cssi/SciSciGPT-SciSciNet huggingface dataset:
Noninteractive Macroscopic Reliability Model for Ceramic Matrix Composites With Orthotropic Material Symmetry

A macroscopic noninteractive reliability model for ceramic matrix composites is presented. The model is multiaxial and applicable to composites that can be characterized as orthotropic. Tensorial invariant theory is used to create an integrity basis with invariants that correspond to physical mechanisms related to fracture. This integrity basis is then used to construct a failure function per unit volume (or area) of material. It is assumed that the overall strength of the composite is governed by weakest link theory. This leads to a Weibull type model similar in nature to the principle of independent action (PIA) model for isotropic monolithic ceramics. An experimental program to obtain model parameters is briefly discussed. In addition, qualitative features of the model are illustrated by presenting reliability surfaces for various model parameters.
Vision Based Target Tracking and Collision Avoidance for Mobile Robots

A real-time object tracking and collision avoidance method is presented for mobile robot navigation in indoors environments using stereo vision and a laser sensor. Stereo vision is used to identify the target and to calculate its relative distance from the mobile robot while laser based range measurements are utilized to avoid collision with surrounding objects. The target is tracked by its predetermined or dynamically defined color. The mobile robot's velocity is dynamically adjusted according to its distance from the target. Experimental results in indoor environments demonstrate the effectiveness of the method.
Highly efficient Heck reactions of aryl bromides with n-butyl acrylate mediated by a palladium/phosphine-imidazolium salt system.

A new phosphine−imidazolium salt, L·HBr (1, L = (1-ethylenediphenylphosphino-3-(mesityl))imidazol-2-ylidene), has been prepared. A combination of 0.5 mol % of Pd(dba)2 and 0.5 mol % of L·HBr in the presence of 2 equiv of Cs2CO3 as base has proven to be highly efficient in the Heck coupling reactions of aryl bromides (from electron-deficient to electron-rich aryl bromides) with n-butyl acrylate.
Coherent control of two-photon induced photocurrents in semiconductors with frequency-dependent response

Two-photon-induced photocurrents in two different semiconductors were coherently controlled simultaneously via femtosecond pulse shaping. Due to their distinct two-photon-absorption spectral responses, their photocurrent yield ratio was maximized (1.20:1) or minimized (0.75:1) using an evolutionary algorithm.
Lipshitz maps from surfaces

We give a simple procedure to estimate the smallest Lipshitz constant of a degree 1 map from a Riemannian 2-sphere to the unit 2-sphere, up to a factor of 10. Using this procedure, we are able to prove several inequalities involving this Lipshitz constant. For instance, if the smallest Lipshitz constant is at least 1, then the Riemannian 2-sphere has Uryson 1-width less than 12 and contains a closed geodesic of length less than 160. Similarly, if a closed oriented Riemannian surface does not admit a degree 1 map to the unit 2-sphere with Lipshitz constant 1, then it contains a closed homologically non-trivial curve of length less than 4π. On the other hand, we give examples of high genus surfaces with arbitrarily large Uryson 1-width which do not admit a map of non-zero degree to the unit sphere with Lipshitz constant 1.
S-(4-Methoxyphenyl) Benzenethiosulfinate (MPBT)/Trifluoromethanesulfonic Anhydride: A Convenient System for the Generation of Glycosyl Triflates from Thioglycosides

[structure] The combination of S-(4-methoxyphenyl) benzenethiosulfinate (MPBT, 1) and trifluoromethanesulfonic anhydride forms a powerful, metal-free, thiophile which readily activates thioglycosides, via glycosyl triflates, at -60 degrees C in dichloromethane, in the presence of 2,6-di-tert-butyl-4-methylpyridine. The glycosyl triflates are rapidly and cleanly converted to glycosides, upon treatment with alcohols, in good yield and selectivity.
Effective core potential studies of transition metal bonding, structure and reactivity

