cssi/SciSciGPT-SciSciNet huggingface dataset:
Commuter response to traffic information on an incident

How traffic information is obtained and how it affects travel behavior when a major freeway is congested are presented and discussed. Immediately following a major highway incident south of San Francisco that caused congestion, a telephone survey was conducted of commuters who use the affected corridor of the highway. The behavior of commuters before and during their commute at the time of the incident was determined, including obtaining traffic information and how the information influenced changes in route, mode of travel, and departure time. The results of the survey suggest that traveler behavior is largely unaffected by individual incidents of congestion. Furthermore, although a fair proportion of commuters do obtain traffic information, they do not often modify their travel behavior in response. This study is one of several that collectively will provide insight into how travel behavior changes over time and allow the authors to assess the impact of TravInfo Traveler Advisory Telephone System in the...
A new Mars radiation environment model with visualization

Abstract A new model for the radiation environment to be found on the planet Mars due to Galactic Cosmic Rays (OCR) has been developed at the NASA Langley Research Center. Solar modulated primary particles rescaled for Mars conditions are transported through the Martian atmosphere, with temporal properties modeled with variable timescales, down to the surface, with altitude and backscattering patterns taken into account. The Martian atmosphere has been modeled by using the Mars Global Reference Atmospheric Model – version 2001 (Mars-GRAM 2001). The altitude to compute the atmospheric thickness profile has been determined by using a model for the topography based on the data provided by the Mars Orbiter Laser Altimeter (MOLA) instrument on board the Mars Global Surveyor (MGS) spacecraft. The Mars surface composition has been modeled based on averages over the measurements obtained from orbiting spacecraft and at various landing sites, taking into account the possible volatile inventory (e.g., CO 2 ice, H 2 O ice) along with its time variation throughout the Martian year. Particle transport has been performed with the HZETRN heavy ion code. The Mars Radiation Environment Model has been made available worldwide through the Space Ionizing Radiation Effects and Shielding Tools (SIREST) website, a project of NASA Langley Research Center.
A scientist on the hill

two decades. Topics covered includethe role of the White House Office ofScience and Technology Policy, thelegislative process, the CongressionalResearch Service, international sd-ence activities in federal agencies. sd-ence in the Judicial Branch, lobbying,the globalization of science and tech-nology, the National Research Coun-cil, Washington's think tanks and the
The Conformal Template and New Perspectives for Quantum Chromodynamics

Conformal symmetry provides a systematic approximation to QCD in both its perturbative and nonperturbative domains. One can use the AdS/CFT correspondence between Anti-de Sitter space and conformal gauge theories to obtain an analytically tractable approximation to QCD in the regime where the QCD coupling is large and constant. For example, there is an exact correspondence between the fifth-dimensional coordinate of AdS space and a specific impact variable which measures the separation of the quark constituents within the hadron in ordinary space-time. This connection allows one to compute the analytic form of the frame-independent light-front wavefunctions of mesons and baryons, the fundamental entities which encode hadron properties and allow the computation of exclusive scattering amplitudes. One can also use conformal symmetry as a template for perturbative QCD predictions where the effects of the nonzero beta function can be systematically included in the scale of the QCD coupling. This leads to fixing of the renormalization scale and commensurate scale relations which relate observables without scale or scheme ambiguity. The results are consistent with the renormalization group and the analytic connection of QCD to Abelian theory at N{sub C} {yields} 0. I also discuss a number of novel phenomenological features of QCD. Initial- and .nal-state interactions from gluon-exchange, normally neglected in the parton model, have a profound effect in QCD hard-scattering reactions, leading to leading-twist single-spin asymmetries, diffractive deep inelastic scattering, di.ractive hard hadronic reactions, the breakdown of the Lam Tung relation in Drell-Yan reactions, and nuclear shadowing and non-universal antishadowing--leading-twist physics not incorporated in the light-front wavefunctions of the target computed in isolation. I also discuss tests of hidden color in nuclear wavefunctions, the use of diffraction to materialize the Fock states of a hadronic projectile and test QCD color transparency, nonperturbative antisymmetric sea quark distributions, anomalous heavy quark e.ects, and the unexpected effects of direct higher-twist processes.
A telescope comparison lemma for THH

We extend to the non-connective case a lemma of Bokstedt about the equivalence of the telescope with a more complicated homotopy colimit of symmetric spectra used in the construction of THH.
Electromagnetic Pump With Thin Metal Walls

This paper treats a liquid-metal flow in a rectangular duct with a strong, uniform, transverse magnetic field and with thin metal walls, except for two finite-length, perfectly conducting electrodes in the side walls, which are parallel to the magnetic field. There are large velocities inside the boundary layers adjacent to the thin metal side walls, but not inside the layers adjacent to the electrodes. Upstream and down-stream of the electrodes, a significant fraction of the total flow leaves and enters the side-wall boundary layers, respectively. For the particularly duct treated here, the fully developed side layers, which carry 38.8 percent of the total flow, are realized at a distance of three characteristic lengths form the ends of the electrodes.
Influence of lattice orientation on growth and structure of graphene on Cu(001)

