Synchrotron X-ray radiography was used to carry out an in-situ observation of the hydrogen bubble evolution in the liquid Al/solid Ni interconnection. The individual bubble mainly grows in a stochastic way during heat...Synchrotron X-ray radiography was used to carry out an in-situ observation of the hydrogen bubble evolution in the liquid Al/solid Ni interconnection. The individual bubble mainly grows in a stochastic way during heating. The size distribution for groups of bubbles follows a Gaussian distribution in the early stage and Lifshitz-Slyozov-Wagner(LSW) diffusion controlled distribution in the final stage. The intermetallic compounds(IMCs) first form during solidification, following by the hydrogen bubbles. The bubbles between two adjacent Al3Ni grains grow unidirectionally along the liquid channel, with the bottom being impeded by the Al3Ni phase and the radius of the growth front being smaller. For the bubbles at triple junctions, they grow along the liquid channel and the crack with morphology transition.展开更多
Unlike traditional silicate glasses,germanate glasses often feature non-monotonic variations in mate-rial properties(e.g.,elastic moduli and glass transition temperature)with varying chemical composition,temperature,a...Unlike traditional silicate glasses,germanate glasses often feature non-monotonic variations in mate-rial properties(e.g.,elastic moduli and glass transition temperature)with varying chemical composition,temperature,and pressure.However,the underlying atomic-scale structural origins remain poorly under-stood.This is because,in most oxide glasses,the structural changes are quantified through solid-state NMR spectroscopy,but unfortunately the only NMR active germanium isotope(73 Ge)has very unfavor-able NMR properties.Here,we circumvent this problem by using high-energy X-ray and neutron total scattering coupled with ab initio molecular dynamics simulations as input for Reverse Monte Carlo mod-eling.In detail,we study the structure and properties of two sodium germanate glasses(10Na2 O-90GeO2 and 20Na2 O-80GeO2)subjected to permanent densification through hot compression up to 2 GPa at the glass transition temperature.While density as well as Young’s and bulk modulus increase with pressure as expected,shear modulus first increases and then decreases slightly at higher pressures.The refined atomistic structure models suggest that the glasses feature a distribution of 4,5,and 6 coordinated Ge with a majority of 4 and 5 coordinated species.Only minor changes in the Ge-O coordination occur upon hot compression,but a notable transformation of edge-to corner-sharing Ge-polyhedra is found.This anomalous polyhedral packing causes a lower number of angular constraints upon higher pressure treatment,explaining the non-monotonic trend of shear modulus with pressure.We also find that the rings become smaller and less circular upon compression,contributing to the volumetric compaction.These findings may aid the future design of germanate glasses with tailored properties and the general understanding of structure-property relations in oxide glasses.展开更多
The aerodynamic levitation provides an efficient technique for the research on thermophysical properties and solidification behavior of refractory materials. However, there is a nonnegligible temperature differences a...The aerodynamic levitation provides an efficient technique for the research on thermophysical properties and solidification behavior of refractory materials. However, there is a nonnegligible temperature differences across sample, causing unexpected uncertainty of measurement, such as, thermal expansivity and undercooling limit. We establish thermal filed model with properly simplified boundary condition, and derive quantitative expressions of this ambiguous temperature difference. Here we show that the temperature difference not only related to the average temperature, relative size and thermal conductivity of sample, but significantly influenced by the rotation pattern of sample. A huge temperature differences is almost inevitable when the sample with low thermal conductivity and high melting point is smelted in stationary suspension pattern, however, a drastically reduction of temperature difference can be fulfilled by simply making the sample rotation in up to down pattern. The thermal filed simulation was used to confirm the validity of these theoretical expressions. This work shed light on temperature difference in aerodynamic levitation. Based on this work, one can simply estimate the extent of temperature difference across the sample, and regulated that conveniently if needed, which benefit for novel material preparation and solidification mechanism study based on this technique.展开更多
