1,333 research outputs found
Development of carbon dioxide laser doppler instrumentation detection of clear air turbulence
The analytical, experimental, and developmental aspects of an airborne, pulsed, carbon dioxide laser-optical radar system are described. The laser detects clear air turbulence and performs Doppler measurements of this air-motion phenomenon. Conclusions and recommendations arising from the development of the laser system are presented
Focused laser Doppler velocimeter
A system for remotely measuring velocities present in discrete volumes of air is described. A CO2 laser beam is focused by a telescope at such a volume, a focal volume, and within the focusable range, near field, of the telescope. The back scatter, or reflected light, principally from the focal volume, passes back through the telescope and is frequency compared with the original frequency of the laser, and the difference frequency or frequencies represent particle velocities in that focal volume
Remote detection of trailing vortices, task 3, modification 3
The operation of a frequency tracker for use with the laser Doppler velocimeter (LDV) is reported. Topics discussed include: laser beam profile, lens matching, and LDV resolution data. It is concluded that the LDV provides good ground wind signals. The loss in sensitivity of the cavity system at high frequencies is partly compensated by an increase in the scattering cross section of the atmosphere due to dust
L1551NE - Discovery of a Binary Companion
L1551NE is a very young (class 0 or I) low-mass protostar located close to
the well-studied L1551 IRS5. We present here evidence, from 1.3mm continuum
interferometric observations at ~1'' resolution, for a binary companion to
L1551NE. The companion, whose 1.3mm flux density is ~1/3 that of the primary
component, is located 1.43'' (~230 A.U. at 160pc) to the southeast. The
millimeterwave emission from the primary component may have been just barely
resolved, with deconvolved size ~0.82"x0.70" (~131x112 A.U.). The companion
emission was unresolved (<100 A.U.). The pair is embedded within a flattened
circum-binary envelope of size ~5.4'' x 2.3'' (~860 x 370 A.U.). The masses of
the three components (i.e. from the cicumstellar material of the primary star
and its companion, and the envelope) are approximately 0.044, 0.014 and 0.023
Mo respectively.Comment: 8 pages, 1 figur
Discovery of a 500 pc shell in the nucleus of Centaurus A
Spitzer Space Telescope mid-infrared images of the radio galaxy Centaurus A
reveal a shell-like, bipolar, structure 500 pc to the north and south of the
nucleus. This shell is seen in 5.8, 8.0 and 24 micron broad-band images. Such a
remarkable shell has not been previously detected in a radio galaxy and is the
first extragalactic nuclear shell detected at mid-infrared wavelengths. We
estimate that the shell is a few million years old and has a mass of order
million solar masses. A conservative estimate for the mechanical energy in the
wind driven bubble is 10^53 erg. The shell could have created by a small few
thousand solar mass nuclear burst of star formation. Alternatively, the
bolometric luminosity of the active nucleus is sufficiently large that it could
power the shell. Constraints on the shell's velocity are lacking. However, if
the shell is moving at 1000 km/s then the required mechanical energy would be
100 times larger.Comment: submitted to ApJ Letter
Metabolic changes in quinolinic acid-lesioned rat striatum detected noninvasively by in vivo 1H NMR spectroscopy
Intrastriatal injection of quinolinic acid (QA) provides an animal model of Huntington disease. In vivo 1H NMR spectroscopy was used to measure the neurochemical profile non-invasively in seven animals 5 days after unilateral injection of 150 nmol of QA. Concentration changes of 16 metabolites were measured from 22 μl volume at 9.4 T. The increase of glutamine ((+25 ± 14)%, mean ± SD, n = 7) and decrease of glutamate (-12 ± 5)%, N-acetylaspartate (-17 ± 6)%, taurine (-14 ± 6)% and total creatine (-9 ± 3%) were discernible in each individual animal (P < 0.005, paired t-test). Metabolite concentrations in control striata were in excellent agreement with biochemical literature. The change in glutamate plus glutamine was not significant, implying a shift in the glutamate-glutamine interconversion, consistent with a metabolic defect at the level of neuronal-glial metabolic trafficking. The most significant indicator of the lesion, however, were the changes in glutathione ((-19 ± 9)%, P < 0.002)), consistent with oxidative stress. From a comparison with biochemical literature we conclude that high-resolution in vivo 1H NMR spectroscopy accurately reflects the neurochemical changes induced by a relatively modest dose of QA, which permits one to longitudinally follow mitochondrial function, oxidative stress and glial-neuronal metabolic trafficking as well as the effects of treatment in this model of Huntington disease. © 2001 Wiley-Liss, Inc
The first NINDS/NIBIB consensus meeting to define neuropathological criteria for the diagnosis of chronic traumatic encephalopathy.
