Imaging Instrument Research Articles

Full-Percutaneous Trans-Kambin Lumbar Interbody Fusion With a Large-Footprint Interbody Cage.

Exploratory prospective observational cohort. Aim of this study was to evaluate clinical and radiologic outcome, and surgical efficiency of a novel universal delivery system that allows full-percutaneous extraforaminal, trans-Kambin lumbar interbody fusion with a large-footprint lumbar interbody cage using only fluoroscopic imaging and open-surgery instrumentation. We prospectively evaluated patients that underwent elective trans-Kambin TLIF surgery with a large-footprint interbody cage using a novel universal delivery system. Clinical follow-up was evaluated pre-and post-operatively with Visual Analogic Scale (VAS) and Oswestry Disability Index (ODI) scores, while radiologic follow-up was performed with a computed tomography scan and standing films post-operatively at hospital discharge and 1year follow-up. A total of 47 patients were evaluated. Clinically, post-operative VAS and ODI scores significantly (P < 0.001) improved compared to pre-operative scores and 29.4months mean follow-up. Radiologic evaluation yielded an intervertebral fusion rate of 90% of the operated levels and a significant increase in segmental lordosis by 3.7°. Median surgical time for interbody cage insertion per level was 28minutes. Complications included 14 (29%) cases with transitory post-operative radiculitis, 4 (8%) cases with partial muscle weakness and 2 (4%) cases that required revision surgery. Post-operative ambulation started at a median 5hours and median hospital length of stay was 28hours. A new universal delivery system allows overcoming most limitations of current full-endoscopic trans-Kambin fusion as it allows a time- efficient full-percutaneous insertion of a large-footprint interbody cage under fluoroscopy imaging only, with standard open-surgery instruments and optional endoscopic visualization.

Three-dimensional localization of tooth germs without ionizing radiation : Proof-of-concept study using magnetic resonance imaging.

This study aimed to evaluate the feasibility and accuracy of using magnetic resonance imaging (MRI) for the three-dimensional (3D) localization of tooth germs. AMRI 3D dataset was compared to acone-beam computed tomography (CBCT) dataset, which is the current gold standard method in the localization of tooth germs. In this proof-of-concept study, the potential of eliminating the exposure of patients to ionizing radiation for tooth germ localization was evaluated. Ahalved pig head (Sus scrofa domestica) was imaged with MRI and CBCT. The MRI data were manually segmented using InVesalius 3.1.1 (Centro de Tecnologia da Informação Renato Archer, Campinas, Brazil) to generate a3D model, later processed in OnyxCeph3™ (Image Instruments GmbH, Chemnitz, Germany). The CBCT data were directly imported into OnyxCeph3™ for processing. Both datasets were combined with intraoral scans, and 12raters took measurements to compare the ability to localize tooth germs with the help of the two modalities. Atotal of 144 measurements were obtained (2modalities × 6measurement sections × 12raters). The interrater reliability was high (intraclass correlation coefficients [ICCs] ≥ 0.99 for both modalities). The average differences between CBCT and MRI measurements ranged between -0.43 mm (Bonferroni-Holm-corrected 90% confidence interval [-0.69 mm, -0.16 mm]) and 0.48 mm [0.34 mm, 0.63 mm] and were equivalent with respect to amargin of -1 mm to 1 mm in all measurement sections (Bonferroni-Holm-corrected P < 0.01 in all sections). MRI demonstrates high potential as anonionizing alternative to CBCT for 3D localization of impacted and displaced teeth, particularly in children and adolescents. The fluid-filled dental follicle provides excellent contrast in MRI, aiding precise localization. Future clinical studies with larger sample sizes are essential for validation.

