2,120 research outputs found

    Revivification of confinement resonances in the photoionization of AA@C60_{60} endohedral atoms far above thresholds

    Full text link
    It is discovered theoretically that significant confinement resonances in an nlnl photoionization of a \textit{multielectron} atom AA encaged in carbon fullerenes, A@C60_{60}, may re-appear and be strong at photon energies far exceeding the nlnl ionization threshold, as a general phenomenon. The reasons for this phenomenon are unraveled. The Ne 2p2p photoionization of the endohedral anion Ne@C605āˆ’_{60}^{5-} in the photon energy region of about a thousand eV above the 2p2p threshold is chosen as case study.Comment: 3 pages, 1 figure, Revtex

    Remote measurement utilizing NASA's scanning laser Doppler systems. Volume 1. Laser Doppler wake vortex tracking at Kennedy Airport

    Get PDF
    Test operations of the Scanning Laser Doppler System (SLDS) at Kennedy International Airport (KIA) during August 1974 through June 1975 are reported. A total of 1,619 data runs was recorded with a totally operational system during normal landing operations at KIA. In addition, 53 data runs were made during cooperative flybys with the C880 for a grand total of 1672 recorded vortex tracks. Test crews were in attendance at KIA for 31 weeks, of which 25 weeks were considered operational and the other six were packing, unpacking, setup and check out. Although average activity equates to 67 recorded landing operations per week, two periods of complete runway inactivity spanned 20 days and 13 days, respectively. The operation frequency therefore averaged about 88 operations per week

    Global auroral responses to magnetospheric compressions by shocks in the solar wind: Two case studies

    Get PDF
    The global auroral responses to shocks in the solar wind at Earth were studied. The z-component of the interplanetary magnetic field, Bz, is negative ahead and behind the first shock and positive for the second case. A sudden-commencement geomagnetic storm develops in each case, with maximum D sub st 190 nT. An immediate auroral response is detected at all longitudes around the auroral oval, in which auroral luminosities increase by a factor of 2 to 3 with the first samples after each sudden commencement. The time delay in obtaining the first sample varies with local time from approx. 1 to 18 mins. No other significant variations in the aurora are associated with the immediate response. Beginning approx. 30 mins after each sudden commencement, the aurora becomes active and displays significant variations in its luminosity and spatial distribution. For Bz 0 an intense substorm develops. A sun-aligned transpolar arc forms when Bz 0, appearing first at local midnight as a polar arc and then lengthening sunward from the auroral oval across the polar cap to noon at an average speed of approx. 1 km/sec

    A Techniques Manual And Video For The Management Of Problem Urban Canada Geese

    Get PDF
    Social and management problems associated with urban Canada geese (Branta canadensis) are increasing in area, scope and magnitude. Although there are many articles on the management of urban Canada geese, none provide enough information for a reader to understand the impact geese have on different people, the ecology of the urban goose, evaluate the effectiveness of potential control options, choose appropriate management techniques, and then implement the chosen techniques. The authors present a manual and video, which in combination, they believe are not deficient in any of these areas. The video is intended to increase the awareness and knowledge of human/goose conflicts in urban and suburban environments. The manual covers the biology of Canada geese relevant to problem management in an urban setting and a comprehensive list of management techniques. Detailed instructions for implementation, permit requirements, sources of equipment and supplies, and a discussion of advantages, disadvantages, and characteristics, are included for each technique. To assist in choosing and locating appropriate techniques, quick reference summary tables are included

    On the azimuthal variation of the equatorial plasmapause

    Get PDF
    Previous results of plasmapause position surveys have been synthesized into a comprehensive description of the plasmapause, taken to represent the boundary between diurnal near-corotation and large-scale circulation streamlines that traverse the entire magnetosphere. The result indicates a plasmapause that has a pronounced bulge in the dusk sector, that rotates sunward and shrinks markedly as geomagnetic activity (and presumably magnetospheric convection) increase. The shape of the plasmapause so determined is significantly different from that associated with the simple superposition of sunward flow and corotation, both in its detailed shape and in its varying orientation. The results imply that the magnetospheric circulation departs from a uniform flow field, having a radial dependence with respect to the Earth that is qualitatively consistent with electrostatic shielding of the convection electric field. Also, the results imply the the inner magnetospheric flow field rotates from duskward to dawnward as its intensity increases

    On the Azimuthal Variation of Core Plasma in the Equatorial Magnetosphere

    Get PDF
    Previous results of plasmapause position surveys have been synthesized into a description of the underlying global distribution of plasmasphere-like or core plasma densities unique to a steady state magnetosphere. Under these steady conditions, the boundary between high- and low-density regions is taken to represent the boundary between diurnal near-corotation and large-scale circulation streamlines that traverse the entire magnetosphere. Results indicate a boundary that has a pronounced bulge in the dusk sector that is rotated westward and markedly reduced in size at increased levels of geomagnetic activity (and presumably magnetospheric convection). The derived profile is empirical confirmation of an underlying 'tear drop' distribution of core plasma, which is valid only for prolonged steady conditions and is somewhat different from that associated with the simple superposition of sunward flow and corotation, both in its detailed shape and in its varying orientation. Variation away from the tear drop profile suggests that magnetospheric circulation departs from a uniform flow field, having a radial dependence with respect to the Earth that is qualitatively consistent with electrostatic shielding of the convection electric field and which is rotated westward at increased levels of geophysical activity

