962 research outputs found
Firewood extraction affects carbon pools and nutrients in remnant fragments of temperate forests at the Mexican Transvolcanic Belt
Globally, remnant fragments of forests represent the main carbon reservoir of terrestrial ecosystems, but they suffer strong degradation due to uncontrolled wood extraction mainly by tree cut for household fuel use and charcoal production. The present study evaluates the degradation caused by wood extraction on carbon pools and soil nutrient dynamics in temperate forests distributed in remnant fragments located in central Mexico. Four sites with different intensity of wood extraction were chosen for measuring carbon pools and nutrient fluxes during two years. Both, aboveground carbon biomass and soil organic carbon values decreased with the intensity of forest degradation. The degraded forest (DF) showed total carbon content 55 % lower than that shown by the seminatural forest (SF). Additionally, litterfall production was reduced in DF as compared to SF; the decomposition rate of standing litter was higher in the latter site. As a consequence, DF had lower organic matter inputs to the soil than that presented by SF. Soil extractable ammonium and microbial biomass-carbon and -nitrogen were lower in DF than in SF. It was concluded that the uncontrolled wood extraction in these remnants of temperate forest in Mexico significantly reduced the carbon pools, carbon and nutrient fluxes through litterfall and consequently, the soil nutrient dynamics were disrupted
Desertification
IPCC SPECIAL REPORT ON CLIMATE CHANGE AND LAND (SRCCL)
Chapter 3: Climate Change and Land: An IPCC special report on climate change, desertification, land degradation, sustainable land management, food security, and greenhouse gas fluxes in terrestrial ecosystem
Efecto de la degradacion de los bosques sobre la captura de C y la disponibilidad de N edafico en la cuenca de Cuitzeo, Michoacan
P10-13. Increased production of alpha-defensins 1–3 by dendritic cells in HIV-infected individuals is associated with a slower disease progression rate
Bases para el diseno de un sistema de monitoreo de la dinamica hidrologica de la cuenca de Cointzio, Michoacan, Mexico
PH-responsive polysaccharide-based polyelectrolyte complexes as nanocarriers for lysosomal delivery of therapeutic proteins
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Moxifloxacin versus levofloxacin against acute exacerbations of chronic bronchitis: the Latin American Cohort
We compared the efficacy and safety of moxifloxacin and levofloxacin for the treatment of patients with acute exacerbations of chronic bronchitis (AECB) using a prospective, randomized, double blind, parallel-group clinical trial design. A total of 563 patients with AECB were enrolled (437 efficacy-valid) at 34 centers in Mexico, Argentina, Brazil, Colombia, and Peru. Patients were randomized to oral therapy with either moxifloxacin 400 mg once daily for 5 days or levofloxacin 500 mg once daily for 7 days. Clinical success was achieved in 201 out of 221 (91.0%) patients in the moxifloxacin group, and in 203 out of 216 (94.0%) in the levofloxacin group, indicating that moxifloxacin is equivalently effective to levofloxacin. Bacteriologic eradication or presumed eradication was also similar in the two treatment groups: 92.8% in the moxifloxacin group and 93.8% in the levofloxacin group. Nausea was the most common drug-related adverse event in each treatment group. the rate of discontinuation because of adverse events was very low (<= 2%). in conclusion, a 5-day course of moxifloxacin is clinically and bacteriologically equivalent to a 7-day course of levofloxacin in the treatment of patients with AECB. the short treatment duration with moxifloxacin may have compliance advantages over other currently used therapies in the 'real-Life' clinical setting. (c) 2006 Elsevier B.V. All rights reserved.Fdn LUSARA, Mexico City 08930, DF, MexicoInst Nacl Enfermedades Resp, Mexico City, DF, MexicoHosp Mi Pueblo, Buenos Aires, DF, ArgentinaUniversidade Federal de São Paulo, São Paulo, BrazilClin Reina Sofia, Bogota, ColombiaClin Ricardo Palma, Lima, PeruBayer Mexico, SA & CV, Mexico City, DF, MexicoUniversidade Federal de São Paulo, São Paulo, BrazilWeb of Scienc
Artillery Shells over Circinus
The recently identified Circinus Galaxy is the nearest (about 4 Mpc) Seyfert
2 galaxy known and we now demonstrate to be one of the best laboratories for
studying the effects of nuclear activity on the surrounding environment. Here
we present new imaging Fabry-Perot observations of Circinus which confirm the
existence of an ionization cone in this object but also show for the first time
a complex of ionized filaments extending radially from the nucleus out to
distances of 1 kpc. Arcs suggestive of bow shocks are observed at the terminus
of some of these filamentary structures. Most spectacular of all, one of the
structures appears to be a scaled-up version of a Herbig-Haro jet. The velocity
field of the filaments confirms that they represent material expelled from the
nucleus (possibly in the form of `bullets') or entrained in a wide-angle wind
roughly aligned with the polar axis of the galaxy. The motions observed across
the ionization cone are highly supersonic, so high-velocity shocks are likely
to contribute to the ionization of the line emitting gas. However, it is not
clear at present whether shock ionization dominates over photoionization by the
Seyfert 2 nucleus. Extrapolation of the filaments to smaller radii comes to
within 1 arcsec (about 20 pc) of the infrared nucleus, therefore suggesting a
AGN or nuclear starburst origin to these features. The complex of radial
filaments detected in the Circinus galaxy is unique among active galaxies. The
frequency of such events is unknown since only a handful of galaxies have been
observed at the sensitivity level of our present observations. The event in the
Circinus galaxy may represent a relatively common evolutionary phase in the
lives of gas-rich active galaxies during which the dusty cocoon surrounding the
nucleus is expelled by the action of jet or wind phenomena.Comment: 22 pages including 5 figures, Latex, requires aasms4.sty. To appear
in ApJ Letters 479 (1997
Analysis of a spatial Lotka-Volterra model with a finite range predator-prey interaction
We perform an analysis of a recent spatial version of the classical
Lotka-Volterra model, where a finite scale controls individuals' interaction.
We study the behavior of the predator-prey dynamics in physical spaces higher
than one, showing how spatial patterns can emerge for some values of the
interaction range and of the diffusion parameter.Comment: 7 pages, 7 figure
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