cssi/SciSciGPT-SciSciNet huggingface dataset:
Turbulent Air Flow Over Rough Surfaces: Mean Flow Parameters

The objective of the study was to examine experimentally the turbulent flow structure near a repeated-rib geometry rough-walled surface as a function of the ratio of roughness height to pipe radius (K/R), the ratio of spacing between the elements to roughness height (P/K), and the axial position with the rib cycle. The centerline axial flow velocity was found to vary sinusoidally in the axial direction within a rib cycle for P/K>10 for K/R = 0.1437 and P/K>13 for K/R = 0.100. The roughness effect on the mean velocity profiles was characterized using a logarithmic equation which utilized an error in origin and a roughness function that was a function of the error in origin. The equation was found to be valid for P/K values of 7 or less for K/R = 0.1437 and 13 for K/R = 0.1 geometries.
CuH-Catalyzed Enantioselective 1,2-Reductions of α,β-Unsaturated Ketones

The first study on a general technology for arriving at valued nonracemic allylic alcohols using asymmetric ligand-accelerated catalysis by copper hydride is described.
Towards the Optimal Screening Collection: A Synthesis Strategy

The development of effective small-molecule probes and drugs entails at least three stages: 1) a discovery phase, often requiring the synthesis and screening of candidate compounds, 2) an optimization phase, requiring the synthesis and analysis of structural variants, 3) and a manufacturing phase, requiring the efficient, large-scale synthesis of the optimized probe or drug. Specialized project groups tend to undertake the individual activities without prior coordination; for example, contracted (outsourced) chemists may perform the first activity while in-house medicinal and process chemists perform the second and third development stages, respectively. The coordinated planning of these activities in advance of the first small-molecule screen tends not to be undertaken, and each project group can encounter a bottleneck that could, in principle, have been avoided with advance planning. Therefore, a challenge for synthetic chemistry is to develop a new kind of chemistry that yields a screening collection comprising small molecules that increase the probability of success in all three phases. Although this transformative chemistry remains elusive, progress is being made. Herein, we review a newly emerging strategy in diversity-oriented small-molecule synthesis that may have the potential to achieve these challenging goals.
Podand-catalyzed nucleophilic aromatic substitutions of anthraquinones: A novel synthetic approach and a mechanistic suggestion from solid-state data

Haloanthraquinones undergo facile nucleophilic substitution by aliphatic alcohols only when a catalytic amount of oligo(ethylene glycol) derivative is present; the latter serves as both nucleophile and leaving group in the transformation
The Price Effects of Using Firewalls as an Antitrust Remedy

Antitrust authorities have imposed firewalls between the previously separate divisions of newly vertically integrated firms in several industries, to address concerns that access to horizontal rivals’ proprietary information may reduce competition. This paper evaluates a specific antitrust concern by modeling the price effect of one seller’s learning its rival’s production costs before bidding in a duopoly procurement contest. The results show that imposing a firewall as a condition for permitting a vertical merger actually can lead to higher prices than if the flow of information were unimpeded, and they provide guidance as to when this unintended outcome occurs.
Growing through cycles

The neoclassical growth model focuses on factor accumulation as an engine of growth, while the neo-Schumpetarian growth model stresses innovation. This paper argues that these two views of growth may capture different phases of a single growth experience. In the model presented below, the balanced growth path is unstable and the economy achieves sustainable growth through cycles under an empirically plausible condition, perpetually moving back and forth between two phases. One phase is characterized by higher output growth, higher investment, no innovation, and a competitive market structure. The other phase is characterized by lower output growth, lower investment, high innovation, and a more monopolistic market structure. Both investment and innovation are essential in sustaining growth indefinitely, and yet they move in an asynchronized way; only one of them appears to play a dominant role in each phase. The economy grows faster along the cycles than along the (unstable) balanced growth path.
Caution in macroeconomic policy: uncertainty and the relative intensity of policy

Abstract In a one-state two-control Quadratic Linear Problem, we use the Riccati equations to examine the effect of an increase in uncertainty in a future time period on the optimal use of the control variables in the first time period. We find that caution or more intensity in the outcome depends on the ratio of the weight on each control variable to the variance of the parameter which multiplies that control. When these ratios are not equal, the control with a smaller weighted variance will always be used more intensely. When these ratios are equal, both control variables will always be used more intensely.
Methods for mechanical geometry formula deriving

A precise formulation for the relations among certain variables under a set of polynomial equations and a set of polynomial inequations (to exclude certain special cases which cannot be excluded by the selection of parameters alone) is given. Several methods are presented to find such relations. The methods have been implemented and used to find geometry formulas, to discover geometry theorems, and to find geometry locus equations. About 120 non-trivial problems have been solved using the methods.
Informal prototyping of continuous graphical interactions by demonstration

