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High-precision of Low Earth orbit (LEO) satellite orbit is essential for some applications having real-time requirements, such as LEO navigation enhancement, real time scientific satellite research, and so on. Currently, more mature means for real-time orbit determination of LEO satellites rely on spaceborne GPS data and RINEX/DORIS 3.0 data. However, most researchers conduct experiments using spaceborne GPS data or RINEX/DORIS 3.0 data separately, and the experiment results from combining the two types of data simultaneously have not been obtained. Therefore, we evaluate simulated real-time orbit determination capability of using the RINEX/DORIS 3.0 phase observations and spaceborne GPS pseudo-range observations from the HY2A satellite in this paper. Since the 1-km precision of the RINEX/DORIS 3.0 pseudo-range observations are unfavorable for the initial orbit, the GPS pseudo-range are used for this computation. But, the RINEX/DORIS 3.0 phase observations are used to solve the real-time orbit of HY2A satellite. Our analysis results are: (1) the three-dimensional (3D) position accuracy of HY2A satellite calculated by the spaceborne GPS pseudo-range is 6.803 m, which meets the initial orbit positional accuracy requirement. The initial orbit velocity requirement can be met when the 5–7th-order Lagrangian interpolation method is used to solve the satellite velocity. The 3D-RMS values of the HY2A satellite velocity is smaller than 0.500 m/s, indicating the initial velocity accuracy requirement is satisfied. (2) After Kalman filter convergence, the agreement of the comparison with the CNES precise orbit shows better than 0.100 m in radial position, an RMS of 0.373 m in 3D total position, and an RMS of 0.374 mm/s in 3D total velocity. The results suggest that the radial position accuracy is better than 0.100 m, and could meet some HY2A altimetry applications. In the course of this study, a Fortran-based prototype real-time orbit determination system RTODLEO (Real-Time Orbit Determination Software for Low Earth Orbit Satellite) was developed and used for the analysis. The results from thirteen-day of real-time orbit determination also validate the RTODLEO software, and show it is reliable.

Rare occurrences of dinosaurian embryos are punctuated by even rarer preservation of their development. Here we report on dental development in multiple embryos of the Early Jurassic Lufengosaurus from China, and compare these to patterns in a hatchling and adults. Histology and CT data show that dental formation and development occurred early in ontogeny, with several cycles of tooth development without root resorption occurring within a common crypt prior to hatching. This differs from the condition in hatchling and adult teeth of Lufengosaurus, and is reminiscent of the complex dentitions of some adult sauropods, suggesting that their derived dental systems likely evolved through paedomorphosis. Ontogenetic changes in successive generations of embryonic teeth of Lufengosaurus suggest that the pencil-like teeth in many sauropods also evolved via paedomorphosis, providing a mechanism for the convergent evolution of small, structurally simple teeth in giant diplodocoids and titanosaurids. Therefore, such developmental perturbations, more commonly associated with small vertebrates, were likely also essential events in sauropod evolution., Dinosaurs had some of the most complex dentitions known. Here, Reisz et al. characterize dental development across embryonic, hatchling and adult Lufengosaurus, an Early Jurassic sauropodomorph dinosaur, and suggest that derived sauropod dentition evolved by paedomorphosis (juvenilization).

This paper proposes an enhanced algorithm to estimate the differential code biases (DCB) on three frequencies of the BeiDou Navigation Satellite System (BDS) satellites. By forming ionospheric observables derived from uncombined precise point positioning and geometry-free linear combination of phase-smoothed range, satellite DCBs are determined together with ionospheric delay that is modeled at each individual station. Specifically, the DCB and ionospheric delay are estimated in a weighted least-squares estimator by considering the precision of ionospheric observables, and a misclosure constraint for different types of satellite DCBs is introduced. This algorithm was tested by GNSS data collected in November and December 2013 from 29 stations of Multi-GNSS Experiment (MGEX) and BeiDou Experimental Tracking Stations. Results show that the proposed algorithm is able to precisely estimate BDS satellite DCBs, where the mean value of day-to-day scattering is about 0.19 ns and the RMS of the difference with respect to MGEX DCB products is about 0.24 ns. In order to make comparison, an existing algorithm based on IGG: Institute of Geodesy and Geophysics, China (IGGDCB), is also used to process the same dataset. Results show that, the DCB difference between results from the enhanced algorithm and the DCB products from Center for Orbit Determination in Europe (CODE) and MGEX is reduced in average by 46 % for GPS satellites and 14 % for BDS satellites, when compared with DCB difference between the results of IGGDCB algorithm and the DCB products from CODE and MGEX. In addition, we find the day-to-day scattering of BDS IGSO satellites is obviously lower than that of GEO and MEO satellites, and a significant bias exists in daily DCB values of GEO satellites comparing with MGEX DCB product. This proposed algorithm also provides a new approach to estimate the satellite DCBs of multiple GNSS systems.

