First-principles electronic theory of non-collinear magnetic order in transition-metal nanowires

The structural, electronic and magnetic properties of one-dimensional 3d transition-metal (TM) monoatomic chains having linear, zigzag and ladder geometries are investigated in the frame-work of first-principles density-functional theory. The stability of long-range magnetic order along the nanowires is determined by computing the corresponding frozen-magnon dispersion relations as a function of the 'spin-wave' vector q. First, we show that the ground-state magnetic orders of V, Mn and Fe linear chains at the equilibrium interatomic distances are non-collinear (NC) spin-density waves (SDWs) with characteristic equilibrium wave vectors q that depend on the composition and interatomic distance. The electronic and magnetic properties of these novel spin-spiral structures are discussed from a local perspective by analyzing the spin-polarized electronic densities of states, the local magnetic moments and the spin-density distributions for representative values q. Second, we investigate the stability of NC spin arrangements in Fe zigzag chains and ladders. We find that the non-collinear SDWs are remarkably stable in the biatomic chains (square ladder), whereas ferromagnetic order (q =0) dominates in zigzag chains (triangular ladders). The different magnetic structures are interpreted in terms of the corresponding effective exchange interactions J(ij) between the local magnetic moments μ(i) and μ(j) at atoms i and j. The effective couplings are derived by fitting a classical Heisenberg model to the ab initio magnon dispersion relations. In addition they are analyzed in the framework of general magnetic phase diagrams having arbitrary first, second, and third nearest-neighbor (NN) interactions J(ij). The effect of external electric fields (EFs) on the stability of NC magnetic order has been quantified for representative monoatomic free-standing and deposited chains. We find that an external EF, which is applied perpendicular to the chains, favors non-collinear order in V chains, whereas it stabilizes the ferromagnetic (FM) order in Fe chains. Moreover, our calculations reveal a change in the magnetic order of V chains deposited on the Cu(110) surface in the presence of external EFs. In this case the NC spiral order, which was unstable in the absence of EF, becomes the most favorable one when perpendicular fields of the order of 0.1 V/Å are applied. As a final application of the theory we study the magnetic interactions within monoatomic TM chains deposited on graphene sheets. One observes that even weak chain substrate hybridizations can modify the magnetic order. Mn and Fe chains show incommensurable NC spin configurations. Remarkably, V chains show a transition from a spiral magnetic order in the freestanding geometry to FM order when they are deposited on a graphene sheet. Some TM-terminated zigzag graphene-nanoribbons, for example V and Fe terminated nanoribbons, also show NC spin configurations. Finally, the magnetic anisotropy energies (MAEs) of TM chains on graphene are investigated. It is shown that Co and Fe chains exhibit significant MAEs and orbital magnetic moments with in-plane easy magnetization axis. The remarkable changes in the magnetic properties of chains on graphene are correlated to charge transfers from the TMs to NN carbon atoms. Goals and limitations of this study and the resulting perspectives of future investigations are discussed.

Influence of farmers educational level on comprehending, acting-upon and sharing of agro advisories

Although short messaging service (SMS) through mobile phones has quickly gained popularity among most other sectors in India, its potential is not fully realised in the agriculture sector as a cost effective service to reach farmers and elicit desirable action. Despite the cost effectiveness, mobile messaging has remained a challenge in the farming sector in terms of its end use and action as far as extension systems are concerned. While there could be many influencing factors affecting the utility of mobile messages, this study assumed that educational level of farmers could be a major factor. A telephone survey was conducted to ascertain the influence of farmers’ education on the level of utilisation of mobile-based advisories. Farmers with higher education level showed better comprehension of advisories, actedupon the advisories more promptly and shared the information with fellow farmers more often than those with lower education level. There was a significant association between comprehending, sharing and acting upon advisories. This has implications to achieve enhanced extension reach with higher efficiency in terms of cost and time.

