cssi/SciSciGPT-SciSciNet huggingface dataset:
Fault‐tolerant control allocation for Mars entry vehicle using adaptive control

Accurate and reliable control of planetary entry is a major challenge for planetary exploration vehicles. For Mars entry, uncertainties in atmospheric properties such as winds aloft and density pose a major problem for meeting precision landing requirements. Anticipated manned missions to Mars will also require levels of safety and fault tolerance not required during earlier robotic missions. This paper develops a nonlinear fault-tolerant controller specifically tailored for addressing the unique environmental and mission demands of future Mars entry vehicles. The controller tracks a desired trajectory from entry interface to parachute deployment, and has an adaptation mechanism that reduces tracking errors in the presence of uncertain parameters such as atmospheric density, and vehicle properties such as aerodynamic coefficients and inertias. This nonlinear control law generates the commanded moments for a discrete control allocation algorithm, which then generates the optimal controls required to follow the desired trajectory. The reaction control system acts as a non-uniform quantizer, which generates applied moments that approximate the desired moments generated by a continuous adaptive control law. If a fault is detected in the control jets, it reconfigures the controls and minimizes the impact of control failures or damage on trajectory tracking. It is assumed that a fault identification and isolation scheme already exists to identify failures. A stability analysis is presented, and fault tolerance performance is evaluated with non real-time simulation for a complete Mars entry trajectory tracking scenario using various scenarios of control effector failures. The results presented in the paper demonstrate that the control algorithm has a satisfactory performance for tracking a pre-defined trajectory in the presence of control failures, in addition to plant and environment uncertainties. Copyright © 2010 John Wiley & Sons, Ltd.
On the Relation Between Open and Closed Topological Strings

We discuss the relation between open and closed string correlators using topological string theories as a toy model. We propose that one can reconstruct closed string correlators from the open ones by considering the Hochschild cohomology of the category of D-branes. We compute the Hochschild cohomology of the category of D-branes in topological Landau-Ginzburg models and partially verify the conjecture in this case.
Systems Analysis of Noise Abatement Procedures Enabled by Advanced Flight Guidance Technology

Advanced flight guidance technologies such as area navigation utilizing the global positioning system offer the potential to reduce the impact of aircraft noise on communities surrounding airports by enabling more flexible approach and departure procedures that reduce noise exposure to the most sensitive areas. A systems analysis is presented of noise abatement procedures enabled by these technologies. NOISIM, the primary systems analysis tool, combines a flight simulator, a noise model, and a geographic information system to create a unique rapid prototyping environment in which the user can simulate an aircraft's operation in existing and potential guidance and navigation environments, while simultaneously evaluating the aircraft's noise impact. The analysis included generic and site specific studies of approach and departure procedures using 737-200 noise estimates. The results of the generic study of approach procedures indicate that a 3-deg decelerating approach provides significant noise reductions in comparison to the baseline instrument landing system (ILS) approach and is preferred by pilots to the more complex vertically segmented approach. In a study of approaches to runway 13L at Kennedy Airport, a 3-deg decelerating approach reduced the population impacted by noise greater than 60 dBA from over 250,000 in the ILS approach to less than 70,000. The results of the generic study of departure procedures indicate that the benefits of noise abatement departures are site specific. In a study of departures from runway 4R at Logan Airport, a noise abatement departure that combined a targeted thrust cutback with a dual turn lateral trajectory reduced the population impacted by peak noise greater than 60 dBA by over 15%.
THE VALUE OF AGRICULTURAL ECONOMICS EXTENSION PROGRAMMING: AN APPLICATION OF CONTINGENT VALUATION

We use the contingent valuation method to estimate participant willingness to pay for agricultural economics extension programming. The data, collected as part of standard evaluation forms for the Ohio State University's 2001 Agricultural Outlook and Policy program series, and subsequent analysis suggest participant benefits exceeded departmental costs of conducting the program (benefit-cost ratios of 1.07 under conservative assumptions and 1.74 under moderate assumptions). We also use the data to explore the revenue generation potential from alternative program pricing and discuss the potential for developing differentiated programs to reach distinct audience segments. Additional research necessary before implementing alternative pricing or program differentiation plans is also discussed.
DISCRETE APPROXIMATIONS OF DIFFERENTIAL EQUATIONS VIA TRIGONOMETRIC INTERPOLATION

To approximate solutions of a linear differential equation, we project, via trigonometric interpolation, its solution space onto a finite-dimensional space of trigonometric polynomials and construct a matrix representation of the differential operator associated with the equation. We compute the ranks of the matrix representations of a certain class of linear differential operators. Our numerical tests show high accuracy and fast convergence of the method applied to several boundary and eigenvalue problems.
The Ionization and Metallicity of the Intervening O VI Absorber at Z=0.1212 in the Spectrum of H1821+643

