Observation of Rabi dynamics with a short-wavelength free-electron laser.

Rabi oscillations are periodic modulations of populations in two-level systems interacting with a time-varying field1. They are ubiquitous in physics with applications in different areas such as photonics2, nano-electronics3, electron microscopy4 and quantum information5. While the theory developed by Rabi was intended for fermions in gyrating magnetic fields, Autler and Townes realized that it could also be used to describe coherent light-matter interactions within the rotating-wave approximation6. Although intense nanometre-wavelength light sources have been available for more than a decade7-9, Rabi dynamics at such short wavelengths has not been directly observed. Here we show that femtosecond extreme-ultraviolet pulses from a seeded free-electron laser10 can drive Rabi dynamics between the ground state and an excited state in helium atoms. The measured photoelectron signal reveals an Autler-Townes doublet and an avoided crossing, phenomena that are both fundamental to coherent atom-field interactions11. Using an analytical model derived from perturbation theory on top of the Rabi model, we find that the ultrafast build-up of the doublet structure carries the signature of a quantum interference effect between resonant and non-resonant photoionization pathways. Given the recent availability of intense attosecond12 and few-femtosecond13 extreme-ultraviolet pulses, our results unfold opportunities to carry out ultrafast manipulation of coherent processes at short wavelengths using free-electron lasers.

4D spatio-temporal electric field characterization of ultrashort light pulses undergoing filamentation.

We present an experimental method capable of capturing the complete spatio-temporal dynamics of filamenting ultrashort laser pulses. By employing spatially resolved Fourier transform spectrometry in combination with the capability to terminate the filament at any length, we can follow the nonlinear dynamics in four dimensions, i.e. the transverse domain, time and filament length. Our method thus not only enables the full characterization of the filamentation process throughout its evolution, but also allows to identify and select laser pulses with desired parameters.

Fano's Propensity Rule in Angle-Resolved Attosecond Pump-Probe Photoionization.

In a seminal article, Fano predicts that absorption of light occurs preferably with increase of angular momentum. We generalize Fano's propensity rule to laser-assisted photoionization, consisting of absorption of an extreme-ultraviolet photon followed by absorption or emission of an infrared photon. The predicted asymmetry between absorption and emission leads to incomplete quantum interference in attosecond photoelectron interferometry. It explains both the angular dependence of the photoionization time delays and the delay dependence of the photoelectron angular distributions. Our theory is verified by experimental results in Ar in the 20-40 eV range.

Enhancement of high-order harmonics in a plasma waveguide formed in clustered Ar gas.

Generation of high-order harmonics (HHs) is intensified by using a plasma waveguide created by a laser in a clustered gas jet. The formation of a plasma waveguide and the guiding of a laser beam are also demonstrated. Compared to the case without a waveguide, harmonics were strengthened up to nine times, and blue-shifted. Numerical simulation by solving the time-dependent Schrödinger equation in strong field approximation agreed well with experimental results. This result reveals that the strengthening is the result of improved phase matching and that the blue shift is a result of change in fundamental laser frequency due to self-phase modulation (SPM).

High-efficiency supercontinuum generation in solid thin plates at 0.1 TW level.

Supercontinuum generation in a solid-state medium was investigated experimentally. A continuum covering 460 to 950 nm was obtained when 0.8 mJ/30 fs Ti:sapphire laser pulses were applied to seven thin fused silica plates at a 1 kHz repetition rate. The primary processes responsible for spectral broadening were self-phase modulation (SPM) and self-steepening, while SPM and self-focusing were balanced to optimize the spectral broadening and suppress the multiphoton process. The output was compressed to a 5.4 fs and a 0.68 mJ pulse, corresponding to two optical cycles and 0.13 TW of peak power.

Compact single-shot d-scan setup for the characterization of few-cycle laser pulses.

We present a compact implementation of the ultrashort pulse measurement technique based on dispersion scans (d-scan), allowing single-shot measurement of few-cycle pulses. The main novelty in our design, making our setup extremely compact and simple, is the use, after a prism, of a spherical mirror in an off-axis geometry. The intentionally introduced strong astigmatism makes it possible to image the output of the crystal in one direction while focusing it in the other direction, resulting in the output face of the prism being imaged into a line in the second-harmonic crystal. The technique is validated by comparing measured dispersion scans, retrieved spectral phases and temporal profiles of this single-shot system with standard d-scan results.

Full quantum trajectories resolved high-order harmonic generation.

