cssi/SciSciGPT-SciSciNet huggingface dataset:
Creating full individual-level location timelines from sparse social media data

In many domain applications, a continuous timeline of human locations is critical; for example for understanding possible locations wherea disease may spread, or the flow of traffic. While data sources such as GPS trackers or Call Data Records are temporally-rich, they are expensive, often not publicly available or garnered only in select locations, restricting their wide use. Conversely, geo-located social media data are publicly and freely available, but present challenges especially for full timeline inference due to their sparse nature. We propose a stochastic framework, Intermediate Location Computing (ILC) which uses prior knowledge about human mobility patterns to predict every missing location from an individual's social media timeline. We compare ILC with a state-of-the-art RNN baseline as well as methods that are optimized for next-location prediction only. For three major cities, ILC predicts the top 1 location for all missing locations in a timeline, at 1 and 2-hour resolution, with up to 77.2% accuracy (up to 6% better accuracy than all compared methods). Specifically, ILC also outperforms the RNN in settings of low data; both cases of very small number of users (under 50), as well as settings with more users, but with sparser timelines. In general, the RNN model needs a higher number of users to achieve the same performance as ILC. Overall, this work illustrates the tradeoff between prior knowledge of heuristics and more data, for an important societal problem of filling in entire timelines using freely available, but sparse social media data.
Bayesian Models and Methods in Public Policy and Government Settings

Starting with the neo-Bayesian revival of the 1950s, many statisticians argued that it was inappropriate to use Bayesian methods, and in particular subjective Bayesian methods in governmental and public policy settings because of their reliance upon prior distributions. But the Bayesian framework often provides the primary way to respond to questions raised in these settings and the numbers and diversity of Bayesian applications have grown dramatically in recent years. Through a series of examples, both historical and recent, we argue that Bayesian approaches with formal and informal assessments of priors AND likelihood functions are well accepted and should become the norm in public settings. Our examples include census-taking and small area estimation, US election night forecasting, studies reported to the US Food and Drug Administration, assessing global climate change, and measuring potential declines in disability among the elderly.
MAGNETOHYDRODYNAMIC-PARTICLE-IN-CELL METHOD FOR COUPLING COSMIC RAYS WITH A THERMAL PLASMA: APPLICATION TO NON-RELATIVISTIC SHOCKS

We formulate a magnetohydrodynamic-particle-in-cell (MHD-PIC) method for describing the interaction between collisionless cosmic ray (CR) particles and a thermal plasma. The thermal plasma is treated as a fluid, obeying equations of ideal MHD, while CRs are treated as relativistic Lagrangian particles subject to the Lorentz force. Backreaction from CRs to the gas is included in the form of momentum and energy feedback. In addition, we include the electromagnetic feedback due to CR-induced Hall effect that becomes important when the electron?ion drift velocity of the background plasma induced by CRs approaches the Alfv?n velocity. Our method is applicable on scales much larger than the ion inertial length, bypassing the microscopic scales that must be resolved in conventional PIC methods, while retaining the full kinetic nature of the CRs. We have implemented and tested this method in the Athena MHD code, where the overall scheme is second-order accurate and fully conservative. As a first application, we describe a numerical experiment to study particle acceleration in non-relativistic shocks. Using a simplified prescription for ion injection, we reproduce the shock structure and the CR energy spectra obtained with more self-consistent hybrid-PIC simulations, but at substantially reduced computational cost. We also show that the CR-induced Hall effect reduces the growth rate of the Bell instability and affects the gas dynamics in the vicinity of the shock front. As a step forward, we are able to capture the transition of particle acceleration from non-relativistic to relativistic regimes, with momentum spectrum connecting smoothly through the transition, as expected from the theory of Fermi acceleration.
Contrasting Various Notions of Convergence in Geometric Analysis

We explore the distinctions between $L^p$ convergence of metric tensors on a fixed Riemannian manifold versus Gromov-Hausdorff, uniform, and intrinsic flat convergence of the corresponding sequence of metric spaces. We provide a number of examples which demonstrate these notions of convergence do not agree even for two dimensional warped product manifolds with warping functions converging in the $L^p$ sense. We then prove a theorem which requires $L^p$ bounds from above and $C^0$ bounds from below on the warping functions to obtain enough control for all these limits to agree.
Conformal symmetry wormholes and the null energy condition

In this paper, we seek a relationship between the assumption of conformal symmetry and the exotic matter needed to hold a wormhole open. By starting with a Morris-Thorne wormhole having a constant energy density, we show that the conformal factor provides an extra degree of freedom sufficient to account for the exotic matter. The same holds for Morris-Thorne wormholes in a noncommutative-geometry setting. Applied to thin shells, a radius that results in a wormhole with positive surface density and negative surface pressure and that violates the null energy condition on a thin shell would exist.
Seiberg–Witten monopoles with multiple spinors on a surface times a circle

