3,001 research outputs found

    Linking carbonate sand fabric and mechanical anisotropy from hollow cylinder tests: motivation and application

    Get PDF
    In addition to density and stress, fabric is also a key state variable strongly affecting soil behavior. While fabric influence on mechanical behavior of soils has been investigated experimentally, the available database is limited in terms of boundary conditions and soil types tested. Offshore carbonate sediments are of special interest for offshore geotechnical analyses due to their prevalence in tropical waters and unique mechanical behavior that stems from their mostly biogenic origin. A key gap in the availability of experimental data on soil fabric relates to the anisotropy of offshore carbonate sediments. In practice, anisotropy studies (whether rigorously correlated to fabric or not) are typically carried out experimentally for simple boundary conditions such as idealized plane strain and axisymmetric states. In real geotechnical applications, stress paths subjected to soil elements in the field are far more complex, often involving the combined variations of both the orientation and magnitude of all three principal stresses. This paper presents a new multi- scale approach to assess soil fabric at the micro-scale level and relate it to the macro- mechanical response observed for generalized loading conditions. A new sampling method is illustrated that enables preservation and evaluation of the fabric of offshore sediments specimens following generalized stress disturbances imparted by a hollow cylinder apparatus. The link between fabric evolution and the observed stress-strain behavior of sand is discussed along with preliminary results. The approach is part of a broad framework that will be used to systematically study the evolution of soil fabric and anisotropy and their relationship to multi-directional loading scenarios

    Widely tunable dual-wavelength optical short pulse generation in a self-seeding scheme

    Get PDF
    Author name used in this publication: Dong Ning Wang2003-2004 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

    Exploring the influence of iron substitution in lithium rich layered oxides Li2Ru1-:XFexO3: Triggering the anionic redox reaction

    Get PDF
    Lithium rich layered materials are an interesting class of materials which exploit both anionic and cationic redox reactions to store energy upwards of 250 mA h g-1. This paper aims to understand the nature of the redox reactions taking place in these compounds. Li2RuO3 was used as the base compound, which is then compared with compounds generated by partially substituting Ru with Ti and Fe respectively. Electrochemical tests indicate that Fe substitution in the sample leads to an improvement in capacity, cycle life and reduction of potential decay. To elucidate the reason for this improvement in operando diffraction experiments were carried out, highlighting the formation of a secondary de-lithiated phase. The distortion of the pristine structure eventually induces frontier orbital reorganization leading to the oxygen redox reaction resulting in extra capacity. Local changes at Fe and Ru ions are recorded using in operando X-ray absorption spectroscopy (XAS). It was noted that while Ru undergoes a reversible redox reaction, Fe undergoes a significant irreversible change in its coordination environment during cycling. The changes in the coordination environment of oxygen and formation of O2n- type species were probed in situ using soft X-rays

    Exploring the influence of iron substitution in lithium rich layered oxides Li2Ru1-xFexO3: triggering the anionic redox reaction

    Get PDF
    Lithium rich layered materials are an interesting class of materials which exploit both anionic and cationic redox reactions to store energy upwards of 250 mA h g−1. This paper aims to understand the nature of the redox reactions taking place in these compounds. Li2RuO3 was used as the base compound, which is then compared with compounds generated by partially substituting Ru with Ti and Fe respectively. Electrochemical tests indicate that Fe substitution in the sample leads to an improvement in capacity, cycle life and reduction of potential decay. To elucidate the reason for this improvement in operando diffraction experiments were carried out, highlighting the formation of a secondary de-lithiated phase. The distortion of the pristine structure eventually induces frontier orbital reorganization leading to the oxygen redox reaction resulting in extra capacity. Local changes at Fe and Ru ions are recorded using in operando X-ray absorption spectroscopy (XAS). It was noted that while Ru undergoes a reversible redox reaction, Fe undergoes a significant irreversible change in its coordination environment during cycling. The changes in the coordination environment of oxygen and formation of O2n− type species were probed in situ using soft X-rays

    Estimating the workload associated with symptoms-based ovarian cancer screening in primary care: an audit of electronic medical records

