Exact Maps in Density Functional Theory for Lattice Models

In the present work, we employ exact diagonalization for model systems on a real-space lattice to explicitly construct the exact density-to-potential and for the first time the exact density-to-wavefunction map that underly the Hohenberg-Kohn theorem in density functional theory. Having the explicit wavefunction-to- density map at hand, we are able to construct arbitrary observables as functionals of the ground-state density. We analyze the density-to-potential map as the distance between the fragments of a system increases and the correlation in the system grows. We observe a feature that gradually develops in the density-to-potential map as well as in the density-to-wavefunction map. This feature is inherited by arbitrary expectation values as functional of the ground-state density. We explicitly show the excited-state energies, the excited-state densities, and the correlation entropy as functionals of the ground-state density. All of them show this exact feature that sharpens as the coupling of the fragments decreases and the correlation grows. We denominate this feature as intra-system steepening. We show that for fully decoupled subsystems the intra-system steepening transforms into the well-known inter-system derivative discontinuity. An important conclusion is that for e.g. charge transfer processes between localized fragments within the same system it is not the usual inter-system derivative discontinuity that is missing in common ground-state functionals, but rather the differentiable intra-system steepening that we illustrate in the present work

Modelling, analysis and verification of a resonant llc converter as a power supply for the electromagnetic driving mechanism of an electromagnetic contactor

The paper presents model based analysis and experimental verification of a half-bridge resonant LLC converter for suppling power to the electromagnetic driving mechanism of an electromagnetic contactor. In the proposed application the convertor - powered either by AC or DC voltage - supplies the coil of the contactor with DC voltage. Analytical and experimental results presented, show several important advantages of the proposed topology: versatility in terms of input voltages – both AC and DC are accepted; stability over wide voltage range; omission of overvoltages – common to electromagnetic systems; reduced power consumption

The exact Hohenberg-Kohn functional for a lattice model

Trabajo presentado al: "Deutsche Physikalische Gesellschaft Spring Meeting" celebrado en Dresden (Alemania) del 30 de marzo al 4 de Abril de 2014.Standard local exchange-correlation and semi-local functionals in ground-state density functional theory are known for their shortcomings in describing correct charge transfer, dissociation energies of molecular ions, and barriers of chemical reactions. To understand the failures of approximate functionals and to gain insight into the behavior of the exact functional, we investigate the exact solution of the many-body Schrödinger equation for a lattice model. Using exact diagonalization, we explicitely construct the exact Hohenberg-Kohn functional and the mapping from densities to wavefunctions. Besides the normal inter-system derivative discontinuity widely discussed in the density-functional theory community, we observe a new feature of the exact functional in the low-density limit. This "intra-system derivative discontinuity" resembles the inter-system derivative discontinuity, but is within the system. The description of many physical phenomena linked to charge-transfer processes (both in the static and dynamical regimes) require a proper account of this "intra-system derivative discontinuity".Peer reviewe

The exact Hohenberg-Kohn functional for a lattice model

Trabajo presentado al: "Deutsche Physikalische Gesellschaft Spring Meeting" celebrado en Dresden (Alemania) del 30 de marzo al 4 de Abril de 2014.Standard local exchange-correlation and semi-local functionals in ground-state density functional theory are known for their shortcomings in describing correct charge transfer, dissociation energies of molecular ions, and barriers of chemical reactions. To understand the failures of approximate functionals and to gain insight into the behavior of the exact functional, we investigate the exact solution of the many-body Schrödinger equation for a lattice model. Using exact diagonalization, we explicitely construct the exact Hohenberg-Kohn functional and the mapping from densities to wavefunctions. Besides the normal inter-system derivative discontinuity widely discussed in the density-functional theory community, we observe a new feature of the exact functional in the low-density limit. This "intra-system derivative discontinuity" resembles the inter-system derivative discontinuity, but is within the system. The description of many physical phenomena linked to charge-transfer processes (both in the static and dynamical regimes) require a proper account of this "intra-system derivative discontinuity".Peer reviewe

Modelling, analysis and comparison of heatsink designs with improved natural convection

The paper presents FEM based study of various heatsink designs. The main aim of the study is to determine and evaluate solutions with improved heat dissipation by utilization of natural convection. Seventeen different cases both classical and proposed by the authors are studied, where each case is examined under three different heat source (in the case with the proposed study a transistor) powers. Results for temperature of the power source and velocity magnitudes in the studied volume are presented and comparted. Experimental verification of the modeling is presented for selected cases

Synthesis and crystal structures of chiral ferrocene and ruthenocene substituted aminomethylnaphthols obtained through Betti-condensation

