cssi/SciSciGPT-SciSciNet huggingface dataset:
Equations of state for nonlinear sigma-models II: Relations between resummation schemes, and crossover phenomena

Abstract It is shown how a recent method to systematically extrapolate and resum the loop expansion for nonlinear sigma-models is related to solutions of the renormalization group equation. This relation is used to generalize the explicit equations of state obtained previously to models which display crossover phenomena. As an example we discuss Wegner's localization model and consider the crossover from symplectic to unitary symmetry.
Renormalizing DLCQ using supersymmetry

Abstract Recent string theory developments suggest the necessity to understand supersymmetric gauge theories non-perturbatively, in various dimensions. In this work we show that there is a standard Hamiltonian formulation that generates a finite and supersymmetric result at every order of the approximation scheme known as discrete light-cone quantization (DLCQ). We present this renormalized DLCQ Hamiltonian and find that it has two novel features: it automatically chooses the 't Hooft prescription for renormalizing the singularities, and it introduces irrelevant operators that serve to preserve the supersymmetry and improve the convergence. We solve for the bound states and the wave functions with and without the irrelevant operators and verify that with the irrelevant operator the exact large- N c supersymmetric DLCQ (SDLCQ) results are reproduced. With the irrelevant operator removed, we show that the bound-state mass and wave functions appear to be converging to the SDLCQ results but very slowly. This is a first step in extending the advantages of SDLCQ to non-supersymmetric theories.
Are Probabilities Used in Markets

Abstract Working in a complete-markets setting, a property of asset demands is identified that is inconsistent with the investor's preference being based on probabilities. In this way, a market counterpart of the Ellsberg Paradox is provided. Journal of Economic Literature Classification Numbers: D00, D80, D81.
The Impact of Legal Status on Immigrants’ Earnings and Human Capital: Evidence from the IRCA 1986

The Immigration Reform and Control Act (IRCA), the largest amnesty in U.S. history, took effect in 1986 and legalized all immigrants who arrived before 1982. The IRCA creates a discontinuity, according to the year of entry, in the probability of having legal status. Therefore, I use the regression discontinuity approach to study the impact of legality on immigrants’ labor market outcomes and human capital. Using Californian Latino immigrants from Census 1990, I find that the 1975–81 arrivals, on average, outperform the 1982–86 arrivals in male wages, female employment probability, and male English-speaking ability. These findings are not due to a general trend in U.S. labor market conditions because the same analysis, using refugees, Puerto Rican migrants and U.S.-born Latinos—three comparison groups without legality issues—indicates no difference in outcomes between the 1975–81 and 1982–86 cohorts. However, the advantage of Latino immigrants of the earlier cohort over the later cohort diminishes in Census 2000.
Radio Emission from the Double-Pulsar System J0737–3039 Revisited

The double pulsar J0737-3039 is the only known system in which the relativistic wind emitted by a radio pulsar demonstrably interacts with the magnetosphere of another one. We report radio interferometric observations of the J0737-3039 system with the VLA at three wavelengths, with each observation spanning a full binary orbit. We detect J0737-3039 at 1.6 and 4.8 GHz, derive a spectral index of -2.3 ± 0.2, and place an upper limit on its flux density at 8.4 GHz. Orbital modulation is detected in the 1.6 GHz data, with a significance of ~2 σ. Both orbital phase-resolved and phase-averaged measurements at 1.6 GHz are consistent with the entire flux density arising from the pulsed emission of the two pulsars. Contrary to prior results, we find no evidence for unpulsed emission, and limit it to less than 0.5 mJy (5 σ).
A Berry-Esseen type inequality for convex bodies with an unconditional basis

Suppose X = (X 1, . . . , X n ) is a random vector, distributed uniformly in a convex body $${K \subset \mathbb R^n}$$ . We assume the normalization $${\mathbb E X_i^2 = 1}$$ for i = 1, . . . , n. The body K is further required to be invariant under coordinate reflections, that is, we assume that (±X 1, . . . , ±X n ) has the same distribution as (X 1, . . . , X n ) for any choice of signs. Then, we show that $$ \mathbb E \left( \, |X| - \sqrt{n} \, \right)^2 \leq C^2,$$ where C ≤ 4 is a positive universal constant, and | · | is the standard Euclidean norm in $${\mathbb R^n}$$ . The estimate is tight, up to the value of the constant. It leads to a Berry-Esseen type bound in the central limit theorem for unconditional convex bodies.
Synthesis of a new N-acetyl thiazolidinethione reagent and its application to a highly selective asymmetric acetate aldol reaction.