Abstract We have used low-energy electron microscopy (LEEM) and diffraction (LEED) to examine the significance of lattice orientation in graphene growth on Cu(0 0 1). Individual graphene domains undergo anisotropic growth on the Cu surface, and develop into lens shapes with their long axes roughly aligned with Cu〈1 0 0〉 in-plane directions. The long axis of a lens-shaped domain is only rarely oriented along a C〈1 1〉 direction, suggesting that carbon attachment at “zigzag” graphene island edges is unfavorable. A kink-mediated adatom attachment process is consistent with the behavior observed here and reported in the literature. The details of the ridged moire pattern formed by the superposition of the graphene lattice on the (0 0 1) Cu surface also evolve with the graphene lattice orientation, and are predicted well by a simple geometric model. Managing the kink-mediated growth mode of graphene on Cu(0 0 1) will be necessary for the continued improvement of this graphene synthesis technique.
Synthesis of Functionalized Olefins by Cross and Ring-Closing Metatheses

The generation of olefins with electron-withdrawing functionality, such as α,β-unsaturated aldehydes, ketones, and esters, remains a difficult task in organic chemistry. A practical method to approach this problem would involve olefin metathesis, utilizing well-defined alkylidenes such as ((CF_3)_2MeCO)_2(ArN)Mo CH(t-Bu) (1) and (Pcy_3)_2Cl_2Ru CHPh (2). However, the generation of olefins with vinylic functionality through the use of cross-metathesis (CM) has met with limited success. In one of the few reports of this reaction, Crowe and Goldberg demonstrated that acrylonitrile participated in cross-metathesis reactions with a variety of terminal olefins. Other π-conjugated olefins, such as enones and enoic esters, were not functional group compatible with alkylidene 1 and failed to react with 2 in cross-metathesis. Recently, the highly active ruthenium-based olefin metathesis catalyst 3, which contains a 1,3-dimesityl-4,5-dihydro-imidazol-2-ylidene ligand, was found to efficiently catalyze the cross-metathesis of 1,1-geminally disubstituted olefins.7 Because ruthenium alkylidene 3 displayed unique activity toward previously metathesis-inactive substrates, we decided to investigate the metathesis of α-functionalized olefins. In this communication, we report the single-step synthesis of α-functionalized olefins by intermolecular cross-metathesis and intramolecular ring-closing metathesis using ruthenium alkylidene 3.
Turbulence modeling using body force potentials

Reynolds averaged Navier–Stokes (RANS) turbulence models are usually concerned with modeling the Reynolds stress tensor. An alternative approach to RANS turbulence modeling is described where the primary modeled quantities are the scalar and vector potentials of the turbulent body force—the divergence of the Reynolds stress tensor. This approach is shown to have a number of attractive properties, most important of which is the ability to model nonequilibrium turbulence situations accurately at a cost and complexity comparable to the widely used two-equation models such as k-e. Like Reynolds stress transport equation models, the proposed model does not require a hypothesized constitutive relation between the turbulence and the mean flow variables. This allows nonequilibrium turbulence to be modeled effectively. However, unlike Reynolds stress transport equation models, the proposed system of partial differential equations is much simpler to model and compute. It involves fewer variables, no realizability c...
Constrained conjugate directions methods for design optimization of large systems

The constrained steepest descent directions obtained as the solution of a quadratic programming subproblem are used to generate the constrained conjugate directions. The resulting algorithm is quite simple, and its finite convergence and other properties have been proved for convex quadratic programing problems. For general problems, instart procedures, step size determination, and potential constraint strategy are discussed
Copper‐Catalyzed Direct Synthesis of 3‐Arylindoles

A direct method for the preparation of various 3-arylindoles from their corresponding nitrosoarenes has been developed. Various substituted nitrosoarenes and alkynes were employed to obtain substituted indoles by using a CuII–Cu0 catalytic system. This is a two-step method that involves annulation of the nitrosoarene and alkyne followed by deoxygenation to give 3-arylindoles.
Depression and Visual Functioning in Patients With Ocular Inflammatory Disease

Purpose To characterize the level of depression in patients with ocular inflammatory disease and to determine predictors of depression in this population. Design Prospective cross-sectional survey and medical record review. Methods Participants were consecutive patients with noninfectious ocular inflammatory disease in a university-based tertiary referral center. Subjects were given the self-administered Beck Depression Inventory-II (BDI-II), National Eye Institute Visual Function Questionnaire-25 (NEI VFQ-25), and additional supplemental questions. Medical records were reviewed for clinical characteristics. Univariate analyses were conducted to compare clinical characteristics between patients with and without a positive screen for depression, and a multivariate regression model was performed to determine the most significant predictors of depression. Results Of the 104 participants, 26.9% screened positive for depression with the BDI-II. Of these subjects, only 39.3% had been previously diagnosed with depression. NEI VFQ-25 scores were significantly lower in depressed patients in all subscales except driving and color vision. Predictors of depression were inadequate emotional support, lower visual functioning (VFQ composite score), history of changing immunomodulatory treatment, and current oral corticosteroid use. Conclusions Depression may be a significant but underrecognized comorbid condition in patients with ocular inflammatory disease. Worse visual function was associated with depression. The authors recommend heightened awareness of potential depression in patients with ocular inflammatory disease.
Fertility Models for Statistical Natural Language Understanding

