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101.
Mark E. Erupe Allegra Liberman-Martin Philip J. Silva Quentin G.J. Malloy Naomi Yonis David R. Cocker III Kathleen L. Purvis-Roberts 《Journal of chromatography. A》2010,1217(13):2070-2073
An ion chromatography method with non-suppressed conductivity detection was developed for the simultaneous determination of methylamines (methylamine, dimethylamine, trimethylamine) and trimethylamine-N-oxide in particulate matter air samples. The analytes were well separated by means of cation-exchange chromatography using a 3 mM nitric acid/3.5% acetonitrile (v/v) eluent solution and a Metrosep C 2 250 (250 mm × 4 mm i.d.) separation column. The effects of the different chromatographic parameters on the separation were also investigated. Detection limits of methylamine, dimethylamine, trimethylamine, and trimethylamine-N-oxide were 43, 46, 76 and 72 μg/L, respectively. The relative standard deviations of the retention times were between 0.42% and 1.14% while the recoveries were between 78.8% and 88.3%. The method is suitable for determining if methylamines and trimethylamine-N-oxide are a significant component of organic nitrogen aerosol in areas with high concentration of these species. 相似文献
102.
Accurate size measurement during nanoparticle production is essential for the continuing innovation, quality and safety of
nano-enabled products. Size measurement by analysing a number of separate particles individually has particular advantages
over ensemble methods. In the latter case nanoparticles have to be well dispersed in a fluid and changes that may occur during
analysis, such as agglomeration and degradation, will not be detected which could lead to misleading results. Atomic force
microscopy (AFM) allows imaging of particles both in air and liquid, however, the strong interactions between the probe and
the particle will cause the broadening of the lateral dimension in the final image. In this paper a new procedure to measure
the size of spherical nanoparticles from AFM images via vertical height measurement is described. This procedure will quickly
analyse hundred of particles simultaneously and reproduce the measurements obtained from electron microscopy (EM). Nanoparticles
samples that were difficult, if not impossible, to analyse with EM were successfully measured using this method. The combination
of this procedure with the use of a metrological AFM moves closer to true traceable measurements of nanoparticle dispersions. 相似文献
103.
N.-C. Yeh M.-L. Teague S. Yeom B.L. Standley R.T.-P. Wu D.A. Boyd M.W. Bockrath 《Surface science》2011,605(17-18):1649-1656
Atomically resolved imaging and spectroscopic characteristics of graphene grown by chemical vapor deposition (CVD) on copper are investigated by means of scanning tunneling microscopy and spectroscopy (STM/STS). For CVD-grown graphene remaining on the copper substrate, the monolayer carbon structures exhibit ripples and appear strongly strained, with different regions exhibiting different lattice structures and electronic density of states (DOS). In particular, ridges appear along the boundaries of different lattice structures, which exhibit excess charging effects. Additionally, the large and non-uniform strain induces pseudo-magnetic field up to ~ 50 T, as manifested by the DOS peaks at quantized energies that correspond to pseudo-magnetic field-induced integer and fractional Landau levels. In contrast, for graphene transferred from copper to SiO2 substrates after the CVD growth, the average strain on the whole diminishes, so do the corresponding charging effects and pseudo-magnetic fields except for sample areas near topological defects. These findings suggest feasible nano-scale “strain engineering” of the electronic states of graphene by proper design of the substrates and growth conditions. 相似文献
104.
105.
J.P. Boyd 《Applied Mathematics Letters》1998,11(6):27-31
W(z) is defined implicitly as the root of W exp(W) = z. It is shown that a simple analytic approximation has a relative error of less than 5% over the whole domain z ε [−exp(−1), ∞] of the principle branch—sufficiently accurate so that four Newton iterations refine this approximation to a relative error smaller than 1.E-12. As a second form of global approximation, the W-function is expanded as a series of rational Chebyshev functions TBj in a shifted, logarithmic coordinate with an error that decreases exponentially fast with the series truncation. 相似文献
106.
Naomi Zeitouni 《Natural Resource Modeling》1991,5(3):293-320
This work develops a theoretical framework that considers the pollution transport in groundwater in an optimization of social benefits from a groundwater resource, and provides a spatial and temporal allocation of the use of contaminating inputs. A space dependent social cost function is constructed, taking into account factors such as the wells' locations and emitting firms' locations, in addition to profits from polluting activities. The social optimization is formulated using the pollution concentrations as state variables and the pollution transport as state dynamics. This optimization yields a spatially differentiated shadow price which leads to optimal policy which is nonuniform in general, and uniform only for special cases. 相似文献
107.
We introduce the classes of locally convex spaces with the local Dunford-Pettis property and locally dual Schur spaces. We
examine their properties and their relationship to other classes of locally convex spaces. In the class of locally convex
spaces with the local Dunford-Pettis property all polynomials are weakly sequentially continuous whereas in the class of locally
dual Schur spaces all polynomials are weakly continuous on bounded sets. 相似文献
108.
We introduce the classes of locally convex spaces with the local Dunford-Pettis property and locally dual Schur spaces. We
examine their properties and their relationship to other classes of locally convex spaces. In the class of locally convex
spaces with the local Dunford-Pettis property all polynomials are weakly sequentially continuous whereas in the class of locally
dual Schur spaces all polynomials are weakly continuous on bounded sets.
Research supported by Science Foundation Ireland, Basic Research Grant 2004. 相似文献
109.
110.
We report results from particle-in-cell simulations of the interaction of intense laser light with overdense plasma designed to examine the effects of plasma waves generated by pulses of fast electrons on high-order harmonic emission from the plasma. We show that the emission spectrum is modulated at the plasma frequency and identify combinations of parameters and circumstances favorable for modulation. In particular, the observed modulation is shown to depend not only on the chosen plasma electron density and intensity of the incident light but on the density profile and pulse shape. 相似文献