cssi/SciSciGPT-SciSciNet huggingface dataset:
Characterizing Arithmetic Read-Once Formulae

An arithmetic Read-Once Formula (ROF for short) is a formula (i.e., a tree of computation) in which the operations are l +, ×r and such that every input variable labels at most one leaf. We give a simple characterization of such formulae. Other than being interesting in its own right, our characterization gives rise to a property-testing algorithm for functions computable by such formulae. To the best of our knowledge, prior to our work, no characterization and/or property-testing algorithm was known for this kind of formulae.
Smooth boosting and learning with malicious noise

We describe a new boosting algorithm which generates only smooth distributions which do not assign too much weight to any single example. We show that this new boosting algorithm can be used to construct efficient PAC learning algorithms which tolerate relatively high rates of malicious noise. In particular, we use the new smooth boosting algorithm to construct malicious noise tolerant versions of the PAC-model p-norm linear threshold learning algorithms described by Servedio (2002). The bounds on sample complexity and malicious noise tolerance of these new PAC algorithms closely correspond to known bounds for the online p-norm algorithms of Grove, Littlestone and Schuurmans (1997) and Gentile and Littlestone (1999). As special cases of our new algorithms we obtain linear threshold learning algorithms which match the sample complexity and malicious noise tolerance of the online Perceptron and Winnow algorithms. Our analysis reveals an interesting connection between boosting and noise tolerance in the PAC setting.
An Algorithm for Two Player Repeated Games with Perfect Monitoring

Consider repeated two-player games with perfect monitoring and discounting. We provide an algorithm that computes the set V ∗ of payoff pairs of all pure-strategy subgame perfect equilibria with public randomization. The algorithm provides significant efficiency gains over the existing implementations of the algorithm from Abreu, Pearce and Stacchetti (1990). These efficiency gains arise from a better understanding of the manner in which extreme points of the equilibrium payoff set are generated. An important theoretical implication of our algorithm is that the set of extreme points E of V ∗ is finite. Indeed, |E |≤ 3|A|, where A is the set of action profiles of the stage game.
On Query Processing and Optimality Using Spectral Locality-Preserving Mappings

A locality-preserving mapping (LPM) from the multi-dimensional space into the one-dimensional space is beneficial for many applications (e.g., range queries, nearest-neighbor queries, clustering, and declustering) when multi-dimensional data is placed into one-dimensional storage (e.g., the disk). The idea behind a locality-preserving mapping is to map points that are nearby in the multi-dimensional space into points that are nearby in the one-dimensional space. For the past two decades, fractals (e.g., the Hilbert and Peano space-filling curves) have been considered the natural method for providing a locality-preserving mapping to support efficient answer for range queries and similarity search queries. In this paper, we go beyond the idea of fractals. Instead, we investigate a locality-preserving mapping algorithm (The Spectral LPM) that uses the spectrum of the multi-dimensional space. This paper provably demonstrates how Spectral LPM provides a globally optimal mapping from the multi-dimensional space to the one-dimensional space, and hence outperforms fractals. As an application, in the context of range queries and nearest-neighbor queries, empirical results of the performance of Spectral LPM validate our analysis in comparison with Peano, Hilbert, and Gray fractal mappings.
The Kauffman bracket skein as an algebra of observables

We prove that the Kauffman bracket skein algebra of a cylinder over a surface with boundary, defined over complex numbers, is isomorphic to the observables of an appropriate lattice gauge field theory.
Targeted temperature management in emergency medicine: current perspectives

Landmark trials in 2002 showed that therapeutic hypothermia (TH) after out-of-hospital cardiac arrest due to ventricular tachycardia or ventricular fibrillation resulted in improved likelihood of good neurologic recovery compared to standard care without TH. Since that time, TH has been frequently instituted in a wide range of cardiac arrest patients regardless of initial heart rhythm. Recent evidence has evaluated how, when, and to what degree TH should be instituted in cardiac arrest victims. We outline early evidence, as well as recent trials, regarding the use of TH or targeted temperature management in these patients. We also provide evidence-based suggestions for the institution of targeted temperature management/TH in a variety of emergency medicine settings.
Time to rethink privatization in transition economies

Worldwide, increasing evidence suggest that privatization improves firm performance. But in some institutionally-weak transition economies, ownership change has so far, not delivered on its promise. The paper responds that mass, and rapid privatization schemes, turned over mediocre assets to people lacking the incentives, skills and resources to manage them appropriately, may be the answer. In fact, most high-quality assets are handled by resourceful, well-connected few, who incidentally, tend not to embark in restructuring practices, thus avoiding justification on assets acquisition. The absence of an institutional framework precludes development, and capitalization, forgoing increased financial results. The paper further questions discontents of privatization following the collapse of the Soviet Union, reviewing the financial fall in Russia, and difficulties in the Czech Republic, arguing that re-nationalization, and/or postponement of privatization, should be accompanied by measures to strengthen governments' managerial, and administrative capacities. Regrettably, the argument may fail, because governments that impair privatization, are likely as well to impair the management of state-owned firms. In the absence of institutional strength, recommendations suggest a progressive course of action, in a case-by-case privatization, with international cooperation, and assistance.
Synchronization of heterogeneous Kuramoto oscillators with arbitrary topology

