Bias Stability Investigation of a Triaxial Navigation-Compatible Accelerometer with an Electrostatic Spring.

The bias stability performance of accelerometers is essential for an inertial navigation system. The traditional pendulous accelerometer usually has a flexible connection structure, which could limit the long-term bias stability. Here, based on the main technologies employed in previous space missions of our group, we developed a terrestrial triaxial navigation-compatible accelerometer. Because there is no mechanical connection between the inertial test mass and the frame, the bias performance relies on the stability of the equivalent electrostatic spring, where further sources are analyzed to get the optimal electrostatic force scheme. To investigate the bias stability under different ranges, the vertical and horizontal measurement ranges are designed at 5 g and ±10 mg, respectively. A low-noise high-voltage levitation scheme is adopted to extend the vertical measurement range from sub-mg to more than earth's 1-g gravity. Finally, the experimental validation results show that the 24-h bias stability of vertical and two horizontal directions come to 13.8 µg, 0.84 µg, and 0.77 µg, respectively.

High-precision ground simulator for laser tracking of gravity satellite.

Inter-satellite laser ranging is a key technology to improve the measurement precision of gravity satellites in future missions. However, it requires a stable laser link between satellites, which would be affected by external disturbances in space and internal couplings of satellite components. This paper presents a dynamic model to describe the tracking error and proposes a high-precision satellite simulator for the validation of inter-satellite laser tracking. Then, the noises of the sensors and actuators are tested to give the theoretical tracking performance of the simulator. Finally, the laser tracking performance is validated through two experiments: fixed-position tracking and motion tracking. The experimental results show that the measured tracking error of the satellite platform is better than 10 mrad/Hz in the fixed-position tracking and 50 mrad/Hz in the motion tracking. Furthermore, the optical platform can reduce the measured tracking error to 80 µrad/Hz in both two experiments. This work provides a theoretical foundation for optimizing laser tracking performance in space missions, and the proposed simulator has demonstrated a potential for mission simulation with laser tracking.

Research progress of iron metabolism in retinal diseases.

Background: Retinal diseases can lead to severe visual impairment and even blindness, but current treatments are limited. For precise targeted therapy, the pathophysiological mechanisms of the diseases still need to be further explored. Iron serves an essential role in many biological activities and helps maintain the function and morphology of the retina. The vision problems caused by retinal diseases are affecting more and more people, the study of iron metabolism in retinal diseases possesses great potential for clinical application. Main text: Iron maintains a dynamic balance in the retina but in excess is toxic to the retina. Iron overload can lead to various pathological changes in the retina through oxidative stress, inflammation, cell death, angiogenesis and other pathways. It is therefore involved in the progression of retinal diseases such as age-related macular degeneration, glaucoma, diabetic retinopathy, retinitis pigmentosa, and hereditary iron overload. In recent years, iron chelators have been shown to be effective in the treatment of retinal diseases, but the exact mechanism is not yet fully understood. This question prompted further investigation into the specific mechanisms by which iron metabolism is involved in retinal disease. Conclusions: This review summarizes iron metabolism processes in the retina and mechanistic studies of iron metabolism in the progression of retinal disease. It also highlights the therapeutic potential of iron chelators in retinal diseases.

In Situ Synthesis of α-Fe2O3/Fe3O4 Heterojunction Photoanode via Fast Flame Annealing for Enhanced Charge Separation and Water Oxidation.

Hematite (α-Fe2O3) is a promising photoanode material in photoelectrochemical (PEC) water splitting. To further improve the catalytic activity, a reasonable construction of heterojunction and surface engineering can effectively improve the photoanode PEC water-splitting performance via improving bulk carrier transport and interfacial charge-transfer efficiency. As Fe3O4 has an excellent conductivity and a suitable energy band position, α-Fe2O3/Fe3O4 heterojunction can be an ideal structure to improve the activity of α-Fe2O3. However, only few studies have been reported on α-Fe2O3/Fe3O4 heterojunctions as photoanodes. In this work, a holey nanorod Fe2O3/Fe3O4 heterojunction photoanode with oxygen vacancies was fabricated using a rapid and facile flame reduction treatment. Compared with pure Fe2O3, the water oxidation performance of the Fe2O3/Fe3O4 photoanode is improved by ninefold at 1.23 VRHE. Our study revealed that the porous nanorod structure providing more active sites and oxygen vacancies as the hole transfer medium, together improve the interface charge transfer performance of the photoanode. At the same time, Fe3O4 can form a Fe2O3/Fe3O4 heterojunction to improve the carrier separation efficiency. More importantly, Fe3O4 can serve as active sites, solving the slow water oxidation kinetic problem of hematite to enhance the catalytic activity. Our work shows that when flame acts on precursors containing oxygen or hydroxide, it is easy to form compounds with different microstructures or compositions in situ.

Structural characterization of low molecular weight polysaccharide from Astragalus membranaceus and its immunologic enhancement in recombinant protein vaccine against systemic candidiasis.

Structure and immunologic enhancement of low molecular weight polysaccharide (LMW-ASP) isolated from the root of Astragalus membranaceus (Fisch) Bge. Were detected in recombinant protein vaccine. Structure analysis of LMW-ASP revealed that LMW-ASP (Mw=5.6kDa) was an acid heteropolysaccharide, which consisted of Glc, Gal, Ara, Xyl and GalA in ratio of 10.0：1.3：1.7：1.0：0.9. Recombinant protein (rP-HSP90C) contained epitope C (LKVIRK) from heat shock protein 90 (HSP90) of Candida albicans was used as a vaccine. The results indicated that LMW-ASP significantly promoted specific antibody titers IgG, IgG1, IgG2b, and IL-2, IL-4, IL-10, IL-12 in sera of mice immunized with rP-HSP90C (p<0.05). It was also found LMW-ASP improved DTH response in HSP90C-injceted mice. More importantly, the mice immunized with rP-HSP90C/LMW-ASP had fewer CFU (colony forming unites) in the kidneys compared to the mice immunized with rP-HSP90C (p<0.05). Therefore, LMW-ASP could be exploited into the novel adjuvant to enhance the efficacy of recombinant protein vaccine.