5,940 research outputs found
The genetics and genomics of Trypanosoma cruzi
Trypanosoma cruzi is a kinetoplastid parasite that causes Chagas disease. Trypanosomes are unusual organisms in many aspects of its genetics and molecular and cellular biology and considered a paradigm of the exception of the rule in the eukaryotic kingdom. The complete genome sequence of T. cruzi was published in 2005, thus, providing a major tool to the understanding of several of his unusual aspects. However, with so many different mechanisms between the parasite and its mammalian host there is still a lack of availability of effective antiparasitic drugs or disease treatments, specially in the chronic phase. This review highlights the fundamentals of the fasci- nating genetics and genomics of T. cruzi with emphasis in the differential mechanisms that could provide interesting therapeutic targets.Fil: Vazquez, Martin Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentin
Ab initio Simulation of Optical Limiting: The Case of Metal-Free Phthalocyanine
We present a fully ab initio, non-perturbative description of the optical
limiting properties of a metal-free phthalocyanine, by simulating the effects
of a broadband electric field of increasing intensity. The results confirm
reverse saturable absorption as leading mechanism for optical limiting
phenomena in this system and reveal that a number of dipole-forbidden
excitations are populated by excited-state absorption, at more intense external
fields. The excellent agreement with the experimental data supports our
approach as a powerful tool to predict optical limiting, in view of
applications
Experimental study of the ageing of building stones exposed to sulfurous and nitric acid atmospheres
During the last few decades, due to remediation procedures, SO2 emissions in the atmosphere have decreased, unlike NOx. Air pollution has changed. Indeed, the aim of this research is to assess the effect of NOx and their interactions with SO2 on stones, particularly on limestones used in Champagne-Ardenne (France) during the restoration processes. Three French building limestones (Courville, Dom and Savonnières) and one reconstituted stone were exposed during 28 days to four strong acid atmospheres i.e. two H2SO3 solutions with different concentrations and two mixed atmospheres with different proportions of HNO3 and H2SO3. These tests produced an intensive acid attack on the stone, allowing the observation of short-term salt precipitation and the evolution of stone properties. Each day, one sample was removed from the acid atmosphere to measure the concentration of SO4(2-) and NO3(-) by ion-chromatography. The surface changes were assessed before and after the tests by 3D scanning and observations with electron microscopy. X-ray microtomography has been performed in the Centre for X-ray Tomography (UGCT) and the Department of Geology at Ghent University (Belgium) in order to observe the penetration of salts and the consequences in stones porosity. First observations showed that exposure to acid atmosphere, led to gypsum efflorescences. Obvious colour changes occurred in all tests. Salt crystallization entailed a change in the porous system, which was evidenced by 3D, mercury porosimetry and X-ray microtomography. Difference between weathered and fresh stone was highlighted by Ion chromatography analyses
Status of the LHCb detector
LHCb is an experiment dedicated to study CP violation and other rare
phenomena in B mesons decays with very high precision. It is one of the four
experiments that will operate at the 14Tev proton-proton Large Hadron Collider
(LHC) at CERN in 2008. Here we briefly describe the current status of the
experiment, as well as plans towards a future upgrade.Comment: 5 pages, presented at Lake Louise Winter Institute 200
The 3D printing of a polymeric electrochemical cell body and its characterisation
An undivided flow cell was designed and constructed using additive manufacturing technology and its mass transport characteristics were evaluated using the reduction of ferricyanide, hexacyanoferrate (III) ions at a nickel surface. The dimensionless mass transfer correlation Sh = aRebScdLee was obtained using the convective-diffusion limiting current observed in linear sweep voltammetry; this correlation compared closely with that reported in the literature from traditionally machined plane parallel rectangular flow channel reactors. The ability of 3D printer technology, aided by computational graphics, to rapidly and conveniently design, manufacture and re-design the geometrical characteristics of the flow cell ishighlighted
The production and detoxification of a potent cytotoxin, nitric oxide, by pathogenic enteric bacteria
The nitrogen cycle is based on several redox reactions that are mainly accomplished by prokaryotic organisms, some archaea and a few eukaryotes, which use these reactions for assimilatory, dissimilatory or respiratory purposes. One group is the Enterobacteriaceae family of Gammaproteobacteria, which have their natural habitats in soil, marine environments or the intestines of humans and other warm-blooded animals. Some of the genera are pathogenic and usually associated with intestinal infections. Our body possesses several physical and chemical defence mechanisms to prevent pathogenic enteric bacteria from invading the gastrointestinal tract. One response of the innate immune system is to activate macrophages, which produce the potent cytotoxin nitric oxide (NO). However, some pathogens have evolved the ability to detoxify NO to less toxic compounds, such as the neuropharmacological agent and greenhouse gas nitrous oxide (N2O), which enables them to overcome the host's attack. The same mechanisms may be used by bacteria producing NO endogenously as a by-product of anaerobic nitrate respiration. In the present review, we provide a brief introduction into the NO detoxification mechanisms of two members of the Enterobacteriaceae family: Escherichia coli and Salmonella enterica serovar Typhimurium. These are discussed as comparative non-pathogenic and pathogenic model systems in order to investigate the importance of detoxifying NO and producing N2O for the pathogenicity of enteric bacteria
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