We study synchronization of coupled Kuramoto oscillators with heterogeneous inherent frequencies and general underlying connectivity. We provide conditions on the coupling strength and the initial phases which guarantee the existence of a Positively Invariant Set (PIS) and lead to synchronization. Unlike previous works that focus only on analytical bounds, here we introduce an optimization approach to provide a computational-analytical bound that can further exploit the particular features of each individual system such as topology and frequency distribution. Examples are provided to illustrate our results as well as the improvement over previous existing bounds.
Regional Economic Growth in Mexico : Recent Evolution and the Role of Governance

There has been substantial research in recent years examining the regional evolution of economic growth across states in Mexico -- with a particular focus on the post North American Free Trade Agreement period. There is also a vast literature using cross-country regressions to examine institutional determinants of economic growth, including government transparency, or"corruption,"as a key institutional variable. This paper uses more recently available data for Mexican states to both update the general state convergence/divergence literature, and incorporate into the analysis more recently developed state level indicators of institutional factors related to government transparency. The authors do not find a systematic relationship between measures of government transparency and gross domestic product per capita growth in Mexico during 2001-2005; however, they do find that corruption is negatively associated with the level of state gross domestic product per capita. The contrasting results may imply that more years of data are necessary to be able to establish statistically significant relationships between state growth rates and measures of corruption.
An improved four-focal zone high-frequency ultrasound analog beamformer

An improved analog beamformer is described that is used to process the data from a high frequency linear array. This unit is a part of a test system, which has the capability to characterize ultrasound transducer arrays up to 128 elements. Improvements include increasing the accuracy of the dynamic focusing capability and an increased bandwidth of the summing circuit.
The Effect of Elevation and Corner Location on Oceanfront Condominium Value

Although previous research indicates that condominium unit location within a development has an effect on its value, no research has examined oceanfront condominium units and the unique influences to which they are exposed. This study analyzes data from condominium sales along the Gulf Coast of Alabama using hedonic pricing models that account for the externalities associated with their location. The findings indicate that the positive externalities associated with upper-floor and corner units have a positive and substantial effect on value. Corner units offer even greater positive externalities and sell at a premium to interior units, primarily due to their more panoramic view. Failure to account for both the positive and negative externalities specific to resort type properties could result in serious misspecification when applying hedonic modeling to these property types.
Microfabricated near-field scanning microwave probes

Design, microfabrication and characterization of co-axial microwave tips compatible with commercial atomic force microscope (AFM) are discussed. Simultaneous microwave and AFM images of materials, cells and devices, obtained using these tips, reveal interesting "inner" structures undetectable using AFM alone. The near-field microwave co-axial tips are capable of performing measurements both in reflection (R) and transmission (T) modes. R/T capability enables them to map the microwave conductivity/permittivity of objects or image electromagnetic near-field radiation patterns near active devices or through various objects over a wide frequency range of 0.5-20 GHz with possible extensions up to 100 GHz.
Regulating SARS in China: Law As an Antidote?

Severe Acute Respiratory Disease (SARS) is caused by a coronavirus, and as of this writing has no known vaccine or cure. Generally, the disease starts with a high fever, headaches, body aches, and mild respiratory symptoms. SARS spreads through respiratory droplets produced by an infected person when he or she coughs or sneezes or through physical contact.The disease was first identified in a southern province of China in November of 2002, and quickly spread to twenty-seven different countries. In March of 2003, the World Health Organization (WHO) declared SARS a global health threat. In China, the economic and social costs of the outbreak were enormous. By June of 2003, 5,327 people were infected, and 329 died as a result of these infections.In the 2003 outbreak, the global effort to combat SARS hinged on how effectively China dealt with the crisis. Unfortunately, initial information about the outbreak in China was concealed for fear of damaging local image and trade. As a result, the epidemic quickly gained momentum and erupted into a national health threat. After the SARS epidemic devastated Beijing in April of 2003, the Chinese government began a transparent approach and openly launched a national campaign against SARS. Newly enacted SARS laws played a crucial role in establishing the SARS reporting system, allocating medical resources, and administering quarantine and isolation. The epidemic was brought under control in June of 2003.Despite this eventual success, however, examination of the legal aspects of the Chinese government’s reaction to the SARS epidemic and in-depth analysis of the new SARS laws shows that SARS could have been much better contained. Further, it reveals that changing China’s traditional indifference toward existing laws would be far more effective in preventing epidemics than its current approach of enacting new laws for the same purpose.
Cotensor products of modules

