Carbon Deficiency in Externally-Polluted White Dwarfs: Evidence for Accretion of Asteroids

Existing determinations show that n(C)/n(Fe) is more than a factor of 10 below solar in the atmospheres of three white dwarfs that appear to be externally-polluted. These results are not easily explained if the stars have accreted interstellar matter, and we re-interpret these measurements as evidence that these stars have accreted asteroids of a chrondritic composition.Comment: 23 pages, 6 figures, accepted for Ap

Alignment and rectifying properties of donor-electron bridge-acceptor molecules

Molecular electronics based on the bottom-up approach appears to be a promising alternative to overcome the limitations of the top-down lithographic fabrication of electronic devices. The ability to manipulate single or small groups of molecules provides a great opportunity to build electronic devices at the molecular level. However, before any device can be constructed, it is vital to understand the parameters that control the device properties such as: molecular structure, conformation and arrangement at the surface, the molecule-substrate and molecule-electrode interactions. This thesis presents an investigation of the alignment of acceptor-electron bridge-donor structures and describes how the molecular structure and arrangement affect rectifying properties of the monolayers. Studies included typical Langmuir-Blodgett (LB), chevron-shaped, and ionically coupled structures that were characterised using various techniques, such as Quartz Crystal Microbalance (QCM), Surface Plasmon Resonance (SPR), Second Harmonic Generation (SHG) and Scanning Tunnelling Spectroscopy (STS). The results obtained showed that to achieve high rectification the molecules must form ordered and stable monolayers that are able to withstand the electric field applied to the junction. It was also shown that due to the disordered monolayer formation and presence of certain ions, it was extremely difficult to state without doubt whether the rectification was a result of the donor-electron bridge-acceptor structure proposed by Aviram and Ratner1. Studies of chevron-shaped molecules confirmed the possibility of depositing them using the LB technique. However, the reduction of long aliphatic chains was very likely balanced by the formation of less ordered or unstable monolayers. The highest rectification ratio of 30 ± 3 at ± 1 V was obtained for 1-butyl-2,6-bis-[2-(4- dibutylamino-phenyl)-vinyl]-pyridinium iodide (dye 7) and the origin of the I-V asymmetry was attributed to back electron transfer from iodide to pyridinium ring. Although dye 1-butyl-2,6-bis-(2-{4-[2-(4-dibutylamino-phenyl)-ethyl]-phenyl}-vinyl)- pyridinium iodide (dye 9) showed electrical asymmetry (RR=16 at plus/minus 1 V) shortly after deposition onto the gold-coated highly oriented pyrolytic graphite (HOPG), it seemed to form an unstable alignment and as a consequence the rectification decayed over a period of a few hours. Improved ordering, stability, and rectification were achieved from ionically coupled structures, where the monolayers were formed using chemisorption and ionic assembly instead of physisorption.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Waist-to-Height Ratio Is More Predictive of Years of Life Lost than Body Mass Index

Objective: Our aim was to compare the effect of central obesity (measured by waist-to-height ratio, WHtR) and total obesity (measured by body mass index, BMI) on life expectancy expressed as years of life lost (YLL), using data on British adults. Methods: A Cox proportional hazards model was applied to data from the prospective Health and Lifestyle Survey (HALS) and the cross sectional Health Survey for England (HSE). The number of years of life lost (YLL) at three ages (30, 50, 70 years) was found by comparing the life expectancies of obese lives with those of lives at optimum levels of BMI and WHtR. Results: Mortality risk associated with BMI in the British HALS survey was similar to that found in US studies. However, WHtR was a better predictor of mortality risk. For the first time, YLL have been quantified for different values of WHtR. This has been done for both sexes separately and for three representative ages. Conclusion: This study supports the simple message ‘‘Keep your waist circumference to less than half your height’’. The use of WHtR in public health screening, with appropriate action, could help add years to life

Medical students’ experiences of health inequalities and inclusion health education

