Km Of Distance Research Articles

The 2021 and 2022 North Coast California Earthquake Sequences and Fault Complexity in the Vicinity of the Mendocino Triple Junction

ABSTRACT The Mendocino Triple Junction (MTJ), one of the most tectonically active and complex regions of California, has damaging earthquakes on the San Andreas and Mendocino faults, within the oceanic and subducting regions of the Gorda section of the Juan de Fuca plate, and within the overriding North American plate (NAP). Two recent earthquake sequences in the MTJ region, starting on 20 December 2021 and 20 December 2022, highlight the complex interactions of regional faults. We explore these sequences to better define the deep faults in the MTJ region, and their rupture modes. Our finite-source analysis shows the 2021 sequence began with two M ∼6.0 earthquakes separated by ∼11 s in time and 30 km in distance. The first earthquake occurred offshore on the Mendocino fault at a depth of 16.5 km. Its S waves triggered an “onshore” intraplate Gorda event at a depth of 27 km, which ruptured a vertical fault toward the northeast. Finite-source analysis of the mainshock of the 2022 sequence, M 6.4, indicates the rupture started offshore north of Cape Mendocino within the Gorda plate and propagated east-northeast, toward populated areas. Damage to towns and infrastructure was exacerbated by directivity and the sediment-filled valleys, as well as by a large aftershock (M 5.4) centered 20 km south-southeast of the mainshock rupture plane. The depths and mechanisms of the onshore 2021 and the 2022 earthquakes and their aftershock sequences indicate that they occurred on different strike-slip faults within the subducted portion of the Gorda plate. The faults active in these earthquakes are unrelated to mapped surface faults in the overriding NAP and are oblique to the tectonic trends seen at the surface. The 2021 and 2022 earthquakes are close to the boundary between two distinct regions of the Gorda plate, where offshore north–south horizontal compression transitions to east–west downslab tension.

Effect of environmental DNA sampling resolution in detecting nearshore fish biodiversity compared to capture surveys.

Sampling and sequencing marine environmental DNA (eDNA) provides a tool that can increase our ability to monitor biodiversity, but movement and mixing of eDNA after release from organisms before collection could affect our inference of species distributions. To assess how conditions at differing spatial scales influence the inferred species richness and compositional turnover, we conducted a paired eDNA metabarcoding and capture (beach seining) survey of fishes on the coast of British Columbia. We found more taxa were typically detected using eDNA compared to beach seining. eDNA identified more taxa with alternative habitat preferences, and this richness difference was greater in areas of high seawater movement, suggesting eDNA has a larger spatial grain influenced by water motion. By contrast, we found that eDNA consistently missed low biomass species present in seining surveys. Spatial turnover of communities surveyed using beach seining differed from that of the eDNA and was better explained by factors that vary at small (10-1000s meters) spatial scales. Specifically, vegetation cover and shoreline exposure explained most species turnover from seining, while eDNA turnover was not explained by those factors and showed a distance decay pattern (a change from 10% to 25% similarity from 2 km to 10 km of distance), suggesting unmeasured environmental variation at larger scales drives its turnover. Our findings indicate that the eDNA sample grain is larger than that of capture surveys. Whereas seining can detect differences in fish distributions at scales of 10s-100s of meters, eDNA can best summarize fish biodiversity at larger scales possibly more relevant to regional biodiversity assessments.

The complete mitochondrial genome and microsatellite discovery of the Chilean kelp crab Taliepus dentatus (Brachuyra, Majoidea)

Abstract The complete sequence of the mitochondrial genome and fifteen microsatellite loci for the Chilean kelp crab Taliepus dentatus are reported for the first time. The DNA assembly obtained from an Illumina sequencing revealed a complete mitochondrial genome of 15 603 bp in length. The gene composition and arrangement were similar to that reported for most decapod crabs, containing 13 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes and a non-coding region. A phylogeny performed with 10 species obtained from GenBank placed T. dentatus close to individuals of the Family Epialtidae. From the 6397 repeated sequences encountered in the data, 15 microsatellite loci primers were designed and five tested for variability in specimens obtained from two sampling sites separated by 300 km of distance. The mean number of alleles per locus was nine (5–15 alleles per locus) and the observed heterozygosities ranged from 0.34 to 0.8. Departure from Hardy–Weinberg equilibrium was observed in two out of the five microsatellites, while none of the loci exhibited significant linkage disequilibrium. This genetic resource will be useful for phylogeny, population genetics and parentage analysis of the commercial species T. dentatus.