A new N-acetyl thiazolidinethione reagent, which undergoes highly diastereoselective aldol reactions upon enolization with dichlorophenylborane and (−)-sparteine and subsequent treatment with a variety of aldehydes, is described. This reagent is pseudoenantiomeric to an l-tert-leucine-derived reagent recently described by us and is useful because it avoids the prohibitively costly d-tert-leucine.
The chemistry of interstellar space

Interstellar space is not empty, but contains gaseous and particulate matter that is concentrated into very large regions known as interstellar clouds. In the denser and cooler clouds, the gas is molecular and most of the molecules detected are organic in nature. The gas-phase molecules are synthesised from precursor atoms by rapid exothermic reactions in the gas and on the surfaces of tiny dust particles. Since dense interstellar clouds collapse to form stars and planetary systems, the molecules produced in the clouds may be eventually incorporated into solid bodies such as comets, meteors, and even planets.
Hazard Alerting Based on Probabilistic Models

Hazard alerting systems alert operators to potential future undesirable events so that action may be taken to mitigate risk. One way to develop a hazard alerting system based on probabilistic models is by using a threshold-based approach, where the probability of the undesirable event without mitigation is compared against a threshold. Another way to develop such a system is to model the system as a Markov decision process and solve for the hazard alerting strategy that maximizes expected utility. This paper analyzes and compares these two methods. The experiments reveal that an expected utility approach performs better than threshold-based approaches when the dynamic stochasticity is high, where accounting for delays or changes in the alert becomes more important. However, for certain system parameters and operating environments, a threshold-based approach may provide comparable performance.
Water Removal From Hydrophilic Fuel Cell Channels

This paper describes an approximate method for analyzing two-phase flow of gas and liquid water in fuel cell channels whose surfaces are sufficiently hydrophilic for liquid water to wick spontaneously into the channel corners. This analysis is used to address the important question of whether the gas flow at typical stoichiometries in such channels is sufficient to remove all the liquid water generated in a Proton Exchange Membrane (PEM) fuel cell. Since fuel channels are usually much narrower than they are long, it is possible to adopt the usual approximations of lubrication theory and decompose the general solution for the liquid motion into two parts: (1) that driven by the channel pressure gradient, and (2) that driven by surface shear stress from the faster moving gas. When both parts of the solution are combined with the mass balance equations, it is possible to derive a pair of partial differential equations for the water depth and gas flow rate that depend on distance down the channel and time. Steady solutions of these equations are explored to determine the amount of liquid water that accumulates in the channel over a broad range of fuel cell operating conditions.Copyright © 2008 by General Motors
Fields of Lorentz transformations on space-time

Abstract Fields of Lorentz transformations on a space-time M are related to tangent bundle self isometries. In other words, a gauge transformation with respect to the −+++ Minkowski metric on each fibre. Any such isometry L :T(M)→T(M) can be expressed, at least locally, as L= e F where F :T(M)→T(M) is antisymmetric with respect to the metric. We find there is a homotopy obstruction and a differential obstruction for a global F . We completely study the structure of the singularity which is the heart of the differential obstruction and we find it is generated by “null” F which are “orthogonal” to infinitesimal rotations F with specific eigenvalues. We find that the classical electromagnetic field of a moving charged particle is naturally expressed using these ideas. The methods of this paper involve complexifying the F bundle maps which leads to a interesting algebraic situation. We use this not only to state and prove the singularity theorems, but to investigate the interaction of the “generic” and “null” F , and we obtain, as a byproduct of our calculus, a interesting basis for the 4×4 complex matrices, and we also observe that there are two different kinds of two-dimensional complex null subspaces.
What can we learn by squeezing a liquid

Relaxation times τ(T,υ) for different temperatures, T, and specific volumes, υ, collapse to a master curve vs Tυγ, with γ a material constant. The isochoric fragility, mV, is also a material constant, inversely correlated with γ. From these experimental facts, we obtain a three-parameter function that accurately fits τ(T,υ) data for several glass-formers over the supercooled regime, without any divergence of τ below Tg. Although the values of the three parameters depend on the material, only γ significantly varies; thus, by normalizing material-specific quantities related to γ, a universal power law for the dynamics is obtained.
Privacy-Preserving Public Information for Sequential Games

In settings with incomplete information, players can find it difficult to coordinate to find states with good social welfare. For instance, one of the main reasons behind the recent financial crisis was found to be the lack of market transparency, which made it difficult for financial firms to accurately measure the risks and returns of their investments. Although regulators may have access to firms' investment decisions, directly reporting all firms' actions raises confiden- tiality concerns for both individuals and institutions. The natural question, therefore, is whether it is possible for the regulatory agencies to publish some information that, on one hand, helps the financial firms understand the risks of their investments better, and, at the same time, preserves the privacy of their investment decisions. More generally, when can the publication of privacy-preserving information about the state of the game improve overall outcomes such as social welfare? In this paper, we explore this question in a sequential resource-sharing game where the value gained by a player on choosing a resource depends on the number of other players who have chosen that resource in the past. Without any knowledge of the actions of the past players, the social welfare attained in this game can be arbitrarily bad. We show, however, that it is possible for the players to achieve good social welfare with the help of privacy-preserving, publicly-announced information. We model the behavior of players in this imperfect information setting in two ways -- greedy and undominated strategic behaviours, and we prove guarantees about the social welfare that certain kinds of privacy-preserving information can help attain. To achieve the social welfare guarantees, we design a counter with improved privacy guarantees under continual observation. In addition to the resource-sharing game, we study the main question for other games including sequential versions of the cut, machine-scheduling and cost-sharing games, and games where the value attained by a player on a particular action is not only a function of the actions of the past players but also of the actions of the future players.
Early results from the Chandra X-ray observatory

