\u3cem\u3eHymenachne Amplexicaluis\u3c/em\u3e [(Rudge) Nees] Genetic Resources Collection in México, a Suitable Grass for Flood Plains in Tropical Areas

Hymenachne amplexicaluis [( Rudge ) Nees; 2n= 2x= 24; Azuche, West Indian marsh grass] is a native Central and South America C3 grass that grows well under intermittent flooding conditions. It produces good seed set and stolons to thrive on new areas assuring its survival, combined with an efficient N metabolism to promote vigorous new growing leaves and tillers (Antel et al., 1998). Azuche is a dual attribute species when introduced to new areas; it has valuable forage attributes but also is a potential weed (Hill, 2000). As Azuche is a native species, one must deal with in the best possible way within Tropical Latin America areas (Enríquez et al., 2004). No report has been found to date on living genetic resources collection and evaluation for this species

Neutron Transfer reactions induced by 8Li on 9Be

Angular distributions for the elastic scattering of 8Li on 9Be and the neutron transfer reactions 9Be(8Li,7Li)10Be and 9Be(8Li,9Li)8Be have been measured with a 27 MeV 8Li radioactive nuclear beam. Spectroscopic factors for 8Li|n=9Li and 7Li|n=8Li bound systems were obtained from the comparison between the experimental differential cross section and finite-range DWBA calculations with the code FRESCO. The spectroscopic factors obtained are compared to shell model calculations and to other experimental values from (d,p) reactions. Using the present values for the spectroscopic factor, cross sections for the direct neutron-capture reactions 7Li(n,g)8Li and 8Li(n,g)9Li were calculated in the framework of a potential model.Comment: 24 pages, 8 Figures, submitted as regular article to PR

In vitro propagation of cedar (Cedrela odorata L.) from juvenile shoots

Garriga, M (Garriga, Miguel); Caligari, PDS (Caligari, Peter D. S.). Univ Talca, Inst Biol Vegetal & Biotecnol, Talca, ChileCedrela odorata L. is one of the most important timber species currently traded in the Caribbean and Central America; however, it has been intensively exploited. In vitro techniques and clonal propagation can help to develop new plantations and assist in establishing improvement programs for this species. The aim of this study was to develop a protocol to establish in vitro conditions and to micropropagate this species from nodal explants from juvenile cuttings taken from field trees. Disinfection of node explants with 5% propiconazole CE 25 during 3 min resulted in 100% explant disinfection and 60% morphogenic response on those established explants. Shoot development was optimized by cultivating in vitro node explants in Murashige and Skoog basal medium supplemented with 2 mg L(-1) 6-bencilaminopurine and 3 mg L(-1) naphthaleneacetic acid. This medium resulted in 100% shoot development from the in vitro node explants with a 3.93 cm mean height. Rooting was also stimulated 6 wk after individualization of the regenerated plants on the same micropropagation medium with a mean of 3.9 roots per plant. In vitro plants did not show morphologic differences when compared to ex vitro seeds

Brane-Antibrane Inflation in Orbifold and Orientifold Models

We analyse the cosmological implications of brane-antibrane systems in string-theoretic orbifold and orientifold models. In a class of realistic models, consistency conditions require branes and antibranes to be stuck at different fixed points, and so their mutual attraction generates a potential for one of the radii of the underlying torus or the 4D string dilaton. Assuming that all other moduli have been fixed by string effects, we find that this potential leads naturally to a period of cosmic inflation with the radion or dilaton field as the inflaton. The slow-roll conditions are satisfied more generically than if the branes were free to move within the space. The appearance of tachyon fields at certain points in moduli space indicates the onset of phase transitions to different non-BPS brane systems, providing ways of ending inflation and reheating the corresponding observable brane universe. In each case we find relations between the inflationary parameters and the string scale to get the correct spectrum of density perturbations. In some examples the small numbers required as inputs are no smaller than 0.01, and are the same small quantities which are required to explain the gauge hierarchy.Comment: 30 pages, 2 figures. Substantial changes on version 1. New cosmological scenarios proposed including the dilaton as the inflaton. Main conclusions unchange

