Electric-field control of magnetic ordering in the tetragonal BiFeO3

We propose a way to use electric-field to control the magnetic ordering of the tetragonal BiFeO3. Based on systematic first-principles studies of the epitaxial strain effect on the ferroelectric and magnetic properties of the tetragonal BiFeO3, we find that there exists a transition from C-type to G-type antiferromagnetic (AFM) phase at in-plane constant a ~ 3.905 {\AA} when the ferroelectric polarization is along [001] direction. Such magnetic phase transition can be explained by the competition between the Heisenberg exchange constant J1c and J2c under the influence of biaxial strain. Interestingly, when the in-plane lattice constant enlarges, the preferred ferroelectric polarization tends to be canted and eventually lies in the plane (along [110] direction). It is found that the orientation change of ferroelectric polarization, which can be realized by applying external electric-field, has significant impact on the Heisenberg exchange parameters and therefore the magnetic orderings of tetragonal BiFeO3. For example, at a ~ 3.79 {\AA}, an electric field along [111] direction with magnitude of 2 MV/cm could change the magnetic ordering from C-AFM to G-AFM. As the magnetic ordering affects many physical properties of the magnetic material, e.g. magnetoresistance, we expect such strategy would provide a new avenue to the application of multiferroic materials.Comment: 4 pages, 4 figure

Fractal dimension and size scaling of domains in thin films of multiferroic BiFeO3

We have analyzed the morphology of ferroelectric domains in very thin films of multiferroic BiFeO3. Unlike the more common stripe domains observed in thicker films BiFeO3 or in other ferroics, the domains tend not to be straight, but irregular in shape, with significant domain wall roughening leading to a fractal dimensionality. Also contrary to what is usually observed in other ferroics, the domain size appears not to scale as the square root of the film thickness. A model is proposed in which the observed domain size as a function of film thickness can be directly linked to the fractal dimension of the domains.Comment: 4 pages, 3 figure

Modelling the sectoral allocation of labour in open economy models

© 2017 Canadian Economics Association Indivisible labour is not the only type of non-convexity affecting labour supply decisions. Another type of non-convexity arises in economies with sectors whenever individuals can work in only one sector at a time. I introduce this restriction into an open economy model with a tradeable and a non-tradeable sector, and I use lotteries to convexify the consumption possibilities set. This approach implies that the aggregate elasticity of labour supply becomes infinite. I compare the performance of the model with an analogous model in which the labour supply elasticity is finite. I find that there is a disconnect between the response of wages to monetary shocks and the open economy variables. The labour supply elasticity plays a more important role in the transmission of technology and government expenditure shocks to the real exchange rate and the terms of trade

Técnicas geomatemáticas para la separación de diferentes series de rocas ígneas a partir de elementos mayores

RESUMEN: En este trabajo se pretende determinar si en un conjunto aleatorio de especímenes de rocas ígneas resulta posible identificar qué series diferentes coexisten y, en tal caso, adscribir cada espécimen a la serie a que pertenece. Para ello se han estudiado cerca de 1.000 especímenes, recogidos de la literatura, pertenecientes a series (1) tholeíticas (2) alcalinas y (3) calcoalcalinas. Se concluye que, para efectuar una separación efectiva entre los distintos tipos de series, es necesario normalizar los especímenes. Se han estudiado dos técnicas de normalización: (1) al 57% de Si02 y (2) al valor cero de las coordenadas sobre la proyección en la primera componente principal. Ambas producen una buena separación, pero la normalización al 57% de Si02 genera un gran número de valores negativos, por lo que el porcentaje de especímenes que deben eliminarse del estudio es mayor que en el caso de utilizar la otra técnica, que por tanto, parece más adecuada

The spatial and compositional evolution of the Jurassic Ghorveh-Dehgolan plutons of the Zagros Orogen, Iran: SHRIMP zircon U-Pb and Sr and Nd isotope evidence

The Ghorveh-Dehgolan plutons of the northern Sanandaj-Sirjan Zone, Zagros Orogen, comprise seven composite intrusive bodies that were generated during northeastward subduction of Neotethys beneath the Iranian sector of the Eurasian plate. Zircon U-Pb SHRIMP dating reveals that the magmatic activity spanned from ~160 to ~140Ma. It started with intrusion of arc-related calc-alkaline mafic to intermediate rocks closely followed by felsic I-type granitoids. This magmatism was post-dated by felsic alkaline A-type granites. In addition to compositional changes over time, the plutons forming the arc young towards the southwest: the north Ghorveh batholith (161±4Ma) and Shanevareh (160±2Ma); Qalaylan (159±3Ma); then central Ghorveh, Galali and Saranjianeh (151±0.2Ma to 148±1Ma); and, lastly, the south Ghorveh batholith (147±3Ma) and Bolbanabad-Havarpan (144±1Ma). Whatever the process driving the changes, be it arc- or ridge-collision with the subducting system, slab roll-back, slab breakoff, subduction initiation transference, etc., the progression from I-type to A-type magmatism appears to mark a significant change from a collisional to an extensional setting in the region in the Late Jurassic. Geochemical and isotopic characteristics of the Ghorveh-Dehgolan plutons indicate that Arabian-Nubian-like crust was an important component of the magmatic sources