Abstract Computational methods for the analysis of transition metal complexes have undergone rapid progress in the recent past. Improved methods, most notably effective core potentials including relativistic correlations, new methods for determining analytic first and second energy derivatives and efficient methods for obtaining multiconfiguration wavefunctions, have been developed. Combined with new computational technologies, most notably the development of parallel hardware and software, this provides exciting new opportunities to investigate quantitatively the bonding, structure and reactivity of complexes incorporating transition metals from the entire series. This review covers recent work from our laboratories, in which all of these emerging technologies have been used. Subjects to be discussed include the nature of multiple bonds between transition metals and main group elements and the activation of prototypical bonds by transition metals. We focus on multiply bonded transition metal-main group (TMMG) complexes of the early transition metals, because of the vigorous experimental research that has been done in this area, particularly as it pertains to catalysis and advanced materials applications. The bonding and structure of alkylidene (L n MC(R)R′), silylidene (L n MSi(R)R') and imido (L n MNR) complexes are reviewed. Some recent results on oxo (L n M0), sulfido (L n MS) and phosphinidine (L n MPR) complexes are also presented. Bonding is, in general, interpreted using the language of valence bond theory, made possible by the development of localization methods for multiconfigurational orbitals. This approach is quite useful, since it conforms to the language used by the experimental community in their analyses of the bonding and reactivity of TMMG complexes, yet it retains the fundamental molecular orbital approach. Of particular interest are the following questions. 1. (1) Can a computational scheme be developed to predict accurately the properties of experimentally characterized TMMG species, thus allowing confidence in studies of TMMG complexes whose reactivity is not conducive to X-ray structural analysis? 2. (2) For a given L n M, how does the basic picture of metal-ligand multiple bonding change from alkylidene to imido to oxo, and from silylidene to phosphinidene to sulfido? 3. (3) What are the essential features of the potential energy surfaces relating to bond activation? 4. (4) How do TMMG species involving the heavier elements (MG  Si, P and S) compare with their lighter congeners? 5. (5) Are any trends in the properties of the transition metal-main group linkage discernible (as a function of M, L n or E), which may provide new insight into the reactivity of these complexes in the various important processes in which they participate, and which may help to design more effective TMMG materials through modification of the chemical environment?
Luminescent Carbon Nanotubes by Surface Functionalization

The coated substrates were left at room temperature for 30 minbefore being subjected to controlled-humidity steaming at 150°C. Thesteaming was done in the same reactor described previously[16].The coated film was examined using atomic force microscopy(AFM, SEIKO SPA-400), UV-vis spectroscopy (Jasco-V-530), con-tact-angle measurement (KYAMO CA-D), and XRD (SHIMADZUXRD-6000) as well as the BL17A1 line of synchrotron radiation inNSRRC, Taiwan.Received: December 5, 2004Final version: August 23, 2005Published online: December 8, 2005
Solid-State NMR Evidence for Inequivalent GvpA Subunits in Gas Vesicles

Gas vesicles are organelles that provide buoyancy to the aquatic microorganisms that harbor them. The gas vesicle shell consists almost exclusively of the hydrophobic 70-residue gas vesicle protein A, arranged in an ordered array. Solid-state NMR spectra of intact collapsed gas vesicles from the cyanobacterium Anabaena flos-aquae show duplication of certain gas vesicle protein A resonances, indicating that specific sites experience at least two different local environments. Interpretation of these results in terms of an asymmetric dimer repeat unit can reconcile otherwise conflicting features of the primary, secondary, tertiary, and quaternary structures of the gas vesicle protein. In particular, the asymmetric dimer can explain how the hydrogen bonds in the β-sheet portion of the molecule can be oriented optimally for strength while promoting stabilizing aromatic and electrostatic side-chain interactions among highly conserved residues and creating a large hydrophobic surface suitable for preventing water condensation inside the vesicle.
Transmetalation of self-assembled, supramolecular complexes

