GNSS-based water vapor estimation and validation during the MOSAiC expedition

Within the transpolar drifting expedition MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate), the Global Navigation Satellite System (GNSS) was used among other techniques to monitor variations in atmospheric water vapor. Based on 15 months of continuously tracked GNSS data including GPS, GLONASS and Galileo, epoch-wise coordinates and hourly zenith total delays (ZTDs) were determined using a kinematic precise point positioning (PPP) approach. The derived ZTD values agree to 1.1 ± 0.2 mm (root mean square (rms) of the differences 10.2 mm) with the numerical weather data of ECMWF's latest reanalysis, ERA5, computed for the derived ship's locations. This level of agreement is also confirmed by comparing the on-board estimates with ZTDs derived for terrestrial GNSS stations in Bremerhaven and Ny-Ålesund and for the radio telescopes observing very long baseline interferometry in Ny-Ålesund. Preliminary estimates of integrated water vapor derived from frequently launched radiosondes are used to assess the GNSS-derived integrated water vapor estimates. The overall difference of 0.08 ± 0.04 kg m−2 (rms of the differences 1.47 kg m−2) demonstrates a good agreement between GNSS and radiosonde data. Finally, the water vapor variations associated with two warm-air intrusion events in April 2020 are assessed

GNSS transpolar earth reflectometry exploriNg system (G-TERN): Mission concept

The global navigation satellite system (GNSS) Transpolar Earth Reflectometry exploriNg system (G-TERN) was proposed in response to ESA's Earth Explorer 9 revised call by a team of 33 multi-disciplinary scientists. The primary objective of the mission is to quantify at high spatio-temporal resolution crucial characteristics, processes and interactions between sea ice, and other Earth system components in order to advance the understanding and prediction of climate change and its impacts on the environment and society. The objective is articulated through three key questions. 1) In a rapidly changing Arctic regime and under the resilient Antarctic sea ice trend, how will highly dynamic forcings and couplings between the various components of the ocean, atmosphere, and cryosphere modify or influence the processes governing the characteristics of the sea ice cover (ice production, growth, deformation, and melt)? 2) What are the impacts of extreme events and feedback mechanisms on sea ice evolution? 3) What are the effects of the cryosphere behaviors, either rapidly changing or resiliently stable, on the global oceanic and atmospheric circulation and mid-latitude extreme events? To contribute answering these questions, G-TERN will measure key parameters of the sea ice, the oceans, and the atmosphere with frequent and dense coverage over polar areas, becoming a "dynamic mapper" of the ice conditions, the ice production, and the loss in multiple time and space scales, and surrounding environment. Over polar areas, the G-TERN will measure sea ice surface elevation (<10 cm precision), roughness, and polarimetry aspects at 30-km resolution and 3-days full coverage. G-TERN will implement the interferometric GNSS reflectometry concept, from a single satellite in near-polar orbit with capability for 12 simultaneous observations. Unlike currently orbiting GNSS reflectometry missions, the G-TERN uses the full GNSS available bandwidth to improve its ranging measurements. The lifetime would be 2025-2030 or optimally 2025-2035, covering key stages of the transition toward a nearly ice-free Arctic Ocean in summer. This paper describes the mission objectives, it reviews its measurement techniques, summarizes the suggested implementation, and finally, it estimates the expected performance

Airborne lipid antigens mobilize resident intravascular NKT cells to induce allergic airway inflammation

Resident intravascular NKT cells exacerbate airway hyperreactivity in mice dependent on dendritic cell co-presentation of glycolipid and peptide antigens

Inflammatory chemokine receptors regulate CD8+ T cell contraction and memory generation following infection

CD8+ T cells lacking CXCR3 and CCR5 expression have impaired contraction and generate an increased number of memory cells after virus infection

Exploiting the Role of Endogenous Lymphoid-Resident Dendritic Cells in the Priming of NKT Cells and CD8+ T Cells to Dendritic Cell-Based Vaccines

