cssi/SciSciGPT-SciSciNet huggingface dataset:
A competition-based connectionist model for information retrieval

In this paper, we adapt a competition-based connectionist model, which has been proposed for diagnostic problem solving, to information retrieval. In our model, documents are treated as "disorders" and user information needs as "manifestations", and a competitive activation mechanism is used which converges to a set of disorders that best explain the given manifestations. By combining the ideas of Bayesian inferencing and diagnostic inferencing using parsimonious covering theory, this model removes many difficulties of direct application of Bayesian inference to information retrieval, such as the unrealistically large number of conditional probabilities required as part of the knowledge base, the computational complexity, and unreasonable independence assumptions. Also, Bayesian inference strengthens the parsimonious covering model by providing a likelihood measure which can be used to rank documents as well as to guide the search to the most likely retrieval. We also incorporate two types of relevance information to improve the model. First, Roget's thesaurus is used to provide semantic relevance information among the index terms. Second, after the neural network has been initialized, it is trained using the available query-document relevance judgements. Our preliminary study demonstrate the efficiency and the retrieval precision of this model, comparable to or better than that of the Bayesian network models reported in the literature. >
Size Anomalies in US Bank Stock Returns: Your Tax Dollars at Work?

Over the last four decades, the average Gaussian-risk-adjusted return on a stock portfolio that goes long in the largest banks and short in the smallest banks is minus 7 %. Moreover, this portfolio provides US investors with insurance against recessions, even though the cash flows of large banks seem more exposed to macroeconomic risk. Using the rare events model of ?, we interpret the 7% as a disaster risk premium. Recessions are periods with a high probability of a disaster. In a calibrated version of the model, we estimate an implicit recovery rate in disaster states that is 44 percentage points higher for the largest banks than for the smallest banks. If these large differences in the implied recovery rates indeed reflect the market’s expectations of the government’s asymmetric actions during a disaster, then the disaster risk discount for large banks represents a large hidden subsidy to large banks and a tax on small
Private capital flows, capital controls, and default risk

Abstract What has been the effect of the shift in emerging market capital flows toward private sector borrowers? Are emerging market capital flows more efficient? If not, can controls on capital flows improve welfare? This paper shows that the answers depend on the form of default risk. When private loans are enforceable, but there is the risk that the government will default on behalf of all residents, private lending is inefficient and capital controls are potentially Pareto-improving. However, when private agents may individually default, capital flow subsidies are potentially Pareto-improving.
The Evolution of Enterprise Reform in Africa: From State-owned Enterprises to Private Participation in Infrastructure - and Back?

Many African state-owned enterprises (SOEs), particularly those in infrastructure, have a long history of poor performance. From the outset, SOE financial and economic performance generally failed to meet the expectations of their creators and funders. By the late 1970s, the situation was alarming, and by early 1980s, critical. The poor financial performance of SOEs became so burdensome to government budgets that it attracted the attention of the international financial institutions, or IFIs. In response, in the 1980s, the World Bank approved SOE reforms that could be summed up in the term “commercialization”. By the mid-1990s, however, the idea of making SOEs function efficiently and effectively under government management was largely abandoned by the IFIs and privatization and private participation in infrastructure, or PPI became the order of the day. Once more, however, the results were disappointing. PPI has not been as widely adopted as anticipated, nor has it generated the massive resources and changes hoped for, nor has it been widely accepted as beneficial by the African public. The findings of recent studies in Africa suggest that PPI should not be jettisoned, and that the more productive path is to recognize the limitations of the approach, and to work harder at creating the conditions needed to make it function effectively. This will entail, as many have recognized, an end to the view that public and private infrastructure provision is a dichotomy – a case of either-or, one or the other – and a better appreciation of the extent to which the performance of each is dependent on the competence of the other. In other words, for the private sector to perform well, public sector capacity must be enhanced. Moreover, proposed tactics of reform should fit more closely with the expectations and sentiments of the affected government, consumer base, and general population. This broader approach implies, probably, a reduction in the scope and, certainly, a reduction in the planned speed of operations. Improving infrastructure performance is a long-term matter.
Accounting for the growth of MNC-based trade using a structural model of U.S. MNCs

In recent decades, U.S. foreign trade grew much faster than GDP, but there is no consensus why. Notably lacking is an understanding of the role of multinational corporations (MNCs), which mediate over half of world trade. We use Bureau of Economic Analysis data on U.S. MNCs to study the rapid growth of MNC-based trade from 1983 to 1996. Using a model of U.S. MNCs and Canadian affiliates, we decompose this growth by source. Tariff reductions can largely explain increases in arms-length MNC-based trade. But intra-firm trade growth is attributed mostly to "technical change." We present additional evidence suggesting just-in-time production facilitated intra-firm trade.
Tunable dual-band subwavelength imaging with a wire medium slab loaded with nanostructured graphene metasurfaces