    Assessing a Novel Adaptation to CCI Devices to Model Human Mild Traumatic Brain Injury

    Get PDF
    Background: Traumatic Brain Injuries (TBIs) are a health crisis with over a million people suffering injuries each year in the United States. The majority of TBIs are mild injuries which often produce no period of unconsciousness and no gross damage to the brain or skull. A range of TBI animal models exist but many produce injuries too severe to characterize as mild. One TBI induction method commonly used is Controlled Cortical Impact (CCI) devices. New Method: The purpose of this study is to assess a novel adaptation to CCI devices that allows for the induction of mild injuries that mimic human mild TBI (mTBI). In this apparatus, the mouse is placed on an elevated platform which utilizes a sensor to collapse the platform as the impactor hits the head. Results: On the first day of injury, the repetitive dropping platform group had a significantly lower Time to Righting (TTR) than both control and single hit stationary platform groups. Additionally, on the first day of injury the single-hit stationary group had a significantly increased Time to Ambulation (TTA) compared to all other groups. Furthermore, this adaptation produces significantly less GFAP than CCI injuries performed without the falling platform. Comparison with existing models: This model incorporates the high control of the CCI device that may be lost in weight-drop models of mild injury while also producing translational mild injuries. Conclusion: This adaptation can be used in any CCI research lab to translationally study mild injuries. This will facilitate murine research into mTBI

    Evolution of precipitates, in particular cruciform and cuboid particles, during simulated direct charging of thin slab cast vanadium microalloyed steels

    Get PDF
    A study has been undertaken of four vanadium based steels which have been processed by a simulated direct charging route using processing parameters typical of thin slab casting, where the cast product has a thickness of 50 to 80mm ( in this study 50 mm) and is fed directly to a furnace to equalise the microstructure prior to rolling. In the direct charging process, cooling rates are faster, equalisation times shorter and the amount of deformation introduced during rolling less than in conventional practice. Samples in this study were quenched after casting, after equalisation, after 4th rolling pass and after coiling, to follow the evolution of microstructure. The mechanical and toughness properties and the microstructural features might be expected to differ from equivalent steels, which have undergone conventional processing. The four low carbon steels (~0.06wt%) which were studied contained 0.1wt%V (V-N), 0.1wt%V and 0.010wt%Ti (V-Ti), 0.1wt%V and 0.03wt%Nb (V-Nb), and 0.1wt%V, 0.03wt%Nb and 0.007wt%Ti (V-Nb-Ti). Steels V-N and V-Ti contained around 0.02wt% N, while the other two contained about 0.01wt%N. The as-cast steels were heated at three equalising temperatures of 1050C, 1100C or 1200C and held for 30-60 minutes prior to rolling. Optical microscopy and analytical electron microscopy, including parallel electron energy loss spectroscopy (PEELS), were used to characterise the precipitates. In the as-cast condition, dendrites and plates were found. Cuboid particles were seen at this stage in Steel V-Ti, but they appeared only in the other steels after equalization. In addition, in the final product of all the steels, fine particles were seen, but it was only in the two titanium steels that cruciform precipitates were present. PEELS analysis showed that the dendrites, plates, cuboids, cruciforms and fine precipitates were essentially nitrides. The two Ti steels had better toughness than the other steels but inferior lower yield stress values. This was thought to be, in part, due to the formation of cruciform precipitates in austenite, thereby removing nitrogen and the microalloying elements which would have been expected to precipitate in ferrite as dispersion hardening particles

    Discrimination as a frame-of-reference effect in overlapping friendship communities of ethnically diverse youth

    Get PDF
    Objectives: To what extent is the frame of reference of overlapping friendship communities important for young peopleā€™s feelings of discrimination and subjective wellbeing? That is, do youth feel better or worse to the extent that they feel less or more discrimination than their friends? Methods: Participants (N=898; Mage=14.13; SDage=3.37; 46% females; 46% Whites; 20% Indigenous; 34% other minorities) were high school students of three ethnically diverse, low SES public schools in New South Wales, Australia. Cross-sectional data were collected to measure felt discrimination, mental health, subjective wellbeing, social support and nominations of close friends. A state-of-the-art method of clustering links was used to identify overlapping friendship communities, and multiple membership multilevel models were run to examine whether community level discrimination moderated the link between individual level discrimination and wellbeing. Results: When the community level discrimination was low, there was no wellbeing related cost or benefit of individual level discrimination. But when the community level discrimination was high, individuals in those communities who themselves felt low discrimination had better wellbeing than individuals who themselves felt high discrimination. Conclusions: We provide evidence for a frame-ofreference effect involving discrimination. Individualsā€™ relative standing in their friendship communities with high group-level discrimination reliably predicted the individualsā€™ wellbeing levels, regardless of ethnicity. The results highlight the importance of identifying overlapping friendship communities for understanding the dynamics of discrimination and wellbeing of ethnically diverse youth

    Occurrence statistics of cold, streaming ions in the nearā€Earth magnetotail: Survey of Polarā€TIDE observations

    Full text link
    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95347/1/jgra17705.pd
    • ā€¦
    corecore