912 research outputs found
Contingency Planning for Feedstock Splits Between the Immobilization and MOX Disposition Routes to Fissile Materials Disposition
In 1997, DOE issued a ROD endorsing a âdual-track â approach for dispositioning excess Pu so that it achieved the âspent-fuel standard. â This assumed 35.6 tonnes of weapons-grade Pu, 7.4 tones of non-weapons-grade Pu plus 7 tonnes of weapons-grade Pu from future retirements would make up the feed stock. The Center for Strategic and International Studies Senior Policy Panel on the Safe, Timely, and Effective Disposition of Surplus U. S. and Russian Weapons-Grade Plutonium [CSIS] deemed this direction as well and soundly conceived. The DOEâs Materials Disposition Program is presently on track to deploy both disposition routes. In this hybrid approach, MOX fuel irradiation route would be used for pure Pu. Immobilization would be used for mixtures that are less practicable to fabricate into fuel or could be used for the full 50 tonnes. Both routes must overcome their uncertainties and obstacles and come on-stream for the complete disposition of the U. S. excess weapons-useable plutonium. However, because these disposition plants are being designed primarily to accommodate the hybrid, not the dual option, they fall short of the glowing praise heaped upon the Disposition Program by the CSIS. However, fairly minor changes to the disposition plants would bring them much closer to the glowing praise of the CSIS. A major problem for the program is the constantly changing status of the feed stock. DOE/EM i
Rocks Associated With the Mississippian-Pennsylvanian Unconformity in Southwestern Indiana
The purpose of this field conference is to acquaint participants with strata that are associated with the Mississippian-Pennsylvanian unconformity in southwestern Indiana. Criteria which aid in distinguishing between Mansfield strata of Pottsville (early Pennsylvanian) age and classic formations of Chester (late Mississippian) age will receive considerable attention in discussions at evening meetings and on the outcrop. Inspection of limestone and sandstone quarries will afford an insight into the economic products of Chester and Mansfield rocks
CrRLK1L receptorâlike kinases HERK1 and ANJEA are female determinants of pollen tube reception
Communication between the gametophytes is vital for angiosperm fertilisation. Multiple CrRLK1Lâtype receptor kinases prevent premature pollen tube burst, while another CrRLK1L protein, FERONIA (FER), is required for pollen tube reception in the female gametophyte. We report here the identification of two additional CrRLK1L homologues, HERCULES RECEPTOR KINASE 1 (HERK1) and ANJEA (ANJ), which act redundantly to promote pollen tube growth arrest at the synergid cells. HERK1 and ANJ localise to the filiform apparatus of the synergid cells in unfertilised ovules, and in herk1 anj mutants, a majority of ovules remain unfertilised due to pollen tube overgrowth, together indicating that HERK1 and ANJ act as female determinants for fertilisation. As in fer mutants, the synergid cellâspecific, endomembrane protein NORTIA (NTA) is not relocalised after pollen tube reception; however, unlike fer mutants, reactive oxygen species levels are unaffected in herk1 anj double mutants. Both ANJ and HERK1 associate with FER and its proposed coâreceptor LORELEI (LRE) in planta. Together, our data indicate that HERK1 and ANJ act with FER to mediate femaleâmale gametophyte interactions during plant fertilisation
Adiabatic following criterion, estimation of the nonadiabatic excitation fraction and quantum jumps
An accurate theory describing adiabatic following of the dark, nonabsorbing
state in the three-level system is developed. An analytical solution for the
wave function of the particle experiencing Raman excitation is found as an
expansion in terms of the time varying nonadiabatic perturbation parameter. The
solution can be presented as a sum of adiabatic and nonadiabatic parts. Both
are estimated quantitatively. It is shown that the limiting value to which the
amplitude of the nonadiabatic part tends is equal to the Fourier component of
the nonadiabatic perturbation parameter taken at the Rabi frequency of the
Raman excitation. The time scale of the variation of both parts is found. While
the adiabatic part of the solution varies slowly and follows the change of the
nonadiabatic perturbation parameter, the nonadiabatic part appears almost
instantly, revealing a jumpwise transition between the dark and bright states.
