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Objective: To investigate the effect of dexmedetomidine (DEX) on the polarization of alveolar macrophages induced by lipopolysaccharide (LPS) and to explore the related mechanisms. Methods: Rat alveolar macrophages NR8383 were cultured in vitro. Experiment one was divided into control group, model group (1 μg/ml LPS), DEX low, medium and high dose groups (1, 5, 10 mg/kg DEX+10 mg/kg LPS). Experiment two was divided into DEX high dose group (10 mg/kg) and DEX high dose+Colivelin (JAK2/STAT3 signaling pathway activator) group (10 mg/kg DEX+0.5 μmol/L Colivelin). The morphological changes of rat alveolar macrophages NR8383 were observed by inverted microscope; RT-PCR method was used to detect the expression levels of iNOS and Arg1 mRNA in NR8383 cells, and flow cytometry was used to detect the expression levels of CD86 and CD163 proteins in NR8383 cells; Western blot was used to detect the expression levels of surface marker proteins TNF-α, iNOS, SOCS, Arg1, TGF-β and JAK2/ STAT3 signaling pathway related proteins in NR8383 cells. Results: Compared with control group, there were a lot of cell debris in the intercellular space of NR8383 in the model group, the proportions of iNOS mRNA, CD86 positive cells, and the expression levels of TNF-α, p-JAK2/JAK2, p-STAT3/STAT3 were significantly increased, the proportions of Arg1 mRNA, CD163 positive cells, and the expression levels of SOCS and TGF-β were significantly reduced (P<0.05); compared with the model group, the NR8383 intercellular cell debris in the DEX low, medium, and high dose groups were decreased, the proportions of iNOS mRNA, CD86 positive cells, and the expression levels of TNF-α, p-JAK2/JAK2, p-STAT3/STAT3 were significantly reduced, the proportions of Arg1 mRNA, CD163 positive cells, and the expression levels of SOCS and TGF- β were significantly increased (P<0.05). The reactivation of the JAK2/ STAT3 signal pathway by Colivelin could weaken the role of DEX in LPS induced NR8383 cell polarization. Conclusion: DEX can inhibit the M1 polarization of NR8383 cells induced by LPS, which may be achieved by inhibiting the JAK2/STAT3 signaling pathway. [ABSTRACT FROM AUTHOR]

Herein, the technical characteristics and programme of Qujing incoherent scatter radar (the first one in China) are described. The measurement ability in the ionosphere, space debris, and the Moon was investigated using the data. The results showed that this radar is of importance useful for the measuring ionospheric climatologic property, analyzing storm-time and abnormal enhancement events analysis, studying E-F valley and its variations, the determining and modeling space debris distribution characteristics and model, and identifying the scatter echo characteristics from the different regions of the Moon. The next work will focus on the measurement of the structure and evolution of the lower ionosphere and the northern ionosphere crest, storm-time variations, and disturbance characteristics property.

Copyright of Reviews of Geophysics & Planetary Physics is the property of Editorial Office of Reviews of Geophysics & Planetary Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Laser Technology is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Remote sensing satellite SiCH-2 from Ukraine was launched in 2011. At present, it has stopped working and is out of control, and it has been forecasted to become space debris by a two-line root (TLE) from the North American Air Defense Command (NORAD). Here, the "cat's eye" effect of the optical system is analyzed, and the satellite laser ranging (SLR) system at Shanghai Observatory is used to measure the echo intensity of satellite SiCH-2, which is very strong, and the ranging accuracy, which is better than 10 cm. The analysis of the measurement capability results shows that the laser reflection echo from satellite SiCH-2 reaches the laser ranging level of the satellite with the reflector, and is consistent with the detection ability of the photoelectric detection equipment "cat's eye" effect analysis. The measurement results also show that satellite SiCH-2 is in a state of rotation, with a period of 4.3 s. In this study, the laser ranging of on-orbit targets based on the "cat's eye" effect is realized for the first time, which provides a new method for analyzing long-distance space targets, promotes the application and development of high-precision laser ranging technology, and is beneficial to monitor the photoelectric detection series of satellites that fail or have abnormal orbits.