Let C be a coalgebra over a field k and A its dual algebra. The category of C-comodules is equivalent to a category of A-modules. We use this to interpret the cotensor product M□N of two comodules in terms of the appropriate Hochschild cohomology of the A-bimodule M ⊗ N, when A is finite-dimensional, profinite, graded or differential-graded. The main applications are to Galois cohomology, comodules over the Steenrod algebra, and the homology of induced fibrations.
Infinite Families of Exact Sums of Squares Formulas, Jacobi Elliptic Functions, Continued Fractions, and Schur Functions

The problem of representing an integer as a sum of squares of integers is one of the oldest and most significant in mathematics. It goes back at least 2000 years to Diophantus, and continues more recently with the works of Fermat, Euler, Lagrange, Jacobi, Glaisher, Ramanujan, Hardy, Mordell, Andrews, and others. Jacobi's elliptic function approach dates from his epic Fundamenta Nova of 1829. Here, the author employs his combinatorial/elliptic function methods to derive many infinite families of explicit exact formulas involving either squares or triangular numbers, two of which generalize Jacobi's (1829) 4 and 8 squares identities to 4n2 or 4n(n+1) squares, respectively, without using cusp forms such as those of Glaisher or Ramanujan for 16 and 24 squares. These results depend upon new expansions for powers of various products of classical theta functions. This is the first time that infinite families of non-trivial exact explicit formulas for sums of squares have been found. The author derives his formulas by utilizing combinatorics to combine a variety of methods and observations from the theory of Jacobi elliptic functions, continued fractions, Hankel or Turanian determinants, Lie algebras, Schur functions, and multiple basic hypergeometric series related to the classical groups. His results (in Theorem 5.19) generalize to separate infinite families each of the 21 of Jacobi's explicitly stated degree 2, 4, 6, 8 Lambert series expansions of classical theta functions in sections 40-42 of the Fundamental Nova. The author also uses a special case of his methods to give a derivation proof of the two Kac and Wakimoto (1994) conjectured identities concerning representations of a positive integer by sums of 4n2 or 4n(n+1) triangular numbers, respectively. These conjectures arose in the study of Lie algebras and have also recently been proved by Zagier using modular forms. George Andrews says in a preface of this book, 'This impressive work will undoubtedly spur others both in elliptic functions and in modular forms to build on these wonderful discoveries.' Audience: This research monograph on sums of squares is distinguished by its diversity of methods and extensive bibliography. It contains both detailed proofs and numerous explicit examples of the theory. This readable work will appeal to both students and researchers in number theory, combinatorics, special functions, classical analysis, approximation theory, and mathematical physics.
PAHs in Comets: An Overview

Polycyclic aromatic hydrocarbon (PAH) molecules, ubiquitously seen in the interstellar medium (ISM) of our own and external galaxies, might have been incorporated into comets if they are formed from relatively unprocessed interstellar matter. The detection of PAHs in comets would be an important link between the ISM and comets. This review compiles our current knowledge on cometary PAHs, based on ground-based and space-borne observations of infrared vibrational and ultraviolet fluorescence spectra of comets, and laboratory analysis of interplanetary dust particles possibly of cometary origin and cometary samples returned to Earth by the {Stardust}\ spacecraft. The latter provided the most unambiguous evidence for the presence of PAHs in cometary nuclei.
Topology from the bottom up

Every soccer ball has 12 pentagons, even when it is deflated. In his Perspective, [Kamien][1] describes how [ Bausch et al .][2] exploit this topological property in the design of complex new materials based on the self-assembly of two-dimensional colloidal crystals on spheres. The work is an example of a growing trend in materials science to control not only the geometry but also the connectivity (and hence topology) of molecules in self-assembled materials. The approach reported by Bausch et al . is particularly powerful because it is not dependent on specific interactions and should therefore allow the assembly of a wide range of hierarchical, self-assembled materials. [1]: http://www.sciencemag.org/cgi/content/full/299/5613/1671 [2]: http://www.sciencemag.org/cgi/content/short/299/5613/1716
A Decoupled Unconditionally Stable Numerical Scheme for the Cahn---Hilliard---Hele-Shaw System

We propose a novel decoupled unconditionally stable numerical scheme for the simulation of two-phase flow in a Hele-Shaw cell which is governed by the Cahn---Hilliard---Hele-Shaw system (CHHS) with variable viscosity. The temporal discretization of the Cahn---Hilliard equation is based on a convex-splitting of the associated energy functional. Moreover, the capillary forcing term in the Darcy equation is separated from the pressure gradient at the time discrete level by using an operator-splitting strategy. Thus the computation of the nonlinear Cahn---Hilliard equation is completely decoupled from the update of pressure. Finally, a pressure-stabilization technique is used in the update of pressure so that at each time step one only needs to solve a Poisson equation with constant coefficient. We show that the scheme is unconditionally stable. Numerical results are presented to demonstrate the accuracy and efficiency of our scheme.
Achieving the trade targets of Millennium Development Goal 8: Status in the least developed countries of Asia and the Pacific

