184 research outputs found
Phytoplankton successions and lake dynamics in Las Vegas Bay, Lake Mead, Nevada
Phytoplankton successions, applications of the general growth equation, and physical measurements have been employed to investigate events occurring at the interface between industrial and sewage effluent contained in Las Vegas Wash and the waters of Lake Mead, Nevada. The data indicate that the entering waters tend to form a density current interrupted at intervals by dynamic effects generated in the lake. The dynamic relationships described here for the spring months suggest that a much more thorough understanding of physical, chemical and biological interactions is necessary to permit solution of the numerous problems of Las Vegas Bay discussed or alluded to by Hoffman et al
Use of secondary sewage water as a culture medium for Chaetoceros gracilis and Thalassiosira Sp (Chrysophyceae) in laboratory conditions
Injection of iodine to the stratosphere
We report a new estimation of the injection of iodine into the stratosphere based on novel daytime (solar zenith angle < 45°) aircraft observations in the tropical tropopause layer and a global atmospheric model with the most recent knowledge about iodine photochemistry. The results indicate that significant levels of total reactive iodine (0.25-0.7 parts per trillion by volume), between 2 and 5 times larger than the accepted upper limits, can be injected into the stratosphere via tropical convective outflow. At these iodine levels, modeled iodine catalytic cycles account for up to 30% of the contemporary ozone loss in the tropical lower stratosphere and can exert a stratospheric ozone depletion potential equivalent to, or even larger than, that of very short-lived bromocarbons. Therefore, we suggest that iodine sources and chemistry need to be considered in assessments of the historical and future evolution of the stratospheric ozone layer.Fil: Saiz LĂłpez, Alfonso. Consejo Superior de Investigaciones CientĂficas. Instituto de QuĂmica FĂsica; España. National Center For Atmospheric Research. Amospheric Chemistry DivisiĂłn; Estados Unidos. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Baidar, S.. Cooperative Institute For Research In Environmental Science; Estados Unidos. State University of Colorado at Boulder; Estados UnidosFil: Cuevas, Carlos Alberto. Consejo Superior de Investigaciones CientĂficas. Instituto de QuĂmica FĂsica; EspañaFil: Koening, T. K.. State University of Colorado at Boulder; Estados UnidosFil: Fernandez, Rafael Pedro. Consejo Superior de Investigaciones CientĂficas. Instituto de QuĂmica FĂsica; España. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Dix, Barbara. State University of Colorado at Boulder; Estados UnidosFil: Douglas E. KINNISON. National Center For Atmospheric Research. Amospheric Chemistry DivisiĂłn; Estados UnidosFil: Jean-Francoise LAMARQUE. National Center For Atmospheric Research. Amospheric Chemistry DivisiĂłn; Estados UnidosFil: Xavier Rodriguez-Lloeveras. Consejo Superior de Investigaciones CientĂficas. Instituto de QuĂmica FĂsica; EspañaFil: Campos, T.L.. National Center For Atmospheric Research. Amospheric Chemistry DivisiĂłn; Estados UnidosFil: Volkamer, Rainer. Cooperative Institute For Research In Environmental Science; Estados Unidos. State University of Colorado at Boulder; Estados Unido
New record of Akashiwo sanguinea(Dinophyta) in the tropical estuarine waters of Northeastern Brazil (Western Atlantic)
Medium effects in high energy heavy-ion collisions
The change of hadron properties in dense matter based on various theoretical
approaches are reviewed. Incorporating these medium effects in the relativistic
transport model, which treats consistently the change of hadron masses and
energies in dense matter via the scalar and vector fields, heavy-ion collisions
at energies available from SIS/GSI, AGS/BNL, and SPS/CERN are studied. This
model is seen to provide satisfactory explanations for the observed enhancement
of kaon, antikaon, and antiproton yields as well as soft pions in the
transverse direction from the SIS experiments. In the AGS heavy-ion
experiments, it can account for the enhanced ratio, the difference
in the slope parameters of the and transverse kinetic energy
spectra, and the lower apparent temperature of antiprotons than that of
protons. This model also provides possible explanations for the observed
enhancement of low-mass dileptons, phi mesons, and antilambdas in heavy-ion
collisions at SPS energies. Furthermore, the change of hadron properties in hot
