First-principles modeling of the interactions of iron impurities with graphene and graphite

Results of first principles modelling of interactions graphene and graphite with iron impurities predict the colossal difference between these two carbon allotropes. Insertion of the iron atoms between the planes of graphite is much more energetically favourable than adsorption of the iron adatom at graphite or graphene surface. High mobility of iron adatom over graphite surface and within bulk graphite is reported. Calculated values of formation energies for the substitutional iron impurities suggest that iron is more destructive for graphite than for graphene. This effect caused formation of uniform carbon environment of the iron atom inside the multilayer system. In contrast to graphene segregation of the substitutional iron impurities in graphite at the ambient conditions is not energetically favourable. Enhancement of interlayer bonding in contaminated graphite and purity of graphene from iron impurities are also reported.Comment: 14 pages, 3 figures, to appear in phis. stat. solidi (b

The use of biomimetic surfaces to reduce single- and dual-species biofilms of Escherichia coli and Pseudomonas putida

The ability of bacteria to adhere to and form biofilms on food contact surfaces poses serious challenges, as these may lead to the cross-contamination of food products. Biomimetic topographic surface modifications have been explored to enhance the antifouling performance of materials. In this study, the topography of two plant leaves, Brassica oleracea var. botrytis (cauliflower, CF) and Brassica oleracea capitate (white cabbage, WC), was replicated through wax moulding, and their antibiofilm potential was tested against single- and dual-species biofilms of Escherichia coli and Pseudomonas putida. Biomimetic surfaces exhibited higher roughness values (SaWC = 4.0 ± 1.0 μm and SaCF = 3.3 ± 1.0 μm) than the flat control (SaF = 0.6 ± 0.2 μm), whilst the CF surface demonstrated a lower interfacial free energy (ΔGiwi) than the WC surface (−100.08 mJ m−2 and −71.98 mJ m−2, respectively). The CF and WC surfaces had similar antibiofilm effects against single-species biofilms, achieving cell reductions of approximately 50% and 60% for E. coli and P. putida, respectively, compared to the control. Additionally, the biomimetic surfaces led to reductions of up to 60% in biovolume, 45% in thickness, and 60% in the surface coverage of single-species biofilms. For dual-species biofilms, only the E. coli strain growing on the WC surface exhibited a significant decrease in the cell count. However, confocal microscopy analysis revealed a 60% reduction in the total biovolume and surface coverage of mixed biofilms developed on both biomimetic surfaces. Furthermore, dual-species biofilms were mainly composed of P. putida, which reduced E. coli growth. Altogether, these results demonstrate that the surface properties of CF and WC biomimetic surfaces have the potential for reducing biofilm formation

“A Good Death” - Palliative Surgery in Trisomy 18

A trissomia 18 caracteriza-se por múltiplas anomalias, incluindo doença cardíaca em 60 a 90% dos casos e elevada mortalidade. O mau prognóstico global, conduz habitualmente a uma politica de “cuidados mínimos” mas, paliar, é também nestas situações, um imperativo ético. Descreve-se o caso de uma recém-nascida sem diagnóstico pré natal, mas com confirmação por cariotipo, com cardiopatia, que condicionou insuficiência cardíaca congestiva e angústia respiratória crescente, inviabilizando alta hospitalar, como era desejo da família. Após consenso entre os pais e o corpo clínico responsável, foi decidida intervenção cirúrgica cardíaca paliativa, que possibilitou melhoria clínica e alta para o domicílio. Os autores defendem que a cirurgia cardíaca pode ser uma atitude a considerar em casos de trissomia 18, pois pode aliviar o sofrimento

Toxicity and genotoxicity of wastewater from gasoline stations

The toxicity and genotoxicity of wastewater from eight gasoline stations in Brasília, Brazil's capital city, was studied by assessing chromosomal aberrations, chromosomal malsegregation and the mitotic index in Alliumcepa root cells, and the occurrence of micronucleus and nuclear abnormalities in peripheral erythrocytes of tilapia fish (Oreochromis niloticus). The content of gasoline station effluents was also analyzed based on several physico-chemical parameters. None of the wastewater samples was genotoxic to A. cepa root cells, although cell proliferation was significantly inhibited, especially at the highest concentrations. Likewise, no micronuclei were observed in O. niloticus peripheral erythrocytes, even after exposure to high concentrations, but there was an increase in the number of nuclear abnormalities and fish mortality. These results show that although the effluent from gasoline stations is processed by an oil/water separation system before being discharged into the main sewage system, the wastewater still contains toxic compounds

