The mHz quasi-regular modulations of 4U 1630--47 during its 1998 outburst

We present the results of a detailed timing and spectral analysis of the quasi-regular modulation (QRM) phenomenon in the black hole X-ray binary 4U 1630--47 during its 1998 outburst observed by Rossi X-ray Timing Explore (RXTE). We find that the $\sim$ 50-110 mHz QRM is flux dependent, and the QRM is detected with simultaneous low frequency quasi-periodic oscillations (LFQPOs). According to the behavior of the power density spectrum, we divide the observations into four groups. In the first group, namely behavior A, LFQPOs are detected, but no mHz QRM. The second group, namely behavior B, a QRM with frequency above $\sim$ 88 mHz is detected and the $\sim$ 5 Hz and $\sim$ 7 Hz LFQPOs are almost overlapping. In the third group, namely behavior C, the QRM frequency below $\sim$ 88 mHz is detected and the LFQPOs are significantly separated. In the forth group, namely behavior D, neither QRM nor LFQPOs are detected. We study the energy-dependence of the fractional rms, centroid frequency, and phase-lag of QRM and LFQPOs for behavior B and C. We then study the evolution of QRM and find that the frequency of QRM increases with hardness, while its rms decreases with hardness. We also analyze the spectra of each observation, and find that the QRM rms of behavior B has a positive correlation with $\rm F_{\rm powerlaw}$ / $\rm F_{\rm total}$. Finally, we give our understanding for this mHz QRM phenomena.Comment: 14pages, 15 figure

In-orbit background simulation of a type-B CATCH satellite

The Chasing All Transients Constellation Hunters (CATCH) space mission plans to launch three types of micro-satellites (A, B, and C). The type-B CATCH satellites are dedicated to locating transients and detecting their time-dependent energy spectra. A type-B satellite is equipped with lightweight Wolter-I X-ray optics and an array of position-sensitive multi-pixel Silicon Drift Detectors. To optimize the scientific payloads for operating properly in orbit and performing the observations with high sensitivities, this work performs an in-orbit background simulation of a type-B CATCH satellite using the Geant4 toolkit. It shows that the persistent background is dominated by the cosmic X-ray diffuse background and the cosmic-ray protons. The dynamic background is also estimated considering trapped charged particles in the radiation belts and low-energy charged particles near the geomagnetic equator, which is dominated by the incident electrons outside the aperture. The simulated persistent background within the focal spot is used to estimate the observation sensitivity, i.e. 4.22$\times$10$^{-13}$ erg cm$^{-2}$ s$^{-1}$ with an exposure of 10$^{4}$ s and a Crab-like source spectrum, which can be utilized further to optimize the shielding design. The simulated in-orbit background also suggests that the magnetic diverter just underneath the optics may be unnecessary in this kind of micro-satellites, because the dynamic background induced by charged particles outside the aperture is around 3 orders of magnitude larger than that inside the aperture.Comment: 24 pages, 13 figures, 7 tables, accepted for publication in Experimental Astronom

A Sweetpotato Auxin Response Factor Gene (IbARF5) Is Involved in Carotenoid Biosynthesis and Salt and Drought Tolerance in Transgenic Arabidopsis

Auxin response factors (ARFs) compose a family of transcription factors and have been found to play major roles in the process of plant growth and development. However, their roles in plant carotenoid biosynthesis and responses to abiotic stresses are rarely known to date. In the present study, we found that the IbARF5 gene from sweetpotato (Ipomoea batatas (L.) Lam.) line HVB-3 increased the contents of carotenoids and enhanced the tolerance to salt and drought in transgenic Arabidopsis. The transgenic Arabidopsis plants exhibited the increased abscisic acid (ABA) and proline contents and superoxide dismutase (SOD) activity and the decreased H2O2 content. Furthermore, it was found that IbARF5 positively regulated the genes associated with carotenoid and ABA biosynthesis and abiotic stress responses. These results suggest that IbARF5 is involved in carotenoid biosynthesis and salt and drought tolerance in transgenic Arabidopsis. This study provides a novel ARF gene for improving carotenoid contents and salt and drought tolerance of sweetpotato and other plants

Trifrequency Reconfigurable Linear Irregular Array with Beam Deflection Capability in X/Ku/Ka-Bands

This paper proposes a trifrequency reconfigurable antenna (FRA), which can work in the X-band, Ku-band, and Ka-band, by controlling only two RF MEMS switches. The antenna element has a frequency ratio beyond 3 : 1 and provides a good candidate for the frequency reconfigurable antenna array, since the size of the antenna is reduced by loading multiple metal shorting holes between the antenna radiating surface and the ground plate, and the overall size is only 0.14λX × 0.35λX (λX is the free-space wavelength at 8.6 GHz). Based on the proposed FRA element, a 1 × 16 linear irregular frequency reconfigurable antenna array (FRAA) with beam deflection ability is designed, which effectively addresses the element spacing problem in the optimization of the array. In addition, the close-coupling in X-band and the grating lobe caused by the long distance of array element spacing in Ka-band are comprehensively considered. With uniform amplitude feeding network, the sidelobe level is below −15 dB under beam deflection. Moreover, both FRA elements and FRAA prototypes have been fabricated and measured to verify their superiority. Good agreements are obtained between simulated and measured results, which indicates that the antenna has potential application in the future multifrequency wireless communication and intelligent radar anti-interference fields

