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Global Navigation Satellite Systems (GNSS) tropospheric tomography is a commonly used technique for the reconstruction of three-dimensional water vapour field, and a priori vertical constraint models are required for water vapour density (WVD) determination which plays a critical role in the quality of tomographic results. However, generalised exponential models were routinely used for vertical constraints and limited research was carried out in the GNSS tomography by taking epoch-by-epoch variations into consideration. In this study, an adaptive four-dimensional (4-D) WVD model for the vertical constraints in GNSS tropospheric tomography was developed based on both ERA5 and surface meteorological data in Hong Kong for each month during the period of 2015–2019, and the back-propagation neural network technique was used to develop the fitting model. Then, the WVD model was used to obtain the WVD of adjacent voxels in the vertical direction to alleviate the mis-representation of the generalised exponential model. The newly developed WVD model used in GNSS tropospheric tomography was validated using GNSS data from the Hong Kong region in the year 2020 and two tomographic epochs (00:00–00:30 UTC and 12:00–12:30 UTC) were evaluated each day. For each topographic epoch, the WVDs of the tomographic voxels including radiosonde profile are evaluated (10 voxels over 10 height layers) using radiosonde data as the reference and the WVDs of all tomographic voxels are evaluated (300 voxels over 10 height layers) using ERA5 data as the reference. Results showed that when radiosonde/ERA5 data were utilized as the references, corresponding monthly mean values of the root mean square errors (RMSEs) in the entire year reduced from 1.97/1.94 g/m3 of the traditional tomographic method to 1.56/1.36 g/m3 of the new method which showed approximately 21/30% improvements. These results suggest a better performance of the tomographic approach using the new WVD model for the vertical constraints proposed by this study by taking epoch-by-epoch information. [ABSTRACT FROM AUTHOR]

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Ionospheric scintillation affects the positioning, navigation and timing services of the Global Navigation Satellite System (GNSS), calling for an urgent need for scintillation monitoring on a global scale. To monitor the ionospheric scintillation with each carrier of the 30-s sampling interval GNSS observations, a scintillation extraction method is proposed based on the Morse wavelet transform, together with the determination of the symmetry parameter, the time-bandwidth product, the characteristic frequency range and the threshold of the scintillation. After testing with four-year observations collected at 15 middle- and high-latitude stations, results show that the extracted scintillation indicator can detect the occurrence but fails to provide the magnitude of the scintillation with the 30-s-sampling-interval observations. Compared to the state-of-the-art scintillation index extracted from the ionospheric scintillation monitoring receiver, the proposed scintillation indicator is applicable in utilizing 30-s sampling interval GNSS observations to monitor scintillations in high-latitude regions, especially for those with long durations, hence making the widely available GNSS observations with low sampling intervals be introduced into the field of ionospheric scintillation monitoring on a global scale. [ABSTRACT FROM AUTHOR]

Atmospheric pressure, temperature and zenith wet delay (ZWD) are important meteorological parameters for GNSS (Global Navigation Satellite Systems) data processing and GNSS meteorology. Due to the fact that not all GNSS stations are physically equipped with meteorological sensors, empirical models are widely used for the prediction of the atmospheric pressure (which can be used for the calculation of zenith hydrostatic delay (ZHD)), temperature and ZWD. However, if the reference height significantly differs from the height of the user site, the quality of the predicted meteorological parameters may be poor due to the height difference between the user site and the reference level. To address these issues, a voxel-based atmospheric pressure and temperature model, named PVoxel, was developed to improve the accuracy in the determination of both atmospheric pressures and temperatures. Ten-year ERA5 monthly mean reanalysis data were used for the development of PVoxel, and each monthly mean atmospheric pressure and temperature at each of the four selected reference heights (0, 4, 10 and 15 km) and the ZWD with its vertical decay parameter at 0 and 4 km over all globally distributed grid points (horizontal resolution 1° × 1°), i.e., at the nodes of the 3D voxels, were determined. Then, the characteristics of the annual and semi-annual variations of these parameters in the temporal domain for each node were modeled. The PVoxel model can be used to predict atmospheric pressure, temperature and ZWD at any geographic location and time. The model was evaluated by comparing the model-predicted results for the sites of all globally distributed radiosonde stations against the corresponding radiosonde data in 2019. The results showed that the atmospheric pressure and temperature predicted by PVoxel were improved significantly compared to four advanced publicly available empirical models, i.e., UNB3m, GPT3, IGPT and GTrop, especially at high altitudes. The significant improvement in the accuracy of the new model is promising for better determination of ZHD and GNSS-based applications. [ABSTRACT FROM AUTHOR]