In this paper, we demonstrate that a wire medium slab loaded with graphene-nanopatch metasurfaces (GNMs) enables the enhancement of evanescent waves for the subwavelength imaging at terahertz (THz) frequencies. The analysis is based on the nonlocal homogenization model for wire medium with the additional boundary condition at the connection of wires to graphene. The physical mechanism behind this lens can be described as the surface plasmons excitement at the lower and upper GNMs which are coupled by an array of metallic wires. The dual nature (capacitive/inductive) of the GNM is utilized in order to design a dual-band lens in which the unique controllable properties of graphene and the structural parameters of wire medium (WM) slab provide more degrees of freedom in controlling two operating frequency bands. The lens can support the subwavelength imaging simultaneously at two tunable distinct frequencies with the resolution better than λ/6 even if the distance between GNMs is a significant fraction of wavelength (>λ/5.5). The major future challenges in the fabrication of the lens have been demonstrated and a promising approach for the practical configuration of the lens has been proposed.
Calibrated, Registered Images of an Extended Urban Area

We describe a dataset of several thousand calibrated, time-stamped, geo-referenced, high dynamic range color images, acquired under uncontrolled, variable illumination conditions in an outdoor region spanning several hundred meters. The image data is clustered into several groups which have little mutual inter-visibility. For each group the calibration data is globally consistent on average to roughly five centimeters and 0.1 °, or about four pixels of epipolar registration. All image, feature and calibration data is available for interactive inspection and downloading at http://city.lcs.mit.edu/data.Calibrated imagery is of fundamental interest in a variety of applications. We have made this data available in the belief that researchers in computer graphics, computer vision, photogrammetry and digital cartography will find it of value as a test set for their own image registration algorithms, as a calibrated image set for applications such as image-based rendering, metric 3D reconstruction, and appearance recovery, and as input for existing GIS applications.
Interstellar scattering of pulsar radiation. I - Scintillation

An investigation of the intensity fluctuations of 28 pulsars near 0.4 GHz indicates that scintillation spectra have a Gaussian shape, scintillation indices are near unity, and the scintillation bandwidth depends linearly on dispersion measure. Observations near 2.5 GHz suggest a strong dependence of the frequency at which scintillation indices fall below unity on dispersion measure. Multistation measurements of scintillation provide values or limits for the scale size of the scattering diffraction pattern. The dependences of scattering parameters on dispersion measure is discussed in terms of the current models. It is suggested that any line of sight through the galaxy encounters increasingly rare, increasingly large deviations of thermal electron density on the scale of 10 to the 11th power cm.
Malnutrition : some measurement and policy issues

The energy and protein norms published by the FAO have been widely misused for assessing the nutritional status of a population in spite of warnings against such use by the FAO itself. The paper points out that the process governing variations in daily energy balances in human beings is not yet fully understood and a satisfactory theoretical framework for it has yet to emerge. Nevertheless, there is some evidence that the process is stochastic-stationary and auto-regressive, and there is a wide variability in energy intakes between otherwise similarly situated healthy individuals and even in the same individual over time. Many of the widely used procedures for assessing nutritional status, by classifying all individuals in a population as malnourished who have intakes below a single average norm for the population as a whole, thereby ignoring intra and inter individual variance in intakes and requirements, will misclassify individuals to varying degrees. This misclassification bias need not cancel out for the population as a whole and there is a danger in overestimating the proportion of truly malnourished.
Paper models of surfaces with curvature creative visualization labs baltimore joint mathematics meetings

A model of a cone can be constructed from a piece of paper by removing a wedge and taping the edges together. The paper models discussed here expand on this idea (one or more wedges are added and/or removed). These models are fiat everywhere, except at the "cone points," so the geodasics are locally straight lines in a natured sense, Non-Euclidean "effects" are easily quantifiable using basic geometry, the Gauss-Bonnet theorem im a naturally intuitive concept, and the connection between hyperbolic and elliptic geometry and curvature is clearly seen.
Predictive state representations: a new theory for modeling dynamical systems

Modeling dynamical systems, both for control purposes and to make predictions about their behavior, is ubiquitous in science and engineering. Predictive state representations (PSRs) are a recently introduced class of models for discrete-time dynamical systems. The key idea behind PSRs and the closely related OOMs (Jaeger's observable operator models) is to represent the state of the system as a set of predictions of observable outcomes of experiments one can do in the system. This makes PSRs rather different from history-based models such as nth-order Markov models and hidden-state-based models such as HMMs and POMDPs. We introduce an interesting construct, the system-dynamics matrix, and show how PSRs can be derived simply from it. We also use this construct to show formally that PSRs are more general than both nth-order Markov models and HMMs/POMDPs. Finally, we discuss the main difference between PSRs and OOMs and conclude with directions for future work.
Creatureliness priming reduces aggression and support for war

