Objective Magnetoreception,the remarkable ability of diverse animals to sense and utilize the geomagnetic field for orientation and navigation,remains a molecularly unresolved mystery in sensory biology.The putative m...Objective Magnetoreception,the remarkable ability of diverse animals to sense and utilize the geomagnetic field for orientation and navigation,remains a molecularly unresolved mystery in sensory biology.The putative magnetoreceptor(MagR,previously known as IscA1)is a highly conserved iron-sulfur protein implicated in both magnetoreception and iron metabolism;however,the functional diversity among its crossspecies homologs remains poorly understood.Cellular morphology is a key genetically determined trait that can be altered through genetic or environmental modifications—a process known as cell morphology engineering.Constructing engineered cells with specific morphological features and magnetic sensitivity to achieve remote,non-invasive magnetic modulation represents a crucial goal in this field with significant application potential.Therefore,this study aims to systematically investigate the effects of MagR heterologous expression on bacterial morphology and magnetic sensing capabilities,screen for MagR-based magnetically sensitive morphology engineering pathways,and reveal the underlying molecular mechanisms.Methods We systematically screened 28 MagR homologous genes from diverse prokaryotic and animal taxa to evaluate their expression and corresponding phenotypic effects in Escherichia coli(E.coli).To compare the differential magnetic responses among bacteria expressing various recombinant MagR proteins,we utilized high-throughput automated brightfield microscopic imaging and scanning electron microscopy(SEM).Furthermore,comprehensive biochemical and biophysical characterizations of iron and iron-sulfur cluster binding were performed using Ferrozine colorimetric assays,electron paramagnetic resonance(EPR)spectroscopy,ultraviolet-visible(UV-Vis)absorption,and circular dichroism(CD)spectroscopy.Additionally,100 mT static magnetic field(SMF)exposure experiments were conducted to assess magnetically tunable phenotypes,while the intrinsic magnetic properties of purified MagR proteins were directly measured using a superconducting quantum interference device(SQUID)magnetometer.Results Our results demonstrated that the heterologous expression of MagR homologs induced varying degrees of bacterial filamentation.From this comprehensive screen,two distinct morphological patterns were identified:hydra(Hydra vulgaris)MagR(hyMagR)promoted uniform cell elongation and filamentation,exhibiting robust magnetic sensitivity manifested as significantly enhanced filamentation under the 100 mT SMF.In contrast,pigeon(Columba livia)MagR(clMagR)induced only low-frequency,extreme filamentation(sporadically exceeding 80μm)with a relatively weaker magnetic morphological response.Mechanistically,our data unambiguously proved that these phenotypic differences are primarily driven by distinct iron redox preferences rather than total cellular iron accumulation.Specifically,hyMagR preferentially binds ferrous iron(Fe^(2+)),whereas clMagR favors ferric iron(Fe^(3+))and forms more stable iron-sulfur clusters.Intriguingly,although SQUID magnetometry showed that purified clMagR exhibited approximately five-fold higher mass magnetic susceptibility than hyMagR,its cellular magnetic response was weaker.We hypothesize that the Fe^(2+)-preferred intracellular environment associated with hyMagR overexpression primes the cell for enhanced generation of reactive oxygen species(ROS)via the Fenton reaction.Exposure to an SMF synergizes with this primed redox state,triggering the bacterial SOS response and upregulating cell division inhibitors to efficiently induce uniform filamentation.Conclusion Our findings identify the Fe^(2+)/Fe^(3+)redox state as a critical determinant of MagRmediated morphological remodeling and magnetic responsiveness.This discovery suggests a potential strategy for engineering magnetically responsive cellular systems for synthetic biology applications,and provides a plausible framework,which potentially combines intrinsic protein magnetism with redox-state modulation,for further investigating the evolutionary mechanisms of MagR-mediated magnetoreception.展开更多