Outbreaks of harmful algal blooms (HABs) exhibit high frequency, large range and damage aggravation characteristics, but existing monitoring methods, such as artificial and optical near-infrared remote sensing, cannot accommodate these characteristics. We propose a new method for monitoring green algae using Global Navigation Satellite System Reflectometry (GNSS-R) observations. The basic principle states that changes in the seawater dielectric constant and sea surface roughness due to the emergence of green algae lead to an increase in brightness temperature, which can be inverted based on the reflection time delay waveform. Shipboard reflection waveform data collected during an Enteromorpha prolifera outbreak in the Qingdao sea area were used for model development and validation of the detection and estimation performance. The results indicated that the root mean square error of GNSS-R-based inversion of the green algae density was 6.74%, indicating the potential of GNSS-R technology for rapid preliminary monitoring of green algae. Moreover, the advantages of a low cost, short return time and no climatic limitations support GNSS-R technology as a new and efficient means of green algae monitoring. [ABSTRACT FROM AUTHOR]

Purpose: Vepoloxamer (VEPO), a rheologic agent, repairs damaged cell membranes, thus inhibiting unregulated Ca2+ entry into cardiomyocytes. This study examined the effects of i.v. infusion of VEPO on LV function in dogs with coronary microembolization–induced heart failure (HF) (LV ejection fraction, EF ~ 30%). Methods: Thirty-five HF dogs were studied. Study 1: 21 of 35 dogs were randomized to 2-h infusion of VEPO at dose of 450 mg/kg (n = 7) or VEPO at 225 mg/kg (n = 7) or normal saline (control, n = 7). Hemodynamics were measured at 2 h, 24 h, 1 week, and 2 weeks after infusion. Study 2: 14 HF dogs were randomized to 2-h infusions of VEPO (450 mg/kg, n = 7) or normal saline (control, n = 7). Each dog received 2 infusions of VEPO or saline (pulsed therapy) 3 weeks apart and hemodynamics measured at 24 h, and 1, 2, and 3 weeks after each infusion. In both studies, the change between pre-infusion measures and measures at other time points (treatment effect, Δ) was calculated. Results: Study 1: compared to pre-infusion, high dose VEPO increased LVEF by 11 ± 2% at 2 h, 8 ± 2% at 24 h (p < 0.05), 8 ± 2% at 1 week (p < 0.05), and 4 ± 2% at 2 weeks. LV EF also increased with low-dose VEPO but not with saline. Study 2: VEPO but not saline significantly increased LVEF by 6.0 ± 0.7% at 2 h (p < 0.05); 7.0 ± 0.7%% at 1 week (p < 0.05); 1.0 ± 0.6% at 3 weeks; 6.0 ± 1.3% at 4 weeks (p < 0.05); and 5.9 ± 1.3% at 6 weeks (p < 0.05). Conclusions: Intravenous VEPO improves LV function for at least 1 week after infusion. The benefits can be extended with pulsed VEPO therapy. The results support development of VEPO for treating patients with acute on chronic HF. [ABSTRACT FROM AUTHOR]

