Emission Frequency Research Articles

A new framework for evaluating dust emission model development using dichotomous satellite observations of dust emission

Dust models are essential for understanding the impact of mineral dust on Earth's systems, human health, and global economies, but dust emission modelling has large uncertainties. Satellite observations of dust emission point sources (DPS) provide a valuable dichotomous inventory of regional dust emissions. We develop a framework for evaluating dust emission model performance using existing DPS data before routine calibration of dust models. To illustrate this framework's utility and arising insights, we evaluated the albedo-based dust emission model (AEM) with its areal (MODIS 500 m) estimates of soil surface wind friction velocity (us∗) and common, poorly constrained grain-scale entrainment threshold (u∗ts) adjusted by a function of soil moisture (H). The AEM simulations are reduced to its frequency of occurrence, P(us∗>u∗tsH). The spatio-temporal variability in observed dust emission frequency is described by the collation of nine existing DPS datasets. Observed dust emission occurs rarely, even in North Africa and the Middle East, where DPS frequency averages 1.8 %, (~7 days y−1), indicating extreme, large wind speed events. The AEM coincided with observed dust emission ~71.4 %, but simulated dust emission ~27.4 % when no dust emission was observed, while dust emission occurrence was over-estimated by up to 2 orders of magnitude. For estimates to match observations, results showed that grain-scale u∗ts needed restricted sediment supply and compatibility with areal us∗. Failure to predict dust emission during observed events, was due to us∗ being too small because reanalysis winds (ERA5-Land) were averaged across 11 km pixels, and inconsistent with us∗ across 0.5 km pixels representing local maxima. Assumed infinite sediment supply caused the AEM to simulate dust emission whenever P(us∗>u∗tsH), producing false positives when wind speeds were large. The dust emission model scales of existing parameterisations need harmonising and a new parameterisation for u∗ts is required to restrict sediment supply over space and time.

Telecom-band quantum dot technologies for long-distance quantum networks.

A future quantum internet is expected to generate, distribute, store and process quantum bits (qubits) over the world by linking different quantum nodes via quantum states of light. To facilitate long-haul operations, quantum repeaters must operate at telecom wavelengths to take advantage of both the low-loss optical fibre network and the established technologies of modern optical communications. Semiconductor quantum dots have thus far shown exceptional performance as key elements for quantum repeaters, such as quantum light sources and spin-photon interfaces, but only in the near-infrared regime. Therefore, the development of high-performance telecom-band quantum dot devices is highly desirable for a future solid-state quantum internet based on fibre networks. In this Review, we present the physics and technological developments towards epitaxial quantum dot devices emitting in the telecom O- and C-bands for quantum networks, considering both advanced epitaxial growth for direct telecom emission and quantum frequency conversion for telecom-band down-conversion of near-infrared quantum dot devices. We also discuss the challenges and opportunities for future realization of telecom quantum dot devices with improved performance and expanded functionality through hybrid integration.

Tunable spectral continuous shift of high-order harmonic generation in atoms by a plasmon-assisted shaping pulse

We delve into the phenomenon of high-order harmonic generation within a helium atom under the influence of a plasmon-assisted shaping pulse. Our findings reveal an intriguing manipulation of the frequency peak position in the harmonic emission by adjusting the absolute phase parameter within the frequency domain of the shaping pulse. This phenomenon holds potential significance for experimental setups necessitating precisely tuned single harmonics. Notably, we observe a modulated shift in the created harmonic photon energy, spanning an impressive range of 1.2 eV. This frequency peak shift is rooted in the asymmetry exhibited by the rising and falling edges of the laser pulse, directly influencing the position of the peak frequency emission. Our study quantifies the dependence of this tuning range and the asymmetry of the laser pulse, offering valuable insights into the underlying mechanisms driving this phenomenon. Furthermore, our investigation uncovers the emergence of semi-integer order harmonics as the phase parameter is altered. We attribute this discovery to the intricate interference between harmonics generated by the primary and secondary return cores. This observation introduces an innovative approach for generating semi-integer order harmonics, thus expanding our understanding of high-order harmonic generation. Ultimately, our work contributes to the broader comprehension of complex phenomena in laser-matter interactions and provides a foundation for harnessing these effects in various applications, particularly those involving precise spectral control and the generation of unique harmonic patterns.

