cssi/SciSciGPT-SciSciNet huggingface dataset:
Entropy Splitting and Numerical Dissipation

A rigorous stability estimate for arbitrary order of accuracy of spatial central difference schemes for initial boundary value problems of nonlinear symmetrizable systems of hyperbolic conservation laws was established recently by Olsson and Oliger (1994, “Energy and Maximum Norm Estimates for Nonlinear Conservation Laws”, RIACS Report, NASA Ames Research Center) and Olsson (1995, Math. Comput.64, 212) and was applied to the two-dimensional compressible Euler equations for a perfect gas by Gerritsen and Olsson (1996, J. Comput. Phys.129, 245) and Gerritsen (1996, “Designing an Efficient Solution Strategy for Fluid Flows, Ph.D. Thesis, Stanford). The basic building block in developing the stability estimate is a generalized energy approach based on a special splitting of the flux derivative via a convex entropy function and certain homogeneous properties. Due to some of the unique properties of the compressible Euler equations for a perfect gas, the splitting resulted in the sum of a conservative portion and a non-conservative portion of the flux derivative, hereafter referred to as the “entropy splitting.” There are several potentially desirable attributes and side benefits of the entropy splitting for the compressible Euler equations that were not fully explored in Gerritsen and Olsson. This paper has several objectives. The first is to investigate the choice of the arbitrary parameter that determines the amount of splitting and its dependence on the type of physics of current interest to computational fluid dynamics. The second is to investigate in what manner the splitting affects the nonlinear stability of the central schemes for long time integrations of unsteady flows such as in nonlinear aeroacoustics and turbulence dynamics. If numerical dissipation indeed is needed to stabilize the central scheme, can the splitting help minimize the numerical dissipation compared to its un-split cousin? Extensive numerical study on the vortex preservation capab ility of the splitting in conjunction with central schemes for long time integrations will be presented. The third is to study the effect of the non-conservative proportion of splitting in obtaining the correct shock location for high speed complex shock-turbulence interactions. The fourth is to determine if this method can be extended to other physical equations of state and other evolutionary equation sets. If numerical dissipation is needed, the Yee, Sandham, and Djomehri (1999, J. Comput. Phys.150, 199) numerical dissipation is employed. The Yee et al. schemes fit in the Olsson and Oliger framework.
Effective conformal theory and the flat-space limit of AdS

We develop the idea of an effective conformal theory describing the low-lying spectrum of the dilatation operator in a CFT. Such an effective theory is useful when the spectrum contains a hierarchy in the dimension of operators, and a small parameter whose role is similar to that of 1/N in a large N gauge theory. These criteria insure that there is a regime where the dilatation operator is modified perturbatively. Global AdS is the natural framework for perturbations of the dilatation operator respecting conformal invariance, much as Minkowski space naturally describes Lorentz invariant perturbations of the Hamiltonian. Assuming that the lowest-dimension single-trace operator is a scalar, $ \mathcal{O} $ , we consider the anomalous dimensions, γ(n, l), of the double-trace operators of the form $ \mathcal{O}{\left( {{\partial^2}} \right)^n}{\left( \partial \right)^l}\mathcal{O} $ . Purely from the CFT we find that perturbative unitarity places a bound on these dimensions of |γ(n, l)| < 4. Non-renormalizable AdS interactions lead to violations of the bound at large values of n. We also consider the case that these interactions are generated by integrating out a heavy scalar field in AdS. We show that the presence of the heavy field “unitarizes” the growth in the anomalous dimensions, and leads to a resonance-like behavior in γ(n, l) when n is close to the dimension of the CFT operator dual to the heavy field. Finally, we demonstrate that bulk flat-space S-matrix elements can be extracted from the large n behavior of the anomalous dimensions. This leads to a direct connection between the spectrum ofanomalous dimensions in d-dimensional CFTs and flat-space S-matrix elements in d + 1 dimensions. We comment on the emergence of flat-space locality from the CFT perspective.
Some remarks on quantized Lie superalgebras of classical type

Abstract In this paper we use the Etingof–Kazhdan quantization of Lie bi-superalgebras to investigate some interesting questions related to Drinfeld–Jimbo type superalgebra associated to a Lie superalgebra of classical type. It has been shown that the D-J type superalgebra associated to a Lie superalgebra of type A-G, with the distinguished Cartan matrix, is isomorphic to the E-K quantization of the Lie superalgebra. The first main result in the present paper is to extend this to arbitrary Cartan matrices. This paper also contains two other main results: (1) a theorem stating that all highest weight modules of a Lie superalgebra of type A-G can be deformed to modules over the corresponding D-J type superalgebra and (2) a super version of the Drinfeld–Kohno theorem.
Alfred Chandler and knowledge management within the firm