The Seiberg-Witten equation with multiple spinors generalises the classical Seiberg-Witten equation in dimension three. In contrast to the classical case, the moduli space of solutions $\mathcal{M}$ can be non-compact due to the appearance of so-called Fueter sections. In the absence of Fueter sections we define a signed count of points in $\mathcal{M}$ and show its invariance under small perturbations. We then study the equation on the product of a Riemann surface and a circle, describing $\mathcal{M}$ in terms of holomorphic data over the surface. We define analytic and algebro-geometric compactifications of $\mathcal{M}$, and construct a homeomorphism between them. For a generic choice of circle-invariant parameters of the equation, Fueter sections do not appear and $\mathcal{M}$ is a compact Kahler manifold. After a perturbation it splits into isolated points which can be counted with signs, yielding a number independent of the initial choice of the parameters. We compute this number for surfaces of low genus.
Avalanches and disorder-induced criticality in artificial spin ices

We show that both square and kagome artificial spin ice systems exhibit disorder-induced nonequilibrium phase transitions, with power law avalanche distributions at the critical disorder level. The different nature of geometrical frustration in the two lattices produces distinct types of critical avalanche behavior. For the square ice, the avalanches involve the propagation of locally stable domain walls separating the two polarized ground states, and the scaling collapse agrees with an interface depinning mechanism. In contrast, avalanches in the fully frustrated kagome ice exhibit pronounced branching behaviors that resemble those found in directed percolation. The kagome ice also shows an interesting crossover in the power-law scaling of the avalanches at low disorder. Our results show that artificial spin ices are ideal systems in which to study nonequilibrium critical point phenomena.
Effects of Persuasive Dialogues: Testing Bot Identities and Inquiry Strategies

Intelligent conversational agents, or chatbots, can take on various identities and are increasingly engaging in more human-centered conversations with persuasive goals. However, little is known about how identities and inquiry strategies influence the conversation's effectiveness. We conducted an online study involving 790 participants to be persuaded by a chatbot for charity donation. We designed a two by four factorial experiment (two chatbot identities and four inquiry strategies) where participants were randomly assigned to different conditions. Findings showed that the perceived identity of the chatbot had significant effects on the persuasion outcome (i.e., donation) and interpersonal perceptions (i.e., competence, confidence, warmth, and sincerity). Further, we identified interaction effects among perceived identities and inquiry strategies. We discuss the findings for theoretical and practical implications for developing ethical and effective persuasive chatbots. Our published data, codes, and analyses serve as the first step towards building competent ethical persuasive chatbots.
Modelling and Using Response Times in Online Courses

Each time a learner in a self-paced online course seeks to answer an assessment question, it takes some time for the student to read the question and arrive at an answer to submit. If multiple attempts are allowed, and the first answer is incorrect, it takes some time to provide a second answer. Here we study the distribution of such “response times.” We find that the log-normal statistical model for such times, previously suggested in the literature, holds for online courses. Users who, according to this model, tend to take longer on submits are more likely to complete the course, have a higher level of engagement, and achieve a higher grade. This finding can be the basis for designing interventions in online courses, such as MOOCs, which would encourage “fast” users to slow down.
Inhomogeneous Anisotropic Cosmology

In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with ``flat'' (including toroidal) and ``open'' (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are ``flat'' or ``open''. Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with ``flat'' or ``open'' topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.
The semigroup of Betti diagrams

The recent proof of the Boij-Soderberg conjectures reveals new structure about Betti diagrams of modules, giving a complete description of the cone of Betti diagrams. We begin to expand on this new structure by investigating the semigroup of Betti diagrams. We prove that this semigroup is finitely gener- ated, and we answer several other fundamental questions about this semigroup.
Efficiency Theory : a Unifying Theory for Information, Computation and Intelligence

AbstractThe paper serves as the first contribution towards the development of the theory of efficiency: a unifying framework for the currently disjoint theories of information, complexity, communication and computation. Realizing the defining nature of the brute force approach in the fundamental concepts in all of the above mentioned fields, the paper suggests using efficiency or improvement over the brute force algorithm as a common unifying factor necessary for the creation of a unified theory of information manipulation. By defining such diverse terms as randomness, knowledge, intelligence and computability in terms of a common denominator we are able to bring together contributions from Shannon, Levin, Kolmogorov, Solomonoff, Chaitin, Yao and many others under a common umbrella of the efficiency theory.
Sharp Dirac's Theorem for DP-Critical Graphs

