Corrosion behavior of 304 stainless steel exposed to a NaCl (3.5 wt %) solution saturated with CO
2
has been analyzed using electrochemical techniques including, potentiodynamic polarization, ...polarization resistance, and electrochemical impedance measurements. The stainless steel samples were evaluated having different surface and pre-oxidation treatments. The oxide scales formed on 304 stainless steel oxidized in different
p
O
2
at 1100°C have also been studied and compared. Different morphologies and chemical composition of the oxide scales were observed after oxidation at low and high oxygen partial pressures. Oxide layers with high chromium content were formed on the ground sample pre-oxidized in Ar while iron-rich oxides were mainly formed under air atmosphere. The electrochemical corrosion results indicate that non-oxidized 304 SS exhibits the best corrosion performance followed by the ground sample heat-treated in argon. For the oxidized stainless steels, the differences in the electrochemical responses are associated to the morphological characteristics and composition of the oxide layer. Homogeneous and dense Cr-rich oxide scale provides protection to 304 SS during exposure to CO
2
-saturated solutions while the formation of Fe-oxides with porous morphology increases the corrosion rate of 304 stainless steel.
The brown smooth-hound shark Mustelus henlei is one of the most abundant species caught by the artisanal elasmobranch fishery off northwestern Mexico. The present study estimates the reproductive ...parameters for M. henlei using, for the first time, histological analysis and survey data collected from May 2008 to May 2016. Mustelus henlei was reported in the landings from February to November each year (n = 1,469). Total length (TL) varied between 450 and 1,530 mm (average = 753 mm, SD = 111). The sex ratio (male:female) was similar to the 1:1 ratio. Gravid females were caught during April, August, and November. Average fecundity was 9. Length at maturity was 656 mm TL for females and 636 mm TL for males, and length at maternity, estimated for the first time for this species, was 676 mm TL. The first phases of spermatogenesis and oogenesis were identified through histological analysis of gonads from immature individuals. Semen storage was detected in the oviducal gland of females at the terminal zone, whereas in males spermatozeugmata was detected in the seminal vesicles. According to the species reproductive parameters, M. henlei can be categorized as a species of high biological productivity among elasmobranchs and can thus support certain level of fishing pressure off northwestern Mexico if adequate fishing management and regulatory measures are employed. Some of the reproductive parameters that were estimated for this species in the present study were different from those estimated for other stocks from Mexican and United States waters.
Key words: reproduction, length at maturity, length at maternity, semen storage, Mustelus henlei.
Structural evolution during the synthesis of B2–NiAl intermetallic compound by mechanical alloying of equiatomic elemental mixtures was studied by Rietveld analysis, DSC and HTXRD. The lattice ...parameter, crystallite size, microstrain, amount of phase and ordering of the B2 phase were monitored as a function of milling time. Formation of the B2–NiAl phase shows a sigmoidal behavior, which suggests that Johnson–Mehl–Avrami nucleation and interface-controlled growth are the responsible mechanisms in the transformation. Almost complete transformation (~ 97 mol%) was obtained after 25 h of milling. A specific phase transformation sequence during milling was not absolutely determined, however, the sequence Ni + Al → NiAl
3
→ Ni
2
Al
3
→ B2–NiAl was identified by HTXRD. This sequence was confirmed by DSC. The transformation temperature of the B2–NiAl phase and the presence of additional intermetallic compounds show a direct dependence on the Ni–Al layer spacing. Using a production-scale Simoloyer horizontal Attritor Mill, the presence of Ni
2
Al
3
phase was observed prior to the full synthesis of B2-NiAl.
The ball milling (BM) of blended Ni and Cr elemental powders was carried out in a Simoloyer performing on high-energy scale mode at maximum production to obtain a nanostructured Ni-20Cr alloy. The ...phase transformations and structural changes occurring during mechanical alloying were investigated by X-ray diffraction (XRD) and optical microscopy (OM). A gradual solid solubility of Cr and the subsequent formation of crystalline metastable solid solutions described in terms of the Avrami-Erofe'ev kinetics model were calculated. The XRD analysis of the structure indicates that cumulative lattice strain contributes to the driving force for solid solution between Ni and Cr during BM. Microstructure evolution has shown, additionally to the lamellar length refinement commonly observed, the folding of lamellae in the final processing stage. OM observations revealed that the lamellar spacing of Ni rich zones reaches a steady value near 500 nm and almost disappears after 30 h of milling.
