Proton acceleration in a near-critical-density gas driven by a light spring (LS) pulse with a helical structure in its intensity profile is investigated using three-dimensional particle-in-cell simulations. Compared with other pulse modes with the same laser power, such as the Gaussian pulse or the donut Laguerre–Gaussian (LG) pulse, the LS structure significantly enhances the peak intensity and drives a stronger longitudinal acceleration field and transverse focusing field. Both the high intensity and helical structure of the LS pulse contribute to the formation of a bubble-like structure with a fine electron column on the axis, which is critical for stable proton acceleration. Therefore, it is very promising to obtain ultra-high-energy protons using LS pulses with a relatively lower power. For example, by using LS pulses with the same power of 4.81 PW, the proton in the gas can be accelerated up to 8.7 GeV, and the witness proton can be accelerated to 10.6 GeV from 0.11 GeV, which shows the overwhelming advantage over the Gaussian and LG pulse cases.

This study is dedicated to achieving efficient active noise control in a supersonic underexpanded planar jet, utilizing control parameters informed by resolvent analysis. The baseline supersonic underexpanded jet exhibits complex wave structures and substantial high-amplitude noise radiations. To perform the active control, unsteady blowing and suction are applied along the nozzle inner wall close to the exit. Employing both standard and acoustic resolvent analyses, a suitable frequency and spanwise wavenumber range for the blowing and suction is identified. Within this range, the control forcing can be significantly amplified in the near field, effectively altering the original sound-producing energetic structure while minimizing far-field amplification to prevent excessive noise. A series of large-eddy simulations are further conducted to validate the control efficiency, demonstrating an over 10 dB reduction in upstream-propagated screech noise. It is identified that the present unsteady control proves more effective than steady control at the same momentum coefficient. The controlled jet flow indicates that the shock structures become more stable, and the stronger the streamwise amplification of the forcing, the more likely it is to modify the mean flow characteristics, which is beneficial for reducing far-field noise radiation. Spectral proper orthogonal decomposition analysis of the controlled flow confirms that the control redistributes energy to higher forcing frequencies and suppresses large-scale antisymmetric and symmetric modes related to screech and its harmonics. The findings of this study highlight the potential of resolvent-guided control techniques in reducing noise in supersonic underexpanded jets and provide a detailed understanding of the inherent mechanisms for effective noise reduction through active control strategies.

Expert drivers possess the ability to execute high sideslip angle maneuvers, commonly known as drifting, during racing to navigate sharp corners and execute rapid turns. However, existing model-based controllers encounter challenges in handling the highly nonlinear dynamics associated with drifting along general paths. While reinforcement learning-based methods alleviate the reliance on explicit vehicle models, training a policy directly for autonomous drifting remains difficult due to multiple objectives. In this paper, we propose a control framework for autonomous drifting in the general case, based on curriculum reinforcement learning. The framework empowers the vehicle to follow paths with varying curvature at high speeds, while executing drifting maneuvers during sharp corners. Specifically, we consider the vehicle’s dynamics to decompose the overall task and employ curriculum learning to break down the training process into three stages of increasing complexity. Additionally, to enhance the generalization ability of the learned policies, we introduce randomization into sensor observation noise, actuator action noise, and physical parameters. The proposed framework is validated using the CARLA simulator, encompassing various vehicle types and parameters. Experimental results demonstrate the effectiveness and efficiency of our framework in achieving autonomous drifting along general paths. The code is available at https://github.com/BIT-KaiYu/drifting.