Background Inclusion health groups experience a significantly larger burden of morbidity and mortality than the general public. Despite this, undergraduate medical education is often limited in its approach to inclusion health curricula, leaving students disengaged and lacking understanding. Methods We conducted two research studies to explore medical students’ experiences of inclusion health education. All participants were studying medicine at the University of Leeds at the time of data collection. We gathered experiences of both compulsory and elective inclusion health education via semi-structured interviews. Interview responses were audio-recorded, transcribed and analysed thematically. Findings We identified several key findings across the two studies. Firstly, medical students felt unprepared to work with inclusion health groups. Further to this, medical students have a preference for interactive teaching and learning in inclusion health education. Finally, encountering inclusion health groups by chance (on placement) or choice (optional initiatives) present different opportunities. Discussion and Conclusion Our research suggests that simply being exposed to inclusion health groups through lectures and on placement is not considered sufficient by medical students, and in fact can lead to the perpetuation of misinformation and stigma. Participants perceived that optional initiatives or ‘choice encounters’ had profoundly positive impacts on attitudes and interest, particularly when there were opportunities to learn directly from individuals with lived experience of exclusion. We suggest that a flipped classroom approach to inclusion health education along with integrated experiential learning would provide medical students with comprehensive and patient-focused learning opportunities

Properties of Ridges in Elastic Membranes

When a thin elastic sheet is confined to a region much smaller than its size the morphology of the resulting crumpled membrane is a network of straight ridges or folds that meet at sharp vertices. A virial theorem predicts the ratio of the total bending and stretching energies of a ridge. Small strains and curvatures persist far away from the ridge. We discuss several kinds of perturbations that distinguish a ridge in a crumpled sheet from an isolated ridge studied earlier (A. E. Lobkovsky, Phys. Rev. E. 53 3750 (1996)). Linear response as well as buckling properties are investigated. We find that quite generally, the energy of a ridge can change by no more than a finite fraction before it buckles.Comment: 13 pages, RevTeX, acknowledgement adde

Structure of 2,5-dimethyl-1,3,4,6-tetraazacycl[3.3.3]azine, C10H9N5

Orientador: Prof. Dr. Ramón Sigifredo Cortés ParedesCoorientadora: Profª. Drª. Maria Lúcia Leite Ribeiro OkimotoTese (doutorado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduação em Engenharia Mecânica. Defesa : Curitiba, 20/02/2019Inclui referências: p. 202-219Área de concentração: ManufaturaResumo: A cor é um dos elementos mais importantes da vida humana, estando conscientes disso ou não. A cor está em tudo, desde a natureza, em todos os ambientes internos e externos, nos objetos circundantes, vestuários e, até mesmo, como forma de expressão verbal, ou seja, inimaginável a vida sem cor. No entanto, milhares de pessoas no mundo não têm acesso a esta informação. O presente trabalho refere-se ao desenvolvimento de código em relevo com o objetivo de possibilitar a identificação das cores às pessoas com deficiência visual por meio do tato. Esta abordagem científica e inovadora é composta de elementos em formato tridimensional, com dimensões mínimas, inspirado no elemento principal do Sistema Braille, o ponto. A abordagem metodológica partiu de revisão bibliográfica sobre o tema, investigação e avaliação criteriosa dos códigos de cores preexistentes e o desenvolvido de um sistema inovador, fundamentado na Teoria da Cor. Os códigos foram produzidos e experimentados em duas técnicas distintas: na técnica da Manufatura Aditiva (impressão em 3D) e na impressão em papel microcapsulado que produz relevos por meio de fusora térmica. Para a realização dos experimentos participaram 18 voluntários divididos em grupos de pessoas cegas, com baixa visão e com visão normal. Sendo nove mulheres e nove homens, com idades entre 25 a 64 anos. Os resultados da pesquisa evidenciaram que este sistema de código foi facilmente assimilado e memorizado pelos participantes com o tempo médio de 18,5 minutos para o ensino-aprendizado. A análise dos valores obtidos com o tempo médio de 14,08 segundos para o reconhecimento das cores através do código, comprovou que este sistema é eficaz e eficiente no que se propôs: o reconhecimento das cores pelo sentido do tato para promover inclusão e a acessibilidade da informação às pessoas com deficiência visual. Palavras-chave: Código de cor. Tecnologia Assistiva. Acessibilidade. Comunicação. Cegueira. Deficiência visual.Abstract: Color is one of the most important elements of human life, whether you are aware of it or not. The color is at all, from nature, in all internal and external environments, in the surrounding objects, garments and, even, as a form of verbal expression, unimaginable life without color. However, thousands of people in the world do not have access to this information. The present work refers to the development of code in relief with the objective of enabling the identification of the colors to people with visual impairment through tact. This scientific and innovative approach is composed of elements in three-dimensional format, with minimal dimensions, inspired by the main element of the Braille System, the point. The methodological approach was based on a bibliographic review of the theme, investigation and judicious evaluation of the pre-existing color codes and the development of an innovative system, grounded in the Color Theory. The codes were produced and tried in two distinct techniques: in the additive manufacturing technique (3D printing) and the microcapsulated paper printing that produces reliefs by means of thermal fuser. Eighteen volunteers were divided into groups of blind people, low vision and normal vision to perform the experiments. Nine women and nine men, aged between 25 and 64 years. The results of the research evidenced that this system of code was easily assimilated and memorized by the participants with an average time of 18,5 minutes for teaching/learning. The analysis of the values obtained with the average time of 14,08 seconds for the recognition of colors through the code, proved that this system is effective and efficient with has been proposed: the recognition of colors by the sense of touch to promote inclusion and accessibility information to visually impaired persons. Keywords: Color code. Assistive Technology. Accessibility. Communication. Blindness. Visual impairment.