Correspondence coloring, or DP-coloring, is a generalization of list coloring introduced recently by Dvořak and Postle. In this paper we establish a version of Dirac's theorem on the minimum number of edges in critical graphs in the framework of DP-colorings. A corollary of our main result answers a question posed by Kostochka and Stiebitz on classifying list-critical graphs that satisfy Dirac's bound with equality.
Eisenstein Hecke algebras and conjectures in Iwasawa theory

We formulate a weak Gorenstein property for the Eisenstein component of the p-adic Hecke algebra associated to modular forms. We show that this weak Gorenstein property holds if and only if a weak form of Sharifi's conjecture and a weak form of Greenberg's conjecture hold.
Soft-gluon corrections in top-quark production

I review calculations of soft-gluon corrections for top-quark production in hadron collisions. I describe theoretical formalisms for their resummation and for finite-order expansions. I show that soft-gluon corrections are dominant for a large number of top-quark processes. I discuss top–antitop pair production as well as single-top production, including total cross sections and differential distributions, and compare with data from the LHC and the Tevatron. I also discuss top-quark production in association with charged Higgs bosons, Z bosons and other particles in models of new physics.
Global divisibility of Heegner points and Tamagawa numbers

We improve Kolyvagin’s upper bound on the order of the p-primary part of the Shafarevich–Tate group of an elliptic curve of rank one over a quadratic imaginary field. In many cases, our bound is precisely that predicted by the Birch and Swinnerton-Dyer conjectural formula.
Exploring color-octet scalar parameter space in minimal R-symmetric models

In this work we study the collider phenomenology of color-octet scalars (sgluons) in minimal supersymmetric models endowed with a global continuous R symmetry. We systematically catalog the significant decay channels of scalar and pseudoscalar sgluons and identify novel features that are natural in these models. These include decays in nonstandard diboson channels, such as to a gluon and a photon; three-body decays with considerable branching fractions; and long-lived particles with displaced vertex signatures. We also discuss the single and pair production of these particles and show that they can evade existing constraints from the Large Hadron Collider, to varying extents, in large regions of reasonable parameter space. We find, for instance, that a 725 GeV scalar and a 350 GeV or lighter pseudoscalar can still be accommodated in realistic scenarios.
D-brane Wess-Zumino actions, T-duality and the cosmological constant

Abstract A geometrical formulation of the T-duality rules for type II superstring Ramond-Ramond fields is presented. This is used to derive the Wess-Zumino terms in superstring D-brane actions, including terms proportional to the mass parameter of the IIA theory, thereby completing partial results in the literature. For non-abelian world-volume gauge groups the massive type IIA D-brane actions contain non-abelian Chern-Simons terms for the Born-Infeld gauge potential, implying a quantization of the IIA cosmological constant.
The bibliometric properties of article readership information

Digital libraries such as the NASA Astrophysics Data System (Kurtz et al., 2005) permit the easy accumulation of a new type of bibliometric measure, the number of electronic accesses (“reads”) of individual articles. We explore various aspects of this new measure. We examine the obsolescence function as measured by actual reads and show that it can be well fit by the sum of four exponentials with very different time constants. We compare the obsolescence function as measured by readership with the obsolescence function as measured by citations. We find that the citation function is proportional to the sum of two of the components of the readership function. This proves that the normative theory of citation is true in the mean. We further examine in detail the similarities and differences among the citation rate, the readership rate, and the total citations for individual articles, and discuss some of the causes. Using the number of reads as a bibliometric measure for individuals, we introduce the read–cite diagram to provide a two-dimensional view of an individual's scientific productivity. We develop a simple model to account for an individual's reads and cites and use it to show that the position of a person in the read–cite diagram is a function of age, innate productivity, and work history. We show the age biases of both reads and cites and develop two new bibliometric measures which have substantially less age bias than citations: SumProd, a weighted sum of total citations and the readership rate, intended to show the total productivity of an individual; and Read10, the readership rate for articles published in the last 10 years, intended to show an individual's current productivity. We also discuss the effect of normalization (dividing by the number of authors on a paper) on these statistics. We apply SumProd and Read10 using new, nonparametric techniques to compare the quality of different astronomical research organizations.
Potentials between static SU(3) sources in the fat-center-vortices model