Copyright of Computer Measurement & Control is the property of Magazine Agency of Computer Measurement & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To study the interaction pattern of nanosecond pulse laser with aluminium debris, a dynamic response model of nanosecond pulse laser irradiation on aluminum debris was established, the dynamic characteristics of plasma expansion plumes under different action times and incident laser powers was investigated by COMSOL software, and the evolution rules of plasma expansion plumes generated by nanosecond pulse laser irradiating the debris were obtained with different laser parameters. The results show that the expansion velocity of plasma plumes increases with the increase of action times based on the same pulse laser power. At the same time, the maximum velocity of plasma expansion plumes increases with the increase of laser powers based on the same pulse laser time. According to the given conditions of this article, the maximum velocity of expansion plumes reached the maximum around 25 µs, and the maximum velocity at 700 kW is 1. 87x104 m/s owing to the plasma shielding effect. At the moment, the diffusion radius of the plasma expansion plumes increases by 17 mm. The study provides a theoretical reference for the engineering application of nanosecond pulse laser irradiation of aluminium space debris de-orbiting removal. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Reviews of Geophysics & Planetary Physics is the property of Editorial Office of Reviews of Geophysics & Planetary Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Systems Engineering & Electronics is the property of Journal of Systems Engineering & Electronics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Railway Investigation & Surveying is the property of Railway Investigation & Surveying Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The large amount of low earth orbit (LEO) space debris has a serious impact on the safe operation of orbital spacecraft. Space-based optical observation is the mainstream development direction for space debris observation. For centimeter sized space debris in LEO, the observable duration obtained by the LEO space-based telescope is relatively short. It is difficult to determine the initial orbit from the single arc of observation, and the error of the initial orbit is difficult to evaluate. Based on the admissible region method, this paper establishes the initial orbit determination and error estimation algorithm. Aiming at the problem that the initial orbit of space-based short-arc optical observation is not easy to be determined, this paper proposes a circular orbit auxiliary admissible region method. The LEO space debris observation experiment on commercial remote sensing satellites is carried out to verify the proposed calculation method, and to lay a foundation for the future research on observation-to-observation association using initial orbits. [ABSTRACT FROM AUTHOR]

The problem of space debris is becoming more and more serious. It is necessary to monitor space debris normally. As an important technology of monitoring, optical observation needs to rely on fait image processing and astronomical positioning to obtain the RA-DEC position of space objects. Star map recognition is a key step in astronomical positioning, which directly affects the speed of image processing and the accuracy of results. In this paper, an improved fast star map recognition method based on fuzzy decision is proposed, which improves the accuracy of star map recognition while maintaining fast processing. This method is tested with the image of 25 cm telescope at Nanshan station in Xinjiang, and the results prove the effectiveness and stability of the algorithm. [ABSTRACT FROM AUTHOR]

As high value geostationary earth orbit (GEO) satellites are under a range of threats, it is helpful to improve the survivability of satellite bus by exploring the technology system of on-orbit strong survivability (TSO2S2). Focusing on this, the concept of TSO2S2 is defined systematically. A protection system including warning and safety protection sub-system is built after the main threat sources are figured out. Firstly, 8 threats are divided into active type and passive type. The threat mechanisms are analyzed and the damage effects are evaluated using qualitative and quantitative methods. Secondly, an integrated space and terrestrial warning scheme is proposed and the equipment is designed which enabled 5 types of threats to be alarmed, including space debris, laser, et al. Finally, the protection technology and methods are summarized systematically, which can provide reference for the GEO satellite platform to improve the orbit safety. [ABSTRACT FROM AUTHOR]

