Monitoreo de la calidad de datos GPS continuo: la Estación UNSJ (San Juan, Argentina)

Como parte de la red de referencia de operación continua de Argentina, la estación GPS (Global Positioning System) denominada UNSJ (Universidad Nacional de San Juan) fue establecida en la ciudad de San Juan el 6 de Marzo de 2007. Los datos registrados de UNSJ son ampliamente utilizados en aplicaciones catastrales, y sirven como base para la definición de los marcos de referencia geodésicos nacional y regional. Como una componente fundamental de la infraestructura geodésica, resulta conveniente un eficiente control de calidad de los datos crudos y el monitoreo de la estabilidad de una estación GPS de referencia. En este trabajo se presentan los resultados del control de calidad de las observaciones UNSJ luego de dos años de operación. Para controjar y caracterizar el desempeño del receptor GPS y además el medio ambiente de la estación, se eligieron cuatro índices. Ellos son el número de observaciones, multicamino en Ll, multicamino en L2 y ocurrencia de saltos de ciclos. También, se evaluó la estabilidad de largo término de la estación UNSJ a través del análisis de las series temporales de las coordenadas semanales provistas por los centros de cálculo SIRGAS (Sistema de Referencia Geocéntrico para las Américas). Completa este estudio el análisis de las coordenadas calculadas por distintos servicios de procesamiento disponibles en Internet. Nuestros resultados indican que durante el período analizado, el funcionamiento de la estación UNSJ fue satisfactorio, produciendo índices de calidad que son aceptables para estándares internacionales.As a part of the Argentine continuously operating reference station network, a GPS (Global Positioning System) station named UNSJ (Universidad Nacional de San Juan) was established in San Juan city on 6th March 2007. The recorded data of UNSJ are widely applied to cadastral surveys and serve as the basis for defining national and regional geodetic reference frames. As a key component of the geodetic infrastructure, an efficient quality control of raw data and stability monitoring of a GPS reference station is highly convenient. In this study, results of quality control of the UNSJ observations after two year of operation are reported. In order to check and characterize the receiver performance and the station environment, four indices were chosen. They are the number of observations, multipath on Ll, multipath on L2 and cycle slips occurrence. Also, the long term stability of UNSJ station was evaluated through the analysis of weekly coordinate time series provided by the SIRGAS (Geocentric Reference System for the Americas) calculus centers. The analysis of the coordinates derived from different online processing services completes this study. The results indicate that during the analyzed period, the functioning of the station UNSJ was satisfactory, producing qualit indexes that are acceptable to international standards.Asociación Argentina de Geofísicos y Geodesta

The 2010 Maule, Chile earthquake: Downdip rupture limit revealed by space geodesy

Radar interferometry from the ALOS satellite captured the coseismic ground deformation associated with the 2010 Mw 8.8 Maule, Chile earthquake. The ALOS interferograms reveal a sharp transition in fringe pattern at ~150 km from the trench axis that is diagnostic of the downdip rupture limit of the Maule earthquake. An elastic dislocation model based on ascending and descending ALOS interferograms and 13 near-field 3-component GPS measurements reveals that the coseismic slip decreases more or less linearly from a maximum of 17 m (along-strike average of 6.5 m) at 18 km depth to near zero at 43–48 km depth, quantitatively indicating the downdip limit of the seismogenic zone. The depth at which slip drops to near zero appears to be at the intersection of the subducting plate with the continental Moho. Our model also suggests that the depth where coseismic slip vanishes is nearly uniform along the strike direction for a rupture length of ~600 km. The average coseismic slip vector and the interseismic velocity vector are not parallel, which can be interpreted as a deficit in strike-slip moment release

Vertical land movements and sea level changes on South Georgia, South Atlantic Ocean: Results from 7 years of geodetic and oceanographic observations on a remote island

