Dynamical density functional theory for dense atomic liquids

Starting from Newton's equations of motion, we derive a dynamical density functional theory (DDFT) applicable to atomic liquids. The theory has the feature that it requires as input the Helmholtz free energy functional from equilibrium density functional theory. This means that, given a reliable equilibrium free energy functional, the correct equilibrium fluid density profile is guaranteed. We show that when the isothermal compressibility is small, the DDFT generates the correct value for the speed of sound in a dense liquid. We also interpret the theory as a dynamical equation for a coarse grained fluid density and show that the theory can be used (making further approximations) to derive the standard mode coupling theory that is used to describe the glass transition. The present theory should provide a useful starting point for describing the dynamics of inhomogeneous atomic fluids.Comment: 14 pages, accepted for publication in J. Phys.: Condens. Matte

Mean-field dynamical density functional theory

We examine the out-of-equilibrium dynamical evolution of density profiles of ultrasoft particles under time-varying external confining potentials in three spatial dimensions. The theoretical formalism employed is the dynamical density functional theory (DDFT) of Marini Bettolo Marconi and Tarazona [J. Chem. Phys. {\bf 110}, 8032 (1999)], supplied by an equilibrium excess free energy functional that is essentially exact. We complement our theoretical analysis by carrying out extensive Brownian Dynamics simulations. We find excellent agreement between theory and simulations for the whole time evolution of density profiles, demonstrating thereby the validity of the DDFT when an accurate equilibrium free energy functional is employed.Comment: 8 pagers, 4 figure

Static and Dynamic Properties of Type-II Composite Fermion Wigner Crystals

The Wigner crystal of composite fermions is a strongly correlated state of complex emergent particles, and therefore its unambiguous detection would be of significant importance. Recent observation of optical resonances in the vicinity of filling factor {\nu} = 1/3 has been interpreted as evidence for a pinned Wigner crystal of composite fermions [Zhu et al., Phys. Rev. Lett. 105, 126803 (2010)]. We evaluate in a microscopic theory the shear modulus and the magnetophonon and magnetoplasmon dispersions of the composite fermion Wigner crystal in the vicinity of filling factors 1/3, 2/5, and 3/7. We determine the region of stability of the crystal phase, and also relate the frequency of its pinning mode to that of the corresponding electron crystal near integer fillings. These results are in good semiquantitative agreement with experiment, and therefore support the identification of the optical resonance as the pinning mode of the composite fermions Wigner crystal. Our calculations also bring out certain puzzling features, such as a relatively small melting temperature for the composite fermion Wigner crystal, and also suggest a higher asymmetry between Wigner crystals of composite fermion particles and holes than that observed experimentally.Comment: Composite Fermion Wigner Crystal; 14 pages, 9 figure

Intrinsic point defects and volume swelling in ZrSiO4 under irradiation

The effects of high concentration of point defects in crystalline ZrSiO4 as originated by exposure to radiation, have been simulated using first principles density functional calculations. Structural relaxation and vibrational studies were performed for a catalogue of intrinsic point defects, with different charge states and concentrations. The experimental evidence of a large anisotropic volume swelling in natural and artificially irradiated samples is used to select the subset of defects that give similar lattice swelling for the concentrations studied, namely interstitials of O and Si, and the anti-site Zr(Si), Calculated vibrational spectra for the interstitials show additional evidence for the presence of high concentrations of some of these defects in irradiated zircon.Comment: 9 pages, 7 (color) figure

Criticality and phase separation in a two-dimensional binary colloidal fluid induced by the solvent critical behavior

We present an experimental and theoretical study of the phase behavior of a binary mixture of colloids with opposite adsorption preferences in a critical solvent. As a result of the attractive and repulsive critical Casimir forces, the critical fluctuations of the solvent lead to a further critical point in the colloidal system, i.e. to a critical colloidal-liquid--colloidal-liquid demixing phase transition which is controlled by the solvent temperature. Our experimental findings are in good agreement with calculations based on a simple approximation for the free energy of the system.Comment: 5 pages, 5 figures, to be published in Europhysics Letter

