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<b>
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SEMINARIOS 2010<br>
Gerencia
Investigacion y Aplicaciones - TANDAR - CNEA<br>
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<br>
Martes 26 de enero, 11:00 Hs.<br>
Aula Nivel 0, TANDAR<br><br>
<br>
"Synchrotron X-rays and DFT to Unveil Molecules in Action:<br>
1) Relaxed Final State DFT Simulations of Sulfur K-edge XANES and<br>
MicroXANES for Catalysis; <br>
2)Applications of XANES to Biology, Medicine (Cancer) and
Chemistry"<br><br>
<br>
</b>
<b>Dra. Ana MIJOVILOVICH
[1]</b>
<br>
<b>Inorganic Chemistry and Catalysis, University of Utrecht, The
Netherlands.<br>
On leave to: The Canadian Light Source, Saskatoon, Canada<br><br>
<br>
</b>X-ray Near Edge Structure (XANES) and the space-resolved microXANES
can<br>
provide qualitative and quantitative information on the fate of Sulfur
in<br>
diverse environments. The DFT used in the works presented here [1],
allows<br>
calculating the experimental spectrum, that is, with the excited core
hole<br>
(after the excitation of the 1s electron during the "X-ray
absorption" <br>
process) and the subsequent relaxation and with the calculation of
the<br>
transition matrix, instead of extrapolating the XANES from the
densities<br>
of states in the ground state. It has proven to be very successful
in<br>
solutions and amino acids [2]. Here examples are shown for the
analysis<br>
of the differences between aliphatic and thiophenic sulfur
compounds,<br>
usually found in oils and coals [3]. The questions that can be
answered<br>
range from identification and quantification of sulfur compounds for<br>
speciation analysis, to the analysis of the electronic structure of
the<br>
sulfur, like the sulfur hybridization, protonation of the compound,
as<br>
well as differentiation of aliphatic and aromatic sulfur. The
advantages<br>
and limitations of the techniques are explained.<br><br>
Study cases:<br>
1) Understanding Sulfur compounds speciation in detail: a) Thiophenic
and<br>
aliphatic sulfur [3]; b) Sulfide-disulfide [4]. DFT simulations
treating<br>
the core hole as "half core hole" give the best approximation
to the<br>
XANES. Including the relaxation of the first excited states and taking
the<br>
non-orthogonal transition moments gives almost a perfect match many
eV<br>
above the edge. This unusual result is due to the use of the diffuse
basis<br>
set, which allows a good description of both the delocalized states
as<br>
well as bound states, in the near edge region. The first LUMO
transitions<br>
and their relation to the spectral features are discussed.<br><br>
2) Theory in action: microspectroscopy of the oligomerization reactions
on<br>
zeolite crystals [5]. We focus on XANES simulations to understand the
fate<br>
of thiophene deposited on zeolite crystals, termally treated.<br><br>
3) Microspectroscopy with spatial resolution to study the fate of
metals<br>
in cancer tissues and cells and the binding of anticancer
metallo-drugs<br>
(Ga and Pt), and studies of the metal accumulation in
hyperaccumulator<br>
plants.<br>
_______________________________________________________<br><br>
[1] E-mail: ana_mijo@yahoo.com<br>
<a href="http://www.anorg.chem.uu.nl/peopleOld/postdoctoralfellows/Ana%20Mijovilovich/index.htm" eudora="autourl">
http://www.anorg.chem.uu.nl/peopleOld/postdoctoralfellows/Ana%20Mijovilovich/index.htm<br>
<br>
<br>
</a>Quedan todos cordialmente invitados !<br><br>
<br>
11:00 hs - Aula Nivel 0, TANDAR<br>
CNEA - Centro Atomico Constituyentes<br>
Av. Gral. Paz y Constituyentes<br>
6772-7065 / 7007<br>
Coordinadores:<br>
Dres. Andres Arazi: < mailto: arazi@tandar.cnea.gov.ar y<br>
Daniel L. Hojman: < mailto: hojman@tandar.cnea.gov.ar<br>
Secretaria: Graciela Mastrogiacomo:<br>
<a href="mailto:gmastro@tandar.cnea.gov.ar" eudora="autourl">
mailto:gmastro@tandar.cnea.gov.ar<br>
</a>
<a href="http://www.tandar.cnea.gov.ar/eventos/seminariosUAF/" eudora="autourl">
http://www.tandar.cnea.gov.ar/eventos/seminariosUAF/<br>
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