South Georgia Island in the South Atlantic Ocean, is a small remote land mass that supports various ground-based instrumental observations (Global Navigation Satellite System (GNSS), tide gauge, meteorological and seismic) in an otherwise largely under sampled oceanic region. Moreover, the South Atlantic Ocean plays an important role in global ocean circulation, con-necting the deep thermohaline circulation of the North Atlantic and Indian Oceans, whilst also linking to the Antarctic Circumpolar Current in the South, where the lack of continental barriers allows a free exchange of water between the major ocean basins. Hence, South Georgia po-tentially lies within a region susceptible to climatic changes before these can be felt further afield. In 2013 and 2014 a total of five GNSS stations were installed covering the area of the main island (approximately 170 x 50 km) with two of those being located close to the King Edward Point (KEP) Research Station and the GLOSS tide gauge (ID 187). Furthermore, precise levelling campaigns in 2013, 2014, 2017 and 2020 supported the analysis of local ground instabilities near the tide gauge. Through these activities the tide gauge datum within the Permanent Ser-vice for Mean Sea Level (PSMSL) has been established, which in turn, makes the derived KEP mean sea level (MSL) record highly valuable for long-term studies and satellite altimetry cali-brations. In this study, we will present the vertical land movement estimates from seven years of GNSS observations, five precise levelling campaigns, and will discuss their impact on the sea level record from the KEP tide gauge and nearby satellite altimetry sea surface heights. Our results confirm uplift all over South Georgia Island while the area at KEP and particularly the jetty with tide gauge are subsiding relative to the rest of the island. Using this information we correct the MSL record for the vertical land movements and investigate its signals together with those from nearby satellite altimetry tracks

Teosinte Inflorescence Phytolith Assemblages Mirror Zea Taxonomy

Molecular DNA analyses of the New World grass (Poaceae) genus Zea, comprising five species, has resolved taxonomic issues including the most likely teosinte progenitor (Zea mays ssp. parviglumis) of maize (Zea mays ssp. mays). However, archaeologically, little is known about the use of teosinte by humans both prior to and after the domestication of maize. One potential line of evidence to explore these relationships is opaline phytoliths produced in teosinte fruit cases. Here we use multidimensional scaling and multiple discriminant analyses to determine if rondel phytolith assemblages from teosinte fruitcases reflect teosinte taxonomy. Our results indicate that rondel phytolith assemblages from the various taxa, including subspecies, can be statistically discriminated. This indicates that it will be possible to investigate the archaeological histories of teosinte use pending the recovery of appropriate samples

Adenoma Formation following Limited Ablation of p120-Catenin in the Mouse Intestine

p120 loss destabilizes E-cadherin and could therefore result in tumor and/or metastasis-promoting activities similar to those caused by E-cadherin downregulation. Previously, we reported that p120 is essential in the intestine for barrier function, epithelial homeostasis and survival. Conditional p120 ablation in the mouse intestine induced severe inflammatory bowel disease, but long-term cancer-related studies were impossible because none of the animals survived longer than 21 days. Here, we used a tamoxifen-inducible mouse model (Vil-Cre-ERT2;p120fl/fl) to limit the extent of p120 ablation and thereby enable long-term studies. Reducing p120 KO to ∼10% of the intestinal epithelium produced long-lived animals outwardly indistinguishable from controls. Effects of prolonged p120 absence were then evaluated at intervals spanning 2 to 18 months. At all time points, immunostaining revealed microdomains of p120-null epithelium interspersed with normal epithelium. Thus, stochastic p120 ablation is compatible with crypt progenitor cell function and permitted lifelong renewal of the p120-null cells. Consistent with previous observations, a barrier defect and frequent infiltration of neutrophils was observed, suggesting that focal p120 loss generates a microenvironment disposed to chronic inflammation. We report that 45% of these animals developed tumors within 18 months of tamoxifen induction. Interestingly, β-catenin was upregulated in the majority, but none of the tumors were p120 null. Although further work is required to directly establish mechanism, we conclude that limited p120 ablation can promote tumorigenesis by an indirect non-cell autonomous mechanism. Given that byproducts of inflammation are known to be highly mutagenic, we suggest that tumorigenesis in this model is ultimately driven by the lifelong inability to heal chronic wounds and the substantially increased rates of stochastic gene mutation in tissue microenvironments subjected to chronic inflammation. Indeed, although technical issues precluded direct identification of mutations, β-catenin upregulation in human colon cancer almost invariably reflects mutations in APC and/or β-catenin

