345 research outputs found
Valence fluctuations in a lattice of magnetic molecules: application to iron(II) phtalocyanine molecules on Au(111)
We study theoretically a square lattice of the organometallic Kondo adsorbate
iron(II) phtalocyanine (FePc) deposited on top of Au(111), motivated by recent
scanning tunneling microscopy experiments. We describe the system by means of
an effective Hubbard-Anderson model, where each molecule has degenerate
effective orbitals with and symmetry, which we solve for
arbitrary occupation and arbitrary on-site repulsion . To that end, we
introduce a generalized slave-boson mean-field approximation (SBMFA) which
correctly describes both the non-interacting limit (NIL) and the
strongly-interacting limit , where our formalism
reproduces the correct value of the Kondo temperature for an isolated FePc
molecule. Our results indicate that while the isolated molecule can be
described by an SU(4) Anderson model in the Kondo regime, the case of the
square lattice corresponds to the intermediate-valence regime, with a total
occupation of nearly 1.65 holes in the FePc molecular orbitals. Our results
have important implications for the physical interpretation of the experiment.Comment: 7 pages, 2 figure
Dissipation-driven superconductor-insulator transition in linear arrays of Josephson junctions capacitively coupled to metallic films
We study the low-temperature properties of linear Josephson-junction arrays
capacitively coupled to a proximate two-dimensional diffusive metal. Using
bosonization techniques, we derive an effective model for the array and obtain
its critical properties and phases at T = 0 using a renormalization group
analysis and a variational approach. While static screening effects given by
the presence of the metal can be absorbed in a renormalization of the
parameters of the array, backscattering originated in the dynamically screened
Coulomb interaction produces a non-trivial stabilization of the insulating
groundstate and can drive a superconductor-insulator transition. We study the
consequences for the transport properties in the low-temperature regime. In
particular, we calculate the resisitivity as a function of the temperature and
the parameters of the array, and obtain clear signatures of a
superconductor-insulator transition that could be observed in experiments.Comment: 10 pages, 5 figures, submitted to Physical Review
Dissipative phase-fluctuations in superconducting wires capacitively coupled to diffusive metals
We study the screening of the Coulomb interaction in a quasi one-dimensional
superconductor given by the presence of either a one- or a two-dimensional
non-interacting electron gas. To that end, we derive an effective low-energy
phase-only action, which amounts to treating the Coulomb and superconducting
correlations in the random-phase approximation. We concentrate on the study of
dissipation effects in the superconductor, induced by the effect of Coulomb
coupling to the diffusive density-modes in the metal, and study its
consequences on the static and dynamic conductivity. Our results point towards
the importance of the dimensionality of the screening metal in the behavior of
the superconducting plasma mode of the wire at low energies. In absence of
topological defects, and when the screening is given by a one-dimensional
electron gas, the superconducting plasma mode is completely damped in the limit
, and consequently superconductivity is lost in the wire. In contrast,
we recover a Drude-response in the conductivity when the screening is provided
by a two-dimensional electron gas.Comment: 16 pages, 8 figures, 1 table, 2 appendice
Estilos de vida en relación a la alimentación y hábitos alimentarios dentro y
Lobos, G (Lobos, German). Univ Talca, Fac Ciencias Empresariales, Escuela Ingn Comercial, Talca, ChileResumen
Objetivo: Distinguir tipologÃas de consumidores en base a su
estilo de vida en relación a la alimentación en las principales
comunas de la Región Metropolitana de Santiago, Chile, y caracterizarlas
según sus hábitos de consumo de alimentos dentro y
fuera del hogar, caracterÃsticas sociodemográficas y su nivel de
satisfacción con su alimentación.
Material y método: Se aplicó un cuestionario estructurado a
una muestra de 951 personas en las principales comunas de la
Región Metropolitana de Santiago (más de 100.000 habitantes).