We use a carrier-envelope-phase stabilized sub-2-cycle laser pulse to generate high-order harmonics and study how the two-dimensional spectrum of harmonics, with the resolutions in temporal frequency and spatial frequency, is shaped by the laser phase. An arrowlike spectrum obtained experimentally when the gas cell is located in front of the laser focus point shows a resolution of full quantum trajectories; i.e., harmonics from different trajectories stand on different positions in this spectrum. In particular, due to the laser phase combined with the classical-like action, the harmonics from short and long trajectories differ maximally in their curvatures of wave fronts in the generation area, and so occupy very different ranges of spatial frequency at the far field. The result directly gives a full map of quantum trajectories in high-order harmonic generation. The conclusion is supported by an analytical model and quantum mechanics simulations.

Effects of brief mindfulness meditation training on attention and dispositional mindfulness in young adult males.

This study examined the impact of brief mindfulness meditation (BMM) training on attention function and dispositional mindfulness in young males. 126 male participants aged 18-26 from the security industry were recruited, with 66 participants (M = 22.84, SD = 2.41) undergoing 4-week mindfulness meditation training and 60 participants (M = 23.07, SD = 2.29) in the active control group. The intervention was integrated into the participants' schedules. Measures included Five Facets Mindfulness Questionnaires (FFMQ), concentration and assignment attention tasks, Attention Network Test (ANT), and saliva cortisol concentration. Findings indicate that brief mindfulness meditation training led to significant improvements in participants' FFMQ scores), with marginally significant enhancements in the executive control network. However, it had no discernible effect on alertness and orientation networks. Additionally, brief mindfulness meditation training enhanced attention allocation to light stimulation and prolonged individual attention. Surprisingly, there was no observed decrease in saliva cortisol concentration among meditation training participants. However, this study did not find a decrease in saliva cortisol concentration in the brief mindfulness meditation group. In conclusion, this study highlights the potential of a 4-week brief mindfulness meditation training program to enhance dispositional mindfulness and specific aspects of attention function in young men, offering practical insights into the benefits of mindfulness meditation practices for this demographic.

Generation of entanglement using a short-wavelength seeded free-electron laser.

Quantum entanglement between the degrees of freedom encountered in the classical world is challenging to observe due to the surrounding environment. To elucidate this issue, we investigate the entanglement generated over ultrafast timescales in a bipartite quantum system comprising two massive particles: a free-moving photoelectron, which expands to a mesoscopic length scale, and a light-dressed atomic ion, which represents a hybrid state of light and matter. Although the photoelectron spectra are measured classically, the entanglement allows us to reveal information about the dressed-state dynamics of the ion and the femtosecond extreme ultraviolet pulses delivered by a seeded free-electron laser. The observed generation of entanglement is interpreted using the time-dependent von Neumann entropy. Our results unveil the potential for using short-wavelength coherent light pulses from free-electron lasers to generate entangled photoelectron and ion systems for studying spooky action at a distance.

Effects of driving laser jitter on the attosecond streaking measurement.

Driving laser jitter is one of the main factors affecting the attosecond streaking measurement. The effect of carrier-envelope phase (CEP) jitter and the pulse energy jitter on the attosecond pulse characterization is studied in this paper. We have theoretically calculated and experimentally confirmed that CEP jitter could result in a symmetry trace in the streaking spectrogram, while the intensity jitter could result in a slight shift and broadening of the trace. Both of them can lead to an underestimate of the retrieved attosecond pulse duration.

Microglial NLRP3 inflammasome activation mediates diabetes-induced depression-like behavior via triggering neuroinflammation.

BACKGROUND: Abundant evidence suggests that the prevalence and risk of depression in people with diabetes is high. However, the pathogenesis of diabetes-related depression remains unclear. Since neuroinflammation is associated with the pathophysiology of diabetic complications and depression, this study aims to elucidate the neuroimmune mechanism of diabetes-related depression. METHODS: Male C57BL/6 mice were injected with streptozotocin to establish a diabetes model. After screening, diabetic mice were treated with the NLRP3 inhibitor MCC950. Then, metabolic indicators and depression-like behaviors were evaluated in these mice, as well as their central and peripheral inflammation. To explore the mechanism of high glucose-induced microglial NLRP3 inflammasome activation, we performed in vitro studies focusing on its canonical upstream signal I (TLR4/MyD88/NF-κB) and signal II (ROS/PKR/P2X7R/TXNIP). RESULTS: Diabetic mice exhibited depression-like behaviors and activation of NLRP3 inflammasome in hippocampus. In vitro high-glucose (50 mM) environment primed microglial NLRP3 inflammasome by promoting NF-κB phosphorylation in a TLR4/MyD88-independent manner. Subsequently, high glucose activated the NLRP3 inflammasome via enhancing intracellular ROS accumulation, upregulating P2X7R, as well as promoting PKR phosphorylation and TXNIP expression, thereby facilitating the production and secretion of IL-1ß. Inhibition of NLRP3 with MCC950 significantly restored hyperglycemia-induced depression-like behavior and reversed the increase in IL-1ß levels in the hippocampus and serum. CONCLUSION: The activation of NLRP3 inflammasome, probably mainly in hippocampal microglia, mediates the development of depression-like behaviors in STZ-induced diabetic mice. Targeting the microglial inflammasome is a feasible strategy for the treatment of diabetes-related depression.