Substituting one metal for another in inorganic and organometallic systems is a proven strategy for synthesizing complex molecules, and in some cases, provides the only route to a particular system. The multivalent nature of the coordination in metal–ligand assemblies lends itself more readily to some types of transmetalation. For instance, a binding site can open up for exchange without greatly effecting the many other interactions holding the structure together. In addition to exchanging the metal and altering the local binding environment, transmetalation in supramolecular systems can also lead to substantial changes in the nature of the secondary and tertiary structure of a larger assembly. In this tutorial review we will cover discrete supramolecular assemblies in which metals are exchanged. First we will address fully formed structures where direct substitution replaces one type of metal for another without changing the overall supramolecular assembly. We will then address systems where the disruptive exchange of one metal for another leads to a larger change in the supramolecular assembly. When possible we have tried to highlight systems that use supramolecular self-assembly in tandem with transmetalation to synthesize new structures not accessible through a more direct approach. At the end of this review, we highlight the use of transmetalation in self-assembled aqueous inorganic clusters and discuss the consequences for material science applications.
Spectroscopy of Blue Stragglers and Turnoff Stars in M67 (NGC 2682)

We have analyzed high-resolution spectra of relatively cool blue stragglers and main-sequence turnoff stars in the old open cluster M67 (NGC 2682). We attempt to identify blue stragglers whose spectra are least contaminated by binary effects (contamination by a binary companion or absorption by circumstellar material). These "best" stragglers have metallicities ([Fe/H] = -0.05) and abundance ratios not significantly different from those of the turnoff stars. Based on arguments from hydrodynamical models of stellar collisions, we assert that the current upper limits for the lithium abundances of all blue stragglers observed in M67 (by us and others) are consistent with a formation process without mixing, assuming pre–main-sequence and main-sequence depletion patterns observed for M67 main-sequence stars. We discuss composition signatures that could more definitively distinguish between blue straggler formation mechanisms in open cluster stars. We confirm the spectroscopic detection of a binary companion to the straggler S1082. From our spectra, we measure a projected rotational speed of 90 ± 20 km s-1 for the secondary and find that its radial velocity varies with a peak-to-peak amplitude of 25 km s-1. Because the radial velocities do not vary with a period corresponding to the partial eclipses in the system, we believe this system is currently undergoing mass transfer. In addition we present evidence that S984 is a true blue straggler (not an unresolved pair). If this can be proved, our detection of lithium may indicate a collisional origin.
The Isomorphism Problem for Computable Abelian p-Groups of Bounded Length

Theories of classification distinguish classes with some good structure theorem from those for which none is possible. Some classes (dense linear orders, for instance) are non-classifiable in general, but are classifiable when we consider only countable members. This paper explores such a notion for classes of computable structures by working out a sequence of examples.We follow recent work by Goncharov and Knight in using the degree of the isomorphism problem for a class to distinguish classifiable classes from non-classifiable. In this paper, we calculate the degree of the isomorphism problem for Abelian p-groups of bounded Ulm length. The result is a sequence of classes whose isomorphism problems are cofinal in the hyperarithmetical hierarchy. In the process, new back-and-forth relations on such groups are calculated.
Temporal evolution of pair attenuation signatures in gamma-ray burst spectra

The spectra obtained above 100 MeV by the EGRET experiment aboard the Compton Gamma Ray Observatory for a handful of gamma-ray bursts (GRBs) have given no indication of any spectral attenuation that might preclude detection of bursts at higher energies. With the discovery of optical afterglows and counterparts to bursts in the last few years, enabling the determination of significant redshifts for these sources, it is anticipated that profound spectral attenuation will arise in the Gamma-Ray Large Area Space Telescope (GLAST) energy band of 30 MeV to 300 GeV for many, if not most, bursts. This paper explores time-dependent expectations for burst spectral properties in the EGRET/GLAST band, focusing on how attenuation of photons by pair creation internal to the source generates distinctive spectral signatures. The energy of spectral breaks and the associated spectral indices provide valuable information that constrains the bulk Lorentz factor of the GRB outflow at a given time. Moreover, the distinct temporal behavior that is present for internal attenuation is easily distinguished from extrinsic absorption due to intervening cosmic background fields. These characteristics define palpable observational goals for both spaced-based hard gamma-ray experiments such as GLAST, and ground-based Cerenkov telescopes, and strongly impact the observability of bursts above 300 MeV.
Adaptive intervention in probabilistic boolean networks