Bridging distances and saving costs: insights from a pilot project of telerheumatology in a rural area of Pakistan.

Enhancing access to healthcare remains a formidable challenge in rural regions of low- and lower-middle-income countries. Amid evolving healthcare challenges, telerheumatology provides opportunities to bridge gaps and expand access to rheumatology care, particularly in remote areas. We describe a pilot telerheumatology program and its cost-, time-, and travel-saving potential in a remote rural setting in northern Pakistan. The telerheumatology program commenced at the Pakistan Institute of Medical Sciences Islamabad, providing services through video consultations to a basic health unit in the Gilgit-Baltistan region. Patients visiting from the Gilgit-Baltistan region willing to participate were recruited in the program. Demographics and logistical metrics were recorded in a dedicated registry. A total of 533 consultations were carried out from April 2022 to April 2023. The majority of the patients were female (318/533, 59.7%). The median age of patients was 50 ± 15.7 years. The average wait time for consultation was 20 ± 13 min. The average travel time to reach telecentre was 59 ± 53 min. The average travel cost to reach telecentre was 379 ± 780 PKR (1.85 ± 3.81 USD). The average duration of consultation was 15 ± 5 min. The most common diagnosis for consultation was knee osteoarthritis (237, 44.5%), chronic low back pain (118, 22.1%), and rheumatoid arthritis (42, 7.9%). On average, patients saved 787 ± 29 km of distance, 15 ± 1 h of traveling, and 6702 ± 535 PKR (33 ± 3 USD) that would have been required to travel to our tertiary care hospital. Telerheumatology substantially reduced travel time, distance, and cost for patients. It has the potential to deliver outpatient rheumatology consultation in an economically efficient manner, effectively breaking geographical barriers and expanding access to essential services for patients in remote areas.

Passive Surveillance as a Key Tool for African Swine Fever Eradication in Wild Boar: A Protocol to Find Carcasses Tested and Validated in the Mediterranean Island of Sardinia.

African swine fever (ASF) is one of the most important and serious contagious hemorrhagic viral diseases affecting domestic pigs and wild boar and is associated with high mortality rates while also having an extensive sanitary and socioeconomic impact on the international trade of animal and swine products. The early detection of the disease is often hampered by inadequate surveillance. Among the surveillance strategies used, passive surveillance of wild boars is considered the most effective method for controlling the African swine fever virus (ASFV). Otherwise, the design of a sufficiently sensitive ASF surveillance system requires a solid understanding of the epidemiology related to the local eco-social context, especially in the absence of virus detection. Even if the number of carcasses needed to demonstrate ASF eradication has been established, the scientific context lacks detail compared to protocols applied in the active search for wild boar carcasses. The aim of this study was to describe the protocol applied in the active search for carcasses, providing detailed information on the number of people and dogs as well as the amount of time and space used within the Mediterranean area. Using a specific tool developed to record, trace, and share field data (the GAIA observer app), a total of 33 active searches for wild boar carcasses were organized during 2021-2023. Most of these searches were planned to find carcasses that had previously been reported by hunters. A total of 24 carcasses were found, with only 2 carcasses not previously reported. The final protocol applied involved four people, with an average speed of 1.5 km/h. When a carcass had been previously reported, about 2 km of distance had to be covered in about 1.5 h to find the carcass, and even less time was spent when a dog (untrained) was present. In conclusion, it can be stated that, when searching for carcasses, solid collaboration with local hunters or other forest visitors is necessary to ensure carcasses are reported. The process involves small groups of experts actively searching for carcasses, possibly with the use of hunting dogs without special training. The data presented could be of valid support for those countries characterized by Mediterranean vegetation that are faced with the need to plan active carcass searches.

Host species and geography impact bee-associated RNA virus communities with evidence for isolation by distance in viral populations.

