Optomagnetic multifunctional composite based on upconversion luminescence nanomaterial is regarded as a promising strategy for bioimaging,disease diagnosis and targeted delivery of drugs.To explore a mesoporous nanost...Optomagnetic multifunctional composite based on upconversion luminescence nanomaterial is regarded as a promising strategy for bioimaging,disease diagnosis and targeted delivery of drugs.To explore a mesoporous nanostructure with excellent water dispersibility and high drug-loading capacity,a novel nanorattle-structured Fe3O4@SiO2@NaYF4:Yb,Er magnetic upconversion nanorattle(MUCNR)was successfully designed by using Fe3O4 as core and NaYF4:Yb,Er nanocrystals as shell.The microstructures and crystal phase of the as-prepared MUCNRs were evaluated by transmission electron microscopy,Xray powder diffraction and N2 adsorption/desorption isotherms.The Kirkendall effect was adapted to explain the formation mechanism of the MUCNRs.The loading content and encapsulation efficiency of doxorubicin hydrochloride(DOX)could reach as high as 18.2%and 60.7%,respectively.Moreover,the DOX loading MUCNR(DOX-MUCNR)system showed excellent sustained drug release and strong p Hdependent performance,which was conducive to drug release at the slightly acidic microenvironment of tumor.Microcalorimetry was used to quantify the interactions between the carrier structure and drug release rate directly.The heat release rates in the heat-flow diagrams are basically consistent with the DOX release rate,thereby showing that microcalorimetry assay not only provides a unique thermodynamic explanation for the structure–activity relationship of Fe3O4@SiO2@NaYF4:Yb,Er MUCNRs but also provides powerful guidance to avoid the blind selection or design of drug carriers.Therefore,our work firmly provided a comprehensive perspective for using Fe3O4@SiO2@NaYF4:Yb,Er MUCNRs as a remarkable magnetic targeted drug carrier.展开更多
The electrochemical instability of traditional ether-based electrolytes poses a challenge for their use in high-voltage lithium metal batteries.Herein,a synergetic optimization strategy was proposed by introducing an ...The electrochemical instability of traditional ether-based electrolytes poses a challenge for their use in high-voltage lithium metal batteries.Herein,a synergetic optimization strategy was proposed by introducing an additive with a strong electron-withdrawing group and significant steric hindrance-isosorbide dinitrate(ISDN),reconstructing the solvation structure and solid electrolyte interphase(SEI),enabling highly stable and efficient lithium metal batteries.We found that ISDN can strengthen the interaction between Li^(+)and the anions of lithium salts and weaken the interaction between Li^(+)and the solvent in the solvation structure.It promotes the formation of a LiF-rich and LiN_(x)O_(y)-rich SEI layer,enhancing the uniformity and compactness of Li deposition and inhibiting solvent decomposition,which effectively expands the electrochemical window to 4.8 V.The optimized Li‖Li cells offer stable cycling over 1000 h with an overpotential of only 57.7 mV at 1 mA cm^(-2).Significantly,Li‖3.7 mA h LiFePO_(4)cells retain 108.3%of initial capacity after 546 cycles at a rate of 3 C.Under high-loading conditions(Li‖4.9 mA h LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)full cells)and a cutoff voltage of 4.5 V,the ISDN-containing electrolyte enables stable cycling for 140 cycles.This study leverages steric hindrance and electron-withdrawing effect to synergistically reconstruct the Li^(+)solvation structure and promote stable SEI formation,establishing a novel electrolyte paradigm for high-energy lithium metal batteries.展开更多
The dicarbon(C_(2))molecule is an important molecular species observed in many carbon-containing gaseous environments.The spectroscopic and dissociative studies of C_(2)have attracted great attention for a long time f...The dicarbon(C_(2))molecule is an important molecular species observed in many carbon-containing gaseous environments.The spectroscopic and dissociative studies of C_(2)have attracted great attention for a long time for understanding its electronic characters as well as the evolution and cycling of carbon in the universe.In this study,the lifetimes of C_(2)populated at the three high-lying electronic states of(2-4)^(3)Δ_(g) in the vacuum ultraviolet(VUV)region have been experimentally measured using a time-of-flight mass spectrometer and the VUV-pump-UV-probe photoionization scheme.The measurements showed that all the rovibronic levels in the 2(g)^(3)Δ_(g) state exhibit shorter lifetimes than the dynamical limit of the experimental method,consistent with the theoretically predicted radiative lifetimes.Dependence of the lifetime on the vibrational level was observed in the 3^(3)Δ_(g) state,and a marginal rotational dependence was noticed in the vʹ=1 vibrational level.For the 4^(3)Δ_(g) state,the rotationally resolved lifetimes in the vʹ=1 vibrational level were found to be slightly longer than those in the vʹ=0 and 2 vibrational levels.Such a complicated dependence of the lifetime on the rovibronic level makes further experimental and theoretical investigations highly desired for understanding the dynamics in the high-lying excited states of C_(2).展开更多
