spl(2,1) dynamical supersymmetry and suppression of ferromagnetism in flat band double-exchange models

The low energy spectrum of the ferromagnetic Kondo lattice model on a N-site complete graph extended with on-site repulsion is obtained from the underlying spl(2,1) algebra properties in the strong coupling limit. The ferromagnetic ground state is realized for 1 and N+1 electrons only. We identify the large density of states to be responsible for the suppression of the ferromagnetic state and argue that a similar situation is encountered in the Kagome, pyrochlore, and other lattices with flat bands in their one-particle density of states.Comment: 7 pages, 1 figur

An OpenDSS implementation of a generic municipal microgrid for co-simulation

This thesis provides a summary of the development process of a microgrid simulation model using OpenDSS software, as well as simulations and co-simulations using said model. Many power system research problems may be solved via the deployment simulations. However, for real-world problems he computational efforts for detailed dynamic modeling may be impractical or excessive. OpenDSS provides a framework within which a model of a small- or large-scale system may be implemented without the representation dynamics, with extensive co-simulation capabilities. We discuss the modeling of a generic 8-bus microgrid that consists of 200 residential loads plus an additional load for the local control building, three generation resources – solar, wind, and gas – and a battery storage resource. We use historical environmental data from Decatur, Illinois, together with realistic consumer load shapes to simulate and analyze various unbalanced and quasi-balanced situations. In addition, we present results of co-simulation studies on such a model in an OpenDSS application to evaluate various potential scenarios

Predicting the coherence resonance curve using a semi-analytical treatment

Emergence of noise induced regularity or Coherence Resonance in nonlinear excitable systems is well known. We explain theoretically why the normalized variance ($V_{N}$) of inter spike time intervals, which is a measure of regularity in such systems, has a unimodal profile. Our semi-analytic treatment of the associated spiking process produces a general yet simple formula for $V_{N}$, which we show is in very good agreement with numerics in two test cases, namely the FitzHugh-Nagumo model and the Chemical Oscillator model.Comment: 5 pages, 5 figure

Stuttering Min oscillations within E. coli bacteria: A stochastic polymerization model

We have developed a 3D off-lattice stochastic polymerization model to study subcellular oscillation of Min proteins in the bacteria Escherichia coli, and used it to investigate the experimental phenomenon of Min oscillation stuttering. Stuttering was affected by the rate of immediate rebinding of MinE released from depolymerizing filament tips (processivity), protection of depolymerizing filament tips from MinD binding, and fragmentation of MinD filaments due to MinE. Each of processivity, protection, and fragmentation reduces stuttering, speeds oscillations, and reduces MinD filament lengths. Neither processivity or tip-protection were, on their own, sufficient to produce fast stutter-free oscillations. While filament fragmentation could, on its own, lead to fast oscillations with infrequent stuttering; high levels of fragmentation degraded oscillations. The infrequent stuttering observed in standard Min oscillations are consistent with short filaments of MinD, while we expect that mutants that exhibit higher stuttering frequencies will exhibit longer MinD filaments. Increased stuttering rate may be a useful diagnostic to find observable MinD polymerization in experimental conditions.Comment: 21 pages, 7 figures, missing unit for k_f inserte

Cytotoxic polyfunctionality maturation of cytomegalovirus-pp65-specific CD4 + and CD8 + T-cell responses in older adults positively correlates with response size

Cytomegalovirus (CMV) infection is one of the most common persistent viral infections in humans worldwide and is epidemiologically associated with many adverse health consequences during aging. Previous studies yielded conflicting results regarding whether large, CMV-specific T-cell expansions maintain their function during human aging. In the current study, we examined the in vitro CMV-pp65-reactive T-cell response by comprehensively studying five effector functions (i.e., interleukin-2, tumor necrosis factor-α, interferon-γ, perforin, and CD107a expression) in 76 seropositive individuals aged 70 years or older. Two data-driven, polyfunctionality panels (IL-2-associated and cytotoxicity-associated) derived from effector function co-expression patterns were used to analyze the results. We found that, CMV-pp65-reactive CD8 + and CD4 + T cells contained similar polyfunctional subsets, and the level of polyfunctionality was related to the size of antigen-specific response. In both CD8 + and CD4 + cells, polyfunctional cells with high cytotoxic potential accounted for a larger proportion of the total response as the total response size increased. Notably, a higher serum CMV-IgG level was positively associated with a larger T-cell response size and a higher level of cytotoxic polyfunctionality. These findings indicate that CMV-pp65-specific CD4 + and CD8 + T cell undergo simultaneous cytotoxic polyfunctionality maturation during aging

