cssi/SciSciGPT-SciSciNet huggingface dataset:
International risk-sharing in the short run and in the long run

International risk-sharing has far-reaching implications both for economic policy and for basic research in economics. When countries do not share consumption risk, individuals experience consumption fluctuations that are undesirable and possibly unnecessary. We investigate bilateral risk-sharing at short vs. long horizons. We find substantial cross-country consumption correlations at trend and business-cycle frequencies. Correlations are particularly high within Europe. Prior research focused on first-difference correlations, which are typically quite low. We argue that this reflects measurement error. At all horizons, we find that consumption correlations are not significantly different from output correlations, implying a lack of deliberate consumption risk-sharing. Le partage international du risque a de grandes implications a la fois pour la politique economique et pour la recherche economique de base. Quand des pays ne partagent pas les risques de consommation, les individus font l’experience de fluctuations de consommation indesirables et possiblement non-necessaires. On examine le partage de risque bilateral a court et a long terme. On decouvre des correlations entre pays tant au niveau des tendances que des frequences du cycle d’affaires. Ces correlations sont particulierement elevees en Europe. Des travaux anterieurs se sont concentres sur les correlations entre premieres differences qui sont typiquement assez faibles. On suggere que ces resultats refletent une erreur de mesure. Pour tous les horizons temporels, on decouvre que les correlations de consommation ne different pas significativement des correlations de production – ce qui implique un manque de partage de risque delibere au niveau de la consommation.
Surveillance of influenza in Finland during the 2009 pandemic, 10 May 2009 to 8 March 2010.

The first infection caused by pandemic influenza A(H1N1)2009 virus was confirmed in Finland on 10 May 2009. The spread of the disease and its impact were monitored using several surveillance systems, such as the national infectious disease register, notifications of clusters of influenza, influenza-like or influenza-related illnesses, as well as virological, hospital, case-based and mortality surveillance. The epidemic started in early October in the north and then spread to the south about two weeks later. Based on the data from laboratory-confirmed cases, the morbidity was highest in children. The daily number of patients hospitalised with influenza A(H1N1)2009 reached a maximum of over 400 in late November. Of the 1,580 hospitalised patients (median age 32 years), 672 (43%) had at least one chronic underlying illness, 35 (2%) were pregnant, 132 (8%) were treated in intensive care units and 74 (5%) required mechanical ventilation. The median age of patients admitted to intensive care units was 48 years and 78 ( 59%) of them had at least one chronic underlying disease, none were pregnant. Altogether 44 deaths related to influenza A(H1N1)2009 were recorded (median age 56 years): 40 belonged to high-risk groups on the basis of underlying chronic diseases. Combining data from different surveillance systems gave timely information about the spread of the pandemic and contributed to identifying risk groups.
Report on the process session at Chinon

A provisional notification of two events was given. Both will take place during the Fall/Autumn 1990. The 1st International Software Process Symposium will take place over two days in Tokyo, Japan. The 6th International Software Process Workshop, “Support for the Process”, will be in Kyoto, Japan.
Parsimonious Tensor Response Regression

ABSTRACTAiming at abundant scientific and engineering data with not only high dimensionality but also complex structure, we study the regression problem with a multidimensional array (tensor) response and a vector predictor. Applications include, among others, comparing tensor images across groups after adjusting for additional covariates, which is of central interest in neuroimaging analysis. We propose parsimonious tensor response regression adopting a generalized sparsity principle. It models all voxels of the tensor response jointly, while accounting for the inherent structural information among the voxels. It effectively reduces the number of free parameters, leading to feasible computation and improved interpretation. We achieve model estimation through a nascent technique called the envelope method, which identifies the immaterial information and focuses the estimation based upon the material information in the tensor response. We demonstrate that the resulting estimator is asymptotically efficient...
TRADE POLICY UNDER IMPERFECT COMPETITION: AN ASSESSMENT OF THE TRQ ON LAMB MEAT

The United States imposed a tariff-rate quota (TRQ) on lamb meat in July 1999. Early analysis suggested the possibility that lamb growers could lose welfare via the creation of packer market power. This paper considers how subsequent events modify that analysis. Observed prices suggest reduced pass-through. Lamb prices are unchanged and more stable. Using an annual quota instead of a quarterly quota reduces the opportunity for market conduct switching. Early termination of the TRQ to comply with the WTO rulings magnifies any welfare loss. Assistance payments prevent welfare losses to growers with little impact on the market.
SOLVING GENERAL EQUILIBRIUM MODELS WITH INCOMPLETE MARKETS AND MANY ASSETS

