4,544 research outputs found
Phase transition in a super superspin glass
We here confirm the occurrence of spin glass phase transition and extract
estimates of associated critical exponents of a highly monodisperse and densely
compacted system of bare maghemite nanoparticles. This system has earlier been
found to behave like an archetypal spin glass, with e.g. a sharp transition
from paramagnetic to non-equilibrium behavior, suggesting that this system
undergoes a spin-glass phase transition at a relatively high temperature,
140 K.Comment: 4 pages, 3 figure
Lifestyle Influence on the Content of Copper, Zinc and Rubidium in Wild Mushrooms
The concentration of 18 trace elements in several species of fungi (arranged in three groups: ectomycorrhizae, saprobes, and epiphytes) has been determined. The measurements were made using the methodology of X-ray fluorescence. Higher contents of Cu and Rb (with statistical support) have been found in the ectomycorrhizal species. The Zn content reached higher concentrations in the saprophytic species. According to the normality test and the search for outliers, the species Clitocybe maxima and Suillus bellini accumulate large amounts of Cu and Rb, respectively, so that both can be named as “outliers.” The leftwards displacement of the density curves and their nonnormality are attributed to the presence of these two species, which exhibit hyperaccumulation skills for Cu and Rb, respectively. Regarding Zn absorption, no particular species were classified as outlier; therefore it can be assumed that the observed differences between the different groups of fungi are due to differences in their nutritional physiology
Geoquímica de las rocas del stock Chinchiná - Santa Rosa
In this study, appears the first analytical results of major elements, trace and rare earth of the protomilonitas of the Stock Chinchiná-Santa Rosa, it is in the Western flank of the Central belt, between the faults Silvia-Pijao, eastwards and Cauca-Almaguer, on the west. The geochemistry characterization in the rocks that they formed in the Stock indicates that this one belongs to the subalkaline series with character toleítico and they are clasified like gabbros and madaly as metagabbro that change according to the grade of deformation between the cataclasites and the milonites. Tectonic discrimination diagrams, allowed to establish that the generation of intrusive body in an dominion distensive of dorsal oceanic type N-MORB; the identification of this environment will allow to set this body in a geotectonic position, forming a part of a complex ophiolitic.En este estudio, se presentan los primeros resultados analíticos de elementos mayores, traza y tierras raras de las rocas que conforman el Stock Chinchiná-Santa Rosa, localizado en el flanco Occidental de la Cordillera Central, entre las fallas Silvia-Pijao, al este y Cauca-Almaguer, al oeste. Los datos geoquímicos de este cuerpo indican que pertenece a la serie subalcalina con carácter toleítico, geoquímicamente se clasifican como gabros y modalmente como metagabros con un grado de deformación que varía de cataclasita a milonita. Los diagramas de discriminación tectónica, permiten establecer que la generación del cuerpo intrusivo ocurrió en un dominio distensivo de dorsal oceánica tipo N-MORB; la identificación de este ambiente permite posicionar geotectónicamente a este cuerpo, como parte de un complejo ofiolítico.
 
EVIDENCES OF THE EARLY CRETACEOUS VOLCANISM IN THE YAVI FORMATION NEAR THE ATACO (TOLIMA) COLOMBIA AND ITS GEODYNAMICS IMPLICATIONS
Proximal volcanism deposits are reported by the first time inter-bedded in Early Cretaceous age sedimentites at the Upper Magdalena Valley. Lapilli tuff, ignimbrites and coarse ash tuff were found outcropping along the road Ataco-Coyaima (Tolima Department) at the upper part of the Yaví Formation. The volcanic rocks fall in the subalcaline and toleitic fields. It is speculate if that volcanism could have connection with contemporary magmatic activity at the Quebradagrande Complex, Oriente basin in Ecuador and Cundinamarca sub-basin in Colombia.
Key words: Volcanism, Yaví Formation, Early Cretaceous, Geodinamic
Por primera vez se reportan productos de volcanismo proximal en depósitos de edad Cretácica Temprana del Valle Superior del Magdalena. Tobas riodacíticas, ignimbritas y tobas de lapilli fueron identificadas en la parte superior de la Formación Yaví entre Ataco y Coyaima (Departamento del Tolima). Las rocas volcánicas se ubican en los campos subalcalino y toleítico. Se especula sobre las relaciones que este volcanismo podría tener con fenómenos magmáticos contemporáneos en el Complejo Quebradagrande, cuenca de Oriente en Ecuador y subcuenca de Cundinamarca en Colombia.
Palabras clave: Volcanismo, Formación Yaví, Cretácico Temprano, Geodinámico
 
Geoquímica de las rocas del stock Chinchiná - Santa Rosa
In this study, appears the first analytical results of major elements, trace and rare earth of the protomilonitas of the Stock Chinchiná-Santa Rosa, it is in the Western flank of the Central belt, between the faults Silvia-Pijao, eastwards and Cauca-Almaguer, on the west. The geochemistry characterization in the rocks that they formed in the Stock indicates that this one belongs to the subalkaline series with character toleítico and they are clasified like gabbros and madaly as metagabbro that change according to the grade of deformation between the cataclasites and the milonites. Tectonic discrimination diagrams, allowed to establish that the generation of intrusive body in an dominion distensive of dorsal oceanic type N-MORB; the identification of this environment will allow to set this body in a geotectonic position, forming a part of a complex ophiolitic.En este estudio, se presentan los primeros resultados analíticos de elementos mayores, traza y tierras raras de las rocas que conforman el Stock Chinchiná-Santa Rosa, localizado en el flanco Occidental de la Cordillera Central, entre las fallas Silvia-Pijao, al este y Cauca-Almaguer, al oeste. Los datos geoquímicos de este cuerpo indican que pertenece a la serie subalcalina con carácter toleítico, geoquímicamente se clasifican como gabros y modalmente como metagabros con un grado de deformación que varía de cataclasita a milonita. Los diagramas de discriminación tectónica, permiten establecer que la generación del cuerpo intrusivo ocurrió en un dominio distensivo de dorsal oceánica tipo N-MORB; la identificación de este ambiente permite posicionar geotectónicamente a este cuerpo, como parte de un complejo ofiolítico.
 
