539 research outputs found
Superfluid-Insulator Transitions of the Fermi Gas with Near-Unitary Interactions in a Periodic Potential
No full textWe consider spin-1/2 fermions of mass m with interactions near the unitary limit. In an applied periodic potential of amplitude V and period a(L), and with a density of an even integer number of fermions per unit cell, there is a second-order quantum phase transition between superfluid and insulating ground states at a critical V = V(c). We compute the universal ratio V(c)ma(L)(2)/h(2) at N = infinity in a model with Sp(2N) spin symmetry. The insulator interpolates between a band insulator of fermions and a Mott insulator of fermion pairs. We discuss implications for recent experiments
Oxidative stress and the role of antioxidative treatment in diabetes mellitus
No full textIt is well known that increased free radical (FR) production or decreased activity of antioxidative system (AOS) lead to an imbalance between pro-oxidants and antioxidants called oxidative stress (OxS). Oxidative stress is involved in numerous diseases including diabetes mellitus (DM).
Elevated blood glucose level and other biochemical disorders accompanied with an inappropriate insulin secretion or improper insulin action are known features of DM. The antioxidative enzyme catalase (CAT) diminishes the production of hydrogen peroxide which is highly toxic for pancreatic cells. The increased activity of this enzyme found in DM type 1 (DMT1) patients signifies the importance of OxS in the pathogenesis of this autoimmune disease with excessive OxS. Additionally, hyperglycemia induces the generation of highly reactive FR and leads to the development of OxS which accelerates the development of DM and its complications associated to the decreased activity of AOS. It is important to point out that high doses of antioxidant agents could paradoxically have pro-oxidant effect. In this article, we present literature data related to relationship between OxS and DM with focus on non-enzymatic antioxidants as a potential novel therapeutical approach in treatment of DM. Dietary supplementation with antioxidant nutritional factors such as micronutrients and vitamins could be used as a novel strategy in both prevention and control of DM type 2 (DMT2)
Discussion on the Comments of Slobodan K. Milonjic on the article entitled "Adsorption of strontium on different sodium-enriched bentonites" by Sanja R. Marinovic, Marija J. Ajdukovic, Natasa P. Jovic-Jovicic, Tihana M. Mudrinic, Bojana N. Nedic-Vasiljevi
Get PDFA thorough discussion on the Comments on the article "Adsorption of strontium on different sodium-enriched bentonites", by Sanja R. Marinovic, Marija J. Ajdukovic, Natasa P. Jovic-Jovicic, Tihana M. Mudrinic, Bojana N. Nedic-Vasiljevic, Predrag T. Bankovic and Aleksandra D. Milutinovic-Nikolic published in the Journal of the Serbian Chemical Society, Volume 82, Issue 4, Pages: 449-463 (2017), given as Letter to the Editor by S. K. Milonjic, is provided in this letter. The authors of the commented paper have considered all the comments, and responded to each of them, point by point
Developing a Generic Agent-Based Model to Explore Servicising Policy
No full textContinuous economic growth, ignoring the incidental recession, is currently still coupled with increases in the use of resources and generation of wastes. The European Commission (EC) is looking for ways to achieve absolute decoupling between economic growth and environmental impacts. A shift from product-based to function-based production and consumption, known as `servicising' of the economy, has the potential to contribute to absolute decoupling. The EC is therefore looking for policy measures on all political levels that may stimulate a servicising shift and thereby contribute to absolute decoupling. In this thesis, I propose a generic agent-based model to inform policy towards absolute decoupling, with a focus on the role of servicising. The model captures interactions between selling and buying `agents' and can be parametrised for many different specific markets. It integrates rational and non-rational considerations, decision making on multiple levels of both producers and consumers, and resulting material flows and impacts, all in a generic way. Also, the model features sophisticated market research as a novel basis for the decision making of agents in an artificial market. The model was developed following the methodology for developing an agent-based model proposed by Van Dam, Nikolic and Lukszo \citep{Dam2012}. A substantial part of this thesis is reserved for a reflection on the methodology. The main conclusion from that part is that although the methodology provides valuable structure to help new modellers through model development, the recommended techniques and practices are mostly suitable for relatively small, domain-specific models. Additional practices are recommended in order to successfully build large and generic models. The proposed model is suitable for the three planned case studies in the pan-European SPREE project, of which the generic model development constituted a central part. The concluding sections of this thesis provide suggestions for future extensions of the model, including the inclusion of social networks, spatial explicitness and chain-level interactions.SEPAMESSTechnology, Policy and Managemen
Modeling Novel Spin Current in 2D Topological Insulator Materials
Get PDFTopological materials are unique states of quantum matter whose inherent non-trivial properties can give rise to exotic charge and spin transport. Over the past decade, the field of condensed matter physics has extensively studied various features of topological materials. In particular, theorists and instrumentalists have examined the protected surface states of topological insulators (TI) for applications in spintronics. Transport via spin-polarization is an attractive alternative to charge transfer due to less dissipation and ease of tuning. One particularly studied transport mechanism in topological insulators is the induction of spin-polarized charge currents via infrared or terahertz radiation, also known as the Photogalvanic effect (PGE). Most of the experiments have been done in 3D topological insulators. In these experiments, oscillating currents are generated in response to linear and circularly polarized light, which can be tuned by shifting polarization and the angle of incidence. A large body of theoretical literature has also been developed to describe the observed PGE as charge currents in materials with broken inversion symmetry as a second-order non-linear response. In recent years, more attention has been given to 2D topological insulators as an alternative to 3D materials due to their unique transport properties and small band gap. In this thesis, we propose an ultra-thin film 2D TI model and examine its topologically preserved features. Our model resembles a quantum well or atomically thin layers made from 3D TI materials with inversion and time reversal symmetries. The top and bottom surfaces are coupled, producing a band gap of . We calculate the spectrum of the electronic states and derive the equations of motion for charge and spin currents and the trajectory on the coupled