Fermi acceleration and its suppression in a time-dependent Lorentz gas

Some dynamical properties for a Lorentz gas were studied considering both static and time-dependent boundaries. For the static case, it was confirmed that the system has a chaotic component characterized with a positive Lyapunov exponent. For the time-dependent perturbation, the model was described using a four-dimensional nonlinear map. The behaviour of the average velocity is considered in two different situations: (i) non-dissipative and (ii) dissipative dynamics. Our results confirm that unlimited energy growth is observed for the non-dissipative case. However, and totally new for this model, when dissipation via inelastic collisions is introduced, the scenario changes and the unlimited energy growth is suppressed, thus leading to a phase transition from unlimited to limited energy growth. The behaviour of the average velocity is described using scaling arguments.     

Bioactive coating on titanium implants modified by Nd:YVO4 laser

Apatite coating was applied on titanium surfaces modified by Nd:YVO₄ laser ablations with different energy densities (fluency) at ambient pressure and atmosphere. The apatites were deposited by biomimetic method using a simulated body fluid solution that simulates the salt concentration of bodily fluids. The titanium surfaces submitted to the fast melting and solidification processes (ablation) were immersed in the simulated body fluid solution for four days. The samples were divided into two groups, one underwent heat treatment at 600 °C and the other dried at 37 °C. For the samples treated thermally the diffractograms showed the formation of a phase mixture, with the presence of the hydroxyapatite, tricalcium phosphate, calcium deficient hydroxyapatite, carbonated hydroxyapatite and octacalcium phosphate phases. For the samples dried only the formation of the octacalcium phosphate and hydroxyapatite phases was verified. The infrared spectra show bands relative to chemical bonds confirmed by the diffraction analyses. The coating of both the samples with and without heat treatment present dense morphology and made up of a clustering of spherical particles ranging from 5 to 20 μm. Based on the results we infer that the modification of implant surfaces employing laser ablations leads to the formation of oxides that help the formation of hydroxyapatite without the need of a heat treatment.     

On the construction and labelling of geometrically uniform signal sets in ℝ2 matched to additive quotient groups

We establish the conditions under which it is possible to construct signal sets satisfying the properties of being geometrically uniform and matched to additive quotient groups. Such signal sets consist of subsets of signal spaces identified to integers rings ?[i] and ?[ω] in ?².     

On-line preconcentration and determination of Zn in natural water samples employing a styrene-divinylbenzene functionalized resin and flame atomic absorption spectrometry.

In this work, flame atomic absorption spectrometry (FAAS) was used as a detector for the determination of zinc in natural water samples with a flow-injection system coupled to solid-phase extraction (SPE). In order to promote the on-line preconcentration of zinc from samples a minicolumn packed with 35 mg of a styrene-divinylbenzene resin functionalized with (S)-2-[hydroxy-bis(4-vinylphenyl)methyl]pyrrolidine-1-carboxylic acid ethyl esther was utilized. The system operation was based on Zn(II) ion retention at pH 9.5 +/- 0.5 in such a minicolumn with analyte elution, at the back flush mode, with 1 mol L(-1) HCl directly to the FAAS nebulizer. The influence of the chemical (sample pH, buffer concentration, HCl eluent concentration and effect of the ionic strength) and flow (sample and eluent flow rates and preconcentration time) parameters that could affect the performance of the system were investigated as well as the possible interferents. At the optimum conditions, for 2 min of preconcentration time (9.9 ml of sample volume), the developed methodology presented a detection limit of 1.1 microg L(-1), a RSD of 3.5% at 10 microg L(-1) and an analytical throughput of 24 h(-1). Whereas, for 4 min of the preconcentration time (19.8 ml of sample volume) a detection limit of 0.98 microg L(-1), a RSD of 6.5% at 5 microg L(-1) and a sampling frequency of 13 h(-1) are reported.     

Correlation between Enterococcus faecalis biofilms development stage and quantitative surface roughness using atomic force microscopy.