This paper examines the progress made so far in achieving the trade targets of Millennium Development Goal 8 (“Building a Global Partnership for Development”) with respect to the Least Developed Countries (LDCs) of Asia and the Pacific. The paper uses data from the OECD, WTO and UNDP, among others, to measure the MDG indicators 8.6, 8.7 and 8.9 with respect to these countries, thereby quantifying some of the impacts in these countries of recent global and national policy changes in the areas of market access, tariff preferences for LDCs and Aid for Trade. This paper concludes that while the market access commitments of the Hong Kong WTO Ministerial Declaration of 2005 have largely been met and LDCs of the Asia-Pacific benefit disproportionately from Aid for Trade, the overall share of LDC exports as a part of total world exports has not increased over the past decade. In its conclusion, this paper suggests that other factors such as non-tariff barriers and product competitiveness play a significant role and should become policy priorities of better targeted Aid for Trade.
Problems in Astrophysical Radiation Hydrodynamics

The basic equations of radiation hydrodynamics are discussed in the regime that the radiation is dynamically as well as thermally important. Particular attention is paid to the question of what constitutes an acceptable approximate non-relativistic system of dynamical equations for matter and radiation in this regime. Further discussion is devoted to two classes of application of these ideas. The first class consists of problems dominated by line radiation, which is sensitive to the velocity field through the Doppler effect. The second class is of problems in which the advection of radiation by moving matter dominates radiation diffusion.
On the dual of Cesàro function space

Abstract The goal of this paper is to present an isometric representation of the dual space to Cesaro function space C p , w , 1 p ∞ , induced by arbitrary positive weight function w on interval ( 0 , l ) where 0 l ⩽ ∞ . For this purpose given a strictly decreasing nonnegative function Ψ on ( 0 , l ) , the notion of essential Ψ -concave majorant f ˆ of a measurable function f is introduced and investigated. As applications it is shown that every slice of the unit ball of the Cesaro function space has diameter 2. Consequently, Cesaro function spaces do not have the Radon–Nikodym property, are not locally uniformly convex and they are not dual spaces.
Partial discharge performance of lapped plastic insulation for superconducting power transmission cables and the dielectric strength of supercritical helium gas

Brookhaven National Laboratory (BNL) has been working on a project to develop a superconducting power transmission cable since 1972. A flexible ac cable with Nb 3 Sn superconductor force-cooled by supercritical helium, was the design selected.1 Any dielectric used in a superconducting cable must have a very low dissipation factor so that the heat load to the refrigeration system is minimized. Differential contraction during cooling makes it impossible to use extruded dielectric, so a lapped, multilayer plastic tape construction was selected, with supercritical helium gas filling the butt spaces between tapes. Evaluation of many different tapes2 has shown biaxially oriented laminated polypropylene tape to be a promising dielectric.
Quantum Critical Metals: Beyond the Order Parameter Fluctuations

The standard description of quantum critical points takes into account only fluctuations of the order parameter, and treats quantum fluctuations as extra dimensions of classical fluctuations. This picture can break down in a qualitative fashion in quantum critical metals: non-Fermi liquid electronic excitations are formed precisely at the quantum critical point and appear as a part of the quantum-critical spectrum. In the case of heavy fermion metals, it has been proposed that the non-Fermi liquid behavior is characterized by the destruction of a Kondo effect. The latter invalidates Hertz’s Gaussian theory of paramagnons and leads to an interacting theory that is ‘‘locally quantum critical’’. We summarize the theoretical and experimental developments on the subject. We also discuss their broader implications, and make contact with recent work on quantum critical magnets.
Can Quality of Care for Patients With Cirrhosis Be Measured

Introduction The ultimate purpose of measuring quality of care is to discriminate between healthcare providers in order to motivate improvement. Recently, a set of evidence-based indicators has been proposed for measurement of processes of care for patients with cirrhosis, for example early endoscopy for variceal bleeding. The objective of this study was to determine whether these indicators can be measured in a reliable and automated fashion in routine practice. Materials and methods We applied the top five indicators, based on agreement of a panel of experts, to hospitalized adults at our institution over a 3-year period. Results Only two of the indicators could be reliably measured on the basis of the published wording, and these two still required physician chart review. After applying some assumptions, the indicators were met in 46‐100% of cases. None of the indicators was linked to a single physician or institution in all cases, and none occurred with sufficient frequency to discriminate quality between
Association between electrocardiographic findings, right heart strain, and short-term adverse clinical events in patients with acute pulmonary embolism.