This essay examines the role of knowledge management, defined as the management of processes affecting the creation, communication, distribution, and exploitation of knowledge concerning corporate strategy, markets, product and process technologies, and management practices within the corporation, in Alfred D. Chandler's work on the modern corporation. Along with efforts to avoid transaction-cost problems, the management of firm-specific information and knowledge was central to the 19th-century transformation of US corporate structure that Chandler examined in The Visible Hand . Knowledge management also played a key role in the creation of intrafirm organizations for managing the creation of knowledge, management of innovation, and acquisition of technologies from external sources. Industrial R&D and the product diversification that emerged from the in-house R&D facilities of many of these firms contributed to the development of the so-called "M-form" corporation (examined by Chandler in Strategy and Structure ), in which corporate management and strategy formulation were organizationally differentiated and separated from functional management. Finally, Chandler's last work on the success and failure of United States, Japanese, and Western European firms in the modern electronics, pharmaceuticals, and chemicals industries emphasized the role of the "integrated learning base" within these firms and the varying degrees of success with which established firms were able to sustain these "learning bases" and/or apply them to new markets and technologies. Copyright 2010 The Author 2010. Published by Oxford University Press on behalf of Associazione ICC. All rights reserved., Oxford University Press.
Electron-hole transport and photovoltaic effect in gated MoS2 Schottky junctions

Semiconducting molybdenum disulfphide has emerged as an attractive material for novel nanoscale optoelectronic devices due to its reduced dimensionality and large direct bandgap. Since optoelectronic devices require electron-hole generation/recombination, it is important to be able to fabricate ambipolar transistors to investigate charge transport both in the conduction band and in the valence band. Although n-type transistor operation for single-layer and few-layer MoS2 with gold source and drain contacts was recently demonstrated, transport in the valence band has been elusive for solid-state devices. Here we show that a multi-layer MoS2 channel can be hole-doped by palladium contacts, yielding MoS2 p-type transistors. When two different materials are used for the source and drain contacts, for example hole-doping Pd and electron-doping Au, the Schottky junctions formed at the MoS2 contacts produce a clear photovoltaic effect.
Bayesian spike inference from calcium imaging data

We present efficient Bayesian methods for extracting neuronal spiking information from calcium imaging data. The goal of our methods is to sample from the posterior distribution of spike trains and model parameters (baseline concentration, spike amplitude etc) given noisy calcium imaging data. We present discrete time algorithms where that the existence of a spike at each time bin using Gibbs methods, as well as continuous time algorithms that sample over the number of spikes and their locations at an arbitrary resolution using Metropolis-Hastings methods for point processes. We provide Rao-Blackwellized extensions that (i) marginalize over several model parameters and (ii) provide smooth estimates of the marginal spike posterior distribution in continuous time. Our methods serve as complements to standard point estimates and allow for quantification of uncertainty in estimating the underlying spike train and model parameters.
Complexity-building annulations of strained cycloalkanes and C═O π bonds.

This Perspective details a developing research program that emerged from simple plans for achieving the synthesis of tetrahydrofurans from cyclopropanes and C═O π bonds. Lewis acid catalyzed annulations of malonate-derived donor−acceptor cyclopropanes with aldehydes are unusually broad in scope and lead to the synthesis of structurally diverse tetrahydrofurans. The reactions are stereospecific, with inversion observed at the cyclopropane donor site. Substituent effects on the aldehyde suggest that it acts as a nucleophile in the reaction. An unusual mechanism emerges in which the aldehyde traps a configurationally stable intimate ion pair to stereospecifically construct the C−O bond. In addition to the stereospecific conversion of enantiomerically enriched cyclopropanes into nonracemic heterocycles, we have also demonstrated that racemic cyclopropane 1,1-diesters can undergo dynamic kinetic asymmetric annulations catalyzed by (pybox)MgI2 complexes. Asymmetric syntheses of (+)-polyanthellin A and (+)-virga...
Algebraic Hamiltonian actions

In this paper we deal with a Hamiltonian action of a reductive algebraic group G on an irreducible normal affine Poisson variety X. We study the quotient morphism $${\mu_{G,X}//G : X//G \rightarrow \mathfrak{g} //G}$$ of the moment map $${\mu_{G,X} : X\rightarrow \mathfrak{g}}$$ . We prove that for a wide class of Hamiltonian actions (including, for example, actions on generically symplectic varieties) all fibers of the morphism μ G,X //G have the same dimension. We also study the “Stein factorization” of μ G,X //G. Namely, let C G,X denote the spectrum of the integral closure of $${\mu_{G,X}^{*}(\mathbb{K}[\mathfrak{g}]^G)}$$ in $${\mathbb{K}(X)^G}$$ . We investigate the structure of the $${\mathfrak{g} //G}$$ -scheme C G,X . Our results partially generalize those obtained by F. Knop for the actions on cotangent bundles and symplectic vector spaces.
THAW: Tangible Interaction with See-Through Augmentation for Smartphones on Computer Screens

