6,331 research outputs found
Reaction Kinetics in the Production of Pd Nanoparticles in Reverse Microemulsions. Effect on Particle Size
In the synthesis of metallic nanoparticles in microemulsions, we hypothesized
that particle size is mainly controlled by the reaction rate. Thus, the changes
observed on the particle sizes as reaction conditions, such as concentrations,
temperature, type of surfactant used, etc., are varied should not be correlated
directly to the modification of those conditions but indirectly to the changes
they produce on the reaction rates. By means of time resolved UV-vis
spectroscopy, we measured the reaction rates in the production of Pd
nanoparticles inside microemulsions at different reactant concentrations,
keeping all the other parameters constant. The measured reaction rates were
then correlated with the particle sizes measured by transmission electron
microscopy (TEM). We found that nanoparticle size increases linearly as the
reaction rates increases, independently of the actual reactant concentrations.
We proposed that the kinetics is controlled mainly by the diffusion of the
reducing agent through the surfactant monolayer covering the microemulsion
membrane. With this model, we predicted that particle size should depend
indirectly, via the reaction kinetics, on the micelle radius (v0 ~ r^-3), the
water volume (v0~vw^3) and the total microemulsion volume (v0~vT^-3), and
temperature (Arrhenius). Some of these predictions were explored in this
article
Curvature(s) of a light wavefront in a weak gravitational field
The geometry of a light wavefront evolving from a flat wavefront under the
action of weak gravity field in the 3-space associated to a post-Newtonian
relativistic spacetime, is studied numerically by means of the ray tracing
method.Comment: 3 pages, 1 fig, Talk given by JFPS at the 12th Marcel Grossmann
conference (Paris, July, 2009), submitted to the Proceeding
Geometry of an accelerated rotating disk
We analyze the geometry of a rotating disk with a tangential acceleration in
the framework of the Special Theory of Relativity, using the kinematic linear
differential system that verifies the relative position vector of time-like
curves in a Fermi reference. A numerical integration of these equations for a
generic initial value problem is made up and the results are compared with
those obtained in other works.Comment: 10 pages, LaTeX, 2 eps figs; typos corrected, added reference, minor
changes; submitte
Cherenkov telescope array extragalactic survey discovery potential and the impact of axion-like particles and secondary gamma rays
The Cherenkov Telescope Array (CTA) is about to enter construction phase and
one of its main key science projects is to perform an unbiased survey in search
of extragalactic sources. We make use of both the latest blazar gamma--ray
luminosity function and spectral energy distribution to derive the expected
number of detectable sources for both the planned Northern and Southern arrays
of the CTA observatory. We find that a shallow, wide survey of about 0.5 hour
per field of view would lead to the highest number of blazar detections.
Furthermore, we investigate the effect of axion-like particles and secondary
gamma rays from propagating cosmic rays on the source count distribution, since
these processes predict different spectral shape from standard extragalactic
background light attenuation. We can generally expect more distant objects in
the secondary gamma-ray scenario, while axion-like particles do not
significantly alter the expected distribution. Yet, we find that, these results
strongly depend on the assumed magnetic field strength during the propagation.
We also provide source count predictions for the High Altitude Water Cherenkov
observatory (HAWC), the Large High Altitude Air Shower Observatory (LHAASO) and
a novel proposal of a hybrid detector.Comment: 16 pages, 4 figures, ApJ 2017 in pres
Geminiviral protein Rep interferes in PCNA sumoylation
Rep is a multifunctional protein essential for replication of geminivirus that interferes with the sumoylation of a key protein in the DNA replication, PCNA (Proliferating Cell Nuclear Antigen). It is known that Rep is capable of interacting with a plethora of plant proteins, including PCNA. Despite the biological significance remains unknown, it’s thought that this interaction should play a key role for generating new copies of the virus genome. Therefore, in order to characterize this interaction, we study which lysines are sumoylated in tomato PCNA (SlPCNA). Considering conservation, location and presence of sumoylation domain criteria, we have identified some candidate lysines and studied how its mutation affects this protein sumoylation in Escherichia coli assays. Finally, we plan to confirm and characterize the Rep interference on SlPCNA sumoylation and determine if this interference occurs in planta.Universidad de Málaga. Campus de Excelencia Internacional AndalucĂa Tech
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