Chronic traumatic encephalopathy (CTE) is a neurodegeneration characterized by the abnormal accumulation of hyperphosphorylated tau protein within the brain. Like many other neurodegenerative conditions, at present, CTE can only be definitively diagnosed by post-mortem examination of brain tissue. As the first part of a series of consensus panels funded by the NINDS/NIBIB to define the neuropathological criteria for CTE, preliminary neuropathological criteria were used by 7 neuropathologists to blindly evaluate 25 cases of various tauopathies, including CTE, Alzheimer's disease, progressive supranuclear palsy, argyrophilic grain disease, corticobasal degeneration, primary age-related tauopathy, and parkinsonism dementia complex of Guam. The results demonstrated that there was good agreement among the neuropathologists who reviewed the cases (Cohen's kappa, 0.67) and even better agreement between reviewers and the diagnosis of CTE (Cohen's kappa, 0.78). Based on these results, the panel defined the pathognomonic lesion of CTE as an accumulation of abnormal hyperphosphorylated tau (p-tau) in neurons and astroglia distributed around small blood vessels at the depths of cortical sulci and in an irregular pattern. The group also defined supportive but non-specific p-tau-immunoreactive features of CTE as: pretangles and NFTs affecting superficial layers (layers II-III) of cerebral cortex; pretangles, NFTs or extracellular tangles in CA2 and pretangles and proximal dendritic swellings in CA4 of the hippocampus; neuronal and astrocytic aggregates in subcortical nuclei; thorn-shaped astrocytes at the glial limitans of the subpial and periventricular regions; and large grain-like and dot-like structures. Supportive non-p-tau pathologies include TDP-43 immunoreactive neuronal cytoplasmic inclusions and dot-like structures in the hippocampus, anteromedial temporal cortex and amygdala. The panel also recommended a minimum blocking and staining scheme for pathological evaluation and made recommendations for future study. This study provides the first step towards the development of validated neuropathological criteria for CTE and will pave the way towards future clinical and mechanistic studies
Comparison of surface and column measurements of aerosol scattering properties over the western North Atlantic Ocean at Bermuda
Light scattering by size-resolved aerosols in near-surface air at Tudor
Hill, Bermuda, was measured between January and June 2009. Vertical
distributions of aerosol backscattering and column-averaged aerosol optical
properties were characterized in parallel with a micro-pulse lidar (MPL) and
an automated sun–sky radiometer. Comparisons were made between extensive
aerosol parameters in the column, such as the lidar-retrieved extinction at
400 m and the aerosol optical depth (AOD), and scattering was measured with a
surface nephelometer. Comparisons were also made for intensive parameters
such as the Ångström exponent and calculations using
AERONET(Aerosol Robotic Network)-derived
aerosol physical parameters (size distribution, index of refraction) and Mie
theory, and the ratio of submicron scattering to total scattering for size-segregated
nephelometer measurements. In these comparisons the <i>r</i><sup>2</sup> was
generally around 0.50. Data were also evaluated based on back trajectories.
The correlation between surface scattering and lidar extinction was highest
for flows when the surface scattering was dominated by smaller particles and
the flow had a longer footprint over land then over the ocean. The
correlation of AOD with surface scatter was similar for all flow regimes.
There was also no clear dependence of the atmospheric lapse rate, as
determined from a nearby radiosonde station, on flow regime. The
Ångström exponent for most flow regimes was 0.9–1.0, but for the
case of air originating from North America, but with significant time over
the ocean, the Ångström exponent was 0.57 ± 0.18. The submicron
fraction of aerosol near the surface (<i>R</i><sub>sub-surf</sub>) was significantly
greater for the flows from land (0.66 ± 0.11) than for the flows which
spent more time over the ocean (0.40 ± 0.05). When comparing
<i>R</i><sub>sub-surf</sub> and the column-integrated submicron scattering fraction,
<i>R</i><sub>sub-col</sub>, the correlation was similar, <i>r</i><sup>2</sup> = 0.50, but
<i>R</i><sub>sub-surf</sub> was generally less than <i>R</i><sub>sub-col</sub>, indicating more large
particles contributing to light scattering at the surface, contrary to
conditions over continents and for polluted continental transport over the
ocean. In general, though, the marginal correlations indicate that the column
optical properties are weakly correlated with the surface optical
measurements. Thus, if it is desired to associate aerosol chemical/physical
properties with their optical properties, it is best to use optical and
chemical/physical measurements with both collected at the surface or both
collected in the column
The time-dependent rearrangement of the epithelial basement membrane in human skin wounds
In 62 human skin wounds (surgical wounds, stab wounds and lacerations after surgical treatment) we analyzed the immunohistochemical localization of collagen IV in the epithelial basement membrane. In 27 of these wounds the distribution of collagen VII, which represents a specific component of the basement membrane of stratified epithelia, was also analyzed. We were able to demonstrate a virtually identical co-distribution of both collagen IV and VII in the wound area with no significant time-dependent differences in the appearance of both collagen types. Fragments of the epithelial basement membrane could be detected in the wound area from as early as 4 days after wounding and after 8 days a complete restitution of the epithelial basement membrane was observed. In all cases with a wound age of more than 21 days the basement membrane was completely reformed over the former lesional area. The period between 8 and 21 days after wounding was characterized by a wide variability ranging from complete restitution to deposition of basement membrane fragments or total lack of the epidermal basement membrane
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