To save content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about saving content to .
To save content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Aqueous corrosion of zirconium alloys has become the major factor limiting prolonged fuel campaigns in nuclear plant. Studies using SEM, TEM and electrochemical impedance measurements have been interpreted as showing a dense inner-most oxide layer, and an increased thickness of the layer has been correlated to a better corrosion resistance. Many authors have reported that an ‘intermediate layer’ at the metal oxide interface has a complex structure or/and stochiometry different to that of both the bulk oxide and bulk metal, sometimes claimed to be a suboxide phase. Diffraction evidence has suggested the presence of both cubic ZrO and rhombohedral Zr3O phases, and compositional analysis has revealed similar variations in local oxygen stoichiometry.
We have carried out a systematic investigation of the structure and chemistry of the metal/oxide interface in samples of commercial ZIRLO corroded for times up to 180 days. We have developed new experimental techniques for the study of these interfaces both by Electron Energy Loss Spectroscopy (EELS) analysis in the Transmission Electron Microscope (TEM) and by Atom Probe Tomography (APT), and exactly the same samples have been investigated by both techniques. Our results show the development of a clearly defined suboxide layer of stoichiometry close to ZrO, and the subsequent disappearance of this layer at the first of the characteristic ‘breakaway’ transitions in the oxidation kinetics. We can correlate this behaviour with changes in the structure of the oxide layer, and particularly the development of interconnected porosity that links the corroding interface with the aqueous environment. Using high resolution SIMS analysis of isotopically spiked samples we demonstrate the penetration of the oxidising species through these porous outer oxide layers.
The relationship between the structure of a free
ligand in solution and the structure of its bound form
in a complex is of great importance to the understanding
of the energetics and mechanism of molecular recognition
and complex formation. In this study, we use a structure-based
thermodynamic approach to study the dissociation of the
complex between the toxin microcystin-LR (MLR) and the
catalytic domain of protein phosphatase-1 (PP-1c) for which
the crystal structure of the complex is known. We have
calculated the thermodynamic parameters (enthalpy, entropy,
heat capacity, and free energy) for the dissociation of
the complex from its X-ray structure and found the calculated
dissociation constant (4.0 × 10−11)
to be in excellent agreement with the reported inhibitory
constant (3.9 × 10−11). We have
also calculated the thermodynamic parameters for the dissociation
of 47 PP-1c:MLR complexes generated by docking an ensemble
of NMR solution structures of MLR onto the crystal structure
of PP-1c. In general, we observe that the lower the root-mean-square
deviation (RMSD) of the docked complex (compared to the
X-ray complex) the closer its free energy of dissociation
(ΔG°d) is to that
calculated from the X-ray complex. On the other hand, we
note a significant scatter between the
and the RMSD of the docked complexes. We have identified a group of
seven docked complexes with ΔG°d
values very close to the one calculated from the X-ray
complex but with significantly dissimilar structures. The
analysis of the corresponding enthalpy and entropy of dissociation
shows a compensation effect suggesting that MLR molecules
with significant structural variability can bind PP-1c
and that substantial conformational flexibility in the
PP-1c:MLR complex may exist in solution.
Email your librarian or administrator to recommend adding this to your organisation's collection.