cssi/SciSciGPT-SciSciNet huggingface dataset:
Sensitivity to missing data assumptions: Theory and an evaluation of the U.S. wage structure

This paper develops methods for assessing the sensitivity of empirical conclusions regarding conditional distributions to departures from the missing at random (MAR) assumption. We index the degree of nonignorable selection governing the missing data process by the maximal Kolmogorov–Smirnov distance between the distributions of missing and observed outcomes across all values of the covariates. Sharp bounds on minimum mean square approximations to conditional quantiles are derived as a function of the nominal level of selection considered in the sensitivity analysis and a weighted bootstrap procedure is developed for conducting inference. Using these techniques, we conduct an empirical assessment of the sensitivity of observed earnings patterns in U.S. Census data to deviations from the MAR assumption. We find that the well documented increase in the returns to schooling between 1980 and 1990 is relatively robust to deviations from the missing at random assumption except at the lowest quantiles of the distribution, but that conclusions regarding heterogeneity in returns and changes in the returns function between 1990 and 2000 are very sensitive to departures from ignorability.
New advances in inference by recursive conditioning

Recursive Conditioning (RC) was introduced recently as an any-space algorithm for inference in Bayesian networks which can trade time for space by varying the size of its cache at the increment needed to store a floating point number. Under full caching, RC has an asymptotic time and space complexity which is comparable to mainstream algorithms based on variable elimination and clustering (exponential in the network treewidth and linear in its size). We show two main results about RC in this paper. First, we show that its actual space requirements under full caching are much more modest than those needed by mainstream methods and study the implications of this finding. Second, we show that RC can effectively deal with determinism in Bayesian networks by employing standard logical techniques, such as unit resolution, allowing a significant reduction in its time requirements in certain cases. We illustrate our results using a number of benchmark networks, including the very challenging ones that arise in genetic linkage analysis.
Bounds on Revenue Distributions in Counterfactual Auctions with Reserve Prices

Measuring auction revenues under counterfactual reserve prices or formats requires knowledge of distributions of bidders’values and private signals. This poses a challenge when bids are observed from …rst-price, common-value auctions. I bound counterfactual revenue distributions without imposing parametric restrictions on the model structure. Using data from U.S. municipal bond auctions, I …nd …rst-price and second-price auctions under optimal reserve prices lead to little improvement in revenues over existing …rst-price formats. The number of bidders has a more signi…cant impact on revenues in optimal auctions. I also …nd invoking an incorrect assumption of private values in counterfactual analyses results in small errors in predicting revenues from optimal SP auctions.
Use of Web-Based Live Demos in Computer Science Courses

Web-based live demos were developed to remedy the lack of interaction in most Web-based courseware. These demos were used as supplemental materials for students to reinforce what they have learned in class. Through the interaction with live demos, students are forced to think proactively and to use what they have learned in class to solve problems. Positive feedback from students indicates that Web-based interactive demos help students to understand key concepts and to improve their problem-solving skills.
Sequential Innovation, Network Effects and the Choice of Compatibility

It is commonly argued that when innovation is sequential, and the product has network externalities, incumbents build a large network that inefficiently blocks the entry of future incompatible innovators. This paper shows that when intellectual property rights permit some degree of compatibility between the technologies of the incumbent and entrant, increased network size is not necessarily a deterrent to entry. In some cases an incumbent might prefer to construct a small network in order to make its capture by an entrant less appealing. Furthermore, the threat of entry may induce an incumbent to underinvest in the quality of his product. Finally, we show that property rights that fail to protect the incumbent are suboptimal, especially when the cost of future research is high. Moreover, weak property rights decrease current welfare by reducing the incumbent's incentives to create a big network in the first place. In most cases, a subsidy of the cost of R\&D of future innovators turns out to be more efficient than allowing entrants to use highly compatible technologies
Hubble expansion in a euclidean framework

There now seems to be strong evidence for a non-cosmological interpretation of the QSO redshift — in any case, so strong that it is of interest to investigate the consequences. The purpose of this paper is to construct a model of the Hubble expansion which is as far as possible from the conventional Big Bang model without coming in conflict with any well-established observational results (while introducing no new laws of physics). This leads to an essentially Euclidean metagalactic model (see Table I) with very little mass outside one-third or half of the Hubble radius. The total kinetic energy of the Hubble expansion need only to be about 5% of the rest mass energy. Present observations support backwards in time extrapolation of the Hubble expansion to a ‘minimum size galaxy’R m , which may have any value in 0<R m <4×1026 cm. Other arguments speak in favor of a size close to the upper value, sayR m =1026 cm (Table II). As this size is probably about 100 times the Schwarzschild limit, an essentially Euclidean description is allowed. The kinetic energy of the Hubble expansion may derive from an intense QSO-like activity in the minimum size metagalaxy, with an energy release corresponding to the annihilation of a few solar masses per galaxy per year. Some of the conclusions based on the Big Bang hypothesis are criticized and in several cases alternative interpretations are suggested. A comparison between the Euclidean and the conventional models is given in Table III.
Practical Statistics for Particle Physicists