Virus symbionts are important mediators of ecosystem function, yet we know little of their diversity and ecology in natural populations. The alarming decline of pollinating insects in many regions of the globe, especially the European honey bee, Apis mellifera, has been driven in part by worldwide transmission of virus pathogens. Previous work has examined the transmission of known honey bee virus pathogens to wild bee populations, but only a handful of studies have investigated the native viromes associated with wild bees, limiting epidemiological predictors associated with viral pathogenesis. Further, variation among different bee species might have important consequences in the acquisition and maintenance of bee-associated virome diversity. We utilized comparative metatranscriptomics to develop a baseline description of the RNA viromes associated with wild bee pollinators and to document viral diversity, community composition, and structure. Our sampling includes five wild-caught, native bee species that vary in social behavior as well as managed honey bees. We describe 26 putatively new RNA virus species based on RNA-dependent RNA polymerase phylogeny and show that each sampled bee species was associated with a specific virus community composition, even among sympatric populations of distinct host species. From 17 samples of a single host species, we recovered a single virus species despite over 600km of distance between host populations and found strong evidence for isolation by distance in associated viral populations. Our work adds to the small number of studies examining viral prevalence and community composition in wild bees.

Assessment of the GNSS-RTK for Application in Precision Forest Operations

A smart thinning operation refers to an advanced method of selecting and cutting trees to be thinned based on digitally captured forest information. In smart thinning operations, workers use the coordinates of individual trees to navigate to the target trees for thinning. However, it is difficult to accurately locate individual trees in a forest stand covered with a canopy, necessitating a precise real-time positioning system that can be used in the forest. Therefore, this study aimed to evaluate the applicability of the global navigation satellite system real-time kinematic (GNSS-RTK) device in a forest stand through analysis of its positioning accuracy within the forest environment and evaluation of the operational range of the single-baseline RTK based on analysis of the positioning precision and radio signal strength index (RSSI) change with increasing distance from the base station. The results showed that the root mean square error (RMSE) of the horizontal positioning error was highly accurate, with an average of 0.26 m in Larix kaempferi stands and 0.48 m in Pinus koraiensis stands. The RSSI decreased to a minimum of −103.3 dBm within 1 km of distance from the base station; however, this had no significant impact on the horizontal positioning precision. The conclusion is that the GNSS-RTK is suitable for use in smart thinning operations.

An ancient genome perspective on the dynamic history of the prehistoric Jomon people in and around the Japanese archipelago

The Jomon people were prehistoric residents of the Japanese archipelago who occupied the region from ca. 16,500 to 2,300 years before present (BP). While recent accumulation of ancient genomes and genome-wide data of the Jomons has substantially enhanced our understanding of their genetic profiles and contribution to present-day populations, their genetic history in the Jomon-period archipelago, spanning over 14,000 years in time and 2,000 km in distance, remains scarcely investigated. Here we report multiple findings illuminating the Jomon genetic history based on the analysis of the genetic relationship between published ancient genome-wide data of 23 Jomon and Jomon-like individuals. First, the Initial Jomon individual from Shikoku, dated to ca. 9,000 BP, forms a common outgroup to the remaining later Jomon individuals, suggesting a population turnover in western Japan. Second, genetically Jomon-like individuals outside the Jomon archaeological context, found in the Miyako Island in Ryukyu and the Yokjido island in the southern coast of Korea, show the closest genetic affinity with the Late Jomon individual from Shikoku, narrowing down their sources in space and time. This study highlights a dynamic history of the Jomon people in and out of the Japanese archipelago and calls for a large-scale investigation of the ancient Jomon genomes.

Development of Railway Track Crack Detection System using Arduino

The Indian Railways has one of the largest railway networks in the world, criss- crossing over 1,15,000 km in distance, all over India. However, with regard to reliability and passenger safety Indian Railways is not up to global standards. Among other factors, cracks developed on the rails due to absence of timely detection and the associated maintenance pose serious questions on the security of operation of rail transport. A recent study revealed that over 25% of the track length is in need of replacement due to the development of cracks on it. Manual detection of tracks is cumbersome and not fully effective owing to much time consumption and requirement of skilled technicians. This paper is aimed towards addressing the issue by developing an automatic railway track crack detection system with the proliferation of Internet of Things (IoT). It is possible to collect massive amount of data for localization and tracking of Railway Fault Detection.