dense matter leads to new signatures of the quark-gluon plasma to hadronic
matter transition in future ultrarelativistic heavy-ion collisions at RHIC/BNL.Comment: RevTeX, 65 pages, including 25 postscript figures, invited topical
review for Journal of Physics G: Nuclear and Particle Physic
Fluctuations In ``BR-Scaled'' Chiral Lagrangians
We develop arguments for "mapping" the effective chiral Lagrangian whose
parameters are given by "BR scaling" to a Landau Fermi-liquid fixed-point
theory for nuclear matter in describing fluctuations in various flavor (e.g.,
strangeness) directions. We use for this purpose the effective Lagrangian used
by Furnstahl, Tang and Serot that incorporates the trace anomaly of QCD in
terms of a light-quark (quarkonium) degree of freedom with the heavy (gluonium)
degree of freedom integrated out. The large anomalous dimension for the scalar field found by Furnstahl et al to be needed for a correct
description of nuclear matter is interpreted as an indication for a
strong-coupling regime and the ground state given by the BR-scaled parameters
is suggested as the background around which fluctuations can be rendered weak
so that mean-field approximation is reliable. We construct a simple model with
BR scaled parameters that provides a satisfactory description of the properties
of matter at normal nuclear matter density. Given this, fluctuations around the
BR scaled background are dominated by tree diagrams. Our reasoning relies
heavily on recent developments in the study of nucleon and kaon properties in
normal and dense nuclear matter, e.g., nucleon and kaon flows in heavy-ion
processes, kaonic atoms, and kaon condensation in dense compact-star matter.Comment: 33 pages, Latex, 5 Postscript figure
A comunidade microfitoplanctÎnica do Arquipélago de São Pedro e São Paulo (Atlùntico Norte-Equatorial): variação diurna e espacial
Mass Spectrometry Analysis of Hepcidin Peptides in Experimental Mouse Models
The mouse is a valuable model for unravelling the role of hepcidin in iron homeostasis, however, such studies still report hepcidin mRNA levels as a surrogate marker for bioactive hepcidin in its pivotal function to block ferroportin-mediated iron transport. Here, we aimed to assess bioactive mouse Hepcidin-1 (Hep-1) and its paralogue Hepcidin-2 (Hep-2) at the peptide level. To this purpose, fourier transform ion cyclotron resonance (FTICR) and tandem-MS was used for hepcidin identification, after which a time-of-flight (TOF) MS-based methodology was exploited to routinely determine Hep-1 and -2 levels in mouse serum and urine. This method was biologically validated by hepcidin assessment in: i) 3 mouse strains (C57Bl/6; DBA/2 and BABL/c) upon stimulation with intravenous iron and LPS, ii) homozygous Hfe knock out, homozygous transferrin receptor 2 (Y245X) mutated mice and double affected mice, and iii) mice treated with a sublethal hepatotoxic dose of paracetamol. The results showed that detection of Hep-1 was restricted to serum, whereas Hep-2 and its presumed isoforms were predominantly present in urine. Elevations in serum Hep-1 and urine Hep-2 upon intravenous iron or LPS were only moderate and varied considerably between mouse strains. Serum Hep-1 was decreased in all three hemochromatosis models, being lowest in the double affected mice. Serum Hep-1 levels correlated with liver hepcidin-1 gene expression, while acute liver damage by paracetamol depleted Hep-1 from serum. Furthermore, serum Hep-1 appeared to be an excellent indicator of splenic iron accumulation. In conclusion, Hep-1 and Hep-2 peptide responses in experimental mouse agree with the known biology of hepcidin mRNA regulators, and their measurement can now be implemented in experimental mouse models to provide novel insights in post-transcriptional regulation, hepcidin function, and kinetics
Phytoplankton composition and abundance assessment in the Nador lagoon (Mediterranean coast of Morocco)
We evaluated phytoplankton abundance, composition and trophic state of the Nador lagoon (Morocco) on the basis of data taken in the period November 2007 to August 2008. Sampling was performed at 11 stations (bottle samples at 0.5 m depth and horizontal plankton net tows with mesh size of 20 mm). Among seven identified phytoplankton classes, diatoms and dinoflagellates dominated with 133 and 169 species, respectively. Frequent phytoplankton blooms were contributed by one to three species in the lagoon. Abundance and seasonality of phytoplankton characterized the Nador lagoon as a highly eutrophicated environment
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