The in-medium isovector pi N amplitude from low energy pion scattering

Differential cross sections for elastic scattering of 21.5 MeV positive and negative pions by Si, Ca, Ni and Zr have been measured as part of a study of the pion-nucleus potential across threshold. The `anomalous' repulsion in the s-wave term was observed, as is the case with pionic atoms. The extra repulsion can be accounted for by a chiral-motivated model where the pion decay constant is modified in the medium. Unlike in pionic atoms, the anomaly cannot be removed by merely introducing an empirical on-shell energy dependence.Comment: 9 pages, 2 figures. Minor changes, to appear in PR

Elastic scattering of low energy pions by nuclei and the in-medium isovector pi N amplitude

Measurements of elastic scattering of 21.5 MeV pi+ and pi- by Si, Ca, Ni and Zr were made using a single arm magnetic spectrometer. Absolute calibration was made by parallel measurements of Coulomb scattering of muons. Parameters of a pion-nucleus optical potential were obtained from fits to all eight angular distributions put together. The `anomalous' s-wave repulsion known from pionic atoms is clearly observed and could be removed by introducing a chiral-motivated density dependence of the isovector scattering amplitude, which also greatly improved the fits to the data. The empirical energy dependence of the isoscalar amplitude also improves the fits to the data but, contrary to what is found with pionic atoms, on its own is incapable of removing the anomaly.Comment: 20 pages, 5 figures, 5 tables. V2 added details on uncertainties,extended discussion. To appear in PR

The relationship between intercultural teaching competence and school and classroom level characteristics

The increasing levels of diversity in primary education make it essential to identify factors that influence Intercultural Teaching Competence (ITC). This study investigates which factors of Educational Effectiveness Research contribute to five dimensions of ITC: openness, classroom management, enriched lesson design, social initiative, and storytelling. Therewith, it contributes to the literature of both fields. Data collected through a cross-sectional survey among 155 Dutch primary school teachers were examined with linear regression analyses. The results showed that some characteristics at the classroom level have a strong significant relationship with dimensions of Intercultural Teaching Competence, whereas school characteristics did not

Low Energy Analyzing Powers in Pion-Proton Elastic Scattering

Analyzing powers of pion-proton elastic scattering have been measured at PSI with the Low Energy Pion Spectrometer LEPS as well as a novel polarized scintillator target. Angular distributions between 40 and 120 deg (c.m.) were taken at 45.2, 51.2, 57.2, 68.5, 77.2, and 87.2 MeV incoming pion kinetic energy for pi+ p scattering, and at 67.3 and 87.2 MeV for pi- p scattering. These new measurements constitute a substantial extension of the polarization data base at low energies. Predictions from phase shift analyses are compared with the experimental results, and deviations are observed at low energies.Comment: 15 pages, 4 figure

Latest results from the PHOBOS experiment

Over the past years PHOBOS has continued to analyze the large datasets obtained from the first five runs of the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. The two main analysis streams have been pursued. The first one aims to obtain a broad and systematic survey of global properties of particle production in heavy ion collisions. The second class includes the study of fluctuations and correlations in particle production. Both type of studies have been performed for a variety of the collision systems, covering a wide range in collision energy and centrality. The uniquely large angular coverage of the PHOBOS detector and its ability to measure charged particles down to very low transverse momentum is exploited. The latest physics results from PHOBOS, as presented at Quark Matter 2008 Conference, are contained in this report.Comment: 9 pages, 9 figures, presented at the 20th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions, "Quark Matter 2008", Jaipur, India, Feb.4-10, 200

On Central Charges and Hamiltonians for 0-brane dynamics

We consider general properties of central charges of zero branes and associated duality invariants, in view of their double role, on the bulk and on the world volume (quantum-mechanical) theory. A detailed study of the BPS condition for the mass spectrum arising from toroidal compactifications is given for 1/2, 1/4 and 1/8 BPS states in any dimensions. As a byproduct, we retreive the U-duality invariant conditions on the charge (zero mode) spectrum and the orbit classification of BPS states preserving different fractions of supersymmetry. The BPS condition for 0-branes in theories with 16 supersymmetries in any dimension is also discussed.Comment: 23 pages, latex fil

Canonical Quantization of Open String and Noncommutative Geometry

We perform canonical quantization of open strings in the $D$-brane background with a $B$-field. Treating the mixed boundary condition as a primary constraint, we get a set of secondary constraints. Then these constraints are shown to be equivalent to orbifold conditions to be imposed on normal string modes. These orbifold conditions are a generalization of the familiar orbifold conditions which arise when we describe open strings in terms of closed strings. Solving the constraints explicitly, we obtain a simple Hamiltonian for the open string, which reveals the nature of noncommutativity transparently.Comment: 14 pages, RevTex, added reference

Symplectic Quantization of Open Strings and Noncommutativity in Branes

We show how to translate boundary conditions into constraints in the symplectic quantization method by an appropriate choice of generalized variables. This way the symplectic quantization of an open string attached to a brane in the presence of an antisymmetric background field reproduces the non commutativity of the brane coordinates.Comment: We included a comparison with previous results obtained from Dirac quantization, emphasizing the fact that in the symplectic case the boundary conditions, that lead to the non commutativity, show up from the direct application of the standard method. Version to appear in Phys. Rev.

Μοντελοποίηση και διερεύνηση εκτονωτών θετικής εκτόπισης σε συστήματα ORC

Lenticel discoloration (LD), under-skin browning (USB) and resin canal disorder (RCD) are three important fruit skin disorders of concern to the Australian mango industry. They result in downgrading of fruit quality and loss of market confidence. LD is confined to the discoloration of lenticels on the fruit skin. USB is a sub-surface spreading grey-brown lesion that may only become evident in the marketplace. RCD is a dark brown discoloration of the finely branched pattern of ramifying sub-surface resin canals. These three browning disorders were compared and contrasted at the cellular level by light microscopy after free-hand sectioning. Discoloured lenticels on the surface of 'Honey Gold' mango fruit typically appeared as small round spots comprised of a dark brown centre surrounded by a white corona. Non-coloured lenticels were visible as small round spots surrounded by a white corona. In cross-section, there was browning of cells surrounding the cavity of discoloured lenticels. Nonetheless, there was no such browning in non-coloured lenticels. USB symptoms in 'Honey Gold' fruit were evident as dark-brown cells in the tissue surrounding the resin ducts. In contrast, RCD, which was evident in 'Kensington Pride' mango fruit, was characterised by browning of the lumen of resin ducts. Accordingly, LD, USB and RCD involve different browning biology processes at the cell and tissue levels. A greater understanding of symptom development and expression could aid in informed management of these physiological disorders