DNA charge transport over 34 nm

Molecular wires show promise in nanoscale electronics but the synthesis of uniform, long conductive molecules is a significant challenge. DNA of precise length, by contrast, is easily synthesized, but its conductivity has not been explored over the distances required for nanoscale devices. Here we demonstrate DNA charge transport (CT) over 34 nm in 100-mer monolayers on gold. Multiplexed gold electrodes modified with 100-mer DNA yield sizable electrochemical signals from a distal, covalent Nile Blue redox probe. Significant signal attenuation upon incorporation of a single base pair mismatch demonstrates that CT is DNA-mediated. Efficient cleavage of these 100-mers by a restriction enzyme indicates that the DNA adopts a native conformation that is accessible to protein binding. Similar electron transfer rates are measured through 100-mer and 17-mer monolayers, consistent with rate-limiting electron tunneling through the saturated carbon linker. This DNA-mediated CT distance of 34 nm surpasses most reports of molecular wires

The kaleidoscopic midwife: A conceptual metaphor illustrating first-time mothers' perspectives of a good midwife during childbirth. A grounded theory study

Background: The literature review reveals general information about a good midwife from a range of perspectives and what childbearing women generally value in a midwife, but there is a lack of information around mothers’ perspectives of what makes a good midwife specifically during labour and birth, and even less in the context of different places of birth. Aim: To conceptualise first-time mothers’ expectations and experiences of a good midwife during childbirth in the context of different birthplaces. Design: Qualitative Straussian grounded theory methodology. Setting: Three National Health Service Trusts in England providing maternity care that offered women the possibility of giving birth in different settings (home, freestanding midwifery unit and obstetric unit). Participants: Fourteen first-time mothers in good general health with a straightforward singleton pregnancy anticipating a normal birth. Methods: Ethical approval was gained. Data were collected through two semi-structured interviews for each participant (before and after birth). Data analysis included the processes of coding and conceptualising data, with constant comparison between data, literature and memos. Findings: The model named ‘The kaleidoscopic midwife: a conceptual metaphor illustrating first-time mothers’ perspectives of a good midwife during childbirth’ was developed. The model is dynamic and woman-centred, and is operationalised as the midwife adapts to each woman's individual needs in the context of each specific labour. Four pillars of intrapartum care were identified for a good midwife in the labour continuum: promoting individuality; supporting embodied limbo; helping to go with the flow; providing information and guidance. The metaphor of a kaleidoscopic figure is used to describe a midwife who is ‘multi-coloured’ and ever changing in the light of the woman's individual needs, expectations and labour journey, in order to create an environment that enables her to move forward despite the uncertainty and the expectations-experiences gap. The following elements are harmonised by the kaleidoscopic midwife: relationship-mediated being; knowledgeable doing; physical presence; immediately available presence. Conclusion: The model presented has relevance to contemporary debates about quality of care and place of birth and can be used by midwives to pursue excellence in caring for labouring mothers. Independently from the place of birth, when the woman is cared for by a midwife demonstrating the above characteristics, she is likely to have an optimum experience of birth. Future research is necessary to tease out individual components of the model in a variety of practice settings

A História da Alimentação: balizas historiográficas

Os M. pretenderam traçar um quadro da História da Alimentação, não como um novo ramo epistemológico da disciplina, mas como um campo em desenvolvimento de práticas e atividades especializadas, incluindo pesquisa, formação, publicações, associações, encontros acadêmicos, etc. Um breve relato das condições em que tal campo se assentou faz-se preceder de um panorama dos estudos de alimentação e temas correia tos, em geral, segundo cinco abardagens Ia biológica, a econômica, a social, a cultural e a filosófica!, assim como da identificação das contribuições mais relevantes da Antropologia, Arqueologia, Sociologia e Geografia. A fim de comentar a multiforme e volumosa bibliografia histórica, foi ela organizada segundo critérios morfológicos. A seguir, alguns tópicos importantes mereceram tratamento à parte: a fome, o alimento e o domínio religioso, as descobertas européias e a difusão mundial de alimentos, gosto e gastronomia. O artigo se encerra com um rápido balanço crítico da historiografia brasileira sobre o tema

Electrochemical Oxidation of Lithium Carbonate Generates Singlet Oxygen.

Solid alkali metal carbonates are universal passivation layer components of intercalation battery materials and common side products in metal-O2 batteries, and are believed to form and decompose reversibly in metal-O2 /CO2 cells. In these cathodes, Li2 CO3 decomposes to CO2 when exposed to potentials above 3.8 V vs. Li/Li+ . However, O2 evolution, as would be expected according to the decomposition reaction 2 Li2 CO3 →4 Li+ +4 e- +2 CO2 +O2 , is not detected. O atoms are thus unaccounted for, which was previously ascribed to unidentified parasitic reactions. Here, we show that highly reactive singlet oxygen (1 O2 ) forms upon oxidizing Li2 CO3 in an aprotic electrolyte and therefore does not evolve as O2 . These results have substantial implications for the long-term cyclability of batteries: they underpin the importance of avoiding 1 O2 in metal-O2 batteries, question the possibility of a reversible metal-O2 /CO2 battery based on a carbonate discharge product, and help explain the interfacial reactivity of transition-metal cathodes with residual Li2 CO3

Layered-rocksalt intergrown cathode for high-capacity zero-strain battery operation.

