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The receiver operating characteristic (ROC) and the area under the curve (AUC), initially developed for signal processing and psychology, are a test for assessing the performance of a binary classification problem at varying threshold values. The ion density (Ni) observed by FORMOSAT‐7/COSMIC‐2 is used to study traveling ionospheric disturbances (TIDs) triggered by the 15 January 2022 Tonga volcanic eruption. We examine parameters of Ni, differential Ni, and standard deviation Ni (STD_Ni) in January 2022, simulate TID wavefronts traveling with various speeds from 10 to 1,000 m/s, and apply the ROC curve to globally identify the significance of TIDs in STD_Ni triggered by the volcanic eruption. ROC and AUC results show that in addition to TIDs related to tsunami/tropospheric Lamb waves and a series of fast‐moving waves with propagation speeds of 180–350 and 450–600 m/s, respectively, those long‐lasting low‐speeds less than 70 m/s and high‐speeds about 690, 860, and 990 m/s meet 95% statistical significance, which confirms TIDs being detected. These show that the FORMOSAT‐7/COSMIC‐2 ion density can be used to globally detect various TIDs triggered by the Tonga volcanic eruption. The ROC test results also show a potential use case for detecting other geophysical signals in future applications. Plain Language Summary: Large‐scale natural phenomena such as volcanoes and tsunami induce prominent traveling atmospheric disturbances (TADs) which also simultaneously and locally influence the above ionosphere activating prominent traveling ionospheric disturbances (TIDs). To assess the significance of such TIDs, we treat the TIDs as a series of signals, and the receiver operating characteristic (ROC) and the area under the curve (AUC), developed to address binary classification problems, are used to evaluate these signals at varying threshold values. The 15 January 2022 Tonga volcanic eruption triggers a series of TADs, TIDs, and tsunami waves propagating around the globe. Measurements of the ion density (Ni) by IVM (ion velocity meter) onboard FORMOSAT‐7/COSMIC‐2 (F7C2) are used to identify TIDs triggered by the volcanic eruption. We examine TIDs of F7C2 Ni, differential Ni, and standard deviation (STD) of Ni in January 2022, and find that TIDs associated with the tsunami waves, tropospheric Lamb waves, and high‐speed waves within 450–600 m/s triggered by the Tonga volcanic eruption on the globe are very prominent on the eruption day. In addition, TIDs with long‐lasting low‐speeds less than 70 m/s and high‐speeds about 690, 860, and 990 m/s can be identified in the ROC curves and AUC indices. Key Points: The FORMOSAT‐7/COSMIC‐2 ion density globally observes various traveling ionospheric disturbances triggered by the Tonga volcanic eruptionThe receiver operating characteristic (ROC) test can detect traveling ionospheric disturbances and potentially other geophysical signalsDisturbances with low‐speeds of 10–70 m/s, tsunami, tropospheric Lamb wave, and high‐speeds of 490/690/860/990 m/s are identified [ABSTRACT FROM AUTHOR]

