Effect of seedbed steaming on Cylindrocladium floridanum, soil microbes and the development of white pine seedlings

Dans une pépinière forestière à racines nues, l'appareil Egedal® de traitement à la valeur des plates-bandes, a produit suffisamment de chaleur pour détruire les microsclérotes du Cylindrocladium floridanum à 5 et 10 cm de profondeur. À une autre pépinière, l'inoculum dans le sol ne fut détruit qu'à une profondeur de 5 cm. Le traitement à la vapeur du sol n'a pas affecté les microsclérotes situés à 15 cm. Le traitement a réduit les populations des pseudomonas fluorescents à des niveaux non détectables jusqu'à une profondeur de 20 cm et les populations des espèces de Trichoderma furent réduites significativement dans les 10 cm supérieurs de la plate-bande. Quatre mois après le traitement, la densité des semis de pin blanc semés dans les plates-bandes traitées était significativement plus élevée (P= 0,05), et leur hauteur, leur diamètre au collet, le poids de leurs tiges et celui de leurs racines étaient significativement plus grands (P= 0,05) que ceux des semis témoins provenant des plates-bandes non traitées.The Egedal® bed steamer produced sufficient heat to kill mierosclerotia of Cylindrocladium floridanum at 5 and 10 cm soil depths in one bareroot forest seedling nursery. At a second nursery, the buried inoculum was killed only to a depth of 5 cm. Soil steaming did not affect the mierosclerotia at 15 cm. The steaming reduced populations of fluorescent pseudomonas to undetectable levels to a depth of 20 cm and populations of Trichoderma species were significantly reduced in the upper 10 cm of the seedbed. Density of white pine seedlings sown in the steamed beds was significantly higher (P= 0.05), and height, root collar diameter, shoot weight and root weight were significantly greater (P= 0.05) 4 months after steaming than that of control seedlings sown in unsteamed beds

Measurement of global polarization of {\Lambda} hyperons in few-GeV heavy-ion collisions

The global polarization of {\Lambda} hyperons along the total orbital angular momentum of a relativistic heavy-ion collision is presented based on the high statistics data samples collected in Au+Au collisions at \sqrt{s_{NN}} = 2.4 GeV and Ag+Ag at 2.55 GeV with the High-Acceptance Di-Electron Spectrometer (HADES) at GSI, Darmstadt. This is the first measurement below the strangeness production threshold in nucleon-nucleon collisions. Results are reported as a function of the collision centrality as well as a function of the hyperon transverse momentum (p_T) and rapidity (y_{CM}) for the range of centrality 0--40%. We observe a strong centrality dependence of the polarization with an increasing signal towards peripheral collisions. For mid-central (20--40%) collisions the polarization magnitudes are (%) = 6.0 \pm 1.3 (stat.) \pm 2.0 (syst.) for Au+Au and (%) = 4.6 \pm 0.4 (stat.) \pm 0.5 (syst.) for Ag+Ag, which are the largest values observed so far. This observation thus provides a continuation of the increasing trend previously observed by STAR and contrasts expectations from recent theoretical calculations predicting a maximum in the region of collision energies about 3 GeV. The observed polarization is of a similar magnitude as predicted by 3D fluid dynamics and the UrQMD plus thermal vorticity model and significantly above results from the AMPT model.Comment: 8 pages, 4 figure

Impact of the Coulomb field on charged-pion spectra in few-GeV heavy-ion collisions

In nuclear collisions the incident protons generate a Coulomb field which acts on produced charged particles. The impact of these interactions on charged-pion transverse-mass and rapidity spectra, as well as on pion–pion momentum correlations is investigated in Au + Au collisions at $\sqrt{^{S}NN}$ = 2.4 GeV. We show that the low-m$_{t}$ region (m$_{t}$ < 0.2 GeV / c$^{2}$) can be well described with a Coulomb-modified Boltzmann distribution that also takes changes of the Coulomb field during the expansion of the fireball into account. The observed centrality dependence of the fitted mean Coulomb potential energy deviates strongly from a $A_{part}^{2/3}$ scaling, indicating that, next to the fireball, the non-interacting charged spectators have to be taken into account. For the most central collisions, the Coulomb modifications of the HBT source radii are found to be consistent with the potential extracted from the single-pion transverse-mass distributions. This finding suggests that the region of homogeneity obtained from two-pion correlations coincides with the region in which the pions freeze-out. Using the inferred mean-square radius of the charge distribution at freeze-out, we have deduced a baryon density, in fair agreement with values obtained from statistical hadronization model fits to the particle yields

Inclusive e+^+e−^- production in collisions of pions with protons and nuclei in the second resonance region of baryons

Inclusive e$^+$e$^-$ production has been studied with HADES in $\pi^-$ + p, $\pi^-$ + C and $\pi^- + \mathrm{CH}_2$ reactions, using the GSI pion beam at $\sqrt{s_{\pi p}}$ = 1.49 GeV. Invariant mass and transverse momentum distributions have been measured and reveal contributions from Dalitz decays of $\pi^0$, $\eta$ mesons and baryon resonances. The transverse momentum distributions are very sensitive to the underlying kinematics of the various processes. The baryon contribution exhibits a deviation up to a factor seven from the QED reference expected for the dielectron decay of a hypothetical point-like baryon with the production cross section constrained from the inverse $\gamma$ n$\rightarrow \pi^-$ p reaction. The enhancement is attributed to a strong four-momentum squared dependence of the time-like electromagnetic transition form factors as suggested by Vector Meson Dominance (VMD). Two versions of the VMD, that differ in the photon-baryon coupling, have been applied in simulations and compared to data. VMD1 (or two-component VMD) assumes a coupling via the $\rho$ meson and a direct coupling of the photon, while in VMD2 (or strict VMD) the coupling is only mediated via the $\rho$ meson. The VMD2 model, frequently used in transport calculations for dilepton decays, is found to overestimate the measured dielectron yields, while a good description of the data can be obtained with the VMD1 model assuming no phase difference between the two amplitudes. Similar descriptions have also been obtained using a time-like baryon transition form factor model where the pion cloud plays the major role.Comment: (HADES collaboration

Proposed three span arch subway of the C. M. & ST. P. RY. over Humboldt boulevard

http://www.archive.org/details/proposedthreespa00greiThesis (B.S.)--Armour Institute of Technology, 1913 B.S. in Civil Engineering, 191