Classical Phase Fluctuations in Incommensurate Peierls Chains

In the pseudogap regime of one-dimensional incommensurate Peierls systems, fluctuations of the phase of the order parameter prohibit the emergence of long-range order and generate a finite correlation length. For classical phase fluctuations, we present exact results for the average electronic density of states, the mean localization length, the electronic specific heat and the spin susceptibility at low temperatures. Our results for the susceptibility give a good fit to experimental data.Comment: 4 Revtex pages, 4 figures, submitted to Phys. Rev. Let

Algorithm for obtaining the gradient expansion of the local density of states and the free energy of a superconductor

We present an efficient algorithm for obtaining the gauge-invariant gradient expansion of the local density of states and the free energy of a clean superconductor. Our method is based on a new mapping of the semiclassical linearized Gorkov equations onto a pseudo-Schroedinger equation for a three-component wave-function psi(x), where one component is directly related to the local density of states. Because psi(x) satisfies a linear equation of motion, successive terms in the gradient expansion can be obtained by simple linear iteration. Our method works equally well for real and complex order parameter, and in the presence of arbitrary external fields. We confirm a recent calculation of the fourth order correction to the free energy by Kosztin, Kos, Stone and Leggett [Phys. Rev. B 58, 9365 (1998)], who obtained a discrepancy with an earlier result by Tewordt [Z. Phys. 180, 385 (1964)]. We also give the fourth order correction to the local density of states, which has not been published before.Comment: 12 preprint pages, added remark concerning Eilenberger equation, accepted for publication in Phys. Rev.

Ferromagnetic Luttinger Liquids

We study weak itinerant ferromagnetism in one-dimensional Fermi systems using perturbation theory and bosonization. We find that longitudinal spin fluctuations propagate ballistically with velocity v_m << v_F, where v_F is the Fermi velocity. This leads to a large anomalous dimension in the spin-channel and strong algebraic singularities in the single-particle spectral function and in the transverse structure factor for momentum transfers q ~ 2 Delta/v_F, where 2 Delta is the exchange splitting.Comment: 4 pages, 3 figure

Second Primary Neoplasms in Patients With Uveal Melanoma: A SEER Database Analysis

PURPOSE: To determine the risk of second primary neoplasms (SPNs) in subjects previously diagnosed with uveal melanoma (UM), including an analysis on whether radiotherapy is a risk factor to develop these SPNs. DESIGN: Retrospective cohort study. METHODS: Using the Surveillance, Epidemiology, and End Results (SEER) 9 database, we identified patients diagnosed with UM as their first malignancy between 1973 and 2011 (n = 3976). We obtained standardized incidence ratios (SIR) and excess absolute risks of SPNs on patients with UM compared to a reference population. Multivariate Cox regression models were used to evaluate the effect of radiotherapy in SPN risk. RESULTS: Sixteen percent (n = 641) of the patients developed SPNs during a median follow-up of 83 months (range, 1-463 months). This represented an 11% excess risk compared to the reference population, mainly owing to a significantly increased risk of skin melanomas (SIR = 2.93, 95% CI: 2.23-3.78) and kidney tumors (SIR = 1.91, 95% CI: 1.27-2.76), primarily in those diagnosed between 30 and 59 years of age. The occurrence of second UM was also increased (SIR = 16.90, 95% CI: 9.00-28.90), which likely includes recurrences misclassified as a second cancer. Radiotherapy was performed in 39% (n = 1538) of the patients. Multivariate analysis revealed that this treatment was not an independent risk factor for SPNs (hazard ratio = 1.06, 95% CI: 0.88-1.26, P = .54). CONCLUSIONS: Patients with UM presented an 11% higher risk of SPNs compared to the reference population. Radiotherapy does not seem to be a risk factor. SPNs should be considered in the surveillance of UM.info:eu-repo/semantics/publishedVersio

Exact Numerical Calculation of the Density of States of the Fluctuating Gap Model

