Determination of Heavy Metal Ions in Tobacco and Tobacco Additives

This paper describes a new method for the simultaneous determination of heavy metal ions in tobacco and tobacco additives by microcolumn high-performance liquid chromatography. The samples were digested by microwave digestion. The lead, cadmium, mercury, nickel, cobalt and tin ions in the digested samples were pre-column derivatized with tetra-(o-aminophenyl)- porphyrin (To-APP) to form coloured chelates. The Hg-To-APP, Cd-To-APP, Pb-To-APP, Ni-To-APP, Co-To-APP and Sn-To-APP chelates were enriched by solid phase extraction with a C18 cartridge resulting in an enrichment factor of 50. The chelates were separated on aWaters Xterra™ RP18 microcolumn (50mm×1.0 mm, 2.5 μm) with a mixture of methanol-tetrahydrofuran (95:5, v/v, containing 0.05 mol L–1 pyrrolidine-acetic acid buffer salt, pH=10.0) as mobile phase at a flow rate of 0.2 mL min–1 and identified with a photodiode array detector at 350–600 nm. The metal chelates were fully separated in 2.0 min. The detection limits for lead, cadmium, mercury, nickel, cobalt and tin in the original digested samples were 4 ng L–1, 3 ngL–1, 6 ngL–1, 5 ngL–1, 5 ngL–1 and 4 ng L–1, respectively. The relative standard deviation for five replicate samples was 2.65~3.24%. The standard recoveries were 95.6~108%. The method was applied with good results to the determination of lead, cadmium, mercury, nickel, cobalt and tin in tobacco and tobacco additives.KEYWORDS: Microcolumn high-performance liquid chromatography, tetra-(o-aminophenyl)-porphyrin, heavy metal ions

Near-infrared Spectral Characterization of Solar-type Stars in the Northern Hemisphere

Although solar-analog stars have been studied extensively over the past few decades, most of these studies have focused on visible wavelengths, especially those identifying solar-analog stars to be used as calibration tools for observations. As a result, there is a dearth of well-characterized solar analogs for observations in the near-infrared, a wavelength range important for studying solar system objects. We present 184 stars selected based on solar-like spectral type and V-J and V-K colors whose spectra we have observed in the 0.8-4.2 micron range for calibrating our asteroid observations. Each star has been classified into one of three ranks based on spectral resemblance to vetted solar analogs. Of our set of 184 stars, we report 145 as reliable solar-analog stars, 21 as solar analogs usable after spectral corrections with low-order polynomial fitting, and 18 as unsuitable for use as calibration standards owing to spectral shape, variability, or features at low to medium resolution. We conclude that all but 5 of our candidates are reliable solar analogs in the longer wavelength range from 2.5 to 4.2 microns. The average colors of the stars classified as reliable or usable solar analogs are V-J=1.148, V-H=1.418, and V-K=1.491, with the entire set being distributed fairly uniformly in R.A. across the sky between -27 and +67 degrees in decl.Comment: 19 pages, 8 figures, 2 table

Probabilistic solution of random homogeneous linear second-order difference equations

This paper deals with the computation of the first probability density function of the solution of random homogeneous linear second-order difference equations by the Random Variable Transformation method. This approach allows us to generalize the classical solution obtained in the deterministic scenario. Several illustrative examples are provided.This work was sponsored by "Ministerio de Economa y Competitividad" of the Spanish Government in the frame of the Project with Reference TRA2012-36932.Casabán Bartual, MC.; Cortés López, JC.; Romero Bauset, JV.; Roselló Ferragud, MD. (2014). Probabilistic solution of random homogeneous linear second-order difference equations. Applied Mathematics Letters. 34:27-32. https://doi.org/10.1016/j.aml.2014.03.010S27323

Lattice Monte Carlo simulation of thermal conductivity in composite materials

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.This paper addresses the numerical simulation of thermal conductivity of composite material. A Lattice Monte Caro method is used in the analysis of two-dimensional two component models with different inclusions, including circular inclusion, elliptical inclusion, square inclusion, random generated circular inclusions. Through simulation on these models, relationships among phase fraction of low conductivity phase (B phase), ratio of thermal conductivities of two phases (B and A) and relative effective thermal conductivities are obtained. Also, thermal conductivity of porous silicon with porosity of 26% is predicted and excellent agreements are achieved when compared with experimental results. Finally, research on thermal conductivity of sintered porous nickel is carried out. Microstructure image which is obtained with scanning electron microscope (SEM) is digitized by image processing method. The results exhibit a good agreement with experimental results in literature.cf201

Thermophysical Characterization of Potential Spacecraft Target (101955) 1999 RQ36

We report on thermal emission measurements of 1999 RQ36 from Spitzer. The derived size is in agreement with radar measurements, and we find a moderately high thermal inertia and homogeneous surface properties

Synthesis of size-tunable polymeric nanoparticles enabled by 3D hydrodynamic flow focusing in single-layer microchannels

Author Manuscript date: 2011 June 27A versatile microfluidic platform to synthesize NPs by nanoprecipitation using 3D hydrodynamic flow focusing isolates the precipitating precursors from channel walls, eliminating fouling of the channels. It is shown that this new method enables robust nanoprecipitation without polymer aggregation, regardless of the polymer molecular weight or precursor concentration implemented, where the size of the resulting polymeric NPs is tunable.David H. Koch (Prostate Cancer Foundation Award in Nanotherapeutics)National Institutes of Health (U.S.) (Grant CA119349)National Science Foundation (U.S.) (Graduate Research Fellowship