44,560 research outputs found
Comment on ``Consistency, amplitudes and probabilities in quantum theory'' by A. Caticha
A carefully written paper by A. Caticha [Phys. Rev. A57, 1572 (1998)] applies
consistency arguments to derive the quantum mechanical rules for compounding
probability amplitudes in much the same way as earlier work by the present
author [J. Math. Phys. 29, 398 (1988) and Int. J. Theor. Phys. 27, 543 (1998)].
These works are examined together to find the minimal assumptions needed to
obtain the most general results
Another self-similar blast wave: Early time asymptote with shock heated electrons and high thermal conductivity
Accurate approximations are presented for the self-similar structures of nonradiating blast waves with adiabatic ions, isothermal electrons, and equation ion and electron temperatures at the shock. The cases considered evolve in cavities with power law ambient densities (including the uniform density case) and have negligible external pressure. The results provide the early time asymptote for systems with shock heating of electrons and strong thermal conduction. In addition, they provide analytical results against which two fluid numerical hydrodynamic codes can be checked
High-resolution [C II] imaging of HDF850.1 reveals a merging galaxy at z=5.185
New high-resolution maps with the IRAM Interferometer of the redshifted [C
II] 158 micron line and the 0.98mm dust continuum of HDF850.1 at z = 5.185 show
the source to have a blueshifted northern component and a redshifted southern
component, with a projected separation of 0.3 arcsec, or 2 kpc. We interpret
these components as primordial galaxies that are merging to form a larger
galaxy. We think it is the resulting merger-driven starburst that makes
HDF850.1 an ultraluminous infrared galaxy, with an L(IR) of 1E13 Lsun. The
observed line and continuum brightness temperatures and the constant
line-to-continuum ratio across the source imply (1) high [C II] line optical
depth, (2) a [C II] excitation temperature of the same order as the dust
temperature, and (3) dust continuum emission that is nearly optically thick at
158 microns. These conclusions for HDF850.1 probably also apply to other
high-redshift submillimeter galaxies and quasar hosts in which the [C II] 158
micron line has been detected, as indicated by their roughly constant [C
II]-to-158 micron continuum ratios, in sharp contrast to the large dispersion
in their [C II]-to-FIR luminosity ratios. In brightness temperature units, the
[C II] line luminosity is about the same as the predicted CO(1-0) luminosity,
implying that the [C II] line can also be used to estimate the molecular gas
mass, with the same assumptions as for CO.Comment: Accepted by Astronomy and Astrophysic
Evaluating force field accuracy with long-time simulations of a tryptophan zipper peptide
We have combined a custom implementation of the fast multiple-time-stepping
LN integrator with parallel tempering to explore folding properties of small
peptides in implicit solvent on the time scale of microseconds. We applied this
algorithm to the synthetic {\beta}-hairpin trpzip2 and one of its sequence
variants W2W9. Each simulation consisted of over 12 {\mu}s of aggregated
virtual time. Several measures of folding behavior showed convergence, allowing
comparison with experimental equilibrium properties. Our simulations suggest
that the electrostatic interaction of tryptophan sidechains is responsible for
much of the stability of the native fold. We conclude that the ff99 force field
combined with ff96 {\phi} and {\psi} dihedral energies and implicit solvent can
reproduce plausible folding behavior in both trpzip2 and W2W9.Comment: 10 pages, 11 figures, submitted to the Journal of Chemical Physics on
June 28, 201
Behavior of soils under impact loading
Experimental soil behavior under impact loadin
Causal Inference When Counterfactuals Depend on the Proportion of All Subjects Exposed
The assumption that no subject's exposure affects another subject's outcome,
known as the no-interference assumption, has long held a foundational position
in the study of causal inference. However, this assumption may be violated in
many settings, and in recent years has been relaxed considerably. Often this
has been achieved with either the aid of a known underlying network, or the
assumption that the population can be partitioned into separate groups, between
which there is no interference, and within which each subject's outcome may be
affected by all the other subjects in the group via the proportion exposed (the
stratified interference assumption). In this paper, we instead consider a
complete interference setting, in which each subject affects every other
subject's outcome. In particular, we make the stratified interference
assumption for a single group consisting of the entire sample. This can occur
when the exposure is a shared resource whose efficacy is modified by the number
of subjects among whom it is shared. We show that a targeted maximum likelihood
estimator for the i.i.d.~setting can be used to estimate a class of causal
parameters that includes direct effects and overall effects under certain
interventions. This estimator remains doubly-robust, semiparametric efficient,
and continues to allow for incorporation of machine learning under our model.
We conduct a simulation study, and present results from a data application
where we study the effect of a nurse-based triage system on the outcomes of
patients receiving HIV care in Kenyan health clinics.Comment: 23 pages main article, 23 pages supplementary materials + references,
4 tables, 1 figur
Multiple Molecular H2 Outflows in AFGL 618
We report high spatial (0.5 arcsec) and high spectral (9 km/s) resolution
spectro-imaging of the 2.12 micron H2 1-0 S(1) line in the proto-planetary
nebula AFGL 618 using BEAR at the CFHT. The observations reveal the presence of
multiple, high-velocity, molecular outflows that align with the remarkable
optical jets seen in HST images. The structure and kinematics of the outflows
show how jets interact with circumstellar gas and shape the environment in
which planetary nebulae form.Comment: 14 pages, 5 figures. To appear in The Astrophysical Journal Letter
Mediation of Long Range Charge Transfer by Kondo Bound States
We present a theory of non-equilibrium long range charge transfer between
donor and acceptor centers in a model polymer mediated by magnetic exciton
(Kondo) bound states. Our model produces electron tunneling lengths easily
exceeding 10, as observed recently in DNA and organic charge transfer
systems. This long ranged tunneling is effective for weak to intermediate
donor-bridge coupling, and is enhanced both by weak to intermediate strength
Coulomb hole-electron attraction (through the orthogonality catastrophe) and by
coupling to local vibrational modes.Comment: Revised content (broadened scope, vibrations added), submitted to
Phys Rev Lett, added autho
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