A novel theoretical model framework for the 3D CdZnTe drift strip detector

Advances in data analysis and model prediction offer new potential for enhancing radiation measurement technologies, particularly in detector characterization and real-time signal analysis. A key challenge is creating realistic detector models that accurately describe the complex physical processes of photon-matter interaction, signal formation including material characteristics, and measurement to enhance design optimization and detector physics understanding. This research study introduces the development of an Advanced Theoretical Detector Model (ATDM) framework to evaluate the physical effects of charge diffusion, repulsion, and trapping, enabling the generation of realistic detector-specific signals through model prediction. Using physics simulations, the ATDM geometry, material properties, electric fields, and electrode weighting potentials are modeled for the DTU Space large-area (16 cm2) 3D CZT drift strip detectors. The simulations are based on the adjoint equations method, which when applied to the charge continuity equation allows deriving a description of underlying Charge Induction Efficiency (CIE) in the model. This allows for precise 3D mapping of induced charge at any time or interaction position. Additionally, Monte Carlo simulations generate recoiled photo-electron trajectories in CZT, which, combined with simulations of their propagation and secondary scattering processes yield a realistic charge cloud distribution. Model verification is achieved through experiments using narrow slit-beam illumination from a 137Cs source, measuring pulse shapes in the 40×40×5 mm3 detector modules with 69 readout channels. The ATDM framework, applicable to various detector types, successfully captures experimental data, offering insights into the pulse shape formation, timing, and intrinsic detector parameters that could guide future electrode configuration optimization and on the fly photon-by-photon measurements. The results also suggest a potential for electron tracking capability in 3D CZT drift strip electrodes, an exciting development that could significantly advance polarimetry and Compton imaging instruments for the future high-energy missions.

Dual-stream disentangled model for microvascular extraction in five datasets from multiple OCTA instruments

IntroductionOptical Coherence Tomography Angiography (OCTA) is a cutting-edge imaging technique that captures retinal capillaries at micrometer resolution using optical instrument. Accurate segmentation of retinal vasculature is essential for eye related diseases measurement and diagnosis. However, noise and artifacts from different imaging instruments can interfere with segmentation, and most existing deep learning models struggle with segmenting small vessels and capturing low-dimensional structural information. These challenges typically results in less precise segmentation performance.MethodsTherefore, we propose a novel and robust Dual-stream Disentangled Network (D2Net) for retinal OCTA microvascular segmentation. Specifically, the D2Net includes a dual-stream encoder that separately learns image artifacts and latent vascular features. By introducing vascular structure as a prior constraint and constructing auxiliary information, the network achieves disentangled representation learning, effectively minimizing the interference of noise and artifacts. The introduced vascular structure prior includes low-dimensional neighborhood energy from the Distance Correlation Energy (DCE) module, which helps to better perceive the structural information of continuous vessels.Results and discussionTo precisely evaluate our method on small vessels, we delicately establish OCTA microvascular labels by performing comprehensive and detailed annotations on the FOCA dataset, which includes data collected from different instruments, and evaluated the proposed D2Net effectively mitigates the challenges of microvasculature region recognition caused by noise and artifacts. The method achieves more refined segmentation performance. In addition, we validated the performance of D2Net on four OCTA datasets (OCTA-500, ROSE-O, ROSE-Z, and ROSE-H) acquired using different instruments, demonstrating its robustness and generalization capabilities in retinal vessel segmentation compared to other state-of-the-art methods.

Focused helium ion beam nanofabrication by near-surface swelling

The focused helium ion beam microscope is a versatile imaging and nanofabrication instrument enabling direct-write lithography with sub-10 nm resolution. Subsurface damage and swelling of substrates due to helium ion implantation is generally unwanted. However, these effects can also be leveraged for specific nanofabrication tasks. To explore this, we investigate focused helium ion beam induced swelling of bulk crystalline silicon and free-standing amorphous silicon nitride membranes using various irradiation strategies. We show that the creation of near-surface voids due to helium ion implantation can be used to induce surface nanostructure and create subsurface nanochannels. By tailoring the ion dose and beam energy, the size and depth of the swollen features can be controlled. Swelling heights of several hundred nanometers are demonstrated, and for the embedded nanochannels, void internal diameters down to 30 nm are shown. Potential applications include the engineering of texturized substrates and the prototyping of on-chip nanofluidic transport devices.

Complete 3D photoelectron momentum vector reconstruction from time-position charged particle imaging

Abstract Many charged particle imaging techniques exist which directly measure, at a detector, the transverse position (x, y) and time-of-flight (t) of individual events in order to obtain a full set of 3D coordinates. Where curved velocity-mapping electric field lines are implemented, as in the case of 3D Velocity Map Imaging (3D VMI) and certain COLTRIMS (Cold Target Recoil Ion Momentum Spectroscopy) instruments, the general transformation of (x, y, t)-data into initial 3D recoil momentum vectors (px , py , pz ) is challenging and has not yet been fully addressed. Here we present a detailed and general method for this transformation, illustrated using our 3D VMI spectrometer and the well-known narrow-band photoionization of nitric oxide, for which we demonstrate quantitative agreement with reported values. We additionally show how to measure and correct (i) small errors in the laser polarization axis alignment at the interaction region of a 3D charged particle imaging spectrometer, and (ii) the spatial variation of gain on a microchannel plate (MCP) detector. Improvements to and characterization of our 3D VMI spectrometer yield an electron time-of-flight resolution of 72 ps across the full 40 mm MCP, in combination with pixel-level spatial resolution.

