Polyembryony has posed a significant impediment to the advancement of citrus hybrid breeding.FhRWP is widely regarded as a pivotal factor governing asexual reproduction in citrus,and prior research has demonstrated th...Polyembryony has posed a significant impediment to the advancement of citrus hybrid breeding.FhRWP is widely regarded as a pivotal factor governing asexual reproduction in citrus,and prior research has demonstrated that FhARID1,acting as an upstream regulator,modulates FhRWP expression.In this study,we performed a genome-wide characterization of the ARID-HMG-related genes using the short juvenile minicitrus Fortunella hindsii.A total of 20 ARID-HMG-related genes were identified.Protein interaction network and enrichment analysis suggested that ARID-HMG-related proteins might might be involved in chromatin remodeling complexes.Knockout of FhARID1 in F.hindsii did not induce the conversion from polyembryony to monoembryony.However,fharid1 plants in T1 generation exhibited abnormal proliferation at axillary buds,which is similar to phenotype of fhrwp plants.Expression analysis of fharid1 ovary tissues revealed the downregulation of FhRWP.The results indicated that FhARID1,as an upstream regulator of FhRWP,has an effect on the development of citrus axillary buds.Expression analysis of overexpressed leaves of FhARID1 lines showed that no significant up-regulation of FhRWP,indicating that FhARID1 is not the sole upstream regulatory factor of FhRWP.Only FhARID2 showed a correlation in expression with FhARID1 among the ARID-related genes,further supporting the notion that this gene may be involved in complex formation rather than acting alone.Yeast two-hybrid and MS/MS spectra further indicated that FhARID1 function requires casein kinase II-mediated post-transcriptional phosphorylation.This study elucidated the function of FhARID1 in citrus apomixis and axillary bud development,providing a fundamental basis for understanding the role of ARID-HMG-related genes.展开更多
The Görtler vortex is a characteristic flow feature observed in the boundary layer on compression ramp in hypersonic flow.In the context of high-enthalpy plasma flows during aerospace re-entry processes,there is ...The Görtler vortex is a characteristic flow feature observed in the boundary layer on compression ramp in hypersonic flow.In the context of high-enthalpy plasma flows during aerospace re-entry processes,there is currently a lack of effective means to visualize the boundary layer.In this study,the Nitric Oxide Planar Laser-Induced Fluorescence(NO-PLIF)technique was employed to visualize the boundary layer of a compression ramp in a 50-MW arc-heated plasma wind tunnel.Görtler-like vortex structures were observed in the boundary layer of the ramp.This is the first time that Görtler vortices have been clearly observed in a high-enthalpy plasma flow.By varying the flow conditions,the Görtler vortices persisted in the boundary layer of the ramp when the total enthalpy of the arc-heated wind tunnel exceeded 12.3 MJ/kg.Several image processing techniques were applied to extract the structure of high-speed Görtler streaks,and the position of the high-speed streaks was found to be non-fixed,whereas the average Görtler wavelength remained at approximately 30 mm at a 10°ramp and showed limited variation with the total enthalpy.Additionally,a sheet-forming optics system with an adjustable angle and height was designed to enable visualization of the Görtler vortices in the boundary layer of the ramp at different angles and heights.The vortices on the low-angle ramp exhibited better stability and shorter wavelengths.Visualization results at different heights confirmed that the Görtler vortex wavelength was approximately twice the boundary layer thickness.This study demonstrates the feasibility and potential of the PLIF technique for the visualization of the boundary layer in plasma flows,especially with regard to Görtler vortices.展开更多
At present,the most common preparation method of amorphous boron powder is magnesium thermal reduction method,but the amorphous boron powder obtained by this method mostly contains impurities such as magnesium and oxy...At present,the most common preparation method of amorphous boron powder is magnesium thermal reduction method,but the amorphous boron powder obtained by this method mostly contains impurities such as magnesium and oxygen which are difficult to remove,and these impurities will seriously affect the application of amorphous boron powder and need to be strictly removed.In this research,the acid-insoluble impurities were modified through sintering and quenching,while the magnesium impurities were optimized via ultrasonic acid leaching.We observed that the quenching temperature played a crucial role in determining the efficiency of magnesium impurity removal.The results show that the magnesium content in amorphous boron powder can be reduced from 5.67%to 2.40%by quenching the amorphous boron powder at 800°C and using ultrasonic assisted acid leaching.Furthermore,the oxidation reaction of boron is influenced by the powder's particle size and specific surface area,with the effective activation energy being intimately tied to both these factors.Post-quenching and acid leaching,we observed an increase in the specific surface area of the boron powder samples,leading to enhanced activity.In conclusion,our study presents an effective strategy to mitigate magnesium impurities and elevate the performance of amorphous boron powder,offering promising avenues for advancing its utilization across diverse industries.展开更多
Few-layer nanosheets(NSs)of hexagonal boron nitride(h-BN)and molybdenum disulfide(MoS_(2))display notable piezoelectric properties.Yet,their integration into polymers typically yields non-piezoelectric composites due ...Few-layer nanosheets(NSs)of hexagonal boron nitride(h-BN)and molybdenum disulfide(MoS_(2))display notable piezoelectric properties.Yet,their integration into polymers typically yields non-piezoelectric composites due to NSs’random distribution.We introduce a facile method for fabricating intrinsic piezoelectric composites incorporated with NSs without electric poling.Our innovative process aligns NSs within polyvinyl alcohol polymer,leveraging ice-water interfacial tension,water crystallization thrust,and directional cross-linking during freezing.The resulting PE composites exhibit a maximum piezoelectric coefficient of up to 25.5-28.4 pC N^(-1),comparable to polyvinylidene difluoride(PVDF),with significant costefficiency,safety,and scalability advantages over conventional materials.Using this composite,we develop highly sensitive wearable pressure and strain sensors,and an ultrasound energy harvester.These sensors detect finger bending and differentiate between walking and running,while the harvester generates1.18 V/2.31μA under 1Wcm^(-2)ultrasound input underwater.This universal method offers a novel manufacturing technique for piezoelectric composites,demonstrating remarkable effectiveness in synthesizing intrinsic piezoelectric composites based on 2D materials.Moreover,its potential extends to applications in wearable electronics and energy harvesting,promising significant advancements in these fields.展开更多
We performed a quantitative analysis of time-resolved laser-induced breakdown air plasma spectra to obtain the evolution of temperatures and species relative fractions.The air plasma was generated by focusing a 100 mJ...We performed a quantitative analysis of time-resolved laser-induced breakdown air plasma spectra to obtain the evolution of temperatures and species relative fractions.The air plasma was generated by focusing a 100 mJ Nd:YAG laser pulse,and the time-resolved spectra were recorded by an intensified charge-coupled device camera with incremental delay.The attention was mainly focused on the emission spectra of the first negative system of nitrogen(N_(2)^(+),B^(2)Σ-(u)^(-)-X^(2)Σ^(+)g)and the violet system of carbon nitride(CN,B^(2)Σ^(+)-X^(2)Σ^(+))located at 383-396 nm.A custom-built model was developed to perform the simulation and fitting of the N_(2)^(+)and the CN spectra from the air plasma.The model was verified by comparing to a published model with a 0.9860 Spearman correlation coefficient.With this model,the time-resolved non-equilibrium temperatures and relative fractions of N_(2)^(+)and CN were obtained with a fitting correlation coefficient higher than 0.9108.展开更多
