1,514 research outputs found
Static stability and control characteristics of two large-dihedral right triangular pyramid lifting reentry configurations at a Mach number of 3.05
Static stability and control characteristics of dihedral right triangular pyramid lifting reentry vehicle configuration
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STANDARD OPERATING PROTOCOLS FOR DECOMMISSIONING
Decommissioning projects at Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) sites are conducted under project-specific decision documents, which involve extensive preparation time, public comment periods, and regulatory approvals. Often, the decision documents must be initiated at least one year before commencing the decommissioning project, and they are expensive and time consuming to prepare. The Rocky Flats Environmental Technology Site (RFETS) is a former nuclear weapons production plant at which hazardous substances and wastes were released or disposed during operations. As a result of the releases, RFETS was placed on the National Priorities List in 1989, and is conducting cleanup activities under a federal facilities compliance agreement. Working closely with interested stakeholders and state and federal regulatory agencies, RFETS has developed and implemented an improved process for obtaining the approvals. The key to streamlining the approval process has been the development of sitewide decision documents called Rocky Flats Cleanup Agreement Standard Operating Protocols or ''RSOPs.'' RSOPs have broad applicability, and could be used instead of project-specific documents. Although no two decommissioning projects are exactly the same and they may vary widely in contamination and other hazards, the basic steps taken for cleanup are usually similar. Because of this, using RSOPs is more efficient than preparing a separate project-specific decision documents for each cleanup action. Over the Rocky Flats cleanup life cycle, using RSOPs has the potential to: (1) Save over 5 million dollars and 6 months on the site closure schedule; (2) Eliminate preparing one hundred and twenty project-specific decision documents; and (3) Eliminate writing seventy-five closure description documents for hazardous waste unit closure and corrective actions
Spike-Train Responses of a Pair of Hodgkin-Huxley Neurons with Time-Delayed Couplings
Model calculations have been performed on the spike-train response of a pair
of Hodgkin-Huxley (HH) neurons coupled by recurrent excitatory-excitatory
couplings with time delay. The coupled, excitable HH neurons are assumed to
receive the two kinds of spike-train inputs: the transient input consisting of
impulses for the finite duration (: integer) and the sequential input
with the constant interspike interval (ISI). The distribution of the output ISI
shows a rich of variety depending on the coupling strength and the
time delay. The comparison is made between the dependence of the output ISI for
the transient inputs and that for the sequential inputs.Comment: 19 pages, 4 figure
A L\'evy input fluid queue with input and workload regulation
We consider a queuing model with the workload evolving between consecutive
i.i.d.\ exponential timers according to a
spectrally positive L\'evy process that is reflected at zero, and
where the environment equals 0 or 1. When the exponential clock
ends, the workload, as well as the L\'evy input process, are modified; this
modification may depend on the current value of the workload, the maximum and
the minimum workload observed during the previous cycle, and the environment
of the L\'evy input process itself during the previous cycle. We analyse
the steady-state workload distribution for this model. The main theme of the
analysis is the systematic application of non-trivial functionals, derived
within the framework of fluctuation theory of L\'evy processes, to workload and
queuing models
Variable Curvature Slab Molecular Dynamics as a Method to Determine Surface Stress
A thin plate or slab, prepared so that opposite faces have different surface
stresses, will bend as a result of the stress difference. We have developed a
classical molecular dynamics (MD) formulation where (similar in spirit to
constant-pressure MD) the curvature of the slab enters as an additional
dynamical degree of freedom. The equations of motion of the atoms have been
modified according to a variable metric, and an additional equation of motion
for the curvature is introduced. We demonstrate the method to Au surfaces, both
clean and covered with Pb adsorbates, using many-body glue potentials.
Applications to stepped surfaces, deconstruction and other surface phenomena
are under study.Comment: 16 pages, 8 figures, REVTeX, submitted to Physical Review
Resonance between Noise and Delay
We propose here a stochastic binary element whose transition rate depends on
its state at a fixed interval in the past. With this delayed stochastic
transition this is one of the simplest dynamical models under the influence of
``noise'' and ``delay''. We demonstrate numerically and analytically that we
can observe resonant phenomena between the oscillatory behavior due to noise
and that due to delay.Comment: 4 pages, 5 figures, submitted to Phys.Rev.Lett Expanded and Added
Reference
Antibody mediated neutralization of myelin associated EphrinB3 accelerates CNS remyelination
This is the final version of the article. It was first available from Springer via
http://dx.doi.org/10.1007/s00401-015-1521-1Remyelination in multiple sclerosis (MS) lesions often remains incomplete despite the presence of oligodendrocyte progenitor cells (OPCs). Amongst other factors, successful remyelination depends on the phagocytic clearance of myelin debris. However, the proteins in myelin debris that act as potent and selective inhibitors on OPC differentiation and inhibit CNS remyelination remain unknown. Here, we identify the transmembrane signalling protein EphrinB3 as important mediator of this inhibition, using a protein analytical approach in combination with a primary rodent OPC assay. In the presence of EphrinB3, OPCs fail to differentiate. In a rat model of remyelination, infusion of EphrinB3 inhibits remyelination. In contrast, masking EphrinB3 epitopes using antibodies promotes remyelination. Finally, we identify EphrinB3 in MS lesions and demonstrate that MS lesion extracts inhibit OPC differentiation while antibody-mediated masking of EphrinB3 epitopes promotes it. Our findings suggest that EphrinB3 could be a target for therapies aiming at promoting remyelination in demyelinating disease.This work was supported by the UK MS Society Grant ref: 941/11. MRNK held a NIHR
Clinical Lectureship. KAN was supported by an ERC advanced award
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