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Galanin and adrenomedullin plasma responses to head-up tilt and lower body negative pressure have been studied previously. However, to what extent short-arm human centrifugation (SAHC) affects these responses is not known. In this study, we assessed how the application of variable gradients of accelerations (ΔGz) via shifting of the rotation axis during centrifugation affects selected hormonal responses. Specifically, we tested the hypothesis, that cardiovascular modulating hormones such as galanin and adrenomedullin will be higher in non-finishers (participants in whom at least one of the pre-defined criteria for presyncope was fulfilled) when compared to finishers (participants who completed the entire protocol in both sessions) during SAHC exposure. Twenty healthy subjects (10 women and 10 men) were exposed to two g-levels [1 Gz and 2.4 Gz at the feet (Gz_Feet)] in two positions (axis of rotation placed above the head and axis of rotation placed at the heart level). Elevated baseline levels of galanin appeared to predict orthostatic tolerance (p = 0.054) and seemed to support good orthostatic tolerance during 1 Gz_Feet SAHC (p = 0.034). In finishers, 2.4 Gz_Feet SAHC was associated with increased galanin levels after centrifugation (p = 0.007). For adrenomedullin, the hypothesized increases were observed after centrifugation at 1 Gz_Feet (p = 0.031), but not at 2.4 Gz_Feet, suggesting that other central mechanisms than local distribution of adrenomedullin predominate when coping with central hypovolemia induced by SAHC (p > 0.14). In conclusion, baseline galanin levels could potentially be used to predict development of presyncope in subjects. Furthermore, galanin levels increase during elevated levels of central hypovolemia and galanin responses appear to be important for coping with such challenges. Adrenomedullin release depends on degree of central hypovolemia induced fluid shifts and a subject’s ability to cope with such challenges. Our results suggest that the gradient of acceleration (ΔGz) is an innovative approach to quantify the grade of central hypovolemia and to assess neurohormonal responses in those that can tolerate (finishers) or not tolerate (non-finishers) artificial gravity (AG). As AG is being considered as a preventing tool for spaceflight induced deconditioning in future missions, understanding effects of AG on hormonal responses in subjects who develop presyncope is important.

In this study, simulation tests for gravity gradient referenced navigation (GGRN) are conducted to verify the effects of various factors such as database (DB) and sensor errors, flight altitude, DB resolution, initial errors, and measurement update rates on the navigation performance. Based on the simulation results, requirements for GGRN are established for position determination with certain target accuracies. It is found that DB and sensor errors and flight altitude have strong effects on the navigation performance. In particular, a DB and sensor with accuracies of 0.1 E and 0.01 E, respectively, are required to determine the position more accurately than or at a level similar to the navigation performance of terrain referenced navigation (TRN). In most cases, the horizontal position error of GGRN is less than 100 m. However, the navigation performance of GGRN is similar to or worse than that of a pure inertial navigation system when the DB and sensor errors are 3 E or 5 E each and the flight altitude is 3000 m. Considering that the accuracy of currently available gradiometers is about 3 E or 5 E, GGRN does not show much advantage over TRN at present. However, GGRN is expected to exhibit much better performance in the near future when accurate DBs and gravity gradiometer are available.

The North–South Seismic Belt was analyzed using gravity observation data from 2011 to 2015, and the nontidal analysis results show that there was a nonlinear gravity change at both the Chengdu and Guza seismostations one month before the Leshan M5.0 earthquake.

Galanin and adrenomedullin plasma responses to head-up tilt and lower body negative pressure have been studied previously. However, to what extent short-arm human centrifugation (SAHC) affects these responses is not known. In this study, we assessed how the application of variable gradients of accelerations (ΔGz) via shifting of the rotation axis during centrifugation affects selected hormonal responses. Specifically, we tested the hypothesis, that cardiovascular modulating hormones such as galanin and adrenomedullin will be higher in non-finishers (participants in whom at least one of the pre-defined criteria for presyncope was fulfilled) when compared to finishers (participants who completed the entire protocol in both sessions) during SAHC exposure. Twenty healthy subjects (10 women and 10 men) were exposed to two g-levels [1 Gz and 2.4 Gz at the feet (Gz_Feet)] in two positions (axis of rotation placed above the head and axis of rotation placed at the heart level). Elevated baseline levels of galanin appeared to predict orthostatic tolerance (p = 0.054) and seemed to support good orthostatic tolerance during 1 Gz_Feet SAHC (p = 0.034). In finishers, 2.4 Gz_Feet SAHC was associated with increased galanin levels after centrifugation (p = 0.007). For adrenomedullin, the hypothesized increases were observed after centrifugation at 1 Gz_Feet (p = 0.031), but not at 2.4 Gz_Feet, suggesting that other central mechanisms than local distribution of adrenomedullin predominate when coping with central hypovolemia induced by SAHC (p > 0.14). In conclusion, baseline galanin levels could potentially be used to predict development of presyncope in subjects. Furthermore, galanin levels increase during elevated levels of central hypovolemia and galanin responses appear to be important for coping with such challenges. Adrenomedullin release depends on degree of central hypovolemia induced fluid shifts and a subject's ability to cope with such challenges. Our results suggest that the gradient of acceleration (ΔGz) is an innovative approach to quantify the grade of central hypovolemia and to assess neurohormonal responses in those that can tolerate (finishers) or not tolerate (non-finishers) artificial gravity (AG). As AG is being considered as a preventing tool for spaceflight induced deconditioning in future missions, understanding effects of AG on hormonal responses in subjects who develop presyncope is important. [ABSTRACT FROM AUTHOR]

