Rosa roxburghii fruit is rich in flavonoids, but little is known about their biosynthetic pathways. In this study, we employed transcriptomics and metabolomics to study changes related to the flavonoids at five differ...Rosa roxburghii fruit is rich in flavonoids, but little is known about their biosynthetic pathways. In this study, we employed transcriptomics and metabolomics to study changes related to the flavonoids at five different stages of R. roxburghii fruit development. Flavonoids and the genes related to their biosynthesis were found to undergo significant changes in abundance across different developmental stages, and numerous quercetin derivatives were identified. We found three gene expression modules that were significantly associated with the abundances of the different flavonoids in R. roxburghii and identified three structural UDP-glycosyltransferase genes directly involved in the synthesis of quercetin derivatives within these modules. In addition, we found that RrBEH4, RrLBD1 and RrPIF8could significantly increase the expression of downstream quercetin derivative biosynthesis genes. Taken together,these results provide new insights into the metabolism of flavonoids and the accumulation of quercetin derivatives in R. roxburghii.展开更多
Developing and excavating new agrochemicals with highly active and safe is an important tactic for protecting crop health and food safety.In this paper,to discover the new bactericide candidates,we designed,prepared a...Developing and excavating new agrochemicals with highly active and safe is an important tactic for protecting crop health and food safety.In this paper,to discover the new bactericide candidates,we designed,prepared a new type of1,2,3,4-tetrahydro-β-carboline(THC)derivatives and evaluated the in vitro and in vivo bioactivities against the Xanthomonas oryzae pv.oryzae(Xoo),Xanthomonas axonopodis pv.citri(Xac),and Pseudomonas syringae pv.actinidiae(Psa).The in vitro bioassay results exhibited that most title molecules possessed good activity toward the three plant pathogenic bacteria,the compound A17 showed the most active against Xoo and Xac with EC50 values of 7.27 and 4.89 mg mL^(-1)respectively,and compound A8 exhibited the best inhibitory activity against Psa with EC50value of 4.87 mg mL^(-1).Pot experiments showed that compound A17 exhibited excellent in vivo antibacterial activities to manage rice bacterial leaf blight and citrus bacterial canker,with protective efficiencies of 52.67 and 79.79%at 200 mgmL^(-1),respectively.Meanwhile,compound A8 showed good control efficiency(84.31%)against kiwifruit bacterial canker at 200 mg mL^(-1).Antibacterial mechanism suggested that these compounds could interfere with the balance of the redox system,damage the cell membrane,and induce the apoptosis of Xoo cells.Taken together,our study revealed that tetrahydro-β-carboline derivatives could be a promising candidate model for novel broadspectrum bactericides.展开更多
In recent years,organic solar cells(OSCs)have garnered significant attention due to their distinctive attributes,such as flexibility,lightweight,and solution processing,which position them as alternatives for next-gen...In recent years,organic solar cells(OSCs)have garnered significant attention due to their distinctive attributes,such as flexibility,lightweight,and solution processing,which position them as alternatives for next-generation solar technologies[1−5].Thanks to breakthroughs in materials development,the power conversion efficiency(PCE)for single-junction OSCs has already surpassed 19%[6−13].The development of photoactive materials is pivotal in enhancing the PCEs,and several reviews have provided insights into materials design[14−18].Herein,we highlight single-junction OSCs based on D18 and its derivatives[19,20].展开更多
Background:Sepsis,a potentially fatal inflammatory disease triggered by infection,carries significant healthimplications worldwide.Timely detection is crucial as sepsis can rapidly escalate if left undetected.Recentad...Background:Sepsis,a potentially fatal inflammatory disease triggered by infection,carries significant healthimplications worldwide.Timely detection is crucial as sepsis can rapidly escalate if left undetected.Recentadvancements in deep learning(DL)offer powerful tools to address this challenge.Aim:Thus,this study proposeda hybrid CNNBDLSTM,a combination of a convolutional neural network(CNN)with a bi-directional long shorttermmemory(BDLSTM)model to predict sepsis onset.Implementing the proposed model provides a robustframework that capitalizes on the complementary strengths of both architectures,resulting in more accurate andtimelier predictions.Method:The sepsis prediction method proposed here utilizes temporal feature extraction todelineate six distinct time frames before the onset of sepsis.These time frames adhere to the sepsis-3 standardrequirement,which incorporates 12-h observation windows preceding sepsis onset.All models were trained usingthe Medical Information Mart for Intensive Care III(MIMIC-III)dataset,which sourced 61,522 patients with 40clinical variables obtained from the IoT medical environment.The confusion matrix,the area under the receiveroperating characteristic curve(AUCROC)curve,the accuracy,the precision,the F1-score,and the recall weredeployed to evaluate themodels.Result:The CNNBDLSTMmodel demonstrated superior performance comparedto the benchmark and other models,achieving an AUCROC of 99.74%and an accuracy of 99.15%one hour beforesepsis onset.These results indicate that the CNNBDLSTM model is highly effective in predicting sepsis onset,particularly within a close proximity of one hour.Implication:The results could assist practitioners in increasingthe potential survival of the patient one hour before sepsis onset.展开更多
In this paper,two crossover hybrid variable-order derivatives of the cancer model are developed.Grünwald-Letnikov approximation is used to approximate the hybrid fractional and variable-order fractional operators...In this paper,two crossover hybrid variable-order derivatives of the cancer model are developed.Grünwald-Letnikov approximation is used to approximate the hybrid fractional and variable-order fractional operators.The existence,uniqueness,and stability of the proposed model are discussed.Adams Bashfourth’s fifth-step method with a hybrid variable-order fractional operator is developed to study the proposed models.Comparative studies with generalized fifth-order Runge-Kutta method are given.Numerical examples and comparative studies to verify the applicability of the used methods and to demonstrate the simplicity of these approximations are presented.We have showcased the efficiency of the proposed method and garnered robust empirical support for our theoretical findings.展开更多
Carbon-based metal-free nanomaterials are promising alternatives to precious metals as electrocatalysts of key energy storage and conversion technologies.Of paramount significance are the establishment of design princi...Carbon-based metal-free nanomaterials are promising alternatives to precious metals as electrocatalysts of key energy storage and conversion technologies.Of paramount significance are the establishment of design principles by understanding the catalytic mechanisms and identifying the active sites.Distinct from sp2-conjugated graphene and carbon nanotube,fullerene possesses unique characteristics that are growingly being discovered and exploited by the electrocatalysis community.For instance,the well-defined atomic and molecular structures,the good electron affinity to tune the electronic structures of other substances,the intermolecular self-assembly into superlattices,and the on-demand chemical modification have endowed fullerene with incomparable advantages as electrocatalysts that are otherwise not applicable to other carbon ma-terials.As increasing studies are being reported on this intriguing topic,it is necessary to provide a state-of-the-art overview of the recent progress.This review takes such an initiative by summarizing the promises and challenges in the electrocatalytic applications of fullerene and its derivatives.The content is structured according to the composition and structure of fullerene,including intact fullerene(e.g.,fullerene composite and superlattices)and fullerene derivatives(e.g.,doped,endohedral,and disintegrated fullerene).The synthesis,characterization,catalytic mechanisms,and deficiencies of these fullerene-based materials are explicitly elaborated.We conclude it by sharing our perspectives on the key aspects that future efforts shall consider.展开更多