Motivation: A basic problem of translational systems biology is to utilize gene regulatory networks as a vehicle to design therapeutic intervention strategies to beneficially alter network and, therefore, cellular dynamics. One strain of research has this problem from the perspective of control theory via the design of optimal Markov chain decision processes, mainly in the framework of probabilistic Boolean networks (PBNs). Full optimization assumes that the network is accurately modeled and, to the extent that model inference is inaccurate, which can be expected for gene regulatory networks owing to the combination of model complexity and a paucity of time-course data, the designed intervention strategy may perform poorly. We desire intervention strategies that do not assume accurate full-model inference. Results: This article demonstrates the feasibility of applying on-line adaptive control to improve intervention performance in genetic regulatory networks modeled by PBNs. It shows via simulations that when the network is modeled by a member of a known family of PBNs, an adaptive design can yield improved performance in terms of the average cost. Two algorithms are presented, one better suited for instantaneously random PBNs and the other better suited for context-sensitive PBNs with low switching probability between the constituent BNs. Contact: edward@ece.tamu.edu
Temporal Coupled-Mode Theory for Fano Resonance in Light Scattering by a Single Obstacle †

We present a theory for Fano interference in light scattering by individual obstacle, based on a temporal coupled-mode formalism. This theory is applicable for obstacles that are much smaller than the incident wavelength, or for systems with two-dimensional cylindrical or three-dimensional spherical symmetry. We show that for each angle momentum channel, the Fano interference effect can be modeled by a simple temporal coupled-mode equation, which provides a line shape formula for scattering and absorption cross-section. We validate the analysis with numerical simulations. As an application of the theory, we design a structure that exhibits strong absorption and weak scattering properties at the same frequency.
Modeling Porous Dust Grains with Ballistic Aggregates. I. Geometry and Optical Properties

We investigate the scattering and absorption of light by random ballistic aggregates of spherical monomers. We present general measures for the size, shape, and porosity of an irregular particle. Three different classes of ballistic aggregates are considered, with different degrees of porosity. Scattering and absorption cross sections are calculated, using the discrete dipole approximation (DDA), for grains of three compositions (50% silicate and 50% graphite; 50% silicate and 50% amorphous carbon; and 100% silicate, where percentages are by volume) for wavelengths from 0.1 to 4 μ m. For a fixed amount of solid material, increased porosity increases the extinction at short wavelengths, but decreases the extinction at wavelengths that are long compared to the overall aggregate size. Scattering and absorption cross sections are insensitive to monomer size as long as the constituent monomers are small compared with the incident wavelength. We compare our accurate DDA results with two other approximations: the analytical multilayer sphere (MLS) model and effective medium theory (EMT). For high porosity and/or absorptive materials, the MLS model does not provide a good approximation for scattering and absorption by ballistic aggregates. The EMT method provides a much better approximation than the MLS model for these aggregates, with a typical difference 20% in extinction and scattering cross sections compared with DDA results, for all types, compositions, and wavelengths probed in this study.
Massless black holes and black rings as effective geometries of the D1–D5 system

We compute correlation functions in the AdS3/CFT2 correspondence to study the emergence of effective spacetime geometries describing complex underlying microstates. The basic argument is that almost all microstates of fixed charges lie close to certain 'typical' configurations. These give a universal response to generic probes, which is captured by an emergent geometry. The details of the microstates can only be observed by atypical probes. We compute two-point functions in typical ground states of the Ramond sector of the D1–D5 CFT, and compare with bulk two-point functions computed in asymptotically AdS3 geometries. For large central charge (which leads to a good semiclassical limit), and sufficiently small time separation, a typical Ramond ground state of vanishing R-charge has the M = 0 BTZ black hole as its effective description. At large time separation this effective description breaks down. The CFT correlators we compute take over, and give a response whose details depend on the microstate. We also discuss typical states with nonzero R-charge, and argue that the effective geometry should be a singular black ring. Our results support the argument that a black hole geometry should be understood as an effective coarse-grained description that accurately describes the results of certain typical measurements, but breaks down in general.
Market reaction to voluntary announcements of audit committee appointments: The effect of financial expertise