Thermodynamic/dynamic modeling of liquid immiscibility in silicates is seriously hindered due to lack of in situ investigation on the structural evolution of the melt.In this work,atomic-scale structural evolution of ...Thermodynamic/dynamic modeling of liquid immiscibility in silicates is seriously hindered due to lack of in situ investigation on the structural evolution of the melt.In this work,atomic-scale structural evolution of a classic binary silicate immiscible system,SiO2–TiO2,is tracked by in situ high energy X-ray diffraction(HE-XRD).It is found that both the configuration of[SiO]and the polymerization between them are closely coupled with embedment and extraction of the metallic cations(Ti^4+).[SiO]monomer goes through deficit-oxygen and excess-polymerization before liquid–liquid separation and enables self-healing after liquid–liquid separation,which challenges the traditional cognition that[SiO4]monomer is immutable.Ti4+cations with tetrahedral oxygen-coordination first participate in the network construction before liquid separation.The four-fold Ti–O bond is broken during liquid separation,which may facilitate the movement of Ti4+across the Si–O network to form TiO2-rich nodules.The structural features of nodules were also investigated and they were found highly analogous to that of molten TiO2,which implies a parallel crystallization behavior in the two circumstances.Our results shed light on the structural evolution scenario in liquid immiscibility at atomic scale,which will contribute to constructing a complete thermodynamic/dynamic framework describing the silicate liquid immiscibility systems beyond current models.展开更多
While lunar bases have been a focus of development in recent years,the complex and extreme environment of the lunar surface remains a considerable challenge for lunar exploration.Unlike those on Earth,lunar day and ni...While lunar bases have been a focus of development in recent years,the complex and extreme environment of the lunar surface remains a considerable challenge for lunar exploration.Unlike those on Earth,lunar day and night temperature variations cause the properties of materials,especially metallic materials,to evolve in completely different manners.In this study,we investigated the property evolution of nine typical highperformance metallic materials using laboratory simulations of the extremely long-period lunar temperature environment.While lunation treatment improves the properties of all metallic materials,the microscopic mechanisms vary for amorphous and crystalline alloys with different structures.The treatment reduces both the loosely packed regions and heterogeneity in amorphous alloys while causing significant phase changes in crystalline alloys.Furthermore,a conservative prediction of the service life of metallic materials on lunar bases is provided based on analyzing microplastic events,followed by the practical material selection recommendations in various lunar application scenarios.展开更多
Despite its significance in both fundamental science and industrial applications,the glass-forming transition in the Al_(2)O_(3)-Y_(2)O_(3)(AY)refractory system is not yet fully understood due to the elusive structure...Despite its significance in both fundamental science and industrial applications,the glass-forming transition in the Al_(2)O_(3)-Y_(2)O_(3)(AY)refractory system is not yet fully understood due to the elusive structure evolution upon cooling.Here,atomic-scale structural changes in AY-bearing melts with different compositions and temperatures are tracked by employing in situ high-energy synchrotron X-ray diffraction and empirical