752 research outputs found
Estudio comparativo de la influencia de las fibras en la retracción de los morteros reciclados
Construction and demolition waste can be used as a substitution of natural aggregate in mortar and concrete elaboration. A poorer quality of recycled aggregates generally has negative impact on mortar properties. Shrinkage is one of the properties that experiences worse outcome due to the higher absorption of recycled aggregates. This research evaluates the potential shrinkage of mortars elaborated with recycled concrete aggregates both with and without fibres addition, as well as the relation between moisture loss and shrinkage caused by mortar drying process using a capacitive sensor of the authors’ own design. Two different mortar dosages 1:3 and 1:4 and three fiber types: polypropylene fiber, fiberglass and steel fiber, in different proportions were used. Obtained results show that the use of polypropylene fiber improves the recycled mortars performance against shrinkage in 0.2%. Moreover, a clear relation between dry shrinkage and moisture loss was observed.Los Residuos de Construcción y Demolición pueden ser usados como sustitución de los áridos naturales en la fabricación de morteros y hormigones. La peor calidad de los áridos reciclados empeora de manera general las propiedades de los morteros, siendo la retracción una de las que más se ve afectada. Esta investigación, estudia la retracción de los morteros elaborados con arena reciclada de hormigón con y sin adicción de fibras, así como la relación existente entre la perdida de humedad y la retracción por secado mediante un sensor capacitivo de diseño propio. Se han empleado dos dosificaciones diferentes 1:3 y 1:4 y tres tipos de fibras: polipropileno, vidrio y acero, en distintas proporciones. Los resultados muestran que la adición de fibras de polipropileno en un 0,2% mejora significativamente la retracción en los morteros reciclados. Además, se ha obtenido una relación clara entre la retracción por secado y la perdida de humedad
Crambescidin-816 Acts as a Fungicidal with More Potency than Crambescidin-800 and -830, Inducing Cell Cycle Arrest, Increased Cell Size and Apoptosis in Saccharomyces cerevisiae
In this paper, we show the effect of crambescidin-816, -800, and -830 on Saccharomyces cerevisiae viability. We determined that, of the three molecules tested, crambescidin-816 was the most potent. Based on this result, we continued by determining the effect of crambescidin-816 on the cell cycle of this yeast. The compound induced cell cycle arrest in G2/M followed by an increase in cell DNA content and size. When the type of cell death was analyzed, we observed that crambescidin-816 induced apoptosis. The antifungal effect indicates that crambescidins, and mostly crambescidin-816, could serve as a lead compound to fight fungal infectionsThe research leading to these results has received funding from the following FEDER cofunded-grants: From Ministerio de Ciencia y Tecnología, Spain: AGL2009-13581-CO2-01, AGL2012-40485-CO2-01. From Xunta de Galicia, Spain: 10PXIB261254 PR. From the European Union’s Seventh Framework Programme managed by REA—Research Executive Agency (FP7/2007-2013) under grant agreement Nos. 211326—CP (CONffIDENCE), 265896 BAMMBO, 265409 µAQUA, and 262649 BEADS, 315285 Ciguatools and 312184 PharmaSea. From the Atlantic Area Programme (Interreg IVB Trans-national): 2009-1/117 PharmatlanticS
Emission spectra of atoms with non-Markovian interaction: Fluorescence in a photonic crystal
We present a formula to evaluate the spontaneous emission spectra of an atom
in contact with a radiation field with non-Markovian effects. This formula is
written in terms of a two-time correlation of system observables and the
environmental correlation function, and depends on the distance between the
emitting atom and the detector. As an example, we use it to analyze the
fluorescence spectra of a two level atom placed as an impurity in a photonic
crystal. The radiation field within those materials has a gap or discontinuity
where electromagnetic modes cannot propagate in the stationary limit. In that
situation, the atomic emission occurs in the form of evanescent waves which are
detected with less efficiency the farther we place the detector. The
methodology presented in this paper may be useful to study the non-Markovian
dynamics of any quantum open system in linear interaction with a harmonic
oscillator reservoir and within the weak coupling approximation
Modeling the spectral energy distribution of ULIRGs I: the radio spectra
As a constraint for new starburst/AGN models of IRAS bright galaxies we
determine the radio spectra of 31 luminous and ultraluminous IRAS galaxies
(LIRGs/ULIRGs). We construct the radio spectra using both new and archival
data. From our sample of radio spectra we find that very few have a straight
power-law slope. Although some sources show a flattening of the radio spectral
slope at high frequencies the average spectrum shows a steepening of the radio