Unmanned combat aerial vehicles require lightweight,stealth-capable exhaust systems.However,traditional metallic nozzles increase radar detectability and reduce range,while advanced composites offer high performance b...Unmanned combat aerial vehicles require lightweight,stealth-capable exhaust systems.However,traditional metallic nozzles increase radar detectability and reduce range,while advanced composites offer high performance but are expensive.Therefore,to improve the operational range and survivability of unmanned combat aerial vehicles,a lightweight,high-temperature-resistant,oxidation-resistant,and low-observable composite exhaust nozzle is developed to replace conventional metallic straight-type nozzles.The nozzle features a double serpentine shape to reduce radar and infrared signatures and is manufactured as a monolithic structure using the filament winding process,accommodating the complex geometry and large size(length:1.8 m,width:0.8 m).The exhaust nozzle consists of a ceramic matrix composite made of silicon carbide fibers and a silicon oxycarbide matrix,which absorbs and scatters radio frequency signals while withstanding prolonged exposure to high-temperature(700℃)oxidizing environments typical of engine exhaust gases.The polysiloxane resin used to produce the silicon oxycarbide matrix poses significant challenges owing to its low tackiness and high viscosity variations depending on the presence of nanoparticles,making filament winding difficult.These challenges are addressed by optimizing resin viscosity and winding pattern design.As a result,the tensile strength of the composite specimens fabricated with the optimized viscosity increases by 228.03% before pyrolysis and 97.68%after pyrolysis,compared with that of the non-optimized specimens.In addition,the density and tensile strength of the composite processed via three cycles of polymer infiltration and pyrolysis increased by 13.08% and 80.37%,respectively,compared to those of the non-densified composite.High-temperature oxidation and flame tests demonstrate exceptional thermal and oxidative stability.Furthermore,when compared with carbon fiber-reinforced ceramic matrix composites,the developed composite exhibits a permittivity at least two levels lower and a reflection loss below7 dB within the frequency range of 9.3-10.9 GHz,underscoring its superior electromagnetic stealth performance.展开更多
Erythrocyte tropomodulin（E-Tmod）is a capping protein at the slow-growing end of the actin filaments and regulates the length of the junctional complex in the erythrocyte membrane skeleton<sup>[1]</sup>.E...Erythrocyte tropomodulin（E-Tmod）is a capping protein at the slow-growing end of the actin filaments and regulates the length of the junctional complex in the erythrocyte membrane skeleton<sup>[1]</sup>.E-Tmod has two alternative promoters,P<sub>E0</sub>,and P<sub>E1</sub>,upstream of exons EO and E1,respectively.They drive the expression of two E-Tmod isoforms,E-Tmod41 and ETmod29,which play different yet coordinated roles in cytoskeleton reorganization<sup>[2]</sup>.This study aimed at investigating the expessions of the two E-Tmod isoforms response to the mechanical stresses,i.e.,shear stress and hydrostatic pressure.A cone-plate flow system and a hydrostatic pressure device were developed.Murine erythroleukemia（MEL）cells were subjected展开更多
In plants,several cellular processes like celldivision,differentiation,polar growth,andresponse to pathogen attack depend on rapidreorganization of the actin cytoskeleton.Thereconstruction of actin filaments is contro...In plants,several cellular processes like celldivision,differentiation,polar growth,andresponse to pathogen attack depend on rapidreorganization of the actin cytoskeleton.Thereconstruction of actin filaments is controlled bya wide variety of actin-binding proteins,ofwhich,profilin is one of the key modulators.展开更多
The periodic variation of motion of 171Yb+ stored ion in a Paul r.f.trap is observed.The reason of which and its influence to the uncertainty and stability of stored ton frequency standard are going to be studied.
