cssi/SciSciGPT-SciSciNet huggingface dataset:
Chemistry and Microbiology of Permeable Reactive Barriers for In Situ Groundwater Clean up

Permeable reactive barriers (PRBs) are receiving a great deal of attention as an innovative, cost-effective technology for in situ clean up of groundwater contamination. A wide variety of materials are being proposed for use in PRBs, including zero-valent metals (e.g., iron metal), humic materials, oxides, surfactant-modified zeolites (SMZs), and oxygen- and nitrate-releasing compounds. PRB materials remove dissolved groundwater contaminants by immobilization within the barrier or transformation to less harmful products. The primary removal processes include: (1) sorption and precipitation, (2) chemical reaction, and (3) biologically mediated reactions. This article presents an overview of the mechanisms and factors controlling these individual processes and discusses the implications for the feasibility and long-term effectiveness of PRB technologies.
IMEX method convergence for a parabolic equation

Abstract Although implicit–explicit (IMEX) methods for approximating solutions to semilinear parabolic equations are relatively standard, most recent works examine the case of a fully discretized model. We show that by discretizing time only, one can obtain an elementary convergence result for an implicit–explicit method. This convergence result is strong enough to imply existence and uniqueness of solutions to a class of semilinear parabolic equations.
MAPS OF SURFACE GROUPS TO FINITE GROUPS WITH NO SIMPLE LOOPS IN THE KERNEL

Let Fg denote the closed orientable surface of genus g. What is the least order finite group, Gg, for which there is a homomorphism ψ:π1(Fg)→Gg so that nontrivial simple closed curve on Fg represents an element in Ker(ψ)? For the torus it is easily seen that G1=Z2×Z2 suffices. We prove here that G2 is a group of order 32 and that an upper bound for the order of Gg is given by g2g+1. The previously known upper bound was greater than 2g22g.
On the Interpretation of Energy as the Rate of Quantum Computation

Over the last few decades, developments in the physical limits of computing and quantum computing have increasingly taught us that it can be helpful to think about physics itself in computational terms. For example, work over the last decade has shown that the energy of a quantum system limits the rate at which it can perform significant computational operations, and suggests that we might validly interpret energy as in fact being the speed at which a physical system is "computing," in some appropriate sense of the word. In this paper, we explore the precise nature of this connection. Elementary results in quantum theory show that the Hamiltonian energy of any quantum system corresponds exactly to the angular velocity of state-vector rotation (defined in a certain natural way) in Hilbert space, and also to the rate at which the state-vector's components (in any basis) sweep out area in the complex plane. The total angle traversed (or area swept out) corresponds to the action of the Hamiltonian operator along the trajectory, and we can also consider it to be a measure of the "amount of computational effort exerted" by the system, or effort for short. For any specific quantum or classical computational operation, we can (at least in principle) calculate its difficulty, defined as the minimum effort required to perform that operation on a worst-case input state, and this in turn determines the minimum time required for quantum systems to carry out that operation on worst-case input states of a given energy. As examples, we calculate the difficulty of some basic 1-bit and n-bit quantum and classical operations in an simple unconstrained scenario
The Beauty Premium: Physical Attractiveness and Gender in Dictator Games

Are beautiful people better negotiators? In this article, I present evidence from a simple bargaining game in which players listened to prerecorded speeches and viewed the pictures of other players.I found that physically attractive players received a greater share of the surplus when their partners could both listen to their speeches and view their pictures.This effect was strongest when the listening partner was female.These results suggest new directions for experimental and empirical research on the role of nonresume characteristics on labor market outcomes, and also has implications for those practitioners involved in negotiations characterized by extreme power imbalances between the parties.
Apollo 12: Opaque oxides

Abstract Electron microprobe analyses of eight optically isotropic chrome spinels (gray and blue) and seven optically anisotropic chrome ulvospinels (tan, pink, khaki) have been carried out on four unshocked microgabbros from the Apollo 12 lunar samples. These analyses fall into two compositionally distinct groups along the join Fe2TiO4 (ulvospinel)-FeCr2O4 (chromite) in the system (Fe,Mg)O-TiO2-(Cr,Al)2O3; compositionally the isotropic minerals range from Usp9Cr91 to Usp25Cr75, whereas the anisotropic phases range from Usp74Cr26 to Usp90Cr10 and hence lie outside the compositional limits of the Apollo 11 samples (Usp53Cr47). Up to 4 percent by weight of Fe2O3 is inferred to be present in the spinels. A khaki spinel containing 90 percent of the ulvospinel molecule is the richest Fe2TiO4 phase yet found in nature. Chrome ulvospinels are considered to be a new series of nonisometric phases along the join Fe2TiO4-FeCr2O4. Based on coexisting Usp90 and Ilm100, estimates for the temperature and ƒO2 of crystallization do not provide a unique solution, but at 1200°C the ƒO2 is 10−11.5.
Modeling geologic storage of carbon dioxide: Comparison of non-hysteretic and hysteretic characteristic curves

