Advanced 3D ordered electrodes for PEMFC applications: From structural features and fabrication methods to the controllable design of catalyst layers

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.

Change of choline compounds in sodium selenite-induced apoptosis of rats used as quantitative analysis by in vitro 9.4T MR spectroscopy

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.

Quantification of choline concentration following liver cell apoptosis using ~1H magnetic resonance spectroscopy

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.

Photophysics and electrochemistry relevant to photocatalytic water splitting involved at solid–electrolyte interfaces

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.

Multi-band optical variability of BL Lac object OQ 530

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.

A highly sensitive bio-barcode immunoassay for multi-residue detection of organophosphate pesticides based on fluorescence antiquenching

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.

Absorption,quenching,and enhancement by tracer in acetone/toluene laser-induced fluorescence

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.

Electrostatic Field Enhanced Photocatalytic CO_(2) Conversion on BiVO_(4) Nanowires

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.

Adversarial Attacks on License Plate Recognition Systems

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.

Comparable outcomes but higher risks of prolonged viral RNA shedding duration and secondary infection in cancer survivors with COVID-19: A multi-center, matched retrospective cohort study

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.

Two Different Dust Storms in Northeast China:the Sources and Influences in East Asia

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.

The expression and function of miR-376a-3p/DLX axis in gastric cancer cells

Gastric cancer(GC)was referred to a malignant tumor of the digestive tract originating from the epithelium of gastric mucosa.Transcription factor DLX5 was verified as an oncogene in various types of tumors,while miR-376a-3p was speculated as a tumor suppressor.Based on the bioinformatics database,we hypothesized that miR-376a participated in the regulation of GC development by targeting DLX5.Compared with adjacent tissue,a significant increase of DLX5 expression was determined in GC tissues,but the expression level is significantly reduced in miR-376a.Similar expression signature of DLX5 and miR-376a was also determined between 4 GC cells(HGC,SGC,MGC,and AGS cell lines)and GES cell line.The level of DLX5 was notably reduced in HGC and MGC cell lines after miR-376a-3p overexpression,and increased after miR-376a-3p inhibition.Then,the inhibition role of miR-376a-3p on DLX5 was further proved by dualluciferase reporter assay.Gain-of-function experiments showed that upregulation of miR-376a-3p in GC cells could inhibit the ability of epithelial-mesenchymal transition,proliferation,and invasion,and enhance the GC cell apoptosis level.However,these roles of miR-376a-3p could be abolished by DLX5 overexpression.This study confirmed that reduction of miR-376a-3p expression level in GC cells would lead to the increase in cell growth and invasion,indicating that upregulation of miR-376a-3p might have a potential therapeutic role on GC.

TeV Blazars as the Sources of Ultra High Energy Cosmic Rays

The origin of ultra high energy cosmic rays (UHECRs) is still an open question in astroparticle physics. TeV blazars are a small group of active galactic nuclei (AGNs). They all have been observed in TeV gamma ray band, and show violent variabilities in flux at all wavelengths. So it is believed that they have abilities to produce UHECRs. To judge whether the TeV blazars can be the candidates of the origin of UHECRs, we collect the information of emission region of 38 TeV blazars, and estimate the maximum energy that the charged particle can be accelerated there. The results show that TeV blazars have abilities to accelerate cosmic rays to the energy above 1018?eV, some even higher than 1020?eV, and they may be the sources of UHECRs.

由超拍电子伏特加速器产生的超高能伽马射线气泡

We report the detection of aγ-ray bubble spanning at least 100deg2 in ultra-high energy(UHE)up to a few PeV in the direction of the star-forming region Cygnus X,implying the presence super PeVatron(s)accelerating protons to at least 10 PeV.A log-parabola form with the photon indexΓ(E)=(2.71±0.02)+(0.11±0.02)×log10(E/10 TeV)is found fitting the gamma-ray energy spectrum of the bubble well.UHE sources,“hot spots”correlated with very massive molecular clouds,and a quasi-spherical amorphousγ-ray emitter with a sharp central brightening are observed in the bubble.In the core of~0.5°,spatially associating with a region containing massive OB association(Cygnus OB2)and a microquasar(Cygnus X-3),as well as previously reported multi-TeV sources,an enhanced concentration of UHEγ-rays is observed with 2 photons at energies above 1 PeV.The general feature of the bubble,the morphology,and the energy spectrum,are reasonably reproduced by the assumption of a particle accelerator in the core,continuously injecting protons into the ambient medium.

Screening antimicrobial peptides and probiotics using multiple deep learning and directed evolution strategies

Owing to their limited accuracy and narrow applicability,current antimicrobial peptide(AMP)prediction models face obstacles in industrial application.To address these limitations,we developed and improved an AMP prediction model using Comparing and Optimizing Multiple DEep Learning(COMDEL)algorithms,coupled with high-throughput AMP screening method,finally reaching an accuracy of 94.8%in test and 88%in experiment verification,surpassing other state-of-the-art models.In conjunction with COMDEL,we employed the phage-assisted evolution method to screen Sortase in vivo and developed a cell-free AMP synthesis system in vitro,ultimately increasing AMPs yields to a range of 0.5-2.1 g/L within hours.Moreover,by multi-omics analysis using COMDEL,we identified Lactobacillus plantarum as the most promising candidate for AMP generation among 35 edible probiotics.Following this,we developed a microdroplet sorting approach and successfully screened three L.plantarum mutants,each showing a twofold increase in antimicrobial ability,underscoring their substantial industrial application values.