The merged GPS navigation files from the International GNSS Service (IGS) data centers, i.e., the Crustal Dynamics Data Information System (CDDIS), the Bundesamt fur Kartographie und Geodasie (BKG), the Scripps Institution of Oceanography (SIO), and the Institut Geographique National (IGN) are occasionally contaminated by anomalies and inconsistent user range accuracy (URA). This contamination impairs the performance assessment of GPS service, especially the system integrity. We remerged these files starting Day of Year (DOY) 1, 2000 using all available navigation data files from IGS stations. To effectively get the upper bound URA, a frequency-dependent pattern recognition method was developed. In addition, a comprehensive comparison between the navigation data remerged by us and those provided by the four IGS data centers was performed. The compared results revealed that TGD and Issue of Data Clock (IODC) were the dominating anomalies in the merged navigation data from CDDIS and SIO for the first several years after 2000, and M0, Ω0, ω, and af0 were the dominant anomalies in the merged data from IGN. In addition to a number of missing records, many records with incorrect PRN (pseudo-random noise number), identifying a GPS satellite, were found in files from the IGS data centers. Although the number of anomalies in the merged files from CDDIS has continued to decrease in recent years, they have not disappeared and would affect system-level assessment and scientific applications to a certain extent. The results also revealed that our remerged files were more complete, clean, compact and consistent, making them more suitable for GPS system performance assessment and related research studies. Moreover, those data are now openly available.

The biofilms (BF) formed by Escherichia coli (E. coli) is an important cause of chronic and recurrent infections due to its capacity to persist on medical surfaces and indwelling devices, demonstrating the importance of inhibiting the formation of E. coli BF and reducing BF infection. Although 2‑mercaptoethane sulfonate (MESNA) exhibits a marked mucolytic effect clinically, the effect of MESNA on the inhibition of E. coli BF formation remains to be elucidated. The present study investigated whether MESNA inhibits the formation of E. coli BF in vitro. The minimum inhibitory concentration of MESNA on E. coli was determined to be 10 mg/ml. Subsequently, the effect of MESNA on BF early adhesion, extracellular polysaccharide (EPS) and extracellular protein were detected. The effect of a subinhibitory concentration of MESNA on BF formation was evaluated, and the inhibitory potency of MESNA against matured BF was assayed. The results revealed that MESNA inhibited early stage adhesion and formation of the E. coli BF, destroyed the mature BF membrane and reduced the EPS and extracellular proteins levels of the BF. In addition, the present study investigated the effects of MESNA on the expression of EPS‑ and adhesion protein‑associated genes using quantitative polymerase chain reaction analysis, which demonstrated that MESNA effectively inhibited the expression of these genes. These results suggested that MESNA possesses anti‑BF formation capability on E. coli in vitro and may be used as a potential reagent for the clinical treatment of E. coli BF‑associated infections.

China is a country of vast territory with complicated geographical environment and climate conditions. With the rapid progress of the Chinese BeiDou satellite navigation system (BDS); more accurate tropospheric models must be applied to improve the accuracy of navigation and positioning. Based on the formula of the Saastamoinen and Callahan models; this study develops two single-site tropospheric models (named SAAS_S and CH_S models) for the Chinese region using radiosonde data from 2005 to 2012. We assess the two single-site tropospheric models with radiosonde data for 2013 and zenith tropospheric delay (ZTD) data from four International GNSS Service (IGS) stations and compare them to the results of the Saastamoinen and Callahan models. The experimental results show that: the mean accuracy of the SAAS_S model (bias: 0.19 cm; RMS: 3.19 cm) at all radiosonde stations is superior to those of the Saastamoinen (bias: 0.62 cm; RMS: 3.62 cm) and CH_S (bias: −0.05 cm; RMS: 3.38 cm) models. In most Chinese regions; the RMS values of the SAAS_S and CH_S models are about 0.51~2.12 cm smaller than those of their corresponding source models. The SAAS_S model exhibits a clear improvement in the accuracy over the Saastamoinen model in low latitude regions. When the SAAS_S model is replaced by the SAAS model in the positioning of GNSS; the mean accuracy of vertical direction in the China region can be improved by 1.12~1.55 cm and the accuracy of vertical direction in low latitude areas can be improved by 1.33~7.63 cm. The residuals of the SAAS_S model are closer to a normal distribution compared to those of the Saastamoinen model. Single-site tropospheric models based on the short period of the most recent data (for example 2 years) can also achieve a satisfactory accuracy. The average performance of the SAAS_S model (bias: 0.83 cm; RMS: 3.24 cm) at four IGS stations is superior to that of the Saastamoinen (bias: −0.86 cm; RMS: 3.59 cm) and CH_S (bias: 0.45 cm; RMS: 3.38 cm) models.