A precise late Permian 40Ar/ 39Ar age for Central Iberian camptonitic lamprophyres

The Avila batholith of central Spain is composed, predominantly, of crustal-melt peraluminous granites cut by small-scale mafic alkaline bodies. Dating of the Gredos sector mafic camptonitic lamprophyre dykes was undertaken to constrain the Late Variscan tectonomagmatic evolution of the region. A well constrained late Permian, Capitanian, age of 264.5 ± 1.3 Ma was obtained by 40Ar/39Ar geochronology using amphibole separates. This new age clearly distinguishes the dykes from other episodes of alkaline mafic magmatism in the region. We suggest that the lamprophyre dykes were emplaced into already solidified granitoids after the tectonic control on magma generation changed from purely extensional to transtensional

Drowning Screens: Social Media Experience and the Emotional Well-Being of Filipino Adolescents

This study explored the social media experience in Facebook and Twitter and its relation to the emotional well-being conditions of twenty (20) senior high school students in Metro Manila. Online in-depth interviews were conducted that centered on the quality of their Facebook and Twitter experience, the prevalence of distress, negative emotions, and life satisfaction. Facebook and Twitter have been utilized for entertainment and maintenance of social networks online. However, Facebook has been maintained as a “les lieux de communication” or a space to communicate with friends, family members, and classmates. Yet, due to its “public” nature, the participants were inhibited from sharing their thoughts and feelings in their Facebook account. On the other hand, multiple Twitter accounts have been maintained: for public consumption and an “exclusive” account. This exclusive Twitter account has been maintained as a “les lieux de emotion” or a social space wherein they could be inhibited on what ideas, opinions, or sentiments they will share. Experiencing distress, negative emotions, and satisfaction with everyday life has been associated with utilization of Facebook and Twitter due to issues on accessibility and unwarranted information, lack of control on popping up pornographic materials, and the threat of hacking and breached in their “les lieux de communication” and “les lieux de emotion.” Moderation and vigilance should be maintained in utilizing social media accounts to mitigate the risks of negative experience and impact on one’s emotional well-being

Registering imagery to ICESat data for measuring elevation changes on Byrd Glacier, Antarctica

This is the published version, also available here: http://dx.doi.org/10.1029/2005GL024328.We present a new approach to derive control information from ICESat data that enables rigorous registration of aerial and satellite imagery. The technique, based on matching terrain features identified from ICESat measurements and aerial imagery, opens the door to transform results of previous studies to a global reference frame. We demonstrate the proposed methodology with historical aerial photographs to determine surface changes between 1979 and 2004 over Byrd Glacier. This is important because there is no satellite radar altimetry coverage south of 81.5° S, which limits mass balance knowledge of outlet glaciers draining the East Antarctic ice sheet through the southern Transantarctic Mountains. Our study indicates that the grounded part of Byrd Glacier is close to being in balance. However, we observe large thinning on the floating part of the glacier, probably induced by increased basal melting

Separating acoustic deviance from novelty during the first year of life: a review of event-related potential evidence

Orienting to salient events in the environment is a first step in the development of attention in young infants. Electrophysiological studies have indicated that in newborns and young infants, sounds with widely distributed spectral energy, such as noise and various environmental sounds, as well as sounds widely deviating from their context elicit an event-related potential (ERP) similar to the adult P3a response. We discuss how the maturation of event-related potentials parallels the process of the development of passive auditory attention during the first year of life. Behavioral studies have indicated that the neonatal orientation to high-energy stimuli gradually changes to attending to genuine novelty and other significant events by approximately 9 months of age. In accordance with these changes, in newborns, the ERP response to large acoustic deviance is dramatically larger than that to small and moderate deviations. This ERP difference, however, rapidly decreases within first months of life and the differentiation of the ERP response to genuine novelty from that to spectrally rich but repeatedly presented sounds commences during the same period. The relative decrease of the response amplitudes elicited by high-energy stimuli may reflect development of an inhibitory brain network suppressing the processing of uninformative stimuli. Based on data obtained from healthy full-term and pre-term infants as well as from infants at risk for various developmental problems, we suggest that the electrophysiological indices of the processing of acoustic and contextual deviance may be indicative of the functioning of auditory attention, a crucial prerequisite of learning and language development