Angular Separation Research Articles

Paleomagnetic study of the 30 ka Aira caldera-forming eruption and 60–45 ka Iwato pyroclastic flow deposits, southern Kyushu, Japan

To constrain the age and duration of large-scale caldera-forming eruptions, we measured paleomagnetic directions of pyroclastic deposits from the 30 ka Aira caldera eruption sequence, and the 60–45 ka Iwato pyroclastic flow deposits around Aira caldera in southern Kyushu, Japan. The 30 ka Aira caldera eruption sequence consists of Osumi pumice fall (OS), Tarumizu pyroclastic flow deposit (TM), Ito ignimbrite (IT) and co-ignimbrite ash (AT), in ascending order. Oriented samples were collected by drilling for OS, TM and welded ignimbrites, and by cubing for non-welded (unconsolidated) pyroclastic flow deposit. We systematically sampled Ito ignimbrite with the degree of welding as: non-welded (IT1), moderately welded (IT2), and strongly welded (IT3) facies that is limitedly distributed in north of Aira caldera. Mean paleomagnetic directions of OS, TM, IT1 and IT2 are consistent with those previously reported for AT and welded facies of IT. Although OS samples were collected from multiple pumice clasts at proximal locations, we obtained well-defined mean paleomagnetic directions corresponding to those of co-eruptive pyroclastic flow (TM). This suggests that even clast-supported and non-welded pumice fall can retain thermoremanent magnetization at the time of deposition. Significance tests for our mean paleomagnetic directions showed that of all sequential units of the Aira caldera-forming eruption deposits, only IT3 has a different paleomagnetic direction. Based on reported paleosecular variation changing rates in Japan, and on the angular difference associated with error of the two paleosecular directions, we estimate the time gap between IT3 and IT2, to be 24.3 ± 16.3 years. A conductive cooling model explains this time difference as due to differences in cooling time between quickly, and slowly cooled parts of a thick single ignimbrite unit. Although the possibility that multiple flow units occurred within tens of years of each other cannot be excluded, there are no observations of clear flow unit boundaries in the Ito ignimbrite to support the suggestion that the Aira caldera-forming eruption sequence was deposited within a shorter time than years. In addition, the age of Iwato pyroclastic flow deposit, which has been situated between 60 and 45 ka, was estimated by calculating the angular distance between the mean paleomagnetic direction and the modeled secular variation curve from the GGF100 ka. As the result, we determine the most probable age to be around 56 ka.Graphical abstract

Fine-grained simulation model for PV power output interval based on two-stage scenario clustering and dual-ensemble compatible learning

Photovoltaic (PV) power simulation is indispensable for the planning and operation of renewable-rich power systems. Among various simulation methods, data-driven indirect simulation methods are the most efficient, primarily involving scenario extraction and power output generation. Typical scenario extraction methods often feature coarse characterizations, which also cannot be expressed by traditional power output generation models lacking the ability of quantifying the uncertainty of the output results. This paper proposes a fine-grained simulation model for PV power output interval, i.e., upper bound and lower bound, based on two-stage clustering of multiple typical scenarios and dual-ensemble compatible learning. The first stage of scenario extraction, considering the impact of total daily irradiance on PV output, employs a line distance index for preliminary scenario division of daily PV output. These scenarios are further divided into five characteristic scenarios with an angular distance index considering the impact of intra-day irradiance variations on power output. PV power output interval is generated from dual-ensemble compatible learning including Stacking and Bagging, which are adaptively selected with a Bias-Variance Selection Index (BS) calculated using the value of scenario characteristics. Stacking and Bagging are driven by three neural network base learners with Bayesian layers, which can output the lower bound and upper bound with confidence at a certain level, thus quantifying the uncertainty of the result accurately. The actual data of Daxing and Gangjialing power stations are used in case study. Results form case study show that compared with the existing methods, the proposed method can improve the Power Coverage Rate (PCR) and Average Power Simulation Accuracy (APA) of uncertainty simulation results by 27.44% and 5.39%, respectively. Meanwhile, the Average Daily Maximum Power Simulation Accuracy (AMPA) is similar to that of existing methods.