The huge influx of mobile display devices is transforming computing into multi-device interaction, demanding a fluid mechanism for using multiple devices in synergy. In this paper, we present a novel interaction system that allows a collocated large display and a small handheld device to work together. The smartphone acts as a physical interface for near-surface interactions on a computer screen. Our system enables accurate position tracking of a smartphone placed on or over any screen by displaying a 2D color pattern that is captured using the smartphone's back-facing camera. As a result, the smartphone can directly interact with data displayed on the host computer, with precisely aligned visual feedback from both devices. The possible interactions are described and classified in a framework, which we exemplify on the basis of several implemented applications. Finally, we present a technical evaluation and describe how our system is unique compared to other existing near-surface interaction systems. The proposed technique can be implemented on existing devices without the need for additional hardware, promising immediate integration into existing systems.
Synthesis of 4-thiazolidinones from rhodanines by thiocarbonyl removal

Abstract A new procedure for synthesis of 4-thiazolidinones from readily available rhodanines is reported. Slow addition of the substrate to excess zinc dust in acetic acid at reflux affords the best yields. Identification of dimeric byproducts led to development of a procedure to suppress their formation.
A new framework for the cycloaromatization of enediynes under mild conditions

Abstract An enediyne unit in a bicyclo[8.3.0] framework with a trans ring fusion has been designed, synthesized, and evaluated as a new functional model for the enediyne toxins. The cycloaromatization reaction proceeds with a half-life time of 13–14 hr at 25 °C.
Ab Initio Study of Magnetic Structure and Chemical Reactivity of Cr2O3 and Its (0001) Surface

We present the first ab initio density functional theory study of the oxygen-terminated Cr2O3 (0001) surface within the local spin-density approximation (LSDA). We find that spin plays a critical role for even the most basic properties of Cr2O3, such as the structure and mechanical response of the bulk material. The surface exhibits strong relaxations and changes in electronic and magnetic structure with important implications for the chemical reactivity and unusual spin-dependent catalytic activity of the surface. Unlike the bulk, the outermost chromium bilayer is ferromagnetically ordered, and the surface oxygen layer exhibits appreciable net spin polarization in the opposite sense. Surprisingly, despite this ferrimagnetic order, the chemically important states near the Fermi level exhibit ferromagnetic order and thus favor electronic spin alignment of species interacting with the surface. Finally, we also find a high density of unoccupied electronic surface states available to participate in the chemic...
Nonlinear Saturation of the Trapped-Ion Mode

A nonlinear model of the collisional trapped-ion mode is presented, in which the energy in long-wavelength instabilities is transferred to short-wavelength modes which are then damped by ion-bounce resonances. Near marginal stability, the saturation of a single unstable Fourier mode is computed. Far from marginal stability, steady-state nonlinear solitary waves containing many Fourier modes are found. Particle transport is estimated in both cases.
Epsilon-net method for optimizations over separable states

We give algorithms for the optimization problem: max ? ? { Q , ? } , where Q is a Hermitian matrix, and the variable ? is a bipartite separable quantum state. This problem lies at the heart of several problems in quantum computation and information, such as the complexity of QMA(2). While the problem is NP-hard, our algorithms are better than brute force for several instances of interest. In particular, they give PSPACE upper bounds on promise problems admitting a QMA(2) protocol in which the verifier performs only a logarithmic number of elementary gates on both proofs, as well as the promise problem of deciding if a bipartite local Hamiltonian has a large or small ground energy. For Q ? 0 , our algorithm runs in time exponential in ? Q ? F . While the existence of such an algorithm was first proved recently by Brandao, Christandl and Yard (2011) 8, our algorithm is conceptually simpler.
A Crash Course in Implementation Theory

This paper is meant to familiarize the audience with some of the fundamental results in the theory of implementation and provide a quick progression to some open questions in the literature.
Laminar boundary layers on helicopter rotors in forward flight.

Several examples of three-dimensi onal boundary layers on helicopter rotors in forward flight are analyzed within the framework of small-crossflow and quasi-steady approximations; these two assumptions are shown to be mutually consistent and to have a wide range of applicability. In laminar flow, the crossflow can be separated into components due to rotation and due to the instantaneous yawing of the rotor blade relative to the direction of flight. Third-order perturbation expansions for a flat-plate blade show the relative importance of the rotational and translational motion, and analysis of the flow over several blade sections with thickness demonstrates the role of chord wise pressure gradients. The results indicate that the crossflow generally tends to delay separation on the retreating side of the rotor disk. The effects of rotation can be large in regions of incipient separation, but elsewhere the boundary layer generally resembles the viscous flow over a swept wing. Also, the detailed structure of the crossflow depends upon whether the primary flow is accelerating or decelerating.
RuCl3 Catalyzed One‐Pot Synthesis of α‐Aminonitriles

Abstract A simple and efficient method was developed for the synthesis of α‐aminonitriles by simply mixing aldehydes, amines, and trimethylsilyl cyanides in the presence of a catalytic amount of RuCl3 at room temperature.
The theory of turbulence in two dimensions

Abstract The methods of conformal field theory are used to obtain series of exact solutions of the fundamental equations of the theory of turbulence. The basic conjecture, proved to be self-consistent, is the conformal invariance of the inertial range. The resulting physical picture is different from the standard one, since the enstrophy transfer is catalyzed by the large-scale motions. The theory gives some unambiguous predictions for the corrections in the inertial range.
The Universe Is Not a Computer

