cssi/SciSciGPT-SciSciNet huggingface dataset:
The Kondo lattice model from strong-coupling viewpoint

Abstract We study the magnetic excitation spectrum of the two-dimensional (2D) square-lattice S= 1 2 Kondo lattice model at finite (hole) doping, by representing the Hamiltonian in terms of a set of local excitations. The location of the paramagnetic–antiferromagnetic phase boundary at T=0 is determined.
Development of correlations to predict biopolymer mobility in porous media

This paper describes the flow and rheological behavior of biopolymer solutions in sandpacks over a wide range of permeability and frontal advance rates. Empirical correlations were developed to estimate polymer mobility in porous media. The correlations are based on porous medium properties, polymer concentration, and rheological parameters for the polymer derived from steady-shear measurements.
Organo-Catalysis : Developing Ketone Catalysts for Asymmetric Epoxidation of Olefins

Dioxiranes are remarkably versatile oxidizing agents that show great potential for asymmetric synthesis, particularly asymmetric epoxidation of olefins. This article outlines some recent progress in this area from the author's laboratories.
Gem-Difluorinated Homoallyl Alcohols, β-Hydroxy Ketones, and syn- and anti-1,3-Diols via γ,γ-Difluoroallylboronates

γ,γ-Difluoroallylboronates have been prepared from trifluoroethanol and utilized for the allylboration of a variety of aldehydes to provide gem-difluorinated homoallylic alcohols. α-Chiral aldehydes were allylborated in 4:1−13:1 diastereoselectivity favoring the anti-isomer. A representative series of difluorinated hydroxyl enol ethers were converted to the corresponding α,α-difluoro-β-hydroxy ketones. Diastereoselective reduction of one of these to either syn- and anti-1,3-diol was also studied.
The Machine Maintenance and Sale Age Model of Kamien and Schwartz Revisited

In this paper, we revisit and clarify the celebrated machine maintenance and sale age model of Kamien and Schwartz (KS) involving a machine subject to failure. KS formulate and solve the problem as a deterministic optimal control problem with the probability of the machine failure as the state variable. Thus, they obtain deterministic optimal maintenance and sale date. We study two underlying stochastic models with known and random machine modes, and clarify the relationship between the resulting value functions to that of KS. In particular, our maintenance and sale date decisions, when the machine is in operation, are precisely the ones obtained from the deterministic solution of KS. We explain why that is so. Moreover, we provide a sufficient condition for an optimal maintenance and sale date policy that is missing in KS. We describe many applications of the KS model in areas other than that of machine maintenance. We conclude the paper with extensions of the KS problem that are stochastic control problems not easily solvable or not at all solvable as deterministic problems.
On the approximation of upper semi-continuous correspondences and the equilibriums of generalized games

In Section 1 we explain some of the definitions and terminology that we use. In Section 2 we prove several theorems concerning the approximation of upper semi-continuous correspondences having for range a locally convex space. Theorems 1 and 2 (and Corollary 1) generalize certain approximation theorems by G. Haddad [16, pp. 1352213541, G. Haddad and J. M. Lasry [ 17, pp. 299-3001, and J. P. Aubin and A. Cellina [2, pp. 86891 (see also F. S. De Blasi [lo] and J. M. Lasry and R. Robert [21]). Although some of the details of the proofs of Theorems 1 and 2 are new, the basic ideas are taken from the above mentioned papers. Theorem 3 shows that the correspondences in the approximating families can be chosen so that they are regular (see Section 1). This theorem (see the remark following its proof) contains a classical result of M. Hukuhara [ 18, pp. 56573. Theorem 3 is proved using Theorem 2 and Propositions 1 and 4. Variants of Propositions 2, 3, and 4 were given in [ 193. In Section 3 we give, among others, Theorem 5, which concerns the existence of equilibriums of generalized games ( = abstract economies). The main purpose of this result is to replace the continuity hypothesis in the W. Shafer-H. Sonnenschein equilibrium theorem for generalized games by an upper semi-continuity one. The proof of Theorem 5 is based on the results on the approximation of upper semi-continuous correspondences obtained in Section 2. Theorem 5 us used in Section 4. In Section 4 we establish Theorems 6 and 7. These theorems show that certain statements concerning the equilibrium of generalized games are equivalent to certain statements concerning minimax inequalities of K. Fan type. Theorems 1, 2, 3, 5, 6, and 7 are the main results of this paper. 267 0022-247X/88 $3.00
Skeletal Effects of Growth Hormone and IGF-I in Adults

Three processes occur in the skeleton; modelling during growth, fracture repair and remodelling. Remodelling is bone resorption coupled to bone formation, and alterations in the remodelling balance ar
Dielectronic recombination and autoionization yields in weak static electric fields