Low Earth orbit (LEO) radio occultation|radio occultations (RO) constellations can provide global electron density profiles (EDPs) to better specify and forecast the ionosphere‐thermosphere (I‐T) system. To inform future RO constellation design, this study uses comprehensive Observing System Simulation Experiments (OSSEs) to assess the ionospheric specification impact of assimilating synthetic EDPs into a coupled I‐T model. These OSSEs use 10 different sets of RO constellation configurations containing 6 or 12 LEO satellites with base orbit parameter combinations of 520 or 800 km altitude, and 24° or 72° inclination. The OSSEs are performed using the Ensemble Adjustment Kalman Filter implemented in the data assimilation (DA) Research Testbed and the Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model (TIEGCM). A different I‐T model is used for the nature run, the Whole Atmosphere Model‐Ionosphere Plasmasphere Electrodynamics (WAM‐IPE), to simulate the period of interest is the St. Patrick's Day storm on March 13–18, 2015. Errors from models and EDP retrieval are realistically accounted for in this study through distinct I‐T models and by retrieving synthetic EDPs through an extension Abel inversion algorithm. OSSE assessment, using multiple metrics, finds that greater EDP spatial coverage leading to improved specification at altitudes 300 km and above, with the 520 km altitude constellations performing best due to yielding the highest observation counts. A potential performance limit is suggested with two 6‐satellite constellations. Lastly, close examination of Abel inversion error impacts highlights major EDP limitations at altitudes below 200 km and dayside equatorial regions with large horizontal gradients and low electron density magnitudes. Plain Language Summary: The upper atmosphere, the region above 100 km altitude, is strongly influenced by space weather events that can negatively impact ground and space‐based technologies. These technologies include communication and navigation systems impacted by radio wave propagation through high altitudes plasma, a region called the ionosphere. Developing observing systems that provide global monitoring of the ionosphere is a critical need for understanding and forecasting space weather changes, such as radio occultations (RO) that provide plasma observations using global positioning radio signals. In this study, we evaluate these hypothetical RO observing systems in simulated experiments using data assimilation (DA), an approach that integrates synthetic observations into a physics‐based model. We find that increased observational coverage corresponds to better estimated plasma states, and that lower orbit altitude constellations yield higher observation counts. This study comprehensively incorporates model and observation errors to more realistically represent real‐world conditions. One limitation of RO data is highlighted in regions near the equator and at lower altitudes (below 250 km) where there is a breakdown in assumptions for observation retrieval. This study illustrates the clear operational benefits of these plasma observations, informing the future observing system design and aiding their use for space weather forecasting. Key Points: OSSE study assessing hypothetical radio occultation (RO) constellations, the first to comprehensively account for forecast model and Abel inversion errorsThe RO constellation with low‐ and high‐inclination orbits at 520 km altitude performs the best with the highest observation countsUncharacterized Abel inversion errors and poorly retrieved low plasma density limit assimilation impact on the equatorial ionosphere [ABSTRACT FROM AUTHOR]

The NASA global‐scale observations of the limb and disk (GOLD) mission is a measurement opportunity to scan the far ultraviolet airglow at ∼134–162 nm over the American Hemisphere since October 2018. The FORMOSAT‐7/COSMIC‐2 (F7/C2) satellite mission has provided thousands of daily radio occultation soundings in the low‐ and mid‐latitude regions since July 2019. The nighttime OI–135.6 nm emission is mainly through radiative recombination, and the radiance is used to derive the peak electron density. Comparison with corresponding F7/C2 observations demonstrates good correlation in low‐latitudes, while is overestimated near mid‐latitudes in winter, induced by the photoelectrons emanating from magnetically conjugate Hemisphere. The machine learning technique Bagged Trees is implemented to develop an intensity to peak density model training from GOLD and F7/C2 observations. The validation demonstrates that Bagged Trees peak‐density has less influence from conjugate photoelectrons and indicates the power of machine learning techniques for geophysics data processing. Plain Language Summary: The global‐scale observations of the limb and disk (GOLD) mission can scan wide ranges of far‐ultraviolet airglow at ∼134–162 nm over the American Hemisphere, providing the intensity of the airglow radiance and related maximum electron density of the ionosphere. Meanwhile, the FORMOSAT‐7/COSMIC‐2 (F7/C2) satellite mission receives GNSS radio signal to do radio occultation soundings and provides more than 4,000 of vertical electron density profiles daily. This study examines the two observations from different sounding techniques and algorithms, which generally yield good agreements, except that in the winter Hemisphere, the GOLD images experience the twilight airglow excited by conjugate photoelectrons emanating during May, June, and July. Moreover, the machine learning technique Bagged Trees is implemented to develop an intensity to peak density model training from two satellite observations, and the validation shows that the machine learning technique can detect and reduce the influence of the conjugate photoelectrons. The results indicate that the model can improve and increase the accuracy of the application of GOLD intensity for retrieving the peak electron density of the ionosphere. Key Points: The F7/C2 NmF2 and global‐scale observations of the limb and disk (GOLD) 135.6 nm airglow peak density are consistent except in the mid‐latitude region in the winter HemisphereThe machine learning technique bagged tree is used to develop an intensity to NmF2 model based on GOLD and F7/C2 observationsThe machine learning model can reduce the overestimation of NmF2 influenced by the photoelectrons emanating from the opposite Hemisphere [ABSTRACT FROM AUTHOR]