The SHIELD’21 deep seismic experiment

The wide-angle reflection and refraction (WARR) SHIELD’21 profile carried out in 2021 crosses from SW to NE the main tectonic of Ukraine. The SHIELD’21 targeted the structure of the Earth’s crust and upper mantle of the southwestern margin of the East European Craton with overlying Neogene Carpathian Foredeep and Vendian-Paleozoic Volyn-Podolian Monocline, Archaean and Paleoproterozoic segments of Ukrainian Shield and Late Paleozoic Dnieper-Donets Basin. The ~650 km long profile is an extension of realized in 2014 RomUkrSeis line in Romania and Ukraine from Apuseni Mountains to southwestern Ukrainian Shield. The field work performed in 2021, included the deployment of autonomous seismic stations and drilling-explosive works. A total of 264 seismic receivers were deployed (160 DATA-CUBE and 104 TEXAN stations) with the average spacing between the observation points about 2.65 km. The sampling interval for all stations was 0.01 s. Seismic energy was generated by 10 shot points with ~50 km of distance between them and total charge in all wells 5775 kg. The SHIELD’21 experiment using TEXAN and DATA-CUBE short-period seismic stations provided high-quality seismic records. The main recorded seismic waves are the refractions of P- and S-waves in sediments, basement, crust and upper-most mantle, and reflections from crustal boundaries, Moho interface and boundaries in the uppermost mantle. Correlation of travel time arrivals of seismic waves provides calculation of the velocity model for both P- and S-waves. The main objective of the SHIELD’21 project is to get new seismic data that increase our knowledge on the lithosphere structure as well as geodynamics of the oil-and-gas-bearing and ore regions of Ukraine.

The Effectiveness of the Clarke & Wright Savings Algorithm in Determining Logistics Distribution Routes (case study PT.XYZ)

A good logistics system is one factor that affects the smooth running of company activities. Currently, transportation costs account for about two-thirds of total logistics costs, so to increase efficiency, companies try to maximize the use of transportation equipment and personnel by determining the optimal distribution route. Route optimization can be done using the Vehicle Routing Problem and the Clarke- Wright Method. PT. XYZ is a company engaged in maintaining ATM machines (Automated Teller Machines). The form of this activity can be in the form of installing air conditioners, TVs and repairing ATM machines. This company faces problems in the logistics section, where the installation target is often not achieved from the specified target. This is because the distance from one point to another is coupled with the congestion level in big cities, so this causes the company to pay large operational costs. Therefore, a distribution route is needed to save time and distribution costs. This study uses the Clarke and Wright Savings Algorithm to solve the problems faced by companies. The results showed that after using the Clarke and Wright Savings Algorithm, the total distance and shipping costs were reduced by saving 97.9 Km of distance and saving costs.

Effects of anthropogenic disturbance on group densities of Thomas' langurs (Presbytis thomasi) within a lowland tropical forest, north Sumatra

AbstractEcosystems around the globe are facing irreversible impacts due to climate change, habitat destruction, hunting, and an ever‐increasing human population. Estimating densities of species across their geographical range helps us to understand natural variation and anthropogenic effects on species densities and to assess the effectiveness of existing conservation measures. Various methods have been used to produce accurate and precise population density estimates, each with associated limitations. Acoustic surveys for species producing loud calls have become common due to their ease of use, low cost, and reduced timescale. Relative to many other mammal taxa, primate species have been studied extensively, producing a wealth of data on socioecology and behavior, but for most species, density estimates over large geographical ranges are still lacking. We used an acoustic spatial capture–recapture model to estimate group density of unhabituated Thomas' langurs (Presbytis thomasi), a primate endemic to the Indonesian island of Sumatra, over a 60 km2 area of lowland dipterocarp forest. We then assessed if vegetation structure and distance from human habitation affected density estimates. Estimates of group density differed almost threefold between survey locations (from 2.79 to 8.08 groups/km2); there was no clear relationship with forest structure, but there was a significantly positive relationship between group density and distance from human habitation, with an increase of 0.38 groups/km2 for every km of distance. Although large‐scale logging within the Sikundur region ceased ~30 years ago, the impacts of logging continue to have detrimental effects on the species within the area.

