P. B. Tavares

Effect of preparation method on the solid state properties and the deN2O performance of CuO–CeO2 oxides

The present work aims at investigating the catalytic decomposition of N2O over CuO–CeO2 single or mixed oxides prepared by different synthesis routes, i.e., impregnation, precipitation and exotemplating. To gain insight into the particular role of CeO2 as well as of CuO–CeO2 interactions, three different types of materials were prepared and tested for N2O decomposition both in the absence and presence of excess O2: (i) bare CeO2 prepared by precipitation and exotemplating, (ii) CuO/CeO2 oxides synthesized by the impregnation of CeO2 samples prepared in (i) with CuO, and iii) single stage CuO–CeO2 mixed oxides synthesized employing the co-precipitation and exotemplating methods. The corresponding commercial samples were also examined for comparison purposes. All materials were characterized by N2 adsorption at −196 °C, X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), micro-Raman spectroscopy (micro-Raman) and scanning electron microscopy (SEM). The results demonstrated the key role of the preparation procedure on the direct catalytic decomposition of N2O. Among the bare CeO2 samples, the best performance was obtained with the samples prepared by the precipitation method, followed by exotemplating, while commercial CeO2 showed the lowest performance. All bare oxides demonstrated low N2O conversion, never exceeding 40% at 600 °C. Amongst the CuO–CeO2 oxides, the optimum performance was observed for those prepared by co-precipitation, which achieved complete N2O conversion at 550 °C. In the presence of excess oxygen in the feed stream, a slight degradation is observed, with the sequence of deN2O performance remaining unchanged. The superiority of the Cu–Ce mixed oxides prepared by precipitation compared to all of the other materials can be mainly ascribed to their excellent redox properties, linked to Ce4+/Ce3+ and Cu2+/Cu+ redox pairs. A redox mechanism for the N2O catalytic decomposition is proposed, involving N2O adsorption on Cu+ sites and their regeneration through Cu–ceria interactions.

Epidermolytic hyperkeratosis with palmoplantar keratoderma in a patient with KRT10 mutation

We report the case of a 12-year-old girl presenting at birth with erythroderma, erosions and blisters scattered over the integument. By the age of 3 she presented generalized hyperkeratotic plaques with a cobblestone pattern and a pungent odour, most prominently around flexures, scalp and palmoplantar areas. Clinical, histological and ultrastructural findings confirmed the diagnosis of epidermolytic hyperkeratosis (EHK). Molecular genetic analysis revealed a mutation in the KRT10 gene. Treatment with oral acitretin was attempted but it was discontinued due to hepatic dysfunction and marked desquamation and blistering. EHK is a rare autosomal dominant disorder of keratinization, caused by mutations in either the KRT1 or KRT10 genes. Although palmoplantar keratoderma is typically found in patients with KRT1 mutation, our patient presents EHK with palmoplantar involvement and KRT10 mutation. Moreover, a poor response to systemic retinoids was observed, contrary to what is expected in patients with KRT10 mutation. Even though management is usually unsatisfactory, some patients with this lifelong and serious condition may experience improvement with age.

Resistive switching in ferroelectric lead-free 0.5Ba (Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 thin films

In this work, resistive switching in pulsed laser deposited ferroelectric lead-free 0.5Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 (0.5BZT–0.5BCT) thin films was investigated. This study reveals that films grown at 5.5 J cm−2 have shown optimal ferroelectric and resistive switching response, which are attributed to high tetragonality, large grain size and less defect concentration. Au/0.5BZT–0.5BCT/Pt capacitors show the electroforming free resistive switching that is explained based on the polarization modulation of the Schottky-like barrier at the 0.5BZT–0.5BCT/Au interface. The polarization induced resistive switching is evidenced by its disappearance as the temperature increases to the Curie temperature. The capacitor based on film grown at 5.5 J cm−2 shows resistive switching characterized by high switching ratio of 106 at a low set/reset voltage ≈1 V, and by a stable memory window, which are highly required for memory applications.

Competing exchanges and spin?phonon coupling in Eu1?xRxMnO3 (R=Y, Lu)

This work is focused on the phase diagrams and physical properties of Y-doped and Lu-doped EuMnO3. The differences in the corresponding phase boundaries in the (x,T) phase diagram could be overcome by considering a scaling of the Y(3+) and Lu(3+) concentrations to the tolerance factor. This outcome evidences that the tolerance factor is in fact a more reliable representative of the lattice deformation induced by doping. The normalization of the phase boundaries using the tolerance factor corroborates previous theoretical outcomes regarding the key role of competitive FM and AFM exchanges in determining the phase diagrams of manganite perovskites. However, significant differences in the nature and number of phases at low temperatures and concentrations could not be explained by just considering the normalization to the tolerance factor. The vertical phase boundary observed just for Lu-doped EuMnO3, close to 10% Lu, is understood by considering a low temperature Peierls-type spin-phonon coupling, which stabilizes the AFM-4 phase in Lu-doped EuMnO3.