The potentials between static sources in various representations in SU(3) are calculated based on the fat-center-vortices model of Faber, Greensite and Olejnik. At intermediate distances, most distributions of the flux within vortices lead to potentials that are qualitatively in agreement with ``Casimir scaling'', which says that the string tension is proportional to the quadratic operator of the representation. However, at the quantitative level, violations of Casimir scaling are generally much larger than those seen in numerical simulations, indicating that additional physical input to the fat-center-vortices model is required. At large distances, screening occurs for zero-triality representations; for the representations with non-zero triality the string tension equals that of the fundamental representation. Some rather ``unphysical'' flux distributions can lead to violations of Casimir scaling at intermediate distances and violations of the expected ordering of representations at large distances.
STEP and fundamental physics

The Satellite Test of the Equivalence Principle (STEP) will advance experimental limits on violations of Einstein's equivalence principle from their present sensitivity of two parts in 1013 to one part in 1018 through multiple comparison of the motions of four pairs of test masses of different compositions in a drag-free earth-orbiting satellite. We describe the experiment, its current status and its potential implications for fundamental physics. Equivalence is at the heart of general relativity, our governing theory of gravity and violations are expected in most attempts to unify this theory with the other fundamental interactions of physics, as well as in many theoretical explanations for the phenomenon of dark energy in cosmology. Detection of such a violation would be equivalent to the discovery of a new force of nature. A null result would be almost as profound, pushing upper limits on any coupling between standard-model fields and the new light degrees of freedom generically predicted by these theories down to unnaturally small levels.
Computational search for magnetic and non-magnetic 2D topological materials using unified spin–orbit spillage screening

Two-dimensional topological materials (2D TMs) have a variety of properties that make them attractive for applications including spintronics and quantum computation. However, there are only a few such experimentally known materials. To help discover new 2D TMs, we develop a unified and computationally inexpensive approach to identify magnetic and non-magnetic 2D TMs, including gapped and semi-metallic topological classifications, in a high-throughput way using density functional theory-based spin–orbit spillage, Wannier-interpolation, and related techniques. We first compute the spin–orbit spillage for the ~1000 2D materials in the JARVIS-DFT dataset, resulting in 122 materials with high-spillage values. Then, we use Wannier-interpolation to carry-out Z2, Chern-number, anomalous Hall conductivity, Curie temperature, and edge state calculations to further support the predictions. We identify various topologically non-trivial classes such as quantum spin-Hall insulators, quantum anomalous-Hall insulators, and semimetals. For a few predicted materials, we run G0W0+SOC and DFT+U calculations. We find that as we introduce many-body effects, only a few materials retain non-trivial band-topology, suggesting the importance of high-level density functional theory (DFT) methods in predicting 2D topological materials. However, as an initial step, the automated spillage screening and Wannier-approach provide useful predictions for finding new topological materials and to narrow down candidates for experimental synthesis and characterization.
A horseshoe with a discontinuous entropy spectrum

Abstract We study the regularity of the entropy spectrum of the Lyapunov exponents for hyperbolic maps on surfaces. It is well-known that the entropy spectrum is a concave upper semi-continuous function which is analytic on the interior of the set of Lyapunov exponents. In this paper we construct a family of horseshoes with a discontinuous entropy spectrum at the boundary of the set of Lyapunov exponents.
Circumventing the optical diffraction limit with customized speckles

Speckle patterns have been used widely in imaging techniques such as ghost imaging, dynamic speckle illumination microscopy, structured illumination microscopy, and photoacoustic fluctuation imaging. Recent advances in the ability to control the statistical properties of speckles has enabled the customization of speckle patterns for specific imaging applications. In this work, we design and create special speckle patterns for parallelized nonlinear pattern-illumination microscopy based on fluorescence photoswitching. We present a proof-of-principle experimental demonstration where we obtain a spatial resolution three times higher than the diffraction limit of the illumination optics in our setup. Furthermore, we show that tailored speckles vastly outperform standard speckles. Our work establishes that customized speckles are a potent tool in parallelized super-resolution microscopy.
GPU-Accelerated Discontinuous Galerkin Methods: 30x Speedup on 345 Billion Unknowns

A discontinuous Galerkin method for the discretization of the compressible Euler equations, the governing equations of inviscid fluid dynamics, on Cartesian meshes is developed for use of Graphical Processing Units via OCCA, a unified approach to performance portability on multi-threaded hardware architectures. A 30x time-to-solution speedup over CPU-only implementations using non-CUDA-Aware MPI communications is demonstrated up to 1,536 NVIDIA V100 GPUs and parallel strong scalability is shown up to 6,144 NVIDIA V100 GPUs for a problem containing 345 billion unknowns. A comparison of CUDA-Aware MPI communication to non-GPUDirect communication is performed demonstrating an additional 24 % speedup on eight nodes composed of 32 NVIDIA V100 GPUs.
PMU based Monitoring and Mitigation of Delayed Voltage Recovery using Admittances

