Source Size Research Articles

Synthetic radio images of structured GRB and kilonova afterglows

ABSTRACT In this paper, we compute and analyse synthetic radio images of gamma-ray bursts (GRBs) and kilonova afterglows. For modelling the former, we consider GRB170817A-inspired set of parameters, while for the latter, we employ ejecta profiles from numerical-relativity simulations. We find that the kilonova afterglow sky map has a doughnut-like structure at early times that becomes more ring-like at late times. This is caused by the fact that the synchrotron emission from electrons following Maxwellian distribution function dominates the early beamed emission, while emissions from electrons following power-law distribution is important at late times. For an on-axis observer, the image flux centroid moves on the image plane, initially away from the observer. The image sizes, we find, are the largest for equal mass merger simulations with the soft equation of state. The presence of a kilonova afterglow affects the properties inferred from the source sky map, even if the GRB afterglow dominates the total flux density. The main effect is the reduction of the mean apparent velocity of the source, and an increase in the source size. However, this effect becomes negligible around the light curve peak of the GRB afterglow. For a far off-axis observer, neglecting the presence of the kilonova afterglow may lead to systematic errors in the inference of GRB properties from the sky map observations. Notably, at the observing angle inferred for GRB170817A, the presence of kilonova afterglow would affect the sky map properties, only at very late times $t\gtrsim 1500\,$ d.

Beam intensity and spectral coherence of Hermite-cosine-Gaussian rectangular multi-Gaussian correlated Schell-model beam in oceanic turbulence

The beam spreading and evolution behavior of a partially coherent, Hermite-cosine-Gaussian (HcosG) rectangular multi-Gaussian correlated Schell-model beam propagating in oceanic turbulence is studied. Analytical expressions for the cross-spectral density function, as well as the root mean square (rms) beam width and the spectral degree of coherence, are derived based on the extended Huygens-Fresnel principle. The HcosG rectangular multi-Gaussian correlated Schell-model beam exhibits a multi-lobe pattern at short propagation distances. The dependencies of the number, size, shape, and centroid of the lobes on displacement parameters, source size, order of field distribution, and displacement are investigated. As the propagation distance increases, the spectral coherence decreases, and the differences between the spectral coherence curves gradually diminish. Additionally, for HcosG rectangular multi-Gaussian correlated Schell-model beams, better propagation performance was found in oceanic turbulence with larger mean square temperature dissipation rate, smaller turbulent kinetic energy dissipation rate per unit mass of fluid, and larger relative strength of temperature and salinity fluctuation.

Evaluation of Uncertainties in the Anthropogenic SO2 Emissions in the USA from the OMI Point Source Catalog.

Satellite remote sensing is a promising method of monitoring emissions that may be missing in inventories, but the accuracy of these estimates is often not clear. We demonstrate here a comprehensive evaluation of errors in anthropogenic sulfur dioxide (SO2) emission estimates from NASA's OMI point source catalog for the contiguous US by comparing emissions from the catalog with high-quality emission inventory data over different dimensions including size of individual sources, aggregate vs individual source errors, and potential bias in individual source estimates over time. For sources that are included in the catalog, we find that errors in aggregate (sum of error for all included sources) are relatively low. Errors for individual sources in any given year can be substantial, however, with over- or underestimates in terms of total error ranging from -80 to 110 kt (roughly 10-90th percentile). We find that these errors are not necessarily random over time and that there can be consistently positive or negative biases for individual sources. We did not find any overall statistical relationship between the degree of isolation of a source and bias, either at a 40 or 70 km scales. For a sub-set of sources where inventory emissions over a radius of 70 km around an OMI detection are larger than twice the emissions within 40 km, the OMI value is consistently overestimated. We find, as expected, that emission sources not included in the catalog are the largest aggregate source of difference between the satellite estimates and inventories, especially in more recent years where source emission magnitudes have been decreasing and note that trends in satellite detections do not necessarily track trends in total emissions. We find that the OMI-based SO2 emissions are accurate in aggregate, when summed over a number of sources, but must be interpreted more cautiously at the individual source level. Similar analyses would be valuable for other satellite emission estimates; however, in many cases, the appropriate high-quality reference data may need to be generated.