This paper presents a new numerical method for solving general equilibrium models with many assets. The method can be applied to models where there are heterogeneous agents, time-varying investment opportunity sets, and incomplete markets. It also can be used to study models where the equilibrium dynamics are non-stationary. We illustrate how the method is used by solving a one-- and two-sector versions of a two--country general equilibrium model with production. We check the accuracy of our method by comparing the numerical solution to the one-sector model against its known analytic properties. We then apply the method to the two-sector model where no analytic solution is available.
An estimation of cattle movement parameters in the Central States of the US

We estimate the movement parameters of cattle across 10 Central States.Large USDA data sets were fed into an optimization procedure to extract parameters.Comparison with other literature suggests a high epidemic risk for US cattle systems. The characterization of cattle demographics and especially movements is an essential component in the modeling of dynamics in cattle systems, yet for cattle systems of the United States (US), this is missing. Through a large-scale maximum entropy optimization formulation, we estimate cattle movement parameters to characterize the movements of cattle across 10 Central States and 1034 counties of the United States. Inputs to the estimation problem are taken from the United States Department of Agriculture National Agricultural Statistics Service database and are pre-processed in a pair of tightly constrained optimization problems to recover non-disclosed elements of data. We compare stochastic subpopulation-based movements generated from the estimated parameters to operation-based movements published by the United States Department of Agriculture. Our novel method to estimate cattle movements across large US regions characterizes county-level stratified subpopulations of cattle for data-driven livestock modeling. Our estimated movement parameters suggest a significant risk of a disease successfully invading the US cattle systems.
An efficient polynomial-time approximation scheme for Steiner forest in planar graphs

We give an O(n log3n) approximation scheme for Steiner forest in planar graphs, improving on the previous approximation scheme for this problem, which runs in O(nf(e)) time.
Independence and Bayesian updating methods

Abstract Duda, Hart, and Nilsson have set forth a method for rule-based inference systems to use in updating the probabilities of hypotheses on the basis of multiple items of new evidence. Pednault, Zucker, and Muresan claimed to give conditions under which independence assumptions made by Duda et al. preclude updating—that is, prevent the evidence from altering the probabilities of the hypotheses. Glymour refutes Pednault et al.'s claim with a counterexample of a rather special form (one item of evidence is incompatible with all but one of the hypotheses); he raises, but leaves open, the question whether their result would be true with an added assumption to rule out such special cases. We show that their result does not hold even with the added assumption, but that it can nevertheless be largely salvaged. Namely, under the conditions assumed by Pednault et al., at most one of the items of evidence can alter the probability of any given hypothesis; thus, although updating is possible, multiple updating for any of the hypotheses is precluded.
Real-Time Lighting Design for Interactive Narrative

Lighting design is an important element of scene composition. Designers use light to influence viewers’ perception by evoking moods, directing their gaze to important areas, and conveying dramatic tension. Lighting is a very time consuming task; designers typically spend hours manipulating lights’ colors, positions, and angles to create a lighting design that accommodates dramatic action and tension. Such manual design is inappropriate for interactive narrative, because the scene’s spatial and dramatic characteristics, including dramatic tension and character actions, change unpredictably, necessitating continual redesign as the scene progresses. In this paper, we present a lighting design system, called ELE (Expressive Lighting Engine), that automatically, in real-time, adjusts angles, positions, and colors of lights to accommodate variations in the scene’s dramatic and spatial characteristics accommodating cinematic and theatrical lighting design theory. ELE uses constraint-based non-linear optimization algorithms to configure lights.
Equivalence of Julesz Ensembles and FRAME Models

In the past thirty years, research on textures has been pursued along two different lines. The first line of research, pioneered by Julesz (1962, IRE Transactions of Information Theory, IT-8:84–92), seeks essential ingredients in terms of features and statistics in human texture perception. This leads us to a mathematical definition of textures in terms of Julesz ensembles (Zhu et al., IEEE Trans. on PAMI, Vol. 22, No. 6, 2000). A Julesz ensemble is a set of images that share the same value of some basic feature statistics. Images in the Julesz ensemble are defined on a large image lattice (a mathematical idealization being Z2) so that exact constraint on feature statistics makes sense. The second line of research studies Markov random field (MRF) models that characterize texture patterns on finite (or small) image lattice in a statistical way. This leads us to a general class of MRF models called FRAME (Filter, Random field, And Maximum Entropy) (Zhu et al., Neural Computation, 9:1627–1660). In this article, we bridge the two lines of research by the fundamental principle of equivalence of ensembles in statistical mechanics (Gibbs, 1902, Elementary Principles of Statistical Mechanics. Yale University Press). We show that 1). As the size of the image lattice goes to infinity, a FRAME model concentrates its probability mass uniformly on a corresponding Julesz ensemble. Therefore, the Julesz ensemble characterizes the global statistical property of the FRAME models 2). For a large image randomly sampled from a Julesz ensemble, any local patch of the image given its environment follows the conditional distribution specified by a corresponding FRAME model. Therefore, the FRAME model describes the local statistical property of the Julesz ensemble, and is an inevitable texture model on finite (or small) lattice if texture perception is decided by feature statistics. The key to derive these results is the large deviation estimate of the volume of (or the number of images in) the Julesz ensemble, which we call the entropy function. Studying the equivalence of ensembles provides deep insights into questions such as the origin of MRF models, typical images of statistical models, and error rates in various texture related vision tasks (Yuille and Coughlan, IEEE Trans. on PAMI, Vol. 2, No. 2, 2000). The second thrust of this paper is to study texture distance based on the texture models of both small and large lattice systems. We attempt to explain the asymmetry phenomenon observed in texture “pop-out” experiments by the asymmetry of Kullback-Leibler divergence. Our results generalize the traditional signal detection theory (Green and Swets, 1988, Signal Detection Theory and Psychophysics, Peninsula Publishing) for distance measures from iid cases to random fields. Our theories are verified by two groups of computer simulation experiments.
Funding games: the truth but not the whole truth

