Generalized parton distributions and double distributions for q q-bar pions

We consider two simple covariant models for pions (one with scalar and the other with spin-1/2 constituents). Pion generalized parton distributions are derived by integration over the light-cone energy. The model distributions are consistent with all known properties of generalized parton distributions, including positivity. We also construct the corresponding double distributions by appealing to Lorentz invariance. These ostensibly constructed double distributions lead to different generalized parton distributions that need not respect the positivity constraints. This inconsistency arises from the ambiguity inherent in defining double distributions in a one-component formalism (even in the absence of the Polyakov-Weiss term). We demonstrate that the correct model double distributions can be calculated from non-diagonal matrix elements of twist-two operators.Comment: 10 pages, 7 figures, RevTex4, reference added, typos correcte

Analysis of the instantaneous Bethe-Salpeter equation for qqˉq\bar{q}-bound-states

We investigate the structure of the instantaneous Bethe-Salpeter equation for $q\bar{q}$-bound states in the general case of unequal quark masses and develop a numerical scheme for the calculation of mass spectra and Bethe-Salpeter amplitudes. In order to appreciate the merits of the various competing models beyond the reproduction of the mass spectra we present explicit formulas to calculate electroweak decays. The results for an explicit quark model will be compared to experimental data in a subsequent paperComment: 11 pages, RevTeX, TK-93-1

A Bethe-Salpeter model for light mesons: spectra and decays

The spectra and electroweak decay properties of light mesons are analyzed within the framework of the instantaneous Bethe-Salpeter equation. The interaction kernel comprises alternative spin-structures for a parameterization of confinement and a residual quark-antiquark interaction based on instanton effects. It is shown that only with a vector confinement the parameters can be chosen such as to yield an excellent description of the light pseudoscalar and vector mesons including weak and two photon decays. However it is found that it is not possible to reconcile this with the Regge behavior of higher lying meson states with the same parameter set.Comment: 12 pages, RevTeX, TK-93-1

KamLAND Bounds on Solar Antineutrinos and neutrino transition magnetic moments

We investigate the possibility of detecting solar electron antineutrinos with the KamLAND experiment. These electron antineutrinos are predicted by spin-flavor oscillations at a significant rate even if this mechanism is not the leading solution to the SNP. KamLAND is sensitive to antineutrinos originated from solar ${}^8$B neutrinos. From KamLAND negative results after 145 days of data taking, we obtain model independent limits on the total flux of solar electron antineutrinos $\Phi({}^8 B)< 1.1-3.5\times 10^4 cm^{-2}\ s^{-1}$, more than one order of magnitude smaller than existing limits, and on their appearance probability$P<0.15%$(95antineutrino production by spin-flavor precession, this upper bound implies an upper limit on the product of the intrinsic neutrino magnetic moment and the value of the solar magnetic field$\mu B< 2.3\times 10^{-21}$MeV 95LMA$(\Delta m^2, \tan^2\theta)$values). Limits on neutrino transition moments are also obtained. For realistic values of other astrophysical solar parameters these upper limits would imply that the neutrino magnetic moment is constrained to be, in the most conservative case,$\mu\lsim 3.9\times 10^{-12} \mu_B$(95CL) for a relatively small field$B= 50$kG. For higher values of the magnetic field we obtain:$\mu\lsim 9.0\times 10^{-13} \mu_B$for field$B= 200$kG and$\mu\lsim 2.0\times 10^{-13} \mu_B$for field$B= 1000$ kG at the same statistical significance.Comment: 13 pages, 2 figure

Cystic Fibrosis Foundation and European Cystic Fibrosis Society Survey of cystic fibrosis mental health care delivery

Background: Psychological morbidity in individuals with cystic fibrosis (CF) and their caregivers is common. The Cystic Fibrosis Foundation (CFF) and European Cystic Fibrosis Society (ECFS) Guidelines Committee on Mental Health sought the views of CF health care professionals concerning mental health care delivery. Methods: An online survey which focused on the current provision and barriers to mental health care was distributed to CF health care professionals. Results: Of the 1454 respondents, many did not have a colleague trained in mental health issues and 20% had no one on their team whose primary role was focused on assessing or treating these issues. Insufficient resources and a lack of competency were reported in relation to mental health referrals. Seventy-three percent of respondents had no experience with mental health screening. Of those who did, they utilized 48 different, validated scales. Conclusions: These data have informed the decision-making, dissemination and implementation strategies of the Mental Health Guidelines Committee sponsored by the CFF and ECFS

Mathematical Model of the Oxidation of a Uranium Carbide Fuel Pellet Including an Adherent Product Layer