Abstract This paper investigates stock returns surrounding the appointment of directors to audit committees. We examine 136 voluntary appointment announcements over 1990–2001. Most of the announcements are issued after year 1999 and by small, NASDAQ firms. We find significantly positive stock price reaction when new members of audit committees have financial expertise. These results are robust to control for state of audit committees prior to director appointment and for an alternative definition of financial expertise. Our evidence suggests that market rewards firms that appoint financial experts to their audit committees.
Correlations among the Parameters of the Spherical Model for Eclipsing Binaries

Correlation coefficients have been computed to investigate the parameters used to describe the spherical model of an eclipsing binary system. Regions in parameter hyperspace have been identified where strong correlations exist and, by implication, the solution determinacy is low. The results are presented in tabular form for a large number of system configurations.
International Trade, Technology Transfer, Growth, and Welfare in a Schumpeterian Model of Endogenous Growth

This paper provides a simple analysis of the role of international technology transfer in the determination of the long-run pattern of trade, growth, and welfare in a two-country world within an endogenous growth framework. It is shown how the possibility and form of technology transfer impinge upon the long-run pattern of trade and therefore long-run growth rates and welfare. The most interesting finding of this paper is that, under certain conditions, there is a case in which restricted trade is growth- and welfare-enhancing compared with free trade.
DMS-A system for defining and managing human-computer dialogues

As the complexity of human-computer interfaces increases, those who use such interfaces as well as those responsible for their design have recognized an urgent need for substantive research in the human factors of software development. Because of the magnitude of the task of producing software for human-computer interfaces, appropriate tools are needed for defining and improving such interfaces, both in research and in production environments. DMS (dialogue management system) is a complete system for defining, modifying, simulating, executing, and monitoring human-computer dialogues. It is based upon the hypotheses that: (1) dialogue software should be designed separately from the code that implements the computational parts of an application, and (2) different roles are defined for the dialogue author and the programmer to achieve that goal. This paper discusses several of the technical aspects underlying the design of DMS.
Repleteness and regular lattice measures

Let X be an abstract set and L a lattice of subsets of X. To each lattice regular measure µ, we associate two induced measures\(\hat \mu \) and\(\tilde \mu \) on suitable lattices of the Wallman space IR(L) and another measure µ′ on the spaceIRσ(L). We will investigate the reflection of smoothness properties of p onto\(\hat \mu \),\(\tilde \mu \) and µ′; and try to set some new criterion for repleteness and measure repleteness.
Total Synthesis of (−)-Aplaminal

The total synthesis and assignment of absolute configuration of (-)-aplaminal ( 1), a cytotoxic metabolite from a sea hare possessing a triazobicyclo[3.2.1]octane skeleton, has been achieved. The synthesis entailed condensation of a monoprotected diamine ( 3) with dimethyl 2-oxomalonate ( 4) to generate the imidazolidine core ( 2). Introduction of the third nitrogen via Mitsunobu activation and azide displacement, followed by reduction and lactam formation (AlMe 3), furnished (-)-aplaminal ( 1). Overall, the synthesis entailed 9 steps and proceeded in 19% overall yield.
Hybrid Inverse Airfoil Design Method for Complex Three-Dimensional Lifting Surfaces