potential structure refinement simulation.We find that the glass-forming abilities(GFA)of AY-bearing melts are intriguingly correlated with the dependence of melt structure on temperature.In the case of the Al_(2)O_(3)and Y_(3)A_(l5)O_(12)(YAG),the observed large structural changes from superheating to under-cooling melt(i.e.,higher temperature susceptibility)correspond to a low GFA.Conversely,the 74Al_(2)O_(3)-26Y_(2)O_(3)(AY26)melt,with the smallest temperature susceptibility,exhibits the highest GFA.Simulation models illustrate that the temperature susceptibility of melt is associated with its atomic arrangement,especially the stability of cation-cation pairs.A balanced network(in AY26 melt),where the unsteady OAl3 tri-clusters are minimized and steady apex-to-apex connections between adjacent network units are abundant,contributes to stabilizing cationic interactions.This,in turn,fosters the formation of largesized Al-O-Al rings,which topologically facilitates the subsequent glass-forming transition.Our findings provide new structural insight into the GFA of AY-bearing melts and may expand to other unconventional glass-forming systems to accelerate glassy materials design.展开更多
Atmospheric carbonyl compounds play significant roles in the cycling of radicals and have exhibited surprisingly high levels in winter that were well correlated to particulate matter,for which the reason have not been...Atmospheric carbonyl compounds play significant roles in the cycling of radicals and have exhibited surprisingly high levels in winter that were well correlated to particulate matter,for which the reason have not been clearly elucidated.Here we measured carbonyl compounds and other trace gasses together with PM_(2.5)over urban Jinan in North China Plain during the winter.Markedly higher carbonyl concentrations(average:14.63±4.21 ppbv)were found during wintertime haze pollution,about one to three-times relative to those on nonhaze days,with slight difference in chemical composition except formaldehyde(HCHO).HCHO(3.68 ppbv),acetone(3.17 ppbv),and acetaldehyde(CH_3CHO)(2.83 ppbv)were the three most abundant species,accounting for~75% of the total carbonylson both haze and non-haze days.Results from observational-based model(OBM)with atmospheric oxidation capacity(AOC)indicated that AOC significantly increased with the increasing carbonyls during the winter haze events.Carbonyl photolysis have supplied key oxidants such as RO_(2) and HO_(2),and thereby enhancing the formation of fine particles and secondary organic aerosols,elucidating the observed haze-carbonyls inter-correlation.Diurnal variation with carbonyls exhibiting peak values at early-noon and night highlighted the combined contribution of both secondary formation and primary diesel-fuel sources.1-butene was further confirmed to be the major precursor for HCHO.This study confirms the great contribution of carbonyls to AOC,and also suggests that reducing the emissions of carbonyls would be an effective way to mitigate haze pollution in urban area of the NCP region.展开更多
La-and Nb-doped BaTi_(2)O_(5)(BT2)spherical glasses were prepared by a containerless aerodynamic levitation method and their glass-forming regions were established.It is found that La-doping on the Ba-site(network-mod...La-and Nb-doped BaTi_(2)O_(5)(BT2)spherical glasses were prepared by a containerless aerodynamic levitation method and their glass-forming regions were established.It is found that La-doping on the Ba-site(network-modifier)and Nb-doping on the Ti-site(network-former)show distinct difference in the glassforming region:less than 10%La can replace Ba whereas 40%Nb can incorporate into BT2 glass.The distinction in glass-forming ability induced by La-and Nb-doping is discussed mainly from the structural arrangement of the glass.Raman spectroscopy analysis shows that La-doping elongates the short Ti-O bonds in the distorted[TiO_(5)]polyhedra and thus relaxes the network.Nb-doping introduces[NbO_(6)]polyhedra into BT_(2) and there exists a critical doping level(20%),below which incorporation of Nb into BT_(2) relaxes the[TiOn]polyhedra by shortening the long Ti-O bond and above which[NbO_(6)]starts to participate in the network skeleton construction resulting in a dramatic change in the glass structure,which is supported by the dramatic change in the exothermic peak on the DTA curves.This work triggers the speculation that the network-modifiers in BT_(2) glass possess a very important role in the structure of network-former skeleton than those in glasses based on traditional network-former oxides such as SiO_(2),GeO_(2) and B_(2)O_(3),which may provide a useful strategy for modifying the properties of these novel glasses by chemical doping.展开更多
