184 research outputs found
Numerical method for analysis of the correlation between ferrofluid optical transmission and its intrinsic properties
A numerical method to simulate the ferrofluid particle distribution evolution is presented. Also, the optical transmission of the distributions obtained is calculated by two numerical methods. The first one consists on a numerical propagation of an electromagnetic wave through the sample. The second one analyzes the aggregates’ mean length to obtain the optical transmission through a mixture law. As an illustration of the possibilities of the method developed, it is applied to analyze how ferrofluid optical transmission changes after magnetic field application depend on intrinsic properties of the colloid such as its nanoparticle concentration and surfactant repulsion represented by means of the final distances between consecutive particles forming chains. Changes in the attenuation factor of these samples show the trends expected from the Literature
Analysis of the optical transmission of a ferrofluid by an electromagnetic mixture law
Evolution of the optical transmission of a ferrofluid after magnetic field commutation is analyzed by means of an approach based on the so-called mixture laws: expressions which predict the effective permittivity of heterogeneous media as a function of their constituents' permittivities, their proportions and the way they are arranged. In particular, this work is based on a law proposed by Sihvola and Kong for the effective permittivity of a host substance with ellipsoidal inclusions. Ferrofluids are peculiar examples of this kind of media: with the solvent as host, the inclusions are nanoparticle agglomerates whose shapes become modified by magnetic field exposure. In this work, experimental optical transmission of a ferrofluid is compared with predictions based on Sihvola and Kong''s law. A remarkable coincidence is obtained both in the absence of magnetic field, without using any fitting parameter, and in the presence of magnetic field, employing the inclusions' average ellipticity as the fitting parameter. The results obtained for time dependent optical transmission of a ferrofluid after magnetic field switch on or off allow one to estimate how the average shape of the agglomerates evolves over time. On the other hand, mixture laws are proven to be an interesting alternative to scattering concepts to model the optical transmission changes experienced by ferrofluids once they are exposed to magnetic fields
Two-dimensional multiscale entropy analysis: applications to image texture evaluation
Complexity measures, defined as measures of irregularity over time scales, are the subject of a growing number of studies as the information they reveal can find utility in a large field of applications. One of the most popular complexity measures is the multiscale entropy. Nevertheless, more and more algorithms dedicated to complexity analyses are proposed to improve the existing ones. However, such measures are available only for one-dimensional time series. For bidimensional data (images), no equivalent algorithm has been proposed to analyze irregularity over spatial scales. We herein introduce a new framework that extends the one-dimensional multiscale entropy (MSE1D) to the bidimensional case (MSE2D). Moreover, a variant of MSE2D is also ModMSE2D). The two new algorithms are tested as new texture analysis frameworks. They are applied to simulated and real data. Our results show that, compared with other existing texture analysis algorithms, MSE2D and ModMSE2D are suitable and powerful tools for image analysis and classification according to their texture patterns. While MSE2D is computationally faster than ModMSE2D, ModMSE2D is more robust to small image sizes. The two methods present interesting performances, and can be as useful as their unidimensional versions in two-dimensional applications
Impact of grass cover management with herbicides on biodiversity, soil cover and humidity in olive groves in the Southern Iberian
In the present work, we studied the effect of herbicide use on extensive olive grove cultivation. To carry out this study, we analysed the effect that herbicide use had on biodiversity, vegetation cover and soil water content. For this purpose, 96 vegetation and soil sampling points were first taken, then georeferenced, and for each sampling point, several bioclimatic variables were interpolated. We concluded that the management of cover crops with herbicides over a long period of time resulted in a decrease in biodiversity, and the dominance of some species that were more resistant to herbicides was increased. Another finding was that the vegetation cover was reduced in the resampling in cases with herbicide management and that the location within the cropland (under the tree canopy, road, boundary or pasture) also has an influence. Finally, the study of soil moisture shows that soil water content was lower in the case of management with herbicides than in the case of management without herbicides. This loss of soil moisture was more accentuated and faster in areas with less vegetation cover. This work highlights the need to change the management models for tree crops in order to preserve biodiversity, soil quality and optimise water resources in a context of accelerated climate change in one of the regions most severely affected by global warming, the Mediterranean belt.info:eu-repo/semantics/publishedVersio
Fermion family recurrences in the Dyson-Schwinger formalism
We study the multiple solutions of the truncated propagator Dyson-Schwinger
equation for a simple fermion theory with Yukawa coupling to a scalar field.