In clinical dermatology,approximately 15%of patients suffer from nail disorders.Different nail diseases may present with similar clinical manifestations.When clinical diagnosis based on symptoms,dermoscopy,and fungal ...In clinical dermatology,approximately 15%of patients suffer from nail disorders.Different nail diseases may present with similar clinical manifestations.When clinical diagnosis based on symptoms,dermoscopy,and fungal tests is inconclusive,nail biopsy becomes the most critical diagnostic tool.Nail specimens are highly rigid,brittle,and adhere poorly to slide glass,making sectioning challenging and posing significant difficulties for pathology technicians.Limited literature exists on nail histology processing techniques.This paper reviews and consolidates the available literature on nail paraffin sectioning techniques,aiming to provide insights and methods for pathology technicians.展开更多
Repetitive transcranial magnetic stimulation （rTMS） is a non-invasive treatment that can enhance the recovery of neurological function after stroke. Whether it can similarly promote the recovery of cognitive functio...Repetitive transcranial magnetic stimulation （rTMS） is a non-invasive treatment that can enhance the recovery of neurological function after stroke. Whether it can similarly promote the recovery of cognitive function after vascular dementia remains unknown, In this study, a rat model for vascular dementia was established by the two-vessel occlusion method. Two days after injury, 30 pulses of rTMS were ad- ministered to each cerebral hemisphere at a frequency of 0.5 Hz and a magnetic field intensity of 1,33 T. The Morris water maze test was used to evaluate learning and memory function. The Karnovsky-Roots method was performed to determine the density of cholinergic neurons in the hippocampal CA1 region. Immunohistochemical staining was used to determine the number of brain-derived neurotroph- ic factor （BDNF）-immunoreactive cells in the hippocampal CA1 region, rTMS treatment for 30 days significantly improved learning and memory function, increased acetylcholinesterase and choline acetyltransferase activity, increased the density of cholinergic neurons, and increased the number of BDNF-immunoreactive cells. These results indicate that rTMS can ameliorate learning and memory deficiencies in rats with vascular dementia, The mechanism through which this occurs might be related to the promotion of BDNF expression and subsequent restoration of cholinergic system activity in hippocampal CA 1 region.展开更多
Cu–Mn bimetal catalysts were prepared to remove nitrogen oxides(NOx)from diesel engine exhaust at low temperatures.At a Cu/Mn ratio of 3:2,the NOx conversions at 200°C reached 65%and 90%on Cu–Mn/ZSM‐5 and Cu–...Cu–Mn bimetal catalysts were prepared to remove nitrogen oxides(NOx)from diesel engine exhaust at low temperatures.At a Cu/Mn ratio of 3:2,the NOx conversions at 200°C reached 65%and 90%on Cu–Mn/ZSM‐5 and Cu–Mn/SAPO‐34,respectively.After a hydrothermal treatment and reaction in the presence of C3H6,the activity of Cu–Mn/SAPO‐34 was more stable than that of Cu–Mn/ZSM‐5.No obvious variations in the crystal structure or dealumination were observed,whereas the physical structure was best maintained in Cu–Mn/SAPO‐34.The atomic concentration of Cu on the surface of Cu–Mn/SAPO‐34 was quite stable,and the consumption of octahedrally coordinated Cu2+could be recovered.Conversely,the proportion of octahedrally coordinated Cu2+on the surface of Cu–Mn/ZSM‐5 significantly decreased.Therefore,besides the structure,the redox cycle between Cu+and octahedrally coordinated Cu2+played an important role in the stability of the catalysts.展开更多
The energy-saving electrohydraulic flow matching （EFM） system opens up an opportunity to minimize valve losses by fully opening the control valves, but the controllability is lost under overrunning load conditions. ...The energy-saving electrohydraulic flow matching （EFM） system opens up an opportunity to minimize valve losses by fully opening the control valves, but the controllability is lost under overrunning load conditions. To address this issue, this paper proposes a valve-based compensator to improve the controllability of the energy-saving EFM system. The valve-based compensator consists of a static compensator and a differential dynamic compensator based on load conditions. The energy effi- ciency, the stability performance, and the damping characteristic are analyzed under different control parameters. A parameter selection method is used to improve the efficiency, ensure the stability performance, and obtain good dynamic behavior. A test rig with a 2-t hydraulic excavator is built, and experimental tests are carried out to validate the proposed valve-based compensator. The experimental results indicate that the controllability of the EFM system is improved, and the characteristic of high energy efficiency is obtained by the proposed compensator.展开更多
