Effect of Zn concentration on microstructure and corrosion resistance of Mg-Zn alloys microalloyed with Ca and Ce

Purpose The influence of Zn concentration on microstructure and corrosion performance of the Mg–xZn alloys microalloyed with Ca and Ce was investigated through optic microscopy, scanning electron microscopy, hydrogen evolution, dynamic polarization and electrochemical impedance spectroscopy experiments. Design/methodology/approach In this paper, Mg–xZn alloys (x = 0.5∼2.0 Wt.%) microalloyed with Ca and Ce (0.2 Wt.% each) were prepared. Findings As the increase of Zn concentration, the number of second phase particles (Mg-Zn-Ca, Mg-Zn-Ce and Mg-Ce phases) increased, and when the Zn concentration increased to 2.0 Wt.%, the new second phase Mg-Zn phase was precipitated. Originality/value The influence of Zn concentration on corrosion mechanism of Mg-xZn alloys microalloyed with Ca and Ce was revealed. Increasing of the Zn concentration resulted in the intensification of galvanic corrosion. When Zn concentration was 0.5 Wt.%, the alloy showed the lowest corrosion rate (0.61 mm y-1), which was about 1/2 of that of Mg-2.0Zn-0.2Ca-0.2Ce alloy.

Identify healthy and dead cells simultaneity of Bacillus subtilis MZ through to use of propidium iodide and acridine orange

The use of microorganism in a lot of process brings the development of new technologies. For guarantee the effect and the impact of the microorganism, even, the production rate when these microorganisms are involved in the production of a particular compound, become necessary know the number and condition of this organism. In the actuality, there are a lot of tools to identify this condition, since kits of staining cells, until, the best microscopy technology. But the use of this tools could become inaccessible due the high cost and in the case of de staining kits had a limited test. Then emerge the necessity to search and implement news methodologies to help us to identify health and death cells in different inoculs or products. In this work, we proposed a new technology for the simultaneous observation of healthy and dead cells trough the staining samples with propidium iodide and acridine orange using an optic microscopy with incandescent light and ultraviolet light.

OPPORTUNITIES FOR THE USE OF THE SMALL-SIZE ACCELERATOR VGIK-1

The experimental data on modification of the surface of metals, alloys and materials coated using the method of irradiation by a heavy-current electron beam with the energy of 300 keV have been given. The specimen surface structure was studied before and after the irradiation using the method of optic microscopy and the surface layer microhardness measurement. The method of electron microscopy was used to analyze the structure and the sizes of dispersed anode material. The films consisting of the crystals with the size of 6 to 8 nm were obtained. The mass transfer processes that occur in the material of metal targets made of Cu, Ti, Mo, Al were studied. The spatial map was compiled for the X-ray field of the plant. The experiments were carried out to define the action of X-ray radiation on the different types of conditionally pathogenic microflora, in particular such bacteria as Escherichia coli, Staphylococcus aureus, and Bacillus subtilis. The fields of application of the plant were defined.

Scanning Electron Microscopy of Sand Flies of the Chagasi Series, Psychodopygus (Diptera: Psychodidae) Genus, Focusing on the Genitalia

Males of cryptic or closely related species present great morphological variation in their genitalia, whereas females, such as those of the Chagasi Series of the Psychodopygus Mangabeira, 1941 genus, are more similar. Therefore, our aim was to study the fine structure of the male genitalia of five species of the Chagasi Series to better understand the variation in their morphology and its influence on the copulatory process. The sand fly species were captured in the following Brazilian states: Psychodopygus chagasi (Costa Lima, 1941) (Rondônia), Psychodopygus complexus (Mangabeira, 1941) (Tocantins), Psychodopygus squamiventris maripaensis (Floch & Abonnenc, 1946) (Amapá), Psychodopygus squamiventris squamiventris (Lutz & Neiva, 1912) (Amazonas), and Psychodopygus wellcomei Fraiha, Shaw & Lainson, 1971 (Pará and Ceará). Insects were stored in ethanol 70% (then dehydrated) and dry after they were sputtered with gold. The samples were observed under a scanning electron microscope. Microtrichiae, two types of trichoid sensilla, coeloconic and chaetic sensillae, were observed on the antenna of all species, with no difference between them. Only on the anepimeron of P. squamiventris squamiventris a modified ‘racket’-like scale was observed. As for the male genitalia, the setae and structures of each species were fully described, such as the small setae on the paramere apex of the P. squamiventris subspecies, and the grooves present in this region and on the paramere lobe of P. complexus and P. wellcomei, which are impossible to observe with optic microscopy. New information is thus provided on the male genitalia, which can contribute to future bionomic studies of these species.

Diet and breed alter community structures of rumen protozoa in cattle subjected to different feeding systems

The objective were to identify and quantify the rumen protozoa from two genetic groups of beef cattle (Nellore and crossbred European beef cattle) subjected to three feeding systems (pasture, pasture supplement, and confined). Samples of rumen contents were obtained from the center of the ruminal mass after slaughter. Quantification and identification of rumen protozoa were performed with a Sedgewick-Rafter counting chamber by optic microscopy. Data were analyzed using general linear analysis methodology with a Poisson distribution (1 %). In addition, the data underwent of Analisys Principal Component. A effect on ruminal protozoa was observed for the diets and breeds analyzed. Was identified 14 genera, among which Entodinium was predominant in all animals analyzed. Ciliates belonging to Entodiniomorphida, Eodinium, Epidinium, Eremoplastron, Eudiplodinium, Metadinium, and Ostracodinium showed highest density in Nellore animals when compared with the crossbreed, Nellore × European. Larger numbers of protozoa from the family Isotrichidae (Dasytricha and Isotricha) were observed in animals maintained by pasture or pasture supplement feeding. According to the kind of feeding, those fed exclusively with pasture had a greater diversity of ciliates in comparison to those restricted to, or supplemented with pasture. In one animal, the occurrence of ciliates belonging to the genus Buetschlia, was observed (prevalence of 1.66 %), which is one of only a few records of this genus in ruminants.

Kinetic study on martensite formation in steels 1045 and 4340 under variable cooling rates

Kinetic study on martensite formation in steels 1045 and 4340 under variable cooling rates Dimitry V. Bubnoff1, Mariana M. O. Carvalho2, Thiago R.M. Lourenço1, Jose Adilson de Castro1 1 PPGEM, Industrial Engineering School/UFF, Volta Redonda/RJ, Brazil 2 Lappeenranta University of Technology/LUT, Skinnarilankatu, Lappeenranta Finland2 DOI: https://doi.org/10.33017/RevECIPeru2015.0011/ Abstract The experiments were carried with two steels with different chemical compositions, aiming at understanding and comparison with the available literature. The microstructures of steels 1045 and 4340 were characterized and quantified using scanning electron microscopy (SEM) and optic microscopy (OM) with quantitative methods. Based on the experimental results, the amount of martensite, the hardness and the microhardness were determined, as a function of the distance from the quenching end, under different cooling conditions. For predicting the evolution of martensitic fraction along the sample, Koistinen-Marburger’s (K-M) model was adopted. It was found that the parameters recommended in the literature for the traditional K-M model do not represent accurately the results obtained for the steel samples under investigation. According to indications found in recent literature, parameter corrections were proposed, leading to a modified K-M model which better represents the transformations observed in the different examined steels. Keywords: Kinetics, martensite, Koistinen-Marburger model.