Huge linear magnetoresistance due to open orbits in γ\gamma-PtBi2_2

Some single-crystalline materials present an electrical resistivity which decreases between room temperature and low temperatures at zero magnetic field as in a good metal and switches to a nearly semiconductinglike behavior at low temperatures with the application of a magnetic field. Often, this is accompanied by a huge and nonsaturating linear magnetoresistance which remains difficult to explain. Here we present a systematic study of the magnetoresistance in single-crystal $\gamma$-PtBi$_2$. We observe that the angle between the magnetic field and the crystalline $c$ axis fundamentally changes the magnetoresistance, going from a saturating to a nonsaturating magnetic field dependence. In between, there is one specific angle where the magnetoresistance is perfectly linear with the magnetic field. We show that the linear dependence of the nonsaturating magnetoresistance is due to the formation of open orbits in the Fermi surface of $\gamma$-PtBi$_2$.Comment: 12 pages, 8 figures including Supplementary Materia

ÉNFASIS EN LA ENTONACIÓN DEL ESPAÑOL DE CHILE EN HABLA ESPONTÁNEA

En aquest article es presenta un estudi de caràcter exploratori sobre les característiques entonatives de l’èmfasi que tenen lloc en el cos del contorn dels enunciats de l’espanyol xilè produïts en parla espontània. S’ha portat a terme seguint el mètode Anàlisi Melòdica de la Parla desenvolupat al Laboratori de Fonètica Aplicada de la Universitat de Barcelona.This paper presents an exploring study about characteristics of intonation emphasis that take place in utterance’s body of Chilean Spanish language produced in spontaneous speech. It has been carried out following the Melodic Analysis of Speech method developed in the Applied Phonetics Laboratory from Universidad de Barcelona.En este artículo se presenta un estudio de carácter exploratorio sobre las características entonativas del énfasis que tienen lugar en el cuerpo del contorno de los enunciados del español chileno emitidos en habla espontánea. Se ha realizado siguiendo el método Análisis Melódico del Habla desarrollado en el Laboratorio de Fonética Aplicada de la Universitat de Barcelona

Prevalencia del síndrome de quemarse por el trabajo (burnout) en profesores de educación secundaria del I.E.S. José Manuel Blecua(Zaragoza, España).

El presente estudio tiene como objetivo evaluar la presencia de burnout en los docentes de educación secundaria del centro J.M. Blecua. A través del instrumento Maslach Burnout Inventory (MBI) se pretende obtener un medida de burnout presente para poder establecer una serie de relaciones con variables propias del individuo como: sexo, edad, estado civil, años en el centro, tipo de contrato o número de hijo. A su vez, se evalúan las variables que pueden estar contribuyendo en el proceso de burnout a través del Cuestionario Seis áreas de vida laboral (WAS). Un 70% de la muestra presenta burnout. La sobrecarga laboral y las recompensas son los principales predictores de los altos índices en energía, implicación y eficacia

A characterization of Chilean farmers based on their marketproduction orientation

Chile’s open trade policy, implemented during the last few decades, has greatly transformed Chilean farmers and their production systems. As a result, farmers can be grouped into three categories based on their market-production orientation: domestic, transitional or export producers. The objective of this paper is to analyze the factors underlying the decision to produce for a particular market and compare the three groups of farmers based on data from the 2007 agricultural census. A generalized ordered logit model was used to analyze different methods of production, and non-parametric methods were used to compare the groups. Results show that some farmers change categories in sequence; farmers that produce for the domestic market can later produce for the foreign market and eventually specialize further in the production of exports. The three types of farmers differ in several aspects. Beyond the indisputable role of geographic attributes and irrigation in producing exportable species, export-oriented producers have more modern characteristics than those producing for the internal market: they are more educated, have access to various financial resources, benefit from state-funded programs, have better managerial skills and are active users of technology.This is the publisher’s final pdf. The published article is copyrighted by Pontificia Universidad Católica de Chile. Facultad de Agronomía e Ingeniería Forestal and can be found at: http://www.rcia.uc.cl/index.php/rcia/indexKeywords: generalized ordered logit model, Agricultural trade, market, export productio

