Commentary: Energy Deregulation in Maine

Recent stories from California of power blackouts, utility bankruptcies, and skyrocketing rates have left many wondering whether Maine is going to suffer a similar fate. Like California, Maine has deregulated its electricity supply—an idea that sounded good to many, but which now has some questioning whether consumers will be made better off or worse. To address these issues, MPR asked six analysts to comment on electricity deregulation in Maine. Some address whether Maine is destined to follow in California’s footsteps. Others question whether regional decision making entities, such as the New England Power Pool and the Independent System Operator of New England, sufficiently represent the public interest. Still others address whether there is a future role for public conservation programs. Together, they suggest Maine will not befall the fate of California, but they also suggest that electricity deregulation in Maine may bring its own troubles if we’re not attentive and forward-thinking today

Hubbard models and state preparation in an optical Lieb lattice

Inspired by the growing interest in probing many-body phases in novel two-dimensional lattice geometries we investigate the properties of cold atoms as they could be observed in an optical Lieb lattice. We begin by computing Wannier functions localised at individual sites for a realistic experimental setup, and determining coefficients for a Hubbard-like model. Based on this, we show how experiments could probe the robustness of edge states in a Lieb lattice with diagonal boundary conditions to the effects of interactions and realise strongly correlated many-body phases in this geometry. We then generalise this to interacting particles in a half-filled 1D Lieb ladder, where excitations are dominated by flat band states. We show that for strong attractive interactions, pair correlations are enhanced even when there is strong mixing with the Dirac cone. These findings in 1D raise interesting questions about the phases in the full 2D Lieb lattice which we show can be explored in current experiments

Kaleidoscopes of Hofstadter butterflies and Aharonov-Bohm caging from 2n-root topology in decorated square lattices

Square-root topology describes models whose topological properties can be revealed upon squaring the Hamiltonian, which produces their respective parent topological insulators. This concept has recently been generalized to 2n-root topology, characterizing models where n squaring operations must be applied to the Hamiltonian to arrive at the topological source of the model. In this paper, we analyze the Hofstadter regime of quasi-one-dimensional and two-dimensional 2n-root models, the latter of which has the square lattice (SL) (known for the Hofstadter Butterfly) as the source model. We show that upon increasing the root-degree of the model, there appear multiple magnetic flux insensitive flat bands, and we analytically determine corresponding eigenstates. These can be recast as compact localized states (CLSs) occupying a finite region of the lattice. For a finite flux, these CLSs correspond to different harmonics contained within the same Aharonov-Bohm cage. Furthermore, as the root-degree increases, a kaleidoscope of butterflies is seen to appear in the Hofstadter diagram, with each butterfly constituting a topologically equivalent replica of the original one of the SL. As such, the index n, which uniquely identifies the root-degree of the model, can be seen as an additional fractal dimension of the 2n-root model present in its Hofstadter diagram. We discuss how these dynamics could be realized in experiments with ultracold atoms, and measured by Bragg spectroscopy or through observing dynamics of initially localized atoms in a quantum gas microscope

Enhanced localization and protection of topological edge states due to geometric frustration

Topologically nontrivial phases are linked to the appearance of localized modes in the boundaries of an open insulator. On the other hand, the existence of geometric frustration gives rise to degenerate localized bulk states. The interplay of these two phenomena may, in principle, result in an enhanced protection/localization of edge states. In this paper, we study a two-dimensional Lieb-based topological insulator with staggered hopping parameters and diagonal open boundary conditions. This system belongs to the C2v class and sustains one-dimensional (1D) boundary modes except at the topological transition point, where the C4v symmetry allows for the existence of localized (0D) corner states. Our analysis reveals that, while a large set of boundary states have a common well-defined topological phase transition, other edge states reflect a topological nontrivial phase for any finite value of the hopping parameters, are completely localized (compact) due to destructive interference, and evolve into corner states when reaching the higher symmetry point. We consider the robustness of these compact edge states with respect to time-dependent perturbations and indicate ways that these states could be prepared and measured in experiments with ultracold atoms