The ionosphere has been considered as one of the major error sources in GNSS signal propagation, and it is still difficult to be modeled precisely, especially for real-time positioning applications. The commonly used ionospheric models are usually based on the one-layer approximation, which neglects the ionospheric variation in the vertical domain and limits the scope of improvement over one-layer models. A new ionospheric model based on the two-layer approximation and two spherical harmonic (SH) functions is proposed in this contribution, where a quasi-globe projection is designed to avoid the inherent ill-posed problem and retain the physical meaning of the SH when regional data are used. GPS and BDS data from the National Positioning Infrastructure of Australia and Crustal Movement Observation Network of China are used for validating the new model's performance in different areas and different periods. Results show (1) the precision of ionospheric TEC estimates from the new model can be improved by about 26% and 31% in the cross-validation experiment compared to the traditional one-layer model in Australian and Chinese regions, respectively; (2) the positioning accuracy of kinematic single-frequency precise point positioning (SF-PPP) in the experimental regions using the new model reaches about 0.7 m and 0.8 m in the horizontal and vertical components, respectively, in comparison with the one-layer model's 1.0 m (horizontal) and 1.4 m (vertical); (3) the convergence time of the SF-PPP using the new model is 5–10 min for achieving a sub-meter level of positioning accuracy in both horizontal and vertical components, whereas it needs 30–40 min in case the one-layer model is used. [ABSTRACT FROM AUTHOR]

Vertical total electron content (VTEC) global ionospheric maps (GIM) are commonly used to correct the ionospheric delay of global navigation satellite system (GNSS) signals for single-frequency positioning and other ionospheric studies. The measurements observed by inhomogeneously distributed ground reference stations are the only data used to generate the GIMs. Thus the accuracy of the GIMs over ocean and polar regions is relatively poor due to the lack of measurements over these regions. In this study, space-borne VTECs obtained from ocean-altimetry and GNSS radio occultation measurements are incorporated into the modelling process. Since the three types of VTEC data have different qualities, the weight for each type of data is determined using the Helmert-variance component estimation (Helmert-VCE) method. In addition, unlike the traditional weighted least squares (WLS) estimation method in which the design matrix of observation equations is fixed, in this study, the design matrix, especially those elements in design matrix that are derived from the coordinates of either tangent point or ionospheric pierce point, are considered to be inaccurate. Thus they are adjusted together with the unknown coefficient parameters of the fitting model using the fast-weighted total least squares (fast-WTLS) technique. The proposed approach, named Helmert-WTLS, was tested using the data in the period of day of year (DOY) 217–224, 2016 and validated using GIMs produced by the research team for ionosphere and precise positioning based on BDS/GNSS (GIPP) at the Academy of Opto-Electronics, Chinese Academy of Sciences (CAS). Comparison results showed that the GIMs (with a 2 h temporal resolution) generated using the new approach can improve the determination of ionospheric TEC by 0.28 TEC units (TECU) over those from the Helmert-VCE-aided WLS approach (w.r.t CAS references, respectively) and by 1.61 TECU better than those from WLS, in terms of the mean of all root-mean-squares errors of all 2 h time slots in the 8-day testing period. In addition, in comparison with out-of-sample Jason-3 observations, results from the proposed method also outperformed Helmert-VCE-aided WLS, CAS and CODE models by 1.5, 2.4 and 2.4 TECU, respectively. [ABSTRACT FROM AUTHOR]

