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Tightly-Coupled Opportunistic Navigation for Deep Urban and Indoor Positioning
A strategy is presented for exploiting the frequency stability,
transmit location, and timing information of ambient radio-frequency “signals of opportunity” for the purpose of
navigating in deep urban and indoor environments. The
strategy, referred to as tightly-coupled opportunistic navigation
(TCON), involves a receiver continually searching
for signals from which to extract navigation and timing
information. The receiver begins by characterizing these
signals, whether downloading characterizations from a collaborative
online database or performing characterizations
on-the-fly. Signal observables are subsequently combined
within a central estimator to produce an optimal estimate
of position and time. A simple demonstration of the
TCON strategy focused on timing shows that a TCONenabled
receiver can characterize and use CDMA cellular
signals to correct its local clock variations, allowing it to
coherently integrate GNSS signals beyond 100 seconds.Aerospace Engineering and Engineering Mechanic
IL-2 Therapy Diminishes Renal Inflammation and the Activity of Kidney-Infiltrating CD4+ T Cells in Murine Lupus Nephritis
An acquired deficiency of interleukin-2 (IL-2) and related disturbances in regulatory T cell (Treg) homeostasis play an important role in the pathogenesis of systemic lupus erythematosus (SLE). Low-dose IL-2 therapy was shown to restore Treg homeostasis in patients with active SLE and its clinical efficacy is currently evaluated in clinical trials. Lupus nephritis (LN), a challenging organ manifestation in SLE, is characterized by the infiltration of pathogenic CD4+ T cells into the inflamed kidney. However, the role of the Treg-IL-2 axis in the pathogenesis of LN and the mode of action of IL-2 therapy in the inflamed kidneys are still poorly understood. Using the (NZB × NZW) F1 mouse model of SLE we studied whether intrarenal Treg are affected by a shortage of IL-2 in comparison with lymphatic organs and whether and how intrarenal T cells and renal inflammation can be influenced by IL-2 therapy. We found that intrarenal Treg show phenotypic signs that are reminiscent of IL-2 deprivation in parallel to a progressive hyperactivity of intrarenal conventional CD4+ T cells (Tcon). Short-term IL-2 treatment of mice with active LN induced an expansion the intrarenal Treg population whereas long-term IL-2 treatment reduced the activity and proliferation of intrarenal Tcon, which was accompanied by a clinical and histological amelioration of LN. The association of these immune pathologies with IL-2 deficiency and their reversibility by IL-2 therapy provides important rationales for an IL-2-based immunotherapy of LN.DFG, SFB 650, Zelluläre Ansätze zur Suppression unerwünschter Immunreaktionen - From Bench to Bedsid
Consequence of reputation in an open-ended Naming Game
We study a modified version of the Naming Game, a recently introduced model
which describes how shared vocabulary can emerge spontaneously in a population
without any central control. In particular, we introduce a new mechanism that
allows a continuous interchange with the external inventory of words. A novel
playing strategy, influenced by the hierarchical structure that individuals'
reputation defines in the community, is implemented. We analyze how these
features influence the convergence times, the cognitive efforts of the agents
and the scaling behavior in memory and time.Comment: 6 pages, 6 figure
On the Stability of Super-Earth Atmospheres
We investigate the stability of super Earth atmospheres around M stars using
a 7-parameter, analytical framework. We construct stability diagrams in the
parameter space of exoplanetary radius versus semi-major axis and elucidate the
regions in which the atmospheres are stable against the condensation of their
major constituents, out of the gas phase, on their permanent nightside
hemispheres. We find that super Earth atmospheres which are nitrogen-dominated
("Earth-like") occupy a smaller region of allowed parameter space, compared to
hydrogen-dominated atmospheres, because of the dual effects of diminished
advection and enhanced radiative cooling. Furthermore, some super Earths which
reside within the habitable zones of M stars may not possess stable
atmospheres, depending on the mean molecular weight and infrared photospheric
pressure of their atmospheres. We apply our stability diagrams to GJ 436b and
GJ 1214b, and demonstrate that atmospheric compositions with high mean
molecular weights are disfavoured if these exoplanets possess solid surfaces
and shallow atmospheres. Finally, we construct stability diagrams tailored to
the Kepler dataset, for G and K stars, and predict that about half of the
exoplanet candidates are expected to habour stable atmospheres if Earth-like
conditions are assumed. We include 55 Cancri e and CoRoT-7b in our stability
diagram for G stars.Comment: Accepted by ApJ. 10 pages, 6 figures. No changes from previous
version, except for added hypen in titl
Lagrangian and Hamiltonian two-scale reduction
Studying high-dimensional Hamiltonian systems with microstructure, it is an
important and challenging problem to identify reduced macroscopic models that
describe some effective dynamics on large spatial and temporal scales. This
paper concerns the question how reasonable macroscopic Lagrangian and
Hamiltonian structures can by derived from the microscopic system.
In the first part we develop a general approach to this problem by
considering non-canonical Hamiltonian structures on the tangent bundle. This
approach can be applied to all Hamiltonian lattices (or Hamiltonian PDEs) and
involves three building blocks: (i) the embedding of the microscopic system,
(ii) an invertible two-scale transformation that encodes the underlying scaling
of space and time, (iii) an elementary model reduction that is based on a
Principle of Consistent Expansions.
In the second part we exemplify the reduction approach and derive various
reduced PDE models for the atomic chain. The reduced equations are either
related to long wave-length motion or describe the macroscopic modulation of an
oscillatory microstructure.Comment: 40 page
Optimization and evaluation of variability in the programming window of a flash cell with molecular metal-oxide storage
We report a modeling study of a conceptual nonvolatile memory cell based on inorganic molecular metal-oxide clusters as a storage media embedded in the gate dielectric of a MOSFET. For the purpose of this paper, we developed a multiscale simulation framework that enables the evaluation of variability in the programming window of a flash cell with sub-20-nm gate length. Furthermore, we studied the threshold voltage variability due to random dopant fluctuations and fluctuations in the distribution of the molecular clusters in the cell. The simulation framework and the general conclusions of our work are transferrable to flash cells based on alternative molecules used for a storage media
Electric field control of nonvolatile four-state magnetization at room temperature
We find the realization of large converse magnetoelectric (ME) effects at
room temperature in a multiferroic hexaferrite
BaSrCoFeO single crystal, in which rapid
change of electric polarization in low magnetic fields (about 5 mT) is coined
to a large ME susceptibility of 3200 ps/m. The modulation of magnetization then
reaches up to 0.62 /f.u. in an electric field of 1.14 MV/m. We find
further that four ME states induced by different ME poling exhibit unique,
nonvolatile magnetization versus electric field curves, which can be
approximately described by an effective free energy with a distinct set of ME
coefficients
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