Passivation of Al–Cr–Fe and Al–Cu–Fe–Cr complex metallic alloys in 1 M H2SO4 and 1 M NaOH solutions

The corrosion mechanisms of Al–Cr–Fe and Al–Cu–Fe–Cr complex metallic alloys have been investigated by potentiodynamic and potentiostatic polarization. Very good passivation of the Al–Cr–Fe surface is exhibited from 1 M H₂SO₄ to 1 M NaOH solutions, which was confirmed by ICP-OES analysis over a period of 273 days. Potentiostatically formed passive films analysed by XPS revealed chromium enrichment in the outermost layer of the aluminium oxy-hydroxide film. Although Al–Cu–Fe–Cr showed passivation during potentiodynamic polarization, heavy active corrosion at OCP was revealed by ICP-OES. For the Al–Cu–Fe–Cr alloy, the 10% content of Cr is insufficient to maintain a protective “chemically stable” Cr oxide/hydroxide.     

Partial Oxidation of Methane Over Co-ZSM-5: Tuning the Oxygenate Selectivity by Altering the Preparation Route

For the first time the possibility to partially oxidize methane to methanol and formaldehyde at low temperature over Co-ZSM-5 using air is shown. The influence of the preparation method on the nature of the cobalt species is investigated. In addition, the catalytic activity and selectivity for methane oxidation as a function of the cobalt speciation is discussed. Based on UV–vis–NIR and FT-IR spectroscopy, H₂-TPR, TEM and kinetic measurements it is concluded that cobalt in ion-exchange positions results mainly in the formation of formaldehyde, while larger Co-oxide particles prepared by impregnation result in the formation of methanol.     

Queering Mobility in Urban Gauteng: Transgender Internal Migrants and Their Experiences of “Transition” in Johannesburg and Pretoria

Migration studies in post-Apartheid South Africa have maintained a strong focus on cross-border mobility while often narrowing health-related research to HIV/AIDS concerns and framing gender in woman-oriented approach with a gradually emerging area of research on migrant sex workers. This article offers to bridge certain gaps in migration research on health, internal mobility, and gender. It revolves around experiences of black unprivileged transgender internal migrants accessing medical services in the public health sector in urban Gauteng, in particular, Johannesburg and Pretoria. The article explores their experiences of migration focusing on analysis of their “transition”—both “gendered transition” (different medical interventions that alter/modify gender-related attributes of the body) and “spatial transition” (diverse mobility patters, relocation, renegotiation of place of living and belonging)—and ways they negotiate belonging. The analysis outlines challenges that transgender individuals face in the public health sector and affects these challenges have on mobility of transgender South Africans. Further, the article delves into exploration of transgender internal migrants’ experiences and understanding of “migration” that arises from sense of (non)belonging and ways to negotiate dynamic subjective sense of being (or not) part of physical (and sometimes imaginary) social groups and places, such as family/home, local (“host”) community, lesbian, gay, bisexual and transgender (LGBT) community, and religion/spirituality.     

Three-dimensional obstacles for bacterial surface motility

Twitching motility enables bacteria to move over surfaces using type IV pili as grappling hooks. Here it is shown that the motility of the round Neisseria gonorrhoeae as well as of rod-shaped Myxococcus xanthus is guided by elevations with dimension and depth corresponding to the size of the bacteria.     

Requirements for tools for ambiguity identification and measurement in natural language requirements specifications

This paper proposes a two-step approach to identifying ambiguities in natural language (NL) requirements specifications (RSs). In the first step, a tool would apply a set of ambiguity measures to a RS in order to identify potentially ambiguous sentences in the RS. In the second step, another tool would show what specifically is potentially ambiguous about each potentially ambiguous sentence. The final decision of ambiguity remains with the human users of the tools. The paper describes several requirements-identification experiments with several small NL RSs using four prototypes of the first tool based on linguistic instruments and resources of different complexity and a manual mock-up of the second tool.