New Insight Into Relative Sea Level Change and Its Constraints on Mantle Viscosity and Deglaciation History Since the Last Glacial Maximum

Studies of glacial isostatic adjustment (GIA), the viscoelastic relaxation of the Earth's mantle stress induced by deglaciation following the last glacial maximum (LGM), have provide important constraints on Late Pleistocene deglaciation history and the viscoelastic structure of the Earth's mantle. Most GIA models assume a Newtonian viscosity in the mantle, but laboratory studies of rock deformation, observational studies of seismic anisotropy, and modeling studies of mantle dynamics show that the upper mantle viscosity is non-Newtonian and stress-dependent. With 3D finite element numerical modelling study, here we demonstrate that the mantle stress beneath glaciated regions increases significantly during rapid deglaciation around 15,000 years ago, leading to regionally reduced upper mantle viscosity by more than an order of magnitude, while the lithospheric stress keeps decreasing with time as ice sheets disappear. As the deglaciation slows down and especially after ice sheets in North America and Fennoscandia disappear, mantle stress decreases and upper mantle viscosity increases. This causes mantle viscosity to be time dependent. The predicted relative sea level (RSL) changes from non-Newtonian models have more rapid sea-level falls associated with the rapid deglaciation followed by a more gradual sea-level variation. This distinct feature may provide a diagnosis for distinguishing non-Newtonian and Newtonian rheology. RSL observations have been used to help construct deglaciation history since the LGM (i.e., ice model), together with observations of glacial isochrons. However, due to use of different RSL datasets and other assumptions, two widely used ice models, ICE-6G and ANU, differ significantly, suggesting the uncertainties in ice models. While ICE-6G shows &gt;1 km thicker ice in the western Canada than the ANU ice model, the latter has &gt; 1 km thicker ice in the eastern Canada. Approximating mantle viscosity structure as 1-D and two layers of viscosity (i.e., upper and lower mantles), for each of these two ice models and each of the six different RSL datasets published by different research groups, the GIA modeling indicates that the preferred mantle viscosity has significantly higher viscosity in the lower mantle. The spatial and temporal distributions of misfits to RSL data show that ICE-6G has significantly larger misfits to the farfield RSL data between 14,000 and 9,000 years ago and to RSL data in the eastern (e.g., St. Lawrence River) and northern Canada, compared with the ANU ice model. The misfit patterns provide guidance on revising ICE-6G to improve the fit to RSL data.&nbsp;</p

Seasonal Variations in Hydrological Influences on Gravity Measurements Using gPhones

Hydrological influences on a local gravity field may reach amplitudes on the order of 10 microgals. Since 2007, fifteen Microg LaCoste gPhones have been successively installed in gravity stations in China. The outputs from gPhones include ten data channels with second sampling such as raw gravity, corrected gravity, long level data and cross level data, ambient and sensor temperature, ambient and sensor pressure, and others. In this study, we select six stations in northwest China (GaoTai, LaSa, LanZhou, ShiQuanHe, WuShi, XiAn) and one station in the northeast (HaiLaEr). We have modeled the major tides (earth solid tide, ocean tide and pole tide), corrected for atmospheric loading effects using local measurements, fitted instrumental drift using segmental fitting based on the distinct characteristics of gravimeter drift, and ultimately obtained the monthly residual gravity with amplitudes of 10 ~ 20 microgals. We find that the results obtained by the gravimeter for those stations with stable conditions and no large disturbances are obviously correlated with hydrologic loading as modeled by the Global Land Data Assimilation System and Climate Prediction Center. We also notice that at some stations there are obvious phase lags with a period of three months or more between the residual gravity and the influence of hydrological loading. These large discrepancies may be associated with local hydrologic effects, local topography or some other complex tectonic movement and geodynamical mechanism, which were not considered in this paper

Factors associated with euphoria in a large subset of cases using propofol sedation during gastrointestinal endoscopy