Based on the elastic theory of cylindrical shells and the theory of composite laminates,a prediction model for the residual prestress of the simplified round composite barrel for railgun is established.Only the fibre ...Based on the elastic theory of cylindrical shells and the theory of composite laminates,a prediction model for the residual prestress of the simplified round composite barrel for railgun is established.Only the fibre pretension is considered in this model.A three dimensional numerical simulation for the residual prestress in the railgun barrel is carried out,by combining the temperature differential method with the element birth and death technology.The results obtained by the two methods are compared.It reveals that the distribution trends of residual prestress are consistent.And the difference for residual prestress in the filament wound composite housing of barrel is relatively small.The same finite element method is used to analysis the residual prestress in the non-simplified composite barrels for railgun,which are under different control modes of winding tension.The results mean that the residual prestress in barrel will increase while the taper coefficient for winding is decreasing.Therefore,the sealing performance in bore is improved,but the strength of the filament wound composite housing drops.In addition,the axial and circumferential residual prestress in the filament wound composite housing with constant torque winding are close to the ones in iso-stress design for barrel.展开更多
Boron has been considered a promising powdered metal fuel for enhancing composite propellants'energy output due to its high energy density.However,the high ignition temperature and low combustion efficiency limit ...Boron has been considered a promising powdered metal fuel for enhancing composite propellants'energy output due to its high energy density.However,the high ignition temperature and low combustion efficiency limit the application of boron powder due to the high boiling point of the boron oxide layer.Much research is ongoing to overcome these shortcomings,and one potential approach is to introduce a small quantity of metal oxide additives to promote the reaction of boron.This study prepared boron-rich fuels with 10 wt%of eight nano-metal oxide additives by mechanical ball milling.The effect of metal oxides on the thermo-oxidation,ignition,and combustion properties of boron powder was comprehensively studied by the thermogravimetric analysis(TG),the electrically heated filament setup(T-jump),and the laser-induced combustion experiments.TG experiments at 5 K/min found that Bi_(2)O_(3),MoO_(3),TiO_(2),Fe_(2)O_(3),and CuO can promote thermo-oxidation of boron.Compared to pure boron,Tonsetcan be reduced from 569℃to a minimum of 449℃(B/Bi_(2)O_(3)).Infrared temperature measurement in T-jump tests showed that when heated by an electric heating wire at rates from 1000 K/s to 25000 K/s,the ignition temperatures of B/Bi_(2)O_(3) are the lowest,even lower than the melting point of boron oxide.Ignition images and SEM for the products further showed that the high heating rate is beneficial to the rapid reaction of boron powder in the single-particle combustion state.Fuels(B/Bi_(2)O_(3),B/MoO_(3),and B/CuO)were mixed with the oxidant AP and ignited by laser to study the combustion performance.The results showed that B/CuO/AP has the largest flame area,the highest BO_(2) characteristic spectral intensity,and the largest burn rate for powder lines.To combine the advantages of CuO and Bi_(2)O_(3),binary metal oxide(CBO,mass ratio of 3:1)was prepared and the test results showed that CBO can very well improve both ignition and combustion properties of boron.Especially B/CBO/AP has the highest burn rate compared with all fuels containing other additives.It was found that multi-component metal-oxide additive can more synergistically improve the reaction characteristics of boron powder than unary additive.These findings contribute to the development of boron-rich fuels and their application in propellants.展开更多
Diamond films were prepared by hot filament chemical vapor deposition(HFCVD) in a gas mixtures system of methane, argon and hydrogen. The composition and morphology in different deposition pressures and filament struc...Diamond films were prepared by hot filament chemical vapor deposition(HFCVD) in a gas mixtures system of methane, argon and hydrogen. The composition and morphology in different deposition pressures and filament structures were investigated, as well as the friction and wear-resistant properties. The sp3-bonded content was measured and nano-mechanics properties were also tested. Results of atomic force microscopy and X-ray photoelectron spectroscopy show that the diamond films whose surface roughness is less than 10 nm and sp3-bonded content is greater than 70% can be prepared by bistratal filament structure with optimized proportion of Ar. It is also shown that the friction coefficient of diamond films is 0.13 and its wear-resistant property is excellent. Nano-mechanics of films shows that its elastic modulus is up to 650 MPa and hardness can reach higher than 60 GPa. The diamond films with excellent performance have a broad application prospect in microelectromechanical systems(MEMS).展开更多
