cssi/SciSciGPT-SciSciNet huggingface dataset:
Semantic analytics visualization

In this paper we present a new tool for semantic analytics through 3D visualization called “Semantic Analytics Visualization” (SAV). It has the capability for visualizing ontologies and meta-data including annotated web-documents, images, and digital media such as audio and video clips in a synthetic three-dimensional semi-immersive environment. More importantly, SAV supports visual semantic analytics, whereby an analyst can interactively investigate complex relationships between heterogeneous information. The tool is built using Virtual Reality technology which makes SAV a highly interactive system. The backend of SAV consists of a Semantic Analytics system that supports query processing and semantic association discovery. Using a virtual laser pointer, the user can select nodes in the scene and either play digital media, display images, or load annotated web documents. SAV can also display the ranking of web documents as well as the ranking of paths (sequences of links). SAV supports dynamic specification of sub-queries of a given graph and displays the results based on ranking information, which enables the users to find, analyze and comprehend the information presented quickly and accurately.
Dynamic Position Auctions with Consumer Search

Building upon the static model of Athey and Ellison [1], we demonstrate the efficient convergence of dynamic position auctions in the presence of consumer search. The entry of low-quality advertisers does not slow this convergence. Our methods are extensions of those introduced by Cary et al. [2]. The applicability of these methods in the presence of consumer search indicates the robustness of the approach and suggests that convergence of dynamic position auction models is demonstrable whenever the associated static equilibrium strategies are sufficiently well-behaved.
Dissipationless flow and superfluidity in gaseous bose-einstein condensates

We study dissipation in a dilute Bose gas induced by the motion of a macroscopic object. A blue-detuned laser beam focused on the center of a trapped gas of sodium atoms was scanned both above and below the BEC transition temperature. The measurements allow for a comparison between the heating rates for the superfluid and normal gas.
Optimizing the Size of Public Road Contracts

Procurement packaging has important effects on not only the bidders' bidding behavior, but also contractors' performance. By changing the size of public contracts, procurers can encourage (or discourage) market competition and improve contract performance, avoiding unnecessary cost overruns and project delays. In practice, there is no single solution about how to package public contracts. With procurement data from road projects in Nepal, this paper examines the optimal size of road contracts in rural areas. The optimum varies depending on policy objectives. To maximize the bidder participation, the length of road should be about 11 kilometers. To minimize cost overruns and delays, the contracts should be much larger at 17 and 21 kilometers, respectively. Compared with the current procurement practices, the findings suggest that procurers take more advantage of enlarging road packages, although contracts that are too large may increase the risk of discouraging firms from participating in public tenders.
Quality of tax administration : how relevant is country size ?

Repeated attempts at uncovering the relevance of country size for various economic factors have produced discouraging results. The present paper sheds new light on the relevance of country size using micro or firm-level data on firms' experience with the quality of tax administration, an important but neglected element of the business climate. The analysis finds that the quality of tax administration is significantly better for small compared with large countries. The instrumental variables regression method confirms that this finding is robust to various endogeneity concerns. The paper also finds some evidence that the country size and tax administration relationship is non-linear, and much stronger for small than large countries. Implications of these findings for the broader literature on country size are discussed.
Some properties of joint probability distributions

Several Artificial Intelligence schemes for reasoning under uncertainty explore either explicitly or implicitly asymmetries among probabilities of various states of their uncertain domain models. Even though the correct working of these schemes is practically contingent upon the existence of a small number of probable states, no formal justification has been proposed of why this should be the case. This paper attempts to fill this apparent gap by studying asymmetries among probabilities of various states of uncertain models. By rewriting the joint probability distribution over a model's variables into a product of individual variables' prior and conditional probability distributions and applying central limit theorem to this product, we can demonstrate that the probabilities of individual states of the model can be expected to be drawn from highly skewed lognormal distributions. With sufficient asymmetry in individual prior and conditional probability distributions, a small fraction of states can be expected to cover a large portion of the total probability space with the remaining states having practically negligible probability. Theoretical discussion is supplemented by simulation results and an illustrative real-world example.
Present state of Tevatron lower temperature operation

Publisher Summary This chapter reviews the present state of Tevatron lower temperature operation. Fermilab continues to work on raising the particle energy of the Tevatron by lowering magnet temperatures using cold vapor compressors. In 1995, another two rounds of power tests were completed. These power tests, although showing significant improvement over the initial tests of 1993-94, have led to the conclusion that 1000 GeV operation cannot be attained without replacing or rearranging magnets with lower quench currents before the next Collider Run. Moreover, development of colder compressor control strategies also continues. Plans are to continue testing while identifying and replacing or relocating limiting magnets. With the experience specialized controls features are developed to address the needs.
A bird's eye view of matrix distributed processing

