283 research outputs found
Employee stock option accounting : FASB 123(R), SEC SAB no. 107 : other recent authoritative developments; Financial reporting alert
https://egrove.olemiss.edu/aicpa_indev/1704/thumbnail.jp
Back pressure effects on variable geometry turbine performances
Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.Turbochargers are widely used in applications to increase
specific power and decrease fuel consumption. However,
recent anti-pollution regulations have became stricter and
pressed automotive engineers to find new solutions to reduce
Nox emissions. Two of these solutions are the catalytic
converter and the intercooler system. All these modifications
will change the initial matching of the turbocharger
performance characteristics to the engine requirements. In this
paper, several compressor wheel sizes are investigated to
evaluate the turbine/compressor matching. The intercooler and
catalytic converter back pressure induced are respectively
modeled by a lower duct section downstream the compressor
stage and a variable valve downstream the turbine stage. The
influences of the different modifications are identified through
the loading and the flow coefficients and also on classical
turbine performance maps. First, an analogy between
compressor wheel size and back pressure effects is underlined.
Second, it is shown that initial control settings of turbine
nozzle vanes are no longer appropriate with a catalytic
converter.vk201
Multiorgan failure after sickle cell vaso occlusive attack: integrated clinical and biological emergency
We describe the case of a 30-year-old patient, suffering from composite S/beta + sickle cell disease. He was hospitalized following a vaso-occlusive attack with acute bone pains. Despite an analgesic treatment and transfusion of three units of red blood cells, a non-regenerative anemia appeared within 24 hours. One day later an acute chest syndrome with atelectasis of the left lung and desaturation and multi-organ failure occurred and necessitated the patient\u27s intubation and required him to be placed in an artificial coma. A bronchoalveolar lavage was performed, which eliminated pneumonia but proved, after staining with oil red O, many neutral fatty acid microvacuoles in more than 80% of macrophages, suggesting a pulmonary fat embolism. The hypothesis of a bone marrow necrosis causing a pulmonary fat embolism was discussed and confirmed the next day by the characteristic appearance of the bone marrow. A therapeutic protocol associating iteratively bleeding and red blood cells transfusion was administered on the second day with the objective of maintaining haemoglobin S at less than 20% rate. Successive haemoglobin S assay was applied using a high performance liquid chromatography (HPLC) technique with a quick response within one hour after transfusion or bleeding. This protocol resulted in an improvement in the patient\u27s condition, with a gradual normalization of vital signs and extubation twelve days later and discharge without sequelae twenty-five days later. The succession of rare but serious sickle cell complications anaemia which occurred in this patient could be controlled by adapting the laboratory for the clinical emergency
Spin configurations in Co2FeAl0.4Si0.6 Heusler alloy thin film elements
We determine experimentally the spin structure of half-metallic
Co2FeAl0.4Si0.6 Heusler alloy elements using magnetic microscopy. Following
magnetic saturation, the dominant magnetic states consist of quasi-uniform
configurations, where a strong influence from the magnetocrystalline anisotropy
is visible. Heating experiments show the stability of the spin configuration of
domain walls in confined geometries up to 800 K. The switching temperature for
the transition from transverse to vortex walls in ring elements is found to
increase with ring width, an effect attributed to structural changes and
consequent changes in magnetic anisotropy, which start to occur in the narrower
elements at lower temperatures.Comment: 4 pages, 4 figure
Magnetic switching in granular FePt layers promoted by near-field laser enhancement
Light-matter interaction at the nanoscale in magnetic materials is a topic of
intense research in view of potential applications in next-generation
high-density magnetic recording. Laser-assisted switching provides a pathway
for overcoming the material constraints of high-anisotropy and high-packing
density media, though much about the dynamics of the switching process remains
unexplored. We use ultrafast small-angle x-ray scattering at an x-ray
free-electron laser to probe the magnetic switching dynamics of FePt
nanoparticles embedded in a carbon matrix following excitation by an optical
femtosecond laser pulse. We observe that the combination of laser excitation
and applied static magnetic field, one order of magnitude smaller than the
coercive field, can overcome the magnetic anisotropy barrier between "up" and
"down" magnetization, enabling magnetization switching. This magnetic switching
is found to be inhomogeneous throughout the material, with some individual FePt
nanoparticles neither switching nor demagnetizing. The origin of this behavior
is identified as the near-field modification of the incident laser radiation
around FePt nanoparticles. The fraction of not-switching nanoparticles is
influenced by the heat flow between FePt and a heat-sink layer
Emergent dynamic chirality in a thermally driven artificial spin ratchet
Modern nanofabrication techniques have opened the possibility to create novel functional materials, whose properties transcend those of their constituent elements. In particular, tuning the magnetostatic interactions in geometrically frustrated arrangements of nanoelements called artificial spin ice1, 2 can lead to specific collective behaviour3, including emergent magnetic monopoles4, 5, charge screening6, 7 and transport8, 9, as well as magnonic response10, 11, 12. Here, we demonstrate a spin-ice-based active material in which energy is converted into unidirectional dynamics. Using X-ray photoemission electron microscopy we show that the collective rotation of the average magnetization proceeds in a unique sense during thermal relaxation. Our simulations demonstrate that this emergent chiral behaviour is driven by the topology of the magnetostatic field at the edges of the nanomagnet array, resulting in an asymmetric energy landscape. In addition, a bias field can be used to modify the sense of rotation of the average magnetization. This opens the possibility of implementing a magnetic Brownian ratchet13, 14, which may find applications in novel nanoscale devices, such as magnetic nanomotors, actuators, sensors or memory cells
Massive Microbiological Groundwater Contamination Associated with a Waterborne Outbreak in Lake Erie, South Bass Island, Ohio
Optical control of 4f orbital state in rare-earth metals
Information technology demands continuous increase of data-storage density.
In high-density magnetic recording media, the large magneto-crystalline
anisotropy (MCA) stabilizes the stored information against decay through
thermal fluctuations. In the latest generation storage media, MCA is so large
that magnetic order needs to be transiently destroyed by heat to enable bit
writing. Here we show an alternative approach to control high-anisotropy
magnets: With ultrashort laser pulses the anisotropy itself can be manipulated
via electronic state excitations. In rare-earth materials like terbium metal,
magnetic moment and high MCA both originate from the 4f electronic state.
Following infrared laser excitation 5d-4f electron-electron scattering
processes lead to selective orbital excitations that change the 4f orbital
occupation and significantly alter the MCA. Besides these excitations within
the 4f multiplet, 5d-4f electron transfer causes a transient change of the 4f
occupation number, which, too, strongly alters the MCA. Such MCA change cannot
be achieved by heating: The material would rather be damaged than the 4f
configuration modified. Our results show a way to overcome this limitation for
a new type of efficient magnetic storage medium. Besides potential
technological relevance, the observation of MCA-changing excitations also has
implications for a general understanding of magnetic dynamics processes on
ultrashort time scales, where the 4f electronic state affects the angular
momentum transfer between spin system and lattice.Comment: Manuscript (14 pages, 3 figures) and Supplementary Information (22
pages, 9 figures
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