These lectures introduce the basic ideas and practices of statistical analysis for particle physicists, using a real-world example to illustrate how the abstractions on which statistics is based are translated into practical application.
Blame the Switchman? Russian Railways Restructuring After Ten Years

The Russian economy relies on the Russian freight railways to an extraordinary degree. In 2001, after years of debate, the Russian government adopted an ambitious plan to transform this vertically integrated, government owned monopoly into a system that would rely more on private investment and competition and less on government ownership and regulation. This paper examines the state of the industry after ten years of reforms, with a focus on competition, tariffs, and private sector participation. Much remains to be decided, in particular the question of whether Russia will settle on its own unique model of railways restructuring or will move in the direction of one of the three standard models seen in other countries: vertical separation as in the UK and Sweden, third party access as in Germany and France, or horizontal separation, as in the US, Canada, and Mexico.
Italy - Assessing Competition and Efficiency in the Banking System

The paper assesses the degree of banking competition and efficiency in Italy? over time as well as compared to that in other countries, such as France, Germany, Spain, the United Kingdom, and the United States. The paper finds competition in the Italian banking sector has intensified in loan and deposit markets in recent years, but banks still operate in a highcost, high-income system, particularly with respect to retail/services, and efficiency gains have yet to fully materialize. The degree of competition falls within the range of estimates for a set of comparator countries. Greater contestability should act as a powerful force to drive banks to become more competitive and efficient. Competition policy will also continue to be an important consideration, both in enforcing Italy's antitrust laws and in ensuring that the procedures for dealing with weak banks and other merger and acquisition reviews focus on stability and competition objectives.
Trade policy analysis in the presence of duty drawbacks

Duty drawback schemes, which typically involve a combination of duty rebates and exemptions, are a feature of many countries' trade regimes. They are used in highly protected developing economies as a means of providing exporters with imported inputs at world prices, thus increasing their competitiveness, while maintaining the protection on the rest of the economy. In China, duty exemptions have been central to the process of trade reform and have led to a tremendous increase in processed exports using imported materials. Despite the widespread use and importance of duty drawbacks, these new trade liberalization instruments have been given relatively little attention in empirical multilateral trade liberalization studies. The paper presents an empirical multi-region general equilibrium model, in which the effects of policy reform are differentiated based on the trade orientation of the firms. The model is useful for analyzing trade liberalization in the presence of duty drawbacks, assessing whether countries should introduce or abolish these types of arrangements, and evaluating the impact of improved duty drawback system administration. The author's analysis shows that failure to account for duty exemptions in the case of China's recent WTO accession will overstate the increase in China's trade flows by 40 percent, welfare by 15 percent, and exports of selected sectors by as much as 90 percent. The magnitude of the bias depends on the level of pre-intervention tariffs and the size of tariff cuts-the larger the initial distortions and tariff reductions, the larger the bias when duty drawbacks are ignored. The bias in the estimates of China's real GDP, trade flows, and welfare changes due to WTO accession increases more than three times when China's pre-intervention tariffs are raised from their 1997 levels to the much higher 1995 levels. These results suggest that trade liberalization studies-focusing on economies in which protection is high, import concessions play an important role, and planned tariff cuts are deep-must treat duty drawbacks explicitly to avoid serious errors in their estimates of sectoral output, trade flows, and welfare changes.
Bayesian Methods for Contingency Tables

Bayesian alternatives to frequentist methods for fundamental problems in categorical data analysis, such as testing independence in two-way contingency tables and estimating probabilities of categories containing no observations, have been considered for at least four decades. Since the 1980s, Bayesian methods of model selection have also seen extensive and continuing development. These attempt to address the tendencies of frequentist approaches to arrive at overly complex models, and to disregard the effects of variability in model selection on model-based estimated effects and predictions. This entry briefly reviews several Bayes and empirical Bayes approaches to estimating probabilities of categories, testing equiprobability in a one-way table, testing independence in a two-way contingency table, and selecting among generalized linear models, with particular attention to loglinear models, for tables of higher dimension. Keywords: Bayesian methods; empirical Bayes; Bayes factors; BIC ; Schwartz criterion; smoothed counts; loglinear models; model selection
A Homotopy Approach to Solving Nonlinear Rational Expectation Problems

