482 research outputs found
Issues of Processing and Multiple Testing of SELDI-TOF MS Proteomic Data
A new data filtering method for SELDI-TOF MS proteomic spectra data is described. We examined technical repeats (2 per subject) of intensity versus m/z (mass/charge) of bone marrow cell lysate for two groups of childhood leukemia patients: acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). As others have noted, the type of data processing as well as experimental variability can have a disproportionate impact on the list of interesting proteins (see Baggerly et al. (2004)). We propose a list of processing and multiple testing techniques to correct for 1) background drift; 2) filtering using smooth regression and cross-validated bandwidth selection; 3) peak finding; and 4) methods to correct for multiple testing (van der Laan et al. (2005)). The result is a list of proteins (indexed by m/z) where average expression is significantly different among disease (or treatment, etc.) groups. The procedures are intended to provide a sensible and statistically driven algorithm, which we argue provides a list of proteins that have a significant difference in expression. Given no sources of unmeasured bias (such as confounding of experimental conditions with disease status), proteins found to be statistically significant using this technique have a low probability of being false positives
Faraday rotation of the supernova remnant G296.5+10.0: Evidence for a Magnetized Progenitor Wind
We present spectropolarimetric radio images of the supernova remnant (SNR)
G296.5+10.0 at frequencies near 1.4 GHz, observed with the Australia Telescope
Compact Array. By applying rotation measure (RM) synthesis to the data, a
pixel-by-pixel map of Faraday rotation has been produced for the entire
remnant. We find G296.5+10.0 to have a highly ordered RM structure, with mainly
positive RMs (mean RM of +28 rad/m**2) on the eastern side and negative RMs
(mean RM of -14 rad/m**2) on the western side, indicating a magnetic field
which is directed away from us on one side and toward us on the other. We
consider several possible mechanisms for creating the observed RM pattern.
Neither Faraday rotation in foreground interstellar gas nor in a homogeneous
ambient medium swept up by the SNR shell can easily explain the magnitude and
sign of the observed RM pattern. Instead, we propose that the observed RMs are
the imprint of an azimuthal magnetic field in the stellar wind of the
progenitor star. Specifically, we calculate that a swept-up magnetized wind
from a red supergiant can produce RMs of the observed magnitude, while the
azimuthal pattern of the magnetic field at large distances from the star
naturally produces the anti-symmetric RM pattern observed. Expansion into such
a wind can possibly also account for the striking bilateral symmetry of the
SNR's radio and X-ray morphologies.Comment: Accepted for publication in The Astrophysical Journa
Heating and cooling of the neutral ISM in the NGC4736 circumnuclear ring
The manner in which gas accretes and orbits within circumnuclear rings has
direct implications for the star formation process. In particular, gas may be
compressed and shocked at the inflow points, resulting in bursts of star
formation at these locations. Afterwards the gas and young stars move together
through the ring. In addition, star formation may occur throughout the ring, if
and when the gas reaches sufficient density to collapse under gravity. These
two scenarios for star formation in rings are often referred to as the `pearls
on a string' and `popcorn' paradigms. In this paper, we use new Herschel PACS
observations, obtained as part of the KINGFISH Open Time Key Program, along
with archival Spitzer and ground-based observations from the SINGS Legacy
project, to investigate the heating and cooling of the interstellar medium in
the nearby star-forming ring galaxy, NGC4736. By comparing spatially resolved
estimates of the stellar FUV flux available for heating, with the gas and dust
cooling derived from the FIR continuum and line emission, we show that while
star formation is indeed dominant at the inflow points in NGC 4736, additional
star formation is needed to balance the gas heating and cooling throughout the
ring. This additional component most likely arises from the general increase in
gas density in the ring over its lifetime. Our data provide strong evidence,
therefore, for a combination of the two paradigms for star formation in the
ring in NGC4736.Comment: accepted for publication in A&
Observation of magnetic circular dichroism in Fe L_{2,3} x-ray-fluorescence spectra
We report experiments demonstrating circular dichroism in the x-ray-fluorescence spectra of magnetic systems, as predicted by a recent theory. The data, on the L_{2,3} edges of ferromagnetic iron, are compared with fully relativistic local spin density functional calculations, and the relationship between the dichroic spectra and the spin-resolved local density of occupied states is discussed
