985 research outputs found
Comment on "Far-field microscopy with a nanometer-scale resolution based on the in-plane image magnification by surface plasmon polaritons"
This is a small comment concerning the work by Smolyaninov et al. in Phys.
Rev. Lett.94, 057401 (2005)
Analytical and experimental stability investigation of a hardware-in-the-loop satellite docking simulator
The European Proximity Operation Simulator (EPOS) of the DLR-German Aerospace
Center is a robotics-based simulator that aims at validating and verifying a
satellite docking phase. The generic concept features a robotics tracking
system working in closed loop with a force/torque feedback signal. Inherent
delays in the tracking system combined with typical high stiffness at contact
challenge the stability of the closed-loop system. The proposed concept of
operations is hybrid: the feedback signal is a superposition of a measured
value and of a virtual value that can be tuned in order to guarantee a desired
behavior. This paper is concerned with an analytical study of the system's
closed-loop stability, and with an experimental validation of the hybrid
concept of operations in one dimension (1D). The robotics simulator is modeled
as a second-order loop-delay system and closed-form expressions for the
critical delay and associated frequency are derived as a function of the
satellites' mass and the contact dynamics stiffness and damping parameters. A
numerical illustration sheds light on the impact of the parameters on the
stability regions. A first-order Pade approximation provides additional means
of stability investigation. Experiments were performed and tests results are
described for varying values of the mass and the damping coefficients. The
empirical determination of instability is based on the coefficient of
restitution and on the observed energy. There is a very good agreement between
the critical damping values predicted by the analysis and observed during the
tests...Comment: 16 page
Plasmonic crystal demultiplexer and multiports
Artificially built periodic optical structures in dielectric and metallic
media have generated considerable interest due to their potential for optical
device miniaturization. In this context plasmonics, i.e., optics based on
surface plasmon polaritons (SPPs) offers new exciting prospects. SPPs are
hybrid light/electron surface waves at the interface between a dielectric and a
metal and as such hold the potential for 2D optical functionality. Indeed, SPP
elements as mirrors, splitters and interferometers have been recently
demonstrated. However, for plasmonics to qualify at the information technology
level requires necessarily the realization of wavelength division
(demultiplexing) which constitutes a fundamental ingredient of optical
communication. In the following we experimentally demonstrate 2D SPP
demultiplexing in the visible spectral range by using photonic crystals for
SPPs (plasmonic crystals). In addition, we demonstrate that plasmonic crystal
are capable of realizing integrated linear multiports which could constitute
building blocks of analog or quantum optical computing.Comment: Nano Lett.7, 1697 (2007
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The Crystallography of Fatigue Crack Initiation in Incoloy-908 and A-286 Steel
Kindlin-3 loss curbs chronic myeloid leukemia in mice by mobilizing leukemic stem cells from protective bone marrow niches.
Kindlin-3 (K3)-mediated integrin adhesion controls homing and bone marrow (BM) retention of normal hematopoietic cells. However, the role of K3 in leukemic stem cell (LSC) retention and growth in the remodeled tumor-promoting BM is unclear. We report that loss of K3 in a mouse model of chronic myeloid leukemia (CML) triggers the release of LSCs from the BM into the circulation and impairs their retention, proliferation, and survival in secondary organs, which curbs CML development, progression, and metastatic dissemination. We found de novo expression of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) on CML-LSCs but not normal hematopoietic stem cells and this enabled us to specifically deplete K3 with a CTLA-4-binding RNA aptamer linked to a K3-siRNA (small interfering RNA) in CTLA-4+ LSCs in vivo, which mobilized LSCs in the BM, induced disease remission, and prolonged survival of mice with CML. Thus, disrupting interactions of LSCs with the BM environment is a promising strategy to halt the disease-inducing and relapse potential of LSCs
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