AIM: To study liver cell apoptosis caused by the toxicity of selenium and observe the alteration of choline compounds using in vitro 9.4T high resolution magnetic resonance spectroscopy. METHODS: Twenty male Wistar ra...AIM: To study liver cell apoptosis caused by the toxicity of selenium and observe the alteration of choline compounds using in vitro 9.4T high resolution magnetic resonance spectroscopy. METHODS: Twenty male Wistar rats were randomly divided into two groups. The rats in the treatment group were intraperitoneally injected with sodium selenite and the control group with distilled water. All rats were sacrifi ced and the livers were dissected. 1H-MRS data were collected using in vitro 9.4T high resolution magnetic resonance spectrometer. Spectra were processed using XWINNMR and MestRe-c 4.3. HE and TUNEL staining was employed to detect and confi rm the change of liver cells. RESULTS: Good 1H-MR spectra of perchloric acid extract from liver tissue of rats were obtained. The conventional metabolites were detected and assigned. Concentrations of different ingredient choline compounds in treatment group vs control group were as follows: total choline compounds,5.08 ± 0.97 mmol/L vs 3.81 ± 1.16 mmol/L (P = 0.05); and free choline,1.07 ± 0.23 mmol/L vs 0.65 ± 0.20 mmol/L (P = 0.00). However,there was no statistical signif icance between the two groups. The hepatic sinus and cellular structure of hepatic cells in treatmentgroup were abnormal. Apoptosis of hepatic cells was confi rmed by TUNEL assay. CONCLUSION: High dose selenium compounds can cause the rat liver lesion and induce cell apoptosis in vivo. High resolution 1H-MRS in vitro can detect diversified metabolism. The changing trend for different ingredient of choline compounds is not completely the same at early period of apoptosis.展开更多
An array of distributed round synthetic jets was used to control a fully developed turbulent boundary layer.The study focused on the related skin friction drag reduction and mechanisms involved.The control effects wer...An array of distributed round synthetic jets was used to control a fully developed turbulent boundary layer.The study focused on the related skin friction drag reduction and mechanisms involved.The control effects were analyzed by measuring the streamwise velocities using a hot-wire anemometer downstream of the array.A reduction in the skin friction was observed both in the regions downstream of the orifices and in the regions between two adjacent orifices.A statistical analysis with the variable-interval time-averaging(VITA)technique demonstrated a weakened bursting intensity with synthetic jet in the near-wall region.The streamwise vortices were lifted by the upwash effect caused by synthetic jet and induced less low-speed streaks.The control mechanism acted in a way to suppress the dynamic interaction between the streamwise vortices and low-speed streaks and to attenuate the turbulence production in the near-wall region.The forcing frequency was found to be a more relevant parameter when synthetic jet was applied in turbulent boundary layer flow control.A higher forcing frequency induced a higher reduction in the skin friction.The power spectral density and autocorrelation of the fluctuating velocities showed that the synthetic jets gradually decayed in the streamwise direction,having an effect as far as 34.5 times the displacement thickness that was on the trailing edge of the distributed synthetic jets array.展开更多
AIM: To evaluate the feasibility of quantifying liver choline concentrations in both normal and apoptotic rabbit livers in vivo, using 1H magnetic resonance spectroscopy (1H-MRS). METHODS: 1H-MRS was performed in 18 r...AIM: To evaluate the feasibility of quantifying liver choline concentrations in both normal and apoptotic rabbit livers in vivo, using 1H magnetic resonance spectroscopy (1H-MRS). METHODS: 1H-MRS was performed in 18 rabbits using a 1.5T GE MR system with an eight-channel head/neck receiving coil. Fifteen rabbits were injected with sodium selenite at a dose of 10 μmol/kg to induce the liver cell apoptosis. Point-resolved spectroscopy sequencelocalized spectra were obtained from 10 livers once before and once 24 h after sodium selenite injection in vivo. T1 and T2 relaxation time of water and choline was measured separately in the livers of three healthy rabbits and three selenite-treated rabbits. Hematoxylin and eosin and dUTP-biotin nick end labeling (TUNEL) staining was used to detect and confirm apoptosis. Choline peak areas were measured relative to unsuppressed water using LCModel. Relaxation attenuation was corrected using the average of T1 and T2 relaxation time. The choline concentration was quantified using a formula, which was tested by a phantom with a known concentration. RESULTS: Apoptosis of hepatic cells was confirmed by TUNEL assay. In phantom experiment, the choline concentration (3.01 mmol/L), measured by 1H-MRS, was in good agreement with the actual concentration (3 mmol/L). The average T1 and T2 relaxation time of choline was 612 ± 15 ms and 74 ± 4 ms in the control group and 670 ± 27 ms and 78 ± 5 ms in apoptotic livers in vivo, respectively. Choline was quantified in 10 rabbits, once before and once after the injection with sodium selenite. The choline concentration decreased from 14.5 ± 7.57 mmol/L before sodium selenite injection to 10.8 ± 6.58 mmol/L (mean ± SD, n = 10) after treatment (Z = -2.395, P < 0.05, two-sample paired Wilcoxon test). CONCLUSION: 1H-MRS can be used to quantify liver choline in vivo using unsuppressed water as an internal reference. Decreased liver choline concentrations are found in sodium selenite-treated rabbits undergoing liver cell apoptosis.展开更多
Direct photon to chemical energy conversion using semiconductor–electrocatalyst–electrolyte interfaces has been extensively investigated for more than a half century. Many studies have focused on screening materials...Direct photon to chemical energy conversion using semiconductor–electrocatalyst–electrolyte interfaces has been extensively investigated for more than a half century. Many studies have focused on screening materials for efficient photocatalysis. Photocatalytic efficiency has been improved during this period but is not sufficient for industrial commercialization. Detailed elucidation on the photocatalytic water splitting process leads to consecutive six reaction steps with the fundamental parameters involved: The photocatalysis is initiated involving photophysics derived from various semiconductor properties(1: photon absorption, 2: exciton separation). The generated charge carriers need to be transferred to surfaces effectively utilizing the interfaces(3: carrier diffusion, 4: carrier transport). Consequently, electrocatalysis finishes the process by producing products on the surface(5: catalytic efficiency, 6: mass transfer of reactants and products). Successful photocatalytic water splitting requires the enhancement of efficiency at each stage. Most critically, a fundamental understanding of the interfacial phenomena is highly desired for establishing 'photocatalysis by design' concepts, where the kinetic bottleneck within a process is identified by further improving the specific properties of photocatalytic materials as opposed to blind material screening. Theoretical modeling using the identified quantitative parameters can effectively predict the theoretically attainable photon-conversion yields. This article provides an overview of the state-of-the-art theoretical understanding of interfacial problems mainly developed in our laboratory.Photocatalytic water splitting(especially hydrogen evolution on metal surfaces) was selected as a topic,and the photophysical and electrochemical processes that occur at semiconductor–metal, semiconductor–electrolyte and metal–electrolyte interfaces are discussed.展开更多