Effect of Transcranial Pulsed Current Stimulation on Fatigue Delay after Medium-Intensity Training

The purpose of this study was to investigate the effect of transcranial pulsed current stimulation (tPCS) on fatigue delay after medium-intensity training. Materials and Methods: Ninety healthy college athletes were randomly divided into an experimental group (n = 45) and control group (n = 45). The experimental group received medium-intensity training for a week. After each training, the experimental group received true stimulation of tPCS (continuous 15 min 1.5 mA current intensity stimulation). The control group received sham stimulation. The physiological and biochemical indicators of participants were tested before and after the experiment, and finally 30 participants in each group were included for data analysis. Results: In the experimental group, creatine kinase (CK), cortisol (C), time-domain heart rate variability indices root mean square of the successive differences (RMSSD), standard deviation of normal R-R intervals (SDNN), and frequency domain indicator low frequency (LF) all increased slowly after the intervention. Among these, CK, C, and SDNN values were significantly lower than those in the control group (p < 0.05). Testosterone (T), T/C, and heart rate variability frequency domain indicator high frequency (HF) in the experimental group decreased slowly after the intervention, and the HF value was significantly lower than that in the control group (p < 0.05). The changes in all of the indicators in the experimental group were smaller than those in the control group. Conclusion: The application of tPCS after medium-intensity training enhanced the adaptability to training and had a significant effect on the maintenance of physiological state. The application of tPCS can significantly promote the recovery of autonomic nervous system function, enhance the regulation of parasympathetic nerves, and delay the occurrence of fatigue

Study on the Effect of Different Transcranial Pulse Current Stimulation Intervention Programs for Eliminating Physical Fatigue

Previous studies have reported the effect of transcranial pulsed current stimulation (tPCS) on eliminating cognitive fatigue, but there is little research on optimizing the intervention program of tPCS. The purpose of this study was to explore the effect of different tPCS intervention programs on the elimination of physical fatigue in college athletes. Accordingly, 40 healthy college athletes were randomly divided into two groups of 20, denoted as A and B. Both groups exercised on treadmills. There were 15 subjects in group A who met the criteria of moderate physical fatigue, and 15 subjects in group B who met the criteria of severe physical fatigue. The subjects in each group were intervened with five different intervention programs of tPCS (intervention programs I, II, III, IV and V). The heart rate variability (HRV) and concentrations of oxygenated hemoglobin (HbO2) were measured before and after each intervention to judge the elimination effects of different intervention programs on different degrees of physical fatigue; the measurement indicators of the HRV include RMSSD, SDNN, HF and LF. The results indicated that tPCS intervention can eliminate both moderate and severe physical fatigue. Programs II, III, and IV had a significant effect on eliminating the moderate physical fatigue of athletes (p p < 0.05), among which program I, with a stimulation time of 30 min and a stimulation intensity of sensory intensity + 0.2 mA, had the best effect. We conclude that different tPCS intervention programs can have different effects on the elimination of physical fatigue. The effects of the five intervention programs on the elimination of physical fatigue in athletes are as follows: program II is most suitable for moderate physical fatigue, and program I is most suitable for severe physical fatigue

A Novel Linear Sparse Array with Reconfigurable Pixel Antenna Elements

In this paper, on the basis of multifunctional reconfigurable pixel antenna (RPA) elements, a novel linear sparse array with an attractive compound reconfigurability is presented. It has the potential advantages of its beam scanning with low gain fluctuation, low sidelobe in two orthogonal planes, and polarization reconfigurable performance. Specifically, an RPA with simultaneous polarization and pattern reconstruction capabilities, consisting of the driven patch and the parasitic pixels on the same layer of dielectric substrate, is firstly designed, which can work in several operation modes corresponding to steerable beam directions θ=0°;θxoz=25°, 45°;θyoz=15° with two circular polarizations in X-band. Cross-slot coupling feed is used to improve polarization reconstruction capability and reduce the complexity of hybrid reconstruction topology optimization. Then, those RPAs are integrated into the 1×8 linear sparse array to realize the reconfiguration of two circular polarizations and beam steering in xoz- and yoz-plane. Simulation results show that the gain fluctuation and sidelobe level of the array during beam scanning have significant advantages over the previous phased array, and the generation of antenna grating lobes is avoided. Moreover, both RPA element and RPA array prototypes have been fabricated and measured to testify the efficiency. The measured results agree well with the simulated ones, which indicates the application potential in the field of modern wireless communication system of the proposed linear sparse array