Global Ionospheric Specification (GIS) is based on the Gauss–Markov Kalman filter to assimilate the slant total electron content (TEC) observed from ground-based GPS receivers and space-based radio occultation instrumentations in order to reconstruct three-dimensional (3D) ionospheric electron density structure, and it can remotely sense and monitor the weather condition in space. In this study, five minutes of high temporal resolution GIS is implemented in order to reconstruct the 3D electron density structure on the 21 August 2017 total solar eclipse and analyze the variations induced by the moon's shadow. To obtain more information of the ionosphere, from the extend 2200 GPS stations on the continental United States, are added for assimilation. The results show the ionosphere peak height (hmF2) uplift was 30–50 km altitude in latitude 25–40°N, and that the electron density depletion at higher altitudes (400 km) has a more noticeable time delay than at low altitudes (200 km), especially in low-latitude regions. [ABSTRACT FROM AUTHOR]

The conversion of airglow intensity to volume emission rate (VER) is a common method for studying the ionosphere, but the contribution of the intensity conversion process to the uncertainty in estimated electron or ion density is significant. The Abel inversion is a commonly used method for retrieving VERs from vertical profiles of airglow intensities accumulated along the rays horizontally at the tangent point, but it requires that the intensities converge to zero at their uppermost height, which is often not the case due to observational limitations. In this study, we present a method for optimizing the retrieval of VER from satellite-measured airglow intensities using the techniques of deep learning and Abel inversion. This method can be applied to fill in unobserved or discontinuous observations in airglow intensity profiles with the Chapman function, allowing them to be used with the Abel inversion to determine VERs. We validate the method using limb 135.6 nm airglow emission intensity data from the NASA Global-scale Observations of the Limb and Disk (GOLD) mission. Our training process involves using three hidden layers with varying numbers of neurons, and we compare the performance of the best-performing deep learning models to Abel-transformed results from real-time observations. The combination of Abel inversion and deep learning has the potential to optimize the process of converting intensity to VER and improve the capacity for analyzing ionospheric observations. [ABSTRACT FROM AUTHOR]

Although beneficial associations between cardiorespiratory fitness and cognitive function have been established, whether cardiorespiratory fitness is related to behavioral and neuroelectric indices of performance during a prolonged inhibitory control task remains unknown. Young adults, categorized into High and Low Fitness groups, completed a 60‐min Stroop task, while the N1 and P3 components of event‐related potentials were measured. The results showed that the High Fitness group demonstrated shorter response times, regardless of the Stroop task congruency or time‐on‐task, than Low Fitness group. The High Fitness group also exhibited larger P3 amplitudes than the Low Fitness group, but no differences in N1 amplitudes were observed. These findings suggest that cardiorespiratory fitness during young adulthood has beneficial effects on task performance and attention allocation during an inhibitory control task, and these benefits can be sustained for 60 min. Beneficial associations between cardiorespiratory fitness (CRF) and cognitive function have been established; however, whether CRF is related to behavioral and neuroelectric indices of performance during a prolonged inhibitory control task remains unknown. Our finding adds the new perspectives that CRF might have a larger influence on later stages of attentional allocation than on earlier stages of perceptual attention gating. Importantly, the neurocognitive benefits of CRF extended throughout a prolonged task involving both general attention and inhibitory control. [ABSTRACT FROM AUTHOR]

A large near-surface perturbation such as the eruption of the Tonga underwater volcano on 15 January 2022 can generate disturbances in the Earth's atmosphere and ionosphere. It is quite challenging to detect and investigate the disturbances in the vertical direction due to the lack of ground-based instruments, especially in the ocean area. To examine the vertical disturbances due to the Tonga eruption, this study utilizes the radio occultation (RO) technique onboard the satellites of the FORMOSAT-7/COSMIC2 (F7/C2) mission to sound the ionospheric electron density (Ne) profiles in the Central Pacific Ocean area around the eruption. The ionospheric Ne profiles show that the eruption almost annihilated the typical Chapman-layer structure over the eruption in the nighttime on 15 January. The Hilbert–Huang transform was applied to expose the vertical changes in the Ne structures as functions of wavelength and altitude. The analysis shows not only the occurrence of the small-scale disturbances with a wavelength of ~20 km from 100 km to 500 km altitudes, but also the significant attenuation of the structures with a wavelength >50 km, which has never been reported before. The time series of the total electron content from the ground-based Global Navigation Satellite System receiver near the eruption also verifies the significant long-lasting disturbances due to the eruption. [ABSTRACT FROM AUTHOR]