Aerodynamic characteristic of limited micro-scale Taylor–Couette flow at hyper-rotate speed

To pursue improvements in the power-to-weight ratio, cost-effectiveness ratio, and reliability in the energy industry, rotating machinery has been developed with higher rotational speeds and smaller sizes, resulting in complex aerodynamic behavior of the rotational shearing flow between rotator and stator. This study reports experimental measurements of the aerodynamic characteristics of a limited micro-scale Taylor–Couette flow (TC flow) at hyper-rotational speeds for the first time. The maximum rotational speed and eccentricity ratio are 6.0 × 104 rpm and 0.8, respectively, and the minimum average clearance height is 100 μm. The static pressure of the shearing flow is measured using a high-response micro-manometer. A large eddy simulation has been employed to unveil flow fields of the gas film between the stator and the rotator. The results show that the micrometer-scale clearance height and end leakage due to limited length dominate the micro-scale Taylor–Couette flow. Decreasing the scale of the clearance height reduces the angular distance between the peak and bottom pressures compared to that observed in the TC flow with a large-scale clearance. Furthermore, ambient pressure cannot fully permeate into central section of the eccentric Taylor–Couette flow with a micrometer-scale clearance and end leakage, and the pressure upstream near the region the minimum size of clearance decreases along the axial end. Owing to the difference in the constraint degree at both ends along the axial direction, the peak value occurs near the region of Z/L = −0.32. The maximum pressure of the limited micro-scale Taylor–Couette flow increases with increasing rotational speed and eccentricity ratio, whereas it decreases with increasing clearance height. Within the scope of the parameters in this study, the maximum pressure is 0.025 MPa. Decreasing the size of gas film restrains the instability of the shearing flow, whereas increasing the rotational speed strengthens the turbulence. In this study, the shearing flow at the middle section (Z/L = 0) is in a nearly laminar state at δ < 0.012, whereas it is highly turbulent near the end of the clearance and in the ambient environment. The end leakage induces additional axial flow, which is conspicuous at a large eccentricity ratio. At hyper-rotational speeds, the micro-scale Taylor–Couette flow with end leakage exhibits distinctive patterns that have never been reported in classic Taylor–Couette flows with large clearances. This work of this study is significant because it can provide theoretical guidance and technical support for the design of actual dynamic pressure gas bearings and floating ring sealing flow.

Learning performance and physiological feedback-based evaluation for human–robot collaboration

The development of Industry 4.0 has resulted in tremendous transformations in the manufacturing sector to supplement the human workforce through collaboration with robots. This emphasis on a human-centered approach is a vital aspect in promoting resilience within manufacturing operations. In response, humans need to adjust to new working conditions, including sharing areas with no apparent separations and with simultaneous actions that might affect performance. At the same time, wearable technologies and applications with the potential to gather detailed and accurate human physiological data are growing rapidly. These data lead to a better understanding of evaluating human performance while considering multiple factors in human–robot collaboration. This study uses an approach for assessing human performance in human–robot collaboration. The assessment scenario necessitates understanding of how humans perceive collaborative work based on several indicators, such as perceptions of workload, performance, and physiological feedback. The participants were evaluated for around 120 min. The results showed that human performance improved as the number of repetitions increased, and the learning performance value was 92%. Other physiological indicators also exhibited decreasing values as the human performance tended to increase. The findings can help the industry to evaluate human performance based on workload, performance, and physiological feedback information. The implication of this assessment can serve as a foundation for enhancing resilience by refining work systems that are adaptable to humans without compromising performance.

Spatial heterogeneity analysis between street network configurations and various service activities: evidence from the Wuhan metropolitan area

China’s economic growth is increasingly being driven by the contemporary service industry in the context of a new economy. This study aims to examine the spatial heterogeneous relationship between various service industry activities and street network design configurations by integrating multisource big data and geospatial analysis to provide insightful implications for human-centered design for compact cities by taking the case study of an inland megacity in central China, Wuhan. Street configurations under the walking/driving modes including closeness, betweenness, severance and efficiency, are characterized from the perspective of spatial design network analysis and angular distance to effectively reflect network shapes and subjective perceptions when navigating through the streets. The point-like, point-axis and ring patterns of various service activities are identified using the kernel density estimation (KDE). Then two sets of densities are analyzed to investigate whether various service activities are spatially associated with specific street metrics and whether spatial stratified heterogeneity exists. The results show that severance and efficiency are two promising indicators to represent the human-scale street design besides the conventional street centrality indices. The spatial mismatch is mainly observed between street metrics and the tourism sector whereas spatial clusters are detected in other types of service activities. Diverse service activities have distinct location preferences for street designs under different transport modes. The walking mode values global closeness and betweenness, while the driving mode values severance and efficiency.