Upon increasing the coupling constant , other parameters being fixed, more
than one non-perturbative solution breaking chiral symmetry becomes possible
and we find these numerically. These ``recurrences'' appear as a mechanism to
generate different fermion generations as quanta of the same fundamental field
in an interacting field theory, without assuming any composite structure. The
number of recurrences or flavors is reduced to a question about the value of
the Yukawa coupling, and has no special profound significance in the Standard
Model. The resulting mass function can have one or more nodes and the
measurement that potentially detects them can be thought of as a collider-based
test of the virtual dispersion relation for the charged
lepton member of each family. This requires three independent measurements of
the charged lepton's energy, three-momentum and off-shellness. We illustrate
how this can be achieved for the (more difficult) case of the tau lepton
Omega®: metodología para la previsión del accidente en poblaciones laborales. aplicación a microempresas
En el presente artículo se plantea una nueva interpretación conceptual del accidente en poblaciones laborales, complementada con un desarrollo metodológico, también novedoso, orientado a su análisis.
El fundamento de dicha interpretación se centra en la "Teoría del Accidente en Poblaciones"(Conte, 2004), teoría en construcción destinada a explicar científicamente dicho "fenómeno natural". Se expone una metodología dirigida a su
"previsión sinóptica" (Conte, J.C. et al.,2004) que abre una nueva etapa en la "prevención del accidente laboral".
Las implicaciones de esta orientación en las diversas fases de gestión preventiva, plantean un
escenario de base objetiva sobre el que poder abordar de forma unificada, tanto la previsión como el control del accidente.N
Método omega®: aplicación a pequeñas y grandes empresas
El presente artículo es una continuación de otro anterior en el que se describe el método OMEGA® y se da un ejemplo de su aplicación al caso de las "microempresas". En este artículo se desarrollan dos nuevos ejemplos referidos a una
"pequeña empresa" (una "estación de esquí" de 130 trabajadores), y a una "gran empresa" ("General Motors España", con 9000 trabajadores). Se comparan los "índices de accidentalidad" de cada una de estas empresas con los resultados obtenidos por OMEGA®.N
Multiple myeloma primary cells show a highly rearranged unbalanced genome with amplifications and homozygous deletions irrespective of the presence of immunoglobulin-related chromosome translocations
Background and Objectives
Multiple myeloma (MM) is a malignant plasma cell neoplasia in which genetic studies
have shown that genomic changes may affect almost all chromosomes, as shown
by fluorescence in situ hybridization (FISH) and comparative genomic hybridization
(CGH). Our objective was the genomic characterization of CD 138 positive primary MM
samples by means of a high resolution array CGH platform.
Design and Methods
For the first time, a high resolution array CGH with more than 40,000 probes, has
been used to analyze 26 primary MM samples after the enrichment of CD138-positive
plasma cells.
Results
This approach identified copy number imbalances in all cases. Bioinformatics strategies
were optimized to perform data analysis allowing the segregation of hyperdiploid
and non-hyperdiploid cases by array CGH. Additional analysis showed that structural
chromosome rearrangements were more frequently seen in hyperdiploid cases. We
also identified the same Xq21 duplication in nearly 20% of the cases, which originated
through unbalanced chromosome translocations. High level amplifications and
homozygous deletions were recurrently observed in our series and involved genes
with meaningful function in cancer biology.
Interpretation and Conclusions
High resolution array CGH allowed us to identify copy number changes in 100% of the
primary MM samples. We segregated different MM subgroups based on their genomic
profiles which made it possible to identify homozygous deletions and amplifications
of great genetic relevance in MM
Chromosomal abnormalities clustering in multiple myeloma reveals cytogenetic subgroups with nonrandom acquisition of chromosomal changes
Epigenetic Signatures Associated with Different Levels of Differentiation Potential in Human Stem Cells
The therapeutic use of multipotent stem cells depends on their differentiation potential, which has been
shown to be variable for different populations. These differences are likely to be the result of key changes in their epigenetic
profiles
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