Terror management theory (TMT) posits that humans distance themselves from, or elevate themselves above, other animals as a way of denying their mortality. The present studies assessed whether the salience of aggressive tendencies that humans share with other animals make thoughts of death salient and whether depicting human aggression as animalistic can mitigate aggressive behaviour and support for aggression. In Study 1, participants primed with human–animal similarities (i.e., human creatureliness) exhibited elevated death-thought accessibility (DTA) after hitting a punching bag. In Studies 2a and 2b, creatureliness priming caused participants to hit a punching bag with less frequency, perceived force, and comfort. In Study 3, participants primed to view violence as animalistic exhibited increased DTA and reported less support for war against Iran. These studies suggest that portraying violence as creaturely may reduce the intensity of aggressive actions and support for violent solutions to international conflicts.
Variable Reuse for Efficient Image Computation

Image computation, that is, computing the set of states reachable from a given set in one step, is a crucial component in typical tools for BDD-based symbolic reachability analysis. It has been shown that the size of the intermediate BDDs during image computation can be dramatically reduced via conjunctive partitioning of the transition relation and ordering the conjuncts for facilitating early quantification. In this paper, we propose to enhance the effectiveness of these techniques by reusing the quantified variables. Given an ordered set of conjuncts, if the last conjunct that uses a variable u appears before the first conjunct that uses another variable v, then v can be renamed to u, assuming u will be quantified immediately after its last use. In general, multiple variables can share the same identifier so the BDD nodes that are inactive but not garbage collected may be activated. We give a polynomial-time algorithm for generating the optimum number of variables that are required for image computation and show how to modify the image computation accounting for variable reuse. The savings for image computation are demonstrated on ISCAS’89 and Texas’97 benchmark models.
Scheduling Strategies for Processing Continuous Queries over Streams

Stream data processing poses many challenges. Two important characteristics of stream data processing – bursty arrival rates and the need for near real-time performance requirement – challenge the allocation of limited resources in the system. Several scheduling algorithms (e.g., Chain strategy) have been proposed for minimizing the maximal memory requirements in the literature. In this paper, we propose novel scheduling strategies to minimize tuple latency as well as total memory requirement. We first introduce a path capacity strategy (PCS) with the goal of minimizing tuple latency. We then compare the PCS and the Chain strategy to identify their limitations and propose additional scheduling strategies that improve upon them. Specifically, we introduce a segment strategy (SS) with the goal of minimizing the memory requirement, and its simplified version. In addition, we introduce a hybrid strategy, termed the threshold strategy (TS), to addresses the combined optimization of both tuple latency and memory requirement. Finally, we present the results of a wide range of experiments conducted to evaluate the efficiency and the effectiveness of the proposed scheduling strategies.
Shares, Coalition Formation and Political Development: Evidence from Seventeenth Century England

A key challenge for developing societies is to build coalitions across disparate interests in favour of beneficial policies. This paper documents the role of a financial innovation-- shares--in aligning disparate interests in favour of representative government during England's Civil War (1642-48). Using novel micro-data, the paper shows that shareholding was a major determinant of support for political reform by members of parliament. The paper suggests that shares allowed a broad spectrum of investors to benefit from new opportunities overseas. However, overseas rights belonged chiefly to the executive. Thus the introduction of shares aligned incentives in favour of political reforms and overseas policies crucial for growth.
The Political Function of the Modern Lie

In this 1943 text, first published in English translation in 1945 in Contemporary Jewish Record, Alexandre Koyre analyzes the open conspiracy and its mechanism, which includes the necessity for the leader to constantly remain in the limelight and to ceaselessly deceive the rank and file among his supporters, and proposes to read totalitarianism itself as functioning like a secret society.
Security in practice - security-usability chasm

Computer systems security area has received increased attention from both academics and in industry. However, recent work indicates that substantial security gaps emerge when systems are deployed, even with the use of state-of-the-art security protocols. Our findings suggest that wide-spread security problems exist even when protocols such as SSL and SSH are deployed because systems today do not give security warnings properly or make it trivial for users to bypass them. Even when these protocols are deployed correctly, systems often leave themselves vulnerable to social-engineering attacks as an artifact of their design. In one of our studies, we examined the web sites of 706 financial institutions and found over 90% of them to have made poor design choices when it comes to security, even though all deployed SSL for communicating passwords and doing transactions. In another study, we examined the usage of SSH within our own department and found that most users would be susceptible to a man-in-the-middle attack. Based on our studies, we postulate that some of the most interesting challenges for security researchers and practitioners lie at the intersection of security theory, their application to practice, and user behavior. We point out some of those challenges and hope that the research community can help address them.
Interpretations and Explanations of Deviance among College Athletes: A Case Study

This case study analyzes a group of college athletes who were involved in a series of larcenies. A focal point of the study is that these athletes did not fit the usual profile of deviants who would commit large-scale crimes. Furthermore, the athletes in question were apparently not committing the crimes for material gain. Differential interpretations that are given to explain the athletes’ behaviors include defective character traits, the use of alcohol, peer pressure, and the quest for excitement. These interpretations and explanations are discussed within a broader interpretive model of behavior.
Islamic Inheritance Law, Son Preference and Fertility Behavior of Muslim Couples in Indonesia