Dielectronic recombination (DR) of ions and electrons occurs via intermediate doubly excited Rydberg states converging to an excited state of the ion, and the total energy-integrated rate is the sum of the rates through the $n$,$\ensuremath{\ell}$ Rydberg states. To make stringent comparisons between calculated and observed rates, it is useful to resolve the contributions to DR of different $n$ and $\ensuremath{\ell}$ states. It is possible to separate experimentally the $n$ states due to their different energies, but it is not possible to separate the nearly degenerate high-$\ensuremath{\ell}$ states. We propose that it should be possible to measure the contribution to DR of energetically unresolved high-$\ensuremath{\ell}$ states by measuring the recombination rate as a function of electric field. As the field is raised, progressively lower $\ensuremath{\ell}$ states are converted to Stark states. Autoionization rates increase as $\ensuremath{\ell}$ is decreased, and when the field is raised to the point that an $\ensuremath{\ell}$ state with an autoionization rate in excess of the radiative decay rate is added to the manifold of Stark states, the DR rate will exhibit an observable increase. To test this proposal we have made measurements of autoionization yields of the autoionizing Ba $6{p}_{1/2}\mathit{nk}$ and $6{p}_{3/2}\mathit{nk}$ Stark states. The autoionization yield is complementary to DR, and the measurements indicate that the proposed approach should work well. Although it is not surprising that this approach works for excited ion states that are isotropic, such as the Ba${}^{+}$ $6{p}_{1/2}$ state, it is less obvious that it should work for an anisotropic ion state, such as the Ba${}^{+}$ $6{p}_{3/2}$ state. In the latter case there are four quantum defects for each $\ensuremath{\ell}$ state instead of one, and the Stark effect of the Ba $6{p}_{3/2}\mathit{nk}$ Stark states is far more complex than that of the Ba $6{p}_{1/2}\mathit{nk}$ Stark states. Calculations of the Stark effect reveal that, while there are four times as many $6{p}_{3/2}\mathit{nk}$ levels as $6{p}_{1/2}\mathit{nk}$ levels, many of the interactions of the $6{p}_{3/2}\mathit{nk}$ levels are negligible, and in practice the problem is no more complicated than the $6{p}_{1/2}\mathit{nk}$ Stark problem.
Atlantic Multidecadal Oscillation and Northern Hemisphere’s climate variability

Proxy and instrumental records reflect a quasi-cyclic 50–80-year climate signal across the Northern Hemisphere, with particular presence in the North Atlantic. Modeling studies rationalize this variability in terms of intrinsic dynamics of the Atlantic Meridional Overturning Circulation influencing distribution of sea-surface-temperature anomalies in the Atlantic Ocean; hence the name Atlantic Multidecadal Oscillation (AMO). By analyzing a lagged covariance structure of a network of climate indices, this study details the AMO-signal propagation throughout the Northern Hemisphere via a sequence of atmospheric and lagged oceanic teleconnections, which the authors term the “stadium wave”. Initial changes in the North Atlantic temperature anomaly associated with AMO culminate in an oppositely signed hemispheric signal about 30 years later. Furthermore, shorter-term, interannual-to-interdecadal climate variability alters character according to polarity of the stadium-wave-induced prevailing hemispheric climate regime. Ongoing research suggests mutual interaction between shorter-term variability and the stadium wave, with indication of ensuing modifications of multidecadal variability within the Atlantic sector. Results presented here support the hypothesis that AMO plays a significant role in hemispheric and, by inference, global climate variability, with implications for climate-change attribution and prediction.
The solution space of the unitary matrix model string equation and the Sato Grassmannian

The space of all solutions to the string equation of the symmetric unitary one-matrix model is determined. It is shown that the string equation is equivalent to simple conditions on pointsV1 andV2 in the big cell Gr(0) of the Sato Grassmannian Gr. This is a consequence of a well-defined continuum limit in which the string equation has the simple form Open image in new window matrices of differential operators. These conditions onV1 andV2 yield a simple system of first order differential equations whose analysis determines the space of all solutions to the string equation. This geometric formulation leads directly to the Virasoro constraintsLn (n≧0), whereLn annihilate the two modified-KdV τ-functions whose product gives the partition function of the Unitary Matrix Model.
The good, the bad and the ugly: agent behavior and efficiency in open and closed organizations

Current literature has largely ignored the fact that some organizations are highly selective when admitting new agents while others are more open. In addition, some organizations audit or sort agent behavior within the organization more aggressively than others. One might expect a priori that closed, highly selective, organizations would always be more efficient because they screen out the worst types, which could lead to better agent behavior. We show that this is not the case. Specifically, when agent behavior in equilibrium is uniform across organizations (i.e., when the number of agents behaving the same way is identical), closed organizations are inefficient. However, when agent behavior varies across organizations, closed organizations may or may not be inefficient, depending on net payoffs to the organization and the agents. Our analysis implies that organizations should choose the open type when screening or sorting costs are high, when there is a high frequency of good agent types in the population, when agent misbehavior does not reduce output significantly, and when penalties for misbehavior are large.
Technological innovation in the airline industry: The impact of regional jets

