553 research outputs found
A proposal for regularly updated review/survey articles: "Perpetual Reviews"
We advocate the publication of review/survey articles that will be updated
regularly, both in traditional journals and novel venues. We call these
"perpetual reviews." This idea naturally builds on the dissemination and
archival capabilities present in the modern internet, and indeed perpetual
reviews exist already in some forms. Perpetual review articles allow authors to
maintain over time the relevance of non-research scholarship that requires a
significant investment of effort. Further, such reviews published in a purely
electronic format without space constraints can also permit more pedagogical
scholarship and clearer treatment of technical issues that remain obscure in a
brief treatment.Comment: This is a draft white paper and we seek comments from the communit
RiteWeight: Randomized Iterative Trajectory Reweighting for Steady-State Distributions Without Discretization Error
Molecular dynamics (MD) and enhanced sampling simulations have become
fundamental tools for studying biomolecular events. A significant challenge in
these simulations is ensuring that sampled configurations and transitions
converge to the stationary distribution of interest, whether equilibrium or
nonequilibrium. Lack of convergence constrains the estimation of mechanisms,
free energy, and rates of complex molecular events. Here, we introduce the
"Randomized Iterative Trajectory Reweighting" (RiteWeight) algorithm to
estimate a stationary distribution from unconverged simulation data. This
method iteratively reweights trajectories in a self-consistent way by solving
for the stationary distribution using a discrete-state transition matrix,
employing a new random clustering in each iteration. The iterative random
clustering mitigates the phase-space discretization error inherent in existing
trajectory reweighting techniques based on one-shot clustering and ultimately
yields numerically unbiased, quasi-continuous configuration-space distributions
and estimates of observables. We demonstrate the efficacy of RiteWeight using
Trp-Cage synthetic MD trajectories.Comment: 11 pages, 4 figure
Transition-Event Durations in One Dimensional Activated Processes
Despite their importance in activated processes, transition-event durations
-- which are much shorter than first passage times -- have not received a
complete theoretical treatment. We therefore study the distribution of
durations of transition events over a barrier in a one-dimensional system
undergoing over-damped Langevin dynamics.Comment: 39 pages, 11 figure
HST and Spitzer Observations of the HD 207129 Debris Ring
A debris ring around the star HD 207129 (G0V; d = 16.0 pc) has been imaged in
scattered visible light with the ACS coronagraph on the Hubble Space Telescope
and in thermal emission using MIPS on the Spitzer Space Telescope at 70 microns
(resolved) and 160 microns (unresolved). Spitzer IRS (7-35 microns) and MIPS
(55-90 microns) spectrographs measured disk emission at >28 microns. In the HST
image the disk appears as a ~30 AU wide ring with a mean radius of ~163 AU and
is inclined by 60 degrees from pole-on. At 70 microns it appears partially
resolved and is elongated in the same direction and with nearly the same size
as seen with HST in scattered light. At 0.6 microns the ring shows no
significant brightness asymmetry, implying little or no forward scattering by
its constituent dust. With a mean surface brightness of V=23.7 mag per square
arcsec, it is the faintest disk imaged to date in scattered light.Comment: 28 pages, 8 figure
Piperacillin-Induced Immune Hemolytic Anemia in an Adult with Cystic Fibrosis
We report a case of drug-induced immune hemolytic anemia (DIIHA) in an adult female with cystic fibrosis (CF), complicating routine treatment of a pulmonary exacerbation with intravenous piperacillin-tazobactam. Workup revealed a positive direct antiglobulin test (DAT) due to red blood cell (RBC)-bound IgG and C3 and piperacillin antibodies detectable in the patient's serum. The potential influence of CF transmembrane conductance regulator mutations on the severity of DIIHA is discussed. This report illustrates the importance of early identification of DIIHA, a rare complication of a commonly utilized medication in CF
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