Many numerical methods have been developed in an attempt to find solutions to nonlinear rational expectations models. Because these algorithms are numerical in nature, they rely heavily on computing power and take sizeable cycles to solve. In this paper we present a numerical tool known as homotopy theory that can be applied to these methods. Homotopy theory reduces the computing time associated with an iterative algorithm by using a rational expectation problem with known solutions and transforming it into the problem at hand. If this transformation is performed slowly, homotopy theory also helps the global convergence properties of the numerical algorithm. We apply homotopy theory to Den Haan and Marcet‘s Parameterized Expectation Approach to show how homotopies improve the computing speed and global convergence properties of this algorithm.
The Era of State Energy Policy Innovation: A Review of Policy Instruments

U.S. energy and climate policy has evolved from the bottom-up, led by state governments, and internationally recognized for the use of unconventional and innovative policy instruments. This study focuses on policy instruments adopted throughout the era of state energy policy innovation that aim to diversify, decentralize, and decarbonize the electricity sector. Specific attention is devoted to the renewable portfolio standard, net metering, interconnection standards, tax incentives, public benefit funds, and energy efficiency resource standards. This analysis synthesizes the findings from the energy policy literature and provides a summary of the current state of understanding about the effects of various state energy policy instruments, and concludes with a discussion of broader trends that have emerged from the use of policy instruments in the state energy policy innovation era.
Searching in dynamic tree-like partial orders

We give the first data structure for the problem of maintaining a dynamic set of n elements drawn from a partially ordered universe described by a tree. We define the LINE-LEAF Tree, a linear-sized data structure that supports the operations: insert; delete; test membership; and predecessor. The performance of our data structure is within an O(log w)-factor of optimal. Here w ≤ n is the width of the partial-order--a natural obstacle in searching a partial order.
Tuning the Diversity of Open-Ended Responses From the Crowd

Crowdsourcing can solve problems beyond the reach of state-of-the-art fully automated systems. A common pattern found in many such systems is for the workers to discover, in parallel, a number of candidate solutions and then vote on the best one to pass forward, often within a fixed amount of time. We present the propose-vote-abstain mechanism for eliciting from crowd workers the proper balance between solution discovery and selection. Each crowd worker is given a choice among proposing an answer, voting among the answers proposed so far, or abstaining, i.e., doing nothing. When a stopping condition is reached, the mechanism returns the answer with the most votes. Workers are paid a base amount, with bonuses if they propose or vote for the winning answer.
Scales of Measurement

Scales of measurement, as conceived by S. S. Stevens, are defined with respect to (1) the extent to which empirical relationships among the measured objects correspond to numerical relationships among the measurements, and (2) the types of transformations that can be applied to the scale without distorting the structure of the scale. Stevens argued that whether or not a particular statistical analysis is ‘permissible’ depends upon the scale of measurement of the data being analyzed. While this assertion has been defended by some statisticians, it has been attacked by others. Many statistical textbooks for social scientists are organized around the assertion that scale of measurement is a critical factor in determining which statistical analysis is appropriate. Here, the authors argue that parametric statistical methods are appropriate only for interval level data and that nonparametric methods should be employed with noninterval data. One's attitude about the relationship between scale of measurement and choice of statistical analysis may follow from one's more basic ideas about measurement and the nature of reality. Ultimately, the distinction between interval and ordinal scales depends on whether one believes the relationship between the measurements and the true amounts of the measured attribute is positive linear (interval) or merely positive monotonic (ordinal), and such beliefs are largely a matter of faith. Keywords: scales of measurement; nominal; ordinal; interval; ratio; S. S. Stevens
Election goals and income redistribution: Recent evidence from Albania

This paper examines the impact of political competition on block grants from federal to sub-federal levels of government. We model the extent and direction of income redistribution as determined proximately by the political agendas of central decision makers and, at a deeper level, by the institutions within which they "nd themselves operating. We contrast two political objective functions that yield di!erent empirical predictions of the ways in which politics should a!ect "scal policy. Lessons learned here may prove important in understanding limits on the types of redistribution possible via block grants, given the institutional framework, in both developing and developed countries. 2001 Elsevier Science B.V. All rights reserved. JEL classixcation: H1; H7; O1
Entrepreneurs or Investors: Do Multi‐unit Franchisees Have Different Philosophical Orientations?