Turpentine is a renewable and resourceful forest product.The deep processing and utilization of turpentine,particularly its primary componentβ-pinene,has garnered widespread attention.This study aimed to synthesize 4...Turpentine is a renewable and resourceful forest product.The deep processing and utilization of turpentine,particularly its primary componentβ-pinene,has garnered widespread attention.This study aimed to synthesize 40 derivatives ofβ-pinene,including nopinone,3-cyanopyridines of nopinone,myrtanyl acid,myrtanyl acylthioureas,and myrtanyl amides.We assessed the antiviral activities of theseβ-pinene derivatives against influenza virus A/Puerto Rico/8/34(H1N1)using the 3-(4,5-dimetylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method.Theβ-pinene derivatives were used before and after cellular infection with the influenza virus to evaluate their preventive and therapeutic effects against the H1N1 virus.The results showed that only compound 10o exhibited a preventive effect against the H1N1 virus with a half-maximal inhibitory concentration(IC50)value of 47.6μmol/L.Among the compounds,4e,4i,and 4l demonstrated therapeutic effects against cellular infection,with compound 4e displaying the most potent therapeutic effect(IC50=17.5μmol/L),comparable to the positive control ribavirin.These findings indicated that certainβ-pinene derivatives exhibited in vitro antiviral activity against the H1N1 influenza A virus,warranting further investigation as potential anti-influenza agents.展开更多
We study two generalized versions of a system of equations which describe the time evolution of the hydrodynamic fluctuations of density and velocity in a linear viscoelastic fluid. In the first of these versions, the...We study two generalized versions of a system of equations which describe the time evolution of the hydrodynamic fluctuations of density and velocity in a linear viscoelastic fluid. In the first of these versions, the time derivatives are replaced by conformable derivatives, and in the second version left-handed Caputo’s derivatives are used. We show that the solutions obtained with these two types of derivatives exhibit significant similarities, which is an interesting (and somewhat surprising) result, taking into account that the conformable derivatives are local operators, while Caputo’s derivatives are nonlocal operators. We also show that the solutions of the generalized systems are similar to the solutions of the original system, if the order α of the new derivatives (conformable or Caputo) is less than one. On the other hand, when α is greater than one, the solutions of the generalized systems are qualitatively different from the solutions of the original system.展开更多
[Objectives]This study was conducted to investigate the effects of piperidine derivatives on the proliferation and apoptosis of tumor cells(Hele).[Methods]The target end product(piperidine derivative)was synthesized t...[Objectives]This study was conducted to investigate the effects of piperidine derivatives on the proliferation and apoptosis of tumor cells(Hele).[Methods]The target end product(piperidine derivative)was synthesized through a series of organic reactions.The MTT assay was adopted to detect the effect of piperidine derivative on the proliferation activity of Hele cells.The ROS fluorescence probe method was used to detect the changes of reactive oxygen species.The JC-1 method was applied to detect the changes of MMP in Hele cells.Flow cytometry was adopted to detect the apoptosis of Hele cells.[Results]The cell survival rates were 70.84%,65.46%and 54.48%when the drug concentration was 100,110 and 120μmol/L,respectively.When the drug concentration increased to 120μmol/L,the cell survival rate decreased by nearly half.The fluorescence intensity of active oxygen in the control group was 1,and when the drug concentrations were 100,110 and 120μmol/L,the fluorescence intensity of active oxygen was,respectively,1.315,1.478 and 1.677,which were higher than that in the control group.The red/green fluorescence intensity of the MMP control group was 1.819,and that of drug groups was,respectively,1.643,1.164 and 0.665,which were lower than that of the control group.The apoptosis rates were 10.79%,22.91%and 38.54%at the drug concentrations of 100,110 and 120μmol/L,respectively,showing a concentration dependent effect.The results showed that the piperidine derivative could inhibit the proliferation of Hele cells and induce apoptosis,which was positively correlated with the concentration.[Conclusions]This study provides theoretical basis and reference for the anti-tumor research of piperidine.展开更多
On December 22,2021,the United States Food and Drug Administration approved the first main protease inhibitor,i.e.,oral antiviral nirmatrelvir(PF-07321332)/ritonavir(Paxlovid),for the treatment of early severe acute r...On December 22,2021,the United States Food and Drug Administration approved the first main protease inhibitor,i.e.,oral antiviral nirmatrelvir(PF-07321332)/ritonavir(Paxlovid),for the treatment of early severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)infection.Nirmatrelvir inhibits SARSCoV-2 infection,but high doses or long-term treatment may cause embryonic developmental toxicity and changes in host gene expression.The chiral structure of nirmatrelvir plays a key role in its antiviral activity.Ritonavir boosts the efficacy of nirmatrelvir by inactivating cytochrome P4503A4 expression and occupying the plasma protein binding sites.Multidrug resistance protein 1 inhibitors may increase the efficacy of nirmatrelvir.However,Paxlovid has many contraindications.Some patients treated with Paxlovid experience a second round of coronavirus disease 2019(COVID-19)symptoms soon after recovery.Interestingly,the antiviral activity of nirmatrelvir metabolites,such as compounds 12e18,is similar to or higher than that of nirmatrelvir.Herein,we review the advances and challenges in using nirmatrelvir and its derivatives with the aim of providing knowledge for drug developers and physicians in the fight against COVID-19.展开更多
Electrochemically reducing CO_(2)to more reduced chemical species is a promising way that not only enables the conversion of intermittent energy resources to stable fuels,but also helps to build a closed-loop anthropo...Electrochemically reducing CO_(2)to more reduced chemical species is a promising way that not only enables the conversion of intermittent energy resources to stable fuels,but also helps to build a closed-loop anthropogenic carbon cycle.Among various electrocatalysts for electrochemical CO_(2)reduction,multifunctional metal–organic frameworks(MOFs)have been employed as highly efficient and selective heterogeneous electrocatalysts due to their ultrahigh porosity and topologically diverse structures.Up to now,great progress has been achieved in the design and synthesis of highly active and selective MOF-related catalysts for electrochemical CO_(2)reduction reaction(CO_(2)RR),and their corresponding reaction mechanisms have been thoroughly studied.In this review,we summarize the recent progress of applying MOFs and their derivatives in CO_(2)RR,with a focus on the design strategies for electrocatalysts and electrolyzers.We first discussed the reaction mechanisms for different CO_(2)RR products and introduced the commonly applied electrolyzer configurations in the current CO_(2)RR system.Then,an overview of several categories of products(CO,HCOOH,CH_(4),CH_(3)OH,and multi-carbon chemicals)generated from MOFs or their derivatives via CO_(2)RR was discussed.Finally,we offer some insights and perspectives for the future development of MOFs and their derivatives in electrochemical CO_(2)reduction.We aim to provide new insights into this field and further guide future research for large-scale applications.展开更多
