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| 2. |
- Gaffney, K J, et al.
(författare)
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Observation of structural anisotropy and the onset of liquidlike motion during the nonthermal melting of InSb
- 2005
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 95:12
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Tidskriftsartikel (refereegranskat)abstract
- The melting dynamics of laser excited InSb have been studied with femtosecond x-ray diffraction. These measurements observe the delayed onset of diffusive atomic motion, signaling the appearance of liquidlike dynamics. They also demonstrate that the root-mean-squared displacement in the [111] direction increases faster than in the [110] direction after the first 500 fs. This structural anisotropy indicates that the initially generated fluid differs significantly from the equilibrium liquid.
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| 3. |
- Cavalieri, A L, et al.
(författare)
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Clocking femtosecond X rays.
- 2005
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Ingår i: Phys Rev Lett. - 0031-9007. ; 94:11
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Tidskriftsartikel (refereegranskat)abstract
- Linear-accelerator-based sources will revolutionize ultrafast x-ray science due to their unprecedented brightness and short pulse duration. However, time-resolved studies at the resolution of the x-ray pulse duration are hampered by the inability to precisely synchronize an external laser to the accelerator. At the Sub-Picosecond Pulse Source at the Stanford Linear-Accelerator Center we solved this problem by measuring the arrival time of each high energy electron bunch with electro-optic sampling. This measurement indirectly determined the arrival time of each x-ray pulse relative to an external pump laser pulse with a time resolution of better than 60 fs rms.
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| 4. |
- Lindenberg, AM, et al.
(författare)
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Atomic-scale visualization of inertial dynamics
- 2005
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 308:5720, s. 392-395
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Tidskriftsartikel (refereegranskat)abstract
- The motion of atoms on interatomic potential energy surfaces is fundamental to the dynamics of liquids and solids. An accelerator-based source of femtosecond x-ray pulses allowed us to follow directly atomic displacements on an optically modified energy landscape, leading eventually to the transition from crystalline solid to disordered liquid. We show that, to first order in time, the dynamics are inertial, and we place constraints on the shape and curvature of the transition-state potential energy surface. Our measurements point toward analogies between this nonequilibrium phase transition and the short-time dynamics intrinsic to equilibrium liquids.
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| 5. |
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| 6. |
- van Maaren, PJ, et al.
(författare)
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Molecular dynamics simulations of water with novel shell-model potentials
- 2001
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Ingår i: JOURNAL OF PHYSICAL CHEMISTRY B. - 1089-5647. ; 105:13, s. 2618-2626
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Tidskriftsartikel (refereegranskat)abstract
- The need for a computationally efficient yet physically realistic water model for molecular simulation is longstanding. To account for intermolecular interactions with other molecules, for example the hydration of biomolecules, the model has to be able to
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| 7. |
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| 8. |
- Behzadi, Hadi, et al.
(författare)
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A density functional study of N-15 chemical shielding tensors in quinolines
- 2009
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 476:4-6, s. 196-200
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Tidskriftsartikel (refereegranskat)abstract
- DFT calculations were carried out to characterize the N-15 shielding tensors in quinolines. This computational study is intended to shed light on the differences between two groups of quinolines: series A (7-chloro 4-aminoalkyls quinolines) and series B (quinolines, 3-, 5-, 6-, 8-amino quinolines and 4,8-dichloro quinoline). Unlike the quinolines in series B, the series A quinolines show considerable beta-hematin inhibition activity which is essential for quinoline-based drugs. The results show that the substitution position significantly affects the sigma(11) and sigma(22) components of N-15 shielding tensors of quinolines. The N-15 shielding components are noticeably different for the two series and can be related to their ability to interact with hematin. (C) 2009 Published by Elsevier B. V.
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| 9. |
- Behzadi, Hadi, et al.
(författare)
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A theoretical study of repeating sequence in HRP II : a combination of molecular dynamics simulations and (17)O quadrupole coupling tensors
- 2008
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Ingår i: Biophysical Chemistry. - : Elsevier BV. - 0301-4622 .- 1873-4200. ; 137:2-3, s. 76-80
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Tidskriftsartikel (refereegranskat)abstract
- Histidine rich protein II derived peptide (HRP II 169-182) was investigated by molecular dynamics, MD, simulation and (17)O electric field gradient, EFG, tensor calculations. MD simulation was performed in water at 300 K with alpha-helix initial structure. It was found that peptide loses its initial alpha-helix structure rapidly and is converted to random coil and bent secondary structures. To understand how peptide structure affects EFG tensors, initial structure and final conformations resulting from MD simulations were used to calculate (17)O EFG tensors of backbone carbonyl oxygens. Calculations were performed using B3LYP method and 6-31+G basis set. Calculated (17)O EFG tensors were used to evaluate quadrupole coupling constants, QCC, and asymmetry parameters, eta(Q). Difference between the calculated QCC and eta(Q) values revealed how hydrogen-bonding interactions affect EFG tensors at the sites of each oxygen nucleus.
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| 10. |
- Behzadi, Hadi, et al.
(författare)
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Role of spin state on the geometry and nuclear quadrupole resonance parameters in hemin complex
- 2008
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Ingår i: Biophysical Chemistry. - : Elsevier BV. - 0301-4622 .- 1873-4200. ; 134:3, s. 200-206
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Tidskriftsartikel (refereegranskat)abstract
- Theoretical calculations of structural parameters, 57Fe, 14N and 17 O electric field gradient (EFG) tensors for full size-hemin group have been carried out using density functional theory. These calculations are intended to shed light on the difference between the geometry parameters, nuclear quadrupole coupling constants (QCC), and asymmetry parameters (eta Q) found in three spin states of hemin; doublet, quartet and sextet. The optimization results reveal a significant change for propionic groups and porphyrin plane in different spin states. It is found that all principal components of EFG tensor at the iron site are sensitive to electronic and geometry structures. A relationship between the EFG tensor at the 14N and 17 O sites and the spin state of hemin complex is also detected.
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