Abstract Numerical models of geologic storage of carbon dioxide (CO 2 ) in brine-bearing formations use characteristic curves to represent the interactions of non-wetting-phase CO 2 and wetting-phase brine. When a problem includes both injection of CO 2 (a drainage process) and its subsequent post-injection evolution (a combination of drainage and wetting), hysteretic characteristic curves are required to correctly capture the behavior of the CO 2 plume. In the hysteretic formulation, capillary pressure and relative permeability depend not only on the current grid-block saturation, but also on the history of the saturation in the grid block. For a problem that involves only drainage or only wetting, a non-hysteretic formulation, in which capillary pressure and relative permeability depend only on the current value of the grid-block saturation, is adequate. For the hysteretic formulation to be robust computationally, care must be taken to ensure the differentiability of the characteristic curves both within and beyond the turning-point saturations where transitions between branches of the curves occur. Two example problems involving geologic CO 2 storage are simulated with TOUGH2, a multiphase, multicomponent code for flow and transport through geological media. Both non-hysteretic and hysteretic formulations are used, to illustrate the applicability and limitations of non-hysteretic methods. The first application considers leakage of CO 2 from the storage formation to the ground surface, while the second examines the role of heterogeneity within the storage formation.
Financial Integration in Antebellum America: Strengthening Bodenhorn's Results

In a recent article in this Journal, Howard Bodenhorn made a remarkable suggestion: “Antebellum financial markets may have outperformed those of the post–Civil War period.” According to Bodenhorn, antebellum capital markets displayed notable integration, as indicated by movements in short-term (60–day) interest rate data for important commercial centers east of the Mississippi. When considered in light of Lance Davis's work, suggesting poor integration of credit markets immediately after the Civil War and only gradual integration thereafter, we believe economic historians will find Bodenhorn's hypothesis provocative—even startling. We found the hypothesis so suggestive that we attempted to replicate Bodenhorn's analysis—a process that generated both “bad news” and “good news.” The “bad news” is that we believe the evidence Bodenhorn provided for his hypothesis is weak or irrelevant. The “good news” is that the data Bodenhorn generated support the integration hypothesis more strongly than even Bodenhorn suggested.
Structural optimization of 3D masonry buildings

In the design of buildings, structural analysis is traditionally performed after the aesthetic design has been determined and has little influence on the overall form. In contrast, this paper presents an approach to guide the form towards a shape that is more structurally sound. Our work is centered on the study of how variations of the geometry might improve structural stability. We define a new measure of structural soundness for masonry buildings as well as cables, and derive its closed-form derivative with respect to the displacement of all the vertices describing the geometry. We start with a gradient descent tool which displaces each vertex along the gradient. We then introduce displacement operators, imposing constraints such as the preservation of orientation or thickness; or setting additional objectives such as volume minimization.
The Escape Model on a Homogeneous Tree

There are two types of particles interacting on a homogeneous tree of degree $d+1$. The particles of the first type colonize the empty space with exponential rate 1, but cannot take over the vertices that are occupied by the second type. The particles of the second type spread with exponential rate $\lambda$. They colonize the neighboring vertices that are either vacant or occupied by the representatives of the opposite type, and annihilate the particles of the type 1 as they reach them. There exists a critical value $\lambda_c=(2d-1)+\sqrt{(2d-1)^2-1}$ such that the first type survives with positive probability for $\lambda \lambda_c$. We also find the growth profile which characterizes the rate of growth of the type 1 in the space-time on the event of survival.
On minimum-time paths of bounded curvature with position-dependent constraints

We consider the problem of a particle traveling from an initial configuration to a final configuration (given by a point in the plane along with a prescribed velocity vector) in minimum time with non-homogeneous velocity and with constraints on the minimum turning radius of the particle over multiple regions of the state space. Necessary conditions for optimality of these paths are derived to characterize the nature of optimal paths, both when the particle is inside a region and when it crosses boundaries between neighboring regions. These conditions are used to characterize families of optimal and nonoptimal paths. Among the optimality conditions, we derive a ''refraction'' law at the boundary of the regions that generalizes the so-called Snell's law of refraction in optics to the case of paths with bounded curvature. Tools employed to deduce our results include recent principles of optimality for hybrid systems. A numerical example is given to demonstrate the derived results.
Big Data in Firms and Economic Research

This paper discusses how firms use “big data” and the role and challenges for economists when getting involved in big data research. The firms’ success stories have taken advantage of building the biggest databases, using the best extraction tools, and using the fastest algorithms for data analysis and management. Although there are already great examples of economists entering big data research, analysts involved at present are mostly statisticians and computer scientists. The challenges economists face lie in computation, publication, and replication when using proprietary big data. The opportunities for economists lie in modeling and designing frameworks for analyzing large observational data panels, as well as developing empirical designs and strategies that are motivated by a model framework; in this way, economists can guide large-scale big data experiments toward identifying causal effects, rather than just correlations.
Bilateral Matching with Latin Squares