In the process of exploration and development of oil and gas fields, the acidic environment of oil reservoir, production and transport processes cause corrosion of pipelines and equipment, resulting in huge economic l...In the process of exploration and development of oil and gas fields, the acidic environment of oil reservoir, production and transport processes cause corrosion of pipelines and equipment, resulting in huge economic losses and production safety risks. Corrosion inhibitors were widely used in oil industry because of simple operation process and economical. In this study, three environmentally friendly corrosion inhibitors were synthesized based on the natural polysaccharide chitosan. Corrosion inhibition of three dendritic chitosan derivatives (We name them BH, CH and DH) on mild steel in 1 mol/L HCl solution with natural ventilation system was evaluated by weight loss experiment, electrochemical analysis and surface morphology characterization. The experimental results showed that when the three dendritic chitosan derivatives added in the corrosive medium were 500 mg L^(−1), the corrosion inhibition efficiencies were all more than 80%. Based on quantum chemical calculation, inhibition mechanisms of three dendritic chitosan derivatives were investigated according to molecular structures. The results showed that the benzene ring, Schiff base and N atom contained in the molecule were the active centers of electron exchange, which were more likely to form a film on the carbon steel surface, thereby slowing or inhibiting corrosion. The results also predicted the corrosion inhibition effect BH > DH > CH, which was consistent with the experimental conclusion.展开更多
Objective:To investigate the pharmacological action and mechanism of cholic acid derivatives in traditional Chinese medicine(TCM)based on the regulation of gene expression.Methods:Genome-wide gene expression profiles ...Objective:To investigate the pharmacological action and mechanism of cholic acid derivatives in traditional Chinese medicine(TCM)based on the regulation of gene expression.Methods:Genome-wide gene expression profiles of Michigan Cancer Foundation-7(MCF-7)cells treated with or without 4 cholic acid derivatives were detected by gene chip technology.Similarities in upregulated and downregulated genes were analyzed using the Connectivity Map(CMap)database.The affinity between cholic acid derivatives and the potential target was confirmed by molecular docking.The cholic acid derivative-regulated pathway enrichment analysis was performed by the STRING database,and the potential pathway was confirmed by in vitro experiments on MD Anderson-Metastatic Breast-231(MDA-MB-231)cells.Results:Compared with the reference genome in the CMap database,the gene expression profiles of cholic acid derivatives were similar to those of antipsychotic,anticancer,anti-inflammatory,and antiinfective drugs.Among them,4 derivatives were associated with antianxiety drugs,and molecular docking results showed that these compounds may act by binding to the ligand-binding site of gammaaminobutyric acid(GABA)receptors.Moreover,the cytoskeletal pathway is one of the pathways enriched in the derivatives.Of them,ursodeoxycholic acid showed significant inhibitory activity on the cytoskeleton formation of MDA-MB-231 cells.Conclusion:The gene expression detection method,combined with CMap and pathway enrichment analysis,could be used to study the mechanism of the active ingredients of TCM.In addition,our research showed that cholic acid derivatives have a potential affinity for membrane receptors,where they can exert anxiolytic activity by modulating opioid receptor,GABA receptor,and dopamine receptor.Moreover,ursodeoxycholic and chenodeoxycholic acid inhibit cytoskeleton formation,probably by acting on membrane proteins to activate the corresponding cytoskeletal pathways.展开更多
A previous study was conducted on the synthesis and antibacterial evaluation of Mannich bases of 2-(thioalkyl)-1H-methylbenzimidazole derivatives. The results of this study showed that certain 2-(thioalkyl)-1H-methylb...A previous study was conducted on the synthesis and antibacterial evaluation of Mannich bases of 2-(thioalkyl)-1H-methylbenzimidazole derivatives. The results of this study showed that certain 2-(thioalkyl)-1H-methylbenzimidazole and 2-(thioalkyl)-methyl-1-(piperidin-1-ylmethyl)benzimidazole derivatives possess antibacterial activities against clinical strains, such as Escherichia coli, Klebsiella pneumonia (Gram-negative bacteria), Staphylococcus aureus and Pseudomonas aeruginosa (Gram-positive bacteria). Following these favorable results, we extended the antibacterial evaluation of this series of molecules to environmental strains. The aim of this study was to assess the impact of the methyl-piperidine group fixed at position-1 of this new series of benzimidazoles on the antibacterial activity of environmental strains. In addition, we first evaluated the antibacterial activity of four 2-(thioalkyl)methylbenzimidazole derivatives and then that of five 2-(thioalkyl)-methyl-1-(piperidin-1-ylmethyl) benzimidazole derivatives. This study allowed us to show that compounds 1d and 1e could inhibit bacterial growth in vitro of the Enterobacteria P1 strain with inhibition diameters of 17.3 ± 0.6 mm and 10 ± 0.0 mm, respectively. However, addition of methyl-piperidinyl in this series showed that five (5) of 2-(thioalkyl)-methyl-1-(piperidin-1-ylmethyl) benzimidazole derivatives had an inhibitory effect on the in vitro growth of bacterial strains used except on Enterobacteria P2 with inhibition diameters between 10.0 ± 0.8 mm and 27.9 ± 1.4 mm. The introduction of the methyl-piperidinyl group at the 1-position of 2-(thioalkyl)-1H-methylbenzimidazole derivatives greatly improved the antibacterial activity against environmental bacteria such as Escherichia coli A1, A2, A3, and A4 and two Enterobacteria P1.展开更多
This study focuses on the dynamics of drug concentration in the blood.In general,the concentration level of a drug in the blood is evaluated by themean of an ordinary and first-order differential equation.More precise...This study focuses on the dynamics of drug concentration in the blood.In general,the concentration level of a drug in the blood is evaluated by themean of an ordinary and first-order differential equation.More precisely,it is solved through an initial value problem.We proposed a newmodeling technique for studying drug concentration in blood dynamics.This technique is based on two fractional derivatives,namely,Caputo and Caputo-Fabrizio derivatives.We first provided comprehensive and detailed proof of the existence of at least one solution to the problem;we later proved the uniqueness of the existing solution.The proof was written using the Caputo-Fabrizio fractional derivative and some fixed-point techniques.Stability via theUlam-Hyers(UH)technique was also investigated.The application of the proposedmodel on two real data sets revealed that the Caputo derivative wasmore suitable in this study.Indeed,for the first data set,the model based on the Caputo derivative yielded a Mean Squared Error(MSE)of 0.03095 with a corresponding best value of fractional order of derivative of 1.00360.Caputo-Fabrizio-basedderivative appeared to be the second-best method for the problem,with an MSE of 0.04324 for a corresponding best fractional derivative order of 0.43532.For the second experiment,Caputo derivative-based model still performed the best as it yielded an MSE of 0.04066,whereas the classical and the Caputo-Fabrizio methods were tied with the same MSE of 0.07299.Another interesting finding was that the MSE yielded by the Caputo-Fabrizio fractional derivative coincided with the MSE obtained from the classical approach.展开更多
