2,016 research outputs found
Off-diagonal helicity density matrix elements for vector mesons produced in polarized e+e- processes
Final state quark-antiquark interactions give origin to non zero values of
the off-diagonal element rho_{1,-1} of the helicity density matrix of vector
mesons produced in e+e- annihilations, as confirmed by recent OPAL data on Phi,
D^* and K^*'s. New predictions are given for rho_{1,-1} of several mesons
produced at large x_E and small p_T -- i.e. collinear with the parent jet -- in
the annihilation of polarized e+ and e-; the results depend strongly on the
elementary dynamics and allow further non trivial tests of the Standard Model.Comment: LaTeX, 20 pages, 6 ps figures, uses epsfig.st
A Generalization of the Brodsky-Lepage Formalism
We present an approach that generalizes in a natural way the perturbative QCD
formalism developed by Brodsky and Lepage for the study of exclusive hadronic
processes to the case of mesons. As an application of our approach we
consider here the production of meson pairs, involving tensor and pseudotensor
mesons, in photon-photon collisions.Comment: LaTeX, 5 pages, 1 embedded ps figure, uses macros sprocl.sty,
epsfig.sty. Talk delivered by F. Murgia at the PHOTON'97 Conference, Egmond
aan Zee, The Netherlands, May 10-15, 1997. To be published in the proceedings
by World Scientifi
Proteomics of Cytochrome c Oxidase-Negative versus -Positive Muscle Fiber Sections in Mitochondrial Myopathy
The mosaic distribution of cytochrome c oxidase(+) (COX+) and COX - muscle fibers in mitochondrial disorders allows the sampling of fibers with compensated and decompensated mitochondrial function from the same individual. We apply laser capture microdissection to excise individual COX+ and COX- fibers from the biopsies of mitochondrial myopathy patients. Using mass spectrometry-based proteomics, we quantify >4,000 proteins per patient. While COX+ fibers show a higher expression of respiratory chain components, COX- fibers display protean adaptive responses, including upregulation of mitochondrial ribosomes, translation proteins, and chaperones. Upregulated proteins include C1QBP, required for mitoribosome formation and protein synthesis, and STOML2, which organizes cardiolipin-enriched microdomains and the assembly of respiratory supercomplexes. Factoring in fast/slow fiber type, COX (-) slow fibers show a compensatory upregulation of beta-oxidation, the AAA(+) protease AFG3L1, and the OPA1-dependent cristae remodeling program. These findings reveal compensatory mechanisms in muscle fibers struggling with energy shortage and metabolic stress
Structure of the magnetoionic medium around the FR Class I radio galaxy 3C 449
The goal of this work is to constrain the strength and structure of the
magnetic field associated with the environment of the radio source 3C 449,
using observations of Faraday rotation, which we model with a structure
function technique and by comparison with numerical simulations. We assume that
the magnetic field is a Gaussian, isotropic random variable and that it is
embedded in the hot intra-group plasma surrounding the radio source. For this
purpose, we present detailed rotation measure images for the polarized radio
source 3C 449, previously observed with the Very Large Array at seven
frequencies between 1.365 and 8.385 GHz. We quantify the statistics of the
magnetic-field fluctuations by deriving rotation measure structure functions,
which we fit using models derived from theoretical power spectra. We quantify
the errors due to sampling by making multiple two-dimensional realizations of
the best-fitting power spectrum.We also use depolarization measurements to
estimate the minimum scale of the field variations. We then make
three-dimensional models with a gas density distribution derived from X-ray
observations and a random magnetic field with this power spectrum. Under these
assumptions we find that both rotation measure and depolarization data are
consistent with a broken power-law magnetic-field power spectrum, with a break
at about 11 kpc and slopes of 2.98 and 2.07 at smaller and larger scales
respectively. The maximum and minimum scales of the fluctuations are around 65
and 0.2 kpc, respectively. The average magnetic field strength at the cluster
centre is 3.5 +/-1.2 micro-G, decreasing linearly with the gas density within
about 16 kpc of the nucleus.Comment: 19 pages; 14 figures; accepted for publication on A&A. For a high
quality version use ftp://ftp.eso.org/pub/general/guidetti
Hybrid areas of work between employment and self-employment : emerging challenges and future research directions
The growth of non-standard employment relations has created one of the major challenges in terms of workers\u2019 rights as well as collective representation in European societies. Among non-standard employment relations, so-called \u201csolo self-employed\u201d\u2014self-employed workers without employees\u2014are challenging the very foundations of our labor markets, that is to say the opposition between employers and employees, fostering the development of emerging \u201chybrid\u201d areas of work. The heterogeneity of the solo self-employed is difficult to capture from official statistics, which are still based on traditional classifications, and questions also the legal categories that
qualify these workers. Moreover, the fact that solo self-employed workers do not form a homogenous group, and are diverse in terms of their activities, interests and needs, calls for changes in the way trade unions, employer organizations, and new freelancer associations develop collective actions, claims-making activities, and strategies of organizing. With the aim to achieve an in-depth understanding of the increasingly extensive and populated categories of the solo self-employed, this contribution aims at reconstructing the state of the art within different fields of study, such as employment relations, labor law, industrial relations and social movements, and at offering some
possible future research directions
The role of Cahn and Sivers effects in Deep Inelastic Scattering
The role of intrinsic \bfk_\perp in inclusive and semi-inclusive Deep
Inelastic Scattering processes () is studied with exact
kinematics within QCD parton model at leading order; the dependence of the
unpolarized cross section on the azimuthal angle between the leptonic and the
hadron production planes (Cahn effect) is compared with data and used to
estimate the average values of both in quark distribution and
fragmentation functions. The resulting picture is applied to the description of
the weighted single spin asymmetry recently
measured by the HERMES collaboration at DESY; this allows to extract some
simple models for the quark Sivers functions. These are compared with the
Sivers functions which succeed in describing the data on transverse single spin
asymmetries in \pup p \to \pi X processes; the two sets of functions are not
inconsistent. The extracted Sivers functions give predictions for the COMPASS
measurement of in agreement with recent
preliminary data, while their contribution to HERMES is
computed and found to be small. Predictions for for kaon production at HERMES are also given.Comment: 21 pages, 12 figures, revtex, version published in PRD, one figure,
comments and references adde
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