2,423 research outputs found
Structural Stability and Renormalization Group for Propagating Fronts
A solution to a given equation is structurally stable if it suffers only an
infinitesimal change when the equation (not the solution) is perturbed
infinitesimally. We have found that structural stability can be used as a
velocity selection principle for propagating fronts. We give examples, using
numerical and renormalization group methods.Comment: 14 pages, uiucmac.tex, no figure
Energy and Charged Particle Flow in 10.8 A GeV/c Au+Au Collisions
Experimental results and a detailed analysis are presented of the transverse
energy and charged particle azimuthal distributions measured by the E877
collaboration for different centralities of Au+Au collisions at a beam momentum
of 10.8 A GeV/c. The anisotropy of these distributions is studied with respect
to the reaction plane reconstructed on an event-by-event basis using the
transverse energy distribution measured by calorimeters. Results are corrected
for the reaction plane resolution. For semicentral events we observe directed
flow signals of up to ten percent. We observe a stronger anisotropy for slow
charged particles. For both the charged particle and transverse energy
distributions we observe a small but non zero elliptic anisotropy with the
major axis pointing into the reaction plane. Combining the information on
transverse energy and charged particle flow we obtain information on the flow
of nucleons and pions. The data are compared to event generators and the need
to introduce a mean field or nucleon-nucleon potential is discussed.Comment: RevTex, 25 pages, 13 figures included as one Postscript file,
submitted to Phys. Rev.
New exact fronts for the nonlinear diffusion equation with quintic nonlinearities
We consider travelling wave solutions of the reaction diffusion equation with
quintic nonlinearities . If the parameters
and obey a special relation, then the criterion for the existence of a
strong heteroclinic connection can be expressed in terms of two of these
parameters. If an additional restriction is imposed, explicit front solutions
can be obtained. The approach used can be extended to polynomials whose highest
degree is odd.Comment: Revtex, 5 page
A Collaboratory, Multi-Disciplinary Approach to Risk Mitigation during HIV Analytical Treatment Interruption
Analytic treatment interruptions (ATIs) are currently the standard for assessing the impact of experimental interventions aimed at inducing sustained antiretroviral therapy (ART)-free remission in trials related to HIV cure. ATIs are associated with substantial risk to both study participants and their sexual partner(s). Two documented HIV transmissions occurring in the context of ATIs have been recently reported, but recommendations for mitigating the risk of such events during ATIs are limited. We outline a practical approach to risk mitigation during ATI studies and describe strategies we are utilising in an upcoming clinical trial that may be applicable to other centres
Multiple Front Propagation Into Unstable States
The dynamics of transient patterns formed by front propagation in extended
nonequilibrium systems is considered. Under certain circumstances, the state
left behind a front propagating into an unstable homogeneous state can be an
unstable periodic pattern. It is found by a numerical solution of a model of
the Fr\'eedericksz transition in nematic liquid crystals that the mechanism of
decay of such periodic unstable states is the propagation of a second front
which replaces the unstable pattern by a another unstable periodic state with
larger wavelength. The speed of this second front and the periodicity of the
new state are analytically calculated with a generalization of the marginal
stability formalism suited to the study of front propagation into periodic
unstable states. PACS: 47.20.Ky, 03.40.Kf, 47.54.+rComment: 12 page
On the validity of the linear speed selection mechanism for fronts of the nonlinear diffusion equation
We consider the problem of the speed selection mechanism for the one
dimensional nonlinear diffusion equation . It has been
rigorously shown by Aronson and Weinberger that for a wide class of functions
, sufficiently localized initial conditions evolve in time into a monotonic
front which propagates with speed such that . The lower value is that predicted
by the linear marginal stability speed selection mechanism. We derive a new
lower bound on the the speed of the selected front, this bound depends on
and thus enables us to assess the extent to which the linear marginal selection
mechanism is valid.Comment: 9 pages, REVTE
2003 Wine Grape Cultivar Trial