Balancing the risks and benefits of organophosphate pesticides(OPs)on human and environmental health relies partly on their accurate measurement.A highly sensitive fluorescence anti-quenching multi-residue bio-barcode...Balancing the risks and benefits of organophosphate pesticides(OPs)on human and environmental health relies partly on their accurate measurement.A highly sensitive fluorescence anti-quenching multi-residue bio-barcode immunoassay was developed to detect OPs(triazophos,parathion,and chlorpyrifos)in apples,turnips,cabbages,and rice.Gold nanoparticles were functionalized with monoclonal antibodies against the tested OPs.DNA oligonucleotides were complementarily hybridized with an RNA fluorescent label for signal amplification.The detection signals were generated by DNA-RNA hybridization and ribonuclease H dissociation of the fluorophore.The resulting fluorescence signal enables multiplexed quantification of triazophos,parathion,and chlorpyrifos residues over the concentration range of 0.01-25,0.01-50,and 0.1-50 ng/mL with limits of detection of 0.014,0.011,and 0.126 ng/mL,respectively.The mean recovery ranged between 80.3% and 110.8% with relative standard deviations of 7.3%-17.6%,which correlate well with results obtained by liquid chromatography-tandem mass spectrometry(LC-MS/MS).The proposed bio-barcode immunoassay is stable,reproducible and reliable,and is able to detect low residual levels of multi-residue OPs in agricultural products.展开更多
Titanium matrix composite reinforced by graphene nanoplatelets(GNPs)was fabricated via powder metallurgy route.Hot isostatic pressing and hot extrusion were used to consolidate the mixed powder of GNPs and TC4 titaniu...Titanium matrix composite reinforced by graphene nanoplatelets(GNPs)was fabricated via powder metallurgy route.Hot isostatic pressing and hot extrusion were used to consolidate the mixed powder of GNPs and TC4 titanium(Ti)alloy.The microstructures,mechanical properties and sliding wear performance of Ti/GNPs composite had been researched to evaluate the rein forcing effect of GNPs on tita nium matrix.Microstructure observation indicates that GNPs could restrain grai n growth slightly in titanium matrix.Titanium matrix and graphene exhibit a clean and firm interface formed by means of metallurgical bonding on atomic scale.Compared with the monolithic titanium alloy,the composite with 1.2 vol.%GNPs exhibits significantly improved elastic modulus and strength.The sliding wear test shows that there is an obvious enhancement in the tribological performance of Ti/GNPs composite with 1.2 vol.%GNPs.The results of this work indicate that GNP is an efficient reinforcenient material in titanium matrix.The strengthening mechanism including precipitates strengthening,load transfer and grain refinement mechanism of GNPs in titanium matrix was discussed.A modified shear-lag model was used to analyze the reinforcement contribution of the stress transfer mechanism.The calculation shows that the stress load mechanism constitutes the main strengthening mechanism in Ti/GNPs composite.展开更多
The catalyst layers(CLs) electrode is the key component of the membrane electrode assembly(MEA) in proton exchange membrane fuel cells(PEMFCs). Conventional electrodes for PEMFCs are composed of carbon-supported, iono...The catalyst layers(CLs) electrode is the key component of the membrane electrode assembly(MEA) in proton exchange membrane fuel cells(PEMFCs). Conventional electrodes for PEMFCs are composed of carbon-supported, ionomer, and Pt nanoparticles, all immersed together and sprayed with a micron-level thickness of CLs. They have a performance trade-off where increasing the Pt loading leads to higher performance of abundant triple-phase boundary areas but increases the electrode cost. Major challenges must be overcome before realizing its wide commercialization. Literature research revealed that it is impossible to achieve performance and durability targets with only high-performance catalysts, so the controllable design of CLs architecture in MEAs for PEMFCs must now be the top priority to meet industry goals. From this perspective, a 3D ordered electrode circumvents this issue with a support-free architecture and ultrathin thickness while reducing noble metal Pt loadings. Herein, we discuss the motivation in-depth and summarize the necessary CLs structural features for designing ultralow Pt loading electrodes. Critical issues that remain in progress for 3D ordered CLs must be studied and characterized. Furthermore, approaches for 3D ordered CLs architecture electrode development, involving material design, structure optimization, preparation technology, and characterization techniques, are summarized and are expected to be next-generation CLs for PEMFCs. Finally, the review concludes with perspectives on possible research directions of CL architecture to address the significant challenges in the future.展开更多
The recombination loss of photo-carriers in photocatalytic systems fatally determines the energy conversion efficiency of photocatalysts.In this work,an electrostatic field was used to inhibit the recombination of pho...The recombination loss of photo-carriers in photocatalytic systems fatally determines the energy conversion efficiency of photocatalysts.In this work,an electrostatic field was used to inhibit the recombination of photo-carriers in photocatalysts by separating photo-holes and photo-electrons in space.As a model structure,(010)facet-exposed BiVO_(4)nanowires were grown on PDMS-insulated piezo-substrate of piezoelectric transducer(PZT).The PZT substrate will generate an electrostatic field under a certain stress,and the photocatalytic behavior of BiVO_(4) nanowires is influenced by the electrostatic field.Our results showed that the photocatalytic performance of the BiVO_(4) nanowires in CO_(2)reduction in the negative electrostatic field is enhanced to 5.5-fold of that without electrostatic field.Moreover,the concentration of methane in the products was raised from 29% to 64%.The enhanced CO_(2) reduction efficiency is mainly attributed to the inhibited recombination loss of photo-carriers in the BiVO_(4) nanowires.The increased energy of photo-carriers and the enhanced surface absorption to polar molecules,which are CO in this case,were also play important roles in improving the photocatalytic activity of the photocatalyst and product selectivity.This work proposed an effective strategy to improve photo-carriers separation/transfer dynamics in the photocatalytic systems,which will also be a favorable reference for photovoltaic and photodetecting devices.展开更多
Historical optical data are combined on the BL Lac object OQ 530. Verifying the existence of correlations among the flux variations in different bands serves as an important tool to investigate emission processes. To ...Historical optical data are combined on the BL Lac object OQ 530. Verifying the existence of correlations among the flux variations in different bands serves as an important tool to investigate emission processes. To examine the possible existence of a lag between variations in different optical bands from this source, a statistical analysis is performed through the discrete correlation function （DCF） method and the z-transformed discrete correlation function （ZDCF） method. Monte Carlo simulations called ＂flux redistribution/random subset selection＂ （FR/RSS） are performed to obtain statistically meaningful values for the cross-correlation time lags and their related uncertainties. The analysis confirms that the variations in different optical light curves are strongly correlated, with zero-lag within the errors. Long term variability of color indexes is also analyzed. The result suggests a strong correlation between color index and brightness. A clear bluer-when-brighter chromatism is found, in the sense that the spectrum steepens as the brightness decreases.展开更多