A method is presented for inverse design of airfoils for complex three-dimensional wings in incompressible e ow. The method allows for prescription of inviscid velocity distributions over different cross sections of the wing in a multipoint fashion. A hybrid approach is used to determine the shapes of the wing cross sections that satisfy the design specie cations. The airfoils forming the cross sections of the wing are generated using an inverse code for isolated airfoil design. A three-dimensional panel method is then used to obtain the velocity distributions over the resulting wing. The isolated airfoil velocity distributions are then used as design variables in a multidimensional Newton iteration method to achieve the design specie cations on the wing. The method is particularly useful for complex geometries such as junctures, where three-dimensional and interference effects have to be accounted for in the design process. Akey feature ofthedesign method is a schemeto avoid using thepanel method for sensitivity computations for the Newton iterations. This scheme not only results in signie cant reductions in computation time but also enables the integration of any readily available three-dimensional analysis code in executable form. Examples are shown to demonstrate the usefulness of the method. Nomenclature Cl = airfoil lift coefe cient, chord D1 c = airfoil/section chord F = vector containing the residuals J = Jacobian matrix n = number of design variables V = airfoil/section velocity nondimensionalized by the freestream velocity v = desired value for the velocity difference over a segment ® = angle of attack, deg 1V = velocity difference over a segment normalized by the freestream velocity ±x = vector containing the corrections to the design variables Subscripts i = index of design variable for the Newton iteration r = property associated with the wing root t = property associated with the wing tip w = property associated with the wing 2D = property associated with an airfoil in isolation 3D = property associated with a cross section of a three-dimensional lifting surface
A High-metallicity Host Environment for the Long-duration GRB 020819

We present spectroscopic observations of the host galaxy and explosion site of long-duration gamma-ray burst GRB 020819. We determine a metallicity for this host environment of log(O/H) + 12 = 9.0 {+-} 0.1, by far the highest metallicity determined for a long-duration gamma-ray burst (LGRB) to date. We compare the metallicity and other properties of the GRB 020819 host environment to existing observations of LGRB host galaxies and consider the implications that this metallicity has for our understanding of LGRB progenitor scenarios. We also consider how this unusually high metallicity may relate to the status of GRB 020819 as a 'dark' burst, with no detected optical afterglow.
Stresses in rectangular cantilever crystal plates under transverse loading

Abstract An approximate second-order theory governing the symmetric flexural vibrations (or deflection) in crystal plates is derived from the Cauchy two-dimensional flexural theory of elastic, anisotropic plates. Close form solutions of the second-order equations of flexure are obtained for rectangular cantilever plates subject to: (a) a uniformly distributed shear load along the edge parallel to the clamped edge, and (b) a uniformly distributed load over the entire plate. For load case (a), two-dimensional displacement and stresses are computed and plotted along the x1 and x3 axes of AT-cut plates of quartz for various values of azimuth angle ψ. As for load case (b), the solution is employed to compute the displacement and stresses in isotropic, elastic plates, so that the present results are compared with several existing results by other analytic and numerical methods.
MR ARTHROGRAPHY OF THE HIP

Radiographic evaluation of patients with hip pain associated with mechanical symptoms of the hip, such as clicking, snapping, and locking, has had limited success. Arthrography combined with MR imaging of the hip can now provide visualization of the articular cartilage, labrum, and capsule as well as the marrow of the femur and the acetabulum. MR arthrography combined with advances in hip arthroscopy has had a significant impact in diagnosis and treatment of these patients.
Clinical relevance of antibodies to Ro/SS-A and La/SS-B in subacute cutaneous lupus erythematosus and related conditions.

Ro/SS-A autoantibodies are frequently associated with subacute cutaneous lupus erythematosus, neonatal lupus erythematosus and Sjogren's syndrome. The Ro/SS-A autoantigen is a ribonucleoprotein complex consisting of at least four protein components and four small cytoplasmic RNA components designated hY RNA 1, 3, 4 and 5. Three of the Ro/SS-A peptides have been isolated and cloned. The function of this ribonucleoprotein complex is as yet unknown.
Canonical Basis and Macdonald Polynomials