We introduce the Funding Game, in which m identical resources are to be allocated among n selfish agents. Each agent requests a number of resources xi and reports a valuation $\tilde{v}_i(x_i)$, which verifiably lower-bounds i's true value for receiving xi items. The pairs $(x_i, \tilde{v}_i(x_i))$ can be thought of as size-value pairs defining a knapsack problem with capacity m. A publicly-known algorithm is used to solve this knapsack problem, deciding which requests to satisfy in order to maximize the social welfare. We show that a simple mechanism based on the knapsack highest ratio greedy algorithm provides a Bayesian Price of Anarchy of 2, and for the complete information version of the game we give an algorithm that computes a Nash equilibrium strategy profile in O(n2 log2m) time. Our primary algorithmic result shows that an extension of the mechanism to k rounds has a Price of Anarchy of $1 + \frac{1}{k}$, yielding a graceful tradeoff between communication complexity and the social welfare.
Cross-country Variation in Factor Shares and its Implications for Development Accounting

The stability of factor shares has long been considered one of the “stylized facts” of macroeconomics. However, the relationship between cross-country factor shares and economic development is dependent on how factor shares are measured. Most factor share studies acknowledge only two factors of production: total capital and total labor. The failure to acknowledge more than two factors yields misleading results. Recent theoretical work predicts a systematic relationship between the stage of economic development and non-reproducible and reproducible factor shares. I disentangle physical capital’s share from natural capital’s share, and I disentangle human capital’s share from unskilled labor’s share. The results reveal that nonreproducible factor shares decrease with the stage of economic development, and reproducible factor shares increase with the stage of economic development. Studies relying on the macroeconomic paradigm of constant factor shares should be revisited. Development accounting nearly always assumes the constancy of factor shares. I perform the development accounting exercise but allow factor shares to vary and distinguish between reproducible and nonreproducible factors. My approach yields results that stand in stark contrast to those previously attained. The general consensus is that at least half of the cross-country variation in output per worker is attributable to cross-country variation in the TFP residual. With my approach, the majority of variation in output per worker accrues to factor shares, specifically physical capital’s share and natural capital’s share. TFP’s explanatory power decreases by more than 30 percentage points. This evidence does not, however, diminish the role of technical change. Rather, the evidence indicates the importance of acknowledging a new type of technical change, one that impacts factor shares. Key Words: Factor Shares, TFP residual
Free Radical Chemistry in Room‐Temperature Ionic Liquids

Ionic liquids are emerging as the largest class of room-temperature organic liquids. These ionic compounds are composed of oddly shaped organic cations and inorganic or organic anions. Ionic liquid solvents combine such properties as electric conductivity, low volatility, and a diverse range of solute–solvent interactions. In this article, we consider the recent advances in free radical chemistry occurring in this new class of organic solvents with particular emphasis on the generation and reactions of free radicals in radiolysis, photolysis, and electrochemistry of ionic liquids. Keywords: ionic liquids; radiolysis; photolysis; electrochemistry; electron paramagnetic resonance; muon spin resonance; neutral radicals; radical ions; ionization of the ions; charge transfer; charge separation; dissociative electron attachment; oxidative fragmentation; dehalogenation
Identity Preservation and Labeling of Genetically Modified Products: System Design and Enforcement Issues