We introduce Monet, a sketch-based tool for prototyping continuous graphical interactions by demonstration. In Monet, designers can prototype continuous widgets and their states of interest using examples. They can also demonstrate compound behaviors involving multiple widgets by direct manipulation. Monet allows continuous interactions to be easily integrated with event-based, discrete interactions. Continuous widgets can be embedded into storyboards and their states can condition or trigger storyboard transitions. Monet achieves these features without using any domain specific knowledge or assuming any application semantics.
A Complete Survey of Case A Binary Evolution with Comparison to Observed Algol-type Systems

We undertake a comparison of observed Algol-type binaries with a library of computed Case A binary evolution tracks. The library consists of 5500 binary tracks with various values of initial primary mass M10, mass ratio q0, and period P0, designed to sample the phase-space of Case A binaries in the range -0.10 ≤ log M10 ≤ 1.7. Each binary is evolved using a standard code with the assumption that both total mass and orbital angular momentum are conserved. This code follows the evolution of both stars to the point where contact or reverse mass transfer occurs. The resulting binary tracks show a rich variety of behavior that we sort into several subclasses of case A and case B. We present the results of this classification, the final mass ratio, and the fraction of time spent in Roche Lobe overflow for each binary system. The conservative assumption under which we created this library is expected to hold for a broad range of binaries, where both components have spectra in the range G0 to B1 and luminosity classes III to V. We gather a list of relatively well-determined, observed hot Algol-type binaries meeting this criterion, as well as a list of cooler Algol-type binaries, for which we expect significant dynamo-driven mass loss and angular momentum loss. We fit each observed binary to our library of tracks using a χ2-minimizing procedure. We find that the hot Algols display overall acceptable χ2, confirming the conservative assumption, while the cool Algols show much less acceptable χ2, suggesting the need for more free parameters, such as mass and angular momentum loss.
Semistandard tableaux for Demazure characters (key polynomials) and their atoms

The Schur function indexed by a partition λ with at most n parts is the sum of the weight monomials for the Young tableaux of shape λ . Let π be an n -permutation. We give two descriptions of the tableaux that contribute their monomials to the key polynomial indexed by π and λ . (These polynomials are the characters of the Demazure modules for G L ( n ) .) The "atom" indexed by π is the sum of weight monomials of the tableaux whose right keys are the "key" tableau for π . Schur functions and key polynomials can be decomposed into sums of atoms. We also describe the tableaux that contribute to an atom, the tableaux that have a left key equal to a given key, and the tableaux that have a left key bounded below by a given key.
Domino dumping II: Anti-dumping

Abstract Domino dumping [Anderson (American Economic Review, 1992, 82, 65–83)] arises when exporting firms dump to obtain more export licenses in the future when there is a positive probability of a future VER. Anti-dumping policy may then be in the public interest for the importing country, via lowering the probability of a VER. Increased enforcement may perversely lead to a rise in dumping. Also it may increase the probability of a VER and may reduce the probability of free trade. It is possible for the public interest to require some enforcement. However, it is normally in the public interest to permit some dumping.
Specific heat of CeRhIn5: pressure-driven transition from antiferromagnetism to heavy-fermion superconductivity

Abstract CeRhIn 5 is known to show an unusual transition at a critical pressure of ∼15 kbar. Specific-heat data show a gradual change in the zero-field “magnetic” specific-heat anomaly from one typical of antiferromagnetic (AF) ordering at ambient pressure to one more characteristic of a Kondo singlet ground state at 21 kbar. However, at 15 kbar there is a discontinuous change from an AF ground state to a superconducting ground state, and evidence of a weak thermodynamic first-order transition. Above the critical pressure, the low-energy excitations are characteristic of superconductivity with line nodes in the energy gap, and, at intermediate pressures, of extended gaplessness.
Improving ecological niche models by data mining large environmental datasets for surrogate models

Abstract WhyWhere is a new ecological niche modeling (ENM) algorithm for mapping and explaining the distribution of species. The algorithm uses image processing methods to efficiently sift through large amounts of data to find the few variables that best predict species occurrence. The purpose of this paper is to describe and justify the main parameterizations and to show preliminary success at rapidly providing accurate, scalable, and simple ENMs. Preliminary results for six species of plants and animals in different regions indicate a significant ( p http://biodi.sdsc.edu/ww_home.html .
A highly active catalyst for Pd-catalyzed amination reactions: cross-coupling reactions using aryl mesylates and the highly selective monoarylation of primary amines using aryl chlorides.

A catalyst system based on a new biarylmonophosphine ligand (BrettPhos) that shows excellent reactivity for C−N cross-coupling reactions is reported. This catalyst system enables the use of aryl mesylates as a coupling partner in C−N bond-forming reactions. Additionally, the use of BrettPhos permits the highly selective monoarylation of an array of primary aliphatic amines and anilines at low catalyst loadings and with fast reaction times, including the first monoarylation of methylamine. Lastly, oxidative addition complexes of BrettPhos are included, which provide insight into the origin of reactivity for this system.
Adaptive walks with noisy fitness measurements.