We present Matrix Distributed Processing, a C++ library for fast development of efficient parallel algorithms. MDP is based on MPI and consists of a collection of C++ classes and functions such as lattice, site and field. Once an algorithm is written using these components the algorithm is automatically parallel and no explicit call to communication functions is required. MDP is particularly suitable for implementing parallel solvers for multi-dimensional differential equations and mesh-like problems.
Time domain DNP with the NOVEL sequence

We present results of a pulsed dynamic nuclear polarization (DNP) study at 0.35 T (9.7 GHz/14.7 MHz for electron/(1)H Larmor frequency) using a lab frame-rotating frame cross polarization experiment that employs electron spin locking fields that match the (1)H nuclear Larmor frequency, the so called NOVEL (nuclear orientation via electron spin locking) condition. We apply the method to a series of DNP samples including a single crystal of diphenyl nitroxide (DPNO) doped benzophenone (BzP), 1,3-bisdiphenylene-2-phenylallyl (BDPA) doped polystyrene (PS), and sulfonated-BDPA (SA-BDPA) doped glycerol/water glassy matrices. The optimal Hartman-Hahn matching condition is achieved when the nutation frequency of the electron matches the Larmor frequency of the proton, ω(1S) = ω(0I), together with possible higher order matching conditions at lower efficiencies. The magnetization transfer from electron to protons occurs on the time scale of ∼100 ns, consistent with the electron-proton couplings on the order of 1-10 MHz in these samples. In a fully protonated single crystal DPNO/BzP, at 270 K, we obtained a maximum signal enhancement of e = 165 and the corresponding gain in sensitivity of e(T1/T(B))(1/2)=230 due to the reduction in the buildup time under DNP. In a sample of partially deuterated PS doped with BDPA, we obtained an enhancement of 323 which is a factor of ∼3.2 higher compared to the protonated version of the same sample and accounts for 49% of the theoretical limit. For the SA-BDPA doped glycerol/water glassy matrix at 80 K, the sample condition used in most applications of DNP in nuclear magnetic resonance, we also observed a significant enhancement. Our findings demonstrate that pulsed DNP via the NOVEL sequence is highly efficient and can potentially surpass continuous wave DNP mechanisms such as the solid effect and cross effect which scale unfavorably with increasing magnetic field. Furthermore, pulsed DNP is also a promising avenue for DNP at high temperature.
Colonoscopy without sedation

PURPOSE AND METHODS: Two hundred fifty-eight consecutive nonsedated colonoscopies were prospectively evaluated over an 18-month period. The cecum was intubated in 250 cases (97 percent). Polypectomies or biopsies were performed in 77 cases (31 percent). Indications for colonoscopy included history of polyps (32 percent), hematochezia (28 percent), family history of colon cancer (16 percent), prior history of colon cancer (9 percent), change in bowel habits (12 percent), abnormal flexible sigmoidoscopy (6 percent), and inflammatory bowel disease (3 percent). RESULTS: Sedation was withheld for the following reasons: patient preference (57 percent), medical problems (2 percent), prior resection (16 percent), surgeon preference (6.5 percent), lack of intravenous access (3 percent), and age (1 percent). Three patients (1.5 percent) required sedation to complete the procedure. Procedure-related pain was based on a scale from zero to three. One hundred thirtynine patients (61 percent) rated their pain as either zero (no pain) or one (mild pain), and 217 percent (8 percent) indicated that they would prefer their next colonoscopy to be performed without sedation. One hundred twelve patients had previously undergone sedated colonoscopy. Ninety-two (92 percent) preferred nonsedated to sedated procedures. Average procedure time was 13.7 (range, 0.5 to 85) minutes. CONCLUSIONS: Several series have studied nonsedated endoscopic upper and lower gastrointestinal evaluations. None, however, have evaluated patient comfort and satisfaction. In our prospective series of 258 consecutive nonsedated colonoscopies, we found the procedure to be safe, effective, and well accepted.
Parsing Images into Region and Curve Processes

Natural scenes consist of a wide variety of stochastic patterns. While many patterns are represented well by statistical models in two dimensional regions as most image segmentation work assume, some other patterns are fundamentally one dimensional and thus cause major problems in segmentation. We call the former region processes and the latter curve processes. In this paper, we propose a stochastic algorithm for parsing an image into a number of region and curve processes. The paper makes the following contributions to the literature. Firstly, it presents a generative rope model for curve processes in the form of Hidden Markov Model (HMM). The hidden layer is a Markov chain with each element being an image base selected from an over-complete basis, such as Difference of Gaussians (DOG) or Difference of Offset Gaussians (DOOG) at various scales and orientations. The rope model accounts for the geometric smoothness and photometric coherence of the curve processes. Secondly, it integrates both 2D region models, such as textures, splines etc with 1D curve models under the Bayes framework. Because both region and curve models are generative, they compete to explain input images in a layered representation. Thirdly, it achieves global optimization by effective Markov chain Monte Carlo methods in the sense of maximizing a posterior probability. The Markov chain consists of reversible jumps and diffusions driven by bottom up information. The algorithm is applied to real images with satisfactory results. We verify the results through random synthesis and compare them against segmentations with region processes only.
Bayesian Mixed Membership Models for Soft Clustering and Classification