We use high-resolution UV (ultraviolet) spectra of the radio-quiet QSO (quasi-stellar object) H1821+643 (z(sub em) = 0.297), obtained with the Space Telescope Imaging Spectrograph (STIS) and the Far Ultraviolet Spectroscopic Explorer (FUSE), to study the ionization and metallicity of an intervening O VI absorption line system at z(sub abs) = 0.1212. This absorber has the following notable properties: (1) Several galaxies are close to the sight line at the absorber redshift, including an actively star-forming galaxy at a projected distance of 144 h(sub 75)(exp -1) kpc. (2) There is a complex cluster of H I Ly(alpha) absorption lines near the O VI redshift, including at least five components spread over a velocity range of approximately 700 km s(exp -1). (3) The strongest Ly(alpha) line in the cluster appears to be composed of a mildly saturated component with a typical b-value blended with a remarkably broad component with b approximately equals 85 km s(exp -1). (4) The O VI absorption is not aligned with the strongest (saturated) H I absorption, but instead is well-aligned with the very broad component. (5) The only detected species (at the 4(sigma) level) are O VI and H I despite coverage of strong transitions of abundant elements (e.g., C II, C III, and C IV). Based on these constraints, we find that the absorption line properties can be produced in collisionally ionized gas with 10(exp 5.3) is equal to or less than T is equal to or less than 10(exp 5.6) K and -1.8 is equal to or less than [O/H] is equal to or less than -0.6. However, we find that photoionization is also viable if the pathlength l through the absorbing gas is long enough; simple photoionization models require 85 is equal to or less than l is equal to or less than 1900 kpc and -1.1 is equal to or less than [O/H] is equal to or less than -0.3. We briefly discuss how observations of X-ray absorption lines due to O VII and O VIII could be used, in principle, to break the ionization mechanism degeneracy, and we conclude with some comments regarding the nature of O VI absorbers.
The accuracy of reports of foreign exchange intervention

Abstract This paper considers both qualitative and quantitative evidence on the accuracy of press reports of foreign exchange intervention by the Federal Reserve between January 1985 and December 1989. The evidence shows that the likelihood of intervention being reported given that it actually occurred was 72 per cent and that the likelihood of intervention actually occurring given that it was reported was 88 per cent. Interventions which were reported were larger on average than those which were not reported and this difference is statistically significant. Multinomial logit analysis also demonstrates that the likelihood of intervention being reported increased with the size of the intervention. (JEL F31).
Homotopical intersection theory I

We give a new approach to intersection theory. Our "cycles" are closed manifolds mapping into compact manifolds and our "intersections" are elements of a homotopy group of a certain Thom space. The results are then applied in various contexts, including fixed point, linking and disjunction problems. Our main theorems resemble those of Hatcher and Quinn [17], but our proofs are fundamentally different. Errata Minor errors were corrected on page 967 (18 February 2008).
A Spitzer Search for Infrared Excesses around Massive Young White Dwarfs

We examine 14 hot white dwarfs for signs of infrared excess using the Spitzer Space Telescope. Twelve of the objects are massive white dwarfs that have been suggested to be the result of binary mergers. The remaining two objects are undermassive white dwarfs that again may be the result of mergers, or of the in-spiral of a substellar companion. In no case do we find any evidence for significant infrared excesses out to wavelengths of 8 μm. This places strong constraints on the presence of orbiting dust and weaker constraints on the presence of close substellar companions.
Shear thickening in concentrated suspensions: phenomenology, mechanisms and relations to jamming

Shear thickening is a type of non-Newtonian behavior in which the stress required to shear a fluid increases faster than linearly with shear rate. Many concentrated suspensions of particles exhibit an especially dramatic version, known as Discontinuous Shear Thickening (DST), in which the stress suddenly jumps with increasing shear rate and produces solid-like behavior. The best known example of such counter-intuitive response to applied stresses occurs in mixtures of cornstarch in water. Over the last several years, this shear-induced solid-like behavior together with a variety of other unusual fluid phenomena has generated considerable interest in the physics of densely packed suspensions. In this review, we discuss the common physical properties of systems exhibiting shear thickening, and different mechanisms and models proposed to describe it. We then suggest how these mechanisms may be related and generalized, and propose a general phase diagram for shear thickening systems. We also discuss how recent work has related the physics of shear thickening to that of granular materials and jammed systems. Since DST is described by models that require only simple generic interactions between particles, we outline the broader context of other concentrated many-particle systems such as foams and emulsions, and explain why DST is restricted to the parameter regime of hard-particle suspensions. Finally, we discuss some of the outstanding problems and emerging opportunities.
Power Series and p-Adic Algebraic Closures

Abstract We describe a presentation of the completion of the algebraic closure of the ring of Witt vectors of an algebraically closed field of characteristic p>0. The construction uses “generalized power series in p” as constructed by Poonen, based on an example of Lampert, and also makes use of an analogous construction of the algebraic closure of a field of power series in positive characteristic.
Secondary characteristic classes and cyclic cohomology of Hopf algebras