Adaptive walks constitute an optimization technique for searching a space of possible solutions, for example, a space of different molecules. The goal is to find a point in space (a molecule) that is optimal or near-optimal in some property, generally referred to as the ‘fitness’, such as its ability to bind to a given receptor. Adaptive walking, an analog of natural selection, is a powerful technique for searching landscapes. However, errors in the measurements will cause errors in the adaptive walks. Mutant molecules of higher fitness may be ignored or mutants of lower fitness may be accepted. To examine the effect of measurement error on adaptive walks, we simulate single-agent hill-climbing walks on NK landscapes of varying ruggedness where Gaussian noise is added to the fitness values to model measurement error. We consider both constant measurement noise and noise whose variance decays exponentially with fitness. We show that fitness-independent noise can cause walks to ‘melt’ off the peaks in a landscape, wandering in larger regions as the noise increases. However, we also show that a small amount of noise actually helps the walk perform better than with no noise. For walks in which noise decreases exponentially with fitness, the most characteristic behavior is that the walk meanders throughout the landscape until it stumbles across a point of relatively high fitness, then it climbs the landscape towards the nearest peak. Finally, we characterize the balance between selection pressure and noise and show that there are several classes of walk dynamic behavior.
Analysis of the Synchrotron Emission from the M87 Jet

We propose that the intensity changes and spectral evolution along the M87 jet can be explained by adiabatic changes to the particle momentum distribution function and the magnetic field. This is supported by the lack of any significant variation in the radio-to-optical spectral index along the jet and by the moderate changes in radio brightness. Assuming a simple scaling law between magnetic field and density, we use the deprojection of a 2 cm VLA intensity map by Sparks, Biretta, & Macchetto to predict the spectral evolution along the jet. We derive limits for the magnetic field and the total pressure by comparing our results with the spatially resolved fit to the spectral data by Neumann, Meisenheimer, & Roser of a model spectrum that cuts off at ≈ 1015 Hz. To explain the weakness of synchrotron cooling along the jet, the magnetic field strength must lie below the equipartition value. Although the inferred pressure in the limit of nonrelativistic bulk flow lies far above the estimated pressure of the interstellar matter in the center of M87, bulk Lorentz factors Γjet in the range of 3-5 and inclination angles θLOS 25° lead to pressure estimates close to the interstellar medium pressure. The average best-fit magnetic fields we derive fall in the range of 20-40 μG, departing from equipartition by a factor ≈ 1.5-5. This model is consistent with the proposal by Bicknell & Begelman that the knots in the M87 jet are weak, oblique shocks. First-order Fermi acceleration will then have a minimal effect on the slope of the radio-to-optical spectrum while possibly accounting for the X-ray spectrum.
Influence of Friction Dampers on Torsional Blade Flutter

This paper deals with the stabilizing effects of dry friction on torsional blade flutter. A lumped parameter model with single degree of freedom per blade has been used to represent the rotor stage. The well-known cascade theories for incompressible and supersonic flows have been used to determine the allowable increase in fluid velocity relative to the blade. It has been found that the effectiveness of friction dampers in controlling flutter can be substantial.
Detection of Equatorward Meridional Flow and Evidence of Double-cell Meridional Circulation inside the Sun

Meridional flow in the solar interior plays an important role in redistributing angular momentum and transporting magnetic flux inside the Sun. Although it has long been recognized that the meridional flow is predominantly poleward at the Sun's surface and in its shallow interior, the location of the equatorward return flow and the meridional flow profile in the deeper interior remain unclear. Using the first 2 yr of continuous helioseismology observations from the Solar Dynamics Observatory/Helioseismic Magnetic Imager, we analyze travel times of acoustic waves that propagate through different depths of the solar interior carrying information about the solar interior dynamics. After removing a systematic center-to-limb effect in the helioseismic measurements and performing inversions for flow speed, we find that the poleward meridional flow of a speed of 15 m s–1 extends in depth from the photosphere to about 0.91 R ☉. An equatorward flow of a speed of 10 m s–1 is found between 0.82 and 0.91 R ☉ in the middle of the convection zone. Our analysis also shows evidence of that the meridional flow turns poleward again below 0.82 R ☉, indicating an existence of a second meridional circulation cell below the shallower one. This double-cell meridional circulation profile with an equatorward flow shallower than previously thought suggests a rethinking of how magnetic field is generated and redistributed inside the Sun.
The case of the missing Ceres family

Abstract Ceres is unusual among large (>250 km) asteroids in lacking a dynamical family. We explore possible explanations, noting that its particularly large size and the ubiquity of families associated with other large asteroids makes avoidance of a sufficiently-sized collision by chance exceedingly unlikely. Current models of Ceres’ thermal history and interior structure favor a differentiated object with an icy near-surface covered by an ∼0.1–1 km lag deposit, which could result in a collisional family of diverse, predominately icy bodies. We predict that sublimation of an icy Ceres family would occur on timescales of hundreds of millions of years, much shorter than the history of the Solar System. Sublimation on a Ceres family body would be aided by a low non-ice fraction and a high average temperature, both of which would inhibit lag deposit development. Because there seems to be no likely mechanism for removing a rocky Ceres family, and because the formation of a Ceres family of some kind seems nearly statistically inevitable, the lack of a Ceres family is indirect but independent evidence for Ceres’ differentiation. All of the other large asteroids lacking dynamical families (704 Interamnia, 52 Europa, and 65 Cybele) have spectral properties similar to Ceres, or otherwise suggesting ice at their surfaces. While other large asteroids with similar spectral properties do have families (24 Themis, 10 Hygiea, 31 Euphrosyne), their families are not well understood, particularly Hygiea.
The Response of Model and Astrophysical Thermonuclear Flames to Curvature and Stretch

