In this paper,a high-efficiency aerothermoelastic analysis method based on unified hypersonic lifting surface theory is established.The method adopts a two-way coupling form that couples the structure,aerodynamic forc...In this paper,a high-efficiency aerothermoelastic analysis method based on unified hypersonic lifting surface theory is established.The method adopts a two-way coupling form that couples the structure,aerodynamic force,and aerodynamic thermo and heat conduction.The aerodynamic force is first calculated based on unified hypersonic lifting surface theory,and then the Eckert reference temperature method is used to solve the temperature field,where the transient heat conduction is solved using Fourier’s law,and the modal method is used for the aeroelastic correction.Finally,flutter is analyzed based on the p-k method.The aerothermoelastic behavior of a typical hypersonic low-aspect ratio wing is then analyzed,and the results indicate the following:(1)the combined effects of the aerodynamic load and thermal load both deform the wing,which would increase if the flexibility,size,and flight time of the hypersonic aircraft increase;(2)the effect of heat accumulation should be noted,and therefore,the trajectory parameters should be considered in the design of hypersonic flight vehicles to avoid hazardous conditions,such as flutter.展开更多
LRP6, a co-receptor for the morphogen Wnt, aids endocytosis of anthrax complexes. Here we report that Dickkopfl （DKK1） protein, a secreted LRP6 ligand and antagonist, is also a modulator of anthrax toxin sensitivity...LRP6, a co-receptor for the morphogen Wnt, aids endocytosis of anthrax complexes. Here we report that Dickkopfl （DKK1） protein, a secreted LRP6 ligand and antagonist, is also a modulator of anthrax toxin sensitivity, shRNA-mediated gene silencing or TALEN-mediated gene knockout of DKK1 reduced sensitivity of cells to PA-dependent hybrid toxins. However, unlike the solely inhibitory effect on Wnt signaling, the effects of DKK1 overexpression on anthrax toxicity were bidirectional, depending on its endogenous expression and cell context. Fluorescence microscopy and biochemical analyses showed that DKK1 facilitates internalization of anthrax toxins and their receptors, an event mediated by DKK1-LRP6-Kremen2 complex. Monoclonal antibodies against DKK1 provided dose-dependent protection to macrophages from killing by anthrax lethal toxin （LT）. Our discovery that DKK1 forms ternary structure with LRP6 and Kremen2 in promoting PA-mediated toxin internalization provides a paradigm for bacterial exploitation of mechanisms that host cells use to internalize signaling proteins.展开更多
We present a new sense amplifier circuit for EEPROM memory. The topology of the sense amplifier uses a voltage sensing method,having low cost and low power consumption as well as high reliability. The sense amplifier ...We present a new sense amplifier circuit for EEPROM memory. The topology of the sense amplifier uses a voltage sensing method,having low cost and low power consumption as well as high reliability. The sense amplifier was implemented in an EEPROM realized with an SMIC 0.35-μm 2P3M CMOS embedded EEPROM process. Under the condition that the power supply is 3.3 V,simulation results showed that the charge time is 35 ns in the proposed sense amplifier,and that the maximum average current consumption during the read period is 40 μA. The novel topology allows the circuit to function with power supplies as low as 1.4 V. The sense amplifier has been implemented in 2-kb EEPROM memory for RFID tag IC applications,and has a silicon area of only 240 μm2.展开更多
Diversity-oriented synthesis （DOS） has been widely applied in the generation of a large collection of highly functionalized molecules with diverse chemical skeletons. Herein, we report the diversity-oriented synthes...Diversity-oriented synthesis （DOS） has been widely applied in the generation of a large collection of highly functionalized molecules with diverse chemical skeletons. Herein, we report the diversity-oriented synthesis of a series of structurally diverse bicyclic substrates via an efficient tandem conjugate addition/aldol process followed by ring-closing metathesis （RCM）. This approach allows us to efficiently prepare a number of structurally complex molecules for the further chemical biology studies.展开更多
Mechanical cues present in the stem cell niche resulting from intracellular processes or external force sources significantly affect the basic functions of stem cells such as self-renewal and differentiation.Creation ...Mechanical cues present in the stem cell niche resulting from intracellular processes or external force sources significantly affect the basic functions of stem cells such as self-renewal and differentiation.Creation of artificial cellular matrices exhibiting intrinsic mechanical cues generated by mechanical movements remains scarce.Herein,we reported on mechanically dynamic hydrogel matrices undergoing photo-induced directional domain sliding movement and their role in regulating embryonic stem cell(ESC)differentiation.The mechanically dynamic hydrogels were prepared via the self-assembly of an alternating hydrophilic and hydrophobic peptide with a photocaged cysteine residue.Upon