Several recent efforts in statistical natural language understanding (NLU) have focused on generating clumps of English words from semantic meaning concepts (Miller et al., 1995; Levin and Pieracini, 1995; Epstein et al., 1996; Epstein, 1996). This paper extends the IBM Machine Translation Group's concept of fertility (Brown et al., 1993) to the generation of clumps for natural language understanding. The basic underlying intuition is that a single concept may be expressed in English as many disjoint clump of words. We present two fertility models which attempt to capture this phenomenon. The first is a Poisson model which leads to appealing computational simplicity. The second is a general nonparametric fertility model. The general model's parameters are boot-strapped from the Poisson model and updated by the EM algorithm. These fertility models can be used to impose clump fertility structure on top of preexisting clump generation models. Here, we present results for adding fertility structure to unigram, bigram, and headword clump generation models on ARPA's Air Travel Information Service (ATIS) domain.
Improved Dispersion of a Fin-Stabilized Projectile Using a Passive Moveable Nose

A key and often quoted metric associated with gun systems is impact point accuracy. Impact dispersion is a complex function of a battery of parameters including gun geometry and tolerances, the fire control system, projectile manufacturing tolerances, etc. The work reported here investigates potential impact point accuracy improvement for a penetrator type projectile realized by replacing the rigid nose cone wind screen with a passive gimballed nose. Toward this end, a gimballed nose projectile dynamic model is derived which consists of the standard six degrees of freedom similar to a rigid projectile plus three additional degrees of freedom associated with rotation of the nose with respect to the main projectile body. By comparing impact point dispersion of a rigid projectile with a similar gimballed nose projectile, it is shown that impact point accuracy can be significantly improved. For the example penetrator projectile considered, impact point dispersion is reduced by more than 50%. The investigation also considers the effect of several design parameters on impact point dispersion including mass ratio of the nose to the total projectile, gimbal joint friction, and the normal force coefficient of the nose cone. Within practical boundaries, the mass ratio of the nose and body does not alter the target dispersion characteristics. However, friction in the gimbal joint does significantly effect the impact point dispersion. As the viscous damper friction coefficient increases, the impact point dispersion slightly increases until a critical value is reached. Beyond the critical value of viscous damping friction coefficient, the nose cone rotational dynamics are unstable and the tip of the nose oscillates about the limit nose cone rotation angle. Also, a steady decrease in impact point accuracy is noted as the normal forces coefficient of the nose is reduced.
Toward a Theory of Enumerations

An attempt is made to show that there is much work in pure recursion theory which implicitly treats computational complexity of algorithmic devices which enumerate sets. The emphasis is on obtaining results which are independent of the particular model one uses for the enumeration technique and which can be obtained easily from known results and known proofs in pure recursion theory.First, it is shown that it is usually impossible to define operators on sets by examining the structure of the enumerating devices unless the same operator can be defined merely by examining the behavior of the devices. However, an example is given of an operator which can be defined by examining the structure but which cannot be obtained merely by examining the behavior.Next, an example is given of a set which cannot be enumerated quickly because there is no way of quickly obtaining large parts of it (perhaps with extraneous elements). By way of contrast, sets are constructed whose elements can be obtained rapidly in conjunction with the enumeration of a second set, but which themselves cannot be enumerated rapidly because there is no easy way to eliminate the members of the second set.Finally, it is shown how some of the elementary parts of the Hartmanis-Stearns theory can be obtained in a general setting.
The role of pacemakers in the management of patients with atrial fibrillation.

This article reviews the wide range of implantable device–based therapies (mainly pacemakers) that are being used in the management of atrial fibrillation (AF), atrial flutter, and atrial tachycardia. The role of pacemakers in the management of patients with AF and in the prevention of AF has been extensively studied. Based on well-designed prospective clinical trials, only a few of these strategies can be recommended for routine clinical use in related subpopulations.
Sterols as ecological indicators

Abstract Plots of the C-27, C-28 and C-29 sterol contents of marine plankton, higher plants, soils, and lacustrine and marine sediments form discrete areas in a triangular diagram. Because the positions of these plots of the various samples are relatable to biological sources, sterol analyses may be used to define ecological systems.
Stable distributions, pseudorandom generators, embeddings, and data stream computation

