292 research outputs found
Exposicion economica al tipo de cambio de las sociedades anonimas chilenas
68 p.Las empresas chilenas, en este caso las sociedades anónimas abiertas,
independientes de si tienen o no operaciones de comercio exterior tienen de una u otra
forma dependencia de las variaciones en el tipo de cambio. Sin embargo existe una limitada
gama de estudios relativos al tema en el ámbito local, y la evidencia disponible proviene en
su mayoría de economías desarrolladas.
En un reciente estudio, Chen et al. (2004) encuentra para Nueva Zelanda, economía
pequeña y abierta, evidencia que indicaría que para este país los movimientos del tipo de
cambio afectan el valor de las empresas transadas en bolsa. Basándose en la similitud con la
economía Neo Zelandesa, nace la inquietud de replicar ese estudio en Chile. Esta
investigación se justifica en el hecho de que a entender del autor no existen estudios
relacionados con el tema en Chile, siendo relevante por al menos dos razones: la alta
volatilidad que ha presentado el tipo de cambio desde que se adoptó la paridad flotante a
mediados del año 1999 (ver apéndice 1) y por el poco desarrollo del mercado de
instrumentos de cobertura.
El propósito fundamental de esta memoria es determinar el nivel de
exposición de las sociedades anónimas chilenas a variaciones en el tipo de
cambio, y analizar algunos factores potenciales que influyen en la magnitud de
esta exposición. Bajo la hipótesis de los mercados eficientes, el efecto del tipo de
cambio debería ser reflejado en el precio de acciones.
Las empresas que cumplen con los criterios de selección son 105, de las cuales
alrededor del 40% presenta un nivel significativo de exposición al riesgo de cambio. El
grado de exposición de las empresas en forma global es de carácter inverso, es decir, a
medida que aumenta el valor del tipo de cambio, el valor de las empresas disminuye. Cabe
destacar que la significancia económica es importante, esto se grafica en los montos que las
empresas ganan o pierden de su capitalización bursátil ante una variación del dólar. A
modo de ejemplo, la empresa menos afectada perdería aproximadamente 351 millones de
pesos ante la subida de un 1% del valor de la divisa
Alveolar recruitment with non-invasive mechanical ventilation (C-PAP) in patients with nonobstructive respiratory failure
VO2 indirect maximum and fitness age of sedentary and non-sedentary
El objetivo es: comparar la edad cronológica con la edad fitness obtenida
por medio del VO2 máximo indirecto, de un grupo de personas sedentarias y no
sedentarias. Método: 253 personas fueron evaluadas respecto a masa corporal,
estatura, perímetro de cintura, frecuencia cardiaca basal y un cuestionario del
modelo web "Fitness Calculator". Los resultados demostraron diferencias
significativas en las variables antropométricas y fisiológicas entre personas
sedentarias y no sedentarias (P<,001). Las personas no sedentarias tienen un
mayor VO2máx en comparación con las personas sedentarias. Las personas
sedentarias indican que presentan una edad fitness que se encuentra sobre 12
años cronológicos promedio de lo esperado. Conclusión: Las personas
sedentarias tienen una mayor edad fitness, esto permite establecer que su
cuerpo se deteriora más rápido que los no sedentarios. El bajo VO2 máx es un
potente predictor de la capacidad cardiorrespiratoria y se establece como un
predictor de enfermedades cardiovascularesThe purpose was to compare chronological age with fitness age obtained
through indirect VO2max in a group of sedentary and non-sedentary people.