Abstract We develop a general procedure to construct pairwise meeting processes characterized by two features. First, in each period the process maximizes the number of matches in the population. Second, over time agents meet everybody else exactly once. We call this type of meetings “absolute strangers.” Our methodological contribution to economics is to offer a simple procedure to construct a type of decentralized trading environments usually employed in both theoretical and experimental economics. In particular, we demonstrate how to make use of the mathematics of Latin squares to enrich the modeling of matching economies.
Kinetics of Electron-Positron Pair Plasmas Using an Adaptive Monte Carlo Method

A new algorithm for implementing the adaptive Monte Carlo method is given. It is used to solve the Boltzmann equations that describe the time evolution of a nonequilibrium electron-positron pair plasma containing high-energy photons. These are coupled nonlinear integro-differential equations. The collision kernels for the photons as well as pairs are evaluated for Compton scattering, pair annihilation and creation, bremsstrahlung, and Coulomb collisions. They are given as multidimensional integrals which are valid for all energies. For an homogeneous and isotropic plasma with no particle escape, the equilibrium solution is expressed analytically in terms of the initial conditions. For two specific cases, for which the photon and the pair spectra are initially constant or have a power-law distribution within the given limits, the time evolution of the plasma is analyzed using the new method. The final spectra are found to be in a good agreement with the analytical solutions. The new algorithm is faster than the Monte Carlo scheme based on uniform sampling and more flexible than the numerical methods used in the past, which do not involve Monte Carlo sampling. It is also found to be very stable. Some astrophysical applications of this technique are discussed.
Momentum Operators in the Unit Square

We investigate the skew-adjoint extensions of a partial derivative operator acting in the direction of one of the sides a unit square. We investigate the unitary equivalence of such extensions and the spectra of such extensions. It follows from our results, that such extensions need not have discete spectrum. We apply our techniques to the problem of finding commuting skew-adjoint extensions of the partial derivative operators acting in the directions of the sides of the unit square. While our results are most easily stated for the unit square, they are established for a larger class of domains, including certain fractal domains.
Effect of groove on bone fracture toughness

When testing for the effects of bone orientation on mode I fracture toughness, compact tension specimens are grooved with a V-notch to provide a crack guide. The effect of grooving on the expressions for the critical stress intensity factor (Kc) and the critical strain energy release rate (Gc) for mode I fracture toughness was investigated. Experiments were performed using grooved and ungrooved bovine compact tension specimens. The results indicate that the standard expression used to determine Kc for a compact tension specimen requires modification. The thickness (B) must be modified to account for the thickness between the grooves (Bn). The thickness used in the standard expression is replaced by an effective thickness written as (BBn)0.5. It was also found that the thickness between the grooves should be used in the standard formula for Gc.
Response of Inconel 600 to Simulated Fusion Reactor Irradiation

Inconel 600 was irradiated in the High Flux Isotope Reactor (HFIR) to provide a partial simulation of fusion reactor service. Specimens were irradiated at 55 to 700°C to investigate swelling and postirradiation tensile properties as a function of irradiation and test temperatures under conditions of concurrent displacement damage and helium production. Helium contents from 600 to 1800 atomic parts per million (appm) and displacement levels of 4 to 9 displacements per atom (dpa) were achieved, and the results are used to estimate performance in a fusion reactor environment. The swelling was weakly dependent on temperature between 300 and 600°C, with swelling ranging from 0 to ∼1 percent, but increased rapidly above 600°C. The swelling values were much larger than expected from fast reactor and ion bombardment results. Cold-work was not effective in suppressing swelling of Inconel 600. Tensile property measurements and fractography on the same specimens showed strength values increased for irradiation at 55 to 400°C but decreased below unirradiated values for irradiations at 600 and 700°C. Elongation values were lowest at the temperature extremes. Total elongations below 1 percent were found only for irradiation and test temperatures of 600 and 700°C. The fractures were completely transgranular for specimens irradiated and tested at 300 and 400°C, of mixed mode but predominately intergranular at 500°C, and fully intergranular at 600 and 700°C. The results suggest that Inconel 600 does not offer any advantages over Type 316 stainless steel and does not warrant further development for fusion reactor application.
Component Mode Synthesis of Large Rotor Systems

A scheme is presented for calculating the vibrations of large multi-component flexible rotor systems based on the component mode synthesis method. It is shown that, by a modal expansion of the elastic interconnecting elements, the system modal equation can be conveniently constructed from the undamped eigen representations of the component subsystems. The capability of the component mode method is demonstrated in two examples: a transient simulation of a two-spool gas turbine engine equipped with a squeeze-film damper; and an unbalance response analysis of the Space Shuttle Main Engine oxygen turbopump in which the dynamics of the rotor and the housing are both considered.
Bias in estimators of archaic admixture.

