Light-cone behavior of the pion Bethe-Salpeter wave function in the ladder model

The Bethe-Salpeter wave function χ(q^ν+P^ν, q^ν) for two spin-½ quarks bound by the exchange of a scalar meson is examined in the ladder model. We seek the behavior of χ as the squared momentum, (q+P)^2, on one leg becomes infinite while the squared momentum, q^2, on the other leg remains fixed. This behavior is investigated by making a Wick rotation, expanding χ in partial-wave amplitudes χ^i_J(q^2) of the group O(4), and then looking for the rightmost poles of χ^i_J(q^2) in the complex J plane. Our results verify (in the ladder model) the useful hypothesis that the locations of these poles are independent of q^2 and can thus be computed in the q^2→∞ limit by using conformal invariance

Large-Q^2 behavior of the pion electromagnetic form factor

We study the large-Q^2 behavior of the electromagnetic form factor of the pion, which is viewed as a quark-antiquark bound state in a (nongauge) quantum field theory. When the pion's Bethe-Salpeter wave function is expanded in O(4) partial waves, it is found that the information needed about the partial-wave amplitudes is their scaling behavior at large momentum and the locations of their poles in the complex J plane. This information is determined by using the operator-product expansion, conformal invariance at short distances, and a regularity property that holds at least in the ladder model. The resulting behavior of the form factor is roughly F(Q^2)~(Q^2)^(-1), with corrections due to anomalous dimensions

Pero López de Ayala as historian and literary artist

Dissertation (Ph.D.)--University of Kansas, Spanish and Portuguese, 1967.Pero López de Ayala (1332-1407) has traditionally been considered to be Castile's first great historian in the modern sense--a pre-Humanist, whose historical veracity and innovations in style paved the way for a new era in Spanish historiography. But despite his high reputation, Ayala and his chronicles have mostly been written about in general histories or in histories of literature; few critics have dealt with him exclusively or in detail. It is my intention, therefore, to present a thorough study of the four chronicles--La Crónica del Rey Don Pedro I (1350-1369), La Crónica del Rey Don Enrique II (1369-1379), La Crónica del Rey Don Juan~ (1379-1390), and La Crónica del Rey Don Enrique III (1390-1396), in order to evaluate the chronicler and his work from both the historical and literary points of view

Next-to-leading order QCD calculations with parton showers II: soft singularities

Programs that calculate observables in quantum chromodynamics at next-to-leading order typically generate events that consist of partons rather than hadrons -- and just a few partons at that. These programs would be much more useful if the few partons were turned into parton showers, which could be given to one of the Monte Carlo event generators to produce hadron showers. In a previous paper, we have seen how to generate parton showers related to the final state collinear singularities of the perturbative calculation for the example of e+ + e- --> 3 jets. This paper discusses the treatment of the soft singularities.Comment: 26 pages with 5 figures. This version is close to the version to be publishe

Urinalysis and Urinary Tract Infection: Update for Clinicians

Dysuria is a common presenting complaint of women and urinalysis is a valuable tool in the initial evaluation of this presentation. Clinicians need to be aware that pyuria is the best determinate of bacteriuria requiring therapy and that values significant for infection differ depending on the method of analysis. A hemocytometer yields a value of ≥ 10 WBC/ mm(3) significant for bacteriuria, while manual microscopy studies show ≥ 8 WBC/high-power field reliably predicts a positive urine culture. In cases of uncomplicated symptomatic urinary tract infection, a positive value for nitrites and leukocyte esterase by urine dipstick can be treated without the need for a urine culture. Automated urinalysis used widely in large volume laboratories provides more sensitive detection of leukocytes and bacteria in the urine.With automated microscopy, a value of > 2 WBC/hpf is significant pyuria indicative of inflammation of the urinary tract. In complicated cases such as pregnancy, recurrent infection or renal involvement, further evaluation is necessary including manual microscopy and urine culture with sensitivities

Biomolecular self-assembly under extreme Martian mimetic conditions

The recent discovery of subsurface water on Mars has challenged our understanding of the natural limits of life. The presence of magnesium perchlorate (Mg(ClO4)2) on the Martian surface raises the possibility that it may also be present in this subsurface lake. Given that the subsurface lakes on Earth, such as Lake Vostok and Lake Whillans, are capable of harbouring surprising amounts of life, these new findings raise interesting possibilities for how biomolecules might self-assemble in this environment on Mars. Here we investigate the self-association and hydration of the amino acid glycine in aqueous Mg(ClO4)2 at 25°C and −20°C using neutron diffraction with hydrogen isotope substitution and subsequent analysis with empirical potential structure refinement to yield a simulated box of atoms consistent with the scattering data. We find that although the highly chaotropic properties of Mg(ClO4)2 disrupt the hydration and hydrogen bonding ability of the amino acid, as well as the bulk water structure, glycine molecules are nonetheless still able to self-associate. This occurs more readily at lower temperature, where clusters of up to three molecules are observed, allowing us to speculate that the formation of biological molecules is possible in the Martian environment

Partons and Jets at the LHC

I review some issues related to short distance QCD and its relation to the experimental program of the Large Hadron Collider (LHC) now under construction in Geneva.Comment: Talk at the conference QCD2002 at IIT Kanpur, India, November 2002. Ten pages with 12 figure