Flame features and dynamics are important to the explanation and prediction of a lean blowout(LBO)phenomenon.In this paper,recognition of near-LBO flame features and oscillation characterization methods were proposed ...Flame features and dynamics are important to the explanation and prediction of a lean blowout(LBO)phenomenon.In this paper,recognition of near-LBO flame features and oscillation characterization methods were proposed based on flame spectroscopic images.High-speed planar laser-induced fluorescence measurements of OH were used to capture unique dynamic features such as the local extinction and reignition feature and entrained reactant pockets.The Zernike moment demonstrated a good performance in recognition of stability and near-LBO conditions,though the geometric moment had more advantages to characterize frequency characteristics.Low-frequency oscillations,especially at the obvious self-excited oscillation frequency around 200 Hz,were found when approaching an LBO condition,which can be expected to be used as a novel prediction characteristic parameter of the flameout limit.Proper orthogonal decomposition(POD)and dynamic mode decomposition(DMD)were used to conduct dynamic analysis of near-LBO flames.POD modes spectra showed the unique frequency characteristics of stable and near-LBO flames,which were basically in line with those at the heat-release frequency.The primary POD modes demonstrated that the radial vibration mode dominated in a stable flame,while the rotation mode was found to exist in a near-LBO flame.Analysis of modal decomposition showed that flame shedding and agminated entrained reactant pockets were responsible for generating self-excited flame oscillations.展开更多
To measure the equivalent ratio distribution of the two-stage lean premixed(DLP)flame,we propose using acetone/toluene planar laser-induced fluorescence(PLIF)technology to simultaneously measure the concentrations of ...To measure the equivalent ratio distribution of the two-stage lean premixed(DLP)flame,we propose using acetone/toluene planar laser-induced fluorescence(PLIF)technology to simultaneously measure the concentrations of the two components.Appropriate excitation laser wavelength and filters are used to assess the influence of acetone and toluene on each other’s fluorescence signal at room temperature.Experimental results show that acetone has a strong absorption effect on toluene’s fluorescence signal,the effective absorption cross-section is 5.77×10-20 cm-2.Acetone has an obvious quenching effect on the toluene fluorescence signal,and the Stern–Volmer coefficient is 0.50 kPa-1.The collisions between the molecules of toluene and acetone will lead to the enhancement of the fluorescence signal of acetone,and the enhancement coefficient is exponential with the acetone’s concentration.The quantitative relationship between the fluorescence intensity and the concentrations of the two tracers is obtained by establishing the photophysical model of toluene and acetone’s fluorescence signals.展开更多
The license plate recognition system(LPRS)has been widely adopted in daily life due to its efficiency and high accuracy.Deep neural networks are commonly used in the LPRS to improve the recognition accuracy.However,re...The license plate recognition system(LPRS)has been widely adopted in daily life due to its efficiency and high accuracy.Deep neural networks are commonly used in the LPRS to improve the recognition accuracy.However,researchers have found that deep neural networks have their own security problems that may lead to unexpected results.Specifically,they can be easily attacked by the adversarial examples that are generated by adding small perturbations to the original images,resulting in incorrect license plate recognition.There are some classic methods to generate adversarial examples,but they cannot be adopted on LPRS directly.In this paper,we modify some classic methods to generate adversarial examples that could mislead the LPRS.We conduct extensive evaluations on the HyperLPR system and the results show that the system could be easily attacked by such adversarial examples.In addition,we show that the generated images could also attack the black-box systems;we show some examples that the Baidu LPR system also makes incorrect recognitions.We hope this paper could help improve the LPRS by realizing the existence of such adversarial attacks.展开更多
Results Sixty-one cancer survivors and 183 matched non-cancer patients were screened from 2,828 COVID-19 infected patients admitted to 4 hospitals in Wuhan,China.The median ages of the cancer survivor cohort and non-c...Results Sixty-one cancer survivors and 183 matched non-cancer patients were screened from 2,828 COVID-19 infected patients admitted to 4 hospitals in Wuhan,China.The median ages of the cancer survivor cohort and non-cancer patient cohort were 64.0(55.0–73.0)and 64.0(54.0–73.5),respectively(P=0.909).Cancer survivors reported a higher incidence of symptom onset than non-cancer patients.Fever(80.3%vs.65.0%;P=0.026)was the most prevalent symptom,followed by cough(65.6%vs.37.7%;P<0.001),myalgia,and fatigue(45.9%vs.13.6%;P<0.001).The risks of the development of severe events(adjusted hazard ratio[AHR]=1.25;95%confidence interval[CI]:0.76–2.06;P=0.378)and mortality(relative risk[RR]=0.90,95%CI:0.79–1.04;P=0.416)in the cancer survivor cohort were comparable to those of the matched non-cancer patient cohort.However,the cancer survivor cohort showed a higher incidence of secondary infection(52.5%vs.30.1%;RR=1.47,95%CI:1.11–1.95;P=0.002)and a prolonged viral RNA shedding duration(32 days[IQR 26.0–46.0]vs.24.0 days[IQR 18.0–33.0];AHR=0.54;95%CI:0.38–0.80;P<0.05).Conclusion Compared to non-cancer patients,cancer survivors with COVID-19 exhibited a higher incidence of secondary infection,a prolonged period of viral shedding,but comparable risks of the development of severe events and mortality.It is helpful for clinicians to take tailored measures to treat cancer survivors with COVID-19.展开更多
An artificial tribological layer was formed on the worn surface during sliding,through supplying MoS_2,Fe_2O_3 or their equiponderant mixtures onto the sliding interface of H13/GCr15 steels.The effect of this tribolog...An artificial tribological layer was formed on the worn surface during sliding,through supplying MoS_2,Fe_2O_3 or their equiponderant mixtures onto the sliding interface of H13/GCr15 steels.The effect of this tribological layer on the wear behavior of H13 steel was studied.The worn surfaces and subsurfaces of H13 steel were thoroughly characterized by using X-ray diffraction（XRD）,scanning electron microscopy（SEM）and energy dispersive spectrometry（EDS）;the wear mechanisms were explored.The research results demonstrated that tribological layer did not exist during sliding of H13 steel with no additive,but it formed with the addition of MoS_2,Fe_2O_3 or their equiponderant mixtures.When there was no tribological layer,the wear rate rapidly increased with an increase of the load.In this case,adhesive and abrasive wear prevailed.As the additives were supplied,the artificial tribological layer was observed to be immediately formed and stably existed on worn surfaces.This tribological layer presented an obvious protective function from wear and friction.Hence,the wear rate and friction coefficient were significantly decreased.MoS_2 as tribological layer seemed to present more obvious protective function than Fe_2O_3.By supplying their mixture,the artificial tribological layer possessed not only the load-carrying capacity of Fe_2O_3,but also the lubricative capacity of MoS_2.These two simultaneous capacities could improve the friction and wear properties of H13 steel further.展开更多
There are two different dust storms in Northeast China, normal dust and alkali dust, from Kerqin sand land and Songnen saline land. As well as visible damages of the dust storms, there are some invisible influences. T...There are two different dust storms in Northeast China, normal dust and alkali dust, from Kerqin sand land and Songnen saline land. As well as visible damages of the dust storms, there are some invisible influences. The authors provide evidences that the bacteria carried by dusts from remote area should not be ignored, but the damages of the alkali dusts are still not clear.展开更多
基金funded by the National Key Research and Development Program of China(Grant No.2022YFF1003100)Modern Citrus Industry Technology System of China(Grant No.CARS-26).