Abstract We present some early results on AGN from the Chandra X-ray Observatory, highlighting high resolution spectroscopy using the High Energy Transmission Grating Spectrometer (HETGS). The quasar PKS 0637–752 was found to have a very bright X-ray jet whose shape is remarkably similar to that of the radio jet on a size scale of 100 kpc, but the X-ray emission is still inexplicably bright. Two BL Lac objects, PKS 2155–304 and Mrk 421, observed with the spectrometer were found to have no strong absorption or emission features. Other radio loud AGN observed with the HETGS show simple power law spectra without obvious features.
RADIATIVE AND KINETIC FEEDBACK BY LOW-MASS PRIMORDIAL STARS

Ionizing UV radiation and supernova (SN) flows amidst clustered minihalos at high redshift regulated the rise of the first stellar populations in the universe. Previous studies have addressed the effects of very massive primordial stars on the collapse of nearby halos into new stars, but the absence of the odd-even nucleosynthetic signature of pair-instability SNe in ancient metal-poor stars suggests that Population III stars may have been less than 100 M ☉. We extend our earlier survey of local UV feedback on star formation to 25-80 M ☉ stars and include kinetic feedback by SNe for 25-40 M ☉ stars. We find radiative feedback to be relatively uniform over this mass range, primarily because the larger fluxes of more massive stars are offset by their shorter lifetimes. Our models demonstrate that prior to the rise of global UV backgrounds, Lyman-Werner (LW) photons from nearby stars cannot prevent halos from forming new stars. These calculations also reveal that violent dynamical instabilities can erupt in the UV radiation front enveloping a primordial halo, but that they ultimately have no effect on the formation of a star. Finally, our simulations suggest that relic H II regions surrounding partially evaporated halos may expel LW backgrounds at lower redshifts, allowing stars to form that were previously suppressed. We provide fits to radiative and kinetic feedback on star formation for use in both semianalytic models and numerical simulations.
Finite energy solutions of quasilinear elliptic equations with sub-natural growth terms

We give an explicit necessary and sufficient condition for the existence of a finite energy solution to the quasilinear elliptic equation $$\begin{aligned} -\Delta _pu=\varvec{\sigma } \, u^q, \qquad u \ge 0 \, \, \, \text {in} ~~ {\mathbb {R}}^n, \end{aligned}$$ where $$\Delta _p$$ is the $$p$$ -Laplacian, $$p>1$$ , and $$\varvec{\sigma } \ge 0$$ is an arbitrary locally integrable function (or measure) on $${\mathbb {R}}^n$$ , in the case $$0<q < p-1$$ (below the “natural growth” rate $$q=p-1$$ ). We also prove that such a solution is unique. Among our main tools are integral inequalities closely associated with this problem, and Wolff potential estimates used to obtain sharp bounds of solutions. More general quasilinear equations with the $$\fancyscript{A}$$ -Laplacian $$\text {div} \fancyscript{A}(x,\nabla \cdot )$$ in place of $$\Delta _p$$ are considered as well.
Individual characteristics vs. city structural characteristics: explaining self-employment differences among Chinese, Japanese, and Filipinos in the United States

Abstract Using data from the 1990 Census Public Use Microdata Sample (PUMS), this paper tests several theories explaining differing rates of self-employment for Chinese, Japanese, and Filipino. The primary purpose is to separate out the effects of individual characteristics versus structural effects by city. The primary conclusions reached are: (1) differences in individual characteristics explain much of the differences in city self-employment rates for Chinese, Japanese, and Filipinos and (2) theories explaining high rates of ethnic self-employment based on ethnic resources, disadvantage/discrimination, differences in self-employment earnings and wage earnings are tested but none universally explain much of the differences in city self-employment rates for any of the three groups.
The effectiveness of the Kozai mechanism in the Galactic Centre

I examine the effectiveness of Kozai oscillations in the centres of galaxies and in particular the Galactic Centre (GC) using standard techniques from celestial mechanics. In particular, I study the effects of a stellar bulge potential and general relativity on Kozai oscillations, which are induced by stellar discs. Lockmann et al. recently suggested that Kozai oscillations induced by the two young massive stellar discs in the GC drive the orbits of the young stars to large eccentricity (e ≈ 1). If some of these young eccentric stars are in binaries, they would be disrupted near pericentre, leaving one star in a tight orbit around the central supermassive black hole and producing the S-star population. I find that the spherical stellar bulge suppresses Kozai oscillations, when its enclosed mass inside a test body is of the order of the mass in the stellar disc(s). Since the stellar bulge in the GC is much larger than the stellar discs, Kozai oscillations due to the stellar discs are likely suppressed. Whether Kozai oscillations are induced from other non-spherical components to the potential (e.g. a flattened stellar bulge) is yet to be determined.
Bargaining with common values

