608 research outputs found

    A quantum mechanical approach to establishing the magnetic field orientation from a maser Zeeman profile

    Full text link
    Recent comparisons of magnetic field directions derived from maser Zeeman splitting with those derived from continuum source rotation measures have prompted new analysis of the propagation of the Zeeman split components, and the inferred field orientation. In order to do this, we first review differing electric field polarization conventions used in past studies. With these clearly and consistently defined, we then show that for a given Zeeman splitting spectrum, the magnetic field direction is fully determined and predictable on theoretical grounds: when a magnetic field is oriented away from the observer, the left-hand circular polarization is observed at higher frequency and the right-hand polarization at lower frequency. This is consistent with classical Lorentzian derivations. The consequent interpretation of recent measurements then raises the possibility of a reversal between the large-scale field (traced by rotation measures) and the small-scale field (traced by maser Zeeman splitting).Comment: 10 pages, 5 Figures, accepted for publication in MNRA

    Differences in the pregnancy gestation period and mean birth weights in infants born to Indian, Pakistani, Bangladeshi and white British mothers in Luton, UK: a retrospective analysis of routinely collected data

    Get PDF
    Objective To compare mean birth weights and gestational age at delivery of infants born to Indian, Pakistani, Bangladeshi and white British mothers in Luton, UK. Design Retrospective analysis using routinely recorded secondary data in Ciconia Maternity information System, between 2008 and 2013. Setting Luton, UK. Participants Mothers whose ethnicity was recorded as white British, Bangladeshi, Pakistani or Indian and living in Luton, aged over 16, who had a live singleton birth over 24 weeks of gestation were included in the analysis (n=14 871). Outcome measures Primary outcome measures were mean birth weight and gestational age at delivery. Results After controlling for maternal age, smoking, diabetes, gestation age, parity and maternal height and body mass index at booking, a significant difference in infants’ mean birth weight was found between white British and Indian, Pakistani and Bangladeshi infants, F(3, 12 287)=300.32, p Conclusions Results show important differences in adjusted mean birth weight between Indian, Pakistani, Bangladeshi and white British women. Moreover, an association was found between primipara Indian mothers and preterm delivery, when compared with Pakistani, Bangladeshi and white British women.</p

    Employing Object Technology to Expose Fundamental Object Concepts

    Get PDF
    We explore technical issues in the design of programming tools, development environments, simulations, code examples, user interface frameworks and pedagogies for a university-level course on object-oriented software development. The course, M206 Computing: An Object-Oriented Approach has been specifically developed for distance learning, and is enrolling over 5,000 students per year (average age 37) in the UK, Europe and Singapore. The course introduces computing via an object-oriented approach. M206 is substantial in extent representing one sixth of a degree. It embodies a practical, industry oriented view of computing and includes programming, analysis, design and group working. Considerable effort has been invested in making the simplicity, consistency and power of object technology accessible to and capable of being applied by beginners. A diverse set of educational media, such as CD-ROMs, TV and the Web, have been deployed as learning resources. We describe the agenda for the course; its object-oriented pedagogy and our strategy for delivery. We explain measures taken to avoid misconceptions about objects, our analysis and design method, and the Smalltalk programming environment we have developed specifically for learners and which is crucial to our approach. We outline how our adherence to the separation of view and domain model leads to technical innovations. Concluding remarks reflect on the benefits a reflexive strategy, both in education and training

    Prolonged transition time between colostrum and mature milk in a bear, the giant panda, Ailuropoda melanoleuca

    Get PDF
    Bears produce the most altricial neonates of any placental mammal. We hypothesized that the transition from colostrum to mature milk in bears reflects a temporal and biochemical adaptation for altricial development and immune protection. Comparison of bear milks with milks of other eutherians yielded distinctive protein profiles. Proteomic and metabolomic analysis of serial milk samples collected from six giant pandas showed a prolonged transition from colostrum to main-phase lactation over approximately 30 days. Particularly striking are the persistence or sequential appearance of adaptive and innate immune factors. The endurance of immunoglobulin G suggests an unusual duration of trans-intestinal absorption of maternal antibodies, and is potentially relevant to the underdeveloped lymphoid system of giant panda neonates. Levels of certain milk oligosaccharides known to exert anti-microbial activities and/or that are conducive to the development of neonatal gut microbiomes underwent an almost complete changeover around days 20–30 postpartum, coincident with the maturation of the protein profile. A potential metabolic marker of starvation was detected, the prominence of which may reflect the natural postpartum period of anorexia in giant panda mothers. Early lactation in giant pandas, and possibly in other ursids, appears to be adapted for the unique requirements of unusually altricial eutherian neonates

    Localization of sterols and oxysterols in mouse brain reveals distinct spatial cholesterol metabolism

    Get PDF
    Dysregulated cholesterol metabolism is implicated in a number of neurological disorders. Many sterols, including cholesterol and its precursors and metabolites, are biologically active and important for proper brain function. However, spatial cholesterol metabolism in brain and the resulting sterol distributions are poorly defined. To better understand cholesterol metabolism in situ across the complex functional regions of brain, we have developed on-tissue enzyme-assisted derivatization in combination with microliquid extraction for surface analysis and liquid chromatography-mass spectrometry to locate sterols in tissue slices (10 µm) of mouse brain. The method provides sterolomic analysis at 400-µm spot diameter with a limit of quantification of 0.01 ng/mm2. It overcomes the limitations of previous mass spectrometry imaging techniques in analysis of low-abundance and difficult-to-ionize sterol molecules, allowing isomer differentiation and structure identification. Here we demonstrate the spatial distribution and quantification of multiple sterols involved in cholesterol metabolic pathways in wild-type and cholesterol 24S-hydroxylase knockout mouse brain. The technology described provides a powerful tool for future studies of spatial cholesterol metabolism in healthy and diseased tissues
    corecore