Cosmography from accurate mass modeling of the lens group SDSS J0100+1818: Five sources at three different redshifts

Systems where multiple sources at different redshifts are strongly lensed by the same deflector allow one to directly investigate the evolution of the angular diameter distances as a function of redshift, and thus to learn about the geometry of the Universe. We present measurements of the values of the total matter density, $ m $, and of the dark energy equation of state parameter, $w$, through a detailed strong lensing analysis of SDSS J0100+1818, a group-scale system at $z=0.581$ with five lensed sources, from $z=1.698$ to $4.95$. We take advantage of new spectroscopic data from the Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope to securely measure the redshift of 65 sources, including the 5 multiply imaged background sources (lensed into a total of 18 multiple images) and 19 galaxies on the deflector plane, all employed to build robust strong lensing models with the software GLEE . The total mass distribution of the deflector is described in a relatively simple way, and includes an extended halo, the brightest group galaxy (BGG) with a measured stellar velocity dispersion of ($380.5 km.s^ $, and fainter members. We measure $ m $ in a flat Lambda cold dark matter (CDM) model, and $ m $ and $w = -1.27_ $ in a flat $w$CDM model. Given the presence of different sources angularly close in projection, we quantify through a multiplane approach their impact on the inferred values of the cosmological parameters. We obtain consistent median values, with uncertainties for only $ m $ increasing by approximately a factor of 1.5. Thanks to the remarkably wide radial interval where the multiple images are observed, ranging from 15 to 77 kpc from the BGG, we accurately measure the total mass profile and infer the stellar over total mass profile of the deflector. They result in a total mass of $(1.55 $ M$_ within 50 kpc and a stellar over total mass profile decreasing from <!PCT!>$ at the BGG effective radius to $(6.6 1.1) <!PCT!>$ at $R 77$ kpc. Our results confirm that SDSS J0100+1818 is one of the most massive (lens) galaxies known at intermediate redshift and one of the most distant candidate fossil systems. We also show that group-scale systems that act as lenses for $ 3$ background sources at different redshifts enable one to estimate the values of the cosmological parameters $ m $ and $w$ with an accuracy that is competitive with that obtained from lens galaxy clusters.

Gathering on a circle with limited visibility by anonymous oblivious robots

A swarm of anonymous oblivious mobile robots, operating in deterministic Look-Compute-Move cycles, is confined within a circular track. All robots agree on the clockwise direction (chirality), they are activated by an adversarial semi-synchronous scheduler (SSYNCH), and an active robot always reaches the destination point it computes (rigidity). Robots have limited visibility: each robot can see only the points on the circle that have an angular distance strictly smaller than a constant ϑ from the robot's current location, where 0<ϑ≤π (angles are expressed in radians).We study the Gathering problem for such a swarm of robots: that is, all robots are initially in distinct locations on the circle, and their task is to reach the same point on the circle in a finite number of turns, regardless of the way they are activated by the scheduler. Note that, due to the anonymity of the robots, this task is impossible if the initial configuration is rotationally symmetric; hence, we have to make the assumption that the initial configuration be rotationally asymmetric.We prove that, if ϑ=π (i.e., each robot can see the entire circle except its antipodal point), there is a distributed algorithm that solves the Gathering problem for swarms of any size. By contrast, we also prove that, if ϑ≤π/2, no distributed algorithm solves the Gathering problem, regardless of the size of the swarm, even under the assumption that the initial configuration is rotationally asymmetric and the visibility graph of the robots is connected.The latter impossibility result relies on a probabilistic technique based on random perturbations, which is novel in the context of anonymous mobile robots. Such a technique is of independent interest, and immediately applies to other Pattern-Formation problems.

Morphometric Measurements of the Incomplete Partition Type II (IP-II) Cochlea and Implications on Cochlear Implantation.