Formation of Structure in Snowfields: Penitentes, Suncups, and Dirt Cones

Penitentes and suncups are structures formed as snow melts, typically high in the mountains. When the snow is dirty, dirt cones and other structures can form instead. Building on previous field observations and experiments, this work presents a theory of ablation morphologies, and the role of surface dirt in determining the structures formed. The glaciological literature indicates that sunlight, heating from air, and dirt all play a role in the formation of structure on an ablating snow surface. The present work formulates a mathematical model for the formation of ablation morphologies as a function of measurable parameters. The dependence of ablation morphologies on weather conditions and initial dirt thickness are studied, focusing on the initial growth of perturbations away from a flat surface. We derive a single-parameter expression for the melting rate as a function of dirt thickness, which agrees well with a set of measurements by Driedger. An interesting result is the prediction of a dirt-induced travelling instability for a range of parameters.Comment: 28 pages, 13 figure

Gene transfer into hepatocytes using asialoglycoprotein receptor mediated endocytosis of DNA complexed with an artificial tetra-antennary galactose ligand

We have constructed an artificial ligand for the hepatocyte-specific asialoglycoprotein receptor for the purpose of generating a synthetic delivery system for DNA. This ligand has a tetra-antennary structure, containing four terminal galactose residues on a branched carrier peptide. The carbohydrate residues of this glycopeptide were introduced by reductive coupling of lactose to the alpha- and epsilon-amino groups of the two N-terminal lysines on the carrier peptide. The C-terminus of the peptide, containing a cysteine separated from the branched N-terminus by a 10 amino acid spacer sequence, was used for conjugation to 3-(2-pyridyldithio)propionate-modified polylysine via disulfide bond formation. Complexes containing plasmid DNA bound to these galactose-polylysine conjugates have been used for asialoglycoprotein receptor-mediated transfer of a luciferase gene into human (HepG2) and murine (BNL CL.2) hepatocyte cell lines. Gene transfer was strongly promoted when amphipathic peptides with pH-controlled membrane-disruption activity, derived from the N-terminal sequence of influenza virus hemagglutinin HA-2, were also present in these DNA complexes. Thus, we have essentially borrowed the small functional domains of two large proteins, asialoglycoprotein and hemagglutinin, and assembled them into a supramolecular complex to generate an efficient gene-transfer system