Statistical Optimization and Partial Characterization of Xylanases Produced by Streptomyces sp. S1M3I Using Olive Pomace as a Fermentation Substrate.

Xylanase production by Streptomyces sp. S1M3I was optimized by response surface methodology (RSM), followed by a partial characterization of these enzymes. Olive pomace was used as a substrate for growing Streptomyces sp. S1M3I in submerged fermentation. Effects of incubation time, pH, temperature, carbon source, nitrogen source, and inoculum size on xylanase production were studied, through the one-factor-at-a-time method. Then, a 33-factorial experimental design with RSM and the Box-Behnken design was investigated for the major influence factors. Maximum xylanase production (11.28 U/mL) was obtained when the strain was grown in mineral medium supplemented with 3% (w/v) of olive pomace powder and 0.3% (w/v) of ammonium sulfate, at a pH 7.4 and an incubation temperature of 40°C. The xylanases in the supernatant degraded all tested substrates, with higher activity for the low-viscosity wheat arabinoxylan substrate. Two xylanases with close molecular masses were detected by zymogram analysis: Xyl-1 and Xyl-2 with molecular masses of 24.14kDa and 27kDa, respectively. The optimization of enzyme production parameters of Streptomyces sp. S1M3I and the characterization of these enzymes are prerequisites to enhancing xylanase production yield, which is crucial for further biotechnological processes.

Optimization of phase contrast imaging with a nano-focus x-ray tube.

Propagation-based phase contrast imaging with a laboratory x-ray source is a valuable tool for studying samples that show only low absorption contrast, either because of low density, elemental composition, or small feature size. If a propagation distance between sample and detector is introduced and the illumination is sufficiently coherent, the phase shift in the sample will cause additional contrast around interfaces, known as edge enhancement fringes. The strength of this effect depends not only on sample parameters and energy but also on the experimental geometry, which can be optimized accordingly. Recently, x-ray lab sources using transmission targets have become available, which provide very small source sizes in the few hundred nanometer range. This allows the use of a high-magnification geometry with a very short source-sample distance, while still achieving sufficient spatial coherence at the sample position. Moreover, the high geometrical magnification makes it possible to use detectors with a larger pixel size without reducing the image resolution. Here, we explore the influence of magnification on the edge enhancement fringes in such a geometry. We find experimentally and theoretically that the fringes become maximal at a magnification that is independent of the total source-detector distance. This optimal magnification only depends on the source size, the steepness of the sample feature, and the detector resolution. A stronger influence of the sample feature on the optimal magnification compared to low-magnification geometries is observed.

The negative beam source with single driver for CRAFT NNBI: design and conditioning results

The Comprehensive Research Facility for Fusion Technology (CRAFT) is a large scientific facility that is preferentially deployed for the construction of major national science and technology infrastructures. A negative beam source based neutral beam injector (NNBI) with beam energy of 200–400 keV, beam power of 2 MW and beam duration of 100 s is one of the devices. A giant radio frequency (RF) based negative beam source was designed for the CRAFT NNBI system. In order to understand the physics and pre-study the engineering problems for RF negative beams source, several beam sources with different scales will be designed and tested. According to the R&D schedule, a negative beam source with a single driver was designed, developed and tested first. The single driver beam source is a quarter of the size of the full size negative beam source. It contains an RF driver, an expansion chamber and a negative ion accelerator with three electrodes, which are a plasma grid (PG), extraction grid (EG) and ground grid (GG). To enhance the negative ion production, Cesium is injected into the plasma chamber and a magnetic filter filed is produced by current flow through the PG to decrease the electron temperature. The negative beam source was tested on the test facility after assembly, including RF plasma generation, negative ion production, extraction and acceleration. The characteristic of plasma discharge, beam extraction and acceleration was studied without and with Cs injection. The long pulse of 105 seconds negative ion beam was achieved successfully. The extracted negative ion current is 4 A and the ratio of electron and negative ion is around 0.8. It lays a good foundation for the R&D of negative ion source with a multi-driver for the CRAFT NNBI system. The details of the design and experimental results of beam source was shown in this paper.

