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J. N. Kavanagh F. J. Currell D. J. Timson M. H. Holzscheiter N. Bassler R. Herrmann K. M. Prise G. Schettino 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,60(1):209-214
Radiotherapy employs ionizing radiation to induce lethal DNA lesions in
cancer cells while minimizing damage to healthy tissues. Due to their
pattern of energy deposition, better therapeutic outcomes can, in theory, be
achieved with ions compared to photons. Antiprotons have been proposed to
offer a further enhancement due to their annihilation at the end of the
path. The work presented here aimed to establish and validate an
experimental procedure for the quantification of plasmid and genomic DNA
damage resulting from antiproton exposure. Immunocytochemistry was used to
assess DNA damage in directly and indirectly exposed human fibroblasts
irradiated in both plateau and Bragg peak regions of a 126 MeV antiproton
beam at CERN. Cells were stained post irradiation with an anti-γ-H2AX antibody. Quantification of the
γ-H2AX foci-dose relationship is consistent with a linear increase in the Bragg peak region. A qualitative analysis of the
foci
detected in the Bragg peak and plateau
region indicates significant differences highlighting the different severity
of DNA lesions produced along the particle path. Irradiation of desalted
plasmid DNA with 5 Gy antiprotons at the Bragg peak resulted in a significant
portion of linear plasmid in the resultant solution. 相似文献
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Muniz-Miranda M Pagliai M Muniz-Miranda F Schettino V 《Chemical communications (Cambridge, England)》2011,47(11):3138-3140
A SERS investigation combined with ab initio computational analysis involving Car-Parrinello molecular dynamics simulations and Density Functional Theory approach allows fundamental information to be obtained on the behaviour of thiazole in silver aqueous suspension where solvation and chemisorption processes competitively occur. 相似文献
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Pagliai M Bellucci L Muniz-Miranda M Cardini G Schettino V 《Physical chemistry chemical physics : PCCP》2006,8(1):171-178
The adsorption of pyridine onto silver colloids has been investigated by Raman spectroscopy experiments and by ab initio DFT and MP2 calculations. The solvation dynamics of the pyridine in water has been studied by a molecular dynamics simulation. The results are compared with the latest available experimental and theoretical data. It is found that the pyridine is essentially hydrogen bonded to one solvent molecule. Calculations based on pyridine-water and pyridine-Ag(+) complexes allow the reproduction of the experimentally observed Raman features and explain the adsorption process of the ligand in silver hydrosols. 相似文献
5.
The absorption intensities of combination bands in the infrared spectrum of crystal SiF4 have been measured. One-and two-phonon energies and densities of states have been calculated with a dipole-dipole interaction potential. The contribution to absorption intensities due to non linear electric moments have been calculated. It is shown that most of the two-phonon infrared absorption is due to phonon-phonon coupling. 相似文献
6.
Miguel A. Schettino Jr. Alfredo G. Cunha Evaristo Nunes Edson C. Passamani Jair C. C. Freitas Francisco G. Emmerich Milton K. Morigaki 《Journal of nanoparticle research》2016,18(4):90
This work describes the production and characterization of carbon-iron nanocomposites obtained from the decomposition of iron pentacarbonyl (Fe(CO)5) mixed with different carbon materials: a high surface area activated carbon (AC), powdered graphite (G), milled graphite (MG), and carbon black (CB). The nanocomposites were prepared either under argon or in ambient atmosphere, with a fixed ratio of Fe(CO)5 (4.0 mL) to carbon precursor (2.0 g). The images of scanning electron microscopy and the analysis of textural properties indicated the presence of nanostructured Fe compounds homogeneously dispersed into the different classes of pores of the carbon matrices. The elemental Fe content was always larger for samples prepared in ambient atmosphere, reaching values in the range of 20–32 wt%. On the other hand, samples prepared under argon showed reduced Fe content, with values in the range 5–10 wt% for samples prepared from precursors with low surface area (G, MG, and CB) and a much higher value (~19 wt%) for samples prepared from the precursor of high surface area (AC). Mössbauer spectroscopy and X-ray diffractometry showed that the nanoparticles were mostly composed of iron oxides in the case of the samples prepared in oxygen-rich ambient atmosphere and also for the AC-derived nanocomposite prepared under argon, which is consistent with the large oxygen content of this precursor. For the other precursors, with reduced or no oxygen content, metallic iron and iron carbides were found to be the dominant phases in samples prepared under oxygen-free atmosphere. The samples prepared in ambient atmosphere and the AC-derived sample prepared under argon exhibited superparamagnetic behavior at room temperature, as revealed by temperature-dependent magnetization curves and Mössbauer spectroscopy. 相似文献
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The reactivity of propene under high pressure has been investigated in the framework of Car-Parrinello molecular dynamics. Changes in structural and electronic properties due to pressure have been analyzed in systems with a density ranging from 0.855 to 2.151 g/cm(3). A ionic collective mechanism which leads to the formation of oligomers has been found by both spin restricted and spin polarized formalism. The maximally localized Wannier centers analysis has allowed us to characterize the addition scheme and to identify a Wannier center with a high spread value involved in the formation of the principal reaction products. 相似文献
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Self-healing umbrella sampling: a non-equilibrium approach for quantitative free energy calculations
Marsili S Barducci A Chelli R Procacci P Schettino V 《The journal of physical chemistry. B》2006,110(29):14011-14013
We propose a new approach for the umbrella sampling method in molecular dynamics simulations of complex systems. An accelerated sampling of the slow degrees of freedom is achieved by generating a single self-adaptive trajectory that tends to span uniformly the reaction coordinate using a time dependent bias potential derived from the preceding history of the system. To show the convergent behavior and the efficiency of the method, we present the free energy surface of alanine dipeptide in water as a function of the backbone dihedral angles. 相似文献