The paper describes and applies a fully Bayesian approach to soft clustering and classification using mixed membership models. Our model structure has assumptions on four levels: population, subject, latent variable, and sampling scheme. Population level assumptions describe the general structure of the population that is common to all subjects. Subject level assumptions specify the distribution of observable responses given individual membership scores. Membership scores are usually unknown and hence we can also view them as latent variables, treating them as either fixed or random in the model. Finally, the last level of assumptions specifies the number of distinct observed characteristics and the number of replications for each characteristic. We illustrate the flexibility and utility of the general model through two applications using data from: (i) the National Long Term Care Survey where we explore types of disability; (ii) abstracts and bibliographies from articles published in The Proceedings of the National Academy of Sciences. In the first application we use a Monte Carlo Markov chain implementation for sampling from the posterior distribution. In the second application, because of the size and complexity of the data base, we use a variational approximation to the posterior. We also include a guide to other applications of mixed membership modeling.
A clustering approach to solving large stochastic matching problems

In this work we focus on efficient heuristics for solving a class of stochastic planning problems that arise in a variety of business, investment, and industrial applications. The problem is best described in terms of future buy and sell contracts. By buying less reliable, but less expensive, buy (supply) contracts, a company or a trader can cover a position of more reliable and more expensive sell contracts. The goal is to maximize the expected net gain (profit) by constructing a close to optimum portfolio out of the available buy and sell contracts. This stochastic planning problem can be formulated as a two-stage stochastic linear programming problem with recourse. However, this formalization leads to solutions that are exponential in the number of possible failure combinations. Thus, this approach is not feasible for large scale problems. In this work we investigate heuristic approximation techniques alleviating the efficiency problem. We primarily focus on the clustering approach and devise heuristics for finding clusterings leading to good approximations. We illustrate the quality and feasibility of the approach through experimental data.
Small cancellation groups and translation numbers

In this paper we prove that C(4)-T(4)-P, C(3)-T(6)-P and C(6)-P small cancellation groups are translation discrete in the strongest possible sense and that in these groups for any g and any n there is an algorithm deciding whether or not the equation xn = g has a solution. There is also an algorithm for calculating for each g the maximum n such that g is an n-th power of some element. We also note that these groups cannot contain isomorphic copies of the group of p-adic fractions and so in particular of the group of rational numbers. Besides we show that for C"(4) T(4) and C"(3) T(6) groups all translation numbers are rational and have bounded denominators.
The power of information : the impact of mobile phones on farmers' welfare in the Philippines

The authors explore the impact of access to information on poor farmers consumption. The analysis combines spatially coded data on mobile phone coverage with household panel data on farmers from some of the poorest areas of the Philippines. Both the ordinary least squares and instrumental variable estimates indicate that purchasing a mobile phone has a large, positive impact on the household-level growth rate of per capita consumption. Estimates range from 11 to 17 percent, depending on the sample and the specification chosen. The authors perform a range of reliability tests, the results of which all suggest that the instruments are valid. They also present evidence consistent with the argument that easier access to information allows farmers to strike better price deals within their existing trading relationships and to make better choices in terms of where they choose to sell their goods.
A composition theorem for the fourier entropy-influence conjecture

The Fourier Entropy-Influence (FEI) conjecture of Friedgut and Kalai [1] seeks to relate two fundamental measures of Boolean function complexity: it states that H[f]≤C· Inf[f] holds for every Boolean function f, where H[f] denotes the spectral entropy of f, Inf[f] is its total influence, and C>0 is a universal constant. Despite significant interest in the conjecture it has only been shown to hold for a few classes of Boolean functions. Our main result is a composition theorem for the FEI conjecture. We show that if g1,…,gk are functions over disjoint sets of variables satisfying the conjecture, and if the Fourier transform of F taken with respect to the product distribution with biases E[g1],..., E[gk] satisfies the conjecture, then their composition F(g1(x1),…,gk(xk)) satisfies the conjecture. As an application we show that the FEI conjecture holds for read-once formulas over arbitrary gates of bounded arity, extending a recent result [2] which proved it for read-once decision trees. Our techniques also yield an explicit function with the largest known ratio of C≥6.278 between H[f] and Inf[f], improving on the previous lower bound of 4.615.
One-Bit Compressive Sensing With Norm Estimation