The Effect of Brief Mindfulness Meditation on Suicidal Ideation, Stress and Sleep Quality.

OBJECTIVES: Suicide is the fourth leading cause of death for individuals aged 15-29 years, and early intervention on suicidal ideation and risk factors should be priortized. Brief mindfulness meditation (BMM) is convenient and cost-effective in improving physical and mental well-being, but less is known about its efficacy for suicidal ideation, stress and sleep quality. We investigated the effects of BMM on suicidal ideation, stress, and sleep quality for individuals with suicide risk. METHODS: Sixty-four college students with high suicidal ideation (aged 18-30 years) were randomly allocated to either a BMM (n = 32) or control group (n = 32). The BMM was based on Anapanasati and core mindfulness concepts. Sixty participants completed all scheduled sessions including pretest, one month of intervention or waiting, and posttest. Suicidal ideation was measured with the Beck Scale for Suicidal Ideation. Stress was evaluated using the Perceived Stress Scale and salivary cortisol levels. Sleep was measured using the Pittsburgh Sleep Quality Index and actigraphy accompanied with 7-day sleep diaries. RESULTS: Post-intervention, the BMM group showed significant decrease in suicidal ideation with a large effect size; the decrease showed a medium effect size in the control group. The BMM group, but not the control group, showed significant decrease in morning salivary cortisol and sleep latency, and improved sleep efficiency. CONCLUSIONS: BMM could help reduce suicidal ideation, stress, and sleep disturbance for individuals with high suicidal ideation and it may implicate effective suicide prevention strategy.

Psychological responses of medical staff during COVID-19 and the adjustment effect of brief mindfulness meditation.

BACKGROUND: COVID-19 has posed an unprecedented threat to public health and remains a critical challenge for medical staff, especially those who have been fighting against the virus in Wuhan, China. Limited data have been reported regarding the psychological status of these medical staff members. Therefore, we conducted this study to explore the mental health status of medical staff and the efficacy of brief mindfulness meditation (BMM) in improving their mental health. METHODS: A survey was conducted between April 18 and May 3, 2020. Upon completing the pre-test, participants in the treatment group received a 15-min BMM intervention every day at 8 p.m. Post-test questionnaires were completed after 16 days of therapy. The questionnaire comprised demographic data and psychological measurement scales. The levels of pre and post-test depression, anxiety, stress, and insomnia were assessed using the 9-item Patient Health Questionnaire, 7-item Generalized Anxiety Disorder Scale, Perceived Stress Scale, and Athens Insomnia Scale, respectively. RESULTS: A total of 134 completed questionnaires were received. Of the medical staff, 6.7%, 1.5%, and 26.7% reported symptoms of depression, anxiety, and insomnia, respectively. Public officials from military hospitals reported experiencing greater pressure than private officials (t = 2.39, p = 0.018, d = 0.50). Additionally, BMM treatment appeared to effectively alleviate insomnia (t = 2.27, p = 0.027, d = 0.28). CONCLUSIONS: The medical staff suffered negative psychological effects during the COVID-19 pandemic. BMM interventions are advantageous in supporting the mental health of medical staff.

Attosecond electron-spin dynamics in Xe 4d photoionization.

The photoionization of xenon atoms in the 70-100 eV range reveals several fascinating physical phenomena such as a giant resonance induced by the dynamic rearrangement of the electron cloud after photon absorption, an anomalous branching ratio between intermediate Xe+ states separated by the spin-orbit interaction and multiple Auger decay processes. These phenomena have been studied in the past, using in particular synchrotron radiation, but without access to real-time dynamics. Here, we study the dynamics of Xe 4d photoionization on its natural time scale combining attosecond interferometry and coincidence spectroscopy. A time-frequency analysis of the involved transitions allows us to identify two interfering ionization mechanisms: the broad giant dipole resonance with a fast decay time less than 50 as, and a narrow resonance at threshold induced by spin-flip transitions, with much longer decay times of several hundred as. Our results provide insight into the complex electron-spin dynamics of photo-induced phenomena.

