Near infrared spectroscopy has been considered as a potentially ideal noninvasive technique for the postoperative monitoring of plastic surgery. In this study, 6 flaps were raised on rhesus monkeys’ forearms. Blood a...Near infrared spectroscopy has been considered as a potentially ideal noninvasive technique for the postoperative monitoring of plastic surgery. In this study, 6 flaps were raised on rhesus monkeys’ forearms. Blood and oxygen delivery to these flaps was monitored following vascular occlusions and inhalation of pure oxygen. Optical fibers were adopted in the probe of the oximeter so that the cutaneous detection could be performed in reflectance mode. Different and repeatable patterns of changes were measured following vascular occlusions on flaps. It is clear that the near infrared spectroscopy is capable of postoperatively monitoring vascular problems in flaps, especially the venous problem. Near infrared spectroscopy showed high sensitivity to detect the dynamic changes in flaps induced by inhalation of pure oxygen in this study. The experimental results indicated that it was potential to assess tissue viability utilizing the dynamic changes induced by some noninvasive stimulation (such as inhaling展开更多
Bleached bamboo kraft pulp was pretreated by 2,2,6,6-tetramethylpiperidine-l-oxy radical （TEMPO）- mediated oxidation using a TEMPO/NaBr/NaC10 system at pH = 10 in water to facilitate mechanical disintegration into T...Bleached bamboo kraft pulp was pretreated by 2,2,6,6-tetramethylpiperidine-l-oxy radical （TEMPO）- mediated oxidation using a TEMPO/NaBr/NaC10 system at pH = 10 in water to facilitate mechanical disintegration into TEMPO-oxidized cellulose nanofibrils （TO-CNs）. A series of TO-CNs with different carboxylate contents were obtained by varying amounts of added NaC10. An increase in carboxylate contents results in aqueous TO-CN dispersions with higher yield, zeta potential values, and optical transparency. When carboxylate groups are introduced, the DPv value of the TO-CNs remarkably decreases and then levels off. And the presence of hemicellulose in the pulp is favorable to TEMPO oxidization. After the oxidization, the native cellulose I crystalline structure and crystal size of bamboo pulp are almost maintained. TEM micrographs revealed that the degree of nanofibrillation is directly proportional to the carboxylate contents. With increasing carboxylate con- tents, the free-standing TO-CN films becomes more transparent and mechanically stronger. The oxygen permeability of PLA films drastically decreases from 355 for neat PLA to 8.4 mL-1 m a. d-1 after coating a thin layer of TO-CN with a carboxylate content of 1.8 mmol.g1. Therefore, inexpensive and abundant bamboo pulp would be a promising starting material to isolate cellulose nanfibrils for oxygen-barrier applications.展开更多
Multifunctional carbon encapsulated Ni@NiO nanocomposites(Ni@NiO@C)were synthesized for applications in oxygen reduction reactions(ORR),oxygen evolution reactions(OER)and lithium-ion batteries(LIB).The morphology was ...Multifunctional carbon encapsulated Ni@NiO nanocomposites(Ni@NiO@C)were synthesized for applications in oxygen reduction reactions(ORR),oxygen evolution reactions(OER)and lithium-ion batteries(LIB).The morphology was investigated via SEM and TEM,suggesting that the Ni@NiO@C nanocomposites have uniform and spherical core-shell structures.When the Ni@NiO@C nanocomposite is used as the catalyst in ORR,90%of the initial current density can be maintained after 15h in O_(2)-saturated 0.1 mol L^-1 KOH at 0.3 V under a rotation speed of 1600rpm.As a catalyst for OER,the highest activity overpotential of the Ni@NiO@C nanocomposite electrocatalyst is 380 mV(vs.RHE)under the current density of 10 mA cm^(-2),and the Tafel slope was calculated to be 55 mV dec^-1 by linear fitting.Electrochemical performances of the Ni@NiO@C nanocomposites used as LIB electrodes exhibited a long cycling life with a high capacity of 750 mA h g^-1 after 400 cycles under 200 mA g^-1.展开更多
Proton exchangemembrane(PEM)water electrolysis represents one of the most promising technologies to achieve green hydrogen production,but currently its practical viability is largely affected by the slow reaction kine...Proton exchangemembrane(PEM)water electrolysis represents one of the most promising technologies to achieve green hydrogen production,but currently its practical viability is largely affected by the slow reaction kinetics of the anodic oxygen evolution reaction(OER)in an acidic environment.While noble metal-based catalysts containing iridium or ruthenium are excellent catalysts for the acidic OER,their practical use in PEM electrolyzers is hindered due to their low abundance and high cost.Most