Although multi-unit ownership has become the dominant form of franchising in the United States, the motivations for either franchisor or franchisee to participate in these agreements continue to be the subject of debate. This study looks at the issue from the perspective of the franchisee. It is argued that some multi-unit franchisees, especially those operating as area developers, are likely to enter the field viewing their franchise as an investment, while others, especially those operating as sequential multi-unit operators, are likely to view their franchise as an opportunity to fulfill more personal, entrepreneurial ambitions. A study of multi-unit franchisees of both types found that both were equally investment-oriented but that the sequential multi-unit operators were more likely to seek fulfillment of entrepreneurial goals. Implications for practitioners and for future research are discussed.
A Data-Driven Approximation of the Koopman Operator: Extending Dynamic Mode Decomposition

The Koopman operator is a linear but infinite-dimensional operator that governs the evolution of scalar observables defined on the state space of an autonomous dynamical system and is a powerful tool for the analysis and decomposition of nonlinear dynamical systems. In this manuscript, we present a data-driven method for approximating the leading eigenvalues, eigenfunctions, and modes of the Koopman operator. The method requires a data set of snapshot pairs and a dictionary of scalar observables, but does not require explicit governing equations or interaction with a “black box” integrator. We will show that this approach is, in effect, an extension of dynamic mode decomposition (DMD), which has been used to approximate the Koopman eigenvalues and modes. Furthermore, if the data provided to the method are generated by a Markov process instead of a deterministic dynamical system, the algorithm approximates the eigenfunctions of the Kolmogorov backward equation, which could be considered as the “stochastic Koopman operator” (Mezic in Nonlinear Dynamics 41(1–3): 309–325, 2005). Finally, four illustrative examples are presented: two that highlight the quantitative performance of the method when presented with either deterministic or stochastic data and two that show potential applications of the Koopman eigenfunctions.
Web-Based Evaluations Showing Differential Learning for Tutorial Strategies Employed by the Ms. Lindquist Tutor

In a previous study, Heffernan and Koedinger [6] reported upon the Ms. Lindquist tutoring system that uses dialog and Heffernan conducted a web-based evaluation [7]. The previous evaluation considered students coming from three separate teachers and analyzed the individual learning gains based on the number of problems completed depending on the tutoring strategy provided. This paper examines a set of new web-based experiments. One set of experiments is targeted at determining if a differential learning gain exists between two of the tutoring strategies provided. Another set of experiments is used to determine if student motivation is dependent on the tutoring strategy. We replicate some findings from [7] with regard to the learning and motivation benefits of Ms Lindquist’s intelligent tutorial dialog. These experiments related to learning report on over 1,000 participants contributing at most 20 minutes each, for a grand total of over 200+ combined student hours.
Argument calculus and networks

A major reason behind the success of probability calculus is that it possesses a number of valuable tools, which are based on the notion of probabilistic independence. In this paper, I identify a notion of logical independence that makes some of these tools available to a class of propositional databases, called argument databases. Specifically, I suggest a graphical representation of argument databases, called argument networks, which resemble Bayesian networks. I also suggest an algorithm for reasoning with argument networks, which resembles a basic algorithm for reasoning with Bayesian networks. Finally I show that argument networks have several applications: Nonmonotonic reasoning, truth maintenance, and diagnosis.
The size, origins, and character of Mongolia's informal sector during the transition

Mongolia's informal sector has expanded far more quickly during the transition than its formal sector, largely because of greater ease of entry into the informal sector. Current policy discourages entry into the formal sector. The explosion of informal entrepreneurial activity during Mongolia's transition to a market economy represents one of the most visible signs of change in this expansive but sparsely populated Asian country. To deepen our understanding of Mongolia's informal sector during the transition, Anderson merges anecdotal experience from qualitative interviews with hard data from a survey of 770 informals in Ulaanbaatar, from a national household survey, and from official employment statistics. Using varied sources, Anderson generates rudimentary estimates of the magnitude of, and trends in, informal activity in Mongolia, estimates that are surprisingly consistent with each other. He evaluates four types of reasons for the burst of informal activity in Mongolia since 1990: ° The crisis of the early and mid-1990s, during which large pools of labor were released from formal employment. ° Rural to urban migration. ° The market`s reallocation of resources toward areas neglected under the old system: services such as distribution and transportation. ° The institutional environments faced by the formal and informal sectors: hindering growth of the formal sector, facilitating entry for the informal sector. Formal labor markets haven't absorbed the labor made available by the crisis and by migration and haven't fully responded to the demand for new services. The relative ease of entering the informal market explains that market's great expansion. The relative difficulty of entering formal markets is not random but is driven by policy. Improving policies in the formal sector could afford the same ease of entry there as is currently being experienced in the informal sector. This paper - a product of the Development Research Group and the South East Asia and Mongolia Country Unit, East Asia and Pacific - is part of a larger program of research on the impact of institutional changes in Mongolia, and on the rule of law in transition economies. The author may be contacted at janderson2@worldbank.org.
Various Magnet Options for a Delta Launched Version of ASTROMAG

