The Amazon is one of the few continental regions where atmospheric aerosol particles and their effects on climate are not dominated by anthropogenic sources. During the wet season, the ambient conditions approach those of the pristine pre-industrial era. We show that the fine submicrometer particles accounting for most cloud condensation nuclei are predominantly composed of secondary organic material formed by oxidation of gaseous biogenic precursors. Supermicrometer particles, which are relevant as ice nuclei, consist mostly of primary biological material directly released from rainforest biota. The Amazon Basin appears to be a biogeochemical reactor, in which the biosphere and atmospheric photochemistry produce nuclei for clouds and precipitation sustaining the hydrological cycle. The prevailing regime of aerosol-cloud interactions in this natural environment is distinctly different from polluted regions.
Zhao X, Zhang L, Ma S, Gao W. Rate-distortion optimized transform for intra-frame coding, in Proceedings of the IEEE International Conference on Acoustics, Speech, and Signal Processing, ICASSP 2010, 14-19 March 2010, Sheraton Dallas Hotel, Dallas, Texas, USA.; 2010:1414–1417. 访问链接
Well-defined 3-dimensional architectures constitute the indispensable structural basis of the versatile, mind-boggling functions of biological macromolecules, such as proteins and nucleic acids. In the past few decades, diversified synthetic systems have been designed to mimic these biological entities in their capability of adopting such specific, higher order structures The relevant research field presents one of the most rapidly developing areas related to supramolecular chemistry The current contribution will focus on the most recent progress related to foldamers consisting of arylene ethynylene building blocks Some of the work features developing novel functions based on previously established arylene ethynylene folding systems, and others have designed and synthesized new arylene ethynylene foldable structures that aim to realize previously uncharted properties (C) 2010 Elsevier B.V. All rights reserved
Herein the recent experiments performed by the authors on fabricated multi walled BN nanotubes and monoatomic BN graphene like nanosheets are reviewed The re suits are presented in several sections namely (i) method for high yield synthesis of thin, defect free BN nanotubes of only a few layers, with external diameters below 10 nm, (ii) verification of BN nanotube piezoelectrical behavior and its electrically induced thermal decomposition under combined resistive heating and electrical charging in a transmission electron microscope, (iii) the first direct measurements of the true tensile strength and Young's modulus of BN nanotubes, using newly developed nanotensile tests inside an electron microscope, the measured values were found to be similar to 30 GPa and similar to 900 GPa, respectively, and (iv) diverse kinetic processes taking place within the prepared monoatomic BN sheets (so called "white graphenes") affiliated with intensive knock on B and N atom displacements under high energy electron beam irradiation in an aberration corrected medium voltage high resolution transmission electron microscope