recently,metal-organic frameworks(MOFs)have been demonstrated as a perfect platform to facilitate the design of acidic OER catalysts with both high efficiency and cost-effectiveness.Here,we pro-vide a timely and comprehensive overview of the recent progress on MOF-based acidic OER catalysts.The fundamental mechanisms of the acidic OER are first introduced,followed by a summary of the development of pristine MOFs and MOF derivatives as acidic OER catalysts.Importantly,a number of catalyst design strategies are discussed aiming at improving the acidic OER catalytic per-formance of MOF-based candidates.The integration of MOF-based catalysts into real PEM water electrolyzers is also included.Finally,future research directions are provided to achieve better MOF-based catalysts operational in acidic envi-ronments and PEM devices.展开更多
A model of the growth curve of microorganisms was proposed,which reveals a relation-ship with the number of a‘golden section’,1.618…,for main parameters of the growth curves.The treatment mainly concerns the ratio ...A model of the growth curve of microorganisms was proposed,which reveals a relation-ship with the number of a‘golden section’,1.618…,for main parameters of the growth curves.The treatment mainly concerns the ratio of the maximum asymptotic value of biomass in the phase of slow growth to the real value of biomass accumulation at the end of exponential growth,which is equal to thc square of the'golden section',i.e.,2.618.There are a few relevant theorems to explain these facts.New,yet simpler,methods were considered for deterrmining the model parameters based on hyperbolic functions.A comparison was made with one of the alternative models to demonstrate the advantage of the proposed model.The proposed model should be useful to apply at various stages of fermentation in scientific and industrial units.Further,the model could give a new impetus to the development of new mathematical knowledge regarding the algebra of the‘golden section'as a whole,as well as in connection with the introduction of a new equation at decomposing of any roots with any degrees for differences between constants and/or variables.展开更多
基金This work was supported by the National Natural Science Foundation of China (Grant No. 69778024) and Science Foundation of the Stomatology Hospital of Peking University.
文摘Near infrared spectroscopy has been considered as a potentially ideal noninvasive technique for the postoperative monitoring of plastic surgery. In this study, 6 flaps were raised on rhesus monkeys’ forearms. Blood and oxygen delivery to these flaps was monitored following vascular occlusions and inhalation of pure oxygen. Optical fibers were adopted in the probe of the oximeter so that the cutaneous detection could be performed in reflectance mode. Different and repeatable patterns of changes were measured following vascular occlusions on flaps. It is clear that the near infrared spectroscopy is capable of postoperatively monitoring vascular problems in flaps, especially the venous problem. Near infrared spectroscopy showed high sensitivity to detect the dynamic changes in flaps induced by inhalation of pure oxygen in this study. The experimental results indicated that it was potential to assess tissue viability utilizing the dynamic changes induced by some noninvasive stimulation (such as inhaling
文摘Bleached bamboo kraft pulp was pretreated by 2,2,6,6-tetramethylpiperidine-l-oxy radical （TEMPO）- mediated oxidation using a TEMPO/NaBr/NaC10 system at pH = 10 in water to facilitate mechanical disintegration into TEMPO-oxidized cellulose nanofibrils （TO-CNs）. A series of TO-CNs with different carboxylate contents were obtained by varying amounts of added NaC10. An increase in carboxylate contents results in aqueous TO-CN dispersions with higher yield, zeta potential values, and optical transparency. When carboxylate groups are introduced, the DPv value of the TO-CNs remarkably decreases and then levels off. And the presence of hemicellulose in the pulp is favorable to TEMPO oxidization. After the oxidization, the native cellulose I crystalline structure and crystal size of bamboo pulp are almost maintained. TEM micrographs revealed that the degree of nanofibrillation is directly proportional to the carboxylate contents. With increasing carboxylate con- tents, the free-standing TO-CN films becomes more transparent and mechanically stronger. The oxygen permeability of PLA films drastically decreases from 355 for neat PLA to 8.4 mL-1 m a. d-1 after coating a thin layer of TO-CN with a carboxylate content of 1.8 mmol.g1. Therefore, inexpensive and abundant bamboo pulp would be a promising starting material to isolate cellulose nanfibrils for oxygen-barrier applications.
