Extrinsic models for the dielectric response of CaCu{3}Ti{4}O{12}

The large, temperature-independent, low-frequency dielectric constant recently observed in single-crystal CaCu{3}Ti{4}O{12} is most plausibly interpreted as arising from spatial inhomogenities of its local dielectric response. Probable sources of inhomogeneity are the various domain boundaries endemic in such materials: twin, Ca-ordering, and antiphase boundaries. The material in and neighboring such boundaries can be insulating or conducting. We construct a decision tree for the resulting six possible morphologies, and derive or present expressions for the dielectric constant for models of each morphology. We conclude that all six morphologies can yield dielectric behavior consistent with observations and suggest further experiments to distinguish among them.Comment: 9 pages, with 1 postscript figure embedded. Uses REVTEX and epsf macros. Also available at http://www.physics.rutgers.edu/~dhv/preprints/mc_ext/index.htm

High renin and prorenin in plasma and pleural exudate of a patient with the ovarian hyperstimulation syndrome

We present the case of a 35-year-old woman with a severe ovarian hyperstimulation syndrome (OHSS) as a complication of ovulation induction for primary infertility. The clinical picture showed massively enlarged ovaries, pleural effusion and haemoconcentration. She needed a thoracentesis for evacuation of the large pleural effusion. High levels of renin and prorenin were observed in plasma and pleural exudate

Towards a first principles description of phonons in Ni50_{50}Pt50_{50} disordered alloys: the role of relaxation

Using a combination of density-functional perturbation theory and the itinerant coherent potential approximation, we study the effects of atomic relaxation on the inelastic incoherent neutron scattering cross sections of disordered Ni$_{50}$Pt$_{50}$ alloys. We build on previous work, where empirical force constants were adjusted {\it ad hoc} to agree with experiment. After first relaxing all structural parameters within the local-density approximation for ordered NiPt compounds, density-functional perturbation theory is then used to compute phonon spectra, densities of states, and the force constants. The resulting nearest-neighbor force constants are first compared to those of other ordered structures of different stoichiometry, and then used to generate the inelastic scattering cross sections within the itinerant coherent potential approximation. We find that structural relaxation substantially affects the computed force constants and resulting inelastic cross sections, and that the effect is much more pronounced in random alloys than in ordered alloys.Comment: 8 pages, 3 eps figures, uses revtex

Flat branches and pressure amorphization

After summarizing the phenomenology of pressure amorphization (PA), we present a theory of PA based on the notion that one or more branches of the phonon spectrum soften and flatten with increasing pressure. The theory expresses the anharmonic dynamics of the flat branches in terms of local modes, represented by lattice Wannier functions, which are in turn used to construct an effective Hamiltonian. When the low-pressure structure becomes metastable with respect to the high-pressure equilibrium phase and the relevant branches are sufficiently flat, transformation into an amorphous phase is shown to be kinetically favored because of the exponentially large number of both amorphous phases and reaction pathways. In effect, the critical-size nucleus for the first-order phase transition is found to be reduced to a single unit cell, or nearly so. Random nucleation into symmetrically equivalent local configurations characteristic of the high-pressure structure is then shown to overwhelm any possible domain growth, and an ``amorphous'' structure results.Comment: 8 pages with 3 postscript figures embedded; Proceedings of the 4th International Discussion Meeting on Relaxations in Complex Systems, Hersonissos, Heraklion, Crete, June 16-23, ed. K. L. Ngai, Special Issues of the Journal of Non-Crystalline Solids, 200

Lattice dielectric response of CdCu{3}Ti{4}O{12} and of CaCu{3}Ti{4}O{12} from first principles

Structural, vibrational, and lattice dielectric properties of CdCu{3}Ti{4}O{12} are studied using density-functional theory within the local spin-density approximation, and the results are compared with those computed previously for CaCu{3}Ti{4}O{12}. Replacing Ca with Cd is found to leave many calculated quantities largely unaltered, although significant differences do emerge in zone-center optical phonon frequencies and mode effective charges. The computed phonon frequencies of CdCu{3}Ti{4}O{12} are found to be in excellent agreement with experiment, and the computed lattice contribution to the intrinsic static dielectric constant (~60) also agrees exceptionally well with a recent optical absorption experiment. These results provide further support for a picture in which the lattice dielectric response is essentially conventional, suggesting an extrinsic origin for the anomalous low-frequency dielectric response recently observed in both materials.Comment: 5 pages; uses REVTEX macros. Also available at http://www.physics.rutgers.edu/~dhv/preprints/lh_cdct/index.htm