spectrum from 1.4 to 22.5 GHz. This is unexpected because in sources with high
rates of star formation we expect flat spectrum, free-free emission to make a
significant contribution to the radio flux at higher radio frequencies. Despite
this trend the radio spectral indices between 8.4 and 22.5 GHz are flatter for
sources with higher values of the FIR-radio flux density ratio q, when this is
calculated at 8.4 GHz. Therefore, sources that are deficient in radio emission
relative to FIR emission (presumably younger sources) have a larger thermal
component to their radio emission. However, we find no correlation between the
radio spectral index between 1.4 and 4.8 GHz and q at 8.4 GHz. Because the low
frequency spectral index is affected by free-free absorption, and this is a
function of source size for a given mass of ionized gas, this is evidence that
the ionized gas in ULIRGs shows a range of densities. The youngest LIRGs and
ULIRGs are characterized by a larger contribution to their high-frequency radio
spectra from free-free emission. However, the youngest sources are not those
that have the greatest free-free absorption at low radio frequencies. The
sources in which the effects of free-free absorption are strongest are instead
the most compact sources. Although these have the warmest FIR colours, they are
not necessarily the youngest sources.Comment: 16 pages. Submitted to A&A Re-submitted, with aesthetic improvements
to the text and figure
Kinks in the Hartree approximation
The topological defects of the lambda phi^4 theory, kink and antikink, are
studied in the Hartree approximation. This allows us to discuss quantum effects
on the defects in both stationary and dynamical systems. The kink mass is
calculated for a number of parameters, and compared to classical, one loop and
Monte Carlo results known from the literature. We discuss the thermalization of
the system after a kink antikink collision. A classical result, the existence
of a critical speed, is rederived and shown for the first time in the quantum
theory. We also use kink antikink collisions as a very simple toy model for
heavy ion collisions and discuss the differences and similarities, for example
in the pressure. Finally, using the Hartree Ensemble Approximation allows us to
study kink antikink nucleation starting from a thermal (Bose Einstein)
distribution. In general our results indicate that on a qualitative level there
are few differences with the classical results, but on a quantitative level
there are some import ones.Comment: 20 pages REVTeX 4, 17 Figures. Uses amsmath.sty and subfigure.sty.
Final version, fixed typo in published versio
The starburst-AGN connection in the merger galaxy Mrk 938: an infrared and X-ray view
Mrk938 is a luminous infrared galaxy in the local Universe believed to be the
remnant of a galaxy merger. It shows a Seyfert 2 nucleus and intense star
formation according to optical spectroscopic observations. We have studied this
galaxy using new Herschel far-IR imaging data in addition to archival X-ray,
UV, optical, near-IR and mid-IR data. Mid- and far-IR data are crucial to
characterise the starburst contribution, allowing us to shed new light on its
nature and to study the coexistence of AGN and starburst activity in the local
Universe. The decomposition of the mid-IR Spitzer spectrum shows that the AGN
bolometric contribution to the mid-IR and total infrared luminosity is small
(Lbol(AGN)/LIR~0.02), which agrees with previous estimations. We have
characterised the physical nature of its strong infrared emission and
constrained it to a relatively compact emitting region of <2kpc. It is in this
obscured region where most of the current star formation activity is taking
place as expected for LIRGs. We have used Herschel imaging data for the first
time to constrain the cold dust emission with unprecedented accuracy. We have
fitted the integrated far-IR spectral energy distribution and derived the
properties of the dust, obtaining a dust mass of 3x10^7Msun. The far-IR is
dominated by emission at 35K, consistent with dust heated by the on-going star
formation activity.Comment: 12 pages, 6 figures, 4 tables, accepted for publication in MNRA
Non-Markovian stochastic description of quantum transport in photosynthetic systems
We analyze several aspects of the transport dynamics in the LH1-RC core of
purple bacteria, which consists basically in a ring of antenna molecules that
transport the energy into a target molecule, the reaction center, placed in the
center of the ring. We show that the periodicity of the system plays an
important role to explain the relevance of the initial state in the transport
efficiency. This picture is modified, and the transport enhanced for any
initial state, when considering that molecules have different energies, and
when including their interaction with the environment. We study this last
situation by using stochastic Schr{\"o}dinger equations, both for Markovian and
non-Markovian type of interactions.Comment: 21 pages, 5 figure
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