In this article, we show several results obtained by combining the use of stable distributions with pseudorandom generators for bounded space. In particular:---We show that, for any p ∈ (0, 2], one can maintain (using only O(log n/e2) words of storage) a sketchC(q) of a point q ∈ lnp under dynamic updates of its coordinates. The sketch has the property that, given C(q) and C(s), one can estimate Vq − sVp up to a factor of (1 p e) with large probability. This solves the main open problem of Feigenbaum et al. [1999].---We show that the aforementioned sketching approach directly translates into an approximate algorithm that, for a fixed linear mapping A, and given x ∈ ℜn and y ∈ ℜm, estimates VAx − yVp in O(n p m) time, for any p ∈ (0, 2]. This generalizes an earlier algorithm of Wasserman and Blum [1997] which worked for the case p = 2.---We obtain another sketch function C′ which probabilistically embeds ln1 into a normed spacelm1. The embedding guarantees that, if we set m = log(1/δ)O(1/e), then for any pair of points q, s ∈ ln1, the distance between q and s does not increase by more than (1 p e) with constant probability, and it does not decrease by more than (1 − e) with probability 1 − δ. This is the only known dimensionality reduction theorem for the l1 norm. In fact, stronger theorems of this type (i.e., that guarantee very low probability of expansion as well as of contraction) cannot exist [Brinkman and Charikar 2003].---We give an explicit embedding of ln2 into lnO(log n)1 with distortion (1 p 1/nΘ(1)).
Pair Production Multiplicities in Rotation-powered Pulsars

We discuss the creation of electron-positron cascades in the context of pulsar polar cap acceleration models and derive several useful analytic and semianalytic results for the spatial extent and energy response of the cascade. Instead of Monte Carlo simulations, we use an integrodifferential equation that describes the development of the cascade energy spectrum in one space dimension quite well, when it is compared to existing Monte Carlo models. We reduce this full equation to a single integral equation, from which we can derive useful results, such as the energy loss between successive generations of photons and the spectral index of the response. We find that a simple analytic formula represents the pair cascade multiplicity quite well, provided that the magnetic field is below 1012 G and that an only slightly more complex formula matches the numerically calculated cascade at all other field strengths. Using these results, we find that cascades triggered by γ-rays emitted through inverse Compton scattering of thermal photons from the neutron star's surface, both resonant and nonresonant, are important for the dynamics of the polar cap region in many pulsars. In these objects, the expected multiplicity of pairs generated by a single input particle is lower than previously found in cascades initiated by curvature emission, frequently being on the order of 10 rather than ~1000 as usually quoted. Such pulsars also are expected to be less luminous in polar cap γ-rays than when curvature emission triggers the cascade, a topic that will be the subject of a subsequent paper.
Freestream turbulence effects on the development of a rotor wake

The effect of freestream turbulence on the development of a three-dimensional wake of a compressor rotor blade was studied experimentally. The turbulence level at the inlet of a rotor was varied systematically using grids upstream of the rotor. The rotor wake was measured with inlet turbulence intensities of 0.5, 3, and 5%. The experimental results indicate that the maxium change in the mean velocity defect is 4% over the range of inlet turbulence levels employed, while the turbulence structure in the wake is altered more substantially. The freestream turbulence effect was also analyzed, numerically, using the modified Reynolds stress closure model. The comparison between numerical prediction and experimental data shows that the freestream turbulence effect can be represented successfully with the turbulence closure model employed in this paper.
Comparison of the Acoustic Characteristics of Large-Scale Models of Several Propulsive-Lift Concepts

Wind-tunnel acoustic investigations were performed to determine the acoustic characteristics and the effect of forward speed on these characteristics of four propulsive lift concepts: the over-the-wing externally-blown jet flap (OTW), the under-the-wing externally-blown jet flap (UTW), the internally-blown jet flap (IBF), and the augmentor wing (AW). The data in this paper represent the basic noise generated by the powered-lift system without acoustic treatment, assuming all other noise sources, such as the turbofan compressor noise, have been suppressed. Under these conditions, when scaled to a 45,500 kg (100,000 Ib) aircraft, the OTW concept exhibited the lowest perceived noise levels because of dominant low-frequency noise and wing shielding of the highfrequency noise. The AW was the loudest configuration because of dominant high-frequency noise created by the high jet velocities and small nozzle dimensions. All four configurations emitted noise 10 to 15 PNdb higher than the noise goal of 95 PNdb at 153 m (500 ft). The AW is the only powered-lift concept which has shown the capability of acoustic suppression to this level. The effect of forward speed did not approach that expected from the relative velocity increments investigated. The dominant low-frequency noise of the OTW and UTW was reduced 2 db by an 80 knot free-stream velocity. The dominant high-frequency noise of the IBF and AW was unaffected by forward speed. Nomenclature OASPL = overall sound pressure level, db PNL = perceived noise level, PNdb SPL = sound pressure level, db referred to 2 x 10'5 N/m2 (0.0002 microbar) Vj = aver age isentropic jet exhaust velocity, m/sec (fps) V^ = freestream velocity, knots (fps) a = angle of attack with respect to wing chord plane, deg df = flap deflection with respect to wing chord plane, deg
The Moderated Influence of Internal Control: An Examination Across Health-Related Behaviors