This paper analyzes economic issues that arise in devising a credible and enforceable system of identity preservation and labeling for genetically modified (GM) and non-GM products. The model represents three stages in the supply chain: farm production, marketing handlers, and final users. The possibility of accidental co-mingling of non-GM products is modeled at the marketing stage. Regulation takes the form of a threshold level of purity for non-GM products, a probability of government testing to verify compliance with the threshold level, and a fine for violators. Uncertainty is modeled explicitly, such that would-be suppliers of non-GM products always face some risk of failing the test and incurring a fine. The paper also presents a novel demand specification for differentiated GM and non-GM products that is particularly useful in our stochastic framework. The results emphasize the role and impact of an uncertain testing technology, a critical feature in this setting. We also highlight the somewhat nonstandard trade-off between frequency of testing and the size of the fine that applies here. Because testing can prevent mislabeled product from reaching the consumer, it can provide a direct welfare benefit. An equilibrium that includes production of the non-GM good may only be supportable with sufficiently high testing frequency (a high penalty for mislabeling may not suffice).
Minimum-sum dipolar spanning tree in R 3

In this paper we consider finding a geometric minimum-sum dipolar spanning tree in R 3 , and present an algorithm that takes O ( n 2 log 2 n ) time using O ( n 2 ) space, thus almost matching the best known results for the planar case. Our solution uses an interesting result related to the complexity of the common intersection of n balls in R 3 , of possible different radii, that are all tangent to a given point p. The problem has applications in communication networks, when the goal is to minimize the distance between two hubs or servers as well as the distance from any node in the network to the closer of the two hubs.
Differential dispersive analysis of e+e− annihilation into hadrons

The previously reported differential dispersive interpretation of the narrow resonances in e+e− annihilation is described in more detail. In addition, the final asymptotic value of the ratioR=σ(e+e−→hadrons)/σ(e+e−→μ+μ−) is found to be related to, but not simply the same as, the sum over the squares of the quark charges. Both this final asymptotic value ofR and the narrow resonances are argued to be consistent with the renormalizability of electrodynamics together with the scale invariance of the hadronic electromagnetic current at large momentum transfer, where only the conventional colored, fractionally charged p, n and λ quarks are involved in this scale-invariant limit. No new quark or new quantum number is necessary.
Approximation algorithm for directed telephone multicast problem

Consider a network of processors modeled by an n-vertex directed graph G = (V,E). Assume that the communication in the network is synchronous, i.e., occurs in discrete "rounds", and in every round every processor is allowed to pick one of its neighbors, and to send him a message.The telephone k-multicast problem requires to compute a schedule with minimal number of rounds that delivers a message from a given single processor, that generates the message, to all the processors of a given set T ⊆ V, |T| = k. The processors of V\T may be left uninformed. The telephone multicast is a basic primitive in distributed computing and computer communication theory. In this paper we devise an algorithm that constructs a schedule with O(max{log k, log n/log k} ċ br* + k1/2)rounds for the directed k-multicast problem, where br* is the value of the optimum solution. This significantly improves the previously best-known approximation ratio of O(k1/3 ċ log n ċ br* + k2/3) due to [EK03]. We show that our algorithm for the directed multicast problem can be used to derive an algorithm with a similar ratio for the directed minimum poise Steiner arborescence problem, that is, the problem of constructing an arborescence that spans a collection T of terminals, minimizing the sum of height of the arborescence plus maximum out-degree in the arborescence.
Optimization of SQL queries for parallel machines

Parallel execution offers a solution to the problem of reducing the response time of SQL queries against large databases. As a declarative language, SQL allows users to avoid the complex procedural details of programming a parallel machine. We address the problem of parallel query optimization which is: Given a SQL query, find the parallel plan that delivers the query result in minimal time. We develop optimization algorithms using models that incorporate the sources of parallelism as well as obstacles to achieving speedup. One obstacle is inherent limits on available parallelism due to parallel and precedence constraints between operators and due to data placement constraints. Another obstacle is that the overheads of parallel execution may offset the benefits. Our experiments with NonStop SQL, a commercial parallel DBMS, show communication of data across processors to be a significant overhead. We adopt a two-phase approach to parallel query optimization: join ordering and query rewrite (JOQR), followed by parallelization. The JOQR phase minimizes the total work to compute a query. The parallelization phase extracts parallelism and schedules resources to minimize response time. Our work is applicable to queries that include operations such as grouping, aggregation, foreign functions, intersection and set difference in addition to joins. We develop algorithms for the JOQR phase that minimize total cost while accounting for the communication cost of repartitioning data. Using a model that abstracts physical characteristics of data, such as partitioning, as colors, we devise tree coloring algorithms that are efficient and guarantee optimality. We model the parallelization phase as scheduling a tree of inter-dependent operators with computation and communication costs represented as node and edge weights. We develop and compare several efficient algorithms for the problem of scheduling a pipelined operator tree in which all operators run in parallel using inter-operator parallelism. We prove worst-case bounds on the performance ratios of our algorithms and measure the average cases using simulation. We also address the problem of scheduling a pipelined operator tree using both pipelined and partitioned parallelism. The results in our thesis enable the construction of SQL compilers that can effectively exploit parallel machines.
Cooperation and Collective Enforcement in Networked Societies

