High-Performance Dual Raman Spectrometer

12 pages, 16 figures.The transformation of an old Raman double monochromator into a dual spectrometer capable of working either as the origin al instrument or as a very high sensitivity scanning single monochromator with multichannel charge-coupled device (CCD) array detection is described. The merits and limitations of this instrument, particularly suited for medium/low resolu tion (0.3 to 2 cm2 1) Raman spectroscopy in the gas phase, are discussed. Example spectra of O2, N2, CO2, H2O, and CCl4 are shown.The Dirección General de Investigación Científica y Técnica (DGICYT), of Spain, is acknowledged for financial support (Research Project PB91-0133).Peer reviewe

Comparison of Ionospheric delays between VLBI and GNSS

editorial reviewedVLBI is a differential technique observing at multiple frequencies. Thus, it can independently provide ionospheric delays. GNSS can supply precise ionospheric delays as well, often with comparable or even better spatial coverage. In this presentation, we compare the VLBI differential ionosphere from two sites with multiple VLBI antennas with the co-located GNSS ionospheric calibrations. In S/X VLBI, a linear combination of X-band and S-band delays is used to provide a calibrated group delay measurement that is free of ionospheric effects to first order. In contrast, the VGOS system is designed to provide group delay and ionospheric delay through a simultaneous fit to measurements in 4 frequency bands distributed over a wide frequency range. The CONT17 VGOS data have been calibrated in terms of ionosphere in advance and thus directly provide TEC for each observation. In this work, we compare the extracted ionospheric delays from dual frequency observations of GNSS with the ones from dual frequency S/X VLBI and from co-located VGOS stations in the CONT17 experiment to better understand how well VLBI can contribute to the study of the ionosphere. Since both source structure and ionosphere effects on geodetic VLBI data analysis are dispersive, in the future we will introduce an optimal match for VLBI and GNSS and compare ionospheric delays obtained from different radio sources to help to improve the modeled structure effect

Radio source position offsets among various radio frames and Gaia

editorial reviewe

Evaluation of VLBI Observations with Sensitivity and Robustness Analyses

Very Long Baseline Interferometry (VLBI) plays an indispensable role in the realization of global terrestrial and celestial reference frames and in the determination of the full set of the Earth Orientation Parameters (EOP). The main goal of this research is to assess the quality of the VLBI observations based on the sensitivity and robustness criteria. Sensitivity is defined as the minimum displacement value that can be detected in coordinate unknowns. Robustness describes the deformation strength induced by the maximum undetectable errors with the internal reliability analysis. The location of a VLBI station and the total weights of the observations at the station are most important for the sensitivity analysis. Furthermore, the total observation number of a radio source and the quality of the observations are important for the sensitivity levels of the radio sources. According to the robustness analysis of station coordinates, the worst robustness values are caused by atmospheric delay effects with high temporal and spatial variability. During CONT14, it is determined that FORTLEZA, WESTFORD, and TSUKUB32 have robustness values changing between 0.8 and 1.3 mm, which are significantly worse in comparison to the other stations. The radio sources 0506-612, NRAO150, and 3C345 have worse sensitivity levels compared to other radio sources. It can be concluded that the sensitivity and robustness analysis are reliable measures to obtain high accuracy VLBI solutions

Structure effects in broadband VGOS data

editorial reviewe

Comparison between time series of closure analysis and source positions since 1980

editorial reviewe

Prevalence and outcomes of patients developing heparin-induced thrombocytopenia during extracorporeal membrane oxygenation