An extension of the theory of planned behavior (Ajzen, 1991) was used to identify whether moderated relationships exist between perceived behavioral control and theoretical constructs within the model. Study 1 examined influences of perceived internal control relative to behavioral category; for a utilitarian behavior (e.g., using sunscreen, donating blood), the moderating relation was of a cognitive nature (i.e., attitude, subjective norm), whereas for hedonic behaviors (e.g., drinking and driving, fast food consumption), the moderating relation was of a noncognitive nature (i.e., affect, past behavior). These relations were manipulated in Study 2 via the framing of neutral behaviors (i.e., chocolate and fat consumption) to explicate the hypothesized patterns of interactions. Theoretical implications of findings are discussed.
Racial profiling as collective definition

Economists and other interested academics have committed significant time and effort to developing a set of circumstances under which an intelligent and circumspect form of racial profiling can serve as an effective tool in crime finding–the specific objective of finding criminal activity afoot. In turn, anti-profiling advocates tend to focus on the immediate efficacy of the practice, the morality of the practice, and/or the legality of the practice. However, the tenor of this opposition invites racial profiling proponents to develop more surgical profiling techniques to employ in crime finding. In the article, I review the literature on group distinction to discern its relevance to the practice and study of racial profiling. I argue that the costs of racial profiling extend beyond inefficient policing and the humiliation of law-abiding minority pedestrians and drivers. Racial profiling is simultaneously a process of perception and articulation of relative human characteristics (both positive and negative); it binds and reifies the concepts of race and criminality, fixing them into the subconscious of the profiled, the profiler, and society at large.
Judicial Iconography in India

Courts often create an ‘image of justice’ that has different meanings for different people. These images of justice are created through the architecture, ceremony, ritual, dress and language that exist within the walls of a court. Therefore, the entire structure of the court can be said to have a story that is linked to its ‘iconography’ that covers its exterior and interior facade creating a particular ‘image of justice’. There are several academic writings in the West on judicial iconography linked to court structures that influence the way justice is imaged. However, this field of academic research is relatively nascent in India. This article relates these existing concepts to judicial iconography in India. The available literature on courts in India is the evidence of the fact that courts in India also provide a particular image of justice. This is seen through examples from the Supreme Court of India, the Bombay High Court, the Rajasthan High Court, a District Court in Tamil Nadu and the High Court o...
A strictly Markovian expansion for plasma turbulence theory

The collision operator that appears in the equation of motion for a particle distribution function that has been averaged over an ensemble of random Hamiltonians is non-Markovian. It is non-Markovian in that it involves a propagated integral over the past history of the ensemble averaged distribution function. All formal expansions of this nonlinear collision operator to date preserve this non-Markovian character term by term yielding an integro-differential equation that must be converted to a diffusion equation by an additional approximation. In this note we derive an expansion of the collision operator that is strictly Markovian to any finite order and yields a diffusion equation as the lowest non-trivial order. The validity of this expansion is seen to be the same as that of the standard quasi-linear expansion.
Engineering flowfield method with angle-of-attack applications

An approximate inviscid flowfield method has been extended to include heat-transfer predictions using a technique to account for variable-entropy edge conditions. The engineering code computes the flowfield over hyperboloids, ellipsoids, paraboloids, and sphere cones at 0 deg angle of attack (AOA). For angle-of-attack applications, an approximation to sphere-cone streamline-spreading effects on the heat transfer along the windward and leeward rays and an empirical circumferential heating technique have been incorporated also in the method. The present engineering calculations yield good comparisons with existing pressure and heating data over sphere cones even at high incidence values with the restriction that the sonic-line location remain on the spherical cap.
The demethylation chemistry of 3-substituted 2-methoxypyridines

Lors de l'acylation d'amino-3 methoxy-2 pyridines sur l'amino-3, on obtient egalement des 1H-pyridones-2 et des pyrido [2,3-b] oxazines-1,4
Anti-markovnikov addition of nucleophiles to a non-conjugated olefin via single electron transfer photochemistry

Abstract Nucleophilic solvent has been added regiospecifically in an anti-Markovnikov manner to a simple non-conjugated olefin, 1-methylcyclohexene, through single electron transfer induced photochemistry using the 1-cyanonaphthalene - biphenyl pair for achieving photooxidation.
Elasticity, Thermal Properties, and Molecular Dynamics Using Non-Empirical Tight-Binding

We have further developed and applied a new non-empirical tight-binding total energy model to properties of Si, Xe, and Fe at high pressures. We have studied elasticity of various phases of each of these, demonstrating that the new model is applicable to a wide range of materials, including semiconductors, rare gases, and transition metals. We have used the particle-in-a-cell method to study the thermal equation of state of hep Fe and find excellent agreement with the shock equation of state. A molecular dynamics code has been developed based on this method, and we have studied the properties of Fe liquid at high pressures.
Polymer Waste Management–Biodegradation, Incineration, and Recycling