Regression analysis on ground motion parameters for the earthquakes (Mw≥4.0) in NE India with special emphasis on 3 Jan 2016 M6.7, Tamenglong earthquake

In the present study, ground motion parameters (GMPs) are estimated by processing 26 earthquake events containing 125 accelerogram records with 375 components that originated in NE, India, and its vicinity with special emphasis on the Jan 3, 2016, M6.7, Tamenglong Earthquake. Moreover, Ground Motion Prediction Equations were developed through multiple regression analysis on observed data of 8 GMPs namely, Peak Ground Acceleration, Peak Ground Velocity, Arias Intensity, Characteristics Intensity, Housner Intensity, Cumulative Absolute Velocity, Effective Design Acceleration, and Acceleration Spectrum Intensity. The developed equations are representative of statistics on changes in amplitudes of parameters with varying distances and magnitude in connection to Northeast India. Besides, newly developed GMPEs can be applied to 4–6.8 magnitude earthquakes and valid up to 525 km of distance. In the case of January 3, 2016, Mw = 6.7, Tamenglong earthquake, a total of 25 parameters are estimated from ground motion recordings. The highest Peak Ground Acceleration (PGA) of 0.05 (g) has been experienced by Kohima station along with Pseudo Spectral Acceleration of 0.2802 (g) at the frequency of 1.72 Hz. The peak pseudo-spectral accelerations for each recording site of the Tamenglong earthquake are perceived within the periods of 0.2s and 0.5s. These estimations help in the characterization of ground motion with varying distances and magnitude which is a prime input to rate damage potential of ground motion and seismic hazard analysis in Northeast India.

Species turnover increases ant–trophobiont interaction dissimilarities along a geographical gradient

Abstract Despite the recent advances regarding the ecological and evolutionary dynamics of ant–trophobiont mutualistic interactions, understanding their spatial variation remains a challenge. An approach involving species interaction networks is a helpful tool to overcome it because it allows us to compare how different species interact among them. Here, we assessed how the dissimilarities in the composition of ant–trophobiont relationships (β‐diversity of interactions) of ants and trophobionts change with increasing geographical distance. For this, we assessed ant–trophobiont interactions in 90 trees along a geographical gradient ranging from 1 to 213 km of distance. We found that the β‐diversity of ant–trophobiont interactions increased with the geographical distance between two sites. Moreover, we observed that the turnover of interacting species was the main component of the β‐diversity of interactions, increasing with the distance between the sampled sites. Even so, interaction rewiring generated by the reassembly of the interactions between the same species in different sites was low and did not change with increasing geographical distance. Our findings indicate that the high species turnover between ant–trophobiont interaction networks could be shaped by the low habitat connectivity between vegetation patches and the low mobility and dispersal capacities of mutualistic partners, generating unique interactions over space.

Developing an exhaustive optimal maintenance schedule for offshore wind turbines based on risk-assessment, technical factors and cost-effective evaluation

Maintenance scheduling is one of the most challenging issues of offshore wind system, because the maintenance decision may impact greatly to cost-effectiveness. The process of maintenance decision making is confronting with uncertainties, including economic, technical, safety and environmental uncertain that make conventional maintenance optimization insufficient. The conventional maintenance optimization in the existing studies only consider factors related to technical and economic aspects in maintenance optimization. No existing study analyzes the effects of health and safety risks of the technicians and the environmental risks of the maintenance activities under the impacts of the complex weather conditions in the marine environment. The occurrence of environmental and safety risks causes catastrophic consequences, especially in harsh weather condition, that make the conventional maintenance techniques insufficient. This paper proposes an approach to optimize maintenance schedule that is designed to maximize the cost-effectiveness while minimizing the environmental and safety risks. The proposed model utilizes fuzzy probabilities to assess the environmental and safety risks. This paper also presents a mathematical model to derive the optimal individual maintenance schedule and group maintenance schedule for various components by considering a number of impacted factors. The results demonstrated that the number of maintenance activities when considering environmental and safety risks is higher than that without considering environmental and safety risks. For example, the number of maintenance activities with and without considering the environmental and safety risks at the location of 25 km of distance to shore is 75 and 86 activities respectively. The effect of risk-assessment model was more apparent for vulnerable components and was less apparent for the durable components.

Radiocaesium accumulation and fluctuating asymmetry in the Japanese mitten crab, Eriocheir japonica, along a gradient of radionuclide contamination at Fukushima

