The purpose of this study was to analyse the clinical characteristics of patients with severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) PCR re-positivity after recovering from coronavirus disease 2019 (COVID-19). Patients (n = 1391) from Guangzhou, China, who had recovered from COVID-19 were recruited between 7 September 2021 and 11 March 2022. Data on epidemiology, symptoms, laboratory test results and treatment were analysed. In this study, 42.7% of recovered patients had re-positive result. Most re-positive patients were asymptomatic, did not have severe comorbidities, and were not contagious. The re-positivity rate was 39%, 46%, 11% and 25% in patients who had received inactivated, mRNA, adenovirus vector and recombinant subunit vaccines, respectively. Seven independent risk factors for testing re-positive were identified, and a predictive model was constructed using these variables. The predictors of re-positivity were COVID-19 vaccination status, previous SARs-CoV-12 infection prior to the most recent episode, renal function, SARS-CoV-2 IgG and IgM antibody levels and white blood cell count. The predictive model could benefit the control of the spread of COVID-19.

In the present study, we investigated the influence of different mid-stage N compensation timings on agronomic and physiological traits associated with grain yield and quality in field experiments. Two japonica rice cultivars with a good tasting quality (Nangeng 9108 and Nangeng 5055) were examined under eight N compensation timings (N1–N6: one-time N compensation at 7-2 weeks before heading; N7: split N compensation at 5 and 3 weeks before heading; N8: split N compensation at 4 and 2 weeks before heading) and a control with no N compensation. The highest yield was obtained with N7, followed by N3. The yield advantage is mainly attributable to the improved population structure (higher productive tiller rate with a stable number of effective panicles), higher total number of spikelets per unit area (large panicles with more grains per panicle), larger leaf area index in the late period and higher photosynthetic production capacity (more dry matter accumulation and transportation in the middle and late periods). Delaying N compensation timing improved the processing and nutritional quality of rice, but decreased the quality of appearance and cooking/eating traits. Our results suggest that, from the perspective of achieving relative coordination between high yield and high quality of japonica rice, the optimal N compensation should be divided equally at 5 and 3 weeks before heading. However, if simplifying the number of operations and the pursuit of eating quality were considered, one-time N compensation should be conducted at 5 weeks before heading.

Trailing-edge serrations inspired by owls are capable of reducing broadband noise. In this study, the wall-resolved large-eddy simulations (LES) are carried out on the flow over NACA-0012 airfoil with additional serrated trailing edges. The computations are conducted with the high-order flux reconstruction method on unstructured meshes. Three kinds of serrations with different lengths are studied and compared with the straight trailing-edge case, and all three types of serration achieved a certain degree of noise reduction. Presently, the medium-length serration achieves the best noise reduction effect. The maximum decrease of overall sound pressure level is approximately 2.4 dB, implying that the length of serration has a substantial impact on the noise reduction effect. The serration has no significant effect on the upstream turbulence statistics, but it changes the flow structure near the serration, such as inducing side vortex pairs attached to the serration edges. Moreover, dynamic mode decomposition shows that the pressure structures vary with the serration length. For the most unstable hydrodynamic wave, the spanwise coherence of the mode structure of pressure in the upstream boundary layer is weakened. In addition, serrations can redistribute the dipole sources on the surfaces of airfoil and serrations. The destructive interference is enhanced to some extent, which is favourable for noise reduction. In contrast with LES simulations, the pure dipole analysis shows that the longest serration case seems to be the best. Furthermore, a recently developed noise theory is used to evaluate the influence of serrations on the flow noise sources qualitatively and quantitatively. It is found that the serrations can mitigate noise source intensity near the serration edges but increase the source intensity in the near wake. The combined effect of serration on the dipole source and flow noise source determines the overall noise reduction effect. To conclude, destructive interference plays a primary role in suppressing noise radiation by serrated trailing edges, and the dual effect of flow noise sources should be considered in future serration designs. As the influence of turbulence structure will make it more difficult to find the optimal serration parameters, the position of high-fidelity simulation will become increasingly important.