Transfer of antigen between antigen-presenting cells (APCs) is potentially a physiologically relevant mechanism to spread antigen to cells with specialized stimulatory functions. Here we show that specific CD8+ T cell responses induced in response to intravenous administration of antigen-loaded bone marrow-derived dendritic cells (BM-DCs), were ablated in mice selectively depleted of endogenous lymphoid-resident langerin+ CD8α+ dendritic cells (DCs), suggesting that the antigen is transferred from the injected cells to resident APCs. In contrast, antigen-specific CD4+ T cells were primed predominantly by the injected BM-DCs, with only very weak contribution of resident APCs. Crucially, resident langerin+ CD8α+ DCs only contributed to the priming of CD8+ T cells in the presence of maturation stimuli such as intravenous injection of TLR ligands, or by loading the BM-DCs with the glycolipid α-galactosylceramide (α-GalCer) to recruit the adjuvant activity of activated invariant natural killer-like T (iNKT) cells. In fact, injection of α-GalCer-loaded CD1d−/− BM-DCs resulted in potent iNKT cell activation, suggesting that this glycolipid antigen can also be transferred to resident CD1d+ APCs. While iNKT cell activation per se was independent of langerin+ CD8α+ DCs, some iNKT cell-mediated activities were reduced, notably release of IL-12p70 and transactivation of NK cells. We conclude that both protein and glycolipid antigens can be exchanged between distinct DC species. These data suggest that the efficacy of DC-based vaccination strategies may be improved by the incorporation of a systemic maturation signal aimed to engage resident APCs in CD8+ T cell priming, and α-GalCer may be particularly well suited to this purpose

Modelling the impact of atherosclerosis on drug release and distribution from coronary stents

Although drug-eluting stents (DES) are now widely used for the treatment of coronary heart disease, there remains considerable scope for the development of enhanced designs which address some of the limitations of existing devices. The drug release profile is a key element governing the overall performance of DES. The use of in vitro, in vivo, ex vivo, in silico and mathematical models has enhanced understanding of the factors which govern drug uptake and distribution from DES. Such work has identified the physical phenomena determining the transport of drug from the stent and through tissue, and has highlighted the importance of stent coatings and drug physical properties to this process. However, there is limited information regarding the precise role that the atherosclerotic lesion has in determining the uptake and distribution of drug. In this review, we start by discussing the various models that have been used in this research area, highlighting the different types of information they can provide. We then go on to describe more recent methods that incorporate the impact of atherosclerotic lesions

Role of the Chemokine Receptors CCR1, CCR2 and CCR4 in the Pathogenesis of Experimental Dengue Infection in Mice

Dengue virus (DENV), a mosquito-borne flavivirus, is a public health problem in many tropical countries. Recent clinical data have shown an association between levels of different chemokines in plasma and severity of dengue. We evaluated the role of CC chemokine receptors CCR1, CCR2 and CCR4 in an experimental model of DENV-2 infection in mice. Infection of mice induced evident clinical disease and tissue damage, including thrombocytopenia, hemoconcentration, lymphopenia, increased levels of transaminases and pro-inflammatory cytokines, and lethality in WT mice. Importantly, infected WT mice presented increased levels of chemokines CCL2/JE, CCL3/MIP-1α and CCL5/RANTES in spleen and liver. CCR1-/- mice had a mild phenotype with disease presentation and lethality similar to those of WT mice. In CCR2-/- mice, lethality, liver damage, levels of IL-6 and IFN-γ, and leukocyte activation were attenuated. However, thrombocytopenia, hemoconcentration and systemic TNF-α levels were similar to infected WT mice. Infection enhanced levels of CCL17/TARC, a CCR4 ligand. In CCR4-/- mice, lethality, tissue injury and systemic inflammation were markedly decreased. Despite differences in disease presentation in CCR-deficient mice, there was no significant difference in viral load. In conclusion, activation of chemokine receptors has discrete roles in the pathogenesis of dengue infection. These studies suggest that the chemokine storm that follows severe primary dengue infection associates mostly to development of disease rather than protection

