibronic transitions between the states A2Σ+ and X2Π are simulated in a wide range of rovibrational excitations. The obtained values are in quantitative agreement with the data available from literature.

SUBSTANTIATION OF THE SPECTRAL RANGE OF PHOTOLUMINESCENT POTATO SOLANIZATION CONTRO

Potato processing is carried out at large automated enterprises, and the industry requires more automated equipment for quality assessment and sorting. There are many ways to increase potato yields, the most effective is planting tubers in the light. However, eating green potatoes can have a detrimental effect on the human body, since solanine is toxic. Therefore, the control of the potato solanization is relevant. (Research purpose) The research purpose is studying the optical luminescent properties of potato tubers in the solanization process and justifying the spectral ranges for creating a system of its control. (Materials and methods) The spectral characteristics of potato tubers were measured using a diffraction spectrofluorimeter. (Results and discussion) The excitation of potato tubers by radiation occurs in the ranges of 310-570 and 590-690 nanometers, the excitation maxima are approximately at wavelengths of 378, 425, 486, 528, 614 and 662 nanometers. Radiation shorter than 310 nanometers and longer than 690 nanometers does not excite luminescence. For the short-wave excitation range, a clear decrease in the integral absorption capacity H is observed during solanization, while the highest value of H is observed for the ranges of 310-404 and 404-474 nanometers. For long-wavelength ranges, the dependence of H(t) has a maximum at the 13th day of observation. The most optimal use of the ratio H404-474/H590-640, which has the highest ratio R2 = 0.89 with polynomial approximation. (Conclusions) The use of spectral ranges 404-474 and 590-640 nanometers is the most optimal for photoluminescent monitoring of the solanization. These results can be used as the basis for the methodology and digital device for monitoring the solanization of potato tubers.

Rapid FRET-based homogeneous immunoassay of procalcitonin using matched carbon dots labels

A novel method for the detection of procalcitonin in a homogeneous system by matched carbon dots (CDs) labeled immunoprobes was proposed based on the principle of FRET and double antibody sandwich method. Blue-emitting carbon dots with a strong fluorescence emission range of 400–550 nm and red-emitting carbon dots with the best excitation range of 410–550 nm were prepared before they reacted with procalcitonin protoclone antibody pairs to form immunoprobes. According to the principles of FRET, blue-emitting carbon dots were selected as the energy donor and red-emitting carbon dots as the energy receptor. The external light source excitation (310 nm) could only cause weak luminescence of CDs. However, once procalcitonin was added, procalcitonin and antibodies would be combined with each other quickly (≤20 min). Here, blue-emitting carbon dots acquired energy could be transferred to red-emitting carbon dots efficiently, causing the emitted fluorescence enhancement of red-emitting carbon dots. The fluorescence detection results in PBS buffer solution and diluted rabbit blood serum showed that the fluorescence intensity variation was linear with the concentration of procalcitonin. There was a good linear relationship between F/F0 and procalcitonin concentrations in PBS buffer solution that ranged from 0 to 100 ng ml−1, and the linear equation was F/F0 = 0.004 * C pct + 0.98359. Detection in the diluted rabbit serum led to the results that were linear in two concentration ranges, including 0–40 ng ml−1 and 40–100 ng ml−1, and the detection limit based on 3σ K−1 was 0.52 ng ml−1. It is likely that this matched CDs labeled immunoprobes system can provide a new mode for rapid homogeneous detection of disease markers.

A Modified Inverse Vector Hysteresis Model for Nonoriented Electrical Steels Considering Anisotropy for FEA

This paper presents a modified Mayergoyz-based vector hysteresis model to describe the anisotropic material behavior of nonoriented (NO) steels over a wide range of rotational excitations. The proposed model adopts a new representation of a vector Everett function, which is actually an elliptical interpolation motivated by the real anisotropic behavior of NO steel, to deal with the uniaxial anisotropy characteristic, which is especially pronounced at low induction levels. The biaxial anisotropy occurring at high densities is described by a nonlinear coefficient, which is actually a function of the magnitude of magnetic flux density. A systematic identification algorithm is given in detail. The validity of this model is verified through comparison with experimental data under both alternating and rotational excitations. The 2-D finite element analysis (FEA) of incorporating this model into TEAM problem 32 simulation is also illustrated.