Consider the recovery of an unknown signal $ {x}$ from quantized linear measurements. In the one-bit compressive sensing setting, one typically assumes that $ {x}$ is sparse, and that the measurements are of the form $ \mathop {\mathrm {sign\kern 0pt}}\nolimits (\langle {a}_{i}, {x} \rangle ) \in \{\pm 1\}$ . Since such measurements give no information on the norm of $ {x}$ , recovery methods typically assume that $\| {x} \|_{2}=1$ . We show that if one allows more generally for quantized affine measurements of the form $ \mathop {\mathrm {sign\kern 0pt}}\nolimits (\langle {a}_{i}, {x} \rangle + b_{i})$ , and if the vectors $ {a}_{i}$ are random, an appropriate choice of the affine shifts $b_{i}$ allows norm recovery to be easily incorporated into existing methods for one-bit compressive sensing. In addition, we show that for arbitrary fixed $ {x}$ in the annulus $r \leq \| {x} \|_{2} \leq R$ , one may estimate the norm $\| {x} \|_{2}$ up to additive error $\delta $ from $m {\gtrsim } R^{4} r^{-2} \delta ^{-2}$ such binary measurements through a single evaluation of the inverse Gaussian error function. Finally, all of our recovery guarantees can be made universal over sparse vectors in the sense that with high probability, one set of measurements and thresholds can successfully estimate all sparse vectors $ {x}$ in a Euclidean ball of known radius.
Successive cancellation decoding of polar codes using stochastic computing

Polar codes have emerged as the most favorable channel codes for their unique capacity-achieving property. To date, numerous approaches for efficient decoding of polar codes have been reported. However, these prior efforts focused on design of polar decoders via deterministic computation, while the behavior of stochastic polar decoder, which can have potential advantages such as low complexity and strong error-resilience, has not been studied in existing literatures. This paper, for the first time, investigates polar decoding using stochastic logic. Specifically, the commonly-used successive cancellation (SC) algorithm is reformulated into the stochastic form. Several methods that can potentially improve decoding performance are discussed and analyzed. Simulation results show that a stochastic SC decoder can achieve similar error-correcting performance as its deterministic counterpart. This work can pave the way for future hardware design of stochastic polar codes decoders.
A Revenue-Based Alternative to the Counter-Cyclical Payment Program

This paper develops a stochastic model for comparing payments to U.S. corn producers of a revenue-based counter-cyclical payment (R-CCP) that is offered as an alternative in the 2007 House "Farm Bill" (H.R. 2419) to the current price-based CCP (P-CCP). We minimize the potential for miss-specification bias in the model by using nonparametric and semi-nonparametric approaches as specification checks in the model. Using this model, the paper examines the sensitivity of the density function for payments to changes in expected price levels. A mean-variance utility function approach is used to assess producer preferences for choice of CCP program alternative. The results show that as risk reduction instruments at the farm level, there appears to be little effective difference between the P-CCP and the R-CCP. At the national level, however, the R-CCP has the potential for increasing Federal budgetary exposure relative to the P-CCP when expected prices are low.
Range estimation from intensity gradient analysis

The authors have developed a depth-recovery technique that completely avoids the computationally intensive steps of feature selection and correspondence required by conventional approaches. The intensity gradient analysis (IGA) technique is a depth-recovery algorithm that utilizes the properties of the MCSO (moving camera, stationary objects) scenario. Depth values are obtained by analyzing temporal intensity gradients arising from the optic flow field induced by known camera motion. In doing so, IGA avoids the feature extraction and correspondence steps of conventional approaches and is therefore very fast. A detailed description of the algorithm is provided along with experimental results from complex laboratory scenes. It is suggested that the most appealing property of this approach is that IGA places little burden on computational resources, and therefore seems ideally suited for real-world robotic applications. >
Optional Stopping Performance under Graphic and Numeric CRT Formatting.

Abstract : Two experiments sought to determine whether, and if so how, performance varies as a function of the manner in which a progressively unfolding decision problem is displayed over time. A hurricane-tracking scenario was adapted to the optional-stopping paradigm, such that subjects elected to continue sampling information or to make a terminal decision (evacuate or stay) at successive points in the storm's development based upon cumulative evidence and future expectations. The display manipulation was minimal in that it applied only to non-predictive historical data (position information). Despite this conservative test, display format had a significant effect when time pressure was involved: subjects reached earlier and better terminal decisions under the analog (graphic) than the numerical format (Experiment 2). The differences reduced to nonsignificances under self-pacing (Experiment 1), although significant improvements were obtained by use of a simple aiding device (calculation of worst case probabilities). Results are generally consistent with Hammond's Cognitive Consistency Theory. (Author)
Astrophotography for the Amateur

Basic Astrophotography tells you how to take pictures of stars, galaxies, planets, the Moon, the Sun, comets, meteors and eclipses using equipment readily available to the amateur astronomer. The first section, 'Getting Started', presupposes little knowledge of photography or astronomy and concentrates on what can be done with minimal equipment. For example, an ordinary 35 mm camera on a tripod, aimed at the sky on a starry night, will photograph more stars than the unaided eye can see and will bring out an awesome variety of colours. Add a telephoto lens, a pair of binoculars, or a small telescope, and you have all that is needed to photograph an eclipse or the main surface features of the moon. The two subsequent sections, 'Advanced Techniques' and 'Equipment and Materials' cover the use of cameras in conjunction with telescopes and constitute a thorough handbook, including technical imformation on optical systems, film characteristics, and processing techniques. Throughout, the emphasis is on current practice. This book will become the standard handbook for amateur astronomers who want to take pictures of the stars and will also appeal to photography enthusiasts who know relatively little about astronomy but are intrigued by spectacular pictures.
Rate-distortion via Markov chain Monte Carlo

