Solid state reaction crystallization and amorphization on thin film Fe-Zr multilayers

We study in this paper the thin multilayered film of the system Fe _x Zr_1-x using conversion electron Mössbauer spectroscopy (CEMS) as well as Rutherford backscattering spectroscopy (RBS). The solid state reaction (SSR) at 500°C for thex=0.33 andx=0.67 concentrations produces crystalline and amorphous phases. For the concentrationx=0.50 only an amorphous phase is obtained. For reactions at 700°C, besides Fe-Zr phases, another one is observed in the CEMS spectrum. This phase may be associated with some FeSi compound since the RBS profile shows the presence of Si at the surface.This work was supported by CNPq, FINEP and FAPERGS.     

Decrease in dielectric loss of CaCu3Ti4O12 by the addition of TeO2

CaCu₃Ti₄O₁₂ (CCTO) has challenged for the last few years the scientific community due to its large dielectric constant, which is almost temperature and frequency independent, from 100 K to 400 K and from 1 kHz to 1 MHz, respectively. This makes the material desirable for many electronic applications. However, the dissipation factor is very large, with tan δ values, at room temperature and 1 kHz, higher than 0.1.In our work we report how the addition of TeO₂ lowers the dielectric loss and, although there is a decrease of dielectric constant of doped samples relatively to the undoped one, high dielectric constant values are still being reached. The sample of doped CCTO with 1.5% of TeO₂ by weight, presents, at room temperature and 60 kHz, a large dielectric constant, over 3000, and a dissipation factor around 0.09, which represents a decrease on tan δ over 30% relatively to the CCTO undoped sample. Two relaxation processes were identified for all the samples, one at MHz region and the other one at low frequency region (< 1 kHz). DC bias voltage was applied up to 40 V and a strong dc bias influence on the low frequency region was observed both at dielectric and impedance responses of the undoped sample, which was much weaker than the dc bias effects on the 4% Te doped sample.Dielectric measurements will be discussed and correlated with the samples' microstructure, supported on internal barrier layer capacitance (IBLC) and surface barrier layer capacitance (SBLC) models.     

Radium equivalent and annual effective dose from geological samples from Pedra – Pernambuco – Brazil

The natural radioactivity of an uranium-anomalous area utilized for agricultural activities in Pedra, Brazil, was monitored. For this, samples from the granite and calcium-silicate amphibole rocks underlying this area and also from samples of the soil derived from these rocks were collected and analyzed by high-resolution gamma spectrometry. The equivalent radium (Ra_eq) was used as a reference for estimating the rate of the effective equivalent dose. The average, minimum and maximum values for the samples were of 319.2 Bq kg^?1 (91.1–758.5 Bq kg^?1) for soil; 327.5 Bq kg^?1 (36.3–1624.0 Bq kg^?1) for granitic rocks and 70,124.5 Bq kg^?1 (16,979.6–147,159.0 Bq kg^?1) for the calcium-silicate amphibole rocks. An estimation of the external exposition was carried out based on the calculation of the parameters obtained.     

A polyhedral approach to the single row facility layout problem

The single row facility layout problem (SRFLP) is the NP-hard problem of arranging facilities on a line, while minimizing a weighted sum of the distances between facility pairs. In this paper, a detailed polyhedral study of the SRFLP is performed, and several huge classes of valid and facet-inducing inequalities are derived. Some separation heuristics are presented, along with a primal heuristic based on multi-dimensional scaling. Finally, a branch-and-cut algorithm is described and some encouraging computational results are given.     

Structural characterization of MnNi and MnPt antiferromagnetic materials for spintronic applications

MnNi and MnPt become antiferromagnetic (AFM) when annealed at high enough temperatures, for which a face-centered cubic (fcc) to face-centered tetragonal (fct) structural transition occurs. Thus, structural information is essential when optimizing exchange bias in these materials. We performed structural (X-ray diffraction), magnetic (Magneto-Optical Kerr effect) and magneto-transport (magnetoresistance) measurements on MnNi based spin valves subjected to different annealing procedures and MnPt/CoFe bilayers with different MnPt thicknesses. We show that high annealing temperatures can in fact lead to the fct antiferromagnetic phase in both materials, but the annealing procedure is also an important factor on the obtained exchange field values. Also, MnPt/CoFe bilayers allowed us to probe the influence of average AFM-grain size on exchange bias.     

Preparation,Characterization and ex vivo Intestinal Permeability Studies of Ibuprofen Solid Dispersion

The aim of the present study was to improve the solubility and dissolution rate of ibuprofen and to evaluate, ex vivo, the intestinal permeation. Solid dispersions (SD) were prepared with Kollicoat IR^® by solvent evaporation technique in different drug:carrier ratios. The permeation intestinal of ibuprofen was evaluated by inverted intestinal sac method. The SD was characterized by solubility equilibrium, FT-IR, DSC, PXRD, SEM, and dissolution rate. The solubility, dissolution rate, and permeability were significantly greater for SD 1:2. The PXRD, SEM and DSC indicated a partial change in the crystalline state of ibuprofen. The solubility equilibrium of SD (1:2) was approximately 15 times greater than the solubility of ibuprofen. Dissolution rate enhancement was attributed to the decreased crystallinity of the ibuprofen, and increase of wettability and decrease of particle size. In conclusion, dissolution rate and intestinal permeability of ibuprofen were enhanced by the use of Kollicoat IR^® carrier in the SD formulation.     

Exposure risk assessment of uranium intake of the milk products from the region of Pernambuco,Brazil

Journal of Radioanalytical and Nuclear Chemistry - Haloperidol (HP) is a dopamine blocking agent. HP was radiolabeled with 125I using direct electrophilic substitution. Different HP formulations...