The preparation of bioactive derivatives from the renewable natural product pinene is a hot research topic in the deep processing and utilization of pinene.In this study,β-pinene was used to develop novel molecules a...The preparation of bioactive derivatives from the renewable natural product pinene is a hot research topic in the deep processing and utilization of pinene.In this study,β-pinene was used to develop novel molecules as a promising new precursor of insecticide.A series of amide-containing derivatives ofβ-pinene were synthesized and characterized.The insecticidal activities of these derivatives against Mythimna separate and Semiaphis heraclei were tested.The structure characterization results showed that the characterization data of amide-containing derivatives were in full agreement with their proposed structures.The insecticidal activities evaluation results indicated that amide-containing derivatives exhibited weak insecticidal activity against Mythimna separate,but exhibited moderate to good insecticidal activity against Semiaphis heraclei.After testing for 72 h,the corrected mortality against Semiaphis heraclei of compounds 5c,5e,5f,5 h,5j,and 5 m was 100%at 1000 mg/L.The structure-activity relationship analysis results showed that the introduction of an amide group into the structure of derivatives improved their insecticidal activity against Semiaphis heraclei.Meanwhile,the amide-containing derivatives containing the F and NO_(2) substituted benzene ring might improve their insecticidal activity against Semiaphis heraclei.This study will be helpful for the high value-added utilization of the natural renewable resourceβ-pinene and the development of novel insecticides.展开更多
A fractional-order thermo-elastic model taking into account the small-scale effects of the thermo-elastic coupled behavior is developed to study the free vibration of a higher-order shear microplate.The nonlocal strai...A fractional-order thermo-elastic model taking into account the small-scale effects of the thermo-elastic coupled behavior is developed to study the free vibration of a higher-order shear microplate.The nonlocal strain gradient theory is modified with the introduction of the fractional-order derivatives and the nonlocal characteristic length.The Fourier heat conduction is replaced by the non-Fourier heat conduction with the introduction of the fractional order and the memory characteristic time.Numerical calculations are performed to analyze the effects of the nonlocal strain gradient parameters,the spatiotemporal fractional order,the nonlocal characteristic length,and the memory characteristic time on the natural frequencies,the vibration attenuation,and the phase shift between the temperature field and the displacement field.The numerical results show that the new thermo-elastic model with the spatiotemporal fractional order can provide more exquisite descriptions of the thermo-elastic behavior at a small scale.展开更多
This work aims to compute stability derivatives in the Newtonian limit in pitch when the Mach number tends to infinity.In such conditions,these stability derivatives depend on the Ogive’s shape and not the Mach numbe...This work aims to compute stability derivatives in the Newtonian limit in pitch when the Mach number tends to infinity.In such conditions,these stability derivatives depend on the Ogive’s shape and not the Mach number.Generally,the Mach number independence principle becomes effective from M=10 and above.The Ogive nose is obtained through a circular arc on the cone surface.Accordingly,the following arc slopes are consideredλ=5,10,15,−5,−10,and−15.It is found that the stability derivatives decrease due to the growth inλfrom 5 to 15 and vice versa.Forλ=5 and 10,the damping derivative declines with an increase inλfrom 5 to 10.Yet,for the damping derivatives,the minimum location remains at a pivot position,h=0.75 for large values ofλ.Hence,whenλ=−15,the damping derivatives are independent of the cone angles for most pivot positions except in the early twenty percent of the leading edge.展开更多
The present article mainly focuses on the fractional derivatives with an exponential kernel(“exponential fractional derivatives”for brevity).First,several extended integral transforms of the exponential fractional d...The present article mainly focuses on the fractional derivatives with an exponential kernel(“exponential fractional derivatives”for brevity).First,several extended integral transforms of the exponential fractional derivatives are proposed,including the Fourier transform and the Laplace transform.Then,the L2 discretisation for the exponential Caputo derivative with a∈(1,2)is established.The estimation of the truncation error and the properties of the coefficients are discussed.In addition,a numerical example is given to verify the correctness of the derived L2 discrete formula.展开更多
The covariant derivative is a generalization of differentiating vectors.The Euclidean derivative is a special case of the covariant derivative in Euclidean space.The covariant derivative gathers broad attention,partic...The covariant derivative is a generalization of differentiating vectors.The Euclidean derivative is a special case of the covariant derivative in Euclidean space.The covariant derivative gathers broad attention,particularly when computing vector derivatives on curved surfaces and volumes in various applications.Covariant derivatives have been computed using the metric tensor from the analytically known curved axes.However,deriving the global axis for the domain has been mathematically and computationally challenging for an arbitrary two-dimensional(2D)surface.Consequently,computing the covariant derivative has been difficult or even impossible.A novel high-order numerical scheme is proposed for computing the covariant derivative on any 2D curved surface.A set of orthonormal vectors,known as moving frames,expand vectors to compute accurately covariant derivatives on 2D curved surfaces.The proposed scheme does not require the construction of curved axes for the metric tensor or the Christoffel symbols.The connectivity given by the Christoffel symbols is equivalently provided by the attitude matrix of orthonormal moving frames.Consequently,the proposed scheme can be extended to the general 2D curved surface.As an application,the Helmholtz‐Hodge decomposition is considered for a realistic atrium and a bunny.展开更多
基金supported in part by the Priority Academic Program Development of Jiangsu Higher Education Institutions and the State Key Laboratory of Crop Genetics and Germplasm Enhancement,China(ZW201813)。
文摘Rosa roxburghii fruit is rich in flavonoids, but little is known about their biosynthetic pathways. In this study, we employed transcriptomics and metabolomics to study changes related to the flavonoids at five different stages of R. roxburghii fruit development. Flavonoids and the genes related to their biosynthesis were found to undergo significant changes in abundance across different developmental stages, and numerous quercetin derivatives were identified. We found three gene expression modules that were significantly associated with the abundances of the different flavonoids in R. roxburghii and identified three structural UDP-glycosyltransferase genes directly involved in the synthesis of quercetin derivatives within these modules. In addition, we found that RrBEH4, RrLBD1 and RrPIF8could significantly increase the expression of downstream quercetin derivative biosynthesis genes. Taken together,these results provide new insights into the metabolism of flavonoids and the accumulation of quercetin derivatives in R. roxburghii.
