933 research outputs found
Stimuli Responsive Shape Memory Microarchitectures
Shape memory polymers (SMPs) respond to heat by generating programmable movement in devices that require substantial deformation and operate at transient temperatures, including stents and embolization coils. To enable their use in small‐scale applications like retinal vasculature stenting, shape transformations must occur in SMPs with complex 3D geometries with nanoscale features. This work describes the synthesis and sculpting of a benzyl methacrylate‐based SMP into 3D structures with <800 nm characteristic critical dimensions via two photon lithography. Dynamic nanomechanical analysis of 8 µm‐diameter cylindrical pillars reveal the initiation of this SMP's glass transition at 60 °C. Shape memory programming of the characterized pillars as well as complex 3D architectures, including flowers with 500 nm thick petals and cubic lattices with 2.5 µm unit cells and overall dimensions of 4.5 µm × 4.5 µm × 10 µm, demonstrate an 86 +/− 4% characteristic shape recovery ratio. These results reveal a pathway toward SMP devices with nanoscale features and arbitrary 3D geometries changing shape in response to temperature
The frictional Schr\"odinger-Newton equation in models of wave function collapse
Replacing the Newtonian coupling G by -iG, the Schrodinger-Newton equation
becomes ``frictional''. Instead of the reversible Schrodinger-Newton equation,
we advocate its frictional version to generate the set of pointer states for
macroscopic quantum bodies.Comment: 6pp LaTeX for J.Phys.Conf.Ser.+2 figs. Talk given at the Int.
Workshop DICE2006 "Quantum Mechanics between Decoherence and Determinism: new
aspects from particle physics to cosmology" Piombino, Sept 11-15, 200
Convergence of the Magnus series
The Magnus series is an infinite series which arises in the study of linear
ordinary differential equations. If the series converges, then the matrix
exponential of the sum equals the fundamental solution of the differential
equation. The question considered in this paper is: When does the series
converge? The main result establishes a sufficient condition for convergence,
which improves on several earlier results.Comment: 11 pages; v2: added justification for conjecture, minor
clarifications and correction
Notes on Certain Newton Gravity Mechanisms of Wave Function Localisation and Decoherence
Both the additional non-linear term in the Schr\"odinger equation and the
additional non-Hamiltonian term in the von Neumann equation, proposed to ensure
localisation and decoherence of macro-objects, resp., contain the same
Newtonian interaction potential formally. We discuss certain aspects that are
common for both equations. In particular, we calculate the enhancement of the
proposed localisation and/or decoherence effects, which would take place if one
could lower the conventional length-cutoff and resolve the mass density on the
interatomic scale.Comment: 8pp LaTex, Submitted to J. Phys. A: Math-Gen, for the special issue
``The Quantum Universe'' in honor of G. C. Ghirard
Management of Anticoagulant and Thrombolytic Agents in Deep Venous Thrombosis
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68445/2/10.1177_153857448201600101.pd
Causal propagation of geometrical fields in relativistic cosmology
We employ the extended 1+3 orthonormal frame formalism for fluid spacetime
geometries , which contains the Bianchi field
equations for the Weyl curvature, to derive a 44-D evolution system of
first-order symmetric hyperbolic form for a set of geometrically defined
dynamical field variables. Describing the matter source fields
phenomenologically in terms of a barotropic perfect fluid, the propagation
velocities (with respect to matter-comoving observers that Fermi-propagate
their spatial reference frames) of disturbances in the matter and the
gravitational field, represented as wavefronts by the characteristic 3-surfaces
of the system, are obtained. In particular, the Weyl curvature is found to
account for two (non-Lorentz-invariant) Coulomb-like characteristic eigenfields
propagating with and four transverse characteristic eigenfields
propagating with , which are well known, and four
(non-Lorentz-invariant) longitudinal characteristic eigenfields propagating
with |v| = \sfrac{1}{2}. The implications of this result are discussed in
some detail and a parallel is drawn to the propagation of irregularities in the
matter distribution. In a worked example, we specialise the equations to
cosmological models in locally rotationally symmetric class II and include the
constraints into the set of causally propagating dynamical variables.Comment: 25 pages, RevTeX (10pt), accepted for publication by Physical Review
Searching for gravitational waves from known pulsars
We present upper limits on the amplitude of gravitational waves from 28
isolated pulsars using data from the second science run of LIGO. The results
are also expressed as a constraint on the pulsars' equatorial ellipticities. We
discuss a new way of presenting such ellipticity upper limits that takes
account of the uncertainties of the pulsar moment of inertia. We also extend
our previous method to search for known pulsars in binary systems, of which
there are about 80 in the sensitive frequency range of LIGO and GEO 600.Comment: Accepted by CQG for the proceeding of GWDAW9, 7 pages, 2 figure
Setting upper limits on the strength of periodic gravitational waves from PSR J1939+2134 using the first science data from the GEO 600 and LIGO detectors
Data collected by the GEO 600 and LIGO interferometric gravitational wave detectors during their first observational science run were searched for continuous gravitational waves from the pulsar J1939+2134 at twice its rotation frequency. Two independent analysis methods were used and are demonstrated in this paper: a frequency domain method and a time domain method. Both achieve consistent null results, placing new upper limits on the strength of the pulsar's gravitational wave emission. A model emission mechanism is used to interpret the limits as a constraint on the pulsar's equatorial ellipticity
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