This paper examines a bargaining model with asymmetric information in which the private valuations of the two bargaining agents are correlated. It shows that equilibria in such models typically exhibit a significant probability of a significant delay to agreement. The paper characterizes the unique perfect Bayesian equilibrium to the game in which an uninformed buyer makes offers to a privately informed seller. It also shows, by example, that in this framework bargainers may rationally break off negotiations even in the presence of commonly known gains from trade.
RADIATION-ASSOCIATED MORBIDITY IN PATIENTS UNDERGOING SMALL-FIELD EXTERNAL BEAM IRRADIATION FOR PROSTATE CANCER

treatment. Only 14% of the entire group required intervention. Of 356 patients, 117 (33%) evaluable for bladder complications developed genitourinary changes: In 14 patients (4%) asymptomatic hematuria occurred, 71 (20%) had mild symptoms not requiring treatment, and 32 (9%) required treatment. Of the 171 patients who were potent prior to radiation, 106 (62%) reported impotence after treatment. No statistically significant association was identified between any clinical or technical variables (including machine energy) assessed and complications. Conclusions: In this retrospective review, treatment-related bowel and bladder side effects were not identified in the majority of patients despite the use of a grading system designed to identify subtle changes. Impotence, however, was common. Although pretreatment clinical characteristics varied among patients, they could not be used to predict the subsequent development of complications. The only treatment-related characteristic that varied in this study was machine energy, which did not correlate with complications. © 1998 Elsevier Science Inc. Prostate cancer, Small-field irradiation, Complications.
Rapid synthesis of the 7-deoxy zaragozic acid core.

[reaction: see text] We have developed an efficient synthesis of the 7-deoxy zaragozic acid core. The synthesis begins with a Feist-Benary reaction that assembles all three carbons of the polycarboxylic acid portion of the core. This reaction is followed by highly diastereoselective aldol and dihydroxylation reactions that set the remaining stereocenters of the core. The synthesis finishes with lactol oxidation and lactone alcoholysis/ketal formation reactions to construct the bicyclic ring system of the core.
Impacts of fluorine on the electrochemical properties of Li[Ni0.5Mn0.5]O2 and Li[Li0.2Ni0.15Co0.1Mn0.55]O2

The impact of the fluorine substitution on the electrochemical properties of layered lithium nickel manganese positive electrode materials for lithium ion batteries is summarized. The addition of a controlled amount of fluorine to the oxygen lattice can effectively improve the capacity retention as well as reduce the impedance of the positive electrode materials. The fluorination of the nickel and manganese based layered oxide cathode material has also led to significant improvement in cycle life and power capability of the battery.
Competitive Effects of Means-Tested School Vouchers

Abstract We use the introduction of a means-tested voucher program in Florida to examine whether increased competitive pressure on public schools affects students’ test scores. We find greater score improvements in the wake of the program introduction for students attending schools that faced more competitive private school markets prior to the policy announcement, especially those that faced the greatest financial incentives to retain students. These effects suggest modest benefits for public school students from increased competition. The effects are consistent across several geocoded measures of competition and isolate competitive effects from changes in student composition or resource levels in public schools. (JEL H75, I21, I22, I28)
A stereospecific synthesis of (-)-bestatin from L-malic acid

Abstract A highly diastereospecific route to (−)-Bestatin from L-Malic Acid has been developed. This approach features a stereocontrolled alkylation of diethyl (S)-malate and proceeds through an oxazolidone via a Curtius Rearrangement.
Are Residues in a Protein Folding Nucleus Evolutionarily Conserved

Abstract Protein is the working molecule of the cell, and evolution is the hallmark of life. It is important to understand how protein folding and evolution influence each other. Several studies correlating experimental measurement of residue participation in folding nucleus and sequence conservation have reached different conclusions. These studies are based on assessment of sequence conservation at folding nucleus sites using entropy or relative entropy measurement derived from multiple sequence alignment. Here we report analysis of conservation of folding nucleus using an evolutionary model alternative to entropy-based approaches. We employ a continuous time Markov model of codon substitution to distinguish mutation fixed by evolution and mutation fixed by chance. This model takes into account bias in codon frequency, bias-favoring transition over transversion, as well as explicit phylogenetic information. We measure selection pressure using the ratio ω of synonymous versus non-synonymous substitution at individual residue site. The ω-values are estimated using the PAML method, a maximum-likelihood estimator. Our results show that there is little correlation between the extent of kinetic participation in protein folding nucleus as measured by experimental φ-value and selection pressure as measured by ω-value. In addition, two randomization tests failed to show that folding nucleus residues are significantly more conserved than the whole protein, or the median ω value of all residues in the protein. These results suggest that at the level of codon substitution, there is no indication that folding nucleus residues are significantly more conserved than other residues. We further reconstruct candidate ancestral residues of the folding nucleus and suggest possible test tube mutation studies for testing folding behavior of ancient folding nucleus.
Random walk beyond Hartree–Fock

We give a brief discussion of the recently developed Constrained-Path Monte Carlo method. This method is a quantum Monte Carlo technique that eliminates the fermion sign problem plaguing simulations of systems of interacting electrons. The elimination is accomplished by trading an exact procedure for an approximate one that has been demonstrated to give very accurate estimates of energies and many-body correlation functions. We also give a short review of its applications, a discussion of several strategies for parallelizing it, and some speculation of its future extensions.
The place of exceptional covers among all diophantine relations