The 2011 Tohoku earthquake-tsunami and the subsequent nuclear accident at the Fukushima Dai-ichi Nuclear Power Station (FDNPS) led to large-scale radionuclide contamination of the marine and freshwater environment. Monitoring studies of marine food products in the Fukushima region have generally demonstrated a declining trend in radiocaesium concentrations. However, the accumulation and elimination of radiocaesium and potential biological effects remain poorly understood for freshwater biota inhabiting highly contaminated areas at Fukushima. Consequently, the present study aimed to assess radiocaesium accumulation and developmental effects on the commercially important catadromous Japanese mitten crab, Eriocheir japonica. E. japonica were collected from four sites along a gradient of radionuclide contamination 4–44 km in distance from the FDNPS in 2017. To determine potential developmental effects, fluctuating asymmetry (FA) was used as a measure of developmental stability. Combined 134Cs and 137Cs values for whole E. japonica from highly contaminated sites 4 and 16 km in distance from the FDNPS were 3040 ± 521 and 2250 ± 908 Bq kg−1 wet weight respectively, 30 and 22 times greater than the Japanese standard limit of 100 Bq kg−1. Estimated total dose rates based on radiocaesium concentrations in whole crabs and sediment ranged from 0.016 to 37.7 μGy h−1. No significant relationship between radiocaesium accumulation and FA was recorded, suggesting that chronic radiation exposure at Fukushima is not inducing developmental effects in E. japonica as measured using fluctuating asymmetry. Furthermore, estimated dose rates were below proposed regulatory limits where significant deleterious effects are expected. The present study will aid in the understanding of the long-term consequences of radiation exposure for non-human biota and the management of radioactively contaminated environments.

Community structure of benthic megafauna on a seamount with cobalt-rich ferromanganese crusts in the northwestern Pacific Ocean

Increasing threats to seamount ecosystems potentially from fishing and seabed mining are creating an urgent demand for research on megafauna to inform conservation and management. We surveyed the community structure of benthic megafauna on the Weijia Seamount, which is covered by cobalt-rich ferromanganese crusts, in the northwestern Pacific Ocean. A multidisciplinary dataset was generated from video recordings taken by a human occupied vehicle (HOV) and remotely operated vehicle (ROV) along transects and bathymetry-derived environmental variables. The spatial variation of community structure and its environmental and spatial factors impacting the community were then explored. A total of 2779 individuals of the megabenthos (from depths of 1533–2763 m, covering 24.4 km in distance and with a maximum of 109 individuals per 100 m by linear observation), was counted and classified into 76 morphospecies, which was dominated by crinoids, ophiuroids, hexactinellids and octocorals. Moderately abundant and diverse megafauna, high beta diversity and distinct assemblages were present in the Weijia Seamount, suggesting a highly patchy pattern within a single seamount. Six clusters of megafauna were revealed, with significant differences in species composition and biodiversity. The results of statistical analyses showed that the megafaunal community was impacted by at least eight environmental variables (latitude, depth, slope, curvature, rugosity, bathymetric position index, topography type, and substrate type), and excluding aspect. Among these variables, the topography and substrate types played key roles in the occurrence of small-scale aggregations of hexactinellids; depth-related variables were key factors, but no gradual depth-related change in terms of abundance, richness or species turnover was observed. This case study on the megabenthic community of the Weijia Seamount can serve as an environmental baseline, providing a reference status for seamount conservation and management.

Simultaneous Radio Occultation Predictions for Inter-Satellite Comparison of Bending Angle Profiles from COSMIC-2 and GeoOptics

The Global Navigation Satellite System (GNSS) radio occultation (RO) is a remote sensing technique that uses International System of Units (SI) traceable GNSS signals for atmospheric limb soundings. The RO bending angle/sounding profiles are needed for assimilation in Numerical Weather Prediction (NWP) models, weather, climate, and space weather applications. Evaluating these RO data to ensure the high data quality for these applications is becoming more and more critical. This study presents a method for predicting radio occultation events, from which simultaneous radio occultation (SRO) for a pair of low-Earth-orbit (LEO) satellites on the limb to the same GNSS satellite can be obtained. The SRO method complements the Simultaneous Nadir Overpass (SNO) method (for nadir viewing satellite instruments), which has been widely used to inter-calibrate LEO to LEO and LEO to geosynchronous-equatorial-orbit (GEO) satellites. Unlike the SNO method, the SRO method involves three satellites: a GNSS and two LEO satellites with RO receivers. The SRO method allows for the direct comparison of bending angles when the simultaneous RO measurements for two LEO satellites receiving the same GNSS signal pass through approximately the same atmosphere within minutes in time and within less than 200 km of distance from each other. The prediction method can also be applied to radiosonde overpass prediction, and coordinate radiosonde launches for inter-comparisons between RO and radiosonde profiles. The main advantage of the SRO comparisons of bending angles is the significantly reduced uncertainties due to the much shorter time and smaller atmospheric path differences than traditional RO comparisons. To demonstrate the usefulness of this method, we present a comparison of the Constellation Observing System for Meteorology, Ionosphere, and Climate-2 (COSMIC-2) and GeoOpitcs RO profiles using SRO data for two time periods: Commercial Weather Data (CWD) data delivery order-1 (DO-1): 15 December 2020–15 January 2021 and CWD DO-2: 17 March 2021–31 August 2021. The results show good agreement in the bending angles between the COSMIC-2 RO measurements and those from GeoOptics, although systematic biases are also found in the inter-comparisons. Instrument and processing algorithm performances for the signal-to-noise ratio (SNR), penetration height, and bending angle retrieval uncertainty are also characterized. Given the efficiency of this method and the many RO measurements that are publicly and commercially available as well as the expansion of receiver capabilities to all GNSS systems, it is expected that this method can be used to validate/inter-calibrate GNSS RO measurements from different missions.