When we want to predict the future, we compute it from what we know about the present. Specifically, we take a mathematical representation of observed reality, plug it into some dynamical equations, and then map the time-evolved result back to real-world predictions. But while this computational process can tell us what we want to know, we have taken this procedure too literally, implicitly assuming that the universe must compute itself in the same manner. Physical theories that do not follow this computational framework are deemed illogical, right from the start. But this anthropocentric assumption has steered our physical models into an impossible corner, primarily because of quantum phenomena. Meanwhile, we have not been exploring other models in which the universe is not so limited. In fact, some of these alternate models already have a well-established importance, but are thought to be mathematical tricks without physical significance. This essay argues that only by dropping our assumption that the universe is a computer can we fully develop such models, explain quantum phenomena, and understand the workings of our universe. (This essay was awarded third prize in the 2012 FQXi essay contest; a new afterword compares and contrasts this essay with Robert Spekkens’ first prize entry.)
Homological Dimension and Critical Exponent of Kleinian Groups

We prove an inequality between the relative homological dimension of a Kleinian group \(\Gamma \subset {\rm Isom}({\mathbb{H}}^n)\) and its critical exponent. As an application of this result we show that for a geometrically finite Kleinian group Γ, if the topological dimension of the limit set of Γ equals its Hausdorff dimension, then the limit set is a round sphere.
Finite element analysis of strain effects on electronic and transport properties in quantum dots and wires

Lattice mismatch in epitaxial layered heterostructures with small characteristic lengths induces large, spatially nonuniform strains. The components of the strain tensor have been shown experimentally to affect the electronic properties of semiconductor structures. Here, a technique is presented for calculating the influence of strain on electronic properties. First, the linear elastic strain in a quantum dot or wire is determined by a finite element calculation. A strain-induced potential field that shifts and couples the valence subbands in the structure is then determined from deformation potential theory. The time-independent Schrodinger equation, including the nonuniform strain-induced potential and a potential due to the heterostructure layers, is then solved, also by means of the finite element method. The solution consists of the wave functions and energies of states confined to the active region of the structure; these are the features which govern the electronic and transport properties of devices. As examples, two SixGe1−x submicron resonant tunneling devices, a quantum wire with two-dimensional confinement and a quantum dot with three-dimensional confinement, are analyzed. Experimentally measured resonant tunneling current peaks corresponding to the valence subbands in the material are modeled by generating densities of confined states in the structures. Size and composition-dependent strain effects are examined for both devices. In both the quantum dot and the quantum wire, the strain effects on the wave functions and energies of confined states are evident in the calculated densities of confined states in the structures, which are found to be consistent with experimentally measured tunneling current/voltage curves for resonant tunneling diodes.
Sarkozy and the ‘American Mirage’ or Why Gaullist Continuity will Overshadow Transcendence

This article argues that the continuity in French approaches to the transatlantic relationship and to the North Atlantic Alliance is structured by deep historical forces and is relatively unaffected by the personal preferences of individual Presidents or other political actors. Nicolas Sarkozy's much discussed ‘return to NATO’ will not affect French foreign policy in any significant way. Indeed, having France inside the tent is likely to generate even greater European-American tension within the Alliance.
Linear Probing and Graphs

Mallows and Riordan showed in 1968 that labeled trees with a small number of inversions are related to labeled graphs that are connected and sparse. Wright enumerated sparse connected graphs in 1977, and Kreweras related the inversions of trees to the so-called ``parking problem'' in 1980. A combination of these three results leads to a surprisingly simple analysis of the behavior of hashing by linear probing, including higher moments of the cost of successful search.
Dynamics of Low Energy Electron Attachment to Formic Acid

Low-energy electrons (<2 eV) can fragment gas phaseformic acid (HCOOH) molecules through resonant dissociative attachmentprocesses. Recent experiments have shown that the principal reactionproducts of such collisions are formate ions (HCOO-) and hydrogen atoms.Using first-principles electron scattering calculations, we haveidentified the responsible negative ion state as a transient \pi* anion.Symmetry considerations dictate that the associated dissociation dynamicsare intrinsically polyatomic: a second anion surface, connected to thefirst by a conical intersection, is involved in the dynamics and thetransient anion must necessarily deform to non-planar geometries beforeit can dissociate to the observed stable products.
Zinc Single-Crystal Deformation Experiments Using a ''6 Degrees of Freedom'' Apparatus

A new experimental technique to study crystallographic slip system activity in metallic single crystals deformed under a condition of uniaxial stress is applied to study the behavior of Zn single crystals. The experimental apparatus promotes unconstrained shape change of inherently anisotropic materials under a condition of uniaxial stress by allowing three translational and three rotational degrees of freedom during compression; hence, we have named the experiment “6 degrees of freedom” (6DOF). The experiments also use a three-dimensional (3-D) digital image correlation (IC) system to measure full-field displacements, which are used to calculate strain and make direct observations of slip system activity. We show that the experimental results associated with a pristine zinc single crystal are precisely consistent with the theoretical predicted shape change (sample distortion) assuming that the most favored slip system on the basal plane is the only one that is active. Another experiment was performed on a processed and annealed Zn single crystal to investigate slip that is inconsistent with the critical resolved shear stress (CRSS) theory. These experiments on zinc illustrate the ability of the 6DOF experiment, together with image correlation (IC) data, to measure slip system activity with a high degree of fidelity.
Using digital cameras as quasi-spectral radiometers to study complex fenestration systems