Rotating Convection in an Anisotropic System

We study the stability of patterns arising in rotating convection in weakly anisotropic systems using a modified Swift-Hohenberg equation. The anisotropy, either an endogenous characteristic of the system or induced by external forcing, can stabilize periodic rolls in the K\"uppers-Lortz chaotic regime. For the particular case of rotating convection with time-modulated rotation where recently, in experiment, chiral patterns have been observed in otherwise K\"uppers-Lortz-unstable regimes, we show how the underlying base-flow breaks the isotropy, thereby affecting the linear growth-rate of convection rolls in such a way as to stabilize spirals and targets. Throughout we compare analytical results to numerical simulations of the Swift-Hohenberg equation

Complexity of equational theory of relational algebras with standard projection elements

The class $\mathsf{TPA}$ of t rue p airing a lgebras is defined to be the class of relation algebras expanded with concrete set theoretical projection functions. The main results of the present paper is that neither the equational theory of $\mathsf{TPA}$ nor the first order theory of $\mathsf{TPA}$ are decidable. Moreover, we show that the set of all equations valid in $\mathsf{TPA}$ is exactly on the $\Pi ^1_1$ level. We consider the class $\mathsf{TPA}^-$ of the relation algebra reducts of $\mathsf{TPA}$’s, as well. We prove that the equational theory of $\mathsf{TPA}^-$ is much simpler, namely, it is recursively enumerable. We also give motivation for our results and some connections to related work

A human septin octamer complex sensitive to membrane curvature drives membrane deformation with a specific mesh-like organization

Septins are cytoskeletal proteins interacting with the inner plasma membrane and other cytoskeletal partners. Being key in membrane remodeling processes, they often localize at specific micrometric curvatures. To analyze the behavior of human septins at the membrane and decouple their role from other partners, we used a combination of bottom-up in vitro methods. We assayed their ultrastructural organization, their curvature sensitivity, as well as their role in membrane reshaping. On membranes, human septins organize into a two-layered mesh of orthogonal filaments, instead of generating parallel sheets of filaments observed for budding yeast septins. This peculiar mesh organization is sensitive to micrometric curvature and drives membrane reshaping as well. The observed membrane deformations together with the filamentous organization are recapitulated in a coarse-grained computed simulation to understand their mechanisms. Our results highlight the specific organization and behavior of animal septins at the membrane as opposed to those of fungal proteins

Tortillas on the roaster: Central America’s maize–bean systems and the changing climate

Maize and beans are a vital component of human diets and culture in Central America. More than a million smallholder families grow these crops for subsistence, producing 70% of the maize and 100% of the beans consumed locally. Average yields are low, however – 1.5 t/ha for maize and 0.7 t/ha for beans – on the approximately 2.5 million hectares of land sown to these crops (40% of the total area harvested) in El Salvador, Guatemala, Honduras, and Nicaragua. In the years to come, a harsher climate together with soil degradation1, widespread poverty, and rural people’s limited access to services and infrastructure will pose challenging obstacles to production. By 2025, these pressures could result in total annual losses of maize and bean production in the four countries of around 350,000 t – with a gross production value of around US$120 million. To ward off this threat to the food security of some 100,000 households, effective adaptation strategies must be developed in collaboration with stakeholders in the maize and bean value chains. These strategies require strong public support and must draw on both scientific and community knowledge

Tortillas en el comal: los sistemas de maíz y fríjol de América Central y el cambio climático

El maíz y el fríjol son un componente vital de las dietas alimenticias de los humanos y la cultura en América Central. Más de un millón de familias de pequeños agricultores siembran estos cultivos para su subsistencia y producen el 70% del maíz y 100% del fríjol que se consume localmente. Sin embargo, los rendimientos promedio son bajos —1.5 t/ha para maíz y 0.7 t/ha para fríjol — en las cerca de 2.5 millones de hectáreas de tierra sembradas con estos cultivos (40% del área total cosechada) en El Salvador, Guatemala, Honduras y Nicaragua. En los próximos años, el cambio climático junto con la degradación del suelo, la pobreza generalizada y el acceso limitado de la población rural a servicios e infraestructura plantearán obstáculos desafiantes para la producción. Para el 2025, estas presiones podrían producir pérdidas anuales totales de la producción de maíz y fríjol en los cuatro países de alrededor de 350.000 t — con un valor bruto de producción cercano a US$120 millones. Para detener esta amenaza para la seguridad alimentaria de alrededor de 100.000 hogares, se deben desarrollar unas estrategias de adaptación efectivas en colaboración con los interesados directos de las cadenas de valor del maíz y el fríjol. Estas estrategias requieren un apoyo público firme y deben aprovechar tanto el conocimiento científico como el saber de las comunidades