基金the supports from National Natural Science Foundation of China(21877021,32160661,and 32202359)the Guizhou Provincial S&T Project China(2018[4007])+2 种基金the the Guizhou Province China[Qianjiaohe KY number(2020)004]the Program of Introducing Talents of Discipline to Universities of China(D20023,111 Program)the Guizhou University(GZU)Found for Newly Enrolled Talent China(202229)。
文摘Developing and excavating new agrochemicals with highly active and safe is an important tactic for protecting crop health and food safety.In this paper,to discover the new bactericide candidates,we designed,prepared a new type of1,2,3,4-tetrahydro-β-carboline(THC)derivatives and evaluated the in vitro and in vivo bioactivities against the Xanthomonas oryzae pv.oryzae(Xoo),Xanthomonas axonopodis pv.citri(Xac),and Pseudomonas syringae pv.actinidiae(Psa).The in vitro bioassay results exhibited that most title molecules possessed good activity toward the three plant pathogenic bacteria,the compound A17 showed the most active against Xoo and Xac with EC50 values of 7.27 and 4.89 mg mL^(-1)respectively,and compound A8 exhibited the best inhibitory activity against Psa with EC50value of 4.87 mg mL^(-1).Pot experiments showed that compound A17 exhibited excellent in vivo antibacterial activities to manage rice bacterial leaf blight and citrus bacterial canker,with protective efficiencies of 52.67 and 79.79%at 200 mgmL^(-1),respectively.Meanwhile,compound A8 showed good control efficiency(84.31%)against kiwifruit bacterial canker at 200 mg mL^(-1).Antibacterial mechanism suggested that these compounds could interfere with the balance of the redox system,damage the cell membrane,and induce the apoptosis of Xoo cells.Taken together,our study revealed that tetrahydro-β-carboline derivatives could be a promising candidate model for novel broadspectrum bactericides.
基金J.Yang thanks the National Key Research and Development Program of China(2022YFB3803300)the National Natural Science Foundation of China(U23A20138 and 52173192)+1 种基金L.Ding thanks the National Key Research and Development Program of China(2022YFB3803300,2023YFE0116800)Beijing Natural Science Foundation(IS23037).
文摘In recent years,organic solar cells(OSCs)have garnered significant attention due to their distinctive attributes,such as flexibility,lightweight,and solution processing,which position them as alternatives for next-generation solar technologies[1−5].Thanks to breakthroughs in materials development,the power conversion efficiency(PCE)for single-junction OSCs has already surpassed 19%[6−13].The development of photoactive materials is pivotal in enhancing the PCEs,and several reviews have provided insights into materials design[14−18].Herein,we highlight single-junction OSCs based on D18 and its derivatives[19,20].
基金the Deputyship for Research&Innovation,Ministry of Education in Saudi Arabia,for funding this research work through Project Number RI-44-0214.
文摘Background:Sepsis,a potentially fatal inflammatory disease triggered by infection,carries significant healthimplications worldwide.Timely detection is crucial as sepsis can rapidly escalate if left undetected.Recentadvancements in deep learning(DL)offer powerful tools to address this challenge.Aim:Thus,this study proposeda hybrid CNNBDLSTM,a combination of a convolutional neural network(CNN)with a bi-directional long shorttermmemory(BDLSTM)model to predict sepsis onset.Implementing the proposed model provides a robustframework that capitalizes on the complementary strengths of both architectures,resulting in more accurate andtimelier predictions.Method:The sepsis prediction method proposed here utilizes temporal feature extraction todelineate six distinct time frames before the onset of sepsis.These time frames adhere to the sepsis-3 standardrequirement,which incorporates 12-h observation windows preceding sepsis onset.All models were trained usingthe Medical Information Mart for Intensive Care III(MIMIC-III)dataset,which sourced 61,522 patients with 40clinical variables obtained from the IoT medical environment.The confusion matrix,the area under the receiveroperating characteristic curve(AUCROC)curve,the accuracy,the precision,the F1-score,and the recall weredeployed to evaluate themodels.Result:The CNNBDLSTMmodel demonstrated superior performance comparedto the benchmark and other models,achieving an AUCROC of 99.74%and an accuracy of 99.15%one hour beforesepsis onset.These results indicate that the CNNBDLSTM model is highly effective in predicting sepsis onset,particularly within a close proximity of one hour.Implication:The results could assist practitioners in increasingthe potential survival of the patient one hour before sepsis onset.
文摘In this paper,two crossover hybrid variable-order derivatives of the cancer model are developed.Grünwald-Letnikov approximation is used to approximate the hybrid fractional and variable-order fractional operators.The existence,uniqueness,and stability of the proposed model are discussed.Adams Bashfourth’s fifth-step method with a hybrid variable-order fractional operator is developed to study the proposed models.Comparative studies with generalized fifth-order Runge-Kutta method are given.Numerical examples and comparative studies to verify the applicability of the used methods and to demonstrate the simplicity of these approximations are presented.We have showcased the efficiency of the proposed method and garnered robust empirical support for our theoretical findings.
基金This study is supported by the National Natural Science Foundation of China(21925104)the Natural Science Foun-dation of Hubei Province(2021CFA020)the start-up funding of Huazhong University of Science and Technology(3004110178).
文摘Carbon-based metal-free nanomaterials are promising alternatives to precious metals as electrocatalysts of key energy storage and conversion technologies.Of paramount significance are the establishment of design principles by understanding the catalytic mechanisms and identifying the active sites.Distinct from sp2-conjugated graphene and carbon nanotube,fullerene possesses unique characteristics that are growingly being discovered and exploited by the electrocatalysis community.For instance,the well-defined atomic and molecular structures,the good electron affinity to tune the electronic structures of other substances,the intermolecular self-assembly into superlattices,and the on-demand chemical modification have endowed fullerene with incomparable advantages as electrocatalysts that are otherwise not applicable to other carbon ma-terials.As increasing studies are being reported on this intriguing topic,it is necessary to provide a state-of-the-art overview of the recent progress.This review takes such an initiative by summarizing the promises and challenges in the electrocatalytic applications of fullerene and its derivatives.The content is structured according to the composition and structure of fullerene,including intact fullerene(e.g.,fullerene composite and superlattices)and fullerene derivatives(e.g.,doped,endohedral,and disintegrated fullerene).The synthesis,characterization,catalytic mechanisms,and deficiencies of these fullerene-based materials are explicitly elaborated.We conclude it by sharing our perspectives on the key aspects that future efforts shall consider.