The present work reports the effect of thermal induced porosity(TIP)on the high-cycle fatigue(HCF)and very high-cycle fatigue(VHCF)behaviors of hot-isostatic-pressed(HIPed)Ti-6Al-4V alloy from gasatomized powder.The r...The present work reports the effect of thermal induced porosity(TIP)on the high-cycle fatigue(HCF)and very high-cycle fatigue(VHCF)behaviors of hot-isostatic-pressed(HIPed)Ti-6Al-4V alloy from gasatomized powder.The results show that the residual pores in the as-HIPed powder compacts present no obvious effect on the HCF life.The regrowth of the residual pores can be observed after solution heat treatment.The pore location ranks the most harmful for the fatigue life compared with the other initiating defects.The maximum stress intensity factors were calculated.The plastic zone size of fine granular area(FGA)is much less than the characteristic size of the microstructure,and the crucial size of the internal pores in this study is about 40μm.The failure types of fatigue specimens in the VHCF regime were classified,and the competition of different failure types was described based on the modified Poisson distribution.展开更多
BACKGROUND Mesenchymal stem cells(MSCs)have been widely investigated in rheumatic disease due to their immunomodulatory and regenerative properties.Recently,mounting studies have implicated the therapeutic potency of ...BACKGROUND Mesenchymal stem cells(MSCs)have been widely investigated in rheumatic disease due to their immunomodulatory and regenerative properties.Recently,mounting studies have implicated the therapeutic potency of MSCs mostly due to the bioactive factors they produce.Extracellular vesicles(EVs)derived from MSCs have been identified as a promising cell-free therapy due to low immunogenicity.Rheumatic disease,primarily including rheumatoid arthritis and osteoarthritis,is a group of diseases in which immune dysregulation and chronic progressive inflammation lead to irreversible joint damage.Targeting MSCs and MSC-derived EVs may be a more effective and promising therapeutic strategy for rheumatic diseases.AIM To evaluate the potential therapeutic effectiveness of MSCs and EVs generated from MSCs in rheumatic diseases.METHODS PubMed was searched for the relevant literature using corresponding search terms alone or in combination.Papers published in English language from January 1999 to February 2020 were considered.Preliminary screening of papers concerning analysis of"immunomodulatory function"or"regenerative function"by scrutinizing the titles and abstracts of the literature,excluded the papers not related to the subject of the article.Some other related studies were obtained by manually retrieving the reference lists of papers that comply with the selection criteria,and these studies were screened to meet the final selection and exclusion criteria.RESULTS Eighty-six papers were ultimately selected for analysis.After analysis of the literature,it was found that both MSCs and EVs generated from MSCs have great potential in multiple rheumatic diseases,such as rheumatoid arthritis and osteoarthritis,in repair and regeneration of tissues,inhibition of inflammatory response,and regulation of body immunity via promoting chondrogenesis,regulating innate and adaptive immune cells,and regulating the secretion of inflammatory factors.But EVs from MSCs exhibit much more advantages over MSCs,which may represent another promising cell-free restorative strategy.Targeting MSCs and MSC-derived EVs may be a more efficient treatment for patients with rheumatic diseases.CONCLUSION The enormous potential of MSCs and EVs from MSCs in immunomodulation and tissue regeneration offers a new idea for the treatment of rheumatism.However,more in-depth exploration is needed before their clinical application.展开更多
In mobile machinery,hydro-mechanical pumps are increasingly replaced by electronically controlled pumps to improve the automation level,but diversified control functions(e.g.,power limitation and pressure cut-off)are ...In mobile machinery,hydro-mechanical pumps are increasingly replaced by electronically controlled pumps to improve the automation level,but diversified control functions(e.g.,power limitation and pressure cut-off)are integrated into the electronic controller only from the pump level,leading to the potential instability of the overall system.To solve this problem,a multi-mode electrohydraulic load sensing(MELS)control scheme is proposed especially considering the switching stability from the system level,which includes four working modes of flow control,load