Summary: Melatonin serves as an endogenous synchronizer of biological rhythms. Age-related changes are evident with a significant reduction in melatonin observed in 24-hour secretion. Melatonin exerts a significant cytoprotective action by buffering free radicals and reversing inflammation. However, few studies have explored the association between physical activity and melatonin level. In this study, we compared melatonin level and actigraphy-derived sleep and activity indicators in older adults across two levels of exercise habit (sedentary-to- light exercise and moderate -to-vigorous exercise), as well as the association of these indicators with melatonin levels. We recruited 104 participants (aged 57– 84 years) who wore a wristwatch device to monitor their activity (MotionWatch 8; CamNtech, Cambridge, UK) for 14 days. Circadian rhythms were estimated using cosinor analysis, lag 1440 mins correlation coefficient, interdaily stability, and non-parametric analysis. Saliva samples were collected every 30 mins from 18:00 pm till one hour before usual bedtime, and maximum melatonin level during this period. A 5-minute Psychomotor Vigilance Task (PVT) was used to evaluate attention. Habits of physical activities were self-reported. Melatonin level was not significantly different between participants with sedentary- to-light and moderate-to-vigorous exercise habits. Analysis showed that participants who had moderate-vigorous exercise habit were older (p = 0.04), having longer sports time (p < 0.001) and WASO (p = 0.02), more occurrence of daytime naps (intradaily variability) (p = 0.05), more fragmentated 24-h sleep-wake cycle (interdaily stability, p = 0.01), and less regular 24h rhythm (lag 1140 mins correlation, p = 0.04). They also showed shorter response time (p = 0.05), and a smaller number of lapses (p = 0.04) in PVT. Regression analysis results showed that weekly exercise time is positively associated with melatonin level. Additionally, a later start hour of M10 is associated with 5.95 pg/ml increase in melatonin level. In consistent, exercise in older adults did not promote a robust sleep- wake cycle but is related to better cognitive function and higher melatonin levels.

Introduction: Late-life depression (LLD) is associated with cognitive deficit with risk of future dementia. By examining the entropy of the spontaneous brain activity, we aimed to understand the neural mechanism pertaining to cognitive decline in LLD.

Methods: We collected MRI scans in older adults with LLD (n = 32), mild cognitive impairment [MCI (n = 25)] and normal cognitive function [NC, (n = 47)]. Multiscale entropy analysis (MSE) was applied to resting-state fMRI data. Under the scale factor (tau) 1 and 2, reliable separation of fMRI data and noise was achieved. We calculated the brain entropy in 90 brain regions based on automated anatomical atlas (AAL). Due to exploratory nature of this study, we presented data of group-wise comparison in brain entropy between LLD vs. NC, MCI vs. NC, and LLD and MCD with a p-value below 0.001.

Results: The mean Mini-Mental State Examination (MMSE) score of LLD and MCI was 27.9 and 25.6. Under tau 2, we found higher brain entropy of LLD in left globus pallidus than MCI (p = 0.002) and NC (p = 0,009). Higher brain entropy of LLD than NC was also found in left frontal superior gyrus, left middle superior gyrus, left amygdala and left inferior parietal gyrus. The only brain region with higher brain entropy in MCI than control was left posterior cingulum (p-value = 0.015). Under tau 1, higher brain entropy was also found in LLD than in MCI in right orbital part of medial frontal gyrus and left globus pallidus (p-value = 0.007 and 0.005).

Conclusions: Our result is consistent with prior hypothesis where higher brain entropy was found during early aging process as compensation. We found such phenomenon particular in left globus pallidus in LLD, which could be served as a discriminative brain region. Being a key region in reward system, we hypothesis such region may be associated with apathy and with unique pathway of cognitive decline in LLD. We will undertake subsequent analysis longitudinally in this cohort

Key words: resting-state fMRI, Late-life depression, Brain entropy, globus pallidus, cognitive decline

We investigate the coupling effects of the two-phase interface, viscosity ratio and density ratio of the dispersed phase to the continuous phase on the flow statistics in two-phase Taylor–Couette turbulence at a system Reynolds number of $6\times 10^3$ and a system Weber number of 10 using interface-resolved three-dimensional direct numerical simulations with the volume-of-fluid method. Our study focuses on four different scenarios: neutral droplets, low-viscosity droplets, light droplets and low-viscosity light droplets. We find that neutral droplets and low-viscosity droplets primarily contribute to drag enhancement through the two-phase interface, whereas light droplets reduce the system's drag by explicitly reducing Reynolds stress due to the density dependence of Reynolds stress. In addition, low-viscosity light droplets contribute to greater drag reduction by further reducing momentum transport near the inner cylinder and implicitly reducing Reynolds stress. While interfacial tension enhances turbulent kinetic energy (TKE) transport, drag enhancement is not strongly correlated with TKE transport for both neutral droplets and low-viscosity droplets. Light droplets primarily reduce the production term by diminishing Reynolds stress, whereas the density contrast between the phases boosts TKE transport near the inner wall. Therefore, the reduction in the dissipation rate is predominantly attributed to decreased turbulence production, causing drag reduction. For low-viscosity light droplets, the production term diminishes further, primarily due to their greater reduction in Reynolds stress, while reduced viscosity weakens the density difference's contribution to TKE transport near the inner cylinder, resulting in a more pronounced reduction in the dissipation rate and consequently stronger drag reduction. Our findings provide new insights into the physics of turbulence modulation by the dispersed phase in two-phase turbulence systems.

