cssi/SciSciGPT-SciSciNet huggingface dataset:
The effects of primordial non-Gaussianity on giant-arc statistics

For over a decade, it has been debated whether the concordance A cold dark matter (ACDM) model is consistent with the observed abundance of giant arcs in clusters. While previous theoretical studies have focused on properties of the lens and source populations, as well as cosmological effects such as dark energy, the impact of initial conditions on the giant-arc abundance is relatively unexplored. Here, we quantify the impact of non-Gaussian initial conditions with the local bispectrum shape on the predicted frequency of giant arcs. Using a path-integral formulation of the excursion set formalism, we extend a semi-analytic model for calculating halo concentrations to the case of primordial non-Gaussianity, which may be useful for applications outside of this work. We find that massive haloes tend to collapse earlier in models with positive f NL , relative to the Gaussian case, leading to enhanced concentration parameters. The converse is true for f NL 0) or suppress (f NL < 0) the probability of giant-arc formation. Using the best value and 95 per cent confidence levels currently available from the Wilkinson Microwave Anisotropy Probe, we find that the giant-arc optical depth for sources at z s ∼ 2 is enhanced by ∼20 and ∼45 per cent for f NL = 32 and 74, respectively. In contrast, we calculate a suppression of ∼5 per cent for f NL = ―10. These differences translate to similar relative changes in the predicted all-sky number of giant arcs.
Further Optimal Regret Bounds for Thompson Sampling

Thompson Sampling is one of the oldest heuristics for multi-armed bandit problems. It is a randomized algorithm based on Bayesian ideas, and has recently generated significant interest after several studies demonstrated it to have comparable or better empirical performance compared to the state of the art methods. In this paper, we provide a novel regret analysis for Thompson Sampling that proves the first near-optimal problem-independent bound of O( √ NT lnT ) on the expected regret of this algorithm. Our novel martingale-based analysis techniques are conceptually simple, and easily extend to distributions other than the Beta distribution. For the version of Thompson Sampling that uses Gaussian priors, we prove a problem-independent bound of O( √ NT lnN) on the expected regret, and demonstrate the optimality of this bound by providing a matching lower bound. This lower bound of Ω( √ NT lnN) is the first lower bound on the performance of a natural version of Thompson Sampling that is away from the general lower bound of O( √ NT ) for the multi-armed bandit problem. Our near-optimal problem-independent bounds for Thompson Sampling solve a COLT 2012 open problem of Chapelle and Li. Additionally, our techniques simultaneously provide the optimal problem-dependent bound of (1+ ǫ) ∑ i lnT d(μi,μ1) +O(Nǫ2 ) on the expected regret. The optimal problem-dependent regret bound for this problem was first proven recently by Kaufmann et al. [2012b]. Appearing in Proceedings of the 16 International Conference on Artificial Intelligence and Statistics (AISTATS) 2013, Scottsdale, AZ, USA. Volume 31 of JMLR: W&CP 31. Copyright 2013 by the authors.
paranasal Sinus Mucocele in Cystic Fibrosis

The relationship between cystic fibrosis, nasal polyposis and chronic sinusitis is clearly defined. Mucoceles of the paranasal sinuses, however, are a well-described complication of chronic sinusitis in adults; but they rarely occur in the pediatric age group. We report a three-year-old who presented with epiphora and fullness at the right medial canthus. Computed tomography confirmed a right ethmoid mucocele which was surgically drained, with resolution of symptoms. Approximately 12 other cases of mucoceles have been reported in the pediatric age group. Although many of these patients had recognized cystic fibrosis, some were previously undiagnosed. Only after presentation with a mucocele, did sweat testing reveal their underlying pathology. No pediatric patients in the literature were found with mucoceles and normal sweat tests. Paranasal sinus mucoceles may be diagnostic of cystic fibrosis and may be the presenting sign in some patients.
Assortative human pair-bonding for partner ancestry and allelic variation of the dopamine receptor D4 (DRD4) gene

The 7 repeat (7R) allele of the dopamine receptor D4 gene has been associated with attention deficit hyperactivity disorder and risk taking. On the cross-population scale, 7R allele frequencies have been shown to be higher in populations with more of a history of long-term migrations. It has also been shown that the 7R allele is associated with individuals having multiple ancestries. Here, we conduct a replication of this latter finding with two independent samples. Measures of subjects’ ancestry are used to examine past reproductive bonds. The individuals’ history of interracial/ancestral dating and their feelings about this are also assessed. Tentative support for an association between multiple ancestries and the 7R allele was found. These results are dependent upon the method of questioning subjects about their ancestries, with only finer-scale measures of ancestry being associated with 7R. Interracial dating and feelings about interracial pairing were not related to the presence of the 7R allele. This study provides continued support for a role for the 7R allele in migration and/or mate choice patterns. However, replications and extensions of this study are needed and the way ancestry/race is assessed must be carefully considered.
A high performance redundancy scheme for cluster file systems

