cssi/SciSciGPT-SciSciNet huggingface dataset:
Adaptive approximate Bayesian computation for complex models

We propose a new approximate Bayesian computation (ABC) algorithm that aims at minimizing the number of model runs for reaching a given quality of the posterior approximation. This algorithm automatically determines its sequence of tolerance levels and makes use of an easily interpretable stopping criterion. Moreover, it avoids the problem of particle duplication found when using a MCMC kernel. When applied to a toy example and to a complex social model, our algorithm is 2---8 times faster than the three main sequential ABC algorithms currently available.
Time and Frequency Transfer via Microwave Link

A two-way microwave link between the Naval Research Laboratory and the Naval Observatory has been established to transfer both time and frequency information with high accuracy. Time and frequency information are transmitted simultaneously by algebraically adding together a precision 1-MHz signal and 1 pps, thus providing continuous phase information for frequency comparison and epoch time by the pulse. Phase resolution is better than 10 ns and determination of epoch time better than 0.1 ??s. Seven precision standards have been intercompared via the microwave link. Continuous phase recording since September 1969 has shown no diumal dependence and very little effect due to seasonal and temperature changes. A second microwave link has been established between the Naval Observatory and the Naval Research Laboratory's satellite research communications terminal in Waldorf, Md.
Consumer Risk Perceptions and Information in Insurance Markets with Adverse Selection

Standard models of adverse selection in insurance markets assume policyholders know their loss distributions. This study examines the nature of equilibrium and the equilibrium value of information in competitive insurance markets where consumers lack complete information regarding their loss probabilities. We show that additional private information is privately and socially valuable. When the equilibrium policies separate types, policyholders can deduce the underlying probabilities from the contracts, so it is information on risk type, rather than loss probability per se, that is valuable. We show that the equilibrium is “as if” policyholders were endowed with complete knowledge if, and only if, information is noiseless and costless. If information is noisy, the equilibrium depends on policyholders' prior beliefs and the amount of noise in the information they acquire.
Discrimination in online ad delivery

A Google search for a person's name, such as “Trevon Jones”, may yield a personalized ad for public records about Trevon that may be neutral, such as “Looking for Trevon Jones? …”, or may be suggestive of an arrest record, such as “Trevon Jones, Arrested?...”. This writing investigates the delivery of these kinds of ads by Google AdSense using a sample of racially associated names and finds statistically significant discrimination in ad delivery based on searches of 2184 racially associated personal names across two websites. First names, previously identified by others as being assigned at birth to more black or white babies, are found predictive of race (88% black, 96% white), and those assigned primarily to black babies, such as DeShawn, Darnell and Jermaine, generated ads suggestive of an arrest in 81 to 86 percent of name searches on one website and 92 to 95 percent on the other, while those assigned at birth primarily to whites, such as Geoffrey, Jill and Emma, generated more neutral copy: the word "arrest" appeared in 23 to 29 percent of name searches on one site and 0 to 60 percent on the other. On the more ad trafficked website, a black-identifying name was 25% more likely to get an ad suggestive of an arrest record. A few names did not follow these patterns: Dustin, a name predominantly given to white babies, generated an ad suggestive of arrest 81 and 100 percent of the time. All ads return results for actual individuals and ads appear regardless of whether the name has an arrest record in the company’s database. Notwithstanding these findings, the company maintains Google received the same ad text for groups of last names (not first names), raising questions as to whether Google's advertising technology exposes racial bias in society and how ad and search technology can develop to assure racial fairness.
Non-parametric inversion of strong lensing systems

We revisit the issue of non-parametric gravitational lens reconstruction and present a new method to obtain the cluster mass distribution using strong lensing data without using any prior information on the underlying mass. The method relies on the decomposition of the lens plane into individual cells. We show how the problem in this approximation can be expressed as a system of linear equations for which a solution can be found. Moreover, we propose to include information about the null space. That is, we make use of the pixels in which we know there are no arcs above the sky noise. The only prior information is an estimation of the physical size of the sources. No priors on the luminosity of the cluster or shape of the haloes are needed, making the results very robust. In order to test the accuracy and bias of the method we make use of simulated strong lensing data. We find that the method reproduces accurately both the lens mass and source positions and provides error estimates.
Endogenous Financial and Trade Openness

The authors study the endogenous determination of financial and trade openness.They construct a theoretical framework leading to two-way feedbacks between financial and trade openness and identify these feedbacks empirically.They find that one standard deviation increase in commercial openness is associated with a 9.5% increase in de facto financial openness (% of GDP). Similarly, an increase in de facto financial openness has powerful effects on future trade openness. De jure restrictions on capital mobility have only a weak impact on de facto financial openness, while de jure restrictions on the current account have a large adverse effect on commercial openness.The authors investigate the relative magnitudes of these directions of causality using Geweke’s (1982) decomposition methodology. They conclude that in an era of rapidly growing trade integration, countries cannot choose financial openness independently of their degree of openness to trade. Dealing with greater exposure to turbulence by imposing restrictions on financial flows is likely to be ineffectual.
Eager combining: a coherency protocol for increasing effective network and memory bandwidth in shared-memory multiprocessors