Dirichlet Branes on Orientifolds

We consider the classification of BPS and non-BPS D-branes in orientifold models. In particular we construct all stable BPS and non-BPS D-branes in the Gimon-Polchinski (GP) and Dabholkar-Park-Blum-Zaffaroni (DPBZ) orientifolds and determine their stability regions in moduli space as well as decay products. We find several kinds of integrally and torsion charged non-BPS D-branes. Certain of these are found to have projective representations of the orientifold $\times$ GSO group on the Chan-Paton factors. It is found that the GP orientifold is not described by equivariant orthogonal K-theory as may have been at first expected. Instead a twisted version of this K-theory is expected to be relevant.Comment: 33 pages, LaTeX, 5 figures. v2 typos corrected, references included, (4,s)-branes re-examine

Photoacoustic Spectroscopy Applied To The Study Of Clay Soils

The study of clay soils using photoacoustic spectroscopy was presented. The observation of the photoacoustic spectra showed the transition bands associated with Fe3+ ions in octahedral or tetrahedral symmetry. Rietveld refinements showed that the Al3+ cations were partially substituted by the Fe3+ cations in the octahedral states of kaolinite structure.741 II355357Alexandre, J., Saboya, F., Marques, B.C., Ribeiro, M.L.P., Salles, C., Da Silva, M.G., Sthel, M.S., Vargas, H., (1999) Analyst, 124, p. 1209Ambikadevi, V.R., Lalithambika, M., (2000) Appl. Clay Sci., 16, p. 133Mehra, O.P., Jackson, M.L., (1960) Clays Clay Miner., 7, p. 317Young, R.A., Sakthivel, A., Moss, T.S., Paiva-Santos, C.O., (1995) J. Appl. Crystallogr., 28, p. 366Sugano, S., Tunabe, Y., Kamimura, H., (1970) Multiplets of Transition-Metal Ions in Crystals, , Academic, New YorkAbritta, T., De Souza Barros, F., (1988) J. Lumin., 40, p. 187Abritta, T., Cella, N., Vargas, H., (1989) Chem. Phys. Lett., 161, p. 12Lima, G.A.R., Baesso, M.L., Arguello, Z.P., Da Silva, E.C., Vargas, H., (1987) Phys. Rev. B, 36, p. 9812Rosencwaig, A., Gersho, A., (1976) J. Appl. Phys., 47, p. 64Baesso, M.L., Mansanares, A.M., Da Silva, E.C., Vargas, H., (1989) Phys. Rev. B, 40, p. 188

Associations between plasma neurofilament light, in vivo brain pathology, and cognition in non-demented individuals with autosomal-dominant Alzheimer's disease

BACKGROUND: Neurofilament light (NfL) is a promising biomarker of early neurodegeneration in Alzheimer's disease (AD). We examined whether plasma NfL was associated with in vivo amyloid beta and tau, and cognitive performance in non-demented presenilin-1 (PSEN1) E280A mutation carriers. METHODS: Twenty-five mutation carriers and 19 non-carriers (age range: 28 to 49 years) were included in this study. Participants underwent 11C Pittsburgh compound B (PiB)-PET (positron emission tomography), flortaucipir-PET, blood sampling, and cognitive testing. RESULTS: Mutation carriers exhibited higher plasma NfL levels than non-carriers. In carriers, higher NfL levels were related to greater regional tau burden and worse cognition, but not amyloid beta load. When we adjusted for age, a proxy of disease progression, elevated plasma NfL levels were only correlated with worse memory recall. CONCLUSIONS: Findings support an association between plasma NfL, cognition, and tau pathology in non-demented individuals at genetic risk for developing AD dementia. Plasma NfL may be useful for selecting individuals at increased risk and tracking disease progression in AD

Near- And Sub-barrier Fusion Of The Be7+ Ni58 System

Evaporation proton yields were measured for the fusion of the radioactive proton-rich nucleus Be-7 onto a Ni-58 target at six near-barrier energies. Total fusion cross sections were deduced by using calculated proton multiplicities. The resulting fusion excitation function shows a considerable enhancement with respect to calculations for a bare potential, even for energies above the Coulomb barrier. Inelastic couplings can account for the enhancement at the highest energy. Total fusion channels nearly saturate the total reaction cross section in the measured energy region. Comparison with previous results scaled appropriately for Be-7 + (Al-27, U-238) shows good agreement