Ground-states of spin-1 bosons in asymmetric double-wells

In this work we investigate the different states of a system of spin-1 bosons in two potential wells connected by tunneling, with spin-dependent interaction. The model utilizes the well-known Bose-Hubbard Hamiltonian, adding a local interaction term that depends on the modulus of the total spin in a well, favoring a high- or low-spin state for different signs of the coupling constant. We employ the concept of fidelity to detect critical values of parameters for which the ground state undergoes significant changes. The nature of the states is investigated through evaluation of average occupation numbers in the wells and of spin correlations. A more detailed analysis is done for a two-particle system, but a discussion of the three-particle case and some results for larger numbers are also presented.Comment: 7 pages, 10 figure

Finite-size effects in Anderson localization of one-dimensional Bose-Einstein condensates

We investigate the disorder-induced localization transition in Bose-Einstein condensates for the Anderson and Aubry-Andre models in the non-interacting limit using exact diagonalization. We show that, in addition to the standard superfluid fraction, other tools such as the entanglement and fidelity can provide clear signatures of the transition. Interestingly, the fidelity exhibits good sensitivity even for small lattices. Effects of the system size on these quantities are analyzed in detail, including the determination of a finite-size-scaling law for the critical disorder strength in the case of the Anderson model.Comment: 15 pages, 7 figure

Assessment of CO2 emissions during acidification, storage and after incorporation to soil of pig slurry

RAMIRAN International ConferenceLarge amounts of pig slurry are produced each year in Portugal leading to environmental problems such as water and air pollution. Previous studies have reported that livestock production is the main source of anthropogenic ammonia (NH3) emissions in Europe (Kai et al., 2008) and an important source of greenhouse gases (Weiske and Petersen, 2006). Effluent treatment has been promoted to improve slurry management and to reduce its environmental impact (Sommer and Hutchings, 2001, Fangueiro et al., 2008a). Solid-liquid separation of slurry is a useful tool at the farm level producing valuable fractions, a liquid that can be used for direct fertilisation and a solid fraction that can be composted (Fangueiro et al., 2008b). Alternatively, acidification of slurry has been proposed to reduce ammonia (NH3) emissions during storage and field application (Kai et al., 2008). Previous works (Misselbrook et al., 2005; Fangueiro et al., 2008a) reported that higher NH3 emissions occurred during storage of liquid fraction of slurry or manure with low dry matter content, probably due to a reduced crust formation that decreases NH3 emissions. Hence, acidification of the liquid fraction of slurry is strongly recommended. Slurry acidification is common practice in The Netherlands and Denmark (Schils et al., 1999; Eriksen et al., 2008) but this technology still needs to be improved to avoid hazards. It is expected that this technology will be used in more countries since the European Directive (2001/81/CE) demands a decrease of atmospheric pollutants such as NH3: targets for lower NH3 emissions have been already set in Spain (Castrillon et al., 2009). Nevertheless, the acidification process leads to significant carbon dioxide (CO2) emissions (Vandré and Clemens, 1997). Such CO2 release is problematic when a closed system of slurry acidification is used (when acidified slurry is flushed back to pig houses) since it may lead to foam formation (Vandré and Clemens, 1997; Borst, 2001). Nevertheless, Fangueiro et al. (2010) reported that acidification of slurry or derived fractions led to a decrease in CO2 emissions following soil addition relative to non acidified materials. The aim of the present work was to measure the CO2 emissions during the acidification process of the liquid fraction of pig slurry and its subsequent impact during storage and after soil incorporation

Desenvolvimento de protótipo embarcado para automatização da medida do tempo de cozimento de feijão.