Let F"q be the order q finite field. An F"q cover @f:X->Y of absolutely irreducible normal varieties has a nonsingular locus. Then, @f is exceptional if it maps one-one on F"q"^"t points for ~-ly many t over this locus. Lenstra suggested a curve Y may have an Exceptional (cover) Tower over F"q Lenstra Jr. [Talk at Glasgow Conference, Finite Fields III, 1995]. We construct it, and its canonical limit group and permutation representation, in general. We know all one-variable tamely ramified rational function exceptional covers, and much on wildly ramified one variable polynomial exceptional covers, from Fried et al. [Schur covers and Carlitz's conjecture, Israel J. Math. 82 (1993) 157-225], Guralnick et al. [The rational function analogue of a question of Schur and exceptionality of permutations representations, Mem. Amer. Math. Soc. 162 (2003) 773, ISBN 0065-9266] and Lidl et al. [Dickson Polynomials, Pitman Monographs and Surveys in Pure and Applied Mathematics, vol. 65, Longman Scientific, New York, 1993]. We use exceptional towers to form subtowers from any exceptional cover collections. This gives us a language for separating known results from unsolved problems. We generalize exceptionality to p(ossibly)r(educible)-exceptional covers by dropping irreducibility of X. Davenport pairs (DPs) are significantly different covers of Y with the same ranges (where maps are nonsingular) on F"q"^"t points for ~-ly many t. If the range values have the same multiplicities, we have an iDP. We show how a pr-exceptional correspondence on F"q covers characterizes a DP. You recognize exceptional covers and iDPs from their extension of constants series. Our topics include some of their dramatic effects*How they produce universal relations between Poincare series. *How they relate to the Guralnick-Thompson genus 0 problem and to Serre's open image theorem. Historical sections capture Davenport's late 1960s desire to deepen ties between exceptional covers, their related cryptology, and the Weil conjectures.
Covariate adjustment in the analysis of microarray data from clinical studies

There is tremendous scientific interest in the analysis of gene expression data in clinical settings, such as oncology. In this paper, we describe the importance of adjusting for confounders and other prognostic factors in order to select for differentially expressed genes for follow-up validation studies. We develop two approaches to the analysis of microarray data in non-randomized clinical settings. The first is an extension of the current significance analysis of microarray procedures, where other covariates are taken into account. The second is a novel covariate-adjusted regression modelling based on the receiver operating characteristic (ROC) curve for the analysis of gene expression data. The ideas are illustrated using data from a prostate cancer molecular profiling study.
Nonvanishing cohomology and classes of Gorenstein rings

Abstract We give counterexamples to the following conjecture of Auslander: given a finitely generated module M over an Artin algebra Λ , there exists a positive integer n M such that for all finitely generated Λ -modules N , if Ext Λ i ( M , N )=0 for all i ≫0, then Ext Λ i ( M , N )=0 for all i ⩾ n M . Some of our examples moreover yield homologically defined classes of commutative local rings strictly between the class of local complete intersections and the class of local Gorenstein rings.
A laboratory-based hard x-ray monochromator for high-resolution x-ray emission spectroscopy and x-ray absorption near edge structure measurements

We report the development of a laboratory-based Rowland-circle monochromator that incorporates a low power x-ray (bremsstrahlung) tube source, a spherically bent crystal analyzer, and an energy-resolving solid-state detector. This relatively inexpensive, introductory level instrument achieves 1-eV energy resolution for photon energies of ∼5 keV to ∼10 keV while also demonstrating a net efficiency previously seen only in laboratory monochromators having much coarser energy resolution. Despite the use of only a compact, air-cooled 10 W x-ray tube, we find count rates for nonresonant x-ray emission spectroscopy comparable to those achieved at monochromatized spectroscopy beamlines at synchrotron light sources. For x-ray absorption near edge structure, the monochromatized flux is small (due to the use of a low-powered x-ray generator) but still useful for routine transmission-mode studies of concentrated samples. These results indicate that upgrading to a standard commercial high-power line-focused x-ray tube or rotating anode x-ray generator would result in monochromatized fluxes of order 106–107 photons/s with no loss in energy resolution. This work establishes core technical capabilities for a rejuvenation of laboratory-based hard x-ray spectroscopies that could have special relevance for contemporary research on catalytic or electrical energy storage systems using transition-metal, lanthanide, or noble-metal active species.
Kazhdan-Lusztig polynomials and canonical basis

In this paper we show that the Kazhdan-Lusztig polynomials (and, more generally, parabolic KL polynomials) for the groupSn coincide with the coefficients of the canonical basis innth tensor power of the fundamental representation of the quantum groupUq\(\mathfrak{s}\mathfrak{l}\)k. We also use known results about canonical bases forUq\(\mathfrak{s}\mathfrak{l}\)2 to get a new proof of recurrent formulas for KL polynomials for maximal parabolic subgroups (geometrically, this case corresponds to Grassmannians), due to Lascoux-Schutzenberger and Zelevinsky.
Removable Matter-Power-Spectrum Covariance from Bias Fluctuations