Li–Pd–Rh-D2O electrochemistry experiments at elevated voltage

In 2013, the U.S. Navy disclosed an electrochemistry procedure intended to produce MeV-energy nuclear particles, based on eV-energy electrical inputs, which may be indicative of a new scientific phenomenon. This work is based on the 2013 disclosure and shows initial evidence validating the prior claims of nuclear particle generation. Additionally, several variations on the 2013 electrochemical recipe are made in order to find a highly repeatable recipe for future replications by other teams. The experiments described here produced dense collections of tracks in solid-state nuclear track detectors, radio frequency (RF) emissions, and anomalous heat flux, which are indicative of potential nuclear, or unusual chemical, reactions. Experimental results include tracks in solid-state nuclear track detectors similar in size to tracks produced by 4.7 MeV alpha particles on identical detectors exposed to radioactive Th-230; RF pulses up to 6 dB above the noise floor, which indicate that these signals were likely not background noise and not caused by known chemical reactions; and heat flux of 10 s of kJ, measured to 6σ significance, over and above input electrical energy, indicative of unknown exothermic reactions. Six out of six nuclear track detectors, utilized in experiments and interrogated for tracks post-experiment, produced positive results that our team attributes to thousands of individual particle impacts in dense clusters, likely with energies between 0.1 and 20 MeV. Similar nuclear particle, thermal, and RF results have separately appeared in prior reports, but in this work, all three categories of anomalous behavior are reported. Results indicate that the 2013 procedure may be a useful guide toward a set of highly repeatable reference experiments, showing initial but not overwhelming evidence of a new scientific phenomenon. Repeatable recipes are shared so that other groups may replicate and extend the present work.

Particles creation from JNW quantum perturbed black holesby minimally coupled Klein Gordon scalar free fields

In this work, we choose a minimal coupling interaction between massive Klein Gordon (KG) quantum scalar free fields and Janis-Newman-Winicour (JNW) spherically symmetric static black hole, to produce its Hawking temperature and luminosity. This is done by calculating asymptotic wave solutions at near and far from the black hole horizon. They are orthogonal mode solutions of local Hilbert spaces. By using these mode solutions, we calculated Bogolubov coefficients and then, we investigated number density matrix of created particles. Mathematical calculations show that this is not exactly similar to the Planck`s black body radiation energy density distribution but, it is “gray” body radiation distribution depended to the emitted Hawking particles frequency. Their difference is a non-vanishing absorptivity factor of backscattered particles after to form horizon of a collapsing body. Our motivation is determination of position of Hawking created pairs in which, two different proposals are proposed, so called as “fairwall” and “quantum atmosphere”.

Gate tunable terahertz cyclotron emission from two-dimensional Dirac fermions

Two-dimensional Dirac fermions in HgTe quantum wells close to the topological phase transition can generate significant cyclotron emission that is magnetic field tunable in the terahertz frequency range. Due to their relativistic-like dynamics, their cyclotron mass is strongly dependent on their electron concentration in the quantum well, providing a second tunability lever and paving the way for a gate-tunable, permanent-magnet Landau laser. In this work, we demonstrate the proof-of-concept of such a back-gate tunable THz cyclotron emitter at a fixed magnetic field. The emission frequency detected at 1.5 T is centered at 2.2 THz and can already be electrically tuned over 250 GHz. With an optimized gate and a realistic permanent magnet of 1.0 T, we estimate that the cyclotron emission could be continuously and rapidly tunable by the gate bias between 1 and 3 THz, that is to say on the less covered part of the THz gap.

Expansion of the Soft X-ray Source and “Magnetic Detonation” in Solar Flares

The detection of radio emission from solar flares at frequencies below ∼2 GHz allows the upperlimits for the characteristic size of the soft X-ray (SXR) source L(t) to be estimated under the assumptionthat the density n(t) is determined by the plasma frequency νp. If the SXR source with a higher density isinside the radio source, then the size of the SXR source will be L(t) (EM(t)/2n(t)2)1/3, where EM(t)is the emission measure. For three flares (C7.2 on December 22, 2009, M2.9 on July 6, 2012, and X1.1 onJuly 6, 2012) we calculate the expansion speeds of the SXR source V (t) ∼ dL(t)/dt, which are comparedwith the estimates of the sound speed and the Alfve´ n speed. By “magnetic detonation” wemean the processof the propagation of magnetic reconnectionwith a supersonic speed in eruptive flares. Magnetic detonationand the succeeding coronal mass ejection (CME) were realized in the December 22, 2009 C7.2 and July 6,2012 X1.1 flares, in which supersonic and super-Alfve´ n speeds were reached if the density of the SXRsource was lower than 2.1 × 109 and 7.4 × 108 cm−3 (νp 410 and 245 MHz), respectively. There wereno magnetic detonation and CME in the July 6, 2012 M2.9 flare, whose radio emission frequencies wereonly above 1415 MHz (n 2.5 × 1010 cm−3). For magnetic detonation in the July 6, 2012 X1.1 flare wehave estimated the magnetic field strength, the reconnection electric field strength, the plasma flow, and theCME mass.