Background Electrocardiographic (ECG) changes may be seen with pulmonary emboli (PE). Whether ECG is associated with short-term adverse clinical events after PE is less well established. Hypothesis ECG findings are associated with short-term clinical deterioration after PE. Methods Consecutive adult PE patients were enrolled in an academic emergency department from 2008 to 2011. The primary outcome was right heart strain (RHS) on echocardiogram or CT pulmonary angiography, or TnT ≥0.1 ng/mL. We derived an ECG (TwiST) score that is associated with RHS and short-term adverse clinical events. Results We enrolled 298 patients with PE. On multivariate analysis, T-wave inversion in leads V1 through V3 (OR: 4.7, 95% confidence interval [CI]: 1.7-13.2), S wave in lead I (OR: 2.0, 95% CI: 1.1-3.5), and tachycardia (OR: 2.5, 95% CI: 1.3-4.8) were associated with RHS. A TwiST score ≤2 (n = 210, 72%) was 84% (95% CI: 77%-90%) sensitive for the absence of RHS, whereas a TwiST score ≥5 (n = 47, 16%) was 93% (95% CI: 88%-97%) specific for the presence of RHS. Conclusions A simple ECG (TwiST) score can identify patients likely or not likely to have RHS with >80% specificity and sensitivity and may assist in identifying patients with acute PE at risk for adverse clinical events before pursuing other advanced imaging tests.
Manufacturing Consent in Cyberspace: China's “Fifty-Cent Army”:

Studies on public expression in China tend to focus on how the state and internet users (netizens) struggle over the limits of online expression. Few have systematically traced discourse competition within state-imposed boundaries, particularly how the authoritarian state has adapted to manage, rather than censor, online expression. This paper explores and evaluates the state’s attempts to manipulate online expression without resorting to censorship and coercion by examining the role of internet commentators, known as the “fifty-cent army”, in Chinese cyberspace. To cope with the challenge of online expression, the authoritarian state has mobilized its agents to engage anonymously in online discussions and produce apparently spontaneous pro-regime commentary. However, due to a lack of proper motivation and the persistence of old propaganda logic, this seemingly smart adaptation has proven ineffective or even counter-productive: It not only decreases netizens’ trust in the state but also, ironically, suppresses the voices of regime supporters.
Posture-dependent human 3He lung imaging in an open-access MRI system: initial results.

Rationale and Objectives The human lung and its functions are extremely sensitive to orientation and posture, and debate continues as to the role of gravity and the surrounding anatomy in determining lung function and heterogeneity of perfusion and ventilation. However, study of these effects is difficult. The conventional high-field magnets used for most hyperpolarized 3 He magnetic resonance imaging (MRI) of the human lung, and most other common radiologic imaging modalities including positron emission tomography and computed tomography, restrict subjects to lying horizontally, minimizing most gravitational effects. Materials and Methods In this article, we review the motivation for posture-dependent studies of human lung function and present initial imaging results of human lungs in the supine and vertical body orientations using inhaled hyperpolarized 3 He gas and an open-access MRI instrument. The open geometry of this MRI system features a “walk-in” capability that permits subjects to be imaged in vertical and horizontal positions and potentially allows for complete rotation of the orientation of the imaging subject in a two-dimensional plane. Results Initial results include two-dimensional lung images acquired with ∼4 × 8 mm in-plane resolution and three-dimensional images with ∼2-cm slice thickness. Conclusions Effects of posture variation are observed, including posture-related effects of the diaphragm and distension of the lungs while vertical.
Foreign Ownership and Real Earnings Management: Evidence from Japan

ABSTRACT: Studying a sample of Japanese firms, we examine whether foreign investors exert a significant influence on earnings management through manipulation of real activities. We find that foreign investors play an independent role in restraining real earnings management, as captured by abnormal cash flow from operations, abnormal discretionary expenses, abnormal production costs, or a composite of the aforementioned three measures. These results are robust to a variety of controls, including economic fundamentals, domestic blockholdings, governance mechanisms, and endogeneity of foreign ownership. Our findings indicate that sophisticated foreign investors, with relatively few business ties to local management, improve the accounting oversight of local firms by curbing earnings manipulation via operating activities. Collectively, our evidence suggests that one potential benefit of capital market globalization is less real earnings management in particular and higher earnings quality in general. JEL Clas...
Excitation mechanisms of Er optical centers in GaN epilayers

We report direct evidence of two mechanisms responsible for the excitation of optically active Er3+ ions in GaN epilayers grown by metal-organic chemical vapor deposition. These mechanisms, resonant excitation via the higher-lying inner 4f shell transitions and band-to-band excitation of the semiconductor host, lead to narrow emission lines from isolated and the defect-related Er optical centers. However, these centers have different photoluminescence spectra, local defect environments, decay dynamics, and excitation cross sections. The photoluminescence at 1.54 μm from the isolated Er optical center which can be excited by either mechanism has the same decay dynamics, but possesses a much higher excitation cross-section under band-to-band excitation. In contrast, the photoluminescence at 1.54 μm from the defect-related Er optical center can only be observed through band-to-band excitation but has the largest excitation cross-section. These results explain the difficulty in achieving gain in Er doped GaN ...
Simulation of electromagnetic aspects of lightning

