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Conductivity as a Sensor for Monitoring Relative Magnesium Corrosion Rates in Real‐time,in Serum‐containing Media under Cell Culture Conditions 下载免费PDF全文
Kolade Ojo Tracy Hopkins Madhura Joshi Pravahan Salunke Guangqi Zhang Keaton Nahan Zhannping Zhang Daoli Zhao Sarah K. Pixley Vesselin Shanov William R. Heineman 《Electroanalysis》2016,28(12):3000-3008
Because controlling the corrosion rate of magnesium metal will be crucial to the success of biomedical implants containing pure magnesium or magnesium alloys, many ways have been sought to improve in vitro tests to analyze corrosion rates, and also to identify new methods of preparing or post‐processing magnesium. In this work, for an in vitro assay, we explored the use of a commercially available conductivity sensor to study magnesium corrosion under cell culture conditions that duplicate many physiologically appropriate parameters. With this sensor, we studied the corrosion of two previously untested magnesium single crystal samples that differed in surface treatments that could alter corrosion rates. The results show that the relative conductivity changes in (mS/cm) over the total time of immersion were proportional to the corrosion rates in (mm/y) and also to the total magnesium released, as detected by inductively coupled plasma mass spectrometry (ICP‐MS). 相似文献
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We prove the existence of smooth positive potentials V(t, x), periodic in time and with compact support in x, for which the Cauchy problem for the wave equation utt ? Δxu + V(t, x)u = 0 has solutions with exponentially growing global and local energy. Moreover, we show that there are resonances, z ∈ ?, |z| > 1, associated to V(t, x). © 2008 Wiley Periodicals, Inc. 相似文献
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The glass transition temperature (Tg), density, refractive index, Raman scattering spectra, and X-ray photoelectron spectra (XPS) for xZnO-yBi2O3-zB2O3 glasses (x=10-65, y=10-50, z=25-60 mol%) are measured to clarify the bonding and structure features of the glasses with large amounts of ZnO. The average electronic polarizability of oxide ions (αO2−) and optical basicity (Λ) of the glasses estimated using Lorentz-Lorenz equation increase with increasing ZnO or Bi2O3 content, giving the values of αO2−=1.963 Å3 and Λ=0.819 for 60ZnO-10Bi2O3-30B2O3 glass. The formation of BOBi and BOZn bridging bonds in the glass structure is suggested from Raman and XPS spectra. The average single bond strength (BMO) proposed by Dimitrov and Komatsu is applied to the glasses and is calculated using single bond strengths of 150.6 kJ/mol for ZnO bonds in ZnO4 groups, 102.5 kJ/mol for BiO bonds in BiO6 groups, 498 kJ/mol for BO bonds in BO3 groups, and 373 kJ/mol for BO bonds in BO4 groups. Good correlations are observed between Tg and BMO, Λ and BMO, and Tg and Λ, proposing that the average single bond strength is a good parameter for understanding thermal and optical properties of ZnOBi2O3B2O3 glasses. 相似文献
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We prove that Gotzmann's Persistence Theorem holds over every Clements–Lindström ring. We also construct the infinite minimal free resolution of a square-free Borel ideal over such a ring. 相似文献
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Keaton S. Nahan Noe Alvarez Vesselin Shanov Anne Vonderheide 《Journal of the American Society for Mass Spectrometry》2017,28(11):2408-2413
Mass spectrometry continues to tackle many complicated tasks, and ongoing research seeks to simplify its instrumentation as well as sampling. The desorption electrospray ionization (DESI) source was the first ambient ionization source to function without extensive gas requirements and chromatography. Electrospray techniques generally have low efficiency for ionization of nonpolar analytes and some researchers have resorted to methods such as direct analysis in real time (DART) or desorption atmospheric pressure chemical ionization (DAPCI) for their analysis. In this work, a carbon nanotube fiber ionization (nanoCFI) source was developed and was found to be capable of solid phase microextraction (SPME) of nonpolar analytes as well as ionization and sampling similar to that of direct probe atmospheric pressure chemical ionization (DP-APCI). Conductivity and adsorption were maintained by utilizing a corona pin functionalized with a multi-walled carbon nanotube (MWCNT) thread. Quantitative work with the nanoCFI source with a designed corona discharge pin insert demonstrated linearity up to 0.97 (R2) of three target PAHs with phenanthrene internal standard. 相似文献
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We study a class of third-order effectively hyperbolic operators P in G={(t,x):0?t?T,x∈U?Rn} with triple characteristics at ρ=(0,x0,ξ),ξ∈Rn?{0}. V. Ivrii introduced the conjecture that every effectively hyperbolic operator is strongly hyperbolic , that is the Cauchy problem for P+Q is locally well posed for any lower-order terms Q. For operators with triple characteristics, this conjecture was established [3] in the case when the principal symbol of P admits a factorization as a product of two symbols of principal type. A strongly hyperbolic operator in G could have triple characteristics in G only for t=0 or for t=T. The operators that we investigate have a principal symbol which in general is not factorizable and we prove that these operators are strongly hyperbolic if T is small enough. 相似文献