The wheat aphid Sitobion miscanthi (CWA) is an important harmful pest in wheat fields. Insecticide application is the main method to effectively control wheat aphids. However, CWA has developed resistance to some insecticides due to its extensive application, and understanding resistance mechanisms is crucial for the management of CWA. In our study, a new P450 gene, CYP4CJ6, was identified from CWA and showed a positive response to imidacloprid and thiamethoxam. Transcription of CYP4CJ6 was significantly induced by both imidacloprid and thiamethoxam, and overexpression of CYP4CJ6 in the imidacloprid-resistant strain was also observed. The sensitivity of CWA to these two insecticides was increased after the knockdown of CYP4CJ6. These results indicated that CYP4CJ6 could be associated with CWA resistance to imidacloprid and thiamethoxam. Subsequently, the posttranscriptional regulatory mechanism was assessed, and miR-316 was confirmed to participate in the posttranscriptional regulation of CYP4CJ6. These results are crucial for clarifying the roles of P450 in the resistance of CWA to insecticides.

Lacustrine sediments are important archives for paleoclimate research, but there are evident carbon reservoir effects. Radiocarbon (14C) ages of lake sediments must be corrected for these effects before applying them to paleoclimate research. The authors review the lacustrine research from the last 20 years from different climatic regions in China, and systematically investigate the 14C age and correction methods used in the studies of 81 lakes. It is found that the climate-vegetation cover and distribution of carbonate around lakes are dominant factor controlling radiocarbon reservoir effects. In eastern China, the average 14C reservoir age is about 500 14C years and is associated with relatively dense vegetation. However, in northwest China and Qinghai-Tibet Plateau, widespread carbonate bedrock may markedly increase the radiocarbon reservoir age which frequently is about 1500 and 2500 14C years. A piecewise linear regression model provides more reliable 14C reservoir age correction that accounts for sedimentary facies and sedimentation rate changes. It is worth mentioning that when analyzing 14C ages deviated greatly from time sequence, the age anomalies may indicate important effects relevant to the study of climate and environmental changes.

To investigate the association between the Metabolic Score for Visceral Fat (METS-VF) and risk of type 2 diabetes mellitus (T2DM) and compare the predictive value of the METS-VF for T2DM incidence with other obesity indices in Chinese people. A total of 12 237 non-T2DM participants aged over 18 years from the Rural Chinese Cohort Study of 2007–2008 were included at baseline and followed up during 2013–2014. The cox proportional hazards regression was used to calculate hazard ratios (HR) and 95 % CI for the association between baseline METS-VF and T2DM risk. Restricted cubic splines were used to model the association between METS-VF and T2DM risk. Area under the receiver operating characteristic curve (AUC) analysis was used to evaluate the ability of METS-VF to predict T2DM incidence. During a median follow-up of 6·01 (95 % CI 5·09, 6·06) years, 837 cases developed T2DM. After adjusting for potential confounding factors, the adjusted HR for the highest v. lowest METS-VF quartile was 5·97 (95 % CI 4·28, 8·32), with a per 1-sd increase in METS-VF positively associated with T2DM risk. Positive associations were also found in the sensitivity and subgroup analyses, respectively. A significant nonlinear dose–response association was observed between METS-VF and T2DM risk for all participants (Pnonlinearity = 0·0347). Finally, the AUC value of METS-VF for predicting T2DM was largest among six indices. The METS-VF may be a reliable and applicable predictor of T2DM incidence in Chinese people regardless of sex, age or BMI.

Cytochrome P450 monooxygenases play a key role in pest resistance to insecticides by detoxification. Four new P450 genes, CYP6AS160, CYP6AS161, CYP4AB73 and CYP4G232 were identified from Solenopsis invicta. CYP6AS160 was highly expressed in the abdomen and its expression could be induced significantly with exposure to fipronil, whereas CYP4AB73 was not highly expressed in the abdomen and its expression could not be significantly induced following exposure to fipronil. Expression levels of CYP6AS160 and CYP4AB73 in workers were significantly higher than that in queens. RNA interference-mediated gene silencing by feeding on double-stranded RNA (dsRNA) found that the levels of this transcript decreased (by maximum to 64.6%) when they fed on CYP6AS160-specific dsRNA. Workers fed dsCYP6AS160 had significantly higher mortality after 24 h of exposure to fipronil compared to controls. Workers fed dsCYP6AS160 had reduced total P450 activity of microsomal preparations toward model substrates p-nitroanisole. However, the knockdown of a non-overexpressed P450 gene, CYP4AB73 did not lead to an increase of mortality or a decrease of total P450 activity. The knockdown effects of CYP6AS160 on worker susceptibility to fipronil, combined with our other findings, indicate that CYP6AS160 is responsible for detoxification of fipronil. Feeding insects dsRNA may be a general strategy to trigger RNA interference and may find applications in entomological research and in the control of insect pests in the field.