sensing,power limitation,and pressure control.Depending on the actual working requirements,the switching rules for the different modes and the switching direction(i.e.,the modes can be switched bilaterally or unilaterally)are defined.The priority of different modes is also defined,from high to low:pressure control,power limitation,load sensing,and flow control.When multiple switching rules are satisfied at the same time,the system switches to the control mode with the highest priority.In addition,the switching stability between flow control and pressure control modes is analyzed,and the controller parameters that guarantee the switching stability are obtained.A comparative study is carried out based on a test rig with a 2-ton hydraulic excavator.The results show that the MELS controller can achieve the control functions of proper flow supplement,power limitation,and pressure cut-off,which has good stability performance when switching between different control modes.This research proposes the MELS control method that realizes the stability of multi-mode switching of the hydraulic system of mobile machinery under different working conditions.展开更多
This work reported the Ar-induced porosity in powder metallurgy Ti-5 Al-2.5 Sn alloy prepared by hot isostatic pressing(HIPing).The obtained microstructures of powder compacts were studied through optical and scanning...This work reported the Ar-induced porosity in powder metallurgy Ti-5 Al-2.5 Sn alloy prepared by hot isostatic pressing(HIPing).The obtained microstructures of powder compacts were studied through optical and scanning electron microscopes,X-ray tomography,and the mechanical properties evaluated through tensile and impact tests.The results showed that the Ar-induced porosity is related to the hollow powder with gas bubble and the Ar leakage of sealed container during the powder densification.The hollow powder with gas bubble shows no obvious effects on mechanical properties of as-HIPed powder compacts.The Ar content decreases with the increasing shrinkage of encapsulated powder.0.7%Ar-induced porosity degrades the impact toughness,but no reductions of tensile properties were obtained.Ar content test is an effective method to detect the powder compacts with Ar concentration.展开更多
Status epilepticus has been shown to activate the proliferation of neural stem cells in the hippocampus of the brain, while also causing a large amount of neuronal death, especially in the subgranular zone of the dent...Status epilepticus has been shown to activate the proliferation of neural stem cells in the hippocampus of the brain, while also causing a large amount of neuronal death, especially in the subgranular zone of the dentate gyrus and the subventricular zone. Simultaneously, proliferating stem cells tend to migrate to areas with obvious damage. Our previous studies have clearly confirmed the effect of sodium valproate on cognitive function in rats with convulsive status epilepticus. However, whether neurogenesis can play a role in the antiepileptic effect of sodium valproate remains unknown. A model of convulsive status epilepticus was established in Wistar rats by intraperitoneal injection of 3 mEq/kg lithium chloride, and intraperitoneal injection of pilocarpine 40 mg/kg after 18–20 hours. Sodium valproate(100, 200, 300, 400, 500, or 600 mg/kg) was intragastrically administered six times every day(4-hour intervals) for 5 days. To determine the best dosage, sodium valproate concentration was measured from the plasma. The effective concentration of sodium valproate in the plasma of the rats that received the 300-mg/kg intervention was 82.26 ± 11.23 μg/mL. Thus, 300 mg/kg was subsequently used as the intervention concentration of sodium valproate. The following changes were seen: Recording excitatory postsynaptic potentials in the CA1 region revealed high-frequency stimulation-induced long-term potentiation. Immunohistochemical staining for BrdU-positive cells in the brain revealed that sodium valproate intervention markedly increased the success rate and the duration of induced long-term potentiation in rats with convulsive status epilepticus. The intervention also reduced the number of newborn neurons in the subgranular area of the hippocampus and subventricular zone and inhibited the migration of newborn neurons to the dentate gyrus. These results indicate that sodium valproate can effectively inhibit the abnormal proliferation and migration of neural stem cells and newborn neurons after convulsive status epilepticus, and improve learning and memory ability.展开更多