An excessive number of remote accesses or a non-uniform distribution of remote accesses can cause even well-designed multiprocessors to exhibit severe memory and network contention. Producer/consumer data generates a particularly common sharing pattern that results in a non-uniform distribution of references. In this paper we quantify the performance impact of producer/consumer sharing as a function of memory and network bandwidth, and argue that the contention caused by this form of sharing severely impacts performance on large-scale machines. We propose a new coherency protocol, called eager combining, which is designed to alleviate this contention. We use execution-driven simulation of parallel programs on a large-scale multiprocessor to show that eager combining can improve the performance of programs with producer/consumer data by a factor of 4 or more. >
Inversion of the Laplace Transform from the Real Axis Using an Adaptive Iterative Method

A new method for inverting the Laplace transform from the real axis is formulated. This method is based on a quadrature formula. We assume that the unknown function 𝑓 ( 𝑡 ) is continuous with (known) compact support. An adaptive iterative method and an adaptive stopping rule, which yield the convergence of the approximate solution to 𝑓 ( 𝑡 ) , are proposed in this paper.
Reduction of Monobenzylic Alcohols with Sodium Borohydride/Trifluoroacetic Acid

Abstract Sodium borohydride/trifluoroacetic acid readily effects the reduction of monobenzylic alcohols to afford the corresponding hydrocarbons in moderate to high yields.
p53 Modulates Hsp90 ATPase Activity and Regulates Aryl Hydrocarbon Receptor Signaling

The aryl hydrocarbon receptor (AhR), a client protein of heat shock protein 90 (Hsp90), is a ligand-activated transcription factor that plays a role in polycyclic aromatic hydrocarbon (PAH)-induced carcinogenesis. Tobacco smoke activates AhR signaling leading to increased transcription of CYP1A1 and CYP1B1, which encode proteins that convert PAHs to mutagens. Recently, p53 was found to regulate Hsp90 ATPase activity via effects on activator of Hsp90 ATPase (Aha1). It is possible, therefore, that AhR-dependent expression of CYP1A1 and CYP1B1 might be affected by p53 status. The main objective of this study was to determine whether p53 modulated AhR-dependent gene expression and PAH metabolism. Here, we show that silencing p53 led to elevated Aha1 levels, increased Hsp90 ATPase activity, and enhanced CYP1A1 and CYP1B1 expression. Overexpression of wild-type p53 suppressed levels of CYP1A1 and CYP1B1. The significance of Aha1 in mediating these p53-dependent effects was determined. Silencing of Aha1 led to reduced Hsp90 ATPase activity and downregulation of CYP1A1 and CYP1B1. In contrast, overexpressing Aha1 was associated with increased Hsp90 ATPase activity and elevated levels of CYP1A1 and CYP1B1. Using p53 heterozygous mutant epithelial cells from patients with Li-Fraumeni syndrome, we show that monoallelic mutation of p53 was associated with elevated levels of CYP1A1 and CYP1B1 under both basal conditions and following treatment with benzo[a]pyrene. Treatment with CP-31398, a p53 rescue compound, suppressed benzo[a]pyrene-mediated induction of CYP1A1 and CYP1B1 and the formation of DNA adducts. Collectively, our results suggest that p53 affects AhR-dependent gene expression, PAH metabolism, and possibly carcinogenesis.
Calculation of the ion extraction boundary of a plasma ion source

The hypothesis that an unmagnetized plasma will form a meniscus sheath above an ion extraction aperture on the electric field magnitude contour, |E|=E/sub p/=T/sub e///spl lambda//sub D/, is tested. The hypothesis is assumed to be true, that the ion extraction surface of a single aperture ion extraction optic is given by the vacuum Laplace electric field magnitude contour equal to E/sub p/. The ion current extracted from this surface for a single aperture is calculated analytically. The analytically calculated current is compared to a particle-in-cell simulation of ion extraction from a single aperture, for densities ranging from 1.49/spl middot/10/sup 14/ to 1.49/spl middot/10/sup 20/ m/sup -3/ and electron temperatures of 1.35-2.7 eV. The simulated extraction current and extraction area agree with the calculated current and area very well, with deviations of only 0.1%-8% relative to the simulated value.
Reform, growth, and poverty in Vietnam

