Race, Democracy, and Empire: Delegates to Congress from DC and the Territories

Both democracy and empire are central to American political development. Yet, the role of Congress—that organ of democratic politics—in the expansion of US empire is not well understood. This article explains how and why Congress institutionalized representation from Washington, DC and the US territories in the mid-twentieth century. We uncover the history of a puzzling position: the Congressional delegate, who is permitted to debate, but not vote. Drawing on extensive original archival research and quantitative analysis of legislative voting behavior, this article explicates how racial attitudes structured conflict over the delegate position. We highlight the centrality of racial ideas to the institutional- ization of American empire in the mid-twentieth century

Few-Shot Machine Learning at the Grid-Edge: Data-Driven Impedance Models for Model-Free Smart Inverters

The future electric grid will be pervasively supported by a large number of smart inverters distributed at the grid edge, whose dynamics are critical for grid stability and resiliency. The operating conditions of these inverters may vary across a wide range, leading to various impedance patterns and complicated grid-inverter interaction behaviors. Existing analytical impedance models require thorough and precise understandings of system parameters and make numerous assumptions to reduce the system complexity. They can hardly capture complete electrical behaviors of physical systems when inverters are controlled with sophisticated algorithms or performing complex functions. Real-world impedance acquisitions across multiple operating points through simulations or measurements are expensive and impractical. Leveraging the recent advances in artificial intelligence and machine learning, we present the InvNet, a few-shot machine learning framework that is capable of characterizing inverter impedance patterns across a wide operation range when only limited impedance data for each inverter is available. The InvNet is capable of extrapolating from physics-based models to real-world models and from inverters to inverters. Comprehensive evaluations were conducted to verify the effectiveness of the proposed approach in various application scenarios. All data and models were open-sourced. We showcase machine learning and neural networks as powerful tools for modeling black-box characteristics of sophisticated grid-edge energy systems and their capabilities of analyzing behaviors of larger-scale systems that cannot be described via traditional analytical methods

Algebraic Program Analysis

This paper is a tutorial on algebraic program analysis. It explains the foundations of algebraic program analysis, its strengths and limitations, and gives examples of algebraic program analyses for numerical invariant generation and termination analysis

Charge-state stability of color centers in wide band gap semiconductors

The NV− color center in diamond has been extensively investigated for applications in quantum sensing, computation, and communication. Nonetheless, charge-state decay from the NV − to its neutral counterpart the NV 0 detrimentally affects the robustness of the NV − center and remains to be fully overcome. In this work, we provide an ab initio formalism for accurately estimating the rate of charge-state decay of color centers in wide band gap semiconductors. Our formalism employs density functional theory calculations in the context of thermal equilibrium. We illustrate the method using the transition of NV − to NV 0 in the presence of substitutional N [see Z. Yuan et al., Phys. Rev. Res. 2, 033263 (2020)]

Reverse Modernization Analysis: Exploring a History of How Vested Interests Were Politically Marginalized before Modern Economic Development.

This working paper experiments with what the author calls “reverse modernization analysis,” that is, revisiting the historical West from the perspective of today’s developing countries instead of the teleological approach of modernization theory (just like engineers do reverse engineering). We know today that democracy and authoritarianism alike have witnessed both positive and negative cases of economic development. Therefore, instead of questioning the economic consequence of polity, the paper commences an exploration of an alternative historiography of development focused on how underproductive vested interests were politically marginalized—a political settlement necessary for modern economic development. It briefly examines five major country cases in the period before the 20th century: Britain, France, Germany, Italy, and Japan. The preliminary empirical analysis shows that the decline of conservative elites, which is divided into three patterns—revolution, ruler’s alliance, and parliamentary politics—was caused by sui generis courses of events rather than by common systematic factors. This finding may be frustrating, but implies that political games are like sports games: even if a team does its best, victory is not guaranteed when the opponent plays well. The team still needs to stay ready to take advantage of windows of opportunity when they open