This work discusses the use of digital cameras fitted with absorption filters as quasi-spectral radiometers. By filtering incident light into selected wavelength intervals, accurate estimates of radiances can be made for unknown spectra. This approach is being employed as part of a new video-projection goniophotometer to study the properties of angularly and spectrally selective complex fenestration systems. Complex fenestration systems are increasingly being used to distribute solar radiation purposefully in buildings. They can be utilized to optimize energy performance and enhance daylighting. Radiance estimates from calibrated digital cameras enable the assessment of quasi-spectral, bi-directional scattering distribution functions of total radiance transmitted or reflected by a fenestration system over desired wavelength intervals. A silicon and an indium gallium arsenide digital camera are used to enable measurements across a 380 to 1700 nm wavelength interval.
Collective Excitations of a Bose-Einstein Condensate in a Dilute Gas

We observe phononlike excitations of a Bose-Einstein condensate (BEC) in a dilute atomic gas. ${}^{87}$Rb atoms are optically trapped and precooled, loaded into a magnetic trap, and then evaporatively cooled through the BEC phase transition to form a condensate. We excite the condensate by applying an inhomogeneous oscillatory force with adjustable frequency and symmetry. We have observed modes with different angular momenta and different energies and have studied how their characteristics depend on interaction energy. We find that the condensate excitations persist longer than their counterparts in uncondensed clouds.
Schreier sets in Ramsey theory

We show that Ramsey theory, a domain presently conceived to guaran- tee the existence of large homogeneous sets for partitions on k-tuples of words (for every natural number k) over a finite alphabet, can be extended to one for partitions on Schreier-type sets of words (of every countable ordinal). Indeed, we establish an extension of the partition theorem of Carlson about words and of the (more general) partition theorem of Furstenberg-Katznelson about combinatorial subspaces of the set of words (generating from k-tuples of words for any fixed natural number k) into a partition theorem about combinatorial subspaces (generating from Schreier-type sets of words of order any fixed countable ordinal). Furthermore, as a result we obtain a strengthening of Carlson's infinitary Nash-Williams type (and Ellentuck type) partition theorem about infinite sequences of variable words into a theorem, in which an infinite sequence of variable words and a binary partition of all the finite sequences of words, one of whose components is, in addition, a tree, are assumed, concluding that all the Schreier-type finite reductions of an infinite reduction of the given sequence have a be- havior determined by the Cantor-Bendixson ordinal index of the tree-component of the partition, falling in the tree-component above that index and in its complement below it.
EXACT WAVE FUNCTIONS FOR GENERALIZED HARMONIC OSCILLATORS

We transform the time-dependent Schrodinger equation for the most general variable quadratic Hamiltonians into a standard autonomous form. As a result, the time evolution of exact wave functions of generalized harmonic oscillators is determined in terms of the solutions of certain Ermakov and Riccatitype systems. In addition, we show that the classical Arnold transform is naturally connected with Ehrenfest’s theorem for generalized harmonic oscillators.
Nucleophilic addition to (3-methylpentadienyl)iron(1+) cations: counterion control of regioselectivity; application to the enantioselective synthesis of 4,5-disubstituted cyclohexenones.

The regioselectivity of malonate addition to (3-methylpentadienyl)Fe(CO)3+ is controlled by the malonate−counterion association. The Li+ salt of malonate proceeds via C1 nucleophilic attack to afford the 1,3Z-diene complex 4a, while reaction of highly dissociated ion pair (i.e., Na+ or Li+/12-crown-4) salt proceeds at the C2 internal carbon to eventually afford cyclohexenone products 6. Reaction of 1a with the sodium salt of bis(8-phenylmenthyl)malonate proceeds with excellent diastereocontrol to afford a single diastereomeric cyclohexenone.
Design of dispersive optomechanical coupling and cooling in ultrahigh-Q/V slot-type photonic crystal cavities

We describe the strong optomechanical dynamical interactions in ultrahigh-Q/V slot-type photonic crystal cavities. The dispersive coupling is based on mode-gap photonic crystal cavities with light localization in an air mode with 0.02(λ/n)3 modal volumes while preserving optical cavity Q up to 5 × 106. The mechanical mode is modeled to have fundamental resonance Ωm/2π of 460 MHz and a quality factor Qm estimated at 12,000. For this slot-type optomechanical cavity, the dispersive coupling gom is numerically computed at up to 940 GHz/nm (Lom of 202 nm) for the fundamental optomechanical mode. Dynamical parametric oscillations for both cooling and amplification, in the resolved and unresolved sideband limit, are examined numerically, along with the displacement spectral density and cooling rates for various operating parameters.
Experience with advanced driver fuels in EBR-II☆