This paper analyzes the delayed voltage recovery phenomenon by simplifying the Western Electricity Coordinating Council (WECC) composite load model using the load admittance and the thermal relay dynamics. From this analysis, a closed form expression approximating the recovery time is derived and the key load parameters impacting the behavior of voltage recovery are identified. A monitoring scheme based on the measured load admittance is then proposed to detect the onset of stalling, even in the presence of voltage oscillations, and estimate the duration of the delayed voltage recovery. A mitigation scheme utilizing smart thermostats and offline learning is also derived to ensure that the voltage recovers to the pre-contingency voltage within a specified time. Both the monitoring and mitigation schemes only need local measurements at a substation making them promising for online applications. Results for the monitoring and mitigation schemes are described in detail for the IEEE 162 bus system validating the various assumptions used for the analysis and establishing the connection between the delayed voltage recovery phenomenon and load admittance.
Supporting Expert Close Analysis of Historical Scientific Writings: A Case Study for Near-by Reading

Distant reading methodologies make use of computational processes to aid in the analysis of large text corpora which might not be pliable to traditional methods of scholarly analysis due to their volume. While these methods have been applied effectively to a variety of types of texts and contexts, they can leave unaddressed the needs of scholars in the humanities disciplines like history, who often engage in close reading of sources. Complementing the close analysis of texts with some of the tools of distant reading, such as visualization, can resolve some of the issues. We focus on a particular category of this intersection—which we refer to as near-by reading—wherein an expert engages in a computer-mediated analysis of a text with which they are familiar. We provide an example of this approach by developing a visual analysis application for the near-by reading of 19th-century scientific writings by J. W. von Goethe and A. P. de Candolle. We show that even the most formal and public texts, such as scientific treatises, can reveal unexpressed personal biases and philosophies that the authors themselves might not have recognized.
New Proximal Newton-Type Methods for Convex Optimization

In this paper, we propose new proximal Newton-type methods for convex optimization problems in composite form. The applications include model predictive control (MPC) and embedded MPC. Our new methods are computationally attractive since they do not require evaluating the Hessian at each iteration while keeping fast convergence rate. More specifically, we prove the global convergence is guaranteed and the superlinear convergence is achieved in the vicinity of an optimal solution. We also develop several practical variants by incorporating quasi-Newton and inexact subproblem solving schemes and provide theoretical guarantee for them under certain conditions. Experimental results on real-world datasets demonstrate the effectiveness and efficiency of new methods.
Studying the Interplay Between Apolipoprotein E and Education on Cognitive Decline in Centenarians Using Bayesian Beta Regression

Apolipoprotein E (APOE) is an important risk factor for cognitive decline and Alzheimer's disease in aging individuals. Among the 3 known alleles of this gene: e2, e3, and e4, the e4 allele is associated with faster cognitive decline and increased risk for Alzheimer's and dementia, while the e2 allele has a positive effect on longevity, and possibly on preservation of cognitive function. Education also has an important effect on cognition and longevity but the interplay between APOE and education is not well-characterized. Previous studies of the effect of APOE on cognitive decline often used linear regression with the normality assumption, which may not be appropriate for analyzing bounded and skewed neuropsychological test scores. In this paper, we applied Bayesian beta regression to assess the effect of APOE alleles on cognitive decline in a cohort of centenarians with longitudinal assessment of their cognitive function. The analysis confirmed the negative association between older age and cognition and the beneficial effect of education that persists even at the extreme of human lifespan in carriers of the e3 allele. In addition, the analysis showed an association between APOE and cognition that is modified by education. Surprisingly, an antagonistic interaction existed between higher education and APOE alleles, suggesting that education may reduce the positive effect of APOE e2 and increase the negative effect of APOE e4 at extreme old age.
Nonbinary Error-Detecting Hybrid Codes

Hybrid codes simultaneously encode both quantum and classical information, allowing for the transmission of both across a quantum channel. We construct a family of nonbinary error-detecting hybrid stabilizer codes that can detect one error while also encoding a single classical bit over the residue class rings $\mathbb{Z}_{q}$ inspired by constructions of nonbinary non-additive codes.
Coupled Boltzmann transport equations of heavy quarks and quarkonia in quark-gluon plasma