Linear instability analysis of a viscous swirling liquid jet surrounded by ambient gas is carried out by considering the significant influence of axial shear effect. The jet azimuthal flow is assumed as a Rankine vortex, and the non-uniform velocity distribution in the jet axial direction is approximated by parabolic and error functions. The enhancement of jet rotation is found to promote the predominant mode with larger azimuthal wavenumbers, and the mode transition is decided by the competition between centrifugal force and axial shear stress. Subsequently, the influence of the axial shear effect is examined through changing the degree of shear stress and the thickness of the gas velocity boundary layer. It is found that an increase of jet average velocity or surface velocity in the axial direction leads to the predominant mode transition to smaller azimuthal wavenumbers, due to the combined effects of shear stress and gas pressure perturbation. A larger velocity difference between ambient gas and liquid jet also promotes the predominant modes with smaller azimuthal wavenumbers, and the physical mechanism is attributed to gas pressure perturbation. Phase diagrams of different azimuthal modes are given and compared with the study of Kubitschek & Weidman (J. Fluid Mech., vol. 572, 2007, pp. 261–286), where a static swirling column without axial shear stress was considered. The strengthened axial shear effect is found to delay the transition of predominant modes with the increase of angular velocity. Experimental studies considering the swirling jets with different axial velocities are further carried out, which validate the theoretical findings. Different instability mechanisms and their transition rules are also identified through energy budget analysis. This study is expected to give scientific guidance on understanding the instability mechanisms of the swirling jets that widely exist in natural phenomena and engineering applications.

Timing of food intake is an emerging aspect of nutrition; however, there is a lack of research accurately assessing food timing in the context of the circadian system. The study aimed to investigate the relation between food timing relative to clock time and endogenous circadian timing with adiposity and further explore sex differences in these associations among 151 young adults aged 18–25 years. Participants wore wrist actigraphy and documented sleep and food schedules in real time for 7 consecutive days. Circadian timing was determined by dim-light melatonin onset (DLMO). The duration between last eating occasion and DLMO (last EO-DLMO) was used to calculate the circadian timing of food intake. Adiposity was assessed using bioelectrical impedance analysis. Of the 151 participants, 133 were included in the statistical analysis finally. The results demonstrated that associations of adiposity with food timing relative to circadian timing rather than clock time among young adults living in real-world settings. Sex-stratified analyses revealed that associations between last EO-DLMO and adiposity were significant in females but not males. For females, each hour increase in last EO-DLMO was associated with higher BMI by 0·51 kg/m2 (P = 0·01), higher percent body fat by 1·05 % (P = 0·007), higher fat mass by 0·99 kg (P = 0·01) and higher visceral fat area by 4·75 cm2 (P = 0·02), whereas non-significant associations were present among males. The findings highlight the importance of considering the timing of food intake relative to endogenous circadian timing instead of only as clock time.

