Classical emulation of quantum-coherent thermal machines

The performance enhancements observed in various models of continuous quantum thermal machines have been linked to the buildup of coherences in a preferred basis. But, is this connection always an evidence of `quantum-thermodynamic supremacy'? By force of example, we show that this is not the case. In particular, we compare a power-driven three-level continuous quantum refrigerator with a four-level combined cycle, partly driven by power and partly by heat. We focus on the weak driving regime and find the four-level model to be superior since it can operate in parameter regimes in which the three-level model cannot, it may exhibit a larger cooling rate, and, simultaneously, a better coefficient of performance. Furthermore, we find that the improvement in the cooling rate matches the increase in the stationary quantum coherences exactly. Crucially, though, we also show that the thermodynamic variables for both models follow from a classical representation based on graph theory. This implies that we can build incoherent stochastic-thermodynamic models with the same steady-state operation or, equivalently, that both coherent refrigerators can be emulated classically. More generally, we prove this for any N-level weakly driven device with a `cyclic' pattern of transitions. Therefore, even if coherence is present in a specific quantum thermal machine, it is often not essential to replicate the underlying energy conversion process.Comment: 13 pages, 4 figures; references updated; appendix adde

Asymptotic Discord and Entanglement of Non-Resonant Harmonic Oscillators in an Equilibrium Environment

In this work, we calculate the exact asymptotic quantum correlations between two interacting non-resonant harmonic oscillators in a common Ohmic bath. We derive \emph{analytical formulas} for the covariances, fully describing any Gaussian stationary state of the system, and use them to study discord and entanglement in the strong and weak dissipation regimes. We discuss the rich structure of the discord of the stationary separable states arising in the strong dissipation regime. Also under strong dissipation, when the modes are not mechanically coupled, these may entangle only through their interaction with the \emph{common} environment. Interestingly enough, this stationary entanglement is only present within a \emph{finite band of frequencies} and increases with the dissipation rate. In addition, robust entanglement between \emph{detuned} oscillators is observed at low temperature.Comment: 4 pages, 5 figures. References updated. Some changes made. Submitte

Ruthenium Catalyzed Oxidative Cleavage of High Oleic Sunflower Oil: Considerations Regarding the Synthesis of a Fully Biobased Triacid

Tricarboxylic acids are molecules of interest for the synthesis of highly cross-linked polymers, for instance, for the curing of epoxy resins. Herein, a synthesis route to a novel high oleic sunflower oil based triacid is described by applying a ruthenium catalyzed oxidative cleavage of its double bonds. A statistical concept is devised for the prediction of the yields of mono-, di-, and trifunctional derivatives that can be formed from high oleic sunflower oil, depending on the overall conversion of double bonds into this functional group and the overall oleic acid content of the used oil. This concept proved to be highly useful for the explanation of seemingly moderate triacid yields, which are inherently dependent on the unsaturated fatty acid content of the used oil. All obtained sunflower oil based polyacids are fully analyzed by attenuated total reflection infrared spectroscopy (ATR-IR), electrospray ionization mass spectrometry (ESI-MS), $^1$H, $^{13}$C, and quantitative $^{31}$P nuclear magnetic resonance (NMR) spectroscopy. In addition, a more sustainable purification procedure is developed to obtain a polymerizable mixture of polyacids containing more than 2.0 carboxylic acids per molecule in average. Practical applications: Tricarboxylic acids are valuable monomers for the synthesis of cross-linked polymers. The herein reported procedure represents a hitherto unknown synthesis route towards a new triacid and polyacid mixture directly from high oleic sunflower oil

Desiring Dual Language Bilingual Education: One Community’s Perspectives on Past and Future Directions for Bilingual Learners

Perceptions and beliefs about past, present, and future bilingual educational programs were gathered from key members of a bilingual community, including teachers, parents, and educational administrators. Participants’ responses were analyzed and three overarching themes emerged. Current perceptions of bilingual education programs are strongly influenced by: (a) sociohistorical and political factors, (b) the effectiveness of instructional techniques; and (c) beliefs about bilingualism in general. Implications of these results are described with a focus on how they can inform policies and practices for bilingual learners