We propose a new approach to lossy source coding. The idea is to sample a reconstruction sequence from a Boltzmann distribution associated with an energy function that incorporates the distortion between the source and reconstruction, the compressibility of the reconstruction, and the point sought on the rate-distortion curve. To sample from this distribution, we use a heat bath algorithm: Starting from an initial candidate reconstruction (say the original source sequence), at every iteration, an index i is chosen and the ith sequence component is replaced by drawing from the conditional probability distribution for that component given all the rest. At the end of this process, the encoder losslessly conveys the reconstruction to the decoder using universal lossless compression. An appropriate choice of the energy function leads to an algorithm whose complexity, in each iteration, is independent of the sequence length and only linearly dependent on a certain context parameter (which grows sub-logarithmically with the sequence length). The algorithm is universal: for any stationary ergodic source, it achieves the optimal rate-distortion performance in the limits of large number of iterations and sequence length. Initial experimentation shows promising performance in practice.
Cancellation for the multilinear Hilbert transform

For any natural number k, consider the k-linear Hilbert transform $$\begin{aligned} H_k( f_1,\dots ,f_k )(x) := {\text {p.v.}} \int _\mathbb {R}f_1(x+t) \dots f_k(x+kt)\ \frac{dt}{t} \end{aligned}$$ for test functions \(f_1,\dots ,f_k: \mathbb {R}\rightarrow \mathbb {C}\). It is conjectured that \(H_k\) maps \(L^{p_1}(\mathbb {R}) \times \dots \times L^{p_k}(\mathbb {R}) \rightarrow L^p(\mathbb {R})\) whenever \(1 < p_1,\dots ,p_k,p < \infty \) and \(\frac{1}{p} = \frac{1}{p_1} + \dots + \frac{1}{p_k}\). This is proven for \(k=1,2\), but remains open for larger k. In this paper, we consider the truncated operators $$\begin{aligned} H_{k,r,R}( f_1,\dots ,f_k )(x) := \int _{r \leqslant |t| \leqslant R} f_1(x+t) \dots f_k(x+kt)\ \frac{dt}{t} \end{aligned}$$ for \(R > r > 0\). The above conjecture is equivalent to the uniform boundedness of \(\Vert H_{k,r,R} \Vert _{L^{p_1}(\mathbb {R}) \times \dots \times L^{p_k}(\mathbb {R}) \rightarrow L^p(\mathbb {R})}\) in r, R, whereas the Minkowski and Holder inequalities give the trivial upper bound of \(2 \log \frac{R}{r}\) for this quantity. By using the arithmetic regularity and counting lemmas of Green and the author, we improve the trivial upper bound on \(\Vert H_{k,r,R} \Vert _{L^{p_1}(\mathbb {R}) \times \dots \times L^{p_k}(\mathbb {R}) \rightarrow L^p(\mathbb {R})}\) slightly to \(o( \log \frac{R}{r} )\) in the limit \(\frac{R}{r} \rightarrow \infty \) for any admissible choice of k and \(p_1,\dots ,p_k,p\). This establishes some cancellation in the k-linear Hilbert transform \(H_k\), but not enough to establish its boundedness in \(L^p\) spaces.
All-Back-Schottky-Contact Thin-Film Photovoltaics

The concept of All-Back-Schottky-Contact (ABSC) thin-film photovoltaic (TFPV) devices is introduced and evaluated using 2D numerical simulation. Reach-through Schottky junctions due to two metals of different work functions in an alternating, side-by-side pattern along the non-illuminated side generate the requisite built-in field. It is shown that our simulation method quantitatively describes existing data for a recently demonstrated heterojunction thin-film cell with interdigitated back contacts (IBCs) of one metal type. That model is extended to investigate the performance of ABSC devices with bimetallic IBCs within a pertinent parameter space. Our calculations indicate that 20% efficiency is achievable with micron-scale features and sufficient surface passivation. Bimetallic, micron-scale IBCs are readily fabricated using photo-lithographic techniques and the ABSC design allows for optically transparent surface passivation layers that need not be electrically conductive. The key advantages of the ABS...
The great equalizer?: Globalization effects on gender equality in Latin America and the Caribbean

This paper assesses the impact of 30 years of globalization on gender equity in well-being in Latin America and the Caribbean. Data indicate that while some gaps in well-being have narrowed, progress is uneven across a set of nine indicators, and in some cases, conditions have worsened. Despite the optimism of market proponents, growth is not found to be an equalizer for gender anymore than it has been shown to be by class. The results here indicate that growth exhibits a negative effect on some indicators, while growth of real government expenditures, female share of the labor force, and structural change variables exert a positive effect.
Optical pulse shaping using optical coherent transients