This paper examines whether the son preference and fertility behavior of Muslim couples respond to the risk of inheritance expropriation by their extended family. According to traditional Islamic inheritance principles, only the son of a deceased man can exclude his male agnates from inheritance and preserve his estate within the nuclear household. The paper exploits cross-sectional and time variation in the application of the Islamic inheritance exclusion rule in Indonesia: between Muslim and non-Muslim populations affected by different legal systems, across men with different sibling sex composition, and before and after a change in Islamic law that allowed female children to exclude male relatives. The analysis finds that Muslim couples more affected by the exclusion rule exhibit stronger son preference, practice sex-differential fertility stopping, attain a higher proportion of sons, and have larger families than non-Muslims or Muslims for whom the exclusion rule is less binding.
Evaluation of Bagging to Extend Storage Life of Wet and Modified Distillers’ Grains—A Demonstration Project

The ethanol industry is rapidly expanding. As much as 40% of the energy cost is associated with drying the feed co-products. Distillers grains are excellent sources of nutrients for the diets of beef cattle, but have a short shelf life. To expand the use of wet distillers feeds to more producers, longer term storage methods are required.
Luminosity Functions of Elliptical Galaxies at z < 1.2

The luminosity functions of E/S0 galaxies are constructed in three different redshift bins (0.2 1) for elliptical galaxies, together with weak evolution of the major merger rate at z < 1.
Improving pushdown system model checking

In this paper, we reduce pushdown system (PDS) model checking to a graph-theoretic problem, and apply a fast graph algorithm to improve the running time for model checking. Several other PDS questions and techniques can be carried out in the new setting, including witness tracing and incremental analysis, each of which benefits from the fast graph-based algorithm.
On the hardness of permanent

We prove that if there is a polynomial time algorithm which computes the permanent of a matrix of order n for any inverse polynomial fraction of all inputs, then there is a BPP algorithm computing the permanent for every matrix. It follows that this hypothesis implies P #P = BPP. Our algorithm works over any sufficiently large finite field (polynomially larger than the inverse of the assumed success ratio), or any interval of integers of similar range. The assumed algorithm can also be a probabilistic polynomial time algorithm. Our result is essentially the best possible based on any black box assumption of permanent solvers, and is a simultaneous improvement of the results of Gemmell and Sudan [GS92], Feige and Lund [FL92] as well as Cai and Hemachandra [CH91], and Toda (see [ABG90]).
The IBM Rich Transcription 2007 Speech-to-Text Systems for Lecture Meetings

The paper describes the IBM systems submitted to the NIST Rich Transcription 2007 (RT07) evaluation campaign for the speech-to-text (STT) and speaker-attributed speech-to-text (SASTT) tasks on the lecture meeting domain. Three testing conditions are considered, namely the multiple distant microphone (MDM), single distant microphone (SDM), and individual headset microphone (IHM) ones --- the latter for the STT task only. The IBM system building process is similar to that employed last year for the STT Rich Transcription Spring 2006 evaluation (RT06s). However, a few technical advances have been introduced for RT07: (a) better speaker segmentation; (b) system combination via the ROVER approach applied over an ensemble of systems, some of which are built by randomized decision tree state-tying; and (c) development of a very large language model consisting of 152M n-grams, incorporating, among other sources, 525M words of web data, and used in conjunction with a dynamic decoder. These advances reduce STT word error rate (WER) in the MDM condition by 16% relative (8% absolute) over the IBM RT06s system, as measured on 17 lecture meeting segments of the RT06s evaluation test set, selected in this work as development data. In the RT07 evaluation campaign, both MDM and SDM systems perform competitively for the STT and SASTT tasks. For example, at the MDM condition, a 44.3% STT WER is achieved on the RT07 evaluation test set, excluding scoring of overlapped speech. When the STT transcripts are combined with speaker labels from speaker diarization, SASTT WER becomes 52.0%. For the STT IHM condition, the newly developed large language model is employed, but in conjunction with the RT06s IHM acoustic models. The latter are reused, due to lack of time to train new models to utilize additional close-talking microphone data available in RT07. Therefore, the resulting system achieves modest WERs of 31.7% and 33.4%, when using manual or automatic segmentation, respectively.
The Asymmetric Median Tree - A New model for Building Consensus Trees