Abstract Gravity forward modeling of the geological model is a necessary part in the investigation of subsurface density structures, and is extremely valuable in developing and testing gravity data processing and inversion algorithms. In dealing with practical problems, the traditional block model based gravity forward procedure is time consuming, and cannot accurately forward the semi-infinite extended model. To deal with these problems, we proposed an improved residual node density model based gravity forward method. In this method, we firstly transform the density model into a residual node density model with a specific boundary condition; and then remove all the zero residual node density points; and then calculate the gravity anomaly with these non-zero residual node density points. We implement the proposed method in both 2D and 3D cases with Fortran language, and then applied it to Marmousi2 (2D) and SEG/EAGE salt model (3D) gravity forward modeling. The result demonstrates that this method is efficient and has advantage in forward semi-infinite extended model with absolute density by providing a specific boundary condition. HighLights • The method can be used to compute gravity anomalies, gravity gradients and other relevant properties. • The proposed method is highly efficient and less memory requirement, especially for large volumes of data. • The proposed method can be used to calculate the semi-infinite density model with different boundary condition. • The proposed method was applied to the calculation of gravity anomalies of the Marmousi2 and SEG/EAGE salt model. [ABSTRACT FROM AUTHOR]

The problem of the finite-time tracking control strategy is studied for a gravity gradient microsatellite BUAA-SAT in maneuvering. The contributions of the work are mainly shown in two aspects: 1) the analysis of the combined forcing action of the gravity and the constant thrust; 2) a method of the adaptive finite-time sliding mode tracking control. In orbital maneuvering, the gravity gradient microsatellite under a constant thrust shows complicated dynamics. The stability and pendular motion of the gravity gradient microsatellite are determined by the combined action of the gravity and the constant thrust. The dynamics characteristics revealed in this paper are conducive to derive an expected attitude trajectory for the attitude tracking control, which not only ensures the flight safety but also reduces the energy consumption of the controller. In order to avoid the vibration and the structure deformation of the coilable mast, the microsatellite is required to track the expected attitude trajectory in a finite time. Compared with existing finite-time sliding mode control methods, a desired tracking error function with a simple polynomial form is designed to eliminate the reaching phase problem and to enable the tracking error to converge to zero in a finite time; besides, an adaptive law is presented to solve the problem of the boundary of uncertainty. The Lyapunov stability analysis is performed to show the global finite-time convergence of tracking errors. A numerical case of the gravity gradient microsatellite is studied to demonstrate the effectiveness of the proposed controller. [ABSTRACT FROM AUTHOR]

Objective: to study the tolerance of the organism for early verticalization, determining the effectiveness of verticalization in prevention, treatment of immobilization syndrome, the effect of early verticalization on the motor recovery of patients. Methods: in the period from January 2015 to March 2018, 110 patients were examined in the Department of Neurorehabilitation of JSC “National Centre for Neurosurgery”: 30 patients with stroke, 60 patients with spinal injury and 20 patients with head injury. Patients were divided into 2 groups: the main (the duration of stay in a horizontal position for more than 7 days) and control (from the duration of stay in a horizontal position from 1 day to 7 days). Patients are equally divided by nosology into groups. Evaluation of the results was made by reaching a vertical angle without developing orthostatic failure for 30-40 minutes. Results: in the control group, 54 (100%) patients were verticalized to 90° for 40 minutes without orthostatic failure events on the 9th day. In the main group, 49 (91%) patients reached a maximum vertical angle of 90° without developing orthostatic failure within 15 minutes only by the end of rehabilitation treatment (18-19 days). The remaining 5 patients are verticalized to 90° per day of discharge. Conclusion: early verticalization is one of the most highly effective means of preventing and treating the immobilization syndrome of patients with stroke, TBI, spinal trauma, who are on bed rest for more than 24 hours. It also stimulates patients’ motivation to restore motor activity, restore walking skills, gain selfcare skills, and reduce dependence on others. [ABSTRACT FROM AUTHOR]