Abstract This article evaluates bias in one class of methods used to estimate archaic admixture in modern humans. These methods study the pattern of allele sharing among modern and archaic genomes. They are sensitive to “ghost” admixture, which occurs when a population receives archaic DNA from sources not acknowledged by the statistical model. The effect of ghost admixture depends on two factors: branch-length bias and population-size bias. Branch-length bias occurs because a given amount of admixture has a larger effect if the two populations have been separated for a long time. Population-size bias occurs because differences in population size distort branch lengths in the gene genealogy. In the absence of ghost admixture, these effects are small. They become important, however, in the presence of ghost admixture. Estimators differ in the pattern of response. Increasing a given parameter may inflate one estimator but deflate another. For this reason, comparisons among estimators are informative. Using such comparisons, this article supports previous findings that the archaic population was small and that Europeans received little gene flow from archaic populations other than Neanderthals. It also identifies an inconsistency in estimates of archaic admixture into Melanesia.
Pattern Recognition System Design with Linear Encoding for Discrete Patterns

Pattern recognition systems based on compressed patterns and compressed sensor measurements can be designed using low-density matrices. We examine truncation encoding where a subset of the patterns and measurements are stored perfrectly while the rest is discarded. We also examine the use of LDPC parity check matrices for compressing measurements and patterns. We show how more general ensembles of good linear codes can be used as the basis for pattern recognition system design, yielding system design strategies for more general noise models.
Back-reactions in the photochemical disproportionation of Cp2Mo2(CO)6 (Cp = C5H4CH3) and the wavelength-dependent photochemistry of the Cp2Mo2(CO)6 complex with PPh3

L'irradiation a 525 nm de Cp 2 Mo 2 (CO) 6 avec PPh 3 dans CH 2 Cl 2 donne: CpMo(CO) 3 PPh 3 + et CpMo(CO) 3 . Dans le benzene, cette dismutation n'a pas de lien. Observation dans certains cas des reactions inverses
High dose uranium ion implantation into silicon

Abstract Implantation of uranium ions into silicon to a dose of 6 × 10 16 atoms/cm 2 , with a maximum concentration of 6 × 10 21 atoms/cm 3 , has been carried out at an ion mean energy of 157 keV. The implanted uranium content was measured by Rutherford backscattering and confirmed by a measurement of the alpha-particle activity of the buried uranium layer. The range and straggling of the uranium implant, and sputtering of the silicon target by uranium, were measured and are compared with theoretical estimates.
Threshold behavior of partial-wave amplitudes

The implications of the known threshold behavior of the partial-wave amplitudes are discussed in terms of the restrictions which it places on the imaginary part. Applying these considerations to theN/D method, it is shown that an arbitrary input, originally inconsistent with the threshold properties, can be modified by the addition of simple poles to bring it into agreement with these properties. A model calculation is carried out for Yukawa potential scattering, and it is shown that the modification procedure does indeed improve the results.
LONG TERM EVOLUTION OF MAGNETIC TURBULENCE IN RELATIVISTIC COLLISIONLESS SHOCKS

We study the long term evolution of magnetic fields generated by an initially unmagnetized collisionless relativistic e+e- shock. Our 2D particle-in-cell numerical simulations show that downstream of such a Weibel-mediated shock, particle distributions are approximately isotropic, relativistic Maxwellians, and the magnetic turbulence is highly intermittent spatially, non-propagating, and decaying. Using linear kinetic theory, we find a simple analytic form for these damping rates. Our theory predicts that the overall magnetic energy decays as (ωp t)-q with q ~ 1, which compares favorably with simulations, but predicts overly rapid damping of short-wavelength modes. The magnetic trapping of particles within the magnetic structures may be the origin of this discrepancy. We conclude that initially unmagnetized relativistic shocks in electron-positron plasmas are unable to form persistent downstream magnetic fields. These results put interesting constraints on synchrotron models for the prompt and afterglow emission from GRBs.
Rational design of 4,5-disubstituted-5,7-dihydro-pyrrolo[2,3-d]pyrimidin-6-ones as a novel class of inhibitors of epidermal growth factor receptor (EGF-R) and Her2(p185erbB) tyrosine kinases

A novel class of 4,5-disubstituted-5,7-dihydro-pyrrolo[2,3-d]pyrimidin-6-ones has been discovered as potent and selective inhibitors of the EGF-R tyrosine kinase family. These compounds selectively inhibit EGF-R kinase activity at low nanomolar concentration and tyrosine autophosphorylation in cells expressing EGF-R or Her2 (p185(erbB)). Structure-activity relationships (SARs) for this class of compounds are presented.
Umbilical Cord Blood Stem Cell Transplantation

Early successes with the transplantation of umbilical cord blood have prompted considerable investigation of this stem cell source. Numerous laboratory investigators have subsequently confirmed the high frequency of primitive hematopoietic progenitors as well as initiated a description of the functional capacities of the neonatal immune system. As a result of these clinical and laboratory observations, the large-scale banking of umbilical cord blood for future transplantation has been initiated worldwide.
Ion flow experiments in a multipole discharge chamber

It has been customary to assume that ions flow nearly equally in all directions from the ion production region within an electron-bombardment discharge chamber. Ion flow measurements in a multipole discharge chamber have shown that this assumption is not true. In general, the electron current through a magnetic field can alter the electron density, and hence the ion density, in such a way that ions tend to be directed away from the region bounded by the magnetic field. When this mechanism is understood, it becomes evident that many past discharge chamber designs have operated with a preferentially directed flow of ions.
Decomposition of analytic measures on groups and measure spaces