Propagation of errors and quantitative quantum simulation with quantum advantage

The rapid development in hardware for quantum computing and simulation has led to much interest in problems where these devices can exceed the capabilities of existing classical computers and known methods. Approaching this for problems that go beyond testing the performance of a quantum device is an important step, and quantum simulation of many-body quench dynamics is one of the most promising candidates for early practical quantum advantage. We analyse the requirements for quantitatively reliable quantum simulation beyond the capabilities of existing classical methods for analogue quantum simulators with neutral atoms in optical lattices and trapped ions. Considering the primary sources of error in analogue devices and how they propagate after a quench in studies of the Hubbard or long-range transverse field Ising model, we identify the level of error expected in quantities we extract from experiments. We conclude for models that are directly implementable that regimes of practical quantum advantage are attained in current experiments with analogue simulators. We also identify the hardware requirements to reach the same level of accuracy with future fault-tolerant digital quantum simulation. Verification techniques are already available to test the assumptions we make here, and demonstrating these in experiments will be an important next step

Effect of input power and temperature on the cavitation intensity during the ultrasonic treatment of molten aluminium

Experimental results of ultrasonic processing of liquid aluminium with a 5 kW magnetostrictive transducer and a 20 mm titanium sonotrode excited at 17 kHz are reported in this study. A unique high-temperature cavitometer sensor, placed at various locations in the liquid melt, measured cavitation activity at various acoustic power levels and different temperature ranges. The highest cavitation intensity in the liquid bulk is achieved below the surface of the sonotrode, at the lowest temperature and with an applied power of 3.5 kW. This two-fold mechanism is related to (a) acoustic shielding and (b) the tendency of liquid aluminium to release hydrogen when the temperature drops, thus promoting multiple cavitation events. Understanding these mechanisms in liquid metals can result in a major breakthrough for the optimization of ultrasound applications to liquid metal processing.This work is performed within the Ultramelt Project supported by the EPSRC Grants EP/K005804/1 and EP/K00588X/1

Bacterial biofilm in salivary gland stones: Cause or consequence?

OBJECTIVE: The pathogenesis of salivary calculi is not yet clear; however, 2 theories have been formulated: (1) "the classic theory," based on calcium microdeposits in serous and ductal acinous cells, successively discharged into the ducts; (2) "the retrograde theory," based on a retrograde migration of food, bacteria, and so on from the oral cavity to the salivary duct. The aim of the present study is to highlight the role of bacteria and biofilm in stone formation. STUDY DESIGN: Case series without comparison. SETTING: Laboratory of the Department of Anatomical Pathology. SUBJECTS AND METHODS: Traditional optic microscopy and scanning electron microscopy were carried out on 15 salivary gland calculi that were collected from 12 patients. A qPCR (quantitative real-time polymerase chain reaction) assay was performed to highlight the presence of bacterial DNA on each stone. RESULTS: Optic microscopy showed formations that-due to their size, shape, and Gram and Giemsa staining-seemed to be Gram-positive bacterial cells. PAS- (periodic acid-Schiff) and alcian-PAS-positive staining matrix was present around them. The ultrastructural observation of the material processed for scanning electron microscopy showed the presence of structures resembling bacterial cells in the middle of the stones, surrounded by soft, amorphous material. Results of qPCR showed the presence of bacterial DNA in the internal part of the tissue sample. CONCLUSIONS: The presence of bacteria and/or bacterial products resembling biofilm in salivary gland stones supports the "retrograde theory." This evidence may support the hypothesis that biofilm could be the causative effect of lithiasic formations

Biomass offsets little or none of permafrost carbon release from soils, streams, and wildfire: an expert assessment

As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release will be offset by increased production of Arctic and boreal biomass; however, the lack of robust estimates of net carbon balance increases the risk of further overshooting international emissions targets. Precise empirical or model-based assessments of the critical factors driving carbon balance are unlikely in the near future, so to address this gap, we present estimates from 98 permafrost-region experts of the response of biomass, wildfire, and hydrologic carbon flux to climate change. Results suggest that contrary to model projections, total permafrost-region biomass could decrease due to water stress and disturbance, factors that are not adequately incorporated in current models. Assessments indicate that end-of-the-century organic carbon release from Arctic rivers and collapsing coastlines could increase by 75% while carbon loss via burning could increase four-fold. Experts identified water balance, shifts in vegetation community, and permafrost degradation as the key sources of uncertainty in predicting future system response. In combination with previous findings, results suggest the permafrost region will become a carbon source to the atmosphere by 2100 regardless of warming scenario but that 65%–85% of permafrost carbon release can still be avoided if human emissions are actively reduced