Abstract This paper explores the impact of the regional jet (RJ), an important new technological innovation in the airline industry, on service patterns and service quality. The paper's theoretical analysis predicts that the frequency advantage of RJs over jets, a consequence of their small size, should have led to the emergence of point-to-point (PP) service in thin markets where such service was previously uneconomical. However, the evidence contradicts this prediction, showing that markets attracting new PP service by RJs had demographic characteristics similar to those of markets that already had jet PP service or attracted it after 1996. Additional descriptive evidence shows that RJs were used to provide service on a large number of new hub-and-spoke (HS) routes, and that they replaced discontinued jet and turboprop service on many such routes, as well as supplementing continuing jet service. When replacement or supplementation by RJs occurred, passengers benefited from better service quality via higher flight frequencies.
Charge density effects in salt‐free polyelectrolyte solution rheology

Solution rheology of 2-vinyl pyridine and N-methyl-2-vinyl pyridinium chloride random copolymers in ethylene glycol was studied over wide ranges of concentration and effective charge. The fraction of quaternized monomers α and the fraction of monomers bearing an effective charge f of these copolymers were measured using counterion titration and dielectric spectroscopy, respectively. Ethylene glycol is a good solvent for neutral poly(2-vinyl pyridine), with very few ionic impurities. The viscosity η and relaxation time T of dilute and semidilute unentangled solutions exhibit the scaling with concentration and effective charge expected by the Dobrynin model. Reduced viscosity data are independent of concentration in dilute solution, giving an intrinsic viscosity that depends on effective charge, and the experimental data obey the Fuoss law in the semidilute unentangled regime. Scaling concentration with the overlap concentration (c/c*) reduces these data to common curves, and c* ∼ f -12/7 as predicted by the Dobrynin model, where f is the fraction of monomers bearing an effective charge. While the overlap concentration depends strongly on effective charge until counterion condensation occurs, the entanglement concentration c e is surprisingly insensitive to effective charge, indicating that entanglement effects are not understood using the Dobrynin model. The terminal modulus G = η/τ depends only on the number density of chains G = ckT/N for c* c e independent of the effective charge.
Voluntary disclosures and insider transactions

Abstract This paper investigates the association between voluntary disclosures and insider transactions (i.e., transactions by managers in their own firms’ shares). The findings suggest that managers do not make insider transactions to profit from news about their own firms just before it becomes publicly available. However, managers appear to employ other strategies for exploiting private information when making insider transactions. Managers cluster insider transactions after voluntary disclosures when doing so results in more favorable stock prices for them. Also, managers take advantage of knowledge about their own firms’ long-term prospects while utilizing voluntary disclosures to shield themselves against profiteering allegations.
Relaxing Standard Hedging Assumptions in the Presence of Downside Risk

Abstract We analyze how the introduction of a downside risk measure and less restrictive assumptions in the standard hedging problem changes the optimal hedge and the opportunity costs of not hedging. Based on a dataset of futures and cash returns for soybeans and S&P 500 returns, the findings indicate that the optimal hedge changes considerably when a one-sided risk measure is adopted and standard assumptions are relaxed. Further, the results suggest that in a downside risk framework with realistic hedging assumptions there is little or no incentive for producers to hedge as the opportunity cost of not hedging is small.
Biquotients with Singly Generated Rational Cohomology

We classify all biquotients whose rational cohomology rings are generated by one element. As a consequence we show that the Gromoll–Meyer 7-sphere is the only exotic sphere which can be written as a biquotient.
The range of united K-theory

Abstract We prove that the united K-theory functor is a surjective functor from the category of real simple separable purely infinite C∗-algebras to the category of countable acyclic CRT-modules. As a consequence, we show that every complex Kirchberg algebra satisfying the universal coefficient theorem is the complexification of a real C ∗ -algebra.
A concise synthesis of methyl 2,6-dideoxy-2-fluoro-β-l-talopyranoside☆

Abstract The 4,6-benzylidene acetal of methyl 2-deoxy-2-fluoro-α,β- d -glucopyranoside underwent inversion at C-3 via an oxidation–reduction sequence, and treatment of the derived 3-acetate with N -bromosuccinimide in carbon tetrachloride gave methyl 3- O -acetyl-4- O -benzoyl-6-bromo-2,6-dideoxy-2-fluoro-α- d -allopyranoside ( 6 ). Dehydrobromination of 6 and reduction of the resultant 5,6-ene gave the 5-epimer of 6 , which after removal of the ester substituents, afforded the title compound in good overall yield.
Accounting for the linkages of agriculture in Hawaii‘s economy with an input-output model: A final demand-based approach

. Agriculture is not a large contributor to Hawaii‘s economy but despite the recent decline in the sugar industry it is an important sector in terms of its contribution to food supply, income, and employment. Agriculture influences the economy as it procures production inputs from and provides inputs to other sectors in the economy. A theoretically sound input-output framework is suggested for investigating the interdependence between agricultural and other sectors of the economy. This paper also provides a review and identifies shortcomings of other approaches used in estimating the industry‘s contributions to the economy. The non-agricultural final demands accounted for about 20% of total agricultural output, value added, labor income, and employment. The indirect contribution of agricultural final demands and related distribution services to other sectors constituted about 20% of total output and labor income, 22% of value added, and 16% of total employment generated by agricultural final demands and related trade and distribution services.
Ion thruster performance calibration.

