Background:Patients with alcohol dependence (AD) can exhibit gut dysbacteria. Dysbacteria may co-occur with disruptions of circadian rhythmicity of the gut flora, which can aggravate AD. Herein, this study aimed to investigate diurnal oscillations of the gut microbiota in AD patients. Methods:Thirty-two patients with AD, based on the Diagnostic and Statistical Manual of Mental Disorders, 4th edition, and 20 healthy subjects were enrolled in this study. Demographic and clinical data were collected by self-report questionnaires. Fecal samples at 7:00 AM, 11:00 AM, 3:00 PM, and 7:00 PM were collected from each subject. 16S rDNA sequencing was conducted. Wilcoxon and Kruskal-Wallis tests were performed to characterize alterations and oscillations of the gut microbiota. Results:We found that β-diversity of the gut microbiota in AD patients oscillated diurnally compared with healthy subjects (p = 0.01). Additionally, 0.66% of operational taxonomic units oscillated diurnally in AD patients versus 1.68% in healthy subjects. At different taxonomic levels, bacterial abundance oscillated diurnally in both groups, such as Pseudomonas and Prevotella pallens (all p < 0.05). β-diversity of the gut microbiota in AD patients with high daily alcohol consumption, high-level cravings, short AD durations, and mild withdrawal symptoms oscillated diurnally compared with other AD patients (all p < 0.05). Conclusion:The gut microbiota in AD patients exhibits disruptions of diurnal oscillation, which may provide novel insights into mechanisms of AD and the development of therapeutic strategies.

This study evaluates the effect of returnee directors on corporate tax avoidance by using data on publicly listed Chinese companies from 2000 to 2012. Returnee directors grow up in China and then study or work abroad before returning home to be listed firms' board directors. We use the introduction of provincial policies toward attracting skilled individuals with foreign experience as an instrumental variable for Returnee directors, which is the fraction of returnee directors divided by the total number of directors within a firm. Using quantile regression, we find a positive relation between Returnee directors and corporate tax avoidance for low levels of tax avoidance but a negative relation for high levels of tax avoidance. The result is robust to a battery of tests. The relation between returnee directors and tax avoidance is stronger for state-owned enterprises (SOEs) than non-SOEs and stronger for returnees who hold MBA degrees, possess a background in accounting or auditing, or are independent directors than other returnees.

Introduction: Accumulating evidence suggests that both sleep loss and gut dysbiosis can lead to metabolic disorders. However, less is known about the impact of total sleep deprivation (SD) and sleep recovery on the composition, function, and metabolic dynamics of the gut microbiota. Methods: Specific-pathogen free Sprague-Dawley rats were subjected to 48 h of SD with gentle handling and then allowed to recover for 1 week. Taxonomic profiles of fecal microbiota were obtained at baseline, 24 h of SD, 48 h of SD, and 1 week of recovery. We used 16S rRNA gene sequencing to analyze the gut microbial composition and function and further characterize microbiota-derived metabolites in rats. Results: The microbiota composition analysis revealed that gut microbial composition and metabolites did not change in the rats after 24 h of SD but were significantly altered after 48 h of SD. These changes were reversible after 1 week of sleep recovery. A functional analysis was performed based on Kyoto Encyclopedia of Genes and Genomes (KEGG) annotations, indicating that 19 KEGG pathways were significantly altered in the gut microbiota in SD rats. These functional changes occurred within 24 h of SD, were more apparent after 48 h of SD, and did not fully recover after 1 week of sleep recovery. Conclusion: These results indicate that acute total SD leads to significant compositional and functional changes in the gut microbiota, and these changes are reversible.

Sleep is a complex physiological process and is a critical determinant of physical and mental health. In the past decades, significant progress has been made in understanding the neural mechanisms of sleep and awakening. However, the initiation and maintenance of the sleep-wake cycle is regulated not only by the central system but is also affected by signals from peripheral tissues. Growing evidence shows that the microbiota-gut-brain axis contributes to the regulation of sleep behavior both directly and indirectly and may play a critical role in the etiology and pathogenesis of sleep disorders. Sleep deprivation leads to dysfunction of gut microbiota and sleep disorders are accompanied by altered gut microbiota composition. In this review, we describe the bidirectional relationships between sleep and gut microbiota and summarize the abnormal characteristics of gut bacteria in distinct conditions including sleep disturbances, sleep disorders and sleep disorders comorbid with neuropsychiatric disorders. We also examine the potential routes of microbiota-gut-brain axis in sleep and gut microbiome interactions, including metabolic, immune, and neural pathways, and propose microbiota-targeted interventions for improving sleep. Manipulating gut microbiota may be a promising avenue for the development of novel interventions for sleep disorders.