High-Throughput Search for Triplet Point Defects with Narrow Emission Lines in 2D Materials.

We employ a first-principles computational workflow to screen for optically accessible, high-spin point defects in wide band gap, two-dimensional (2D) crystals. Starting from an initial set of 5388 point defects, comprising both native and extrinsic, single and double defects in ten previously synthesized 2D host materials, we identify 596 defects with a triplet ground state. For these defects, we calculate the defect formation energy, hyperfine (HF) coupling, and zero-field splitting (ZFS) tensors. For 39 triplet transitions exhibiting particularly low Huang-Rhys factors, we calculate the full photoluminescence (PL) spectrum. Our approach reveals many spin defects with narrow PL line shapes and emission frequencies covering a broad spectral range. Most of the defects are hosted in hexagonal BN (hBN), which we ascribe to its high stiffness, but some are also found in MgI2, MoS2, MgBr2 and CaI2. As specific examples, we propose the defects vSMoS0 and NiSMoS0 in MoS2 as interesting candidates with potential applications to magnetic field sensors and quantum information technology.

Heterogeneous Traffic Flow Signal Control and CAV Trajectory Optimization Based on Pre-Signal Lights and Dedicated CAV Lanes

This paper proposes a control system to address the efficiency and pollutant emissions of heterogeneous traffic flow composed of human-operated vehicles (HVs) and connected and automated vehicles (CAVs). Based on the comprehensive collection of information on the flow of heterogeneous traffic, the control system uses a two-layer optimization model for signal duration calculation and CAV trajectory planning. The upper model optimizes the phase duration in real time based on the actual total number and type of vehicles entering the control adjustment zone, while the lower model optimizes CAV lane-changing strategies and vehicle acceleration optimization curves based on the phase duration optimized by the upper model. The target function accounts for reducing fuel usage, carbon emission lane-changing costs, and vehicle travel delays. Based on the Webster optimal cycle formula, an improved cuckoo algorithm with strong search performance is created to solve the model. The numerical data confirmed the benefits of the suggested signal control and CAV trajectory optimization method based on pre-signal lights and dedicated CAV lanes for heterogeneous traffic flow. Intersection capacity was significantly enhanced, CAV average fuel consumption, carbon emission and lane-changing frequency were significantly reduced, and traffic flow speed and delay were significantly improved.

Frequency Tunable, Cavity-Enhanced Single Erbium Quantum Emitter in the Telecom Band.

Single quantum emitters embedded in solid-state hosts are an ideal platform for realizing quantum information processors and quantum network nodes. Among the currently investigated candidates, Er^{3+} ions are particularly appealing due to their 1.5 μm optical transition in the telecom band as well as their long spin coherence times. However, the long lifetimes of the excited state-generally in excess of 1ms-along with the inhomogeneous broadening of the optical transition result in significant challenges. Photon emission rates are prohibitively small, and different emitters generally create photons with distinct spectra, thereby preventing multiphoton interference-a requirement for building large-scale, multinode quantum networks. Here we solve this challenge by demonstrating for the first time linear Stark tuning of the emission frequency of a single Er^{3+} ion. Our ions are embedded in a lithium niobate crystal and couple evanescently to a silicon nanophotonic crystal cavity that provides a strong increase of the measured decay rate. By applying an electric field along the crystal c axis, we achieve a Stark tuning greater than the ion's linewidth without changing the single-photon emission statistics of the ion. These results are a key step towards rare earth ion-based quantum networks.

Effects of Patterned Electromagnetic Fields and Light-Emitting Diodes on Cancer Cells: Impact on Cell Density and Biophoton Emission When Applied Individually vs. Simultaneously

It has been previously reported that time-varying EMFs and LEDs have the potential to modulate cellular activity and cell viability. It has also been shown that cellular activity and state can be inferred by measuring the biophoton emission derived from these same cells. To identify if the brief application (15 min) of an LED (635 nm at 3 klx) or EMF (1–3 uT) could influence cell growth and subsequent biophoton emission characteristics, B16-BL6 cells were grown to confluence and exposed to a time-varying, frequency-modulated EMF, LED, or both. Before and after EMF and LED exposure, photon emission measurements were taken for 1 min at a 50 Hz sampling rate. Following the exposure and photon emission measurements, cell viability was assessed via the use of a hemocytometer. The results demonstrated that after only 15 min of exposure to a time-varying EMF, there was a 41.6% reduction in viable cells when compared to sham controls [t(25) = 2.4, p = 0.02]. This effect approached significance in the LED alone condition [p = 0.07] but was completely absent in the condition wherein the LED and EMF were applied simultaneously [p < 0.8]. Additionally, following exposure to only the LED, there was a significant increase in biophoton emission SPD values at 13 Hz from whole cell cultures [t(60) = 2.3, p = 0.021]. This biophoton emission frequency was also strongly correlated with the number of nonviable cells [r = −0.514] in the dish. Taken together, these data point to biophotons emitted from cell cultures at 13 Hz as a potential indicator of the number of nonviable cells in vitro. The summation of data here corroborates previous work demonstrating the efficacy of specific time-varying EMFs as a novel therapeutic for the inhibition of cancer cell growth. It also furthers our assertion that biophoton emission can be used as a novel detection tool for cell activity.