Purpose: Abnormalities of MITO dynamics occur in HF and have been implicated in disease progression. This study describes the broad range abnormalities of mitochondrial (MITO) dynamics in Heart Failure with reduced ejection fraction (HF) and evaluates the effects of long-term therapy with elamipretide (ELAM), a MITO-targeting peptide, on these abnormalities.Methods: Studies were performed in left ventricular tissue from dogs and humans with HF, and were compared with tissue from healthy dogs and healthy donor human hearts. Dogs with HF were randomized to 3 months therapy with ELAM or vehicle. The following were evaluated in dog and human hearts: (1) regulators of MITO biogenesis, including endothelial nitric oxide synthase (eNOS), cyclic guanosine monophosphate (cGMP), and peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α, a transcription factor that drives MITO biogenesis); (2) regulators of MITO fission and fusion, including fission-1, dynamin-related protein-1, mitofusion-2, dominant optic atrophy-1, and mitofilin; and (3) determinants of cardiolipin (CL) synthesis and remodeling, including CL synthase-1, tafazzin-1, and acyl-CoA:lysocardiolipin acyltransferase-1.Results: The study showed decreased levels of eNOS, cGMP, and PGC-1α in HF (dog and human). Increased levels of fission-associated proteins, decreased levels of fusion-associated proteins, decreased mitofilin, and abnormalities of CL synthesis and remodeling were also observed. In all instances, these maladaptations were normalized following long-term therapy with ELAM.Conclusions: Critical abnormalities of MITO dynamics occur in HF and are normalized following long-term therapy with ELAM. The findings provide support for the continued development of ELAM for the treatment of HF. [ABSTRACT FROM AUTHOR]

Transformer is one of the critical equipments for electric power transmission and distribution, and its safety situation plays an important role on stability and security level of power systems. Therefore, the diagnosis of its abnormal situation has always drawn enormous attention from both domestic and international scholars. Dissolved gas analysis (DGA) is a widely used method in transformer fault diagnosis field. However, the conventional DGA is not well suitable for transformer fault diagnosis because transformer's structure is complex and operating environment is changeable. On the other hand, the back propagation (BP) neural network, frequently employed in related field, also has some inherent disadvantages, such as local optimization, over-fitting and difficulties in convergence. So simply integrating conventional DGA to BP is not a good approach for fault diagnosis. Moreover, disturbance or noises within the training data, which is unavoidable due to systematic errors, may greatly influence the accuracy of diagnosis model with the growing size of the data. Thus, in this study, we integrate a combination ratio of taking advantages of IEC and Doernenburg, instead of usual DGA, into genetic algorithm (GA) and fuzzy c-means clustering algorithm (FCM) optimized BP, successfully building a novel model which has not been reported previously. Our results show this model has a better diagnosis accuracy rate and generalization ability than other models, and FCM and GA can significantly overcome the disadvantages of training data and BP, offering the potential of implementation for real-time diagnosis systems. [ABSTRACT FROM AUTHOR]

We provide suggestions for the approved COSMIC-2 satellite mission regarding the field of view (FOV) and the clock stability of its future GNSS receiver based on numerical analyses using COSMIC GPS data. While the GRACE GPS receiver is mounted on the zenith direction, the precise orbit determination (POD) antennas of COSMIC are not. The COSMIC antenna design results in a narrow FOV and a reduction in the number of GPS observations. To strengthen the GPS geometry, GPS data from two POD antennas of COSMIC are used to estimate its orbits. The phase residuals of COSMIC are at the centimeter level, compared to the millimeter level of GRACE. The receiver clock corrections of COSMIC and GRACE are at the microsecond and nanosecond levels, respectively. The clock spectra of COSMIC at the frequencies of 0-0.005 Hz contain significant powers, indicating potential systematic errors in its clock corrections. The clock stability, expressed by the Allan deviation, of COSMIC ranges from 10 to 10 over 1 to 10 s, compared to 10 to 10 for GRACE. Compared to USO-based clock of GRACE, the clock of COSMIC is degraded in its stability and is linked to the reduction of GPS data quality. Lessons for improvement of COSMIC-2 over COSMIC in FOV and receiver clock stability are given. [ABSTRACT FROM AUTHOR]