Vietnam grew rapidly in the 1990s, and yet by many measures it has poor economic institutions. Dollar seeks to explain this apparent anomaly. Between the 1980s and 1990s Vietnam carried out significant economic reforms, notably stabilization, the introduction of positive real interest rates, trade liberalization, and initial property rights reform in agriculture. Relating these changes to the empirical growth literature, the author finds that Vietnam's growth acceleration is about what would be predicted. Conditional convergence also suggests that the country's high growth rate will decelerate unless further reforms are taken. The author then looks at the level of institutional and policy development in Vietnam compared with other emerging market economies. While Vietnam's policies have improved, they did so starting from a very low base. So, it can be simultaneously true that Vietnam's policies have improved a lot and yet are rather poor in comparative perspective. A comparison of governance indicators, financial sector issues, and the infrastructure of international integration reveals serious institutional weaknesses in Vietnam that need to be addressed if a high growth rate is to be sustained.
Applications toolkit for accelerator control and analysis

The Advanced Photon Source (APS) has taken a unique approach to creating high-level software applications for accelerator operation and analysis. The approach is based on self-describing data, modular program toolkits, and scripts. Self-describing data provide a communication standard that aids the creation of modular program toolkits by allowing compliant programs to be used in essentially arbitrary combinations. These modular programs can be used as part of an arbitrary number of high-level applications. At APS, a group of about 70 data analysis, manipulation, and display tools is used in concert with about 20 control-system-specific tools to implement applications for commissioning and operations. High-level applications are created using scripts, which are relatively simple interpreted programs. The Tcl/Tk script language is used, allowing creating of graphical user interfaces (GUIs) and a library of algorithms that are separate from the interface. This last factor allows greater automation of control by making it easy to take the human out of the loop. Applications of this methodology to operational tasks such as orbit correction, configuration management, and data review are discussed.
Nonlinear waves in double-stranded DNA.

We propose a nonlinear model derived from first principles, to describe bubble dynamics of DNA. Our model equations include a term derived from the dissipative effect of intermolecular vibrational modes. Such modes are excited by the propagating bubble, and we term this ‘curvature dissipation’. The equations that we derive allow for stable pinned localized kinks which form the bubble. We perform the stability analysis and specify the energy requirements for the motion of the localized solutions. Our findings are consistent with properties of DNA dynamics, and can be used in models for denaturation bubbles, RNA and DNA transcription, nucleotide excision repair and meiotic recombination.
p53 enables metabolic fitness and self-renewal of nephron progenitor cells

Contrary to its classic role in restraining cell proliferation, we demonstrate here a divergent function of p53 in the maintenance of self-renewal of the nephron progenitor pool in the embryonic mouse kidney. Nephron endowment is regulated by progenitor availability and differentiation potential. Conditional deletion of p53 in nephron progenitor cells (Six2Cre+;p53fl/fl) induces progressive depletion of Cited1+/Six2+ self-renewing progenitors and loss of cap mesenchyme (CM) integrity. The Six2(p53-null) CM is disorganized, with interspersed stromal cells and an absence of a distinct CM-epithelia and CM-stroma interface. Impaired cell adhesion and epithelialization are indicated by decreased E-cadherin and NCAM expression and by ineffective differentiation in response to Wnt induction. The Six2Cre+;p53fl/fl cap has 30% fewer Six2(GFP+) cells. Apoptotic index is unchanged, whereas proliferation index is significantly reduced in accordance with cell cycle analysis showing disproportionately fewer Six2Cre+;p53fl/fl cells in the S and G2/M phases compared with Six2Cre+;p53+/+ cells. Mutant kidneys are hypoplastic with fewer generations of nascent nephrons. A significant increase in mean arterial pressure is observed in early adulthood in both germline and conditional Six2(p53-null) mice, linking p53-mediated defects in kidney development to hypertension. RNA-Seq analyses of FACS-isolated wild-type and Six2(GFP+) CM cells revealed that the top downregulated genes in Six2Cre+;p53fl/fl CM belong to glucose metabolism and adhesion and/or migration pathways. Mutant cells exhibit a ∼50% decrease in ATP levels and a 30% decrease in levels of reactive oxygen species, indicating energy metabolism dysfunction. In summary, our data indicate a novel role for p53 in enabling the metabolic fitness and self-renewal of nephron progenitors.
Finding all Nash equilibria of a finite game using polynomial algebra

The set of Nash equilibria of a finite game is the set of nonnegative solutions to a system of polynomial equations. In this survey article, we describe how to construct certain special games and explain how to find all the complex roots of the corresponding polynomial systems, including all the Nash equilibria. We then explain how to find all the complex roots of the polynomial systems for arbitrary generic games, by polyhedral homotopy continuation starting from the solutions to the specially constructed games. We describe the use of Grobner bases to solve these polynomial systems and to learn geometric information about how the solution set varies with the payoff functions. Finally, we review the use of the Gambit software package to find all Nash equilibria of a finite game.
Adaptive control of nonlinear multivariable systems using neural networks

Abstract Most practical systems have multiple inputs and multiple outputs, and the applicability of neural networks as practical adaptive controllers will eventually be judged by their success in multivariable problems. The representation, identification, and control of nonlinear multivariable systems are rendered difficult by the coupling as well as the delays that exist between the inputs and outputs. In the first part of the paper, theoretical questions related to system representation and existence of a desired control input are discussed. The second part of the paper develops a design methodology using neural networks. It is shown that under appropriate conditions, it may be possible to design efficient neural controllers for nonlinear multivariable systems for which linear controllers are inadequate.
A MATLAB software tool for the introduction of speech coding fundamentals in a DSP course