Abstract Let X be a manifold on which a discrete (pseudo)group of diffeomorphisms Γ acts, and let E be a Γ-equivariant vector bundle on X. We give a construction of cyclic cocycles on the cross product algebra C0∞(X)⋊Γ representing the equivariant characteristic classes of E. Our formulas can be viewed as a higher-dimensional analogue of Connes’ Godbillon–Vey cyclic cocycle. An essential tool for our construction, which allows us to overcome difficulties arising in the higher-dimensional case, is Connes–Moscovici's theory of cyclic cohomology of Hopf algebras.
Cognate Space Identification for Forced Response Structural Redesign

Large admissible perturbations (LEAP) is a general methodology, which solves redesign problems of complex structures with, among others, forced response amplitude constraints. In previous work, two LEAP algorithms, namely the incremental method (IM) and the direct method (DM), were developed. A powerful feature of LEAP is the general perturbation equations derived in terms of normal modes, the selection of which is a determinant factor for a successful redesign. The normal modes of a structure may be categorized as stretching, bending, torsional, and mixed modes and grouped into cognate spaces. In the context of redesign by LEAP, the physical interpretation of a mode-to-response cognate space lies in the fact that a mode from one space barely affects change in a mode from another space. Perturbation equations require computation of many perturbation terms corresponding to individual modes. Identifying modes with negligible contribution to the change in forced response amplitude eliminates a priori computation of numerous perturbation terms. Two methods of determining mode-to-response cognate spaces, one for IM and one for DM, are presented and compared. Trade-off between computational time and accuracy is assessed in order to provide practical guidelines to the designer. The developed LEAP redesign algorithms are applied to the redesign of a simple cantilever beam and a complex offshore tower.
Beat Cepheids as Probes of Stellar and Galactic Metallicity

The mere location of a beat Cepheid model in a period ratio versus period diagram (Petersen diagram) puts very tight constraints on its metallicity Z. The beat Cepheid Petersen diagrams are revisited with linear nonadiabatic turbulent convective models, and their accuracy as a probe for stellar metallicity is evaluated. They are shown to be largely independent of the helium content Y, and they are also only weakly dependent on the mass-luminosity relation that is used in their construction. However, they are found to show sensitivity to the relative abundances of the elements that are lumped into the metallicity parameter Z. Rotation is estimated to have but a small effect on the "pulsation metallicities." A composite Petersen diagram is presented that allows one to read off upper and lower limits on the metallicity Z from the measured period P0 and period ratio P10.
Exact zero-temperature correlation functions for two-leg Hubbard ladders and carbon nanotubes

Motivated by recent work of Lin, Balents, and Fisher [Phys. Rev. B 58, 1794 (1998)], we compute correlation functions at zero temperature for weakly coupled two-leg Hubbard ladders and $(N,N)$ armchair carbon nanotubes. In this paper it was argued that such systems renormalize towards the SO(8) Gross-Neveu model, an integrable theory. We exploit this integrability to perform the computation at the SO(8) invariant point. Any terms breaking the SO(8) symmetry can be treated systematically in perturbation theory, leading to a model with the same qualitative features as the integrable theory. Using said correlators, we determine the optical conductivity, the single-particle spectral function, and the $I\ensuremath{-}V$ curve for tunneling into the system from an external metallic lead. The frequency, \ensuremath{\omega}, dependent optical conductivity is determined exactly for $\ensuremath{\omega}l3m$ $(m$ being the fermion particle mass in the SO(8) Gross-Neveu model). It is characterized by a sharp ``exciton'' peak at $\ensuremath{\omega}=\sqrt{3}m,$ followed by the onset of the particle-hole continuum beginning at $\ensuremath{\omega}=2m.$ Interactions modify this onset to $\ensuremath{\sigma}(\ensuremath{\omega}+2m)\ensuremath{\sim}{\ensuremath{\omega}}^{1/2}$ and not the ${\ensuremath{\omega}}^{\ensuremath{-}1/2}$ one would expect from the van Hove singularity in the density of states. Similarly, we obtain the exact single-particle spectral function for energies less than $3m.$ The latter possesses a $\ensuremath{\delta}$ function peak arising from single-particle excitations, together with a two-particle continuum for $\ensuremath{\omega}g~2m.$ The final quantity we compute is the tunneling $I\ensuremath{-}V$ curve to lowest nonvanishing order in the tunneling matrix elements. For this quantity, we present exact results for voltages, $Vl(1+\sqrt{3})m.$ The resulting differential conductance is marked by a finite jump at $\ensuremath{\omega}=2m,$ the energy of the onset of tunneling into the continuum of two-particle states. Through integrability, we are able to characterize this jump exactly. All calculations are done through form-factor expansions of correlation functions. These give exact closed form expressions for spectral functions because the SO(8) Gross-Neveu model is massive: each term in the expansion has an energy threshold below which it does not contribute. Thus, we obtain exact results below certain thresholds by computing a finite number of terms in this series. Previous to this paper, the only computed form factor of SO(8) Gross-Neveu was the two-particle form factor of an SO(8) current with two fundamental fermions. In this paper we compute the set of all one- and two-particle form factors for all relevant fields, the currents as well as the kinks and fermions.
Ensemble of metamodels with optimized weight factors