Uranium carbide is a candidate fuel for Generation IV nuclear reactors. However, like any candidate fuel, a reprocessing route should be established before implementation. One proposed method involves a pre-oxidation step, where the carbide fuel is oxidised to an oxide and then reprocessed as normal. A mathematical model has been developed to simulate such an oxidation using finite difference approximations of the heat and mass transfer processes occurring. Available literature was consulted to provide coefficients for the reaction rates and importantly the diffusion of oxygen through the adherent oxide layer that forms on the carbide: the rate limiting step. The transient temperature, oxygen and carbon monoxide distributions through the system are modelled in order to predict oxidation completion times and the temperatures reached. It was found that for a spherical pellet of radius 0.935cm, the oxidation can take between 1 h to 19 h depending on the oxidation conditions and reach temperatures of up to 1556°C. A robust model results that offers increased understanding of a process crucial to the sustainable use of carbide fuels in energy generation

Status of Grey Leaf Spot Disease In Kenyan Maize Production Ecosystems

Grey leaf spot disease (GLS), Cercospora zeae-maydis, which has previously been attributed to diverse pathogen species in other countries, has become a serious biotic constraint to production of maize ( Zea mays L.) in Kenya. It is necessary to determine the distribution and aetiology of the disease across all the maize production agro-ecologies in order to inform the development of appropriate management strategies against the disease. Samples were collected from maize growing areas in Kenya with GLS symptoms on maize crops and other plants. On the basis of cultural and morphological examinations, and restricted fragment length polymorphism and taxon-specific PCR analyses, Cercospora zeae-maydis group II and C. sorghi var. maydis were identified from typical GLS lesions on maize, with the former being predominant (&gt;96% of the cases) and distributed throughout the country. The latter exhibited minor incidence (&lt;4%) in western Kenya. Nucleotide sequence analyses further provided evidence that C. zeae-maydis group II and C. sorghi var. maydis were distinct fungi.La maladie de t\ue2che grise de la feuille (GLS), Cercospora zeae-maydis, attribu\ue9e aux esp\ue8ces de pathogens diverses dans d'autres pays, est devenue une s\ue9rieuse contrainte biotique \ue0 la production de ma\uefs ( Zea mays L.) au Kenya. Il est n\ue9cessaire de d\ue9terminer la distribution et l'\ue9tiologie de la maladie \ue0 travers toutes les r\ue9gions agro-\ue9cologques productrices de ma\uefs pour mieux d\ue9velopper des strat\ue9gies appropri\ue9es de gestion contre la maladie. Des \ue9chantillons \ue9taient recueillis dans des r\ue9gions producteurs du ma\uefs au Kenya tenant compte de la pr\ue9sence des sympt\uf4mes GLS sur les ma\uefs et autres cultures. Sur base des examens culturales et morphologiques ainsi que du polymorphisme de la longueur du fragment isol\ue9 et les analyses PCR du taxon sp\ue9cifique, Cercospora zeae-maydis le groupe II de Cercospora zeae-maydis et C. sorghi var. maydis \ue9taient identifi\ue9s par des l\ue9sions typiques de GLS sur le ma\uefs, ce dernier \ue9tant le plus pr\ue9dominant (&gt; 96 % de tous les cas) et distribu\ue9 \ue0 travers tout le pays avec une incidence mineur de 4 % dans l'ouest du Kenya. L'analyse de s\ue9quences de nucl\ue9otides avait par la suite montr\ue9 avec evidence que le C. zeae-maydis group II et C. sorghi var. maydis \ue9taient de champignons distincts

Star and cluster formation in extreme environments

Current empirical evidence on the star-formation processes in the extreme, high-pressure environments induced by galaxy encounters (mostly based on high-resolution Hubble Space Telescope observations) strongly suggests that star CLUSTER formation is an important and perhaps even the dominant mode of star formation in such starburst events. The sizes, luminosities, and mass estimates of the young massive star clusters (YMCs) are entirely consistent with what is expected for young Milky Way-type globular clusters (GCs). Recent evidence lends support to the scenario that GCs, which were once thought to be the oldest building blocks of galaxies, are still forming today. Here, I present a novel empirical approach to assess the shape of the initial-to-current YMC mass functions, and hence their possible survival chances for a Hubble time.Comment: 6 pages, LaTeX with Kluwer style files included; to appear in: "Starbursts - from 30 Doradus to Lyman break galaxies" (Cambridge UK, September 2004; talk summary), Astrophysics & Space Science Library, eds. de Grijs R., Gonzalez Delgado R.M., Kluwer: Dordrech