Stochastic Polarization Instability in PbTiO_{3}.

Although discussions of structural phase transitions in prototypical ferroelectric systems with the perovskite structure, such as BaTiO_{3} and PbTiO_{3}, started almost seventy years ago, an atomic-level description of the polar characteristics as a function of temperature, pressure, and composition remains topical. Here we provide a novel quantitative description of the temperature-driven local structural correlations in PbTiO_{3} via the development of characteristic relative cationic shifts. The results give new insights into the phase transition beyond those reliant on the long-range order. The ferroelectric-to-paraelectric transition of PbTiO_{3} is realized by the extent of a stochastic polarization instability driven by a progressive misalignment instead of a complete disappearance of the local dipoles, which further suggests that such polarization instability is chemically induced at the morphotropic phase boundary of PbTiO_{3}-based solid solutions with giant piezoelectric effect. As such, our results not only identify the evolving atomistic disorder in a perovskite-based ferroelectric system, but also suggest that polarization instability can serve as a generic fingerprint for phase transitions as well as for better understanding structure-property relationships in PbTiO_{3}-based ferroelectric solid solutions.

Multistep coupling of preexisting local ferroic distortions in PbTiO3 above the Curie temperature.

Temperature-dependent Raman spectroscopic analyses were performed for the prominent ferroelectric PbTiO3 in the temperature range 130-1040 K, focusing particularly on its paraelectric state above the Curie temperature [Formula: see text] K. The temperature evolution of the anomalous Raman scattering reveals that not only local ferroic distortions persist at temperatures well above [Formula: see text], but also there is a sequence of different coupling processes preceding the appearance of long-range ferroelectric order at [Formula: see text]. Our results indicate that, similar to relaxor ferroelectrics, the paraelectric phase of PbTiO3 can be considered as an ergodic system of local ferroic distortions, which only on average appears to have cubic symmetry.

POLYGLANDULAR AUTOIMMUNE SYNDROME ASSOCIATED WITH MULTIPLE AUTOIMMUNE CONDITIONS AND ATOPIC DERMATITIS - AN UNUSUAL MANIFESTATION OF A POLYAUTOIMMUNITY PHENOTYPE.

INTRODUCTION: The polyglandular autoimmune syndrome (PAS) type III is a rare condition defined as the coexistence of autoimmune thyroid disorder with other endocrine autoimmune diseases, including type 1 diabetes, without adrenal dysfunction. PAS may associate with other non-endocrine autoimmune diseases, overlapping with the multiple autoimmune syndromes (MAS). We present a case of PAS III/ MAS type 3, including autoimmune thyroiditis, autoimmune diabetes, vitiligo, lupus erythematosus, associated with adult-onset atopic dermatitis, a combination not reported previously. CASE REPORT: A 40 years old woman, registered as nurse working in dialysis unit, previously diagnosed with vitiligo, euthyroid autoimmune thyroiditis and disseminated granuloma annulare, with personal and familial history of atopic disorders, presented in our clinic for disseminated eczematous and lichenoid cutaneous rashes. She was tested positive for antinuclear, anti-double stranded DNA and anti-histone antibodies, with inflammatory syndrome and marginal lymphopenia and she was diagnosed with systemic lupus erythematosus (SLE). Subsequently, moderate hyperglycemia, positive anti-glutamic acid decarboxylase antibodies and low C-peptide level prompted the diagnosis of autoimmune diabetes. Recurrent flexural eczematous rashes, with negative epicutaneous tests but positive specific IgE tests for common allergens fulfilled the clinical criteria for the diagnosis of atopic dermatitis. The clinical, immunological and glycemic status were controlled with low doses of oral prednisone (<0.5 mg/kg), methotrexate (10mg/week), antimalarials, metformin, emollients and photoprotection. After changing her workplace, the immunosuppressive treatment could be discontinued, and the patient maintained normal immunological and biochemical profile at 6 months follow-up.This case brings a unique perspective on the evolution, associations spectrum and the management challenges of endocrine polyautoimmunity associated with atopic diathesis.

Thorium determination in intercomparison samples and in some Romanian building materials by gamma ray spectrometry.

Thorium content in zircon sand, thorium ore and a thorium liquid sample (EU Laboratories Network Intercomparison), as well as in some Romanian building materials: sand, wood, tufa, asbestos-cement. cement mill dust, coal fly ash, bricks, and tile (28 samples) was deterimined by gamma ray spectrometry. For the building materials, 226Ra, 40K and 137Cs specific activities were also measured. The results were compared with the Romanian legal norms concerning the highest admissible levels for 232Th, 226Ra. and 40K radioactivity. and to Th, U, and K concentration values previously determined in our laboratory on similar types of samples.