El instrumento de recogida de información incluyó una adaptación
del cuestionario de estilos de vida en relación a la alimentación
(FRL) y la escala SWFL (Satisfaction with Food-related
Life). Se consultaron los hábitos de consumo de alimentos dentro
y fuera del hogar y variables de clasificación sociodemográfica de
los encuestados.
Resultados: Mediante análisis cluster se distinguieron cinco
tipologÃas con diferencias significativas en los cinco componentes
obtenidos del FRL, con análisis factorial de componentes principales.
Las tipologÃas presentaron distinto perfil de género, edad y
nivel socioeconómico y difirieron en los puntajes obtenidos en la
SWFL. Se diferenciaron en la frecuencia en que la persona
almuerza, toma once y cena en su hogar. Respecto a las comidas
fuera del hogar, las tipologÃas se distinguieron según la frecuencia
de comidas en restaurantes, locales de comida rápida y en la compra
de comida preparada.
Conclusiones: Un estilo de vida en relación a la alimentación con
baja implicación y disfrute de los alimentos se asocia con un mayor
nivel socioeconómico y menor edad de las personas. Adicionalmente,
se asocia con comportamientos alimentarios poco saludables
y no beneficiosos para las personas, como una mayor frecuencia
de comidas en restaurantes y de compra de comida preparada,
junto a una menor frecuencia de comidas en el hogar, lo que estarÃa
influyendo en un nivel inferior de satisfacción con la alimentación
Preferencias hacia carne de cordero en supermercados de Temuco, región de la AraucanÃa, Chile
Lobos, G (Lobos, German). Univ Talca, Escuela Ingn Comercial, Talca, ChileThe low levels of consumption of lamb meat in Chile suggest the need for studies on consumer preferences in order to orient production. A study with this object was carried out to evaluate preferences for various cuts, breeds, state (fresh or frozen) and price of lamb's meat among supermarket buyers in Temuco, Chile, and the existence of different market segments, through a survey of 400 persons. Using a fractional factorial design for conjoint analysis, it was determined that the state of the meat was more important than the cut, the price and the breed, with a preference for meat in half carcasses and quarters, Araucano lamb, fresh, at a medium price level. Four consumer segments were distinguished by analysis of hierarchic conglomerates. The majority group (47.7%) was sensitive to the state and the cut, with preference for meat in quarters, fresh, Texel breed. The second group (25.3%) was sensitive to the breed, presenting the strongest preferences for meat in whole carcass, fresh, Araucano lamb. The third group (14.3%) was sensitive to the price, preferred meat in quarters, fresh, Araucano lamb. The minority group (12.7%) was sensitive to the state and price, preferring meat in quarters, Texel breed, and was the only group which preferred frozen meat and would pay a higher price. The segments were distinguished by age, ethnic origin and satisfaction with food-related life. Thus the commercialisation strategy for lamb in supermarkets in Temuco should concentrate principally on the sale of fresh meat cut in quarter
Papel del método biplot canónico en el estudio de compuestos volátiles en quesos de composición variable
The canonical biplot method (CB) is used to determine the discriminatory power of volatile chemical compounds in cheese. These volatile compounds were used as variables in order to differentiate among 6 groups or populations of cheeses (combinations of two seasons (winter and summer) with 3 types of cheese (cow, sheep and goat’s milk). We analyzed a total of 17 volatile compounds by means of gas chromatography coupled with mass detection. The compounds included aldehydes and methyl-aldehydes, alcohols (primary, secondary and branched chain), ketones, methyl-ketones and esters in winter (WC) and summer (SC) cow’s cheeses, winter (WSh) and summer (SSh) sheep’s cheeses and in winter (WG) and summer (SG) goat’s cheeses. The CB method allows differences to be found as a function of the elaboration of the cheeses, the seasonality of the milk, and the separation of the six groups of cheeses, characterizing the specific volatile chemical compounds responsible for such