| 1. |
- Richards, Stephen, et al.
(författare)
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The genome of the model beetle and pest Tribolium castaneum.
- 2008
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Ingår i: Nature. - 1476-4687. ; 452:7190, s. 949-55
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Tidskriftsartikel (refereegranskat)abstract
- Tribolium castaneum is a representative of earth’s most numerous eukaryotic order, a powerful model organism for the study of generalized insect development, and also an important pest of stored agricultural products. We describe its genome sequence here. This omnivorous beetle has evolved an ability to interact with a diverse chemical environment as evidenced by large expansions in odorant and gustatory receptors, as well as p450 and other detoxification enzymes. Developmental patterns in Tribolium are more representative of other arthropods than those found in Drosophila, a fact represented in gene content and function. For one, Tribolium has retained more ancestral genes involved in cell-cell communication than Drosophila, and some are expressed in the growth zone crucial for axial elongation in short germ development. Systemic RNAi in T. castaneum appears to use mechanisms distinct from those found in C. elegans, but nevertheless offers similar power for the elucidation of gene function and identification of targets for selective insect control.
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| 2. |
- Rosen, Johanna, et al.
(författare)
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Ab initio studies of adsorption and migration surface processes on an α-Al2O3 surface
- 2005
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Ingår i: Solid State Communications. - : Elsevier BV. - 0038-1098 .- 1879-2766. ; 135:1-2, s. 90-94
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Tidskriftsartikel (refereegranskat)abstract
- Surface processes on α-Al2O3 (0001) have been investigated theoretically using density functional theory. Ion–surface interactions prior to collision were investigated by means of ab initio molecular dynamics simulations, showing an adsorbate trajectory towards a preferred adsorption site. Furthermore, the adsorption process at different surface sites was investigated, together with calculations of barriers for migration between these sites. Although the equilibrium (bulk) adsorption site was energetically favourable, the presence and magnitude of the migration barriers indicate that activation energy is necessary to form the equilibrium surface structure. These results are of importance for a fundamental understanding of ion–surface interactions.
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| 3. |
- Emmerlich, Jens, et al.
(författare)
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Thermal stability of Ti3SiC2 thin films
- 2007
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Ingår i: Acta Materialia. - : Elsevier BV. - 1359-6454 .- 1873-2453. ; 55:4, s. 1479-1488
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Tidskriftsartikel (refereegranskat)abstract
- The thermal stability of Ti3SiC2(0 0 0 1) thin films is studied by in situ X-ray diffraction analysis during vacuum furnace annealing in combination with X-ray photoelectron spectroscopy, transmission electron microscopy and scanning transmission electron microscopy with energy dispersive X-ray analysis. The films are found to be stable during annealing at temperatures up to 1000 °C for 25 h. Annealing at 1100–1200 °C results in the rapid decomposition of Ti3SiC2 by Si out-diffusion along the basal planes via domain boundaries to the free surface with subsequent evaporation. As a consequence, the material shrinks by the relaxation of the Ti3C2 slabs and, it is proposed, by an in-diffusion of O into the empty Si-mirror planes. The phase transformation process is followed by the detwinning of the as-relaxed Ti3C2 slabs into (1 1 1)-oriented TiC0.67 layers, which begin recrystallizing at 1300 °C. Ab initio calculations are provided supporting the presented decomposition mechanisms.
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| 4. |
- Music, Denis, et al.
(författare)
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Elastic properties of Fe-Mn random alloys studied by ab initio calculations
- 2007
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 91:19
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the influence of the Mn content on the elastic properties of Fe-Mn random alloys (space group of Fm (3) over barm) using ab initio calculations. The magnetic effects in Fe-Mn alloys have a strong influence on the elastic properties, even above the Neel temperature. As the Mn content is increased from 5 to 40 at. %, the C-44 elastic constant is unaffected, while C-11 and C-12 decrease. This behavior can be understood based on the magnetovolume effect which softens the lattice. Since the amplitude of local magnetic moments is less sensitive to volume conserving distortions, the softening is not present during shearing.
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| 5. |
- Music, Denis, et al.
(författare)
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Electronic structure and lattice dynamics of CaPd3B studied by first-principles methods
- 2006
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Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 356:3, s. 251-254
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Tidskriftsartikel (refereegranskat)abstract
- Using first-principles methods, we have studied the electronic structure and lattice dynamics of CaPd3B and compared them to isostructural MgNi3C- CaPd3B possesses less electronic states at the Fermi level, but more phonon modes at low frequencies, than MgNi3C. According to the phonon density of states, low frequency acoustic modes are dominated by Pd states, corresponding to Ni in MgNi3C. Furthermore, these Pd modes show soft phonons, which may be significant for second-order phase transitions. Based on the comparison to MgNi3C, we suggest that the properties of these two compounds may be similar.