We develop a powerful numerical algorithm for calculating the density of states rho(omega) of the fluctuating gap model, which describes the low-energy physics of disordered Peierls and spin-Peierls chains. We obtain rho(omega) with unprecedented accuracy from the solution of a simple initial value problem for a single Riccati equation. Generating Gaussian disorder with large correlation length xi by means of a simple Markov process, we present a quantitative study of the behavior of rho (omega) in the pseudogap regime. In particular, we show that in the commensurate case and in the absence of forward scattering the pseudogap is overshadowed by a Dyson singularity below a certain energy scale omega^{ast}, which we explicitly calculate as a function of xi.Comment: 4 revtex pages, 3 figure

Morphological features and mucin expression profile of breast carcinomas with signet-ring cell differentiation

Signet-ring cells are relatively common in breast cancers but are frequently overlooked. Although previously defined as a subtype of mucin producing carcinomas, breast carcinomas with signet-ring cell (SRC) differentiation nowadays are not considered a distinct entity.The objective of the present study was to characterize the morphological features and mucin expression profile of breast carcinomas with SRC differentiation. All breast carcinomas diagnosed at Centro Hospitalar S. Joao between 1996 and 2006 in which the pathology report mentioned the presence of SRCs (n= 11) and four mucinous carcinomas were included in the study. The frequency of SRCs and immunohistochemistry expression of MUC1/MUC2/MUC5AC/MUC6 were evaluated.We confirmed that SRC differentiation can occur in different histological types, including ductal, lobular, mucinous and metaplastic carcinomas. The proportion of SRCs was highly variable (range: 8-70%). Tumors encompassed SRCs of intracytoplasmic lumina and goblet-cell type. A higher percentage of SRCs was associated with lymphovascular invasion (p= 0.047). All tumors expressed cytoplasmic and membranous MUC1. Secretory mucins were more frequent in mucinous carcinomas and in carcinomas with extensive SRC differentiation.We conclude that besides the usefulness of mucin immunodetection for the differential diagnosis of carcinomas with SRC differentiation of breast origin, it is important to report SRC differentiation regardless of histological type because of its intrinsic prognostic value.We especially thank Professor Sobrinho-Simões for the careful review of the manuscript. IPATIMUP integrates the i3S Research Unit, which is partially supported by FCT, the Portuguese Foundation for Science and Technology. This work is funded by FEDER funds through the Operational Program for Competitiveness Factors-COMPETE and National Funds through the FCT-Foundation for Science and Technology , under the projects: PEst-C/SAU/LA0003/2013 and PTDC/BBB-EBI/0786/2012

Optical conductivity of a quasi-one-dimensional system with fluctuating order

We describe a formally exact method to calculate the optical conductivity of a one-dimensional system with fluctuating order. For classical phase fluctuations we explicitly determine the optical conductivity by solving two coupled Fokker-Planck equations numerically. Our results differ considerably from perturbation theory and in contrast to Gaussian order parameter fluctuations show a strong dependence on the correlation length.Comment: 7 pages, 2 figure

Subgap tunneling through channels of polarons and bipolarons in chain conductors

We suggest a theory of internal coherent tunneling in the pseudogap region where the applied voltage is below the free electron gap. We consider quasi 1D systems where the gap is originated by a lattice dimerization like in polyacethylene, as well as low symmetry 1D semiconductors. Results may be applied to several types of conjugated polymers, to semiconducting nanotubes and to quantum wires of semiconductors. The approach may be generalized to tunneling in strongly correlated systems showing the pseudogap effect, like the family of High Tc materials in the undoped limit. We demonstrate the evolution of tunneling current-voltage characteristics from smearing the free electron gap down to threshold for tunneling of polarons and further down to the region of bi-electronic tunneling via bipolarons or kink pairs.Comment: 14 pages, 8 postscript figure

Collective fields in the functional renormalization group for fermions, Ward identities, and the exact solution of the Tomonaga-Luttinger model

