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Large and rapidly changing Doppler shift poses a huge challenge on fast carrier acquisition for hypersonic vehicle communications. In this study, a novel Doppler shift acquisition method is proposed to increase the acquisition probability and reduce the acquisition time simultaneously. Firstly, the Doppler rate is estimated with a proposed fast blind estimation algorithm. The order of Doppler shift is reduced though twice instantaneous delay autocorrelation operation on the received signal and the modulated information is cancelled, and the Doppler rate can be obtained by the corresponding spectrum analysis. Secondly, the received signal is compensated by the estimated Doppler rate. Finally, the maximum value of the average power spectrum of the compensated result over multiple symbols is detected, and the Doppler shift and Doppler rate can be jointly determined. Furthermore, to improve the acquisition speed, a corrected narrower range, which is determined by the flight conditions of the hypersonic vehicles, is proposed to constrain the search range of the power spectrum peak. Simulation results indicate that, under typical hypersonic flight conditions, the acquisition probability of the Doppler rate increases from 0.52 to 0.86 under − 20 dB. The processing speed can be improved by 75.47% when the length of the combined symbols is 1000.

In order to investigate the effect of Wolbachia on fitness of their hosts, the biological characteristics of a primarily parthenogenetic line and a bisexual restored line (obtained by antibiotic treatment) of Trichogramma pretiosum were compared in the laboratory. Results indicated that both the mean longevity and fecundity of parthenogenetic line (14.2 d and 165 eggs/female) were significantly higher than those in bisexual restored line (8.4 d and 124.2 eggs/female). Both lines of T. pretiosum had the highest daily fecundity (23.3 eggs/female for parthenogenetic line and 19.8 eggs/female for bisexual restored line) on the first day during their reproduction period, and their survival rate and daily fecundity decreased gradually with age; however, the survival rate and daily fecundity of the parthenogenetic line were always higher than those of bisexual restored line, during the entire experimental period. There was no significant difference in emergence rate and deformity rate between the two T. pretiosum lines. The life-table parameter results indicated that net reproduction rate (R0) and mean generation time (T) in parthenogenetic line (133 and 16.8) were significantly higher than those in bisexual restored line (61.7 and 15.5); intrinsic rate of natural increase (rm) and finite rate of increase (λ) in parthenogenetic line (0.29 and 1.34) were higher than those in bisexual restored line (0.26 and 1.3). Based on these results, it can be confirmed that the removal of Wolbachia in the parthenogenetic line had an adverse effect on fitness of T. pretiosum.

During hypersonic flight, the communication link is affected by the multipath effect and plasma sheath. As a result, envelopes and phases of the wireless signals fluctuate with time. In this paper, an integrated channel model is proposed based on geometric propagation theory. The statistical characteristics of the plasma sheath channel are carefully studied. The probability density functions, the correlation coefficient between envelope and phase, the autocorrelation function, the level-crossing rate, and the average fade duration are derived and detailed based on electromagnetic propagation theory. Two numerical examples are also used to demonstrate the effectiveness of the model. All statistical curves agree with the theoretical curves. The proposed model comprehensively considers the multipath effect, the Doppler effect, and the plasma sheath effect. It is crucial to plausibly understand the blackout problem to facilitate performance evaluations of hypersonic vehicle communication systems.

Limb ischemia/reperfusion (I/R) can induce inflammation, causing acute lung injury. The Toll-like receptor 4 (TLR4)/NF-κB pathway plays an important role in acute and chronic inflammatory disorders. Several studies have demonstrated the efficacy of acupuncture in lung inflammatory injury. The aim of the present study was to elucidate the mechanism underlying the protective effect of electroacupuncture (EA) against lung injury induced by limb I/R. EA applied at the Zusanli and Sanyinjiao acupoints attenuated lung injury and decreased the secretion of inflammatory factors such as tumor necrosis factor-α, interleukin (IL)-1, IL-6 and myeloperoxidase. Moreover, the expression levels of TLR4 and NF-κB were suppressed by EA. Thus, the present findings suggested that EA can reduce pulmonary inflammation induced by limb I/R injury, possibly via the inhibition of the TLR4/NF-κB pathway.

The envelope of a hypersonic vehicle is affected by severe fluctuating pressure, which causes the airborne antenna to vibrate slightly. This vibration mixes with the transmitted signals and thus introduces additional multiplicative phase noise. Antenna vibration and signal coupling effects as well as their influence on the lock threshold of the hypersonic vehicle carrier tracking system of the Ka band are investigated in this study. A vibration model is initially established to obtain phase noise in consideration of the inherent relationship between vibration displacement and electromagnetic wavelength. An analytical model of the Phase-Locked Loop (PLL), which is widely used in carrier tracking systems, is established. The coupling effects on carrier tracking performance are investigated and quantitatively analyzed by imposing the multiplicative phase noise on the PLL model. Simulation results show that the phase noise presents a Gaussian distribution and is similar to vibration displacement variation. A large standard deviation in vibration displacement exerts a significant effect on the lock threshold. A critical standard deviation is observed in the PLL of Binary Phase Shift Keying (BPSK) and Quadrature Phase Shift Keying (QPSK) signals. The effect on QPSK signals is more severe than that on BPSK signals. The maximum tolerable standard deviations normalized by the wavelength of the carrier are 0.04 and 0.02 for BPSK and QPSK signals, respectively. With these critical standard deviations, lock thresholds are increased from −12 and −4 dB to 3 and −2 dB, respectively. Keywords: Antenna vibration, Carrier tracking performance, Lock threshold, Phase locked loop, Tracking Telemetry and Command (TT&C) signals

