La edad de los hombres: ¿una era cristiana?

A la luz de un análisis de las costumbres practicadas por la sociedad griega heroica, en la presente contribución se intenta esclarecer por qué la visión cristiana del mundo puede ser considerada paso fundamental hacia eso que Vico llama “Edad de los Hombres”This paper tries to explain –in the light of an analysis of customs practiced in the heroic Greek society– why the Christian conception of the world can be considered as a fundamental step towards what Vico calls the “Age of Men

Wireless Content Caching for Small Cell and D2D Networks

The fifth generation wireless networks must provide fast and reliable connectivity while coping with the ongoing traffic growth. It is of paramount importance that the required resources, such as energy and bandwidth, do not scale with traffic. While the aggregate network traffic is growing at an unprecedented rate, users tend to request the same popular contents at different time instants. Therefore, caching the most popular contents at the network edge is a promising solution to reduce the traffic and the energy consumption over the backhaul links. In this paper, two scenarios are considered, where caching is performed either at a small base station, or directly at the user terminals, which communicate using Device-to-Device (D2D) communications. In both scenarios, joint design of the transmission and caching policies is studied when the user demands are known in advance. This joint design offers two different caching gains, namely, the pre-downloading and local caching gains. It is shown that the finite cache capacity limits the attainable gains, and creates an inherent tradeoff between the two types of gains. In this context, a continuous time optimization problem is formulated to determine the optimal transmission and caching policies that minimize a generic cost function, such as energy, bandwidth, or throughput. The jointly optimal solution is obtained by demonstrating that caching files at a constant rate is optimal, which allows reformulation of the problem as a finite-dimensional convex program. The numerical results show that the proposed joint transmission and caching policy dramatically reduces the total cost, which is particularised to the total energy consumption at the Macro Base Station (MBS), as well as to the total economical cost for the service provider, when users demand economical incentives for delivering content to other users over the D2D links

Las progresiones como indicador de la comprensión del concepto de sucesión numérica en alumnos de segundo ciclo de enseñanza secundaria obligatoria

Este trabajo forma parte de una investigación que aborda la compresión del concepto de sucesión numérica en los estudiantes de secundaria. La perspectiva proporcionada por la obra de Piaget y García en relación con el desarrollo de un esquema a través de varios niveles (intra, inter y trans), nos proporciona la prueba empírica de cómo el uso de las progresiones por parte de los estudiantes en la resolución de una tarea, proporciona información del desarrollo de la comprensión. Este uso nos permite profundizar sobre los niveles en el desarrollo del concepto sucesión numérica

Desarrollo de embriones de bovino obtenidos por fecundación in vitro cultivados con células oviductales o medio condicionado y transferidos a hembras receptoras