Migration of Anomalous Displacements on the Flanks of a Preparing Earthquake Source: A Swing Model

The geomechanical modeling results on the stress-strain state dynamics before the 2019 M = 7.1 Ridgecrest earthquake, Southern California, show the alternating development of maximum displacements at the fault’s ends, which simulates the process of “swinging” of the epicentral zone of the earthquake. These results together with the existing theoretical ideas about the block structure of the Earth’s crust and the corresponding connections between blocks are used to construct a geomechanical “swing” model based on the stick-slip motion of three interconnected blocks. The model parameters are related to the rheological properties of the Earth’s crust in the region of the rupture of the bridging isthmus which determines the source size of the seismic event.

The Tiered Radio Extragalactic Continuum (T-RECS) simulation II: H i emission and continuum-H i cross-correlation.

Abstract In this paper we extend the Tiered Radio Extragalactic Continuum Simulation (T-RECS) to include ${\rm H\, {\small I}}$ emission. The ${\rm H\, {\small I}}$ T-RECS model is based on the most recent ${\rm H\, {\small I}}$ mass function estimates, combined with prescriptions to convert ${\rm H\, {\small I}}$ mass to total integrated ${\rm H\, {\small I}}$ flux. It further models source size, morphology and kinematics, including rotational velocity and ${\rm H\, {\small I}}$ line width. The continuum T-RECS model is updated to improve the agreement with deeper number counts available at 150 MHz. The model for star-forming galaxies (SFGs) is also modified according to the most recent indications of a star formation rate (SFR)–radio luminosity relation, which depends primarily on stellar mass rather than redshift. We further introduce prescriptions to associate an ${\rm H\, {\small I}}$ mass to the T-RECS radio continuum SFG and Active Galactic Nuclei (AGN) populations. This gives us a way to meaningfully associate counterparts between ${\rm H\, {\small I}}$ and continuum catalogues, thus building ${\rm H\, {\small I}}$ × continuum simulated observations. Clustering properties of the sources in both ${\rm H\, {\small I}}$ and continuum are reproduced by associating the galaxies to dark matter haloes of a cosmological simulation. We deliver a set of mock catalogues, as well as the code to produce them, which can be used for simulating observations and predicting results from radio surveys with existing and forthcoming radio facilities, such as the Square Kilometre Array (SKA).

Assessing long-term tephra fallout hazard in southern Italy from Neapolitan volcanoes

Abstract. Nowadays, modeling of tephra fallout hazard is coupled with probabilistic analysis that takes into account the natural variability of the volcanic phenomena in terms of eruption probability, eruption sizes, vent position, and meteorological conditions. In this framework, we present a prototypal methodology to carry out the long-term tephra fallout hazard assessment in southern Italy from the active Neapolitan volcanoes: Somma–Vesuvius, Campi Flegrei, and Ischia. The FALL3D model (v.8.0) has been used to run thousands of numerical simulations (1500 per eruption size class), considering the ECMWF ERA5 meteorological dataset over the last 30 years. The output in terms of tephra ground load has been processed within a new workflow for large-scale, high-resolution volcanic hazard assessment, relying on a Bayesian procedure, in order to provide the mean annual frequency with which the tephra load at the ground exceeds given critical thresholds at a target site within a 50-year exposure time. Our results are expressed in terms of absolute mean hazard maps considering different levels of aggregation, from the impact of each volcanic source and eruption size class to the quantification of the total hazard. This work provides, for the first time, a multi-volcano probabilistic hazard assessment posed by tephra fallout, comparable with those used for seismic phenomena and other natural disasters. This methodology can be applied to any other volcanic areas or over different exposure times, allowing researchers to account for the eruptive history of the target volcanoes that, when available, could include the occurrence of less frequent large eruptions, representing critical elements for risk evaluations.