light irradiation,the assemblies of the caged peptide were converted to non-equilibrated non-caged peptide bilayers that underwent the directional domain sliding motion induced by the thermodynamically favorable hydrophobic collapse transition.Culturing murine ESCs on the mechanically dynamic hydrogels resulted in biased differentiation toward the ectodermal lineage.We further showed that the mechanically dynamic hydrogels stimulated the translocation of a mechanotransduction protein Yes-associated protein(YAP)into the nucleus,implicating a potential mechanotransduction mechanism for the biased differentiation of ESCs.The finding of the biased ectodermal differentiation of ESCs induced by the mechanically dynamic hydrogels implies the great potency of the mechanically dynamic hydrogels as biomaterials for disease therapy and tissue regeneration in the future.展开更多
A two-way satellite time and frequency transfer(TWSTFT) device equipped in the BeiDou navigation satellite system(BDS)can calculate clock error between satellite and ground master clock. TWSTFT is a real-time method w...A two-way satellite time and frequency transfer(TWSTFT) device equipped in the BeiDou navigation satellite system(BDS)can calculate clock error between satellite and ground master clock. TWSTFT is a real-time method with high accuracy because most system errors such as orbital error, station position error, and tropospheric and ionospheric delay error can be eliminated by calculating the two-way pseudorange difference. Another method, the multi-satellite precision orbit determination(MPOD)method, can be applied to estimate satellite clock errors. By comparison with MPOD clock estimations, this paper discusses the applications of the BDS TWSTFT clock observations in satellite clock measurement, satellite clock prediction, navigation system time monitor, and satellite clock performance assessment in orbit. The results show that with TWSTFT clock observations, the accuracy of satellite clock prediction is higher than MPOD. Five continuous weeks of comparisons with three international GNSS Service(IGS) analysis centers(ACs) show that the reference time difference between BeiDou time(BDT) and golbal positoning system(GPS) time(GPST) realized IGS ACs is in the tens of nanoseconds. Applying the TWSTFT clock error observations may obtain more accurate satellite clock performance evaluation in the 104 s interval because the accuracy of the MPOD clock estimation is not sufficiently high. By comparing the BDS and GPS satellite clock performance, we found that the BDS clock stability at the 103 s interval is approximately 10.12, which is similar to the GPS IIR.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11172025 and 91116005)
文摘In this paper,a high-efficiency aerothermoelastic analysis method based on unified hypersonic lifting surface theory is established.The method adopts a two-way coupling form that couples the structure,aerodynamic force,and aerodynamic thermo and heat conduction.The aerodynamic force is first calculated based on unified hypersonic lifting surface theory,and then the Eckert reference temperature method is used to solve the temperature field,where the transient heat conduction is solved using Fourier’s law,and the modal method is used for the aeroelastic correction.Finally,flutter is analyzed based on the p-k method.The aerothermoelastic behavior of a typical hypersonic low-aspect ratio wing is then analyzed,and the results indicate the following:(1)the combined effects of the aerodynamic load and thermal load both deform the wing,which would increase if the flexibility,size,and flight time of the hypersonic aircraft increase;(2)the effect of heat accumulation should be noted,and therefore,the trajectory parameters should be considered in the design of hypersonic flight vehicles to avoid hazardous conditions,such as flutter.
基金supported in part by the National Natural Science Foundation of China(30770465,31070115)the National Basic Research Program of China(2010CB911800)+1 种基金the Peking-Tsinghua Center for Life Sciences(to WenSheng Wei)by an award(HDTRA1-06-C-0039)from the US Defense Threat Reduction Agency(to Stanley N.Cohen)
文摘LRP6, a co-receptor for the morphogen Wnt, aids endocytosis of anthrax complexes. Here we report that Dickkopfl （DKK1） protein, a secreted LRP6 ligand and antagonist, is also a modulator of anthrax toxin sensitivity, shRNA-mediated gene silencing or TALEN-mediated gene knockout of DKK1 reduced sensitivity of cells to PA-dependent hybrid toxins. However, unlike the solely inhibitory effect on Wnt signaling, the effects of DKK1 overexpression on anthrax toxicity were bidirectional, depending on its endogenous expression and cell context. Fluorescence microscopy and biochemical analyses showed that DKK1 facilitates internalization of anthrax toxins and their receptors, an event mediated by DKK1-LRP6-Kremen2 complex. Monoclonal antibodies against DKK1 provided dose-dependent protection to macrophages from killing by anthrax lethal toxin （LT）. Our discovery that DKK1 forms ternary structure with LRP6 and Kremen2 in promoting PA-mediated toxin internalization provides a paradigm for bacterial exploitation of mechanisms that host cells use to internalize signaling proteins.