Hydraulic erecting systems are widely used in missile and rocket launchers because of their high power density.The double-acting telescopic hydraulic cylinder(DATHC)plays a decisive role in the safe and proper operati...Hydraulic erecting systems are widely used in missile and rocket launchers because of their high power density.The double-acting telescopic hydraulic cylinder(DATHC)plays a decisive role in the safe and proper operation of such systems.In particular,improper design of effective areas of a DATHC could potentially lead to an overspeed descent with severe damage for the erecting system.Unfortunately,there is no design constraint for DATHC to prevent this.Therefore,in this paper,a simplified and practical design constraint is proposed.Based on a developed mathematical model of a typical erecting system,we simulated and analyzed not only six cases meeting and not meeting the design constraint,but also the effectiveness of the design constraint under different loads.Experiments were then carried out under four cases.Simulation and experimental results validate the simplified design constraint,a constraint inequation guiding the design of diameters of effective areas for a DATHC.展开更多
基金supported by the Key Research and Development Plan of Shaanxi Province(2020GY-313)the Specialized Research Fund of Education Department of Shaanxi Province(19JK0255)+1 种基金the Specialized Scientific Research Fund Projects of Academician Shengyong Zhang(18YSZX001)the Science and Technology Innovation Team of Shangluo University(20SCX02)。
文摘Optomagnetic multifunctional composite based on upconversion luminescence nanomaterial is regarded as a promising strategy for bioimaging,disease diagnosis and targeted delivery of drugs.To explore a mesoporous nanostructure with excellent water dispersibility and high drug-loading capacity,a novel nanorattle-structured Fe3O4@SiO2@NaYF4:Yb,Er magnetic upconversion nanorattle(MUCNR)was successfully designed by using Fe3O4 as core and NaYF4:Yb,Er nanocrystals as shell.The microstructures and crystal phase of the as-prepared MUCNRs were evaluated by transmission electron microscopy,Xray powder diffraction and N2 adsorption/desorption isotherms.The Kirkendall effect was adapted to explain the formation mechanism of the MUCNRs.The loading content and encapsulation efficiency of doxorubicin hydrochloride(DOX)could reach as high as 18.2%and 60.7%,respectively.Moreover,the DOX loading MUCNR(DOX-MUCNR)system showed excellent sustained drug release and strong p Hdependent performance,which was conducive to drug release at the slightly acidic microenvironment of tumor.Microcalorimetry was used to quantify the interactions between the carrier structure and drug release rate directly.The heat release rates in the heat-flow diagrams are basically consistent with the DOX release rate,thereby showing that microcalorimetry assay not only provides a unique thermodynamic explanation for the structure–activity relationship of Fe3O4@SiO2@NaYF4:Yb,Er MUCNRs but also provides powerful guidance to avoid the blind selection or design of drug carriers.Therefore,our work firmly provided a comprehensive perspective for using Fe3O4@SiO2@NaYF4:Yb,Er MUCNRs as a remarkable magnetic targeted drug carrier.
基金Recruitment Program of Global Experts(China)the Hundred-Talent Project of Fujian+1 种基金Fuzhou UniversityFuda Zijin Hydrogen Energy Technology Co.,Ltd for the financial support。
文摘The electrochemical instability of traditional ether-based electrolytes poses a challenge for their use in high-voltage lithium metal batteries.Herein,a synergetic optimization strategy was proposed by introducing an additive with a strong electron-withdrawing group and significant steric hindrance-isosorbide dinitrate(ISDN),reconstructing the solvation structure and solid electrolyte interphase(SEI),enabling highly stable and efficient lithium metal batteries.We found that ISDN can strengthen the interaction between Li^(+)and the anions of lithium salts and weaken the interaction between Li^(+)and the solvent in the solvation structure.It promotes the formation of a LiF-rich and LiN_(x)O_(y)-rich SEI layer,enhancing the uniformity and compactness of Li deposition and inhibiting solvent decomposition,which effectively expands the electrochemical window to 4.8 V.The optimized Li‖Li cells offer stable cycling over 1000 h with an overpotential of only 57.7 mV at 1 mA cm^(-2).Significantly,Li‖3.7 mA h LiFePO_(4)cells retain 108.3%of initial capacity after 546 cycles at a rate of 3 C.Under high-loading conditions(Li‖4.9 mA h LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)full cells)and a cutoff voltage of 4.5 V,the ISDN-containing electrolyte enables stable cycling for 140 cycles.This study leverages steric hindrance and electron-withdrawing effect to synergistically reconstruct the Li^(+)solvation structure and promote stable SEI formation,establishing a novel electrolyte paradigm for high-energy lithium metal batteries.
基金supported by the National Natural Science Foundation of China(No.22122308)Beijing National Laboratory for Molecular Sciences(BNLMS).Hong Gao is also partially supported by the Innovation Capability Support Program of Shaanxi Province(2023-CX-TD-49)supported by the China Postdoctoral Science Foundation(No.2020TQ0324).