Surface reflectivity in polar regions retrieved from TDS-1 mission data

Comunicación expuesta online en el 23rd EGU General Assembly (2021) el 26 de abrilIn current times of a changing global climate, a special interest is focused on thelarge-scale recording of sea ice. Among the existing remote sensing methods, bi-statically reflected signals of Global Navigation Satellite Systems (GNSS) couldplay an important role in fulfilling the task. Within this project, sensitivity ofGNSS signal reflections to sea ice properties like its occurrence, sea ice thick-ness (SIT) and sea concentration (SIC) is evaluated. When getting older, seaice tends go get thicker. Because of decreasing salinity, i.e. less permittivity,as well as relatively higher surface roughness of older ice, it can be assumedthat reflected signal strength decreases with increasing SIT. The reflection dataused were recorded in the years 2015 and 2016 by the TechDemoSat-1 (TDS-1)satellite over the Arctic and Antarctic. It includes a down-looking antenna forthe reflected as well as an up-looking antenna dedicated to receive the direct sig-nal. The raw data, provided by the manufacturer SSTL, were pre-processed byIEEC/ICE-CSIC to derive georeferenced signal power values. The reflectivitywas estimated by comparing the power of the up- and down-looking links. Theproject focuses on the signal link budget to apply necessary corrections. For thisreason, the receiver antenna gain as well as the Free-Space Path Loss (FSPL)were calculated and applied for reflectivity correction. Differences of nadir andzenith antenna FSPL and gain show influence of up to 6 dB and ‑9 dB to 9 dBrespectively on the recorded signal strength. All retrieved reflectivity values arecompared to model predictions based on Fresnel coefficients but also to avail-able ancillary truth data of other remote sensing missions to identify possiblepatterns: SIT relations are investigated using Level-2 data of the Soil Moistureand Ocean Salinity (SMOS) satellite. The SIC comparison was done with anAMSR-2 product. The results show sensitivity of the reflectivity value to bothSIT and SIC simultaneously, whereby the surface roughness is also likely tohave an influence. This on-going study aims at the consolidation of retrievalalgorithms for sea-ice observation. The resolution of different ice types and theretrieval of SIT and SIC based on satellite data is a challenge for future workin this respect

A zeppelin experiment to study airborne altimetry using specular Global Navigation Satellite System reflections

This paper describes an altimetric method based on data recorded during experimental zeppelin flights over Lake Constance. Interferometric observations for this method are obtained using a Master-Slave receiver configuration. These observations contain the relative phasing of direct and reflected signals and are used for altimetry. Separated antennas are attached to the receiver to record direct and reflected signals at slant elevation angles. Filtering is required to remove direct contributions in this slant geometry. Filtered observations are corrected using an altimetric model, and thus Doppler residuals are retrieved. This correction reduces the width of the spectral reflection peak from 3 mHz to less than 10 mHz. Doppler residuals are sensitive to surface height. Lake level is estimated inversely for the residuals at different trial heights. A case study of reflection events is presented. Lake level is estimated using data from antennas with right-handed and left-handed circular polarization. Reference level is determined from tide gauge data for stations around the lake. Mean deviation of estimates from reference level is 50 cm. Doppler shifts of different model corrections are compared. The altimetric correction is the most important, with mean Doppler shifts between 316 and 560 mHz. Mean Doppler shifts are much smaller for baseline correction (less than 0.2 mHz) and water-vapor correction (0.1–1.0 mHz). In addition, the geoid undulation effect (up to 25 cm amplitude) is predicted with mean Doppler shifts between 0.1 and 0.9 mHz. Precision of Doppler residuals (0.5–0.6 mHz) is insufficient to resolve the geoid undulation effect. The resolution from phase residuals is better. The effect of geoid undulation, however, is not dominant in phase residuals