Abstract Several metallic fuel element designs have been tested and used as driver fuel in Experimental Breeder Reactor II (EBR-II). The most recent advanced designs have all performed acceptably in EBR-II and can provide reliable performance to high burnups. Fuel elements tested have included use of U-10Zr metallic fuel with either D9, 316 or HT9 stainless steel cladding; the D9 and 316-clad designs have been used as standard driver fuel. Experimental data indicate that fuel performance characteristics are very similar for the various designs tested. Cladding materials can be selected that optimize performance based on reactor design and operational goals.
The impact of early occupational choice on health behaviors

Occupational choice is a significant input into workers’ health investments, operating in a manner that can be either health-promoting or health-depreciating. Recent studies have highlighted the potential importance of initial occupational choice on subsequent outcomes pertaining to morbidity. This study is the first to assess the existence and strength of a causal relationship between initial occupational choice at labor entry and subsequent health behaviors and habits. We utilize the Panel Study of Income Dynamics to analyze the effect of first occupation, as identified by industry category and blue collar work, on subsequent health outcomes relating to obesity, alcohol misuse, smoking, and physical activity in 2005. Our findings suggest blue collar work early in life is associated with increased probabilities of obesity, at-risk alcohol consumption, and smoking, and increased physical activity later in life, although effects may be masked by unobserved heterogeneity. The weight of the evidence bearing from various methodologies, which account for non-random unobserved selection, indicates that at least part of this effect is consistent with a causal interpretation. These estimates also underscore the potential durable impact of early labor market experiences on later health.
Prenatal exposures and congenital heart defects in Down syndrome infants

The purpose of this study was to determine whether there are important differences in maternal and environmental prenatal risk factors between liveborn Down syndrome infants with congenital heart defects and Down syndrome infants without heart defects. Using a case control study design, we evaluated the risk associated with maternal illness, drug ingestion, substance usage, and chemical exposures in the home or workplace. The period of risk selected was 3 months before and 3 months after the last menstrual period, because cardiac development occurs early, before the mother may become aware of her pregnancy. Because fetal survival in Down syndrome may be more vulnerable to various exposures, controls were selected who also had trisomy 21. Of 171 infants studied, 89 were cases with congenital heart disease, and 82 were controls without heart disease. All interviews were performed by one nurse practitioner using a structured standardized questionnaire. Cases and controls had similar maternal ages, family incomes, parental education levels, and contraceptive practices before pregnancy. No differences were found between case and control mothers for maternal illness, medication use, or consumption of caffeinated beverages, cigarettes, or alcohol. Reporting of recreational drug usage was infrequent, may reflect underreporting, and did not differ between cases and controls. Maternal exposures were commonly reported for pesticides (50%), hair dyes (22%), craft paints (8%), varnishes (7%), and solvents (3.5%). However, in none of the categories was maternal exposure significantly more prevalent among case mothers than among control mothers. The failure of this study to identify risk factors for cardiac malformations may be attributable to the small differences in reported frequencies reducing statistical power or to the possibility that cardiac malformation in Down syndrome is a direct result of chromosomal duplication.
Comparison of Two Techniques for Proving Nonexistence of Strongly Regular Graphs

We show that the method of counting closed walks in strongly regular graphs rules out no parameter sets other than those ruled out by the method of counting eigenvalue multiplicities.
Recent advances of ionic liquids in separation science and mass spectrometry

Ionic liquids (ILs) have drawn considerable interest for their use in various analytical techniques including chromatography, extractions, and mass spectrometry. This is largely due to the flexibility in tuning the physicochemical properties of ILs. There has been a significant increase in the number of publications over the last decade in which ILs have been employed as a chromatographic stationary phase, extraction solvent, or sorbent material in various preconcentration techniques. This review article highlights the recent advancements in the use of ILs in separation science including gas chromatography, high-performance liquid chromatography, capillary electrophoresis, extraction and microextraction techniques as well as mass spectrometry.
Synthesis of Contiguously Substituted Nitro Aromatics via Directed Ortho-Metalation Nitration

Abstract A new protocol for the synthesis of contiguously substituted aromatic nitro compounds based on directed orttho-metalation followed by reaction with methyl nitrate is described.
Splints of classical root systems

We define and classify splints of root systems of complex semisimple Lie algebras. In a few instances, splints play a role in determining branching rules of a module over a complex semisimple Lie algebra when restricted to a subalgebra. In these particular cases, the set of submodules with respect to the subalgebra themselves may be regarded as the character of an auxiliary Lie algebra which may or may not be another Lie subalgebra.
Arctic Ocean Tides from GRACE Satellite Accelerations