The initial orbit determination (IOD) of the very‐short‐arc (VSA) and the association between them are the key steps for expanding the catalogue with optical observations obtained from ground‐based or space ‐based telescopes. For this reason, the distance search method for IOD and the geometrical method for their association were proposed. With optical observations from ground ‐based small telescopes array at Changchun Observatory, National Astronomical Observatories, China Academy of Sciences in Changchun and simulated observations from space‐based telescope, the IOD and the association between the IODs are performed. The successful rates of getting an IOD solution for an optical arc with the distance search method is about 90%. For two kinds of observations. The IOD association results show that the true positive (assert that they are from same object for IODs from a same object) rate is over 80% in most cases. Ant the effects on the association accuracy of filtered different IODs are analyzed in depth. With actual optical observations obtained at Changchun, the results of IOD and their association show the validity of the IOD method and association method used in this paper and they can be used to expand the space object catalogue. [ABSTRACT FROM AUTHOR]

In order to analyze the impact of large low Earth orbit (LEO) constellation deployment on the future space environment, the space object long-term evolution model ( SOLEM), is used to study the impact of the factors such as the number, the mass, the area, the orbit altitude of satellites and the post mission disposal (PMD) in large constellations on the number of collisions and debris. The analysis shows that the important factors affecting the collision are the number and area of satellites, while the main factor affecting the number of the new debris generated by collisions is the satellite mass. However, under the condition of satisfying the task, operators can consider the relationship of these three factors comprehensively to select the most appropriate plan. At the same time, it has a great impact on the space debris environment when deploying at 1 100 km and the success rate of PMD should be increased to more than 95% on the premise of complying with the 25-year rule. [ABSTRACT FROM AUTHOR]

Copyright of Rare Metal Materials & Engineering is the property of Northwest Institute for Nonferrous Metal Research and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Systems Engineering & Electronics is the property of Journal of Systems Engineering & Electronics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Computer Measurement & Control is the property of Magazine Agency of Computer Measurement & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Orbital covariance propagation plays a vital role in the space situation awareness tasks such as the space conjunction analysis and space mission planning. Orbital errors, usually expressed by the orbital covariance matrix, can be propagated with linear models or non-linear models. Linear models are analytical and computationally fast since only the state transition matrix is needed. However, the propagation accuracy declines quickly with the time due to the linearization of highly nonlinear orbital dynamic systems. The non-linear models are accurate but computationally intensive, and thus are less attractive in the orbital covariance propagation for massive space debris. On the basis of the analysis of the propagated orbital errors, this paper proposes a dynamic calibration method to improve the accuracy of orbit error propagation. The method has three steps:the generation of realistic initial orbit covariance matrix, the linear propagation of the covariance matrix, and dynamic calibration of the propagated covariance using past observations. Experiments of real data processing show that the accuracy of calibrated orbit covariance can be improved by more than 60% compared to the linearly propagated covariance, and can provide more accurate propagated covariance for many space applications require high-accuracy such as the space collision probability computation. [ABSTRACT FROM AUTHOR]

The stuffed shield with multi-layer insulation(MLI) was designed by improving on Al Whipple shield, and a series of high-velocity impact tests were practiced with a two-stage light gas gun facility at vacuum environment. The damage model of the stuffed shield with different MLI location by Al-sphere projectile impacting was obtained. The effect of MLI on damage of the stuffed shield by high-velocity impact was studied. The results indicate when the MLI is located at front side of the first Al-plate, the protection performance of the stuffed shield is improved with the larger perforation diameter of the first Al-plate and more impact kinetic energy dissipation of the projectile. When MLI is arranged at back side of the first Al-plate, the expansion of the secondary debris cloud from projectile impacting the first Al-plate is restrained, it is not good to improve the protection performance of the stuffed shield. When MLI is arranged at front side of the stuffed wall, the perforation size of the stuffed wall increases; when MLI is arranged at front side of the rear wall, the distribution range of crater on the rear wall decreases.