A known issue in the design of striped file systems is their vulnerability to disk failures. In this paper, we address the challenges of augmenting an existing striped file system with traditional RAID redundancy, and propose a novel redundancy scheme designed to maximise disk throughput seen by applications. We implement our new scheme in CSAR, a proof-of-concept redundant file system based on the parallel virtual file system, along with two other well-known schemes. Our tests using both microbenchmarks and representative scientific applications show that our scheme consistently performs as well as the best of the other two schemes. The application-dependent, potentially larger storage occupation of our scheme is justified by current technological trends that put I/O bandwidth at a premium over disk space.
Ergodic Averages for Independent Polynomials and Applications

Szemeredi's theorem states that a set of integers with positive upper density contains arbitrarily long arithmetic progressions. Bergelson and Leibman generalized this, showing that sets of integers with positive upper density contain arbitrarily long polynomial configurations; Szemeredi's theorem corresponds to the linear case of the polynomial theorem. We focus on the case farthest from the linear case, that of rationally independent polynomials. We derive results in ergodic theory and in combinatorics for rationally independent polynomials, showing that their behavior differs sharply from the general situation.
Femto-macro cellular interference control with subband scheduling and interference cancelation

A significant technical challenge in deploying fem-tocells is controlling the interference from the underlay of femtos onto the overlay of macros. This paper presents a novel interference control method where the macrocell bandwidth is partitioned into subbands, and the short-range femtocell links adaptively allocate their power across the subbands based on a load-spillage power control method. The scheme can improve rate distribution in the macro network while also providing opportunities for short-range communication as well. Moreover, the proposed scheme requires minimal interference coordination communication between the femtos and macros, which is one of the main challenges in femtocell systems. Also, simulations show certain advantages over simpler orthogonalization schemes or power control schemes without subband partitioning. Further modest gains may also be possible with interference cancelation.
A node discovery protocol for ad hoc underwater acoustic networks

Motivated by the advances in acoustic modem technology and the growing number of applications that call for ad hoc deployable autonomous underwater systems (floating sensors, crawlers, vehicles), we address the problem of network initialization upon deployment. A neighbor discovery protocol is proposed, whose goal is to establish communication links over a large area, with a finite power budget that mandates multi-hopping to provide full coverage. The protocol uses random access to eliminate the need for scheduling (i.e., enable system operation without a global clock reference) and power control to ensure that full connectivity is provided using shortest links (i.e., to conserve batteries and prolong the system's lifetime). Transmit power allocation takes into account the acoustic propagation loss, while additional large-scale variation in the average received power is modeled via log-normal fading which is confirmed by experimental observations. System performance is assessed through simulation, by measuring the energy consumption, time to completion, and reliability in the presence of fading. Fading is shown to have a degrading effect on the system reliability, and protocol adjustments are proposed to recover the performance under the constraint on maximum power. The key features of the protocol are simplicity of implementation and efficient use of power.Copyright © 2012 John Wiley & Sons, Ltd.
Male wages and female welfare: private markets, public goods, and intrahousehold inequality

We show how an apparently welfare improving phenomenon like an increase in the wage of the male member of a family can result in a seemingly paradoxical result where the entire family is worse off. There is male and female specialization in activities such that the female member is involved in a community level public good. A rise in the male wage leads to adjustment of household time allocation with the male working more in the market and less on household activities. In turn, the female works more on household activities and less on the community public good, failing to internalize the negative externality imposed on other members of the community. Under quite general conditions the implied negative effect can more than offset the positive effect of the male wage raise, and the entire family is worse off. The theoretical results are consistent with empirical findings in the literature. Copyright 2008 , Oxford University Press.
Modeling of crack initiation, propagation and coalescence in rocks

One of the most successful criteria proposed so far to describe the initiation and propagation of cracks under quasi-static loading in rock-like materials is a stress-based criterion developed by Bobet (Fracture coalescence in rock materials: experimental observations and numerical predictions. Sc. D, Thesis, Massachusetts Institute of Technology, 1997) which is embedded in FROCK, a Displacement Discontinuity code that was developed by the rock mechanics group at MIT. Even though the predictions obtained with this criterion generally correspond to the experimental results, there are cases in which the quasi-static crack propagation results obtained with FROCK are not satisfactory. For this reason, a qualitative study using the Finite Element code, ABAQUS, was conducted to analyze stress-, strain- and energy-based criteria used for modeling crack development. Based on the ABAQUS relative quantitative analysis, it was found that the strain- and stress-based criteria may be more appropriate than the energy-based criterion to model quasi-static crack development. Thus, a strain-based and a normal stress-dependent criterion were implemented in FROCK. The cracking patterns obtained with these proposed criteria were compared with those obtained using Bobet’s original stress-based criterion and with experimental observations made in molded gypsum specimens. The proposed strain-based criterion implemented in FROCK appeared to yield better results than Bobet’s stress-based criterion. The influence of the friction angle ( $$\upvarphi $$ ) on the cracking patterns was studied with the proposed normal stress-dependent criterion and showed that friction angles closer to $$0^{\circ }$$ yielded the best results, which may indicate that, at least for the microscale, the critical shear stress at which rock fails does not depend upon the normal stresses applied.
Urban and industrial deconcentration in developing economies: An analytical framework