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| 6. |
- Music, D., et al.
(författare)
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Electronic structure of M2AlC(0001) surfaces (M = Ti, V, Cr)
- 2006
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 18:39, s. 8877-8881
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the correlation between the valence electron configuration and the electronic structure of M2AlC(0001) surfaces (M = Ti, V, Cr) using ab initio calculations. Based on our surface energy data, we find that the Al termination is the most stable configuration. As the M valence electron population is increased, the surface energy increases. This can be understood by analysing the valence electron concentration induced changes of the electronic structure. Antibonding states are present as Ti is substituted by Cr in M2AlC(0001). These results are of relevance for vapour phase condensation as well as oxidation.
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| 7. |
- Rosén, Johanna, et al.
(författare)
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Ab initio molecular dynamics study of hydrogen removal by ion–surface interactions
- 2005
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Ingår i: Journal of Physics: Condensed Matter. ; 17, s. L137-L142
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Tidskriftsartikel (refereegranskat)abstract
- The energy dependence of surface reactions has been investigated through ab initio MD simulations for collisions between Al1+ and a gibbsite surface. No change in surface composition was observed for 0 eV initial kinetic energy of Al1+. An increase in energy to 3.5 eV resulted in extended surface migration of hydrogen, subsequent H2 formation and desorption from the surface. These results may be understood based on thermodynamics and an increase in entropy upon H2 formation. They are of fundamental importance for an increased understanding of thin film growth through the correlation between ion energy and film composition. They may also indicate a pathway to affect impurity incorporation during film growth.
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| 8. |
- Rosen, Johanna, et al.
(författare)
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Ab initio molecular dynamics study of ion-surface interactions
- 2005
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Ingår i: Solid State Communications. - : Elsevier BV. - 0038-1098 .- 1879-2766. ; 134, s. 333-336
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Tidskriftsartikel (refereegranskat)abstract
- Ion-surface collisions have been investigated theoretically using ab initio molecular dynamics within density functional theory. The temporal evolution of the position of the bombarding ion, as well as its nearest neighbors, was studied for initial kinetic energies of 0 and 3.5 eV (0 and 5 km/s, respectively). Also investigated was the ion-surface interaction prior to collision and the following energy transfer, as indicated by changes in ion velocity. At 3.5 eV collision energy, the calculation results suggest the formation of local structural disorder within the simulation time frame studied. These results are of fundamental importance for an increased understanding of the ion-surface interaction during a collision event, with resulting changes in atomic level structure.
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| 9. |
- Rosen, Johanna, et al.
(författare)
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Charge state dependence of cathodic vacuum arc ion energy and velocity distributions
- 2006
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Ingår i: Applied Physics Letters. - : American Institute of Physics. - 0003-6951 .- 1077-3118. ; 89:14, s. 141502-
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Tidskriftsartikel (refereegranskat)abstract
- In the literature, conflicting conclusions are reported concerning the charge state dependence of cathodic arc ion energy and velocity distributions. It appears that data from electrostatic energy analyzers indicate charge state dependence of ion energy, whereas time-of-flight methods support charge state independence of ion velocity. Here the authors present charge-state-resolved ion energy distributions and calculate the corresponding ion velocity distributions in aluminum vacuum arc plasma. They show that the conflicting conclusions reported in the literature for the two different characterization techniques may originate from the commonly employed data interpretation of energy and velocity, in which peak values and average values are not carefully distinguished.
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| 10. |
- Snyders, Rony, et al.
(författare)
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Influence of the chemical composition on the phase constitution and the elastic properties of RF sputtered hydrozyapatite coatings
- 2008
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Ingår i: Plasma Processes and Polymers. - : Wiley. - 1612-8850 .- 1612-8869. ; 5:2, s. 168-174
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the influence of chemical composition on the constitution and elastic properties of dense radio-frequency (RF)-sputtered hydroxyapatite (HA) coatings. The chemical composition was modified by varying the RF sputtering power density (P-D). As the P-D was increased by 240%, the Ca/P ratio measured by X-ray photoelectron spectroscopy increased from approximate to 1.51 to approximate to 1.82. X-ray diffraction indicates phase pure hexagonal HA except for the sample prepared at the highest P-D where CaO and Ca-3(PO4)(2) also form. Deviations from the stoichiometric Ca/P ratio result in reduction of the elastic modulus. For Ca/P = 1.51 +/- 0.02, the elastic modulus decreases by approximate to 15%. This maybe due to incorporation of Ca vacancies in the lattice, while for Ca/P = 1.82 +/- 0.02, the average elastic modulus decreases by approximate to 10% due to formation of additional phases.
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