648 research outputs found
J/Psi Production from Electromagnetic Fragmentation in Z decay
The rate for is suprisingly large
with about one event for every million decays. The reason for this is
that there is a fragmentation contribution that is not suppressed by a factor
of . In the fragmentation limit with
fixed, the differential decay rate for factors into electromagnetic decay rates and universal
fragmentation functions. The fragmentation functions for lepton fragmentation
and photon fragmentation into are calculated to lowest order in
. The fragmentation approximation to the rate is shown to match the
full calculation for greater than about .Comment: 16 pages and 8 figure
Minimum EMG burst duration in healthy controls : implications for electrodiagnosis in movement disorders
Background
EMG burst duration can provide additional diagnostic information when investigating hyperkinetic movement disorders, particularly when a functional movement disorder is suspected. It is generally accepted that EMG bursts <50ms are pathological.
Objective
To re‐assess minimum physiological EMG burst duration.
Methods
Surface EMG was recorded from face, trunk and limb muscles in controls (n=60; age 19‐85). Subjects were instructed to generate the briefest possible ballistic movements involving each muscle (40 repetitions) or, in muscles spanning joints, to generate rapid rhythmic alternating movements (20‐30s), or both.
Results
We found no effect of age on EMG burst duration. However, EMG burst duration varied significantly between body regions. Rhythmic EMG bursts were shorter than ballistic bursts but only significantly so for lower limbs (p<0.001). EMG bursts of duration <50ms were frequently observed, particularly in appendicular muscles.
Conclusion
We present normal reference data for minimum EMG burst duration, which may assist clinical interpretation when investigating hyperkinetic movement disorders
QCD Corrections and the Endpoint of the Lepton Spectrum in Semileptonic B Decays
Recently, Neubert has suggested that a certain class of nonperturbative
corrections dominates the shape of the electron spectrum in the endpoint region
of semileptonic decay. Perturbative QCD corrections are important in the
endpoint region. We study the effects of these corrections on Neubert's
proposal. The connection between the endpoint of the electron spectrum in
semileptonic decay and the photon spectrum in is
outlined.Comment: 18 pages, uses REVTeX, UCSD/PTH 93-38, CALT-68-1910, JHU-TIPAC-930029
(some changes to the discussion of subleading radiative corrections, and
minor typos fixed
On the Influence of Noise on the Critical and Oscillatory Behavior of a Predator-Prey Model: Coherent Stochastic Resonance at the Proper Frequency
Noise induced changes in the critical and oscillatory behavior of a
Prey-Predator system are studied using power spectrum density and Spectral
Amplification Factor (SAF) analysis. In the absence of external noise, the
population densities exhibit three kinds of asymptotic behavior, namely:
Absorbing State, Fixed Point (FP) and an Oscillatory Regime (OR) with a well
defined proper (natural) frequency. The addition of noise destabilizes the FP
phase inducing a transition to a new OR. Surprisingly, it is found that when a
periodic signal is added to the control parameter, the system responds
robustly, without relevant changes in its behavior. Nevertheless, the "Coherent
Stochastic Resonance" phenomenon is found only at the proper frequency. Also, a
method based on SAF allows us to locate very accurately the transition points
between the different regimes.Comment: RevTex, 18 pgs, 6 figures. Submitted to Physics Letters A (2000
The 16th moment of the three loop anomalous dimension of the non-singlet transversity operator in QCD
We present the result of the three loop anomalous dimension of non-singlet
transversity operator in QCD for the Mellin moment N=16. The obtained result
coincides with the prediction from arXiv:1203.1022 and can serve as a
confirmation of the correctness of the general expression for three loop
anomalous dimension of non-singlet transversity operator in QCD for the
arbitrary Mellin moment.Comment: 7 pages, 1 figure, minor changes in the tex
Assessing ground support of plastic pipes using ultrasound
The ability to detect early signs of failure in buried pipe infrastructure is necessary to facilitate the continued use of ageing infrastructure for delivery of society’s essential services and move beyond disruptive and expensive reactive maintenance and repair. This paper reports detailed experiments on the use of in-pipe ultrasound techniques for assessment of ground conditions around buried plastic pipes. Two sets of ultrasonic experiment on the soil conditions are presented: (1) existence, shape, and dimension of void, and (2) water content in the soil. The ultrasound technique is shown to be capable for detecting water filled voids and assessing the soil support, critical early indicators of failure. The technique requires water as the transmission media hence is naturally suited to application in operational water distribution systems. The work represents an important advance in in-pipe condition assessment of plastic pipes, demonstrates the practical capability of the ultrasound technique, which is critical for progression towards proactive maintenance, offering cost and service improvements
Riparian buffer strips influence nitrogen losses as nitrous oxide and leached N from upslope permanent pasture