Abstract Deconcentration is studied by means of a mixed integer-continuous linear program. Social costs and policy measures are discussed in the light of this framework.
Design of Attitude and Rate Command Systems for Helicopters Using Eigenstructure Assignment

This paper describes the use of eigenstructur e assignment in the direct design of attitude and attitude rate command systems for helicopter flight control. Eigenvalue assignment is used to achieve desired bandwidth based on the handling qualities specifications, and eigenvector assignment is used to achieve decoupling of lateral, longitudinal, heave, and yaw modes and the desired command-response characteristics. Eigenstructure techniques are also used to design a state estimator that gives desired closed-loop frequency response. The stability robustness of the control system is evaluated with respect to an error model that includes rotor, actuator, flexure, and sensor dynamics and computational and sampling delays in the flight control system. The controlled helicopter is shown to exhibit both good frequency and time-response characteristics. Nomenclature Scalars g = acceleration of gravity m = number of controls n = number of states p — roll rate, rad/s q — pitch rate, rad/s
Black Carbon and West African Monsoon precipitation: observations and simulations

Abstract. We have recently investigated large-scale co-variability between aerosol and precipitation and other meteorological variables in the West African Monsoon (WAM) region using long term satellite observations and reanalysis data. In this study we compared the observational results to a global model simulation including only direct radiative forcing of black carbon (BC). From both observations and model simulations we found that in boreal cold seasons anomalously high African aerosols are associated with significant reductions in cloud amount, cloud top height, and surface precipitation. These results suggest that the observed precipitation reduction in the WAM region is caused by radiative effect of BC. The result also suggests that the BC effect on precipitation is nonlinear.
Deciphering subsampled data: adaptive compressive sampling as a principle of brain communication

A new algorithm is proposed for a) unsupervised learning of sparse representations from subsampled measurements and b) estimating the parameters required for linearly reconstructing signals from the sparse codes. We verify that the new algorithm performs efficient data compression on par with the recent method of compressive sampling. Further, we demonstrate that the algorithm performs robustly when stacked in several stages or when applied in undercomplete or over-complete situations. The new algorithm can explain how neural populations in the brain that receive subsampled input through fiber bottlenecks are able to form coherent response properties.
The Impact of Global Warming on U.S. Agriculture: An Econometric Analysis of Optimal Growing Conditions

We link farmland values to climatic, soil, and socioeconomic variables for U.S. counties east of the 100th meridian, the historical boundary of agriculture not primarily dependent on irrigation. Degree days, a nonlinear transformation of the climatic variables suggested by agronomic experiments as more relevant to crop yield, gives an improved fit and increased robustness. Estimated coefficients are consistent with the experimental results. The model is employed to estimate the potential impacts on farmland values for a range of recent warming scenarios. The predictions are very robust, and more than 75% of the counties in our sample show a statistically significant effect, ranging from moderate gains to large losses, with losses in the aggregate that can become quite large under scenarios involving sustained heavy use of fossil fuels.
Document image decoding using Markov source models

Document image decoding (DID) is a communication theory approach to document image recognition. In DID, a document recognition problem is viewed as consisting of three elements: an image generator, a noisy channel and an image decoder. A document image generator is a Markov source (stochastic finite-state automaton) that combines a message source with an imager. The message source produces a string of symbols, or text, that contains the information to be transmitted. The imager is modeled as a finite-state transducer that converts the 1D message string into an ideal 2D bitmap. The channel transforms the ideal image into a noisy observed image. The decoder estimates the message, given the observed image, by finding the a posteriori most probable path through the combined source and channel models using a Viterbi-like dynamic programming algorithm. The proposed approach is illustrated on the problem of decoding scanned telephone yellow pages to extract names and numbers from the listings. A finite-state model for yellow page columns was constructed and used to decode a database of scanned column images containing about 1100 individual listings. >
Unramified cohomology of classifying varieties for exceptional simply connected groups

Let BG be a classifying variety for an exceptional simple simply connected algebraic group G. We compute the degree 3 unramified Galois cohomology of BG with values in (Q/Z)'(2) over an arbitrary field F. Combined with a paper by Merkurjev, this completes the computation of these cohomology groups for G semisimple simply connected over all fields. These computations provide another family of examples of simple simply connected groups G such that BG is not stably rational.
Core Requirements for the Economics Major.