Aim Jaundice, potentially fatal encephalopathy, is common in approximately two-thirds of all well term infants. It is largely due to low expression of constitutive androstane receptor (CAR) in newborns; however, the mechanisms for this low expression were poorly understood. Materials and methods Expression of miR-137 and CAR was compared between neonatal and adult mice and between healthy and a mouse model of obstructive jaundice (OJ) using real-time RT-PCR and Western blot methods. Rate of bilirubin clearance was measured. DNA methylation of miR-137 was analyzed. Key findings Inverse expressions of miR-137 and CAR were consistently observed between newborn and adult mice, with a significantly higher miR-137 level and lower CAR protein and mRNA levels in neonatal liver than in adult liver. Similar reciprocal relationship was found existing between adult OJ mice and healthy control animals with a higher miR-137 level and lower CAR protein and mRNA levels in OJ than in healthy mice. Forced expression of miR-137 in primary hepatocytes repressed CAR protein levels, which was prevented by the inhibitor of miR-137. Knockdown of endogenous miR-137 by its inhibitor increased the rate of bilirubin clearance in OJ mice. Finally, we found that miR-137 was epigenetically over-activated due to hypomethylation in neonatal mice and in adult OJ mice, relative to adult healthy animals. Significance Our findings indicate that miR-137 is a repressor of CAR and thus a critical determinant of bilirubin clearance and may be considered a molecular target for the treatment of neonatal hyperbilirubinemia.

For precise orbit determination of geosynchronous earth orbit (GEO) satellites using transfer ranging observations, it is generally assumed that the variation of the satellite transponder delay is very small and that it can be solved as a constant parameter together with satellite orbit parameters. However, this assumption is too general and it reduces the accuracy of orbit determination for GEO satellites. To study and analyse the impact of the satellite transponder delay on GEO satellites orbit determination, two schemes were proposed. First, the satellite transponder delay was eliminated by forming single-difference observations between two ground stations; second, the satellite transponder delay was described as a constant parameter. The preliminary results demonstrate a difference of about 1–2 m between the two schemes when used for precise orbit determination of GEO satellites. By fixing the GEO satellite orbit and other relevant parameters estimated by single-difference model, we inversed the instantaneous transponder delay from non-difference observation. It was found that the satellite transponder delay has a distinct diurnal variation, with an amplitude of 3–4 m. The findings of this paper are helpful in establishing an accurate model of satellite transponder delay and in improving the accuracy of GEO satellites orbit determinations and predictions.

Tritylodontids are specialised, herbivorous cynodonts whose exact phylogenetic position is controversial, with some authors regarding them as close relatives of mammaliaforms and others as members of the eucynodont clade Traversodontidae. The tritylodontid pelvis has been claimed to resemble that of mammaliaforms in having a narrow, rod-like ilium, but such claims have been strongly challenged because of the incompleteness of previously available tritylodontid pelvic material. However, a partial tritylodontid skeleton from the Lower Jurassic of China preserves nearly complete examples of all three pelvic elements in addition to both femora, providing unprecedented insight into the structure of the tritylodontid pelvis and the configuration of the hip joint. This specimen confirms that the iliac blade is rod-like, adding to the evidence for a close relationship between tritylodontids and mammaliaforms. Furthermore, femoral retraction appears to have been driven partly by gluteus musculature in tritylodontids, as in mammaliaforms. (C) 2012 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

Attention has recently been paid to the algorithm for determining the orbit of navigation satellites autonomously through inter-satellite observation. Through the analyses of the structure of the normal equation for the parameter estimation when using inter-satellite distance observations only, three singular values in the normal equation are found which are significantly smaller than the others. The normal equation is therefore ill-conditioned. If the appropriate measures are not used, this ill-conditioned situation would seriously affect the accuracy and stability of the orbit determination. Based on the discussion of the concrete causes of ill-conditioning, the fitting method by selection of the parameter weights is imported, and the algorithm of adding constraints based on the a priori information of some parameters of the satellites is proposed. The necessary number and type of parameters to be constrained are investigated in detail. How to set the regularization matrix and the regularization...

During the period when a GPS satellite, the Earth and the Sun are approximately collinear, the phenomenon of eclipsing the satellite occurs, when the satellite yaw attitude deviates from its nominal case, i.e. the body X-axis cannot point towards the Sun for Block II&IIA or away from it for Block IIR satellites. The yaw attitude of the eclipsing satellites has a significant influence on both the satellite clock estimation at each International GNSS Service (IGS) Analysis Center (AC) and for users of the precise point positioning (PPP) implementations. It is known that, during the eclipsing periods, inconsistent yaw attitude models among the ACs will contribute to the errors of the IGS combined clock products. As for the PPP user, the influence of the eclipsing satellite is two-fold. First, as the satellite clocks are always kept fixed during PPP implementation, the above-mentioned problematic IGS clocks will inevitably be passed on to the PPP estimates. Second, the improper yaw attitude modeling of the eclipsing satellite will cause a correction bias exceeding 1 dm for the two kinds of attitude-related systematic errors, namely the phase wind-up and satellite antenna phase center offset, which will further deteriorate the accuracy of the PPP solutions. A yaw attitude model is introduced in this paper with the aim of improving the reliability of PPP solutions during the satellite eclipsing period.