Coronal bright point statistics II. Magnetic polarities and mini loops

The solar corona maintains temperatures of a million Kelvin or more. The plasma heating mechanisms responsible for these extreme temperatures are still unclear. Large regions of magnetic activity in the photosphere cause extreme ultraviolet (EUV) emission in the corona. Even smaller regions with bipolar and multipolar magnetic fields can generate coronal bright points (CBPs). We performed a statistical analysis of 346 CBPs. We used Solar Dynamics Observatory (SDO) images to track CBPs on a continuous basis. Therefore, we were able to collect a database of information on the CPB's lifetime, shape, polarity, flux emergence, and merging behavior, as well as their magnetic evolution, using the SDO Helioseismic and Magnetic Imager (SDO-HMI) instrument. We searched the SDO data archive for the longest continuous interval of uninterrupted observations in 2015. The longest such interval contains 12 consecutive days of full-disk images from the EUV channels of the SDO-AIA instrument. To analyze the properties of CBPs, we employed an automated tracking algorithm to follow the evolution of the CBPs. Furthermore, we manually checked the shape, underlying magnetic polarities, and merging behavior of each CBP. We provide statistics on the magnetic polarity, emergence, and merging of CBPs. We established a relationship between the CBP's merging behavior and both its shape and magnetic polarities. Brighter CBPs are visible in all SDO-AIA channels and exhibit strong radiative energy losses. The category of CBPs with a bipolar field has the highest probability of being emissive in all SDO-AIA channels. The majority of CBPs have two opposite polarities below them. The merging of two CBPs is an unusual phenomenon that is related to complex multipolar magnetic regions. Moreover, loop-shaped CBPs usually appear above bipolar fields. Faint CBPs have shorter lifetimes and are less likely to merge with another CBP.

Drug pairs of Huangqi and Danggui alleviates pyroptosis by promoting autophagy activity via AMPK/mTOR signaling pathway in middle-cerebral artery occlusion/reperfusion in rats

Ethnopharmacological relevanceCerebral ischemia-reperfusion (I/R) injury is a common complication of ischemic stroke, with autophagy and pyroptosis playing key roles. Huangqi and Danggui (HQDG) are a commonly used drug pair of Chinese traditional medicine for clinical treatment of ischemic stroke. Aim of the studyThe study aims to investigate the interaction between autophagy and pyroptosis regulated by HQDG through the AMPK/mTOR signaling pathway during cerebral I/R injury. Materials and methodsModel of middle-cerebral artery occlusion/reperfusion (MCAO/R) in SD rats was established using the Longa suture method. The components of traditional Chinese medicine were detected by liquid chromatography coupled to quadrupole orbitrap high resolution mass spectrometry (LC/MS). Neurological deficits were evaluated by neurological function score. Changes of cerebral blood flow were detected by a laser speckle blood flow imaging instrument. The volume of cerebral infarction was observed by 2,3,5-Chlorotriphenyltetrazolium (TTC) staining. The permeability of the blood-brain barrier was measured by Evans blue test. Neurovascular unit and autophagosomes in brain tissue were assessed by transmission electron microscopy. Neuronal pyroptosis was detected by terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL)/Caspase-1 staining. The expression of autophagy related proteins, pyroptosis related proteins, and AMPK/mTOR pathway related proteins were detected by Western blot. ResultsAfter cerebral I/R injury, autophagy and pyroptosis, were characterized by increased number of autophagosomes and pyroptosis cells, upregulated expression of Beclin 1, LC3-II/LC3-I, NLRP3, cleaved Caspase-1, IL-1beta, IL-18 proteins, and downregulated expression of P62 proteins. HQDG significantly improved neurological function, reduced the volume of cerebral infarction, increased cerebral blood flow, improved blood-brain barrier permeability and the function of neurovascular units. Autophagy was further activated and pyroptosis was significantly inhibited by HQDG, which promoted increased number of autophagosomes, enhanced expression of Beclin 1, LC3-II/LC3-I proteins, reduced expression of P62, NLRP3, cleaved Caspase-1, IL-1beta, and IL-18 proteins, and downregulated the number of pyroptosis cells. On the other hand, after administering 3-Methyladenine (3-MA) to inhibit autophagy, the above effects of HQDG were significantly inhibited. Besides, HQDG promoted AMPK phosphorylation, and weakened mTOR phosphorylation. However, after the administration of AMPK inhibitor Compound C, HQDG caused increase in Beclin 1 and LC3-II/LC3-I, reduced P62 and NLRP3, and cleaved Caspase-1 protein expression, whereas cerebral blood flow decreased. ConclusionHQDG alleviated pyroptosis by promoting autophagy via AMPK/mTOR signaling pathway after middle-cerebral artery occlusion/reperfusion in rats, showing its potential for treatment of cerebral I/R injury in humans.