Abstract Increasing volumes of synthetic polymers are manufactured for various applications. The disposal of the used materials is becoming a serious problem. Unlike natural polymers, most synthetic macromolecules cannot be assimilated by microorganisms. Although polymers represent slightly over 10% of total municipal waste, the problem of nonbiodegradability is highlighted by overflowing landfills, polluted marine waters, and unsightly litter. Existing government regulations in Europe and anticipated regulations in the United States will greatly limit the use of polymers in large volume applications (packaging, water treatment, paper and textile sizing, etc.) unless acceptable means of waste management are available. Total management of polymer wastes requires complementary combinations of biodegradation, incineration, and recycling. Biodegradation is the most desirable long-term future solution and requires intensive research and development before it becomes practical. On the other hand, incineration a...
Recent Studies of Rubberlike Elasticity

Forming elastomeric networks by end linking functionally-terminated polymer chains has the advantage of minimizing imperfections in the network structure, with associated improvements in ultimate properties. These improvements are found to be particularly marked when mixtures of very short and relatively long chains are end linked, thus giving bimodal networks. Such (unfilled) networks show very large increases in reduced stress or modulus at high elongations and, since such a toughening effect is of interest with regard to both fundamental questions and potential applications, a variety of experiments were carried out to elucidate its origin. These experiments included stress-strain isotherms over a wide range in temperature and degree of swelling, stress-temperature coefficients, and birefringence-temperature coefficients. All of the experimental results indicate the origin of the upturns in modulus to be intramolecular, specifically non-Gaussian effects arising from the very limited extensibility of the short chains present in the networks. This limited extensibility and its effects on elastomeric properties were investigated using a theory of rubberlike elasticity based on network distribution functions generated from rotational isomeric state models for the specific chains of interest. Polymers studied to date by this theoretical approach are poly(dimethylsiloxane), (amorphous) polyethylene, polymeric sulfur, and polymeric selenium.
Clumping and quantum order: quantum gravitational dynamics of NUT charge

Gravitational instantons with NUT charge are magnetic monopoles upon dimensional reduction. We determine whether NUT charge can proliferate via the Polyakov mechanism and partially screen gravitational interactions. In semiclassical Einstein gravity, Taub-NUT instantons experience a universal attractive force in the path integral that prevents proliferation. This attraction further leads to semiclassical clumping instabilities, similar to the known instabilities of hot flat space and the Kaluza-Klein vacuum. Beyond pure Einstein gravity, NUT proliferation depends on the following question: is the mass of a gravitational instanton in the theory always greater than its NUT charge? Using spinorial methods we show that the answer to this question is ‘yes’ if all matter fields obey a natural Euclidean energy condition. Therefore, the attractive force between instantons in the path integral wins out and gravity is dynamically protected against screening. Semiclassical gravity with a compactified circle can be self-consistently quantum ordered, at the cost of suffering from clumping instabilities.
Computer simulation of pressure wave generation in biological media by pulsed lasers with various beam profiles

Pressure waves can be generated in biological tissues by pulsed lasers which deposit optical energy in absorbing structures such as blood vessels. Arrays of acoustic detectors on a tissue surface can sense the arrival of such waves. Analysis of the time-resolved signals can be used to reconstruct the 3-D distribution of the absorbing structures. In this report, a computer simulation was developed (see code listed in Appendix) to predict the time-resolved spatial distribution of pressure in a tissue in response to a pulse laser beam. In particular, the temporal history of pressure generated in a sphere of uniform energy deposition was calculated to illustrate the calibration of the computation. The temporal histories of pressures generated by a flat-field beam and a Gaussian-profile beam are also presented. The results show that the sharp edge of the flat-field beam yields tensile pressure wave and the pressure pattern is significantly different than the pressures produced by the smoother Gaussia-profile beam. The computer simulation is a very simple computation that is a valuable tool for predicting expected experimental results, and may be used in a reconstruction algorithm. This paper can be viewed at http://optics.sgu.ru/SFM/2002/internet/Jacques/index.htm.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Decreasing Relative Risk Aversion and Tests of Risk Sharing

The relative risk aversion (RRA) coefficient of a household whose consumption is close to the subsistence level may be very high. For example, if consumption is exactly at the subsistence level, the household may not be willing to bear any risk. If this is the case, then the RRA coefficient must be a decreasing function of wealth for poor households. Therefore we should allow the possibility of decreasing RRA (DRRA) in testing the full risk sharing hypothesis. However, existing tests in the empirical literature are derived using preferences that exhibit either increasing or constant RRA even when they are applied to data containing low-income households. We therefore use a Hyperbolic Absolute Risk Aversion (HARA) utility, which implies increasing, constant, and decreasing RRA as special cases, to test full risk-sharing hypothesis. Using the International Food Policy Research Institute (IFPRI) and the International Crops Research Institute of the Semi-Arid Tropics (ICRISAT) household level data sets, we find evidence in support of the DRRA hypothesis, along with evidence favoring full risk-sharing hypothesis at the village level, and evidence against the hypothesis at the inter-village level. When RRA is restricted to be constant, we replicate the previous results in the literature: reject the full risk-sharing hypothesis at both levels. Our tests, however, reject this restriction and favor DRRA in almost all cases. These results suggest that it is important to allow for DRRA in testing the full risk-sharing hypothesis when data containing low-income households are investigated.
Explaining the Overruling of U.S. Supreme Court Precedent

