1,219 research outputs found
Cholesterol is the major component of native lipoproteins activating the p38 mitogen-activated protein kinases
Elevated low-density lipoprotein (LDL) levels induce activation of the p38 mitogen-activated protein kinase (MAPK), a stress-activated protein kinase potentially participating in the development of atherosclerosis. The nature of the lipoprotein components inducing p38 MAPK activation has remained unclear however. We show here that both LDLs and high-density lipoproteins (HDLs) have the ability to stimulate the p38 MAPKs with potencies that correlate with their cholesterol content. Cholesterol solubilized in methyl-β-cyclodextrin was sufficient to activate the p38 MAPK pathway. Liposomes made of phosphatidylcholine (PC) or sphingomyelin, the two main phospholipids found in lipoproteins, were unable to stimulate the p38 MAPKs. In contrast, PC liposomes loaded with cholesterol potently activated this pathway. Reducing the cholesterol content of LDL particles lowered their ability to activate the p38 MAPKs. Cell lines representative of the three main cell types found in blood vessels (endothelial cells, smooth muscle cells and fibroblasts) all activated their p38 MAPK pathway in response to LDLs or cholesterol-loaded PC liposomes. These results indicate that elevated cholesterol content in lipoproteins, as seen in hypercholesterolemia, favors the activation of the stress-activated p38 MAPK pathway in cells from the vessel wall, an event that might contribute to the development of atherosclerosi
Learning Design through the Lens of Service: A Qualitative Study
Twenty-four senior-level capstone engineering design projects were completed at a large, public, primarily undergraduate university involving 85 students (70 male and 15 female). All projects involved the design of equipment to facilitate physical activity for people with disabilities. The effects on: i) learning design, ii) attitude towards people with disabilities, iii) motivation to complete team design projects and iv) interdisciplinary collaboration were analyzed through 24 one-hour focus groups. We explored the student experience using a constructivist approach and grounded theory. Four major themes (with associated sub-themes) emerged from our data analysis: learning design (project management, iterative design process, and user-centered design), motivation to complete design (engineering, disabilities, user), perceptions of people with disabilities (previous experience, changed attitudes and beliefs), and multidisciplinary collaboration (etiquette presentation, communication between disciplines, defining roles and expectations). Students completing these projects were shown to appreciate user-centered design, exhibit greater motivation when able to meet and develop a relationship with their client in person, discuss altruistic factors regarding their capstone experience, and were able to develop strong multidisciplinary skills
Information on antiprotonic atoms and the nuclear periphery from the PS209 experiment
In the PS209 experiments at CERN two kinds of measurements were performed:
the in-beam measurement of X-rays from antiprotonic atoms and the
radiochemical, off-line determination of the yield of annihilation products
with mass number A_t -1 (less by 1 than the target mass). Both methods give
observables which allows to study the peripheral matter density composition and
distribution.Comment: LaTeX (espcrc1 style), 6 pages, 3 EPS figures, 1 table, Proceedings
of the Sixth Biennal Conference on Low-Energy Antiproton Physics LEAP 2000,
Venice, Ital
Neutron density distributions from antiprotonic 208Pb and 209Bi atoms
The X-ray cascade from antiprotonic atoms was studied for 208Pb and 209Bi.
Widths and shifts of the levels due to the strong interaction were determined.