Metal organic chemical vapor deposition(MOCVD) is a key equipment in the manufacturing of semiconductor optoelectronic devices and microwave devices in industry. Heating system is a vital part of MOCVD. Specific heati...Metal organic chemical vapor deposition(MOCVD) is a key equipment in the manufacturing of semiconductor optoelectronic devices and microwave devices in industry. Heating system is a vital part of MOCVD. Specific heating device and thermal control technology are needed for each new reactor design. By using resistance-wire heating MOCVD reaction chamber model, thermal analysis and structure optimization of the reactor were developed from the vertical position and the distance between coils of the resistance-wire heater. It is indicated that, within a certain range, the average temperature of the graphite susceptor varies linearly with the vertical distance of heater to susceptor, and with the changed distances between the coils; furthermore, single resistance-wire heater should be placed loosely in the internal and tightly in the external. The modulate accuracy of the temperature field approximately equals the change of the average temperature corresponding to the change of the coil position.展开更多
Hyperphosphorylated tau in the form of paired helical filament is the major protein component of neurofibrillary tangle,which is positively correlated with the degree of dementia in patients with Alzheimer disease(AD)...Hyperphosphorylated tau in the form of paired helical filament is the major protein component of neurofibrillary tangle,which is positively correlated with the degree of dementia in patients with Alzheimer disease(AD),the most common cause of dementia in the elderly.Activation of protein kinases or/and inhibition of protein phosphatases is responsible for tau hyperphosphorylation.Among various kinases.展开更多
Laboratory experiments were conducted to investigate the transformation and performance of a granular sequence batch reactor(SBR) under the conventional organic loading rate(OLR) condition.Aerobic granules were succes...Laboratory experiments were conducted to investigate the transformation and performance of a granular sequence batch reactor(SBR) under the conventional organic loading rate(OLR) condition.Aerobic granules were successfully cultivated in a SBR by means of alternative feeding load combined with reducing settling time after 60 d operational period.Subsequently,the black fungal granules were presented in reactor because of the filamentous overgrowth on the surface of aerobic granules.A small amount of fungal granules had no effect on the performance of granular SBR.Aerobic granules completely vanished and fungal granules eventually became the dominant species in subsequent 90 d operation after granulation.The three-dimensional excitation emission matrix(EEM) spectra result shows that the extracellular polymeric substances(EPS) component in both granules has no much difference,whereas the content of EPS in fungal granules is higher than that in bacterial granules.Due to their low bioactivity,the chemical oxidation demand(COD) and NH4-N removal efficiencies gradually decrease from 90.4%–96.5% and 99.5% to 71.8% and 32.9% respectively while the fungal granules become dominant in the SBR.展开更多
Nanocrystalline diamond films were deposited on Co-cemented carbide substrates using acetone/H<sub>2</sub>/Ar gas mixture by bias-enhanced hot filament chemical vapor deposition(HFCVD)technique.The evidenc...Nanocrystalline diamond films were deposited on Co-cemented carbide substrates using acetone/H<sub>2</sub>/Ar gas mixture by bias-enhanced hot filament chemical vapor deposition(HFCVD)technique.The evidence of nanocrystallinity,smoothness and purity was obtained by characterizing the sample with scanning electron microscopy(SEM),X-ray diffraction(XRD),Raman spectroscopy,atomic force microscopy(AFM),and field emission transmission electron microscopy(FE-TEM).The results show that nanocrystalline diamond films consists of nanocrystalline diamond grains with sizes range from 20 to 80 nm and contain a large amount of grain boundaries.The surface roughness of the films is measured as R<sub>a</sub>【50nm.The Raman spectroscopy,XRD pattern,and FE-TEM image of the films indicate the presence of nanocrystalline diamond.A new process is used to deposit composite diamond coatings by a two-step chemical vapor deposition procedure,including first the deposition of the rough polycrystalline diamond and then the smooth fine-grained nanocrystalline diamond film.Such composite diamond coatings not only display good adhesion and wear resistant properties,but also have smooth surfaces that are liable to polishing.This coating technology can not only meet the requirement of the adhesion of diamond coatings,but also reduce surface roughness of diamond coatings effectively,thus remove the obstacles for the industrialization of CVD diamond coatings.The diamondcoated dies with these composite coatings show obvious effect in the practical application.展开更多
