2,010 research outputs found

    Lunar science prior to Apollo 11

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    Evolutional aspects and geological interpretations in lunar scienc

    Quantitative estimation of plant characteristics using spectral measurement: A survey of the literature

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    There are no author-identified significant results in this report

    Gram-negative bacterial molecules associate with Alzheimer disease pathology.

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    ObjectiveWe determined whether Gram-negative bacterial molecules are associated with Alzheimer disease (AD) neuropathology given that previous studies demonstrate Gram-negative Escherichia coli bacteria can form extracellular amyloid and Gram-negative bacteria have been reported as the predominant bacteria found in normal human brains.MethodsBrain samples from gray and white matter were studied from patients with AD (n = 24) and age-matched controls (n = 18). Lipopolysaccharide (LPS) and E coli K99 pili protein were evaluated by Western blots and immunocytochemistry. Human brain samples were assessed for E coli DNA followed by DNA sequencing.ResultsLPS and E coli K99 were detected immunocytochemically in brain parenchyma and vessels in all AD and control brains. K99 levels measured using Western blots were greater in AD compared to control brains (p < 0.01) and K99 was localized to neuron-like cells in AD but not control brains. LPS levels were also greater in AD compared to control brain. LPS colocalized with Aβ1-40/42 in amyloid plaques and with Aβ1-40/42 around vessels in AD brains. DNA sequencing confirmed E coli DNA in human control and AD brains.ConclusionsE coli K99 and LPS levels were greater in AD compared to control brains. LPS colocalized with Aβ1-40/42 in amyloid plaques and around vessels in AD brain. The data show that Gram-negative bacterial molecules are associated with AD neuropathology. They are consistent with our LPS-ischemia-hypoxia rat model that produces myelin aggregates that colocalize with Aβ and resemble amyloid-like plaques

    Analysis of the pulsar P-Ṗ distribution

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    A new technique for the systematic evaluation of models of pulsar period evolution on the basis of a complete observational sample is outlined and applied to the existing incomplete sample. Possible selection effects are discussed. It is concluded that the simple law for the rate of change of period P, Ṗ ∝ P^(2−n) is incompatible with the assumption of stationarity and pulsar ‘death’ at large periods, if n > 2. Models with n < 2, or with n ≳ 2.5 and torque decay on a time-scale of 1 Myr are consistent with the data. Another possibility is that the beaming fraction decreases by a factor ∼5 as a pulsar slows down. A new procedure for deriving a rigorous lower limit to the creation rate of pulsars within the sample is presented, and it is shown that most pulsars appear to be born with large values of Ṗ

    Timing the millisecond pulsars in 47 Tucanae

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    In the last 10 years 20 millisecond pulsars have been discovered in the globular cluster 47 Tucanae. Hitherto, only 3 of these had published timing solutions. Here we improve upon these 3 and present 12 new solutions. These measurements can be used to determine a variety of physical properties of the pulsars and of the cluster. The 15 pulsars have positions determined with typical uncertianties of only a few milliarcsec and they are all located within 1.2 arcmin of the cluster centre. We have also measured the proper motions of 5 of the pulsars, which are consistent with the proper motion of 47 Tuc based on Hipparcos data. The period derivatives measured for many of the pulsars are dominated by the dynamical effects of the cluster gravitational field, and are used to constrain the surface mass density of the cluster. All pulsars have characteristic ages T > 170 Myr and magnetic fields B < 2.4e9 Gauss, and the average T > 1 Gyr. We have measured the rate of advance of periastron for the binary pulsar J0024-7204H, implying a total system mass 1.4+-0.8 solar masses.Comment: 17 pages, 11 included figures, accepted for publication in MNRA
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