Critically understanding the standard candle-like behavior of Type Ia supernovae requires understanding their explosion mechanism. One family of models for Type Ia supernovae begins with a deflagration in a carbon-oxygen white dwarf that greatly accelerates through wrinkling and flame instabilities. While the planar speed and behavior of astrophysically relevant flames is increasingly well understood, more complex behavior, such as the flame's response to stretch and curvature, has not been extensively explored in the astrophysical literature; this behavior can greatly enhance or suppress instabilities and local flame-wrinkling, which in turn can increase or decrease the bulk burning rate. In this paper, we explore the effects of curvature on both nuclear flames and simpler model flames to understand the effect of curvature on the flame structure and speed.
A NEW SYNTHESIS OF TRANS-3,4-DIHYDROXY-ANTI-1,2-EPOXY-1,2,3,4-TETRAHYDRO-7,12-DIMETHYLBENZ(A)ANTHRACENE

Abstract A facile synthesis of trans-3,4-dihydroxy-anti-1,2-epoxy-1,2,3,4-tetrahydro-7,12-dimethylbenz(a) anthracene 1 ; a highly carcinogenic metabolite of 7,12-dimethylbenz(a) anthracene (DMBA) have been described.
Lateral lithiation of ethyl 4-acetyl-5-methyl-3-isoxazolyl carboxylate with 5,5-dimethyl-1,3-dioxanyl as a directing group

Abstract Lateral lithiation of ethyl 4-acetyl-5-methyl-3-isoxazolyl carboxylate, a functionalized isoxazole AMPA analog, occurs cleanly at the C-5 methyl group with 5,5-dimethyl-1,3-dioxanyl as a directing group. The 4-acetyl isoxazole derivatives were transformed selectively by a modified Willgerodt-Kindler reaction into the corresponding homologated methyl esters after deprotection.
Partitions of unity and coverings

Abstract The aim of this paper is to prove all well-known metrization theorems using partitions of unity. To accomplish this, we first discuss sufficient and necessary conditions for existence of U -small partitions of unity (partitions of unity subordinated to an open cover U of a topological space X).
Pseudo-random number generation for Brownian Dynamics and Dissipative Particle Dynamics simulations on GPU devices

Brownian Dynamics (BD), also known as Langevin Dynamics, and Dissipative Particle Dynamics (DPD) are implicit solvent methods commonly used in models of soft matter and biomolecular systems. The interaction of the numerous solvent particles with larger particles is coarse-grained as a Langevin thermostat is applied to individual particles or to particle pairs. The Langevin thermostat requires a pseudo-random number generator (PRNG) to generate the stochastic force applied to each particle or pair of neighboring particles during each time step in the integration of Newton's equations of motion. In a Single-Instruction-Multiple-Thread (SIMT) GPU parallel computing environment, small batches of random numbers must be generated over thousands of threads and millions of kernel calls. In this communication we introduce a one-PRNG-per-kernel-call-per-thread scheme, in which a micro-stream of pseudorandom numbers is generated in each thread and kernel call. These high quality, statistically robust micro-streams require no global memory for state storage, are more computationally efficient than other PRNG schemes in memory-bound kernels, and uniquely enable the DPD simulation method without requiring communication between threads.
Strategic export subsidies and reciprocal trade agreements: The natural monopoly case

Abstract Why do governments seek restrictions on the use of export subsidies through reciprocal trade agreements such as GATT? In this paper, we emphasize that subsidy competition between governments can serve to coordinate the entry decisions of firms, finding that consumers in the importing countries may suffer if the coordination afforded exporters by government subsidy programs does more to prevent entry than to promote it. In such circumstances, we show that the existence of export subsidy programs can lead to inefficiencies, and importing countries and the world as a whole can be better off when such programs are banned.
Direct Numerical Simulations of Flow Past an Array of Distributed Roughness Elements

Direct numerical simulation was used to describe the subsonic flow past an array of distributed cylindrical roughness elements mounted on a flat plate. Solutions were obtained for element heights corresponding to a roughness-based Reynolds number (Re k ) of both 202 and 334. The numerical method used a sixth-order-accurate centered compact finite difference scheme to represent spatial derivatives, which was used in conjunction with a tenth-order low-pass Pade-type nondispersive filter operator to maintain stability. An implicit approximately factored time-marching algorithm was employed, and Newton-like subiterations were applied to achieve second-order temporal accuracy. Calculations were carried out on a massively parallel computing platform, using domain decomposition to distribute subzones on individual processors. A high-order overset grid approach preserved spatial accuracy on the mesh system used to represent the roughness elements. Features of the flowfields are described, and results of the computations are compared with experimentally measured velocity components of the time-mean flowfield, which are available only for Re k = 202. Flow about the elements is characterized by a system of two weak corotating horseshoe vortices. For Re k = 334, an unstable shear layer emanating from the top of the cylindrical element generated nonlinear unsteady disturbances of sufficient amplitude to produce explosive bypass transition downstream of the array. The Re k = 202 case displayed exponential growth of turbulence energy in the streamwise direction, which may eventually result in transition.
Silicon Device Scaling to the Sub-10-nm Regime