In this study, we present a boronizing treatment on a steel microalloy that was performed according to dehydrated paste-pack boriding. The temperatures conducted were at 1173, 1223 and 1273 K; at ...various exposure times of 1, 3, 6 and 9 h. As a result of the boriding process, diffusion-controlled growth of the FeB/Fe2B layers was obtained at the surface of the micro-alloy steel, and the kinetics of the growth process changed parabolically over time. The results of these examination properties of the boride layer as revealed by Optical Microscopy (OP) showed the morphology of the boride layer as a saw-tooth with a thickness ranging from 33 μm to 220 μm depending on the boronizing time. The analysis of Scanning Electron Microscopy (SEM-EDS); showed a distribution of the alloying elements that were detected by Energy Dispersive Spectrometry. The X-ray diffraction (XRD) technique indicated that the surface was a mixture of FeB and Fe2B borides. The evaluation of adhesion of the layers was determined by the technique of Rockwell-C hardness. Young’s modulus and hardness of the layer were evaluated by a nanoindentation technique with a load of 250 mN. The paste dehydrate boriding of micro-alloy reveal a change of properties on the surface; also the coatings FeB and Fe2B, to make a sacrificial function in the steels micro alloyed as widely used in pipelines transporting oil.
This article discusses the community collaboration and systems advocacy domains of the ACA (American Counseling Association) Advocacy Competencies (J. A. Lewis, M. S. Arnold, R. House, & R. L. ...Toporek, 2002). A case illustration is presented, and the 8 Advocacy Competencies within each domain are applied to the case study.
Although many nursing programs provide diversity training to enhance the understanding of cultural influences on health care, little is known about outcomes. This is due in part to a lack of ...consensus regarding definitions and measures. The purpose of this study was to examine a set of self-perceptions defined as personal growth, attributed by graduate nursing students (N = 41) to an eight-week diversity course. Participants reported modest levels of personal growth. Educators can adapt the instrument and method of this study to measure student attributions of growth to any aspect of nursing education.
In this descriptive exploratory study, the Posttraumatic Growth Inventory (PTGI; Tedeschi & Calhoun, 1996) was used to measure levels of personal growth attributed by college students (N = 117) to a ...semester of university life in retrospective self‐reports. Results reflect attributions of substantial total growth in the range reported in the posttraumatic studies and attributions of substantial growth to a variety of specific experiences. The results suggest that personal growth as defined by the PTGI is not necessarily adversarial and that personal growth can be intentionally facilitated by educational activities.
The adsorption of isopropyl xanthate ions, (CH
3)
2CH–OCS
2
−, onto arsenopyrite (FeAsS) was studied through electrokinetics, voltammetry and rest potential measurements at pH 6. The electrokinetic ...behavior of droplets of isopropyl dixanthogen, (CH
3)
2CH–OCS
2–S
2CO–CH(CH
3)
2, in solutions of isopropyl xanthate ions was also determined at the same pH value. Adsorption occurred first as isopropyl dixanthogen through an anodic oxidation reaction of the xanthate ions on arsenopyrite, with no effect on the zeta potential of arsenopyrite. Then as isopropyl xanthate ions through hydrophobic bonding with the dixanthogen adsorbed at the arsenopyrite/aqueous solution interface, increasing negatively the zeta potential of arsenopyrite. The negative electric charge at the dixanthogen-arsenopyrite/aqueous solution interface limited the two adsorption steps. Microflotation studies showed that arsenopyrite floated highly owing to dixanthogen. This flotation was not affected by the polar group (OCS
2
−) of the isopropyl xanthate ions at the dixanthogen-arsenopyrite/aqueous solution interface.
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