文摘The dicarbon(C_(2))molecule is an important molecular species observed in many carbon-containing gaseous environments.The spectroscopic and dissociative studies of C_(2)have attracted great attention for a long time for understanding its electronic characters as well as the evolution and cycling of carbon in the universe.In this study,the lifetimes of C_(2)populated at the three high-lying electronic states of(2-4)^(3)Δ_(g) in the vacuum ultraviolet(VUV)region have been experimentally measured using a time-of-flight mass spectrometer and the VUV-pump-UV-probe photoionization scheme.The measurements showed that all the rovibronic levels in the 2(g)^(3)Δ_(g) state exhibit shorter lifetimes than the dynamical limit of the experimental method,consistent with the theoretically predicted radiative lifetimes.Dependence of the lifetime on the vibrational level was observed in the 3^(3)Δ_(g) state,and a marginal rotational dependence was noticed in the vʹ=1 vibrational level.For the 4^(3)Δ_(g) state,the rotationally resolved lifetimes in the vʹ=1 vibrational level were found to be slightly longer than those in the vʹ=0 and 2 vibrational levels.Such a complicated dependence of the lifetime on the rovibronic level makes further experimental and theoretical investigations highly desired for understanding the dynamics in the high-lying excited states of C_(2).
文摘In clinical dermatology,approximately 15%of patients suffer from nail disorders.Different nail diseases may present with similar clinical manifestations.When clinical diagnosis based on symptoms,dermoscopy,and fungal tests is inconclusive,nail biopsy becomes the most critical diagnostic tool.Nail specimens are highly rigid,brittle,and adhere poorly to slide glass,making sectioning challenging and posing significant difficulties for pathology technicians.Limited literature exists on nail histology processing techniques.This paper reviews and consolidates the available literature on nail paraffin sectioning techniques,aiming to provide insights and methods for pathology technicians.
基金supported by a grant from the Major Project of Educational Commission of Hubei Province of China,No.D20152101
文摘Repetitive transcranial magnetic stimulation （rTMS） is a non-invasive treatment that can enhance the recovery of neurological function after stroke. Whether it can similarly promote the recovery of cognitive function after vascular dementia remains unknown, In this study, a rat model for vascular dementia was established by the two-vessel occlusion method. Two days after injury, 30 pulses of rTMS were ad- ministered to each cerebral hemisphere at a frequency of 0.5 Hz and a magnetic field intensity of 1,33 T. The Morris water maze test was used to evaluate learning and memory function. The Karnovsky-Roots method was performed to determine the density of cholinergic neurons in the hippocampal CA1 region. Immunohistochemical staining was used to determine the number of brain-derived neurotroph- ic factor （BDNF）-immunoreactive cells in the hippocampal CA1 region, rTMS treatment for 30 days significantly improved learning and memory function, increased acetylcholinesterase and choline acetyltransferase activity, increased the density of cholinergic neurons, and increased the number of BDNF-immunoreactive cells. These results indicate that rTMS can ameliorate learning and memory deficiencies in rats with vascular dementia, The mechanism through which this occurs might be related to the promotion of BDNF expression and subsequent restoration of cholinergic system activity in hippocampal CA 1 region.
基金supported by the National Natural Science Foundation of China(51008277)the Natural Science Foundation of Zhejiang Province(LY14E080001)the Key Project of Zhejiang Provincial Science and Technology Program(2012C03003-4)~~
文摘Cu–Mn bimetal catalysts were prepared to remove nitrogen oxides(NOx)from diesel engine exhaust at low temperatures.At a Cu/Mn ratio of 3:2,the NOx conversions at 200°C reached 65%and 90%on Cu–Mn/ZSM‐5 and Cu–Mn/SAPO‐34,respectively.After a hydrothermal treatment and reaction in the presence of C3H6,the activity of Cu–Mn/SAPO‐34 was more stable than that of Cu–Mn/ZSM‐5.No obvious variations in the crystal structure or dealumination were observed,whereas the physical structure was best maintained in Cu–Mn/SAPO‐34.The atomic concentration of Cu on the surface of Cu–Mn/SAPO‐34 was quite stable,and the consumption of octahedrally coordinated Cu2+could be recovered.Conversely,the proportion of octahedrally coordinated Cu2+on the surface of Cu–Mn/ZSM‐5 significantly decreased.Therefore,besides the structure,the redox cycle between Cu+and octahedrally coordinated Cu2+played an important role in the stability of the catalysts.