We develop a new formulation of the functional renormalization group (RG) for interacting fermions. Our approach unifies the purely fermionic formulation based on the Grassmannian functional integral, which has been used in recent years by many authors, with the traditional Wilsonian RG approach to quantum systems pioneered by Hertz [Phys. Rev. B 14, 1165 (1976)], which attempts to describe the infrared behavior of the system in terms of an effective bosonic theory associated with the soft modes of the underlying fermionic problem. In our approach, we decouple the interaction by means of a suitable Hubbard-Stratonovich transformation (following the Hertz-approach), but do not eliminate the fermions; instead, we derive an exact hierarchy of RG flow equations for the irreducible vertices of the resulting coupled field theory involving both fermionic and bosonic fields. The freedom of choosing a momentum transfer cutoff for the bosonic soft modes in addition to the usual band cutoff for the fermions opens the possibility of new RG schemes. In particular, we show how the exact solution of the Tomonaga-Luttinger model emerges from the functional RG if one works with a momentum transfer cutoff. Then the Ward identities associated with the local particle conservation at each Fermi point are valid at every stage of the RG flow and provide a solution of an infinite hierarchy of flow equations for the irreducible vertices. The RG flow equation for the irreducible single-particle self-energy can then be closed and can be reduced to a linear integro-differential equation, the solution of which yields the result familiar from bosonization. We suggest new truncation schemes of the exact hierarchy of flow equations, which might be useful even outside the weak coupling regime.Comment: 27 pages, 15 figures; published version, some typos correcte

Canine ovarian gonadoblastoma with dysgerminoma overgrowth: A case study and literature review

Background: Gonadoblastoma (GB) is a rare mixed germ cell-sex cord-stromal tumour, first described in humans, commonly found in dysgenetic gonads of intersex patients that have a Y chromosome. However, this entity in not recognized in the WHO classification of tumours of genital system of domestic animals. Herein, we describe a case of ovarian gonadoblastoma with proliferation of dysgerminoma and sex cord-stromal tumour components, in a phenotypically and cytogenetically normal bitch. Case presentation: A 17-year-old cross-breed bitch had a firm, grey-white multinodular mass in the left ovary. The tumour was submitted to histopathological examination and Y chromosome detected through karyotype analysis and PCR studies. Microscopically, the ovary was almost replaced by an irregular neoplasm composed of three distinct, intermixed elements: dysgerminoma, mixed germ cell-sex cord-stromal tumour resembling human GB and a proliferative sex cord-stromal tumour component. The germ cells of gonadoblastoma and dysgerminoma components were immunoreactive for c-KIT. Sex cord-stromal cells of gonadoblastoma were immunoreactive for a-inhibin. The sex cord-stromal tumour was immunoreactive for AE1/AE3, occasionally for a-inhibin and negative for epithelial membrane antigen (EMA). The karyotype was 78, XX and PCR analysis confirmed the absence of the Y chromosome. Conclusion: Based on these findings, a diagnosis of gonadoblastoma with proliferation of dysgerminoma and sex cord-stromal tumour was made. This is the first case of ovarian gonadoblastoma in a female dog.Ana R. Flores (SFRH/BD/116373/2016) and João Lobo (SFRH/BD/132751/2017) acknowledge FCT, the Portuguese Foundation for Science and Technology, for financial support. IPATIMUP integrates the i3S Research Unit, which is partially supported by FEDER through the Operational Programme for Competitiveness Factors-COMPETE and National Funds through the Portuguese Foundation for Science and Technology (FCT), under the project number PEst-C/SAU/LA0003/2013. We kindly thank Professor Beatriz Porto and Mrs. Cláudia Oliveira from laboratory of Cytogenetics of the ICBAS-UP for the karyotype analysis and Msc. Patrícia Barradas who provided PCR technical support. We would like to thank Paulo Flores for help with scientific illustration