BackgroundThe utilization of Propofol, a widely used intravenous sedative or anesthetic, is characterized by its quick onset, predictable control, and fleeting half-life during both general anesthesia and intensive care unit sedation. Recent evidence, however, has highlighted propofol’s propensity to induce euphoria, particularly in patients undergoing painless procedures such as gastrointestinal or gastric endoscopy. Given its widespread use in patients undergoing such procedures, this study aims to investigate the clinical evidence and factors that may influence propofol-induced euphoria in these settings.MethodsThe Addiction Research Center Inventory-Chinese Version (ARCI-CV) scale was administered to 360 patients undergoing gastric or gastrointestinal endoscopy using propofol as a sedative. Patient characteristics including past medical history, depression, anxiety, alcohol abuse, and sleep disturbance were recorded through history taking and assessment using various questionnaires prior to the examination. The euphoric and sedative statuses were assessed at 30 min and 1 week post-examination.ResultsThe experimental results of a survey of 360 patients who underwent gastric or gastrointestinal endoscopy using propofol showed that the mean Morphine–Benzedrine Group (MBG) score before the procedure and after 30 min of the procedure was 4.23 and 8.67, respectively. The mean Pentobarbital–Chlorpromazine–Alcohol Group (PCAG) score before the procedure and after 30 min of the procedure was 3.24 and 6.22, respectively. These results showed that both MBG and PCAG scores increased significantly after the procedure. Certain factors, such as dreaming, propofol dose, duration of anesthesia, and etomidate dose, were all correlated with MBG both at 30 min and 1 week after the examination. In addition, etomidate had an effect of decreasing MBG scores and increasing PCAG scores both at 30 min and 1 week after the examination.ConclusionTaken together, propofol may elicit euphoria and potentially contribute to propofol addiction. There are several risk factors for the development of propofol addiction, including dreaming, propofol dose, duration of anesthesia, and etomidate dose. These findings suggest that propofol may have a euphoric effect and may have the potential for drug addiction and abuse

Real-time Monitoring for the Next Core-Collapse Supernova in JUNO

Core-collapse supernova (CCSN) is one of the most energetic astrophysical events in the Universe. The early and prompt detection of neutrinos before (pre-SN) and during the SN burst is a unique opportunity to realize the multi-messenger observation of the CCSN events. In this work, we describe the monitoring concept and present the sensitivity of the system to the pre-SN and SN neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO), which is a 20 kton liquid scintillator detector under construction in South China. The real-time monitoring system is designed with both the prompt monitors on the electronic board and online monitors at the data acquisition stage, in order to ensure both the alert speed and alert coverage of progenitor stars. By assuming a false alert rate of 1 per year, this monitoring system can be sensitive to the pre-SN neutrinos up to the distance of about 1.6 (0.9) kpc and SN neutrinos up to about 370 (360) kpc for a progenitor mass of 30$M_{\odot}$ for the case of normal (inverted) mass ordering. The pointing ability of the CCSN is evaluated by using the accumulated event anisotropy of the inverse beta decay interactions from pre-SN or SN neutrinos, which, along with the early alert, can play important roles for the followup multi-messenger observations of the next Galactic or nearby extragalactic CCSN.Comment: 24 pages, 9 figure

External calibration of GOCE data using regional terrestrial gravity data

This paper reports on a study of the methodology of external calibration of GOCE data, using regional terrestrial-gravity data. Three regions around the world are selected in the numerical experiments. The result indicates that this calibration method is feasible. The effect is best with an accuracy of scale factor at 10−2 level, in Australia, where the area is smooth and the gravity data points are dense. The accuracy is one order of magnitude lower in both Canada where the area is smooth but the data points are sparse, and Norway, where the area is rather tough and the data points are sparse

CitcomSVE: A Three‐Dimensional Finite Element Software Package for Modeling Planetary Mantle’s Viscoelastic Deformation in Response to Surface and Tidal Loads