A MATLAB educational simulation program was developed to explore and understand standardized speech coding algorithms such as the FS-1015 LPC-10e, the FS-1016 CELP, the ETSI GSM, the IS-54 VSELP, the G.721 ADPCM, and the G.728 LD-CELP algorithms. The simulation software provides an interactive environment that allows users to display time- and frequency-domain representations of input and reconstructed speech on an IBM PC compatible equipped with a standard sound card. Scores associated with subjective and objective performance measures are computed using simulation tools. This tool is used in undergraduate and graduate DSP courses to introduce speech coding fundamentals.
Antiferromagnetic and van Hove scenarios for the cuprates: Taking the best of both worlds.

A theory for the high temperature superconductors is proposed. The dispersion of carriers in the 2D t-J model is calculated using numerical and analytical techniques, and compared with recent photoemission experimental results that reported a flat dispersion near the X and Y points. Good agreement is observed between theory and experiments. The density of states (DOS) of these dressed quasiparticles has a van Hove singularity. From the two carriers problem in an antiferromagnet, an effective Hamiltonian for holes is proposed. This effective model has superconductivity in the dx2−y2 channel, a critical temperature Tc ∼ 100Kat the optimal hole density, x = 0.15, and a quasiparticle lifetime linearly dependent with energy. The appearance of an optimal concentration is a consequence of the van Hove singularity in the DOS. Other experimental results are also quantitatively reproduced by the theory. The present contribution is based on two recent papers by the authors (Phys. Rev. Lett.73, 728 (1994) and NHMFL preprint, July 1994).
Exact two-level minimization of hazard-free logic with multiple-input changes

This paper describes a new method for exact hazard-free logic-minimization of Boolean functions. Given an incompletely-specified Boolean function, the method produces a minimum-cost sum-of-products implementation which is hazard-free for a given set of multiple-input changes, if such a solution exists. The method is a constrained version of the Quine-McCluskey algorithm. It has been automated and applied to a number of examples. Results are compared with results of a comparable non-hazard-free method (espresso-exact). Overhead due to hazard elimination is shown to be negligible. >
Vertical Redistribution of Oceanic Heat Content

AbstractEstimated values of recent oceanic heat uptake are on the order of a few tenths of a W m−2, and are a very small residual of air–sea exchanges, with annual average regional magnitudes of hundreds of W m−2. Using a dynamically consistent state estimate, the redistribution of heat within the ocean is calculated over a 20-yr period. The 20-yr mean vertical heat flux shows strong variations in both the lateral and vertical directions, consistent with the ocean being a dynamically active and spatially complex heat exchanger. Between mixing and advection, the two processes determining the vertical heat transport in the deep ocean, advection plays a more important role in setting the spatial patterns of vertical heat exchange and its temporal variations. The global integral of vertical heat flux shows an upward heat transport in the deep ocean, suggesting a cooling trend in the deep ocean. These results support an inference that the near-surface thermal properties of the ocean are a consequence, at least...
The Spatial Mixing of Genomes in Secondary Contact Zones

Recent genomic studies have highlighted the important role of admixture in shaping genome-wide patterns of diversity. Past admixture leaves a population genomic signature of linkage disequilibrium (LD), reflecting the mixing of parental chromosomes by segregation and recombination. These patterns of LD can be used to infer the timing of admixture, but the results of inference can depend strongly on the assumed demographic model. Here, we introduce a theoretical framework for modeling patterns of LD in a geographic contact zone where two differentiated populations have come into contact and are mixing by diffusive local migration. Assuming that this secondary contact is recent enough that genetic drift can be ignored, we derive expressions for the expected LD and admixture tract lengths across geographic space as a function of the age of the contact zone and the dispersal distance of individuals. We develop an approach to infer age of contact zones, using population genomic data from multiple spatially sampled populations by fitting our model to the decay of LD with recombination distance. To demonstrate an application of our model, we use our approach to explore the fit of a geographic contact zone model to three human genomic data sets from populations in Indonesia, Central Asia, and India and compare our results to inference under different demographic models. We obtain substantially different results from those of the commonly used model of panmictic admixture, highlighting the sensitivity of admixture timing results to the choice of demographic model.
A PSPACE-complete first-order fragment of computability logic

In a recently launched research program for developing logic as a formal theory of (interactive) computability, several very interesting logics have been introduced and axiomatized. These fragments of the larger Computability Logic aim not only to describe what can be computed, but also provide a mechanism for extracting computational algorithms from proofs. Among the most expressive and fundamental of these is CL4, known to be (constructively) sound and complete with respect to the underlying computational semantics. Furthermore, the ∀, ∃-free fragment of CL4 was shown to be decidable in polynomial space. The present work extends this result and proves that this fragment is, in fact, PSPACE-complete.
A Nanophotonic Interconnect for High-Performance Many-Core Computation