CAC controlled services sharing a link with connectionless data services in an ATM network: a performance evaluation study

In the B-ISDN there is a provision for four classes of services, all of them supported by a single transport network (the ATM network). Three of these services, the connected oriented (CO) ones, permit connection access control (CAC) but the fourth, the connectionless oriented (CLO) one, does not. Therefore, when CLO service and CO services have to share the same ATM link, a conflict may arise. This is because a bandwidth allocation to obtain maximum statistical gain can damage the contracted ATM quality of service (QOS); and vice versa, in order to guarantee the contracted QOS, the statistical gain have to be sacrificed. The paper presents a performance evaluation study of the influence of the CLO service on a CO service (a circuit emulation service or a variable bit-rate service) when sharing the same link

EdShare: Sharing for learning and teaching

A powerpoint presentation given by Hugh Davis and Debra Morris at the University of Southampton Learning and Teaching Week event 2 April 2008.

Experiences, sensations and demands of citizen (in)security: recent complex configurations in Argentina

Over the last decades the issue of insecurity due to an increase in crime rates and its possible impact on the stability of Latin American democracies has sparked an ongoing debate. In this context, the present article studies, for the case of Argentina, how experiences and sensations of insecurity may be articulated to demands for greater punitive rigor. The analysis is based on two types of information. Initially, data from international surveys such as Latinoabarometer are considered. Then, these are compared to data from prolonged on-site observations in a poor neighborhood of a mid-sized Argentine city. The combination of these different types of data shows the complexity of the process. Contrary to what is often assumed, experiences and sensations of insecurity do not lineally lead to demands for greater punitive rigor. The way in which social actors elaborate their experiences of insecurity is highly situational and not systematic. We have found that there is not necessarily a consistent process of ‘meaning construction’ that articulates experiences and sensations of insecurity with political demands.

Modelo de gestión del conocimiento para una empresa del sector de insumos químicos para la industria farmacéutica, cosmética y de alimentos: caso Disaromas S.A.

La creación de conocimiento al interior de las organizaciones es visible mediante la dirección adecuada del conocimiento de los individuos, sin embargo, cada individuo debe interactuar de tal manera que forme una red o sistema de conocimiento organizacional que consolide a largo plazo las empresas en el entorno en el que se desenvuelven. Este documento revisa elementos centrales acerca de la gestión de conocimiento visto desde varios autores y perspectivas e identifica puntos clave para diseñar un modelo de gestión de conocimiento para una empresa del sector de insumos químicos para la industria farmacéutica, cosmética y de alimentos de la ciudad de Bogotá.

Heterogeneity and the formation of risk - sharing coalitions

We offer a new explanation of partial risk sharing based on coalition formation and segmentation of society in a risky environment, without assuming limited commitment and imperfect information. Heterogenous individuals in a society freely choose with whom they will share risk. A partition belonging to the core of the membership game obtains. Perfect risk sharing does not necessarily arise. Focusing on mutual insurance rule and assuming that individuals only differ with respect to risk, we show that the core partition is homophily-based. The distribution of risk affects the number and size of these coalitions. Individuals may pay a lower risk premium in riskier societies. A higher heterogeneity in risk leads to a lower degree of risk sharing. We discuss how the endogenous partition of society into risk-sharing coalitions may shed light on empirical evidence on partial risk sharing. The case of heterogenous risk aversion leads to similar results.

Beliefs about the effects of social sharing of emotion in alexithymia

Resumen tomado de la publicación

Differences in added stable gain between manufacturers, audiometric configurations, earmold styles, and frequency bands

Added stable gain (ASG) was measured to assess the differences in feedback reduction algorithms across six manufacturers, two earmold styles, ten audiograms, and three frequency bands.

Sharing and visualizing environmental data using Virtual Globes

Virtual globe technology holds many exciting possibilities for environmental science. These easy-to-use, intuitive systems provide means for simultaneously visualizing four-dimensional environmental data from many different sources, enabling the generation of new hypotheses and driving greater understanding of the Earth system. Through the use of simple markup languages, scientists can publish and consume data in interoperable formats without the need for technical assistance. In this paper we give, with examples from our own work, a number of scientific uses for virtual globes, demonstrating their particular advantages. We explain how we have used Web Services to connect virtual globes with diverse data sources and enable more sophisticated usage such as data analysis and collaborative visualization. We also discuss the current limitations of the technology, with particular regard to the visualization of subsurface data and vertical sections.