O presente trabalho propicia o fortalecimento do protocolo de intenções entre a Pontifícia Universidade Católica de Goiás ? PUC-GO e a Embrapa, na geração de benefícios sociais, envolvendo equipe multidisciplinar, que propõe a finalização e validação de um produto envolvendo o hardware e software para se obter a automatização dessa análise laboratorial.CONAFE

Critical exponents of the disorder-driven superfluid-insulator transition in one-dimensional Bose-Einstein condensates

We investigate the nature of the superfluid-insulator quantum phase transition driven by disorder for non-interacting ultracold atoms on one-dimensional lattices. We consider two different cases: Anderson-type disorder, with local energies randomly distributed, and pseudo-disorder due to a potential incommensurate with the lattice, which is usually called the Aubry-Andr\'e model. A scaling analysis of numerical data for the superfluid fraction for different lattice sizes allows us to determine quantum critical exponents characterizing the disorder-driven superfluid-insulator transition. We also briefly discuss the effect of interactions close to the non-interacting quantum critical point of the Aubry-Andr\'e model.Comment: 5 pages, 4 figure

Magnetic and superconducting instabilities in the periodic Anderson model: an RPA stud

We study the magnetic and superconducting instabilities of the periodic Anderson model with infinite Coulomb repulsion U in the random phase approximation. The Neel temperature and the superconducting critical temperature are obtained as functions of electronic density (chemical pressure) and hybridization V (pressure). It is found that close to the region where the system exhibits magnetic order the critical temperature T_c is much smaller than the Neel temperature, in qualitative agreement with some T_N/T_c ratios found for some heavy-fermion materials. In our study, all the magnetic and superconducting physical behaviour of the system has its origin in the fluctuating boson fields implementing the infinite on-site Coulomb repulsion among the f-electrons.Comment: 9 pages, 2 figure

Developing social capital in implementing a complex intervention: a process evaluation of the early implementation of a suicide prevention intervention in four European countries

<p>Background: Variation in the implementation of complex multilevel interventions can impact on their delivery and outcomes. Few suicide prevention interventions, especially multilevel interventions, have included evaluation of both the process of implementation as well as outcomes. Such evaluation is essential for the replication of interventions, for interpreting and understanding outcomes, and for improving implementation science. This paper reports on a process evaluation of the early implementation stage of an optimised suicide prevention programme (OSPI-Europe) implemented in four European countries.</p> <p>Methods: The process analysis was conducted within the framework of a realist evaluation methodology, and involved case studies of the process of implementation in four European countries. Datasets include: repeated questionnaires to track progress of implementation including delivery of individual activities and their intensity; serial interviews and focus groups with stakeholder groups; and detailed observations at OSPI implementation team meetings.</p> <p>Results: Analysis of local contexts in each of the four countries revealed that the advisory group was a key mechanism that had a substantial impact on the ease of implementation of OSPI interventions, particularly on their ability to recruit to training interventions. However, simply recruiting representatives of key organisations into an advisory group is not sufficient to achieve impact on the delivery of interventions. In order to maximise the potential of high level ‘gatekeepers’, it is necessary to first transform them into OSPI stakeholders. Motivations for OSPI participation as a stakeholder included: personal affinity with the shared goals and target groups within OSPI; the complementary and participatory nature of OSPI that adds value to pre-existing suicide prevention initiatives; and reciprocal reward for participants through access to the extended network capacity that organisations could accrue for themselves and their organisations from participation in OSPI.</p> <p>Conclusions: Exploring the role of advisory groups and the meaning of participation for these participants revealed some key areas for best practice in implementation: careful planning of the composition of the advisory group to access target groups; the importance of establishing common goals; the importance of acknowledging and complementing existing experience and activity; and facilitating an equivalence of benefit from network participation.</p&gt

Unveiling oxygen vacancy impact on lizardite thermo and mechanical properties

Here, we performed a systematic DFT study assisted by the workflow framework SimStack for the mechanical and thermodynamic properties of the clay mineral lizardite in pristine and six different types of O vacancies configurations. In most cases, the defect caused a structural phase transition in the lizardite from the trigonal (pristine) to the triclinic phase. The results show that oxygen vacancies in lizardite significantly reduce the lattice thermal conductivity, accompanied by an elastic moduli reduction and an anisotropy index increase. Through the P–V relation, an increase in compressibility was evidenced for vacancy configurations. Except for the vacancy with the same crystalline structure as pristine lizardite, the sound velocities of the other vacancy configurations produce a decrease in these velocities, and it is essential to highlight high values for the Grüneisen parameter. We emphasize the great relevance of the punctual-defects introduction, such as O vacancies, in lizardite, since this microstructural design is responsible for the decrease of the lattice thermal conductivity in comparison with the pristine system by decreasing the heat transfer ability, turning lizardite into a promising candidate for thermoelectric materials