differences.El m.todo biplot can.nico (CB) se utiliza para determinar el poder discriminatorio de compuestos qu.micos vol.tiles en queso. Los compuestos vol.tiles se utilizan como variables con el fin de diferenciar entre los 6 grupos o poblaciones de quesos (combinaciones de dos temporadas (invierno y verano) con 3 tipos de queso (vaca, oveja y cabra). Se analizan un total de 17 compuestos vol.tiles por medio de cromatograf.a de gases acoplada con detecci.n de masas. Los compuestos incluyen aldeh.dos y metil-aldeh.dos, alcoholes (primarios de cadena, secundaria y ramificada), cetonas, metil-cetonas y .steres. Los seis grupos de quesos son, quesos de vaca de invierno (WC) y verano (SC); quesos de oveja de invierno (WSh) y verano (SSh) y quesos de cabra de invierno (WG) y verano (SG). El m.todo CB permite la separaci.n de los seis grupos de quesos y encontrar las diferencias en funci.n del tipo y estacionalidad de la leche, caracterizando los compuestos qu.micos vol.tiles espec.ficos responsables de tales diferencias
Isolation and characterization of homokaryotic strains from the ligninolytic basidiomycete Ceriporiopsis subvermispora
Indexación: Scopus.Genetic analyses of the lignin-degrading fungus Ceriporiopsis subvermispora is complicated by a dikaryotic nuclear condition and the absence of spore forms. Previous investigations had identified a family of closely related sequences encoding manganese peroxidase (MnP), but the relationship between genes and allelic variants could not be experimentally established. Addressing this issue, homokaryotic derivatives of C. subvermipora strain FP105752 were isolated from regenerated protoplasts. Designated CsA and CsB, their homokaryotic nature was established by polymerase chain reaction amplification and sequence analysis of the allelic variants of three MnP genes. Isoelectrofocusing revealed fewer MnP isoenzymes in filtrates of homokaryon cultures relative to the parental strain. The homokaryotic strains will simplify genetic analyses, particularly the identification of new genes.https://academic-oup-com.recursosbiblioteca.unab.cl/femsle/article/199/1/91/55387
Interleukin-10 Production by T and B Cells Is a Key Factor to Promote Systemic Salmonella enterica Serovar Typhimurium Infection in Mice
Indexción: Scopus.Salmonella enterica serovar Typhimurium (S. Typhimurium) is a Gram-negative bacterium that produces disease in numerous hosts. In mice, oral inoculation is followed by intestinal colonization and subsequent systemic dissemination, which leads to severe pathogenesis without the activation of an efficient anti-Salmonella immune response. This feature suggests that the infection caused by S. Typhimurium may promote the production of anti-inflammatory molecules by the host that prevent efficient T cell activation and bacterial clearance. In this study, we describe the contribution of immune cells producing the anti-inflammatory cytokine interleukin-10 (IL-10) to the systemic infection caused by S. Typhimurium in mice. We observed that the production of IL-10 was required by S. Typhimurium to cause a systemic disease, since mice lacking IL-10 (IL-10-/-) were significantly more resistant to die after an infection as compared to wild-type (WT) mice. IL-10-/- mice had reduced bacterial loads in internal organs and increased levels of pro-inflammatory cytokines in serum at 5 days of infection. Importantly, WT mice showed high bacterial loads in tissues and no increase of cytokines in serum after 5 days of S. Typhimurium infection, except for IL-10. In WT mice, we observed a peak of il-10 messenger RNA production in ileum, spleen, and liver after 5 days of infection. Importantly, the adoptive transfer of T or B cells from WT mice restored the susceptibility of IL-10-/- mice to systemic S. Typhimurium infection, suggesting that the generation of regulatory cells in vivo is required to sustain a systemic infection by S. Typhimurium. These findings support the notion that IL-10 production from lymphoid cells is a key process in the infective cycle of S. Typhimurium in mice due to generation of a tolerogenic immune response that prevents bacterial clearance and supports systemic dissemination
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