Investigating Performance of High-Rate GNSS-PPP and PPP-AR for Structural Health Monitoring: Dynamic Tests on Shake Table

© 2020 American Society of Civil Engineers. This paper investigates the usability of Global Navigation Satellite System (GNSS) Precise Point Positioning (PPP) methods, traditional PPP with a float-ambiguity solution and with ambiguity resolution (PPP-AR), in structural health monitoring applications based on experimental tests using a single-axis shake table. To evaluate the performance of the PPP methodologies, harmonic oscillations of the motion table with amplitudes ranging from 5 to 10 mm and frequency between 0.1 and 3 Hz were generated representing a wide range of possible structural motions. In addition, ground motion similar to those experienced during a real earthquake, the 1995 Kobe earthquake, and step motions were generated on the shake table. GNSS PPP-derived positioning results at 20 Hz were compared, in both of the frequency and time domains, with reference data comprising LVDT data and relative positioning data. Results show that both PPP methods' measurements can be used in the computation of harmonic oscillation frequencies compared to the LVDT and relative positioning values. The observed amplitudes of the harmonic oscillations are slightly different from the LVDT values on the order of millimeters. The results of a step motion experiment demonstrated that PPP-AR is better than traditional PPP in exhibiting quasi-static or static displacement. Moreover, the capabilities of traditional PPP and PPP-AR methods are evaluated with respect to the natural frequency of a small-scale structural model excited on the shake table. The frequency spectrum of this small-scale structural model derived from the PPP methods is consistent with finite-element model (FEM)-predicted values and relative positioning. The research presented here demonstrates the potential of the high-rate GNSS PPP and PPP-AR methods to reliably monitor structural and earthquake-induced vibration frequencies and amplitudes for both structural and seismological applications. Specifically, all results reveal that high-rate PPP-AR is more accurate than traditional PPP for both dynamic and static displacement detection

Light-dark O2 dynamics in submerged leaves of C3 and C4 halophytes under increased dissolved CO2: clues for saltmarsh response to climate change

Waterlogging and submergence are the major constraints to which wetland plants are subjected, with inevitable impacts on their physiology and productivity. Global warming and climate change, as driving forces of sea level rise, tend to increase such submersion periods and also modify the carbonate chemistry of the water column due to the increased concentration of CO2 in the atmosphere. In the present work, the underwater O2 fluxes in the leaves of two abundant Mediterranean halophytes were evaluated at different levels of dissolved CO2. Photosynthetic enhancement due to increased dissolved CO2 was confirmed for both Halimione portulacoides and Spartina maritima, probably due to high tissue porosity, formation of leaf gas films and reduction of the oxygenase activity of Rubisco. Enhancement of the photosynthetic rates in H. portulacoides and S. maritima was concomitant with an increase in energy trapping and transfer, mostly due to enhancement of the carboxylation reaction of Rubisco, leading to a reduction of the energy costs for carbon fixation. Transposing these findings to the ecosystem, and assuming increased dissolved CO2 concentration scenarios, the halophyte community displays a new ecosystem function, increasing the water column oxygenation and thus reinforcing their role as principal primary producers of the estuarine system

Slip distribution and source parameters of the 20 July 2017 Bodrum-Kos earthquake (Mw6.6) from GPS observations

Greek-Turkish boundary near the cities Kos and Bodrum has been shaken on July 20, 2017 by a Mw6.6 earthquake. The mainshock is located offshore and did not generate an on-land surface rupture. Analyzing pre-and post-earthquake continuous/survey-type static GPS observations, we investigated co-seismic surface displacements at 20 sites to characterize source parameters and slip-distribution of the mainshock. Fault plane solutions as well as co-seismic slip distribution have been acquired through the inversion of co-seismic GPS displacements modeling the event as elastic dislocations in a half space. Fault plane solution shows a southward dipping normal-type fault segment extending a depth down to similar to 12 km, which remains within the brittle upper crust. Results from the distributed slip inversion show that the mainshock activated a similar to 65 km fault section, which has three high slip patches, namely western, central and eastern patches, where the coseismic slips reach up to 13, 26, and 5 cm, respectively. This slip pattern indicates that the pre-earthquake coupling, which is storing the slip deficit, occurred on these three patches

