383 research outputs found
Influence of the Tungurahua eruption on the ice core records of Chimborazo, Ecuador
International audienceThe comparison of two shallow ice cores recovered in 1999 and 2000 from the same place on the Chimborazo summit glacier revealed the influence of the coincident Tungurahua volcanic eruption on their stable isotope and chemical records. The surface snow melting and water percolation induced from the ash deposition caused a preferential elution and re-localization of certain ionic species, while the stable isotope records were not affected. Additionally, the comparison of the ionic amount and some selected ion ratios preserved along the ice core column reports under which processes the chemical species are introduced in the snow pack, as snow flake condensation nuclei, by atmospheric scavenging or by dry deposition. This preliminary study is essential for the interpretation of the deep Chimborazo ice core, or for other sites where surrounding volcanic activity influences the glaciochemical records
Avaliação do grau de humidificação da matéria orgânica de solo irrigado com efluente por espectroscopia de fluorescência na região do UV/Vis e determinação de carbono via úmida.
Identfication and quantfication of giant bioaerosol particles over the Amazon rainforest
Eukarya dominate the coarse primary biological aerosol (PBA) above the Amazon rainforest canopy, but their vertical profile and seasonality is currently unknown. In this study, the stratification of coarse and giant PBA >5 µm were analyzed from the canopy to 300 m height at the Amazon Tall Tower Observatory in Brazil during the wet and dry seasons. We show that >2/3 of the coarse PBA were canopy debris, fungal spores commonly found on decaying matter were second most abundant (ranging from 15 to 41%), followed by pollens (up to 5%). The atmospheric roughness layer right above the canopy had the greatest giant PBA abundance. Measurements over 5 years showed an increased abundance of PBA during a low-rainfall period. Giant particles, such as pollen, are reduced at 300 m, suggesting their limited dispersal. These results give insights into the giant PBA emissions of this tropical rainforest, and present a major step in understanding the type of emitted particles and their vertical distribution
Structural characterization of human Vaccinia-Related Kinases (VRK) bound to small-molecule inhibitors identifies different P-loop conformations
The human genome encodes two active Vaccinia-related protein kinases (VRK), VRK1 and VRK2. These proteins have been implicated in a number of cellular processes and linked to a variety of tumors. However, understanding the cellular role of VRKs and establishing their potential use as targets for therapeutic intervention has been limited by the lack of tool compounds that can specifically modulate the activity of these kinases in cells. Here we identified BI-D1870, a dihydropteridine inhibitor of RSK kinases, as a promising starting point for the development of chemical probes targeting the active VRKs. We solved co-crystal structures of both VRK1 and VRK2 bound to BI-D1870 and of VRK1 bound to two broad-spectrum inhibitors. These structures revealed that both VRKs can adopt a P-loop folded conformation, which is stabilized by different mechanisms on each protein. Based on these structures, we suggest modifications to the dihydropteridine scaffold that can be explored to produce potent and specific inhibitors towards VRK1 and VRK2
Centrality dependence of pi^[+/-], K^[+/-], p and p-bar production from sqrt(s_NN)=130 GeV Au + Au collisions at RHIC
Identified pi^[+/-] K^[+/-], p and p-bar transverse momentum spectra at
mid-rapidity in sqrt(s_NN)=130 GeV Au-Au collisions were measured by the PHENIX
experiment at RHIC as a function of collision centrality. Average transverse
momenta increase with the number of participating nucleons in a similar way for
all particle species. The multiplicity densities scale faster than the number
of participating nucleons. Kaon and nucleon yields per participant increase
faster than the pion yields. In central collisions at high transverse momenta
(p_T greater than 2 GeV/c), anti-proton and proton yields are comparable to the
pion yields.Comment: 6 pages, 3 figures, 1 table, 307 authors, accepted by Phys. Rev.
Lett. on 9 April 2002. This version has minor changes made in response to
referee Comments. Plain text data tables for the points plotted in figures
for this and previous PHENIX publications are publicly available at
http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm
Centrality Dependence of Charged Particle Multiplicity in Au-Au Collisions at sqrt(s_NN)=130 GeV
We present results for the charged-particle multiplicity distribution at
mid-rapidity in Au - Au collisions at sqrt(s_NN)=130 GeV measured with the
PHENIX detector at RHIC. For the 5% most central collisions we find
. The results,
analyzed as a function of centrality, show a steady rise of the particle
density per participating nucleon with centrality.Comment: 307 authors, 43 institutions, 6 pages, 4 figures, 1 table Minor
changes to figure labels and text to meet PRL requirements. One author added:
M. Hibino of Waseda Universit
Net Charge Fluctuations in Au + Au Interactions at sqrt(s_NN) = 130 GeV
Data from Au + Au interactions at sqrt(s_NN) = 130 GeV, obtained with the
PHENIX detector at RHIC, are used to investigate local net charge fluctuations
among particles produced near mid-rapidity. According to recent suggestions,
such fluctuations may carry information from the Quark Gluon Plasma. This
analysis shows that the fluctuations are dominated by a stochastic distribution
of particles, but are also sensitive to other effects, like global charge
conservation and resonance decays.Comment: 6 pages, RevTeX 3, 3 figures, 307 authors, submitted to Phys. Rev.
Lett. on 21 March, 2002. Plain text data tables for the points plotted in
figures for this and previous PHENIX publications are (will be made) publicly
available at http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm
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