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- Jiang, A., et al.
(författare)
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Theoretical study of the thermal behaviour of free and alumina-supported Fe-C nanoparticles
- 2007
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 75:20
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Tidskriftsartikel (refereegranskat)abstract
- The thermal behavior of free and alumina-supported iron-carbon nanoparticles is investigated via molecular-dynamics simulations, in which the effect of the substrate is treated with a simple Morse potential fitted to ab initio data. We observe that the presence of the substrate raises the melting temperature of medium and large Fe1-xCx nanoparticles (x=0-0.16, N=80-1000, nonmagic numbers) by 40-60 K; it also plays an important role in defining the ground state of smaller Fe nanoparticles (N=50-80). The main focus of our study is the investigation of Fe-C phase diagrams as a function of the nanoparticle size. We find that as the cluster size decreases in the 1.1-1.6-nm-diameter range, the eutectic point shifts significantly not only toward lower temperatures, as expected from the Gibbs-Thomson law, but also toward lower concentrations of C. The strong dependence of the maximum C solubility on the Fe-C cluster size may have important implications for the catalytic growth of carbon nanotubes by chemical-vapor deposition.
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| 3. |
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| 4. |
- Harutyunyan, Avetik, et al.
(författare)
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Hidden features of the catalyst nanoparticles favorable for single-walled carbon nanotube growth
- 2007
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Ingår i: APPLIED PHYSICS LETTERS. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 90:16
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Tidskriftsartikel (refereegranskat)abstract
- Combining in situ studies of the catalyst activity during single-walled carbon nanotube (SWCNT) growth by mass spectrometry with differential scanning calorimetry and Raman spectroscopy results, the authors expose the favorable features of small catalyst for SWCNT growth and their relationship with synthesis parameters. The sequential introduction of C-12 and C-13 labeled hydrocarbon reveals the influence of catalyst composition on its lifetime and the growth termination path. Ab initio and molecular dynamics simulations corroborate "V"-shape liquidus line of metal-carbon nanoparticle binary phase diagram, which explains observed carbon-induced solid-liquid-solid phase transitions during nanotube growth.
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| 6. |
- Kulyte, A, et al.
(författare)
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Inhibition of Mycobacterium smegmatis gene expression and growth using antisense peptide nucleic acids
- 2005
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Ingår i: Journal of molecular microbiology and biotechnology. - : S. Karger AG. - 1464-1801. ; 9:2, s. 101-109
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Tidskriftsartikel (refereegranskat)abstract
- Antisense agents that inhibit genes at the mRNA level are attractive tools for genome-wide studies and drug target validation. The approach may be particularly well suited to studies of bacteria that are difficult to manipulate with standard genetic tools. Antisense peptide nucleic acids (PNA) with attached carrier peptides can inhibit gene expression in <i>Escherichia coli </i>and<i> Staphylococcus aureus</i>. Here we asked whether peptide-PNAs could mediate antisense effects in <i>Mycobacterium smegmatis</i>. We first targeted the <i>gfp</i> reporter gene and observed dose- and sequence-dependent inhibition at low micromolar concentrations. Sequence alterations within both the PNA and target mRNA sequences eliminated inhibition, strongly supporting an antisense mechanism of inhibition. Also, antisense PNAs with various attached peptides showed improved anti-<i>gfp</i> effects. Two peptide-PNAs targeted to the essential gene <i>inhA</i> were growth inhibitory and caused cell morphology changes that resemble that of InhA-depleted cells. Therefore, antisense peptide-PNAs can efficiently and specifically inhibit both reporter and endogenous essential genes in mycobacteria.
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