文摘Polyembryony has posed a significant impediment to the advancement of citrus hybrid breeding.FhRWP is widely regarded as a pivotal factor governing asexual reproduction in citrus,and prior research has demonstrated that FhARID1,acting as an upstream regulator,modulates FhRWP expression.In this study,we performed a genome-wide characterization of the ARID-HMG-related genes using the short juvenile minicitrus Fortunella hindsii.A total of 20 ARID-HMG-related genes were identified.Protein interaction network and enrichment analysis suggested that ARID-HMG-related proteins might might be involved in chromatin remodeling complexes.Knockout of FhARID1 in F.hindsii did not induce the conversion from polyembryony to monoembryony.However,fharid1 plants in T1 generation exhibited abnormal proliferation at axillary buds,which is similar to phenotype of fhrwp plants.Expression analysis of fharid1 ovary tissues revealed the downregulation of FhRWP.The results indicated that FhARID1,as an upstream regulator of FhRWP,has an effect on the development of citrus axillary buds.Expression analysis of overexpressed leaves of FhARID1 lines showed that no significant up-regulation of FhRWP,indicating that FhARID1 is not the sole upstream regulatory factor of FhRWP.Only FhARID2 showed a correlation in expression with FhARID1 among the ARID-related genes,further supporting the notion that this gene may be involved in complex formation rather than acting alone.Yeast two-hybrid and MS/MS spectra further indicated that FhARID1 function requires casein kinase II-mediated post-transcriptional phosphorylation.This study elucidated the function of FhARID1 in citrus apomixis and axillary bud development,providing a fundamental basis for understanding the role of ARID-HMG-related genes.
基金supported by the National Natural Science Foundation of China(Nos.62175053,62305087)。
文摘The Görtler vortex is a characteristic flow feature observed in the boundary layer on compression ramp in hypersonic flow.In the context of high-enthalpy plasma flows during aerospace re-entry processes,there is currently a lack of effective means to visualize the boundary layer.In this study,the Nitric Oxide Planar Laser-Induced Fluorescence(NO-PLIF)technique was employed to visualize the boundary layer of a compression ramp in a 50-MW arc-heated plasma wind tunnel.Görtler-like vortex structures were observed in the boundary layer of the ramp.This is the first time that Görtler vortices have been clearly observed in a high-enthalpy plasma flow.By varying the flow conditions,the Görtler vortices persisted in the boundary layer of the ramp when the total enthalpy of the arc-heated wind tunnel exceeded 12.3 MJ/kg.Several image processing techniques were applied to extract the structure of high-speed Görtler streaks,and the position of the high-speed streaks was found to be non-fixed,whereas the average Görtler wavelength remained at approximately 30 mm at a 10°ramp and showed limited variation with the total enthalpy.Additionally,a sheet-forming optics system with an adjustable angle and height was designed to enable visualization of the Görtler vortices in the boundary layer of the ramp at different angles and heights.The vortices on the low-angle ramp exhibited better stability and shorter wavelengths.Visualization results at different heights confirmed that the Görtler vortex wavelength was approximately twice the boundary layer thickness.This study demonstrates the feasibility and potential of the PLIF technique for the visualization of the boundary layer in plasma flows,especially with regard to Görtler vortices.
基金support on this research from the Talent Training Program of Yunnan of China(Grant Nos.202005AC160041 and KKXY202252002)the"Xingdian Talent"Industry Innovation Talent Program in Yunnan Province(Grant No.XDYC-CYCX-2022-0042)。
文摘At present,the most common preparation method of amorphous boron powder is magnesium thermal reduction method,but the amorphous boron powder obtained by this method mostly contains impurities such as magnesium and oxygen which are difficult to remove,and these impurities will seriously affect the application of amorphous boron powder and need to be strictly removed.In this research,the acid-insoluble impurities were modified through sintering and quenching,while the magnesium impurities were optimized via ultrasonic acid leaching.We observed that the quenching temperature played a crucial role in determining the efficiency of magnesium impurity removal.The results show that the magnesium content in amorphous boron powder can be reduced from 5.67%to 2.40%by quenching the amorphous boron powder at 800°C and using ultrasonic assisted acid leaching.Furthermore,the oxidation reaction of boron is influenced by the powder's particle size and specific surface area,with the effective activation energy being intimately tied to both these factors.Post-quenching and acid leaching,we observed an increase in the specific surface area of the boron powder samples,leading to enhanced activity.In conclusion,our study presents an effective strategy to mitigate magnesium impurities and elevate the performance of amorphous boron powder,offering promising avenues for advancing its utilization across diverse industries.
基金funded by the Key Research Project of Zhejiang(LD22E030007)the“Leading Goose”R&D Program of Zhejiang Province(No.2022C01136)+2 种基金National Science Foundation of China(NSFC No.61974037,No.61904042,No.62274049)Zhejiang University Education Foundation Global Partnership Fund(No.100000-11320)the support of the Micro-nano Fabrication Center of International campus of Zhejiang University.
文摘Few-layer nanosheets(NSs)of hexagonal boron nitride(h-BN)and molybdenum disulfide(MoS_(2))display notable piezoelectric properties.Yet,their integration into polymers typically yields non-piezoelectric composites due to NSs’random distribution.We introduce a facile method for fabricating intrinsic piezoelectric composites incorporated with NSs without electric poling.Our innovative process aligns NSs within polyvinyl alcohol polymer,leveraging ice-water interfacial tension,water crystallization thrust,and directional cross-linking during freezing.The resulting PE composites exhibit a maximum piezoelectric coefficient of up to 25.5-28.4 pC N^(-1),comparable to polyvinylidene difluoride(PVDF),with significant costefficiency,safety,and scalability advantages over conventional materials.Using this composite,we develop highly sensitive wearable pressure and strain sensors,and an ultrasound energy harvester.These sensors detect finger bending and differentiate between walking and running,while the harvester generates1.18 V/2.31μA under 1Wcm^(-2)ultrasound input underwater.This universal method offers a novel manufacturing technique for piezoelectric composites,demonstrating remarkable effectiveness in synthesizing intrinsic piezoelectric composites based on 2D materials.Moreover,its potential extends to applications in wearable electronics and energy harvesting,promising significant advancements in these fields.
基金Project supported by the National Natural Science Foundation of China(Grant No.62305087)。
文摘We performed a quantitative analysis of time-resolved laser-induced breakdown air plasma spectra to obtain the evolution of temperatures and species relative fractions.The air plasma was generated by focusing a 100 mJ Nd:YAG laser pulse,and the time-resolved spectra were recorded by an intensified charge-coupled device camera with incremental delay.The attention was mainly focused on the emission spectra of the first negative system of nitrogen(N_(2)^(+),B^(2)Σ-(u)^(-)-X^(2)Σ^(+)g)and the violet system of carbon nitride(CN,B^(2)Σ^(+)-X^(2)Σ^(+))located at 383-396 nm.A custom-built model was developed to perform the simulation and fitting of the N_(2)^(+)and the CN spectra from the air plasma.The model was verified by comparing to a published model with a 0.9860 Spearman correlation coefficient.With this model,the time-resolved non-equilibrium temperatures and relative fractions of N_(2)^(+)and CN were obtained with a fitting correlation coefficient higher than 0.9108.