基金supported by the National Natural Science Foundation of China(Grant Number 32260370)Youth Talent Project of Major Academic and Technical Leaders Training Program of Jiangxi Province(Grant Number 20204BCJL23045)+2 种基金Special Research Project on Camphor Tree(KRPCT)of Jiangxi Forestry Department(Grant Number 2020CXZX07)Innovative Leading Talent Short-Term Project in Natural Science Area of Jiangxi Province(Grant Number jxsq2018102072)the Key Research and Development Program of Jiangxi Province(Grant Number 20192BBFL60014).
文摘Turpentine is a renewable and resourceful forest product.The deep processing and utilization of turpentine,particularly its primary componentβ-pinene,has garnered widespread attention.This study aimed to synthesize 40 derivatives ofβ-pinene,including nopinone,3-cyanopyridines of nopinone,myrtanyl acid,myrtanyl acylthioureas,and myrtanyl amides.We assessed the antiviral activities of theseβ-pinene derivatives against influenza virus A/Puerto Rico/8/34(H1N1)using the 3-(4,5-dimetylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method.Theβ-pinene derivatives were used before and after cellular infection with the influenza virus to evaluate their preventive and therapeutic effects against the H1N1 virus.The results showed that only compound 10o exhibited a preventive effect against the H1N1 virus with a half-maximal inhibitory concentration(IC50)value of 47.6μmol/L.Among the compounds,4e,4i,and 4l demonstrated therapeutic effects against cellular infection,with compound 4e displaying the most potent therapeutic effect(IC50=17.5μmol/L),comparable to the positive control ribavirin.These findings indicated that certainβ-pinene derivatives exhibited in vitro antiviral activity against the H1N1 influenza A virus,warranting further investigation as potential anti-influenza agents.
文摘We study two generalized versions of a system of equations which describe the time evolution of the hydrodynamic fluctuations of density and velocity in a linear viscoelastic fluid. In the first of these versions, the time derivatives are replaced by conformable derivatives, and in the second version left-handed Caputo’s derivatives are used. We show that the solutions obtained with these two types of derivatives exhibit significant similarities, which is an interesting (and somewhat surprising) result, taking into account that the conformable derivatives are local operators, while Caputo’s derivatives are nonlocal operators. We also show that the solutions of the generalized systems are similar to the solutions of the original system, if the order α of the new derivatives (conformable or Caputo) is less than one. On the other hand, when α is greater than one, the solutions of the generalized systems are qualitatively different from the solutions of the original system.
基金Supported by Undergraduate Innovation and Entrepreneurship Training Program of Suzhou University in 2024(Synthesis and Application of Novel Thiazole Fluorescent Probes)Key Project of Natural Science Research in Colleges and Universities of Department of Education of Anhui Province(KJ2021A1109).
文摘[Objectives]This study was conducted to investigate the effects of piperidine derivatives on the proliferation and apoptosis of tumor cells(Hele).[Methods]The target end product(piperidine derivative)was synthesized through a series of organic reactions.The MTT assay was adopted to detect the effect of piperidine derivative on the proliferation activity of Hele cells.The ROS fluorescence probe method was used to detect the changes of reactive oxygen species.The JC-1 method was applied to detect the changes of MMP in Hele cells.Flow cytometry was adopted to detect the apoptosis of Hele cells.[Results]The cell survival rates were 70.84%,65.46%and 54.48%when the drug concentration was 100,110 and 120μmol/L,respectively.When the drug concentration increased to 120μmol/L,the cell survival rate decreased by nearly half.The fluorescence intensity of active oxygen in the control group was 1,and when the drug concentrations were 100,110 and 120μmol/L,the fluorescence intensity of active oxygen was,respectively,1.315,1.478 and 1.677,which were higher than that in the control group.The red/green fluorescence intensity of the MMP control group was 1.819,and that of drug groups was,respectively,1.643,1.164 and 0.665,which were lower than that of the control group.The apoptosis rates were 10.79%,22.91%and 38.54%at the drug concentrations of 100,110 and 120μmol/L,respectively,showing a concentration dependent effect.The results showed that the piperidine derivative could inhibit the proliferation of Hele cells and induce apoptosis,which was positively correlated with the concentration.[Conclusions]This study provides theoretical basis and reference for the anti-tumor research of piperidine.
基金supported by the Qingdao Major Scientific and Technological Project for Distinguished Scholars(Project No.:20170103)the Laoshan Major Scientific and Technological Project for Distinguished Scholars(Project No.:20181030)+2 种基金the Natural Science Foundation of Shandong Province(Project No.:ZR2020MH369)the Hospital Pharmacy Research Foundation of Guangdong Province(Project No.:2022A01)the Science and Technology Planning Project in Zhuhai(Project No.:ZH2202200090HJL).
文摘On December 22,2021,the United States Food and Drug Administration approved the first main protease inhibitor,i.e.,oral antiviral nirmatrelvir(PF-07321332)/ritonavir(Paxlovid),for the treatment of early severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)infection.Nirmatrelvir inhibits SARSCoV-2 infection,but high doses or long-term treatment may cause embryonic developmental toxicity and changes in host gene expression.The chiral structure of nirmatrelvir plays a key role in its antiviral activity.Ritonavir boosts the efficacy of nirmatrelvir by inactivating cytochrome P4503A4 expression and occupying the plasma protein binding sites.Multidrug resistance protein 1 inhibitors may increase the efficacy of nirmatrelvir.However,Paxlovid has many contraindications.Some patients treated with Paxlovid experience a second round of coronavirus disease 2019(COVID-19)symptoms soon after recovery.Interestingly,the antiviral activity of nirmatrelvir metabolites,such as compounds 12e18,is similar to or higher than that of nirmatrelvir.Herein,we review the advances and challenges in using nirmatrelvir and its derivatives with the aim of providing knowledge for drug developers and physicians in the fight against COVID-19.
