The mechanisms of plasma post-oxidation of plasma nitrided AISI 1045 plain steel were investigated. The influence of plasma post-oxidation temperature and time on the oxide layer thickness, ...morphology, and composition were addressed. The oxide thickness grows exponentially with temperature, with activation energy of 68±5kJmol −1. The time dependence of the oxide layer thickness, on the other hand, is governed by a diffusion-reaction process. It was verified that temperature plays an important role on the morphology of the oxide. Indeed, at the highest temperature, 550°C, the oxide layer is not homogeneous and has a lower hardness than oxide layers obtained at 480 to 500°C. The latter seem to be more favorable temperatures to grow compact, homogeneous, and harder oxide layers. The oxide–nitride bi-layer produced here contains a mixture of γ′-Fe4N and ε-Fe2-3N and only one iron oxide, Fe3O4 (magnetite). The proportions between these phases vary with the plasma processing temperature and time.
►Oxygen and nitrogen profiles were determined by alpha-particle resonant scattering. ►The oxide thickness as a function of time does not follow a pure parabolic law. ►The oxidation process is governed by a diffusion-reaction mechanism.
The nanoscale friction of partially oxidized silicon nitride thin films deposited by reactive magnetron sputtering was investigated. Post deposition thermal annealing in O2, trying to simulate the ...oxidation by atmospheric oxygen in working conditions, formed a partially oxidized layer at the surface with maximum thickness around 10nm. Unidirectional sliding tests showed a decrease of the low-load friction coefficients of the sliding pair for the samples annealed in oxygen as compared to the non-annealed ones. The results are discussed on the lights of our extension of the crystal chemistry model, which establishes a relationship between ionic potential and friction coefficient.
► The nanoscale friction behavior of partially oxidized Si3N4 thin films is studied. ► A modification of the crystal chemistry model for tribology is suggested. ► Ultra-low friction coefficients for SiOxNy are observed.
We investigated the low load friction behavior of plasma post-oxidized, plasma- nitrided AISI 1045 plain steel, using unidirectional sliding tests. The hydrogen content in the post-oxidation plasma ...was varied between 0 and 25%. The nitrided or oxidized layer thicknesses ranged from approximately 340–380 μm or 0.7–1.1 μm, respectively. The outermost iron oxide layer decreases the friction, whereas the underneath iron nitride layer increases the mechanical strength. The incorporation of hydrogen in the oxidative plasma mixture allows to control the type of iron oxide phase. It is observed that the presence of a superficial magnetite layer leads to a decrease of the friction coefficient with respect to the non-oxidized nitrided steel. The results are interpreted on the lights of crystal chemistry and with a model to explain the in-depth effects of hydrogen in the oxidative plasma.
► Hydrogen improves the oxidation performance in terms of oxide layer thickness. ► Magnetite reduces both friction and roughness. ► The hydrogen effect takes place in-depth at the whole layer.
Lifelong adherence to antiretroviral treatment remains challenging for people living with HIV (PLHIV). The aim of this study was to investigate whether any of 2 digital adherence tools could improve ...adherence among PLHIV in Kilimanjaro, Tanzania.
We performed a parallel 3-arm, nonblinded, randomized controlled trial with 1:1:1 allocation. We included adults aged between 18 and 65 years, living in Kilimanjaro region, and who were on antiretroviral treatment for at least 6 months. Their adherence, as judged by the study nurses, had to be suboptimal. In one arm, participants received reminder short message service (SMS) texts, followed by a question SMS. In the second arm, participants received a real-time medication monitoring (RTMM) device (Wisepill) with SMS reminders. In the third arm, participants received standard care only. The primary outcome of mean adherence over 48 weeks was compared between arms using between-group t tests in a modified intention-to-treat analysis.
In each arm, we randomized 83 participants: data of 82 participants in the RTMM arm, 80 in the SMS arm, and 81 in the standard care arm were analyzed. The average (over 48 weeks) adherence in the SMS, RTMM, and control arms was 89.6%, 90.6%, and 87.9% for pharmacy refill; 95.9%, 95.0%, and 95.2% for self-report in the past week; and 97.5%, 96.6%, and 96.9% for self-report in the past month, respectively (P values not statistically significant).
Receiving reminder SMS or RTMM combined with feedback about adherence levels and discussion of strategies to overcome barriers to adherence did not improve adherence to treatment and treatment outcome in PLHIV.
PACTR201712002844286.
