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C20H22Br2N2O4, triclinic, P1‾$P\overline{1}$ (no. 2), a = 5.0060(12) Å, b = 9.135(2) Å, c = 11.650(3) Å, V = 518.6(2) Å3, Z = 1, Rgt(F) = 0.0474, wRref(F2) = 0.1270, T = 273(2) K, β = 78.492(7).

We report the results of a search for radio pulsars in five supernova remnants (SNRs) with the FAST telescope. The observations were made using the 19-beam receiver in "snapshot" mode. The integration time for each pointing was 10 min. We discovered a new pulsar, PSR J1845–0306, which has a spin period of 983.6 ms and a dispersion measure of 444.6 ± 2.0 cm−3⋅pc, in observations of SNR G29.6+0.1. To judge the association between the pulsar and the SNR, further verification is needed. We also re-detected some known pulsars in the data from SNRs G29.6+0.1 and G29.7–0.3. No pulsars were detected in the observations of the other three SNRs. [ABSTRACT FROM AUTHOR]

We did 194 epochs of simultaneous 2.25/8.60 GHz observations of XTE J1810−197 in 926 days shortly following its reactivation in 2018 with Shanghai Tian Ma Radio Telescope (TMRT). Although its integrated profiles changed with both time and frequency during this period, they could be classified into 12 types according to phase areas of active radiation components. After MJD 59015, XTE J1810−197 turned from the normal emission state into the spiky emission state that was manifesting as a series of bright narrow sub-pulse bursts at both 2.25 and 8.60 GHz. Due to its variable integrated profiles and unsteady rotations, we got the spin frequency ν and spin-frequency derivatives ν ̇ with the piecewise fitting method. In addition, its long-term declining trend of ν was also obtained as ν ̇ = − 3.2 (1) × 10 − 13 s−2 with the linear fitting method based on our observations spanning a comparatively longer period. We found its flux densities went through three stages: sharp decrease, stabilization, and day-to-day fluctuations in our dual-frequency observations. Although the flux density showed different stages, XTE J1810−197 showed a relatively flat spectrum (α > –1) in most observations. Assuming an ideal dipole magnetic field as some previous research works, we obtained the emission heights of XTE J1810−197 were about 7.5(9) × 104 km and 2.38(7) × 104 km at 2.25 and 8.60 GHz, respectively. We also found that its emission heights would decrease rapidly with the degree of magnetic field twisting. [ABSTRACT FROM AUTHOR]

Hermetic pressurized buildings have been developed to reduce the effects of high altitude. The behavior and effect of fire in this new type of building have not been studied before. Unlike common buildings, the inside pressure in this new type of building is maintained at around standard atmospheric pressure, which is significantly higher than the outside environment pressure in high altitude regions. In addition, at the early stage of a fire, the oxygen required to maintain combustion in the sealed building is supplied by mechanical vents (if in operation) instead of opening windows or doors as in common buildings. This paper presents a case study on the behavior of fire in a sealed pressurized hotel building located in Tibet. Fire dynamics simulator (FDS) is used to study fire behavior under different design fire scenarios. Available evacuation time under different fire scenarios are obtained by analyzing oxygen concentration, gas content, temperature, visibility and other indicators. Based on this, a fire protection design scheme is suggested. [ABSTRACT FROM AUTHOR]

We present timing solutions of PSR B0950+08, using 14 years of observations from the Nanshan 26-m Radio Telescope of Xinjiang Astronomical Observatory. The braking index of PSR B0950+08 varies from –367 392 to 168 883, which shows an oscillation with large amplitude (∼105) and uncertainty. Considering the variation of braking indices and the most probable kinematic age of PSR B0950+08, a model with long-term magnetic field decay modulated by short-term oscillations is proposed to explain the timing data. With this magnetic field decay model, we discuss the spin and thermal evolution of PSR B0950+08. The uncertainties of its age are also considered. The results show that three-component oscillations are the more reasonable for the spin-frequency derivative distributions of PSR B0950+08, and the initial spin period of PSR B0950+08 must be shorter than |$97\rm \ ms$| when the age is equal to the lower bound of its kinematic age. The standard cooling model could explain the surface temperature of PSR B0950+08 with its most probable kinematic age. Vortex creep heating with a long-term magnetic field decay could maintain a relatively high temperature at the later stages of evolution and explain the thermal emission data of old and warm pulsars. Coupling with the long-term magnetic field decay, an explanation of the temperature of PSR B0950+08 with roto-chemical heating needs an implausibly short initial rotation period (⁠|$P_0 \lesssim 17\rm { ms}$|⁠). The spin and thermal evolution of pulsars should be studied simultaneously. Future timing, ultraviolet or X-ray observations are essential for studying the evolution and interior properties of pulsars. [ABSTRACT FROM AUTHOR]