We develop a framework of coupled transport equations for open heavy flavor and quarkonium states, in order to describe their transport inside the quark-gluon plasma. Our framework is capable of studying simultaneously both open and hidden heavy flavor observables in heavy-ion collision experiments and can account for both, uncorrelated and correlated recombination. Our recombination implementation depends on real-time open heavy quark and antiquark distributions. We carry out consistency tests to show how the interplay among open heavy flavor transport, quarkonium dissociation and recombination drives the system to equilibrium. We then apply our framework to study bottomonium production in heavy-ion collisions. We include ϒ(1S), ϒ(2S), ϒ(3S), χb(1P) and χb(2P) in the framework and take feed-down contributions during the hadronic gas stage into account. Cold nuclear matter effects are included by using nuclear parton distribution functions for the initial primordial heavy flavor production. A calibrated 2 + 1 dimensional viscous hydrodynamics is used to describe the bulk QCD medium. We calculate both the nuclear modification factor RAA of all bottomonia states and the azimuthal angular anisotropy coefficient v2 of the ϒ(1S) state and find that our results agree reasonably with experimental measurements. Our calculations indicate that correlated cross-talk recombination is an important production mechanism of bottomonium in current heavy-ion experiments. The importance of correlated recombination can be tested experimentally by measuring the ratio of RAA(χb(1P)) and RAA(ϒ(2S)).
Anderson acceleration for contractive and noncontractive operators

A one-step analysis of Anderson acceleration with general algorithmic depths is presented. The resulting residual bounds within both contractive and noncontractive settings reveal the balance between the contributions from the higher and lower order terms, which are both dependent on the success of the optimization problem solved at each step of the algorithm. The new residual bounds show the additional terms introduced by the extrapolation produce terms that are of a higher order than was previously understood. In the contractive setting, these bounds sharpen previous convergence and acceleration results. The bounds rely on sufficient linear independence of the differences between consecutive residuals, rather than assumptions on the boundedness of the optimization coefficients, allowing the introduction of a theoretically sound safeguarding strategy. Several numerical tests illustrate the analysis primarily in the noncontractive setting, and demonstrate the use of the method, the safeguarding strategy, and theory-based guidance on dynamic selection of the algorithmic depth, on a p-Laplace equation, a nonlinear Helmholtz equation, and the steady Navier-Stokes equations with high Reynolds number in three spatial dimensions.
O ideal da imparcialidade e o público cívico

Resumo O texto analisa criticamente o ideal da imparcialidade, questionando sua viabilidade e sua adequacao do ponto de vista politico. As principais criticas sao ao fato de que esse ideal reduz as diferencas a unidade, nega a pluralidade, suspende as particularidades e apresenta perspectivas parciais dos grupos dominantes como se fossem universais. A autora propoe uma nocao de justica publica que incorpora a heterogeneidade e o discurso parcial. Palavras-chave: imparcialidade, perspectiva, justica, heterogeneidade, pluralidade. Abstract The text evaluates the ideal of impartiality, questioning its viability and political adequacy. Criticisms are directed, especially, to the fact that that ideal reduces differences to unities, denies plurality, brackets particularities and presents partial perspectives from dominant groups as if they were universal values. The author proposes a definition of public fairness that incorporates heterogeneity and partial discourses. Key-words: impartiality, perspective, justice, heterogeneity, plurality.
Enforcing Safety at Runtime for Systems with Disturbances

An assured controller is one that enforces safety online by filtering a desired control input at runtime, and control barrier functions (CBFs) provide an assured controller that renders a safe subset of the statespace forward invariant. In this work, we present a problem formulation for CBF-based runtime assurance for systems with disturbances, and controllers that solve this problem must, in some way, incorporate the online computation of reachable sets. In general, computing reachable sets in the presence of disturbances is computationally costly and cannot be directly incorporated in a CBF framework. To that end, we present a particular solution to the problem, whereby reachable sets are approximated via the mixed-monotonicity property. Efficient algorithms exist for over-approximating reachable sets for mixed-monotone systems with hyperrectangles, and we show that such approximations are suitable for incorporating into a CBF-based runtime assurance framework.
The Output Effects of Government Sponsored Cartels During the New Deal

This paper uses the National Industrial Recovery Act of 1933, which set up industry-wide cartels in the manufacturing sector of the US economy, to gain empirical insight into the current debate on the output effects of cartels. Recent theoretical studies have demonstrated ways in which cartels could expand, rather than reduce output as is traditionally thought. The New Deal cartel experiment does not support this ‘efficient cartel’ view. On the contrary, the legislation brought about a reduction in manufacturing output, as traditional cartel theory would predict.
Reputation Effects and the Limits of Contracting: A Study of the Indian Software Industry

This paper examines evidence of the role that reputation plays in determining contractual outcomes. We conduct an empirical analysis of the Indian customized software industry, using a data set we collected containing detailed information on 230 projects carried out by 125 software firms. We propose a model ofthe industry where reputation determines contractual outcomes. The evidence supports the view that reputation matters. Ex ante contracts, as well as the outcome after ex post renegotiation, vary with firms' characteristics plausibly associated with reputation. This holds after controlling for project, client, and firm characteristics.
Do Physicians Respond to Liability Standards