A simple method to prepare of DNA template suitable for PCR amplification from filamentous fungi will be valuable for improving experimental efficiency.Here,a method was developed which just needed ultrasonic treatmen...A simple method to prepare of DNA template suitable for PCR amplification from filamentous fungi will be valuable for improving experimental efficiency.Here,a method was developed which just needed ultrasonic treatment of the mycelium at usual condition,and the produced solution could directly be used as DNA template for internal transcribed spacer(ITS)amplification successfully.The PCR could be improved by additional treatment of 60℃water baths,but was not centrifugation.When the template amount was 0.5-2μL and the ultrasonic time was 7-11 min,there was no distinctly influences on PCR.The method was commonly used for M.purpureus,I.cicadae,Lentinula sp.,Flammul sp.and Dictyophora sp.etc.to detect target sequences of ITS,hygromycin resistance gene(Hyg),CRISPR-associated protein 9(Cas9),Citrinin gene C(CtnC),Citrinin gene D(CtnD),large subunit rRNA gene(NL),and so on.The method could provide a simple,rapid,safe and economic approach to prepare the DNA template for large-scale PCR of the special filamentous fungi materials.展开更多
文摘Objective Magnetoreception,the remarkable ability of diverse animals to sense and utilize the geomagnetic field for orientation and navigation,remains a molecularly unresolved mystery in sensory biology.The putative magnetoreceptor(MagR,previously known as IscA1)is a highly conserved iron-sulfur protein implicated in both magnetoreception and iron metabolism;however,the functional diversity among its crossspecies homologs remains poorly understood.Cellular morphology is a key genetically determined trait that can be altered through genetic or environmental modifications—a process known as cell morphology engineering.Constructing engineered cells with specific morphological features and magnetic sensitivity to achieve remote,non-invasive magnetic modulation represents a crucial goal in this field with significant application potential.Therefore,this study aims to systematically investigate the effects of MagR heterologous expression on bacterial morphology and magnetic sensing capabilities,screen for MagR-based magnetically sensitive morphology engineering pathways,and reveal the underlying molecular mechanisms.Methods We systematically screened 28 MagR homologous genes from diverse prokaryotic and animal taxa to evaluate their expression and corresponding phenotypic effects in Escherichia coli(E.coli).To compare the differential magnetic responses among bacteria expressing various recombinant MagR proteins,we utilized high-throughput automated brightfield microscopic imaging and scanning electron microscopy(SEM).Furthermore,comprehensive biochemical and biophysical characterizations of iron and iron-sulfur cluster binding were performed using Ferrozine colorimetric assays,electron paramagnetic resonance(EPR)spectroscopy,ultraviolet-visible(UV-Vis)absorption,and circular dichroism(CD)spectroscopy.Additionally,100 mT static magnetic field(SMF)exposure experiments were conducted to assess magnetically tunable phenotypes,while the intrinsic magnetic properties of purified MagR proteins were directly measured using a superconducting quantum interference device(SQUID)magnetometer.Results Our results demonstrated that the heterologous expression of MagR homologs induced varying degrees of bacterial filamentation.From this comprehensive screen,two distinct morphological patterns were identified:hydra(Hydra vulgaris)MagR(hyMagR)promoted uniform cell elongation and filamentation,exhibiting robust magnetic sensitivity manifested as significantly enhanced filamentation under the 100 mT SMF.In contrast,pigeon(Columba livia)MagR(clMagR)induced only low-frequency,extreme filamentation(sporadically exceeding 80μm)with a relatively weaker magnetic morphological response.Mechanistically,our data unambiguously proved that these phenotypic differences are primarily driven by distinct iron redox preferences rather than total cellular iron accumulation.Specifically,hyMagR preferentially binds ferrous iron(Fe^(2+)),whereas clMagR favors ferric iron(Fe^(3+))and forms more stable iron-sulfur clusters.Intriguingly,although SQUID magnetometry showed that purified clMagR exhibited approximately five-fold higher mass magnetic susceptibility than hyMagR,its cellular magnetic response was weaker.We hypothesize that the Fe^(2+)-preferred intracellular environment associated with hyMagR overexpression primes the cell for enhanced generation of reactive oxygen species(ROS)via the Fenton reaction.Exposure to an SMF synergizes with this primed redox state,triggering the bacterial SOS response and upregulating cell division inhibitors to efficiently induce uniform filamentation.Conclusion Our findings identify the Fe^(2+)/Fe^(3+)redox state as a critical determinant of MagRmediated morphological remodeling and magnetic responsiveness.This discovery suggests a potential strategy for engineering magnetically responsive cellular systems for synthetic biology applications,and provides a plausible framework,which potentially combines intrinsic protein magnetism with redox-state modulation,for further investigating the evolutionary mechanisms of MagR-mediated magnetoreception.
基金supported by the Agency for Defense Development Grant Funded by the Korean Government(Grant No.912822501).
