Compatibility of quantitative X-ray spectroscopy with continuous distribution models of water at ambient conditions

Gold nanoparticles can be used to increase the dose of the tumor due to its high atomic number as well as being free from apparent toxicity. The aim of this study is to evaluate the effect of distribution of gold nanoparticles models, as well as changes in nanoparticle sizes and spectrum of radiation energy along with the effects of nanoparticle penetration into surrounding tissues in dose enhancement factor DEF. Three mathematical models were considered for distribution of gold nanoparticles in the tumor, such as 1-uniform, 2- non-uniform distribution with no penetration margin and 3- non-uniform distribution with penetration margin of 2.7 mm of gold nanoparticles. For this purpose, a cube-shaped water phantom of 50 cm size in each side and a cube with 1 cm side placed at depth of 2 cm below the upper surface of the cubic phantom as the tumor was defined, and then 3 models of nanoparticle distribution were modeled. MCNPX code was used to simulate 3 distribution models. DEF was evaluated for sizes of 20, 25, 30, 50, 70, 90 and 100 nm of gold nanoparticles, and 50, 95, 250 keV and 4 MeV photon energies. In uniform distribution model the maximum DEF was observed at 100 nm and 50 keV being equal to 2.90, in non-uniform distribution with no penetration margin, the maximum DEF was measured at 100 nm and 50 keV being 1.69, and in non-uniform distribution with penetration margin of 2.7 mm, the maximum DEF was measured at 100 nm and 50 keV as 1.38, and the results have been showed that the dose was increased by injecting nanoparticles into the tumor. It is concluded that the highest DEF could be achieved in low energy photons and larger sizes of nanoparticles. Non-uniform distribution of gold nanoparticles can increase the dose and also decrease the DEF in comparison with the uniform distribution. The non-uniform distribution of nanoparticles with penetration margin showed a lower DEF than the non-uniform distribution without any margin and uniform distribution. Meanwhile, utilization of the real X-ray spectrum brought about a smaller DEF in comparison to mono-energetic X-ray photons.

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Towards characterization of photo-excited electron transfer and catalysis in natural and artificial systems using XFELs

Faraday Discussions ◽

10.1039/c6fd00084c ◽

2016 ◽

Vol 194 ◽

pp. 621-638 ◽

Cited By ~ 10

Author(s):

R. Alonso-Mori ◽

K. Asa ◽

U. Bergmann ◽

A. S. Brewster ◽

R. Chatterjee ◽

...

Keyword(s):

Energy Dispersive Spectrometer ◽

Emission Spectra ◽

Atomic Scale ◽

Temperature Structure ◽

Ambient Conditions ◽

X Ray ◽

X Ray Crystallography ◽

Inorganic Systems ◽

Redox Active ◽

Catalytic Sites

The ultra-bright femtosecond X-ray pulses provided by X-ray Free Electron Lasers (XFELs) open capabilities for studying the structure and dynamics of a wide variety of biological and inorganic systems beyond what is possible at synchrotron sources. Although the structure and chemistry at the catalytic sites have been studied intensively in both biological and inorganic systems, a full understanding of the atomic-scale chemistry requires new approaches beyond the steady state X-ray crystallography and X-ray spectroscopy at cryogenic temperatures. Following the dynamic changes in the geometric and electronic structure at ambient conditions, while overcoming X-ray damage to the redox active catalytic center, is key for deriving reaction mechanisms. Such studies become possible by using the intense and ultra-short femtosecond X-ray pulses from an XFEL, where sample is probed before it is damaged. We have developed methodology for simultaneously collecting X-ray diffraction data and X-ray emission spectra, using an energy dispersive spectrometer, at ambient conditions, and used this approach to study the room temperature structure and intermediate states of the photosynthetic water oxidizing metallo-protein, photosystem II. Moreover, we have also used this setup to simultaneously collect the X-ray emission spectra from multiple metals to follow the ultrafast dynamics of light-induced charge transfer between multiple metal sites. A Mn–Ti containing system was studied at an XFEL to demonstrate the efficacy and potential of this method.

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Signature of the hydrogen-bonded environment of liquid water in X-ray emission spectra from first-principles calculations

Frontiers of Physics ◽

10.1007/s11467-017-0700-z ◽

2017 ◽

Vol 13 (1) ◽

Cited By ~ 3

Author(s):

Huaze Shen ◽

Mohan Chen ◽

Zhaoru Sun ◽

Limei Xu ◽

Enge Wang ◽

...

Keyword(s):

Liquid Water ◽

First Principles ◽

Emission Spectra ◽

First Principles Calculations ◽

X Ray ◽

Hydrogen Bonded

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On the Relationship Between Hydrogen-Bonding Motifs and the 1b1 Splitting in the X-ray Emission Spectrum of Liquid Water

10.26434/chemrxiv.13474659.v1 ◽

2020 ◽

Author(s):

Vinicius Cruzeiro ◽

Andrew Wildman ◽

Xiasong Li ◽

Francesco Paesani

Keyword(s):

Hydrogen Bonding ◽

Liquid Water ◽

Density Functional ◽

Potential Energy Function ◽

Ambient Conditions ◽

Functional Theory ◽

Systematic Analysis ◽

X Ray ◽

Td Dft ◽

The Relationship

The split of the 1b1 peak observed in the X-ray emission (XE) spectrum of liquid water has been the focus of intense research over the last two decades. Although several hypotheses have been proposed to explain the origin of the 1b1 splitting, a general consensus has not yet been reached. In this study, we introduce a novel theoretical/computational approach which, combining path-integral molecular dynamics (PIMD) simulations carried out with the MB-pol potential energy function and time-dependent density functional theory (TD-DFT) calculations, correctly predicts the split of the 1b1 peak in liquid water and not in crystalline ice. A systematic analysis in terms of the underlying local structure of liquid water at ambient conditions indicates that several different hydrogen-bonding motifs contribute to the overall XE lineshape in the energy range corresponding to emissions from the 1b1 orbitals, which suggests that it is not possible to unambiguously attribute the split of the 1b1 peak to only two specific structural arrangements of the underlying hydrogen-bonding network.

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On the Relationship Between Hydrogen-Bonding Motifs and the 1b1 Splitting in the X-ray Emission Spectrum of Liquid Water

10.26434/chemrxiv.13474659 ◽

2020 ◽

Author(s):

Vinicius Cruzeiro ◽

Andrew Wildman ◽

Xiasong Li ◽

Francesco Paesani

Keyword(s):

Hydrogen Bonding ◽

Liquid Water ◽

Density Functional ◽

Potential Energy Function ◽

Ambient Conditions ◽

Functional Theory ◽

Systematic Analysis ◽

X Ray ◽

Td Dft ◽

The Relationship

The split of the 1b1 peak observed in the X-ray emission (XE) spectrum of liquid water has been the focus of intense research over the last two decades. Although several hypotheses have been proposed to explain the origin of the 1b1 splitting, a general consensus has not yet been reached. In this study, we introduce a novel theoretical/computational approach which, combining path-integral molecular dynamics (PIMD) simulations carried out with the MB-pol potential energy function and time-dependent density functional theory (TD-DFT) calculations, correctly predicts the split of the 1b1 peak in liquid water and not in crystalline ice. A systematic analysis in terms of the underlying local structure of liquid water at ambient conditions indicates that several different hydrogen-bonding motifs contribute to the overall XE lineshape in the energy range corresponding to emissions from the 1b1 orbitals, which suggests that it is not possible to unambiguously attribute the split of the 1b1 peak to only two specific structural arrangements of the underlying hydrogen-bonding network.

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