10,208 research outputs found

    Sub-femtosecond electron bunches created by direct laser acceleration in a laser wakefield accelerator with ionization injection

    Full text link
    In this work, we will show through three-dimensional particle-in-cell simulations that direct laser acceleration in laser a wakefield accelerator can generate sub-femtosecond electron bunches. Two simulations were done with two laser pulse durations, such that the shortest laser pulse occupies only a fraction of the first bubble, whereas the longer pulse fills the entire first bubble. In the latter case, as the trapped electrons moved forward and interacted with the high intensity region of the laser pulse, micro-bunching occurred naturally, producing 0.5 fs electron bunches. This is not observed in the short pulse simulation.Comment: AAC 201

    Observation of Instabilities of Coherent Transverse Ocillations in the Fermilab Booster

    Full text link
    The Fermilab Booster - built more than 40 years ago - operates well above the design proton beam intensity of 4x10**12 ppp. Still, the Fermilab neutrino experiments call for even higher intensity of 5.5x10**12 ppp. A multitude of intensity related effects must be overcome in order to meet this goal including suppression of coherent dipole instabilities of transverse oscillations which manifest themselves as a sudden drop in the beam current. In this report we present the results of observation of these instabilities at different tune, coupling and chromaticity settings and discuss possible cures.Comment: 3 pp. 3rd International Particle Accelerator Conference (IPAC 2012) 20-25 May 2012, New Orleans, Louisian

    Reconciliation and transformation through mutual learning: Outlining a framework for arts-based service learning with Indigenous communities in Australia

    Get PDF
    Service learning is described as a socially just educational process that develops two-way learning and social outcomes for community and student participants. Despite the focus on mutuality in service learning, very little of this literature specifically deals with the intense importance of mutuality and reciprocity when working with Indigenous community partners and participants. This is problematic for Indigenous service learning projects that seek to partner respectfully with Indigenous communities in Australia and elsewhere. To address this issue, the paper draws on existing international literature and data from an Indigenous arts based service learning project conducted in the Northern Territory of Australia to propose a framework centred on relationships, reciprocity, reflexivity and representation that can be adapted for future Indigenous service learning partnerships and research

    Plasma deposition of constrained layer damping coatings

    No full text
    Plasma techniques are used to generate constrained layer damping (CLD) coatings on metallic substrates. The process involves the deposition of relatively thick, hard ceramic layers on to soft polymeric damping materials while maintaining the integrity of both layers. Reactive plasma sputter-deposition from an aluminium alloy target is used to deposit alumina layers, with Young's modulus in the range 77-220GPa and thickness up to 335 μ, on top of a silicone film. This methodology is also used to deposit a 40 μ alumina layer on a conventional viscoelastic damping film to produce an integral damping coating. Plasma CLD systems are shown to give at least 50 per cent more damping than equivalent metal-foil-based treatments. Numerical methods for rapid prediction of the performance of such coatings are discussed and validated by comparison with experimental results

    Cause-specific child mortality in a mountainous community in Pakistan by verbal autopsy

    Get PDF
    In Pakistan\u27s rural areas population-based cause of death data from systematic verbal autopsies are rare. Using verbal autopsy algorithms with multiple coding and decision rules, we assigned causes of death among 79% of children under age five years dying between July, 1988 and December, 1991 in Oshikhandass, a remote mountainous community in Pakistan\u27s Northern Areas. Main causes of death were pneumonia (44%), diarrhoea (35%), and neonatal sepsis (6%). Combined (main plus associated) analysis revealed 48% died with diarrhoea, 46% with malnutrition, 44% with pneumonia, 15% with neonatal sepsis, and 15% with low birth weight. Median age of death with pneumonia was 2 months, with diarrhoea 8 months. Half died by month 4. The inquiry was well received by villagers. Population-based verbal autopsy surveillance is a cost-effective strategy to guide health managers. Plans are underway to institute it for the surrounding population of 400,000. Creative ways to access, treat and reduce risk among young infants are needed

    Profile: The Kilifi Health and Demographic Surveillance System (KHDSS).

    Get PDF
    The Kilifi Health and Demographic Surveillance System (KHDSS), located on the Indian Ocean coast of Kenya, was established in 2000 as a record of births, pregnancies, migration events and deaths and is maintained by 4-monthly household visits. The study area was selected to capture the majority of patients admitted to Kilifi District Hospital. The KHDSS has 260 000 residents and the hospital admits 4400 paediatric patients and 3400 adult patients per year. At the hospital, morbidity events are linked in real time by a computer search of the population register. Linked surveillance was extended to KHDSS vaccine clinics in 2008. KHDSS data have been used to define the incidence of hospital presentation with childhood infectious diseases (e.g. rotavirus diarrhoea, pneumococcal disease), to test the association between genetic risk factors (e.g. thalassaemia and sickle cell disease) and infectious diseases, to define the community prevalence of chronic diseases (e.g. epilepsy), to evaluate access to health care and to calculate the operational effectiveness of major public health interventions (e.g. conjugate Haemophilus influenzae type b vaccine). Rapport with residents is maintained through an active programme of community engagement. A system of collaborative engagement exists for sharing data on survival, morbidity, socio-economic status and vaccine coverage

    Cognitive Organization, Perceptions of Parenting and Depression Symptoms in Early Adolescence

    Get PDF
    Despite its strong relation to depression and theorized development across childhood and adolescence, cognitive schema organization has not been explored in early adolescence, a sensitive developmental period for first depression onset. Schema organization is theorized to derive from childhood cognitive internalizations of caregiving relationships, such as critical parenting experiences (e.g., Young et al. in Schema therapy: a practitioner’s guide. Guilford Press, New York, 2003). Thus, the current investigation considers the organization of positive and negative schemas with youth’s perceptions of parental warmth and psychological control and self-reported emotional functioning. Participants were 198 boys and girls aged 9–14 years who completed the Psychological Distance Scaling Task, measures of perceptions of parenting behaviors, anxiety symptoms and depression symptoms. Consistent with hypotheses, higher depression, but not anxiety symptoms were associated with a loosely-interconnected positive schema organization and a tightly-interconnected negative schema organization. Parental responsiveness emerged as the strongest predictor of negative schema structure. Implications for cognitive-developmental theories of depression and early identification of depression risk are discussed
    • …
    corecore