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  • 2020-2024  (6)
  • 1995-1999  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    Genomic and phenotypic characterization of the bacterium causing blight of kiwifruit in New Zealand (1997)
    Oxford, UK : Blackwell Science Ltd
    Plant pathology 46 (1997), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Strains of the pathogen causing bacterial blight of kiwifruit in New Zealand, previously identified as Pseudomonas viridiflava, were examined using phenotypic and genotypic methods. Percentage DNA–DNA reassociation values for strains of the pathogen, with the type strains representing P. viridiflava and P. savastanoi, and representative strains within P. syringae, were obtained using the S1 endonuclease method. Strains of the pathogen were most similar to the type strain of P. savastanoi. This similarity was supported by examination of the ΔTm between representative strains. It is concluded that the pathogen can be considered as a member of the P. savastanoi genomic species. The pathogen from kiwifruit in New Zealand was also differentiated in genomic terms from P. syringae pv. actinidiae. Strains of the kiwifruit pathogen compared using the Biomerieux API Biotype 100 system exhibited consistent determinative tests which distinguished the pathogen from P. viridiflava and P. syringae pv. actinidiae. The origins of the pathogen in New Zealand are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1997.d01-72.x
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    Paper (German National Licenses)
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  • 2
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    Reversible change in transformation temperatures of a Ti-51at%Ni alloy associated with alternating aging (1999)
    Elsevier
    Details
    Publication Date: 1999-10-01
    Print ISSN: 1359-6462
    Electronic ISSN: 1872-8456
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Elsevier
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  • 3
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    Regulation of the small GTP-binding protein Rho by cell adhesion and the cytoskeleton (1999)
    EMBO Press
    Details
    Publication Date: 1999-02-01
    Print ISSN: 0261-4189
    Electronic ISSN: 1460-2075
    Topics: Biology , Medicine
    Published by EMBO Press on behalf of European Molecular Biology Organization.
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  • 4
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    Compressed sensing based on dictionary learning for 4D ionospheric electron density modeling (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-04-18
    Description: Inadequate and inhomogeneous GNSS (Global Navigation Satellite System) observation severely restricts the advancement of the voxel-based computerized ionospheric tomography (CIT) technique. Various inversion algorithms, exemplified by the algebraic reconstruction technique (ART), have been proposed for estimating ionospheric electron density (IED). However, using ART techniques, the IEDs of voxels that are not crossed by GNSS rays cannot be accurately estimated. In this study, we proposed a compressed sensing technique (CST) for ionospheric tomography using the K-SVD algorithm for dictionary learning. Given a set of IED values that are derived from the NeQuick-2 model, the K-SVD algorithm uses the orthogonal matching pursuit for sparse coding and the singular value decomposition (SVD) approach for dictionary updating. When compared to the multiplicative algebraic reconstruction method (MART) algorithm, both simulation and real experiments proved the viability and superiority of the CST technique. When the NeQuick-2 model was employed for dictionary learning, it was discovered that the tomographic performances of the CST method were better than those of the MART algorithm. Besides, the tomographic results were used for dictionary learning in CST-based tomography. It showed that the CST algorithm can further improve tomographic performances when compared to the MART algorithm. Additionally, there was a better agreement between the IED profiles derived from radio occultation data and the electron density profiles produced by the CST method.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 5
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    Impacts of the wintertime North Pacific subtropical and subarctic oceanic frontal zones on the atmosphere (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-07-26
    Description: Oceanic frontal zone is key region of the oceanic feedback to the atmosphere in the extratropics. The oceanic frontal zone in the wintertime North Pacific exhibits a unique double fronts structure, with a subtropical oceanic frontal zone (STFZ) and a subarctic frontal zone (SAFZ). The feedback of the variability of the two oceanic frontal zones in the wintertime North Pacific on the atmosphere are investigated using daily observational data. The anomalies of the STFZ and SAFZ are both associated with the dipolar SST anomalies with cold (warm) anomalies in the north (south). Following the peak of the STFZ and SAFZ, the dipolar SST anomalies can both maintain almost 30 days. For the STFZ, the anomalous upward surface heat flux in the south of the STFZ indicates the warming effect of the warm SST anomalies on the overlying atmosphere, resulting in the positive anomalies of the near-surface air temperature. The combined effects of the warm anomalies of the near-surface air temperature in the south of the STFZ and cold anomalies of the near-surface air temperature induced by the atmospheric advection result in the enhancement of the near-surface baroclinicity over the STFZ. However, with weak and insignificant anomalous upward surface heat flux, we find that the feedback of the SAFZ on the atmosphere is much weaker. The weak feedback is attributed to downstream of the anomalous atmospheric circulations associated with the SAFZ, which results in the weak air-sea humidity difference and wind speed.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 6
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    Ionospheric scintillation effects on Multi-frequency BDS Signals over the Brazilian region (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-07-19