Evidence for particle acceleration approaching PeV energies in the W51 complex

Theγ-ray emission from the W51 complex is widely acknowledged to be attributed to the interaction between the cosmic rays(CRs)accelerated by the shock of supernova remnant(SNR)W51C and the dense molecular clouds in the adjacent star-forming region,W51B.However,the maximum acceleration capability of W51C for CRs remains elusive.Based on observations conducted with the Large High Altitude Air Shower Observatory(LHAASO),we report a significant detection ofγrays emanating from the W51 complex,with energies from 2 to 200 TeV.The LHAASO measurements,for the first time,extend theγ-ray emission from the W51 complex beyond 100 TeV and reveal a significant spectrum bending at tens of TeV.By combining the"π^(0)-decay bump"featured data from Fermi-LAT,the broadbandγ-ray spectrum of the W51 region can be well-characterized by a simple pp-collision model.The observed spectral bending feature suggests an exponential cutoff at~400 TeV or a power-law break at~200 TeV in the CR proton spectrum,most likely providing the first evidence of SNRs serving as CR accelerators approaching the PeV regime.Additionally,two young star clusters within W51B could also be theoretically viable to produce the most energeticγrays observed by LHAASO.Our findings strongly support the presence of extreme CR accelerators within the W51 complex and provide new insights into the origin of Galactic CRs.

Generating Baikal-GVD high energy cascade-like neutrino events with a GEANT4-based simulation toolkit

Using the GEANT4 and Cosmic Ray Monte Carlo(CRMC)software packages,we developed a new simulation toolkit for astrophysical neutrino telescopes.By configuring the Baikal-GVD detector and comparing the vertex position and direction of incident particles,as well as the channel-by-channel signals,to the events detected by Baikal-GVD,we successfully generated 13 high-energy cascade neutrino events with the toolkit.Our analysis revealed a systematic offset between the reconstructed shower position and the true interaction position,with a distance close to the scale of the shower maximum of−0.54±1.29 m.We achieved a good linear relationship between the photoelectron number of neutrino events obtained by simulation and the real data measured by Baikal-GVD.The simulation toolkit could serve as a reliable basis for studying the performance of astrophysical neutrino telescopes.

Clinical characteristics and impactof comorbidities on the prognosis of senileepilepsy in Southwest China:a retrospectivecohort study

Background Senile epilepsy and its comorbidities pose a tremendous burden on patients and the society.Thisstudy was aimed to investigate the clinical characteristics and comorbidities of senile epilepsy,as well as the impactof comorbidities on the prognosis of senile epilepsy.Methods Information of patients with senile epilepsy was retrospectively collected from three tertiary hospitalsin Southwest China between December 2014 and December 2022.A total of 154 patients met the inclusion criteriaand were divided into two groups based on the presence or absence of comorbidities.The prevalence,type,charac-teristics,and impacts of the comorbidities were investigated.The characteristics of patients with and without comor-bidities were also compared.Results Eighty-one percent of patients with senile epilepsy had at least one comorbidity,and 36%had three or morecomorbidities.Eighteen different types of comorbidities were identified.The most common comorbidities were neu-rological(61%),followed by cardiovascular(45%)and psychiatric(26%)comorbidities.More than one-third of patientshad bidirectional comorbidities,whereas more than half of the patients had additional causal comorbidities.Amongall types of comorbidities,neurological and psychiatric comorbidities were found to be associated with an increasedrisk of recurrent seizures.Compared to patients without bidirectional comorbidities,those with at least one bidirec-tional comorbidity had a lower rate of achieving seizure freedom.The higher the number of bidirectional comor-bidities,the lower the seizure-free rate.Survival analysis revealed that patients with neurological comorbidities hada higher risk of death.Conclusions This study revealed a high comorbidity rate and a low seizure-freedom rate among patients with senileepilepsy.In particular,neuropsychiatric comorbidities can increase the risk of seizures and affect the survival rateof patients with senile epilepsy.Therefore,preventing and managing these comorbidities may improve seizure out-comes and reduce mortality in this special population.

Optimization of performance of the KM2A full array using the Crab Nebula

The full array of the Large High Altitude Air Shower Observatory(LHAASO)has been in operation since July 2021.For its kilometer-square array(KM2A),we optimized the selection criteria for very high and ultrahigh energyγ-rays using data collected from August 2021 to August 2022,resulting in an improvement in significance of the detection in the Crab Nebula of approximately 15%,compared with that of previous cuts.With the implementation of these new selection criteria,the angular resolution was also significantly improved by approximately 10%at tens of TeV.Other aspects of the full KM2A array performance,such as the pointing error,were also calibrated using the Crab Nebula.The resulting energy spectrum of the Crab Nebula in the energy range of 10-1000 TeV are well fitted by a log-parabola model,which is consistent with the previous results from LHAASO and other experiments.