EVIDENCES OF THE EARLY CRETACEOUS VOLCANISM IN THE YAVI FORMATION NEAR THE ATACO (TOLIMA) COLOMBIA AND ITS GEODYNAMICS IMPLICATIONS
Proximal volcanism deposits are reported by the first time inter-bedded in Early Cretaceous age sedimentites at the Upper Magdalena Valley. Lapilli tuff, ignimbrites and coarse ash tuff were found outcropping along the road Ataco-Coyaima (Tolima Department) at the upper part of the Yaví Formation. The volcanic rocks fall in the subalcaline and toleitic fields. It is speculate if that volcanism could have connection with contemporary magmatic activity at the Quebradagrande Complex, Oriente basin in Ecuador and Cundinamarca sub-basin in Colombia.
Key words: Volcanism, Yaví Formation, Early Cretaceous, Geodinamic
Por primera vez se reportan productos de volcanismo proximal en depósitos de edad Cretácica Temprana del Valle Superior del Magdalena. Tobas riodacíticas, ignimbritas y tobas de lapilli fueron identificadas en la parte superior de la Formación Yaví entre Ataco y Coyaima (Departamento del Tolima). Las rocas volcánicas se ubican en los campos subalcalino y toleítico. Se especula sobre las relaciones que este volcanismo podría tener con fenómenos magmáticos contemporáneos en el Complejo Quebradagrande, cuenca de Oriente en Ecuador y subcuenca de Cundinamarca en Colombia.
Palabras clave: Volcanismo, Formación Yaví, Cretácico Temprano, Geodinámico
 
A model of Mira's cometary head/tail entering the Local Bubble
We model the cometary structure around Mira as the interaction of an AGB wind
from Mira A, and a streaming environment. Our simulations introduce the
following new element: we assume that after 200 kyr of evolution in a dense
environment Mira entered the Local Bubble (low density coronal gas). As Mira
enters the bubble, the head of the comet expands quite rapidly, while the tail
remains well collimated for a 100 kyr timescale. The result is a
broad-head/narrow-tail structure that resembles the observed morphology of
Mira's comet. The simulations were carried out with our new adaptive grid code
WALICXE, which is described in detail.Comment: 12 pages, 8 figures (4 in color). Accepted for publication in The
Astrophysical Journa
Proteome analysis during a new chondrogenesis model from mesenchymal stem cells of human umbilical cord stroma
Comunicaciones a congreso
P-T OF THE ACTINOLITIC SCHIST OF THE CAJAMARCA COMPLEX TO THE SOUTHEAST THE MONTEBELLO, ANTIOQUIA
La historia de evolución presión y temperatura (P-T) para los esquistos actinolíticos en el sector suroccidental del municipio de Montebello, departamento de Antioquia, revelan un peak de temperaturas entre 320 a 475 ºC y presiones de 2 a 6 kilobares, con base en las relaciones texturales y termobarométricas de los minerales metamórficos. Los datos de (P-T-t) definen una posible trayectoria antihoraria y en el campo de las facies de los esquistos verdes. El protolito de estas rocas corresponde a basaltos generados en zonas de dorsal oceánica confirmado, además, por la fase mineral ígnea.
Palabras claves: Termobarometría, esquistos actinolíticos, Complejo Cajamarca
The P-T conditions were determinated in actinolitics schist of the basament of the Colombian Central Cordillera, in the southeast sector of Montebello, (Antioquia), the estimation of the pressure and temperature conditions was from 320 to 475 °C and 2 to 6 kbar; according to the textural and thermobarometric relations of the metamorphic minerals. A reconstruction in space and time of these P-T-t paths allows an estimate counterclockwise evolution in the greenschist facies field. The protolith of these rocks indicates them to be derived from oceanic floor basalts, in adition, for the igneous mineral phase.
Key words : Thermobarometry, actinolitic schist, Cajamarca Complex
 
Phase transitions of hadronic to quark matter at finite T and \mu_B
The phase transition of hadronic to quark matter and the boundaries of the
mixed hadron-quark coexistence phase are studied within the two Equation of
State (EoS) model. The relativistic effective mean field approach with constant
and density dependent meson-nucleon couplings is used to describe hadronic
matter, and the MIT Bag model is adopted to describe quark matter. The
boundaries of the mixed phase for different Bag constants are obtained solving
the Gibbs equations.
We notice that the dependence on the Bag parameter of the critical
temperatures (at zero chemical potential) can be well reproduced by a fermion
ultrarelativistic quark gas model, without contribution from the hadron part.
At variance the critical chemical potentials (at zero temperature) are very
sensitive to the EoS of the hadron sector. Hence the study of the hadronic EoS
is much more relevant for the determination of the transition to the
quark-gluon-plasma at finite baryon density and low-T. Moreover in the low
temperature and finite chemical potential region no solutions of the Gibbs
conditions are existing for small Bag constant values, B < (135 MeV)^4. Isospin
effects in asymmetric matter appear relevant in the high chemical potential
regions at lower temperatures, of interest for the inner core properties of
neutron stars and for heavy ion collisions at intermediate energies.Comment: 24 pages and 16 figures (revtex4
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