Purpose: GP531 is a second generation adenosine regulating agent (ARA) that increases concentrations of endogenous adenosine, a natural cardioprotective agent, in ischemic/hypoxic tissue. This study examined the effects of acute intravenous infusions of GP531 on left ventricular (LV) systolic and diastolic function in dogs with advanced chronic heart failure (HF) (LV ejection fraction, EF <30 %). Methods: Six dogs with intracoronary microembolization-induced HF received a constant intravenous infusion of GP531 (10 μg/kg/min) or vehicle (normal saline) for 6 h in random order 1 week apart. Hemodynamic measurements were made at baseline and at 1, 2, 3, 4, 5 and 6 h after initiating drug infusion. Myocardial oxygen consumption (MVO 2) was measured at baseline and 4 and 6 h. LV pressure-volume relationship (PVR) was measured at baseline and 6 h. Results: Vehicle infusions had no effect on indexes of LV systolic and diastolic function. GP531 infusion had no effect on heart rate or mean aortic pressure but significantly decreased LV end-diastolic pressure, end-diastolic volume, end-systolic volume and end-diastolic wall stress. GP531 significantly increased LV EF (27 ± 1 at baseline to 34 ± 1 after 6 h of drug infusion, p < 0.05), deceleration time of early mitral inflow velocity and the slope of end-systolic PVR without increasing MVO 2. Conclusions: Results of the study indicate that approaches which increase the local release of adenosine in failing LV myocardium, such as ARAs, have a favorable impact on LV performance. These observations support the continued development of ARA’s for the treatment of acute HF syndromes. [ABSTRACT FROM AUTHOR]

Rhesus putative epidermal stem cells are being investigated for their potential use in regenerative corneal epithelium-like cells, which may provide a practical source of autologous seed cells for the construction of bioengineered corneas. The goal of this study was to investigate the potential of epidermal stem cells for trans-differentiation into corneal epithelium-like cells. Rhesus putative epidermal stem cells were isolated by type IV collagen attachment method. Flow cytometry analysis, immunohistology and RT-PCR were conducted to identify the expression of specific markers (β1m α6 integrin, K15, K1/K10, K3/K12 and CD71) on the isolated rapid attaching cells. The isolated cells were cocultured with human corneal limbal stroma and corneal epithelial cells. After coculture, the expression of the same specific markers was evaluated in order to identify expression difference caused by the coculture conditions. K3/K12 expression was analyzed in coculture cells on day 2, 4, 6, 8 and 10. Putative epidermal stem cells in conditioned culture media were used as control. Putative epidermal stem cells were predominant in rapid attaching cells by type IV collagen attachment isolation. Before being cocultured, the rhesus putative epidermal stem cells expressed K15, α6 and β1 integrin, but no CD71, K1/K10 and K3/K12. After coculture, these cells expressed K3/K12 (a marker of corneal epithelial cells), K15 and β1 integrin, but no K1/K10. Cells being not coculture converted into terminally differentiated cells expressing K1/K10. These results indicate that rhesus putative epidermal stem cells can trans-differentiate into corneal epithelium-like cells and, therefore, may have potential therapeutic application as autologous seed cells for the construction of bioengineered corneas. [ABSTRACT FROM AUTHOR]

This paper presents the current progress of the River Level Monitoring using GPS Heighting (RiGHt) project. The aim of the project is to develop an integrated system to allow the continuous monitoring of river heights using a buoy equipped with Global Positioning System (GPS) and satellite communications and using Geographical Information System (GIS) techniques. © 2000 John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