The calibration of a typical 20-cm diameter ion thrustor was examined to determine performance penalties that must be assessed in projecting measured performance into a space environment. Four specific areas were investigated. These include (1) double ion content of the beam, (2) back ingestion from the vacuum facility, (3) beam spreading, and (4) propellant flow rate measurements. The double ion content was measured and found to be as high as 5.5% at an arc voltage of 35 volts. Back ingestion was observed to become significant above tank pressures of 6 microtorr. Beam spreading reduced effective thrust on the order of 2.5%.
Theoretical aspects of VLSI pin limitations

This paper presents a formal model of the pin requirements of a parallel computer. This model is then used to obtain bounds on the pin requirements of different parallel machines and on the tradeoffs between pins and time. Specifically, two new bounds are established on the relationship between pin requirements and the time needed to sort or permute data. This paper also gives new lower bounds on the pin requirements of mesh-connected, cube-connected-cycles, shuffle-exchange, and Ajtai–Komlos–Szemeredi (AKS) computers, and it gives new upper bounds on the pin requirements of shuffle-exchange and AKS computers. All of these bounds are tight to within a constant factor. Finally, the bounds on pin requirements are used to prove a tight lower bound on the time required to implement the AKS sorting algorithm on a shuffle-exchange or cube-connected-cycles computer.
The efficiency of multimodal interaction for a map-based task

This paper compares the efficiency of using a standard direct-manipulation graphical user interface (GUI) with that of using the QuickSet pen/voice multimodal interface for supporting a military task. In this task, a user places military units and control measures (e.g., various types of lines, obstacles, objectives) on a map. Four military personnel designed and entered their own simulation scenarios via both interfaces. Analyses revealed that the multimodal interface led to a 3 to 4-fold speed improvement in the average entity creation time, including all error handling. Time to repair errors also was significantly faster when interacting multimodally. These results indicate a substantial efficiency advantage for multimodal over GUI-based interaction during map-based tasks.
Internal rotation and structure of isobutylene

Abstract The high-resolution rotational spectrum of isobutylene was measured for transitions with J ≤ 7, using a modified Balle-Flygare Fourier transform microwave spectrometer with a pulsed supersonic nozzle as the sample source. Previously improved by the addition of a computer-based IBM PC-AT controller and averager [C. Chuang et al., Rev. Sci. Instrum. 61, 1629–1635 (1990)], the spectrometer has been fitted with software which provides Autosearch operation. Analysis of the fine structure of the observed transitions, caused by internal rotation of the two methyl groups, gives the V3 barrier to be 2176(3) cal/mole and the angle θ between the methyl top and b-axes to be 58.5(3)°, with the latter perhaps decreasing slightly at higher J. Rotational constants reported previously for six isotopic species of isobutylene and those now obtained for (CH3)2 13CCH2 at natural abundance were fitted to obtain an effective (r0) structure. The results indicate that the methyl groups are distorted slightly from C3ν symmetry. This tilts the CH3 axis 0.8(2)° away from coaxiality with the CC bond axis toward the double bond.
Detection of X-Rays from Galaxy Groups Associated with the Gravitationally Lensed Systems PG 1115+080 and B1422+231

Gravitational lenses that produce multiple images of background quasars can be an invaluable cosmological tool. Deriving cosmological parameters, however, requires modeling the potential of the lens itself. It has been estimated that up to a quarter of lensing galaxies are associated with a group or cluster that perturbs the gravitational potential. Detection of X-ray emission from the group or cluster can be used to better model the lens. We report on the first detection in X-rays of the group associated with the lensing system PG 1115+080 and the first X-ray image of the group associated with the system B1422+231. We find a temperature and rest-frame luminosity of 0.8 keV and 7 × 1042 ergs s-1, respectively, for PG 1115+080 and 1.0 keV and 8 × 1042 ergs s-1, respectively, for B1422+231. We compare the spatial and spectral characteristics of the X-ray emission with the properties of the group galaxies, with lens models, and with the general properties of groups at lower redshift.
The Gravitational Lens Candidate FBQ 1633+3134*

We present our ground-based optical imaging, spectral analysis, and high-resolution radio mapping of the gravitational lens candidate FBQ 1633+3134. This z = 1.52, B = 17.7 quasar appears double on CCD images with an image separation of 066 and a relatively constant flux ratio of ~3 : 1 across B, V, R, and I filters. A single 0.27 mJy radio source is detected at 8.46 GHz, coincident within an arcsecond of both optical components, but no companion at radio wavelengths is detected for the system down to a flux level of 0.1 mJy (3 σ). Spectral observations reveal a rich metal-line absorption system consisting of a strong Mg II doublet and associated Fe I and Fe II absorption features, all at an intervening redshift of z = 0.684, suggestive of a lensing galaxy. Point-spread function subtraction of ground-based images however shows no obvious signs of a third object between the two quasar images and places a detection limit of I 23.0 if such an object exists. Although the possibility that FBQ 1633+3134 is a binary quasar cannot be ruled out, the evidence presented here is consistent with FBQ 1633+3134 being a single quasar lensed by a faint, metal-rich galaxy.
MDS: a unique project in computer-assisted mathematics