New geodetic constraints to reveal seismic potential of central Marmara region, Turkey

The North Anatolian Fault (NAF) is a fault zone that produced destructive earthquakes (Erzincan 1939 and 1992, Ladik 1943, Gerede 1944, Duzce 1999, Izmit 1999) in the last century. After this destructive earthquake migration, it is forecasted that the next seismic event on the NAF could be in the western part of the fault, which passes through the Marmara region. Due to the possibility of an earthquake in Istanbul, the most crowded and historical city in Turkey, researchers have increasingly paid attention to the western segment of the NAF within the Marmara Sea since the 1999 earthquakes. Many scientists from different disciplines such as geodesy, geology, geophysics, etc. have been trying to understand this phenomenon. However, it is understood from the literature that a comprehensive geodetic study is crucial to constrain the NAF segment between Istanbul and Tekirdag provinces. Therefore, we created a new network consisting of continuous GPS stations with 10-km interdistances along the shoreline, which was integrated with existing GNSS networks in the Marmara region. Data acquisition was carried out between August 2017 and February 2020. In this study, preliminary results obtained from the integration of the newly established network with the other GNSS networks are presented

Diagnostic performance of a newly developed salivary cortisol and cortisone measurement using an LC-MS/MS method with simple and rapid sample preparation

BACKGROUND: Late-night salivary cortisol level is one of the first-line tests recommended by the Endocrine Society for the diagnosis of endogenous hypercortisolism. Most routine laboratories measure cortisol levels using immunoassay tests which fail to determine low cortisol levels accurately due to the numerous interfering substances. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method with simple and rapid sample preparation was developed for the simultaneous measurement of cortisol and cortisone and its performance in the diagnosis of endogenous hypercortisolism was evaluated. METHODS: 324 late-night saliva samples were analyzed from which 272 samples were derived from patients with a suspected diagnosis of endogenous hypercortisolism. Salivary cortisol levels were assayed using an electrochemiluminescent immunoassay (ECLIA, Cortisol II, Roche), and simultaneous measurement of cortisol and cortisone was performed using an LC-MS/MS method. RESULTS: A strong correlation between cortisol results measured using ECLIA and LC-MS/MS (r 2 = 0.892) was demonstrated. Receiver operating characteristics (ROC) analysis showed good diagnostic performance of cortisol and cortisone levels assayed using LC-MS/MS method and for cortisol measured using ECLIA. CONCLUSIONS: Late-night salivary cortisol and cortisone are useful parameters for the diagnosis of hypercortisolism. Using samples obtained from patients where the diagnosis of hypercortisolism is extremely challenging cut-off values for midnight salivary cortisol and cortisone measured by LC-MS/MS method were established

Hydroxyethyl Starch 6%, 130/0.4 Vs. A Balanced Crystalloid Solution In Cardiopulmonary Bypass Priming: A Randomized, Prospective Study

Background Since the advent of cardiopulmonary bypass, many efforts have been made to avoid the complications related with it. Any component of the pump participates in occurrence of these adverse events, one of which is the type of prime solution. In this study, we aimed to compare the effects of 6% hydroxyethyl starch 130/0.4 with a commonly used balanced electrolyte solution on postoperative outcomes following coronary bypass surgery. Methods Two hundred patients undergoing elective coronary bypass surgery were prospectively studied. The patients were randomized in to two groups. First group received a balanced electrolyte solution and the second group received 6% hydoxyethyl starch 130/0.4 as prime solution. The postoperative outcomes of the patients were studied. Results The mean age of the patients was 61.81 ± 10.12 in the crystalloid group whereas 61.52 ± 9.29 in the HES group. There were 77 male patients in crystalloid group and 74 in HES group. 6% hydroxyethyl starch 130/0.4 did not have any detrimental effects on renal and pulmonary functions. The intensive care unit stay and postoperative hospital length of stay were shorter in hydroxyethyl starch group (p  0.05). Conclusions 6% hydroxyethyl starch 130/0.4 when used as a prime solution did not adversely affect postoperative outcomes including renal functions and postoperative blood transfusion following coronary bypass surgery.PubMedWoSScopu