Background: The novel coronavirus 2019 (COVID-19) pandemic and related compulsory measures have triggered a wide range of psychological issues. However, the effect of COVID-19 on mental health in late-middle-aged adults remains unclear. Methods: This cross-sectional, web-based survey recruited 3,730 participants (≥ 50 years old) between February 28 and March 11 of 2020. The Patient Health Questionnaire-9, Generalized Anxiety Disorder-7, Insomnia Severity Index, and Acute Stress Disorder Scale were used to evaluate depression, anxiety, insomnia, and acute stress symptoms. Multivariate logistic regression analysis was fitted to explore risk factors that were associated with the selected outcomes. Results: The mean age of the participants was 54.44 ± 5.99 years, and 2,026 (54.3%) of the participants were female. The prevalence of depression, anxiety, insomnia, and acute stress symptoms among late-middle-aged adults in China during the COVID-19 pandemic was 20.4, 27.1, 27.5, and 21.2%, respectively. Multivariable logistic regression analyses showed that participants who were quarantined had increased odds ratios for the four mental health symptoms, and those with a good understanding of the COVID-19 pandemic displayed a decreased risk for all mental health symptoms among late-middle-aged adults. In addition, participants with a low income and with a risk of COVID-19 exposure at work had a remarkably high risk of depression, anxiety, and acute stress symptoms. Conclusions: Mental health symptoms in late-middle-aged adults in China during the COVID-19 pandemic are prevalent. Population-specific mental health interventions should be developed to improve mental health outcomes in late-middle-aged adults during this public health emergency.

Sleep deprivation (SD) is increasingly common in modern society, which can lead to the dysregulation of inflammatory responses and cognitive impairment, but the mechanisms remain unclear. Emerging evidence suggests that gut microbiota plays a critical role in the pathogenesis and development of inflammatory and psychiatric diseases, possibly via gut microbiota–brain interactions and neuroinflammation. The present study investigated the impact of SD on gut microbiota composition and explored whether alterations of the gut microbiota play a causal role in chronic inflammatory states and cognitive impairment that are induced by SD. We found that SD-induced gut dysbiosis, inflammatory responses, and cognitive impairment in humans. Moreover, the absence of the gut microbiota suppressed inflammatory response and cognitive impairment induced by SD in germ-free (GF) mice. Transplantation of the “SD microbiota” into GF mice activated the Toll-like receptor 4/nuclear factor-κB signaling pathway and impaired cognitive function in the recipient mice. Mice that harbored “SD microbiota” also exhibited increases in neuroinflammation and microglial activity in the hippocampus and medial prefrontal cortex. These findings indicate that gut dysbiosis contributes to both peripheral and central inflammatory processes and cognitive deficits that are induced by SD, which may open avenues for potential interventions that can relieve the detrimental consequences of sleep loss.

Novel ionic transporting phenomena emerge as nanostructures approach the molecular scale. At the sub-2nm scale, widely used continuum equations, such as the Nernst-Planck equation, break down. Here, we extend the Nernst-Planck equation by adding a partial dehydration effect. Our model agrees with the reported ion fluxes through graphene oxide laminates with sub-2nm interlayer spacing, outperforming previous models. We also predict that the selectivity sequences of alkali metal ions depend on the geometries of the nanostructures. Our model opens a new avenue for the investigation of the underlying mechanisms in nanofluidics at the sub-2nm scale.

We report a damped coherent population trapping (CPT) process, which has the very same mechanism as the coherent population beating (CPB). A differential CPB scheme is proposed based on the optical path delay, through which the left- and right-hand circularly polarized lights are modulated with a phase difference of π/2. The CPB signals oscillate with the frequency in a radio frequency (RF) range, which makes the detuning frequency equal to the splitting frequency between the hyperfine energy level of the ground state of cesium. The differential CPB signal with non-zero amplitude is obtained after the two signals being subtracted from each other, thereby improving the signal-to-noise ratio of the CPB. The measurements are explained well with a simple, four-level model and are interpreted as a simple harmonic oscillator interaction with four light fields. The Allan variance of the CPB atomic clock is measured in the conventional and the differential detection configurations. The 1-s stability of the differential CPB scheme is , which is better than that of under the conventional configuration. The results confirm that the differential CPB scheme can improve the signal-to-noise ratio and hence the short-term stability.