Method: 253 people were evaluated for body mass, height, waist circumference,
basal heart rate and a web model questionnaire "Fitness Calculator". The
results: showed significant differences in anthropometric and physiological
variables between sedentary and non-sedentary people (P <.001). Non-
Sedentary people have a greater higher VO2máx group compared to sedentary
people. This indicates that sedentary people have a fitness age 12 years over
their expected chronological average age. Conclusion: Sedentary people have
a higher fitness age; therefore your body deteriorates faster than the nonsedentary
people. A low level of VO2máx is a powerful predictor of
cardiorespiratory capacity and of cardiovascular diseasesEl estudio fue financiado por la Escuela de Kinesiología de la Universidad Bernardo O`higgin
Network dynamics of encoding and retrieval of behavioural spike sequences during theta and ripples in a CA1 model of the hippocampus
Correlation effects in ionic crystals: I. The cohesive energy of MgO
High-level quantum-chemical calculations, using the coupled-cluster approach
and extended one-particle basis sets, have been performed for (Mg2+)n (O2-)m
clusters embedded in a Madelung potential. The results of these calculations
are used for setting up an incremental expansion for the correlation energy of
bulk MgO. This way, 96% of the experimental cohesive energy of the MgO crystal
is recovered. It is shown that only 60% of the correlation contribution to the
cohesive energy is of intra-ionic origin, the remaining part being caused by
van der Waals-like inter-ionic excitations.Comment: LaTeX, 20 pages, no figure
Ecohydrology and ecosystem services of a natural and an artificial bofedal wetland in the central Andes
High-altitude wetlands of the Central Andes, locally known as bofedales, provide important ecosystem services, particularly carbon storage, forage provisioning, and water regulation. Local communities have artificially expanded bofedales by irrigating surrounding grasslands to maximise areas for alpaca grazing. Despite their importance, biophysical processes of both natural and artificial bofedales are still poorly studied, which hinders the development of adequate management and conservation strategies. We analyse and compare the vegetation composition, hydrological variables, groundwater chemistry, and soil characteristics of a natural and an artificial bofedal of at least 10 years old in southern Peru, to understand their interrelations and the consequences for ecosystem service provisioning. We do not find statistically significant differences in the soil, water, and vegetation characteristics. Soil organic carbon (SOC) content, which we use as a proxy for carbon storage, is negatively correlated to dissolved oxygen, pH, and soil water temperature. In addition, Non-Metric Multidimensional Scaling analysis shows a positive relation between plant community composition, SOC content, and water electric conductivity. Our results suggest a three-way interaction between hydrological, soil, and vegetation characteristics in the natural bofedal, which also holds for the artificial bofedal. Vegetation cover of two of the most highly nutritious species for alpaca, Lachemilla diplophylla and Lilaeopsis macloviana with 19-22% of crude protein, are weakly or not correlated to environmental variables, suggesting grazing might be obscuring these potential relationships. Given the high economic importance of alpaca breeding for local communities, expanding bofedales artificially appears an effective strategy to enhance their ecosystem services with minimal impact on the ecohydrological properties of bofedales
Enteric infection with an obligate intracellular parasite, Encephalitozoon cuniculi, in an experimental model.
Rabbits were intrarectally infected with 3 doses (5 x 10(3), 5 x 10(5), and 5 x 10(7] of an obligate intracellular parasite, Encephalitozoon cuniculi, with or without prior colonic lavages. Although chronic administration of enemas seems to interfere to some degree with the intestinal translocation of the parasite, systemic infection was observed in both manipulated and nonmanipulated animals. The animals responded with antibodies of immunoglobulin A (IgA) and IgG isotypes, reflecting the route of infection. They also produced significant amounts of circulating immune complexes composed of IgA and IgG antibodies and E. cuniculi antigens. Lesions compatible with encephalitozoonosis were seen in the liver, kidney, lung, and brain. In all instances, nonmanipulated animals had more severe lesions than manipulated rabbits given the same dose of parasites. Levels of serum antibodies, circulating immune complexes, and histopathologic changes were associated with the infection dose. The presented data suggest that human microsporidiosis may also be transmitted via the rectal route. It is, therefore, of clinical relevance in view of several reports of microsporidian infections in patients with acquired immunodeficiency
Ab initio many-body calculations on infinite carbon and boron-nitrogen chains
In this paper we report first-principles calculations on the ground-state
electronic structure of two infinite one-dimensional systems: (a) a chain of
carbon atoms and (b) a chain of alternating boron and nitrogen atoms. Meanfield
results were obtained using the restricted Hartree-Fock approach, while the
many-body effects were taken into account by second-order M{\o}ller-Plesset
perturbation theory and the coupled-cluster approach. The calculations were
performed using 6-31 basis sets, including the d-type polarization
functions. Both at the Hartree-Fock (HF) and the correlated levels we find that
the infinite carbon chain exhibits bond alternation with alternating single and
triple bonds, while the boron-nitrogen chain exhibits equidistant bonds. In
addition, we also performed density-functional-theory-based local density
approximation (LDA) calculations on the infinite carbon chain using the same
basis set. Our LDA results, in contradiction to our HF and correlated results,
predict a very small bond alternation. Based upon our LDA results for the
carbon chain, which are in agreement with an earlier LDA calculation
calculation [ E.J. Bylaska, J.H. Weare, and R. Kawai, Phys. Rev. B 58, R7488
(1998).], we conclude that the LDA significantly underestimates Peierls
distortion. This emphasizes that the inclusion of many-particle effects is very
important for the correct description of Peierls distortion in one-dimensional
systems.Comment: 3 figures (included). To appear in Phys. Rev.