In this article, the authors are the first to describe the core economics curriculum requirements for economics majors at all American colleges and universities, as opposed to a sample of institutions. Not surprisingly, principles of economics is nearly universally required and implemented as a two-semester course in 85 percent of economics major programs. Most schools do not prescribe the order in which the principles sequence is taken. The intermediate courses are commonly required, although variation exists across institution types. While the quantitative requirement for the major has increased since 1980, significant differences exist among institutions and by academic rankings. As compared to 1950, there has been an increase in the number of required economics credit hours for the major.
Quantum phase transitions and the breakdown of classical general relativity

Abstract It is proposed that the infinite-red-shift surface of a black hole is a quantum phase transition of the vacuum of space-time analogous to the liquid-vapour critical point of a Bose fluid. The equations of classical general relativity remain valid arbitrarily close to the horizon yet fail there through the divergence of a characteristic coherence length E. The integrity of global time, required for conventional quantum mechanics to be defined, is maintained. The metric inside the event horizon is different from that predicted by classical general relativity and may be de Sitter space. The deviations from classical behaviour lead to distinct spectroscopic and bolometric signatures that can, in principle, be observed at large distances from the black hole.
Context Effects and Social Change

Strack and Martin (1987) have proposed that although prob ability samples of general populations are needed for studying attitude content, psychological processes such as context and other response ef fects can be investigated quite well or even better with homogeneous convenience samples. The present paper shows that, in contrast, when social change is included as an essential variable in a study of a well known context effect, the process itself is weakened and may even disap pear. The distinction between content and process is not always tenable in surveys once we include long-term social change as a variable, as we must as the horizon for survey research extends further and further into the future. The replication of a classic experiment on question context effects originally reported by Hyman and Sheatsley (1950) points to the importance of continuing to study response effects using probability samples from general populations? in the present case, the population of American adults. The results challenge the position taken by some cognitive psychologists, as developed forcefully by Strack and Martin (1987). Their argument was that because cognitive re searchers are interested in knowledge about processes, rather than about con tent, it is unnecessary to do experiments on response effects in sample surveys of general populations, with all the additional costs and time that such sur veys require. In addition, they go further and hold that it is even better to use homogeneous convenience samples to avoid unwanted variation due to asso ciations between responses and social background variables (e.g., education). This makes for greater efficiency, they point out, in detecting variation due to the experimental manipulation that is of primary interest, which in the Hyman and Sheatsley case was question order. Without doubting the value of sometimes employing classroom and other convenience samples to study response effects, this article indicates limits to
Modeling the adoption and use of social media by nonprofit organizations

This study examines what drives organizational adoption and use of social media through a model built around four key factors – strategy, capacity, governance and environment. Using Twitter, Facebook, and other data on 100 large US nonprofit organizations, the model is employed to examine the determinants of three key facets of social media utilization: (1) adoption, (2) frequency of use and (3) dialogue. We find that organizational strategies, capacities, governance features and external pressures all play a part in these social media adoption and utilization outcomes. Through its integrated, multi-disciplinary theoretical perspective, this study thus helps foster understanding of which types of organizations are able and willing to adopt and juggle multiple social media accounts, to use those accounts to communicate more frequently with their external publics, and to build relationships with those publics through the sending of dialogic messages.
Economic growth, inequality, and poverty : findings from a new data set

The author uses new data from 50 developing countries and 101 intervals to examine the impact of economic growth on poverty and inequality. He finds that growth represents an important means for reducing poverty in the developing world. When economic growth is measured by survey mean income (consumption), there is a strong, statistical link between growth and poverty reduction. When economic growth is measured by GDP per capita, the statistical relationship between growth and poverty reduction is still present, albeit not quite as strong. Economic growth reduces poverty because growth has little impact on income inequality. In the data set income inequality rises on average less than 1.0 percent a year. Since income distributions are relatively stable over time, economic growth tends to raise incomes for all members of society, including the poor. When growth is measured by survey mean income (consumption), the elasticity of poverty with respect to growth is -2.59. In other words, on average, a 10 percentage point increase in economic growth (measured by survey mean income) will produce a 25.9 percent decrease in the proportion of people living in poverty ($1 a person a day).
Performance of a Wind-Profiling Lidar in the Region of Wind Turbine Rotor Disks