In testing complex electronic systems for their vulnerability to lightning interference and electrical damage, it is necessary that the test include a simulation. For a simulation one requires that the experimental conditions be sufficiently close to the true physical environment that valid conclusions can be drawn concerning the response in such a criterion environment. Present commonly used test procedures, particularly for the direct-strike case, are in general not simulations. For the case of distant lightning, commonly used EMP simulation techniques are applicable with some modification in the sources (pulsers).
Including all the lines

Abstract I present a progress report on including all the lines in the line lists, including all the lines in the opacities, and including all the lines in the model atmosphere and spectrum synthesis calculations. The increased opacity will improve stellar atmosphere, pulsation, stellar interior, asteroseismology, nova, supernova, and other radiation-hydrodynamics calculations. I also report on producing high-resolution, high-signal-to-noise atlases for use in verifying the line data and spectrum calculations, and as tools for extending laboratory spectrum analyses to higher energy levels. All the data are available on my web site: kurucz.harvard.edu.
Divide and conquer kernel ridge regression: a distributed algorithm with minimax optimal rates

We study a decomposition-based scalable approach to kernel ridge regression, and show that it achieves minimax optimal convergence rates under relatively mild conditions. The method is simple to describe: it randomly partitions a dataset of size N into m subsets of equal size, computes an independent kernel ridge regression estimator for each subset using a careful choice of the regularization parameter, then averages the local solutions into a global predictor. This partitioning leads to a substantial reduction in computation time versus the standard approach of performing kernel ridge regression on all N samples. Our two main theorems establish that despite the computational speed-up, statistical optimality is retained: as long as m is not too large, the partition-based estimator achieves the statistical minimax rate over all estimators using the set of N samples. As concrete examples, our theory guarantees that the number of subsets m may grow nearly linearly for finite-rank or Gaussian kernels and polynomially in N for Sobolev spaces, which in turn allows for substantial reductions in computational cost. We conclude with experiments on both simulated data and a music-prediction task that complement our theoretical results, exhibiting the computational and statistical benefits of our approach.
On the existence of 0/1 polytopes with high semidefinite extension complexity

In Rothvoβ (Math Program 142(1---2):255---268, 2013) it was shown that there exists a 0/1 polytope (a polytope whose vertices are in $$\{0,1\}^{n}$${0,1}n) such that any higher-dimensional polytope projecting to it must have $$2^{\varOmega (n)}$$2Ω(n) facets, i.e., its linear extension complexity is exponential. The question whether there exists a 0/1 polytope with high positive semidefinite extension complexity was left open. We answer this question in the affirmative by showing that there is a 0/1 polytope such that any spectrahedron projecting to it must be the intersection of a semidefinite cone of dimension $$2^{\varOmega (n)}$$2Ω(n) and an affine space. Our proof relies on a new technique to rescale semidefinite factorizations.
On the Existence of Low-Rank Explanations for Mixed Strategy Behavior

Nash equilibrium is used as a model to explain the observed behavior of players in strategic settings. For example, in many empirical applications we observe player behavior, and the problem is to determine if there exist payoffs for the players for which the equilibrium corresponds to observed player behavior. Computational complexity of Nash equilibria is important in this framework. If the payoffs that explain observed player behavior requires players to have solved a computationally hard problem, then the explanation provided is questionable. In this paper we provide conditions under which observed behavior of players can be explained by games in which Nash equilibria are easy to compute. We identify three structural conditions and show that if the data set of observed behavior satisfies any of these conditions, then it can be explained by payoff matrices for which Nash equilibria are efficiently computable.
Bayesian mechanism design with efficiency, privacy, and approximate truthfulness

Recently, there has been a number of papers relating mechanism design and privacy (e.g., see [1-6]). All of these papers consider a worst-case setting where there is no probabilistic information about the players' types. In this paper, we investigate mechanism design and privacy in the Bayesian setting, where the players' types are drawn from some common distribution. We adapt the notion of differential privacy to the Bayesian mechanism design setting, obtaining Bayesian differential privacy. We also define a robust notion of approximate truthfulness for Bayesian mechanisms, which we call persistent approximate truthfulness. We give several classes of mechanisms (e.g., social welfare mechanisms and histogram mechanisms) that achieve both Bayesian differential privacy and persistent approximate truthfulness. These classes of mechanisms can achieve optimal (economic) efficiency, and do not use any payments. We also demonstrate that by considering the above mechanisms in a modified mechanism design model, the above mechanisms can achieve actual truthfulness.
Decision problems for additive regular functions

Additive Cost Register Automata (ACRA) map strings to integers using a finite set of registers that are updated using assignments of the form "x:=y+c" at every step. The corresponding class of additive regular functions has multiple equivalent characterizations, appealing closure properties, and a decidable equivalence problem. In this paper, we solve two decision problems for this model. First, we define the register complexity of an additive regular function to be the minimum number of registers that an ACRA needs to compute it. We characterize the register complexity by a necessary and sufficient condition regarding the largest subset of registers whose values can be made far apart from one another. We then use this condition to design a pspace algorithm to compute the register complexity of a given ACRA, and establish a matching lower bound. Our results also lead to a machine-independent characterization of the register complexity of additive regular functions. Second, we consider two-player games over ACRAs, where the objective of one of the players is to reach a target set while minimizing the cost. We show the corresponding decision problem to be exptime-complete when the costs are non-negative integers, but undecidable when the costs are integers.
Sponsoring a race to the top : the case for results-based intergovernmental finance for merit goods