Selective ion transport is an essential feature of biological ion channels. Due to the subnanometer size and negatively charged surface of ion channels, the ion selectivity is affected by both dehydration effects and electrostatic interactions. Their coupled effect on selective ion transport, however, has been elusive. Here, using molecular dynamics simulations, we study ion (Li+ and Mg2+) transport through subnanometer carbon nanotubes (CNTs) with varying charge densities. Our results indicate that the dehydration effect governs the ionic transport at low surface charge densities, hence the nanochannel shows a selectivity for Li+ ions. In contrast, the nanochannel switches to a selectivity for Mg2+ ions as the electrostatic interaction between the cations and the negatively charged wall dominates the transport at high surface charge densities.

A De Pangher-type long counter was constructed at Peking University for neutron fluence measurement. The responses and effective centers of the long counter were calculated using the Monte Carlo method. The variations with neutron energy of the position of the effective center, calculated by the Monte Carlo code, was experimentally validated with a (AmBe)-Am-241 neutron source and several mono-energetic neutron sources ranging from 100 keV to 6 MeV. Long counter calibration was performed using a radionuclide source from Peking University, and neutron fluence measured by the calibrated long counter was successfully compared to values determined with reference instruments (two recoil proton counters and a U-238 fission chamber). The relative deviations were lower than 6% along the whole energy range. The calibrated long counter was thus successfully applied in the calibration of a Bonner sphere spectrometer.

Fear is prone to return following extinction that is the basis of exposure therapy for fear-related disorders. Manipulations that enhance the extinction process can be beneficial for treatment. Animal studies have shown that fasting or caloric restriction can enhance extinction and inhibit the return of fear. The present study examined the effects of fasting on fear acquisition, extinction, and the return of fear in humans. One hundred and twenty-five male participants were randomized into a fasting group and food group and exposed to a Pavlovian fear conditioning paradigm. Changes in plasma cortisol and ghrelin levels were examined using enzyme-linked immunosorbent assays. One-night fasting had no effect on fear acquisition but enhanced fear extinction retention and prevented the return of fear, and this effect persisted for at least 6 months. This procedure was also effective for remote fear memory. Plasma ghrelin levels were elevated after fasting and had a negative relationship with the fear response in spontaneous recovery test. However, overnight fasting did not affect cortisol levels. These findings indicate that fasting enhances extinction retention and prevents the return of fear, without influencing fear memory formation. We propose that this novel procedure may open new avenues for promoting extinction-based therapies for fear-related disorders.

12-μm-thick polyethylene terephthalate (PET) track membranes with sub-nanometer pores fabricated with the newly developed track-UV technique without chemical etching showed ultrahigh selective ionic transport yet low permeability. We discovered that the permeability of these track membranes were irreversibly improved by two to three orders of magnitude via heat treatment. Meanwhile, these heat-treated track membranes maintained the high selectivity of ions. Our experimental results suggest heat treatment on the track membranes with sub-nanometer pores could provide a reliable and controllable way to enlarge nanopore size, and bring the track membrane to promising applications on ion separations, water purification, diaphragm material and so on.

An accurate frequency control method and atomic clock based on the coherent population beating (CPB) phenomenon is implemented. In this scheme, the frequency difference of an rf and an atomic transition frequency can be digitally obtained by measuring the CPB oscillation frequency. The frequency measurement resolution of several milli-hertz can be achieved by using a 10 MHz oven controlled crystal oscillator as the reference. The expression of the Allan deviation of the CPB clock is theoretically deduced and it is revealed that the Allan deviation is inversely proportional to the signal-to-noise ratio and proportional to the line-width of coherent population trapping spectrum. We also approve that the CPB atomic clock has a large toleration of the drift of the local oscillator. In our CPB experimental system, a frequency instability of 3.0 × 10−12 at 1000s is observed. The important feature of high frequency measurement resolution of the CPB method may also be used in magnetometers, atomic spectroscopy, and other related research.

We present a long-term chip scale stabilization scheme for optoelectronic oscillators (OEOs) based on a rubidium coherent population trapping (CPT) atomic resonator. By locking a single mode of an OEO to the 85Rb 3.035-GHz CPT resonance utilizing an improved phase-locked loop (PLL) with a PID regulator, we achieved a chip scale frequency stabilization system for the OEO. The fractional frequency stability of the stabilized OEO by overlapping Allan deviation reaches 6.2 × 10-11 (1 s) and ~1.45 × 10-11 (1000 s). This scheme avoids a decrease in the extra phase noise performance induced by the electronic connection between the OEO and the microwave reference in common injection locking schemes. The total physical package of the stabilization system is 20 cm3 and the total power consumption is 400 mW, which provides a chip scale and portable frequency stabilization approach with ultra-low power consumption for OEOs.