The decision to overrule U.S. Supreme Court precedent, we argue, results from the justices' pursuit of their policy preferences within intra- and extra-Court constraints. Based on a duration analysis of cases decided from the 1946 through 1995 terms, we show that ideological incongruence between a precedent and a subsequent Court increases the chance of it being overruled. Two legal norms also exert substantive effects as the Court is less likely to overrule statutory precedents and more likely to overrule precedents that previously have been interpreted negatively by the Court. While certain precedent characteristics also influence this decision, the political environment exerts no such effect. Consequently, one of the principal implications of this research is that legal norms influence Supreme Court decision making.
Trade openness and cultural creative destruction

Purpose – This paper seeks to analyze empirically the net effect of trade openness on “economic culture”, measured by indicators of trust, respect, level of self‐determination, and obedience. Openness to international trade means that societies are more likely to be exposed to alternative attitudes, beliefs, ideas, and values leading to a Schumpeterian process of creative destruction whereby culture is destroyed on some margins and enhanced on others.Design/methodology/approach – Using data on trade openness from Quinn and Sachs and Warner, the paper empirically evaluates the impact of trade openness on economic culture. The paper's measure of culture is taken from Tabellini and Williamson and Kerekes, where data from the World Values Survey is aggregated to create a culture variable. The paper isolates the impact of trade policies on economic culture through a variety of empirical strategies including both panel and cross sectional analysis.Findings – The central finding of the study is that a society's ...
Catalytic Combustion of Natural Gas Over Supported Platinum: Flow Reactor Experiments and Detailed Numerical Modeling

The use of a noble-metal combustion catalyst such as platinum or palladium in a natural-gas fired turbine can lower NOx (nitrogen oxides, consisting of both NO and NO2) emissions for two reasons. First, most of the combustion occurs on the catalyst surface; surface production of NOx is low or nonexistent. Second, the catalyst permits low temperature combustion below the traditional lean limit, thus inhibiting NOx formation routes in the gas phase. Due to the complexity of the catalytic combustion process, the catalyst has traditionally been modeled as a “black box” that produces a desired amount of fuel conversion. While this approach has been useful for proof-of-concept studies, we expect practical applications to emerge from a greater understanding of the details of the catalytic combustion process.We have constructed a numerical model of catalytic combustion based on the well-accepted CHEMKIN chemical kinetics formalism for gas-phase and surface chemistry. To support the model development, we built a research combustor. We present measured and modeled axial profiles of temperature, fuel conversion, and pollutant emissions for natural-gas combustion over platinum catalysts supported on ceramic honeycomb monoliths. NOx emissions are below 1 ppm, and CO is observed at ppm levels. The data are taken at several lean equivalence ratios and flow rates. Fuel conversion rates occur in two regimes: a low, constant conversion rate and a higher conversion rate that increases linearly with equivalence ratio.The agreement of the numerical model with the measured data is good at temperatures below 900 K; above this temperature, fuel conversion is underpredicted by as much as a factor of two. The predicted surface ignition temperatures agree well with the measured values. Results from the numerical model indicate that the fractional conversion rate of fuel has a linear dependence on the fraction of available surface reaction sites.Copyright © 1996 by ASME
Dithering Strategies for Efficient Self-Calibration of Imaging Arrays

With high-sensitivity imaging arrays, accurate calibration is essential to achieve the limits of detection of space observatories. One can simultaneously extract information about the scene being observed and the calibration properties of the detector and imaging system from redundant dithered images of a scene. There are large differences in the effectiveness of dithering strategies for allowing the separation of detector properties from sky brightness measurements. In this paper, we quantify these differences by developing a figure of merit (FOM) for dithering procedures based on their usefulness for allowing calibration on all spatial scales. The figure of merit measures how well the gain characteristics of the detector are encoded in the measurements, and is independent of the techniques used to analyze the data. Patterns similar to the antenna arrangements of radio interferometers with good u-v plane coverage are found to have good figures of merit. We present patterns for both deep surveys of limited sky areas and for shallow surveys. By choosing a strategy that encodes the calibration in the observations in an easily extractable way, we enhance our ability to calibrate our detector systems and to reach the ultimate limits of sensitivity that are required to achieve the promise of many missions.
CHONDRULE FORMATION IN BOW SHOCKS AROUND ECCENTRIC PLANETARY EMBRYOS