The sudden eruption of the Tonga underwater volcano (20.53°S, 175.38°W) on 15 January 2022 generated explosions that triggered blast waves traveling away from the eruption. In this study, the analysis of the geomagnetic field observations on the ground shows that the eruption perturbed the E‐region current density by 22–55 mA/m within a radius of 8,000 km away from the eruption. The perturbation evolved into large scales of ∼5 hr and thousands of kilometers as it traveled away. The traveling speed of the leading front is ∼740 m/s that is near acoustic in the ionosphere. The magnetic fields and total electron content observations suggest that the dynamics changes further induced significant ionospheric disturbances that lasted ∼10 hr after the eruption. The examination of the Tonga volcanic eruption inspires us that a near‐surface perturbation can change the dynamics of the upper atmosphere. Plain Language Summary: As we drop a stone into the still water, the water piles up around the rock and induces ripples in the form of concentric circles that expand and travel away from the center point. A similar phenomenon happened in the atmosphere after the eruption of the Tonga underwater volcano (20.53°S, 175.38°W) at ∼04:15 UT on 15 January 2022. The Earth's atmosphere is a pond of air. The explosive eruption triggered prosperous waves, which is similar to dropping a stone into water. The waves, ripples, and disturbances in different spheres are fantastic due to the eruption (Figure S8 in Supporting Information S1). Besides the tsunamis, atmospheric concentric ripples, and ionospheric traveling disturbances, this study for the first time showed that the blast wave due to the eruption changed the dynamics of the ionosphere or thermosphere (upper atmosphere). It is well known that a significant volcanic eruption can release tremendous ashes and gases into the troposphere and stratosphere (lower atmosphere), which change the chemical and dynamic process there. The observations in this study surprisingly show that the eruption changed the dynamics of the upper atmosphere, where the volcanic cloud cannot reach. Key Points: The eruption of the Tonga underwater volcano perturbed the E‐region current and, in turn, changed the geomagnetic field by ∼20–50 nTA large near‐surface perturbation can modulate the ionospheric dynamics and further induce ionospheric disturbancesThe significant ionospheric disturbances with periods ranging from several minutes to hours lasted more than 10 hr after the eruption [ABSTRACT FROM AUTHOR]

This paper provides an overview of the contributions of the space-based global navigation satellite system (GNSS) radio occultation (RO) measurements from the FORMOSAT-7/COSMIC2 (F7/C2) mission in advancing our understanding of ionospheric plasma physics in the purview of space weather. The global positioning system (GPS) occultation experiment (GOX) onboard FORMOSAT-3/COSMIC (F3/C), with more than four and half million ionospheric RO soundings during April 2006–May 2020, offered a unique three-dimensional (3D) perspective to examine the global electron density distribution and unravel the underlying physical processes. The current F7/C2 carries TGRS (Tri-GNSS radio occultation system) has tracked more than 4000 RO profiles within ±35° latitudes per day since 25 June 2019. Taking advantage of the larger number of low-latitude soundings, the F7/C2 TGRS observations were used here to examine the 3D electron density structures and electrodynamics of the equatorial ionization anomaly, plasma depletion bays, and four-peaked patterns, as well as the S4 index of GNSS signal scintillations in the equatorial and low-latitude ionosphere, which have been previously investigated by using F3/C measurements. The results demonstrated that the denser low-latitude soundings enable the construction of monthly global electron density maps as well the altitude-latitude profiles with higher spatial and temporal resolution windows, and revealed longitudinal and seasonal characteristics in greater detail. The enhanced F7/C2 RO observations were further applied by the Central Weather Bureau/Space Weather Operation Office (CWB/SWOO) in Taiwan and the National Oceanic and Atmospheric Administration/Space Weather Prediction Center (NOAA/SWPC) in the United States to specify the ionospheric conditions for issuing alerts and warnings for positioning, navigation, and communication customers. A brief description of the two models is also provided. [ABSTRACT FROM AUTHOR]