Silicon nanophotonics holds the promise of revolutionizing computing by enabling parallel architectures that combine unprecedented performance and ease of use with affordable power consumption. Here we describe the results of a detailed multiyear design study of dense wavelength division multiplexing (DWDM) on-chip and off-chip interconnects and the device technologies that could improve computing performance by a factor of 20 above industry projections over the next decade.
The Flattening Firm and Product Market Competition: The Effect of Trade Liberalization on Corporate Hierarchies

This paper establishes a causal effect of product market competition on various characteristics of organizational design. Using a unique panel dataset on firm hierarchies of large US firms (1986-1999) and a quasi-natural experiment (trade liberalization), we find that competition leads firms to flatten their hierarchies: firms reduce the number of positions between the CEO and division managers, and firms increase the number of positions reporting directly to the CEO. The results illustrate how firms redesign their organizational struc ture through a set of complementary choices in response to changes in their environment. We discuss several possible interpretations of these changes. (JEL D23, F13, G34, M12, M51)
Non-cooperative Bargaining and Union Formation

We study a union formation decision problem when workers consist of two groups distinguished by different productivities. Workers may form either a joint union or two separate unions. The whole decision process is modelled as an extensive-form bargaining game. Workers form a joint union when the sizes or productivities of the groups are similar. In the first case, there is a wage differential which is more (less) than proportional to the productivity difference if the size of the more productive is smaller (larger) than that of the less productive. In the second case, there is no wage differential. In this paper we study a union formation decision problem when workers consist of two groups distinguished by different productivities. They may form either a joint union or two separate unions, depending on the relative size and productivity of the two groups. The whole decision process is modelled as an extensive-form bargaining game in which the two groups of workers bargain with each other as well as with a firm. The labour market is sharply distinguished from the goods market by the widespread practice of collective bargaining. Usually several groups of workers with different characteristics (for example, skill level or geographical location) are represented as a single unit, and/or several employers form a single bargaining unit against a giant union. This multiplicity of bargaining units creates a complicated bargaining structure and makes the outcome hard to analyse. The purpose of this paper is to provide a model which captures this complexity and, at the same time, clarifies the underlying structure of bargaining power. Although economists have been aware of the multiplicity problem for a long time, it has been received little rigorous theoretical treatment until recently.' Davidson (1985) examined the possible gains that can be obtained by trade unions through joint bargaining in an oligopolistic industry. There is a positive externality due to the fact that a higher wage rate in one firm generates a larger demand (hence a higher wage) in competing firms. When a joint union is organized, these externalities are internalized to the benefit of workers. Horn and Wolinsky (1985) investigated the equilibrium pattern of unionization in an industry where a firm employs two types of workers. They found that workers tend to form a single union when the two types are substitutes in the sense that the incremental contribution of one group to the firm's revenue is decreasing with respect to the size of the other group. Since workers' bargaining power comes from the loss that they can
Group homomorphisms as error correcting codes

We investigate the minimum distance of the error correcting code formed by the homomorphisms between two finite groups $G$ and $H$. We prove some general structural results on how the distance behaves with respect to natural group operations, such as passing to subgroups and quotients, and taking products. Our main result is a general formula for the distance when $G$ is solvable or $H$ is nilpotent, in terms of the normal subgroup structure of $G$ as well as the prime divisors of $|G|$ and $|H|$. In particular, we show that in the above case, the distance is independent of the subgroup structure of $H$. We complement this by showing that, in general, the distance depends on the subgroup structure of $H$.
Graphs and matrices with maximal energy

Abstract Given a complex m × n matrix A, we index its singular values as σ 1 ( A ) ⩾ σ 2 ( A ) ⩾ ⋯ and call the value E ( A ) = σ 1 ( A ) + σ 2 ( A ) + ⋯ the energy of A, thereby extending the concept of graph energy, introduced by Gutman. Koolen and Moulton proved that E ( G ) ⩽ ( n / 2 ) ( 1 + n ) for any graph G of order n and exhibited an infinite family of graphs with E ( G ) = ( v ( G ) / 2 ) ( 1 + v ( G ) ) . We prove that for all sufficiently large n, there exists a graph G = G ( n ) with E ( G ) ⩾ n 3 / 2 / 2 − n 11 / 10 . This implies a conjecture of Koolen and Moulton. We also characterize all square nonnegative matrices and all graphs with energy close to the maximal one. In particular, such graphs are quasi-random.
Symbolic Computation of Conserved Densities for Systems of Nonlinear Evolution Equations