基金Project (No. 2006AA01Z226) supported by the Hi-Tech Research and Development Program (863) of China
文摘We present a new sense amplifier circuit for EEPROM memory. The topology of the sense amplifier uses a voltage sensing method,having low cost and low power consumption as well as high reliability. The sense amplifier was implemented in an EEPROM realized with an SMIC 0.35-μm 2P3M CMOS embedded EEPROM process. Under the condition that the power supply is 3.3 V,simulation results showed that the charge time is 35 ns in the proposed sense amplifier,and that the maximum average current consumption during the read period is 40 μA. The novel topology allows the circuit to function with power supplies as low as 1.4 V. The sense amplifier has been implemented in 2-kb EEPROM memory for RFID tag IC applications,and has a silicon area of only 240 μm2.
文摘Diversity-oriented synthesis （DOS） has been widely applied in the generation of a large collection of highly functionalized molecules with diverse chemical skeletons. Herein, we report the diversity-oriented synthesis of a series of structurally diverse bicyclic substrates via an efficient tandem conjugate addition/aldol process followed by ring-closing metathesis （RCM）. This approach allows us to efficiently prepare a number of structurally complex molecules for the further chemical biology studies.
基金supported by the National Key R&D Program of China (2018YFC1313003)the Fundamental Research Funds for the Central Universities+1 种基金the National Natural Science Foundation of China (21774065 and 31622038)the Natural Science Foundation of Tianjin (18JCQNJC14100 and 18JCJQJC48400)
文摘Mechanical cues present in the stem cell niche resulting from intracellular processes or external force sources significantly affect the basic functions of stem cells such as self-renewal and differentiation.Creation of artificial cellular matrices exhibiting intrinsic mechanical cues generated by mechanical movements remains scarce.Herein,we reported on mechanically dynamic hydrogel matrices undergoing photo-induced directional domain sliding movement and their role in regulating embryonic stem cell(ESC)differentiation.The mechanically dynamic hydrogels were prepared via the self-assembly of an alternating hydrophilic and hydrophobic peptide with a photocaged cysteine residue.Upon light irradiation,the assemblies of the caged peptide were converted to non-equilibrated non-caged peptide bilayers that underwent the directional domain sliding motion induced by the thermodynamically favorable hydrophobic collapse transition.Culturing murine ESCs on the mechanically dynamic hydrogels resulted in biased differentiation toward the ectodermal lineage.We further showed that the mechanically dynamic hydrogels stimulated the translocation of a mechanotransduction protein Yes-associated protein(YAP)into the nucleus,implicating a potential mechanotransduction mechanism for the biased differentiation of ESCs.The finding of the biased ectodermal differentiation of ESCs induced by the mechanically dynamic hydrogels implies the great potency of the mechanically dynamic hydrogels as biomaterials for disease therapy and tissue regeneration in the future.
基金supported by the National Natural Sciences Foundation of China(Grant No.41574029)Youth Innovation Promotion Association CAS(Grant No.2016242)
文摘A two-way satellite time and frequency transfer(TWSTFT) device equipped in the BeiDou navigation satellite system(BDS)can calculate clock error between satellite and ground master clock. TWSTFT is a real-time method with high accuracy because most system errors such as orbital error, station position error, and tropospheric and ionospheric delay error can be eliminated by calculating the two-way pseudorange difference. Another method, the multi-satellite precision orbit determination(MPOD)method, can be applied to estimate satellite clock errors. By comparison with MPOD clock estimations, this paper discusses the applications of the BDS TWSTFT clock observations in satellite clock measurement, satellite clock prediction, navigation system time monitor, and satellite clock performance assessment in orbit. The results show that with TWSTFT clock observations, the accuracy of satellite clock prediction is higher than MPOD. Five continuous weeks of comparisons with three international GNSS Service(IGS) analysis centers(ACs) show that the reference time difference between BeiDou time(BDT) and golbal positoning system(GPS) time(GPST) realized IGS ACs is in the tens of nanoseconds. Applying the TWSTFT clock error observations may obtain more accurate satellite clock performance evaluation in the 104 s interval because the accuracy of the MPOD clock estimation is not sufficiently high. By comparing the BDS and GPS satellite clock performance, we found that the BDS clock stability at the 103 s interval is approximately 10.12, which is similar to the GPS IIR.