This Report compares various superconducting magnet options for use in a particle astrophysics experiment to be launched with a Delta rocket into a sun synchronous orbit and an earth trailing solar orbit. The goals of the experiment are to study the incidence of anti particles coming from deep space and to study populations of light nuclei (up to atomic number 8) and gammas from deep space. The proposed superconducting coils, which would be made with an aluminum stabilized niobium titanium superconductor, would be cooled using stored super fluid helium. Both a sun synchronous orbit and an earth trailing solar orbit permit one to shield the magnet and cryogen vessel behind the solar panels. This permits one to reduce the temperature of the cryostat outer vessel that increases to cryogen life time for the experiment. A number of superconducting coil and cryostat options were looked at in terms of total magnet and cryostat mass, cryogen life time, complexity and overall particle astrophysics capability for attached detectors.
Two-hop secure communication using an untrusted relay

We consider a source-destination pair that can only communicate through an untrusted intermediate relay node. The intermediate node is willing to employ a designated relaying scheme to facilitate reliable communication between the source and the destination. Yet, the information it relays needs to be kept secret from it. In this two-hop communication scenario, where the use of the untrusted relay node is essential, we find that a positive secrecy rate is achievable. The center piece of the achievability scheme is the help provided by either the destination node with transmission capability, or an external "good samaritan" node. In either case, the helper performs cooperative jamming that confuses the eavesdropping relay and disables it from being able to decipher what it is relaying. We next derive an upper bound on the secrecy rate for this system. We observe that the gap between the upper bound and the achievable rate vanishes as the power of the relay node goes to infinity. Overall, the paper presents a case for intentional interference, that is, cooperative jamming, as an enabler for secure communication.
Search for Rare and Forbidden Decays of D Mesons to Final States with Electrons

Using the CLEO-c detector and a data sample of 0.8 million D+D- pairs at the Psi(3770) a search has been performed for flavor changing neutral current and lepton number violating decays of D+ mesons to final states with dielectrons. No signals are observed and 90% confidence limits are set for specific decay modes in the range of a few times ten to the minus six.
FFT-oriented feedback

In the SLC many feedback systems keep the beam under control. Here we concentrate on feedback systems which operate at 120 Hz or lower frequencies, so software can be used to make some decisions. The linac steering feedback uses beam position monitor data and corrects magnet settings to keep the beam orbit to the desired values (mostly flat). Looking at the fast Fourier transformation (FFT) of the data, a reduction in the zero and very low frequency component is observed, while on the other hand noise at higher frequencies is amplified. To improve this situation, the FFT can be used to alter the feedback so a flat spectrum can be achieved, indicating the lowest white noise level. If there is a spike at, for example, 2 or 7 Hz or another feedback is oscillating, this feedback would adjust itself till this spike is reduced to the white noise level (not beyond). Different simulation results for the frequency response are presented. >
Analytic Time Evolution, Random Phase Approximation, and Green Functions for Matrix Product States

This chapter summarizes the Hartree–Fock (HF) and Matrix product states (MPS) approaches to stationary states to establish notation and illustrate the parallel structure of the theories. It derives analytic equations of motion for MPS time evolution using the Dirac–Frenkel variational principle. The chapter shows that the resulting evolution is optimal for MPS of fixed auxiliary dimension. It discusses the relationship of this approach to time evolution to schemes currently in use. The chapter explains how excitation energies and dynamical properties can be obtained from a linear eigenvalue problem. The relationship of this MPS random phase approximation (RPA) to other dynamical approaches for matrix product states is discussed. Finally, the chapter explores the site-based Green functions that emerge naturally within the theory of MPS and use the fluctuation-dissipation theory to analyze the stationary-state correlations introduced at the level of the MPS RPA.
Bdbms. A database management system for biological data

Biologists are increasingly using databases for storing and managing their data. Biological databases typically consist of a mixture of raw data, metadata, sequences, annotations, and related data obtained from various sources. Current database technology lacks several functionalities that are needed by biological databases. In this paper, we introduce bdbms, an extensible prototype database management system for supporting biological data. bdbms extends the functionalities of current DBMSs with: (1) Annotation and provenance management including storage, indexing, manipulation, and querying of annotation and provenance as rst class objects in bdbms, (2) Local dependency tracking to track the dependencies and derivations among data items, (3) Update authorization to support data curation via content-based authorization, in contrast to identity-based authorization, and (4) New access methods and their supporting operators that support pattern matching on various types of compressed biological data types. This paper presents the design of bdbms along with the techniques proposed to support these functionalities including an extension to SQL. We also outline some open issues in building bdbms.
Little Black Holes: Dark Matter and Ball Lightning

Small, quiescent black holes can be considered as candidates for the missing dark matter of the universe, and as the core energy source of ball lightning. By means of gravitational tunneling, unidirectional radiation is emitted from black holes in a process much attenuated from that of Hawking radiation, P, which has proven elusive to detect. Gravitational tunneling emission is similar to electric field emission of electrons from a metal in that a second body is involved which lowers the barrier and gives the barrier a finite rather than infinite width. Hawking deals with a single isolated black hole. The radiated power here is P ∝ e-2Δγ P, where e-2Δγ is the transmission probability.
Real rational curves in Grassmannians

