Search

The orbit solution of near-Earth asteroids heavily relies on ground-based optical observations. The orbit uncertainty is limited by the insufficient observation quantity and quality. The Chinese Tianwen-2 mission targets a near-Earth asteroid (469219) Kamo'oalewa and a main-belt comet, 311P/PANSTARRS. To accurately determine the orbit of Kamo'oalewa, more optical observations are needed. Autonomous observation experiments focusing on Kamo'oalewa were carried out using the 2.16-m telescope at the Xinglong Observatory of the National Astronomical Observatory of China. We found that this telescope could observe near-Earth asteroids as faint as a magnitude of 22.8. Based on the stacking method and trailed star extraction algorithm, 14 optical observations were obtained from 2022 to 2024. The orbit for Kamo'oalewa was determined by combining our observations with historical observations between 2004 and 2024. The inclusion of our observations results in improved orbital uncertainties of Kamo'oalewa by 18.67, 7.93, and 11.12 km (1σ) in the X, Y , and Z directions, respectively. Furthermore, by combining all existing and simulated observations, the uncertainty of the orbital determination of Kamo'oalewa was analysed. When using an additional 180 group observations from 3 Chinese observatories over 2 yr, the orbital uncertainties of Kamo'oalewa in the 3 directions could be reduced to 30 km (1σ). [ABSTRACT FROM AUTHOR]

Perturbations in the Main Belt Asteroids (MBAs) are the major obstacle for achieving increased prediction accuracy in planetary ephemerides, especially for Mars, as the large quantities of asteroids make ephemeris calculations computationally difficult and complex. In this study, a multiple-ring model of the main asteroid belt is proposed according to the distribution of MBAs proper elements. A new algorithm is adopted for the highly-accurate perturbation calculation from ring model, without the limitation for outer belt planets. This solution can account for more than 98% of the total effect induced by MBAs. A strategy to select representative asteroids is provided, based on a comparative analysis of the perturbation from the main-belt population and the multiple-ring model. The perturbation error on the Mars–Earth distances induced by the difference between the main-belt population and the ring model was estimated numerically. The error is below 0.5 meters over 10 years. This accuracy meets the range measurement accuracy requirements for current Mars missions and makes possible further improvements in the Mars ephemerides estimation. • The multiple-ring model is proposed to represent the main asteroid belt. • An algorithm was adopted for highly-accurate perturbation calculations using the ring model, without the limitation from outer belt planets. • This ring model meets the range measurement accuracy requirements for current Mars missions. [ABSTRACT FROM AUTHOR]

Background: Licorice (Glycyrrhiza uralensis Fisch.), a well-known traditional medicine, is traditionally used for the treatment of respiratory disorders, such as cough, sore throat, asthma and bronchitis. We aim to investigate the effects of liquiritin (LQ), the main bioactive compound in licorice against acute lung injury (ALI) and explore the potential mechanism. Methods: Lipopolysaccharide (LPS) was used to induce inflammation in RAW264.7 cells and zebrafish. Intratracheal instillation of 3 mg/kg of LPS was used for induction an ALI mice model. The concentrations of IL-6 and TNF-α were tested using the enzyme linked immunosorbent assay. Western blot analysis was used to detect the expression of JNK/Nur77/c-Jun related proteins. Protein levels in bronchoalveolar lavage fluid (BALF) was measured by BCA protein assay. The effect of JNK on Nur77 transcriptional activity was determined by luciferase reporter assay, while electrophoretic mobility shift assay was used to examine the c-Jun DNA binding activity. Results: LQ has significant anti-inflammatory effects in zebrafish and RAW264.7 cells. LQ inhibited the expression levels of p-JNK (Thr183/Tyr185), p-Nur77 (Ser351) and p-c-Jun (Ser63), while elevated the Nur77 expression level. Inhibition of JNK by a specific inhibitor or small interfering RNA enhanced the regulatory effect of LQ on Nur77/c-Jun, while JNK agonist abrogated LQ-mediated effects. Moreover, Nur77-luciferase reporter activity was suppressed after JNK overexpression. The effects of LQ on the expression level of c-Jun and the binding activity of c-Jun with DNA were attenuated after Nur77 siRNA treatment. LQ significantly ameliorated LPS-induced ALI with the reduction of lung water content and BALF protein content, the downregulation of TNF-α and IL-6 levels in lung BALF and the suppression of JNK/Nur77/c-Jun signaling, which can be reversed by a specific JNK agonist. Conclusion: Our results indicated that LQ exerts significant protective effects against LPS-induced inflammation both in vivo and in vitro via suppressing the activation of JNK, and consequently inhibiting the Nur77/c-Jun signaling pathway. Our study suggests that LQ may be a potential therapeutic candidate for ALI and inflammatory disorders. [ABSTRACT FROM AUTHOR]