Glycogen Synthase Kinase (GSK) 3β phosphorylates and protects nuclear myosin 1c from proteasome-mediated degradation to activate rDNA transcription in early G1 cells
Nuclear myosin 1c (NM1) mediates RNA polymerase I (pol I) transcription activation and cell cycle progression by facilitating PCAF-mediated H3K9 acetylation, but the molecular mechanism by which NM1 is regulated remains unclear. Here, we report that at early G1 the glycogen synthase kinase (GSK) 3β phosphorylates and stabilizes NM1, allowing for NM1 association with the chromatin. Genomic analysis by ChIP-Seq showed that this mechanism occurs on the rDNA as active GSK3β selectively occupies the gene. ChIP assays and transmission electron microscopy in GSK3β-/- mouse embryonic fibroblasts indicated that at G1 rRNA synthesis is suppressed due to decreased H3K9 acetylation leading to a chromatin state incompatible with transcription. We found that GSK3β directly phosphorylates the endogenous NM1 on a single serine residue (Ser-1020) located within the NM1 C-terminus. In G1 this phosphorylation event stabilizes NM1 and prevents NM1 polyubiquitination by the E3 ligase UBR5 and proteasome-mediated degradation. We conclude that GSK3β-mediated phosphorylation of NM1 is required for pol I transcription activation
Role of C/EBPβ Transcription Factor in Adult Hippocampal Neurogenesis
[Background]: The dentate gyrus of the hippocampus is one of the regions in which neurogenesis takes place in the adult brain. We have previously demonstrated that CCAAT/enhancer binding protein β (C/EBPβ) is expressed in the granular layer of the dentate gyrus of the adult mouse hippocampus. Taking into account the important role of C/EBPβ in the consolidation of long term memory, the fact that newborn neurons in the hippocampus contribute to learning and memory processes, and the role of this transcription factor, previously demonstrated by our group, in regulating neuronal differentiation, we speculated that this transcription factor could regulate stem/progenitor cells in this region of the brain.
[Methodologu/Principal Findings]: Here, we show, using C/EBPβ knockout mice, that C/EBPβ expression is observed in the subset of newborn cells that proliferate in the hippocampus of the adult brain. Mice lacking C/EBPβ present reduced survival of newborn cells in the hippocampus, a decrease in the number of these cells that differentiate into neurons and a diminished number of cells that are proliferating in the subgranular zone of the dentate gyrus. These results were further confirmed in vitro. Neurosphere cultures from adult mice deficient in C/EBPβ present less proliferation and neuronal differentiation than neurospheres derived from wild type mice.
[Conclusions/Significance]: In summary, using in vivo and in vitro strategies, we have identified C/EBPβ as a key player in the proliferation and survival of the new neurons produced in the adult mouse hippocampus. Our results support a novel role of C/EBPβ in the processes of adult hippocampal neurogenesis, providing new insights into the mechanisms that control neurogenesis in this region of the brain.This work was supported by a postdoctoral fellowship of the Consejo Superior de Investigaciones Cientificas (M.C.-C.) Grant Sponsor: Ministerio de Investigación y Ciencia; Grant numbers: SAF2007-62811 and SAF2010-16365. CIBERNED is funded by the Instituto de Salud Carlos III.Peer reviewe
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