In the next decade, advances in complementary metal-oxide semiconductor fabrication will lead to devices with gate lengths (the region in the device that switches the current flow on and off) below 10 nanometers (nm), as compared with current gate lengths in chips that are now about 50 nm. However, conventional scaling will no longer be sufficient to continue device performance by creating smaller transistors. Alternatives that are being pursued include new device geometries such as ultrathin channel structures to control capacitive losses and multiple gates to better control leakage pathways. Improvement in device speed by enhancing the mobility of charge carriers may be obtained with strain engineering and the use of different crystal orientations. Here, we discuss challenges and possible solutions for continued silicon device performance trends down to the sub-10-nm gate regimes.
Total Synthesis of (+/-)-Tremulenolide A and (+/-)-Tremulenediol A via a Stereoselective Cyclopropanation/Cope Rearrangement Annulation Strategy.

Short total syntheses of (±)-tremulenolide A (1) and (±)-tremulenediol A (2) are described. The critical step is a dirhodium tetracarboxylate-catalyzed tandem cyclopropanation/Cope rearrangement between the vinyldiazoacetate 4 and the 2(Z),4(E)-hexadiene 5. This step results in full control of the relative stereochemistry at the three stereogenic centers that exist in the natural products. Due to problems with alkene face selectivity, the approach was not amenable to an efficient asymmetric synthesis of 1 and 2.
A detailed analytic study of the asymptotic quasinormal modes of Schwarzschild?anti de Sitter black holes

We analyze analytically the asymptotic regions of the quasinormal mode frequency spectra with infinitely large overtone numbers for D-dimensional Schwarzschild black holes in anti de Sitter spacetimes. In this limit, we confirm the analytic results obtained previously in the literature using different methods. In addition, we show that in certain spacetime dimensions these techniques imply the existence of other regions of the asymptotic quasinormal mode frequency spectrum which have not previously appeared in the literature. For large black holes, some of these modes have a damping rate of 1.2TH, where TH is the Hawking temperature. This is less than the damping rate of the lowest overtone quasinormal mode calculated by other authors. It is not completely clear whether these modes actually exist or are an artifact of an unknown flaw in the analytic techniques being used. We discuss the possibility of the existence of these modes and explore some of the consequences. We also examine the possible connection between the asymptotic quasinormal modes of Schwarzschild–anti de Sitter black holes and the quantum level spacing of their horizon area spectrum.
Quarkonium production at ATLAS

The production of quarkonium is an important testing ground for QCD calculations. The J /ψ and γ production cross-sections are measured in proton-proton collisions at a centre-of-mass energy of 7 TeV with the ATLAS detector at the LHC. Differential cross-sections are presented as a function of transverse momentum and rapidity. The fraction of J /ψ produced in B-hadron decays is also measured and the differential cross-sections of prompt and non-prompt J /ψ production determined separately. Measurements of the fiducial production crosssection of the γ(1S) and observation of the χc,bJ states are also discussed.
FINITE-SAMPLE MOMENTS OF THE COEFFICIENT OF VARIATION

We study the finite-sample bias and mean squared error, when properly defined, of the sample coefficient of variation under a general distribution. We employ a Nagar-type expansion and use moments of quadratic forms to derive the results. We find that the approximate bias depends on not only the skewness but also the kurtosis of the distribution, whereas the approximate mean squared error depends on the cumulants up to order 6.
Magnetic Relaxation in Dysprosium-dysprosium Collisions

The collisional magnetic reorientation rate constant ${g}_{R}$ is measured for magnetically trapped atomic dysprosium (Dy), an atom with large magnetic dipole moments. Using buffer gas cooling with cold helium, large numbers ($g{10}^{11}$) of Dy are loaded into a magnetic trap and the buffer gas is subsequently removed. The decay of the trapped sample is governed by collisional reorientation of the atomic magnetic moments. We find ${g}_{R}=1.9\ifmmode\pm\else\textpm\fi{}0.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$ cm${}^{3}$ s${}^{\ensuremath{-}1}$ at 390 mK. We also measure the magnetic reorientation rate constant of holmium (Ho), another highly magnetic atom, and find ${g}_{R}=5\ifmmode\pm\else\textpm\fi{}2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}$ cm${}^{3}$ ${\mathrm{s}}^{\ensuremath{-}1}$ at 690 mK. The Zeeman relaxation rates of these atoms are greater than expected for the magnetic dipole-dipole interaction, suggesting that another mechanism, such as an anisotropic electrostatic interaction, is responsible. Comparison with estimated elastic collision rates suggests that Dy is a poor candidate for evaporative cooling in a magnetic trap.
On the complexity of cutting-plane proofs using split cuts