Abstract In the basic representation of[formula]realized via the algebra of symmetric functions, we compare the canonical basis with the basis of Macdonald polynomials where t = q 2 . We show that the Macdonald polynomials are invariant with respect to the bar involution defined abstractly on the representations of quantum groups. We also prove that the Macdonald scalar product coincides with the abstract Kashiwara form. This implies, in particular, that the Macdonald polynomials form an intermediate basis between the canonical basis and the dual canonical basis, and the coefficients of the transition matrix are necessarily bar invariant. We also verify that the Macdonald polynomials (after a natural rescaling) form a sublattice in the canonical basis lattice which is invariant under the divided powers action. The transition matrix with respect to this rescaling is integral and we conjecture its positivity. For level k , we expect a similar relation between the canonical basis and Macdonald polynomials with q 2 = t k .
DIRECT DETERMINATIONS OF THE REDSHIFT BEHAVIOR OF THE PRESSURE, ENERGY DENSITY, AND EQUATION OF STATE OF THE DARK ENERGY AND THE ACCELERATION OF THE UNIVERSE

One of the goals of current cosmological studies is the determination of the expansion and acceleration rates of the universe as functions of redshift, and the determination of the properties of the dark energy that can explain these observations. Here the expansion and acceleration rates are determined directly from the data, without the need for the specification of a theory of gravity, and without adopting an a priori parameterization of the form or redshift evolution of the dark energy. We use the latest set of distances to SN standard candles from Riess et al. (2004), supplemented by data on radio galaxy standard ruler sizes, as described by Daly & Djorgovski (2003, 2004). We find that the universe transitions from acceleration to deceleration at a redshift of zT≈0.4, with the present value of q0=-0.35±0.15. The standard "concordance model" with Ω0=0.3 and Λ=0.7 provides a reasonably good fit to the dimensionless expansion rate as a function of redshift, though it fits the dimensionless acceleration rate as a function of redshift less well. The expansion and acceleration rates are then combined with a theory of gravity to determine the pressure, energy density, and equation of state of the dark energy as functions of redshift. Adopting General Relativity as the correct theory of gravity, the redshift trends for the pressure, energy density, and equation of state of the dark energy out to z~1 are determined, and are found to be generally consistent with the concordance model; they have zero redshift values of p0=-0.6±0.15, f0=0.62±0.05, and w0=-0.9±0.1.
On learning monotone DNF under product distributions

We show that the class of monotone 2O(√logn)-term DNF formulae can be PAC learned in polynomial time under the uniform distribution from random examples only. This is an exponential improvement over the best previous polynomial-time algorithms in this model, which could learn monotone o(log2 n)-term DNF. We also show that various classes of small constant-depth circuits which compute monotone functions are PAC learnable in polynomial time under the uniform distribution. All of our results extend to learning under any constant-bounded product distribution.
Dicotomías narrativas en "El árbol" de María Luisa Bombal

In this article I analyze how Maria Luisa Bombal reflects the condition of the Hispanic woman through her social and historical textualization. In all of her...
Accelerated Electrons in Cassiopeia A: Thermal and Electromagnetic Effects

We consider in more detail a model previously proposed for the hard X-ray (>10 keV) emission observed from the supernova remnant Cas A, whereby electrons are accelerated by lower hybrid waves and radiate bremsstrahlung. We consider both cold and thermal plasma limits of the modified two-stream instability that generates the lower hybrid waves and, by studying the time-dependent ionization balance for various components of the Cas A ejecta and shocked circumstellar medium, find locations within the shell where one or other of the instabilities may occur. Either instability can be effective, with the cold plasma instability imposing fewer constraints on the shocked reflected ion population responsible for exciting the waves. The instability must be located in the ejecta shocked at the earliest times and therefore closest to the contact discontinuity where magnetic fields are expected to be the strongest. The energy deposited in this ejecta by collisions between accelerated and ambient electrons is broadly consistent with that required to reheat this ejecta to the observed temperature of ~ 4 × 107 K.
Degrees of Freedom of the $K$ User $M \times N$ MIMO Interference Channel