This study examined the sour grapes/sweet lemons rationalization through 2 conditions: ‘attainable’ (sweet lemons) and ‘unattainable’ (sour grapes), reflecting China’s 2019-nCoV vaccination strategy. The aim was to find ways to change people’s beliefs and preferences regarding vaccines by easing their safety concerns and encouraging more willingness to get vaccinated. An online survey was conducted from January 22 to 27, 2021, with 3,123 residents across 30 provinces and municipalities in the Chinese mainland. The direction of belief and preference changed in line with the sour grapes/sweet lemons rationalization. Using hypothetical and real contrasts, we compared those for whom the vaccine was relatively unattainable (‘sour grapes’ condition) with those who could get the vaccine easily (‘sweet lemons’). Whether the vaccine was attainable was determined in the early stage of the vaccine roll-out by membership in a select group of workers that was supposed to be vaccinated to the greatest extent possible, or, by being in the second stage when the vaccine was available to all. The attainable conditions demonstrated higher evaluation in vaccine safety, higher willingness to be vaccinated, and lower willingness to wait and see. Hence, we propose that the manipulation of vaccine attainability, which formed the basis of the application of sour grapes/sweet lemons rationalization, can be utilized as a means to manipulate the choice architecture to nudge individuals to ease vaccine safety concerns, reducing wait-and-see tendencies, and enhancing vaccination willingness. This approach can expedite universal vaccination and its associated benefits in future scenarios resembling the 2019-nCoV vaccine rollout.

This study explores the relationships between group-affect tone, teams’ transactive memory systems (TMSs), and teams’ incremental creativity. Data were collected from 334 team members and 70 team leaders across 70 teams. Results indicate that positive group-affect tone enhances TMS, while negative group-affect tone impedes it. TMS positively impacts team incremental creativity. Additionally, both types of group-affect tone influence incremental creativity through TMS mediation. This research advances TMS theory and group-affect tone, substantiating the affect-cognition model and deepening the understanding of TMS’s role in incremental creativity.

The delay-shift of the pre-pulse may mislead the determination of its origination and cause problems for the temporal contrast improvement of high-peak-power lasers, especially when the corresponding post-pulse is beyond the time window of the measurement device. In this work, an empirical formula is proposed to predict the delay-shift of pre-pulses for the first time. The empirical formula shows that the delay-shift is proportional to the square of the post-pulse’s initial delay, and also the ratio of the third-order dispersion to the group delay dispersion’s square, which intuitively reveals the main cause for the delay-shift and may provide a convenient routing for identifying the real sources of pre-pulses in both chirped-pulse amplification (CPA) and optical parametric chirped-pulse amplification (OPCPA) systems. The empirical formula agrees well with the experimental results both in the CPA and the OPCPA systems. Besides, a numerical simulation is also carried out to further verify the empirical formula.

In this paper, a capsule endoscopy system with a sensing function is proposed for medical devices. A single-arm spiral antenna is designed for data transmission and is combined with the voltage controlled oscillator to achieve sensing capabilities. The designed antenna operates at a 900 MHz industrial scientific medical band. By establishing a three-layer cylindrical model of the stomach, it was concluded that the antenna in the stomach has a high peak gain of −1.1 dBi. Additionally, the antenna achieved a −10 dB impedance bandwidth of 5%. The capsule endoscopy was experimentally measured in both actual stomach and simulated environments. The maximum working distance of the capsule endoscope was measured to be 6.8 m. Additionally, the proposed capsule endoscope was tested for its sensing function using solutions with different dielectric constants. Finally, it was confirmed through link analysis that it has good communication capabilities. The results and analysis confirm that the proposed capsule endoscope can be used for examining gastric diseases.

Caryocaridids are a unique representative of pelagic arthropods from the Ordovician period. They are typically found as flattened carapaces in mudstones and shales. This study reports on a species of caryocaridids, Soomicaris cedarbergensis, discovered in the Lower Ordovician of northwestern Xinjiang, NW China. The species shows the rare enrolled carapaces with a preserved cuticular ultrastructure. These specimens of caryocaridids from Xinjiang are the first reported in the Yili Block, and provide the substantial evidence that the paleogeographic distribution of caryocaridid phyllocarids could extend to the Central Asian Orogenic Belt. This species existed from the late Tremadocian until the end of the Ordovician (Hirnantian), making it the longest-ranging known species of caryocaridids. The carapace cuticle of S. cedarbergensis is composed of carbonate-fluorapatite and can be divided into three mineralized lamellae: outer, middle, and inner. The outer and inner lamellae each consist of three layers that correspond to the epicuticle, exocuticle, and endocuticle of extant crustacean carapaces. Moreover, the polygonal reticulation structure of the carapace in archaeostracans appears to be similar in shape and size to the hemolymph sinuses of leptostracans. This unique ultrastructure of the carapace cuticle in caryocaridids is believed to be better suited for a pelagic lifestyle.