Coulomb-correlated electron number states in a transmission electron microscope beam

While correlated electrons are at the heart of many phenomena in condensed matter, as well as atomic and molecular physics, Coulomb interactions in free-electron beams are generally considered detrimental. Here, we demonstrate the generation of Coulomb-correlated pair, triple and quadruple states of free electrons by femtosecond photoemission from a nanoscale field emitter inside a transmission electron microscope. Event-based electron spectroscopy allows the spatial and spectral characterization of the electron ensemble emitted by each laser pulse. We identify distinctive energy and momentum correlations arising from acceleration-enhanced interparticle energy exchange, revealing strong few-body Coulomb interactions at an energy scale of 2 eV. State-sorted beam caustics show a discrete increase in virtual source size and longitudinal source shift for few-electron states, associated with transverse momentum correlations. We observe field-controllable electron antibunching, attributed primarily to transverse Coulomb deflection. The pronounced spatial and spectral characteristics of these electron number states allow filtering schemes that control the statistical distribution of the pulse charge. In this way, the fraction of specific few-electron states can be actively suppressed or enhanced, facilitating the preparation of highly non-Poissonian electron beams for microscopy and lithography, including future heralding schemes and correlated multi-electron probing.

Diffuse sources, clustering, and the excess anisotropy of the radio synchrotron background

ABSTRACT We present the largest low frequency (120 MHz) arcminute resolution image of the radio synchrotron background (RSB) to date, and its corresponding angular power spectrum of anisotropies (APS) with angular scales ranging from 3° to 0.3 arcmin. We show that the RSB around the north celestial pole has a significant excess anisotropy power at all scales over a model of unclustered point sources based on source counts of known source classes. This anisotropy excess, which does not seem attributable to the diffuse Galactic emission, could be linked to the surface brightness excess of the RSB. To better understand the information contained within the measured APS, we model the RSB varying the brightness distribution, size, and angular clustering of potential sources. We show that the observed APS could be produced by a population of faint clustered point sources only if the clustering is extreme and the size of the Gaussian clusters is ≲1 arcmin. We also show that the observed APS could be produced by a population of faint diffuse sources with sizes ≲1 arcmin, and this is supported by features present in our image. Both of these cases would also cause an associated surface brightness excess. These classes of sources are in a parameter space not well probed by even the deepest radio surveys to date.

Matching LOFAR sources across radio bands

Aims. The recent preliminary release of the LOFAR LBA Sky Survey (LoLSS) is the first wide-area, ultra-low frequency observation published from the Low Frequency Array (LOFAR). Our aim is to combine this data set with other surveys at higher frequencies to study the spectral properties of a large sample of radio sources. Methods. We present a new cross-matching algorithm that takes into account the sizes of the radio sources. We applied it to the LoLSS-PR, LoTSS-DR1, LoTSS-DR2 (all LOFAR), TGSS-ADR1 (GMRT), WENSS (WSRT), and NVSS (VLA) catalogues. We then studied the number of matched counterparts for LoLSS radio sources and their spectral properties. Results. We found counterparts for 22 607 (89.5%) LoLSS sources. The remaining 2640 sources (10.5%) were identified either as an artefact in the LoLSS survey (3.6%) or flagged due to their closeness to bright sources (6.9%). We found an average spectral index of α = −0.77 ± 0.18 between LoLSS and NVSS. Between LoLSS and LoTSS-DR2, we found α = −0.71 ± 0.31. The average spectral index is independent of the flux density above S54 = 181 mJy. A comparison of the spectral slopes from LoLSS-LoTSS-DR2 with LoTSS-DR2–NVSS indicates that the probed population of radio sources shows evidence of a negative spectral curvature.