Sustained effect of zero-valent iron nanoparticles under semi-continuous anaerobic digestion of sewage sludge: Evolution of nanoparticles and microbial community dynamics

The effects of adding zero-valent iron nanoparticles (nZVI) on the physicochemical, biological and biochemical responses of a semi-continuous anaerobic digestion of sewage sludge have been assessed. Two sets of consecutive experiments of 103 and 116 days, respectively, were carried out in triplicate. nZVI were magnetically retained in the reactors, and the effect of punctual doses (from 0.27 to 4.33 g L) over time was studied. Among the different parameters monitored, only methane content in the biogas was significantly higher when nZVI was added. However, this effect was progressively lost after the addition, and in 5–7 days, the methane content returned to initial values. The increase in the oxidation state of nanoparticles seems to be related to the loss of effect over time. Higher dose (4.33 g L) sustained positive effects for a longer time along with higher methane content, but this fact seems to be related to microbiome acclimation. Changes in microbial community structure could also play a role in the mechanisms involved in methane enhancement. In this sense, the microbial consortium analysis reported a shift in the balance among acetogenic eubacterial communities, and a marked increase in the relative abundance of members assigned to Methanothrix genus, recognized as acetoclastic species showing high affinity for acetate, which explain the rise in methane content in the biogas. This research demonstrates that biogas methane enrichment in semicontinuous anaerobic digesters can be achieved by using nZVI nanoparticles, thus increasing energy production or reducing costs of a later biogas upgrading process.Raquel Barrena is grateful to TECNIOspring fellowship programme (TECSPR15-1-0051) co-financed by the European Union through the Marie Curie Actions and ACCIÓ (Generalitat de Catalunya)

Sustained effect of zero-valent iron nanoparticles under semi-continuous anaerobic digestion of sewage sludge : Evolution of nanoparticles and microbial community dynamics

Altres ajuts: Acord transformatiu CRUE-CSICThe effects of adding zero-valent iron nanoparticles (nZVI) on the physicochemical, biological and biochemical responses of a semi-continuous anaerobic digestion of sewage sludge have been assessed. Two sets of consecutive experiments of 103 and 116 days, respectively, were carried out in triplicate. nZVI were magnetically retained in the reactors, and the effect of punctual doses (from 0.27 to 4.33 g L) over time was studied. Among the different parameters monitored, only methane content in the biogas was significantly higher when nZVI was added. However, this effect was progressively lost after the addition, and in 5-7 days, the methane content returned to initial values. The increase in the oxidation state of nanoparticles seems to be related to the loss of effect over time. Higher dose (4.33 g L) sustained positive effects for a longer time along with higher methane content, but this fact seems to be related to microbiome acclimation. Changes in microbial community structure could also play a role in the mechanisms involved in methane enhancement. In this sense, the microbial consortium analysis reported a shift in the balance among acetogenic eubacterial communities, and a marked increase in the relative abundance of members assigned to Methanothrix genus, recognized as acetoclastic species showing high affinity for acetate, which explain the rise in methane content in the biogas. This research demonstrates that biogas methane enrichment in semicontinuous anaerobic digesters can be achieved by using nZVI nanoparticles, thus increasing energy production or reducing costs of a later biogas upgrading process

An optimization model for line planning and timetabling in automated urban metro subway networks

In this paper we present a Mixed Integer Nonlinear Programming model that we developed as part of a pilot study requested by the R&D company Metrolab in order to design tools for finding solutions for line planning and timetable situations in automated urban metro subway networks. Our model incorporates important factors in public transportation systems from both, a cost-oriented and a passenger-oriented perspective, as time-dependent demands, interchange stations, short-turns and technical features of the trains in use. The incoming flows of passengers are modeled by means of piecewise linear demand functions which are parameterized in terms of arrival rates and bulk arrivals. Decisions about frequencies, train capacities, short-turning and timetables for a given planning horizon are jointly integrated to be optimized in our model. Finally, a novel Math-Heuristic approach is proposed to solve the problem. The results of extensive computational experiments are reported to show its applicability and effectiveness to handle real-world subway networksComment: 30 pages, 6 figures, 9 table