Crystal and phase morphologies and structures determined by self-organization of crystalline-amorphous diblockcopolymers, crystallization of the crystallizable blocks, and vitrification of the amorphous blocks are rev...Crystal and phase morphologies and structures determined by self-organization of crystalline-amorphous diblockcopolymers, crystallization of the crystallizable blocks, and vitrification of the amorphous blocks are reviewed through asystematic study on a series of poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymers. On the base ofcompetitions among these three processes, molecular and supramolecular ordering in confined environments can beinvestigated. In a concentration-fluctuation-induced disordered (D_(CF)) diblock copolymer, the competition between crystalli-zation of the PEO blocks and vitrification of the PS blocks is momtored by time-resolved simultaneous small angle X-rayscattering (SAXS) and wide angle X-ray diffraction (WAXD) techniques. In the case of T_c<T_g^(PS-rich), the crystallization of thePEO blocks is observed to be confined within the bicontinuous D_(CF) phase due to the rapid vitrification of the PS-rich phase.Overall crystallization rate, crystal melting behavior, and crystallinity results further confirm the competition betweencrystallization and vitrification at different temperatures. In an ordered lamellar PEO-b-PS diblock copolymer, the crystalli-zation of the PEO blocks is completely confined within the ordered lamellae due to rapid vitrification of the PS layers asobserved by time-resolved SAXS and WAXD experiments. From the combined two-dimensional SAXS and WAXDmeasurements, the crystal orientation within the confined lamellar geometry is found parallel to the lamellar surface normalwhen it is isothermally crystallized at 35℃. In an ordered cylindrical PEO-b-PS sample, the crystallization of the PEO blocksis also observed to be confined within the ordered cylinders because of rapid vitrification of the PS matrix. The crystalorientation within the confined cylinders is found perpendicular to the cylinder axis as it is crystallized at 35℃.展开更多
Low molecular weight organic acids （LMWOAs） are prevalent on the earth＇s surface. They are vital intermediate products during metabolic pathways of organic matter and participate in the tricarboxylic acid cycle dur...Low molecular weight organic acids （LMWOAs） are prevalent on the earth＇s surface. They are vital intermediate products during metabolic pathways of organic matter and participate in the tricarboxylic acid cycle during life activities. Photochemical reactions are pivotal for LMWOAs＇ origination and play a large role in determining their diversity and their ultimate fate. Within the long time that organic matter is preserved in sediments, it can be decomposed and converted to release organic and inorganic pollutants as well as C, N, and P nutrients, which are of potential ecological risk in causing secondary pollution to lake water. The sediment pool is a comprehensive and complex compartment closely associated with overlying water by various biochemical processes, during which LMWOAs play critical roles to transport and transform elements. This article elucidates geochemical behaviors of LMWOAs in the surface environment in details, taking natural water, soil, and aerosol as examples, focusing on reviewing research developments on sources and characteristics, migration and mineralization of LMWOAs and relevant environmental effects. Simultaneously, this review article depicts the categories and contents of LMWOAs or their contribution to DOC in environmental media, and evaluates their importance during organic matter early diagenesis. Through concluding and discussing the conversion mechanisms and influencing factors, the next research orientations on LMWOAs in lake ecosystems are determined, mainly concerning relationships with hydrochemical parameters and microorganisms, and interactions with pollutants. This will enrich the knowledge on organic matter degradation and related environmental effects, and help reconstruct a theoretical framework for organic compound succession and influencing factors, providing basic data for lake eutrophication and ecological risk assessment, conducive to better control over water pollution and proper management of water quality.展开更多
