Environmental dynamics, correlations, and the emergence of noncanonical equilibrium states in open quantum systems

Quantum systems are invariably open, evolving under surrounding influences rather than in isolation. Standard open quantum system methods eliminate all information on the environmental state to yield a tractable description of the system dynamics. By incorporating a collective coordinate of the environment into the system Hamiltonian, we circumvent this limitation. Our theory provides straightforward access to important environmental properties that would otherwise be obscured, allowing us to quantify the evolving system-environment correlations. As a direct result, we show that the generation of robust system-environment correlations that persist into equilibrium (heralded also by the emergence of non-Gaussian environmental states) renders the canonical system steady-state almost always incorrect. The resulting equilibrium states deviate markedly from those predicted by standard perturbative techniques and are instead fully characterised by thermal states of the mapped system-collective coordinate Hamiltonian. We outline how noncanonical system states could be investigated experimentally to study deviations from canonical thermodynamics, with direct relevance to molecular and solid-state nanosystems.Comment: 10 pages, 4 figures, close to published versio

HvZ Website: The Re-Engineering

As part of our Software Design and Development class, we were given a customer and tasked with providing them a product that they specifically request. Our customer was the Humans vs Zombies (HvZ) student group here on campus. They are a group that periodically plays a campus-wide game of tag using their own online resources, and they requested that we provide them a new, updated website. Their problem was that they needed to both update their site and acquire a more maintable version. The current site that they own now is three years old with code that is difficult to decipher

Corn Ethanol Expansion and the Evolution of US Crop Patterns

The 2007 expansion of the U.S. Renewable Fuel Standard (the so-called RFS2) has had significant, and controversial, impacts on U.S. agriculture. We combine rich spatial data on observed crop choices with two metrics of corn demand by the ethanol industry to estimate the impact of the RFS2 on crop patterns. Crop choices are observed at the field level using two recent extensions of the Cropland Data Layer database. The time path of the RFS2 mandate captures its corn demand expansion at the aggregate level, and the heterogeneous impact of this biofuel policy across space is measured by a novel local ethanol demand index computed at the field level. This framework permits us to characterize both the local and overall impacts of the RFS2. We find that the ceteris paribus local presence of RFS2-induced ethanol plants, for the 13 Midwest states in the analysis, increased total corn area by 1.6%, increased the area of corn following corn by 4.3%, and had a small, spatially heterogeneous impact on soybeans. Of more consequence is the overall impact of the RFS2, which is estimated to have increased total corn area by 9.7% and corn following corn by 16.8%. Interestingly, total soybean area was also significantly impacted by the RFS2, increasing by 6.7%, and corn-soybean rotations increased by about 10%. These results indicate a major impact of the RFS2 on the geography of corn and soybean cultivation—intensification in the heart of the Corn Belt, and significant expansion near the periphery of the Corn Belt—which included the conversion of 13.9% of land previously used for other crops and/or conservation to corn/soybean production

Quantum correlations of light and matter through environmental transitions

One aspect of solid-state photonic devices that distinguishes them from their atomic counterparts is the unavoidable interaction between system excitations and lattice vibrations of the host material. This coupling may lead to surprising departures in emission properties between solid-state and atomic systems. Here we predict a striking and important example of such an effect. We show that in solid-state cavity quantum electrodynamics, interactions with the host vibrational environment can generate quantum cavity-emitter correlations in regimes that are semiclassical for atomic systems. This behaviour, which can be probed experimentally through the cavity emission properties, heralds a failure of the semiclassical approach in the solid-state, and challenges the notion that coupling to a thermal bath supports a more classical description of the system. Furthermore, it does not rely on the spectral details of the host environment under consideration and is robust to changes in temperature. It should thus be of relevance to a wide variety of photonic devices.Comment: 8 pages, 7 figures. v2 - minor edits. v3 - more substantial edits to the text. Title changed and new results on correlations added in Fig. 3. v4 - close to published version, presentation clarifie

Procurement Contracts and Buyer Power: Insights from Hotelling

This paper analyzes a Hotelling duopsony model with location-based price discrimination and procurement contracts pegged to the average spot-market price. This setup captures key features of US beef processors’ procurement of cattle supplies, which relies heavily on (controversial) spot-price contracts known as Alternative Marketing Arrangements. We show that use of these contracts increases the equilibrium price markdown in the market; and, as spot-price contracts become more prevalent, the markdown increases at an increasing rate. Both of these conclusions also apply to the standard case of uniform mill pricing.JEL Codes: L13, L66, Q13This research was supported in part by the Economic Research Service, US Department of Agriculture (cooperative agreement No. 58-3000-1-0121). The views expressed in this paper are those of the authors and not necessarily those of the U.S. Department of Agriculture

Interleukin 6 plays a role in the migration of magnetically levitated mesenchymal stem cells spheroids

Mesenchymal stem cells (MSCs) reside quiescently within a specialised ‘niche’ environment in the bone marrow. However, following appropriate signalling cues, MSCs mobilise and migrate out from the niche, typically toward either sites of injury (a regenerative response) or toward primary tumours (an intrinsic homing response, which promotes MSCs as cellular vectors for therapeutic delivery). To date, very little is known about MSC mobilisation. By adopting a 3D MSC niche model, whereby MSC spheroids are cultured within a type I collagen gel, recent studies have highlighted interleukin-6 (IL-6) as a key cytokine involved in MSC migration. Herein, the ability of IL-6 to induce MSC migration was further investigated, and the key matrix metalloproteinases used to effect cell mobilisation were identified. Briefly, the impact of IL-6 on the MSC migration in a two-dimensional model systems was characterised—both visually using an Ibidi chemotaxis plate array (assessing for directional migration) and then via a standard 2D monolayer experiment, where cultured cells were challenged with IL-6 and extracted media tested using an Abcam Human MMP membrane antibody array. The 2D assay displayed a strong migratory response toward IL-6 and analysis of the membrane arrays data showed significant increases of several key MMPs. Both data sets indicated that IL-6 is important in MSC mobilisation and migration. We also investigated the impact of IL-6 induction on MSCs in 3D spheroid culture, serving as a simplistic model of the bone marrow niche, characterised by fluorescently tagged magnetic nanoparticles and identical membrane antibody arrays. An increase in MMP levels secreted by cells treated with 1 ng/mL IL-6 versus control conditions was noted in addition to migration of cells away from the central spheroid mass