We explore the sensitivity of the clinical decisions of physicians to the standards of care expected of them under the law, drawing on the abandonment by states over time of rules holding physicians to standards determined by local customs and the contemporaneous adoption of national-standard rules. Using data on broad rates of surgical interventions at the county-by-year level from the Area Resource File, we find that local surgery rates converge towards national surgery rates upon the adoption of national-standard rules. Moreover, we find that these effects are more pronounced among rural counties.
Vintage Capital and Inequality

Abstract If machines are indivisible, a vintage capital model must give rise to income inequality. If new machines are always better than old ones and if society cannot provide everyone with a new machine all of the time, inequality will result. I explore this mechanism in detail. If technology resides in machines and if a firm or worker must use just one technology at a time, a variety of machines will be in use, and workers' productivities will differ. This is because not everyone can be given the latest vintage machine all of the time. Inequality thus originates in the limited capacity of the capital goods sector. If machine quality and skill are complements, a worker who is paired with the best machine will acquire more skill, and inequality persists indefinitely. Moreover, if the used equipment market or the process of labor turnover function without frictions, a perfect positive assignment between the quality of labor and of capital can be maintained by a process of continual reassignment. This serves to enhance the degree of equilibrium inequality. Paradoxically, in this type of model, free migration of labor across borders raises cross-country inequality instead of lowering it as it does in some other models. Journal of Economic Literature Classification Number: O31.
Dosimetric and deformation effects of image-guided interventions during stereotactic body radiation therapy of the prostate using an endorectal balloon

Purpose: During stereotactic body radiation therapy (SBRT) for the treatment of prostate cancer, an inflatable endorectal balloon (ERB) may be used to reduce motion of the target and reduce the dose to the posterior rectal wall. This work assessed the dosimetric impact of manual interventions on ERB position in patients receiving prostate SBRT and investigated the impact of ERB interventions on prostate shape. Methods: The data of seven consecutive patients receiving SBRT for the treatment of clinical stage T1cN0M0 prostate cancer enrolled in a multi-institutional, IRB-approved trial were analyzed. The SBRT dose was 50 Gy in five fractions to a planning target volume (PTV) that included the prostate (implanted with three fiducial markers) with a 3-5 mm margin. All plans were based on simulation images that included an ERB inflated with 60 cm{sup 3} of air. Daily kilovoltage cone-beam computed tomography (CBCT) imaging was performed to localize the PTV, and an automated fusion with the planning images yielded displacements required for PTV relocalization. When the ERB volume and/or position were judged to yield inaccurate repositioning, manual adjustment (ERB reinflation and/or repositioning) was performed. Based on all 59 CBCT image sets acquired, a deformable registration algorithm was used to determine themore » dose received by, displacement of, and deformation of the prostate, bladder (BLA), and anterior rectal wall (ARW). This dose tracking methodology was applied to images taken before and after manual adjustment of the ERB (intervention), and the delivered dose was compared to that which would have been delivered in the absence of intervention. Results: Interventions occurred in 24 out of 35 (69%) of the treated fractions. The direct effect of these interventions was an increase in the prostate radiation dose that included 95% of the PTV (D95) from 9.6 {+-} 1.0 to 10.0 {+-} 0.2 Gy (p = 0.06) and an increase in prostate coverage from 94.0% {+-} 8.5% to 97.8% {+-} 1.9% (p = 0.03). Additionally, ERB interventions reduced prostate deformation in the anterior-posterior (AP) direction, reduced errors in the sagittal rotation of the prostate, and increased the similarity in shape of the prostate to the radiotherapy plan (increased Dice coefficient from 0.76 {+-} 0.06 to 0.80 {+-} 0.04, p = 0.01). Postintervention decreases in prostate volume receiving less than the prescribed dose and decreases in the voxel-wise displacement of the prostate, bladder, and anterior rectal wall were observed, which resulted in improved dose-volume histogram (DVH) characteristics. Conclusions: Image-guided interventions in ERB volume and/or position during prostate SBRT were necessary to ensure the delivery of the dose distribution as planned. ERB interventions resulted in reductions in prostate deformations that would have prevented accurate localization of patient anatomy.« less
More on Unemployment and Vacancy Fluctuations