Debris cloud can be produced by hypervelocity impact of a projectile on a thin plate, which has been used in protection against meteoroid/orbital debris. The study of debris cloud during normal impact is reviewed to summarize the research progress and insufficiency in recent thirty years, including the formation process, distribution characteristic, modeling and penetration performance of debris cloud. According to the current lacks of research contents on debris cloud, some suggestions are also made for coming studies. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Heilongjiang University of Science & Technology is the property of Journal of Heilongjiang University of Science & Technology Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The explosion breakup debris distribution of the cylindrically simulated satellite with thin-walled aluminum alloy is researched by the sandpit retrievable experiment and theoretical analysis. The experimental results show that the explosion breakup behavior of simulated satellite is significantly influenced by the wall thickness and the residual propellant mass. The amount of explosion breakup debris increases with the decrease in wall thickness and the increase in residual propellant mass. Moreover, the explosion breakup debris mass shows a wide range from less than 0. 2 g particles to more than 100 g irregular debris. By incorporating the experimental results into the covered explosive explosion breakup model and simulated satellite low intensity explosion breakup model, respectively, both the amount and mass distribution models of simulated satellite explosion breakup debris are presented, contributing to the assessment of satellite breakup debris distribution characteristics in accident. [ABSTRACT FROM AUTHOR]

To analyze the accuracy and effectiveness of using SGP4 model for orbit prediction and collision alert, the space object collision alert software was made to realize it. For the three space collisions that ever happened, the space objects' position and speed were calculated to get the collision probability, using the TLEs which NORAD announced 1, 3, 5, 7 and 10 days before the collision, and then analyzed the accuracy and effectiveness of SGP4 model. The results show that, the alert collision time calculated using SGP4 model for orbit prediction and collision alert is consistent with the actual collision time, and the collision probability gets the alert warning. However, the accuracy and effectiveness of SGP4 model decrease with the increase of the alert days, and SGP4 model works best when the alert day is less than 5. [ABSTRACT FROM AUTHOR]

The average velocity of space debris impacting on on-orbit spacecrafts is 10 km/s, and 90% of them in low earth orbit are the middle and low density materials. The experiments of Mylar foil and Al flyer impacting on Al shield structure at 14 km/s and about 9 km/s, respectively, are done by electric gun and magnetic driving technology, and the damage results of Mylar foil and Al flyer impacting on shield structure are obtained. The results show that the debris cloud created by Al flyer impacting on Al shielding slab at about 9km/s contains fluid state and even gas state, and the debris cloud created by Mylar foil impacting on Al shielding material at 14km/s is solid state. For the Mylar foil flyer, the shielding effect of double shield structure is better than that of the single layer structure. [ABSTRACT FROM AUTHOR]

Aluminum foam is a new type of material for shield of spacecrafts which bears fine characteristics when subjected to hypervelocity impact of space debris. A microstructure model of geometry for metallic foams was set up based on their manufacturing process and hypervelocity impact numerical simulations were conducted by self-programmed Smooth Particle Hydrodynamics. Six types of M-foam stuffed shields were calculated and their ballistic limits were compared with each other. The results indicated that shield performance of Al-foam stuffed shield was better than that of solid Al-plate stuffed shield with the same areal density if the Al-foam was stuffed at appropriate position. The analyses of characteristic parameters of debris cloud of different shields indicated that Al-foam had better shield performance on small-size debris. The microstructure of Al-foam could effectively spread the perpendicular momentum of debris cloud and significantly increase the proportion of material liquefaction and gasification in debris cloud through multi-shock. [ABSTRACT FROM AUTHOR]

To obtain an approach to describe the characteristics of debris clouds produced by hypervelocity impacts with thin sheets, results from the Swift model, the Piekutowski model and the Bless model were analyzed by comparing them with simulation results. The Swift model was modified. The results showed that the Piekutowski model and the Bless model were fit for the debris clouds produced by hypervelocity impacts of discs with thin sheets, and the modified Swift model was fit for the cases with spherical projectiles. [ABSTRACT FROM AUTHOR]

A GUI based meteoroid and orbital debris risk assessment system(MODRAS) is developed for assessing risks to spacecraft from meteoroid and debris impact. Instance a spacecraft as an example for M/OD risk assessment is conducted. The distribution of debris flux, exposed area of spacecraft and impact data are obtained. The results show that the relative impact possibility for a spacecraft depends on the spacecraft's altitude and orbital inclination, as well as debris size. Changes in shuttle mission operations, flight rules, and flight planning were adopted to reduce meteoroid and debris risks. [ABSTRACT FROM AUTHOR]