Antiproton-proton partial-wave analysis below 925 MeV/c

A partial-wave analysis of all antiproton-proton scattering data below 925 MeV/c antiproton laboratory momentum is presented. The method used is adapted from the Nijmegen phase-shift analyses of pp and np scattering data. The Nijmegen 1993 antiproton-proton database, consisting of 3646 antiproton-proton scattering data, is presented and discussed. The best fit to this database results in chi^2_min/Ndata = 1.043. The pseudovector coupling constant of the charged pion to nucleons is determined to be (f_c)^2 = 0.0732(11) at the pion pole, where the error is statistical.Comment: Report THEF-NYM 93.02 42 pages REVTeX, 7 separate postscript figures appended. Accepted for publication in Phys. Rev.

Designer quantum states of matter created atom-by-atom

With the advances in high resolution and spin-resolved scanning tunneling microscopy as well as atomic-scale manipulation, it has become possible to create and characterize quantum states of matter bottom-up, atom-by-atom. This is largely based on controlling the particle- or wave-like nature of electrons, as well as the interactions between spins, electrons, and orbitals and their interplay with structure and dimensionality. We review the recent advances in creating artificial electronic and spin lattices that lead to various exotic quantum phases of matter, ranging from topological Dirac dispersion to complex magnetic order. We also project future perspectives in non-equilibrium dynamics, prototype technologies, engineered quantum phase transitions and topology, as well as the evolution of complexity from simplicity in this newly developing field

The nucleon-sigma coupling constant in QCD Sum Rules

The external-field QCD Sum Rules method is used to evaluate the coupling constant of the light isoscalar-scalar meson (``$\sigma$'' or \epsilon) to the nucleon. The contributions that come from the excited nucleon states and the response of the continuum threshold to the external field are calculated. The obtained value of the coupling constant is compatible with the large value required in one-boson exchange potential models of the two-nucleon interaction.Comment: 11 pages, 4 figure

Synonchium capense n. sp. from South Africa (Nematoda : Cyatholaimidae)

#Synonchium capense n. sp. provenant de dunes sableuses des côtes d'Afrique du Sud est décrit. Il diffère de l'espèce type, #S. obtusum Cobb, 1920, par la présence de trois dents de même taille à l'apex de chaque mandibule et par l'absence de ponctuations sur la cuticule. La nouvelle espèce est également comparée à #S. depressum Gerlach, 1954 et #S. pacificum Yeates, 1967, et une clé d'identification est proposée pour les quatre espèces connues. La morphologie des papilles labiales et céphaliques et l'anatomie de la gonade mâle chez les espèces du genre sont discutées. Un important organe glandulaire associé au système reproducteur femelle est décrit chez #S. capense$ n. sp. (Résumé d'auteur

The renormalization transformation for two-type branching models

This paper studies countable systems of linearly and hierarchically interacting diffusions taking values in the positive quadrant. These systems arise in population dynamics for two types of individuals migrating between and interacting within colonies. Their large-scale space-time behavior can be studied by means of a renormalization program. This program, which has been carried out successfully in a number of other cases (mostly one-dimensional), is based on the construction and the analysis of a nonlinear renormalization transformation, acting on the diffusion function for the components of the system and connecting the evolution of successive block averages on successive time scales. We identify a general class of diffusion functions on the positive quadrant for which this renormalization transformation is well-defined and, subject to a conjecture on its boundary behavior, can be iterated. Within certain subclasses, we identify the fixed points for the transformation and investigate their domains of attraction. These domains of attraction constitute the universality classes of the system under space-time scaling.Comment: 48 pages, revised version, to appear in Ann. Inst. H. Poincare (B) Probab. Statis

Spatial and temporal variation in otolith chemistry for tautog (Tautoga onitis) in Narragansett Bay and Rhode Island coastal ponds

The elemental composition of otoliths may provide valuable information for establishing connectivity between fish nursery grounds and adult fish populations. Concentrations of Rb, Mg, Ca, Mn, Sr, Na, K, Sr, Pb, and Ba were determined by using solution-based inductively coupled plasma mass spectrometry in otoliths of young-of-the year tautog (Tautoga onitis) captured in nursery areas along the Rhode Island coast during two consecutive years. Stable oxygen (δ18O) and carbon (δ13C) isotopic ratios in young-of-the year otoliths were also analyzed with isotope ratio mass spectrometry. Chemical signatures differed significantly among the distinct nurseries within Narragansett Bay and the coastal ponds across years. Significant differences were also observed within nurseries from year to year. Classification accuracy to each of the five tautog nursery areas ranged from 85% to 92% across years. Because accurate classification of juvenile tautog nursery sites was achieved, otolith chemistry can potentially be used as a natural habitat tag

Description of three new Xiphinema species from South Africa (Nematoda : Dorylaimida)

Trois nouvelles espèces de #Xiphinema sont décrites provenant de prélèvements de sol dans des plantations d'arbres exotiques et d'essences indigènes dans les forêts domaniales de Berlin et de Nelshooge, en Afrique du Sud. Ces espèces - #X. spinosum n. sp., #X. maraisae n. sp. et #X. silvicola n. sp. - présentent toutes une ornementation vulvaire, une queue allongée et un tractus génital femelle pourvu à la fois d'une différenciation Z et d'épines utérines. Cela porte à cinq le nombre d'espèces sud-africaines de #Xiphinema ayant une ornementation vulvaire, les deux autres espèces étant #X. ornativulvatum Kruger & Heyns, 1987 et #X. ornatizulu Hutsebaut, Heyns & Coomans, 1989. Parmi ces espèces, #X. spinosum n. sp., peut être distingué par la structure particulière de la différenciation Z - corps granuleux avec projections -, la faiblesse de l'ornementation vulvaire et le dimorphisme sexuel de la queue. #X. maraisae n. sp. se différencie par la combinaison de caractères suivants : différenciation Z comportant des structures spiniformes, trois à quatre indentations transversales prononcées de chaque côté de la fente vulvaire et queue allongée chez les mâles et les femelles. #X. silvicola n. sp. diffère essentiellement des quatre autres espèces par l'ornementation vulvaire bien visible, le corps trapu, les inclusions variées - arrondies et anguleuses - de la différenciation Z et la forme de la queue de la femelle. (Résumé d'auteur