基金The National Natural Science Foundation of China,No.30570480
文摘AIM: To study liver cell apoptosis caused by the toxicity of selenium and observe the alteration of choline compounds using in vitro 9.4T high resolution magnetic resonance spectroscopy. METHODS: Twenty male Wistar rats were randomly divided into two groups. The rats in the treatment group were intraperitoneally injected with sodium selenite and the control group with distilled water. All rats were sacrifi ced and the livers were dissected. 1H-MRS data were collected using in vitro 9.4T high resolution magnetic resonance spectrometer. Spectra were processed using XWINNMR and MestRe-c 4.3. HE and TUNEL staining was employed to detect and confi rm the change of liver cells. RESULTS: Good 1H-MR spectra of perchloric acid extract from liver tissue of rats were obtained. The conventional metabolites were detected and assigned. Concentrations of different ingredient choline compounds in treatment group vs control group were as follows: total choline compounds,5.08 ± 0.97 mmol/L vs 3.81 ± 1.16 mmol/L (P = 0.05); and free choline,1.07 ± 0.23 mmol/L vs 0.65 ± 0.20 mmol/L (P = 0.00). However,there was no statistical signif icance between the two groups. The hepatic sinus and cellular structure of hepatic cells in treatmentgroup were abnormal. Apoptosis of hepatic cells was confi rmed by TUNEL assay. CONCLUSION: High dose selenium compounds can cause the rat liver lesion and induce cell apoptosis in vivo. High resolution 1H-MRS in vitro can detect diversified metabolism. The changing trend for different ingredient of choline compounds is not completely the same at early period of apoptosis.
基金The authors would like to acknowledge the financial support received from the project“Drag Reduction via Turbulent Boundary Layer Flow Control(DRAGY)”.The DRAGY project(April 2016-March 2019)is a China-EU Aeronautical Cooperation project,which is co-funded by Ministry of Industry and Information Technology(MIIT),China,and Directorate-General for Research and Innovation(DG RTD),European Commission.
文摘An array of distributed round synthetic jets was used to control a fully developed turbulent boundary layer.The study focused on the related skin friction drag reduction and mechanisms involved.The control effects were analyzed by measuring the streamwise velocities using a hot-wire anemometer downstream of the array.A reduction in the skin friction was observed both in the regions downstream of the orifices and in the regions between two adjacent orifices.A statistical analysis with the variable-interval time-averaging(VITA)technique demonstrated a weakened bursting intensity with synthetic jet in the near-wall region.The streamwise vortices were lifted by the upwash effect caused by synthetic jet and induced less low-speed streaks.The control mechanism acted in a way to suppress the dynamic interaction between the streamwise vortices and low-speed streaks and to attenuate the turbulence production in the near-wall region.The forcing frequency was found to be a more relevant parameter when synthetic jet was applied in turbulent boundary layer flow control.A higher forcing frequency induced a higher reduction in the skin friction.The power spectral density and autocorrelation of the fluctuating velocities showed that the synthetic jets gradually decayed in the streamwise direction,having an effect as far as 34.5 times the displacement thickness that was on the trailing edge of the distributed synthetic jets array.
基金Supported by Grants from Medical Scientific Research Foundation of Guangdong Province, China, No. B2008128National Natural Science Foundation of China, No. 30930027 and No. 60971075, in part
文摘AIM: To evaluate the feasibility of quantifying liver choline concentrations in both normal and apoptotic rabbit livers in vivo, using 1H magnetic resonance spectroscopy (1H-MRS). METHODS: 1H-MRS was performed in 18 rabbits using a 1.5T GE MR system with an eight-channel head/neck receiving coil. Fifteen rabbits were injected with sodium selenite at a dose of 10 μmol/kg to induce the liver cell apoptosis. Point-resolved spectroscopy sequencelocalized spectra were obtained from 10 livers once before and once 24 h after sodium selenite injection in vivo. T1 and T2 relaxation time of water and choline was measured separately in the livers of three healthy rabbits and three selenite-treated rabbits. Hematoxylin and eosin and dUTP-biotin nick end labeling (TUNEL) staining was used to detect and confirm apoptosis. Choline peak areas were measured relative to unsuppressed water using LCModel. Relaxation attenuation was corrected using the average of T1 and T2 relaxation time. The choline concentration was quantified using a formula, which was tested by a phantom with a known concentration. RESULTS: Apoptosis of hepatic cells was confirmed by TUNEL assay. In phantom experiment, the choline concentration (3.01 mmol/L), measured by 1H-MRS, was in good agreement with the actual concentration (3 mmol/L). The average T1 and T2 relaxation time of choline was 612 ± 15 ms and 74 ± 4 ms in the control group and 670 ± 27 ms and 78 ± 5 ms in apoptotic livers in vivo, respectively. Choline was quantified in 10 rabbits, once before and once after the injection with sodium selenite. The choline concentration decreased from 14.5 ± 7.57 mmol/L before sodium selenite injection to 10.8 ± 6.58 mmol/L (mean ± SD, n = 10) after treatment (Z = -2.395, P < 0.05, two-sample paired Wilcoxon test). CONCLUSION: 1H-MRS can be used to quantify liver choline in vivo using unsuppressed water as an internal reference. Decreased liver choline concentrations are found in sodium selenite-treated rabbits undergoing liver cell apoptosis.
基金supported by funding from King Abdullah University of Science and Technology(KAUST)
文摘Direct photon to chemical energy conversion using semiconductor–electrocatalyst–electrolyte interfaces has been extensively investigated for more than a half century. Many studies have focused on screening materials for efficient photocatalysis. Photocatalytic efficiency has been improved during this period but is not sufficient for industrial commercialization. Detailed elucidation on the photocatalytic water splitting process leads to consecutive six reaction steps with the fundamental parameters involved: The photocatalysis is initiated involving photophysics derived from various semiconductor properties(1: photon absorption, 2: exciton separation). The generated charge carriers need to be transferred to surfaces effectively utilizing the interfaces(3: carrier diffusion, 4: carrier transport). Consequently, electrocatalysis finishes the process by producing products on the surface(5: catalytic efficiency, 6: mass transfer of reactants and products). Successful photocatalytic water splitting requires the enhancement of efficiency at each stage. Most critically, a fundamental understanding of the interfacial phenomena is highly desired for establishing 'photocatalysis by design' concepts, where the kinetic bottleneck within a process is identified by further improving the specific properties of photocatalytic materials as opposed to blind material screening. Theoretical modeling using the identified quantitative parameters can effectively predict the theoretically attainable photon-conversion yields. This article provides an overview of the state-of-the-art theoretical understanding of interfacial problems mainly developed in our laboratory.Photocatalytic water splitting(especially hydrogen evolution on metal surfaces) was selected as a topic,and the photophysical and electrochemical processes that occur at semiconductor–metal, semiconductor–electrolyte and metal–electrolyte interfaces are discussed.