Single-frequency (SF) Precise Point Positioning (PPP) is a promising technique for real-time positioning and navigation at sub-meter (about 0.5 m) accuracy level because of its convenience and low cost. With satellite orbit and clock error being greatly mitigated by the precise products from the International GNSS Service (IGS), ionospheric delay becomes the bottleneck of SF PPP users. There are five commonly used approaches to mitigate ionospheric delay in SF PPP: (1) broadcast ionospheric model in Global Navigation Satellite System (GNSS) navigation message; (2) global ionospheric map released by the IGS; (3) local ionospheric model generated using GNSS data from surrounding reference stations; (4) satellite based ionospheric model; (5) the parameter estimation method. Those approaches are briefly reviewed in our contribution and the performances of some classical ionospheric approaches for SF PPP are validated and compared using GPS data from two networks in China and the Netherlands respectively. Validation results show that a set of reference stations is critical for SF PPP with sub-meter positioning accuracy, especially in China. It is better to model the ionospheric delay in a satellite by satellite mode rather than an integral mode under the assumption of a thin-layer ionosphere. Comparing to GIM, the suggested approach, satellite based ionospheric model (SIM), can improve the horizontal positioning accuracy of SF PPP from 0.40 to 0.10 m in China and from 0.20 to 0.05 m in the Netherlands, while it can improve the vertical accuracy from 0.70 to 0.15 m (China) and from 0.20 to 0.10 m (the Netherlands). Furthermore, the recommended ionospheric model has been applied to GPS/BDS data for SF PPP as well. The experiment in Beijing shows that the positioning of about 0.5 m accuracy can be achieved by single epoch SF PPP based on a reference network of about 40 km inter-station distance. The accuracy of SF PPP based on an accumulation of 10–15 min of observations in dynamic mode is about 0.04 m (horizontal) and 0.04–0.08 m (vertical) using only GPS data, while it is about 0.03 m (horizontal) and 0.03–0.06 m (vertical) by combining GPS and BDS data.

Analysis of an Early Jurassic dinosaur bone bed reveals the rapid early growth stages of sauropodomorph embryos as well as the earliest evidence of in situ organic remains from a terrestrial vertebrate. Fossil dinosaur embryos are extremely rare, and mainly restricted to the Late Cretaceous period. Hence the interest in a newly uncovered bone bed of Lower Jurassic sauropodomorph embryos from China, which at about 190–197 million years old is the oldest assemblage of such bones ever found. A three-year multinational programme of excavation and research has yielded a treasure trove of embryonic bones, and the oldest known evidence of organic remains. Study of bones preserved at various developmental stages indicates that these large dinosaurs had a short incubation time and flexed their muscles while still in the egg, preparing the growing skeleton for life in the outside world. Fossil dinosaur embryos are surprisingly rare, being almost entirely restricted to Upper Cretaceous strata that record the late stages of non-avian dinosaur evolution1,2. Notable exceptions are the oldest known embryos from the Early Jurassic South African sauropodomorph Massospondylus3,4 and Late Jurassic embryos of a theropod from Portugal5. The fact that dinosaur embryos are rare and typically enclosed in eggshells limits their availability for tissue and cellular level investigations of development. Consequently, little is known about growth patterns in dinosaur embryos, even though post-hatching ontogeny has been studied in several taxa6. Here we report the discovery of an embryonic dinosaur bone bed from the Lower Jurassic of China, the oldest such occurrence in the fossil record. The embryos are similar in geological age to those of Massospondylus and are also assignable to a sauropodomorph dinosaur, probably Lufengosaurus7. The preservation of numerous disarticulated skeletal elements and eggshells in this monotaxic bone bed, representing different stages of incubation and therefore derived from different nests, provides opportunities for new investigations of dinosaur embryology in a clade noted for gigantism. For example, comparisons among embryonic femora of different sizes and developmental stages reveal a consistently rapid rate of growth throughout development, possibly indicating that short incubation times were characteristic of sauropodomorphs. In addition, asymmetric radial growth of the femoral shaft and rapid expansion of the fourth trochanter suggest that embryonic muscle activation played an important role in the pre-hatching ontogeny of these dinosaurs. This discovery also provides the oldest evidence of in situ preservation of complex organic remains in a terrestrial vertebrate.