Revisiting the multi-planetary system of the nearby star HD 20794

Context. Close-by Earth analogs and super-Earths are of primary importance because they will be preferential targets for the next generation of direct imaging instruments. Bright and close-by G-to-M type stars are preferential targets in radial velocity surveys to find Earth analogs. Their brightness allows us to achieve the best precision on RV measurements and search for signals with amplitudes of less than 1 m s−1. Aims. We present an analysis of the RV data of the star HD 20794, a target whose planetary system has been extensively debated in the literature. The broad time span of the observations makes it possible to find planets with signal semi-amplitudes below 1 m s−1 in the habitable zone. Methods. We analyzed RV datasets spanning more than 20 years. We monitored the system with ESPRESSO. We joined ESPRESSO data with the HARPS data, including archival data and new measurements from a recent program. We applied the post-processing pipeline YARARA to HARPS data to correct systematics, improve the quality of RV measurements, and mitigate the impact of stellar activity. Results. We confirm the presence of three planets, with periods of 18.3142 ± 0.0022 d, 89.68 ± 0.10 d, and 647.6−2.7+2.5 d, along with masses of 2.15 ± 0.17 M⊕, 2.98 ± 0.29 M⊕, and 5.82 ± 0.57 M⊕ respectively. For the outer planet, we find an eccentricity of 0.45−0.11+0.10, whereas the inner planets are compatible with circular orbits. The latter is likely to be a rocky planet in the habitable zone of HD 20794. From the analysis of activity indicators, we find evidence of a magnetic cycle with a period of ~3000 d, along with evidence pointing to a rotation period of ~39 d. Conclusions. We have determined the presence of a system of three planets orbiting the solar-type star HD 20794. This star is bright (V=4.34 mag) and close (d = 6.04 pc), and HD 20794 d resides in the stellar habitable zone, making this system a high-priority target for future atmospheric characterization with direct imaging facilities.

Modeling the parameters necessary for constructing the correct shape of the dental arch depending on the features of teleradiometric indicators using the Steiner or Tweed methods and computed tomography dimensions of teeth