A new algorithm for the symbolic computation of polynomial conserved densities for systems of nonlinear evolution equations is presented. The algorithm is implemented inMathematica. The programcondens.mautomatically carries out the lengthy symbolic computations for the construction of conserved densities. The code is tested on several well-known partial differential equations from soliton theory. For systems with parameters,condens.mcan be used to determine the conditions on these parameters so that a sequence of conserved densities might exist. The existence of a large number of conservation laws is a predictor for integrability of the system.
Better Mini-Batch Algorithms via Accelerated Gradient Methods

Mini-batch algorithms have been proposed as a way to speed-up stochastic convex optimization problems. We study how such algorithms can be improved using accelerated gradient methods. We provide a novel analysis, which shows how standard gradient methods may sometimes be insufficient to obtain a significant speed-up and propose a novel accelerated gradient algorithm, which deals with this deficiency, enjoys a uniformly superior guarantee and works well in practice.
Oxide-supported metal clusters: models for heterogeneous catalysts

Understanding the size-dependent electronic, structural and chemical properties of metal clusters on oxide supports is an important aspect of heterogeneous catalysis. Recently model oxide-supported metal catalysts have been prepared by vapour deposition of catalytically relevant metals onto ultra-thin oxide films grown on a refractory metal substrate. Reactivity and spectroscopic/microscopic studies have shown that these ultra-thin oxide films are excellent models for the corresponding bulk oxides, yet are sufficiently electrically conductive for use with various modern surface probes including scanning tunnelling microscopy (STM). Measurements on metal clusters have revealed a metal to nonmetal transition as well as changes in the crystal and electronic structures (including lattice parameters, band width, band splitting and core-level binding energy shifts) as a function of cluster size. Size-dependent catalytic reactivity studies have been carried out for several important reactions, and time-dependent catalytic deactivation has been shown to arise from sintering of metal particles under elevated gas pressures and/or reactor temperatures. In situ STM methodologies have been developed to follow the growth and sintering kinetics on a cluster-by-cluster basis. Although several critical issues have been addressed by several groups worldwide, much more remains to be done. This article highlights some of these accomplishments and summarizes the challenges that lie ahead.
Capacity withholding in restructured wholesale power markets: An agent-based test bed study

This study uses a dynamic 5-bus test case implemented via the AMES Wholesale Power Market Test Bed to investigate strategic capacity withholding by generation companies (GenCos) in restructured wholesale power markets under systematically varied demand conditions. The strategic behaviors of the GenCos are simulated by means of a stochastic reinforcement learning algorithm motivated by human-subject laboratory experiments. The learning GenCos attempt to improve their earnings over time by strategic selection of their reported supply offers. This strategic selection can involve both physical capacity withholding (reporting of lower-than-true maximum operating capacity) and economic capacity withholding (reporting of higher-than-true marginal costs). We explore the ability of demand conditions to mitigate incentives for capacity withholding by letting demand bids vary from 100% fixed demand to 100% price-sensitive demand.
On strict inclusions in hierarchies of convex bodies

Let Ik be the class of convex k-intersection bodies in R n (in the sense of Koldobsky) and I m be the class of convex origin-symmetric bodies all of whose m-dimensional central sections are k-intersection bodies. We show that 1) I m k 6⊂ I m+1 k , k + 3 ≤ m < n, and 2) Il 6⊂ Ik, 1 ≤ k < l < n − 3.
Sound generation by turbulence in simulated rocket motor cavities

The present investigation is motivated by vibration problems in solid-propell ant rocket motors. A class of interior flows modeled to simulate flow conditions inside rocket motor cavities is considered. The turbulence generated pressure fluctuation consists of two components, acoustic and hydrodynamic. The Bernoulli enthalpy theory of aeroacoustics is employed to extract acoustic pressure spectra from experimentally obtained turbulence data and acoustic impedance values at flow boundaries. The effects of turbulence intensities, sidewall acoustic impedance, length-to-diameter ratio of the cavity, and different mass flux on the acoustic pressure level are investigated in experimental configurations. Typical pressure levels inside rocket motor environments are calculated utilizing the A-B representation for propellant response.
A strained-layer InGaAs-GaAs-AlGaAs single quantum well broad spectrum LED by selective-area metalorganic chemical vapor deposition

Three-step selective area metalorganic chemical vapor deposition is used to fabricate strained layer InGaAs-GaAs-AlGaAs single quantum well broad spectrum LEDs. We have fabricated a device with a continuous variation in quantum well thickness along its length by using a tapered oxide width mask for the active region regrowth. A spectral emission width of 80 nm is obtained. >
Studies on Aqueous Two Phase Polymer Systems Useful for Partitioning of Biological Materials