Cryptococcus neoformans is an encapsulated yeast causing mainly opportunistic infections. DNA molecular typing techniques divided C. neoformans into four major molecular types (AFLP1/VNI, AFLP1A/VNB/VNII, AFLP1B/ VNII...Cryptococcus neoformans is an encapsulated yeast causing mainly opportunistic infections. DNA molecular typing techniques divided C. neoformans into four major molecular types (AFLP1/VNI, AFLP1A/VNB/VNII, AFLP1B/ VNII, AFLP3/VNIII, AFLP2/VNIV) characterized by different pathogenicity, geographical distribution and susceptibility to antifungal treatments. In this study 170 Italian C. neoformans clinical isolates (CI) and 32 environmental isolates (EI), collected and serotyped during a ten-year period (1985 to 1995), were genotyped using [GACA]4 microsatellite PCR fingerprinting. The molecular types were compared to their geographic distribution, specimen sources and patient’s risk factors. All four molecular types were described among the CI and only VNI and VNIV among the EI. VNIV molecular type was isolated with significant prevalence among the CI and VNI among the EI. A different geographical distribution of molecular types was detected: VNIV was the most prevalent in the North and Center of Italy;VNIII was isolated almost exclusively in the Center. No significant correlation among molecular types versus predisposing diseases or isolation sources was detected. The strains isolated from different body sites of the same patient (17 cases) were of the same genotype. Five out 9 cases relapsed with a different molecular type. This preliminary investigation shows a high intraspecies variability and reveals a nonhomogeneous distribution of C. neoformans molecular types in Italy.展开更多
The aim of this paper is to analyze the change in the active structure of lignite during the process of lowtemperature oxidation by constructing a molecular structure model for lignite. Using quantum computation combi...The aim of this paper is to analyze the change in the active structure of lignite during the process of lowtemperature oxidation by constructing a molecular structure model for lignite. Using quantum computation combined with experimental results of proximate analysis, ultimate analysis, Fourier transform infrared spectroscopy(FTIR) and X-ray photoelectron spectroscopy(XPS), a structural model for the large molecular structure was constructed. By analyzing the bond lengths in the model molecule, the evolution law for the active structure of lignite was predicted for the process of low-temperature oxidation. In low-temperature oxidation,alkanes and hydroxyls are the primary active structures observed in lignite, though ether may also react. These active functional groups react with oxygen to release heat, thereby speeding up the reaction between coal and oxygen. Finally, the content of various functional groups in the process of lignite low-temperature oxidation was analyzed by infrared analysis, and the accuracy of the model was verified.展开更多
文摘Crystal and phase morphologies and structures determined by self-organization of crystalline-amorphous diblockcopolymers, crystallization of the crystallizable blocks, and vitrification of the amorphous blocks are reviewed through asystematic study on a series of poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymers. On the base ofcompetitions among these three processes, molecular and supramolecular ordering in confined environments can beinvestigated. In a concentration-fluctuation-induced disordered (D_(CF)) diblock copolymer, the competition between crystalli-zation of the PEO blocks and vitrification of the PS blocks is momtored by time-resolved simultaneous small angle X-rayscattering (SAXS) and wide angle X-ray diffraction (WAXD) techniques. In the case of T_c<T_g^(PS-rich), the crystallization of thePEO blocks is observed to be confined within the bicontinuous D_(CF) phase due to the rapid vitrification of the PS-rich phase.Overall crystallization rate, crystal melting behavior, and crystallinity results further confirm the competition betweencrystallization and vitrification at different temperatures. In an ordered lamellar PEO-b-PS diblock copolymer, the crystalli-zation of the PEO blocks is completely confined within the ordered lamellae due to rapid vitrification of the PS layers asobserved by time-resolved SAXS and WAXD experiments. From the combined two-dimensional SAXS and WAXDmeasurements, the crystal orientation within the confined lamellar geometry is found parallel to the lamellar surface normalwhen it is isothermally crystallized at 35℃. In an ordered cylindrical PEO-b-PS sample, the crystallization of the PEO blocksis also observed to be confined within the ordered cylinders because of rapid vitrification of the PS matrix. The crystalorientation within the confined cylinders is found perpendicular to the cylinder axis as it is crystallized at 35℃.