Through an Iowa Department of Agriculture and Land Stewardship (IDALS) specialty crops grant awarded to the Iowa Grape Growers Association (now the Iowa Wine Growers Association) and contracted to the ISU Department of Horticulture, a wine grape cultivar trial was established in 2003 to evaluate the adaptability, productivity, and wine-making quality of up to 20 cultivars or advanced selections. Four ISU farms representing different geographic, climatic, and soil conditions were selected for the trial: the Horticulture Station (Hort Station), Ames; the Armstrong Research Farm, Lewis; the Southeast Research Farm, Crawfordsville; and the Northeast Research Farm, Nashua. Cultivars and selections planted in 2003 included Rubiana (GR-7), NY73.136.17, NY84.0101.04, NY70.0809.10, La Crescent, Prairie Star, Cayuga White, Chancellor, DeChaunac, Esprit, Landot 4511, Leon Millot, St. Vincent, and Vidal Blanc. An additional five cultivars (NY76.0844.24, Frontenac Gris, Briana, MN-1211, and MN-1198) were added to the trial in 2004
Modelling the economic efficiency of using different strategies to control Porcine Reproductive & Respiratory Syndrome at herd level
PRRS is among the diseases with the highest economic impact in pig production worldwide. Different strategies have been developed and applied to combat PRRS at farm level. The broad variety of available intervention strategies makes it difficult to decide on the most cost-efficient strategy for a given farm situation, as it depends on many farm-individual factors like disease severity, prices or farm structure. Aim of this study was to create a simulation tool to estimate the cost-efficiency of different control strategies at individual farm level. Baseline is a model that estimates the costs of PRRS, based on changes in health and productivity, in a specific farm setting (e.g. farm type, herd size, type of batch farrowing).
The model evaluates different intervention scenarios: depopulation/repopulation (D/R), close & roll-over (C&R), mass vaccination of sows (MS), mass vaccination of sows and vaccination of piglets (MS + piglets), improvements in internal biosecurity (BSM), and combinations of vaccinations with BSM. Data on improvement in health and productivity parameters for each intervention were obtained through literature review and from expert opinions. The economic efficiency of the different strategies was assessed over 5 years through investment appraisals: the resulting expected value (EV) indicated the most cost-effective strategy. Calculations were performed for 5 example scenarios with varying farm type (farrow-to-finish – breeding herd), disease severity (slightly – moderately – severely affected) and PRRSV detection (yes – no). The assumed herd size was 1000 sows with farm and price structure as commonly found in Germany. In a moderately affected (moderate deviations in health and productivity parameters from what could be expected in an average negative herd), unstable farrow-to-finish herd, the most cost-efficient strategies according to their median EV were C&R (€1′126′807) and MS + piglets (€ 1′114′649). In a slightly affected farrow-to-finish herd, no virus detected, the highest median EV was for MS + piglets (€ 721′745) and MS (€ 664′111). Results indicate that the expected benefits of interventions and the most efficient strategy depend on the individual farm situation, e.g. disease severity. The model provides new insights regarding the cost-efficiency of various PRRSV intervention strategies at farm level. It is a valuable tool for farmers and veterinarians to estimate expected economic consequences of an intervention for a specific farm setting and thus enables a better informed decision
Nb-substitution suppresses the superconducting critical temperature of pressurized MoB
A recent work has demonstrated that MoB, transforming to the same
structure as MgB (), superconducts at temperatures above 30 K near
100 GPa [C. Pei . Natl. Sci. Rev., nwad034 (2023)], and
Nb-substitution in MoB stabilizes the structure down to ambient
pressure [A. C. Hire . Phys. Rev. B 106, 174515 (2022)]. The current
work explores the high pressure superconducting behavior of Nb-substituted
MoB (NbMoB). High pressure x-ray diffraction
measurements show that the sample remains in the ambient pressure
structure to at least 160 GPa. Electrical resistivity measurements demonstrate
that from an ambient pressure of 8 K (confirmed by specific heat to be a
bulk effect), the critical temperature is suppressed to 4 K at 50 GPa, before
gradually rising to 5.5 K at 170 GPa. The critical temperature at high pressure
is thus significantly lower than that found in MoB under pressure (30 K),
revealing that Nb-substitution results in a strong suppression of the
superconducting critical temperature. Our calculations indeed find a reduced
electron-phonon coupling in NbMoB, but do not account
fully for the observed suppression, which may also arise from inhomogeneity and
enhanced spin fluctuations.Comment: 8 pages, 5 figures, 1 tabl
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