| 1. |
- Li, Yu, et al.
(författare)
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Spectroscopic characterization of aluminum plasma using laser-induced breakdown spectroscopy
- 2014
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Ingår i: Optik. - : Elsevier BV. - 0030-4026. ; 125:12, s. 2851-2855
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Tidskriftsartikel (refereegranskat)abstract
- A detailed investigation of aluminum plasma induced by a 1064 nm Nd:YAG laser in air was performed. The emission of spectral lines arising from Al I transition at 396.07 nm, Al II transition at 358.46 nm, Al Ill transition at 360.72 nm and Al IV transition at 363.05 nm were well-resolved. The plasma parameters including electron temperature and electron density were determined through the Boltzmann plot method using the emission line intensities of the same ionized stages of aluminum atoms and the Stark-broadening profiles of Al II emission line, respectively. The temporal evolutions of the spectral lines belonging to atomic and ionic aluminum elements and the plasma parameters were investigated at three different laser pulse energies. Moreover, the validity of local thermodynamic equilibrium was elucidated in our experimental condition. (c) 2014 Elsevier GmbH. All rights reserved.
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| 2. |
- Gao, Tao, et al.
(författare)
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Pdx1 Maintains beta Cell Identity and Function by Repressing an alpha Cell Program
- 2014
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Ingår i: Cell Metabolism. - : Elsevier BV. - 1550-4131 .- 1932-7420. ; 19:2, s. 259-271
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Tidskriftsartikel (refereegranskat)abstract
- Pdx1 is a homeobox-containing transcription factor that plays a key role in pancreatic development and adult beta cell function. In this study, we traced the fate of adult beta cells after Pdx1 deletion. As expected, beta-cell-specific removal of Pdx1 resulted in severe hyperglycemia within days. Surprisingly, a large fraction of Pdx1-deleted cells rapidly acquired ultrastructural and physiological features of a cells, indicating that a robust cellular reprogramming had occurred. Reprogrammed cells exhibited a global transcriptional shift that included derepression of the alpha cell transcription factor MafB, resulting in a transcriptional profile that closely resembled that of alpha cells. These findings indicate that Pdx1 acts as a master regulator of beta cell fate by simultaneously activating genes essential for beta cell identity and repressing those associated with alpha cell identity. We discuss the significance of these findings in the context of the emerging notion that loss of beta cell identity contributes to the pathogenesis of type 2 diabetes.
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| 3. |
- Garcia-Martinez, Javier, et al.
(författare)
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Evidence of Intracrystalline Mesostructured Porosity in Zeolites by Advanced Gas Sorption, Electron Tomography and Rotation Electron Diffraction
- 2014
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Ingår i: ChemCatChem. - : Wiley. - 1867-3880 .- 1867-3899. ; 6:11, s. 3110-3115
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Tidskriftsartikel (refereegranskat)abstract
- The small size of micropores (typically <1 nm) in zeolites causes slow diffusion of reactant and product molecules in and out of the pores and negatively impacts the product selectivity of zeolite based catalysts, for example, fluid catalytic cracking (FCC) catalysts. Size-tailored mesoporosity was introduced into commercial zeolite Y crystals by a simple surfactant-templating post-synthetic mesostructuring process. The resulting mesoporous zeolite Y showed significantly improved product selectivity in both laboratory testing and refinery trials. Advanced characterization techniques such as electron tomography, three-dimensional rotation electron diffraction, and high resolution gas adsorption coupled with hysteresis scanning and density functional theory, unambiguously revealed the intracystalline nature and connectivity of the introduced mesopores. They can be considered as molecular highways that help reactant and product molecules diffuse quickly to and away from the catalytically active sites within the zeolite crystals and, thus, shift the selectivity to favor the production of more of the valuable liquid fuels at reduced yields of coke and unconverted feed.
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