We find a simple, accurate model for the covariance matrix of the real-space cosmological matter power spectrum on slightly nonlinear scales (k ~ 0.1-0.8 h Mpc–1 at z = 0), where off-diagonal matrix elements become substantial. The model includes a multiplicative, scale-independent modulation of the power spectrum. It has only one parameter, the variance (among realizations) of the variance of the nonlinear density field in cells, with little dependence on the cell size between 2 and 8 h –1 Mpc. Furthermore, we find that this extra covariance can be modeled out by instead measuring the power spectrum of δ/σcell, i.e., the ratio of the overdensity to its dispersion in grid cells. Dividing δ by σcell essentially removes the non-Gaussian part of the covariance matrix, nearly diagonalizing it.
Energy dissipation in sheared granular flows

Granular material flows describe flows of solid particles in which the interstitial fluid plays a negligible role in the flow mechanics. Examples include the transport of coal, food products, detergents, pharmaceutical tablets, and toner particles in high-speed printers. Using a two-dimensional discrete element computer simulation of a bounded, gravity-free Couette flow of particles, the heat dissipation rate per unit area is calculated as a function of position in the flow as well as overall solid fraction. The computation results compare favorably with the kinetic theory analysis for rough disks. The heat dissipation rate is also measured for binary mixtures of particles for different small to large solid fraction ratios, and for diameter ratios of ten, five, and two. The dissipation rates increase significantly with overall solid fraction as well as local strain rates and granular temperatures. The thermal energy equation is solved for a Couette flow with one adiabatic wall and one at constant temperature. Solutions use the simulation measurements of the heat dissipation rate, solid fraction, and granular temperature to show that the thermodynamic temperature increases with solid fraction and decreases with particle conductivity. In mixtures, both the dissipation rate and the thermodynamic temperature increase with size ratio andmore » with decreasing ratio of small to large particles.« less
Gold Nanowires and Their Chemical Modifications

Equilibrium structure, local densities of states, and electronic transport in a gold nanowire made of a four atom chain supported by two gold electrodes, which has been imaged recently by high-resolution electron microscopy, and chemical modification of the wire via the adsorption of a methylthiol molecule, are investigated with ab initio local density functional simulations. In the bare wire at the imaged geometry the middle two atoms dimerize, and the structure is strongly modified by the adsorption of the molecule with an accompanying increase of the ballistic conductance through the wire.
Circumferential Negative-Pressure Dressing (VAC) to Bolster Skin Grafts in the Reconstruction of the Penile Shaft and Scrotum

Abstract:This paper presents 4 consecutive cases using negative-pressure dressings (VAC) to bolster skin grafts in male genital reconstruction. In this series reconstruction followed 1 case of tumor ablation and 3 cases of debridement of abscesses or Fornier’s gangrene. The VAC was applied circumfer
Probe-Position Error Correction in Planar Near Field Measurements at 60 GHz: Experimental Verification

This study was conducted to verify that the probe-position error correction can be successfully applied to real data obtained on a planar near-field range where probe position errors are known. Since probe position-error correction is most important at high frequencies, measurements were made at 60 GHz. Six planar scans at z positions separated by 0.03 A were obtained. The correction technique was applied to an error-contaminated near field constructed out of the six scans according to a discretized periodic error function. The results indicate that probe position errors can be removed from real near-field data as successfully as from simulated data; some residual errors, which are thought to be due to multiple reflections, residual drift in the measurement system, and residual probe position errors in all three coordinates, are observed.
General bounds on statistical query learning and PAC learning with noise via hypothesis boosting

Abstract We derive general bounds on the complexity of learning in the statistical query (SQ) model and in the PAC model with classification noise. We do so by considering the problem of boosting the accuracy of weak learning algorithms which fall within the SQ model. This new model was introduced by Kearns to provide a general framework for efficient PAC learning in the presence of classification noise. We first show a general scheme for boosting the accuracy of weak SQ learning algorithms, proving that weak SQ learning is equivalent to strong SQ learning. The boosting is efficient and is used to show our main result of the first general upper bounds on the complexity of strong SQ learning. Since all SQ algorithms can be simulated in the PAC model with classification noise, we also obtain general upper bounds on learning in the presence of classification noise for classes which can be learned in the SQ model.
Enantioselective Synthesis of the Elaiophylin Aglycon.