Biofilms are assemblages of microorganisms and their associated extracellular products at an interface and typically with an abiotic or biotic surface. The study of the morphology of biofilms is important because they are associated with processes of biofouling, corrosion, catalysis, pollutant transformation, dental caries, drug resistance, and so forth. In the literature, biofilms have been examined by atomic force microscopy (AFM), which has proven to be a potent tool to study different aspects of the biofilm development on solid surfaces. In this work, we used AFM to investigate topographical changes during the development process of Enterococcus faecalis biofilms, which were generated on sterile cellulose nitrate membrane (CNM) filters in brain heart infusion (BHI) broth agar blood plates after 24, 36, 72, 192, and 360 h. AFM height images showed topographical changes due to biofilm development, which were used to characterize several aspects of the bacterial surface, such as the presence of extracellular polymeric substance, and the biofilm development stage. Changes in the development stage of the biofilm were shown to correlate with changes in the surface roughness as quantified through the mean roughness.     

Role of the oriented attachment mechanism in the phase transformation of oxide nanocrystals

"Bottom-up" methods to obtain nanocrystals usually result in metastable phases, even in processes carried out at room temperature or under soft annealing conditions. However, stable phases, often associated with anisotropic shapes, are obtained in only a few special cases. In this paper we report on the synthesis of two well-studied oxides-titanium and zirconium oxide-in the nanometric range, by a novel route based on the decomposition of peroxide complexes of the two metals under hydrothermal soft conditions, obtaining metastable and stable phases in both cases through transformation. High-resolution transmission electron microscopy analysis reveals the existence of typical defects relating to growth by the oriented attachment mechanism in the stable crystals. The results suggest that the mechanism is associated to the phase transformation of these structures.     

Study of pyrolysis kinetic of green corn husk

In this paper, it was suggested the use of green corn husk, which is a biomass from agro-industry, as an alternative source of energy through its pyrolysis. Green corn husk characterization was done through immediate and elemental analysis of its components: cellulose, hemicelluloses, and lignin. It was also measured its higher calorific value. The pyrolysis study of green corn husk was done by the isoconversion and the Master plots method. Thermogravimetric plots were obtained at heating rates of 5, 10, 15, and 20 °C min^?1. The pyrolysis kinetics parameters were studied through the Flynn–Wall–Ozawa (FWO), Kissinger, and Friedman models. The Master plots method was used to determine the pyrolysis reaction order. The results of the reaction energy activation were found to be in the range 105.21–157.46 kJ mol^?1 by the FWO method, 150.50 kJ mol^?1 by the Kissinger method, and ranged 120.66–163.81 kJ mol^?1 by the Friedman method. The Master plots method showed a three-way-transport diffusional kinetics for the biomass de-volatilization process. The higher calorific value found for green corn husk was 16.14 MJ kg^?1. The simulation showed correlation between the experimental data and the proposed model for conversion values up to 0.8.

     

Use of INAA in the homogeneity evaluation of a bovine kidney candidate reference material

Instrumental neutron activation analysis was used to evaluate the between bottle homogeneity and the minimum sample intake of a bovine kidney candidate reference material. The mass fractions of ten inorganic constituents were determined, obtaining satisfactory homogeneity results for all of them. Statistical analysis of the results was performed using a one way analysis of variance and multivariate techniques were applied as complementary techniques, confirming the usefulness of these techniques for homogeneity assessment.

     

Secretome of the preimplantation human embryo by bottom-up label-free proteomics

A bottom-up label-free mass spectrometric proteomic strategy was used to analyse the protein profiles of the human embryonic secretome. Culture media samples used for embryonic culture of patients undergoing intracytoplasmic sperm injection cycles were selected as a test case for this exploratory proof-of-principle study. The media were stored after embryo transfer and then pooled into positive (n = 8) and negative (n = 8) implantation groups. The absolute quantitative bottom-up technique employed a multidimensional protein identification technology based on separation by nano-ultra-high pressure chromatography and identification via tandem nano-electrospray ionization mass spectrometry with data-independent scanning in a hydrid QqTOF mass spectrometer. By applying quantitative bottom-up proteomics, unique proteins were found exclusively in both the positive- and negative-implantation groups, which suggest that competent embryos express and secrete unique biomarker proteins into the surrounding culture medium. The selective monitoring of these possible secretome biomarkers could make viable procedures using single-embryo transfer.