AbstractAs the wind energy sector continues to grow, so does the need for reliable vertical wind profiles in the assessment of wind resources and turbine performance. In situ instrumentation mounted on meteorological towers can rarely probe the atmosphere across the full span of modern turbine rotor disks, which typically extend from 40 to 120 m above the surface. However, by measuring the Doppler shift of laser light backscattered by particles in the atmosphere, remote sensing lidar is capable of estimating wind speeds and turbulence at several altitudes in this range and above. Consequently, lidar has proven a promising technology for both wind resource assessment and turbine response characterization. The aim of this study is to quantify data availability for a coherent detection wind-profiling lidar—namely, the Leosphere Windcube.To determine situations of suitable data return rates, a Windcube, collocated with a Vaisala CL31 ceilometer, was deployed as part of the Skywatch Observatory at the Universi...
The gesture recognition toolkit

The Gesture Recognition Toolkit is a cross-platform open-source C++ library designed to make real-time machine learning and gesture recognition more accessible for non-specialists. Emphasis is placed on ease of use, with a consistent, minimalist design that promotes accessibility while supporting flexibility and customization for advanced users. The toolkit features a broad range of classification and regression algorithms and has extensive support for building real-time systems. This includes algorithms for signal processing, feature extraction and automatic gesture spotting.
Why Executive Power Centralizes Government

This article examines the effects of political parties, executive power, and efficiency on federal structure. It proposes and tests a model of federalism in which different levels of veto power can lead to varying degrees of centralization in the provision of central and local governmental services when executive and legislative branches have disparate preferences over which level should provide services. Results for the United States (1982-1992) find state and local spending centralizes with increased veto power because, absent offsetting political party advocacy for decentralization, central government spending interests dominate local government spending interests.
The Initial Hours of Metastasis: The Importance of Cooperative Host–Tumor Cell Interactions during Hematogenous Dissemination

Tumor cells transit from the primary tumor via the blood circulation to form metastases in distant organs. During this process, tumor cells encounter a number of environmental challenges and stimuli that profoundly impact their metastatic potential. Here, we review the cooperative and dynamic host-tumor cell interactions that support and promote the hematogenous dissemination of cancer cells to sites of distant metastasis. In particular, we discuss what is known about the crosstalk occurring among tumor cells, platelets, leukocytes and endothelial cells and how these cell-cell interactions are organized both temporally and spatially at sites of extravasation and in the early metastatic niche.
Synthesis of bridged azabicyclic structures via ring-closing olefin metathesis.

A new strategy for the facile synthesis of azabicyclo[m.n.1]alkenes (m = 3−5; n = 3, 2) has been developed that involves the ring-closing metathesis (RCM) reaction of cis-2,6-dialkenyl-N-acyl piperidine derivatives. The requisite 2,6-dialkenylpiperidines may be readily prepared in six steps starting from glutarimide (11) or three steps from 4-methoxypyridine (25). In one example that establishes the practical utility of the procedure, the functionalized 8-azabicyclo[3.2.1]octane 32, which is a potential intermediate for the syntheses of various tropane alkaloids, was prepared. Additionally, a new route for the construction of the bridged tetrahydro-β-carboline ring system 5 has been developed that features the ring-closing metathesis of the enyne 45 to construct the bridging ring in 46. This concise route to 46 also features a potentially general and useful procedure for the one-step preparation of a terminal alkyne from an ester function. Selective oxidation of the vinyl group in 46 afforded the unsatura...
Reactivity and Enantioselectivity in the Reactions of Scalemic Stereogenic α-(N-Carbamoyl)alkylcuprates

Stereogenic 2-(N-carbamoyl)pyrrolidinylcuprates prepared from scalemic (i.e., enantioenriched) N-Boc-2-lithiopyrrolidine and THF soluble CuCN·2LiCl react with vinyl iodides, vinyl triflates, β-iodo-α,β-enoates, propargyl mesylates, and allyl bromide to afford the substitution products with excellent enantioselectivity. Excellent enantiomeric ratios are obtained in the conjugate addition reactions with methyl vinyl ketone while low enantiomeric ratios can be achieved with acrylate esters using HMPA/TMSCl activation. Enantiomeric ratios vary with substrate substitution patterns and the observed enantioselectivities appear to be more a function of cuprate−electrophile reactivities than of the reaction type (e.g., substitution, conjugate addition). Low enantiomeric ratios are obtained with the α-(N-carbamoyl)benzylcuprates. The lithium−copper transmetalation and cuprate vinylation reactions proceed with retention of configuration.
Steiner symmetrization using a finite set of directions

Let v"1,...,v"m be a finite set of unit vectors in R^n. Suppose that an infinite sequence of Steiner symmetrizations are applied to a compact convex set K in R^n, where each of the symmetrizations is taken with respect to a direction from among the v"i. Then the resulting sequence of Steiner symmetrals always converges, and the limiting body is symmetric under reflection in any of the directions v"i that appear infinitely often in the sequence. In particular, an infinite periodic sequence of Steiner symmetrizations always converges, and the set functional determined by this infinite process is always idempotent.
Powered control mechanisms contributing to dynamically stable swimming in porcupine puffers (Teleostei: Diodon holocanthus)