We endogenize social network formation and social interaction using a model in which players interact bilaterally and repeatedly along costly links. Cooperation is supported by the threat of collective punishment. When the society is homogeneous, the optimal network consists of many separate cliques. Introducing heterogeneity gives rise to more realistic networks, with high clustering, small diameter, and global organization.
Evolution of Particle-in-Cell Plasma Simulation

Particle-in-cell (PIC) methods first made it feasible to simulate plasmas and microwave devices in two dimensions on 1960s computers. In this approach, the electromagnetic interactions between charged particles are mediated by a spatial mesh, on which currents and field are defined. The dominance of long-range forces in weakly coupled plasma means that the mesh and time-step do not have to resolve nearest neighbor interactions. Advances in algorithms and parallel computers have greatly expanded the applicability of PIC. We review this evolution, with particular emphasis on the contributions of Prof. Ned Birdsall and those he influenced.
Choosing among interpretations of probability

There is available an ever-increasing variety of procedures for managing uncertainty. These methods are discussed in the literature of artificial intelligence, as well as in the literature of philosophy of science. Heretofore these methods have been evaluated by intuition, discussion, and the general philosophical method of argument and counterexample. Almost any method of uncertainty management will have the property that in the long run it will deliver numbers approaching the relative frequency of the kinds of events at issue. To find a measure that will provide a meaningful evaluation of these treatments of uncertainty, we must look, not at the long run, but at the short or intermediate run. Our project attempts to develop such a measure in terms of short or intermediate length performance. We represent the effects of practical choices by the outcomes of bets offered to agents characterized by two uncertainty management approaches: the subjective Bayesian approach and the Classical confidence interval approach. Experimental evaluation suggests that the confidence interval approach can outperform the subjective approach in the relatively short run.
Kinetic Simulations of Plasma Plume Potential in a Vacuum Chamber

Direct simulation Monte Carlo and particle-in-cell simulations are carried out to study the potential of a mesothermal plasma plume in a vacuum chamber. The results show that the beam potential with respect to the ambient in a vacuum chamber is different from that in space because the facility plasma can prematurely terminate the plume expansion process. As a result, the plume potential measured in a vacuum chamber may be significantly lower than that under the in-space condition. This can lead to underestimation of the backflow of charge-exchange ions and ionized contaminants in plasma thruster plume modeling.
Spontaneous dissociation of (85)Rb Feshbach molecules

The spontaneous dissociation of $^{85}\mathrm{R}\mathrm{b}$ dimers in the highest lying vibrational level has been observed in the vicinity of the Feshbach resonance that was used to produce them. The molecular lifetime shows a strong dependence on magnetic field, varying by 3 orders of magnitude between 155.5 G and 162.2 G. Our measurements are in good agreement with theoretical predictions in which molecular dissociation is driven by inelastic spin relaxation. Molecule lifetimes of tens of milliseconds can be achieved within approximately a 1 G wide region directly above the Feshbach resonance.
Type A molecules are Kazhdan---Lusztig

Let (W, S) be a Coxeter system. A W-graph is an encoding of a representation of the corresponding Iwahori---Hecke algebra. Especially important examples include the W-graph corresponding to the action of the Iwahori---Hecke algebra on the Kazhdan---Lusztig basis, as well as this graph's strongly connected components (cells). In 2008, Stembridge identified some common features of the Kazhdan---Lusztig graphs and gave a combinatorial characterization of all W-graphs that have these features. He conjectured, and checked up to $$n=9$$n=9, that all such $$A_n$$An-cells are Kazhdan---Lusztig cells. The current paper provides a first step toward a potential proof of the conjecture. More concretely, we prove that the connected subgraphs of $$A_n$$An-cells consisting of simple (i.e., directed both ways) edges are dual equivalence graphs in the sense of Assaf and thus are the same as the ones in the Kazhdan---Lusztig cells.
Grain Alignment in Molecular Clouds

One of the most informative techniques of studying magnetic fields in molecular clouds is based on the use of starlight polarization and polarized emission arising from aligned dust. How reliable the interpretation of the polarization maps in terms of magnetic fields is the issue that the grain alignment theory addresses. I briefly review basic physical processes involved in grain alignment.
Persistence and Success in the Attention Economy

A hallmark of the attention economy is the competition for the attention of others. Thus people persistently upload content to social media sites, hoping for the highly unlikely outcome of topping the charts and reaching a wide audience. And yet, an analysis of the production histories and success dynamics of 10 million videos from YouTube revealed that the more frequently an individual uploads content the less likely it is that it will reach a success threshold. This paradoxical result is further compounded by the fact that the average quality of submissions does increase with the number of uploads, with the likelihood of success less than that of playing a lottery.
Capacity of the AWGN channel with random battery recharges