The devastating Hunga Tonga-Hunga Ha'apai underwater volcano erupted at ~04:15 UT on 15 January 2022. We captured the waves that erupted from the volcano propagating in the ionosphere by monitoring total electron content (TEC) perturbations utilizing ground-based global navigation satellite system (GNSS) receivers that receive electromagnetic signals transmitted from the geostationary satellites operated by the BeiDou Navigation Satellite System (BDS). Meanwhile, ground barometers detected unusual enhancements of air pressure traveling in the troposphere. A novel phenomenon shows that the waves can individually propagate with a speed of ~335 m/s in the ionosphere, which is faster than its' ~305 m/s in the troposphere. We further examined multiple geophysical data at the particular site of the novel instrumental array. Analytical results show that the pressure enhancements traveling in the troposphere not only downward trigger ground vibrations mainly in the horizontal components without obvious time difference, but also upward, leading the secondary TEC perturbations with a ~12-min delay. [ABSTRACT FROM AUTHOR]

The ionospheric total electron content (TEC) derived from dense ground‐based Global Navigation Satellite System receivers over the continental United States and those from global ionosphere maps are utilized to find the ionosphere response to the August 21, 2017 total solar eclipse. Maximum obscurations and their associated TEC major depressions appear simultaneously at midlatitudes, while major depressions elongate toward the magnetic equator with some delays in the equatorial ionization anomaly (EIA) region. The former is due to the photochemical loss process, while the latter is caused by the plasma transport of E×B drifts and lunar gravitation forces. TECs of predawn reductions, morning enhancements, afternoon reductions, and nighttime enhancements reveal that the semidiurnal lunar tide are essential. Since a solar eclipse always occurs on a new moon day, the lunar tide results in the early EIA appearance and major depressions being underestimated/diminished before and overestimated/enhanced after about 14:00 local time. Plain Language Summary: Observations during an eclipse offer a special opportunity for studying the Earth's ionospheric response to changes in solar ionizing radiation. Although ionospheric solar eclipse signatures in many events have been studied, we report the lunar tide effect on the signatures for the first time. A total solar eclipse swept across the continental United States (CONUS) from the west to east coast on August 21, 2017. The total electron content (TEC) along seven longitudes of the US continent derived from more than 2,200 ground‐based Global Navigation Satellite System receivers in the CONUS and extracted from global ionosphere maps (GIMs) is employed to study ionospheric solar eclipse signatures. The most prominent solar eclipse signature is major depressions (MDs) in both the CONUS and GIM TECs, when the maximum obscuration occurs. TEC extrema of predawn reductions, morning enhancements, afternoon reductions, and nighttime enhancements reveal that the semidiurnal lunar tide of about 12.42‐h period is prominent. The lunar tide causes the early appearance of equatorial ionization anomalies, which further results in the MDs being weakened in the morning and enhanced in the afternoon on the solar eclipse day. The lunar tide has to be taken into consideration for studying ionospheric solar eclipse effects. Key Points: The lunar tide results in the early appearance of the equatorial ionization anomaly on solar eclipse daysTotal electron contents tend to enhance before and decrease after 14:00 local time (LT) on a solar eclipse dayThe lunar tide causes major depressions being weakened before and enhanced after 14:00 LT [ABSTRACT FROM AUTHOR]