Balances of multiple varying forces must be the basis for the unusually great dynamic stability of swimming pufferfishes. We used high-speed digital video recordings to study biomechanics and kinematics of rectilinear swimming at different speeds of five porcupine puffers in a water tunnel. We measured critical swimming speeds (U crit ); fin biomechanics, kinematics, and coordination; recoil movements; and gait changes. Major propulsors were pectoral fins at lower speeds; dorsal, anal, and caudal fins at higher speeds. Precise coordination of fin movements produced small recoil movements at speeds below U crit . The unusual body shape probably contributes to unconscious stability control.
Thumbs Up or Thumbs Down? Semantic Orientation Applied to Unsupervised Classification of Reviews

This paper presents a simple unsupervised learning algorithm for classifying reviews as recommended (thumbs up) or not recommended (thumbs down). The classification of a review is predicted by the average semantic orientation of the phrases in the review that contain adjectives or adverbs. A phrase has a positive semantic orientation when it has good associations (e.g., "subtle nuances") and a negative semantic orientation when it has bad associations (e.g., "very cavalier"). In this paper, the semantic orientation of a phrase is calculated as the mutual information between the given phrase and the word "excellent" minus the mutual information between the given phrase and the word "poor". A review is classified as recommended if the average semantic orientation of its phrases is positive. The algorithm achieves an average accuracy of 74% when evaluated on 410 reviews from Epinions, sampled from four different domains (reviews of automobiles, banks, movies, and travel destinations). The accuracy ranges from 84% for automobile reviews to 66% for movie reviews.
Enantioselective Synthesis of (R)‐2‐Methylalkanoic Acids: A Convenient Approach to α‐Substituted Chiral Carboxylic Acid Derivatives

Abstract Racemization‐free deacylation of N‐acylimidazolidine‐2‐ones using lithium hydroperoxide affords the corresponding α‐substituted chiral carboxylic acids in high yield while permitting recovery of the chiral auxiliary.
A Monte Carlo simulation study of wind turbine loads in thunderstorm downbursts

The simulation of thunderstorm downbursts and of associated loads on a utility-scale wind turbine loads are the focus of this study. Using a deterministic-stochastic hybrid model, downburst-related wind fields are generated separately from non-turbulent and turbulent parts. The non-turbulent part builds on available analytical models developed from data sets that include recorded downburst events; the turbulent part is simulated as a stochastic process using standard turbulence power spectral density functions and coherence functions adjusted by information on parameters such as the thunderstorm’s translation velocity. Key thunderstorm downburst-related parameters include the maximum radial velocity; the height and radial distance to the maximum radial velocity; the storm intensity; the storm translation velocity; and the storm translation direction. In addition, the ambient (environmental) winds, and the storm touchdown location relative to the wind turbine are also important in turbine load computation. A utility-scale 5MW wind turbine model is selected and loads are generated using stochastic simulation of the aeroelastic response. Information available in the literature on recorded downbursts is used to define the cases studied. A single storm simulation and associated turbine response simulation is first discussed to illustrate loads computation and highlight storm-related parameters of interest. Next, a Monte Carlo simulation study is performed to investigate the influence of touchdown locations and translation direction on turbine extreme loads.
The “dark side” of gravitational experiments

Theoretical speculations about the quantum nature of the gravitational interaction have motivated many recent experiments. But perhaps the most profound and puzzling questions that these investigations address surround the observed cosmic acceleration, or Dark Energy. This mysterious substance comprises roughly two-thirds of the energy density of the universe. Current gravitational experiments may soon have the sensitivity to detect subtle clues that will reveal the mechanism behind the cosmic acceleration. On the laboratory scale, short-range tests of the Newtonian inverse-square law (ISL) provide the most sensitive measurements of gravity at the Dark Energy length scale, \(\lambda _{\rm d} = (\hbar\hbox{c}/\rho_{\rm d})^{1/4}\approx 85 {\mu\hbox{m}},\) where \(\rho_{\rm d} \approx 3.8 \hbox{keV/cm}^{3}\) is the observed Dark Energy density. This length scale may also have fundamental significance that could be related to the “size” of the graviton. At the University of Washington, we are conducting the world’s most sensitive, short-range test of the Newtonian ISL.
Issues regarding the design and acceptance of intelligent support systems for reactor operators

The central premise is that conventional expert systems which encode experimental knowledge in production rules are not a suitable vehicle for the creation of practical operator support systems. The principal difficulty is the need for real-time operation. Intelligent support systems will have to be heavily instrumented and the associated knowledge bases will require a hierarchical organization to emulate human approaches to analysis. Arguments to support the findings are made by first examining the needs of licensed reactor operators and then reviewing the capabilities of conventional expert systems. Differences between existing expert systems and proposed intelligent support tools are identified by comparing certain design features including the source and content of the knowledge base, the mode of interaction with the user, knowledge organization, the inference engine, and the man-machine interface. Issues related to operator acceptance of intelligent support tools are reviewed. Possible applications are described and the relative merits of the machine- and human-centered approaches to the implementation of intelligent support systems are enumerated. >
Financing Manufacturing Innovation in Argentina, 1890–1930