Inferring the consensus of a set of different evolutionary trees for a given species set is a well-studied problem, for which several different models have been proposed. In this paper, we propose a new optimization problem for consensus tree construction, which we call the asymmetric median tree, or AMT. Our main theoretical result is the equivalence between the asymmetric median tree problem on k trees and the maximum independent set (MIS) problem on k-colored graphs. Although the problem is NP-hard for three or more trees, we have polynomial time algorithms to construct the AMT for two trees and an approximation algorithm for three or more trees. We define a measure of phylogenetic resolution and show that our algorithms (both exact and approximate) produce consensus trees that on every input are at least as resolved as the standard models (strict consensus and majority tree) in use. Finally, we show that the AMT combines desirable features of many of the standard consensus tree models in use.
Evaluation of the Utility of Static and Adaptive Mesh Refinement for Idealized Tropical Cyclone Problems in a Spectral Element Shallow-Water Model

AbstractThe utility of static and adaptive mesh refinement (SMR and AMR, respectively) are examined for idealized tropical cyclone (TC) simulations in a two-dimensional spectral element f-plane shallow-water model. The SMR simulations have varying sizes of the statically refined meshes (geometry based) while the AMR simulations use a potential vorticity (PV) threshold to adaptively refine the mesh to the evolving TC. Numerical simulations are conducted for four cases: (i) TC-like vortex advecting in a uniform flow, (ii) binary vortex interaction, (iii) barotropic instability of a PV ring, and (iv) barotropic instability of a thin strip of PV. For each case, a uniform grid high-resolution “truth” simulation is compared to two different SMR simulations and three different AMR simulations for accuracy and efficiency. The multiple SMR and AMR simulations have variations in the number of fully refined elements in the vicinity of the TC. For these idealized cases, it is found that the SMR and AMR simulations ar...
On primitive covering numbers

In 2007, Zhi-Wei Sun defined a covering number to be a positive integer L such that there exists a covering system of the integers where the moduli are distinct divisors of L greater than 1. A covering number L is called primitive if no proper divisor of L is a covering number. Sun constructed an infinite set ℒ of primitive covering numbers, and he conjectured that every primitive covering number must satisfy a certain condition. In this paper, for a given L ∈ℒ, we derive a formula that gives the exact number of coverings that have L as the least common multiple of the set M of moduli, under certain restrictions on M. Additionally, we disprove Sun’s conjecture by constructing an infinite set of primitive covering numbers that do not satisfy his primitive covering number condition.
Rotation curves of giant LSB galaxies.

We present optical and H I rotation curves of a sample of giant, low surface brightness (LSB) galaxies including the prototype, Malin 1. The rotation curves of these diffuse systems are expected to more faithfully reflect the structure of their dark matter halos due to the reduced contribution of the disk to the overall gravitational potential. Indeed, the curves we derive generally exhibit the slowly rising behavior expected for dark matter dominated systems. In several cases, the rotation curves continue to rise out to the last measured points at radii of 50--70 kpc/h100. By comparison with cosmological N-body simulations such as those of Navarro et al. (1996, in press) the shapes of these curves can be used to constrain cosmological parameters. The results obtained to date indicate that dark matter halos are significantly less concentrated than predicted by the standard CDM cosmogony. Low density models with a cosmological constant appear to be favored by our preliminary results.
Approximation algorithms for inventory problems with submodular or routing costs

We consider the following two deterministic inventory optimization problems with non-stationary demands. Submodular joint replenishment problem. This involves multiple item types and a single retailer who faces demands over a finite planning horizon of T periods. In each time period, any subset of item-types can be ordered incurring a joint ordering cost which is submodular. Moreover, items can be held in inventory while incurring a holding cost. The objective is to find a sequence of orders that satisfies all demands and minimizes the total ordering and holding costs. Inventory routing problem. This involves a single depot that stocks items, and multiple retailer locations facing demands over a finite planning horizon of T periods. In each time period, any subset of locations can be visited using a vehicle originating from the depot. There is also cost incurred for holding items at any retailer. The objective here is to satisfy all demands while minimizing the sum of routing and holding costs. We present a unified approach that yields $$\mathcal {O}\left( \frac{\log T}{\log \log T}\right) $$OlogTloglogT-factor approximation algorithms for both problems when the holding costs are polynomial functions. A special case is the classic linear holding cost model, wherein this is the first sub-logarithmic approximation ratio for either problem.
High-Reynolds number liquid flow measurements

Liquid flow facilities are usually categorized as towing tanks, seakeeping and maneuvering basins, circulating water channels, blowdown facilities, and water tunnels. A very complete listing of such facilities has been compiled by the 16th International Towing Tank Conference (ITTC) (1985) and it includes most of the major water facilities in, the world. A description of new and planned cavitation facilities is given in Moll and Billet (1987). The intent of this chapter is to discuss the various experimental techniques used in hydrodynamic testing at high Reynolds numbers. This usually implies that water tunnels or tow tanks are used. Because Gad-el-Hak (1987) recently reviewed tow tank testing, our emphasis here is on water (or other liquid) tunnel measurements.
Optimal measurement of ice-sheet deformation from surface-marker arrays