Glycyrrhizic acid as an adjunctive treatment for depression through anti-inflammation: A randomized placebo-controlled clinical trial.

BACKGROUND: Recently, abundant evidence indicated proinflammatory cytokines might play a crucial role in pathophysiology and treatment of depression. According to our preclinical research, we propose glycyrrhizic acid (GZA) for an adjunctive treatment owing to its safety, economical and anti-inflammatory profile. METHODS: Eligible participants were recruited and randomly allocated into independent treatment groups of SSRI+GZA (n = 30) and SSRI+PBO (placebo, n = 26). Depressive symptoms and specific serum biomarkers were detected during the 4-week treatment course. Afterward, the relationships between biomarkers and clinical effects were explored. RESULTS: Depressive symptoms relieved more in SSRI+GZA than SSRI+PBO, both at week 2 (P = 0.003) and week 4 (P = 0.016). Meanwhile, at week 4, both response rate (P = 0.035) and remission rate (P = 0.031) acutely became higher in SSRI+GZA compared with SSRI+PBO. Mediation analysis further demonstrated that TNF-α reduction mediated the association between GZA treatment and clinical improvement, the indirect effect lay between 0.124 and 3.514 (95% CI). The exploratory analysis also suggested that the symptomatic improvement existed in patients with high-inflammation (baseline CRP > 3 mg/L) rather than those with low-inflammation (baseline CRP ≤ 3 mg/L). LIMITATIONS: The sample size in this study was not large enough and the follow-up duration was relatively short. CONCLUSIONS: This study offers a novel strategy for the diagnosis, categorization, individualization and prognosis regarding upgrading traditional antidepressant therapy, which is from biomarkers to diagnostic indicator and therapeutic target. Patients are necessary to be classified according to the inflammatory state, those with high levels of baseline inflammation should receive combined treatment with anti-inflammatory agents like GZA.

Brief Mindfulness Meditation Improves Emotion Processing.

Mindfulness-based interventions have previously been shown to have positive effects on psychological well-being. However, the time commitment, teacher shortage, and high cost of classic mindfulness interventions may have hindered efforts to spread the associated benefits to individuals in developing countries. Brief mindfulness meditation (BMM) has recently received attention as a way to disseminate the benefits of mindfulness-based interventions. Most existing BMM methods are adaptations of the classic approach. Few studies have investigated the mechanisms underlying the beneficial effects of BMM. We developed a 15-min BMM named JW2016, which is based on the core concepts of mindfulness, Anapanasati (breath meditation of Buddhist Vipassana), our practical experience, and the results of scientific reports on meditation. We investigated the effects of this BMM on mood and emotion processing in an effort to create an effective, convenient, safe, and standardized BMM method that could benefit individuals with limited time or money to devote to meditation. Forty-six healthy participants (aged 18-25 years) were randomly allocated to the BMM group (n = 23) or the emotional regulation education (ERE) control group (n = 23). Forty-two of the study participants cooperated fully in all measurements and interventions (one time daily for seven consecutive days). Mood was measured with the Centre for Epidemiological Studies-Depression scale (CES-D) and the State Anxiety Inventory (SAI). Emotion processing was evaluated by assessing performance on an emotion intensity task, an emotional memory task, and an emotional dot-probe task. After intervention, the BMM group, but not the ERE group, showed a significant decreases in emotional intensity in response to positive as well as negative emotional stimuli, response time for emotional memory, and duration of attention bias toward negative emotional stimuli. Negative effects on mood state were found in the ERE group but not in the BMM group. This study demonstrated that BMM may improve aspects of emotion processing such as emotion intensity, emotional memory, and emotional attention bias. JW2016 BMM may be an effective, convenient, safe and standardized way to help practitioners remain focused and peaceful without any negative effect on emotion.

Anisotropic photoemission time delays close to a Fano resonance.

Electron correlation and multielectron effects are fundamental interactions that govern many physical and chemical processes in atomic, molecular and solid state systems. The process of autoionization, induced by resonant excitation of electrons into discrete states present in the spectral continuum of atomic and molecular targets, is mediated by electron correlation. Here we investigate the attosecond photoemission dynamics in argon in the 20-40 eV spectral range, in the vicinity of the 3s-1np autoionizing resonances. We present measurements of the differential photoionization cross section and extract energy and angle-dependent atomic time delays with an attosecond interferometric method. With the support of a theoretical model, we are able to attribute a large part of the measured time delay anisotropy to the presence of autoionizing resonances, which not only distort the phase of the emitted photoelectron wave packet but also introduce an angular dependence.