Neutral Silicon-Vacancy Centers in Diamond via Photoactivated Itinerant Carriers

Neutral silicon-vacancy (Si-V0) centers in diamond are promising candidates for quantum network applications because of their exceptional optical properties and spin coherence. However, the stabilization of Si-V0 centers requires careful Fermi-level engineering of the diamond host material, making further technological development challenging. Here, we show that Si-V0 centers can be efficiently stabilized by photoactivated itinerant carriers. Even in this nonequilibrium configuration, the resulting Si-V0 centers are stable enough to allow for resonant optical excitation and optically detected magnetic resonance. Our results pave the way for on-demand generation of Si-V0 centers as well as other emerging quantum defects in diamond

A Telecom O-Band Emitter in Diamond

Color centers in diamond are promising platforms for quantum technologies. Most color centers in diamond discovered thus far emit in the visible or near-infrared wavelength range, which are incompatible with long-distance fiber communication and unfavorable for imaging in biological tissues. Here, we report the experimental observation of a new color center that emits in the telecom O-band, which we observe in silicon-doped bulk single crystal diamonds and microdiamonds. Combining absorption and photoluminescence measurements, we identify a zero-phonon line at 1221 nm and phonon replicas separated by 42 meV. Using transient absorption spectroscopy, we measure an excited state lifetime of around 270 ps and observe a long-lived baseline that may arise from intersystem crossing to another spin manifold

Probing itinerant carrier dynamics at the diamond surface using single nitrogen vacancy centers

Color centers in diamond are widely explored for applications in quantum sensing, computing, and networking. Their optical, spin, and charge properties have extensively been studied, while their interactions with itinerant carriers are relatively unexplored. Here, we show that NV centers situated 10 ± 5 nm of the diamond surface can be converted to the neutral charge state via hole capture. By measuring the hole capture rate, we extract the capture cross section, which is suppressed by proximity to the diamond surface. The distance dependence is consistent with a carrier diffusion model, indicating that the itinerant carrier lifetime can be long, even at the diamond surface. Measuring dynamics of near-surface NV centers offers a tool for characterizing the diamond surface and investigating charge transport in diamond devices

Microphysics of liquid water in sub-10 nm ultrafine aerosol particles

Ultrafine aerosol particles with sizes smaller than 50 nm have been shown in recent studies to serve as a large source of cloud condensation nuclei that can promote additional cloud droplet formation under supersaturation conditions. Knowledge of the microphysics of liquid water in these droplets remains limited, particularly in the sub-10 nm particle size range, due to experimental and theoretical challenges associated with the complexity of aerosol components and the small length scales of interest (e.g., difficulty of precisely sampling the liquid–air interface, questionable validity of mean-field theoretical representations). Here, we carried out molecular dynamics (MD) simulations of aerosol particles with diameters between 1 and 10 nm and characterized atomistic-level structure and water dynamics in well-mixed and phase-separated systems with different particle sizes, NaCl salinities, and pimelic acid (PML) organic surface loadings as a function of distance from the time-averaged Gibbs dividing interface or instantaneous water–air interface. We define a sphericity factor (ϕ) that can shed light on the phase-mixing state of nanodroplets, and we reveal an unexpected dependence of mixing state on droplet size. Our results also evidence an ion concentration enhancement in ultrafine aerosols, which should modulate salt nucleation kinetics in sub-10 nm droplets, and provide detailed characterization of the influence of droplet size on surface tension and on water self-diffusivity near the interface. Analysis of water evaporation free energy and water activity demonstrates the validity of the Kelvin equation and Köhler theory at droplet sizes larger than 4 nm under moderate salinities and organic loadings and the need for further extension to account for ion concentration enhancement in sub-10 nm aerosols, droplet-size-dependent phase separation effects, and a sharp decrease in the cohesiveness of liquid water in sub-4 nm droplets. Finally, we show that an idealized fractional surface coating factor (fs) can be used to categorize and reconcile water accommodation coefficients (α*) observed in MD simulations and experimental results in the presence of organic coatings, and we resolve the droplet size dependence of α*