Elaiophylin (1) was isolated in 1959 by Arcamone and co-workers from cultures of Streptomyces melanosporus.1 Subsequently, this natural product has also been obtained from other strains of Streptomyces.2 Structure elucidation of 1, including assignment of absolute stereochemistry, was based on chemical degradation,3 NMR studies,4 and ultimately X-ray crystallographic analysis.5 Isolation and characterization of the elaiophylin aglycon, elaiolide (2), was accomplished by Zeeck and Bindseil in 1993 through deglycosylation of 1.6
Array technology for terahertz imaging

Heterodyne terahertz (0.3 - 3THz) imaging systems are currently limited to single or a low number of pixels. Drastic improvements in imaging sensitivity and speed can be achieved by replacing single pixel systems with an array of detectors. This paper presents an array topology that is being developed at the Jet Propulsion Laboratory based on the micromachining of silicon. This technique fabricates the array's package and waveguide components by plasma etching of silicon, resulting in devices with precision surpassing that of current metal machining techniques. Using silicon increases the versatility of the packaging, enabling a variety of orientations of circuitry within the device which increases circuit density and design options. The design of a two-pixel transceiver utilizing a stacked architecture is presented that achieves a pixel spacing of 10mm. By only allowing coupling from the top and bottom of the package the design can readily be arrayed in two dimensions with a spacing of 10mm x 18mm.
Enantioconvergent synthesis of functionalized γ-butyrolactones via (3 + 2)-annulation.

A dynamic kinetic resolution of β-halo α-keto esters in an asymmetric homoenolate reaction is described. A chiral N-hetereocyclic carbene catalyzes the a3 → d3-umpolung addition of α,β-enals to racemic α-keto esters, forming γ-butyrolactones with three contiguous stereocenters. The addition occurs with high regio-, diastereo-, and enantiocontrol. This methodology constitutes an intermolecular DKR process to set three stereocenters during the key bond forming event.
Reactant Jetting in Unstable Detonation

We note the common existence of a supersonic jet structure locally embedded within a surrounding transonic flow field in the hitherto unrelated phenomena of unstable gaseous detonation and hypervelocity blunt body shock wave interaction. Extending prior results that demonstrate the consequences of reduced endothermic reaction rate for the supersonic jet fluid in the blunt body case, we provide an explanation for observations of locally reduced OH PLIF signal in images of the keystone reaction zone structure of weakly unstable detonations. Modeling these flow features as exothermically reacting jets with similarly reduced reaction rates, we demonstrate a mechanism for jetting of bulk pockets of unreacted fluid with potentially differing kinetic pathways into the region behind the primary detonation front of strongly unstable mixtures. We examine the impact of mono-atomic and diatomic diluents on transverse structure. The results yield insight into the mechanisms of transition and characteristic features of both weakly and strongly unstable mixtures.
Effects of atrial cardioplegia on the ischemic right ventricle after acute coronary artery occlusion and reperfusion

Abstract Right atrial cardioplegia has been advocated as a simple method of delivering retrograde cardioplegia. Passive disteition of the right heart inherent with right atrial cardioplegia has been shown to impair right ventricular function in a canine model of global ischemia. This study was designed to compare right ventricular performance after right atrial cardioplegia administered intermittently (n = 5) and continuously (n = 5) with coronary sinus retrograde cardioplegia (n = 9) and aortic root cardioplegia (n = 8) in a canine model of acute right ventricular ischemia and reperfusion. Right ventricular performance was assessed using the load-independent relationship of end-systolic pressure versus dimension (myorardial fiber length). Right ventricular performance was well preserved after reperfusion in those dogs protected with intermittent right atrial cardioplegia (95% of control). Results with continuous right atrial cardioplegia (66% of control) and coronary sinus retrograde cardioplegia (40% of control) demonstrated diminished postreperfusion right ventricular performance. Right ventricular performance in the group protected with aortic root cardioplegia was significantly impaired after reperfusion when compared with all retrograde groups (34% of control, p
Effects of caloric restriction or augmentation in adult rats: longevity and lesion biomarkers of aging.

Caloric restriction (CR) initiated in young rodents has been thoroughly documented to enhance longevity, but its efficacy when introduced at older ages has not been well investigated. Cohorts of 18- and 26-month-old male F344 × BN F1 hybrid rats were fed either: 1) NIH-31 meal (C); 2) vitamin and mineral fortified NIH-31 meal (R); or 3) vitamin and mineral fortified NIH-31 meal supplemented with corn oil and sweetened condensed milk (S). The C control rats were fed ad libitum, R rats were restricted to 32% of the caloric intake of the controls, and S rats were allowed to consume not more than 8% more calories than C rats. After 6 weeks, the average weights were significantly different between all diet and age groups. Although calorie manipulation altered body weight, no significant effect of the dietary intervention on longevity was found. The average lesion burden, including tumor burden and prevalence of nearly all commonly occurring lesions, were comparable between the groups. Thus, the manipulation of weight at ages beyond middle age has a much less profound impact than similar interventions during growth and maturation in rats.
Couplings in asymmetric orbifolds and grand unified string models

Abstract Using the bosonic supercurrent (or covariant lattice) formalism, we review how to compute scattering amplitudes in asymmetric orbifold string models. This method is particularly useful for calculating scattering of multiple asymmetrically twisted string states, where the twisted states are rewritten as ordinary momentum states. We show how to reconstruct some of the three-family grand unified string models in this formalism, and identify the quantum numbers of the massless states in their spectra. The discrete symmetries of these models are rather intricate. The superpotentials for the three-family E 6 model and a closely related SO (10) model are discussed in some detail. The forms of the superpotentials of the two three-family SU (6) models (with asymptotically free hidden sectors SU (3) and SU (2) ⊗ SU (2)) are also presented.
Collider signatures from the brane world