We consider communication over the AWGN channel with a transmitter whose battery is recharged with RF energy transfer at random times known to the receiver. We assume that the recharging process is i.i.d. Bernoulli. We characterize the capacity of this channel as the limit of an n-letter maximum mutual information rate under both causal and noncausal transmitter knowledge of the battery recharges. With noncausal knowledge, it is possible to explicitly identify the maximizing input distribution, which we use to demonstrate that the capacity with noncausal knowledge of the battery recharges is strictly larger than that with causal knowledge. We then proceed to derive explicit upper and lower bounds on the capacity, which are within 1.05 bits/s/Hz of each other for all parameter values.
Optimal and sub optimal integration of position and doppler sensors for target tracking

Abstract This paper considers the optimal and sub-optimal integration of radar Doppler and position measurements to track a maneuvering target The optimal integration scheme for position and Doppler measurements within one algorithm is the Kalman Filter. It is shown that the four steady state tracking parameters are dependent only on the Tracking Index, Ʌ (the ratio of the target maneuver to the position measurement noise), and Sensor Noise Ratio, S. The proposed sub-optimal integration process considers the independent operations of an α-β Filter for the position measurements and α-β Filter for the Doppler measurements. The output of the filters are linearly combined to form a target track. An example is presented to show the performance of the α-β tracker; the α-β and β trackers with the linear combiner; and the two-sensor Kalman Filter
The Statistics Of Nearly On-Axis Gravitational Lensing Events

A small volume of space, nearly on-axis behind a gravitational lens with respect to a given source, will receive a greatly increased radiation flux. In the idealized case of a point mass lens acting on a point source in complete isolation, the volume will approach zero only as the flux tends to infinity; in fact, the volume weighted rms flux is divergent. In realistic cases, finite source size and the effects of other gravitational deflections (i.e., non-zero shear) limit the maximum flux and considerably complicate the physics, but very large fluxes are still produced in small volumes. We consider the physics and statistics of these Extreme Gravitational Lensing Events (EGLE) and present an initial examination of their possible astrophysical effects for various known and putative populations of lensing objects and sources, with particular attention to the case in which finite source size is important but shear is not.
Nonconvergence results for the application of the moment method (Galerkin's method) for some simple problems,

When one encounters numerical instability in solving electromagnetic field problems by the momemt method, one often puts the blame on the choice of expansion and weighting functions and so on. The objective of this presentation is to show that the numerical instabilities may not be due to the choice of expansion or weighting functions but is inherent in the method. Three examples are presented to illustrate this point.
Product reservoir computing: Time-series computation with multiplicative neurons

Echo state networks (ESN), a type of reservoir computing (RC) architecture, are efficient and accurate artificial neural systems for time series processing and learning. An ESN consists of a core of recurrent neural networks, called a reservoir, with a small number of tunable parameters to generate a high-dimensional representation of an input, and a readout layer which is easily trained using regression to produce a desired output from the reservoir states. Certain computational tasks involve real-time calculation of high-order time correlations, which requires nonlinear transformation either in the reservoir or the readout layer. Traditional ESN employs a reservoir with sigmoid or tanh function neurons. In contrast, some types of biological neurons obey response curves that can be described as a product unit rather than a sum and threshold. Inspired by this class of neurons, we introduce a RC architecture with a reservoir of product nodes for time series computation. We find that the product RC shows many properties of standard ESN such as short-term memory and nonlinear capacity. On standard benchmarks for chaotic prediction tasks, the product RC maintains the performance of a standard nonlinear ESN while being more amenable to mathematical analysis. Our study provides evidence that such networks are powerful in highly nonlinear tasks owing to high-order statistics generated by the recurrent product node reservoir.
Are PILOTs Property Taxes for Nonprofits

Abstract Nonprofit charitable organizations are exempt from most taxes, including local property taxes, but U.S. cities and towns increasingly request that nonprofits make payments in lieu of taxes (known as PILOTs). Strictly speaking, PILOTs are voluntary, though nonprofits may feel pressure to make them, particularly in high-tax communities. Evidence from Massachusetts indicates that PILOT rates, measured as ratios of payments to the value of local tax-exempt property, are higher in towns with higher property tax rates: a one percentage point higher property tax rate is associated with a 0.2 percentage point higher PILOT rate. PILOTs appear to discourage nonprofit activity: a one percentage point higher PILOT rate is associated with 0.8% lower real property ownership by local nonprofits, 0.2% lower total assets, and 0.2% lower revenues of local nonprofits. These patterns are consistent with voluntary PILOTs acting in a manner similar to low-rate, compulsory real estate taxes.
A comparison of thermal infrared to fiber-optic distributed temperature sensing for evaluation of groundwater discharge to surface water.

