High Fidelity Adiabatic Quantum Computation via Dynamical Decoupling

We introduce high-order dynamical decoupling strategies for open system adiabatic quantum computation. Our numerical results demonstrate that a judicious choice of high-order dynamical decoupling method, in conjunction with an encoding which allows computation to proceed alongside decoupling, can dramatically enhance the fidelity of adiabatic quantum computation in spite of decoherence.Comment: 5 pages, 4 figure

Spontaneous Symmetry Breakdown in non-relativistic Quantum Mechanics

The advantages and disadvantages of some pedagogical non-relativistic quantum-mechanical models, used to illustrate spontaneous symmetry breakdown, are discussed. A simple quantum-mechanical toy model (a spinor on the line, subject to a magnetostatic interaction) is presented, that exhibits the spontaneous breakdown of an internal symmetry.Comment: 19 pages, 5 figures. arXiv admin note: substantial text overlap with arXiv:1111.1213. Equations (30) and (31) have been corrected. Other minor correction

Numerical simulation of the von Kármán sodium dynamo experiment

We present hydrodynamic and magnetohydrodynamic (MHD) simulations of liquid sodium flows in the von Kármán sodium (VKS) set-up. The counter-rotating impellers made of soft iron that were used in the successful 2006 experiment are represented by means of a pseudo-penalty method. Hydrodynamic simulations are performed at high kinetic Reynolds numbers using a large eddy simulation technique. The results compare well with the experimental data: the flow is laminar and steady or slightly fluctuating at small angular frequencies; small scales fill the bulk and a Kolmogorov-like spectrum is obtained at large angular frequencies. Near the tips of the blades the flow is expelled and takes the form of intense helical vortices. The equatorial shear layer acquires a wavy shape due to three coherent co-rotating radial vortices as observed in hydrodynamic experiments. MHD computations are performed: at fixed kinetic Reynolds number, increasing the magnetic permeability of the impellers reduces the critical magnetic Reynolds number for dynamo action; at fixed magnetic permeability, increasing the kinetic Reynolds number also decreases the dynamo threshold. Our results support the conjecture that the critical magnetic Reynolds number tends to a constant as the kinetic Reynolds number tends to infinity. The resulting dynamo is a mostly axisymmetric axial dipole with an azimuthal component concentrated near the impellers as observed in the VKS experiment. A speculative mechanism for dynamo action in the VKS experiment is proposed

Orobanche cumana wallr. resistance of commercial sunflower cultivars grown in Argentina

La planta parásita Orobanche cumana Wallr. (jopo) es una de las mayores limitantes de la producción de girasol en los principales países productores del mundo. Sin embargo, está ausente en el centro de origen y en las áreas de cultivo de girasol en América. No ha quedado claro aún si la naturalización de O. cumana en los hábitats de girasol de Argentina está limitada por restricciones abióticas o por la resistencia de los cultivares comerciales. El objetivo de este estudio fue investigar la resistencia a O. cumana de los cultivares comerciales de girasol en Argentina. En general, más del 95% de los cultivares probados fue susceptible al ataque de jopo; solamente uno de ellos mostró completa resistencia a O. cumana. Esto descarta la posibilidad de considerar a la resistencia genética de los cultivares utilizados como la causa de la ausencia de jopo en Argentina. Por lo tanto, los estudios futuros deberían focalizarse en otros factores bióticos y abióticos que, por afectar el crecimiento y desarrollo del jopo, podrían ser responsables potenciales de la ausencia de este parásito en Argentina.The parasitic weed Orobanche cumana Wallr. (broomrape) is one of the major limiting factors in worldwide sunflower production. However, it is absent in the centre of origin and in the sunflower crop areas of América. It has not yet been elucidated if O. cumana naturalization in sunflower habitats in Argentina is restricted as a result of either abiotic constraints or resistance in grown commercial cultivars. The aim of the present study was to assess the degree of resistance of commercial sunflower cultivars grown in Argentina to O. cumana. More than 95% of the tested sunflower cultivars were, in general, susceptible to broomrape attack. Although three cultivars were found to evidence an acceptable response to broomrape attack, only one of them showed complete resistance to O. cumana. This disregards genetic resistance of grown cultivars as being the reason for the absence of broomrape in Argentina. In view of this, future studies should focus on other biotic and abiotic factors affecting broomrape growth and development which could be potentially responsible for the absence of O. cumana in Argentina.Fil: Miladinovic, D.. Institute of Field and Vegetable Crops; SerbiaFil: Dedic, B.. Institute of Field and Vegetable Crops; SerbiaFil: Quiroz, F.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce; ArgentinaFil: Alvarez, D.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Córdoba. Estación Experimental Agropecuaria Manfredi; ArgentinaFil: Poverene, Maria Monica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiarida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiarida; Argentina. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Cantamutto, M.. Universidad Nacional del Sur; Argentin

Neutron Transfer reactions induced by 8Li on 9Be

Angular distributions for the elastic scattering of 8Li on 9Be and the neutron transfer reactions 9Be(8Li,7Li)10Be and 9Be(8Li,9Li)8Be have been measured with a 27 MeV 8Li radioactive nuclear beam. Spectroscopic factors for 8Li|n=9Li and 7Li|n=8Li bound systems were obtained from the comparison between the experimental differential cross section and finite-range DWBA calculations with the code FRESCO. The spectroscopic factors obtained are compared to shell model calculations and to other experimental values from (d,p) reactions. Using the present values for the spectroscopic factor, cross sections for the direct neutron-capture reactions 7Li(n,g)8Li and 8Li(n,g)9Li were calculated in the framework of a potential model.Comment: 24 pages, 8 Figures, submitted as regular article to PR