The objective of this study is to obtain comprehensive morphometric measurements of the incomplete partition type II (IP-II) cochlea to provide a better understanding of intracochlear anatomy and important considerations for electrode selection and insertion. IP-II is the most common bony inner ear malformation that often requires cochlear implantation. Currently, there is significant controversy on electrode selection due to a lack of research that can provide reliable, high-resolution measurements. Three-dimensional reconstructions of the cochlea were made from hematoxylin and eosin-stained slides from 11 archival human temporal bones from 8 adult IP-II patients (one paired) and 2 fetuses. Detailed measurements of the angular and linear length of the spiral ganglion neurons and cochlear duct at the modiolar and lateral wall of the scala tympani as well as cross-sectional areas and vertical height measurements of the scala tympani at 90-degree intervals were measured. The spiral ganglia neurons terminated at 540.5 ± 45.4 degrees, which corresponded to the beginning of the interscalar septal defect. The corresponding Rosenthal's canal length was 12.75 ± 0.82 mm, and the lateral wall length was 23.95 ± 1.04. The average cochlear duct length was 32.44 mm ± 1.58 mm, corresponding to an average angular distance of 951.6 ± 80 degrees. The modiolar height demonstrated less variation within the scala tympani but was significantly smaller at 0 and 90 degrees compared with the normal cochlea. The lateral wall height was also significantly smaller at 0, 180, and 540 degrees. There was a drastic decrease in lateral wall height at 540 degrees to 0.4 mm, which is smaller than the apical dimension of many electrodes. This is the first study to provide detailed morphometric measurements of the IP-II cochlea including spiral ganglion neuron length and scala tympani height. These measurements directly relate to electrode selection for cochlear implantation.

Digital Cephalometric Analysis: Unveiling the Role and Reliability of Semi-automated OneCeph, Artificial Intelligence-Powered WebCeph Mobile App, and Semi-automated Computer-Aided NemoCeph Software in Orthodontic Practice.

Background Cephalometric analysis is essential in orthodontic diagnosis and treatment planning. With the emergence of digital tools for cephalometric analysis such as OneCeph, WebCeph, and NemoCeph, there is growing interest in their reliability compared to traditional manual tracings. This study aimed to compare the reliability of these digital tools with manual tracings in doing cephalometric analysis. Methodology Cephalometric radiographs from a diverse patient population were analyzed using OneCeph (NXS, Hyderabad, India), WebCeph (AssembleCircle Corp., Republic of Korea), NemoCeph (Nemotec, Madrid, Spain), and manual tracings by experienced orthodontists. Interobserver reliability and agreement with manual tracings were assessed using the intraclass correlation coefficient (ICC). Results The comparison of cephalometric measurements using the four methods - manual, OneCeph, WebCeph, and NemoCeph - revealed significant differences in the Sella-Nasion to Point A angle (SNA) (P = 0.002) and angle of difference between Sella-Nasion to Point A angleand Sella-Nasion to Point B angle(ANB) (P<0.001). Specifically, WebCeph produced significantly higher SNA measurements than manual tracing, while NemoCeph, OneCeph, and WebCeph yielded higher ANB measurements than manual tracing. There were no significant differences in other measurements, including Sella-Nasion to Point B angle (SNB), Nasion to Point A (N to Pt A), Nasion to Point B (N to Pt B), Gonion-Gnathion to Sella-Nasion angle (Go-Gn to SN), Lower Anterior Facial Height (LAFH), Y-axis (growth axis angle), facial axis, the sum of posterior measurements, and various angular and linear distances [1 to NA, 1 to SN, 1 to NB, 1 to Apog, Incisor Mandibular Plane Angle (IMPA), Sella to Upper Lip (S to UL), and Sella to Lower Lip (S to LL)]. The reliability analysis indicated a strong internal consistencywith Cronbach's α values of 0.811 for manual vs. NemoCeph, 0.859 for manual vs. OneCeph, and 0.861 for manual vs. WebCeph, and good agreement in the ICC(P<0.001). Conclusion OneCeph, WebCeph, and NemoCeph demonstrate promising reliability for cephalometric analysis. However, the results should be interpreted with caution, considering the limitations of digital tools. Ongoing research and collaboration among developers, researchers, and clinicians are essential to validate these the performance of these tools and improve their clinical applicability.