Summary Groundwater has a predictable thermal signature that can be used to locate discrete zones of discharge to surface water. As climate warms, surface water with strong groundwater influence will provide habitat stability and refuge for thermally stressed aquatic species, and is therefore critical to locate and protect. Alternatively, these discrete seepage locations may serve as potential point sources of contaminants from polluted aquifers. This study compares two increasingly common heat tracing methods to locate discrete groundwater discharge: direct-contact measurements made with fiber-optic distributed temperature sensing (FO-DTS) and remote sensing measurements collected with thermal infrared (TIR) cameras. FO-DTS is used to make high spatial resolution (typically m) thermal measurements through time within the water column using temperature-sensitive cables. The spatial–temporal data can be analyzed with statistical measures to reveal zones of groundwater influence, however, the personnel requirements, time to install, and time to georeference the cables can be burdensome, and the control units need constant calibration. In contrast, TIR data collection, either from handheld, airborne, or satellite platforms, can quickly capture point-in-time evaluations of groundwater seepage zones across large scales. However the remote nature of TIR measurements means they can be adversely influenced by a number of environmental and physical factors, and the measurements are limited to the surface “skin” temperature of water features. We present case studies from a range of lentic to lotic aquatic systems to identify capabilities and limitations of both technologies and highlight situations in which one or the other might be a better instrument choice for locating groundwater discharge. FO-DTS performs well in all systems across seasons, but data collection was limited spatially by practical considerations of cable installation. TIR is found to consistently locate groundwater seepage zones above and along the streambank, but submerged seepage zones are only well identified in shallow systems (e.g.
Coordinating multilimbed robots for generating large Cartesian force

The coordination of the arm and main body of multilimbed robots to generate large Cartesian forces is discussed. Two methods are developed. In the first method, motions for the arm and main body are separately considered. For a given Cartesian force, an optimal configuration is determined for the arm. Based on the arm configuration, the main body is adjusted to satisfy the constraints of the position and orientation of the end-effector. To reduce the energy consumption, the nonlinear programming techniques could be further applied to the main body to obtain an optimal configuration. The second method treats the multilimbed robot as a single system and directly applies the nonlinear programming technique to the arm and main body with the arm torque limitation as an added set of constraints. Since the multilimbed robot is considered as a single system, the method had the least sense of coordination and is computationally more complicated than the first method. >
New “Einstein Cross” Gravitational Lens Candidates in HST WFPC2 Survey Images

We report the serendipitous discovery of quadruple gravitational lens candidates using the Hubble Space Telescope. We have so far discovered two good examples of such lenses, each in the form of four faint blue images located in a symmetric configuration around a red elliptical galaxy. The high resolution of HST has facilitated the discovery of this optically selected sample of faint lenses with small (∼1″) separations between the (I ∼ 25–27) lensed components and the much brighter (I∼19–22) lensing galaxies. The sample has been discovered in the routine processing of HST fields through the Medium Deep Survey pipeline, which fits simple galaxy models to broad band filter images of all objects detected in random survey fields using WFPC2.
Impact Resistance of Unidirectional Fiber Composites

Investigation of impact resistance of unidirectional fiber composites using Izod impact tests
Explicit Modular Towers

We give a general recipe for explicitly constructing asymptotically optimal towers of modular curves such as {X0(l)}n>1. We illustrate the method by giving equations for eight towers with various geometric features. We conclude by observing that such towers are all of a specific recursive form and speculate that perhaps every tower of this form which attains the Drinfeld-Vladuţ bound is modular. Introduction. Explicit equations for modular curves have attracted interest at least since the classical work of Fricke and Klein. Recent renewed interest in such equations has been stimulated on the one hand by the availability of software for symbolic computation and on the other hand by specific applications. In [E] we considered the use of modular curves to count rational points on elliptic curves over large finite fields, and illustrated some other applications of equations for the curves X0(N) with small N (say N 1. It turns out that only information about the first few levels of the tower is needed, and that this information can be obtained for modular elliptic curves using the methods of [E], and for some Shimura curves using only the ramification structure. We then illustrate the method by giving explicit formulas for eight asymptotically optimal towers: six of elliptic modular curves, namely X0(l) for l = 2, 3, 4, 5, 6, and X0(3 · 2); and two of Shimura modular curves. Over any finite field whose characteristic does not divide the level of these modular curves, the towers are tamely ramified, making it easy to calculate the genus of every curve in the tower. [This contrasts with the wildly ramified tower of [GS1], whose genus computation required some ingenuity; we show elsewhere that that tower too is modular, of Drinfeld type.] For each finite field k over which one of our towers is asymptotically optimal, the optimality can then be shown by elementary means, independent of the tower’s modular provenance, by exhibiting the coordinates of the rational (supersingular) points. These formulas may also have other uses, e.g. in finding explicit modular parametrizations of elliptic curves with smooth conductor, or in connection with generalizations of the arithmetic-geometric mean (which corresponds to the X0(2) tower) as in [S1,S2]; we hope to pursue these connections in future papers. We conclude this paper with a speculation concerning the modularity of “any” asymptotically optimal tower.
Diversity and Phylogeny of Cardinium (Bacteroidetes) in Armored Scale Insects (Hemiptera: Diaspididae)