文摘Unmanned combat aerial vehicles require lightweight,stealth-capable exhaust systems.However,traditional metallic nozzles increase radar detectability and reduce range,while advanced composites offer high performance but are expensive.Therefore,to improve the operational range and survivability of unmanned combat aerial vehicles,a lightweight,high-temperature-resistant,oxidation-resistant,and low-observable composite exhaust nozzle is developed to replace conventional metallic straight-type nozzles.The nozzle features a double serpentine shape to reduce radar and infrared signatures and is manufactured as a monolithic structure using the filament winding process,accommodating the complex geometry and large size(length:1.8 m,width:0.8 m).The exhaust nozzle consists of a ceramic matrix composite made of silicon carbide fibers and a silicon oxycarbide matrix,which absorbs and scatters radio frequency signals while withstanding prolonged exposure to high-temperature(700℃)oxidizing environments typical of engine exhaust gases.The polysiloxane resin used to produce the silicon oxycarbide matrix poses significant challenges owing to its low tackiness and high viscosity variations depending on the presence of nanoparticles,making filament winding difficult.These challenges are addressed by optimizing resin viscosity and winding pattern design.As a result,the tensile strength of the composite specimens fabricated with the optimized viscosity increases by 228.03% before pyrolysis and 97.68%after pyrolysis,compared with that of the non-optimized specimens.In addition,the density and tensile strength of the composite processed via three cycles of polymer infiltration and pyrolysis increased by 13.08% and 80.37%,respectively,compared to those of the non-densified composite.High-temperature oxidation and flame tests demonstrate exceptional thermal and oxidative stability.Furthermore,when compared with carbon fiber-reinforced ceramic matrix composites,the developed composite exhibits a permittivity at least two levels lower and a reflection loss below7 dB within the frequency range of 9.3-10.9 GHz,underscoring its superior electromagnetic stealth performance.
基金supported by Natural Science Foundation of China(No.31170886)
文摘Erythrocyte tropomodulin（E-Tmod）is a capping protein at the slow-growing end of the actin filaments and regulates the length of the junctional complex in the erythrocyte membrane skeleton<sup>[1]</sup>.E-Tmod has two alternative promoters,P<sub>E0</sub>,and P<sub>E1</sub>,upstream of exons EO and E1,respectively.They drive the expression of two E-Tmod isoforms,E-Tmod41 and ETmod29,which play different yet coordinated roles in cytoskeleton reorganization<sup>[2]</sup>.This study aimed at investigating the expessions of the two E-Tmod isoforms response to the mechanical stresses,i.e.,shear stress and hydrostatic pressure.A cone-plate flow system and a hydrostatic pressure device were developed.Murine erythroleukemia（MEL）cells were subjected
文摘In plants,several cellular processes like celldivision,differentiation,polar growth,andresponse to pathogen attack depend on rapidreorganization of the actin cytoskeleton.Thereconstruction of actin filaments is controlled bya wide variety of actin-binding proteins,ofwhich,profilin is one of the key modulators.
文摘The periodic variation of motion of 171Yb+ stored ion in a Paul r.f.trap is observed.The reason of which and its influence to the uncertainty and stability of stored ton frequency standard are going to be studied.
文摘Based on the elastic theory of cylindrical shells and the theory of composite laminates,a prediction model for the residual prestress of the simplified round composite barrel for railgun is established.Only the fibre pretension is considered in this model.A three dimensional numerical simulation for the residual prestress in the railgun barrel is carried out,by combining the temperature differential method with the element birth and death technology.The results obtained by the two methods are compared.It reveals that the distribution trends of residual prestress are consistent.And the difference for residual prestress in the filament wound composite housing of barrel is relatively small.The same finite element method is used to analysis the residual prestress in the non-simplified composite barrels for railgun,which are under different control modes of winding tension.The results mean that the residual prestress in barrel will increase while the taper coefficient for winding is decreasing.Therefore,the sealing performance in bore is improved,but the strength of the filament wound composite housing drops.In addition,the axial and circumferential residual prestress in the filament wound composite housing with constant torque winding are close to the ones in iso-stress design for barrel.