Study on a novel dual-row vertical axis wind turbine with J-Shaped blades by using numerical methods and optimization

ABSTRACT This study investigates the benefits of using J-shaped blades in a dual-row Darrieus wind turbine (DDWT), combining two innovative ideas whose simultaneous impact on the self-starting capability of Darrieus turbines has not been explored. The performance of the turbine was simulated using Computational Fluid Dynamics (CFD) and optimized using both the Taguchi method and a combined Machine Learning and Genetic Algorithm (ML-GA) technique. Three main operating parameters, including the tip speed ratio (λ), radial ratio (δ), and angular distance (ϕ) of dual-row turbines, were investigated across four levels using an L25 orthogonal array design. According to the Taguchi analysis, the impact of the parameters on the power output was ranked in the order of λ > δ > ϕ. After comparison, the optimized turbine predicted by the ML-GA technique was chosen due to the superior accuracy of the ML-GA approach compared to the Taguchi method. The optimal configuration of a DDWT with J-shaped blades was predicted at λ = 2.15, δ = 1.39, and ϕ = 75.36, with a Cp of 0.49 based on CFD simulations. Compared to the single-row wind turbine, the proposed turbine showed a significant increase of the Cp at low tip speed ratios resulting in a better self-starting performance.

Strong lensing as a probe of braneworld

For the first time, we use the Event Horizon Telescope (EHT) data to constrain the parameters of braneworld black holes which constrain ϵ = 0.0285+0.0888+0.1456 -0.0895-0.1475 for the anisotropic black hole and q = -0.0305+0.1034+0.1953 -0.0895-0.1470 for the tidal Reissner-Nordström (RN) black hole. Based on the fitted data and physical requirement, we calculate the photon deflection, the angular separation and time delay between different relativistic images of the anisotropic black hole and the tidal RN black hole in the ranges -0.1190 < ϵ < 0 and -0.1775 < q < 0. And furthermore, we study the quasinormal modes (QNMs) for the braneworld black holes. The results shed light on existence of extra dimension.

QSO MUSEUM

Extended Lyα emission is routinely found around single quasars across cosmic time. However, few studies have investigated how such emission changes in fields with physically associated quasar pairs, which should reside in dense environments and are predicted to be linked through intergalactic filaments. We present VLT/MUSE snapshot observations (45 minutes/source) to unveil extended Lyα emission on scales of the circumgalactic medium (CGM) around the largest sample of physically associated quasar pairs to date, encompassing eight pairs (14 observed quasars) at z ∼ 3 with an i-band magnitude between 18 and 22.75, corresponding to absolute magnitudes Mi(z = 2) between −29.6 and −24.9. The pairs are either at close (∼50–100 kpc, five pairs) or wide (∼450–500 kpc, three pairs) angular separation and have velocity differences of Δv ≤ 2000 km s−1. We detected extended emission around 12 of the 14 targeted quasars and investigated the luminosity, size, kinematics, and morphology of these Lyα nebulae. On average, they span about 90 kpc and are 2.8 × 1043 erg s−1 bright. Irrespective of the quasars’ projected distance, the nebulae often (∼45%) extend toward the other quasar in the pair, leading to asymmetric emission whose flux-weighted centroid is at an offset position from any quasar location. We show that large nebulae are preferentially aligned with the large-scale structure, as traced by the direction between the two quasars, and conclude that the cool gas (104 K) in the CGM traces well the direction of cosmic web filaments. Additionally, the radial profile of the Lyα surface brightness around quasar pairs can be described by a power law with a shallower slope (∼−1.6) with respect to single quasars (∼−2), indicative of increased CGM densities out to large radii and/or an enhanced contribution from the intergalactic medium (IGM) due to the dense environments expected around quasar pairs. The sample presented in this study contains excellent targets for ultra-deep observations to directly study filamentary IGM structures in emission. This work demonstrates that a large snapshot survey of quasar pairs will pave the way to direct statistical study of the IGM.