In the education of the deaf, are there problems so special that their solution justifies the use of a computer? And if there are such problems, how can the computer best be used to solve them? Early in the history of the National Technical Institute for the Deaf, its administrators voted "Yes" on the first question and "Let's find out" on the second. As a result of these decisions, an IBM 1500 Instructional System was included in the Institute's original home on the campus of the Rochester Institute of Technology.
Tandem Favorskii Intermediate/Cyclization Leading to Tricyclo[4.4.0.0]decanediones

Abstract The mechanism of dehydrobromination of the bromodiketone 8 leading to the unusual ring system of tricyclo[4.4.0.0]decanediones (9 and 10) is described. An entry into the ring system of the sesquiterpenoid hydrocarbons copaene and ylangene, 8 to 9, is achieved in three steps starting with enone 6. Compound 9 was either derived from a direct internal SN2 cyclization of 8 or the Favorskii intermediate 8a. Formation of compound 10, on the other hand, can only occur via the Favorskii intermediate 8a. Structure assignments of 9 and 10 were determined using both one‐ and two‐dimensional NMR experiments.
Evaluating the Moisture Conditions in the Fractured Rock at Yucca Mountain: The Impact of Natural Convection Processes in Heated Emplacement Drifts

The energy output of the high-level radioactive waste to be emplaced in the proposed geologic repository at Yucca Mountain, NV, will strongly affect the thermal–hydrological (TH) conditions in the near-drift fractured rock. Heating of rock water to above-boiling conditions will induce large water saturation changes and flux perturbations close to the waste emplacement tunnels (drifts) that will last several thousand years. Understanding these perturbations is important for the performance of the repository, because they could increase, for example, the amount of formation water seeping into the open drifts and contacting waste packages. Recent computational fluid dynamics analysis has demonstrated that the drifts will act as important conduits for gas flows driven by natural convection. As a result, vapor generated from boiling of formation water near elevatedtemperature sections of the drifts may effectively be transported to cooler end sections (where no waste is emplaced), where it would condense and subsequently drain into underlying rock units. Thus, natural convection processes have great potential for reducing the near-drift moisture content in heated drift sections, which has positive ramifications for repository performance. To study these processes, we have developed a new simulation method that couples existing tools for simulating TH conditions in the fractured formation with modules that approximate natural convection and evaporation conditions in heated emplacement drifts. The new method is applied to evaluate the impact of in-drift natural convection on the future TH conditions at Yucca Mountain in a three-dimensional model domain comprising a representative emplacement drift and the surrounding fractured rock.
Unconditional bases and unconditional finite-dimensional decompositions in Banach spaces

LetX be a Banach space with an unconditional finite-dimensional Schauder decomposition (E n). We consider the general problem of characterizing conditions under which one can construct an unconditional basis forX by forming an unconditional basis for eachE n. For example, we show that if sup n dimE n<∞ andX has Gordon-Lewis local unconditional structure thenX has an unconditional basis of this type. We also give an example of a non-Hilbertian spaceX with the property that wheneverY is a closed subspace ofX with a UFDD (E n) such that sup n dimE n<∞ thenY has an unconditional basis, showing that a recent result of Komorowski and Tomczak-Jaegermann cannot be improved.
Measurement of Fresnel drag in moving media using a ring-resonator technique

Measurements of the Fresnel drag in moving glass media were performed using a passive ring-resonator method. The effective drag coefficient was measured for various glass samples of different indices of refraction and dispersions. When we averaged 15 separate measurements, we obtained overall agreement with theory that was well within our ±2.8 × 10−4 measurement uncertainty, thus providing, to our knowledge, the most accurate verification of Fresnel drag thus far.
On Rationality of Verbal Subsets in a Group

Let F be a free non-abelian group. We show that for any group word w the set w[F] of all values of w in F is rational in F if and only if w[F]=1 or w[F]=F. We generalize this to a wide class of free products of groups.
Direct observation of atomic processes: Silicon adatoms on tungsten surfaces

A wide variety of the behaviors of single silicon adatoms on tungsten surfces have been studied in the field ion microscope (FIM). Existing works are summarized, and some new results are presented. Diffusion parameters for single silicon atoms on the W{110} plane were found to be Ed = 0.70±0.07 eV and D0 = 3.1 × 10-4 × 10±1.28 cm2 s-1, where Ed is the activation energy of diffusion and D0 the diffusivity. Although chain-form atomic clusters were often formed when more than one adatom was present on a plane, the clusters were not stable during diffusion. Silicon atom transport on the W{110} plane is thus achieved dominantly by migration of single silicon atoms. The desorption field as a function of radial distance from the W{110} plane center was measured, and the data were related to the field distribution on the plane at a given applied voltage. The binding energy of silicon adatoms on the W{110} plane was estimated from the desorption field. Relative pair energies for the Si-Si interaction on the W{110} plane for several bond lenghts were obtained from the relative frequencies of observing these bonds in the FIM. The maximum binding occured at a separation √2a, with the bond aligned in the [110] direction, the maximum antibinding occured at a distance a in the [001] direction, and a weak binding occured at 2a along the [001] direction; a was the substrate lattice constant. Using the pair energy data, the relative binding energy in an adlayer for various adlayer structures was calculated. The [2√2√3×4√3R 35.26° superstructure, which is conventionally expressed as p(2×1), had the lowest energy. Our subsequent thermal equilibration experiments with deposited silicon adatoms at about 300 K confirmed the existence of such a structure. Since further heatings at about 300 K changed only the adlayer shape and composites, but did not change the structure of the superlattice, the observed superstructure was the equilibrium adlayer structure at a low degree of coverage at about 300 K. Monte Carlo computer simulations using the measured pair energies predicted the same equilibrium superstructure. In addition, many growth defects of the two-dimensional lattice, such as antiphase domains and stacking faults, were observed. The computer simulations also showed these and other defects. On the W{112} plane, no cooperative walk of silicon adatoms similar to that of metal adatoms was found. However, the staggered and straight bond configurations were observed much more often than that expected from a random distribution. When two silicon adatoms were deposited onto the same surface channel, they were mobile although the √3a bond separation seemed to occur more often. In addition, interactions of plane edges with silicon adatoms and some other observations are discussed.
Diffuse auroral precipitation.

