53,681 research outputs found
Coulomb gauge confinement in the heavy quark limit
The relationship between the nonperturbative Green's functions of Yang-Mills
theory and the confinement potential is investigated. By rewriting the
generating functional of quantum chromodynamics in terms of a heavy quark mass
expansion in Coulomb gauge, restricting to leading order in this expansion and
considering only the two-point functions of the Yang-Mills sector, the
rainbow-ladder approximation to the gap and Bethe-Salpeter equations is shown
to be exact in this case and an analytic, nonperturbative solution is
presented. It is found that there is a direct connection between the string
tension and the temporal gluon propagator. Further, it is shown that for the
4-point quark correlation functions, only confined bound states of
color-singlet quark-antiquark (meson) and quark-quark (baryon) pairs exist.Comment: 22 pages, 6 figure
A computer program for estimating the aerodynamic characteristics of NACA 16-series airfoils
A computer program written in a table ""look-up'' format, is presented which provides a comprehensive data base on NACA 16-series airfoils. The geometry covered is limited to cambers for a design-lift coefficient from 0.0 to 0.7 and thickness ratios from 4 to 21%. The data include Mach numbers from 0.3 to 1.6, angles of attack from -4 to 8 degrees, and lift coefficients from 0.0 to 0.8. Extrapolation is used to obtain data from Mach numbers, angles of attack, and lift coefficients beyond those for which data are available. A routine to adjust the lift and drag coefficients beyond stall is included. The uses and limitations of the program are also discussed
Crucifixion and median neuropathy.
Crucifixion as a means of torture and execution was first developed in the 6th century B.C. and remained popular for over 1000 years. Details of the practice, which claimed hundreds of thousands of lives, have intrigued scholars as historical records and archaeological findings from the era are limited. As a result, various aspects of crucifixion, including the type of crosses used, methods of securing victims to crosses, the length of time victims survived on the cross, and the exact mechanisms of death, remain topics of debate. One aspect of crucifixion not previously explored in detail is the characteristic hand posture often depicted in artistic renditions of crucifixion. In this posture, the hand is clenched in a peculiar and characteristic fashion: there is complete failure of flexion of the thumb and index finger with partial failure of flexion of the middle finger. Such a "crucified clench" is depicted across different cultures and from different eras. A review of crucifixion history and techniques, median nerve anatomy and function, and the historical artistic depiction of crucifixion was performed to support the hypothesis that the "crucified clench" results from proximal median neuropathy due to positioning on the cross, rather than from direct trauma of impalement of the hand or wrist
Understanding Astrophysical Noise from Stellar Surface Magneto-Convection
To obtain cm/s precision, stellar surface magneto-convection must be
disentangled from observed radial velocities (RVs). In order to understand and
remove the convective signature, we create Sun-as-a-star model observations
based on a 3D magnetohydrodynamic solar simulation. From these Sun-as-a-star
model observations, we find several line characteristics are correlated with
the induced RV shifts. The aim of this campaign is to feed directly into future
high precision RV studies, such as the search for habitable, rocky worlds, with
forthcoming spectrographs such as ESPRESSO.Comment: 6 pages, 3 figures; presented at the 18th Cambridge Workshop on Cool
Stars, Stellar Systems, and the Sun (CoolStars18); to appear in the
proceedings of Lowell Observatory (9-13 June 2014), edited by G. van Belle &
H. Harris. Updated with correct y-axis units on righthand plot in figure
An analysis of prop-fan/airframe aerodynamic integration
An approach to aerodynamic integration of turboprops and airframes, with emphasis placed upon wing mounted installations is addressed. Potential flow analytical techniques were employed to study aerodynamic integration of the prop fan propulsion concept with advanced, subsonic, commercial transport airframes. Three basic configurations were defined and analyzed: wing mounted prop fan at a cruise Mach number of 0.8, wing mounted prop fan in a low speed configuration, and aft mounted prop fan at a cruise Mach number of 0.8
Perturbation Theory of Coulomb Gauge Yang-Mills Theory Within the First Order Formalism
Perturbative Coulomb gauge Yang-Mills theory within the first order formalism
is considered. Using a differential equation technique and dimensional
regularization, analytic results for both the ultraviolet divergent and finite
parts of the two-point functions at one-loop order are derived. It is shown how
the non-ultraviolet divergent parts of the results are finite at spacelike
momenta with kinematical singularities on the light-cone and subsequent branch
cuts extending into the timelike region.Comment: 23 pages, 6 figure
Nitrogen transfer between clover and wheat in an intercropping experiment
A novel approach to the problem of improving nitrogen supply in organic farming is to use intercropping of cereals with a legume to provide nitrogen transfer within a season and/or to following crops. The affects of intercropping were studied in a column experiment using mixtures of winter wheat (Triticum aestivum cv. Claire), with white clover (w.c.) (Trifolium repens cv. Barblanca) and with red clover (r.c.) (Trifolium pratense cv. Britta). The effects of cutting and removal above ground clover material with and without additional soil disturbance were compared to leaving clover plants in situ and intercropped with wheat in a split root design. Wheat and clover plants, as monocultures, were used for the controls. 15N ammonium nitrate solution was applied. The wheat seeds were sown into the column without nitrogen. We found that the cutting treatment produced the highest yield of wheat. Available ammonium-N in the soil was greatest in the clover control treatment for the column with only red clover roots and in the cutting+soil disturbance treatment for the column with only white clover roots. Available nitrate-N was greatest in the soil disturbance treatment in the column with clover and wheat roots for both red and white clover. The cutting treatment produced the highest yield of wheat
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