Surface strain rate is best observed by fitting a strain-rate ellipsoid to the measured movement of a stake network or other collection of surface features, using a least squares procedure. Error of the resulting fit varies as 1/(L delta t square root of N), where L is the stake separation, delta is the time period between initial and final stake survey, and n is the number of stakes in the network. This relation suggests that if n is sufficiently high, the traditional practice of revisiting stake-network sites on successive field seasons may be replaced by a less costly single year operation. A demonstration using Ross Ice Shelf data shows that reasonably accurate measurements are obtained from 12 stakes after only 4 days of deformation. It is possible for the least squares procedure to aid airborne photogrammetric surveys because reducing the time interval between survey and re-survey permits better surface feature recognition.
Posets from Admissible Coxeter Sequences

We study the equivalence relation on the set of acyclic orientations of an undirected graph $\Gamma$ generated by source-to-sink conversions. These conversions arise in the contexts of admissible sequences in Coxeter theory, quiver representations, and asynchronous graph dynamical systems. To each equivalence class we associate a poset, characterize combinatorial properties of these posets, and in turn, the admissible sequences. This allows us to construct an explicit bijection from the equivalence classes over $\Gamma$ to those over $\Gamma'$ and $\Gamma"$, the graphs obtained from $\Gamma$ by edge deletion and edge contraction of a fixed cycle-edge, respectively. This bijection yields quick and elegant proofs of two non-trivial results: $(i)$ A complete combinatorial invariant of the equivalence classes, and $(ii)$ a solution to the conjugacy problem of Coxeter elements for simply-laced Coxeter groups. The latter was recently proven by H. Eriksson and K. Eriksson using a much different approach.
EVOLUTION OF NEUTRAL-BEAM-DRIVEN CURRENT IN TOKAMAK PLASMAS

Neutral-beam heating and current induction have been analyzed with a one-dimensional model that includes a Fokker-Planck analysis of the circulating ion current, the time and space dependence of the electron ''return'' current, and the steady electron shielding current including electron trapping effects. With 1.2 MW of 40 keV H/sup 0/ injected tangentially into a 25-cm radius PLT plasma with = 2.0 x 10/sup 13/ cm/sup -3/, the maximum beam-driven current is about 100 kA and results in a 0.24-V reduction in loop voltage. Reversed loop voltages should be observable in low density plasmas in ISX-B and TFTR, which would provide an unambiguous detection of the beam-driven current. When the radial profiles of beam-driven current are less peaked than the ohmic-current profile, the profiles of the ''safety factor'' q should be more stable to n = 1, m = 1 and n = 1, m = 2 kink modes, if the total plasma current is kept constant.
Learning finite-state controllers for partially observable environments

Reactive (memoryless) policies are sufficient in completely observable Markov decision processes (MDPS), but some kind of memory is usually necessary for optimal control of a partially observable MDP. Policies with finite memory can be represented as finite-state automata. In this paper, we extend Baird and Moore's VAPS algorithm to the problem of learning general finite-state automata. Because it performs stochastic gradient descent, this algorithm can be shown to converge to a locally optimal finitestate controller. We provide the details of the algorithm and then consider the question of under what conditions stochastic gradient descent will outperform exact gradient descent. We conclude with empirical results comparing the performance of stochastic and exact gradient descent, and showing the ability of our algorithm to extract the useful information contained in the sequence of past observations to compensate for the lack of observability at each time-step.
Two Molecular Information Processing Systems Based on Catalytic Nucleic Acids

Mixtures of molecules are capable of powerful information processing [1]. This statement is in the following way self-evident: it is a hierarchically organized complex mixture of molecules that is formulating it to other similarly organized mixtures of molecules. By making such a statement I am not endorsing the extreme forms of reductionism; rather, I am making what I think is a small first step towards harnessing information processing prowess of molecules and, hopefully, overcoming some limitations of more traditional computing paradigms. There are different ideas on how to understand and use molecular information processing abilities and I will list some below. My list is far from inclusive, and delineations are far from clear-cut; whenever available, I will provide examples from our research efforts. I should stress, for a computer science audience that I am a chemist. Thus, my approach may have much different focus and mathematical rigor, then if it would be taken by a computer scientist.
Subspaces of knot spaces

The inclusion of the space of all knots of a prescribed writhe in a particular isotopy class into the space of all knots in that isotopy class is a weak homotopy equivalence.
Satellite Attitude Estimation with Measurements Available at Random Points in Time

Summary The state, measurement model, and linear filter for estimating the three small rotation angles between the measured attitude of a spacecraft and the actual attitude of the spacecraft are developed. The measured spacecraft and actual spacecraft have different attitudes due to gyro errors. The measurements available for the small angle estimation are voltage pip times caused by star images crossing slits on the reticles of star sensors rigidly mounted to the spacecraft body. Attitude measurements are generated by comparing one component of the catalogued star vector in the actual spacecraft frame with the same component in the measured spacecraft frame. The pip times for each slit are modeled as a Poisson counting process. This assumption leads to derivation of a suboptimal filter using a gain that is independent of the pip arrival time sequence.
The convergence of social and technological networks

