105 research outputs found
Chronic Kidney Disease of Unknown aetiology (CKDu) and multiple-ion interactions in drinking water
Recent experimental work on the nephrotoxicity of contaminants in drinking
water using laboratory mice, motivated by the need to understand the origin of
chronic kidney disease of unknown aetiology is examined within our
understanding of the hydration of ions and proteins. Qualitative considerations
based on Hofmeister-type action of these ions, as well as quantitative
electrochemical models for the Gibbs free-energy change for ion-pair formation
are used to explain why Cd in the presence of F and water hardness
due to Mg ions (but not Ca) can be expected to be more
nephrotoxic, while AsO in the presence of F and hardness may be
expected to be less nephrotoxic. The analysis is applied to a variety of ionic
species typically found in water to predict their likely combined
electro-chemical action. These results clarify the origins of chronic kidney
disease in the north-central province of Sri Lanka. The conclusion is further
strengthened by a study of the dietary load of Cd and As, where the dietary
loads are found to be safe, especially when the mitigating effects of
micronutrient ionic forms of Zn and Se, as well as corrections for
bio-availability are taken in to account. The resulting aetiological picture
supports the views that F, Cd (to a lesser extent), and Mg
ions found in stagnant household well water act together with enhanced
toxicity, becoming the most likely causative factor of the disease. Similar
incidence of CKDu found in other tropical climates may have similar geological
origins.Comment: 14 pages, one figur
Current issues in finite- density-functional theory and Warm-Correlated Matter
Finite-temperature DFT has become of topical interest, partly due to the
increasing ability to create novel states of warm-correlated matter (WCM).
Subclasses of WCM are Warm-dense matter (WDM), ultra-fast matter (UFM), and
high-energy density matter (HEDM), containing electyrons (e) and ions (i).
Strong e-e, i-i and e-i correlation effects and partial degeneracies are found
in these systems where the electron temperature is comparable to the
electron Fermi energy. The ion subsystem may be solid, liquid or plasma, with
many states of ionization with ionic charge . Quasi-equilibria with the
ion temperature are common. The ion subsystem in WCM can no longer
be treated as a passive "external potential", as is customary in density
functional theory (DFT) dominated by solid-state theory or quantum chemistry.
Hohenberg-Kohn-Mermin theory can be used for WCMs if finite-
exchange-correlation (XC) functionals are available. They are functionals of
both the one-body electron density and the one-body ion densities
. A method of approximately but accurately mapping the quantum
electrons to a classical Coulomb gas enables one to treat electron-ion systems
entirely classically at any temperature and arbitrary spin polarization, using
exchange-correlation effects calculated {\it in situ}, directly from the
pair-distribution functions. This eliminates the need for any XC-functionals,
or the use of a Born-Oppenheimer approximation. This classical map has been
used to calculate the equation of state of WDM systems, and construct a
finite- XC functional that is found to be in close agreement with recent
quantum path-integral simulation data. In this review current developments and
concerns in finite- DFT, especially in the context of non-relativistic
warm-dense matter and ultra-fast matter will be presented.Comment: Presented at the DFT16 meeting in Debrecen, Hungary, September 2015,
held on the 50th anniversary of Kohn-Sham Theory, 10 pages, 3 figure
Ground-state energy and Wigner crystallization in thick 2D-electron systems
The ground state energy of the 2-D Wigner crystal is determined as a function
of the thickness of the electron layer and the crystal structure. The method of
evaluating the exchange-correlation energy is tested using known results for
the infinitely-thin 2D system. Two methods, one based on the local-density
approximation(LDA), and another based on the constant-density approximation
(CDA) are established by comparing with quantum Monte-Carlo (QMC) results. The
LDA and CDA estimates for the Wigner transition of the perfect 2D fluid are at
and 32 respectively, compared with from QMC. For thick-2D
layers as found in Hetero-junction-insulated-gate field-effect transistors, the
LDA and CDA predictions of the Wigner transition are at and 15.5
respectively. Impurity effects are not considered here.Comment: Last figure and Table are modified in the revised version.
Conclusions regarding the Wigner transition in thick layers are modified in
the revised version. Latex manuscript, four figure
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