The FORMOSAT‐7/COSMIC‐2 (F7/C2) satellite mission was launched on 25 June 2019 with six low‐Earth‐orbit satellites and can provide thousands of daily radio occultation (RO) soundings in the low‐latitude and midlatitude regions. This study shows the preliminary results of space weather data products based on F7/C2 RO sounding: global ionospheric specification (GIS) electron density and Ne‐aided Abel and Abel electron density profiles. GIS is the ionospheric data assimilation product based on the Gauss‐Markov Kalman filter, assimilating the ground‐based Global Positioning System and space‐based F7/C2 RO slant total electron content, providing continuous global three‐dimensional electron density distribution. The Ne‐aided Abel inversion implements four‐dimensional climatological electron density constructed from previous RO observations, which has the advantage of providing altitudinal information on the horizontal gradient to reduce the retrieval error due to the spherical symmetry assumption of the Abel inversion. The comparisons show that climatological structures are consistent with each other above 300 km altitude. Both the Abel electron density profiles and GIS detect electron density variations during a minor geomagnetic storm that occurred within the study period. Moreover, GIS is further capable of reconstructing the variation of equatorial ionization anomaly crests. Detailed validations of all the three products are carried out using manually scaled digisonde NmF2 (hmF2), yielding correlation coefficients of 0.885 (0.885) for both Abel inversions and 0.903 (0.862) for GIS. The results show that both GIS and Ne‐aided Abel are reliable products in studying ionosphere climatology, with the additional advantage of GIS for space weather research and day‐to‐day variations. Plain Language Summary: This study presents two ionosphere products from the innovative satellite constellation mission launched recently. Global ionospheric specification is an ionospheric data product that assimilates ground‐based Global Positioning System and FORMOSAT‐7/COSMIC‐2 radio occultation observation of total electron content, to generate hourly global three‐dimensional electron density for monitoring space weather condition. Ne‐aided Abel electron density profile is an improved retrieval product of FORMOSAT‐7/COSMIC‐2 radio occultation observations by imposing asymmetry information of ionosphere to mitigate the error introduced by the assumption of spherical symmetry in the Abel inversion. The comparisons and validations confirm that these two data products are reliable for the study of ionosphere climatology and weather. They are operationally produced and released at Taiwan Analysis Center for COSMIC. Key Points: All the three F7/C2 products capture similar climatological structure of ionosphere in longitudes (Wave 4) and latitudes (EIA crests)Abel electron density profiles detect responses to geomagnetic storm, but GIS performs better in reconstructing the EIA crests variationsDigisonde validations demonstrate that the GIS NmF2 has excellent performance when there are RO observations available for assimilation [ABSTRACT FROM AUTHOR]

The strength, appearance time, and latitudinal location of the equatorial ionization anomaly (EIA) crest response to the lunar phase are examined using the total electron content of global ionosphere maps during the 18‐year period of 2000–2017. The total electron content of the EIA crest reveals semidiurnal tides with 12.42‐hr period, while the appearance time and latitude of the EIA crests present prominent semimonthly lunar tides of 14.77‐day period. The EIA crests on new/full moon (first/third quarter) lead (lag) those of the overall 18‐year average by about 20–40 min, while the EIA crests move the furthest poleward and equatorward 2–5 days after new/full moon and first/third quarter, respectively. Amplitudes of the semimonthly lunar tide in the EIA crest appearance times and latitudes yield the greatest value around perihelion and the smallest value around aphelion, which shows that the solar declination and seasonal effects are important. Plain Language Summary: The most prominent feature in the ionosphere is the equatorial ionization anomaly (EIA), which is characterized by two enhanced plasma crests at low latitudes straddling the magnetic equator. Global ionosphere maps of total electron content are analyzed to see how the ionospheric EIA crests respond to changes in lunar phases and solar declinations. The results show that the EIA crests exhibit prominent semimonthly lunar tides with 14.77‐day period. Appearance times of the EIA crests on new/full moon (first/third quarter) lead (lag) those on the associated overall 18‐year average by about 20–40 min, while the EIA crests move the furthest poleward during new/full moon and equatorward during first/third quarter with the delays of about 2–5 days. These indicate that the lunar phase can significantly modulate the ionospheric EIA. The semimonthly lunar tide in the crest appearance times and latitudes become most prominent around perihelion but the least around aphelion, which shows that the solar declination and seasonal effects are important. Key Points: Appearance times of the EIA crests on new/full moon lead those on first/third quarterThe EIA crests move most poleward (equatorward) 2–5 days after new/full moon (first/third quarter)The semimonthly lunar tide of the EIA crest becomes most prominent around perihelion [ABSTRACT FROM AUTHOR]

S4 index is the rapid modification of signals when propagating through small-scale structures in the ionosphere, called ionospheric irregularities. The rapid modification of the signal causes the scintillation of the power. The purpose of this letter is to confirm the superposition property of the S4 index by using the ray-tracing method to simulate the signal propagation path through the ionospheric irregularities and then calculate the amplitude and S4 index of the received signal. The relation between the ionospheric scintillation S4 index and the signal propagation path can be understood. Then, the assimilation method for the S4 index can be developed to monitor the ionospheric irregularity in the future. [ABSTRACT FROM AUTHOR]