We prove a monotone interpolation property for split cuts which, together with results from Pudlak (1997) [20], implies that cutting-plane proofs which use split cuts (or, equivalently, mixed-integer rounding cuts or Gomory mixed-integer cuts) have exponential length in the worst case.
Optimizing web servers using page rank prefetching for clustered accesses

This paper presents a Page rank-based prefetching technique for accesses to Web page clusters. The approach uses the link structure of a requested page to determine the "most important" linked pages and to identify the page(s) to be prefetched. The underlying premise of our approach is that in the case of cluster accesses, the next pages requested by users of the Web server are typically based on the current and previous pages requested. Furthermore, if the requested pages have a lot of links to some "important" page, that page has a higher probability of being the next one requested. An experimental evaluation of the prefetching mechanism is presented using real server logs. The results show that the Page rank-based scheme does better than random prefetching for clustered accesses, with hit rates of 90% in some cases.
Mechanisms of hemolysis after mitral valve repair: assessment by serial echocardiography

Abstract Objectives. We sought to determine, using serial echocardiography, the hydrodynamic mechanisms involved in the occurrence of hemolysis after mitral valve repair. Background. Recently, fluid dynamic simulation models have identified distinct patterns of mitral regurgitant flow disturbances in patients with mitral prosthetic hemolysis that were associated with high shear stress and may therefore produce clinical hemolysis. Rapid acceleration, fragmentation, and collision jets were associated with high shear stress and hemolysis whereas slow deceleration and free jets were not. Methods. We reviewed serial echocardiographic studies of 13 consecutive patients with hemolytic anemia after mitral valve repair who were referred for mitral reoperation between January 1985 and December 1996 (group 1). Thirteen patients undergoing reoperation for mitral regurgitation after mitral valve repair but without hemolysis served as controls (group 2). Results. The mitral regurgitant jet was central in origin in 12 group 1 patients and 9 group 2 patients (Fisher exact test, p = 0.3). The other patients had para-ring regurgitation. Group 1 patients had collision (n = 11), rapid acceleration (n = 2) or fragmentation (n = 1) jets whereas group 2 patients had slow deceleration (n = 11) or free jets (n = 2) (Fisher exact test, p Conclusion. Distinct patterns of flow disturbance associated with high shear stress were identified by color Doppler imaging in patients with hemolysis after mitral valve repair. The majority (92%) of these color flow disturbances were not present during intraoperative postbypass TEE study after initial mitral repair and subsequently developed in the early postoperative period.
Metal insulator transition in two-dimensional electron systems

The interplay between strong Coulomb interactions and randomness has been a long-standing problem in condensed matter physics. According to the scaling theory of localization in two-dimensional systems of non-interacting or weakly interacting electrons, the ever-present randomness causes the resistance to rise as the temperature is decreased, leading to an insulating ground state. However, new evidence has emerged within the past decade indicating a transition from the insulating to metallic phase in two-dimensional systems of strongly interacting electrons. We review earlier experiments that demonstrate the unexpected presence of a metallic phase in two dimensions, and present an overview of recent experiments with emphasis on the anomalous magnetic properties that have been observed in the vicinity of the transition.
A direct solver with O(N) complexity for integral equations on one-dimensional domains

An algorithm for the direct inversion of the linear systems arising from Nystrom discretization of integral equations on one-dimensional domains is described. The method typically has O(N) complexity when applied to boundary integral equations (BIEs) in the plane with non-oscillatory kernels such as those associated with the Laplace and Stokes’ equations. The scaling coefficient suppressed by the “big-O” notation depends logarithmically on the requested accuracy. The method can also be applied to BIEs with oscillatory kernels such as those associated with the Helmholtz and time-harmonic Maxwell equations; it is efficient at long and intermediate wave-lengths, but will eventually become prohibitively slow as the wave-length decreases. To achieve linear complexity, rank deficiencies in the off-diagonal blocks of the coefficient matrix are exploited. The technique is conceptually related to the ℋ- and ℋ2-matrix arithmetic of Hackbusch and co-workers, and is closely related to previous work on Hierarchically Semi-Separable matrices.
Norm of a Bethe Vector and the Hessian of the Master Function

We show that the norm of a Bethe vector in the $sl_{r+1}$ Gaudin model is equal to the Hessian of the corresponding master function at the corresponding critical point. In particular the Bethe vectors corresponding to non-degenerate critical points are non-zero vectors. This result is a byproduct of functorial properties of Bethe vectors studied in this paper. As another byproduct of functoriality we show that the Bethe vectors form a basis in the tensor product of several copies of first and last fundamental $sl_{r+1}$ -modules.
Reward structures and the allocation of talent

As relative rewards that different professions receive are a key factor in the allocation of talent, what determines the reward structure of a society is an important question. This paper develops an equilibrium model of the allocation of talent between productive and unproductive activities (such as rent-seeking). The existence of rent-seeking creates a negative externality on productive agents and implies that relative rewards are endogenously determined. The same externality can also lead to the existence of multiple equilibria, each with different reward structures. In a dynamic setting, allocations of past generations as well as expectations of future allocations influence current rewards and the society may get trapped in a ‘rent-seeking’ steady state equilibrium. The paper also discusses how the non-pecuniary reward structure can be influenced by equilibrium selection and a historical example that suggests the presence of a causal link from the allocation of talent to non-pecuniary rewards.
Nonsurgical treatment of hepatocellular carcinoma.