Summary from only given. We present a novel method of pulse shaping using optical coherent transients (OCT's) that expands on our previous work with temporally overlapped linear frequency chirps (TOLFCs) to produce true-time delay gratings. By using multiple TOLFCs in the programming process, multiple true time delay gratings are created that can be probed using a single pulse producing multiple echo pulses at the chosen time delays.
On the algorithms of radiative cooling in semi- analytic models

We study the behaviour of multiple radiative-cooling algorithms implemented in seven semi-analytic models (SAMs) of galaxy formation, including a new model we propose in this paper. We use versions of the models without feedback and apply them to dark matter haloes growing in a cosmological context, which have final virial masses that range from 1011 to 1014 M⊙. First, using simplified smoothly growing halo models, we demonstrate that the different algorithms predict cooling rates and final cold gas masses that differ by a factor of ∼5 for massive haloes (≥1012 M⊙). The algorithms are in better agreement for less massive haloes because they cool efficiently and, therefore, their cooling rates are largely limited by the halo accretion rate. However, for less massive haloes, all the SAMs predict less cooling than corresponding 1D hydrodynamic models. Secondly, we study the gas-accretion history of the central galaxies of dark matter haloes using merger trees. The inclusion of mergers alters the cooling history of haloes by locking up gas in galaxies within small haloes at early times. For realistic halo models, the dispersion in the cold gas mass predicted by the algorithms is 0.5 dex for high-mass haloes and 0.1 dex for low-mass haloes, while the dispersion in the accretion rate is about two times larger. Comparing to cosmological smoothed particle hydrodynamic simulations, we find that most SAMs systematically underpredict the gas-accretion rates for low-mass haloes but overpredict the gas-accretion rates for massive haloes. Although the models all include both ‘rapid’- and ‘slow’-mode accretion, the transition between the two accretion modes varies between models and also differs from the simulations. Finally, we construct a new phenomenological model that explicitly incorporates cold halo gas and a gradual transition between the cold and hot modes of gas accretion to illustrate that such a class of models can better match the results from cosmological hydrodynamic simulations. The large dispersion in cooling rates between different SAMs influences parameter choices for other galaxy physics, including star formation and feedback. Therefore, careful parametrizations of the multimode gas cooling and accretion mechanisms in simulations are necessary to ensure that the predictions from SAMs are reliable.
GLOBULAR CLUSTER DISTANCE DETERMINATIONS

The distance scale to globular clusters is of great interest for two principal reasons. Firstly, the best estimates for the absolute ages of globular clusters require that the distance to the clusters be known (e.g. Renzini 1991; Chaboyer 1996). These age determinations provide the best estimate for the age of the universe, but are very sensitive to the adopted globular cluster distance scale. For example, a revision in the distance scale by 0.10 mag changes the derived ages by 10%. The second reason for the interest in the globular cluster distance scale is that globular clusters contain stellar populations (RR Lyrae stars, tip of the red giant branch) which are commonly used as distance indicators in astronomy. Thus, globular clusters can serve as nearby calibrators of these standard candles.
Effective string theory for vortex lines in fluids and superfluids

We discuss the effective string theory of vortex lines in ordinary fluids and low-temperature superfluids, by describing the bulk fluid flow in terms of a two-form field to which vortex lines can couple. We derive the most general low-energy effective Lagrangian that is compatible with (spontaneously broken) Poincare invariance and worldsheet reparameterization invariance. This generalizes the effective action developed in [1, 2]. By applying standard field-theoretical techniques, we show that certain low-energy coupling constants — most notably the string tension — exhibit RG running already at the classical level. We discuss applications of our techniques to the study of Kelvin waves, vortex rings, and the coupling to bulk sound modes.
Muscle rehabilitation: its effect on muscular and functional performance of patients with knee osteoarthritis.

Abstract Muscle function and functional performance are limited in patients with osteoarthritis (OA). Although aerobic exercise can increase aerobic power and reduce fatigue, it does not appear to improve muscle function. The purpose of this study was to demonstrate the effect of a muscle rehabilitation program on muscle strength, endurance, speed, and function for patients with OA of the knees. Fifteen men (67.6 ± 6.1 years) with OA of the knees underwent a four-month exercise program, three times per week. Muscle strength, endurance, and speed were 50% less in OA patients than in controls. After rehabilitation, there was a significant increase in strength (35%), endurance (35%), and speed (50%). Deficiencies and improvements in the muscles were greater at longer muscle lengths. Increases in muscle function were associated with decreased dependency (10%), difficulty (30%), and pain (40%). The average increase in all measured parameters was 10% and 25% after two and four months of rehabilitation, respectively. Improvements were sustained for eight months after rehabilitation. The muscle rehabilitation program was designed specifically to improve function; the improved muscle function was translated into improved functional performance.
A unified framework for the realization problem in linear digital filtering