Approximate mathematical models (metamodels) are often used as surrogates for more computationally intensive simulations. The common practice is to construct multiple metamodels based on a common training data set, evaluate their accuracy, and then to use only a single model perceived as the best while discarding the rest. This practice has some shortcomings as it does not take full advantage of the resources devoted to constructing different metamodels, and it is based on the assumption that changes in the training data set will not jeopardize the accuracy of the selected model. It is possible to overcome these drawbacks and to improve the prediction accuracy of the surrogate model if the separate stand-alone metamodels are combined to form an ensemble. Motivated by previous research on committee of neural networks and ensemble of surrogate models, a technique for developing a more accurate ensemble of multiple metamodels is presented in this paper. Here, the selection of weight factors in the general weighted-sum formulation of an ensemble is treated as an optimization problem with the desired solution being one that minimizes a selected error metric. The proposed technique is evaluated by considering one industrial and four benchmark problems. The effect of different metrics for estimating the prediction error at either the training data set or a few validation points is also explored. The results show that the optimized ensemble provides more accurate predictions than the stand-alone metamodels and for most problems even surpassing the previously reported ensemble approaches.
Income level and the energy consumption–GDP nexus: Evidence from Sub-Saharan Africa

This study tests the relationship between energy consumption and economic growth in Sub-Saharan Africa, using a panel co-integration approach. Country-level time series data of energy consumption and economic growth are pooled and used to estimate the model. Sub-Saharan African countries in the sample are classified into low income and middle income countries. The findings support the neutrality hypothesis in the short-run, except for middle income countries, and a strong causation running in both directions is found in the long-run. The different results for low and middle income countries provide evidence of the importance of income level in the causal relationship. This study helps to explain the interdependence of energy consumption and economic growth in Sub-Saharan Africa. Results are critical in formulating sustainable development policies that are geared to the efficient allocation of resources which are expected to increase access to energy services in the study region.
Clifford Code Constructions of Operator Quantum Error-Correcting Codes

Recently, operator quantum error-correcting codes have been proposed to unify and generalize decoherence free subspaces, noiseless subsystems, and quantum error-correcting codes. This correspondence introduces a natural construction of such codes in terms of Clifford codes, an elegant generalization of stabilizer codes due to Knill. Character-theoretic methods are used to derive a simple method to construct operator quantum error-correcting codes from any classical additive code over a finite field, which obviates the need for self-orthogonal codes.
Spatially Distributed Transducers: Part II—Augmented Transmission Line Models

We present a class of models which is useful for spatially distributed transducers in which the response at one location is coupled to that at other locations. If only one element is used at every location to represent the interaction of the transducer and the environment, and only one type of source is present, then there are only four general models which need to be considered
Dynamics of a family of piecewise-linear area-preserving plane maps III. Cantor set spectra

This paper studies the behavior under iteration of the maps T ab (x,y) = (F ab (x) − y, x) of the plane ℝ2, in which F ab (x) = ax if x ≥ 0 and bx if x < 0. These maps are area-preserving homeomorphisms of ℝ2 that map rays from the origin to rays from the origin. Orbits of the map correspond to solutions of the nonlinear difference equation x n+2 = 1/2(a − b)|x n+1|+1/2(a+b)x n+1 − x n . This difference equation can be rewritten in an eigenvalue form for a nonlinear difference operator of Schrodinger type − x n+2+2x n+1 − x n +V μ(x n+1)x n+1 = Ex n+1, in which μ = (1/2)(a − b) is fixed, and V μ(x) = μ(sgn(x)) is an antisymmetric step function potential, and the energy E = 2 − 1/2(a+b). We study the set Ω SB of parameter values where the map T ab has at least one bounded orbit, which correspond to l ∞-eigenfunctions of this difference operator. The paper shows that for transcendental μ the set Spec∞[μ] of energy values E having a bounded solution is a Cantor set. Numerical simulations suggest the possibil...
Theoretical study of phase-shifted quantum beats in time-resolved luminescence spectra from a biased asymmetric double quantum well

Abstract Analytical expressions have been developed for time-dependent luminescence intensities for a practically feasible asymmetric double quantum well under bias and numerically demonstrated to elucidate the characteristic of π-phase-shifted quantum beats. It is clear analytically as well as numerically that the magnitude of the tunneling interaction can be quantitatively estimated by the beat modulation depth.
Sponsor Prominence and Responses Patterns to an Online Survey

This research note examines the effects of sponsor prominence on response patterns, namely the response rate and break-off rate, on University of Wisconsin-Madison faculty, staff, and students asked to participate in a survey on campus transportation issues by either the campus transportation department or campus survey center. Sponsor-prominence did not have a significant effect on response rate, but it did have an effect on the break-off rate.
Statistical Analysis of Molecular Signal Recording