Fulton asked how many solutions to a problem of enumerative geometry can be real, when that problem is one of counting geometric figures of some kind having specified position with respect to some given general figures [5]. For the problem of plane conics tangent to five general (real) conics, the surprising answer is that all 3264 may be real [13]. Similarly, given any problem of enumerating p-planes incident on some given general subspaces, there are real subspaces such that each of the (finitely many) incident p-planes is real [17]. We show that the problem of enumerating parameterized rational curves in a Grassmannian satisfying simple (codimension 1) conditions may have all of its solutions real. This problem of enumerating rational curves in a Grassmannian arose in at least two distinct areas of mathematics. The number of such curves was predicted by the formula of Vafa and Intriligator [20, 8] from mathematical physics. It is also the number of complex dynamic compensators which stabilize a given linear system, and the enumeration was solved in this context [12, 11]. The question of real solutions also arose in systems theory [3]. This application will be discussed in Section 4.
Sparse regression and marginal testing using cluster prototypes

We propose a new approach for sparse regression and marginal testing, for data with correlated features. Our procedure first clusters the features, and then chooses as the cluster prototype the most informative feature in that cluster. Then we apply either sparse regression (lasso) or marginal significance testing to these prototypes. While this kind of strategy is not entirely new, a key feature of our proposal is its use of the post-selection inference theory of Taylor and others (2014, Exact post-selection inference for forward stepwise and least angle regression, Preprint, arXiv:1401.3889) and Lee and others (2014, Exact post-selection inference with the lasso, Preprint, arXiv:1311.6238v5) to compute exact [Formula: see text]-values and confidence intervals that properly account for the selection of prototypes. We also apply the recent "knockoff" idea of Barber and Candes (2014, Controlling the false discovery rate via knockoffs, Preprint, arXiv:1404.5609) to provide exact finite sample control of the FDR of our regression procedure. We illustrate our proposals on both real and simulated data.
Optimal pricing is hard

We show that computing the revenue-optimal deterministic auction in unit-demand single-buyer Bayesian settings, i.e. the optimal item-pricing, is computationally hard even in single-item settings where the buyer's value distribution is a sum of independently distributed attributes, or multi-item settings where the buyer's values for the items are independent. We also show that it is intractable to optimally price the grand bundle of multiple items for an additive bidder whose values for the items are independent. These difficulties stem from implicit definitions of a value distribution. We provide three instances of how different properties of implicit distributions can lead to intractability: the first is a #P-hardness proof, while the remaining two are reductions from the SQRT-SUM problem of Garey, Graham, and Johnson [14]. While simple pricing schemes can oftentimes approximate the best scheme in revenue, they can have drastically different underlying structure. We argue therefore that either the specification of the input distribution must be highly restricted in format, or it is necessary for the goal to be mere approximation to the optimal scheme's revenue instead of computing properties of the scheme itself.
A Super-Fast Distributed Algorithm for Bipartite Metric Facility Location

The facility location problem consists of a set of facilities \(\mathcal{F}\), a set of clients \(\mathcal{C}\), an opening cost f i associated with each facility x i , and a connection cost D(x i ,y j ) between each facility x i and client y j . The goal is to find a subset of facilities to open, and to connect each client to an open facility, so as to minimize the total facility opening costs plus connection costs. This paper presents the first expected-sub-logarithmic-round distributed O(1)-approximation algorithm in the \(\mathcal{CONGEST}\) model for the metric facility location problem on the complete bipartite network with parts \(\mathcal{F}\) and \(\mathcal{C}\). Our algorithm has an expected running time of O((loglogn)3) rounds, where \(n = |\mathcal{F}| + |\mathcal{C}|\). This result can be viewed as a continuation of our recent work (ICALP 2012) in which we presented the first sub-logarithmic-round distributed O(1)-approximation algorithm for metric facility location on a clique network. The bipartite setting presents several new challenges not present in the problem on a clique network. We present two new techniques to overcome these challenges.
Local temperature of an interacting quantum system far from equilibrium

A theory of local temperature measurement of an interacting quantum electron system far from equilibrium via a floating thermoelectric probe is developed. It is shown that the local temperature so defined is consistent with the zeroth, first, second, and third laws of thermodynamics, provided the probe-system coupling is weak and broadband. For non-broadband probes, the local temperature obeys the Clausius form of the second law and the third law exactly, but there are corrections to the zeroth and first laws that are higher order in the Sommerfeld expansion. The corrections to the zeroth and first laws are related, and can be interpreted in terms of the error of a nonideal temperature measurement. These results also hold for systems at negative absolute temperature.
No Condition is Permanent: Middle Class in Nigeria in the Last Decade