Titanium dioxide(TiO_(2))has broad applications in photo(electro)catalysis,sensors,batteries,supercapacitors,pol-lutant degradation and so on[1-5].Pure TiO_(2)has a band gap of 3.0-3.2 eV,which limits its optical abso...Titanium dioxide(TiO_(2))has broad applications in photo(electro)catalysis,sensors,batteries,supercapacitors,pol-lutant degradation and so on[1-5].Pure TiO_(2)has a band gap of 3.0-3.2 eV,which limits its optical absorption to ultraviolet light[6]and results in an insulating electrical behavior[7].To tune the band gap.展开更多
Fibroblast growth factor 21(FGF21)is an atypical member of the FGF family that functions as an endocrine factor.In obese animals,elevation of plasma FGF21 levels by either pharmacological or genetic approaches reduces...Fibroblast growth factor 21(FGF21)is an atypical member of the FGF family that functions as an endocrine factor.In obese animals,elevation of plasma FGF21 levels by either pharmacological or genetic approaches reduces body weight,decreases hyperglycemia and hyperlipidemia,alleviates fatty liver and increases insulin sensitivity.FGF21 exerts its pleiotropic metabolic effects through its actions on multiple targets,including adipose tissue,liver,brain and pancreas.The expression of FGF21 is under the control of both peroxisome proliferator-activated receptor gamma(PPARγ)and peroxisome proliferator.-activated receptor alpha(PPARα).A growing body of evidence suggests that the metabolic benefits of these two nuclear receptors are mediated in part by induction of FGF21.In humans,plasma levels of FGF21 are elevated in obese subjects and patients with type 2 diabetes,but are reduced in patients with autoimmune diabetes.This review summarizes recent advances in understanding the physiological roles of FGF21 and the molecular pathways underlying its actions,and also discusses the future prospective of developing FGF21 or its agonists as therapeutic agents for obesity-related medical complications.展开更多
基金supported by the National Key Research and Development Program (2017YFA0403800)the National Natural Science Foundation of China (51374144, 51727802)+2 种基金the Shanghai Municipal Natural Science Foundation (13ZR1420600)Shanghai Rising-Star Program (14QA1402300)The support of synchrotron radiation phase-contrast imaging by the BL13W1 beam line of Shanghai Synchrotron Radiation Facility (SSRF), China, is gratefully acknowledged
文摘Synchrotron X-ray radiography was used to carry out an in-situ observation of the hydrogen bubble evolution in the liquid Al/solid Ni interconnection. The individual bubble mainly grows in a stochastic way during heating. The size distribution for groups of bubbles follows a Gaussian distribution in the early stage and Lifshitz-Slyozov-Wagner(LSW) diffusion controlled distribution in the final stage. The intermetallic compounds(IMCs) first form during solidification, following by the hydrogen bubbles. The bubbles between two adjacent Al3Ni grains grow unidirectionally along the liquid channel, with the bottom being impeded by the Al3Ni phase and the radius of the growth front being smaller. For the bubbles at triple junctions, they grow along the liquid channel and the crack with morphology transition.
基金supported by grants from the European Union(ERC,NewGLASS,No.101044664)the MSCA Postdoctoral Fel-lowship(No.101062110)from the Horizon Europe Framework Pro-gramme+2 种基金the computational resources sup-plied by EuroHPC Joint Undertaking with access to Vega at IZUM,Slovenia(No.EHPC-REG-2022R02-224)Aalborg University(No.CLAAUDIA)Mikkel Juelsholt and Kirsten M.Ø.Jensen are grate-ful for funding from the Villum Foundation(No.VKR00015416).