Microscopic defect dynamics during a brittle-to-ductile transition

Deformation of all materials necessitates the collective propagation of various microscopic defects. On Earth, fracturing gives way to crystal-plastic deformation with increasing depth resulting in a "brittle-to-ductile" transition (BDT) region that is key for estimating the integrated strength of tectonic plates, constraining the earthquake cycle, and utilizing deep geothermal resources. Here, we show that the crossing of a BDT in marble during deformation experiments in the laboratory is accompanied by systematic increase in the frequency of acoustic emissions suggesting a profound change in the mean size and propagation velocity of the active defects. We further identify dominant classes of emitted waveforms using unsupervised learning methods and show that their relative activity systematically changes as the rocks cross the brittle-ductile transition. As pressure increases, long-period signals are suppressed and short-period signals become dominant. At higher pressures, signals frequently come in avalanche-like patterns. We propose that these classes of waveforms correlate with individual dominant defect types. Complex mixed-mode events indicate that interactions between the defects are common over the whole pressure range, in agreement with postmortem microstructural observations. Our measurements provide unique, real-time data of microscale dynamics over a broad range of pressures (10 to 200 MPa) and can inform micromechanical models for semi-brittle deformation.

Unidirectional spin wave emission by traveling pair of magnetic field profiles

We demonstrate that the spin wave Cherenkov effect can be used to design the unidirectional spin wave emitter with tunable frequency and switchable direction of emission. In our numerical studies, we propose to use a pair of traveling profiles of the magnetic field which generate the spin waves, for sufficiently large velocity of their motion. In the considered system, the spin waves of shorter (longer) wavelengths are induced at the front (back) of the moving profiles and interfere constructively or destructively, depending on the velocity of the profiles. Moreover, we showed that the spin waves can be confined between the pair of traveling profiles of the magnetic field. This work opens the perspectives for the experimental studies in hybrid magnonic-superconducting systems where the magnetic vortices in a superconductor can be used as moving sources of the magnetic field driving the spin waves in the ferromagnetic subsystem.

Biosonar sampling strategies in frequency-modulated echolocating bats

Echolocating bats dynamically control multiple aspects of their biosonar emissions (emission rate, frequency, bandwidth, duration, and direction) in parallel as a function of their surroundings and current goals. As environments become more difficult to navigate and tasks become more complex, bats converge on sampling strategies that have less variability in the timing and spatial changes of their echolocation. We investigated these biosonar dynamics within a virtual echo target presentation paradigm where we challenged big brown bats sitting on a platform to localize a single echo target, which was either stationary or moved unpredictably in azimuth. Acoustic clutter was also added at varying distances to investigate its effect on their sampling strategies during the task. Bats modified their biosonar strategies differently depending on the distance of added acoustic clutter and the distance that a target shifted, and individuals tended to converge on similar strategies. We also show that certain perceptual contexts can lead to unexpected biosonar strategies in individual bats, such as the use of longer-duration emissions with less emission ‘clustering’ when localizing a virtual target against nearby clutter.

Sub-terahertz feedback interferometry and imaging with emitters in 130 nm BiCMOS technology

In this work, we present the effect of self-mixing in compact terahertz emitters implemented in a 130 nm SiGe BiCMOS technology. The devices are based on a differential Colpitts oscillator topology with optimized emission frequency at the fundamental harmonic. The radiation is out-coupled through the substrate side using a hyper-hemispheric silicon lens. The first source is optimized for 200 GHz and radiates up to 0.525 mW of propagating power. The second source emits up to 0.325 mW at 260 GHz. We demonstrate that in these devices, feedback radiation produces the change in bias current, the magnitude of which can reach up to several percent compared to the bias current itself, enabling feedback interferometric measurements. We demonstrate the applicability of feedback interferometry to perform coherent reflection-type raster-scan imaging.