A molecular device that records time-varying signals would enable new approaches in neuroscience. We have recently proposed such a device, termed a “molecular ticker tape”, in which an engineered DNA polymerase (DNAP) writes time-varying signals into DNA in the form of nucleotide misincorporation patterns. Here, we define a theoretical framework quantifying the expected capabilities of molecular ticker tapes as a function of experimental parameters. We present a decoding algorithm for estimating time-dependent input signals, and DNAP kinetic parameters, directly from misincorporation rates as determined by sequencing. We explore the requirements for accurate signal decoding, particularly the constraints on (1) the polymerase biochemical parameters, and (2) the amplitude, temporal resolution, and duration of the time-varying input signals. Our results suggest that molecular recording devices with kinetic properties similar to natural polymerases could be used to perform experiments in which neural activity is compared across several experimental conditions, and that devices engineered by combining favorable biochemical properties from multiple known polymerases could potentially measure faster phenomena such as slow synchronization of neuronal oscillations. Sophisticated engineering of DNAPs is likely required to achieve molecular recording of neuronal activity with single-spike temporal resolution over experimentally relevant timescales.
Pollution claim settlements under private information

Abstract The classical problem of resolving a nuisance dispute between a pollution-generating firm and nearby residents is modelled here as a mechanism-design problem. We assume that the designer of the mechanism is the firm, that it is uncertain about the actual losses suffered by residents and that the initial assignment of property rights is one where each resident is entitled to prevail. We derive a profitmaximizing scheme under the individual-rationality and incentive-compatibility constraints and examine its properties. It is shown that the outcomes it yields are sometimes inefficient. Moreover, when many residents are affected by pollution and the degree of uncertainty with respect to the losses they suffer is large, these inefficiencies become rampant.
Quantum Transport in Semiconductor Devices

It is clear that continued scaling of semiconductor devices will bring us to a regime in which device gate lengths are less than 50 nm within another decade. Pushing to dimensional sizes such as this will probe the transition from classical to quantum transport, and there is no present approach to the quantum regime that has proved effective. Contrary to the classical case in which electrons are negligibly small, the finite extent of the momentum space available to the electron sets size limitations on the minimum wave packet—this is of the order of a few nanometers. While quantum transport formalism has been applied to a variety of problems, in most cases it has not been overly successful. In this paper, we discuss the problems and some of the approximate approaches which will ease the above-mentioned transition.
Scattering of zero branes off elementary strings in matrix theory

We consider the scattering of zero-branes off an elementary string in Matrix theory or equivalently gravitons off a longitudinally wrapped membrane. The leading supergravity result is recovered by a one-loop calculation in zero-brane quantum mechanics. Simple scaling arguments are used to show that there are no further corrections at higher loops, to the leading term in the large impact parameter, low velocity expansion. The mechanism for this agreement is identified in terms of properties of a recently discovered boundary conformal field theory.
Structural Breaks and Predictive Regression Models of Aggregate U.S. Stock Returns

In this article we examine the structural stability of predictive regression models of U.S. quarterly aggregate real stock returns over the postwar era. We consider predictive regressions models of S&P 500 and CRSP equal-weighted real stock returns based on eight financial variables that display predictive ability in the extant literature. We test for structural stability using the popular Andrews SupF statistic and the Bai subsample procedure in conjunction with the Hansen heteroskedastic fixed-regressor bootstrap. We also test for structural stability using the recently developed methodologies of Elliott and Muller, and Bai and Perron. We find strong evidence of structural breaks in five of eight bivariate predictive regression models of S&P 500 returns and some evidence of structural breaks in the three other models. There is less evidence of structural instability in bivariate predictive regression models of CRSP equal-weighted returns, with four of eight models displaying some evidence of structural breaks. We also obtain evidence of structural instability in a multivariate predictive regression model of S&P 500 returns. When we estimate the predictive regression models over the different regimes defined by structural breaks, we find that the predictive ability of financial variables can vary markedly over time. Copyright 2006, Oxford University Press.
A Better Deal for Cohabiting Fathers' Union Status Differences in Father Involvement

We use investment theory to study the trajectory of father involvement over time as a function of union status and union transition. Data on 4,311 mother-father pairs are from the Fragile Families and Child Well-Being Study. Fathers who remain in a continuous co-residential union, who transition from cohabitation to marriage, or who transition from a non-coresidential state to a co-residential union experience the highest levels of father involvement. Fathers who are continuously nonresident exhibit the lowest levels of involvement. Cohabiting fathers exhibit higher levels of father involvement than married fathers. A positive coparenting relationship is associated with higher levels of involvement. We discuss the place of cohabiting families in light of our findings.
Distributed storage for intermittent energy sources: Control design and performance limits

