A three—component enzyme system that catalyzes in vivo the oxidation of CH_4 to CH_3OH has been purified with high specific activity from an unusual type I methanotroph through the use of stabilizing reagents.
In the interlayer expansion of the layered zeolite precursor COK-5, a Sn, salt, bis（2,4-pentanedionate）- dichlorotin [Sn（acac）2CL2], instead of a silylating agent was used to link the layers at 180 ℃. The obtaine...In the interlayer expansion of the layered zeolite precursor COK-5, a Sn, salt, bis（2,4-pentanedionate）- dichlorotin [Sn（acac）2CL2], instead of a silylating agent was used to link the layers at 180 ℃. The obtained material, which is designed as Sn-COE-5, shows a shift of the first XRD reflection, which is very similar to that of COK-5 interlayer expanded with dichlorodimethylsilane （DCDMS）, indicating an increase in interlayer distance. X-ray diffraction （XRD）, N2 sorption isotherms, inductively coupled plasma （ICP）, and X-ray photo- electron spectroscopy （XPS） support the incorporation of isolated Sn sites in the sample. In the conversion of glucose to levulinic acid. Sn-COE-5 exhibits much higher activity than COK-5, which is due to the presence of Lewis acidic sites in the Sn-COE-5.展开更多
Ce/BEA has great potential as a passive NO_(x)absorber(PNA)to reduce the NO_(x)emissions during the cold start phase especially in diesel engine for its high resistance to CO and suitable NO_(x)desorption temperature ...Ce/BEA has great potential as a passive NO_(x)absorber(PNA)to reduce the NO_(x)emissions during the cold start phase especially in diesel engine for its high resistance to CO and suitable NO_(x)desorption temperature range.However,as a novel material,its physical and chemical properties still remain unknown.In this work,Ce/BEA was synthesized by ion-exchange method to identify the active species in NO_(x)adsorption,compared with aggregated Ce species in Ce/SiAlO_(x) prepared by impregnation method.X-ray diffraction(XRD),high resolution-transmission electron microscopy(HR-TEM)and aberration-corrected-scanning transmission electron microscopy(AC-STEM)were performed to confirm the isolated single atom formation of Ce species in Ce/BEA.UV-vis diffraction reflection spectra(DRS)and X-ray photoelectron spectroscopy(XPS)were conducted to find the difference of chemical environment between the isolated Ce species and aggregated ones.PNA performance evaluation and temperature programmed reduction of hydrogen(H_(2)-TPR)results show the high NO_(x)storage capacity and active oxygen species quantity in Ce/BEA.It is also found that the main NO_(x)adsorption species are Ce^(4+)-O^(∗)rather than Ce^(3+).NO_(x)-diffuse reflectance infrared Fourier transform spectroscopy(NO_(x)-DRIFTS)confirms that the bidentate nitrite species are the critical NO_(x)adsorption intermediates and the conception of NO_(x)adsorption and desorption processes is proposed.展开更多
Natural hybridization frequently occurs in plants and can facilitate gene flow between species, possibly resulting in species refusion. However, various reproductive barriers block the formation of hybrids and maintai...Natural hybridization frequently occurs in plants and can facilitate gene flow between species, possibly resulting in species refusion. However, various reproductive barriers block the formation of hybrids and maintain species integrity. Here, we conducted a field survey to examine natural hybridization and reproductive isolation （RI） between sympatric populations of Primula secundiflora and P. poissonii using ten nuclear simple sequence repeat （SSR） loci. Although introgressive hybridization occurred, species boundaries between P. secundiflora and P. poissonii were maintained through nearly complete reproductive isolation. These interfertite species provide an excellent model for studying the RI mechanisms and evolutionary forces that maintain species boundaries.展开更多
文摘A three—component enzyme system that catalyzes in vivo the oxidation of CH_4 to CH_3OH has been purified with high specific activity from an unusual type I methanotroph through the use of stabilizing reagents.
基金supported by the National Natural Science Foundation of China (21422306 and 21403192)Zhejiang Provincial Natural Science Foundation of China under grant no. LR15B030001the Fundamental Research Funds for the Central Universities (2015XZZX004-04)
文摘In the interlayer expansion of the layered zeolite precursor COK-5, a Sn, salt, bis（2,4-pentanedionate）- dichlorotin [Sn（acac）2CL2], instead of a silylating agent was used to link the layers at 180 ℃. The obtained material, which is designed as Sn-COE-5, shows a shift of the first XRD reflection, which is very similar to that of COK-5 interlayer expanded with dichlorodimethylsilane （DCDMS）, indicating an increase in interlayer distance. X-ray diffraction （XRD）, N2 sorption isotherms, inductively coupled plasma （ICP）, and X-ray photo- electron spectroscopy （XPS） support the incorporation of isolated Sn sites in the sample. In the conversion of glucose to levulinic acid. Sn-COE-5 exhibits much higher activity than COK-5, which is due to the presence of Lewis acidic sites in the Sn-COE-5.
基金Project supported by the National Key R&D Program of China(2021YFB3503200)the Innovative Research Groups of the National Natural Science Foundation of China(51921004)+1 种基金Young Elite Scientists Sponsorship Program by CAST(2021QNRC001)the Key R&D project of Shandong Province(2021CXGC010703,2022CXGC020311)。
文摘Ce/BEA has great potential as a passive NO_(x)absorber(PNA)to reduce the NO_(x)emissions during the cold start phase especially in diesel engine for its high resistance to CO and suitable NO_(x)desorption temperature range.However,as a novel material,its physical and chemical properties still remain unknown.In this work,Ce/BEA was synthesized by ion-exchange method to identify the active species in NO_(x)adsorption,compared with aggregated Ce species in Ce/SiAlO_(x) prepared by impregnation method.X-ray diffraction(XRD),high resolution-transmission electron microscopy(HR-TEM)and aberration-corrected-scanning transmission electron microscopy(AC-STEM)were performed to confirm the isolated single atom formation of Ce species in Ce/BEA.UV-vis diffraction reflection spectra(DRS)and X-ray photoelectron spectroscopy(XPS)were conducted to find the difference of chemical environment between the isolated Ce species and aggregated ones.PNA performance evaluation and temperature programmed reduction of hydrogen(H_(2)-TPR)results show the high NO_(x)storage capacity and active oxygen species quantity in Ce/BEA.It is also found that the main NO_(x)adsorption species are Ce^(4+)-O^(∗)rather than Ce^(3+).NO_(x)-diffuse reflectance infrared Fourier transform spectroscopy(NO_(x)-DRIFTS)confirms that the bidentate nitrite species are the critical NO_(x)adsorption intermediates and the conception of NO_(x)adsorption and desorption processes is proposed.
基金supported by the National Natural Science Foundation of China(31500194 and U1202261)
文摘Natural hybridization frequently occurs in plants and can facilitate gene flow between species, possibly resulting in species refusion. However, various reproductive barriers block the formation of hybrids and maintain species integrity. Here, we conducted a field survey to examine natural hybridization and reproductive isolation （RI） between sympatric populations of Primula secundiflora and P. poissonii using ten nuclear simple sequence repeat （SSR） loci. Although introgressive hybridization occurred, species boundaries between P. secundiflora and P. poissonii were maintained through nearly complete reproductive isolation. These interfertite species provide an excellent model for studying the RI mechanisms and evolutionary forces that maintain species boundaries.