X/γ-rays have many potential applications in laboratory astrophysics and particle physics. Although several methods have been proposed for generating electron, positron, and X/γ-photon beams with angular momentum (AM), the generation of ultra-intense brilliant γ-rays is still challenging. Here, we present an all-optical scheme to generate a high-energy γ-photon beam with large beam angular momentum (BAM), small divergence, and high brilliance. In the first stage, a circularly polarized laser pulse with intensity of 1022 W/cm2 irradiates a micro-channel target, drags out electrons from the channel wall, and accelerates them to high energies via the longitudinal electric fields. During the process, the laser transfers its spin angular momentum (SAM) to the electrons’ orbital angular momentum (OAM). In the second stage, the drive pulse is reflected by the attached fan-foil and a vortex laser pulse is thus formed. In the third stage, the energetic electrons collide head-on with the reflected vortex pulse and transfer their AM to the γ-photons via nonlinear Compton scattering. Three-dimensional particle-in-cell simulations show that the peak brilliance of the γ-ray beam is $\sim 1{0}^{22}$ photons·s–1·mm–2·mrad–2 per 0.1% bandwidth at 1 MeV with a peak instantaneous power of 25 TW and averaged BAM of $1{0}^6\hslash$/photon. The AM conversion efficiency from laser to the γ-photons is unprecedentedly 0.67%.

Fullerene dimers have attracted extensive attention due to their unique structures and fascinating properties. Here, fullerene dimer derivatives with four to six carbon atoms in the esters are designed and synthesized. The property differences that caused by the carbon number in the esters of the fullerene dimers are investigated by performing their electrochemical, optical, and photoelectric measurements. As the carbon atom numbers in the esters increase from four to five and six, the absorption intensities increase to 1.6- and 4.4-folds. The intensities of the fluorescence spectra increase to 1.8- and 5.2-folds. Their photocurrent increases to 2- and 7-folds under the irradiation of a 405-nm laser. The LUMO energy levels move downward slightly from −3.89 to −3.90 and −3.92 eV, respectively. Our results indicate that as the carbon number increases, the carbon chain lengths in the ester structures increase, very slight effects produced on the energy levels of the fullerene dimers, but strongly contribute to their chemical activities and thus the photoelectronic efficiencies.

We present an experimental study on controlling the number of vortices and the torque in a Taylor–Couette flow of water for Reynolds numbers from 660 to 1320. Different flow states are achieved in the annulus of width $d$ between the inner rotating and outer stationary cylinders through manipulating the initial height of the water annulus. We show that the torque exerted on the inner cylinder of the Taylor–Couette system can be reduced by up to 20 % by controlling the flow at a state where fewer than the nominal number of vortices develop between the cylinders. This flow state is achieved by starting the system with an initial water annulus height $h_0$ (which nominally corresponds to $h_0/d$ vortices), then gradually adding water into the annulus while the inner cylinder keeps rotating. During this filling process the flow topology is so persistent that the number of vortices does not increase; instead, the vortices are greatly stretched in the axial (vertical) direction. We show that this state with stretched vortices is sustainable until the vortices are stretched to around 2.05 times their nominal size. Our experiments reveal that by manipulating the initial height of the liquid annulus we are able to generate different flow states and demonstrate how the different flow states manifest themselves in global momentum transport.

Klebsiella pneumoniae is a common pathogen associated with nosocomial infections and is characterised serologically by capsular polysaccharide (K) and lipopolysaccharide O antigens. We surveyed a total of 348 non-duplicate K. pneumoniae clinical isolates collected over a 1-year period in a tertiary care hospital, and determined their O and K serotypes by sequencing of the wbb Y and wzi gene loci, respectively. Isolates were also screened for antimicrobial resistance and hypervirulent phenotypes; 94 (27.0%) were identified as carbapenem-resistant (CRKP) and 110 (31.6%) as hypervirulent (hvKP). isolates fell into 58 K, and six O types, with 92.0% and 94.2% typeability, respectively. The predominant K types were K14K64 (16.38%), K1 (14.66%), K2 (8.05%) and K57 (5.46%), while O1 (46%), O2a (27.9%) and O3 (11.8%) were the most common. CRKP and hvKP strains had different serotype distributions with O2a:K14K64 (41.0%) being the most frequent among CRKP, and O1:K1 (26.4%) and O1:K2 (17.3%) among hvKP strains. Serotyping by gene sequencing proved to be a useful tool to inform the clinical epidemiology of K. pneumoniae infections and provides valuable data relevant to vaccine design.

