Metastable monoclinic [110] layered perovskite Dy2Ti2O7 thin films for ferroelectric applications.

Using the Combinatorial Substrate Epitaxy (CSE) approach, we report the stabilization of Dy2Ti2O7 epitaxial monoclinic, layered-perovskite phase Dy2Ti2O7 thin films. To achieve this, the films are deposited on high density, polished La2Ti2O7 polycrystalline ceramic substrates, which are stable as monoclinic layered-perovskites, and were prepared by conventional sintering. Microstructural analysis using electron backscatter diffraction (EBSD), electron diffraction (ED), and high-resolution transmission electron microscopy (HRTEM) support this observation. Further, they reveal that the cubic pyrochlore phase is observed far from the interface as films are grown thicker (100 nm), confirming the importance of substrate-induced phase and space group selection. This works reinforces the vast potential of CSE to promote the stabilization of metastable phases, thus giving access to new functional oxide materials, across a range of novel material systems including ferroelectrics.

Total-reflection inelastic X-ray scattering from a 10-nm thick La0.6Sr0.4CoO3 thin film.

To study equilibrium changes in composition, valence, and electronic structure near the surface and into the bulk, we demonstrate the use of a new approach, total-reflection inelastic x-ray scattering, as a sub-keV spectroscopy capable of depth profiling chemical changes in thin films with nanometer resolution. By comparing data acquired under total x-ray reflection and penetrating conditions, we are able to separate the O K-edge spectra from a 10 nm La0.6Sr0.4CoO3 thin film from that of the underlying SrTiO3 substrate. With a smaller wavelength probe than comparable soft x-ray absorption measurements, we also describe the ability to easily access dipole-forbidden final states, using the dramatic evolution of the La N4,5 edge with momentum transfer as an example.

Cation disorder in Ga1212.

Substitution of calcium for strontium in LnSr2-xCaxCu2GaO7 (Ln = La, Pr, Nd, Gd, Ho, Er, Tm, and Yb) materials at ambient pressure and 975 degrees C results in complete substitution of calcium for strontium in the lanthanum and praseodymium systems and partial substitution in the other lanthanide systems. The calcium saturation level depends on the size of the Ln cation, and in all cases, a decrease in the lattice parameters with calcium concentration was observed until a common, lower bound, average A-cation size is reached. Site occupancies from X-ray and neutron diffraction experiments for LnSr2-xCaxCu2GaO7 (x = 0 and x = 2) confirm that the A-cations distribute between the two blocking-layer sites and the active-layer site based on size. A quantitative link between cation distribution and relative site-specific cation enthalpy for calcium, strontium, and lanthanum within the gallate structure is derived. The cation distribution in other similar materials can potentially be modeled.

[Osmolarity and arginine-vasopressin in children born after acute fetal-neonatal distress]. / Control osmolar y arginina vasopresina en niños nacidos después de un sufrimiento fetoneonatal agudo.

A study of urinary osmolarities and plasmatic level of arginine-vasopressin (AVP) 48 hours after birth in a group of 70 newborns (30 of which are normal and 40 of which have acute perinatal hypoxia), selected according to previously established criteria is carried out. An evolutionary study of urinary osmolarities of newborns with acute perinatal hypoxia, osmolar index and its relation to plasmatic levels of AVP during the first week of life is also considered. AVP 48 hours after birth was blatantly more elevated among those newborns who had shown acidosis at birth (p less than 0.001) which correlated significantly with urinary osmolarity, although it showed low figures (p less than 0.05). This same correlation (p less than 0.001 and p less than 0.05) appears with osmolar index and urinary osmolarity on successive days, but it is important to point out that vasopressin decreased to base values at the end of the first week of life while osmolarities in urine increased. Conclusions are: 1) AVP is higher after 48 hours of life among those newborns with acute perinatal hypoxia and decreases progressively during the first week of life, being comparable to values obtained from normally born children 48 hours after birth at the eight day of life. 2) Renal response to this hormone is slight during the first days of life.

[Relation between the basal levels of prolactin and the decree of breast function during lactation inhibition]. / Relacion entre niveles basales de prolactina y grado de funcion mamaria durante la inhibicion de la lactancia.

PIP: The authors report on 59 cases of lactation inhibition by different drugs (placebo, etilbestrol, vitamin B6 and bromocriptine). The patients were between 20-30 and did not wish to breastfeed. Relation between basal levels of prolactin (PRLH) and breast turgency, pain, and milk secretion was studied. Examinations were done 24 hours after delivery, and again 7 and 14 days later. There was a significant correlation between basal levels of PRLH and breast turgency at every examination. Pain was related to prolactinemia only 7 and 14 days after delivery, while milk secretion had a significant correlation with prolactinemia 24 hours after delivery, and again 7 days later, but not at the time of the third examination.^ieng