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$^{2+}$ in the presence of F$^-$ and water hardness due to Mg$^{2+}$ ions (but not Ca$^{2+}$) can be expected to be more nephrotoxic, while AsO$_3^{3-}$ 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$^{2+}$ (to a lesser extent), and Mg$^{2+}$ 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

Spin and temperature dependent study of exchange and correlation in thick two-dimensional electron layers

The exchange and correlation $E_{xc}$ of strongly correlated electrons in 2D layers of finite width are studied as a function of the density parameter $r_s$, spin-polarization $\zeta$ and the temperature $T$. We explicitly treat strong-correlation effects via pair-distribution functions, and introduce an equivalent constant-density approximation (CDA) applicable to all the inhomogeneous densities encountered here. The width $w$ defined via the CDA provides a length scale defining the $z$-extension of the quasi-2D layer resident in the $x$-$y$ plane. The correlation energy $E_c$ of the quasi-2D system is presented as an interpolation between a 1D gas of electron-rods (for $w/r_s>1$) coupled via a log(r) interaction, and a 3D Coulomb fluid closely approximated from the known {\it three-dimensional} correlation energy when $w/r_s$ is small. Results for the $E_{xc}(r_s,\zeta,T)$, the transition to a spin-polarized phase, the effective mass $m^*$, the Land\'e $g$-factor etc., are reported here.Comment: Revtex manuscript, 9 postscript figure

Current issues in finite-TT 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 $T_e$ is comparable to the electron Fermi energy. The ion subsystem may be solid, liquid or plasma, with many states of ionization with ionic charge $Z_j$. Quasi-equilibria with the ion temperature $T_i\ne T_e$ are common. The ion subsystem in WCM can no longer be treated as a passive "external potential", as is customary in $T=0$ density functional theory (DFT) dominated by solid-state theory or quantum chemistry. Hohenberg-Kohn-Mermin theory can be used for WCMs if finite-$T$ exchange-correlation (XC) functionals are available. They are functionals of both the one-body electron density $n_e$ and the one-body ion densities $\rho_j$. 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-$T$ 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-$T$ 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