A multimodal analysis for an updated vision of women in music videos

A democratic society is characterised by the respect accorded to the dignity and rights of all its members. These values are also transmitted by high-consumption media cultural products such as music videos. This article discusses the representation of women in music videos published in Spanish on music broadcast platforms in 2019 in order to observe the multimodal discourses to which our society is exposed. After identifying a total of 4197 videos, 47 of the highest emission frequencies were extracted. Using the qualitative data analysis programme Atlas.ti, narrative, linguistic and visual resources, as well as cinematographic components, were analysed. The results reveal clear attacks on female dignity. Normalised sexist violence is observed in songs on the Hispanic market, where women are commodified as sexual objects on both audio-visual and linguistic levels. Hierarchical relationships are also shown, which position women on an inferior plane. In conclusion, commercial channels broadcast music videos from the Hispanic market that violate feminine dignity.

Circularly Polarized Luminescence from Chiral Photonic Crystals of Caesium Lead Halide Perovskites

AbstractThe generation and detection of circularly polarized light (CPL) are of importance in many modern technologies such as digital communications, machine vision, bio‐imaging, and 3D displays. In this study, inspired by the fact that various species of plants and animals can efficiently produce and/or perceive CPL with chiral photonic crystal structures, efforts are made to fabricate luminescent chiral photonic crystals with caesium lead halide perovskites, a class of solution‐processable semiconductors that have excellent luminescence properties and readily tunable electronic band gaps. Coupling between the emission frequency of the perovskite and the cavity resonance frequency of the photonic crystal structure can be established at any desired point in the visible region, giving rise to CPL output with a dissymmetry factor up to −0.34. These results suggest a new approach to chiral light‐emitting materials and may contribute to the development of semiconductors with ordered microstructures.

Artificial neural networks for laser frequency stabilization.

In order to stabilize a laser's emission frequency, absolute references such as molecular absorption lines are widely used. To automate the stabilization process, the desired absorption line needs to be identified reliably from a spectrum by a computer. We present an artificial neural network solving this task using the iodine spectrum as an example. The neural network is trained using only simulated data and subsequently tested using measured data. We show that this approach is robust against large variations of operating and environmental conditions.

Green perspectives of finance, technology innovations, and energy consumption in restraining carbon emissions in China: Fresh insights from Wavelet approach

ABSTRACT Carbon dioxide (CO2) emission is a major contributor to global climate change and needs an instant reduction to preserve the environmental quality of the planet. To ensure this, our study examines the role of green factors in terms of finance, technology, and energy in reducing CO2 emissions in China using quarterly data spanning 2001Q1-2020Q4. A recently developed frequency- and time-varying technique named “Wavelet Local Multiple Correlation” is applied to examine the impact of considered factors on CO2 emission dynamics in short-, medium-, and long-term. Thus, our study is the first to provide detailed insights into the role of green factors in reducing CO2 emission in China in a multivariate context. The outcomes confirm the long-term positive connectedness among green finance, green technology, and green energy consumption. Secondly, all these factors are asymmetrically and negatively correlated to CO2 emissions in long-term frequencies. However, green energy and green finance are highly affecting the CO2 in long-term, while green technology in medium-term. Finally, the multivariate analysis confirms that all the explanatory variables follow a similar trend in affecting CO2 emission; though, green finance is the dominant factor in the correlation. Based on the findings, the study recommends promoting green innovations, financial measures, and renewable energy that help China to limit CO2 emissions and promote environmental quality.

The Relationship between the Evaluation of Public Transport Services and Travel-Based CO2 Emissions from Private Transport Modes in Regional and Metropolitan Areas in Japan

Promoting public transport use is expected to contribute to reducing CO2 emissions in the transport sector. Using Okayama City and Central Tokyo as representative case studies of regional and metropolitan areas in Japan, this study examines the impact of the evaluation of the ‘hard’ and ‘soft’ attributes of rail and bus services on the overall evaluation. This study then explores the relationship between the overall evaluation and usage frequency of rail and bus services, as well as the relationship between the usage frequency and travel-based CO2 emissions from private transport modes. Furthermore, this study investigates whether the emissions cause differences in the evaluation of the ‘hard’ and ‘soft’ attributes of public transport services. The findings suggest prioritising an improvement in ‘hard’ rather than ‘soft’ attributes in order to reduce emissions through the use of public transport in regional areas. However, in metropolitan areas, no relationship was found between the evaluation of public transport services and emissions, presumably because of the lower ownership rate of private cars that residents can use freely and the markedly higher level of rail and bus services. This study provides a methodological reference for analysing the potential to reduce travel-based emissions from private transport modes by enhancing public transport service contents.