The article discusses a method for determining the atomic fraction of isotopes in boron trifluoride, boron carbide, boron anhydride, ferroboron and boric acid, by converting them into potassium tetrafluoroborate. This...The article discusses a method for determining the atomic fraction of isotopes in boron trifluoride, boron carbide, boron anhydride, ferroboron and boric acid, by converting them into potassium tetrafluoroborate. This compound is then analyzed using the spectrometric electron bombardment method. This technique is known for its high accuracy and “self-verifying” capabilities, meaning that the mass fraction of isotopes can be calculated using different mass lines, allowing for the identification of any potential errors.展开更多
Humic substances constitute the major organic fractions of soils, sediments and natural waters, and play a dominant role in the binding, mobilization, transport and ultimate fate of organic contaminants in subsurface ...Humic substances constitute the major organic fractions of soils, sediments and natural waters, and play a dominant role in the binding, mobilization, transport and ultimate fate of organic contaminants in subsurface systems. In this paper, two humic acid samples, Guanting and Tianjin, with different origin and chemical compositions have been investigated with AFM imaging for their adsorption and aggregation behaviors on mica. While the Tianjin humic sample is found to form small spheres with 250 to 330 nm in diameter at lower concentrations, irregular loop-chain assemblies of hundreds of nanometer in diameter with the chain width of about 40 nm are dominant for the Guanting humic sample, which may attribute to the more polar aliphatic fractions in the chemical composition in the latter. The heterogeneous and polydisperse nature of humic substances with multiple structural features, such as sponge-like structures, perforated sheets, aggregate of spheres, branches and chain-like assemblies etc., is apparent at higher concentrations for both humic samples, showing morphologically new evidence for the dominant view of the humic dual-mode sorption model. With naphthalene introduced, the assemblies of Guanting humic substances clearly become more compact with significantly narrowed branches and less porous the perforated sheet-like structures. It is indica- tive of that smaller nanometer scale rings present along the perforated assemblies could potentially represent hydrophobic domains, which may facilitate the adsorption and aggregation of naphthalene onto the natural particle surfaces and therefore lead to an important role of dissolved humic sub- stances in the sorption of environmental pollutants.展开更多
The author thinks that the endless and timeless Universe is a permanent substance and energy flow as well as motion of celestial systems and bodies. Celestial bodies may have physical and biological life. Our Earth ha...The author thinks that the endless and timeless Universe is a permanent substance and energy flow as well as motion of celestial systems and bodies. Celestial bodies may have physical and biological life. Our Earth has both lives which can be divided into different periods of time. Its physical life can mainly be characterized by the atomic evolution, sterility, appearance of water and abiotic chemical reactions. Essence of the biological life is the existence of the living unit. Biological life of our Globe started with the first living unit/microorganism which began to influence on its environment which is a closed system for substance, flora, creature and man but not for hit of celestial bodies and for arrival of different kinds of energy from the space as well as for radiation of heat. The biological life of our Earth can be divided into four parts: before photosynthesis, before mankind, before 1778 and after the industrial revolution.展开更多
文摘The article discusses a method for determining the atomic fraction of isotopes in boron trifluoride, boron carbide, boron anhydride, ferroboron and boric acid, by converting them into potassium tetrafluoroborate. This compound is then analyzed using the spectrometric electron bombardment method. This technique is known for its high accuracy and “self-verifying” capabilities, meaning that the mass fraction of isotopes can be calculated using different mass lines, allowing for the identification of any potential errors.
基金This research was supported by the National Natural Science Foundation of China (Grant Nos. 20037010 and 20277042).
文摘Humic substances constitute the major organic fractions of soils, sediments and natural waters, and play a dominant role in the binding, mobilization, transport and ultimate fate of organic contaminants in subsurface systems. In this paper, two humic acid samples, Guanting and Tianjin, with different origin and chemical compositions have been investigated with AFM imaging for their adsorption and aggregation behaviors on mica. While the Tianjin humic sample is found to form small spheres with 250 to 330 nm in diameter at lower concentrations, irregular loop-chain assemblies of hundreds of nanometer in diameter with the chain width of about 40 nm are dominant for the Guanting humic sample, which may attribute to the more polar aliphatic fractions in the chemical composition in the latter. The heterogeneous and polydisperse nature of humic substances with multiple structural features, such as sponge-like structures, perforated sheets, aggregate of spheres, branches and chain-like assemblies etc., is apparent at higher concentrations for both humic samples, showing morphologically new evidence for the dominant view of the humic dual-mode sorption model. With naphthalene introduced, the assemblies of Guanting humic substances clearly become more compact with significantly narrowed branches and less porous the perforated sheet-like structures. It is indica- tive of that smaller nanometer scale rings present along the perforated assemblies could potentially represent hydrophobic domains, which may facilitate the adsorption and aggregation of naphthalene onto the natural particle surfaces and therefore lead to an important role of dissolved humic sub- stances in the sorption of environmental pollutants.
文摘The author thinks that the endless and timeless Universe is a permanent substance and energy flow as well as motion of celestial systems and bodies. Celestial bodies may have physical and biological life. Our Earth has both lives which can be divided into different periods of time. Its physical life can mainly be characterized by the atomic evolution, sterility, appearance of water and abiotic chemical reactions. Essence of the biological life is the existence of the living unit. Biological life of our Globe started with the first living unit/microorganism which began to influence on its environment which is a closed system for substance, flora, creature and man but not for hit of celestial bodies and for arrival of different kinds of energy from the space as well as for radiation of heat. The biological life of our Earth can be divided into four parts: before photosynthesis, before mankind, before 1778 and after the industrial revolution.