The study of the parameters of the dental arch, taking into account teleradiometric indicators and tooth sizes, is important for planning orthodontic treatment, which contributes to achieving stable and functionally optimal results. The Steiner and Tweed methods, widely used to assess craniofacial proportions, allow identifying key anthropometric features that affect the shape of the dental arch. The additional use of computed tomography measurements provides high accuracy in analyzing tooth sizes, which is especially important for individualizing orthodontic approaches. The aim of the work is to build and analyze regression models of parameters necessary for constructing the correct shape of the dental arch in Ukrainian young men and young women with physiological occlusion, depending on the features of teleradiometric indicators according to the Steiner or Tweed methods and computed tomography sizes of the teeth. On standardly obtained teleradiograms and created in the 3D Slicer v5.4.0 software on teleradiograms with points marked on 3D objects (41 Ukrainian young men and 68 young women with physiological occlusion from the data bank of the Department of Pediatric Dentistry and the Scientific and Research Center of the National Pirogov Memorial Medical University, Vinnytsya), measurements according to the Steiner S. S. and Tweed C. H. methods were carried out in the OnyxCeph³™ application, version 3DPro, from Image Instruments GmbH, Germany. On computer tomograms for morphometric study of teeth and dental arches we used software applications i-Dixel One Volume Viewer (Ver.1.5.0) J Morita Mfg. Cor, and Planmeca Romexis Viewer (ver. 3.8.3.R 15.12.14) Planmeca OY. Regression models were built using the licensed package “Statistica 6.0”. It was found that in young men, taking into account the Steiner method, all 18 possible reliable models with a coefficient of determination greater than 0.6 were built (R2= from 0.611 to 0.911, p&lt;0.001), and taking into account the Tweed method, 17 models (R2= from 0.638 to 0.872, p&lt;0.001); and young women – only 5 reliable models with a coefficient of determination greater than 0.6 when taking into account the Steiner method (R2= from 0.613 to 0.782, p&lt;0.001) and only 4 reliable models when taking into account the Tweed method (R2= from 0.619 to 0.745, p&lt;0.001). When analyzing the frequency of occurrence in the regression equations of computed tomography sizes of teeth and teleradiometric indicators according to the Steiner or Tweed methods, it was established: in young men, the width of the crown part of the tooth in the mesio-distal and vestibulo-oral planes, the length of the tooth in the mesio-distal and vestibulo-oral planes and teleradiometric indicators are most often included in the models; and in young women: when taking into account the indicators according to the Steiner method - the width of the crown part of the tooth in the mesio-distal and vestibulo-oral plane and teleradiometric indicators; when taking into account the indicators according to the Tweed method - the width of the crown part of the tooth in the mesio-distal and vestibulo-oral plane, the length of the tooth in the mesio-distal and vestibulo-oral planes, teleradiometric indicators and the length of the crown part of the tooth in the mesio-distal plane. When analyzing the frequency of occurrence in the regression equations of the corresponding teeth, it was found that in young men, the models that take into account the teleradiometric indicators according to the Steiner or Tweed methods most often include the upper and lower incisors, upper and lower premolars and upper canines; and in young women – upper and lower incisors, upper and lower canines, lower premolars and upper first molars taking into account teleradiometric indicators according to the Steiner method, as well as upper and lower incisors and lower premolars taking into account teleradiometric indicators according to the Tweed method.

Development of Binding Ability Assay of Lactococcus lactis Isolated from Cucumber to Mycotoxins by Surface Plasmon Resonance Imaging Assay

Some microorganisms, including lactic acid bacteria (LAB), can bind to mycotoxins. Its binding ability is useful for mycotoxin mitigation. Conventionally, the binding assay for this ability of microorganisms to mycotoxins has been performed by the so-called in vitro assay. We previously reported that Lactococcus lactis isolated from cucumber had the ability to bind to aflatoxins using the in vitro assay., However, this is an indirect method by which binding ability is estimated from the mycotoxin residue in supernatant after some processes such as mix, incubation, and centrifugation and it takes time. In the present study, we developed a direct and rapid assay to assess their binding ability using a surface plasmon resonance imaging (SPRi) instrument. It could observe the binding ability as a visual image in real time. The efficacy of this SPRi assay was compared with the in vitro assay. Aflatoxin M1-bovine serum albumin conjugate (AFM1-BSA) and deoxynivalenol-BSA conjugate (DON-BSA) were immobilized on the surface of the sensor prism in SPRi assay. The above L. lactis was used to prove the binding ability to the aflatoxin. In vitro assay showed that the binding ratio to AFM1 was higher than that to DON in both live bacterial cells and heated cells. In the SPRi assay, the binding of live cells to AFM1 was confirmed by % of the refractivity change (%ΔR) and visual imaging in real-time. The %ΔR of DON was poor, and no visual image was recognized. On the other hand, the heated cells did not bind to any mycotoxins. The results indicate that the SPRi assay can monitor the binding ability of live cells more rapidly and simpler than in vitro assay. It would be a useful tool for the selection of beneficial mycotoxin-detoxifying LAB.

Astrometric Calibration of MagAO-X with Updated Solutions for HD 165054 Field Stars

Abstract MagAO-X is a recently commissioned extreme adaptive optics instrument for the Magellan Clay 6.5 m telescope at Las Campanas Observatory in Chile. MagAO-X had first light in 2019 and subsequent commissioning observations in 2022 and 2023. An essential step for the commissioning of any new instrument is the calibration of the conversion of detector coordinates to angular sky coordinates, which we accomplish with observations of HD 165054. The background stars adjacent to HD 165054 in Baade’s Window are in a fortuitous configuration for the astrometric calibration of natural-guide-star high-contrast imaging instruments. We extend past work to connect these stars’ positions to absolute astrometry for HD 165054 itself using Gaia Data Release 3 data, and bootstrap the creation of an astrometric solution for our new high-contrast imaging instrument. Through Markov Chain Monte Carlo analysis of the historical data and position measurements from MagAO-X, we obtain updated astrometric parameters for the seven background stars and an astrometric calibration of the MagAO-X science cameras.