Between 1890 and 1930, Argentina's manufacturers invested in imported machinery. Although they aligned with political allies to advance and protect their companies, their dependence on imported machinery, raw materials, fuel, and expensive skilled labor were obstacles to their success. Two factors slowed the progress of these entrepreneurs: their lack of technological capabilities and the absence of government policies to address the problems entailed in importing foreign machinery. Several political factions supported industry's efforts to reduce dependence on imported products and to diversify the economy. While these supporters hoped to promote industry through the passage of legislation to raise the tariff rate, their strategy represented a compromise that stifled the drive to innovate that is so necessary for long-run economic growth and industrial development.
The behavioral response to voluntary provision of an environmental public good: Evidence from residential electricity demand

Abstract This paper develops a theory of voluntary provision of a public good in which a household's decision to engage in a form of environmentally friendly behavior is based on the desire to offset another behavior that is environmentally harmful. The model generates predictions about (1) participation in a green-electricity program at the extensive and intensive margins, and (2) changes in electricity consumption in response to participation. We test the theory using billing data for participants and nonparticipants in a green-electricity program in Memphis, Tennessee. High-consumption households are more likely to participate, and they participate at higher levels. In terms of a behavioral response, households participating above the minimum threshold level do not change electricity consumption, but those participating at the minimum threshold increase electricity consumption 2.5 percent after enrolling in the program. The result is based on identification strategies that exploit before–after differences between participants and nonparticipants, and differences in the timing of enrollment among participants only. Despite the increase in electricity demand upon the purchase of green electricity for the households with a “buy-in” mentality, the net effect for the buy-in households is a reduction in pollution emissions, as the behavioral response is not large enough to offset the environmental benefit of the green-electricity purchase.
A perspective of theoretical and applied computational fluid dynamics

O heighten his understanding of the fluid dynamics and aerodynamics pertinent to the early stages of the atmospheric flight-vehicle design process, the aerodynamicist has at his disposal three standard tools: analytical methods, computational procedures, and experimentation. Some of the advantages and disadvantages of each design tool are summarized in Fig. 1. Analytical methods provide quick, closed-form solutions, but they require unduly restrictive assumptions, can treat only simple configurations, and capture only the idealized aerodynamics. Through experimentation, representative or actual configurations can be tested and representative and complete aerodynamic data can be produced. Experimentation is costly, however, both in terms of the model and actual test time. In addition, the limited conditions that can be attained in wind tunnels restrict the scope of ex
Spirodienones via a thermal uncatalyzed [1,3]-oxygen-to-carbon migration

Abstract Exocyclic vinyl ethers derived from p -quinols, readily available from aryllithium addition to quinone monoketals, undergo high-yield thermal [1,3]-oxygen-to-carbon migration, yielding spirodienones.
Chebyshev action on finite fields

Given a polynomial @f(x) and a finite field F"q one can construct a directed graph where the vertices are the values in the finite field, and emanating from each vertex is an edge joining the vertex to its image under @f. When @f is a Chebyshev polynomial of prime degree, the graphs display an unusual degree of symmetry. In this paper we provide a complete description of these graphs, and then use these graphs to determine the decomposition of primes in the Chebyshev radical extensions.
Time-space optimal parallel merging and sorting

The authors present a parallel merging algorithm that, on an exclusive-read exclusive-write (EREW) parallel random-access machine (PRAM) with k processors merges two sorted lists of total length n in O(n/k+log n) time and constant extra space per processor, and hence is time-space optimal for any value of k >
Model uncertainty, performance persistence and flows

Model uncertainty makes it difficult to draw clear inference about mutual fund performance persistence. I propose a new performance measure, Bayesian model averaged (BMA) alpha, which explicitly accounts for model uncertainty. Using BMA alphas, I find evidence of performance persistence in a large sample of US funds. There is a positive and asymmetric relation between flows and past BMA alphas, suggesting that fund investors respond to the information in BMA alphas. My findings are robust to various sensitivity analyses, including alternative measures of post-ranking performance, flows and total net assets, and alternative econometric model specifications.
Resistive tapers that place nulls in the scattering patterns of strips