The growth of social media and on-line social networks has opened up a set of fascinating new challenges and directions for the field of computing. Some of the basic issues around these developments are the design of information systems in the presence of complex social feedback effects, and the emergence of a growing research interface between computing and the social sciences. In this talk, we will review two key sets of challenges that arise in designing and analyzing on-line social systems. The first is to understand how information flows through these systems, and how the behavior of individuals is affected by the behavior of their neighbors in the network. The second is to understand the subtle processes by which individuals on these systems evaluate and form opinions about each other, and the ways in which these evaluations create incentives that drive behavior.
Gender Dimensions of Pension Reform in the Former Soviet Union

The authors analyze the gender implications of pension reform in Kazakhstan, the Kygyz Republic, Latvia, and Moldova. The new systems deliberately penalize early retirement and reward longer careers, so that with no change in behavior or policy, women's pensions will be lower than men's on average. Still, the implicit financial returns for women remain higher on average than returns for men, because of women's longer life expectancy and because of redistributory minimum pensions. Overall, however, the net change in wealth resulting from the reforms will be larger on average for men than for women, because they will work longer and get a larger pension. Women's longer life expectancy means that women can expect to spend the last years of their lives alone. If their pensions are too low because of their work histories, poverty among elderly women may increase.
Nonuniform Graph Partitioning with Unrelated Weights

We give a bi-criteria approximation algorithm for the Minimum Nonuniform Partitioning problem, recently introduced by Krauthgamer, Naor, Schwartz and Talwar (2014). In this problem, we are given a graph G = (V,E) on n vertices and k numbers ρ 1,…, ρ k . The goal is to partition the graph into k disjoint sets P 1,…, P k satisfying |P i | ≤ ρ i n so as to minimize the number of edges cut by the partition. Our algorithm has an approximation ratio of \(O(\sqrt{\log n \log k})\) for general graphs, and an O(1) approximation for graphs with excluded minors. This is an improvement upon the O(logn) algorithm of Krauthgamer, Naor, Schwartz and Talwar (2014). Our approximation ratio matches the best known ratio for the Minimum (Uniform) k-Partitioning problem.
Economic Preparation for Retirement

Defines and estimates measures of economic preparation for retirement based on an inventory of economic resources while taking into account the risk of living to advanced old age and the risk of high out-of-pocket spending for health care services.
AMS WITHOUT 4-WISE INDEPENDENCE ON PRODUCT DOMAINS

In their seminal work, Alon, Matias, and Szegedy introduced several sketching techniques, including showing that $4$-wise independence is sufficient to obtain good approximations of the second frequency moment. In this work, we show that their sketching technique can be extended to product domains $[n]^k$ by using the product of $4$-wise independent functions on $[n]$. Our work extends that of Indyk and McGregor, who showed the result for $k = 2$. Their primary motivation was the problem of identifying correlations in data streams. In their model, a stream of pairs $(i,j) \in [n]^2$ arrive, giving a joint distribution $(X,Y)$, and they find approximation algorithms for how close the joint distribution is to the product of the marginal distributions under various metrics, which naturally corresponds to how close $X$ and $Y$ are to being independent. By using our technique, we obtain a new result for the problem of approximating the $\ell_2$ distance between the joint distribution and the product of the marginal distributions for $k$-ary vectors, instead of just pairs, in a single pass. Our analysis gives a randomized algorithm that is a $(1\pm \epsilon)$ approximation (with probability $1-\delta$) that requires space logarithmic in $n$ and $m$ and proportional to $3^k$.
An observable measure of entanglement for pure states of multi-qubit systems

Recently, Meyer and Wallach [D.A. Meyer and N.R. Wallach (2002), J. of Math. Phys., 43, pp. 4273] proposed a measure of multi-qubit entanglement that is a function on pure states. We find that this function can be interpreted as a physical quantity related to the average purity of the constituent qubits and show how it can be observed in an efficient manner without the need for full quantum state tomography. A possible realization is described for measuring the entanglement of a chain of atomic qubits trapped in a 3D optical lattice.
Constants count: practical improvements to oblivious RAM

Oblivious RAM (ORAM) is a cryptographic primitive that hides memory access patterns as seen by untrusted storage. This paper proposes Ring ORAM, the most bandwidth-efficient ORAM scheme for the small client storage setting in both theory and practice. Ring ORAM is the first tree-based ORAM whose bandwidth is independent of the ORAM bucket size, a property that unlocks multiple performance improvements. First, Ring ORAM's overall bandwidth is 2.3× to 4× better than Path ORAM, the prior-art scheme for small client storage. Second, if memory can perform simple untrusted computation, Ring ORAM achieves constant online bandwidth (∼ 60× improvement over Path ORAM for practical parameters). As a case study, we show Ring ORAM speeds up program completion time in a secure processor by 1.5× relative to Path ORAM. On the theory side, Ring ORAM features a tighter and significantly simpler analysis than Path ORAM.
Late Pleistocene and Holocene groundwater recharge from the chloride mass balance method and chlorine-36 data