An e6a2 BCR-ABL fusion transcript in a CML patient having an iliac chloroma at initial presentation

Philadelphia chromosome (Ph1), which results from the reciprocal translocation t(9;22)(q34;q11), is the hallmark of almost all the cases of chronic myeloid leukemia (CML). Most patients express eit...

THz and infrared studies of multiferroic hexagonal Y1− x Eu x MnO3 (x = 0–0.2) ceramics

We report an investigation of hexagonal Y1− x Eu x MnO3 ceramics with x = 0, 0.1, and 0.2 using infrared (IR) and terahertz (THz) spectroscopies in the temperature range between 5 and 900 K. The temperature dependence of the THz permittivity reveals a kink near the antiferromagnetic (AFM) phase transition temperature T N ≈ 70 K, giving evidence of a strong spin–lattice coupling. Below T N, two absorption peaks were revealed in the THz spectra close to 43 and 73 cm−1. While the first peak corresponds to a sharp AFM resonance exhibiting softening on heating towards T N, the second one may be attributed to an impurity mode or a multiphonon absorption peak. High-temperature THz spectra measured up to 900 K reveal only small gradual increase of the permittivity in agreement with a weak phonon softening observed in the IR reflectance spectra upon heating. This corresponds to an improper ferroelectric character of the phase transition proposed from first principle calculations by Fennie and Rabe (Phys. Rev. B 72: 100103(R), 2005).

Magnetically-induced lattice distortions and ferroelectricity in magnetoelectric GdMnO3

In this work we investigate the magnetic field dependence of A(g) octahedra rotation (tilt) and B(2g) symmetric stretching modes frequencies at different temperatures. Our field-dependent Raman investigation at 10 K is interpreted by an ionic displacive nature of the magnetically-induced ferroelectric phase transition. The increasing frequency of the A(g) tilt mode with magnetic field gives evidence for the increase of the MnO(6) tilt angle, which in turn leads to a weakening of the ferromagnetic exchange interaction, yielding the necessary conditions for the onset of ferroelectricity on the basis of the inverse Dzyaloshinskii-Moriya interaction. The frequency change of the B(2g) symmetric stretching mode at the ferroelectric phase transition enables one to estimate the shift of oxygen ion positions and the corresponding spontaneous polarization of 480 μC m(-2) in magnitude, which is of the same order as earlier reported values in single crystals.

On the ferroelectric and magnetoelectric mechanisms in low Fe3+ doped TbMnO3

Abstract This work addresses the effect of substituting Mn 3+ by Fe 3+ at the octahedral site of TbMnO 3 on the magnetic phase sequence, ferroelectric and magnetoelectric properties, keeping the Fe 3+ concentration below 5%. The temperature dependence of the specific heat, dielectric permittivity and electric polarization was studied as a function of Fe 3+ concentration and applied magnetic field. From the experimental results a strong decrease of the electric polarization with increasing Fe 3+ substitution is observed, vanishing above a concentration of 4%. However, within this range, a significant increase of the magnetic sensitivity of the electric polarization is obtained by increasing Fe 3+ concentration. For Fe 3+ concentration above 4%, a non-polar phase emerges, whose spin structure prevents ferroelectricity according to the Dzyaloshinskii-Moriya model. The experimental results here reported reveal the crucial effect of B-site substitution on the magnetic phase sequence, as well as, on the polar and magnetoelectric properties, evidencing the important role played by the e g electrons on the stabilization of the magnetic structures that are suitable for the emergence of electric polarization.

Cat eye syndrome and growth hormone deficiency with pituitary anomalies: a case report and review of the literature.

Cat eye syndrome is a rare congenital disease characterized by the existence of a supernumerary chromosome derived from chromosome 22, with a variable phenotype comprising anal atresia, coloboma of the iris and preauricular tags or pits. We report a girl with cat eye syndrome, presenting short stature, with growth hormone deficiency due to posterior pituitary ectopia. Short stature is a common feature of this syndrome, and the association with a structural pituitary anomaly has been described, however growth hormone deficiency and the underlying mechanisms are rarely reported. A review on short stature and growth hormone deficiency in cat eye syndrome is conducted.

Kallmann syndrome in a female adolescent: a new mutation in the FGFR1 gene

The Kallmann syndrome is characterised by the association of hypogonadotropic hypogonadism and hypo/anosmia. It represents a phenotypically and genotypically heterogeneous clinical entity, with six genes identified so far in the literature—KAL1, FGFR1, PROKR2, PROK2, CHD7 and FGF8. Mutations in the FGFR1 gene can be found in approximately 10% of the patients. The authors present the case of a female adolescent with hypogonadotropic hypogonadism and impaired olfactory acuity in the presence of hypoplasia of the nasal sulcus and agenesis of the olfactory bulbs. The molecular analysis of the fibroblast growth factor receptor 1 identified a heterozygous mutation c.1377_78insA (p.V460SfsX3) in exon 10 of FGFR1 gene. This mutation has not yet been reported in the literature. A theoretical review of clinical features and therapeutic approach of this syndrome is also presented.