Tsunami waves can induce tsunami traveling ionospheric disturbances (TTIDs) of the total electron content (TEC). In this study, we examine the TEC derived by ground-based receivers of the global positioning system (GPS) and identify TTIDs induced by 2004 Indian Ocean tsunami. Simulations of the COMCOT (Cornell multi-grid coupled tsunami) model and analyses of the circle method, the ray-tracing technique, and the beam-forming technique are used to show that TTIDs can be quickly detected and confirmed after the tsunami occurrence. Finally, the ionospheric TEC derived by existing ground-based GNSS (Global Navigation Satellite Systems) receiving stations is demonstrated to be useful to support the tsunami early warning system. [ABSTRACT FROM AUTHOR]

Abstract: A moon shadow of the total solar eclipse swept through the continent of United States (CONUS) from west to east on 21 August 2017. Massive total electron content (integration of electron density from 0 km to 20,200 km altitude) observations from 2,255 ground‐based Global Navigation Satellite System receivers show that the moon shadow ship generates a great ionospheric bow wave front which extends ~1,500 km away from the totality path covering the entire CONUS. The bow wave front consists of the acoustic shock wave due to the supersonic/near‐supersonic moon shadow ship and the significant plasma recombination due to the reduction in solar irradiation within the shadow area. The deep bow wave trough (−0.02 total electron content unit (1 TECU = 1016 el m−2) area) nearly coincides with the 100% obscuration moving along the totality path over the CONUS through the entire eclipse period. The supersonic moon shadow ship induces a bow wave crest in front of the ship (~80% obscuration). It is the first time to find the acoustic shock wave‐formed bow wave trough and crest near the totality. [ABSTRACT FROM AUTHOR]

Animal cells and cell lines, such as HEK-293 cells, are commonly cultured at 37°C. These cells are often used to express recombinant proteins. Having a higher expression level or a higher protein yield is generally desirable. As we demonstrate in this study, dropping culture temperature to 33°C, but not lower, 24 hours after transient transfection in HEK-293S cells will give rise to ~1.5-fold higher expression of green fluorescent protein (GFP) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. By following the time course of the GFP-expressing cells growing at 37°C and 33°C from 24 hours after transfection (including 19 hours recovery at 37°C in the normal growth medium), we found that a mild hypothermia (i.e., 33°C) reduces the growth rate of HEK-293S cells, while increasing cellular productivity of recombinant proteins. As a result, green cells remain undivided in a longer period of time. Not surprisingly, the property of a recombinant protein expressed in the cells grown at 33°C is unaffected, as shown by the use of AMPA receptors. We further demonstrate with the use of PC12 cells that this method may be especially useful when a recombinant protein is difficult to express using a chemical-based, transient transfection method. [ABSTRACT FROM AUTHOR]

Abstract: 2′-Fluoro modified RNAs are useful as potential therapeutics and as special substrates for studying RNA function. 2′-Fluoro modified RNAs generally need to be purified after they are prepared either enzymatically or by solid-phase synthesis. Here we introduce a protocol by which 2′-fluoro modified RNAs with 57 and 58 nucleotides can be resolved and purified using ion-pair, reverse-phase high-performance liquid chromatography (HPLC). Because the size of our RNA samples is in the range of many known RNA aptamers of therapeutic values, our protocol should be generally useful. [Copyright &y& Elsevier]

Abstract: In this work we report a lithium ion battery characterized by very high rate capability, environmental compatibility, and potentially low cost. The battery is based on a lithium alloying, Sn–C, anode and an optimized lithium iron phosphate, LiFePO4, cathode. The morphology and structure of the materials were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques, while the electrochemical performances were evaluated by galvanostatic cycling and electrochemical impedance spectroscopy (EIS). Both the anode and the cathode reveal enhanced structure and morphology as well as excellent properties in terms of specific capacity, cycle life and, in particular, rate capability. The full Sn–C/LiFePO4 lithium ion battery operates at 2.8 V with a stable capacity of about 120 mAh g−1 for 100 cycles at the high rate of 3C. The cell has an energy density of 350 W h kg−1 and a power density of 2.4 kW kg−1. These interesting properties candidate the lithium ion battery here reported as a very appealing energy storage system, in particular for applications requiring high power densities. [Copyright &y& Elsevier]