[1] Models are routinely used to remove the effects of global ocean tides from GRACE data during processing to reduce temporal aliasing into monthly GRACE solutions. These models have typically been derived using data from satellite altimeters such as TOPEX/Poseidon. Therefore the Arctic ocean components of tide models are not constrained by altimetry data, potentially resulting in errors that are likely to alias into monthly GRACE gravity fields at all latitudes. Seven years of GRACE inter-satellite accelerations are inverted to solve for corrections to the amplitude and phase of major solar and lunar ocean tides at latitudes north of 50°N using a mascon approach. The tide model originally applied to our data was FES2004, truncated to maximum degree lmax = 90. Simulations are performed to verify that our inversion algorithm works as designed. Uncertainty estimates are derived from tidal solutions on land, and by subtracting two independent solutions that each use 3.5 years of data. Features above the noise floor in the M2, K1, S2, and O1 solutions likely represent errors in FES2004. Errors due to truncating the spherical harmonic expansion of FES2004 are too small, and errors in the land mask model (needed to transform sea surface heights into mass) only affect coastal areas and do not produce similar relative amplitudes for any examined tides. In the oceans north of 50°N, these residuals tend to reduce the FES2004 amplitudes for M2, K1, S2, and O1. Reductions in the variance of accelerations not used in our inversion suggest that our results can be used to improve GRACE processing.
Two bounds for the X-ray transform

Weusethearithmetic-combinatorialmethodofKatzandTaotogivemixed-norm estimates for the X-ray transform on R d when d ≥ 4.
Optimal tax and tariff policies with tax credits

Abstract This paper examines the optimal tax and tariff policies for a small open economy when mobile capital receives a tax credit for taxes paid to the host country. For a capital-importing country, a tax on capital equal to the source country tax rate (to capture tax revenue) combined with a subsidy to encourage capital imports is the optimal policy. Results are also derived for cases in which only one of the instruments can be varied. For a capital-exporting country that cannot reduce its capital tax rate, a subsidy to the sector using exported capital is desirable.
Vibrational spectra and structure of cis- and trans-1,2- dimethoxyethylenes

Abstract The vapor, liquid and CCl4 solution infrared spectra of cis- and trans-1,2-dimethoxyethylene were recorded in the region 250–4000 cm−1. The laser-Raman spectra were obtained in the liquid state only. The vibrational spectra show that at least two rotational isomers exist for each molecule. Further, the spectra indicate that for both the cis- and trans molecules, one of the rotational isomers has at least one planar conformer. Some vibrational assignments are made for the observed infrared and Raman bands of the cis- and trans- 1,2-dimethoxyethylenes.
Greedy routing via embedding graphs onto semi-metric spaces

In this paper, we generalize the greedy routing concept to use semi-metric spaces. We prove that any connected n-vertex tree T admits a greedy embedding, onto an appropriate semi-metric space such that (1) each vertex v of the tree is represented by k=deg(v) virtual coordinates (where the numbers are from 1 to 2n-2); and (2) using an appropriate distance definition, the unique simple path between any two vertices in T is always a distance decreasing path between the two vertices. Applying the result to an arbitrary connected graph G, such a greedy embedding of any of its spanning tree T onto a semi-metric space becomes a greedy embedding of G onto the same semi-metric space. In particular, for 3-connected plane graphs, we prove that, for a 3-connected plane graph G, there is a greedy embedding of G such that: (1) the greedy embedding can be obtained in linear time; (2) each vertex can be represented by at most 3 virtual coordinates from 1 to 2n-2; and (3) the distance between two vertices can be computed in constant time. To our best knowledge, this is the first greedy routing algorithm for 3-connected plane graphs, albeit with non-standard notions of greedy embedding and greedy routing, such that: (1) it runs in linear time to compute the virtual coordinates for the vertices; and (2) the virtual coordinates are represented succinctly in O(logn) bits.
Establishment Size by Sector and County-Level Economic Growth

Median household income is found to grow faster in counties with smaller manufacturing, retail, wholesale, and service establishments.
Secular cooling of the Earth as a source of intraplate stress

As a result of secular cooling and contraction of the earth, an increasingly extensional horizontal stress is imposed on the central portions of the plates. While the rate of increase of this stress is small in most situations, it is enhanced for large plates and during any episodes of accelerated global cooling. This source of stress may have contributed to the rifting and breakup of long-lived supercontinental plates.
Rhombohedral-to-triclinic phase transition in BaMo6S8*

The rhombohedral, R 3 ¯ , to triclinic, P 1 ¯ , transition in BaMo6S8 at 175 K has been studied by neutron powder diffraction. The first order nature of the transition, as required by Landau theory, is suggested by the temperature dependence of the triclinic distortion; however, no volume discontinuity can be seen with the precision of this measurement. The triclinic structure is characterized by a distortion of the Mo6 octahedra and a shear of the axial sulfur atoms which allows the Ba ion to localize at the origin position.
Carbonyl assisted intramolecular ring opening of 2-oxetanones: A stereoselective route to 2,5-disubstituted tetrahydrofurans

Abstract A carbonyl oxygen may serve as an internal nucleophile to open a 2-oxetanone ring by a β-cleavage process. A sequence incorporating this strategy has been used to prepare 2,5-disubstituted tetrahydrofurans.
Using mixture models for collaborative filtering