Evaluating Landsat- and Sentinel-2-Derived Burn Indices to Map Burn Scars in Chyulu Hills, Kenya

Chyulu Hills, Kenya, serves as one of the region’s water towers by supplying groundwater to surrounding streams and springs in southern Kenya. In a semiarid region, this water is crucial to the survival of local people, farms, and wildlife. The Chyulu Hills is also very prone to fires, and large areas of the range burn each year during the dry season. Currently, there are no detailed fire records or burn scar maps to track the burn history. Mapping burn scars using remote sensing is a cost-effective approach to monitor fire activity over time. However, it is not clear whether spectral burn indices developed elsewhere can be directly applied here when Chyulu Hills contains mostly grassland and bushland vegetation. Additionally, burn scars are usually no longer detectable after an intervening rainy season. In this study, we calculated the Differenced Normalized Burn Ratio (dNBR) and two versions of the Relative Differenced Normalized Burn Ratio (RdNBR) using Landsat Operational Land Imager (OLI) and Sentinel-2 MultiSpectral Instrument (MSI) data to determine which index, threshold values, instrument, and Sentinel near-infrared (NIR) band work best to map burn scars in Chyulu Hills, Kenya. The results indicate that the Relative Differenced Normalized Burn Ratio from Landsat OLI had the highest accuracy for mapping burn scars while also minimizing false positives (commission error). While mapping burn scars, it became clear that adjusting the threshold value for an index resulted in tradeoffs between false positives and false negatives. While none were perfect, this is an important consideration going forward. Given the length of the Landsat archive, there is potential to expand this work to additional years.

Variable structures in the stellar wind of the HMXB Vela X-1

Context. Strong stellar winds are an important feature in wind-accreting high-mass X-ray binary (HMXB) systems. Exploring their structure provides valuable insights into stellar evolution and their influence on surrounding environments. However, the long-term evolution and temporal variability of these wind structures are not fully understood. Aims. This work probes the archetypal wind-accreting HMXB Vela X-1 using the Monitor of All-sky X-ray Image (MAXI) instrument to study the orbit-to-orbit absorption variability in the 2 − 10 keV energy band across more than 14 years of observations. Additionally, the relationship between hardness ratio trends in different binary orbits and the spin state of the neutron star is investigated. Methods. We calculated X-ray hardness ratios to track absorption variability, comparing flux changes across various energy bands, as the effect of absorption on the flux is energy-dependent. We assessed variability by comparing the hardness ratio trends in our sample of binary orbits to the long-term averaged hardness ratio evolution derived from all available MAXI data. Results. Consistent with prior research, the long-term averaged hardness ratio evolution shows a stable pattern. However, the examination of individual binary orbits reveals a different hardness ratio evolution between consecutive orbits with no evident periodicity within the observed time span. We find that fewer than half of the inspected binary orbits align with the long-term averaged hardness evolution. Moreover, neutron star spin-up episodes exhibit more harder-than-average hardness trends compared to spin-down episodes, although their distributions overlap considerably. Conclusions. The long-term averaged hardness ratio dispersion and evolution are consistent with absorption column densities reported in literature from short observations, indicating that a heterogeneous wind structure – from accretion wakes to individual wind clumps – likely drives these variations. The variability observed from orbit to orbit suggests that pointed X-ray observations provide limited insights into the overall behaviour of the wind structure. Furthermore, the link between the spin state of the neutron star and the variability in orbit-to-orbit hardness trends highlights the impact of accretion processes on absorption. This connection suggests varying accretion states influenced by fluctuations in stellar wind density.

Solar flares in the Solar Orbiter era: Short-exposure EUI/FSI observations of STIX flares

Aims. This paper aims to demonstrate the importance of short-exposure extreme ultraviolet (EUV) observations of solar flares in the study of particle acceleration, heating, and energy partition in flares. This work highlights the observations now available from the Extreme Ultraviolet Imager (EUI) instrument suite on board Solar Orbiter while operating in short-exposure mode. Methods. A selection of noteworthy flares observed simultaneously by the Spectrometer Telescope for Imaging X-rays (STIX) and the Full Sun Imager of EUI (EUI/FSI) are detailed. New insights are highlighted and potential avenues of investigation are demonstrated, including forward-modelling of the atmospheric response to a non-thermal beam of electrons using the RADYN 1D hydrodynamic code, in order to compare the predicted and observed EUV emission. Results. The examples given in this work demonstrate that short-exposure EUI/FSI observations are providing important diagnostics during flares. A dataset of more than 9000 flares observed by STIX (from November 2022 until December 2023) with at least one short-exposure EUI/FSI 174 Å image is currently available. The observations reveal that the brightest parts of short-exposure observations consist of substructure in flaring ribbons that spatially overlap with the hard X-ray emission observed by STIX in the majority of cases. We show that these observations provide an opportunity to further constrain the electron energy flux required for flare modelling, among other potential applications.