基金financially supported by the National Natural Sciences Foundation of China(No.41373138,41003055,41261140337)the National Science and Technology Major Special Project(No.2011ZX07212-007)State Key Laboratory of Environmental Geochemistry(No.SKLEG2013404),Institute of geochemistry, Chinese Academy of Sciences
文摘Low molecular weight organic acids （LMWOAs） are prevalent on the earth＇s surface. They are vital intermediate products during metabolic pathways of organic matter and participate in the tricarboxylic acid cycle during life activities. Photochemical reactions are pivotal for LMWOAs＇ origination and play a large role in determining their diversity and their ultimate fate. Within the long time that organic matter is preserved in sediments, it can be decomposed and converted to release organic and inorganic pollutants as well as C, N, and P nutrients, which are of potential ecological risk in causing secondary pollution to lake water. The sediment pool is a comprehensive and complex compartment closely associated with overlying water by various biochemical processes, during which LMWOAs play critical roles to transport and transform elements. This article elucidates geochemical behaviors of LMWOAs in the surface environment in details, taking natural water, soil, and aerosol as examples, focusing on reviewing research developments on sources and characteristics, migration and mineralization of LMWOAs and relevant environmental effects. Simultaneously, this review article depicts the categories and contents of LMWOAs or their contribution to DOC in environmental media, and evaluates their importance during organic matter early diagenesis. Through concluding and discussing the conversion mechanisms and influencing factors, the next research orientations on LMWOAs in lake ecosystems are determined, mainly concerning relationships with hydrochemical parameters and microorganisms, and interactions with pollutants. This will enrich the knowledge on organic matter degradation and related environmental effects, and help reconstruct a theoretical framework for organic compound succession and influencing factors, providing basic data for lake eutrophication and ecological risk assessment, conducive to better control over water pollution and proper management of water quality.
文摘Cryptococcus neoformans is an encapsulated yeast causing mainly opportunistic infections. DNA molecular typing techniques divided C. neoformans into four major molecular types (AFLP1/VNI, AFLP1A/VNB/VNII, AFLP1B/ VNII, AFLP3/VNIII, AFLP2/VNIV) characterized by different pathogenicity, geographical distribution and susceptibility to antifungal treatments. In this study 170 Italian C. neoformans clinical isolates (CI) and 32 environmental isolates (EI), collected and serotyped during a ten-year period (1985 to 1995), were genotyped using [GACA]4 microsatellite PCR fingerprinting. The molecular types were compared to their geographic distribution, specimen sources and patient’s risk factors. All four molecular types were described among the CI and only VNI and VNIV among the EI. VNIV molecular type was isolated with significant prevalence among the CI and VNI among the EI. A different geographical distribution of molecular types was detected: VNIV was the most prevalent in the North and Center of Italy;VNIII was isolated almost exclusively in the Center. No significant correlation among molecular types versus predisposing diseases or isolation sources was detected. The strains isolated from different body sites of the same patient (17 cases) were of the same genotype. Five out 9 cases relapsed with a different molecular type. This preliminary investigation shows a high intraspecies variability and reveals a nonhomogeneous distribution of C. neoformans molecular types in Italy.
基金Supported by the Fundamental Research Funds for the Central Universities(2017XKQY066)
文摘The aim of this paper is to analyze the change in the active structure of lignite during the process of lowtemperature oxidation by constructing a molecular structure model for lignite. Using quantum computation combined with experimental results of proximate analysis, ultimate analysis, Fourier transform infrared spectroscopy(FTIR) and X-ray photoelectron spectroscopy(XPS), a structural model for the large molecular structure was constructed. By analyzing the bond lengths in the model molecule, the evolution law for the active structure of lignite was predicted for the process of low-temperature oxidation. In low-temperature oxidation,alkanes and hydroxyls are the primary active structures observed in lignite, though ether may also react. These active functional groups react with oxygen to release heat, thereby speeding up the reaction between coal and oxygen. Finally, the content of various functional groups in the process of lignite low-temperature oxidation was analyzed by infrared analysis, and the accuracy of the model was verified.