Time-varying plasma sheath likely causes parasitic amplitude and phase modulation effects on communication signals. It can increase the carrier tracking error of tracking telemetry and command systems for hypersonic vehicles flying in near space, and it may lead to loss of lock under serious conditions. This paper comprehensively analyzes the influence mechanism of the amplitude modulation effects on the loss threshold of Type3-phase-locked loop (PLL) in phase-locked receivers. Analysis result shows that amplitude fading in time-varying plasma sheaths is similar to the Gaussian distribution unrelated to the fluctuant densities. The standard deviation of amplitude fading increases with the fluctuant intensity. The 8% fluctuant intensity of electron density begins to have a significant impact on the lock probability of Type3-PLL. On the basis of the analysis results and the amplitude modulation effects, Type3-PLL with a prefiltering (PF-Type3-PLL) method is proposed to mitigate the amplitude modulation effects. PF is placed before the discriminators of Type3-PLL to restrict the amplitude variation within a reasonable range. The tracking loop PF-Type3-PLL is tested with spatial–temporal fluctuant plasma sheath model and compared with the traditional Type3-PLL. Tracking results show that PF-Type3-PLL is more robust than the traditional Type3-PLL. The phase error jitter is significantly reduced when the fluctuant intensity is 8%, and the loss threshold is reduced by 4 dB. The robustness is also enhanced under different loop noise bandwidths (5–15 Hz).

During reentry, plasma sheath is affected by many flight factors, such as trajectory, velocity, angle of attack, and fluid turbulence. As a result, the plasma parameters are time-varied and nonstationary. The nonstationary effects of reentry plasma sheath on electromagnetic (EM) wave propagation are investigated in this paper. First, the factors that affect the plasma sheath are analyzed, and the plasma sheath variation is divided into three scales. A multiscale reentry plasma sheath electron density model is established. A compatible modeling method is proposed, and this method is proven effective. Finally, we analyze the effects of plasma sheath on EM wave at 1.57542, 2.2, and 5 GHz, which are generally used in GPS and telemetry, tracking, and command systems. Results show that the statistical parameters of complex transmission coefficients are time-varied and nonstationary.

Time-varying plasma sheath likely causes a parasitic phase modulation effect on communication signals. It is essential to understand the effect of plasma sheath on the tracking telemetry and command (TT&C) systems for blackout mitigation. This paper comprehensively investigates the impact of parasitic phase modulation effect on the TT&C tracking system of Ka band signals, especially single-frequency and phase-modulated signals. A fluctuant electron density model in the space-time domain is initially established. The phase noise caused by the time-varying plasma sheath is then obtained through wave impedance numerical calculation method. The effect of the time-varying plasma sheath with different fluctuant intensities on the carrier tracking performance is investigated and quantitatively analyzed by imposing phase noise on a phase-locked loop model. Simulation results show that a large fluctuant intensity corresponds to a great impact on the lockout threshold. A critical fluctuant intensity is observed in the three typical TT&C signals. The effect of the time-varying plasma sheath on phase-modulated signals is more severe than that on single-frequency signals. The maximum tolerable fluctuant intensities are 12%, 10%, and 6% for single-frequency signals, binary phase shift keying signals, and quadrature phase shift keying signals, respectively. With the critical fluctuant intensity, their lockout thresholds are increased to 0, 6, and 4 dB, respectively.

Synchronization of large acquisition bandwidth brings great challenges to the traditional second-order phase-locked loop (PLL). To address the contradiction between acquisition bandwidth and noise suppression capability of the traditional PLL, a new second-order PLL coupled with a nonlinear element is proposed. The proposed nonlinear second-order PLL regulates the loop noise bandwidth adaptively by the nonlinear module. When a large input–output phase error occurs, this PLL reduces the frequency offset quickly by taking advantage of the large bandwidth. When the phase error is reduced by the loop control, the proposed PLL suppresses noises by using the small bandwidth to increase the tracking accuracy. Simulation results demonstrate that the tracking speed of the proposed PLL is increased considerably, and its acquisition bandwidth is increased to 18.8 kHz compared with that of the traditional second-order PLL (4 kHz).

Sepsis is a systemic inflammatory reaction caused by infection. Multiple organ failure ultimately leads to high morbidity and mortality. Unfortunately, therapies against these responses have been unsuccessful due to the insufficient underlying pathophysiological evidence. Protein interacting with C-kinase 1 (PICK1) has received considerable attention because of its important physiological functions in many tissues. However, its role in sepsis-induced acute lung injury (ALI) is unclear. In this study, we used cecal ligation and puncture (CLP) to establish a septic model and found that decreased microtubule-associated protein-1light chain 3 (LC3)-II/LC3-I in PICK1−/− septic mice was caused by autophagy dysfunction. Consistently, the transmission electron microscopy (TEM) of bone marrow-derived macrophages (BMDMs) from PICK1−/− mice showed the accumulation of autophagosomes as well. However, more serious damage was caused by PICK1 deficiency indicating that the disrupted autophagic flux was harmful to sepsis-induced ALI. We also observed that it was the impaired lysosomal function that mediated autophagic flux blockade, and the autophagy progress was relevant to PI3K-Akt-mTOR pathway. These findings will aid in the potential development of PICK1 with novel evidence of autophagy in sepsis treatment and prevention.