Astrophysical implications of Weyl geometric black holes: Shadows and strong gravitational lensing

We consider the astrophysical properties of an exact black hole solution obtained in Weyl geometric gravity theory from the simplest conformally invariant action, constructed from the square of the Weyl scalar and the strength of the Weyl vector only. The action is linearized in the Weyl scalar by introducing an auxiliary scalar field. In static spherical symmetry, this theory admits an exact black hole solution, which generalizes the standard Schwarzschild solution through the presence of two new terms in the metric, having a linear and a quadratic dependence on the radial coordinate. To test the astrophysical validity properties of the solution, we perform a detailed analysis of its lensing properties in the strong field regimes. In particular, we consider the shadow of the Weyl geometric black hole, and we obtain a first set of constraints on the solution parameters by using the observational data from the shadows of the M87* and Sgr A* supermassive black holes. As a second possibility of observationally testing the Weyl geometric black hole and constraining its free parameters, we consider the strong lensing in this geometry. We investigate in detail the basic strong lensing observables, including the angular position of the images, the angular separation, the relative magnification, the radii of the Einstein ring, and the relativistic time delay. For all these quantities, a comparison with the predictions of the standard Schwarzschild black hole solution is performed by using realistic astrophysical data. The obtained results may lead to the possibility of testing Weyl geometry, Weyl geometric gravity, and their effects at galactic and extragalactic levels by using the observational properties of the black hole solutions of the theory.

The power spectrum of luminosity distance fluctuations in General Relativity

At low redshift, it is possible to combine spectroscopic information of galaxies with their luminosity or angular diameter distance to directly measure the projection of peculiar velocities (PV) along the line-of-sight. A PV survey probing a large fraction of the sky is subject to so-called wide-angle effects, arising from the variation of the line-of-sight across the sky, and other sub-leading projection effects due to the propagation of the photons in a perturbed cosmological background. In this work, for the first time, we provide a complete description, within linear theory and General Relativity, of the power spectrum of luminosity distance fluctuations, clarifying its relation to the observables in a PV survey. We find that wide-angle effects will be detected at high significance by future observations and will have to be included in the cosmological analysis. Other relativistic projections effects could also be detected provided accurate, per object, distances are available.

Measurements of Sunspot Group Tilt Angles Based on SOHO/MDI and SDO/HMI Magnetograms

The tilt angle of sunspot groups plays a crucial role in solar dynamo models for the generation of the poloidal field, yet the statistical properties of the tilt angle are not fully comprehended. This study employs magnetograms from the Solar and Heliospheric Observatory/Michelson Doppler Imager and Solar Dynamics Observatory/Helioseismic and Magnetic Imager to measure the tilt angles of 11,373 sunspot groups over the period from 2008 to 2023. This comprehensive analysis examines the relationship between the tilt angle and latitude of the sunspot groups, as well as the correlation between the tilt angle and solar cycle strength. The methodology involves calculating tilt angles within the ±45° central meridian distance, comparing mean-based and median-based measurements, and applying specific angular separation criteria. The findings reveal that during solar cycle 24, the tilt angles increase by approximately 4° for every 10° increase in latitude, in line with Joy’s law. A significant anticorrelation is observed between the latitude-normalized tilt angle (γ/∣L∣) and solar cycle strength. The research also uncovers a substantial hemispheric asymmetry in tilt angle parameters, with the southern hemisphere (m Joy: 0.23 ± 0.092 ∼ 0.24 ± 0.074, γ = 8.°14 ± 0.°43 ∼ 9.°04 ± 0.°486) consistently showing larger tilt angles than the northern hemisphere (m Joy: 0.47 ± 0.096 ∼ 0.51 ± 0.062, γ = 6.°14 ± 0.°304 ∼ 6.°64 ± 0.°334).

Contemporaneous high-angular-resolution imaging of the AGB star W Hya in vibrationally excited H2O lines and visible polarized light with ALMA and VLT/SPHERE-ZIMPOL