The economic debate on existence and definition of the middle class has become particularly lively in many developing countries. Despite this growing interest, the identification of the middle class group in these countries remains quite challenging. Building on a recently developed framework to define the middle class, this paper tries to estimate the Nigerian middle class size in a rigorous quantitative manner. By exploiting publicly available panel data, the expenditure associated to a 10 percent probability of falling into poverty is estimated, and this is used as the middle class threshold for Nigeria. The threshold expenditure for the middle class in Nigeria is found to be 378.39 Naira per capita per day (2010 PPP). Relying on this threshold and through survey-to-survey imputation the size of Nigeria's middle class in 2003 is also estimated. The results show that there has been considerable improvement on the size of the middle class and poverty reduction between 2003 and 2013. Poverty decreased between 2003 and 2013 from 45 to 33 percent, while the middle class increased from 13 percent to 19 percent. Nevertheless the results still paint a heterogeneous picture of poverty and the middle class in Nigeria, where the largest portion of the population, although above the poverty threshold, continues to live with average or high vulnerability to poverty.
Modular RADAR: An Immune System Inspired Search and Response Strategy for Distributed Systems

The Natural Immune System (NIS) is a distributed system that solves challenging search and response problems while operating under constraints imposed by physical space and resource availability. Remarkably, NIS search and response times do not scale appreciably with the physical size of the animal in which its search is conducted. Many distributed systems are engineered to solve analogous problems, and the NIS demonstrates how such engineered systems can achieve desirable scalability. We hypothesize that the architecture of the NIS, composed of a hierarchical decentralized detection network of lymph nodes (LN) facilitates efficient search and response. A sub-modular architecture in which LN numbers and size both scale with organism size is shown to efficiently balance tradeoffs between local antigen detection and global antibody production, leading to nearly scale-invariant detection and response. We characterize the tradeoffs as balancing local and global communication and show that similar tradeoffs exist in distributed systems like LN inspired artificial immune system (AIS) applications and peer-to-peer (P2P) systems. Taking inspiration from the architecture of the NIS, we propose a modular RADAR (Robust Adaptive Decentralized search with Automated Response) strategy for distributed systems. We demonstrate how two existing distributed systems (a LN inspired multi-robot control application and a P2P system) can be improved by a modular RADAR strategy. Such a sub-modular architecture is shown to balance the tradeoffs between local communication (within artificial LNs and P2P clusters) and global communication (between artificial LNs and P2P clusters), leading to efficient search and response.
Are the outflows in FU Orionis systems driven by the stellar magnetic field

FU Orionis (FUOR) outbursts are major optical brightening episodes in low-mass protostars that evidently correspond to rapid mass-accretion events in the innermost region of a protostellar disc. The outbursts are accompanied by strong outflows, with the inferred mass outflow rates reaching 10% of the mass inflow rates. Shu et al. proposed that the outflows represent accreted disc material that is driven centrifugally from the spun-up surface layers of the protostar by the stellar magnetic field. This model was critiqued by Calvet et al., who argued that it cannot reproduce the photospheric absorption-line shifts observed in the prototype object FU Ori. Calvet et al. proposed that the wind is launched, instead, from the surface of the disc on scales of a few stellar radii by a non-stellar magnetic field. In this paper we present results from numerical simulations of disc accretion on to a slowly rotating star with an aligned magnetic dipole moment that gives rise to a kilogauss-strength surface field. We demonstrate that, for parameters appropriate to FU Ori, such a system can develop a strong, collimated disc outflow of the type previously identified by Romanova et al. in simulations of protostars with low and moderate accretion rates. At the high accretion rate that characterizes the FUOR outburst phase, the radius rm at which the disc is truncated by the stellar magnetic field moves much closer to the stellar surface, but the basic properties of the outflow, which is launched from the vicinity of rm along opened-up stellar magnetic field lines, remain the same. These properties are distinct from those of the X-celerator (or the closely related X-wind) mechanism proposed by Shu et al. ‐ in particular, the outflow is driven from the start by the magnetic pressuregradient force, not centrifugally, and it is more strongly collimated. We show that the simulated outflow can in principle account for the main observed characteristics of FUOR winds, including the photospheric line shifts measured in FU Ori. A detailed radiative-transfer calculation is, however, required to confirm the latter result.
1,3‐Propanediol binds inside the water‐conducting pore of aquaporin 4: Does this efficacious inhibitor have sufficient potency?