Emerging Roles of PAR-1 and PAFR in Melanoma Metastasis

Melanoma growth, angiogenesis and metastatic progression are strongly promoted by the inflammatory tumor microenvironment due to high levels of cytokine and chemokine secretion by the recruited inflammatory and stromal cells. In addition, platelets and molecular components of procoagulant pathways have been recently emerging as critical players of tumor growth and metastasis. In particular, thrombin, through the activity of its receptor protease-activated receptor-1 (PAR-1), regulates tumor cell adhesion to platelets and endothelial cells, stimulates tumor angiogenesis, and promotes tumor growth and metastasis. Notably, in many tumor types including melanoma, PAR-1 expression directly correlates with their metastatic phenotype and is directly responsible for the expression of interleukin-8, matrix metalloproteinase-2 (MMP-2), vascular endothelial growth factor, platelet-derived growth factor, and integrins. Another proinflammatory receptor–ligand pair, platelet-activating factor (PAF) and its receptor (PAFR), have been shown to act as important modulators of tumor cell adhesion to endothelial cells, angiogenesis, tumor growth and metastasis. PAF is a bioactive lipid produced by a variety of cells from membrane glycerophospholipids in the same reaction that releases arachidonic acid, and can be secreted by platelets, inflammatory cells, keratinocytes and endothelial cells. We have demonstrated that in metastatic melanoma cells, PAF stimulates the phosphorylation of cyclic adenosine monophosphate response element-binding protein (CREB) and activating transcription factor 1 (ATF-1), which results in overexpression of MMP-2 and membrane type 1-MMP (membrane type 1-MMP). Since only metastatic melanoma cells overexpress CREB/ATF-1, we propose that metastatic melanoma cells are better equipped than their non-metastatic counterparts to respond to PAF within the tumor microenvironment. The evidence supporting the hypothesis that the two G-protein coupled receptors, PAR-1 and PAFR, contribute to the acquisition of the metastatic phenotype of melanoma is presented and discussed

Membrane vesicles, current state-of-the-art: emerging role of extracellular vesicles

Release of membrane vesicles, a process conserved in both prokaryotes and eukaryotes, represents an evolutionary link, and suggests essential functions of a dynamic extracellular vesicular compartment (including exosomes, microparticles or microvesicles and apoptotic bodies). Compelling evidence supports the significance of this compartment in a broad range of physiological and pathological processes. However, classification of membrane vesicles, protocols of their isolation and detection, molecular details of vesicular release, clearance and biological functions are still under intense investigation. Here, we give a comprehensive overview of extracellular vesicles. After discussing the technical pitfalls and potential artifacts of the rapidly emerging field, we compare results from meta-analyses of published proteomic studies on membrane vesicles. We also summarize clinical implications of membrane vesicles. Lessons from this compartment challenge current paradigms concerning the mechanisms of intercellular communication and immune regulation. Furthermore, its clinical implementation may open new perspectives in translational medicine both in diagnostics and therapy

Seasonal fluctuations in the mass of the Amazon River system and Earth’s elastic response

[1] A GPS station in Manaus, near the center of the Amazon basin, manifests an annual cycle of vertical displacement with a peak-to-peak amplitude of 50-75 mm. This is by far the largest crustal oscillation observed to date, and nearly 2 -3 times larger than the amplitude predicted for this region. Vertical ground displacement is strongly anticorrelated with the local stage height of the Amazon river, with no detectable time lag between the two time series. This suggests that we are observing, for the first time, a purely elastic response to changes in the weight of a flowing river system. We use a simple hydrological model to relate stage height to the regional pattern of flooding, and argue that the elastic oscillations observed in Manaus are dominated by changes in water loading developed within $200 km of the GPS station. Citation

Consolidating Observation of Land and Sea Level Changes around South Georgia Island