Abstract We discuss some collider signatures of the brane world. In addition to the usual bulk (closed string) fields and brane (open string) fields in the Type I string picture, there are closed string fields, namely, twisted modes, which are not confined on the branes but nonetheless are localized in the extra compactified dimensions. While the coupling of the Standard Model (brane) fields with a bulk mode (such as the graviton) is suppressed by powers of the Planck mass, their coupling to a twisted mode is suppressed only by powers of the string scale Ms, which can be as low as a few TeV. This means these localized twisted fields can have important observable effects in the TeV range, including resonances in dijet invariant mass distributions in p p,pp→ jets + X. Given the current lower bound on the fundamental higher-dimensional Planck scale, the experimental effects of these twisted fields may turn out to be larger than the effects of virtual and real KK gravity modes. The collider signatures of anomalous U(1) gauge symmetries as well as other phenomenological implications of the brane world are also discussed.
Asymmetric synthesis of isoquinoline alkaloids

Abstract The use of chiral formamidines affixed to variously substituted tetrahydroisoquinolines, allows asymmetric C-C bond forming reactions to occur α- to the amino group. In this manner, a wide variety of (S)-1-alkyl-1,2,3,4-tetrahydroisoquinolines were constructed in > 90% enantiomeric excess. Choosing the proper substituents and skeletal features, an efficient entry into the benzylisoquinoline, tetrahydroprotoberberine, aporphine, and isopavine class of alkaloids was achieved.
Addition Spectra of Quantum Dots: the Role of Dielectric Mismatch

Using atomistic pseudopotential wave functions, we calculate the electron and hole addition energies and the quasi-particle gap of InAs quantum dots. We find that the addition energies and the quasi-particle gap depend strongly on the dielectric constant eout of the surrounding material, and that when eout is much smaller than the dielectric constant of the dot the electron−electron and hole−hole interactions are dominated by surface polarization effects. We predict the addition energies and the quasi-particle gap as a function of size and eout, and compare our results with recent single-dot tunneling spectroscopy experiments.
Directed Vapor Deposition of Amorphous and Polycrystalline Electronic Materials: Nonhydrogenated a‐Si

A novel directed vapor deposition (DVD) process for creating amorphous and polycrystalline electronic materials is reported. Initial experimental results for DVD of nonhydrogenated a-Si indicate that growth rates at least between 0.02 and 1.0 {micro}m/min can be achieved. In this process, evaporated silicon is efficiently entrained in a previously formed low pressure supersonic He jet. The silicon is evaporated using a high energy, high voltage, electron beam. The collimated jet of He entrained with silicon is used to deposit thin films of a-Si at room temperature on glass substrates. Initial TEM microstructure analysis and optical absorption analysis is presented.
Consistency and serializability in concurrent database systems

The main results of this paper show that serialization is both necessary and sufficient for consistency in concurrent database systems. This is true for both the final database and the views of the database seen by individual transactions. The model of a transaction includes both read and write operations which may be performed in any order (except an entity must be read before being written).
Really Cool Stars at the Galactic Center

New and existing K-band spectra for 19 Galactic center late-type stars have been analyzed along with representative spectra of disk and bulge M giants and supergiants. Absorption strengths for strong atomic and molecular features have been measured. The Galactic center stars generally exhibit stronger absorption features centered near Na I (2.206 microns) and Ca I (2.264 microns) than representative disk M stars at the same CO absorption strength. Based on the absolute K - band magnitudes and CO and H2O absorption strengths for the Galactic center stars and known M supergiants and asymptotic giant branch (AGB) stars, we conclude that only IRS 7 must be a supergiant. Two other bright stars in our Galactic center sample are likely supergiant as well. The remaining bright, cool stars in the Galactic center that we have observed are most consistent with being intermediate mass/age AGB stars. We identify four of the Galactic center stars as long period variables based on their K-band spectral properties and associated photometric variability. Estimates of initial masses and ages for the GC stars suggest multiple epochs of star formation have occurred in the Galactic center over the last 7-100 Myr. 0 1996 American Astronomical Society.
Simultaneous offers and the inefficiency of bargaining: A two-period example

Abstract It is shown that the Pareto optimal outcomes in a two period simultaneous move bargaining model violate forwards induction rationality when the players are sufficiently patient. This bargaining model describes a situation where a principal is represented by an agent whose flexibility is restricted. Hence, a bargaining process with such agents can create costly delays. The result also provides another example of the power of forwards induction and stability.
Transfer reaction experiments with radioactive beams: from halos to the r-process

Transfer reactions are a powerful probe of the properties of atomic nuclei. When used in inverse kinematics with radioactive ion beams they can provide detailed information on the structure of exotic nuclei and can inform nucleosynthesis calculations. There are a number of groups around the world who use these reactions, usually with particle detection in large silicon arrays. Sometimes these arrays are coupled to gamma-ray detectors, and occasionally smaller arrays of silicon detectors are mounted within a solenoid magnet. Modern techniques using transfer reactions in inverse kinematics are covered, with specific examples, many from measurements made with beams from the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory.