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EP Sheretov VS Gurov MV Dubkov OV Korneeva 《Rapid communications in mass spectrometry : RCM》1999,13(16):1699-1702
In this article we compare the classical monopole mass filter of von Zahn and the monopole mass filter with a hyperbolic V-shaped electrode. The experimental results and those of computer simulation for both mass spectrometers are presented. We show that the replacement of a conventional 90 degrees V-shaped electrode by an electrode with a hyperbolic profile substantially improves the peak shape of any given mass, and increases the mass resolution by a factor of 3-4 and the abundance sensitivity by a factor of 100. The potential of high analytical performance combined with electroforming techniques for electrode manufacture indicate future practical uses of such instruments. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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Giordanino MV Strauch SM Villafañe VE Helbling EW 《Journal of photochemistry and photobiology. B, Biology》2011,103(1):68-77
During the late austral spring of 2009 we carried out experiments (4days of duration) with four cyanobacteria species, Anabaena sp., Nostoc sp., Arthrospira platensis and Microcystis sp., to assess the combined effects of temperature and solar radiation on photosynthesis performance and morphology. Two experimental temperatures (18°C and 23°C, simulating a 5°C increase under a scenario of climate change) and three radiation treatments (by using different filters/materials) were implemented: (i) P (PAR, 400-700nm), (ii) PA (PAR+UV-A, 320-700nm) and, (iii) PAB (PAR+UV-A+UV-B, 280-700nm). In general, samples under the P treatment had less decrease/higher recovery rates of effective photochemical quantum yield (Y) than those receiving UV-A or UV-A+UV-B. The effects of increased temperature were species-specific: At the end of the experiments, it was seen that increased temperature benefited photosynthetic performance of Anabaena sp. and Nostoc sp. but not of Microcystis sp. and A. platensis. Higher temperature was also associated to an increase in the chain area of Anabaena sp., and to bigger trichomes in A. platensis; however, no morphological effects were observed in Microcystis sp. In addition, in Nostoc sp. the increase in temperature counteracted the UVR impact on the reduction of the chain area. How these effects and mechanisms will affect the trophodynamics and production of aquatic ecosystems is still uncertain, but the specificity of the responses suggests that not all cyanobacteria would be equally benefited by temperature increases therefore affecting the balance and interaction among species in the water column. 相似文献
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E. Borfecchia K. A. Lomachenko F. Giordanino H. Falsig P. Beato A. V. Soldatov S. Bordiga C. Lamberti 《Chemical science》2015,6(1):548-563
Cu-SSZ-13 is a highly active NH3-SCR catalyst for the abatement of harmful nitrogen oxides (NOx, x = 1, 2) from the exhausts of lean-burn engines. The study of Cu-speciation occurring upon thermal dehydration is a key step for the understanding of the enhanced catalytic properties of this material and for identifying the SCR active sites and their redox capability. Herein, we combined FTIR, X-ray absorption (XAS) and emission (XES) spectroscopies with DFT computational analysis to elucidate the nature and location of the most abundant Cu sites in the activated catalyst. Different Cu species have been found to be dominant as a function of the dehydration temperature and conditions. Data analysis revealed that the dehydration process of Cu cations is essentially completed at 250 °C, with the formation of dehydrated [CuOH]+ species hosted in close proximity to 1-Al sites in both d6r and 8r units of the SSZ-13 matrix. These species persist at higher temperatures only if a certain amount of O2 is present in the gas feed, while under inert conditions they undergo virtually total “self-reduction” as a consequence of an OH extra-ligand loss, resulting in bi-coordinated bare Cu+ cations. Synchrotron characterization supported by computational analysis allowed an unprecedented quantitative refinement of the local environment and structural parameters of these Cu(ii) and Cu(i) species. 相似文献
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DC magnetization, neutron depolarization and neutron diffraction (with both polarized and unpolarized neutrons) measurements
have been reported for the Co1.1−x
Zn
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Ge0.1Fe1.2O1 spinels with x=0.5, 0.6 and 0.7. Neutron depolarization and neutron diffraction measurements confirm the presence of a long range ferrimagnetic
ordering of the local canted spins in these ferrite samples. The observed features of low field magnetization have been explained
under the framework of thermally activated domain wall movement of ferrimagnetic arrangement of local canted spins. An important
role of magnetic anisotropy (due to the presence of Co2+ ions) in establishing the magnetic ordering and domain kinetics in these ferrites has been observed. 相似文献
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Eilertsen EA Giordanino F Lamberti C Bordiga S Damin A Bonino F Olsbye U Lillerud KP 《Chemical communications (Cambridge, England)》2011,47(43):11867-11869
A new zeotype titanium silicate oxidation catalyst with the STT topology has been synthesized from direct synthesis. Ti-STT has a microporous structure with small pore openings, allowing shape selective oxidation catalysis. The isomorphous substitution of Si by Ti in the framework has been confirmed by Raman, FT-IR, UV-VIS and XANES spectroscopies. 相似文献
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MV Muftakhov YV Vasil'ev VA Mazunov 《Rapid communications in mass spectrometry : RCM》1999,13(12):1104-1108
Appearance energies of [M-H](-) ions from carbonyl compounds R-CO-R' (R,R' = H, CH(3), NH(2), OH) have been measured by means of negative ion mass spectrometry in resonant electron capture mode. Values of electron affinity of the corresponding radicals, CH(2)&dbond;C(X)O, NH&dbond;C(X)O and O&dbond;C(X)O, have been determined. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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