surfaces. Our derivations predict spin-momentum locking of surface electrons, which leads to a helical spin trajectory with a precession frequency proportional to the magnitude of electron momentum. Given that the collisions in this type of system are mostly elastic, the spin precession frequency is conserved unless impurity perturbationssignificantly change the potential energy of the electron. We further examine particle-hole transitions in our 2D TI model in response to polarized radiation and characterize the PGE using the Fermi-Dirac distribution function and first-order perturbation theory. Our results show that linear and circular PGE are observable as pure spin currents in our model by projecting currents to a single surface. Numerically, our plots mimic the observed experimental data when recorded from 3D TI surface state measurements. Our results also show the dependence of the spin current magnitude on polarization and the angle of incidence of the incoming light. We, therefore, introduce a novel 2D TI model for tunable spin-polarized transport in response to infrared radiation that can be used for spintronics applications
Superconductors and Magnets with Topological Spin Currents Induced by Spin-Orbit Coupling
Get PDFTopologically non-trivial states of quantum matter have, by definition, some global property that cannot be changed by local and gradual state transformations. Since the discovery of quantum Hall liquids, many topological systems have been identified theoretically as well as experimentally, and their potential applications in quantum information processing have been envisioned. Usually, the exploration of topological systems is focused on spatially uniform states. However, this thesis studies an important class of non-uniform topological states that host periodic lattices of topological defects. The Abrikosov vortex lattice in type-2 superconductors is the best-known state of this kind. Numerical studies have shown that the quantum melting of a vortex lattice can produce a fractional quantum Hall state. Here we consider lattices of spin-current topological defects whose quantum melting is similarly expected to yield fractionalized states of quantum matter. In condensed matter systems, spin-orbit coupling can impart background spin-currents on electrons in their ground state. This is particularly relevant to topological superconductors where the background spin-currents affect the order parameter of the spontaneously broken symmetries. It has been shown in recent work that an ultra-thin film of a topological insulator exposed to a superconducting proximity effect can naturally realize a peculiar phase of spin-current vortices and anti-vortices. In the first part of this thesis, we study the Bogoliubov quasiparticles of this state and find that the quasiparticle spectrum consists of a number of Dirac nodes pinned to zero energy by the particle-hole symmetry. Some nodes are ``accidental'' and move through the first Brillouin zone along high-symmetry directions as the order parameter magnitude or the strength of the spin-orbit coupling is varied. At special parameter values, nodes forming neutral quadruplets merge and become gapped out, temporarily producing a quadratic band-touching spectrum. All these features are tunable by controlling the order parameter magnitude via a gate voltage in a heterostructure device, making this system a platform for generating zero-energy quadratic band-touching that is known to produce non-Fermi liquid dynamics. The second half of this thesis analyzes magnetic topological defects in chiral magnets. The most studied magnetic topological defect is skyrmion. However, this is a line defect in three dimensions that cannot enjoy topological protection, and it is vulnerable to quantum fluctuations even in two dimensions. The real magnetic topological defect in three dimensions is a "hedgehog". Hedgehogs are analogous to monopoles and form robustly when certain kinds of chiral and Dzyaloshinskii-Moriya (DM) interactions are present in the spin Hamiltonian. The needed interactions microscopically arise from the same kind of spin-orbit coupling that is responsible for the Weyl electron spectrum in topological semimetals. Here we employ Monte Carlo simulations of a classical nearest-neighbor ferromagnetic Heisenberg model on the simple cubic lattice which includes a variety of chiral and DM interactions. We discover a prominent ground state in the phase diagram that hosts a lattice of localized hedgehogs and anti-hedgehogs. The real-space structure of this bipartite topological defect array is the same as that of sodium-chloride (NaCl). The separation between nearest-neighbor defects is proportional to the chiral interaction strength and also depends on the DM interaction. Currently, Monte Carlo identifies a single-phase transition to a high-temperature phase without magnetic order. The results find a natural interpretation within a recent theory of topological magnetism, where the chiral and DM interactions are mathematically represented by gauge fields so that the dynamics of magnetic topological defects have much in common with the dynamics of vortices in superconductors
On the Relationship Between Education and Emancipation
No full textThis chapter provides a brief history of the concept of emancipation and its applications in and relationship with education, starting with the Enlightenment and considering both the continuation and the critique of this tradition that has further shaped the relationship between education and emancipation. The tension between two meanings of emancipation—personal, intellectual emancipation on the one hand, and political emancipation of the oppressed and the entire society on the other—comes into view in the divergence between Kantian and Marxists paths to emancipation. The chapter goes on to consider the ideas by notable classic thinkers who further developed the Enlightenment ideal of emancipatory education by democratizing it (Freire, Habermas, Dewey, Popper), but also outright questioned some of its main aspects (Peirce, Berlin, Rancière). Nevertheless, even the critics of the Enlightenment mentioned here stay faithful to the ideals of equality and freedom that were formulated in the Age of Reason. And here we are, facing “new” and “old” challenges and media
The Incorporation of International Law in the Swiss Legal System
No full textThe paper examines the incorporation of international law into Swiss legal system. Under a realistic approach, founding its roots in the Italian School of International Law, the problematic and uniqueness of Swiss legal system is explained under an alternative dimension. The intention of the author is that of (re)conceptualizing the methodology of interpretation of relationship between international law and internal law through a realistic analyze of the phenomenon, based on the social origin and nature of international law. The principal accent is given to the necessary distinction between relationship and mechanisms of adaptation. Bringing the scientific debate on social binaries might help scholars and commentators to better identify the real object and purpose of the realistic approach
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