The paper summarizes the development of a plausibly coherent view of the self-consistent coupling of convection in the plasma sheet to auroral particle precipitation and the ionosphere. Attention is given to an understanding of the plasma instabilities responsible for diffuse auroral precipitation. The electrostatic ion and electron cyclotron harmonic loss-cone instabilities seem to be the best candidates, although they depend sensitively upon the cold electron density and temperature deep in space on auroral field lines. However, there is little or no experimental or theoretical information about these parameters. For this reason, further theoretical progress on cyclotron harmonic instabilities will be limited until the cold electron temperature is known. Also necessary are a complete phenomenological understanding of ion harmonic modes and a modeling of the cold electron distribution on auroral field lines.
Quantum Lattice Gases and Their Invariants

The one-particle sector of the simplest one-dimensional quantum lattice-gas automaton has been observed to simulate both the (relativistic) Dirac and (nonrelativistic) Schrodinger equations, in different continuum limits. By analyzing the discrete analogues of plane waves in this sector we find conserved quantities corresponding to energy and momentum. We show that the Klein paradox obtains so that in some regimes the model must be considered to be relativistic and the negative energy modes interpreted as positive energy modes of antiparticles. With a formally similar approach — the Bethe ansatz — we find the evolution eigenfunctions in the two-particle sector of the quantum lattice-gas automaton and conclude by discussing consequences of these calculations and their extension to more particles, additional velocities, and higher dimensions.
Kernel estimation in high-energy physics

Kernel estimation provides an unbinned and non-parametric estimate of the probability density function from which a set of data is drawn. In the first section, after a brief discussion on parametric and non-parametric methods, the theory of kernel estimation is developed for univariate and multivariate settings. The second section discusses some of the applications of kernel estimation to high-energy physics. The third section provides an overview of the available univariate and multivariate packages. This paper concludes with a discussion of the inherent advantages of kernel estimation techniques and systematic errors associated with the estimation of parent distributions.
The Use of Wavelet Transforms in the Solution of Two-Phase Flow Problems

In this paper the authors present the use of wavelets to solve the non-linear Partial Differential Equation (PDE) of two-phase flow in one dimension. The wavelet transforms allow a drastically different approach in the discretization of space. In contrast to the traditional trigonometric basis functions, wavelets approximate a function not by cancellation but by placement of wavelets at appropriate locations. When an abrupt change, such as a shock wave or a spike, occurs in a function, only local coefficients in a wavelet approximation will be affected. The unique feature of wavelets is their Multi-Resolution Analysis (MRA) property, which allows seamless investigation at nay spatial resolution. The use of wavelets is tested in the solution of the one-dimensional Buckley-Leverett problem against analytical solutions and solutions obtained from standard numerical models. Two classes of wavelet bases (Daubechies and Chui-Wang) and two methods (Galerkin and collocation) are investigated. The authors determine that the Chui-Wang wavelets and a collection method provide the optimum wavelet solution for this type of problem. Increasing the resolution level improves the accuracy of the solution, but the order of the basis function seems to be far less important. The results indicate that wavelet transforms are an effective and accuratemore » method which does not suffer from oscillations or numerical smearing in the presence of steep fronts.« less
Renormalization of an inverse-scattering theory for inhomogeneous dielectrics

Renormalized solutions are obtained for an inverse-scattering problem that are equivalent to the second-order regular perturbation approximations for the exact (Gel’fand-Levitan-Marchenko) theory. We have developed an inversion method for reconstruction the permittivity profiles of inhomogeneous dielectric slabs from reflection-coefficient data. Solutions with increased radii of convergence are obtained. Numerical examples are demonstrated for simulated-scattering data from Gaussian and parabolic profiles and homogeneous slabs.
Catalyst-controlled regioselectivity in the synthesis of branched conjugated dienes via aerobic oxidative Heck reactions.