Tapering the resistivity on the surface of an object modifies the scattering patterns of that object. For instance, gradually tapering the resistivity on a strip, half-plane, or an antenna ground plane reduces the edge effects of that surface. Greater control over the sidelobe response of the scattering pattern of a strip is possible by relating the resistive taper to a low sidelobe taper via physical optics. The idea of relating antenna aperture tapers to scattering patterns is extended to placing nulls in the sidelobes of scattering patterns of strips. A resistive taper for placing nulls is found by solving the scattering integral equations of a resistive strip for the resistivity, then substituting the desired nulling current density taper into the appropriate equation and solving for the resistive taper. This method is capable of placing multiple nulls in the bistatic scattering pattern or a single null in the backscattering pattern. >
PRIME: peer-to-peer receiver-driven mesh-based streaming

The success of file swarming mechanisms such as BitTorrent has motivated a new approach for scalable streaming of live content that we call mesh-based Peer-to-Peer (P2P) streaming. In this approach, participating end-systems (or peers) form a randomly connected mesh and incorporate swarming content delivery to stream live content. Despite the growing popularity of this approach, neither the fundamental design tradeoffs nor the basic performance bottlenecks in mesh-based P2P streaming are well understood. In this paper, we follow a performance-driven approach to design PRIME, a scalable mesh-based P2P streaming mechanism for live content. The main design goal of PRIME is to minimize two performance bottlenecks, namely bandwidth bottleneck and content bottleneck. We show that the global pattern of delivery for each segment of live content should consist of a diffusion phase which is followed by a swarming phase. This leads to effective utilization of available resources to accommodate scalability and also minimizes content bottleneck. Using packet level simulations, we carefully examine the impact of overlay connectivity, packet scheduling scheme at individual peers and source behavior on the overall performance of the system. Our results reveal fundamental design tradeoffs of mesh-based P2P streaming for live content.
The large number coincidence, the cosmic coincidence and the critical acceleration

The coincidence problem among the pure numbers of order near 10 40 is resolved with the Raychaudhuri and Friedmann–Robertson–Lemaitre–Walker equations and a trivial relationship involving the fine structure constant. The fact that the large number coincidence occurs only in the same epoch in which other coincidences among cosmic parameters occur could be considered a distinct coincidence problem suggesting an underlying physical connection. A natural set of scaling laws for the cosmological constant and the critical acceleration is identified that would resolve the coincidence among cosmic coincidences.
Velocity estimation in laterally varying media

In areas of large lateral variations in velocity, stacking velocities computed on the basis of hyperbolic moveout can differ substantially from the actual root mean square (rms) velocities. This paper addresses the problem of obtaining rms or migration velocities from stacking velocities in such areas. The first‐order difference between the stacking and the vertical rms velocities due to lateral variations in velocity are shown to be related to the second lateral derivative of the rms slowness (1/νrms). Approximations leading to this relation are straight raypaths and that the vertical rms slowness to a given interface can be expressed as a second‐order Taylor series expansion in the midpoint direction. Under these approximations, the effect of the first lateral derivative of the slowness on the traveltime is negligible. The linearization of the equation relating the stacking and true velocities results in a set of equations whose inversion is unstable. Stability is achieved, however, by adding a nonphysi...
Evaluation of a cyclopentane-based γ-amino acid for the ability to promote α/γ-peptide secondary structure.

We report the asymmetric synthesis of the γ-amino acid (1R,2R)-2-aminomethyl-1-cyclopentane carboxylic acid (AMCP) and an evaluation of this residue’s potential to promote secondary structure in α/γ-peptides. Simulated annealing calculations using NMR-derived distance restraints obtained for α/γ-peptides in chloroform reveal that AMCP-containing oligomers are conformationally flexible. However, additional evidence suggests that an internally hydrogen-bonded helical conformation is partially populated in solution. From these data, we propose characteristic NOE patterns for the formation of the α/γ-peptide 12/10-helix and discuss the apparent conformational frustration of AMCP-containing oligomers.
High-Speed Photoconductive Detectors Fabricated in Heteroepitaxial GaAs Layers

Response times of ∼60 and 25 ps (FWHM), respectively, have been measured for photoconductive detectors fabricated in GaAs layers grown by molecular beam epitaxy on silicon substrates and silicon-on-sapphire substrates. Photoconductive detectors, which can be readily combined with GaAs logic devices such as MESFETs to provide high-speed optical to electrical conversion, could be used in optical interconnects that are integrated with Si circuits on monolithic GaAs/Si wafers. Transconductance values of 120 mS/mm have been obtained for MESFET’s fabricated in GaAs layers grown on silicon-on-sapphire substrates.
Remarkably mild and efficient intramolecular Friedel-Crafts cyclization catalyzed by In(III).

Indium(III) salts were found to be highly effective catalysts for the intramolecular Friedel−Crafts reaction of simple allylic bromides and arenes. In(III) salts appear to be the most general and possess unique halophilic properties as a Lewis acid for this reaction among the catalysts evaluated to date. Deactivated arenes possessing chloride, bromide, and fluoride underwent smooth reaction when activated by InCl3.