Engineering the electronic bandgaps and band edge positions in carbon-substituted 2D boron nitride: a first-principles investigation

Modification of graphene to open a robust gap in its electronic spectrum is essential for its use in field effect transistors and photochemistry applications. Inspired by recent experimental success in the preparation of homogeneous alloys of graphene and boron nitride (BN), we consider here engineering the electronic structure and bandgap of C2xB1−xN1−x alloys via both compositional and configurational modification. We start from the BN end-member, which already has a large bandgap, and then show that (a) the bandgap can in principle be reduced to about 2 eV with moderate substitution of C (x < 0.25); and (b) the electronic structure of C2xB1−xN1−x can be further tuned not only with composition x, but also with the configuration adopted by C substituents in the BN matrix. Our analysis, based on accurate screened hybrid functional calculations, provides a clear understanding of the correlation found between the bandgap and the level of aggregation of C atoms: the bandgap decreases most when the C atoms are maximally isolated, and increases with aggregation of C atoms due to the formation of bonding and anti-bonding bands associated with hybridization of occupied and empty defect states. We determine the location of valence and conduction band edges relative to vacuum and discuss the implications on the potential use of 2D C2xB1−xN1−x alloys in photocatalytic applications. Finally, we assess the thermodynamic limitations on the formation of these alloys using a cluster expansion model derived from first-principles

Breast cancer incidence, stage, treatment and survival in ethnic groups in South East England

Studies from the US have shown variations in breast cancer incidence, stage distribution, treatment and survival between ethnic groups. Data on 35 631 women diagnosed with breast cancer in South East England between 1998 and 2003 with self-assigned ethnicity information available were analysed. Results are reported for White, Indian, Pakistani, Bangladeshi, Black Caribbean, Black African and Chinese women. Age-standardised breast cancer incidence rate ratios, patterns of stage of disease at diagnosis, treatment, overall and breast cancer-specific survival were examined. All ethnic groups studied had lower age-standardised breast cancer incidence rates than White women, with Bangladeshi women having the lowest rate ratio (0.23, 95% CI: 0.20–0.26). White women were the most likely to have a stage recorded at diagnosis (adjusted proportion 75%), and least likely to be diagnosed with metastatic disease (7%). Black African women were the least likely to have a record of cancer surgery (63%) or hormone therapy (32%), and most likely to receive chemotherapy (38%). After fully adjusting for age, socioeconomic deprivation, stage of disease and treatment received, there was no significant variation in breast cancer-specific survival. However, Black African women had significantly worse overall survival (hazard ratio 1.24, P=0.025). These findings suggest that a strategy of earlier detection should be pursued in Black and South Asian women

Biological decolorization of xanthene dyes by anaerobic granular biomass

Biodegradation of a xanthene dyes was investigated for the first time using anaerobic granular sludge. On a first screening, biomass was able to decolorize, at different extents, six azo dye solutions: acid orange 7, direct black 19, direct blue 71, mordant yellow 10, reactive red 2 and reactive red 120 and two xanthene dyes—Erythrosine B and Eosin Y. Biomass concentration, type of electron donor, induction of biomass with dye and mediation with activated carbon (AC) were variables studied for Erythrosine B (Ery) as model dye. Maximum color removal efficiency was achieved with 4.71 g VSS L−1, while the process rates were independent of the biomass concentration above 1.89 g VSS L−1. No considerable effects were observed when different substrates were used as electron donors (VFA, glucose or lactose). Addition of Ery in the incubation period of biomass led to a fivefold increase of the decolorization rate. The rate of Ery decolorization almost duplicated in the presence of commercial AC (0.1 g L−1 AC0). Using different modified AC samples (from the treatment of AC0), a threefold higher rate was obtained with the most basic one, \textAC\textH2ACH2, as compared with non-mediated reaction. Higher rates were obtained at pH 6.0. Chemical reduction using Na2S confirmed the recalcitrant nature of this dye. The results attest that decolorization of Ery is essentially due to enzymatic and adsorption phenomena.This work was supported by the PTDC/AMB/69335/2006 project grants (Fundacao para a Ciencia e Technologia, FCT, Portugal), BRAIN project (ID 6681, European Social Found and Romanian Government and the grant of the Romanian National Authority for Scientific Research, CNCS-UEFISCDI, project number PN-II-ID-PCE-2011-3-0559, Contract 265/2011