One of the most important challenges in the integration of renewable energy sources into the power grid lies in their ‘intermittent’ nature. The power output of sources like wind and solar varies with time and location due to factors that cannot be controlled by the provider. Two strategies have been proposed to hedge against this variability: 1) use energy storage systems to effectively average the produced power over time; 2) exploit distributed generation to effectively average production over location. We introduce a network model to study the optimal use of storage and transmission resources in the presence of random energy sources. We propose a Linear-Quadratic based methodology to design control strategies, and show that these strategies are asymptotically optimal for some simple network topologies. For these topologies, the dependence of optimal performance on storage and transmission capacity is explicitly quantified.
Thermodynamic aspects of the crevice corrosion of iron in chromate/chloride solutions

Abstract Potential-pH data are reported for the crevice corrosion of iron in 23 different chromate/chloride solutions. In all solutions where there was crevice corrosion, the steady-state electrode potential of iron with the crevice was −0.600 to 0.650 V(Ag/AgCl); and the crevice pH was between 4.5 and 6.0. These values correspond to the region of the Fe/H 2 O equilibrium diagram where iron undergoes corrosion as Fe 2+ and where hydrogen evolution is thermodynamically possible. For the CrO 4 2− /Cl − solutions where crevice corrosion was inhibited, the potential-pH values correspond to the domain of passivation by Fe 2 O 3 + Cr 2 O 3 . Surfaces which pit when open do not necessarily undergo crevice corrosion when shielded. Electrode potentials for the initiation of crevice corrosion are more negative than the critical pitting potential for open iron surfaces in the same solution, and the electrode potential in the active crevice becomes more negative with time. The resulting steady-state potential of −0.630 ± 0.025 V(Ag/AgCl) is in good agreement with experimental values for scaled-up models of crevices or pits and with the theoretical value calculated previously from concentrated solution thermodynamics.
Multiple-Trace Operators and Non-Local String Theories

We propose that a novel deformation of string perturbation theory, involving non-local interactions between strings, is required to describe the gravity duals of field theories deformed by multiple-trace operators. The new perturbative expansion involves a new parameter, which is neither the string coupling nor the coefficient of a vertex operator on the worldsheet. We explore some of the properties of this deformation, focusing on a special case where the deformation in the field theory is exactly marginal.
Self-stabilizing population protocols

This article studies self-stabilization in networks of anonymous, asynchronously interacting nodes where the size of the network is unknown. Constant-space protocols are given for Dijkstra-style round-robin token circulation, leader election in rings, two-hop coloring in degree-bounded graphs, and establishing consistent global orientation in an undirected ring. A protocol to construct a spanning tree in regular graphs using O(log D) memory is also given, where D is the diameter of the graph. A general method for eliminating nondeterministic transitions from the self-stabilizing implementation of a large family of behaviors is used to simplify the constructions, and general conditions under which protocol composition preserves behavior are used in proving their correctness.
Spitzer Spectra of a 10 mJy Galaxy Sample and the Star Formation Rate in the Local Universe

A complete flux-limited sample of 50 galaxies is presented having fν(24 μm) > 10 mJy, chosen from a survey with MIPS on Spitzer of 8.2 deg2 in the NOAO Deep Wide-Field Survey (NDWFS) region in Bootes. Spectra obtained with the low-resolution modules of IRS on Spitzer are described for 36 galaxies in this sample; 25 show strong PAH emission features characteristic of starbursts, and 11 show silicate absorption or emission, emission lines, or featureless spectra characteristic of AGNs. Infrared or optical spectral classifications are available for 48 of the entire sample of 50; 33 galaxies are classified as starbursts and 15 as AGNs. [There are an additional 19 Galactic stars with fν(24 μm) > 10 mJy in the survey area.] Using a relation between 7.7 μm PAH luminosity and SFR derived from previous IRS observations of starbursts, the SFR per unit volume of the local universe (SFRD) is determined from the complete sample and is found to be 0.008 M☉ yr-1 Mpc-3. This provides an extinction-free measurement of SFRD independent of optical properties and provides a parameter that can be used for direct comparison to high-redshift starbursts being discovered with Spitzer. Individual sources in the sample have SFRs from 0.14 to 160 M☉ yr-1. The derived value for the local SFRD is about half that of the local SFRD deduced from bolometric luminosities of the IRAS 60 μm Bright Galaxy Sample, with the deficiency being at lower luminosities and arising primarily from the small number of low-luminosity sources in the 10 mJy sample. The agreement for higher luminosities confirms the validity of using the 7.7 μm PAH feature as a measure of SFRD in the high-redshift universe, where this is often the only indicator available for faint sources.
A potassium Faraday anomalous dispersion optical filter

Abstract The characteristics of a potassium Faraday anomalous dispersion optical filter operating on the blue and near infrared transitions are calculated. The results show that the filter can be designed to provide high transmission, very narrow pass bandwidth, and low equivalent noise bandwidth.
Micro-undulator research at UCSB

Abstract Research has been conducted over the past year on micro-undulators at the University of California at Santa Barbara. Our design has many advantages, but several unique problems have been found that are highlighted in this report: (1) smaller fields than other pure permanent-magnet undulators; (2) dc and long-period field errors; and (3) large end fields. Possible methods to overcome these problems are discussed.
The physical attributes and testing aspects of the symbol system

