492 research outputs found
Tilted Pion Sources from Azimuthally Sensitive HBT Interferometry
Intensity interferometry in noncentral heavy ion collisions provides access
to novel information on the geometry of the effective pion-emitting source. We
demonstrate analytically that, even for vanishing pair momentum, the cross
terms and of the HBT correlation function in general show
a strong first harmonic in their azimuthal dependence. The strength of this
oscillation characterizes the tilt of the major axis of the spatial emission
ellipsoid away from the direction of the beam. Event generator studies indicate
that this tilt can be large (>20 degrees) at AGS energies which makes it by far
the most significant azimuthally sensitive HBT signal at these energies.
Moreover, transport models suggest that for pions this spatial tilt is directed
opposite to the tilt of the directed flow ellipsoid in momentum space. A
measurement of the azimuthal dependence of the HBT cross terms and
thus probes directly the physical origin of directed pion flow.Comment: submitted to Phys. Rev. Lett; revised version has some wording
changes/clarification, finer binning in q leads to tiny changes in Fig. 2,
one new referenc
Internationalization Through Americanization
Based on Bourdieu’s concepts of sociology, this article explores the International Communication Association’s internationalization effort involving recruiting non-U.S. scholars into top positions. Therefore, it examines both the habitus and the capital of the 26 communication researchers from outside the United States who have been distinguished as ICA presidents and fellows. The study contributes to the discipline’s reflexivity and shows that despite the expansion of ICA’s leadership, the field’s power pole is still a U.S.-centered enterprise. Today, ICA’s international leadership is located in
world regions closely linked to the United States and educated at U.S. universities or heavily influenced by North American research traditions, even if it includes a numerous contributions from other associations and alternative approaches. Consequently, this internationalization hardly changed ICA but instead changed the world’s communication
field. At least up to a certain extent, new perspectives are perceived at the discipline’s power pole. However, in return, national academic environments in U.S.-affiliated countries became Americanized, especially via ICA fellows serving as role models to get scientific capital. Thus, ICA’s efforts to expand its leadership are assumed to have an unintended effect of conserving the power structures in the field
Relating different approaches to nuclear broadening
Transverse momentum broadening of fast partons propagating through a large
nucleus is proportional to the average color field strength in the nucleus. In
this work, the corresponding coefficient is determined in three different
frameworks, namely in the color dipole approach, in the approach of Baier et
al. and in the higher twist factorization formalism. This result enables one to
use a parametrization of the dipole cross section to estimate the values of the
gluon transport coefficient and of the higher twist matrix element, which is
relevant for nuclear broadening. A considerable energy dependence of these
quantities is found. In addition, numerical calculations are compared to data
for nuclear broadening of Drell-Yan dileptons, J/psi and Upsilon mesons. The
scale dependence of the strong coupling constant leads to measurable
differences between the higher twist approach and the other two formalisms.Comment: 11 pages, 3 figures; v2: some changes in presentation, reference
added, accepted for publication in PL
Substituted bisphosphanylamines as ligands in gold(I) chemistry – synthesis and structures
Dimethyl 5-aminoisophthalate, which is a building block of amino-substituted tetralactam macrocycles, was used as ligand in gold(I) chemistry to form model complexes for macrocyclic gold compounds. Reaction of dimethyl 5-aminoisophthalate with chlorodiphenylphosphine gave the diphosphine compound dimethyl 5-[N,N-bis(diphenylphosphanyl)amino]isophthalate (dmbpaip). This compound can further be reacted with [AuCl(tht)] (tht = tetrahydrothiophene) to give the dinuclear complex [Au(2),Cl(2)(dmbpaip)]. In contrast, treatment of dinbpaip with [Au(tht)(2)]ClO(4) resulted in the ionic compound [Au(2)(dmbpaip)(2)](ClO(4))(2) in which the cation forms an eight-membered Au(2)P(4)N(2) heterocycle. In both gold(I) compounds Au center dot center dot center dot Au interactions are observed. All new compounds were characterized by single-crystal X-ray diffraction
Spontaneous polyploidisation of interspecific and intersectional Pelargonium hybrids during embryo rescue
Modern Pelargonium crispum hybrids (section Pelargonium) show low genetic and phenotypic variation due to the domestication effect. Species of the sections Cortusina, Ligularia, and Pelargonium are potential breeding partners at the diploid level (2n = 2x = 22). Five P. Ă— crispum cultivars were used as seed parents and pollinated with one genotype of P. grandiflorum (section Pelargonium) and three genotypes of P. fulgidum (section Ligularia). In both combinations, embryo rescue was necessary. Embryos were rescued and cultured on Murashige & Skoog medium supplemented with phytohormones. After callus and adventitious shoot regeneration 15 viable interspecific hybrids were obtained from crossbreeding with P. grandiflorum and 11 intersectional hybrids from crossings with P. fulgidum, respectively. The hybrids were cultivated in the greenhouse until flowering. Their hybrid character was evident due to the intermediate morphological traits. Molecular investigations using dp-RAPD analysis confirmed this. Within the F1 population P. Ă— crispum with P. grandiflorum three hybrids and after crossing with P. fulgidum one hybrid possessed larger flowers and fully developed anthers, respectively. Their ploidy level was confirmed as tetraploid using flow cytometry. Therefore, a spontaneous polyploidisation occurred during in vitro regeneration. The tetraploid F1 hybrids are fertile and could be used for further breeding
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