Abstract This article presents a comprehensive benchmark study for the newly updated and publicly available finite element code CitcomSVE for modeling dynamic deformation of a viscoelastic and incompressible planetary mantle in response to surface and tidal loading. A complete description of CitcomSVE’s finite element formulation including calculations of the sea‐level change, polar wander, apparent center of mass motion, and removal of mantle net rotation is presented. The 3‐D displacements and displacement rates and the gravitational potential anomalies are solved with CitcomSVE for three benchmark problems using different spatial and temporal resolutions: (a) surface loading of single harmonics, (b) degree‐2 tidal loading, and (c) the ICE‐6G GIA model. The solutions are compared with semi‐analytical solutions for error analyses. The benchmark calculations demonstrate the accuracy and efficiency of CitcomSVE. For example, for a typical ICE‐6G GIA calculation with a 122‐ky glaciation‐deglaciation history, time increment of 100 years, and ∼50 km (or ∼0.5°) surface horizontal resolution, it takes ∼4.5 hr on 96 CPU cores to complete with about 1% and 5% errors for displacements and displacement rates, respectively. Error analyses shows that CitcomSVE achieves a second order accuracy, but the errors are insensitive to temporal resolution. CitcomSVE achieves the parallel computational efficiency >75% for using up to 6,144 CPU cores on a parallel supercomputer. With its accuracy, computational efficiency and its open‐source public availability, CitcomSVE provides a powerful tool for modeling viscoelastic deformation of a planetary mantle with 3‐D mantle viscous and elastic structures in response to surface and tidal loading problems

Characteristics of satellite-gravity variations in the North-south Seismic Belt before the 2013 Lushan earthquake

To study the characteristics of gravity variations in and near the North-south Seismic Belt before the 2013 Lushan earthquake, we used the geopotential-field models based on monthly data of the RL05 GRACE satellite to calculate the gravity changes. Here we present the patterns of annually cumulative variation, differentiatial variation and secular trend, as well as the continuous time-series at 4 characteristic sites during 2004–2012. The result shows that the anomalous positive-to-negative transition zone, in which the epicenter of the 2008 Wenchuan earthquake was located, did not show any new gravity change before the Lushan earthquake, though located in the same zone

Low-frequency variability of terrestrial water budget in China using GRACE satellite measurements from 2003 to 2010

Mass variations in terrestrial water storage (TWS) obtained from eight years of satellite data from the Gravity Recovery and Climate Experiment (GRACE) are used to describe low frequency TWS through Empirical Orthogonal Function (EOF) analysis. Results of the second seasonal EOF mode show the influence of the Meiyu season. Annual variability is clearly shown in the precipitation distribution over China, and two new patterns of interannual variability are presented for the first time from observations, where two periods of abrupt acceleration are seen in 2004 and 2008. GRACE successfully measures drought events in southern China, and in this respect, an association with the Arctic Oscillation and El Nino-Southern Oscillation is discussed. This study demonstrates the unique potential of satellite gravity measurements in monitoring TWS variations and large-scale severe drought in China

Outlier detection algorithm for satellite gravity gradiometry data using wavelet shrinkage de-noising

On the basis of wavelet theory, we propose an outlier-detection algorithm for satellite gravity gradiometry by applying a wavelet-shrinkage-de-noising method to some simulation data with white noise and outliers. The result shows that this novel algorithm has a 97% success rate in outlier identification and that it can be efficiently used for pre-processing real satellite gravity gradiometry data

Study on Installation Angle of the Milling Wheel Accurate Estimation and Compensation

An accurate estimation and compensation algorithm is proposed to calculate the manufacture deviation of the milling wheel based on optical measurement. Firstly, the spatial position of the cutting tool tip and the installation angle of the cutting tool are calculated based on measured data from hand held coordinate measuring instrument. Secondly, the installation angle field between the measurement model and CAD modelis calculated and analyzed by statistics methods. Thirdly, the deviation compensation strategy is given to correct the manufacturing process base on the results of the analysis. The feasibility of the proposed method has been validated by an illustrated experiment at last. The comparison results show that the deviation of the installation angle can be effectively constrained and the proposed method is helpful for the improvement of quality and accuracy in milling wheel