Pd-catalyzed aerobic oxidative coupling of vinylboronic acids and electronically unbiased alkyl olefins provides regioselective access to 1,3-disubstituted conjugated dienes. Catalyst-controlled regioselectivity is achieved by using 2,9-dimethylphenanthroline as a ligand. The observed regioselectivity is opposite to that observed from a traditional (nonoxidative) Heck reaction between a vinyl bromide and an alkene. DFT computational studies reveal that steric effects of the 2,9-dimethylphenanthroline ligand promote C–C bond formation at the internal position of the alkene.
Transition metal atoms on different alumina phases: The role of subsurface sites on catalytic activity

Transition metals (Pt, Pd, Rh, Cr, etc.) are widely used as catalysts on \ensuremath{\gamma}- and \ensuremath{\eta}-alumina, two phases of ${\mathrm{Al}}_{2}{\mathrm{O}}_{3},$ but the catalytic activity of Cr on \ensuremath{\gamma}-alumina degrades rapidly. We report density-functional calculations that trace the origin of the effect to differences in surface reconstruction caused by different distributions of bulk cation vacancies. On \ensuremath{\eta}-alumina, Cr atoms remain on the surface, threefold-coordinated and reactive; on \ensuremath{\gamma}-alumina, they get trapped in subsurface octahedral sites and become inactive. Some metal atoms (e.g., Mn) also get trapped, but the other catalytic elements (Pt, Pd, Rh) do not. Steric constraints, size effects, or other qualitative considerations are not adequate to account for the results.
Influence of boundary approximations and conditions on finite-difference solutions

Abstract Numerical representations of boundary approximations and conditions for three problems are investigated to determine the resulting global accuracy of the steady-state solution. Numerical accuracy with various boundary approximations is determined for quasi-one-dimensional inviscid flow in a duct with the interior grid points evaluated using the MacCormack scheme. When an extrapolation approximation with first-order local truncation error is used, the global second-order accuracy of the difference scheme can be destroyed. For one-dimensional flow in a porous medium, an implicit midpoint difference scheme which is consistent with the boundary conditions is developed without the need of boundary approximations. A dissipative model problem is solved with the boundary conditions discretized with first- and second-order accuracy. The overall second-order accuracy of the difference scheme is destroyed if first-order numerical representation of one of the boundary conditions is used. With a boundary approximation, the second-order global accuracy of the model problem is retained if either second-order extrapolation or first-order representation of the governing equation is used.
Tau functions for the Dirac operator on the Poincare' disk

In this paper we define tau functions for holonomic fields associated with the Dirac operator on the Poincare disk. The deformation analysis of the tau functions is worked out and in the case of the two point function, the tau function is expressed in terms of a Painleve function of type VI.
Brunn–Minkowski inequalities for contingency tables and integer flows

We establish approximate log-concavity for a wide family of combinatorially defined integer-valued functions. Examples include the number of non-negative integer matrices (contingency tables) with prescribed row and column sums (margins), as a function of the margins and the number of integer feasible flows in a network, as a function of the excesses at the vertices. As a corollary, we obtain approximate log-concavity for the Kostant partition function of type A. We also present an indirect evidence that at least some of the considered functions might be genuinely log-concave
Surface recombination in semiconductors

Abstract The surface recombination and generation process in silicon and germanium is studied theoretically and experimentally. The theory for a uniform distribution of surface recombination-generation centers is given in a form which is applicable both to the non-equilibrium MOS method employed in the case of thermally oxidized silicon and to the photoconductive-decay method traditionally employed for etched germanium surfaces. Results of this theory are compared with measurements in thermally oxidized silicon structures and with previously published data relating to etched germanium surfaces. It is shown that the two surface systems are quite similar, and that the surface recombination and generation process in both systems can be adequately characterized by assuming that the recombination-generation centers are uniformly distributed in energy in the central region of the forbidden gap.
A comparison of oxidation and oxygen substitution in MoS2 solid film lubricants

Abstract Significant advancements in the production of low friction, long wear life, sputter-deposited MoS 2 lubricant coatings have been made in the last decade. The introduction of multi-layered coatings, the establishment of careful controls on doping during DC and magnetron sputter deposition, and the implementation of ion assisted deposition have resulted in lubricants with substantially longer wear lives (up to a factor of ten greater than in the early 1980s) and lower sliding friction coefficients. A major research effort, designed to improve the performance of solid lubricants, involved a number of laboratories during this time period, resulting in these major breakthroughs. However, even with this concentrated effort, the typical investigation involved making an educated guess, based on previous experience, of the deposition conditions, target compositions, or post treatments that might be expected to provide improved performance of resulting coatings. One notable discovery during this time period was that typical MoS 2 films contain large quantities (up to 20 atom %) of oxygen substituted for sulfur in individual crystal lattices. In this paper we will compare the effects of this oxygen substitution with the effects of oxidation which involves a change in the oxidation number of the central molybdenum atoms within the crystals. A discussion of the relationship(s) between chemistry and coating structure and tribological performance will be presented with emphasis on defect chemistry and multiple phase interactions. Speculations on the role of coating chemistry in determining coating performance in applications such as in ball bearings will be presented.
A Search for Wide Companions to the Extrasolar Planetary System HR 8799