基金the National Key Research and Development Program of China(2022YFB4102000)NSFC(22102018 and 52171201)+5 种基金the Natural Science Foundation of Sichuan Province(2022NSFSC0194)the“Pioneer”and“Leading Goose”R&D Program of Zhejiang(No.2023C03017)the Hefei National Research Center for Physical Sciences at the Microscale(KF2021005)the University of Electronic Science and Technology of China for startup funding(A1098531023601264)Q.J.acknowledges the China Postdoctoral Science Foundation funded project(2022M710601)the University of Electronic Science and Technology of China for startup funding(Y030212059003039).
文摘Electrochemically reducing CO_(2)to more reduced chemical species is a promising way that not only enables the conversion of intermittent energy resources to stable fuels,but also helps to build a closed-loop anthropogenic carbon cycle.Among various electrocatalysts for electrochemical CO_(2)reduction,multifunctional metal–organic frameworks(MOFs)have been employed as highly efficient and selective heterogeneous electrocatalysts due to their ultrahigh porosity and topologically diverse structures.Up to now,great progress has been achieved in the design and synthesis of highly active and selective MOF-related catalysts for electrochemical CO_(2)reduction reaction(CO_(2)RR),and their corresponding reaction mechanisms have been thoroughly studied.In this review,we summarize the recent progress of applying MOFs and their derivatives in CO_(2)RR,with a focus on the design strategies for electrocatalysts and electrolyzers.We first discussed the reaction mechanisms for different CO_(2)RR products and introduced the commonly applied electrolyzer configurations in the current CO_(2)RR system.Then,an overview of several categories of products(CO,HCOOH,CH_(4),CH_(3)OH,and multi-carbon chemicals)generated from MOFs or their derivatives via CO_(2)RR was discussed.Finally,we offer some insights and perspectives for the future development of MOFs and their derivatives in electrochemical CO_(2)reduction.We aim to provide new insights into this field and further guide future research for large-scale applications.
文摘In the process of exploration and development of oil and gas fields, the acidic environment of oil reservoir, production and transport processes cause corrosion of pipelines and equipment, resulting in huge economic losses and production safety risks. Corrosion inhibitors were widely used in oil industry because of simple operation process and economical. In this study, three environmentally friendly corrosion inhibitors were synthesized based on the natural polysaccharide chitosan. Corrosion inhibition of three dendritic chitosan derivatives (We name them BH, CH and DH) on mild steel in 1 mol/L HCl solution with natural ventilation system was evaluated by weight loss experiment, electrochemical analysis and surface morphology characterization. The experimental results showed that when the three dendritic chitosan derivatives added in the corrosive medium were 500 mg L^(−1), the corrosion inhibition efficiencies were all more than 80%. Based on quantum chemical calculation, inhibition mechanisms of three dendritic chitosan derivatives were investigated according to molecular structures. The results showed that the benzene ring, Schiff base and N atom contained in the molecule were the active centers of electron exchange, which were more likely to form a film on the carbon steel surface, thereby slowing or inhibiting corrosion. The results also predicted the corrosion inhibition effect BH > DH > CH, which was consistent with the experimental conclusion.
基金supported by the National Natural Science Foundation of China(22067016).
文摘Objective:To investigate the pharmacological action and mechanism of cholic acid derivatives in traditional Chinese medicine(TCM)based on the regulation of gene expression.Methods:Genome-wide gene expression profiles of Michigan Cancer Foundation-7(MCF-7)cells treated with or without 4 cholic acid derivatives were detected by gene chip technology.Similarities in upregulated and downregulated genes were analyzed using the Connectivity Map(CMap)database.The affinity between cholic acid derivatives and the potential target was confirmed by molecular docking.The cholic acid derivative-regulated pathway enrichment analysis was performed by the STRING database,and the potential pathway was confirmed by in vitro experiments on MD Anderson-Metastatic Breast-231(MDA-MB-231)cells.Results:Compared with the reference genome in the CMap database,the gene expression profiles of cholic acid derivatives were similar to those of antipsychotic,anticancer,anti-inflammatory,and antiinfective drugs.Among them,4 derivatives were associated with antianxiety drugs,and molecular docking results showed that these compounds may act by binding to the ligand-binding site of gammaaminobutyric acid(GABA)receptors.Moreover,the cytoskeletal pathway is one of the pathways enriched in the derivatives.Of them,ursodeoxycholic acid showed significant inhibitory activity on the cytoskeleton formation of MDA-MB-231 cells.Conclusion:The gene expression detection method,combined with CMap and pathway enrichment analysis,could be used to study the mechanism of the active ingredients of TCM.In addition,our research showed that cholic acid derivatives have a potential affinity for membrane receptors,where they can exert anxiolytic activity by modulating opioid receptor,GABA receptor,and dopamine receptor.Moreover,ursodeoxycholic and chenodeoxycholic acid inhibit cytoskeleton formation,probably by acting on membrane proteins to activate the corresponding cytoskeletal pathways.
文摘A previous study was conducted on the synthesis and antibacterial evaluation of Mannich bases of 2-(thioalkyl)-1H-methylbenzimidazole derivatives. The results of this study showed that certain 2-(thioalkyl)-1H-methylbenzimidazole and 2-(thioalkyl)-methyl-1-(piperidin-1-ylmethyl)benzimidazole derivatives possess antibacterial activities against clinical strains, such as Escherichia coli, Klebsiella pneumonia (Gram-negative bacteria), Staphylococcus aureus and Pseudomonas aeruginosa (Gram-positive bacteria). Following these favorable results, we extended the antibacterial evaluation of this series of molecules to environmental strains. The aim of this study was to assess the impact of the methyl-piperidine group fixed at position-1 of this new series of benzimidazoles on the antibacterial activity of environmental strains. In addition, we first evaluated the antibacterial activity of four 2-(thioalkyl)methylbenzimidazole derivatives and then that of five 2-(thioalkyl)-methyl-1-(piperidin-1-ylmethyl) benzimidazole derivatives. This study allowed us to show that compounds 1d and 1e could inhibit bacterial growth in vitro of the Enterobacteria P1 strain with inhibition diameters of 17.3 ± 0.6 mm and 10 ± 0.0 mm, respectively. However, addition of methyl-piperidinyl in this series showed that five (5) of 2-(thioalkyl)-methyl-1-(piperidin-1-ylmethyl) benzimidazole derivatives had an inhibitory effect on the in vitro growth of bacterial strains used except on Enterobacteria P2 with inhibition diameters between 10.0 ± 0.8 mm and 27.9 ± 1.4 mm. The introduction of the methyl-piperidinyl group at the 1-position of 2-(thioalkyl)-1H-methylbenzimidazole derivatives greatly improved the antibacterial activity against environmental bacteria such as Escherichia coli A1, A2, A3, and A4 and two Enterobacteria P1.