Se comparó el desarrollo in vitro de ovocitos obtenidos de ovarios de vaca de matadero, madurados, fecundados y cultivados in vitro bajo dos sistemas. Los ovocitos fueron cultivados en un medio de maduración a 39 °C, 5 % de CO2 y humedad relativa de 95 % durante 22 horas. Posteriormente, fueron incubados con espermatozoides seleccionados a través de una gradiente discontinua de Percoll. La tasa de maduración nuclear y fecundación fueron de 93,7 % (74/79) y 76,9 % (50/65) respectivamente. Un total de 252 ovocitos fecundados fueron cultivados in vitro. El porcentaje de desarrollo in vitro a las 2 días post-inseminación (embriones de 4-8 células) fue de 62,7 % (64/102) para los cigotos cultivados con células oviductales y de 67 % (100/150) para los cultivados en medio condicionado (P0,05). El porcentaje de desarrollo de mórulas fue de 17,6 % (18/102) para los cigotos cultivados con células oviductales y de 13,3 % (20/150) para los cultivados con medio condicionado (P0,05). Se obtuvo una tasa de desarrollo del 15,7 % (16/102) de blastocistos para aquellos cigotos cultivados con células oviductales. No se obtuvo blastocistos a partir de cigotos cultivados en medio condicionado. Cuatro blastocistos fueron transferidos a dos hembras receptoras. A los 42 y 57 días se encontró la presencia de un feto en cada hembraThe in vitro development of matured and fertilized bovine oocytes was compared between two culture systems. Oocytes were collected by aspiration of follicles of 3-8 mm in diameter using an 18g needle. After morphological selection the oocytes were incubated at 39 0C, 5 % C02 y 95 % relative humidity, during 22 hours. Afterwards, oocytes were incubated with spermatozoa selected by Percoll gradient system. The rate of nuclear maturation and fertilization was 93,7 % (74/79) and 76,9 % (50/65), respectively. A total of 252 zygotes were cultured, 102 with oviductal cells and 150 in conditioned medium. The in vitro development on day 2 of culture (4- or 8-cell embryos) was 62,7 % (64/102) for the zygotes co-cultured with oviductal cells and 66,7 % (100/150) for the zygotes cultured in conditioned medium. The development to the morula stage was 17,6 % (18/102) for the zygotes co-cultured with oviductal cells and 13,3 % (20/150) for the zygotes cultured in conditioned medium. A statiscally significant difference was not found in the development of 4, 8-cell embryos or morula. The development of embryos up to the blastocyst stage was 15,7 % (16/102) for the zygotes co-cultured with oviductal cells. Two blastocysts were transferred to the uterine horn ipsilateral to the CL in two recipients by non-surgical embryo transfer. Pregnancy was confirmed by ultrasonography at 42 and 57 days detecting the presence of one conceptus in each animal. This work has shown that in vitro inseminated of bovine oocytes with espermatozoa prepared with modified BO and co-cultured with oviductal cells, can develop to the blastocysts stage, unlike those that were cultured with conditioned medium. Finally, it is important to mention that this is the first communication in Chile of pregnancy after in vitro fertilization of bovine oocyte

Reduced Brace Section (RXS) Proof of Concept: Phase 1B

This report presents the results from the second phase of a proof-of-concept series of tests of the reduced braced section (RXS) system. This system is intended to provide a cost-effective alternative for the design of Concentrically Braced Frames (CBFs) under earthquake loads. The second test investigated the behavior of the RXS system under cyclic loading. The hysteretic behavior of the specimen indicated that the behavior of the RXS system was sensitive to the eccentricity of the load imposed on the brace. Eccentric loading caused premature local bucking of the reduced section, which reduced the ability of the system to dissipate energy under repeated load reversals into the nonlinear range of response. The behavior observed during the test shows that local buckling is a mode of failure that must be prevented in this type of system because of its adverse effect on the ability of the system to dissipate energy. Also, the design of the system must take into account a minimum eccentricity of the load transmitted to the brace at the brace-frame connection. An alternative to improve the behavior of the system under repeated load reversals is to reinforce the reduced section in order to increase the local bucking load. This report includes the applicable information specified in TEST REPORTING REQUIREMENTS [AISC, 2002, S9].This research was sponsored in part by Butler Heavy Structures

An Effective Surrogate Tracer Technique for S. aureus Bioaerosols in a Mechanically Ventilated Hospital Room Replica Using Dilute Aqueous Lithium Chloride

Finding a non-pathogenic surrogate aerosol that represents the deposition of typical bioaerosols in healthcare settings is beneficial from the perspective of hospital facility testing, general infection control and outbreak analysis. This study considers aerosolization of dilute aqueous lithium chloride (LiCl) and sodium chloride (NaCl) solutions as surrogate tracers capable of representing Staphylococcus aureus bioaerosol deposition on surfaces in mechanically ventilated rooms. Tests were conducted in a biological test chamber set up as a replica hospital single patient room. Petri dishes on surfaces were used to collect the Li, Na and S. aureus aerosols separately after release. Biological samples were analyzed using cultivation techniques on solid media, and flame atomic absorption spectroscopy was used to measure Li and Na atom concentrations. Spatial deposition distribution of Li tracer correlated well with S. aureus aerosols (96% of pairs within a 95% confidence interval). In the patient hospital room replica, results show that the most contaminated areas were on surfaces 2 m away from the source. This indicates that the room’s airflow patterns play a significant role in bioaerosol transport. NaCl proved not to be sensitive to spatial deposition patterns. LiCl as a surrogate tracer for bioaerosol deposition was most reliable as it was robust to outliers, sensitive to spatial heterogeneity and found to require less replicates than the S. aureus counterpart to be in good spatial agreement with biological results