The major goals of the SYMBOL computer research project have been to provide a more effective man-machine interface and to reduce the total cost of a digital system to the user. The development of the multi-processing/multi-programming computer architecture with much of the executive system, memory management, and high-level language implemented in hardware is described in other related papers. The SYMBOL project also has investigated low-cost construction techniques suitable for equipment to be used in commercial/industrial environments.
A proof of a cyclic version of Deligne’s conjecture via Cacti

We generalize our results on Deligne's conjecture to prove the statement that the normalized Hochschild co--chains of a finite--dimensional associative algebra with a non--degenerate, symmetric, invariant inner product are an algebra over a chain model of the framed little discs operad which is given by cacti. In particular, in characteristic zero they are a BV algebra up to homotopy and the Hochschild cohomology of such an algebra is a BV algebra whose induced bracket coincides with Gerstenhaber's bracket. To show this, we use a cellular chain model for the framed little disc operad in terms of normalized cacti. This model is given by tensoring our chain model for the little discs operad in terms of spineless cacti with natural chain models for $(S^1)^{\times n}$ adapted to cacti.
On the framing of one kind of indefinite referring expression: learning challenges and pedagogical implications

The paper shows that two key principles of communication (the Shared Knowledge Principle and the Economy Principle), which monitor the framing of all well-formed referring expressions, are manifest in a specialized mode in the framing of focal specific indefinite referring expressions. It is suggested that the special features associated with this type of reference pose a challenge for a group of advanced learners whose L1 is Cantonese. The strategies that these learners adopt in framing this category of indefinite referring expressions are examined and compared to those customarily used by educated native speakers. Pedagogical implications are explored.
A novel α,β-unsaturated nitrone-aryne [3+2] cycloaddition and its application in the synthesis of the cortistatin core

We describe here a novel α,β-unsaturated nitrone-aryne [3+2] cycloaddition. The resulting benzoisoxazolines underwent N-O bond reduction-elimination-electrocyclization sequence to furnish a variety of polysubstituted 2H or 2-alkylated-1-benzo-pyrans. The application of this methodology was further demonstrated in the synthesis of the oxa[3.2.1]octene moiety of cortistatin A.
The likelihood encoder for source coding

The likelihood encoder with a random codebook is demonstrated as an effective tool for source coding. Coupled with a soft covering lemma (associated with channel resolvability), likelihood encoders yield simple achievability proofs for known results, such as rate-distortion theory. They also produce a tractable analysis for secure rate-distortion theory and strong coordination.
Prognostic Significance of Intrarenal Resistance Indices in Patients With Renal Artery Interventions: A Preliminary Duplex Sonographic Study

No non-invasive test can predict the clinical outcome of renal revascularization procedures. Because duplex sonographic measurements of intrarenal flow patterns reflect the resistance to flow within the kidney, the prognostic value of the cortical end-diastolic to peak systolic (d/s) velocity ratio was investigated in patients undergoing intervention for renal artery stenosis. The clinical and duplex sonographic data on 32 patients with 35 interventions (30 percutaneous transluminal angioplasties and five operations) on 42 renal artery sides were analysed. Twenty-three patients had atherosclerotic renal artery stenosis and nine patients had fibromuscular dysplasia resulting in > or = 60% renal artery stenosis. Measurements of the renal to aortic velocity ratio and cortical d/s ratio were performed before and after intervention. In the atherosclerotic patients, three interventions were clinically and technically successful, eight were technically successful but clinical failures, and 14 were clinically and technically unsuccessful. In the fibromuscular dysplasia patients, eight interventions were clinically and technically successful, and two were clinically and technically unsuccessful. The difference between the corresponding d/s ratios for atherosclerotic and fibromuscular dysplasia sides was significant on both the treated and not-treated sides (P < 0.02, two-tailed unpaired t-test). None of the 11 clinically successful procedures had a d/s ratio below 0.3, compared with seven values below 0.3 in the 24 clinically unsuccessful interventions (P = 0.05, one-tailed Fisher's exact test). It is concluded that: (1), a d/s ratio below 0.3 correlates with clinical failure in subsequent treatment of hypertension by renal revascularization, while a value above 0.3 has no prognostic significance; (2), despite technical success, not all atherosclerotic patients have clinical success from renal artery interventions; (3), in fibromuscular dysplasia patients, all clinical failures of renal artery interventions are associated with technical failures; and (4), the difference in d/s ratio between atherosclerotic and fibromuscular dysplasia patients may be a consequence of the more advanced age, longer duration of hypertension and additional risk factors in atherosclerotic patients.
Weak isomorphisms between Bernoulli shifts

In this note, we prove that if G is a countable group that contains a nonabelian free subgroup then every pair of nontrivial Bernoulli shifts over G are weakly isomorphic.
GLUEBALLS AND ADS/CFT