While surgical resection and tumor ablation are the preferred therapies for hepatocellular carcinoma (HCC), these are available or appropriate in only a minority of patients. This reflects the usual comorbidity of severe underlying liver disease that either precludes surgery or makes the surgical approach extremely dangerous. Nonetheless, regional control of HCC is highly relevant and many regional strategies have been explored, including hepatic intra-arterial chemotherapy transarterial chemoembolization, lipiodol chemoembolization, radiation therapy, cryosurgery, percutaneous ethanol injection, and radiofrequency ablation. In addition, a variety of systemic chemotherapeutic agents have been tested in HCC, including various combinations of 5-fluorouracil, doxorubicin, epirubicin, etoposide, cisplatin, and mitoxantrone, as well as interferon, tamoxifen, capecitabine, thalidomide, and octreotide. Published data regarding these regional and systemic therapies will be discussed in this review.
A Mixed-Flow Cascade Passage Design Procedure Based on a Power Series Expansion

Flow passage design and analysis procedures employing a TAYLOR series expansion across the flow field were first suggested as far back as 1908. With very few exceptions the early work addressed only the problem of symmetrical convergent-divergent passages. A generalization and an extension of the approach permits it to be used for the design of arbitrary cascade passages in subsonic, supersonic, or mixed-flow regimes. The method will give fast, realistic solutions in situations where shock-free flow is meaningful, and where the cascade gap-chord ratio is not excessive. It assumes inviscid, irrotational flow and employs a fourth-order TAYLOR series expansion across the cascade passage. Numerous examples are given, with comparisons with experimental data and other analytic solutions.
Spatial Interaction, Spatial Multipliers and Hospital Competition

Abstract The hospital competition literature shows that estimates of the effect of local market structure (concentration) on pricing (competition) are sensitive to geographic market definition. Our spatial lag model approach effects smoothing of the explanatory variables across the discrete market boundaries, resulting in robust estimates of the impact of market structure on hospital pricing, which can be used to estimate the full effect of changes in prices inclusive of spillovers that cascade through the neighboring hospital markets. The full amount, generated by the spatial multiplier effect, is a robust estimate of the impacts of market factors on hospital competition. We contrast ordinary least squares and spatial lag estimates to demonstrate the importance of robust estimation in analysis of hospital market competition. In markets where concentration is relatively high before a proposed merger, we demonstrate that Ordinary Least Squares (OLS) can lead to the wrong policy conclusion while the more co...
NASA High Contrast Imaging for Exoplanets

Described is NASA's ongoing program for detection and characterization of exo-solar planets via high-contrast imaging. Some of the more promising proposed techniques under assessment may enable detection of life outside our solar system.
Damping of Terrestrial-Planet Eccentricities by Density-Wave Interactions with a Remnant Gas Disk

We examine the damping of terrestrial-planet eccentricities via density-wave interactions with a remnant gas disk that postdated the accretionary epoch. A lower limit is estimated for the gas surface density present in the terrestrial zone required for acoustic damping to be effective, and a simple model for describing the disk's influence on the planet eccentricities is presented. The results suggest that the terrestrial-planet eccentricities could be reduced from values permitting crossing orbits to the present-day values by a remnant disk with gas surface density of ~10-3-10-4 times the minimum-mass solar nebula value and characteristic gas dissipation timescales of 106-107 yr.
The 1.6 m off-axis New Solar Telescope (NST) in Big Bear

The 1.6-m New Solar Telescope (NST) has been used to observe the Sun for more than three years with ever increasing capabilities as its commissioning phase winds down. The NST is the first facility-class solar telescope built in the U.S. in a generation, and it has an off-axis design as is planned for the 4 m Advanced Technology Solar Telescope. Lessons learned will be discussed. Current NST post-focus instrumentation includes adaptive optics (AO) feeding photometric and near-IR polarimetric sytems, as well as an imaging spectrograph. On-going instrumentation projects will be sketched, including Multi-Conjugate AO (MCAO), next generation (dual Fabry- Perot) visible light and near-IR polarimeters and a fully cryogenic spectrograph. Finally, recent observational results illustrating the high resolution capabilities of the NST will be shown.
Vanadium–phosphatase complexes: Phosphatase inhibitors favor the trigonal bipyramidal transition state geometries