A new approach to characterizing the problem of implementing linear digital filtering operations on finite-state machines is presented. In this formulation, the implementation of shift-invariant or shift-varying, one-dimensional or multi-dimensional filters as single-input or multiple-input, time-invariant or time-varying systems are all treated in the same framework. This framework is based on the representation of an input/output specification for a linear filter by a unique, possibly infinite transmission matrix. To treat two- or higher dimensional filters, the concept of transmission matrix is extended to include arrays of higher than two dimensions. The framework also uses matrices whose entries are arrays of arbitrary dimensions. A set of notations and operation rules for these arrays and matrices is presented. Within this framework, all possible implementations of a filter are characterized as factorizations of its transmission array.
The essence of javascript

We reduce JavaScript to a core calculus structured as a small-step operational semantics. We present several peculiarities of the language and show that our calculus models them. We explicate the desugaring process that turns JavaScript programs into ones in the core. We demonstrate faithfulness to JavaScript using real-world test suites. Finally, we illustrate utility by defining a security property, implementing it as a type system on the core, and extending it to the full language.
Increasing public expenditure efficiency in oil-rich economies : a proposal

This paper proposes that, to increase the efficiency of public spending in oil-rich economies, some or all of the oil revenues be transferred to citizens, and fiscal instruments such as taxation be used to finance public expenditures. The authors develop the case as follows. First, they confirm the well-known result that public-expenditure efficiency is lower in oil-rich countries compared with other developing countries. Second, they show that this efficiency gap is associated with differences in accountability to citizens of government's spending decisions. They find that various measures of accountability are systematically weaker in oil-rich countries. They attribute this difference to the fact that oil revenues typically accrue directly to the government, unlike tax revenues, which pass through the hands of citizens. Third, they show that, controlling for a number of factors, accountability is stronger in countries that rely more on direct taxation to finance public spending. They conclude that accountability, and hence public expenditure efficiency, can be increased by transferring oil revenues to citizens and then taxing them to finance public spending. The paper reviews existing schemes that redistribute oil revenues to the population, such as the Alaska Citizen Fund, to assess the feasibility of a modest proposal in African countries. The authors conclude that, while it may be difficult to implement such a proposal in existing oil producers, there is scope for introducing it in some of Africa's new oil producers.
Solving wave Equations on Unstructured Geometries

Every wave solver serving the computational study of waves meets a trade-off of two figures of merit—its computational speed and its accuracy. The use of Discontinuous Galerkin (DG) methods on graphical processing units (GPUs) significantly lowers the cost of obtaining accurate solutions. DG methods for the numerical solution of partial differential equations have enjoyed considerable success because they are both flexible and robust. They allow arbitrary unstructured geometries and easy control of accuracy without compromising simulation stability. The resulting locality in memory access is one of the factors that enables DG to run on off-the-shelf, massively parallel graphics processors (GPUs). In addition, DG's high-order nature lets it require fewer data points per represented wavelength and hence fewer memory accesses, in exchange for higher arithmetic intensity. Both of these factors work significantly in favor of a GPU implementation of DG. Discontinuous Galerkin methods are most often used to solve hyperbolic systems of conservation laws in the time domain. Parabolic and elliptic equations can also be solved using DG methods.
Low-complexity optimal scheduling over correlated fading channels with ARQ feedback

We investigate the downlink scheduling problem under Markovian ON/OFF fading channels, where the instantaneous channel state information is not directly accessible, but is revealed via ARQ-type feedback. The scheduler can exploit the temporal correlation/channel memory inherent in the Markovian channels to improve network performance. However, designing low-complexity and throughput-optimal algorithms under temporal correlation is a challenging problem. In this paper, we find that under an average number of transmissions constraint, a low-complexity index policy is throughput-optimal. The policy usesWhittle's index value, which was previously used to capture opportunistic scheduling under temporally correlated channels. Our results build on the interesting finding that, under the intricate queue length and channel memory evolutions, the importance of scheduling a user is captured by a simple multiplication of its queue length and Whittle's index value. The proposed queue-weighted index policy has provably low complexity which is significantly lower than existing optimal solutions.
Anchoring in Payment: Evaluating a Judgmental Heuristic in Field Experimental Settings

AbstractAnchoring, the biasing of estimates toward a previously considered value, is a long-standing and oft-studied phenomenon in consumer research. However, most anchoring work has been in the lab, and the results from field work have been mixed. Here, the authors use real transactions from an empirically investigated and commercially-employed pricing scheme (“pay what you want”) to better understand how anchors influence payments. Sixteen field studies (N = 21,997) and four hypothetical studies (N = 3,174) reveal four main points: (1) Although anchoring replicates both with and without financial consequences (Studies 1–2), the percentile rank gap between anchors in the distribution of payments is a much stronger predictor of anchoring emerging than merely the absolute gap between the anchors on a number line (Studies 3–5). (2) Low anchors influence payments more than high anchors (Studies 6a–b). (3) Findings from the literature that should enhance anchoring effects—anchor precision, descriptive and inj...
An embedded mesh method for treating overlapping finite element meshes

