1,008 research outputs found
Keeper of the Western Door: The Life and Legacy of Donehogawa, or Ely S. Parker
Senior Project submitted to The Division of Social Studies of Bard College
Solar system constraints on Rindler acceleration
We discuss the classical tests of general relativity in the presence of
Rindler acceleration. Among these tests the perihelion shifts give the tightest
constraints and indicate that the Pioneer anomaly cannot be caused by a
universal solar system Rindler acceleration. We address potential caveats for
massive test-objects. Our tightest bound on Rindler acceleration that comes
with no caveats is derived from radar echo delay and yields |a|<3nm/s^2.Comment: 7 pages, v2: minor changes, added references, v3: corrected typos,
extended Table 1, corrected bound on measurement of gravitational redshif
Strongly correlated double Dirac fermions
Double Dirac fermions have recently been identified as possible
quasiparticles hosted by three-dimensional crystals with particular
non-symmorphic point group symmetries. Applying a combined approach of
ab-initio methods and dynamical mean field theory, we investigate how
interactions and double Dirac band topology conspire to form the electronic
quantum state of BiCuO. We derive a downfolded eight-band model of the
pristine material at low energies around the Fermi level. By tuning the model
parameters from the free band structure to the realistic strongly correlated
regime, we find a persistence of the double Dirac dispersion until its
constituting time reveral symmetry is broken due to the onset of magnetic
ordering at the Mott transition. We analyze pressure as a promising route to
realize a double-Dirac metal in BiCuO
Formation and observation of a quasi-two-dimensional electron liquid in epitaxially stabilized SrLaTiO thin films
We report the formation and observation of an electron liquid in
SrLaTiO, the quasi-two-dimensional counterpart of SrTiO,
through reactive molecular-beam epitaxy and {\it in situ} angle-resolved
photoemission spectroscopy. The lowest lying states are found to be comprised
of Ti 3 orbitals, analogous to the LaAlO/SrTiO interface and
exhibit unusually broad features characterized by quantized energy levels and a
reduced Luttinger volume. Using model calculations, we explain these
characteristics through an interplay of disorder and electron-phonon coupling
acting co-operatively at similar energy scales, which provides a possible
mechanism for explaining the low free carrier concentrations observed at
various oxide heterostructures such as the LaAlO/SrTiO interface
Solutions to muscle fiber equations and their long time behaviour
We consider the nonlinear initial-boundary value problem governing the dynamical displacements of a one dimensional solid body with specific stress-strain law. This constitutive law results from the modelization of the mechanisms that rules the electrically activated mechanical behaviour of cardiac muscle fibers at the microscopic level. We prove global existence and uniqueness of solutions and we study their asymptotic behaviour in time. In particular we show that under vanishing external forcing solutions asymptotically converge to an equilibrium
Interplay of Dirac nodes and Volkov-Pankratov surface states in compressively strained HgTe
Preceded by the discovery of topological insulators, Dirac and Weyl
semimetals have become a pivotal direction of research in contemporary
condensed matter physics. While easily accessible from a theoretical viewpoint,
these topological semimetals pose a serious challenge in terms of experimental
synthesis and analysis to allow for their unambiguous identification. In this
work, we report on detailed transport experiments on compressively strained
HgTe. Due to the superior sample quality in comparison to other topological
semimetallic materials, this enables us to resolve the interplay of topological
surface states and semimetallic bulk states to an unprecedented degree of
precision and complexity. As our gate design allows us to precisely tune the
Fermi level at the Weyl and Dirac points, we identify a magnetotransport regime
dominated by Weyl/Dirac bulk state conduction for small carrier densities and
by topological surface state conduction for larger carrier densities. As such,
similar to topological insulators, HgTe provides the archetypical reference for
the experimental investigation of topological semimetals.Comment: 8 pages, 7 figures, accepted in PRX, added kp calculation and
supplementar
Putting a “C60 Ball” and Chain to Chlorin e6 Improves Its Cellular Uptake and Photodynamic Performances
Chlorin e6 (Ce6) and fullerene (C60) are among the most used photosensitizers (PSs) for photodynamic therapy (PDT). Through the combination of the chemical and photophysical properties of Ce6 and C60, in principle, we can obtain an “ideal” photosensitizer that is able to bypass the limitations of the two molecules alone, i.e., the low cellular uptake of Ce6 and the scarce solubility and absorption in the red region of the C60. Here, we synthesized and characterized a Ce6–C60 dyad. The UV-Vis spectrum of the dyad showed the typical absorption bands of both fullerene and Ce6, while a quenching of Ce6 fluorescence was observed. This behavior is typical in the formation of a fullerene–antenna system and is due to the intramolecular energy, or electron transfer from the antenna (Ce6) to the fullerene. Consequently, the Ce6–C60 dyad showed an enhancement in the generation of reactive oxygen species (ROS). Flow cytometry measurements demonstrated how the uptake of the Ce6 was strongly improved by the conjugation with C60. The Ce6–C60 dyad exhibited in A431 cancer cells low dark toxicity and a higher PDT efficacy than Ce6 alone, due to the enhancement of the uptake and the improvement of ROS generation
Forward Symplectic Integrators and the Long Time Phase Error in Periodic Motions
We show that when time-reversible symplectic algorithms are used to solve
periodic motions, the energy error after one period is generally two orders
higher than that of the algorithm. By use of correctable algorithms, we show
that the phase error can also be eliminated two orders higher than that of the
integrator. The use of fourth order forward time step integrators can result in
sixth order accuracy for the phase error and eighth accuracy in the periodic
energy. We study the 1-D harmonic oscillator and the 2-D Kepler problem in
great details, and compare the effectiveness of some recent fourth order
algorithms.Comment: Submitted to Phys. Rev. E, 29 Page
The evolution of tensor perturbations in scalar-tensor theories of gravity
The evolution equations for tensor perturbations in a generic scalar tensor
theory of gravity are presented. Exact solution are given for a specific class
of theories and Friedmann-Lema\^{i}tre-Robertson-Walker backgrounds. In these
cases it is shown that, although the evolution of tensor models depends on the
choice of parameters of the theory, no amplification is possible if the
gravitational interaction is attractive.Comment: 11 pages, 2 figures, submitted to Physical Review
- …