The two phase systems that result when aqueous solutions of dextran and poly(ethylene glycol) (PEG) are mixed above a critical concentration of a few percent provide a useful medium for the separation of biological cell subpopulations via partition between the top, PEG-rich phase and the liquid-liquid phase boundary. Interfacial tensions of such systems have been measured by the rotating drop technique and found to range between 10 −1 and 10 2 μN m −1 . The tension was found to depend on the length of the tie line describing the system on a phase diagram, via a power law relationship which differed depending on the concentration of Na phosphate buffer present. The electrokinetic properties of drops of one phase suspended in the other were studied for a variety of systems. It was found that the droplet electrophoretic mobility increased monotonically with phosphate concentration and drop diameter but exhibited the opposite sign from that anticipated from phosphate partition measurements. It was possible to take advantage of these electrokinetic properties and dramatically enhance the speed of phase separation through application of relatively small electric fields.
Search for extra dimensions at LHC

Some of the studies performed by the ATLAS and CMS collaborations to establish the future sensitivity of the experiments to extra dimension signals are reviewed. The discrimination of those signals from other new physics signals and the extraction of the underlying parameters of the extra dimension models are discussed.
A direct characterization of L/sub 2/-gain controllers for LPV systems

In this paper, a class of linear parameter dependent output feedback controllers that satisfy quadratic stability and an induced L/sub 2/-norm bound for a given linear parameter-varying (LPV) plant is considered. By using a parameter-independent common Lyapunov function, the solvability conditions are expressed in terms of finite dimensional linear matrix inequalities (LMI) evaluated at the extreme points of the admissible parameter set. Conditions under which strictly proper controllers can be used are obtained. By restricting some of the controller matrices to be constant, the input and output matrices can be parameter-varying without destroying the problem's convexity. Cases where the controller matrices can be obtained without interpolation are also discussed, thereby simplifying the implementation of the controller. A numerical example is included which demonstrates the application of the results.
Mechanistic simulations explain paradoxical saquinavir metabolism during in vitro vectorial transport study

We were confronted by an unexpected observation: in a Transwell study of confluent, Cyp3A4 and P-gp-expressing Caco-2 cells, higher intracellular saquinavir levels, yet less first metabolite (M7) formation were observed following apical dosing, compared to basal dosing [1]. To test two seemingly plausible hypothesized explanations, we constructed an in silico working analogue using the synthetic method. Neither mechanism alone was sufficient, but when combined and tuned within the analogue, the results generated were a semi-quantitative match to the experimental data. After 60 cycles, more of the simulated dose was present within analogue cells as parent drug after apical dosing. Furthermore, less M7 was present after apical dose. The paradox disappeared by having simulated drugs equilibrate among separate intracellular zones. Building, studying, and exploring mechanistic explanations for complex wet-lab phenomena using the new methods improved insight into the referent system, while providing a straightforward, scientific means of testing the plausibility of mechanistic hypotheses.
Strategic Information Disclosure: The Case of Multi-Attribute Products with Heterogeneous Consumers

We examine the incentives for firms to voluntarily disclose otherwise private information about quality attributes of differentiated products. In particular, we focus on the case of differentiated products with multiple attributes and consumers that are heterogeneous in their preferences over these attributes. We show that there exist certain configurations of consumer preferences under which a firm producing a high-quality product, even with zero costs of disclosure, may choose not to reveal the quality of its product. This failure of firms to voluntarily disclose the quality of their products will arise when providing consumers with more information results in more elastic demands for these products, which, in turn, triggers more intensive price competition and leads to lower prices and profits for all firms. As a result, the equilibrium in which disclosure is voluntary may diverge from that in which disclosure is mandatory.
Using processor affinity in loop scheduling on shared-memory multiprocessors

Loops are the single largest source of parallelism in many applications. One way to exploit this parallelism is to execute loop iterations in parallel on different processors. Previous approaches to loop scheduling attempted to achieve the minimum completion time by distributing the workload as evenly as possible while minimizing the number of synchronization operations required. The authors consider a third dimension to the problem of loop scheduling on shared-memory multiprocessors: communication overhead caused by accesses to nonlocal data. They show that traditional algorithms for loop scheduling, which ignore the location of data when assigning iterations to processors, incur a significant performance penalty on modern shared-memory multiprocessors. They propose a new loop scheduling algorithm that attempts to simultaneously balance the workload, minimize synchronization, and co-locate loop iterations with the necessary data. They compare the performance of this new algorithm to other known algorithms by using five representative kernel programs on a Silicon Graphics multiprocessor workstation, a BBN Butterfly, a Sequent Symmetry, and a KSR-1, and show that the new algorithm offers substantial performance improvements, up to a factor of 4 in some cases. The authors conclude that loop scheduling algorithms for shared-memory multiprocessors cannot afford to ignore the location of data, particularly in light of the increasing disparity between processor and memory speeds. >
Progress in Supramolecular Chemistry of Gases

The current progress in molecular recognition and supramolecular chemistry of gases is presented. The structure and properties of supramolecular gas-receptor complexes is discussed. Novel chromophoric and fluorophoric sensors for detection of gases are introduced. Studies on molecules and materials for gas entrapment, separation, storage and release that involve synthetic containers, capsules and nanotubes are overviewed. It is shown that supramolecular fixation of gases leads to stable and selective chemical reagents. Gases can also be used as building blocks. Polymers and reversible, dynamic nanostructures from gases are presented. Their potential application as storing and separating materials is discussed.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Hybrid algorithms for complete exchange in 2D meshes