Abstract Over the past two decades increasing information about the function and structural detail of phosphatases has become available detailing the interaction with vanadate or other vanadium compounds. Considering the importance of the phosphorylation reaction in signal transductions the structural details of the interaction of vanadate or other vanadium species with many phosphatases are used to provide information on the nature of successful inhibitors of these enzymes. Analysis shows that most of the available X-ray structures of vanadium–phosphatase complexes contain vanadium with five coordinating atoms in trigonal bipyramidal coordination geometries even though corresponding small molecule analog compounds may have square pyramidal geometries. This finding for the static structures in their solid state documents the fact that the variety of phosphatases all stabilize a vanadium geometry that is closer to the trigonal bipyramidal geometry than square pyramidal geometry. We also review the efficacy of vanadium-based inhibitors and examine both oxometalates and vanadium coordination complexes. The evaluation of the inhibitory efficacies of the oxometalates provides the opportunity to identify product-based inhibitors and transition-state-based inhibitors. Whether initial coordination geometry is important to inhibitor design geometry was examined. For vanadium–phosphatase complexes, regardless of what form was added to the protein crystal in all but one case vanadate was found bound in the phosphatase. Because of speciation considerations and prior hydrolysis of potential vanadium complexes, this result may be a consequence of the experimental conditions. With regard to inhibition we find that the coordination geometry of the starting complex does not need to be trigonal bipyramidal to result in a effective phosphatase inhibitor and that all reported phosphatase inhibitors span a range of only three orders of magnitude in K i across all phosphatases examined.
Electronic control of helical chirality

Chiral phenomena are common in living systems. Despite the fact that development of materials has often been inspired by chemistry from the biological world, materials that take advantage of inherent chirality have found relatively few applications. It is therefore probable that much remains to be gained from novel applications of molecular, macromolecular and supramolecular chirality. Among the most intriguing recent advances in studies of chiral materials is the development of mechanisms to control the shape and properties of chiral molecules. Photo-induced helical chirality inversions have been studied for several years and significant achievements have been reported. Recently, electronically triggered systems have drawn significant attention. These technologies offer the potential for development of novel materials that take advantage of photonic or electronic modulation of molecular recognition, optical or mechanical properties.
Expectations for the Difference between Local and Global Measurements of the Hubble Constant

There are irreducible differences between the Hubble constant measured locally and the global value. They are due to density perturbations, a finite sample volume (cosmic variance), and a finite number of objects in the sample (sampling variance). We quantify these differences for a suite of COBE-normalized cold dark matter models that are consistent with the observed large-scale structure. For small samples of objects that only extend to 10,000 km s-1, the variance can approach 4%. For the largest samples of Type Ia supernovae (SNe Ia), which include about 40 objects and extend to almost 40,000 km s-1, the variance is 1%-2% and is dominated by sampling variance. Sampling and cosmic variance may be an important consideration in comparing local determinations of the Hubble constant with precision determinations of the global value that will be made from high-resolution maps of cosmic background radiation anisotropy.
Polymerization of Pu(IV) in aqueous nitric acid solutions

Abstract The polymerization of Pu(IV) in aqueous nitric acid solutions has been studied spectrophotometrically both to determine the effects of large UO2(NO3)2 concentrations on the polymerization rates and, more generally, to review the influence of other major parameters on the polymer reaction. Typically, experiments have been performed at 50°C and at 0.05M Pu in aqueous solutions of HNO3 at concentrations ranging from 0.07 to 0.4M. An induction period usually precedes the polymer growth stage, during which time it is believed that primary hydrolysis products form and begin to aggregate. Uranyl nitrate retards the polymerization reaction by approximately 35% despite the counteracting influence of the nitrate ions associated with this solute. The rate of polymer formation at 50°C has been shown to be third order in Pu(IV) concentration.
The Orbifold Higgs

We introduce and systematically study an expansive class of “orbifold Higgs” theories in which the weak scale is protected by accidental symmetries arising from the orbifold reduction of continuous symmetries. The protection mechanism eliminates quadratic sensitivity of the Higgs mass to higher scales at one loop (or more) and does not involve any new states charged under the Standard Model. The structures of the Higgs and top sectors are universal and determined exclusively by group theoretical considerations. The twin Higgs model fits within our framework as the simplest example of an orbifold Higgs. Our models admit UV completions as geometric orbifolds in higher dimensions, and fit naturally within frameworks of low scale gauge coupling unification.
Phonon-mediated detection of X-rays in silicon crystals using superconducting transition edge phonon sensors

Abstract We present data on the operation of thin film superconducting strips of titanium as phonon sensors on the surface of silicon crystals. The superconducting films are biased at the foot of the resistive transition in temperature, and below the critical latching current (the current above which a normal region in the film grows from self-heating). The interaction of an incident X-ray in the Si crystal generates a phonon source which propogates to the surface at the speed of sound. Such an event produces a several μs long self-terminating voltage pulse which is proportional to the amount of the sensor area driven normal. We show that these Ti superconducting transition edge (TE) sensors operated at 0.3 K have sufficient resolution for detecting particles with energy deposition above several keV, which makes them good candidates for use in neutrino (and other) experiments.