    Description: Ionospheric scintillation adversely degrades the accuracy and reliability of satellite operation, communications, and navigation. At present, extensive ionospheric surveys and climatological statistics addressing GNSS scintillation have been conducted using mainly global positioning system (GPS) observations. Nevertheless, the current investigation about ionospheric scintillation in terms of the signals from the newly-developed BeiDou navigation satellite system (BDS) is limited, especially its multifrequency signals, which have significantly affected the BDS high-precision ionospheric research and applications. In this report, we focus on investigating the effects of ionospheric scintillation on multi-frequency BDS signals based on ionospheric scintillation monitor receivers (ISMR) data at different geomagnetic latitudes in the Brazilian territory. The result illustrates that the S4(B2) and S4(B3) linearly increase with S4(B1) for S4(B1)≤0.6, which is consistent with weak scattering theories. Meanwhile, the probability of the ionospheric scintillation events on B2 and B3 signals is approximately twice (S4≥0.7) as B1 signals in the equatorial ionization anomaly (EIA) regions. Additionally, we evaluated the inter-frequency relationship of two scintillation spectral characteristic parameters among three BDS frequencies (the strength at 1 Hz T and slope p) widely applied in GNSS positioning solutions. In terms of p and T, the performances among B1, B2, and B3 frequencies have a higher correlation respectively, and their values for B2 and B3 signals are more susceptible to be impacted by ionospheric scintillation. It is expected that the inter-frequency relation of these scintillation parameters among the BDS signals could support the robustness of GNSS receiver design and subsequent high-precision positioning applications under ionospheric scintillation conditions.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 7
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    Precise prediction of LEO satellite orbital atmospheric mass density based on deep learning (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-05-22
    Description: In recent years, the construction and development of Low-Earth-Orbit (LEO) satellites have received more and more attention. Therefore, the space weather conditions of the LEO operation area have also become a research hotspot. The accurate prediction of the thermosphere atmospheric mass density, especially the density at the satellite orbit, is very important for the safe operation of the satellite. However, the short-term prediction of atmospheric density, especially in special environments such as storms, is still a challenge. This paper proposes a novel deep-learning model for real-time satellite orbital atmospheric mass density prediction based on the Gated Recurrent Unit (GRU). In the model training and prediction phase, the atmospheric mass densities retrieved based on precise orbit determination (POD), satellite position information, and solar activity data are used as input parameters. The performance of the proposed model has been comprehensively verified under different satellites, datasets, orbital heights, and environmental conditions. The experiment shows that the influence of storms on the atmospheric mass density of the thermosphere is obvious. Meanwhile, the results show that the proposed model is robust under different environmental conditions for the different satellite datasets. Under extreme conditions such as magnetic storms, the proposed model has at least a 77.1% improvement compared with the empirical model NRLMSISE-00.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 8
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    Investigating GNSS PPP–RTK with external ionospheric constraints (2022)
    In:  Satellite Navigation
    Details
    Publication Date: 2023-02-01
    Description: Real-Time Kinematic Precise Point Positioning (PPP–RTK) is inextricably linked to external ionospheric information. The PPP–RTK performances vary much with the accuracy of ionospheric information, which is derived from different network scales, given different prior variances, and obtained under different disturbed ionospheric conditions. This study investigates the relationships between the PPP–RTK performances, in terms of precision and convergence time, and the accuracy of external ionospheric information. The statistical results show that The Time to First Fix (TTFF) for the PPP–RTK constrained by Global Ionosphere Map (PPP–RTK-GIM) is about 8–10 min, improved by 20%–50% as compared with that for PPP Ambiguity Resolution (PPP-AR) whose TTFF is about 13–16 min. Additionally, the TTFF of PPP–RTK is 4.4 min, 5.2 min, and 6.8 min, respectively, when constrained by the external ionospheric information derived from different network scales, e.g. small-, medium-, and large-scale networks, respectively. To analyze the influences of the optimal prior variances of external ionospheric delay on the PPP–RTK results, the errors of 0.5 Total Electron Content Unit (TECU), 1 TECU, 3 TECU, and 5 TECU are added to the initial ionospheric delays, respectively. The corresponding convergence time of PPP–RTK is less than 1 min, about 3, 5, and 6 min, respectively. After adding the errors, the ionospheric information with a small variance leads to a long convergence time and that with a larger variance leads to the same convergence time as that of PPP-AR. Only when an optimal prior variance is determined for the ionospheric delay in PPP–RTK model, the convergence time for PPP–RTK can be shorten greatly. The impact of Travelling Ionospheric Disturbance (TID) on the PPP–RTK performances is further studied with simulation. It is found that the TIDs increase the errors of ionospheric corrections, thus affecting the convergence time, positioning accuracy, and reliability of PPP–RTK.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 9
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    Combination of GNSS and LEO satellites for large-scale traveling ionospheric disturbance detections (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-09-06
    Description: Large-scale traveling ionospheric disturbances (LSTIDs) are wave-like ionospheric manifestations of atmospheric gravity waves. Their harmonic signatures of quasi-periodic structures allow them to be detected by different instruments, among which ground-based GNSS receivers play a key role in TID detections. However, it is a challenging problem for ground-based GNSS measurements to interpret the vertical propagation features of LSTIDs at various altitudes as well as the global propagating characteristics of LSTIDs, especially across the ocean and polar areas. The global morphology of LSTID during the St. Patrick's Day geomagnetic storm on March 17, 2015, was thoroughly investigated in this study using GNSS observations from both ground-based and space-borne GNSS receivers as well as the space-borne in-situ data. The 2-D ground-based detrended total electron content (TEC) maps created by thousands of GNSS stations throughout the world were used to identify the remarkable global LSTID wave-like characteristics. In places with limited ground-based GNSS data, such as the polar regions and over oceans, additional space-borne TEC data and in-situ data were also employed to find TID signals. These data are ideal supplements to ground-based GNSS data for global LSTID detections. Space-borne TEC data and in-situ data might be used to find topside TIDs propagating at various altitudes, supporting both the horizontal and vertical detections of LSTIDs during the storm time.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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