This paper revisits the commonly held view that small countries do not exhibit significant regional disparities. The issue is framed as one in which the attributes of small size (land area, population and the magnitude of the economy) are mediated by a series of spatial and non‐spatial factors such as distance, density, factor mobility, natural resources, land supply, social cohesion and governance structure. Given the existence of these mediators, the magnitude of regional disparities in small countries is not as surprising as it may seem at first glance.
We present a broadband dielectric spectroscopy study of potassium tantalate niobate (KTN) crystals, doped with varying amounts of Cu ions. The dielectric landscape in frequency and temperature is rich, with multiple processes in different temperature phases of the crystals. Of particular interest are the processes resulting from Cu and Nb ions in the paraelectric phase of the crystal and from Cu ions in the ferroelectric phase. The linear dependence of the ferroelectric transition temperature in KTN crystals (KTa0.62Nb0.38O3Cu) on the concentration of Nb, as well as the dielectric behavior of the ferroelectric phase transition in these crystals, are well known. We concentrate of the dielectric relaxation resulting from the Cu ions in the crystal lattice. Cu dopants in very small concentrations have been added in the past to enhance the photoreftractive properties of KTN crystals. However the small ionic radius of such dopants, relative to their lattice site, results in virtual dipoles exhibiting dielectric relaxation. The random nature of their distribution throughout the ordered KTN lattice leads to relaxation behavior reminiscent of glass formers. In particular Vogel Fulcher Tammann relaxation of these ions is evident in the paraelectric phase of the crystal. This cooperativity is broken at a critical temperature (T = 354 K) and the relaxation becomes Arrhenius in nature. An explanation in terms of Adam-Gibbs theory is presented where the cooperative cluster is realized by polarized Nb ions linking the widely space Cu ions. At the phase transition (T-c = 295.6 K) this relaxation is 'frozen' by large internal fields caused by the structural shift of the Nb ion in the unit cell. As the temperature drops the Cu ions undergo a reorganization about the multiwell potential leading to a saddle-like process characteristic of liquids in confined systems. An explanation for this behavior is proposed based on free volume concepts, where the relatively small ionic radius of the Cu ions provides the free volume for the relaxing species. The role of the oxygen octahedra as the relaxing species is discussed. (c) 2005 Published by Elsevier BV.
An ab initio method is developed for variational grand-canonical molecular electronic structure of open systems based on the Gibbs–Peierls–Boguliobov inequality. We describe the theory and a practical method for performing the calculations within standard quantum chemistry codes using Gaussian basis sets. The computational effort scales similarly to the ground-state Hartree–Fock method. The quality of the approximation is studied on a hydrogen molecule by comparing to the exact Gibbs free energy, computed using full configuration-interaction calculations. We find the approximation quite accurate, with errors similar to those of the Hartree–Fock method for ground-state zero-temperature calculations. A further demonstration is given of the temperature effects on the bending potential curve for water. Some future directions and applications of the method are discussed. Several appendices give the mathematical and algorithmic details of the method.
The results of harmonic and anharmonic frequency calculations on a guanine-cytosine complex with an enolic structure (a tautomeric form with cytosine in the enol form and with a hydrogen at the 7-position on guanine) are presented and compared to gas-phase IR-UV double resonance spectral data. Harmonic frequencies were obtained at the RI-MP2/cc-pVDZ, RI-MP2/TZVPP, and semiempirical PM3 levels of electronic structure theory. Anharmonic frequencies were obtained by the CC-VSCF method with improved PM3 potential surfaces; the improved PM3 potential surfaces are obtained from standard PM3 theory by coordinate scaling such that the improved PM3 harmonic frequencies are the same as those computed at the RI-MP2/cc-pVDZ level. Comparison of the data with experimental results indicates that the average absolute percentage deviation for the methods is 2.6% for harmonic RI-MP2/cc-pVDZ (3.0% with the inclusion of a 0.956 scaling factor that compensates for anharmonicity), 2.5% for harmonic RI-MP2/TZVPP (2.9% with a 0.956 anharmonicity factor included), and 2.3% for adapted PM3 CC-VSCF; the empirical scaling factor for the ab initio harmonic calculations improves the stretching frequencies but decreases the accuracy of the other mode frequencies. The agreement with experiment supports the adequacy of the improved PM3 potentials for describing the anharmonic force field of the G(...)C base pair in the spectroscopically probed region. These results may be useful for the prediction of the pathways of vibrational energy flow upon excitation of this system. The anharmonic calculations indicate that anharnionicity along single mode coordinates can be significant for simple stretching modes. For several other cases, coupling between different vibrational modes provides the main contribution to anharmonicity. Examples of strongly anharmonically coupled modes are the symmetric stretch and group torsion of the hydrogen-bonded NH2 group on guanine, the OH stretch and torsion of the enol group on cytosine, and the NH stretch and NH out-of-plane bend of the non-hydrogen-bonded NH group on guanine.
This work develops and tests a theory of voter choice in parliamentary elections. I demonstrate that voters are concerned with policy outcomes and hence incorporate the way institutions convert votes to policy into their choices. Since policy is often the result of institutionalized multiparty bargaining and thus votes are watered down by power-sharing, voters often compensate for this watering-down by supporting parties whose positions differ from (and are often more extreme than) their own. I use this insight to reinterpret an ongoing debate between proximity and directional theories of voting, showing that voters prefer parties whose positions differ from their own views insofar as these parties pull policy in a desired direction. Utilizing data from four parliamentary democracies that vary in their institutional design, I test my theory and show how institutional context affects voter behavior.
The small-bias conductance of the C-6 molecule, stretched between two metallic leads, is studied using time-dependent density functional theory within the adiabatic local density approximation. The leads are modeled by jellium slabs, the electronic density and the current density are described on a grid, whereas the core electrons and the highly oscillating valence orbitals are approximated using standard norm-conserving pseudopotentials. The jellium leads are supplemented by a complex absorbing potential that serves to absorb charge reaching the edge of the electrodes and hence mimic irreversible flow into the macroscopic metal. The system is rapidly exposed to a ramp potential directed along the C-6 axis, which gives rise to the onset of charge and current oscillations. As time progresses, a fast redistribution of the molecular charge is observed, which translates into a direct current response. Accompanying the dc signal, alternating current fluctuations of charge and currents within the molecule and the metallic leads are observed. These form the complex impedance of the molecule and are especially strong at the plasmon frequency of the leads and the lowest excitation peak of C-6. We study the molecular conductance in two limits: the strong coupling limit, where the edge atoms of the chain are submerged in the jellium and the weak coupling case, where the carbon atoms and the leads do not overlap spatially. (C) 2004 American Institute of Physics.
Hutchinson-Gilford progeria syndrome (HGPS) is a premature aging disorder, commonly caused by a point mutation in the lamin A gene that results in a protein lacking 50 aa near the C terminus, denoted LADelta50. Here we show by light and electron microscopy that HGPS is associated with significant changes in nuclear shape, including lobulation of the nuclear envelope, thickening of the nuclear lamina, loss of peripheral heterochromatin, and clustering of nuclear pores. These structural defects worsen as HGPS cells age in culture, and their severity correlates with an apparent increase in LADelta50. Introduction of LADelta50 into normal cells by transfection or protein injection induces the same changes. We hypothesize that these alterations in nuclear structure are due to a concentration-dependent dominant-negative effect of LADelta50, leading to the disruption of lamin-related functions ranging from the maintenance of nuclear shape to regulation of gene expression and DNA replication.