SUMMARY A new technique for treating the mechanical interactions of overlapping finite element meshes is presented. Such methods can be useful for numerous applications, for example, fluid–solid interaction with a superposed meshed solid on an Eulerian background fluid grid. In this work, we consider the interaction of two elastic domains: one mesh is the foreground and defines the surface of interaction, the other is a background mesh and is often a structured grid. Many of the previously proposed methods employ surface defined Lagrange multipliers or penalties to enforce the boundary constraints. It has become apparent that these methods will cause mesh locking under certain conditions. Appropriately applied, the Nitsche method can overcome this locking, but, in its canonical form, is generally not applicable to non-linear materials such as hyperelastics. The relationship between interior point penalty, discontinuous Galerkin and Nitsche's method is well known. Based on this relationship, a nonlinear theory analogous to the Nitsche method is proposed to treat nonlinear materials in an embedded mesh. Here, a discontinuous Galerkin derivative based on a lifting of the interface surface integrals provides a consistent treatment for non-linear materials and demonstrates good behavior in example problems. Published 2012. This article is a US Government work and is in the public domain in the USA.
The propagation of U.S. shocks to Canada: Understanding the role of real financial linkages

This paper examines the transmission of U.S. real and financial shocks to Canada and, in particular, the role of financial frictions in affecting the transmission of these shocks. These questions are addressed within the Bank of Canada's Global Economy Model (de Resende et al. forthcoming), a dynamic stochastic general-equilibrium model with an active banking sector and a detailed role for financial frictions.
Avoiding the Fragility Trap in Africa

Not only do Africa's fragile states grow more slowly than non-fragile states, but they seem to be caught in a"fragility trap". For instance, the probability that a fragile state in 2001 was still fragile in 2009 was 0.95. This paper presents an economic model where three features -- political instability and violence, insecure property rights and unenforceable contracts, and corruption -- conspire to create a slow-growth-poor-governance equilibrium trap into which these fragile states can fall. The analysis shows that, by addressing the three problems, fragile countries can emerge from the fragility trap and enjoy a level of sustained economic growth. But addressing these issues requires resources, which are scarce because external aid is often tailored to the country's performance and cut back when there is instability, insecurity, and corruption. The implication is that, even if aid is seemingly unproductive in these weak-governance environments, it could be hugely beneficial if it is invested in such a way that it helps these countries tackle the root causes of instability, insecurity, and corruption. Empirical estimations corroborate the postulated relationships of the model, supporting the notion that it is possible for African fragile countries to avoid the fragility trap.
Evolution at the Subgene Level: Domain Rearrangements in the Drosophila Phylogeny

Although the possibility of gene evolution by domain rearrangements has long been appreciated, current methods for reconstructing and systematically analyzing gene family evolution are limited to events such as duplication, loss, and sometimes, horizontal transfer. However, within the Drosophila clade, we find domain rearrangements occur in 35.9% of gene families, and thus, any comprehensive study of gene evolution in these species will need to account for such events. Here, we present a new computational model and algorithm for reconstructing gene evolution at the domain level. We develop a method for detecting homologous domains between genes and present a phylogenetic algorithm for reconstructing maximum parsimony evolutionary histories that include domain generation, duplication, loss, merge (fusion), and split (fission) events. Using this method, we find that genes involved in fusion and fission are enriched in signaling and development, suggesting that domain rearrangements and reuse may be crucial in these processes. We also find that fusion is more abundant than fission, and that fusion and fission events occur predominantly alongside duplication, with 92.5% and 34.3% of fusion and fission events retaining ancestral architectures in the duplicated copies. We provide a catalog of ∼9,000 genes that undergo domain rearrangement across nine sequenced species, along with possible mechanisms for their formation. These results dramatically expand on evolution at the subgene level and offer several insights into how new genes and functions arise between species.
Many Worlds, the Born Rule, and Self-Locating Uncertainty

We provide a derivation of the Born Rule in the context of the Everett (Many-Worlds) approach to quantum mechanics. Our argument is based on the idea of self-locating uncertainty: in the period between the wave function branching via decoherence and an observer registering the outcome of the measurement, that observer can know the state of the universe precisely without knowing which branch they are on. We show that there is a uniquely rational way to apportion credence in such cases, which leads directly to the Born Rule. [Editors note: for a video of the talk given by Prof. Carroll at the Aharonov-80 conference in 2012 at Chapman University, see quantum.chapman.edu/talk-14.]
Dependency networks for collaborative filtering and data visualization

We describe a graphical representation of probabilistic relationships--an alternative to the Bayesian network--called a dependency network. Like a Bayesian network, a dependency network has a graph and a probability component. The graph component is a (cyclic) directed graph such that a node's parents render that node independent of all other nodes in the network. The probability component consists of the probability of a node given its parents for each node (as in a Bayesian network). We identify several basic properties of this representation, and describe its use in collaborative filtering (the task of predicting preferences) and the visualization of predictive relationships.