The final version of this paper appears in: "Studia Mathematica" 146 (2001): 261-284. Print.
A simple method of dethioacetalization

Abstract Thioacetals and thioketals can be cleaved to carbonyl compounds in high yields by treatment with bis (trifluoroacetoxy)iodobenzene
Coordinated interaction using reliable broadcast in mobile wireless networks

We consider the challenges of supporting collaborative decision making and applications requiring coordinated interaction in mobile ad hoc networks. This environment makes group coordination difficult due to relatively high packet loss and the presence of a continuously evolving network topology that leads to a changing set of participants. We describe and evaluate an application-level mobile reliable broadcast protocol (M-RBP) that provides applications with network characteristics well-suited to supporting coordinated interaction, such as reliable broadcast with data consistency and global ordering. The protocol is time-, rather than event-driven, providing it with unique, deterministic operational characteristics that can be verified in a relatively straightforward manner.
Rank One Lattice Type Vertex Operator Algebras and Their Automorphism Groups

Abstract LetLbe a positive definite even lattice of rank one andV + Lbe the fixed points of the lattice VOAVLassociated toLunder an automorphism ofVLlifting the −1 isometry ofL. A set of generators and the full automorphism group ofV + Lare determined.
STUDY OF THE EFFECT OF SOLUBLE SALTS PRESENT IN ENAMEL MILL LIQUORS

Studies were made of the solution of the frit during milling, the soluble salts derived from the frit were identified and studied, and some properties of the slips and mill liquors were investigated. The influence of some soluble salts present in cover-coat enamels on enamel film strength is shown, and a theory regarding the mechanism of tearing has been developed. The function of some salts, particularly sodium hydroxide and sodium nitrite, in eliminating tearing was studied, and the manner in which these salts improve film strength is reported.
Generalized in situ adaptive tabulation for constitutive model evaluation in plasticity

A database storage, search and retrieval method of constitutive model responses for use in plasticity simulations is developed to increase the computational efficiency of finite element simulations employing complex nonlinear material models. The method is based in the in situ adaptive tabulation method that has been successfully applied in the field of combustion chemistry, but is significantly modified to better handle the system of equations in plasticity. When using the database, the material response is estimated by a linear extrapolation from an appropriate database entry. This is shown to provide a response with an acceptable error tolerance. Two different example problems are chosen to demonstrate the behavior of the constitutive model estimation technique: a dynamic shock simulation, and a quasi-static inhomogeneous deformation simulation. This generalized in situ adaptive tabulation method shows promise for enabling simulations with complex multi-physics and multi-length scale constitutive descriptions.
Hydrodynamic Simulation of the Cosmological X-Ray Background

We use a hydrodynamic simulation of an inflationary cold dark matter model with a cosmological constant to predict properties of the extragalactic X-ray background (XRB). We focus on emission from the intergalactic medium (IGM), with particular attention to diffuse emission from warm-hot gas that lies in relatively smooth filamentary structures between galaxies and galaxy clusters. We also include X-rays from point sources associated with galaxies in the simulation, and we make maps of the angular distribution of the emission. Although much of the X-ray luminous gas has a filamentary structure, the filaments are not evident in the simulated maps because of projection effects. In the soft (0.5-2 keV) band, our calculated mean intensity of radiation from intergalactic and cluster gas is 2.3 × 10-12 ergs-1 cm-2 deg-2, 35% of the total softband emission. This intensity is compatible at the ~1 σ level with estimates of the unresolved soft background intensity from deep ROSAT and Chandra measurements. Only 4% of the hard (2-10 keV) emission is associated with intergalactic gas. Relative to active galactic nuclei flux, the IGM component of the XRB peaks at a lower redshift (median z ~ 0.45) and spans a narrower redshift range, so its clustering makes an important contribution to the angular correlation function of the total emission. The clustering on the scales accessible to our simulation (01-10') is significant, with an amplitude roughly consistent with an extrapolation of recent ROSAT results to small scales. A cross-correlation analysis of the XRB against nearby galaxies taken from a simulated redshift survey also yields a strong signal from the IGM. Our conclusions about the soft background intensity differ from those of some recent papers that have argued that the expected emission from gas in galaxy, group, and cluster halos would exceed the observed background unless much of the gas is expelled by supernova feedback. We obtain reasonable compatibility with current observations in a simulation that incorporates cooling, star formation, and only modest feedback. A clear prediction of our model is that the unresolved portion of the soft XRB will remain mostly unresolved even as observations reach deeper point-source sensitivity.
Some survey remarks on Whitham theory and EM duality

The nature of the BA function and its adjoint for KP-Toda is traced through the averaging method in generating the Whitham equations, differentials, and symplectic forms, with connections to EM duality.
Corrigendum to “An equivalence of categories for graded modules over monomial algebras and path algebras of quivers” [J. Algebra 353 (1) (2012) 249–260]