This jump happens when the nonadiabatic perturbation parameter takes its
maximum value.Comment: 33 pages, 8 figures, submitted to PRA on 28 Oct. 200
Scale-free memory model for multiagent reinforcement learning. Mean field approximation and rock-paper-scissors dynamics
A continuous time model for multiagent systems governed by reinforcement
learning with scale-free memory is developed. The agents are assumed to act
independently of one another in optimizing their choice of possible actions via
trial-and-error search. To gain awareness about the action value the agents
accumulate in their memory the rewards obtained from taking a specific action
at each moment of time. The contribution of the rewards in the past to the
agent current perception of action value is described by an integral operator
with a power-law kernel. Finally a fractional differential equation governing
the system dynamics is obtained. The agents are considered to interact with one
another implicitly via the reward of one agent depending on the choice of the
other agents. The pairwise interaction model is adopted to describe this
effect. As a specific example of systems with non-transitive interactions, a
two agent and three agent systems of the rock-paper-scissors type are analyzed
in detail, including the stability analysis and numerical simulation.
Scale-free memory is demonstrated to cause complex dynamics of the systems at
hand. In particular, it is shown that there can be simultaneously two modes of
the system instability undergoing subcritical and supercritical bifurcation,
with the latter one exhibiting anomalous oscillations with the amplitude and
period growing with time. Besides, the instability onset via this supercritical
mode may be regarded as "altruism self-organization". For the three agent
system the instability dynamics is found to be rather irregular and can be
composed of alternate fragments of oscillations different in their properties.Comment: 17 pages, 7 figur
Analysis of LIGO data for gravitational waves from binary neutron stars
We report on a search for gravitational waves from coalescing compact binary
systems in the Milky Way and the Magellanic Clouds. The analysis uses data
taken by two of the three LIGO interferometers during the first LIGO science
run and illustrates a method of setting upper limits on inspiral event rates
using interferometer data. The analysis pipeline is described with particular
attention to data selection and coincidence between the two interferometers. We
establish an observational upper limit of 1.7 \times 10^{2}M_\odot$.Comment: 17 pages, 9 figure
Orbital anastomoses of the anterior deep temporal artery
The anterior deep temporal artery may provide a major collateral pathway to the intracranial circulation through anastomoses with branches of the ophthalmic artery. Review of carotid angiograms in 26 patients with internal carotid artery occlusive disease revealed anterior deep temporal to ophthalmic artery anastomoses in 16 cases. This route of collateral blood flow was associated in most instances with total occlusion of the cervical portion of the internal carotid artery. Three cases demonstrating the angiographic anatomy of the anterior deep temporal artery and its potential anastomoses with branches of the ophthalmic artery are presented. L'artĂšre temporale profonde antĂ©rieure peut ĂȘtre Ă l'origine de circulation colatĂ©rale grĂące Ă ses anastomoses avec l'artĂšre ophtalmique. Une telle anastomose a Ă©tĂ© constatĂ©e 16 fois sur 26 cas de thrombose de l'artĂšre carotide interne. Ăber die A. temporalis anterior ist ĂŒber Anastomosen zu den Ăsten der A. ophthalmica ein Kollateral-Kreislauf zu den intracraniellen GefĂ€Ăabschnitten möglich. Bei 26 Patienten mit einem A. carotis interna-VerschluĂ zeigte sich dieser Kreislauf in 16 FĂ€llen. Es wird ĂŒber 3 FĂ€lle ausfĂŒhrlich berichtet, bei denen die angiographische Anatomie der A. temporalis anterior und die möglichen Anastomosen mit Ăsten der A. ophthalmica besprochen wird.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46672/1/234_2004_Article_BF00335020.pd
Heavy quarkonium: progress, puzzles, and opportunities
A golden age for heavy quarkonium physics dawned a decade ago, initiated by
the confluence of exciting advances in quantum chromodynamics (QCD) and an
explosion of related experimental activity. The early years of this period were
chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in
2004, which presented a comprehensive review of the status of the field at that
time and provided specific recommendations for further progress. However, the
broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles
could only be partially anticipated. Since the release of the YR, the BESII
program concluded only to give birth to BESIII; the -factories and CLEO-c
flourished; quarkonium production and polarization measurements at HERA and the
Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the
deconfinement regime. All these experiments leave legacies of quality,
precision, and unsolved mysteries for quarkonium physics, and therefore beg for
continuing investigations. The plethora of newly-found quarkonium-like states
unleashed a flood of theoretical investigations into new forms of matter such
as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the
spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b},
and b\bar{c} bound states have been shown to validate some theoretical
approaches to QCD and highlight lack of quantitative success for others. The
intriguing details of quarkonium suppression in heavy-ion collisions that have
emerged from RHIC have elevated the importance of separating hot- and
cold-nuclear-matter effects in quark-gluon plasma studies. This review
systematically addresses all these matters and concludes by prioritizing
directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K.
Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D.
Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A.
Petrov, P. Robbe, A. Vair
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