基金Project supported by the National Natural Science Foundation of China （No. 51375431）, the Open Fund of the State Key Laboratory of Fluid Power and Mechatronic Systems （No. GZKF-201503）, and the Research Fund of the State Key Laboratory of Mechanical Transmission （No. SKLMT-ZZKT-2015Z10）, China
文摘The energy-saving electrohydraulic flow matching （EFM） system opens up an opportunity to minimize valve losses by fully opening the control valves, but the controllability is lost under overrunning load conditions. To address this issue, this paper proposes a valve-based compensator to improve the controllability of the energy-saving EFM system. The valve-based compensator consists of a static compensator and a differential dynamic compensator based on load conditions. The energy effi- ciency, the stability performance, and the damping characteristic are analyzed under different control parameters. A parameter selection method is used to improve the efficiency, ensure the stability performance, and obtain good dynamic behavior. A test rig with a 2-t hydraulic excavator is built, and experimental tests are carried out to validate the proposed valve-based compensator. The experimental results indicate that the controllability of the EFM system is improved, and the characteristic of high energy efficiency is obtained by the proposed compensator.
基金financially supported by the Natural Science Foundation of Shanxi Province,China(No.201901D211085)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(STIP)
文摘The present work reports the effect of thermal induced porosity(TIP)on the high-cycle fatigue(HCF)and very high-cycle fatigue(VHCF)behaviors of hot-isostatic-pressed(HIPed)Ti-6Al-4V alloy from gasatomized powder.The results show that the residual pores in the as-HIPed powder compacts present no obvious effect on the HCF life.The regrowth of the residual pores can be observed after solution heat treatment.The pore location ranks the most harmful for the fatigue life compared with the other initiating defects.The maximum stress intensity factors were calculated.The plastic zone size of fine granular area(FGA)is much less than the characteristic size of the microstructure,and the crucial size of the internal pores in this study is about 40μm.The failure types of fatigue specimens in the VHCF regime were classified,and the competition of different failure types was described based on the modified Poisson distribution.
基金Supported by National Natural Science Foundation of China,No.81601408.
文摘BACKGROUND Mesenchymal stem cells(MSCs)have been widely investigated in rheumatic disease due to their immunomodulatory and regenerative properties.Recently,mounting studies have implicated the therapeutic potency of MSCs mostly due to the bioactive factors they produce.Extracellular vesicles(EVs)derived from MSCs have been identified as a promising cell-free therapy due to low immunogenicity.Rheumatic disease,primarily including rheumatoid arthritis and osteoarthritis,is a group of diseases in which immune dysregulation and chronic progressive inflammation lead to irreversible joint damage.Targeting MSCs and MSC-derived EVs may be a more effective and promising therapeutic strategy for rheumatic diseases.AIM To evaluate the potential therapeutic effectiveness of MSCs and EVs generated from MSCs in rheumatic diseases.METHODS PubMed was searched for the relevant literature using corresponding search terms alone or in combination.Papers published in English language from January 1999 to February 2020 were considered.Preliminary screening of papers concerning analysis of"immunomodulatory function"or"regenerative function"by scrutinizing the titles and abstracts of the literature,excluded the papers not related to the subject of the article.Some other related studies were obtained by manually retrieving the reference lists of papers that comply with the selection criteria,and these studies were screened to meet the final selection and exclusion criteria.RESULTS Eighty-six papers were ultimately selected for analysis.After analysis of the literature,it was found that both MSCs and EVs generated from MSCs have great potential in multiple rheumatic diseases,such as rheumatoid arthritis and osteoarthritis,in repair and regeneration of tissues,inhibition of inflammatory response,and regulation of body immunity via promoting chondrogenesis,regulating innate and adaptive immune cells,and regulating the secretion of inflammatory factors.But EVs from MSCs exhibit much more advantages over MSCs,which may represent another promising cell-free restorative strategy.Targeting MSCs and MSC-derived EVs may be a more efficient treatment for patients with rheumatic diseases.CONCLUSION The enormous potential of MSCs and EVs from MSCs in immunomodulation and tissue regeneration offers a new idea for the treatment of rheumatism.However,more in-depth exploration is needed before their clinical application.