The extrasolar planetary system around HR 8799 is the first multiplanet system ever imaged. It is also, by a wide margin, the highest mass system with >27 Jupiters of planetary mass past 25 AU. This is a remarkable system with no analog in any other known planetary system. In the first part of this paper, we investigated the nature of two faint objects imaged near the system. These objects are considerably fainter (H = 20.4 and 21.6 mag) and more distant (projected separations of 612 and 534 AU) than the three known planetary companions b, c, and d (68-24 AU). It is possible that these two objects could be lower mass planets (of mass ~5M Jup and ~3M Jup) that have been scattered to wider orbits. We make the first direct comparison of newly reduced archival Gemini adaptive optics images to archival Hubble Space Telescope/NICMOS images. With nearly a decade between these epochs, we can accurately assess the proper motion nature of each candidate companion. We find that both objects are unbound to HR 8799 and are background. We estimate that HR 8799 has no companions of H 600 AU or less than 3 M Jup in mass. In the second part of this paper, we search for any sign of a "reverse parallax signature" in the astrometric residuals of HR 8799b. No such signal was found and we conclude, as expected, that HR 8799b has the same parallax as HR 8799A. In the third part of this paper, we carry out a search for wider common proper motion objects. We found one object within 1 deg2 in the Palomar Observatory Sky Survey-Digitized Sky Survey images with similar (<2σ) proper motions to HR 8799 at a separation of 40. We conclude that it is not likely a bound companion to HR 8799 based on available photometry.
Control of Shock Loading from a Jet in the Presence of a Flexible Structure

The control of shock noise or screech from a jet near a flexible structure is discussed. The pressure from the supersonic jet consists of a shock with spiral and flapping nonaxisymmetric modes superimposed on broadband response. This shock induces a nonlinear-nonstationary loading problem associated with acoustic wave generation and propagation coupled with structural vibration. Control of the shock is achieved by placing a ring at the nozzle lip oscillating at the shock fundamental frequency. The ring prevents the shock characteristics originating in the column of the shear layer from sustaining connection with the out-of-phase surface vibration. Shock-free flow is maintained over a large pressure ratio. The peak power pressure level is reduced by 40 dB.
How does the estate tax affect the number of firms

Purpose – The purpose of this paper is to estimate the effect of the combined (Federal and state) estate, inheritance, and gift (EIG) tax burden per decedent on the number of firms in the USA. Design/methodology/approach – Estimates are based on a longitudinal panel of 50 American states from 1988 to 2006. Findings – The paper finds that the growth in the EIG tax burden per decedent significantly reduces the growth in the number of firms, especially small firms. The higher dissolution rate among small firms can be attributed to the asymmetric liquidity effect, which limits the ability of small business owners to raise the funds needed to pay the estate tax without liquidating their estates. Practical implications – The estimates suggest that the reductions in EIG taxes, brought about by the passage of 2001 EGTRRA, have lead to a higher growth in the number of firms, ceteris paribus. Social implications – As of this writing, the future of the Federal estate tax looks uncertain. Policymakers should note tha...
Semileptonic decays: An update down under

Heavy-meson semileptonic decays calculations on the lattice are reviewed. The focus is upon obtaining reliable matrix elements. Errors that depend upon the lattice spacing, a, are an important source of systematic error. Full O(a) improvement of matrix elements for arbitrary-mass four-component quarks is discussed. With improvement, bottom-quark matrix elements can be calculated directly using current lattices. Momentum dependent errors for O(a)-improved quarks and statistical noise limit momenta to around 1 GeV/c with current lattices. Hence, maximum recoil momenta can be reached for D decays while only a fraction of the maximum recoil momentum can be reliably studied for the light-meson decay modes of the B. Differential decay rates and partial widths are phenomenologically important quantities in B decays that can be reliably determined with present lattices.
How to Interpret a Tau Excess at LEP2 within the MSSM

Neutralino and tau slepton pair production can naturally produce an excess of tau lepton pairs at the current LEP collider energies. We describe the constraints this has on the values of the mass parameters in the softly broken Supersymmetric Lagrangian, and consider the consequences for superpartner production at LEP and at the Fermilab Tevatron collider. The pair production of the LSP and a heavier neutralino, followed by a 2-body decay to a tau slepton and tau lepton, is consistent with the present LEP data, predicts a chargino mass below 125 GeV, and provides an interesting Cold Dark Matter component, with Ωh2∼0.1–0.2.
On the optimality of age-dependent taxes and the progressive U.S. tax system

Abstract In life-cycle economies, where an individual's optimal consumption-work plan is almost never constant, the optimal marginal tax rates on capital and labor income vary with age. Conversely, the progressivity imbedded in the U.S. tax code implies that marginal tax rates vary with age because tax rates vary with earnings and earnings vary with age. Using numerical simulations, this paper shows that if the tax authority is prevented from conditioning tax rates on age, some degree of progressivity is desirable as progressive taxation better imitates optimal age-dependent taxes than an optimal age-independent tax system. This role for progressive taxation emanates from efficiency reasons and does not rely on any insurance nor re-distribution arguments.