Riparian buffer strips can have a significant role in reducing nitrogen (N) transfers from agricultural land to freshwater primarily via denitrification and plant uptake processes, but an unintended trade-off can be elevated nitrous oxide (N2O) production rates. Against this context, our replicated bounded plot scale study investigated N2O emissions from un-grazed ryegrass pasture served by three types of riparian buffer strips with different vegetation, comprising: (i) grass riparian buffer with novel deep-rooting species, (ii) willow (young trees at establishment phase) riparian buffer, and (iii) deciduous woodland (also young trees at establishment phase) riparian buffer. The experimental control was ryegrass pasture with no buffer strip. N2O emissions were measured at the same time as total oxidized N in run-off, and soil and environmental characteristics in the ri parian buffer strips and upslope pasture between 2018 and 2019. During most of the sampling days, the no-buffer control treatment showed significantly (P < 0.05) greater N2O fluxes and cumulative N2O emissions compared to the remainder of the treatments. Our results also showed that the grass riparian buffer strip is a sink of N2O equivalent to − 2310.2 g N2O-N ha− 1 day− 1 (95% confidence interval:− 535.5 to 492). Event-based water quality results obtained during storms (12 November 2018 and 11 February 2019) showed that the willow riparian buffer treatment had the highest flow-weighted mean N concentrations (N-FWMC) of 0.041 ± 0.022 and 0.031
± 0.015 mg N L− 1, when compared to the other treatments. Our 9-month experiment therefore, shows that ri parian buffer strips with novel deep-rooting grass can therefore potentially address emissions to both water and air. The results imply that over a shorter timeline similar to the current study, the grass riparian buffer strip can potentially address N emission to both air and water, particularly when serving a permanent pasture in similar settings as the current experiment.Fil: Dlamini, J.C. Crop and Climate Sciences. Departament of Soil; Sudáfrica. Rothamsted Research. Sustainable Agriculture Sciences; Reino Unido. University of Pretoria. Department of Plant and Soil Sciences; SudáfricaFil: Cardenas, L.M. Rothamsted Research. Sustainable Agriculture Sciences; Reino Unido.Fil: Tesfamarian, E.H. University of Pretoria. Department of Plant and Soil Sciences; SudáfricaFil: Dunn, R.M. Rothamsted Research. Sustainable Agriculture Sciences; Reino Unido.Fil: Loick, N. Rothamsted Research. Sustainable Agriculture Sciences; Reino Unido.Fil: Charteris, A.F. Rothamsted Research. Sustainable Agriculture Sciences; Reino Unido.Fil: Cocciaglia, L. Università degli Studi di Perugia. Dipartimento di Scienze Agrarie, Alimentari e Ambientali; ItaliaFil: Vangeli, Sebastián. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Clima y Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Ingeniería Agrícola y Uso de la Tierra. Cátedra de Manejo y Conservación de Suelo; ArgentinaFil: Blackwell, M.S.A. Rothamsted Research. Sustainable Agriculture Sciences; Reino Unido.Fil: Upadhayay, H.R. Rothamsted Research. Sustainable Agriculture Sciences; Reino Unido.Fil: Hawkins, J.M.B. Rothamsted Research. Sustainable Agriculture Sciences; Reino Unido.Fil: Evans, J. Rothamsted Research. Computational and Analytical Sciences; Reino UnidoFil: Collins, A.L. Rothamsted Research. Sustainable Agriculture Sciences; Reino Unido
The Extraction of from Inclusive B Decays and the Resummation of End Point Logs
In this paper we discuss the theoretical difficulties in extracting
using the data from inclusive B decays. Specifically, we address the issue of
the end point singularities. We perform the resummation of both the leading and
next to leading end point logs and include the leading corrections to the hard
scattering amplitude. We find that the resummation is a effect in
the end point region where the resummation is valid. Furthermore, the resummed
sub-leading logs dominate the resummed double logs. The consequences of this
result for a model independent extraction of the mixing angle are
explored.Comment: Published Version. Minor changes in discussion. 31 pages, 4 figure
Thermal diffusion of supersonic solitons in an anharmonic chain of atoms
We study the non-equilibrium diffusion dynamics of supersonic lattice
solitons in a classical chain of atoms with nearest-neighbor interactions
coupled to a heat bath. As a specific example we choose an interaction with
cubic anharmonicity. The coupling between the system and a thermal bath with a
given temperature is made by adding noise, delta-correlated in time and space,
and damping to the set of discrete equations of motion. Working in the
continuum limit and changing to the sound velocity frame we derive a
Korteweg-de Vries equation with noise and damping. We apply a collective
coordinate approach which yields two stochastic ODEs which are solved
approximately by a perturbation analysis. This finally yields analytical
expressions for the variances of the soliton position and velocity. We perform
Langevin dynamics simulations for the original discrete system which fully
confirm the predictions of our analytical calculations, namely noise-induced
superdiffusive behavior which scales with the temperature and depends strongly
on the initial soliton velocity. A normal diffusion behavior is observed for
very low-energy solitons where the noise-induced phonons also make a
significant contribution to the soliton diffusion.Comment: Submitted to PRE. Changes made: New simulations with a different
method of soliton detection. The results and conclusions are not different
from previous version. New appendixes containing information about the system
energy and soliton profile
First lattice QCD estimate of the g_{D^* D pi} coupling
We present the results of the first lattice QCD study of the strong coupling
g_{D^* D pi}. From our simulations in the quenched approximation, we obtain
g_{D^* D pi} = 18.8 +/- 2.3^{+1.1}_{-2.0} and hat(g)_c = 0.67 +/-
0.08^{+0.04}_{-0.06}. Whereas previous theoretical studies gave different
predictions, our result favours a large value for hat(g)_c. It agrees very well
with the recent experimental value by CLEO. hat(g) varies very little with the
heavy mass and we find in the infinite mass limit hat(g)_infinity = 0.69(18).Comment: 24 pages, 7 figures; references added, corrected typos, Comments
added about the continuum limi
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