Phase separation in fluids exposed to spatially periodic external fields

We consider the liquid-vapor type phase transition for fluids confined within spatially periodic external fields. For a fluid in d=3 dimensions, the periodic field induces an additional phase, characterized by large density modulations along the field direction. At the triple point, all three phases (modulated, vapor, and liquid) coexist. At temperatures slightly above the triple point and for low (high) values of the chemical potential, two-phase coexistence between the modulated phase and the vapor (liquid) is observed. We study this phenomenon using computer simulations and mean-field theory for the Ising model. The theory shows that, in order for the modulated phase to arise, the field wavelength must exceed a threshold value. We also find an extremely low tension of the interface between the modulated phase and the vapor/liquid phases. The tension is of the order 10^{-4} kB T per squared lattice spacing, where kB is the Boltzmann constant, and T the temperature. In order to detect such low tensions, a new simulation method is proposed. We also consider the case of d=2 dimensions. The modulated phase then does not survive, leading to a radically different phase diagram.Comment: 11 pages, 14 figure

Thermodynamically consistent description of the hydrodynamics of free surfaces covered by insoluble surfactants of high concentration

In this paper we propose several models that describe the dynamics of liquid films which are covered by a high concentration layer of insoluble surfactant. First, we briefly review the 'classical' hydrodynamic form of the coupled evolution equations for the film height and surfactant concentration that are well established for small concentrations. Then we re-formulate the basic model as a gradient dynamics based on an underlying free energy functional that accounts for wettability and capillarity. Based on this re-formulation in the framework of nonequilibrium thermodynamics, we propose extensions of the basic hydrodynamic model that account for (i) nonlinear equations of state, (ii) surfactant-dependent wettability, (iii) surfactant phase transitions, and (iv) substrate-mediated condensation. In passing, we discuss important differences to most of the models found in the literature.Comment: 31 pages, 2 figure

Revision of basal macropodids from the Riversleigh World Heritage Area with descriptions of new material of Ganguroo bilamina Cooke, 1997 and a new species

The relationship of basal macropodids (Marsupialia: Macropodoidea) from the Oligo-Miocene of Australia have been unclear. Here, we describe a new species from the Bitesantennary Site within the Riversleigh's World Heritage Area (WHA), Ganguroo bites n. sp., new cranial and dental material of G. bilamina, and reassess material previously described as Bulungamaya delicata and 'Nowidgee matrix'. We performed a metric analysis of dental measurements on species of Thylogale which we then used, in combination with morphological features, to determine species boundaries in the fossils. We also performed a phylogenetic analysis to clarify the relationships of basal macropodid species within Macropodoidea. Our results support the distinction of G. bilamina, G. bites and B. delicata, but 'Nowidgee matrix' appears to be a synonym of B. delicata. The results of our phylogenetic analysis are inconclusive, but dental and cranial features suggest a close affinity between G. bilamina and macropodids. Finally, we revise the current understanding of basal macropodid diversity in Oligocene and Miocene sites at Riversleigh WHA

The oldest fossil record of bandicoots (Marsupialia; Peramelemorphia) from the late Oligocene of Australia

Two new late Oligocene representatives of the marsupial order Peramelemorphia (bandicoots and bilbies) from the Etadunna Formation of South Australia are described here. Bulungu muirheadae sp. nov., from Zone B (Ditjimanka Local Fauna [LF]), is represented by several dentaries and isolated upper and lower molars. Bulungu campbelli sp. nov., from Zone C (Ngapakaldi LF), is represented by a single dentary and maxilla. Together, they represent the oldest fossil bandicoots described to date. Both are small (estimated body mass o

Implementing medical revalidation in the United Kingdom: Findings about organisational changes and impacts from a survey of Responsible Officers.

Objective To describe the implementation of medical revalidation in healthcare organisations in the United Kingdom and to examine reported changes and impacts on the quality of care. Design A cross-sectional online survey gathering both quantitative and qualitative data about structures and processes for medical revalidation and wider quality management in the organisations which employ or contract with doctors (termed 'designated bodies') from the senior doctor in each organisation with statutory responsibility for medical revalidation (termed the 'Responsible Officer'). Setting United Kingdom Participants Responsible Officers in designated bodies in the United Kingdom. Five hundred and ninety-five survey invitations were sent and 374 completed surveys were returned (63%). Main outcome measures The role of Responsible Officers, the development of organisational mechanisms for quality assurance or improvement, decision-making on revalidation recommendations, impact of revalidation and mechanisms for quality assurance or improvement on clinical practice and suggested improvements to revalidation arrangements. Results Responsible Officers report that revalidation has had some impacts on the way medical performance is assured and improved, particularly strengthening appraisal and oversight of quality within organisations and having some impact on clinical practice. They suggest changes to make revalidation less 'one size fits all' and more responsive to individual, organisational and professional contexts. Conclusions Revalidation appears primarily to have improved systems for quality improvement and the management of poor performance to date. There is more to be done to ensure it produces wider benefits, particularly in relation to doctors who already perform well