Opposition Observations of 162173 Ryugu: Normal Albedo Map Highlights Variations in Regolith Characteristics

Abstract On 2019 January 8, the Telescopic Optical Navigation Camera (ONC-T) on board the Hayabusa2 spacecraft observed the Cb-type asteroid 162173 Ryugu under near-opposition illumination and viewing conditions from approximately 20 km in distance. Although opposition observations have never been used for mapping purposes of a planetary body, we found three advantages for mapping under these conditions: (1) images are free of topographic shadows, (2) the reflectance is nearly independent of the orientation of the surface, and (3) spurious color artifacts that may appear near shadowed terrain are avoided. We present normal albedo maps, one for each of the seven filters (0.40–0.95 μm), using an empirical photometric correction. Global coverage of Ryugu is 99.4%. The 0.55 μm band average normal albedo is 4.06% ± 0.10%. Various spectral variations are derived from these maps. Spectral features of regions and boulders are quantified by examining the normal albedo-derived spectral slope and UV index (spectral slope from visible to ultraviolet wavelength) value. In terms of space weathering, three spectral characteristics are observed over the majority of Ryugu: (1) reddening, (2) increases in reflectance at ultraviolet wavelengths compared to visible, and (3) darkening. By contrast, the bright boulders (“type 3”) show a different trend, with wide variations in the 0.95 μm albedo and UV index. Finally, principal component analysis (PCA) comparisons with other asteroids strongly suggest that the main components of Ryugu belong to the B-Cb-type populations. The PCA feature of the fresh material on Ryugu is close to the Eulalia family.

A tale of two Tweefonteins: What physical correlation, geochronology, magnetic polarity stratigraphy, and palynology reveal about the end-Permian terrestrial extinction paradigm in South Africa

Abstract The contact between the Daptocephalus to Lystrosaurus declivis (previously Lystrosaurus) Assemblage Zones (AZs) described from continental deposits of the Karoo Basin was commonly interpreted to represent an extinction crisis associated with the end-Permian mass-extinction event at ca. 251.901 ± 0.024 Ma. This terrestrial extinction model is based on several sections in the Eastern Cape and Free State Provinces of South Africa. Here, new stratigraphic and paleontologic data are presented for the Eastern Cape Province, in geochronologic and magnetostratigraphic context, wherein lithologic and biologic changes are assessed over a physically correlated stratigraphy exceeding 4.5 km in distance. Spatial variation in lithofacies demonstrates the gradational nature of lithostratigraphic boundaries and depositional trends. This pattern is mimicked by the distribution of vertebrates assigned to the Daptocephalus and L. declivis AZs where diagnostic taxa of each co-occur as lateral equivalents in landscapes dominated by a Glossopteris flora. High-precision U-Pb zircon (chemical abrasion-isotope dilution-thermal ionization mass spectrometry) age results indicate maximum Changhsingian depositional dates that can be used as approximate tie points in our stratigraphic framework, which is supported by a magnetic polarity stratigraphy. The coeval nature of diagnostic pre- and post-extinction vertebrate taxa demonstrates that the L. declivis AZ did not replace the Daptocephalus AZ stratigraphically, that a biotic crisis and turnover likely is absent, and a reevaluation is required for the utilization of these biozones here and globally. Based on our data set, we propose a multidisciplinary approach to correlate the classic Upper Permian localities of the Eastern Cape Province with the Free State Province localities, which demonstrates their time-transgressive nature.