The dependence on lithium-ion batteries leads to a pressing demand for advanced cathode materials. We demonstrate a new concept of layered-rocksalt intergrown structure that harnesses the combined figures of merit from each phase, including high capacity of layered and rocksalt phases, good kinetics of layered oxide and structural advantage of rocksalt. Based on this concept, lithium nickel ruthenium oxide of a main layered structure (R[Formula: see text]m) with intergrown rocksalt (Fm[Formula: see text]m) is developed, which delivers a high capacity with good rate performance. The interwoven rocksalt structure successfully prevents the anisotropic structural change that is typical for layered oxide, enabling a nearly zero-strain operation upon high-capacity cycling. Furthermore, a design principle is successfully extrapolated and experimentally verified in a series of compositions. Here, we show the success of such layered-rocksalt intergrown structure exemplifies a new battery electrode design concept and opens up a vast space of compositions to develop high-performance intergrown cathode materials

Layered-rocksalt intergrown cathode for high-capacity zero-strain battery operation.

The dependence on lithium-ion batteries leads to a pressing demand for advanced cathode materials. We demonstrate a new concept of layered-rocksalt intergrown structure that harnesses the combined figures of merit from each phase, including high capacity of layered and rocksalt phases, good kinetics of layered oxide and structural advantage of rocksalt. Based on this concept, lithium nickel ruthenium oxide of a main layered structure (R[Formula: see text]m) with intergrown rocksalt (Fm[Formula: see text]m) is developed, which delivers a high capacity with good rate performance. The interwoven rocksalt structure successfully prevents the anisotropic structural change that is typical for layered oxide, enabling a nearly zero-strain operation upon high-capacity cycling. Furthermore, a design principle is successfully extrapolated and experimentally verified in a series of compositions. Here, we show the success of such layered-rocksalt intergrown structure exemplifies a new battery electrode design concept and opens up a vast space of compositions to develop high-performance intergrown cathode materials

Elucidating anionic oxygen activity in lithium-rich layered oxides.

Recent research has explored combining conventional transition-metal redox with anionic lattice oxygen redox as a new and exciting direction to search for high-capacity lithium-ion cathodes. Here, we probe the poorly understood electrochemical activity of anionic oxygen from a material perspective by elucidating the effect of the transition metal on oxygen redox activity. We study two lithium-rich layered oxides, specifically lithium nickel metal oxides where metal is either manganese or ruthenium, which possess a similar structure and discharge characteristics, but exhibit distinctly different charge profiles. By combining X-ray spectroscopy with operando differential electrochemical mass spectrometry, we reveal completely different oxygen redox activity in each material, likely resulting from the different interaction between the lattice oxygen and transition metals. This work provides additional insights into the complex mechanism of oxygen redox and development of advanced high-capacity lithium-ion cathodes

Elucidating anionic oxygen activity in lithium-rich layered oxides.

Recent research has explored combining conventional transition-metal redox with anionic lattice oxygen redox as a new and exciting direction to search for high-capacity lithium-ion cathodes. Here, we probe the poorly understood electrochemical activity of anionic oxygen from a material perspective by elucidating the effect of the transition metal on oxygen redox activity. We study two lithium-rich layered oxides, specifically lithium nickel metal oxides where metal is either manganese or ruthenium, which possess a similar structure and discharge characteristics, but exhibit distinctly different charge profiles. By combining X-ray spectroscopy with operando differential electrochemical mass spectrometry, we reveal completely different oxygen redox activity in each material, likely resulting from the different interaction between the lattice oxygen and transition metals. This work provides additional insights into the complex mechanism of oxygen redox and development of advanced high-capacity lithium-ion cathodes

Evolution of the Solid-Electrolyte Interphase on Carbonaceous Anodes Visualized by Atomic-Resolution Cryogenic Electron Microscopy.

The stability of modern lithium-ion batteries depends critically on an effective solid-electrolyte interphase (SEI), a passivation layer that forms on the carbonaceous negative electrode as a result of electrolyte reduction. However, a nanoscopic understanding of how the SEI evolves with battery aging remains limited due to the difficulty in characterizing the structural and chemical properties of this sensitive interphase. In this work, we image the SEI on carbon black negative electrodes using cryogenic transmission electron microscopy (cryo-TEM) and track its evolution during cycling. We find that a thin, primarily amorphous SEI nucleates on the first cycle, which further evolves into one of two distinct SEI morphologies upon further cycling: (1) a compact SEI, with a high concentration of inorganic components that effectively passivates the negative electrode; and (2) an extended SEI spanning hundreds of nanometers. This extended SEI grows on particles that lack a compact SEI and consists primarily of alkyl carbonates. The diversity in observed SEI morphologies suggests that SEI growth is a highly heterogeneous process. The simultaneous emergence of these distinct SEI morphologies highlights the necessity of effective passivation by the SEI, as large-scale extended SEI growths negatively impact lithium-ion transport, contribute to capacity loss, and may accelerate battery failure