Do not fear the supernatural! : the relevance of ritual plant use for traditional culture, nature conservation, and human health in western Africa

Summary Plants still play an overriding role in African traditional medicine, as large sectors of the continent’s population prefer or considerably rely on herbal treatments as their primary source of health care. Traditional medicine, which is defined as the sum of knowledge, skills, and practices used to prevent and treat diseases, often involves consultation with spiritual healers and diviners, who in turn consult supernatural entities to diagnose their patients. At the same time, these traditions and the rites that are related to their practice are categorised as “obscure” and considered unscientific by academia. The overall aim of this thesis was to advance the understanding of the different dimensions of plant use in the context of traditional religions in two western African countries: Benin and Gabon. First, by documenting the use of plants by adepts of Vodoun in Benin and Bwiti in Gabon; and second, by exploring the associated knowledge that sustains these practices. Its purpose was to contribute to an improved plant resource management and, ultimately, the development of culturally appropriate interventions aimed at the conservation of useful plant species and their ecosystems, as well as the improvement of human health in settings similar to those of our countries of study. Departing from the disciplinary perspective of ethnobotany, this work included theories and quantitative and qualitative methods of data collection and analysis drawn from botany, anthropology, ethnology, ecology, and pharmacology. Data were collected in a period of more than a year, which was divided in two fieldwork stays, each in Benin and Gabon. This thesis was organised into six chapters. In Chapter One, I laid out the conceptual framework and introduced the study sites. Based on an assessment of the relevance of this study, I framed its overall objective and research questions. Medicinal plants are not only acknowledged for their importance in satisfying the health needs of people in sub-Saharan Africa, but also for the role their commercialization plays as a source of income for vulnerable groups. In spite of this recognition, little is known about the implications of medicinal plant trade for the sustainability of the plant species involved, especially when data on the volume and diversity of species sold at the markets are not available. In Chapter Two, we addressed this gap by providing an estimation of the volume and economic value of the domestic market in herbal medicine in Benin. We also highlighted local health concerns reflected by the medicinal plant market and found that ritual plants were the largest use category for which vendors catered in the markets of Benin. Additionally, we suggested some species with possible sustainability issues. In Chapter Three, we explored the potential link between two different social mechanisms that regulate the use of plant resources (taboos and sacrifices) and the scarcity of ritual plants in Benin and Gabon. The scholarly discussion around the origin and necessity of taboos has found these to exist either as a means to avoid potential diseases or to control the use of natural resources. Moreover, empirical data has shown that taboos reflect resource abundance. These studies, however, have primarily focussed on the use of wild animals as food. By providing quantitative data based on questionnaires with local informants, we found evidence that restrictions (such as taboos and sacrifices) were an indication of resource scarcity of ritual plants, thus advancing new explanations to the existence of these social mechanisms. In Chapter Four, we revised two of the notions that are central to our study: ‘religion’ and ‘traditional religion’, this time as defined by the people who profess these faiths in Benin and Gabon. Plant use in the context of traditional religions has been commonly described from an outsider’s perspective. The same is true for religion and traditional religions. In this chapter, we learnt that plants played a central role in the religious traditions of Benin and Gabon, both for adepts and non-adepts of Vodoun and Bwiti. In Western science, the effects of ritual plants on human health have been proposed to be a matter of belief. In Chapter Five, we discussed the potential pharmacological effect of culturally salient and economically important ritual plants on their users. We did that by contrasting their mode of application to proven pharmacological properties gathered from the literature. Additionally, we described folk categories of illness related to supernatural agents (e.g. evil spirits, ancestors, and sorcerers), as well as diseases recognised by biomedicine but that are attributed supernatural causes by people in Benin and Gabon. We discovered that in both countries an important proportion of the ritual applications of plants suggest a pharmacological effect on their users. Finally, in Chapter Six, I addressed the research questions formulated in Chapter One and discussed our work’s methodological issues as well as its implications to other scientific disciplines. I also highlighted the possible applications of the research results in informing nature conservation and human development interventions, as well as some possibilities for future research. Moreover, I reached five conclusions about Bwiti and Vodoun in our countries of study: (1) Plants and other elements of the natural world play a central role in the religious traditions of Benin and Gabon, both for adepts and non-adepts of these traditions. (2) Social mechanisms such as taboos and sacrifices are a form of adaptive management of plant resources that respond to perceived scarcity of ritual plants by their users. (3) Ritual applications of plants used in our countries of study suggest a pharmacological effect on their users, as opposed to the previous assumption that their effectiveness is a matter of belief. (4) By being the backbone of the medinal plant trade in Benin and Gabon, ritual plants represent an important source of income for a substancial sector of the population of these two countries. (5) The Western notion of ‘ritual’ in the context of western African plant use is an important mechanism for the preservation and transmission of ecological, historical, and medicinal knowledge. These conclusions point to the need to question the assumptions upon which the study of plant use in the western African context has been typically approached. Finally, I concluded that as long as the exercise of agency by supernatural entities is acknowledged, considering these practices as ‘religious’ is justified from an etic perspective. </p