To overcome the steric effect of norbornene (NB), first-generation Grubbs’ catalyst (GC1) was used as the catalyst to graft NB onto the polypropylene (PP) chain by reactive extrusion. Instead of harsh reaction conditions, such as anhydrous, which was the general method to synthesize NB polymers, this convenient method would be easier to industrialize. The mechanism of grafting was studied by using Fourier Transform InfraRed spectra and differential scanning calorimetry. It was found that GC1 could initiate the ring-opening metathesis polymerization of NB to obtain short NB chain-grafted PP-g-NB. The rheological behavior showed that the grafted NB short chains on PP-g-NB increase the shear thinning of the polymers and decrease the system viscosity.

Coronavirus disease 2019 (COVID-19) patients were classified into four clinical stages (uncomplicated illness, mild, severe and critical pneumonia) depending on disease severity. We aim to investigate the corresponding clinical, radiological and laboratory characteristics between different clinical stages. A retrospective, single-centre study of 101 confirmed patients with COVID-19 at Renmin Hospital of Wuhan University from 2 January to 28 January 2020 was enrolled; follow-up endpoint was on 8 February 2020. Clinical data were collected and compared during the course of illness. The median age of the 101 patients was 51.0 years and 33.6% were medical staff. Fever (68%), cough (50%) and fatigue (23%) are the most common symptoms. About 26% patients underwent the mechanical ventilation and 98% patients were treated with antibiotics. Thirty-seven per cent patients were cured and 11 died. On admission, the number of patients with uncomplicated illness, mild, severe and critical pneumonia were 2 [2%], 86 [85%], 11 [11%] and 2 [2%]. Forty-four of the 86 mild pneumonia progressed to severe illness within 4 days, with nine patients worsened due to critical pneumonia within 4 days. Two of the 11 severe patients improved to mild condition while three others deteriorated. Significant differences were observed among groups of different clinical stages in numbers of influenced pulmonary segments (6 vs. 12 vs. 17, P < 0.001). A significantly upward trend was witnessed in ground-glass opacities overlapped with striped shadows (33% vs. 42% vs. 55% vs. 80%, P < 0.001), while pure ground-glass opacities gradually decreased as disease progressed (45% vs. 35% vs. 24% vs. 13%, P < 0.001) within 12 days. Lymphocytes, prealbumin and albumin showed a downtrend as disease progressed from mild to severe or critical condition, an uptrend was found in white blood cells, C-reactive protein, neutrophils and lactate dehydrogenase. The proportions of serum amyloid A > 300 mg/l in mild, severe and critical conditions were 18%, 46% and 71%, respectively.

We investigate the phased evolution and variation of the South Asian monsoon and resulting weathering intensity and physical erosion in the Himalaya–Karakoram Mountains since late Pliocene time (c. 3.4 Ma) using a comprehensive approach. Neodymium and strontium isotopic compositions and single-grain zircon U–Pb age spectra reveal the sources of the deposits in the east Arabian Sea, and show a combination of sources from the Himalaya and the Karakoram–Kohistan–Ladakh Mountains, with sediments from the Indian Peninsula such as the Deccan Traps or Craton. We interpret shifts in the sediment sources to have been forced by sea-level changes that correlate with South Asian monsoon rainfall variation since late Pliocene time. We collected 908 samples from the International Ocean Discovery Program Hole U1456A, which was drilled in the east Arabian Sea. Time series of hematite content and grain size of the sediments were examined downcore. We found South Asian monsoon precipitation and weathering intensity experienced three phases from late Pliocene time. Lower monsoon precipitation, with a lower variability and strong weathering intensity, occurred during 3.4–2.4 Ma; an increased and more variable South Asian monsoon rainfall, along with strengthened but fluctuating weathering intensity, occurred at 1.8–1.1 Ma; and a reduced rainfall with lower South Asian monsoon precipitation variability and moderate weathering intensity marked the period 1.1–0.1 Ma. Maximum entropy spectral analysis and wavelet transform show that there were orbital-dominated cycles of periods c. 100 and c. 41 ka in these proxy-based time series. We propose that the monsoon, sea level, global temperature and insolation together forced the weathering and erosion in SW Asia.