Ferrocene- and ruthenocenecarboxaldehydes have been employed in Betti-type condensation reactions with 2-naphthol and (S)-phenylethylamine to give metallocenyl-substituted aminomethylnaphthols in a diastereoisomerically pure form. The absolute configurations of the new chiral compounds have been determined by means of NMR experiments and confirmed by X-ray crystallography. The chiral metallocenyl-aminomethylnaphthols have been tested as pre-catalysts for the addition of diethyl zinc to aldehydes, with enantioselectivities of up to 88% ee

A Parsimonious Generalised Height-Diameter Model for Scots Pine Plantations in Bulgaria: a Pragmatic Approach

Considering the state-of-the-art of forest inventory in Bulgaria, our investigation pursued development of a parsimonious generalised height-diameter model for the Scots pine plantations in the country. A number of 2-, 3- and 4-predictor candidate models were examined and compared based on their goodness-of-fit statistics. Data records obtained in variable-sized sample plots, established throughout the distribution range of the plantations and covering the variety of sites, densities and growth stages were used to fit the models. Two hundred twenty-four plot-level measurements and 3056 tree height-diameter pairs were utilised for parameterization. An independent data set of tree-level measurements and two sets of dominant height-diameter pairs, estimated for differently defined top height tree collectives, were used for model validation. Statistical analyses were carried out using packages nlstools, moments, equivalence, car, nlme, stats and the results were illustrated with ggplot2 and graphics packages of R software environment. A modified form of Gaffrey’s model was selected, which estimates the height of a tree through the breast-height tree diameter, mean stand height and diameter, and accounts for the tree social status. It was fitted by generalised non-linear least squares method, with residual variance weighted by a product of tree diameter and mean stand height exponential functions. An adjusted coefficient of determination of 0.917 and residual standard error of 0.794 m indicated the high predictive potential of the derived model. Validation tests showed that the estimated regression line is very well fitted to the independent data and is appropriate to forecast dominant stand heights. The range of errors, relative to the predicted dominant height values, was narrow, ±25-30%, with low magnitude of the average of their absolute values (4-5%). The equivalence tests rejected the null hypothesis of dissimilarity regarding model bias (observations-predictions line intercept) for all validation data sets, for a region of equivalence as narrow as ±5%. The 3-predictor generalised height-diameter model developed in our study needs information readily available from the inventories and therefore can be broadly used. Its application in dominant stand height prediction is recommended

Urinary neopterin concentrations in patients with Balkan endemic nephropathy (BEN)

Urinary neopterin concentrations in patients with Balkan endemic nephropathy (BEN).BackgroundBalkan endemic nephropathy (BEN) is of great clinical importance in restricted areas of Bulgaria, Serbia, Croatia, Bosnia, Herzegovina, and Romania, since the etiology of BEN is still unknown.MethodsIn urine samples from 48 patients (41 females and 7 males, aged 65.6 ± 6.87years) with BEN living in an endemic area of Vratza district, Bulgaria, neopterin concentrations were measured by high-pressure liquid chromatography (HPLC) and compared with other clinical and laboratory investigations, including creatinine, hemoglobin, and erythrocyte sedimentation rates (ESRs).ResultsUrinary neopterin concentrations were 263 ± 128 (mean ± SD; range, 78 to 786 μmol/mol creatinine), 24 (50%) of BEN patients presented with increased concentrations as compared to the established normal ranges. Average ESRs were increased (1hour, 29.0 ± 14.7mm/hour) and hemoglobin was decreased (109.3 ± 16.4g/L). Hemoglobin correlated inversely with ESRs (rs = -0.787 and –0.780) and creatinine concentrations (r = -0.690, all P < 0.001), but not with neopterin concentrations. Neopterin concentrations also did not correlate with serum creatinine levels. There existed an age relationship of ESR, creatinine, and hemoglobin, but not of neopterin. Neopterin concentrations were slightly lower in five females with low titers of antibodies against local B1 hantavirus strain (P < 0.05).ConclusionThe findings can support an immune-mediated inflammatory process in the pathogenesis of BEN only in a subgroup of patients

Modelling, analysis and comparison of heat sink designs with improved natural convection

The paper presents FEM based study of various heatsink designs. The main aim of the study is to determine and evaluate solutions with improved heat dissipation by utilization of natural convection. Seventeen different cases both classical and proposed by the authors are studied, where each case is examined under three different heat source (in the case with the proposed study a transistor) powers. Results for temperature of the power source and velocity magnitudes in the studied volume are presented and comparted. Experimental verification of the modeling is presented for selected cases