基金supported by the National Natural Science Foundation of China(51571172,51672240,51571171,and 11404280)the Natural Science Foundation for Distinguished Young Scholars of Hebei Province(E2017203095)+1 种基金the Natural Science Foundation of Hebei Province(E2016203484 and A2015203337)the Research Program of the College Science&Technology of Hebei Province(ZD2017083 and QN2014047)
文摘Multifunctional carbon encapsulated Ni@NiO nanocomposites(Ni@NiO@C)were synthesized for applications in oxygen reduction reactions(ORR),oxygen evolution reactions(OER)and lithium-ion batteries(LIB).The morphology was investigated via SEM and TEM,suggesting that the Ni@NiO@C nanocomposites have uniform and spherical core-shell structures.When the Ni@NiO@C nanocomposite is used as the catalyst in ORR,90%of the initial current density can be maintained after 15h in O_(2)-saturated 0.1 mol L^-1 KOH at 0.3 V under a rotation speed of 1600rpm.As a catalyst for OER,the highest activity overpotential of the Ni@NiO@C nanocomposite electrocatalyst is 380 mV(vs.RHE)under the current density of 10 mA cm^(-2),and the Tafel slope was calculated to be 55 mV dec^-1 by linear fitting.Electrochemical performances of the Ni@NiO@C nanocomposites used as LIB electrodes exhibited a long cycling life with a high capacity of 750 mA h g^-1 after 400 cycles under 200 mA g^-1.
基金This work was supported by the Australian Research Council Discovery Projects(Grant Nos.ARC DP200103332 and ARC DP200103315).
文摘Proton exchangemembrane(PEM)water electrolysis represents one of the most promising technologies to achieve green hydrogen production,but currently its practical viability is largely affected by the slow reaction kinetics of the anodic oxygen evolution reaction(OER)in an acidic environment.While noble metal-based catalysts containing iridium or ruthenium are excellent catalysts for the acidic OER,their practical use in PEM electrolyzers is hindered due to their low abundance and high cost.Most recently,metal-organic frameworks(MOFs)have been demonstrated as a perfect platform to facilitate the design of acidic OER catalysts with both high efficiency and cost-effectiveness.Here,we pro-vide a timely and comprehensive overview of the recent progress on MOF-based acidic OER catalysts.The fundamental mechanisms of the acidic OER are first introduced,followed by a summary of the development of pristine MOFs and MOF derivatives as acidic OER catalysts.Importantly,a number of catalyst design strategies are discussed aiming at improving the acidic OER catalytic per-formance of MOF-based candidates.The integration of MOF-based catalysts into real PEM water electrolyzers is also included.Finally,future research directions are provided to achieve better MOF-based catalysts operational in acidic envi-ronments and PEM devices.
文摘A model of the growth curve of microorganisms was proposed,which reveals a relation-ship with the number of a‘golden section’,1.618…,for main parameters of the growth curves.The treatment mainly concerns the ratio of the maximum asymptotic value of biomass in the phase of slow growth to the real value of biomass accumulation at the end of exponential growth,which is equal to thc square of the'golden section',i.e.,2.618.There are a few relevant theorems to explain these facts.New,yet simpler,methods were considered for deterrmining the model parameters based on hyperbolic functions.A comparison was made with one of the alternative models to demonstrate the advantage of the proposed model.The proposed model should be useful to apply at various stages of fermentation in scientific and industrial units.Further,the model could give a new impetus to the development of new mathematical knowledge regarding the algebra of the‘golden section'as a whole,as well as in connection with the introduction of a new equation at decomposing of any roots with any degrees for differences between constants and/or variables.