As the establishment of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific T cell memory in children remains largely unexplored, we recruited convalescent COVID-19 children and ...adults to define their circulating memory SARS-CoV-2-specific CD4+ and CD8+ T cells prior to vaccination. We analyzed epitope-specific T cells directly ex vivo using seven HLA class I and class II tetramers presenting SARS-CoV-2 epitopes, together with Spike-specific B cells. Unvaccinated children who seroconverted had comparable Spike-specific but lower ORF1a- and N-specific memory T cell responses compared with adults. This agreed with our TCR sequencing data showing reduced clonal expansion in children. A strong stem cell memory phenotype and common T cell receptor motifs were detected within tetramer-specific T cells in seroconverted children. Conversely, children who did not seroconvert had tetramer-specific T cells of predominantly naive phenotypes and diverse TCRαβ repertoires. Our study demonstrates the generation of SARS-CoV-2-specific T cell memory with common TCRαβ motifs in unvaccinated seroconverted children after their first virus encounter.
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•SARS-CoV-2-specific T cells detected ex vivo in unvaccinated seroconverted children•Comparable Spike-T cell memory responses but lower ORF1a/N-responses found in children•Reduced clonal expansions within tetramer+ T cells seen in children compared with adults•Prevalent Tscm phenotype and TCR motif occur in SARS-CoV-2-specific T cells in children
Children are at lower risk of developing severe COVID-19, yet their primary and memory immune responses are understudied. Rowntree et al. define ex vivo CD8+ and CD4+ T cell responses toward SARS-CoV-2 using peptide-HLA tetramers. They find that children have comparable Spike-specific but lower ORF1a- and N-specific memory T cell magnitude with less clonal expansion in comparison with adults.
CD8
T cells provide robust antiviral immunity, but how epitope-specific T cells evolve across the human lifespan is unclear. Here we defined CD8
T cell immunity directed at the prominent influenza ...epitope HLA-A*02:01-M1
(A2/M1
) across four age groups at phenotypic, transcriptomic, clonal and functional levels. We identify a linear differentiation trajectory from newborns to children then adults, followed by divergence and a clonal reset in older adults. Gene profiles in older adults closely resemble those of newborns and children, despite being clonally distinct. Only child-derived and adult-derived A2/M1
CD8
T cells had the potential to differentiate into highly cytotoxic epitope-specific CD8
T cells, which was linked to highly functional public T cell receptor (TCR)αβ signatures. Suboptimal TCRαβ signatures in older adults led to less proliferation, polyfunctionality, avidity and recognition of peptide mutants, although displayed no signs of exhaustion. These data suggest that priming T cells at different stages of life might greatly affect CD8
T cell responses toward viral infections.
Upon host cell invasion the apicomplexan parasiteToxoplasma gondii resides in a specialized compartment termed the parasitophorous vacuole that is derived from the host cell membrane but modified by ...the parasite. Despite the segregation of the parasitophorous vacuole from the host endocytic network, the intravacuolar parasite has been shown to acquire cholesterol from the host cell. In order to characterize further the role of sterol metabolism in T. gondii biology, we focused our studies on the activity of acyl-CoA:cholesterol acyltransferase (ACAT), a key enzyme for maintaining the intracellular homeostasis of cholesterol through the formation of cholesterol esters. In this study, we demonstrate that ACAT and cholesterol esters play a crucial role in the optimal replication of T. gondii. Moreover, we identified ACAT activity in T. gondii that can be modulated by pharmacological ACAT inhibitors with a consequent detrimental effect on parasite replication.
A 15 kb DNA fragment from the Bacillus subtilis chromosome between citB and ppsC has been sequenced, and new ORFs encoding putative enzymes involved in lipopolypeptide synthesis, which complete a ...partial operon previously reported, and a new set of enzymes responsible for lipid metabolism have been identified. From the analysis of DNA sequence homology of the fragment it was deduced that these new peptide synthetase genes are part of an operon for the biosynthesis of the fungicide fengycin.
Combined experimental and numerical tools are used to analyze the effect of convective and radiative heat transport, faceting phenomena, and the optical thickness of the Bi
4Ge
3O
12 (BGO) crystal on ...the measurement and calculation of melt/crystal interface kinetics during the axial heat flux close to the phase interface growth of BGO single crystals. Results show that, in the general case, accurate determination of growth kinetic relations requires the application of models which account for all of the above phenomena (radiative and convective heat transport, faceting phenomena, etc.). Failure to take these into account may result not only in quantitative errors, but also even in qualitatively wrong determination of interfacial kinetic mechanisms.
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