文摘Unlike traditional silicate glasses,germanate glasses often feature non-monotonic variations in mate-rial properties(e.g.,elastic moduli and glass transition temperature)with varying chemical composition,temperature,and pressure.However,the underlying atomic-scale structural origins remain poorly under-stood.This is because,in most oxide glasses,the structural changes are quantified through solid-state NMR spectroscopy,but unfortunately the only NMR active germanium isotope(73 Ge)has very unfavor-able NMR properties.Here,we circumvent this problem by using high-energy X-ray and neutron total scattering coupled with ab initio molecular dynamics simulations as input for Reverse Monte Carlo mod-eling.In detail,we study the structure and properties of two sodium germanate glasses(10Na2 O-90GeO2 and 20Na2 O-80GeO2)subjected to permanent densification through hot compression up to 2 GPa at the glass transition temperature.While density as well as Young’s and bulk modulus increase with pressure as expected,shear modulus first increases and then decreases slightly at higher pressures.The refined atomistic structure models suggest that the glasses feature a distribution of 4,5,and 6 coordinated Ge with a majority of 4 and 5 coordinated species.Only minor changes in the Ge-O coordination occur upon hot compression,but a notable transformation of edge-to corner-sharing Ge-polyhedra is found.This anomalous polyhedral packing causes a lower number of angular constraints upon higher pressure treatment,explaining the non-monotonic trend of shear modulus with pressure.We also find that the rings become smaller and less circular upon compression,contributing to the volumetric compaction.These findings may aid the future design of germanate glasses with tailored properties and the general understanding of structure-property relations in oxide glasses.
基金supported by the National Key Research and Development Program (2017YFB0305302)the National Natural Science Foundation of China (51374144, 51774201, 51821001)+1 种基金the Shanghai Municipal Natural Science Foundation (13ZR1420600)the Shanghai Rising-Star Program (14QA1402300)
文摘The aerodynamic levitation provides an efficient technique for the research on thermophysical properties and solidification behavior of refractory materials. However, there is a nonnegligible temperature differences across sample, causing unexpected uncertainty of measurement, such as, thermal expansivity and undercooling limit. We establish thermal filed model with properly simplified boundary condition, and derive quantitative expressions of this ambiguous temperature difference. Here we show that the temperature difference not only related to the average temperature, relative size and thermal conductivity of sample, but significantly influenced by the rotation pattern of sample. A huge temperature differences is almost inevitable when the sample with low thermal conductivity and high melting point is smelted in stationary suspension pattern, however, a drastically reduction of temperature difference can be fulfilled by simply making the sample rotation in up to down pattern. The thermal filed simulation was used to confirm the validity of these theoretical expressions. This work shed light on temperature difference in aerodynamic levitation. Based on this work, one can simply estimate the extent of temperature difference across the sample, and regulated that conveniently if needed, which benefit for novel material preparation and solidification mechanism study based on this technique.
基金supported by the National Natural Science Foundation of China-Excellent Young Scholars(No.51922068)the National Key Research and Development Program(No.2017YFA0403800)+1 种基金the National Natural Science Foundation of China(Nos.51727802,51821001 and 51971138)Shanghai Pujiang Program(No.19PJ1404400)。
文摘Thermodynamic/dynamic modeling of liquid immiscibility in silicates is seriously hindered due to lack of in situ investigation on the structural evolution of the melt.In this work,atomic-scale structural evolution of a classic binary silicate immiscible system,SiO2–TiO2,is tracked by in situ high energy X-ray diffraction(HE-XRD).It is found that both the configuration of[SiO]and the polymerization between them are closely coupled with embedment and extraction of the metallic cations(Ti^4+).[SiO]monomer goes through deficit-oxygen and excess-polymerization before liquid–liquid separation and enables self-healing after liquid–liquid separation,which challenges the traditional cognition that[SiO4]monomer is immutable.Ti4+cations with tetrahedral oxygen-coordination first participate in the network construction before liquid separation.The four-fold Ti–O bond is broken during liquid separation,which may facilitate the movement of Ti4+across the Si–O network to form TiO2-rich nodules.The structural features of nodules were also investigated and they were found highly analogous to that of molten TiO2,which implies a parallel crystallization behavior in the two circumstances.Our results shed light on the structural evolution scenario in liquid immiscibility at atomic scale,which will contribute to constructing a complete thermodynamic/dynamic framework describing the silicate liquid immiscibility systems beyond current models.