Aims. We present contemporaneous high-angular-resolution millimeter imaging and visible polarimetric imaging of the nearby asymptotic giant branch (AGB) star W Hya to better understand the dynamics and dust formation within a few stellar radii. Methods. The star W Hya was observed in two vibrationally excited H2O lines at 268 and 251 GHz with Atacama Large Millimeter/submillimeter Array (ALMA) at a spatial resolution of 16 × 20 mas and at 748 and 820 nm at a resolution of 26 × 27 mas with the Very Large Telescope (VLT)/Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE)-Zurich Imaging Polarimeter (ZIMPOL). Results. ALMA’s high spatial resolution allowed us to image strong emission of the vibrationally excited H2O line at 268 GHz (v2 = 2, JKa, Kc = 65, 2–74, 3) over the stellar surface instead of absorption against the continuum, which is expected for thermal excitation. Strong, spotty emission was also detected along and just outside the stellar disk limb at an angular distance of ∼40 mas (∼1.9 R⋆), extending to ∼60 mas (∼2.9 R⋆). Another H2O line (v2 = 2, JKa, Kc = 92, 8–83, 5) at 251 GHz with a similar upper-level energy was tentatively identified, which shows absorption over the stellar surface. This suggests that the emission over the surface seen in the 268 GHz H2O line is suprathermal or even maser emission. The estimated gas temperature and H2O density are consistent with the radiatively pumped masers. The 268 GHz H2O line reveals global infall at up to ∼15 km s−1 within 2–3 R⋆, but outflows at up to ∼8 km s−1 are also present. The polarized intensity maps obtained in the visible reveal clumpy dust clouds forming within ∼40 mas (∼1.9 R⋆) with a particularly prominent cloud in the SW quadrant and a weaker cloud in the east. The 268 GHz H2O emission overlaps very well with the visible polarized intensity maps, which suggests that both the nonthermal and likely maser H2O emission and the dust originate from dense, cool pockets in the inhomogeneous atmosphere within ∼2–3 R⋆.

Design of ION Thruster

Ion thrusters represent a significant advancement in electric propulsion, enhancing fuel efficiency by accelerating ions for thrust generation. These systems, demonstrated in missions such as Deep Space 1 and Dawn, facilitate substantial velocity changes with minimal propellant, making them suitable for long-duration space missions. This paper outlines the design of an ion thruster aimed at achieving a thrust of 0.2 Newton, focusing on the use of xenon as the propellant and employing highvoltage grids for ion acceleration. Key design aspects include an efficient power supply delivering at least 26 W, effective thermal management, and the integration of control systems. Performance metrics target a specific impulse of 3,000 seconds and a thrust-to-power efficiency ratio greater than 0.5. Through detailed calculations, including arc distance, flow configuration and velocity analyses and testing using different materials, this study identifies optimal configurations for thrust generation. The developed ion thruster is tailored for small satellites (700-800 kg) to enhance trajectory control and station-keeping, underscoring the importance of ion propulsion in modern space exploration

An optically dark merging system at z ∼ 6 detected by JWST

Context. Near- to mid-infrared observations (from Spitzer and JWST) have revealed a hidden population of galaxies at redshift z = 3 − 6 called optically dark objects, which are believed to be massive and dusty star-formers. They contribute substantially to the cosmic star-formation rate (SFR) density at z ∼ 4 − 5 (up to 30 − 40%). Aims. While optically dark sources are widely recognized as a significant component of the stellar mass function, the history of their stellar mass assembly (and the evolution of their interstellar medium) remains unexplored. However, they are thought to be the progenitors of the more massive early-type galaxies found in present-day groups and clusters. It is thus important to examine the possible connection between dark sources and merging events in order to understand the environment in which they live. Methods. Here, we report our search for close companions in a sample of 19 optically-dark objects identified in the SMACS0723 JWST deep field. They were selected in the NIRCam F444W band and undetected below 2 μm. We restricted our analysis to the reddest (i.e., F277W–F444W &gt; 1.3) and brightest (F444W &lt; 26 mag) objects. Results. We identified KLAMA, an optically dark source showing a very close companion (angular distance &lt; 0.5″). The spatially resolved SED fitting procedure indicates that all components lying within 1.5″ of who is it the dark source are indeed at z ∼ 5.7. Tidal features (leading to a whale-shaped morphology) corroborate the hypothesis that KLAMA is the most massive (log(M⋆/M⊙) &gt; 10.3) and dusty (AV ∼ 3 at the core) system of an ongoing merger with a mass ratio of ∼10. Thus, around ten similar merger events would be required to double the stellar mass of KLAMA. Merging systems with properties similar to KLAMA are identified in the SERRA simulations, allowing us to reconstruct their stellar-mass assembly history and predict their molecular gas properties (in particular, the [CII] emission for the simulated system). Conclusions. The discovery of mergers within dark galaxies at the end of the Epoch of Reionization highlights the importance of conducting a statistical search for additional candidates in deep NIRCam fields. Such research will aid in our understanding of the significance of merging processes during the obscured phase of stellar-mass accumulation.

