22 research outputs found
Signal Obstructions at GNSS Stations: Benefits From Multi-GNSS Observations
The current accuracy of IGS products, few centimeter level, requires amongst other things that the location for GNSS antennas are nearly optimal for GNSS observations. This includes a low multipath environment and little to no signal obstructions. However, this is not guaranteed for every station especially in urban areas and mountainous regions. As some applications such as GNSS for sea level studies or to monitor landslides require GNSS antennas to be installed at a specific site, it is clear that the environment might not be favourable for GNSS observations. In this study, we investigate the effect of signal obstructions on station positions, specifically the height component, based on simulated obstruction scenarios using a modified Bernese GNSS Software version 5.2 (BSW52). The behaviours of different obstruction scenarios and the impact of multi-GNSS (GPS+GLONASS for now) observations for both clear and obstructed stations are discussed
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Staphylococcus aureus small colony variants impair host immunity by activating host cell glycolysis and inducing necroptosis
Staphylococcus aureus small colony variants (SCVs) are frequently associated with chronic infection, yet they lack expression of many virulence determinants associated with the pathogenicity of wild-type strains. We found that both wild-type S. aureus and a ΔhemB SCV prototype potently activate glycolysis in host cells. Glycolysis and the generation of mitochondrial reactive oxygen species were sufficient to induce necroptosis, a caspase-independent mechanism of host cell death that failed to eradicate S. aureus and instead promoted ΔhemB SCV pathogenicity. To support ongoing glycolytic activity, the ΔhemB SCV induced over a 100-fold increase in the expression of fumC, which encodes an enzyme that catalyses the degradatin of fumarate, an inhibitor of glycolysis. Consistent with fumC-dependent depletion of local fumarate, the ΔhemB SCV failed to elicit trained immunity and protection from a secondary infectious challenge in the skin. The reliance of the S. aureus SCV population on glycolysis accounts for much of its role in the pathogenesis of S. aureus skin infection
GENESIS: Co-location of Geodetic Techniques in Space
Improving and homogenizing time and space reference systems on Earth and,
more directly, realizing the Terrestrial Reference Frame (TRF) with an accuracy
of 1mm and a long-term stability of 0.1mm/year are relevant for many scientific
and societal endeavors. The knowledge of the TRF is fundamental for Earth and
navigation sciences. For instance, quantifying sea level change strongly
depends on an accurate determination of the geocenter motion but also of the
positions of continental and island reference stations, as well as the ground
stations of tracking networks. Also, numerous applications in geophysics
require absolute millimeter precision from the reference frame, as for example
monitoring tectonic motion or crustal deformation for predicting natural
hazards. The TRF accuracy to be achieved represents the consensus of various
authorities which has enunciated geodesy requirements for Earth sciences.
Today we are still far from these ambitious accuracy and stability goals for
the realization of the TRF. However, a combination and co-location of all four
space geodetic techniques on one satellite platform can significantly
contribute to achieving these goals. This is the purpose of the GENESIS
mission, proposed as a component of the FutureNAV program of the European Space
Agency. The GENESIS platform will be a dynamic space geodetic observatory
carrying all the geodetic instruments referenced to one another through
carefully calibrated space ties. The co-location of the techniques in space
will solve the inconsistencies and biases between the different geodetic
techniques in order to reach the TRF accuracy and stability goals endorsed by
the various international authorities and the scientific community. The purpose
of this white paper is to review the state-of-the-art and explain the benefits
of the GENESIS mission in Earth sciences, navigation sciences and metrology.Comment: 31 pages, 9 figures, submitted to Earth, Planets and Space (EPS
Der Wert gemeinsamer Visionen für eine klimaneutrale Gesellschaft
Konkrete Visionen einer wünschenswerten Zukunft helfen uns, von einer Problemfokussierung hin zu einer Lösungsorientierung zu wechseln. Werden Visionen gemeinsam erarbeitet, können sie als Kompass für gemeinsame Entwicklungs- und Transformationsprozesse dienen. Wir stellen in diesem Beitrag ein Beispiel aus dem Berner Oberland vor
Effect of unmodelled tidal displacements in GPS and GLONASS coordinate time series
This study demonstrates the different effects of unmodelled (sub-)daily tidal displacement in
Global Positioning System (GPS) and GLObalnaya NAvigatsionnaya Sputnikovaya Sistema
(GLONASS) coordinate time-series. The results show that more than two propagated periodic
signals appear in GPS and GLONASS Precise Point Positioning (PPP) coordinate time-series
in the presence of an unmodelled M2 /O1 tidal displacements as a result of a non-overlapping
24-hr data sampling. To summarize the propagated periodic signals at the fortnightly period,
an unmodelled M2 tidal displacement propagates predominately into two long-period signals
at 13.6x (x is a positive integer) and 14.76 d for GPS, while only one significant propagated
periodic signal at 14.76 d is discernible for GLONASS. Similarly, significant propagated
periodic signals at 13.6x and 14.19 d for GPS and only at 14.19 d for GLONASS are evident
as a result of an unmodelled O1 tidal displacement. However, an unmodelled M f (long-
period) signal results in a strong power of similar magnitude at 13.6x d (∼13.66 d) for both
GPS and GLONASS solutions. The appearance of different periodic signals as a result of
the same unmodelled tidal displacement is attributed to the different ground repeat periods
of the constellations. The latter is likely to explain the reason why the 13.6x-d fortnightly
signal is present only in GPS solutions. Comparing the powers of the M2 propagated periodic
signals at 13.6x and 14.76 d on average from 32 globally distributed stations, the amplitude
of the former is larger than for the latter by an order of magnitude. The results of this
study demonstrate that the 13.6x-d periodic signal in GPS/GNSS (Global Navigation Satellite
System) derived products is a joint contribution of the propagation of unmodelled (sub-)daily
tidal displacements and errors at longer periods with the former appearing to contribute more.
Significant reduction of the propagated periodic signals is achieved from combined-system
solutions where including Galileo (the European GNSS) to the combined solution already
shows benefits by reducing the effect even before the system has reached its full constellation.
Combined GNSS solutions will benefit the applications of GNSS time-series for retrieving
tidal harmonic signals such as Mf as they reduce constellation specific propagation effects