    Get PDF
    BACKGROUND: Ovarian cancer is the most lethal gynaecological malignancy in the United Kingdom (UK). Studies have found that many women with ovarian cancer have symptoms for several months before diagnosis. Using a symptoms-based tool to diagnose ovarian cancer (OC) earlier is appealing, but may increase general practitioner (GP) workload because the symptoms are typically vague and non-specific. This study aimed to provide estimates of the GP workload associated with offering symptoms-based ovarian cancer screening. METHODS: A cross-sectional analysis of electronic records from four general practices in England, UK. We downloaded anonymous data on women aged 45–74 who consulted over one week to estimate the proportion who would be offered ‘screening’ according to the UK National Institute for Health and Care Excellence (NICE) guidelines and a symptoms index (Index 2) over one year. We used previous consultations (censoring women with no prior symptom at the date of their last recorded consultation) to estimate the proportion of women presenting with a new (not recorded in previous 12 months) NICE symptom each year. RESULTS: Data were obtained from 19,558 women. The proportion presenting over one week varied between practices (5%-14%), however, the proportion with an OC symptom was similar (17% overall). Over one year, an estimated 51.8% (95% CI 44.0%-59.7%) would present with an OC symptom, 26.6% (95% CI 19.3%-35.1%) with a NICE symptom and 20.3% (95% CI 13.7%-28.5%) with an Index 2 symptom. Each year, an estimated 11.9% (95% CI 5.0%-18.3%) of women would present with a new NICE symptom. CONCLUSION: One in two women aged 45–74 present to primary care at least once a year with an OC symptom, 11.9% with a new NICE symptom. This would be comparable to 2 to 8 yearly screening (depending on what symptoms triggered testing)

    Structural Performance of Reinforced Concrete Flat Plate Buildings Subjected to Fire

    Get PDF
    El siguiente artículo se propone estudiar la poesía de Luis Hernández a partir de los problemas que surgen al intentar estudiar su obra reunida. Antes que ser valorada como una poesía “inacabada”, la deliberada asistematicidad de su poética debe ser entendida como el resultado de un calculado y consciente ejercicio artístico, cuyas fuentes filosóficas tradicionalmente han pugnado por una ontología del movimiento frente a una metafísica de la permanencia. Bajo esta perspectiva, la obra de Hernández se revela como un “plano de inmanencia”, desde el cual acontece el sentido de su poesía en el quehacer de la escritura.The article aims to study Luis Hernández’ poetry from the point of view of the problems that emerge when trying to analyze his Complete Works. Rather than being assessed as “unfinished”, the deliberate and unsystematic appearance of his poetic, should rather be understood as the result of a calculated and conscious artistic practice that stems from philosophical trends which traditionally have fostered an ontology of movement against a metaphysics of permanence. Under this view, Hernández work shows up as “plane of immanence” from where sense becomes an event for the creative writing process.El següent article es proposa estudiar la poesia de Luis Hernández a partir dels problemes que sorgeixen al tractar d’estudiar la seva obra reunida. Abans de ser valorada com una poesia “incabada”, la deliberada asistematicitat de la seva poètica deu ser entesa com el resultat d’un calculat i conscient exercici artístic, fonts filosòfiques de les quals han pugnat tradicionalment per una ontologia del moviment davant una metafísica de la permanència. Sota aquesta perspectiva, l’obra d’Hernàndez es revela com un “pla d’inmanència”, des del qual esdevé el sentit de la seva poesia en el afer de l’escriptura

    A Predator from East Africa that Chooses Malaria Vectors as Preferred Prey

    Get PDF
    BACKGROUND: All vectors of human malaria, a disease responsible for more than one million deaths per year, are female mosquitoes from the genus Anopheles. Evarcha culicivora is an East African jumping spider (Salticidae) that feeds indirectly on vertebrate blood by selecting blood-carrying female mosquitoes as preferred prey. METHODOLOGY/PRINCIPAL FINDINGS: By testing with motionless lures made from mounting dead insects in lifelike posture on cork discs, we show that E. culicivora selects Anopheles mosquitoes in preference to other mosquitoes and that this predator can identify Anopheles by static appearance alone. Tests using active (grooming) virtual mosquitoes rendered in 3-D animation show that Anopheles' characteristic resting posture is an important prey-choice cue for E. culicivora. Expression of the spider's preference for Anopheles varies with the spider's size, varies with its prior feeding condition and is independent of the spider gaining a blood meal. CONCLUSIONS/SIGNIFICANCE: This is the first experimental study to show that a predator of any type actively chooses Anopheles as preferred prey, suggesting that specialized predators having a role in the biological control of disease vectors is a realistic possibility
    corecore