QUASII: QUery-Aware Spatial Incremental Index.

With large-scale simulations of increasingly detailed models and improvement of data acquisition technologies, massive amounts of data are easily and quickly created and collected. Traditional systems require indexes to be built before analytic queries can be executed efficiently. Such an indexing step requires substantial computing resources and introduces a considerable and growing data-to-insight gap where scientists need to wait before they can perform any analysis. Moreover, scientists often only use a small fraction of the data - the parts containing interesting phenomena - and indexing it fully does not always pay off. In this paper we develop a novel incremental index for the exploration of spatial data. Our approach, QUASII, builds a data-oriented index as a side-effect of query execution. QUASII distributes the cost of indexing across all queries, while building the index structure only for the subset of data queried. It reduces data-to-insight time and curbs the cost of incremental indexing by gradually and partially sorting the data, while producing a data-oriented hierarchical structure at the same time. As our experiments show, QUASII reduces the data-to-insight time by up to a factor of 11.4x, while its performance converges to that of the state-of-the-art static indexes

Spreading Electron Density Thin: Increasing the Chromophore Size in Polyaromatic Wires Decreases Interchromophoric Electronic Coupling

The development of novel polychromophoric materials using extended polycyclic aromatic hydrocarbons as a single large chromophore holds promise for long-range charge-transfer applications in photovoltaic devices and molecular electronics. However, it is not well-understood how the interchromophoric electronic coupling varies with the chromophore size in linearly connected molecular wires. Here, we show with the aid of electrochemistry, electronic spectroscopy, density functional theory calculations, and theoretical modeling that as the number of aromatic moieties in a single chromophore increases, the interchromophoric electronic coupling decreases and may reach negligible values if the chromophore is sufficiently large. The origin of this initially surprising result becomes clear when one considers this problem with the aid of Hückel molecular orbital theory, as at the polymeric limit energies of the molecular orbitals cluster to form bands and thus the energy spacing between orbitals, and thereby the electronic coupling must decrease with the chromophore expansion

Molecular Actuators in Action: Electron-Transfer-Induced Conformation Transformation in Cofacially Arrayed Polyfluorenes

There is much current interest in the design of molecular actuators, which undergo reversible, controlled motion in response to an external stimulus (light, heat, oxidation, etc.). Here we describe the design and synthesis of a series of cofacially arrayed polyfluorenes (MeFnHm) with varied end-capping groups, which undergo redox-controlled electromechanical actuation. Such cofacially arrayed polyfluorenes are a model molecular scaffold to investigate fundamental processes of charge and energy transfer across a π-stacked assembly, and we show with the aid of NMR and optical spectroscopies, X-ray crystallography and DFT calculations that in the neutral state the conformation of MeFnH1 and MeFnH2 is open rather than cofacial, with a conformational dependence that is highly influenced by the local environment. Upon (electro)chemical oxidation, these systems undergo a reversible transformation into a closed fully π-stacked conformation, driven by charge-resonance stabilization of the cationic charge. These findings are expected to aid the design of novel wire-like cofacially arrayed systems capable of undergo redox-controlled actuation

Sovereign Debt Restructuring: A Model-Law Approach

The existing contractual framework for sovereign debt restructuring is sorely inadequate. Whether or not their fault, nations sometimes take on debt burdens that become unsustainable. Until resolved, the resulting sovereign debt problem hurts not only those nations (such as Greece) but also their citizens, their creditors, and—by posing serious systemic risks to the international financial system—the wider economic community. The existing contractual framework functions poorly to resolve the problem because it often leaves little alternative between a sovereign debt bailout, which is costly and creates moral hazard, and a default, which raises the specter of systemic financial contagion. Most observers therefore want to strengthen the legal framework for resolving sovereign debt problems. International organizations, including the United Nations, have been contemplating strengthening that framework through treaties. The political economy of treaty-making, however, makes that approach highly unlikely to succeed in the near future. This article argues, in contrast, that a model-law approach should not only strengthen that legal framework but also should be politically and economically feasible. Model laws have long been used in cross-border lawmaking, but they are different than treaties. Unlike a treaty, a model law would not require general acceptance for its implementation. Only one or two jurisdictions, for example, need enact the text of this article’s proposed model law for it to become widely effective. Once that occurs, a debtor-state whose debt contracts are governed by those jurisdictions’ laws, or by its own laws, could restructure that debt without needing to amend any of those contracts. A model-law approach should also be desirable. This article’s model law, for example, would reduce uncertainty and should also achieve significant cost advantages—both to debtor-states and to their creditors—over the sovereign-debt-restructuring status quo. Because it would require only a ministerial supervisory process, the model law would not interfere with the exercise of a sovereign’s political discretion. Moreover, the model law provides incentives to motivate fair bargaining on behalf of debtor-states and their creditors, while restricting rent-seeking holdouts. It also enables the type of interim funding of day-to-day debts that a debtor-state needs during its debt restructuring. Debtor-states should therefore want (and creditors, other than rent-seeking holdouts, should want them) to enact into law this article’s proposed model-law text. Regardless of whether that enactment occurs, however, the article should serve its underlying purpose: to provide a conceptual and legal analysis of how a model law could be structured and how a model-law approach could be used to solve the problem of unsustainable sovereign debt burdens, and to help develop the norms required to facilitate those goals

Building a Better Seating Chart for Sovereign Restructurings

Every sovereign debt restructuring in recent memory has wrestled with the problem of inter-creditor equity. Governments have discriminated among creditors in ways that were hard to predict and often were not revealed until after a debt default. In contrast, debts of firms, individuals and even localities are ranked in order of priority established by contract and statute. This ranking is known at borrowing, generally corresponds to the order of repayment in bankruptcy liquidation, and helps define the creditors\u27 relative bargaining power in reorganization. Without a bankruptcy backstop, most debts of national governments are legally equal. Yet in practice, sovereign immunity empowers a government to choose the order of repayment among its creditors based on political imperatives, financing needs, reputational concerns or any other considerations. A transparent, enforceable priority system for sovereign debt could reduce the risk of involuntary subordination, the attraction of lending to overindebted governments and the need for collateral. When all else fails, such a system could make restructuring less messy. But an effort to imagine sovereign priorities shows both the utility and the limits of domestic bankruptcy as a source for solutions to sovereign debt crises. This article suggests that while incremental improvement is possible and desirable, in the sovereign context, the most robust priority structures are doomed to fail