Intergovernmental finance is a significant source of sub-national finance in most countries. In both industrial and developing countries, formula based "manna from heaven" general purpose transfers dominate but co-exist with highly intrusive micro-managed "command and control" specific purpose transfers. Both these types of transfers undermine political and fiscal accountability. Reforms to bring in design elements that incorporate incentives for results-based accountability are resisted by both donors and recipients alike. This is because the donors perceive such reforms as attempts at chipping away at their powers and recipients fear such programs will be intrusive. This paper presents conceptual and practical underpinnings of grant designs that could further simplicity, objectivity, and local autonomy objectives while furthering citizen-centric results-based accountability. The paper further highlights a few notable recent initiatives in both industrial and developing countries that embrace such directions for reform. The paper concludes that results-based intergovernmental finance offers significant potential to minimize tradeoffs between local autonomy and accountability while furthering access to merit goods.
Spin-Orbit Locking as a Protection Mechanism of the Odd-Parity Superconducting State against Disorder

Unconventional superconductors host a plethora of interesting physical phenomena. However, the standard theory of superconductors suggests that unconventional pairing is highly sensitive to disorder, and hence can only be observed in ultraclean systems. We find that due to an emergent chiral symmetry, spin-orbital locking can parametrically suppress pair decoherence introduced by impurity scattering in odd-parity superconductors. Our work demonstrates that disorder is not an obstacle to realize odd-parity superconductivity in materials with strong spin-orbit coupling.
Binary join trees

The main goal of this paper is to describe a data structure called binary join trees that are useful in computing multiple marginals efficiently using the Shenoy-Shafer architecture. We define binary join trees, describe their utility, and sketch a procedure for constructing them.
rscore: a Stata module to compute responsiveness scores

This paper presents rscore, a Stata module to compute unit responsiveness scores using a iterated random coefficient regression (RCR). The basic econometrics of this model can be found in Wooldridge (2002, pp. 638-642). The model estimated by rscore starts from a classical regression of Y, the target variable, on a series of factors X (the regressors), by assuming a different reaction (or responsiveness) of each unit to each factor contained in X. This is done by using a random coefficient regression (RCR), an approach in which the usual regression coefficients vary across units. The application of such an approach can convey new and interesting analytical findings compared to the traditional regression approach. In particular, by measuring a unit-specific regression coefficient for each regressor this model allows for: (i) ranking units according to the level of the responsiveness score obtained; (ii) detecting factors that are more influential in driving unit performance; (iii) studying, more in general, the distribution (variety) of the factors’ responsiveness scores across units. The knowledge of these idiosyncratic scores can be also exploited to test the presence of increasing, constant, or decreasing returns of Y to X in a straightforward and graphically easy-to-read way.
Lensing and High-z Supernova Surveys

Gravitational lensing causes the distribution of observed brightnesses of standard candles at a given redshift to be highly non-Gaussian. The distribution is strongly, and asymmetrically, peaked at a value less than the expected value in a homogeneous Robertson-Walker universe. Therefore, given any small sample of observations in an inhomogeneous universe, the most likely observed luminosity is at flux values less than the Robertson-Walker value. This Letter explores the impact of this systematic error due to lensing upon surveys predicated on measuring standard candle brightnesses. We reanalyze recent results from the high-z supernova team (Riess and coworkers), both when most of the matter in the universe is in the form of compact objects (represented by the empty-beam expression, corresponding to the maximal case of lensing) and when the matter is continuously distributed in galaxies. We find that the best-fit model remains unchanged (at Ωm=0, ΩΛ=0.45), but the confidence contours change size and shape, becoming larger (and thus allowing a broader range of parameter space) and dropping toward higher values of matter density Ωm (or correspondingly, lower values of the cosmological constant ΩΛ). These effects are slight when the matter is continuously distributed. However, the effects become considerably more important if most of the matter is in compact objects. For example, neglecting lensing, the Ωm=0.5, ΩΛ=0.5 model is more than 2 σ away from the best fit. In the empty-beam analysis, this cosmology is at 1 σ.
X‐Ray Imaging, Medical: Tomography and Radiography

First page of article Keywords: x-ray imaging, medical-tomography and radiography; x-ray nature and production
Loss Severity on Residential Mortgages: Evidence from Freddie Mac’s Newest Data