Tailoring Organic-Organic Poly(vinylpyrrolidone) Microparticles and Fibers with Multiwalled Carbon Nanotubes for Reinforced Composites

Polymeric-based microparticles and fibers are tailorable for a wide range of common industrial and biomedical applications, while multiwalled carbon nanotubes (MWCNTs) are among the most useful macromolecules based on their outstanding electronic, mechanical, and optical properties at the nanoscale. If one combines these nanostructures with various polymeric precursors, their range of potential applications becomes even greater. One of the simplest and most affordable methods for fabricating micro- and nanostructures is electrospinning. Herein we demonstrate how MWCNTs may be used to produce tailor-made organic-organic poly(vinylpyrrolidone) (PVP) microparticles and fibers via electrospinning by studying their structural, vibrational, rheological, and mechanical properties' dependence on their solvent (ethanol (EtOH) or dimethylformamide (DMF)) and resulting morphology. Specifically, we find clear differences in morphologies from perfectly spherical and isolated microparticles to fibers mats, or a combination of fibers with entangled beads, with solvent type and concentration. On the basis of our findings, we propose that the mechanism governing the shape and size of the particles is a competition between the solvent's surface tension, dielectric constant, and viscoelastic properties. We show, based on both our experimental results and density functional theory (DFT) calculations, that OH functionalization of the MWCNTs is essential for achieving high PVP coverages and promoting the stability of the resulting PVP/MWCNT nanocomposite. Finally, by fabricating PVP/MWCNT fiber mats, we demonstrate that low concentrations (0.01-0.1 wt %) of MWCNTs led to a qualitative improvement (â250%) in the resulting mechanical properties, i.e., a reinforced composite. These results show how by controlling the solvent's dielectric constant, surface tension, and polymer concentration, one may produce tailor-made polymeric nanomaterials in combination with other organic/inorganic nanoparticles, i.e., silver, gold, or carbon allotropes, for next-generation applications

Field Instrumentation and Analysis of the Tuttle Creek Bridge

Fatigue cracking has been an extensive problem for many steel bridges designed prior to the identification of fatigue-prone details. Distortion in bridges coupled with stress concentrations within bridge components can eventually lead to crack initiation. The Tuttle Creek Bridge, built in 1962, has developed fatigue cracks like many older steel bridges. The structure is a 5,350 ft. long, plate-girder bridge with two girders supporting a non-composite concrete deck. The majority of the cracks on the bridge are found in the upper web-gap region, which lies between the vertical connection stiffener and the upper flange. Cracks also have occurred in the transverse welds attaching the lateral gusset plates to the lower flange. Both these crack types are believed to be caused by differential deflection of the two girders. In 1986, the bridge was retrofitted to prevent further cracking. Cracking, however, continued after the 1986 retrofit. In 2000, the Kansas Department of Transportation retained the services of the University of Kansas to investigate the fatigue cracking. Finite element models were created to estimate the stresses in the upper web-gap regions in order to determine a proper repair plan. The recommended repair scheme was to positively attach the connection stiffener to the upper flange, which was also successfully performed in similar web-gap repairs. The University of Kansas also was retained to perform two load tests on the bridge to investigate the effectiveness of the repair. The first load test, which this report entails, examined the stresses within the fatigued regions prior to retrofit. A second test will be conducted after the repairs have been performed. Measurements taken during both tests will be compared to determine the fatigue improvement within the structure. Also, information gathered during the first test will also provide insight to improving the finite element models. This report includes information about the Tuttle Creek Bridge and a summary of its structural deficiencies. Details of the gage installation and load testing are provided. Stresses induced by the truck loadings are presented in addition to the inferences from the measurements taken