For previous studies of global navigation satellite system (GNSS) troposphere tomography, only the GNSS observations derived from ground-based stations located inside the tomographic area were considered; however, stations distributed outside the area of interest in a dense regional network were neglected. This wastes valuable GNSS data and decreases the number of voxels traveled by satellite rays. This becomes the focus of this work, which tries to use GNSS receivers located outside the tomographic region to participate in the establishment of a tomographic observation equation. A new troposphere tomography algorithm is proposed with a truncation factor model (TFM), while the ability of the TFM to calculate the sectional slant water vapor inside the tomographic area, derived from the receivers outside this area, has been verified. The proposed algorithm is validated using the observed data collected over 31 days from the continuously operating reference system network of Zhejiang Province, China. At elevation angle masks of 10°, the number of satellite rays used has increased by 21.27% while the number of voxels transited by satellite rays has increased by 13.97% from 65.44 to 79.23% when adopting the TFM. The compared result of integrated water vapor with those from radiosonde data reveals that the RMS error and bias of the proposed algorithm are 4.1 mm and 0.06 mm, respectively, while those of the conventional method are 4.8 mm and − 0.34 mm, respectively. Water vapor profile comparison also shows that the RMS error and bias of the proposed algorithm are superior with average values of 1.17 g m−3 and 0.02 g m−3 to that of the conventional algorithm with values of 1.44 g m−3 and 0.03 g m−3, respectively. The PWV differences between tomography and GAMIT further indicate a good performance of the proposed algorithm with the values of RMS error and bias of 8.7 mm and 0.5 mm, respectively, while those of the traditional method are 12.6 mm and 0.9 mm, respectively. [ABSTRACT FROM AUTHOR]

Tropical cyclones are a serious natural disaster concern in Australia due to El Niño and La Niña phenomena. However, little attention has been paid to the ionospheric responses to severe typhoons that have occurred in Australia. In this study, dual-frequency GPS measurements and ionosonde data were used to investigate the variations in ionospheric total electron content (TEC) and the critical frequency of the F2 layer (foF2) during Typhoons Ingrid, George, Pancho and Gillian. The results showed that the variations in the solar-terrestrial environment during all these typhoons were not significant, with the first three typhoons yielding similar TEC and foF2 results (both increased within 2 days of the day when the wind speed reached the peak). However, the results for Typhoon Gillian were different, as its TEC and foF2 values decreased within 2 days of the peak wind speed. To further investigate the spatial variation in the ionospheric electron density (IED) during Typhoon Gillian, the IEDs obtained from the FORMOAST-3/COSMIC ionospheric profiles were constructed for both reference and observation periods. The results showed that the differences between the two IED periods in the region around the storm eye ranged from − 1.0 to − 1.5 × 106 el/cm3, which is equivalent to about − 37.5 to − 50%. These low IED values were mainly focused in the 300-350 km altitude range, especially at the 300 km altitude level. The results also showed that all the ionospheric anomalies were located at the edge of the typhoon rather than the storm eye. This study will be helpful in deepening our understanding of the ionospheric responses to typhoons in Australia. [ABSTRACT FROM AUTHOR]

This contribution is the first of a two-part investigation into an unseasonal post-sunset equatorial F-region irregularity (EFI) event over the Southeast Asian region on the evening of 28 July 2014. Ground-based GPS scintillation data, space-based GPS radio occultation (RO) data, and ionosonde data show the existence of EFIs shortly after sunset over a region spanning 30° in longitude and 40° in latitude, centered on the geomagnetic equator. This post-sunset EFI event was observed during a time of the year when post-sunset equatorial plasma bubbles (EPBs) are very infrequent in the Southeast Asian longitude sector. GPS RO data shows that the EFI event over Southeast Asia coincided with the suppression of peak-season EPBs in the African and Pacific longitude sectors. Ionosonde data shows the presence of a strong pre-reversal enhancement (PRE) in the upward plasma drift over Southeast Asia prior to the detection of EFIs. Further, it is reported that this PRE was significantly stronger than on any other day of July 2014. An analysis of the geophysical conditions during this event reveals that this enhanced PRE was not caused by disturbed geomagnetic activity. Therefore, it is hypothesized that forcing from lower altitudes, perhaps tidal/planetary waves, was the potential cause of this strong PRE, and the subsequent EPB/EFI activity, on this day over the Southeast Asian sector. [ABSTRACT FROM AUTHOR]