In the cold winter, the concrete strength of box girder under steam curing is not enough and early cracks appear because of volume expansion, poor temperature control and other reasons. The electric heating furnace can provide enough temperature for concrete curing and will not produce a lot of water vapor to make the concrete expand. The construction section of the box girder of the long-span prestressed continuous rigid frame bridge is taken as the research object. The early-age thermal field of concrete under the curing of the electric heating furnace in the cold winter is studied by the method of finite element analysis and field test comparison. The comparison shows that the initial temperature growth of box girder mainly depends on the hydration heat in cement. When the temperature reaches the peak value, it is closely linked to the external conditions. The concrete curing by electric heating furnace can achieve better curing effect in the cold winter. The research results provide a cheap and efficient curing method for concrete curing in the cold winter and a scientific basis for concrete curing by electric heating furnace. [ABSTRACT FROM AUTHOR]

• Expand the application of singularity functions for cable configuration. • Provide the mathematical derivation defining the cable deflection and forces when subject to point loads. • Define the procedure to employ the developed method for determining cable configuration during varied construction stages. • Provide an example of determining cable configuration by using developed method when main span cable is subject to point loads from suspenders. This paper presents a solution procedure for cable configurations, such as the ones used for suspension and cable stayed bridges. It employs a semi analytical method with direct integration of singularity functions. The procedure is rigorous and more efficient than other solution techniques for this class of structures. It can include any number of discontinuous and continuous loads and can take into account the initial configuration of the cable. Because of its efficiency the solution process compared to other solution methods such as finite element analysis is suitable for parametric studies that are needed during the design and construction processes. The procedure may also be used for developing a macro element of cable and its suspenders for use in an efficient finite element solution. [ABSTRACT FROM AUTHOR]

The unstable change of early temperature field during concrete curing of box girder could lead to the thermal deformation and autogenous shrinkage deformation of concrete, make the concrete crack early, and even affect the subsequent mechanical performance. In order to study the variation law of the early-age temperature field of the box girder concrete and to seek the method to control the variation of the temperature field of the box girder concrete, the No.0 box segment with the most complex structure and the largest volume in the bridge was selected as the research object. The early-age temperature field of No.0 box segment after pouring was simulated by Midas/FEA and the correctness of the simulation was verified by field measurement. Then the time-history law of early-age temperature field of the box girder under the coupling effect of hydration heat and ambient temperature was studied, and the time-history law of the early-age temperature field of the box girder was investigated by changing different concrete curing parameters. The results show that the larger the local size is, the larger the temperature difference is. The selection of formwork's material and thickness should integrate the factors of formwork bearing capacity and thermal insulation performance. The reasonable selection of formwork can effectively control the core temperature and the temperature difference between the inside and outside of the box girder. Formwork installation temperature and wind velocity have a great influence on the temperature difference between the inside and outside of the box girder. The research results can provide technical support for controlling the early-age temperature field changes of box girder concrete, be used to provide a theoretical basis for the best selection of formwork and the selection of the best concrete curing conditions, and help to improve efficiencies in the uses of human capital, energy, and building materials in engineering construction. [ABSTRACT FROM AUTHOR]