Among the thirteen types of water channel proteins, aquaporins (AQPs), which play various essential roles in human physiology, AQP4 is richly expressed in cells of the central nervous system and implicated in pathological conditions such as brain edema. Therefore, researchers have been looking for ways to inhibit AQP4's water-conducting function. Many small molecules have been investigated for their interactions with the residues that form the AQP4 channel entry vestibule on the extracellular side and their interruption of waters entering into the conducting pore. Conducting all-atom simulations on the basis of CHARMM 36 force field, we study one such inhibitor, 5-acetamido-1,3,4-thiadiazole-2-sulfonamide (AZM), to achieve quantitative agreement between the computed and the experimentally measured values of AZM-AQP4 binding affinity. Using the same method, we examine the possibility of plugging up the AQP4 channel around the Asn-Pro-Ala motifs located near the channel center because a small molecule bound there would totally occlude water conduction through AQP4. We compute the binding affinities of 1,2-ethanediol (EDO) and 1,3-propanediol (PDO) inside the AQP4 conducting pore and identify the specificities of the interactions. The EDO-AQP4 interaction is weak with a dissociation constant of 80 mM. The PDO-AQP4 interaction is rather strong with a dissociation constant of 328 μM, which indicates that PDO is an efficacious AQP4 inhibitor with sufficiently high potency. Considering the fact that PDO is classified by the US Food and Drug Administration as generally safe, we predict that 1,3-propanediol could be an effective drug for brain edema and other AQP4-correlated neurological conditions.
The Ladder: A Reliable Leaderboard for Machine Learning Competitions

The organizer of a machine learning competition faces the problem of maintaining an accurate leaderboard that faithfully represents the quality of the best submission of each competing team. What makes this estimation problem particularly challenging is its sequential and adaptive nature. As participants are allowed to repeatedly evaluate their submissions on the leaderboard, they may begin to overfit to the holdout data that supports the leaderboard. Few theoretical results give actionable advice on how to design a reliable leaderboard. Existing approaches therefore often resort to poorly understood heuristics such as limiting the bit precision of answers and the rate of resubmission. In this work, we introduce a notion of leaderboard accuracy tailored to the format of a competition. We introduce a natural algorithm called the Ladder and demonstrate that it simultaneously supports strong theoretical guarantees in a fully adaptive model of estimation, withstands practical adversarial attacks, and achieves high utility on real submission files from an actual competition hosted by Kaggle. Notably, we are able to sidestep a powerful recent hardness result for adaptive risk estimation that rules out algorithms such as ours under a seemingly very similar notion of accuracy. On a practical note, we provide a completely parameter-free variant of our algorithm that can be deployed in a real competition with no tuning required whatsoever.
Extreme moisture transport into the Arctic linked to Rossby wave breaking

The transport of moisture into the Arctic is tightly connected to midlatitude dynamics. We show that the bulk of the transient poleward moisture transport across 60°N is driven by extreme transport (fluxes greater than the 90th percentile) events. We demonstrate that these events are closely related to the two types of Rossby wave breaking (RWB)—anticyclonic wave breaking (AWB) and cyclonic wave breaking (CWB). Using a RWB tracking algorithm, we determine that RWB can account for approximately 68% of the extreme poleward moisture transport by transients across 60°N in winter and 56% in summer. Additional analysis suggests that the seasonality of such RWB-related moisture transport is determined approximately equally by (1) the magnitude of transport (which is largely a function of the background moisture gradient) and (2) the frequency of RWB occurrence. The seasonality of RWB occurrence is, in turn, tied to the seasonal variation of the latitude of the jet streams—AWB-related (CWB-related) transport occurs more frequently when the jet is shifted poleward (equatorward). The interannual variability of RWB-related transport across 60°N in winter is shown to be strongly influenced by climate variability captured by the El Nino/Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). In the positive (negative) phase of ENSO, AWB transports less (more) moisture through the Bering Strait and CWB transports more (less) through western Canada. In the positive (negative) phase of the NAO, AWB transports more (less) moisture through the Norwegian Sea and CWB transports less (more) along the west coast of Greenland. These results highlight that low-frequency climate variability outside of the polar regions can influence the Arctic water vapor by modulating extreme synoptic transport events.
Functionalized Metalated Cavitands via Imidation and Late‐Stage Elaboration

Efficient methods for the preparation of functionalized metallated cavitands are described. Functional groups can be either introduced by an imidation of metal-oxo complexes or by a late-stage elaboration of the imido ligands. By using diversified iminophosphorane (PPh3=NR) reagents, π-conjugated pyrene, redox active ferrocene and polymerizable norbornene moieties were successfully introduced. Furthermore, the iodo and alkynyl groups on the imido ligands are capable of undergoing efficient Sonogashira cross-coupling and copper-catalyzed azide alkyne cycloaddition reactions, thereby providing facile access to complex architectures containing metallated cavitands.