基金supported by the Central Public Interest Scientific Institution Basal Research Fund for the Chinese Academy of Agricultural Sciences(Grant No.:Y2021PT05)National Institute of Environmental Health Science Superfund Research Program(Grant No.:P42 ES004699)+1 种基金National Academy of Sciences(Subaward No.:2000009144)Ningbo Innovation Project for Agro-Products Quality and Safety(Grant No.:2019CXGC007).
文摘Balancing the risks and benefits of organophosphate pesticides(OPs)on human and environmental health relies partly on their accurate measurement.A highly sensitive fluorescence anti-quenching multi-residue bio-barcode immunoassay was developed to detect OPs(triazophos,parathion,and chlorpyrifos)in apples,turnips,cabbages,and rice.Gold nanoparticles were functionalized with monoclonal antibodies against the tested OPs.DNA oligonucleotides were complementarily hybridized with an RNA fluorescent label for signal amplification.The detection signals were generated by DNA-RNA hybridization and ribonuclease H dissociation of the fluorophore.The resulting fluorescence signal enables multiplexed quantification of triazophos,parathion,and chlorpyrifos residues over the concentration range of 0.01-25,0.01-50,and 0.1-50 ng/mL with limits of detection of 0.014,0.011,and 0.126 ng/mL,respectively.The mean recovery ranged between 80.3% and 110.8% with relative standard deviations of 7.3%-17.6%,which correlate well with results obtained by liquid chromatography-tandem mass spectrometry(LC-MS/MS).The proposed bio-barcode immunoassay is stable,reproducible and reliable,and is able to detect low residual levels of multi-residue OPs in agricultural products.
基金National Natural Science Foundation of China(51802296)Beijing Municipal Science and Technology Commission(Z171100002017016,Z191100005619006).
文摘Titanium matrix composite reinforced by graphene nanoplatelets(GNPs)was fabricated via powder metallurgy route.Hot isostatic pressing and hot extrusion were used to consolidate the mixed powder of GNPs and TC4 titanium(Ti)alloy.The microstructures,mechanical properties and sliding wear performance of Ti/GNPs composite had been researched to evaluate the rein forcing effect of GNPs on tita nium matrix.Microstructure observation indicates that GNPs could restrain grai n growth slightly in titanium matrix.Titanium matrix and graphene exhibit a clean and firm interface formed by means of metallurgical bonding on atomic scale.Compared with the monolithic titanium alloy,the composite with 1.2 vol.%GNPs exhibits significantly improved elastic modulus and strength.The sliding wear test shows that there is an obvious enhancement in the tribological performance of Ti/GNPs composite with 1.2 vol.%GNPs.The results of this work indicate that GNP is an efficient reinforcenient material in titanium matrix.The strengthening mechanism including precipitates strengthening,load transfer and grain refinement mechanism of GNPs in titanium matrix was discussed.A modified shear-lag model was used to analyze the reinforcement contribution of the stress transfer mechanism.The calculation shows that the stress load mechanism constitutes the main strengthening mechanism in Ti/GNPs composite.
基金funded by the Natural Science Foundation of Shandong Province, China (ZR2023MB049)the China Postdoctoral Science Foundation (2020M670483)the Science Foundation of Weifang University (2023BS11)。
文摘The catalyst layers(CLs) electrode is the key component of the membrane electrode assembly(MEA) in proton exchange membrane fuel cells(PEMFCs). Conventional electrodes for PEMFCs are composed of carbon-supported, ionomer, and Pt nanoparticles, all immersed together and sprayed with a micron-level thickness of CLs. They have a performance trade-off where increasing the Pt loading leads to higher performance of abundant triple-phase boundary areas but increases the electrode cost. Major challenges must be overcome before realizing its wide commercialization. Literature research revealed that it is impossible to achieve performance and durability targets with only high-performance catalysts, so the controllable design of CLs architecture in MEAs for PEMFCs must now be the top priority to meet industry goals. From this perspective, a 3D ordered electrode circumvents this issue with a support-free architecture and ultrathin thickness while reducing noble metal Pt loadings. Herein, we discuss the motivation in-depth and summarize the necessary CLs structural features for designing ultralow Pt loading electrodes. Critical issues that remain in progress for 3D ordered CLs must be studied and characterized. Furthermore, approaches for 3D ordered CLs architecture electrode development, involving material design, structure optimization, preparation technology, and characterization techniques, are summarized and are expected to be next-generation CLs for PEMFCs. Finally, the review concludes with perspectives on possible research directions of CL architecture to address the significant challenges in the future.
基金financially supported by the National Natural Science Foundation of China(21607066,51972153)Natural Science Foundation of Gansu Province of China(21JR7RA469)the Fundamental Research Funds for the Central Universities(lzujbky-2021-76).
文摘The recombination loss of photo-carriers in photocatalytic systems fatally determines the energy conversion efficiency of photocatalysts.In this work,an electrostatic field was used to inhibit the recombination of photo-carriers in photocatalysts by separating photo-holes and photo-electrons in space.As a model structure,(010)facet-exposed BiVO_(4)nanowires were grown on PDMS-insulated piezo-substrate of piezoelectric transducer(PZT).The PZT substrate will generate an electrostatic field under a certain stress,and the photocatalytic behavior of BiVO_(4) nanowires is influenced by the electrostatic field.Our results showed that the photocatalytic performance of the BiVO_(4) nanowires in CO_(2)reduction in the negative electrostatic field is enhanced to 5.5-fold of that without electrostatic field.Moreover,the concentration of methane in the products was raised from 29% to 64%.The enhanced CO_(2) reduction efficiency is mainly attributed to the inhibited recombination loss of photo-carriers in the BiVO_(4) nanowires.The increased energy of photo-carriers and the enhanced surface absorption to polar molecules,which are CO in this case,were also play important roles in improving the photocatalytic activity of the photocatalyst and product selectivity.This work proposed an effective strategy to improve photo-carriers separation/transfer dynamics in the photocatalytic systems,which will also be a favorable reference for photovoltaic and photodetecting devices.
基金Supported by the National Natural Science Foundation of China (Grant No. 10975145)funded by Fuyang Normal College, the Research Foundation of the Department of Education of Anhui Province (KJ2010B159)
文摘Historical optical data are combined on the BL Lac object OQ 530. Verifying the existence of correlations among the flux variations in different bands serves as an important tool to investigate emission processes. To examine the possible existence of a lag between variations in different optical bands from this source, a statistical analysis is performed through the discrete correlation function （DCF） method and the z-transformed discrete correlation function （ZDCF） method. Monte Carlo simulations called ＂flux redistribution/random subset selection＂ （FR/RSS） are performed to obtain statistically meaningful values for the cross-correlation time lags and their related uncertainties. The analysis confirms that the variations in different optical light curves are strongly correlated, with zero-lag within the errors. Long term variability of color indexes is also analyzed. The result suggests a strong correlation between color index and brightness. A clear bluer-when-brighter chromatism is found, in the sense that the spectrum steepens as the brightness decreases.