[1] The chloride mass balance (CMB) method for estimating groundwater recharge is economic and effective, provided that the hydrological conditions for its applications are met and the modeling parameters are known. However, modeling parameters such as precipitation and Cl− deposition rates vary temporally, most notably as a result of the climatic changes from late Pleistocene to Holocene. The temporal variability of atmospheric Cl− input and annual precipitation were considered in this study by using a discrete steady state CMB model with different parameters for late Pleistocene and Holocene. Cl− deposition rates, estimated from 36Cl data, were lower in late Pleistocene than Holocene at Yucca Mountain, Nevada, but higher in late Pleistocene than Holocene at Black Mesa, Arizona. Paleoclimate proxies at both Yucca Mountain and Black Mesa point to higher precipitation rates in late Pleistocene than Holocene. The resulting average recharge estimates for Black Mesa are 9 ± 5 mm/yr for Holocene and 35 ± 22 mm/yr for late Pleistocene. Local recharge rates at Yucca Mountain were estimated from the 36Cl/Cl ratios and Cl− concentrations in perched waters. The estimated recharge for Yucca Mountain is 5 ± 1 mm/yr for Holocene and 15 ± 5 mm/yr for late Pleistocene. These recharge rates are comparable to results of independent numerical groundwater flow models and watershed-scale infiltration models at Black Mesa and Yucca Mountain, respectively.
Non‐dissipative tidal synchronization in accreting binary white dwarf systems

We study a non-dissipative hydrodynamical mechanism that can stabilize the spin of the accretor in an ultracompact double white dwarf (WD) binary. This novel synchronization mechanism relies on a non-linear coupling between tides and the uniform (or rigid) rotation mode, which spins down the background star. The essential physics of the synchronization mechanism is summarized as follows. As the compact binary coalesces due to gravitational wave emission, the largest star eventually fills its Roche lobe and accretion starts. The accretor then spins up due to infalling material and eventually reaches a spin frequency where a normal mode of the star is resonantly driven by the gravitational tidal field of the companion. If the resonating mode satisfies a set of specific criteria, which we elucidate in this paper, it exchanges angular momentum with the background star at a rate such that the spin of the accretor locks at this resonant frequency, even though accretion is ongoing. Some of the accreted angular momentum that would otherwise spin up the accretor is fed back to the orbit through this resonant tidal interaction. In this paper we solve analytically a simple dynamical system that captures the essential features of this mechanism. Our analytical study allows us to identify two candidate Rossby modes that may stabilize the spin of an accreting WD in an ultracompact binary. These two modes are the l=4, m=2 and l=5, m=3 Chandrasekhar–Friedman–Schutz (CFS) unstable hybrid r modes, which, for an incompressible equation of state, stabilize the spin of the accretor at frequency 2.6 ωorb and 1.54 ωorb, respectively, where ωorb is the binary's orbital frequency. For an n= 3/2 polytrope, the accretor's spin frequency is stabilized at 2.13 ωorb and 1.41 ωorb, respectively. Since the stabilization mechanism relies on continuously driving a mode at resonance, its lifetime is limited since eventually the mode amplitude saturates due to non-linear mode–mode coupling. Rough estimates of the lifetime of the effect lie from a few orbits to possibly millions of years. We argue that one must include this hydrodynamical stabilization effect to understand stability and survival rate of ultracompact binaries, which is relevant in predicting the Galactic WD gravitational background that LISA will observe.
Resolving the vacuum fluctuations of an optomechanical system using an artificial atom

Vacuum fluctuations in a ground-state mechanical oscillator are hard to distinguish from noise, but by using the coupling with a superconducting qubit in a microwave cavity one can amplify and convert them to directly measurable real photons. Heisenberg’s uncertainty principle results in one of the strangest quantum behaviours: a mechanical oscillator can never truly be at rest. Even at a temperature of absolute zero, its position and momentum are still subject to quantum fluctuations1,2. However, direct energy detection of the oscillator in its ground state makes it seem motionless1,3, and in linear position measurements detector noise can masquerade as mechanical fluctuations4,5,6,7. Thus, how can we resolve quantum fluctuations? Here, we parametrically couple a micromechanical oscillator to a microwave cavity to prepare the system in its quantum ground state8,9 and then amplify the remaining vacuum fluctuations into real energy quanta10. We monitor the photon/phonon-number distributions using a superconducting qubit11,12,13, allowing us to resolve the quantum vacuum fluctuations of the macroscopic oscillator’s motion. Our results further demonstrate the ability to control a long-lived mechanical oscillator using a non-Gaussian resource, directly enabling applications in quantum information processing and enhanced detection of displacement and forces.