A collaborative filtering system at an e-commerce site or similar service uses data about aggregate user behavior to make recommendations tailored to specific user interests. We develop recommendation algorithms with provable performance guarantees in a probabilistic mixture model for collaborative filtering proposed by Hofmann and Puzicha. We identify certain novel parameters of mixture models that are closely connected with the best achievable performance of a recommendation algorithm; we show that for any system in which these parameters are bounded, it is possible to give recommendations whose quality converges to optimal as the amount of data grows. All our bounds depend on a new measure of independence that can be viewed as an L"1-analogue of the smallest singular value of a matrix. Using this, we introduce a technique based on generalized pseudoinverse matrices and linear programming for handling sets of high-dimensional vectors. We also show that standard approaches based on L"2 spectral methods are not strong enough to yield comparable results, thereby suggesting some inherent limitations of spectral analysis.
Maximum-likelihood estimation of a process with random transitions (failures)

A process with random transitions is represented by the difference equation x_{n} = x_{n-1}+ u_{n} where u n is a nonlinear function of a Gaussian sequence w_{n}. The nonlinear function has a threshold such that u_{n} =0 for |w_{n}| \leq W . This results in a finite probability of no failure at every step. Maximum likelihood estimation of the sequence X_{n}={x_{0},...,x_{n}} given a sequence of observations Y_{n} = { y_{1},...,y_{n} } gives rise to a two-point boundary value (TPBV) problem, the solution of which is suggested by the analogy with a nonlinear electrical ladder network. Examples comparing the nonlinear filter that gives an approximate solution of the TPBV problem with a linear recursive filter are given, and show the advantages of the former. Directions for further investigation of the method are indicated.
Constrained Control Allocation

This paper addresses the problem of the allocation of several airplane flight controls to the generation of specified body-axis moments. The number of controls is greater than the number of moments being controlled, and the ranges of the controls are constrained to certain limits. They are assumed to be individually linear in their effect throughout their ranges of motion and independent of one another in their effects. The geometries of the subset of the constrained controls and of its image in moment space are examined. A direct method of allocating these several controls is presented that guarantees the maximum possible moment can be generated within the constraints of the controls. It is shown that no single generalized inverse can yield these maximum moments everywhere without violating some control constraint. A method is presented for the determination of a generalized inverse that satisfies given specifications which are arbitrary but restricted in number. We then pose and solve a minimization problem that yields the generalized inverse that best approximates the exact solutions. The results are illustrated at each step by an example problem involving three controls and two moments.
Gassman's intramolecular [2 + 2] cationic cycloaddition. formal total syntheses of raikovenal and epi-raikovenal.

The first intramolecular version of Gassman’s cationic [2 + 2] cycloaddition employing vinyl acetals tethered to an unactivated olefin and its application in the formal syntheses of raikovenal and epi-raikovenal are described.
Developments in the production of mushroom mycelium in submerged liquid culture

The process for the production of mushroom mycelium for food purposes has great potentiality. It would offer a simple, mechanized, inexpensive method for producing a nutritious food. Mushroom mycelium can be cultivated in submerged liquid culture on simple carbohydrate and nitrogen compounds with mineral salts. Yields are high and no special production problems are involved. Those species reported to have flavour are Agaricus campestris, Morchella crassipes, Lepiota rachodes, and Coprinus comatus. The mycelial growth is usually either in ball form or dispersed. The dispersed form, characterized by fine mycelium and secondary spores, may be a physiological mutation which gives greater yield but less flavour. Mycelium grown on solid media is said to have greater flavour than mycelium grown in submerged culture. Several methods for enhancing the flavour of the mycelium have been investigated. The taste of the mycelium has been variously reported from flavourless to equivalent or even preferable to that of the fruiting bodies. The fact remains, however, that it is only the problem of taste that has kept the process from commercial exploitation.
COULOMB AND HARD CORE SKYRMION TAILS

Quantum Hall skyrmions are quantized solitons of a ferromagnetic O(3) σ-model. The reference, classical, solutions depend upon the interaction between the electrons and exhibit completely different asymptotic profiles for the physical Coulomb interaction than for the hard core interaction frequently used to generate variational wavefunctions. In this note we show, by means of numerical calculations on (large) finite size systems at ν=1, that this physically important difference, crucial for a sharp definition of their statistics, persists for the quantized skyrmions at ν=1.
A bubble-powered micro-rotor: conception, manufacturing, assembly and characterization

A steady fluid flow, called microstreaming, can be generated in the vicinity of a micro-bubble excited by ultrasound. In this paper, we use this phenomenon to assemble and power a microfabricated rotor at rotation speeds as high as 625 rpm. The extractible power is estimated to be of the order of a few femtowatts. A first series of experiments with uncontrolled rotor shapes is presented, demonstrating the possibility of this novel actuation scheme. A second series of experiments with 65 µm rotors micromanufactured in SU-8 resin is then presented. Variables controlling the rotation speed and rotor stability are investigated, such as the bubble diameter, the acoustic excitation frequency and amplitude and the rotor geometry. Finally, an outlook is provided on developing this micro-rotor into a MEMS-based motor capable of delivering tunable, infinitesimal rotary power at the microscale. M This article features online multimedia enhancements (Some figures in this article are in colour only in the electronic version)