基金supported by the Heilongjiang Provincial Natural Science Foundation of China(No.LH2021F028)。
文摘Flame features and dynamics are important to the explanation and prediction of a lean blowout(LBO)phenomenon.In this paper,recognition of near-LBO flame features and oscillation characterization methods were proposed based on flame spectroscopic images.High-speed planar laser-induced fluorescence measurements of OH were used to capture unique dynamic features such as the local extinction and reignition feature and entrained reactant pockets.The Zernike moment demonstrated a good performance in recognition of stability and near-LBO conditions,though the geometric moment had more advantages to characterize frequency characteristics.Low-frequency oscillations,especially at the obvious self-excited oscillation frequency around 200 Hz,were found when approaching an LBO condition,which can be expected to be used as a novel prediction characteristic parameter of the flameout limit.Proper orthogonal decomposition(POD)and dynamic mode decomposition(DMD)were used to conduct dynamic analysis of near-LBO flames.POD modes spectra showed the unique frequency characteristics of stable and near-LBO flames,which were basically in line with those at the heat-release frequency.The primary POD modes demonstrated that the radial vibration mode dominated in a stable flame,while the rotation mode was found to exist in a near-LBO flame.Analysis of modal decomposition showed that flame shedding and agminated entrained reactant pockets were responsible for generating self-excited flame oscillations.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51536002,61405048,and 91441130)。
文摘To measure the equivalent ratio distribution of the two-stage lean premixed(DLP)flame,we propose using acetone/toluene planar laser-induced fluorescence(PLIF)technology to simultaneously measure the concentrations of the two components.Appropriate excitation laser wavelength and filters are used to assess the influence of acetone and toluene on each other’s fluorescence signal at room temperature.Experimental results show that acetone has a strong absorption effect on toluene’s fluorescence signal,the effective absorption cross-section is 5.77×10-20 cm-2.Acetone has an obvious quenching effect on the toluene fluorescence signal,and the Stern–Volmer coefficient is 0.50 kPa-1.The collisions between the molecules of toluene and acetone will lead to the enhancement of the fluorescence signal of acetone,and the enhancement coefficient is exponential with the acetone’s concentration.The quantitative relationship between the fluorescence intensity and the concentrations of the two tracers is obtained by establishing the photophysical model of toluene and acetone’s fluorescence signals.
基金This work is supported by the National Natural Science Foundation of China under Grant Nos.U1636215,61902082the Guangdong Key R&D Program of China 2019B010136003National Key R&D Program of China 2019YFB1706003.
文摘The license plate recognition system(LPRS)has been widely adopted in daily life due to its efficiency and high accuracy.Deep neural networks are commonly used in the LPRS to improve the recognition accuracy.However,researchers have found that deep neural networks have their own security problems that may lead to unexpected results.Specifically,they can be easily attacked by the adversarial examples that are generated by adding small perturbations to the original images,resulting in incorrect license plate recognition.There are some classic methods to generate adversarial examples,but they cannot be adopted on LPRS directly.In this paper,we modify some classic methods to generate adversarial examples that could mislead the LPRS.We conduct extensive evaluations on the HyperLPR system and the results show that the system could be easily attacked by such adversarial examples.In addition,we show that the generated images could also attack the black-box systems;we show some examples that the Baidu LPR system also makes incorrect recognitions.We hope this paper could help improve the LPRS by realizing the existence of such adversarial attacks.
基金Supported by grants from the SGC’s Rapid Response Funding for Bilgateral Collaborative Emergence COVID-19 Project between China and Germany(No.C-0065)COVID-19 Emergency Project of Huazhong University of Science and Technology(No.2020kfyXGYJ062)Hepatobiliary and Pancreatic Cancer Grant,Hubei Chen Xiaoping Science and Technology Development Foundation(No.CXPJJH12000001-2020344).
文摘Results Sixty-one cancer survivors and 183 matched non-cancer patients were screened from 2,828 COVID-19 infected patients admitted to 4 hospitals in Wuhan,China.The median ages of the cancer survivor cohort and non-cancer patient cohort were 64.0(55.0–73.0)and 64.0(54.0–73.5),respectively(P=0.909).Cancer survivors reported a higher incidence of symptom onset than non-cancer patients.Fever(80.3%vs.65.0%;P=0.026)was the most prevalent symptom,followed by cough(65.6%vs.37.7%;P<0.001),myalgia,and fatigue(45.9%vs.13.6%;P<0.001).The risks of the development of severe events(adjusted hazard ratio[AHR]=1.25;95%confidence interval[CI]:0.76–2.06;P=0.378)and mortality(relative risk[RR]=0.90,95%CI:0.79–1.04;P=0.416)in the cancer survivor cohort were comparable to those of the matched non-cancer patient cohort.However,the cancer survivor cohort showed a higher incidence of secondary infection(52.5%vs.30.1%;RR=1.47,95%CI:1.11–1.95;P=0.002)and a prolonged viral RNA shedding duration(32 days[IQR 26.0–46.0]vs.24.0 days[IQR 18.0–33.0];AHR=0.54;95%CI:0.38–0.80;P<0.05).Conclusion Compared to non-cancer patients,cancer survivors with COVID-19 exhibited a higher incidence of secondary infection,a prolonged period of viral shedding,but comparable risks of the development of severe events and mortality.It is helpful for clinicians to take tailored measures to treat cancer survivors with COVID-19.
基金sponsored by National Natural Science Foundation of China(No.51071078)Jiangsu Provincial Key Laboratory for International Medical Devices(No.jr1506)the Initial Fund of Jiangsu University Senior Talent(No.15JDG076)
文摘An artificial tribological layer was formed on the worn surface during sliding,through supplying MoS_2,Fe_2O_3 or their equiponderant mixtures onto the sliding interface of H13/GCr15 steels.The effect of this tribological layer on the wear behavior of H13 steel was studied.The worn surfaces and subsurfaces of H13 steel were thoroughly characterized by using X-ray diffraction（XRD）,scanning electron microscopy（SEM）and energy dispersive spectrometry（EDS）;the wear mechanisms were explored.The research results demonstrated that tribological layer did not exist during sliding of H13 steel with no additive,but it formed with the addition of MoS_2,Fe_2O_3 or their equiponderant mixtures.When there was no tribological layer,the wear rate rapidly increased with an increase of the load.In this case,adhesive and abrasive wear prevailed.As the additives were supplied,the artificial tribological layer was observed to be immediately formed and stably existed on worn surfaces.This tribological layer presented an obvious protective function from wear and friction.Hence,the wear rate and friction coefficient were significantly decreased.MoS_2 as tribological layer seemed to present more obvious protective function than Fe_2O_3.By supplying their mixture,the artificial tribological layer possessed not only the load-carrying capacity of Fe_2O_3,but also the lubricative capacity of MoS_2.These two simultaneous capacities could improve the friction and wear properties of H13 steel further.
文摘There are two different dust storms in Northeast China, normal dust and alkali dust, from Kerqin sand land and Songnen saline land. As well as visible damages of the dust storms, there are some invisible influences. The authors provide evidences that the bacteria carried by dusts from remote area should not be ignored, but the damages of the alkali dusts are still not clear.