基金financially supported by Taishan Scholars Program of Shandong Province(No.tsqn201909010)the Key Basic and Applied Research Program of Guangdong Province(No.2019B030302010)+1 种基金the National Natural Science Foundation of China(Nos.51901139,51971120 and U1902221)the Key R&D Program of Shandong Province(No.2022CXGC020308)。
文摘While lunar bases have been a focus of development in recent years,the complex and extreme environment of the lunar surface remains a considerable challenge for lunar exploration.Unlike those on Earth,lunar day and night temperature variations cause the properties of materials,especially metallic materials,to evolve in completely different manners.In this study,we investigated the property evolution of nine typical highperformance metallic materials using laboratory simulations of the extremely long-period lunar temperature environment.While lunation treatment improves the properties of all metallic materials,the microscopic mechanisms vary for amorphous and crystalline alloys with different structures.The treatment reduces both the loosely packed regions and heterogeneity in amorphous alloys while causing significant phase changes in crystalline alloys.Furthermore,a conservative prediction of the service life of metallic materials on lunar bases is provided based on analyzing microplastic events,followed by the practical material selection recommendations in various lunar application scenarios.
基金supported by the National Natural Science Foundation of China-Key Program(No.52234010)National Natural Science Foundation of China(No.51971138)+2 种基金National Natural Science Foundation of China-Distinguished Young Scholars(No.52325407)National Key Basic Research Program of China(No.2020YFA0406101)the fund of the State Key Laboratory of Solidification Processing in NWPU(No.SKLSP202102).
文摘Despite its significance in both fundamental science and industrial applications,the glass-forming transition in the Al_(2)O_(3)-Y_(2)O_(3)(AY)refractory system is not yet fully understood due to the elusive structure evolution upon cooling.Here,atomic-scale structural changes in AY-bearing melts with different compositions and temperatures are tracked by employing in situ high-energy synchrotron X-ray diffraction and empirical potential structure refinement simulation.We find that the glass-forming abilities(GFA)of AY-bearing melts are intriguingly correlated with the dependence of melt structure on temperature.In the case of the Al_(2)O_(3)and Y_(3)A_(l5)O_(12)(YAG),the observed large structural changes from superheating to under-cooling melt(i.e.,higher temperature susceptibility)correspond to a low GFA.Conversely,the 74Al_(2)O_(3)-26Y_(2)O_(3)(AY26)melt,with the smallest temperature susceptibility,exhibits the highest GFA.Simulation models illustrate that the temperature susceptibility of melt is associated with its atomic arrangement,especially the stability of cation-cation pairs.A balanced network(in AY26 melt),where the unsteady OAl3 tri-clusters are minimized and steady apex-to-apex connections between adjacent network units are abundant,contributes to stabilizing cationic interactions.This,in turn,fosters the formation of largesized Al-O-Al rings,which topologically facilitates the subsequent glass-forming transition.Our findings provide new structural insight into the GFA of AY-bearing melts and may expand to other unconventional glass-forming systems to accelerate glassy materials design.
基金supported by the National Natural Science Foundation of China(Nos.42005092,42275127,42075112and 41775127)the Natural Science Foundation of Shandong Province(No.ZR2020QD058)。
文摘Atmospheric carbonyl compounds play significant roles in the cycling of radicals and have exhibited surprisingly high levels in winter that were well correlated to particulate matter,for which the reason have not been clearly elucidated.Here we measured carbonyl compounds and other trace gasses together with PM_(2.5)over urban Jinan in North China Plain during the winter.Markedly higher carbonyl concentrations(average:14.63±4.21 ppbv)were found during wintertime haze pollution,about one to three-times relative to those on nonhaze days,with slight difference in chemical composition except formaldehyde(HCHO).HCHO(3.68 ppbv),acetone(3.17 ppbv),and acetaldehyde(CH_3CHO)(2.83 ppbv)were the three most abundant species,accounting for~75% of the total carbonylson both haze and non-haze days.Results from observational-based model(OBM)with atmospheric oxidation capacity(AOC)indicated that AOC significantly increased with the increasing carbonyls during the winter haze events.Carbonyl photolysis have supplied key oxidants such as RO_(2) and HO_(2),and thereby enhancing the formation of fine particles and secondary organic aerosols,elucidating the observed haze-carbonyls inter-correlation.Diurnal variation with carbonyls exhibiting peak values at early-noon and night highlighted the combined contribution of both secondary formation and primary diesel-fuel sources.1-butene was further confirmed to be the major precursor for HCHO.This study confirms the great contribution of carbonyls to AOC,and also suggests that reducing the emissions of carbonyls would be an effective way to mitigate haze pollution in urban area of the NCP region.