基金State Key Laboratory of Explosion Science and Safety Protection of China (Grant No.QNKT21-8)National Natural Science Foundation of China (Grant No.12302432)to provide financial support。
文摘Boron has been considered a promising powdered metal fuel for enhancing composite propellants'energy output due to its high energy density.However,the high ignition temperature and low combustion efficiency limit the application of boron powder due to the high boiling point of the boron oxide layer.Much research is ongoing to overcome these shortcomings,and one potential approach is to introduce a small quantity of metal oxide additives to promote the reaction of boron.This study prepared boron-rich fuels with 10 wt%of eight nano-metal oxide additives by mechanical ball milling.The effect of metal oxides on the thermo-oxidation,ignition,and combustion properties of boron powder was comprehensively studied by the thermogravimetric analysis(TG),the electrically heated filament setup(T-jump),and the laser-induced combustion experiments.TG experiments at 5 K/min found that Bi_(2)O_(3),MoO_(3),TiO_(2),Fe_(2)O_(3),and CuO can promote thermo-oxidation of boron.Compared to pure boron,Tonsetcan be reduced from 569℃to a minimum of 449℃(B/Bi_(2)O_(3)).Infrared temperature measurement in T-jump tests showed that when heated by an electric heating wire at rates from 1000 K/s to 25000 K/s,the ignition temperatures of B/Bi_(2)O_(3) are the lowest,even lower than the melting point of boron oxide.Ignition images and SEM for the products further showed that the high heating rate is beneficial to the rapid reaction of boron powder in the single-particle combustion state.Fuels(B/Bi_(2)O_(3),B/MoO_(3),and B/CuO)were mixed with the oxidant AP and ignited by laser to study the combustion performance.The results showed that B/CuO/AP has the largest flame area,the highest BO_(2) characteristic spectral intensity,and the largest burn rate for powder lines.To combine the advantages of CuO and Bi_(2)O_(3),binary metal oxide(CBO,mass ratio of 3:1)was prepared and the test results showed that CBO can very well improve both ignition and combustion properties of boron.Especially B/CBO/AP has the highest burn rate compared with all fuels containing other additives.It was found that multi-component metal-oxide additive can more synergistically improve the reaction characteristics of boron powder than unary additive.These findings contribute to the development of boron-rich fuels and their application in propellants.
基金Projects(5130121121271188)supported by the National Natural Science Foundation of China+4 种基金Project(ZZ13005)supported by the Foundation of Laboratory of Ultra Precision Manufacturing Technology of China Academy of Engineering PhysicsProject(2010A0302013)supported by Research Foundation of China Academy of Engineering PhysicsProject(2012M521541)supported by the China Postdoctoral Science FoundationProject(20110933K)supported by the State Key Laboratory of Powder Metallurgy(Central South University),ChinaProject(CSU2013016)supported by the Open-End Fund for Valuable and Precision Instruments of Central South University,China
文摘Diamond films were prepared by hot filament chemical vapor deposition(HFCVD) in a gas mixtures system of methane, argon and hydrogen. The composition and morphology in different deposition pressures and filament structures were investigated, as well as the friction and wear-resistant properties. The sp3-bonded content was measured and nano-mechanics properties were also tested. Results of atomic force microscopy and X-ray photoelectron spectroscopy show that the diamond films whose surface roughness is less than 10 nm and sp3-bonded content is greater than 70% can be prepared by bistratal filament structure with optimized proportion of Ar. It is also shown that the friction coefficient of diamond films is 0.13 and its wear-resistant property is excellent. Nano-mechanics of films shows that its elastic modulus is up to 650 MPa and hardness can reach higher than 60 GPa. The diamond films with excellent performance have a broad application prospect in microelectromechanical systems(MEMS).
基金Projects(61376076,61274026,61377024)supported by the National Natural Science Foundation of ChinaProjects(12C0108,13C321)supported by the Scientific Research Fund of Hunan Provincial Education Department,ChinaProjects(2013FJ2011,2013FJ4232)supported by the Science and Technology Plan of Hunan Province,China
文摘Metal organic chemical vapor deposition(MOCVD) is a key equipment in the manufacturing of semiconductor optoelectronic devices and microwave devices in industry. Heating system is a vital part of MOCVD. Specific heating device and thermal control technology are needed for each new reactor design. By using resistance-wire heating MOCVD reaction chamber model, thermal analysis and structure optimization of the reactor were developed from the vertical position and the distance between coils of the resistance-wire heater. It is indicated that, within a certain range, the average temperature of the graphite susceptor varies linearly with the vertical distance of heater to susceptor, and with the changed distances between the coils; furthermore, single resistance-wire heater should be placed loosely in the internal and tightly in the external. The modulate accuracy of the temperature field approximately equals the change of the average temperature corresponding to the change of the coil position.