Swift  J1818.0–1607 discovered in early 2020 is not only the fifth magnetar known with periodic radio pulsations but also the fastest rotating one. Simultaneous 2.25/8.60 GHz observations of Swift  J1818.0–1607 were carried out with Shanghai Tian Ma Radio Telescope (TMRT) from MJD 58936 to 59092. The spin-frequency ν and first-order derivative |$\dot{\nu }$| of this magnetar were obtained with piecewise fitting method because of its instable timing properties. We found that the amplitude of short-term |$\dot{\nu }$| fluctuations decreased with time, and the long-term declining trend of ν discovered previously continued in our observations. The best fit long-term |$\dot{\nu }$| were about |$-2.25\times 10^{-11} \, \mathrm{s}^{-2}$| using our observation data spanning 156 d. The derived characteristic age was about 522 yr, supporting the recent viewpoint that this magnetar may be older than initially thought shortly after its discovery. The flux density of this magnetar was increased at both 2.25 and 8.60 GHz during our observations, and its radio spectrum became flatter at the same time. We also detected bright-quiet type emission mode switching in Swift  J1818.0–1607. [ABSTRACT FROM AUTHOR]

A pulsar's position, proper motion, and parallax are important parameters in timing equations. It is challenging to fit astrometric parameters accurately through pulsar timing, especially for pulsars that show irregular timing properties. With the fast development of related techniques, it is possible to measure astrometric parameters of more and more pulsars in a model-independent manner with very-long-baseline interferometry (VLBI). In this work we select 16 normal pulsars, whose parallax and proper motion have not been successfully fitted with timing observations or show obvious differences from the corresponding latest VLBI solutions, and do further studies on their timing properties. After updating the astrometric parameters in pulsar ephemerides with the latest VLBI measurements, we derive the latest rotation solutions of these pulsars with observation data in the S and C bands obtained from the Shanghai Tian Ma Radio Telescope. Compared with the spin frequency ν inferred from previous rotation solutions, the newly fitted ν show differences larger than 10−9 Hz for most pulsars. The contribution of the Shklovsky effect to the period derivative |$\dot{P}$| can be properly removed by taking advantage of the accurate proper motion and distance of target pulsars measured by VLBI astrometry. This further leads to a precise estimate of the intrinsic characteristic age τc. The differences between the newly measured τc and corresponding previous results are as large as 2% for some pulsars. VLBI astrometric parameter solutions also lead to better measurements of timing irregularities. For PSR B0154+61, the glitch epoch (MJD 58279.5) measured with a previous ephemeris is about 13 d later than the result (MJD 58266.4) obtained with VLBI astrometric parameter solutions. [ABSTRACT FROM AUTHOR]

The thraustochytrids, the heterotrophic marine microorganisms, have received increasing attention because of their capacity for the production of high‐value products such as docosahexaenoic acid (DHA), carotenoids, and sterols. In this study, three potential Δ5,7‐sterols, showing similar UV absorption spectra to that of ergosterol, in the thraustochytrid Schizochytrium sp. S31, were estimated by the ultraperformance liquid chromatography (UPLC) − APCI−MS/MS method. The proposed structures of three Δ5,7‐sterols were ergosta‐5,7,24(28)‐trien‐3β‐ol, ergosta‐5,7‐dien‐3β‐ol, and 24‐ethylcholesta‐5,7,22‐trien‐3β‐ol. The contents of astaxanthin, ergosterol, and the other three Δ5,7‐sterols in Schizochytrium sp. S31 during the cultivation performed in three separate batches were analyzed by a fast UPLC–PDA method. The results demonstrated that astaxanthin, ergosterol, and ergosta‐5,7‐dien‐3β‐ol were the predominant carotenoid and Δ5,7‐sterols, respectively, and their contents kept increasing during the growth and reached a maximum after 23 days of cultivation. The estimated maximum contents of astaxanthin and four Δ5,7‐sterols, including ergosterol, ergosta‐5,7‐dien‐3β‐ol, ergosta‐5,7,24(28)‐trien‐3β‐ol, and 24‐ethylcholesta‐5,7,22‐trien‐3β‐ol were 2.31, 4.02, 3.43, 0.30, and 0.97 mg g−1 dry biomass, respectively. These findings are different to other strains reported in the composition and accumulation of Δ5,7‐sterols and carotenoids. The present study suggests that Schizochytrium sp. S31 might be a promising marine microorganism for the productions of high‐value natural pigment astaxanthin, the provitamin D2 ergosterol, and the provitamin D4 ergosta‐5,7‐dien‐3β‐ol, and taken as a model organism to study the sterologenesis of the microorganisms because of its complexity of sterol compositions. [ABSTRACT FROM AUTHOR]

C20H22Br2N2O4, triclinic, P 1 ‾ (no. 2), a = 5.0060(12) Å, b = 9.135(2) Å, c = 11.650(3) Å, V = 518.6(2) Å3, Z = 1, Rgt(F) = 0.0474, wRref(F2) = 0.1270, T = 273(2) K, β = 78.492(7). [ABSTRACT FROM AUTHOR]