The Role of Micro Propulsion in Enabling Autonomous Operations of Nanosatellites

Micro-Electro-Mechanical Systems (MEMS)-based propulsion devices have significant potential for providing high specific power. The application of Micro Power Generation technology to space propulsion systems can enhance orbit and station-keeping capabilities, potentially at lower costs. New-generation spacecraft and satellites are becoming smaller and require micro-propulsion systems for all aspects of their operations. The development of micro-propulsion systems with associated combustors for micro-electricity generation, utilizing liquid fuel, presents major challenges in fuel injection, mixing, combustion, and chemical reactor systems. A micro-spacecraft with high-accuracy station-keeping and attitude control capabilities needs to have low mass and deliver small impulses. Each nanosatellite will weigh a maximum of 10 kg, including the propellant mass. Provisions for orbital manoeuvres, attitude control, multiple sensors, and instruments, along with full autonomy, will result in a highly capable miniaturized satellite. All onboard electronics will endure a total radiation dose of 100 k rads over a two-year mission lifetime. Nanosatellites designed for in-situ measurements will be spin-stabilized and equipped with a complement of particles and fields instruments. Nanosatellites intended for remote measurements will be three-axis stabilized and equipped with imaging and radio wave instruments. Key technologies under development include: advanced, miniaturized chemical propulsion systems; miniaturized sensors; highly integrated, compact electronics; autonomous onboard and ground operations; miniaturized onboard orbit determination methods; onboard RF communications capable of transmitting data to Earth from significant distances; lightweight and efficient solar array panels; lightweight, high-output battery cells; a miniaturized heat transport system; lightweight yet strong composite materials for nano-satellite and deployer-ship structures; and simple, reusable ground systems.

Inter-Sensor Level 1 Radiometric Comparisons Using Deep Convective Clouds

To evaluate the radiometric performance of top-of-atmosphere reflectance images, Deep Convective Clouds (DCCs) can be used as temporally, spatially and spectrally stable targets. The DCCs method has been developed more than 20 years ago and applied recently to Sentinel-2 and Sentinel-3 sensors. In this paper, among other developments, we built a new methodology upon those existing by using the bootstrap method and spectral band adjustment factors computed with the Hyper-Spectral Imager (HSI) from the Environmental Mapping and Analysis Program (EnMAP). This methodology is applied to the two Multi-Spectral Imager (MSI) instruments onboard Sentinel-2A and 2B, but also the two Operational Land Imager (OLI) instruments onboard Landsat 8 and 9, from visible wavelength at 442 nm to shortwave-infrared at 2200 nm, using images with a ground resolution spanning from 10 m to 60 m. The results demonstrate the good inter-calibration of MSI units A and B, which are within one percent of relative difference on average between January 2022 and June 2024 for all visible, near-infrared and shortwave-infrared bands, except for the band at 1375 nm for which saturation prevents the use of the method. Similarly, OLI and OLI-2 are found to have a relative difference on the same period lower than one percent for all 30 m resolution bands. Evaluation of the relative difference between the MSI sensors and the OLI sensors with the DCCs method gives values lower than three percent. Finally, these validation results are compared to those obtained with Pseudo-Invariant Calibration Sites (PICSs) over Libya-4: an agreement better than two percent is found between the DCCs and PICSs methods.