With its mid-ocean location in the Southern Atlantic Ocean South Georgia Island is in a key position for the oceanic and geodetic global monitoring networks. Since 2013 the tide gauge at King Edward Point (KEP) with GLOSS ID 187 has been monitored using a GNSS station nearby on Brown Mountain. By accurately geo-referencing the tide gauge and monitoring any vertical land movements, a continuous record of its datum within the Permanent Service for Mean Sea Level (PSMSL) can be established, which in turn makes the recorded and averaged sea levels useful for long-term studies and satellite altimetry calibrations. In 2014 another GNSS station was installed at KEP after local subsidence was sus-pected and later on three additional GNSS stations came to service at the periphery of the main island, making it possible to monitor uplift/subsidence wider afield. Further-more, together with four precise levelling campaigns of the KEP benchmark network in 2013, 2014 and two in 2017, it has also been possible to investigate the very local character of the vertical motions near KEP, i.e. the stability of the jetty upon which the tide gauge is mounted. In this study, we will present the results from the GNSS and precise levelling meas-urements, and will discuss their impact on the sea level record from the KEP tide gauge and nearby satellite altimetry sea surface heights. This study comes at a timely manner as during the Austral Summer 2019/2020 the jetty will be stabilized and en-larged, and consequently the current tide gauge will be replaced by a new one. Our measurements show that uplift is observed all over South Georgia Island while the ar-ea at KEP and particularly the jetty with tide gauge are subsiding relative to the rest of the island. In contrast, results for the tide gauge record show a lower magnitude of ob-served sea level rise than expected from nearby satellite altimetry. We will revisit all geodetic and oceanic observations in an attempt to improve the agreement between these measurements to summarize the status before the work at the jetty begins

Present-Day Land and Sea Level Changes around South Georgia Island: Results from Precise Levelling, GNSS, Tide Gauge and Satellite Altimetry Measurements

South Georgia Island, the main land outcrop on the South Georgia microcontinent (SGM), is located approximately 1,400 km east of the Falkland Islands and approximately 1,400 km northeast of the northernmost tip of the Antarctic peninsular. The SGM is believed to lie south of the North Scotia Ridge (NSR), which forms the boundary to the South America Plate, while to the south it is bordered by the Scotia Plate (SP). In its sub-Antarctic location, the island is largely covered by mountain glaciers which have been reported to be retreating due to climatic change. Furthermore, during past glaciation periods the island and its shelf area, stretching much of the SGM, have been ice covered as was revealed by scarring of the sub-oceanic topography. Together with ongoing tectonics along the NSR and recent seismicity at the SP boundary, these processes have the ability to produce significant uplift on local to regional scales. With its mid-ocean location in the Southern Atlantic Ocean South Georgia Island is in a key position for the oceanic and geodetic global monitoring networks. As these net-works suffer from a Hemisphere imbalance with the number of stations in the Northern Hemisphere outnumbering those in the Southern Hemisphere, operating these stations to the highest standards is of key scientific value. It is of particular interest to monitor the tide gauge (GLOSS ID 187) at King Edward Point (KEP) for vertical land movements to establish a continuous record of its datum within the Permanent Service for Mean Sea Level (PSMSL), which in turn makes it useful for long-term sea level studies and satellite altimetry calibrations. With the establishment of five GNSS stations on the islands by teams from Luxembourg, the UK and the USA during 2013 to 2015, and the scientific analysis of these data within a global network of stations, it has now become possible to study present-day vertical land movements and their impacts. Furthermore, together with four precise levelling campaigns of the KEP benchmark network in 2013, 2014 and two in 2017, it has also been possible to investigate the very local character of the vertical motions near KEP, i.e. the stability of the jetty upon which the tide gauge is mounted. In this study, we will present the still preliminary results from the GNSS and levelling measurements and will discuss their impact on the sea level record from the KEP tide gauge. Our measurements show that while South Georgia Island and the area around KEP are rising, the jetty and tide gauge are subsiding, leading to a lower magnitude of the observed sea level change than expected from satellite altimetry. In order to improve the agreement between these measurements both local and regional vertical land movements need to be monitored