Identification and Characterization of a Large Sample of Distant Active Dwarf Galaxies in XMM-SERVS

Active dwarf galaxies are important because they contribute to the evolution of dwarf galaxies and can reveal their hosted massive black holes. However, the sample size of such sources beyond the local universe is still highly limited. In this work, we search for active dwarf galaxies in the recently completed XMM-Spitzer Extragalactic Representative Volume Survey (XMM-SERVS). XMM-SERVS is currently the largest medium-depth X-ray survey covering 13 deg2 in three extragalactic fields, which all have well-characterized multiwavelength information. After considering several factors that may lead to misidentifications, we identify 73 active dwarf galaxies at z < 1, which constitutes the currently largest X-ray-selected sample beyond the local universe. Our sources are generally less obscured than predictions based on the massive-AGN (active galactic nucleus) X-ray luminosity function and have a low radio-excess fraction. We find that our sources reside in environments similar to those of inactive dwarf galaxies. We further quantify the accretion distribution of the dwarf-galaxy population after considering various selection effects and find that it decreases with X-ray luminosity, but redshift evolution cannot be statistically confirmed. Depending on how we define an AGN, the active fraction may or may not show a strong dependence on stellar mass. Their Eddington ratios and X-ray bolometric corrections significantly deviate from the expected relation, which is likely caused by several large underlying systematic biases when estimating the relevant parameters for dwarf galaxies. Throughout this work, we also highlight problems in reliably measuring photometric redshifts and overcoming strong selection effects for distant active dwarf galaxies.

Distance Duality Test: The Evolution of Radio Sources Mimics a Nonexpanding Universe

Distance duality relation (DDR) marks a fundamental difference between expanding and nonexpanding universes, as an expanding metric causes angular diameter distance smaller than luminosity distance by an extra factor of (1 + z). Here we report a test of this relation using two independent samples of ultracompact radio sources observed at 2.29 GHz and 5.0 GHz. The test with radio sources involves only geometry, so it is independent of cosmological models. Since the observed radio luminosities systematically increase with redshift, we do not assume a constant source size. Instead, we start with assuming the intensive property, luminosity density, does not evolve with redshift and then infer its evolution from the resultant DDR. We make the same assumption for both samples, and find it results in the same angular size–redshift relation. Interestingly, the resultant DDR is fully consistent with a nonexpanding universe. Imposing the DDR predicted by the expanding universe, we infer the radio luminosity density evolves as ρ L ∝ (1 + z)3. However, the perfect agreement with a nonexpanding universe under the assumption of constant luminosity densities poses a conspiracy and fine-tuning problem: the size and luminosity density of ultracompact radio sources evolve in the way that precisely mimics a nonexpanding universe.

Analytical Parasitic Resistance and Capacitance Models for Nanosheet Field-Effect Transistors

We developed analytical compact models of parasitic resistance and capacitance ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> ) for nanosheet field-effect transistors (NSFETs) with metal contact structures. The proposed model accurately captures the number of sheets, sheet geometry, gate, source, drain, and contact sizes. The parasitic resistance model generated in each region was modeled using the transmission line method (TLM) and the spread resistance model. The parasitic capacitance model was modeled using the conformal mapping method based on the distribution of the electric field. The developed models were validated by changing the structural parameters. The proposed models were implemented in Berkeley short-channel IGFET model (BSIM)-common multi-gate (CMG) to enable circuit performance prediction. With our proposed model, we can accurately predict the circuit performance of NSFETs, capturing the recent scaling trends and process variations in the proposed NSFET.

Analysis of Experimental Data from Household Off-Grid System in Latvia

Abstract Autonomous off-grid systems might be seen as a favourable option when it comes to high grid connection fees and for a sustainable electric system in transition to a low-carbon, renewable-based decentralized system. To ensure such a system, accurate analysis of different scenarios is required to determine the optimal energy source mix and sizing of the off-grid system. Software computing techniques or mathematical models can help solve this task, but, unfortunately, it is unpredictable how actually such systems will perform in real life. There are not so many publications, where the real data and off-grid systems are analysed and compared to simulation results. Thus, this paper examines an experimental stand-alone electrical off-grid solution in Latvia. The operational data of real autonomous off-grid system are obtained for the off-grid system performance and control strategy analysis, which is highly relevant for the planning and dimensioning of affordable renewable off-grid systems.