Objectives Unfractionated heparin (UFH) is the commonly used anticoagulant to prevent clotting of the ECMO circuit and thrombosis of the cannulated vessels. A side effect of UFH is heparin-induced thrombocytopenia (HIT). Little is known about HIT during ECMO and the impact of changing anticoagulation in ECMO patients with newly diagnosed HIT. The aim of the study was to determine the prevalence, complications, impact of switching anticoagulation to argatroban and outcomes of patients developing heparin-induced thrombocytopenia (HIT) during either veno-venous (VV) or veno-arterial (VA) ECMO. Methods Retrospective observational single centre study of prospectively collected data of consecutive patients receiving VV ECMO therapy for severe respiratory failure and VA ECMO for circulatory failure from January 2006 to December 2016 of the Medical intensive care unit (ICU) of the University Hospital of Regensburg. Treatment of HIT on ECMO was done with argatroban. Results 507 patients requiring ECMO were included. Further HIT-diagnostic was conducted if HIT-4T-score was ≥4. The HIT-confirmed group had positive HIT-enzyme-linked-immunosorbent-assay (ELISA) and positive heparin-induced-platelet-activation (HIPA) test, the HIT-suspicion group a positive HIT-ELISA and missing HIPA but remained on alternative anticoagulation until discharge and the HIT-excluded group a negative or positive HIT-ELISA, however negative HIPA. These were compared to group ECMO-control without any HIT suspicion. The prevalence of HIT-confirmed was 3.2%, of HIT-suspicion 2.0% and HIT-excluded 10.8%. Confirmed HIT was trendwise more frequent in VV than in VA (3.9 vs. 1.7% p = 0.173). Compared to the ECMO control group, patients with confirmed HIT were longer on ECMO (median 13 vs. 8 days, p = 0.002). Different types of complications were higher in the HIT-confirmed than in the ECMO-control group, but in-hospital mortality was not different (31% vs. 41%, p = 0.804). Conclusion HIT is rare on ECMO, should be suspected, if platelets are decreasing, but seems not to increase mortality if treated promptly

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

Observable quality assessment of broadband very long baseline interferometry system

The next-generation, broadband geodetic very long baseline interferometry system, named VGOS, is developing its global network, and VGOS networks with a small size of 3–7 stations have already made broadband observations from 2017 to 2019. We made quality assessments for two kinds of observables in the 21 VGOS sessions currently available: group delay and differential total electron content (δTEC). Our study reveals that the random measurement noise of VGOS group delays is at the level of less than 2 ps (1ps=10-12 s), while the contributions from systematic error sources, mainly source structure related, are at the level of 20 ps. Due to the significant improvement in measurement noise, source structure effects with relatively small magnitudes that are not overwhelming in the S/X VLBI system, for instance 10 ps, are clearly visible in VGOS observations. Another critical error source in VGOS observations is discrete delay jumps, for instance, a systematic offset of about 310 ps or integer multiples of that. The predominant causative factor is found to be related to source structure. The measurement noise level of δTEC observables is about 0.07 TECU, but the systematic effects are five times larger than that. A strong correlation between group delay and δTEC observables is discovered with a trend of 40 ps/TECU for observations with large structure effects; there is a second trend in the range 60–70 ps/TECU when the measurement noise is dominant.Peer reviewe

Evidence of the Gaia-VLBI position differences being related to radio source structure

We report the relationship between the Gaia--VLBI position differences and the magnitudes of source structure effects in VLBI observations. Because the Gaia--VLBI position differences are statistically significant for a considerable number of common sources, we attempt to discuss and explain these position differences based on VLBI observations and available source images at cm-wavelengths. Based on the derived closure amplitude root-mean-square (CARMS), which quantifies the magnitudes of source structure effects in the VLBI observations used for building the third realization of the International Celestial Reference Frame, the arc lengths and normalized arc lengths of the position differences are examined in detail. The radio jet directions and the directions of the Gaia--VLBI position differences are investigated for a small sample of sources. Both the arc lengths and normalized arc lengths of the Gaia and VLBI positions are found to increase with the CARMS values. The majority of the sources with statistically significant position differences are associated with the sources having extended structure. Radio source structure is the one of the major factors of these position differences, and it can be the dominate factor for a number of sources. The vectors of the Gaia and VLBI position differences are parallel to the radio-jet directions, which is confirmed with stronger evidence.Peer reviewe