Using modern antiproton-nucleus optical potentials the neutron densities in the
nuclear periphery were deduced. Assuming two parameter Fermi distributions
(2pF) describing the proton and neutron densities the neutron rms radii were
deduced for both nuclei. The difference of neutron and proton rms radii /\r_np
equal to 0.16 +-(0.02)_{stat} +- (0.04)_{syst} fm for 208Pb and 0.14 +-
(0.04)_{stat} +- (0.04)_{syst} fm for 209Bi were determined and the assigned
systematic errors are discussed. The /\r_np values and the deduced shapes of
the neutron distributions are compared with mean field model calculations.Comment: 22 pages, 8 tables, 15 figure
Single waveguide silicon-organic hybrid modulator
We present a novel silicon-organic hybrid modulator based on an integrated dual-mode interferometer. The modulator offers a compact, simplified design and enhanced robustness to on-chip fluctuations of temperature compared to conventional Mach-Zehnder based systems. A prototype modulator showing a voltage dependent transmission spectrum is obtained by cladding a dual-mode waveguide in a 250 nm silicon-on-insulator technology with a customized organic electro-optic layer. Estimated phase shifts and corresponding figures of merit are discussed in this contribution. The used organic layer is based on the guest-host approach with customized donor-acceptor chromophore embedded and poled in a poly(methylmethacrylate) matrix. The presented prototype is to the best of the authors'' knowledge the first integrated single waveguide silicon-organic hybrid modulator
The ORFEUS II Echelle Spectrometer: Instrument description, performance and data reduction
During the second flight of the ORFEUS-SPAS mission in November/December
1996, the Echelle spectrometer was used extensively by the Principal and Guest
Investigator teams as one of the two focal plane instruments of the ORFEUS
telescope. We present the in-flight performance and the principles of the data
reduction for this instrument. The wavelength range is 90 nm to 140 nm, the
spectral resolution is significantly better than lambda/(Delta lambda) = 10000,
where Delta lambda is measured as FWHM of the instrumental profile. The
effective area peaks at 1.3 cm^2 near 110 nm. The background is dominated by
straylight from the Echelle grating and is about 15% in an extracted spectrum
for spectra with a rather flat continuum. The internal accuracy of the
wavelength calibration is better than +/- 0.005 nm.Comment: 8 pages, 8 figure
Distribution and Kinematics of O VI in the Galactic Halo
FUSE spectra of 100 extragalactic objects are analyzed to obtain measures of
O VI absorption along paths through the Milky Way thick disk/halo. Strong O VI
absorption over the approximate velocity range from -100 to 100 km/s reveals a
widespread but highly irregular distribution of thick disk O VI, implying the
existence of substantial amounts of hot gas with T ~ 3x10^5 K in the Milky Way
halo. Large irregularities in the distribution of the absorbing gas are found
to be similar over angular scales extending from less than one to 180 degrees,
indicating a considerable amount of small and large scale structure in the gas.
The overall distribution of Galactic O VI is not well described by a
symmetrical plane-parallel layer of patchy O VI absorption. The simplest
departure from such a model that provides a reasonable fit to the observations
is a plane-parallel patchy absorbing layer with a scale height of 2.3 kpc, and
a 0.25 dex excess of O VI in the northern Galactic polar region. The O VI
absorption has a Doppler parameter b = 30 to 99 km/s, with an average value of
60 km/s . Thermal broadening alone cannot explain the large observed profile
widths. The average O VI absorption velocities toward high latitude objects
range from -46 to 82 km/s, with a sample average of 0 km/s and a standard
deviation of 21 km/s. O VI associated with the thick disk moves both toward and
away from the plane with roughly equal frequency. A combination of models
involving the radiative cooling of hot fountain gas, the cooling of supernova
bubbles in the halo, and the turbulent mixing of warm and hot halo gases is
required to explain the presence of O VI and other highly ionized atoms found
in the halo. (abbreviated)Comment: 70 pages, single-spaced, PDF format. Bound copies of this manuscript
and two accompanying articles are available upon request. Submitted to ApJ
Absolute Energy Calibration of X-ray TESs with 0.04 eV Uncertainty at 6.4 keV in a Hadron-Beam Environment
A performance evaluation of superconducting transition-edge sensors (TESs) in
the environment of a pion beam line at a particle accelerator is presented.
Averaged across the 209 functioning sensors in the array, the achieved energy
resolution is 5.2 eV FWHM at Co (6.9 keV) when the pion beam is
off and 7.3 eV at a beam rate of 1.45 MHz. Absolute energy uncertainty of
0.04 eV is demonstrated for Fe (6.4 keV) with in-situ energy
calibration obtained from other nearby known x-ray lines. To achieve this small
uncertainty, it is essential to consider the non-Gaussian energy response of
the TESs and thermal cross-talk pile-up effects due to charged-particle hits in
the silicon substrate of the TES array.Comment: Accepted for publication in J. Low Temperature Physics, special issue
for the proceedings of the Low Temperature Detectors 16 conferenc
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