Abstract Our published paper contains an incorrect statement of a result due to Artin and Zhang. This corrigendum gives the correct statement of their result and includes a new result that allows us to use the correct version of Artin and Zhangʼs Theorem to prove our main theorem. Thus the main theorem of our published paper is correct as stated but its proof must be modified.
Photo-inhibition of passivity breakdown on nickel

Abstract Passivity breakdown on polycrystalline nickel in buffered (pH 9.2) chloride-containing solution at 25°C is found to be inhibited by incident white light. The photo-inhibition is attributed to the generation of electron—hole pairs within the passive film, which tends to quench the electric field thereby decreasing the driving force for the movement of cation vacancies across the film. The net effect is that the breakdown voltage becomes more positive, and the distribution in this quantity is depressed, as predicted by the Point Defect Model for passivity breakdown.
Investigation of functionalized α-chloroalkyllithiums for a stereospecific reagent-controlled homologation approach to the analgesic alkaloid (-)-epibatidine.

Four putative functionalized α-chloroakyllithiums RCH2CHLiCl, where R=CHCH2 (18 a), CCH (18 b), CH2OBn (18 c), and CH[O(CH2)2O] (18 d), were generated in situ by sulfoxide–lithium exchange from α-chlorosulfoxides, and investigated for the stereospecific reagent-controlled homologation (StReCH) of phenethyl and 2-chloropyrid-5-yl (17) pinacol boronic esters. Deuterium labeling experiments revealed that α-chloroalkyllithiums are quenched by proton transfer from their α-chlorosulfoxide precursors and it was established that this effect compromises the yield of StReCH reactions. Use of α-deuterated α-chlorosulfoxides was discovered to ameliorate the problem by retarding the rate of acid-base chemistry between the carbenoid and its precursor. Carbenoids 18 a and 18 b showed poor StReCH efficacy, particularly the propargyl group bearing carbenoid 18 b, the instability of which was attributed to a facile 1,2-hydride shift. By contrast, 18 d, a carbenoid that benefits from a stabilizing interaction between O and Li atoms gave good StReCH yields. Boronate 17 was chain extended by carbenoids 18 a, 18 b, and 18 d in 16, 0, and 68 % yield, respectively; α-deuterated isotopomers D-18 a and D-18 d gave yields of 33 and 79 % for the same reaction. Double StReCH of 17 was pursued to target contiguous stereodiads appropriate for the total synthesis of (−)-epibatidine (15). One-pot double StReCH of boronate 17 by two exposures to (S)-D-18 a (≤66 % ee), followed by work-up with KOOH, gave the expected stereodiad product in 16 % yield (d.r.∼67:33). The comparable reaction using two exposures to (S)-D-18 d (≤90 % ee) delivered the expected bisacetal containing stereodiad (R,R)-DD-48 in 40 % yield (≥98 % ee, d.r.=85:15). Double StReCH of 17 using (S)-D-18 d (≤90 % ee) followed by (R)-D-18 d (≤90 % ee) likewise gave (R,S)-DD-48 in 49 % yield (≥97 % ee, d.r.=79:21). (R,S)-DD-48 was converted to a dideuterated isotopomer of a synthetic intermediate in Corey’s synthesis of 15.
Implementation of a Monte Carlo based inverse planning model for clinical IMRT with MCNP code

Inaccurate dose calculations and limitations of optimization algorithms in inverse planning introduce systematic and convergence errors to treatment plans. This work was to implement a Monte Carlo based inverse planning model for clinical IMRT aiming to minimize the aforementioned errors. The strategy was to precalculate the dose matrices of beamlets in a Monte Carlo based method followed by the optimization of beamlet intensities. The MCNP 4B (Monte Carlo N-Particle version 4B) code was modified to implement selective particle transport and dose tallying in voxels and efficient estimation of statistical uncertainties. The resulting performance gain was over eleven thousand times. Due to concurrent calculation of multiple beamlets of individual ports, hundreds of beamlets in an IMRT plan could be calculated within a practical length of time. A finite-sized point source model provided a simple and accurate modeling of treatment beams. The dose matrix calculations were validated through measurements in phantoms. Agreements were better than 1.5% or 0.2 cm. The beamlet intensities were optimized using a parallel platform based optimization algorithm that was capable of escape from local minima and preventing premature convergence. The Monte Carlo based inverse planning model was applied to clinical cases. The feasibility and capability of Monte Carlo based inverse planning for clinical IMRT was demonstrated. Systematic errors in treatment plans of a commercial inverse planning system were assessed in comparison with the Monte Carlo based calculations. Discrepancies in tumor doses and critical structure doses were up to 12% and 17%, respectively. The clinical importance of Monte Carlo based inverse planning for IMRT was demonstrated.
Dimension, Halfspaces, and the Density of Hard Sets