In this article, we analyze new loan-level data recently released by Freddie Mac on more than 17 million single-family mortgages to reveal a range of new and useful insights into the ultimate financial losses associated with a loan after it experiences a credit event. We conclude that mortgage insurance significantly lowers loss severities. We show that actual loss severities are higher than the preset severity schedule for loans with a loan-to-value (LTV) ratio of 60–80, relatively accurate for higher-LTV loans. We also find that small loans have higher severity than larger loans, that real-estate-owned (REO) sales have higher severity than short sales, and that there is no stable relationship between the state of origination and severity. Finally, we review the components of loss—liquidation value, direct expenses, and lost interest—and find that direct expenses and loss interest contribute significantly to the ultimate loss.
Conspicuous Consumption and Inequality

We analyze the change in consumer demand following a mean preserving change in consumption inequality when there is conspicuous consumption. We model interdependent preferences including “keeping up with the Joneses” (imitating others) and “running away from the Joneses” (distinguishing oneself from others) with multiple peer groups and peer group effects (envy and snob effects). An individual not directly involved in the redistribution increases consumption of the more conspicuous good when she demonstrates i) ‘keeping up’ and a relatively stronger envy effect, or ii) ‘running away’ and a relatively stronger snob effect. Behaviors generated by existing models emerge as special cases.
Characterization and Suppression Techniques for Degree of Radiation Damping in Inversion Recovery Measurements

Radiation damping is a phenomenon in which transverse nuclear magnetization couples with the current in a coil used in nuclear magnetic resonance experiments. This results in an additional magnetic field that increases the relaxation pathway for the magnetization, which then relaxes back to equilibrium more quickly. Radiation damping has been shown to affect longitudinal relaxation time (T1) measurement in inversion recovery experiments. In this work, we demonstrate that the extent of radiation damping depends upon the T1 of the sample. Radiation damping difference spectroscopy is used to characterize the severity of radiation damping, while gradient inversion recovery is used for radiation damping suppression in T1 measurements. At field strength of 9.4 T, for the radiation damping characteristic time (Trd) of 50 ms, these investigations show non-negligible radiation damping effects for T1 values greater than Trd, with severe distortions for T1 longer than about 150 ms, showing reasonable agreement with ...
Turbulent Structure of the Interstellar Medium

How does turbulence contribute to the formation and structure of the dense interstellar medium (ISM)? Molecular clouds are dense, high-pressure objects. It is usually argued that gravitational confinement causes the high pressures, and that the clouds are (magneto)hydrostatic objects supported by a balance between magnetic and turbulent pressures and gravity. However, magnetic pressures appear too weak, and MHD turbulent support not only requires driving, but also results in continuing gravitational collapse, as has now been demonstrated in simulations reaching 5123 zones. Models of supernova-driven, magnetized turbulence readily form transient, high-pressure, dense regions that may form molecular clouds. They are contained not by self-gravity, but by turbulent ram pressures from the larger flow. Apparent virialization may actually be a geometrical effect. Turbulent clouds are unlikely to be in hydrostatic equilibrium, instead either collapsing or expanding, although they may appear well-fit by projected equilibrium Bonnor-Ebert spheres. Collapsing clouds probably form stars efficiently, while expanding ones can still form stars by turbulent compression, but rather inefficiently.
Machine-generated algorithms, proofs and software for the batch verification of digital signature schemes

As devices everywhere increasingly communicate with each other, many security applications will require low-bandwidth signatures that can be processed quickly. Pairing-based signatures can be very short, but are often costly to verify. Fortunately, they also tend to have efficient batch verification algorithms. Finding these batching algorithms by hand, however, can be tedious and error prone.We address this by presenting AutoBatch, an automated tool for generating batch verification code in either Python or C++ from a high level representation of a signature scheme. AutoBatch outputs both software and, for transparency, a LaTeX file describing the batching algorithm and arguing that it preserves the unforgeability of the original scheme.We tested AutoBatch on over a dozen pairing-based schemes to demonstrate that a computer could find competitive batching solutions in a reasonable amount of time. In particular, it found an algorithm that is faster than a batching algorithm from Eurocrypt 2010. Another novel contribution is that it handles cross-scheme batching, where it searches for a common algebraic structure between two distinct schemes and attempts to batch them together.In this work, we expand upon our paper on AutoBatch appearing in ACM CCS 2012 [in: Proceedings of the 2012 ACM Conference on Computer and Communications Security, CCS'12, ACM, New York, NY, USA, 2012, pp. 474487] in a number of ways. We add a new loop-unrolling technique and show that it helps cut the batch verification cost of one scheme by roughly half. We describe our pruning and search algorithms in greater detail, including pseudocode and diagrams. All experiments were also re-run using the RELIC pairing library. We compare those results to our earlier results using the MIRACL library, and discuss why RELIC outperforms MIRACL in all but two cases. Automated proofs of several new batching algorithms are also included.AutoBatch is a useful tool for cryptographic designers and implementors, and to our knowledge, it is the first attempt to outsource to machines the design, proof writing and implementation of signature batch verification schemes.