Detecting and sizing the Earth with PLATO: A feasibility study based on solar data

Context. The PLAnetary Transits and Oscillations of stars (PLATO) mission will observe the same area of the sky continuously for at least two years in an effort to detect transit signals of an Earth-like planet orbiting a solar-like star. Aims. We aim to study how short-term solar-like variability caused by oscillations and granulation would affect PLATO’s ability to detect and size Earth if PLATO were to observe the Solar System itself. We also compare different approaches to mitigate noise caused by short-term solar-like variability and perform realistic transit fitting of transit signals in PLATO-like light curves. Methods. We injected Earth-like transit signals onto real solar data taken by the Helioseismic and Magnetic Imager (HMI) instrument on board the Solar Dynamics Observatory (SDO). We isolated short-term stellar variability in the HMI observations by removing any variability with characteristic timescales longer than five hours using a smooth Savitzky-Golay filter. We then added a noise model for a variety of different stellar magnitudes computed by PlatoSim assuming an observation by all 24 normal cameras. We first compared four different commonly used treatments of correlated noise in the time domain by employing them in a transit fitting scheme. We then tried to recover pairs of transit signals using an algorithm similar to the transit least squares algorithm. Finally, we performed transit fits using realistic priors on planetary and stellar parameters and assessed how accurately the pair of two injected transits was recovered. Results. We find that short-term solar-like variability affects the correct retrieval of Earth-like transit signals in PLATO data. Variability models accounting for variations with typical timescales at the order of one hour are sufficient to mitigate these effects. We find that when the limb-darkening coefficients of the host star are properly constrained, the impact parameter does not negatively affect the detectability of a transit signal or the retrieved transit parameters, except for high values (b &gt; 0.8). For bright targets (8.5–10.5 mag), the transit signal of an Earth analogue can reliably be detected in PLATO data. For faint targets a detection is still likely, though the results of transit search algorithms have to be verified by transit-fitting algorithms to avoid false positive detections being flagged. For bright targets (V-mag ≤ 9.5), the radius of an Earth-like planet orbiting a solar-like star can be correctly determined at a precision of 3% or less, assuming that at least two transit events are observed and the characteristics of the host star are well understood.

Numerical simulation of temperature in forming surroundings for E-Glass fiber

In spinning, the temperature of the glass melt and the forming surroundings play a crucial role in determining the diameter of the electrical glass (E-glass) filament. It is essential to control or predict the temperature of the forming surroundings. In this study, a simplified cooling model of the fin for G75 E-glass fiber was constructed and simulated to explore the influence of ambient temperature on the forming process of E-glass fiber. The multi-physical field coupling of solid-fluid conjugate heat transferring and surface-to-surface radiation imitates the cooling model. The temperature of the bottom of the bushing plate was measured with an infrared thermal imaging instrument, and the ambient temperature of the area of filament root forming was measured with a thermocouple. Considering the device is fixed, the key experimental variable of the numerical simulation is the distance from the top of the cooling fin to the bottom surface of the bushing plate. The simulated results are compared with the actual measurements, proving that it is feasible for the simplified cooling model to simulate the forming of E-glass fiber. The results of numerical simulations also show that (1) the temperature of the glass melt at the outlet of the nozzle is 1400 K and the ambient temperature of the filament root forming dropped by >500 K; (2) when the top of the cooling fin is 4 mm away from the bottom surface of the bushing plate, the fin has the best cooling effect on the E-glass fiber.

Investigation of coupling DSSAT with SCOPE-RTMo via sensitivity analysis and use of this coupled crop-radiative transfer model for sensitivity-based data assimilation

The increasing availability of remote sensing (RS) data and the advancement of computation abilities, combined with the demands for enhancing crop production, encourages the creation of a framework in which crop growth simulation can be updated sequentially to serve as a yield predictor and be part of a decision support system. However, crop model outputs and RS data must be linked via a radiative transfer model (RTM), which simulates the interaction between the crop and the intercepted radiation. In this study, a comprehensive coupling scheme between a crop model (DSSAT-CROPGRO-tomato) and an RTM (SCOPE-RTMo) was formulated and investigated through global sensitivity analysis (SA) and by testing the coupled model in a synthetic data assimilation (DA) experiment. The DA experiment utilized a sensitivity-based particle filter (PF) in which the SA results were used to enhance the PF convergence rate and accuracy. The SA results provide the sensitivity of simulated reflectance at different wavelengths to DSSAT-CROPGRO parameters throughout the season. This information can help guide future data assimilation experiments by choosing imaging instruments with appropriate spectral bands and timing the measurements to enhance model calibration. The results of the synthetic DA experiment showed a good convergence of the particle filter towards the ground truth. The results also demonstrated the strong relation between LAI and reflectance, as several model runs with different initial values of DSSAT-CROPGRO parameters all converged and predicted the synthetic LAI observations very well. The convergence of DSSAT-CROPGRO parameters to their ground truth values was only partial, and phenology-related parameters tended to converge better than growth-related parameters.