Growth and magnetic characterization of Co nanoparticles obtained by femtosecond pulsed laser deposition
We present a detailed study on the morphology and magnetic properties of Co nanostructures deposited onto oxidized Si substrates by femtosecond pulsed laser deposition. Generally, Co disks of nanometric dimensions are obtained just above the ablation threshold, with a size distribution characterized by an increasingly larger number of disks as their size diminishes, and with a maximum disk size that depends on the laser power
density. In Au/Co/Au structures, in-plane magnetic anisotropy is observed in all cases, with no indication of superparamagnetism regardless of the amount of material or the laser power density. Magnetic force microscopy observations show coexistence of single-domain and vortex states for the magnetic domain structure of
the disks. Superconducting quantum interference device magnetometry and x-ray magnetic circular dichroism measurements point to saturation magnetization values lower than the bulk, probably due to partial oxidation of the Co resulting from incomplete coverage by the Au capping layer.Work was supported in part by the U.S. Department of Energy, Basic Energy Sciences (Grant No. DE-FG02-06ER46273), NSF FOCUS Center, the Spanish Ministerio de
Educación y Ciencia (References No. PR2005-0017 and No.MAT2005-05524-C02), Comunidad de Madrid (Reference No. S-0505/MAT/0194 NANOMAGNET), and CSIC (Reference No. 200650I130). Support from the SRS staff during the XMCD experiments is greatly acknowledged. Y.H. and L.M. also acknowledge financial support from the “Ramón y
Cajal” and “Juan de la Cierva” programs, respectively, from the Spanish Ministerio de Investigación y Ciencia and Consejo
Superior de Investigaciones Científicas (CSIC).Peer reviewe
Strategic foresight: towards enhancing leadership capabilities and business sustainability
СЕКЦИЯ 9. АКТУАЛЬНЫЕ ФИНАНСОВЫЕ И ЭКОНОМИЧЕСКИЕ АСПЕКТЫ
РАЗВИТИЯ ОТРАСЛЕ
Measurement of the proton electric to magnetic form factor ratio from \vec ^1H(\vec e, e'p)
We report the first precision measurement of the proton electric to magnetic
form factor ratio from spin-dependent elastic scattering of longitudinally
polarized electrons from a polarized hydrogen internal gas target. The
measurement was performed at the MIT-Bates South Hall Ring over a range of
four-momentum transfer squared from 0.15 to 0.65 (GeV/c).
Significantly improved results on the proton electric and magnetic form factors
are obtained in combination with previous cross-section data on elastic
electron-proton scattering in the same region.Comment: 4 pages, 2 figures, submitted to PR
Convergence Acceleration via Combined Nonlinear-Condensation Transformations
A method of numerically evaluating slowly convergent monotone series is
described. First, we apply a condensation transformation due to Van Wijngaarden
to the original series. This transforms the original monotone series into an
alternating series. In the second step, the convergence of the transformed
series is accelerated with the help of suitable nonlinear sequence
transformations that are known to be particularly powerful for alternating
series. Some theoretical aspects of our approach are discussed. The efficiency,
numerical stability, and wide applicability of the combined
nonlinear-condensation transformation is illustrated by a number of examples.
We discuss the evaluation of special functions close to or on the boundary of
the circle of convergence, even in the vicinity of singularities. We also
consider a series of products of spherical Bessel functions, which serves as a
model for partial wave expansions occurring in quantum electrodynamic bound
state calculations.Comment: 24 pages, LaTeX, 12 tables (accepted for publication in Comput. Phys.
Comm.
Resonant Auger spectroscopy at the L2,3 shake-up thresholds as a probe of electron correlation effects in nickel
The excitation energy dependence of the three-hole satellites in the
L3-M4,5M4,5 and L2-M4,5M4,5 Auger spectra of nickel metal has been measured
using synchrotron radiation. The satellite behavior in the non-radiative
emission spectra at the L3 and L2 thresholds is compared and the influence of
the Coster-Kronig channel explored. The three-hole satellite intensity at the
L3 Auger emission line reveals a peak structure at 5 eV above the L3 threshold
attributed to resonant processes at the 2p53d9 shake-up threshold. This is
discussed in connection with the 6-eV feature in the x-ray absorption spectrum.Comment: 8 pages, 4 figures; http://prb.aps.org/abstract/PRB/v58/i7/p3677_
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