Prospective evaluation of transcatheter aortic valve implantation (TAVI) with coronary alignment and impact on coronary access

Abstract Introduction Transcatheter aortic valve implantation (TAVI) with optimised coronary alignment aims to reduce coronary-commissural overlap (CCO) to facilitate future coronary intervention and reduce the risk of coronary obstruction after re-do TAVI, however, in-vivo data are lacking. Aims To determine the feasibility of TAVI with coronary alignment assessed by post-TAVI CT. Secondary endpoints included the incidence of adverse anatomical features which could impede coronary access (severe CCO and ostia below valve skirt) and their association with coronary engagement during invasive angiography. Methods 30 patients underwent TAVI with optimised coronary alignment with either ACURATE neo2 or Evolut Pro+ and invasive coronary angiography and cardiac CT performed after valve deployment. Results 15 patients received ACURATE neo2 (50%) and 26 patients (86.7%) underwent CT after TAVI. The mean inter-coronary angle was 140 (19.5)° and the median observed angular deviation from perfect alignment (0°) was 0.8° (IQR -4.5 to +10) ° with perfect alignment (±15°) observed in 21/26 cases (80.8%) and ≤mild misalignment (±30°) in 24/26 of cases (92.3%). The remaining two cases had moderate misalignment (30-45°) with no cases of severe misalignment. The angle between the coronary ostia and the nearest TAVI commissure was 46 (40 - 57) ° for the RCA and 50.5 (43 - 54) ° for the LCA which did not differ significantly from the native situation (both p&amp;gt;0.2), with 1 (3.8%) case of severe overlap. 46/55 (83.6%) coronary engagements were selective, 7/55 (12.7%) semi-selective and 2/55 (3.6%) unable to intubate. Non-selective engagement/unable to engage affected the RCA more than the LCA (6/27 [22.2%] vs. 3/28 [10.7%]) and was three-fold more common with the Evolut (7/29 [24.1%]) than the Acurate (2/26 [7.7%]. Coronary&amp;gt;commissural angle in those with unselective engagement was 43° (IQR 37 to 51°). Conclusions TAVI with optimised coronary alignment is technically feasible, safe and reduces coronary-commissural overlap which is important for future re-do TAVI procedures. Difficult coronary access was encountered more frequently following Evolut Pro+ and when engaging the RCA, but was unrelated to angular distance to nearest commissure.

A Clustering Approach to Unveil User Similarities in 6-DoF Extended Reality Applications

The advent in our daily life of Extended Reality (XR) technologies, such as Virtual and Augmented Reality, has led to the rise of user-centric systems, offering higher level of interaction and presence in virtual environments. In this context, understanding the actual interactivity of users is still an open challenge and a key step to enabling user-centric system. In this work, our goal is to construct an efficient clustering tool for 6 Degree-of-Freedom (DoF) navigation trajectories by extending the applicability of existing behavioural tool. Specifically, we first compare the navigation in 6-DoF with its 3-DoF counterpart, highlighting the main differences and novelties. Then, we investigate new metrics aimed at better modelling behavioural similarities between users in a 6-DoF system. More concretely, we define and compare 11 similarity metrics which are based on different distance features ( i.e. , user positions in the 3D space, user viewing directions) and distance measurements ( i.e. , Euclidean, Geodesic, angular distance). Our solutions are validated and tested on real navigation paths of users interacting with dynamic volumetric media in both 6-DoF Virtual Reality and Augmented Reality conditions. Results show that metrics based on both user position and viewing direction better perform in detecting user similarity while navigating in a 6-DoF system. Such easy-to-use but robust metrics allow us to answer a fundamental question for user-centric systems: “how do we detect if users look at the same content in 6-DoF?”, opening the gate to new solutions based on users interactivity, such as viewport prediction, live streaming services optimised based on users behaviour but also for user-based quality assessment methods.