Abstract Shimer [Shimer, R., 2005a. The cyclical behavior of equilibrium unemployment and vacancies. American Economic Review 95 (March), 25–49] argues that the textbook equilibrium search model of unemployment explains less than 10% of the volatility in US vacancies and unemployment when fluctuations are driven by productivity shocks. His paper as well as other recent work inspired by it are reviewed and extended here. Although there seems to be excessive feedback from the job-finding rate to the wage built into the Nash bargaining mechanism assumed to determine wages in the model, we argue that he and others overemphasize the need for wage rigidity to explain the data on labor-market fluctuations. Indeed, a modified version of the model can explain the magnitude of the empirical relationship between the vacancy–unemployment ratio and labor productivity when wages are the outcome of a strategic bargaining game and when the elasticity of the matching function and the opportunity cost of a match are set at reasonable values. The modified model also explains almost two thirds of the volatility in the ratio relative to that of productivity when separation shocks are taken into account, as well as the strong negative correlation between vacancies and unemployment found in Shimer's data.
Incentives for innovation and centralized versus delegated capital budgeting

Abstract We study a setting wherein a divisional manager undertakes personally costly effort to improve the profitability of an investment project. The manager's choice of innovation effort is subject to a holdup problem because of the ex post opportunism on the part of headquarters. We analyze and contrast the performance of centralized and delegated forms of investment decision-making. We find that delegation improves the manager's innovation incentives. We identify conditions for each of the two organizational forms to emerge as the optimal choice, and relate these conditions to characteristics of firms' investment opportunity sets.
Shareholder litigation, shareholder–creditor conflict, and the cost of bank loans

Abstract I study how shareholder litigation affects the cost of bank loans via its impact on the distribution of bankruptcy estate and the conflict of interests between shareholders and creditors. Using a natural experiment based on a ruling by the Ninth Circuit Court of Appeals, I find that increasing the difficulty of class action suits decreases loan spreads. The effect is stronger for firms with higher institutional ownership, which is consistent with the argument that class actions suits help shareholders extract wealth from creditors when the firm is in bankruptcy. Further analysis shows that the effect is weaker for firms with stronger creditor protection in bankruptcy.
Digital Consumer Networks and Producer-Consumer Collaboration: Innovation and Product Development in the Video Game Industry

This paper examines new forms of collaboration between producers and consumers that are emerging in the digital entertainment space. Taking the case of the video game industry, we show how some firms have opened a portion of their proprietary content for transformation by consumers and allowed the development of consumer-designed and consumer-implemented derivative products. By reappropriating these derivatives, video game firms are successfully outsourcing parts of their game design and development process to digital consumer networks. Applying economic analysis, we explore the potential benefits and risks associated with outsourcing to networks of consumers. We also derive the optimal combination of copyright enforcement and consumer compensation. Our results suggest that profit-maximizing producers of video games have incentive to partially open game content to their users and to remunerate the most innovative ones, under the condition that the derivatives constitute complements to, and not substitutes for, the original product. We discuss the implications on firm strategy for innovation.
Prospect theory and liquidation decisions

We solve a liquidation problem for an agent with preferences consistent with the prospect theory of Kahneman and Tversky [Econometrica 47 (1979) 263–291]. We find that the agent is willing to hold a risky project with a relatively inferior Sharpe ratio if the project is currently making losses, and intends to liquidate it when it breaks even. On the other hand, the agent may liquidate a project with a relatively superior Sharpe ratio if its current profits rise or drop to the break-even point. Our results capture the spirit of the disposition effect and the break-even effect documented in empirical and experimental studies.
The differential impact of investor sentiment on the value relevance of book value versus earnings

This study investigates the impact of investor sentiment on the allocation of investor attention across different information sources. Specifically, I examine the differential role of investor sentiment on the value relevance of book value versus earnings. I predict and find that the value relevance of book value is higher during low sentiment relative to high sentiment periods, and conversely that the value relevance of earnings is higher during high sentiment relative to low sentiment periods. Additional analyses suggest that this sentiment effect is more pronounced for book value components that are closely related to abandonment value, and for earnings components that have strong indication of future earnings. This study also provides empirical evidence for the 'limited attention' theory suggested by psychology research by showing that investor skepticism leads to their placing greater emphasis on financial statement information.
A Cyber Age Privacy Doctrine: More Coherent, Less Subjective, and Operational

In a previous paper, I outlined a privacy doctrine — a cyber age privacy doctrine, or a CAPD — that seeks to account for important differences between the paper age and the digital one. This paper attempts to show that the CAPD provides a coherent normative doctrine that can be employed by the courts and legislatures and that is more systematic, less subjective, and at least as operational as the prevailing privacy doctrines. It deals with the right to privacy vis-a-vis the United States government rather than as a protection from intrusions by private actors such as corporations. Part I summarizes and develops the previously-published doctrine. Part II compares the coherence and objectivity of the CAPD to those of other doctrines and indicates the ways the CAPD can be operationalized.