基金the National Natural Science Foundation of China(Nos.51971138,51727802 and 51821001)the National Natural Science Foundation of ChinaExcellent Young Scholars(No.51922068)+1 种基金the National Key Research and Development Program(No.2017YFA0403800)the Shanghai Pujiang Program(No.19PJ1404400)。
文摘La-and Nb-doped BaTi_(2)O_(5)(BT2)spherical glasses were prepared by a containerless aerodynamic levitation method and their glass-forming regions were established.It is found that La-doping on the Ba-site(network-modifier)and Nb-doping on the Ti-site(network-former)show distinct difference in the glassforming region:less than 10%La can replace Ba whereas 40%Nb can incorporate into BT2 glass.The distinction in glass-forming ability induced by La-and Nb-doping is discussed mainly from the structural arrangement of the glass.Raman spectroscopy analysis shows that La-doping elongates the short Ti-O bonds in the distorted[TiO_(5)]polyhedra and thus relaxes the network.Nb-doping introduces[NbO_(6)]polyhedra into BT_(2) and there exists a critical doping level(20%),below which incorporation of Nb into BT_(2) relaxes the[TiOn]polyhedra by shortening the long Ti-O bond and above which[NbO_(6)]starts to participate in the network skeleton construction resulting in a dramatic change in the glass structure,which is supported by the dramatic change in the exothermic peak on the DTA curves.This work triggers the speculation that the network-modifiers in BT_(2) glass possess a very important role in the structure of network-former skeleton than those in glasses based on traditional network-former oxides such as SiO_(2),GeO_(2) and B_(2)O_(3),which may provide a useful strategy for modifying the properties of these novel glasses by chemical doping.
文摘Titanium dioxide(TiO_(2))has broad applications in photo(electro)catalysis,sensors,batteries,supercapacitors,pol-lutant degradation and so on[1-5].Pure TiO_(2)has a band gap of 3.0-3.2 eV,which limits its optical absorption to ultraviolet light[6]and results in an insulating electrical behavior[7].To tune the band gap.
基金This work is supported by Collaborative Research Fund(HKU3/CRF/09)General Research Fund(784111M)from the Research Grant Council of Hong Kong。
文摘Fibroblast growth factor 21(FGF21)is an atypical member of the FGF family that functions as an endocrine factor.In obese animals,elevation of plasma FGF21 levels by either pharmacological or genetic approaches reduces body weight,decreases hyperglycemia and hyperlipidemia,alleviates fatty liver and increases insulin sensitivity.FGF21 exerts its pleiotropic metabolic effects through its actions on multiple targets,including adipose tissue,liver,brain and pancreas.The expression of FGF21 is under the control of both peroxisome proliferator-activated receptor gamma(PPARγ)and peroxisome proliferator.-activated receptor alpha(PPARα).A growing body of evidence suggests that the metabolic benefits of these two nuclear receptors are mediated in part by induction of FGF21.In humans,plasma levels of FGF21 are elevated in obese subjects and patients with type 2 diabetes,but are reduced in patients with autoimmune diabetes.This review summarizes recent advances in understanding the physiological roles of FGF21 and the molecular pathways underlying its actions,and also discusses the future prospective of developing FGF21 or its agonists as therapeutic agents for obesity-related medical complications.