基金supported through the Annual Funding Track by the Deanship of Scientific Research,Vice Presidency for Graduate Studies and Scientific Research,King Faisal University,Saudi Arabia[Project No.AN000273],granted after a successful application by M.A.
文摘This study focuses on the dynamics of drug concentration in the blood.In general,the concentration level of a drug in the blood is evaluated by themean of an ordinary and first-order differential equation.More precisely,it is solved through an initial value problem.We proposed a newmodeling technique for studying drug concentration in blood dynamics.This technique is based on two fractional derivatives,namely,Caputo and Caputo-Fabrizio derivatives.We first provided comprehensive and detailed proof of the existence of at least one solution to the problem;we later proved the uniqueness of the existing solution.The proof was written using the Caputo-Fabrizio fractional derivative and some fixed-point techniques.Stability via theUlam-Hyers(UH)technique was also investigated.The application of the proposedmodel on two real data sets revealed that the Caputo derivative wasmore suitable in this study.Indeed,for the first data set,the model based on the Caputo derivative yielded a Mean Squared Error(MSE)of 0.03095 with a corresponding best value of fractional order of derivative of 1.00360.Caputo-Fabrizio-basedderivative appeared to be the second-best method for the problem,with an MSE of 0.04324 for a corresponding best fractional derivative order of 0.43532.For the second experiment,Caputo derivative-based model still performed the best as it yielded an MSE of 0.04066,whereas the classical and the Caputo-Fabrizio methods were tied with the same MSE of 0.07299.Another interesting finding was that the MSE yielded by the Caputo-Fabrizio fractional derivative coincided with the MSE obtained from the classical approach.
基金This work is financially supported by the Youth Talent Project of Major Academic and Technical Leaders Training Program of Jiangxi Province(Grant No.20204BCJL23045)the National Natural Science Foundation of China(Grant No.31800493)+1 种基金the Special Research Project on Camphor Tree(KRPCT)of Jiangxi Forestry Department(Grant No.2020CXZX07)the Innovative Leading Talent Short-Term Project in the Natural Science Area of Jiangxi Province(jxsq2018102072).
文摘The preparation of bioactive derivatives from the renewable natural product pinene is a hot research topic in the deep processing and utilization of pinene.In this study,β-pinene was used to develop novel molecules as a promising new precursor of insecticide.A series of amide-containing derivatives ofβ-pinene were synthesized and characterized.The insecticidal activities of these derivatives against Mythimna separate and Semiaphis heraclei were tested.The structure characterization results showed that the characterization data of amide-containing derivatives were in full agreement with their proposed structures.The insecticidal activities evaluation results indicated that amide-containing derivatives exhibited weak insecticidal activity against Mythimna separate,but exhibited moderate to good insecticidal activity against Semiaphis heraclei.After testing for 72 h,the corrected mortality against Semiaphis heraclei of compounds 5c,5e,5f,5 h,5j,and 5 m was 100%at 1000 mg/L.The structure-activity relationship analysis results showed that the introduction of an amide group into the structure of derivatives improved their insecticidal activity against Semiaphis heraclei.Meanwhile,the amide-containing derivatives containing the F and NO_(2) substituted benzene ring might improve their insecticidal activity against Semiaphis heraclei.This study will be helpful for the high value-added utilization of the natural renewable resourceβ-pinene and the development of novel insecticides.
基金the National Natural Science Foundation of China(Nos.12072022 and 11872105)the Fundamental Research Funds for the Central Universities(Nos.FRF-TW-2018-005 and FRF-BR-18-008B)。
文摘A fractional-order thermo-elastic model taking into account the small-scale effects of the thermo-elastic coupled behavior is developed to study the free vibration of a higher-order shear microplate.The nonlocal strain gradient theory is modified with the introduction of the fractional-order derivatives and the nonlocal characteristic length.The Fourier heat conduction is replaced by the non-Fourier heat conduction with the introduction of the fractional order and the memory characteristic time.Numerical calculations are performed to analyze the effects of the nonlocal strain gradient parameters,the spatiotemporal fractional order,the nonlocal characteristic length,and the memory characteristic time on the natural frequencies,the vibration attenuation,and the phase shift between the temperature field and the displacement field.The numerical results show that the new thermo-elastic model with the spatiotemporal fractional order can provide more exquisite descriptions of the thermo-elastic behavior at a small scale.
文摘This work aims to compute stability derivatives in the Newtonian limit in pitch when the Mach number tends to infinity.In such conditions,these stability derivatives depend on the Ogive’s shape and not the Mach number.Generally,the Mach number independence principle becomes effective from M=10 and above.The Ogive nose is obtained through a circular arc on the cone surface.Accordingly,the following arc slopes are consideredλ=5,10,15,−5,−10,and−15.It is found that the stability derivatives decrease due to the growth inλfrom 5 to 15 and vice versa.Forλ=5 and 10,the damping derivative declines with an increase inλfrom 5 to 10.Yet,for the damping derivatives,the minimum location remains at a pivot position,h=0.75 for large values ofλ.Hence,whenλ=−15,the damping derivatives are independent of the cone angles for most pivot positions except in the early twenty percent of the leading edge.
文摘The present article mainly focuses on the fractional derivatives with an exponential kernel(“exponential fractional derivatives”for brevity).First,several extended integral transforms of the exponential fractional derivatives are proposed,including the Fourier transform and the Laplace transform.Then,the L2 discretisation for the exponential Caputo derivative with a∈(1,2)is established.The estimation of the truncation error and the properties of the coefficients are discussed.In addition,a numerical example is given to verify the correctness of the derived L2 discrete formula.
基金the National Research Foundation of Korea(NRF-2021R1A2C109297811).
文摘The covariant derivative is a generalization of differentiating vectors.The Euclidean derivative is a special case of the covariant derivative in Euclidean space.The covariant derivative gathers broad attention,particularly when computing vector derivatives on curved surfaces and volumes in various applications.Covariant derivatives have been computed using the metric tensor from the analytically known curved axes.However,deriving the global axis for the domain has been mathematically and computationally challenging for an arbitrary two-dimensional(2D)surface.Consequently,computing the covariant derivative has been difficult or even impossible.A novel high-order numerical scheme is proposed for computing the covariant derivative on any 2D curved surface.A set of orthonormal vectors,known as moving frames,expand vectors to compute accurately covariant derivatives on 2D curved surfaces.The proposed scheme does not require the construction of curved axes for the metric tensor or the Christoffel symbols.The connectivity given by the Christoffel symbols is equivalently provided by the attitude matrix of orthonormal moving frames.Consequently,the proposed scheme can be extended to the general 2D curved surface.As an application,the Helmholtz‐Hodge decomposition is considered for a realistic atrium and a bunny.