200 research outputs found
An information filter approach to rapid system identification - Convergence speed and noise sensitivity
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76081/1/AIAA-1998-4510-927.pd
Accelerated convergence of neural network system identification algorithms via principal component analysis
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76898/1/AIAA-1998-4440-926.pd
MACE II - A Space Shuttle experiment for investigating adaptive control of flexible spacecraft
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76987/1/AIAA-1998-4319-483.pd
Graded Interface Models for More Accurate Determination of van der Waals-London Dispersion Interactions Across Grain Boundaries
Attractive van der WaalsâLondon dispersion interactions between two half crystals arise from local physical property gradients within the interface layer separating the crystals. Hamaker coefficients and London dispersion energies were quantitatively determined for ÎŁ5 and near-ÎŁ13 grain boundaries in SrTiO3 by analysis of spatially resolved valence electron energy-loss spectroscopy (VEELS) data. From the experimental data, local complex dielectric functions were determined, from which optical properties can be locally analyzed. Both local electronic structures and optical properties revealed gradients within the grain boundary cores of both investigated interfaces. The results show that even in the presence of atomically structured grain boundary cores with widths of less than 1 nm, optical properties have to be represented with gradual changes across the grain boundary structures to quantitatively reproduce accurate van der WaalsâLondon dispersion interactions. London dispersion energies of the order of 10% of the apparent interface energies of SrTiO3 were observed, demonstrating their significance in the grain boundary formation process. The application of different models to represent optical property gradients shows that long-range van der WaalsâLondon dispersion interactions scale significantly with local, i.e., atomic length scale property variations
XMM-Newton observations of the supernova remnant IC443: I. soft X-ray emission from shocked interstellar medium
The shocked interstellar medium around IC443 produces strong X-ray emission
in the soft energy band (E<1.5 keV). We present an analysis of such emission as
observed with the EPIC MOS cameras on board the XMM-Newotn observatory, with
the purpose to find clear signatures of the interactions with the interstellar
medium (ISM) in the X-ray band, which may complement results obtained in other
wavelenghts. We found that the giant molecular cloud mapped in CO emission is
located in the foreground and gives an evident signature in the absorption of
X-rays. This cloud may have a torus shape and the part of torus interacting
with the IC443 shock gives rise to 2MASS-K emission in the southeast. The
measured density of emitting X-ray shocked plasma increases toward the
northeastern limb, where the remnant is interacting with an atomic cloud. We
found an excellent correlation between emission in the 0.3-0.5 keV band and
bright optical/radio filament on large spatial scales. The partial shell
structure seen in this band therefore traces the encounter with the atomic
cloud.Comment: 10 pages, 10 figures, accepted for publication in ApJ (20 September
2006, v649). For hi-res figures, see
http://www.astropa.unipa.it/Library/OAPA_preprints/ic443ele1.ps.g
A Survey of Hydroxyl Toward Supernova Remnants: Evidence for Extended 1720 MHz Maser Emission
We present the results of GBT observations of all four ground-state hydroxyl
(OH) transitions toward 15 supernova remnants (SNRs) which show OH(1720 MHz)
maser emission. This species of maser is well established as an excellent
tracer of an ongoing interaction between the SNR and dense molecular material.
For the majority of these objects we detect significantly higher flux densities
with a single dish than has been reported with interferometric observations. We
infer that spatially extended, low level maser emission is a common phenomenon
that traces the large-scale interaction in maser-emitting SNRs. Additionally we
use a collisional pumping model to fit the physical conditions under which OH
is excited behind the SNR shock front. We find the observed OH gas associated
with the SNR interaction having columns less than approximately 10^17 per
square cm, temperatures of 20 to 125 K, and densities 10^5 per cubic cm.Comment: 24 pages, 23 figures, Accepted to ApJ, March 26, 2008; v2 - added
Figure 6, minor clarifications to text in Sections 3 and
Foxp3 expression in macrophages associated with RENCA tumors in mice.
The transcription factor Foxp3 represents the most specific functional marker of CD4+ regulatory T cells (TRegs). However, previous reports have described Foxp3 expression in other cell types including some subsets of macrophages, although there are conflicting reports and Foxp3 expression in cells other than Treg is not well characterized. We performed detailed investigations into Foxp3 expression in macrophages in the normal tissue and tumor settings. We detected Foxp3 protein in macrophages infiltrating mouse renal cancer tumors injected subcutaneously or in the kidney. Expression was demonstrated using flow cytometry and Western blot with two individual monoclonal antibodies. Further analyses confirmed Foxp3 expression in macrophages by RT PCR, and studies using ribonucleic acid-sequencing (RNAseq) demonstrated a previously unknown Foxp3 messenger (m)RNA transcript in tumor-associated macrophages. In addition, depletion of Foxp3+ cells using diphtheria toxin in Foxp3DTR mice reduced the frequency of type-2 macrophages (M2) in kidney tumors. Collectively, these results indicate that tumor-associated macrophages could express Foxp3
GBT Observations of IC 443: the Nature of OH(1720 MHz) Masers and OH Absorption
We present results of spectral line observations of the ground state
transitions of hydroxyl(OH) toward supernova remnant IC 443 carried out with
the Green Bank Telescope. At a spatial resolution of 7.2 arcminutes we detect
weak, extended OH(1720 MHz) maser emission with OH(1667/5,1612 MHz) absorption
along the southern extent of the remnant, where no bright compact maser sources
have been observed previously. These newly detected SNR-type masers are
coincident with known molecular clumps and a ridge of shocked molecular
hydrogen indicative of the SNR shock front interacting with the adjacent
molecular cloud. Simultaneous observation of all four ground-state transitions
of OH permits us to fit physical conditions of the shocked gas at the
interaction site. A simple two-component model for the line profiles yields the
physical parameters for detected regions of maser emission including excitation
temperature, OH column density and filling factor. Observed line profiles
suggest the shock is largely propagating toward the line-of-sight in the region
of these newly identified weak masers. The implications of shock geometry and
physical parameters in producing extended OH maser emission in SNRs are
explored. We also present VLA radio continuum observations at 330 MHz for
comparison with OH line observations of the remnant.Comment: 20 pages, 4 figures, 3 tables, submitted to Ap
The Relation Between the Surface Brightness and the Diameter for Galactic Supernova Remnants
In this work, we have constructed a relation between the surface brightness
() and diameter (D) of Galactic C- and S-type supernova remnants
(SNRs). In order to calibrate the -D dependence, we have carefully
examined some intrinsic (e.g. explosion energy) and extrinsic (e.g. density of
the ambient medium) properties of the remnants and, taking into account also
the distance values given in the literature, we have adopted distances for some
of the SNRs which have relatively more reliable distance values. These
calibrator SNRs are all C- and S-type SNRs, i.e. F-type SNRs (and S-type SNR
Cas A which has an exceptionally high surface brightness) are excluded. The
Sigma-D relation has 2 slopes with a turning point at D=36.5 pc: (at 1
GHz)=8.4 D
WmHzster (for
WmHzster and D36.5 pc) and (at 1
GHz)=2.7 10 D
WmHzster (for
WmHzster and D36.5 pc). We discussed the theoretical
basis for the -D dependence and particularly the reasons for the change
in slope of the relation were stated. Added to this, we have shown the
dependence between the radio luminosity and the diameter which seems to have a
slope close to zero up to about D=36.5 pc. We have also adopted distance and
diameter values for all of the observed Galactic SNRs by examining all the
available distance values presented in the literature together with the
distances found from our -D relation.Comment: 45 pages, 2 figures, accepted for publication in Astronomical and
Astrophysical Transaction
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