Growing up with juvenile vulvar lichen sclerosus, the experiences and care needs of adult women with lichen sclerosus since childhood:A qualitative exploration

BackgroundVulvar lichen sclerosus (VLS) is a chronic remitting condition that affects the genital skin of females of all ages. Although qualitative studies have been conducted that have focused on women with VLS in mid-life or beyond, less is known about the experiences of individuals with VLS from childhood or adolescence onward.Objectives To gain an understanding of the experiences of women with a history of juvenile VLS (JVLS) with regard to the impact of the disease on their personal lives, and their experiences and needs regarding care and guidance.Methods A qualitative study was conducted consisting of 27 in-depth face-to-face interviews with adult women with a histologically confirmed history of JVLS, striving for maximum variation and saturation. Interviews were audio recorded and transcribed verbatim. A thorough thematic content analysis was performed.Results Three main themes were identified. Theme 1 was named 'Varying impact of living with JVLS': women experienced diverse emotional and physical impacts, from shame and denial to complete acceptance, from restrictions in daily functioning to no limitations; they felt hindered by their own lack of knowledge about JVLS and generally expressed positivity in sharing their experiences with people close to them. Theme 2 was entitled 'Finding one's way in care and guidance': while navigating care and guidance, women often felt hindered by knowledge gaps among healthcare professionals (HCPs), lack of continuity in care and guidance, lack of life phase-adjusted and future-oriented information provision, inadequate guidance around life events and insufficient monitoring of determinants of treatment adherence. Theme 3 was named 'Need for patient-tailored care involving appropriate and compassionate care and guidance': patients stressed the need for age-appropriate and life phase-adjusted information, guidance around life events and compassionate contact with knowledgeable HCPs aware of the determinants of treatment adherence and influencing factors.Conclusions Age-appropriate, life phase-adjusted, individually tailored care for women diagnosed with VLS in childhood or adolescence is needed. Care and guidance from childhood onward should encompass a standard of care adapted to the individual as their needs change over time. This involves taking interpersonal differences into account, including differences in support network and coping strategies. These findings demonstrate the need to improve awareness and knowledge about JVLS/VLS among HCPs, especially primary care providers, and among the general public

Structured analysis of histopathological characteristics of vulvar lichen sclerosus in a juvenile population

Genital lichen sclerosus (LS), a chronic noninfectious dermatosis, is not rare in pediatric dermatology. The histopathological diagnosis in children and adults in both genital and nongenital LS is considered to be the same and encompasses a broad range of possible characteristics. Clinical manifestations and treatment options of genital LS in children are different depending on gender. The vast majority of boys are treated with circumcision, making for a larger amount of information on the histopathology of genital LS in boys, whereas substantial information on the histopathology of juvenile vulvar LS is lacking. In girls, vulvar LS almost always persists beyond puberty and, therefore, presents a particular challenge to clinicians and cause for concern for the patient. Vulvar LS in childhood and adolescence (juveniles) is underreported, and there are uncertainties with regard to the long-term course of the disease when it occurs at an age when the vulva is still developing. The present study investigates biopsi

Local Isoelectronic Reactivity of Solid Surfaces

The quantity w^N(r) = ( 1/ k^2 T_el)[partial n(r, T_el) / partial T_el]_(v(r),N) is introduced as a convenient measure of the local isoelectronic reactivity of surfaces. It characterizes the local polarizability of the surface and it can be calculated easily. The quantity w^N(r) supplements the charge transfer reactivity measured e.g. by the local softness to which it is closely related. We demonstrate the applicability and virtues of the function w^N(r) for the example of hydrogen dissociation and adsorption on Pd(100).Comment: RevTeX, 13 pages, 3 figures, to appear in Phys. Rev. Let

Phonons in random alloys: the itinerant coherent-potential approximation

We present the itinerant coherent-potential approximation(ICPA), an analytic, translationally invariant and tractable form of augmented-space-based, multiple-scattering theory in a single-site approximation for harmonic phonons in realistic random binary alloys with mass and force-constant disorder. We provide expressions for quantities needed for comparison with experimental structure factors such as partial and average spectral functions and derive the sum rules associated with them. Numerical results are presented for Ni_{55} Pd_{45} and Ni_{50} Pt_{50} alloys which serve as test cases, the former for weak force-constant disorder and the latter for strong. We present results on dispersion curves and disorder-induced widths. Direct comparisons with the single-site coherent potential approximation(CPA) and experiment are made which provide insight into the physics of force-constant changes in random alloys. The CPA accounts well for the weak force-constant disorder case but fails for strong force-constant disorder where the ICPA succeeds.Comment: 19 pages, 12 eps figures, uses RevTex