Abstract: Inferring seafloor topography from gravity anomaly currently is the dominant method to obtain a global view of the oceans. Standard techniques rely on an approximate, linear relationship between topography and gravity, which is valid only if the local topography is smooth compared with the regional topography, so the estimation accuracy in the very rugged areas is low. Current methods can be improved by removing the linear approximation and estimating the topography through simulated annealing and by using gravity gradiometry that is more sensitive to topography at short wavelengths than the gravity anomaly. Simulated annealing is a global optimization technique that can process nonlinear inverse problems. It is developed to estimate the seafloor depths by minimizing the difference between the observed and forward‐computed vertical gravity gradients. The method is tested on altimetry‐derived gravity gradients in a 2∘×2∘ area of rugged seafloor topography in the West Pacific Ocean and results in estimates with a root‐mean‐square error of ±236 m. Compared to estimates from an existing model obtained by standard techniques this represents an accuracy improvement of 22%. [ABSTRACT FROM AUTHOR]

Considering the effects of the gravity gradient, the solar radiation pressure (SRP) and the thermal radiation, the coupling dynamical model is established for a super large flexible beam structure, which moves in the orbital plane around the earth. The effects of environmental disturbances on the orbital motion, the attitude motion and the structural vibration are analyzed simultaneously. Influences of the initial attitude angle, the structure size and other system parameters have been investigated for the coupling dynamics. The results show that the envelop shapes of the vibration responses are dependent on the attitude motion, and the perturbation of orbital motion increases with the growth of the initial attitude angle. When the structural fundamental frequency is close to the attitude frequency with the increase of the structure size, the average orbit altitude would decrease slightly. The main frequency component of the attitude motion decreases and the frequency component related to the structural vibration encounters and grows up. The resonance then leads to system instability. Moreover, the magnitude of the attitude motion can also be influenced by the slightly intense structural vibration, which might be excited by the momentum exchange devices of the attitude control system. In addition, in the presence of the SRP, the orbital radius is perturbed obviously and the eccentricity of orbital motion is generally changed. The effects of the thermal radiation and the gravity gradient are in the same order of magnitude on the structural vibration in the low orbit while the former one turns to be dominant in geostationary orbit. [ABSTRACT FROM AUTHOR]

Traditional torque type gravity gradiometer has an important pole in gravity gradient measurements, while it is relatively inefficient and with the precision of about 1 E mainly caused by the static operating mode. In this paper, we develop an improved torque type gravity gradiometer to improve the measuring efficiency, which is based on the dynamic modulation. The dynamic modulation keeps the gradiometer rotating on a turntable steadily, measures the deflection angle of the torsion pendulum continuously and then obtains the gravity gradients. The result shows that after using the improved gradiometer, the gradients Wxz and Wyz are obtained with precisions of 0.45 E and 0.32 E respectively in a cycle of 20 min. [ABSTRACT FROM AUTHOR]

[Display omitted] • The direct function relationships between three-dimensional Moho topography and Γ xy Γ xz as well as Γ yz of GOCE gravity gradients are deduced. • The deepest Moho in the Tibetan Plateau is approximately 72 km, located at western Kunlun Block. • Clear Moho folds are identified and their dominated wavelengths are approximately 700 km. For understanding the structure of crust and upper mantle underneath the Tibetan Plateau, it is important to determine the Moho topography. The spatial resolution of Moho topography beneath the Tibetan Plateau inverted by seismic methods is relatively low due to the uneven and sparse seismic stations. In recent years after the implementation of gravity satellite missions, gravity method has been used extensively for various purposes because of precise and globally evenly distributed gravity observations. Compared with gravity data, gravity gradients are more sensitive to Moho undulation and can provide more details. Therefore, a method of determining three-dimensional Moho topography by using Γ xy , Γ xz and Γ yz of GOCE gravity gradients is developed in this paper. The Moho topography of the Tibetan Plateau is obtained and the result show that, the deepest Moho may reach to ∼72 km depth, located at western Kunlun Block; the dominated wavelengths of Moho undulations in west-east direction are approximately 754 km, and those in north–south direction are approximately 708 km; more tectonic information can be observed in our inverted Moho topography than that from CRUST1.0. By comparing results with previous publications, our method is precise and effective and provides an optional way to estimate Moho topography. [ABSTRACT FROM AUTHOR]