We use the connection between resource-bounded dimension and the online mistake-bound model of learning to show that the following classes have polynomial-time dimension zero. The class of problems which reduce to nondense sets via a majority reduction. The class of problems which reduce to nondense sets via an iterated reduction that composes a bounded-query truth-table reduction with a conjunctive reduction. Intuitively, polynomial-time dimension is a means of quantifying the size and complexity of classes within the exponential time complexity class E. The class P has dimension 0, E itself has dimension 1, and any class with dimension less than 1 cannot contain E. As a corollary, it follows that all sets which are hard for E under these types of reductions are exponentially dense. The first item subsumes two previous results and the second item answers a question of Lutz and Mayordomo. Our proofs use Littlestone’s Winnow2 algorithm for learning r-of-k threshold functions and Maass and Turan’s algorithm for learning halfspaces.
An Efficient, Simple Synthesis of 4-Azidobenzaldehyde

Abstract A three-pot synthesis of 4-azidobenzaldehyde from 4-nitrobenz-aldehyde in overall yield of 71% is described. The new synthesis is superior in its ease of reproducibility and reduction of waste side products.
Copyright and Social Movements in Late Nineteenth-Century America

The cultural turn in copyright law identified authorship as a rhetorical construct employed by economic interests to strengthen claims to property rights. Grassroots intellectual property political movements have been seen as both a means of countering these interests’ everexpanding proprietary control of knowledge and establishing a more public regarding copyright system. This Article examines one of the most notable intellectual property political movements, the emergence of late nineteenth-century agitation to provide copyright protection for foreign authors as a social movement. It places this political and legal activism within the larger framework of Progressive Era reform. During this period, activists promoted the idea of the public — and not simply the author — as primary to the workings of American copyright. The framing of the purposes of copyright, the appeal to a broader public, and the complex negotiations surrounding the passage of an international copyright act after a long period of gestation was formative to the creation of modern United States copyright law. Ironically, the movement for international copyright also sharpened the identification of interest groups. The first modern American comprehensive copyright legislation, the 1909 Copyright Act, was drafted by gathering together these groups for negotiations remarkably similar in style to those which led to the protection of the rights of foreign authors — but which would strongly embrace a proprietary model.
Microdynamic issues in large deployable space telescopes

This paper discusses a framework for microdynamic analysis -- analyzing a structure for nonlinear dynamic behavior in the nanometric regime -- and illustrates how microdynamic behaviors such as microlurch, joint snaps, and harmonic distortion fit within the framework.
Wind Interaction Models for Gamma-Ray Burst Afterglows: The Case for Two Types of Progenitors

Beginning with the γ-ray bursts GRB 970228 and GRB 970508, a standard model for the interpretation of gamma-ray burst (GRB) afterglows emerged involving synchrotron emission from a constant-energy blast wave expanding into a constant-density, "interstellar" medium. However, a massive star origin for GRBs implies a stellar wind environment, probably a Wolf-Rayet star, and we have previously suggested wind interaction models for the afterglows of GRBs 980326, 980519, and 980425/SN 1998bw. Here, we extend the theory of afterglows in winds, considering strong cooling phases, the transition to nonrelativistic motion, jets, and prompt reverse-shock emission. We find that, compared to the interstellar case, the optical prompt emission in the wind case could have a comparable magnitude but would die off faster. We examine the afterglows of other well-observed GRBs in the context of wind interaction models and find that GRBs 970228 and 970508 are likely wind interactors. The revision in the nonthermal afterglow emission from GRB 970228 caused by the recognition of late supernova emission favors wind interaction. The radio evolution of GRB 970508 provides especially strong evidence for wind interaction. For GRB 970508, the observations suggest a density that is compatible with that expected in a Wolf-Rayet star wind. Finally, observations of the afterglow evolution of GRBs 990123 and 990510 and the prompt optical emission from GRB 990123 favor interstellar interaction models, which would suggest compact star merger progenitors for these objects.
Total Synthesis of Himastatin: Confirmation of the Revised Stereostructure.

A stereoisomer of the natural product and not himastatin, an unusual dimeric depsipeptide with promising antibiotic and antitumor properties, was obtained from pyrroloindoline anti-cis-1. This result led to a revision of the proposed stereostructure. The new stereostructure was confirmed by the total synthesis, which involves stereoselective access to the pyrroloindoline syn-cis-1 and the 5-hydroxypiperazic acid subunit and features a Stille coupling for the formation of the central carbon-carbon bond.
Revisiting the magnification of type Ia supernovae with SDSS

We cross-correlate the sample of type Ia supernovae from Riess A. G. et al. with the SDSS DR2 photometric galaxy catalogue. In contrast to recent work, we find no detectable correlation between supernova magnitude and galaxy overdensity on scales ranging between 1 and 10 arcmin. Our results are in accord with theoretical expectations for gravitational lensing of supernovae by large-scale structure. Future supernova surveys such as SNAP will be capable of detecting unambiguously the predicted lensing signal.
Videoconferencing in the Field: A Heuristic Processing Model

This research uses dual-process cognitive theory to describe how people process information differently when it is delivered via videoconference rather than when it is delivered face-to-face. According to this theory, relative to face-to-face communication, people in videoconferences tend to be more influenced by heuristic cues---such as how likeable they perceive the speaker to be---than by the quality of the arguments presented by the speaker. This is due to the higher cognitive demands that videoconferencing places on participants. We report on a field study of medical professionals in which we found differences in information processing as predicted: participants attending a seminar via videoconference were more influenced by the likeability of the speaker than by the quality of the arguments presented, whereas the opposite pattern was true for participants attending in-person. We also found that differences in cognitive load explain these effects. The discussion on the theoretical model and associated findings explains why prior videoconference studies have not consistently found main effects for media. The findings also show that videoconferencing is not like face-to-face communication, despite apparent similarities.
Optimal st-orientations for plane triangulations