Impact of cell size on morphogen gradient precision.

Tissue patterning during embryonic development is remarkably precise. In this paper, we numerically determine the impact of the cell diameter, gradient length, and the morphogen source on the variability of morphogen gradients. In this way, we show that the positional error increases with the gradient length relative to the size of the morphogen source, and with the square root of the cell diameter and the readout position. We provide theoretical explanations for these relationships, and show thatthey enable high patterning precision over developmental time for readouts that scale with expanding tissue domains, as observed in the Drosophila wing disc. Our analysis suggests that epithelial tissues generally achieve higher patterning precision with small cross-sectional cell areas. An extensive survey of measured apical cell areas shows that they are indeed small in developing tissues that are patterned by morphogen gradients. Enhanced precision may thus have led to the emergence of pseudostratification in epithelia, a phenomenon for which the evolutionary benefit had so far remained elusive.

A stress defect state measurement method based on low-frequency ACMFL excitation and Hall sensor array collection

The safety testing of ferromagnetic materials, which are the main materials for various machines and equipment, is particularly important. Stress concentration zones (stress defects) cause stress corrosion of ferromagnetic materials, and also have the potential to cause direct damage to ferromagnetic materials. Estimation of stress sources state using electromagnetic nondestructive measurement methods is a critical and difficult problem. In this paper, a visual and intelligent identification method of stress defects in ferromagnetic materials by low frequency AC magnetic flux leakage (ACMFL) technique is proposed. A new three-point compression experiment was designed in this paper. Time-difference vision is established to analyze the ACMFL signal caused by stress defects. A visual transformed convolutional neural network deep learning algorithm has been proposed to identify grayscale patterns pre-processed by the time-difference vision. The results show that the method proposed in this paper elucidates the relationship between the time-difference vision of a stress defect and the stress source state of the mechanical stress. Our proposed method allows to analyze the pressure indenter size of the pressure source of stress defects.

Pre-Sizing Approach of a Fuel Cell-Battery Hybrid Power System with Interleaved Converters

This paper proposes a design methodology that is dedicated to improving the concept of a modular hybrid power chain that uses interleaved converters. The approach involves optimising the system under multi-physical constraints, where the number of cells in the interleaved converters is considered as a key modular parameter. The methodology uses analytical models to strike a balance between computation time and result accuracy. This compromise is indispensable to the construction of a smart design approach under multi-physical constraints, such as electric, efficiency, volume, and thermal constraints. The proposed approach has been applied to a hybrid fuel cell and battery power system for automotive applications; the goal is to obtain a global optimal architecture chain by optimising the number of interleaved converter cells and by determining appropriate power electronics components and the optimal sizing of sources. This constitutes the primary step for providing an effective pre-design support tool for considering architecture modularity, facilitating the use of new technologies in the early design stage. The results showed that the interleaving concept allows for better flexibility in respecting the design constraints to improve the design of hybrid power systems. The analysis also highlights the current limitations and performance of the optimisation method and suggests new areas for future work.

Numeric Simulation of Subsidence of Loess Soil under Wetting in a Limited Area

Loess and loess-like soils, when exposed to water, lose their strength characteristics, and physical and mechanical properties and change their original structure. The stress-strain state is transformed in these soils when wetted. Therefore, the problem of building on loess soils and studying the mechanisms of subsidence of loess soils is relevant. In this article, we consider the problem of determining the subsidence and stress state of the loess soil stratum under its own weight on a limited wetted area. To determine the distribution of water in soil, the method of changing stationary states is used, and to determine the subsidence and stress state, the finite difference method is used. The initial conditions are obtained by solving problems for the natural wetting of the layers of loess soil. The numerical results obtained of the subsidence of the free surface of the layer of loess soil 40 m thick agree well with experimental data on the duration of wetting at a limited size of the source of water. The effect of the duration and moisture content on the process of subsidence and transformation of the stress state are determined. An increase in the size of the water source in soil led to an increase in the high moisture content of the area and an increase in the subsidence of the free surface of loess soil.