Towards Meson Spectroscopy Instead of Bump Hunting

Mesonic resonances are generally observed in data as narrow, moderately broad, or wide peaks in scattering or production processes. In the eyes of nearly all experimentalists, any suchlike bump is a true resonance as soon as its statistical significance exceeds certain minimal values. However, this simple point of view ignores possible effects from competing hadronic channels and the opening of the corresponding thresholds. On the other hand, most theoretical hadron-model builders consider mesons merely bound states of a quark and an antiquark, or of more exotic combinations sometimes involving valence gluons as well. Also the latter description is much too naive, since considerable mass shifts or even the dynamical generation of extra states due to unquenching are equally ignored. In the present paper, a largely empirical yet very successful approach to meson spectroscopy is revisited, in which all the above phenomena can be accounted for non-perturbatively, with concrete examples of some enigmatic mesonic states described in detail. First, the X(4260) charmonium enhancement is argued to be a non-resonant structure resulting from depletion effects due to competing channels and resonances. Then, the X(3872) charmonium-like meson is described as a unitarised $J^{PC}=1^{++}$ $c\bar{c}$ state. Also, the unusual pattern of masses and widths of the open-charm axial-vector mesons $D_1(2420)$, $D_1(2430)$, $D_{s1}(2536)$, and $D_{s1}(2460)$ is shown to follow from highly non-perturbative coupled-channel and mixing effects. Finally, first indications of a very light scalar boson are presented, on the basis of published BABAR data.Comment: Invited seminar given by G. Rupp at the International School of Nuclear Physics, 33rd course: "From Quarks and Gluons to Hadrons and Nuclei", Erice, Sicily, Italy, 16 - 24 September 2011; 7 pages, 5 figures (9 plots), style of Progress in Particle and Nuclear Physic

Biocompatibility and tissue regenerating capacity of crosslinked dermal sheep collagen

The biocompatibility and tissue regenerating capacity of four crosslinked dermal sheep collagens (DSC) was studied. In vitro, the four DSC versions were found to be noncytotoxic or very low in cytoxicity. After subcutaneous implantation in rats, hexamethylenediisocyanatecrcrosslinked DSC (HDSC) seldom induced an increased infiltration of neutrophils or macrophages, as compared with normal wound healing; whereas new formation of collagen was observed. DSC crosslinked with glutaraldehyde (GDSC) followed by reaction with NaBH4 shortly after implantation showed an increased infiltration of neutrophils with a deviant morphology. Furthermore, a high incidence of calcification was observed, which may explain the minor ingrowth of giant cells and fibroblasts, and the poor formation of new rat collagen. Acyl azide-crosslinked DSC (AaDSC) first induced an increased infiltration of macrophages, and then of giant cells, both with high lipid formation. AaDSC degraded at least twice as slowly as HDSC and GDSC, finally leaving a matrix of newly formed rat collagen. Samples crosslinked with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide (ENDSC) induced the same mild cellular reaction as HDSC; whereas, similar to AaDSC, the degradation rate was slow and an optimal rat collagen matrix was formed. Of the crosslinked DSC samples, ENDSC seems most promising for tissue regeneration

Attentional bias towards pain-related information diminishes the efficacy of distraction

Distraction is a strategy that is commonly used to cope with pain. Results concerning the efficacy of distraction from both experimental and clinical studies are variable, however, and indicate that its efficacy may depend on particular circumstances. Several models propose that distraction may be less effective for people who display a large attentional bias towards pain-related information. This hypothesis was tested in an experimental context with 53 pain-free volunteers. First, attentional bias towards cues signalling the occurrence of pain (electrocutaneous stimuli) and towards words describing the sensory experience of this painful stimulus was independently assessed by means of 2 behavioural paradigms (respectively, spatial cueing task and dot-probe task). This was followed by a subsequent distraction task during which the efficacy of distraction, by directing attention away from the electrocutaneous stimuli, was tested. In addition, state-trait anxiety, catastrophic thinking, and initial pain intensity were measured. Results indicated that people who display a large attentional bias towards predictive cues of pain or who initially experience the pain as more painful benefit less from distraction on a subsequent test. No effects were found between attentional bias towards pain words, state-trait anxiety, catastrophic thinking, and the efficacy of distraction. Current findings suggest that distraction should not be used as a 'one size fits all' method to control pain, but only under more specific conditions

Goodness-of-fit tests in many dimensions

A method is presented to construct goodness-of-fit statistics in many dimensions for which the distribution of all possible test results in the limit of an infinite number of data becomes Gaussian if also the number of dimensions becomes infinite. Furthermore, an explicit example is presented, for which this distribution as good as only depends on the expectation value and the variance of the statistic for any dimension larger than one.Comment: 14 page

Some comments on Laplacian gauge fixing

Laplacian gauge fixing was introduced to find a unique representative of the gauge orbit, which on the lattice could be implemented by a ``finite'' algorithm. What was still lacking was a perturbative formulation of this gauge, which will be presented here. However, renormalizability is still to be demonstrated. For torodial and spherical geometries a detailed comparison with the Landau (or Coulomb) gauge will be made.Comment: Contribution to Lattice '94, 3 pages PostScrip

Investigating ‘Churnalism’ in real time news

Language Use in Past and Presen

Marker-assisted optimization of an expert-based strategy for the acquisition of modern lettuce varieties to improve a genebank collection

To regularly improve the composition of the lettuce collection of the Centre for Genetic Resources, the Netherlands (CGN) with modern varieties, feedback from crop experts is used to select approximately 10% of the new material for incorporation in the collection. In the present study, assessments of six experts were compared to microsatellite data of 414 new varieties and 1408 existing accessions. Based on the microsatellite data, the extent to which the genetic diversity of the collection would be enriched (added value) was calculated for specific sets of new varieties. When individual assessments of experts were evaluated, the total added value of expert-based selections was not significantly higher compared to randomly chosen groups, except for a single expert. Unfamiliarity with new varieties was shown to be a crucial factor in the assessment of crop experts. According to the current acquisition protocol that seeks for consensus among experts, varieties are selected based on recommendations from at least three experts. This protocol also did not perform better than randomly chosen groups of new varieties. However, significantly better results were obtained with alternative protocols. It was concluded that breeding value was a more decisive criterion in the current acquisition protocol than maximal extension of the genetic diversity within the collection. A modified protocol addressing both commercial and diversity aspects was suggested in order to meet the demands of plant breeders as well as conservationist

Interplay of air and sand: Faraday heaping unravelled

We report on numerical simulations of a vibrated granular bed including the effect of the ambient air, generating the famous Faraday heaps known from experiment. A detailed analysis of the forces shows that the heaps are formed and stabilized by the airflow through the bed while the gap between bed and vibrating bottom is growing, confirming the pressure gradient mechanism found experimentally by Thomas and Squires [Phys. Rev. Lett. 81, 574 (1998)], with the addition that the airflow is partly generated by isobars running parallel to the surface of the granular bed. Importantly, the simulations also explain the heaping instability of the initially flat surface and the experimentally observed coarsening of a number of small heaps into a larger one