Spin waves in the (0,pi) and (0,pi,pi) ordered SDW states of the t-t' Hubbard model: Application to doped iron pnictides

Spin waves in (0,pi) and (0,pi,pi) ordered spin-density-wave (SDW) states of the t-t' Hubbard model are investigated at finite doping. In the presence of small t', these composite ferro-antiferromagnetic (F-AF) states are found to be strongly stabilized at finite hole doping due to enhanced carrier-induced ferromagnetic spin couplings as in metallic ferromagnets. Anisotropic spin-wave velocities, spin-wave energy scale of around 200meV, reduced magnetic moment, and rapid suppression of magnetic order with electron doping x (corresponding to F substitution of O atoms in La O_{1-x} F_x Fe As or Ni substitution of Fe atoms in Ba Fe_{2-x} Ni_x As_2) obtained in this model are in agreement with observed magnetic properties of doped iron pnictides.Comment: 13 pages, 3 figure

Frustrated multiband superconductivity

We show that a clean multiband superconductor may display one or several phase transitions with increasing temperature from or to frustrated configurations of the relative phases of the superconducting order parameters. These transitions may occur when more than two bands are involved in the formation of the superconducting phase and when the number of repulsive interband interactions is odd. These transitions are signalled by slope changes in the temperature dependence of the superconducting gaps.Comment: 5 pages, 3 figure

Protocol for the purification of replisomes from the <i>Xenopus laevis</i> egg extract system for single-particle cryo-EM analysis

Here, we present a large-scale FLAG immunoprecipitation protocol to isolate large protein complexes driving DNA replication at replicating chromatin assembled in Xenopus laevis egg extract. We describe how to prepare demembranated sperm nuclei (DNA) and low-speed supernatant egg extract (LSS) and present detailed procedures for sample preparation and application onto grids for negative stain electron microscopy (NS-EM) and cryoelectron microscopy (cryo-EM). For complete details on the use and execution of this protocol, please refer to Cvetkovic et al.1</p

De las clases de gestión en la FAMURP a la acción: El plan estratégico 2017-2021 de la sociedad científica médico estudiantil peruana

Se conoce que la participación en Sociedades Científicas de Estudiantes de Medicina (SOCIEMS) permite que los estudiantes de medicina humana adscritos a éstas adquieran competencias principalmente en el ámbito de la investigación científica, sin embargo un aspecto adicional es la adquisición en paralelo de habilidades en gestión1 . La mayoría de facultades de medicina de nuestro país incorporan en sus mallas curriculares cursos en gestión en salud dirigidos a estudiantes de medicina de los últimos años; a esta realidad no es ajena la FAMURP: Facultad de Medicina Humana de la Universidad Ricardo Palma, en la cual dicho curso es impartido en el Ciclo XI del Sexto Año de la carrera2 . En dicho curso se brindan los conocimientos, herramientas y metodologías para desarrollar competencias que faciliten la participación en gestión efectiva y eficiente de los establecimientos de salud y servicios basados en la atención primaria de salud . DOI:https://doi.org/10.25176/RFMH.v17.n1.75

Theory of Andreev reflection in a two-orbital model of iron-pnictide superconductors

A recently developed theory for the problem of Andreev reflection between a normal metal (N) and a multiband superconductor (MBS) assumes that the incident wave from the normal metal is coherently transmitted through several bands inside the superconductor. Such splitting of the probability amplitude into several channels is the analogue of a quantum waveguide. Thus, the appropriate matching conditions for the wave function at the N/MBS interface are derived from an extension of quantum waveguide theory. Interference effects between the transmitted waves inside the superconductor manifest themselves in the conductance. We provide results for a FeAs superconductor, in the framework of a recently proposed effective two-band model and two recently proposed gap symmetries: in the sign-reversed s-wave ($\Delta\cos(k_x)\cos(k_y)$) scenario resonant transmission through surface Andreev bound states (ABS) at nonzero energy is found as well as destructive interference effects that produce zeros in the conductance; in the extended s-wave ($\Delta[\cos(k_x)+\cos(k_y)]$) scenario no ABS at finite energy are found.Comment: 4 pages, 5 figure

A complete characterization of plateaued Boolean functions in terms of their Cayley graphs

In this paper we find a complete characterization of plateaued Boolean functions in terms of the associated Cayley graphs. Precisely, we show that a Boolean function $f$ is $s$-plateaued (of weight $=2^{(n+s-2)/2}$) if and only if the associated Cayley graph is a complete bipartite graph between the support of $f$ and its complement (hence the graph is strongly regular of parameters $e=0,d=2^{(n+s-2)/2}$). Moreover, a Boolean function $f$ is $s$-plateaued (of weight $\neq 2^{(n+s-2)/2}$) if and only if the associated Cayley graph is strongly $3$-walk-regular (and also strongly $\ell$-walk-regular, for all odd $\ell\geq 3$) with some explicitly given parameters.Comment: 7 pages, 1 figure, Proceedings of Africacrypt 201

WHAT SHOULD AI KNOW? INFORMATION DISCLOSURE IN HUMAN-AI COLLABORATION

AI-assisted Design Thinking shows great potential for supporting collaborative creative work. To foster creative thinking processes within teams with individualized suggestions, AI has to rely on data provided by the teams. As a prerequisite, team members need to weigh their disclosure preferences against the potential benefits of AI when disclosing information. To shed light on these decisions, we identify relevant information such as emotional states or discussion arguments that design thinking teams could provide to AI to enjoy the benefits of its support. Using the privacy calculus as theoretical lens, we draft a research design to analyze user preferences for disclosing different information relevant to the service bundles that AI provides for respective information. We make explorative contributions to the body of knowledge in terms of AI use and its corresponding information disclosure. The findings are relevant for practice as they guide the design of AI that fosters information disclosure

Spin-1/2 particles moving on a 2D lattice with nearest-neighbor interactions can realize an autonomous quantum computer

What is the simplest Hamiltonian which can implement quantum computation without requiring any control operations during the computation process? In a previous paper we have constructed a 10-local finite-range interaction among qubits on a 2D lattice having this property. Here we show that pair-interactions among qutrits on a 2D lattice are sufficient, too, and can also implement an ergodic computer where the result can be read out from the time average state after some post-selection with high success probability. Two of the 3 qutrit states are given by the two levels of a spin-1/2 particle located at a specific lattice site, the third state is its absence. Usual hopping terms together with an attractive force among adjacent particles induce a coupled quantum walk where the particle spins are subjected to spatially inhomogeneous interactions implementing holonomic quantum computing. The holonomic method ensures that the implemented circuit does not depend on the time needed for the walk. Even though the implementation of the required type of spin-spin interactions is currently unclear, the model shows that quite simple Hamiltonians are powerful enough to allow for universal quantum computing in a closed physical system.Comment: More detailed explanations including description of a programmable version. 44 pages, 12 figures, latex. To appear in PR