I review the calculation of the glueball spectrum in non-supersymmetric Yang-Mills theory (in 3 and 4 dimensions) using the conjectured duality between supergravity and large N gauge theories. The glueball masses are obtained by solving the supergravity wave equations in a black hole geometry. The masses obtained this way are in unexpectedly good agreement with the available lattice data, and are much better than strong-coupling expansion results. I also show how to use a modified version of the duality to calculate the glueball mass spectrum with some of the Kaluza-Klein states of the supergravity theory decoupled from the spectrum.
On-line learning of linear functions

We present an algorithm for the on-line learning of linear functions which is optimal to within a constant factor with respect to bounds on the sum of squared errors for a worst case sequence of trials. The bounds are logarithmic in the number of variables. Furthermore, the algorithm is shown to be optimally robust with respect to noise in the data (again to within a constant factor).
Cosmic Strings and Baryon Decay

We briefly review the current literature on baryon decay catalysis by cosmic strings, presenting a summary of the main arguments for decay catalysis.
The large N limit of the (2,0) superconformal field theory

Abstract We discuss the large N limit of the (2,0) field theory in six dimensions. We do this by assuming the validity of Maldacena's conjecture of the correspondence between large N gauge theories and supergravity backgrounds, here AdS 7 × S 4 . We review the spectrum of the supergravity theory and compute the spectrum of primary operators of the conformal algebra of arbitrary spin.
Breakdown phenomena in high-power klystrons

In the course of developing new high-peak-power klystrons, high electric fields in several regions of these devices have become an important source of vacuum breakdown. In addition, a renewed interest in breakdown phenomena for nanosecond-pulse, megavolt-per-centimeter fields has been sparked by recent work in the area of gigawatt RF sources. The most important regions of electrical breakdown are in the output cavity gap area, the RF ceramic windows, and the gun ceramic insulator. The experiments and results on the breakdown in these regions are discussed, as well as the solutions to alleviate this breakdown problem. >
Interannual Variability in the Large-Scale Dynamics of the South Asian Summer Monsoon

This study identifies coherent and robust large-scale atmospheric patterns of interannual variability of the South Asian summer monsoon (SASM) in observational data. A decomposition of the water vapor budget into dynamic and thermodynamic components shows that interannual variability of SASM net precipitation (P − E) is primarily caused by variations in winds rather than in moisture. Linear regression analyses reveal that strong monsoons are distinguished from weak monsoons by a northward expansion of the cross-equatorial monsoonal circulation, with increased precipitation in the ascending branch. Interestingly, and in disagreement with the view of monsoons as large-scale sea-breeze circulations, strong monsoons are associated with a decreased meridional gradient in the near-surface atmospheric temperature in the SASM region. Teleconnections exist from the SASM region to the Southern Hemisphere, whose midlatitude poleward eddy energy flux correlates with monsoon strength. Possible implications of these teleconnection patterns for understanding SASM interannual variability are discussed.
A New Paradigm for Carbon−Carbon Bond Formation: Aerobic, Copper-Templated Cross-Coupling

Thiol esters and boronic acids react to produce ketones under aerobic conditions in the presence of catalytic quantities of a CuI or CuII salt. The reaction occurs at reasonable rates between room temperature and 50 °C at neutral pH using thiol esters derived from bulky 2° amides of thiosalicylamides such as those based on N-tert-butyl-2-mercaptobenzamide. In this mechanistically unprecedented reaction system, the carbon−carbon bond formation occurs through templating of the thiol ester and the boronic acid at copper; the system is rendered catalytic in copper under the aerobic conditions.
History matching with an ensemble Kalman filter and discrete cosine parameterization

History matching of large hydrocarbon reservoirs is challenging because of several reasons including: (1) scarcity of available measurements relative to the number of unknowns, leading to an ill-posed inverse problem, (2) computational effort required for large reservoir problems, and (3) the need to insure that solutions are geologically realistic. All of these problems can be helped by using algorithms that rely on efficient and parsimonious descriptions (or parameterizations) of reservoir properties. This paper demonstrates the use of a novel parameterization approach, the discrete cosine transform, for history matching with a recently introduced sequential estimation technique, i.e., the ensemble Kalman filter. The proposed approach exploits the structure of the estimation and parameterization algorithms to reduce the size of reservoir states (pressures and saturations) as well as parameters (e.g., intrinsic permeability) with a marginal loss in accuracy. The introduced methodology eliminates redundancy in posing the estimation problem and results in additional computational savings. Application and generality of this approach are demonstrated using two waterflooding experiments characterized by different types of geological variability.
Exports, investment and production growth: A dynamic heterogeneous firm model with learning and entry costs

We analyze a firm’s joint decision to export and invest using a model that incorporates the essential features of self-selection and learning-by-exporting theories of firm-level dynamics. We calibrate the model to 2002–2007 Chilean manufacturing plant data and simulate it under different assumptions, finding that neither self-selection nor learning-by-exporting alone can adequately explain the observed cross-sectional relationship between firm level exports and capital, favoring instead a model that allows both mechanisms to work in tandem.