For plane triangulations, it has been proved that there exists a plane triangulation G with n vertices such that for any st-orientation of G, the length of the longest directed paths of G in the st-orientation is $\geq\lfloor\frac{2n}{3}\rfloor$ (Zhang and He in Lecture Notes in Computer Science, vol. 3383, pp. 425–430, 2005). In this paper, we prove the bound $\frac{2n}{3}$ is optimal by showing that every plane triangulation G with n-vertices admits an st-orientation with the length of its longest directed paths bounded by $\frac{2n}{3}+O(1)$ . In addition, this st-orientation is constructible in linear time. A by-product of this result is that every plane graph G with n vertices admits a visibility representation with height $\le\frac{2n}{3}+O(1)$ , constructible in linear time, which is also optimal.
Comments on noncommutative perturbative dynamics

We analyze further the IR singularities that appear in noncommutative field theories on d. We argue that all IR singularities in nonplanar one loop diagrams may be interpreted as arising from the tree level exchanges of new light degrees of freedom, one coupling to each relevant operator. These exchanges are reminiscent of closed string exchanges in the double twist diagrams in open string theory. Some of these degrees of freedom are required to have propagators that are inverse linear or logarithmic. We suggest that these can be interpreted as free propagators in one or two extra dimensions respectively. We also calculate some of the IR singular terms appearing at two loops in noncommutative scalar field theories and find a complicated momentum dependence which is more difficult to interpret.
Can classical noise enhance quantum transmission

A modified quantum teleportation protocol broadens the scope of the classical forbidden-interval theorems for stochastic resonance. The fidelity measures performance of quantum communication. The sender encodes the two classical bits for quantum teleportation as weak bipolar subthreshold signals and sends them over a noisy classical channel. Two forbidden-interval theorems provide a necessary and sufficient condition for the occurrence of the nonmonotone stochastic resonance effect in the fidelity of quantum teleportation. The condition is that the noise mean must fall outside a forbidden interval related to the detection threshold and signal value. An optimal amount of classical noise benefits quantum communication when the sender transmits weak signals, the receiver detects with a high threshold and the noise mean lies outside the forbidden interval. Theorems and simulations demonstrate that both finite-variance and infinite-variance noise benefit the fidelity of quantum teleportation.
Monte Carlo simulation of ion transport of high strain ionomeric with cluster morphology

The transport of charge due to electric stimulus is the primary mechanism of actuation for a class of polymeric active materials known as ionomeric polymer transducers (IPT). Due to the fact that a universally accepted morphological model for the structure of Nafion has not been defined, this initial work is aimed to investigate the relationship between ion transport performance inside Nafion and the cluster morphology. A two-dimensional ion hopping model has been built to describe ion transport in IPT with Monte-Carlo simulation. In the simulation, a 50nm x 50nm x 1nm lattice holds 200 cations and 200 anions. The initial distribution of anions is varied from uniformly random distribution to one with 15 clusters, 8 clusters and 4 clusters. A step voltage is applied between the electrodes of the IPT, causing thermally activated hopping. Periodic boundary conditions are applied when ions hop in the direction perpendicular to the electric field. The influence of the electrodes on both faces of IPT is presented by the method of image charges. The results of current response, charge density and ion distribution are compared for different initial ion distributions.
A Free Energy Model of Boron Carbide

The assessed phase diagram of the boron-carbon system contains a single nonstoichiometric boron-carbide phase of rhombohedral symmetry with a broad, thermodynamically improbable, low temperature composition range. We combine first principles total energy calculations with phenomenological thermodynamic modeling to propose a revised low temperature phase diagram that contains two boron-carbide phases of differing symmetries and compositions. One structure has composition B4C and consists of B11C icosahedra and C-B-C chains, with the placement of carbon on the icosahedron breaking rhombohedral symmetry. This phase is destabilized above 600 K by the configurational entropy of alternate carbon substitutions. The other structure, of ideal composition B13C2, has a broad composition range at high temperature, with rhombohedral symmetry throughout, as observed experimentally.
Stiefel—Whitney currents

A canonically defined mod 2 linear dependency current is associated to each collection v of sections, v1,…,vm, of a real rank n vector bundle. This current is supported on the linear dependency set of v. It is defined whenever the collection v satisfies a weak measure theoretic condition called “atomicity.” Essentially any reasonable collection of sections satisfies this condition, vastly extending the usual general position hypothesis. This current is a mod 2 d-closed locally integrally flat current of degree q = n −m + 1 and hence determines a ℤ2-cohomology class. This class is shown to be well defined independent of the collection of sections. Moreover, it is the qth Stiefel-Whitney class of the vector bundle.