文摘Hyperphosphorylated tau in the form of paired helical filament is the major protein component of neurofibrillary tangle,which is positively correlated with the degree of dementia in patients with Alzheimer disease(AD),the most common cause of dementia in the elderly.Activation of protein kinases or/and inhibition of protein phosphatases is responsible for tau hyperphosphorylation.Among various kinases.
基金Project(51078036) supported by the National Natural Science Foundation of China
文摘Laboratory experiments were conducted to investigate the transformation and performance of a granular sequence batch reactor(SBR) under the conventional organic loading rate(OLR) condition.Aerobic granules were successfully cultivated in a SBR by means of alternative feeding load combined with reducing settling time after 60 d operational period.Subsequently,the black fungal granules were presented in reactor because of the filamentous overgrowth on the surface of aerobic granules.A small amount of fungal granules had no effect on the performance of granular SBR.Aerobic granules completely vanished and fungal granules eventually became the dominant species in subsequent 90 d operation after granulation.The three-dimensional excitation emission matrix(EEM) spectra result shows that the extracellular polymeric substances(EPS) component in both granules has no much difference,whereas the content of EPS in fungal granules is higher than that in bacterial granules.Due to their low bioactivity,the chemical oxidation demand(COD) and NH4-N removal efficiencies gradually decrease from 90.4%–96.5% and 99.5% to 71.8% and 32.9% respectively while the fungal granules become dominant in the SBR.
基金Supported by the National Natural Science Foundation of China(50575135)
文摘Nanocrystalline diamond films were deposited on Co-cemented carbide substrates using acetone/H<sub>2</sub>/Ar gas mixture by bias-enhanced hot filament chemical vapor deposition(HFCVD)technique.The evidence of nanocrystallinity,smoothness and purity was obtained by characterizing the sample with scanning electron microscopy(SEM),X-ray diffraction(XRD),Raman spectroscopy,atomic force microscopy(AFM),and field emission transmission electron microscopy(FE-TEM).The results show that nanocrystalline diamond films consists of nanocrystalline diamond grains with sizes range from 20 to 80 nm and contain a large amount of grain boundaries.The surface roughness of the films is measured as R<sub>a</sub>【50nm.The Raman spectroscopy,XRD pattern,and FE-TEM image of the films indicate the presence of nanocrystalline diamond.A new process is used to deposit composite diamond coatings by a two-step chemical vapor deposition procedure,including first the deposition of the rough polycrystalline diamond and then the smooth fine-grained nanocrystalline diamond film.Such composite diamond coatings not only display good adhesion and wear resistant properties,but also have smooth surfaces that are liable to polishing.This coating technology can not only meet the requirement of the adhesion of diamond coatings,but also reduce surface roughness of diamond coatings effectively,thus remove the obstacles for the industrialization of CVD diamond coatings.The diamondcoated dies with these composite coatings show obvious effect in the practical application.
基金Supported by the National Natural Science Foundation of China(81960692)the Science and Technology Support Program of Guizhou Province(2019-2776)。
文摘A simple method to prepare of DNA template suitable for PCR amplification from filamentous fungi will be valuable for improving experimental efficiency.Here,a method was developed which just needed ultrasonic treatment of the mycelium at usual condition,and the produced solution could directly be used as DNA template for internal transcribed spacer(ITS)amplification successfully.The PCR could be improved by additional treatment of 60℃water baths,but was not centrifugation.When the template amount was 0.5-2μL and the ultrasonic time was 7-11 min,there was no distinctly influences on PCR.The method was commonly used for M.purpureus,I.cicadae,Lentinula sp.,Flammul sp.and Dictyophora sp.etc.to detect target sequences of ITS,hygromycin resistance gene(Hyg),CRISPR-associated protein 9(Cas9),Citrinin gene C(CtnC),Citrinin gene D(CtnD),large subunit rRNA gene(NL),and so on.The method could provide a simple,rapid,safe and economic approach to prepare the DNA template for large-scale PCR of the special filamentous fungi materials.