基金National Key Research and Development Program of China(Grant No.2020YFB2009702)National Natural Science Foundation of China(Grant Nos.52075055,U21A20124 and 52111530069)Chongqing Natural Science Foundation of China(Grant No.cstc2020jcyj-msxmX0780)。
文摘In mobile machinery,hydro-mechanical pumps are increasingly replaced by electronically controlled pumps to improve the automation level,but diversified control functions(e.g.,power limitation and pressure cut-off)are integrated into the electronic controller only from the pump level,leading to the potential instability of the overall system.To solve this problem,a multi-mode electrohydraulic load sensing(MELS)control scheme is proposed especially considering the switching stability from the system level,which includes four working modes of flow control,load sensing,power limitation,and pressure control.Depending on the actual working requirements,the switching rules for the different modes and the switching direction(i.e.,the modes can be switched bilaterally or unilaterally)are defined.The priority of different modes is also defined,from high to low:pressure control,power limitation,load sensing,and flow control.When multiple switching rules are satisfied at the same time,the system switches to the control mode with the highest priority.In addition,the switching stability between flow control and pressure control modes is analyzed,and the controller parameters that guarantee the switching stability are obtained.A comparative study is carried out based on a test rig with a 2-ton hydraulic excavator.The results show that the MELS controller can achieve the control functions of proper flow supplement,power limitation,and pressure cut-off,which has good stability performance when switching between different control modes.This research proposes the MELS control method that realizes the stability of multi-mode switching of the hydraulic system of mobile machinery under different working conditions.
基金the Natural Science Foundation of Shanxi Province,China(No.201901D211085)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(STIP)。
文摘This work reported the Ar-induced porosity in powder metallurgy Ti-5 Al-2.5 Sn alloy prepared by hot isostatic pressing(HIPing).The obtained microstructures of powder compacts were studied through optical and scanning electron microscopes,X-ray tomography,and the mechanical properties evaluated through tensile and impact tests.The results showed that the Ar-induced porosity is related to the hollow powder with gas bubble and the Ar leakage of sealed container during the powder densification.The hollow powder with gas bubble shows no obvious effects on mechanical properties of as-HIPed powder compacts.The Ar content decreases with the increasing shrinkage of encapsulated powder.0.7%Ar-induced porosity degrades the impact toughness,but no reductions of tensile properties were obtained.Ar content test is an effective method to detect the powder compacts with Ar concentration.
基金supported by the National Natural Science Foundation of China for Youth Science Project,No.81201507(to PW)
文摘Status epilepticus has been shown to activate the proliferation of neural stem cells in the hippocampus of the brain, while also causing a large amount of neuronal death, especially in the subgranular zone of the dentate gyrus and the subventricular zone. Simultaneously, proliferating stem cells tend to migrate to areas with obvious damage. Our previous studies have clearly confirmed the effect of sodium valproate on cognitive function in rats with convulsive status epilepticus. However, whether neurogenesis can play a role in the antiepileptic effect of sodium valproate remains unknown. A model of convulsive status epilepticus was established in Wistar rats by intraperitoneal injection of 3 mEq/kg lithium chloride, and intraperitoneal injection of pilocarpine 40 mg/kg after 18–20 hours. Sodium valproate(100, 200, 300, 400, 500, or 600 mg/kg) was intragastrically administered six times every day(4-hour intervals) for 5 days. To determine the best dosage, sodium valproate concentration was measured from the plasma. The effective concentration of sodium valproate in the plasma of the rats that received the 300-mg/kg intervention was 82.26 ± 11.23 μg/mL. Thus, 300 mg/kg was subsequently used as the intervention concentration of sodium valproate. The following changes were seen: Recording excitatory postsynaptic potentials in the CA1 region revealed high-frequency stimulation-induced long-term potentiation. Immunohistochemical staining for BrdU-positive cells in the brain revealed that sodium valproate intervention markedly increased the success rate and the duration of induced long-term potentiation in rats with convulsive status epilepticus. The intervention also reduced the number of newborn neurons in the subgranular area of the hippocampus and subventricular zone and inhibited the migration of newborn neurons to the dentate gyrus. These results indicate that sodium valproate can effectively inhibit the abnormal proliferation and migration of neural stem cells and newborn neurons after convulsive status epilepticus, and improve learning and memory ability.
基金This work is supported by the National Natural Science Foundation of China(No.91748210)the National Outstanding Youth Science Foundation of China(No.51922093).
文摘Hydraulic erecting systems are widely used in missile and rocket launchers because of their high power density.The double-acting telescopic hydraulic cylinder(DATHC)plays a decisive role in the safe and proper operation of such systems.In particular,improper design of effective areas of a DATHC could potentially lead to an overspeed descent with severe damage for the erecting system.Unfortunately,there is no design constraint for DATHC to prevent this.Therefore,in this paper,a simplified and practical design constraint is proposed.Based on a developed mathematical model of a typical erecting system,we simulated and analyzed not only six cases meeting and not meeting the design constraint,but also the effectiveness of the design constraint under different loads.Experiments were then carried out under four cases.Simulation and experimental results validate the simplified design constraint,a constraint inequation guiding the design of diameters of effective areas for a DATHC.