Recent isotopic studies of Martian meteorites by Dauphas and Pourmand have established that large ({approx}3000 km radius) planetary embryos existed in the solar nebula at the same time that chondrules-millimeter-sized igneous inclusions found in meteorites-were forming. We model the formation of chondrules by passage through bow shocks around such a planetary embryo on an eccentric orbit. We numerically model the hydrodynamics of the flow and find that such large bodies retain an atmosphere with Kelvin-Helmholtz instabilities allowing mixing of this atmosphere with the gas and particles flowing past the embryo. We calculate the trajectories of chondrules flowing past the body and find that they are not accreted by the protoplanet, but may instead flow through volatiles outgassed from the planet's magma ocean. In contrast, chondrules are accreted onto smaller planetesimals. We calculate the thermal histories of chondrules passing through the bow shock. We find that peak temperatures and cooling rates are consistent with the formation of the dominant, porphyritic texture of most chondrules, assuming a modest enhancement above the likely solar nebula average value of chondrule densities (by a factor of 10), attributable to settling of chondrule precursors to the midplane of the disk or turbulent concentration. We calculate themore » rate at which a planetary embryo's eccentricity is damped and conclude that a single planetary embryo scattered into an eccentric orbit can, over {approx}10{sup 5} years, produce {approx}10{sup 24} g of chondrules. In principle, a small number (1-10) of eccentric planetary embryos can melt the observed mass of chondrules in a manner consistent with all known constraints.« less
On the Origin of Oscillations in a Solar Diameter Observed through the Earth’s Atmosphere: A Terrestrial Atmospheric or a Solar Phenomenon

Interpretations of current and past results from ground-based solar diameter measurements, as well as the planning of scientific programs for the 1980’s, are strongly dependent on the perceived level of the degrading effects of the Earth’s atmosphere. One of the more effective approaches has been to design the observing program and the subsequent data analysis such that the solar diameter measurements themselves could provide an evaluation of atmospheric effects. Many important results have been obtained in studies of this type and these results are collected here to help in appraising the current situation. This evidence all points in one direction: the Earth’s atmosphere, while complicating the design of observational programs, is not the source of the oscillations observed in solar diameter measurements. Further, this same evidence indicates that the Earth’s atmosphere will not pose any serious limitations in ground-based solar diameter studies during the 1980’s.
Conformational analysis of n-butyl cyanide

Abstract Infrared and Raman spectra have been obtained for n-butyl cyanide, and normal coordinate and molecular mechanics calculations made for all four possible conformers. The results show that all four conformers exist, in concentrations ranging from 11 to 46%. The structures of the four conformers are very nearly the same as for the structurally similar compound 1-hexyne. Vibrational assignments are proposed, and partial structures are given for all four conformers.
Topological BF field theory description of topological insulators

Abstract Topological phases of matter are described universally by topological field theories in the same way that symmetry-breaking phases of matter are described by Landau–Ginzburg field theories. We propose that topological insulators in two and three dimensions are described by a version of abelian BF theory. For the two-dimensional topological insulator or quantum spin Hall state, this description is essentially equivalent to a pair of Chern–Simons theories, consistent with the realization of this phase as paired integer quantum Hall effect states. The BF description can be motivated from the local excitations produced when a π flux is threaded through this state. For the three-dimensional topological insulator, the BF description is less obvious but quite versatile: it contains a gapless surface Dirac fermion when time-reversal-symmetry is preserved and yields “axion electrodynamics”, i.e., an electromagnetic E · B term, when time-reversal symmetry is broken and the surfaces are gapped. Just as changing the coefficients and charges of 2D Chern–Simons theory allows one to obtain fractional quantum Hall states starting from integer states, BF theory could also describe (at a macroscopic level) fractional 3D topological insulators with fractional statistics of point-like and line-like objects.
Atomic physics studies of highly charged ions on tokamaks using X-ray spectroscopy☆

Abstract An overview is given of atomic physics issues which have been studied on tokamaks with the help of high-resolution X-ray spectroscopy. The issues include the testing of model calculations predicting the excitation of line radiation, the determination of rate coefficients, and accurate atomic structure measurements. Recent research has focused primarily on highly charged heliumlike (22 ≤ Z ≤ 28) and neonlike (34 ≤ Z ≤ 63) ions, and results are presented from measurements on the PLT and TFTR tokamaks. Many of the measurements have been aided by improved instrumental design and new measuring techniques. Remarkable agreement has been found between measurements and theory in most cases. However, in this review those areas are stressed where agreement is worst and where further investigations are needed.
Radical Additions of Aryl Iodides to Arenes Are Facilitated by Oxidative Rearomatization with Dioxygen

Inter- and intramolecular additions of aryl radicals derived from aryl iodides to arenes are promoted by tris(trimethylsilyl)silane and occur under exceptionally mild conditions (15-30 min at 25 degrees C) in nondegassed benzene. A chain mechanism involving reaction of the intermediate cyclohexadienyl radical with oxygen to directly generate the aromatized product and the hydroperoxy radical is proposed.