Species of Cardinium are intracellular endosymbionts of arthropods. They are known to interfere with the mode of reproduction in some parasitoid wasp and mite hosts, and they are associated with parthenogenesis in the oleander scale, Aspidiotus nerii Bouche (Hemiptera: Diaspididae). Here, we survey A. nerii more broadly for presence of Cardinium species. In total, we tested 593 individuals in 301 populations, representing 132 identified species of armored scale insects, by using polymerase chain reaction (PCR) and sequencing of 16S rDNA. We obtained positive PCR results in 67 individuals of 34 populations, representing 20 species and one unidentified individual. Sequencing of these PCR products yields 20 new Cardinium haplotypes, raising the number of known insect-associated Cardinium haplotypes from 15 to 35. The new host-list elucidates the ecology of Cardinium, which in insects seems to be specialized on plant-feeding Hemiptera and associated parasitoid Hymenoptera. A phylogenetic analysis of all known insect-associated Cardinium 16S sequences reveals deep diversity in armored scale insects and implies horizontal transfer of Cardinium among armored scale insects and their parasitoids.
OnionBots: Subverting Privacy Infrastructure for Cyber Attacks

Over the last decade botnets survived by adopting a sequence of increasingly sophisticated strategies to evade detection and take overs, and to monetize their infrastructure. At the same time, the success of privacy infrastructures such as Tor opened the door to illegal activities, including botnets, ransomware, and a marketplace for drugs and contraband. We contend that the next waves of botnets will extensively attempt to subvert privacy infrastructure and cryptographic mechanisms. In this work we propose to preemptively investigate the design and mitigation of such botnets. We first, introduce OnionBots, what we believe will be the next generation of resilient, stealthy botnets. OnionBots use privacy infrastructures for cyber attacks by completely decoupling their operation from the infected host IP address and by carrying traffic that does not leak information about its source, destination, and nature. Such bots live symbiotically within the privacy infrastructures to evade detection, measurement, scale estimation, observation, and in general all IP-based current mitigation techniques. Furthermore, we show that with an adequate self-healing network maintenance scheme, that is simple to implement, OnionBots can achieve a low diameter and a low degree and be robust to partitioning under node deletions. We develop a mitigation technique, called SOAP, that neutralizes the nodes of the basic OnionBots. In light of the potential of such botnets, we believe that the research community should proactively develop detection and mitigation methods to thwart OnionBots, potentially making adjustments to privacy infrastructure.
Prograde and retrograde black holes: whose jet is more powerful?

The outflow efficiency (η) from black hole (BH) accretion disc systems is known to depend upon both the BH spin (a) and the amount of large-scale magnetic flux threading the BH and disc. Semi-analytical flux-trapping models suggest retrograde BHs should trap much more large-scale magnetic flux near the BH leading to much higher η than for prograde BHs. We self-consistently determine the amount of large-scale magnetic flux trapped by rapidly spinning (a=−0.9 and 0.9) BHs using global 3D time-dependent non-radiative general relativistic magnetohydrodynamic simulations of thick (h/r≈ 0.3–0.6) discs. We find that BH-trapped flux builds up until it is strong enough to disrupt the inner accretion disc. Contrary to prior flux-trapping models, which do not include the back-reaction of magnetic flux on the disc, our simulations show prograde BHs trap more magnetic flux, leading to about three times higher η than retrograde BHs for |a|= 0.9. Both spin orientations can produce highly efficient jets, η∼ 100 per cent, with increasing η for increasing disc thickness. The similarity of η for prograde and retrograde BHs makes it challenging to infer the sign of a based on jet energetics alone.
The attenuation of aircraft noise by wood stud walls

Measurements were made according to the ASTM E90 procedure but with the frequency range of measurements extended from 50 to 5 kHz. The overall performance of the walls was rated using the ASTM Outdoor-Indoor Transmission Class (OITC). In general, it was found that the overall sound insulation of wood stud exterior walls is limited by poor performance at the low frequencies due to one of 2 types of low frequency resonance.