Parallel algorithms for several common problems such as sorting and the FFT involve a personalized exchange of data among all the processors. Past approaches to doing complete exchange have taken one of two broad approaches: direct exchange or the indirect message-combining approaches. While combining approaches reduce the number of message startups, direct exchange minimizes the volume of data transmitted. This paper presents a family of hybrid algorithms for wormhole-routed 2D meshes that can effectively utilize the complementary strengths of these two approaches to complete exchange. The performance of hybrid algorithms using Cyclic Exchange and Scott's Direct Exchange are studied using analytical models, simulation, and implementation on a Cray T3D system. The results show that hybrids achieve lower completion times than either pure algorithm for a range of mesh sizes, data block sizes, and message startup costs. It is also demonstrated that barriers may be used to enhance performance by reducing message contention, whether or not the target system provides hardware support for barrier synchronization. The analytical models are shown useful in selecting the optimum hybrid for any given combination of system parameters (mesh size, message startup time, flit transfer time, and barrier cost) and the problem parameter (data block size).
AN EXAMINATION OF DIFFERENT TYPES OF ADVERSE SELECTION IN FEDERAL CROP INSURANCE

Different types of adverse selection-type of insurance product, type of unit, type of coverage and number of actual yields reported in Federal crop insurance is examined utilizing binomial and ordered logit discrete choice models for all U.S. cotton producers, 1997-2000. The associated costs of adverse selection in U.S. cotton range from $32 Million to $359 Million for the four-year period.
Direct variance design-a multiobjective control theory

A theory for designing linear state feedback controllers to directly accommodate variance constraints imposed on the system states is offered. Such controllers guarantee an average closed-loop response to Gaussian input disturbances. The method provides a mechanism for directly assigning all variance values (the diagonal elements of the covariance matrix) to the closed-loop system. The theory may be viewed as offering direct access to a new set of design variables: the state variances. >
Pulse compression on the Mark III FEL using energy chirping

Abstract We have performed preliminary simulations of the optical-pulse formation in the Mark III FEL using electron micropulses which exhibit a linear energy dependence on time, and have demonstrated optical pulses whose frequency chirps agree fairly well with those obtained analytically by assuming that the resonance condition determines the lasing wavelength during the pulse. In a typical case, we project pulse compression by a factor of 13.3, from an initial pulse width of 3.13 ps to a final pulse width of 236 fs, at a wavelength of 3.35 μm and an electron energy chirp of +2% (energy increasing towards the back of the pulse). This represents an optical pulse less than half as short as the slippage length of 47 magnet periods for this wavelength.
CAI: research requirements for instructional strategies

The current developments of computer-assisted instruction (CAI) can be characterized as a phased transition from the creation of hardware and language systems for implementation into the more fundamental examination of the features of optimal instructional strategies for CAI applications. Instructional strategies are the plans by which informational presentations are matched with the current requirements of a learner in order to optimize on a set of criterion objectives. The research approaches into the nature and process of instructional strategies has been twofold, namely, naturalistic and systematic.
Bering Strait throughflow and the thermohaline circulation

Received 25 August 2005; revised 10 November 2005; accepted 14 November 2005; published 21 December 2005. [1] In this study, we employ a global coupled climate model to show that the Bering Strait is important to the variations of the thermohaline circulation. Three experiments are analyzed, a present day control run, and two freshwater hosing runs. Results show that as the thermohaline circulation weakens due to freshwater forcing in the northern North Atlantic, the Bering Strait throughflow weakens, and even reverses its direction, and the export of the Arctic freshwater into the northern North Atlantic is reduced, or the Arctic even takes freshwater from the latter, thus helping the thermohaline circulation to recover relatively quickly after the end of the freshwater hosing. Citation: Hu, A., and G. A. Meehl (2005), Bering Strait throughflow and the thermohaline circulation, Geophys. Res. Lett., 32, L24610, doi:10.1029/2005GL024424.
Artificial Intelligence: A Modern Approach

The long-anticipated revision of this #1 selling book offers the most comprehensive, state of the art introduction to the theory and practice of artificial intelligence for modern applications. Intelligent Agents. Solving Problems by Searching. Informed Search Methods. Game Playing. Agents that Reason Logically. First-order Logic. Building a Knowledge Base. Inference in First-Order Logic. Logical Reasoning Systems. Practical Planning. Planning and Acting. Uncertainty. Probabilistic Reasoning Systems. Making Simple Decisions. Making Complex Decisions. Learning from Observations. Learning with Neural Networks. Reinforcement Learning. Knowledge in Learning. Agents that Communicate. Practical Communication in English. Perception. Robotics. For computer professionals, linguists, and cognitive scientists interested in artificial intelligence.