We demonstrate a synchronously stimulation method for achieving coherent population beating (CPB) atomic clock with the CPB signal which have continuous wave and higher signal-to-noise ratio. In this method we synchronously apply the coherent population trapping (CPT) resonant stimulating lights together with the detuned detecting lights to obtain continuous CPB oscillation signal. Under the stimulation, the ground state coherence is maintained and the problem of CPB signal decaying is solved, which is beneficial for the measurement accuracy of the CPB frequency and the stability of the clock. The table experimental system of the synchronously stimulated CPB clock has been experimentally implemented and a stability of 7.7 × 10 -11 at 1 second, 9.6 × 10 -13 at 1000 second was observed.

Coherent population beating (CPB) phenomenon occurs in a typical three-level system. When the frequency difference between two coherent pumping laser fields has a certain detuning from the ground-state hyperfine splitting, the excited state population will experience a transient oscillation before reaching equilibrium, and the oscillation frequency is equal to the detuning. The CPB phenomenon enables us to directly obtain the beat frequency between the measured radio frequency (RF) signal and the atomic transition frequency. Then we can get the standard frequency by compensating the beat frequency to the RF. We propose a scheme to implement atomic clock based on the CPB phenomenon in 2009, and the scheme has been implemented. When this effect is used to achieve an atomic clock, the frequency stability is directly related to the amplitude and SNR (signal to noise ratio) of the CPB signal. Influence of the ground-state hyperfine sublevels' coherence on CPB signal is theoretically simulated and experimentally investigated in this paper. A formula of the CPB signal is derived by using the semi-classical model of the interaction of atoms with light, and the theoretical simulation is done using the formula obtained. In the experiment two coherent pumping laser fields are used to interact with 87Rb atoms. A CPB process includes the coherence build-up and the CPB stimulation. The coherence of the ground-state hyperfine sublevels is achieved by controlling the pumping time of the coherent laser fields that are resonant to the ground-state hyperfine sublevels. With this method, the relationship between CPB signal and coherence of the ground-state hyperfine sublevels can be observed. Result shows that the amplitude of CPB signal is proportional to the ground-state hyperfine sublevels' coherence. The hign quality CPB signal can be achieved when the CPB stimulation is started with a pure coherent population trapping (CPT) state. In the CPB process, the coherence build-up rate is approximately equal to the coherence decay rate. So a 50% duty cycle square wave can be used to modulate the RF, and the period of the square wave had better be twice of the decay time of the ground-state hyperfine sublevels' coherence. To improve the SNR of CPB signal and the stability of atomic frequency standard, the ground-state hyperfine sublevels' coherence must be built up, improved, and maintained before the CPB stimulation. The feasibility of applying CPB phenomenon to the weak magnetic field measurement and other applications is also discussed in this paper.

We proposed a novel magnetic field measurement method extended from the CPT method. It is based on the coherent population beating (CPB) phenomenon. CPB occurs in a typical three-level system, when the frequency difference of the two pump laser fields have a detuning from the ground states splitting, and the CPB oscillation frequency is equal to the detuning. We are able to detect the beat frequency shift with the external magnetic field changing via digital processing, thus we can acquire the Zeeman frequency shift and then calculate external magnetic field intensity accurately.

We have demonstrated an atomic frequency micrometer based on the coherent population beating phenomenon, which enables us to obtain the beat frequency between the measured signal and the atomic transition frequency. The beat frequency and its fluctuations are detected and accurately measured through digital signal processing, which is capable of up to mHz or higher frequency resolutions (for GHz signal). The frequency discrimination via our method is comparable to that of the Ramsey fringes method, and the working range is no longer limited by the width of line shape. This enables us to achieve an atomic clock by actively compensating the frequency shift, which eliminates the need for a phase locking loop, and broadens the working range with increasing reliability. This novel scheme could be extended to the optical frequency region, implying possible future applications in optical atomic clocks, optical frequency comb, atomic spectroscopy and other related researches.

The authors are developing chip-scale atomic clocks (CSACs) based on the 85 Rb coherent population trap (CPT) transition. As an intermediate milestone, we have developed a miniature atomic clock prototype. In this paper, we report on the design combing the miniature physics part, low-power digital control circuits and low-power microwave system, and the process that enable an atomic clock to be made with an overall size of 20 cm 3 volume, power consumption about 400 mWatts, and an Allen Deviation at 100 s of 2.9E-11.