We provide inner bound and outer bound for the total number of degrees of freedom of the K user multiple-input multiple-output (MIMO) Gaussian interference channel with M antennas at each transmitter and N antennas at each receiver if the channel coefficients are time-varying and drawn from a continuous distribution. The bounds are tight when the ratio [(max(M,N))/(min(M,N))]=R is equal to an integer. For this case, we show that the total number of degrees of freedom is equal to min(M,N)K if K ≤ R and min(M,N)[(R)/(R+1)]K if K > R. Achievability is based on interference alignment. We also provide examples where using interference alignment combined with zero forcing can achieve more degrees of freedom than merely zero forcing for some MIMO interference channels with constant channel coefficients.
Asymmetric Total Synthesis of ent-(−)-Roseophilin: Assignment of Absolute Configuration

An asymmetric total synthesis of ent-(-)-roseophilin (1), the unnatural enantiomer of a novel naturally occurring antitumor antibiotic, is described. The approach enlists a room temperature heterocyclic azadiene inverse electron demand Diels-Alder reaction of dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate (7) with the optically active enol ether 6 bearing the C23 chiral center followed by a reductive ring contraction reaction for formation of an appropriately functionalized pyrrole ring in a key 1,2,4,5-tetrazine --> 1,2-diazine --> pyrrole reaction sequence. A Grubbs' ring closing metathesis reaction was utilized to close the unusual 13-membered macrocycle prior to a subsequent 5-exo-trig acyl radical-alkene cyclization that was used to introduce the fused cyclopentanone and complete the preparation of the tricylic ansa-bridged azafulvene core 32. Condensation of 32 with 33 under the modified conditions of Tius and Harrington followed by final deprotection provided (22S,23S)-1. Comparison of synthetic (22S,23S)-1 ([alpha](25)(D), CD) with natural 1 established that they were enantiomers and enabled the assignment of the absolute stereochemistry of the natural product as 22R,23R. Surprisingly, ent-(-)-1 was found to be 2-10-fold more potent than natural (+)-1 in cytotoxic assays, providing an unusually rewarding culmination to synthetic efforts that provided the unnatural enantiomer.
Why Marx still matters

This article explores why a deep understanding of Marx’s project is essential for developing an adequate science of society. Marx focused on two aspects of social reality that are critical to its understanding, but are absent from the contemporary practice of social science. First, he viewed humanity’s struggle to overcome nature’s scarcity as causally and dynamically related to social organisation and social consciousness. Second, he unfolded a theory of our self-creation, the manner in which products of our manual and intellectual labour act back upon us to create us socially and intellectually. To the extent that we lose consciousness of this authorship, our freedom is constrained. We are controlled by our own creations. Our freedom requires a social science with Marx’s breadth to enable us to recover awareness of our authorship of our social creations and thereby be empowered to control them, as opposed to being their victims.
Porous Composites for Adhering Artificial Cartilage to Bone

Artificial cartilage can be grown from cultured chondrocytes, but adhering this tissue to bone presents a challenge. Porous polymer/bioactive glass composites are candidate materials for engineering the artificial cartilage/bone interface and possibly other soft-to-hard tissue (ligament/bone, tendon/bone) interfaces. A phase separation technique was used to make porous polymer/bioactive glass composites. The composites (thickness: 200-500 μm) have asymmetric structures with dense top layers and porous structures beneath. The porous structures consist of large pores (>100 μm) in a network of smaller (<10 μm) interconnected pores. The dense layers were removed and large pores exposed by abrasion or salt leaching from the casting surface. The tissue bonding abilities of the composites were studiedin vitro in simulated body fluid (SBF) and in rabbit chondrocyte culture. Culture studies revealed that composite surfaces were suitable for attachment, spreading and proliferation of chondrocytes. The growth of hydroxycarbonate apatite (HCA) inside and on the composites after soaking in the SBF for two weeks demonstrates their potential for integration with bone. The results indicate the potential for the composites to facilitate growth and attachment of artificial cartilage to bone.
Electric quadrupole excitations in relativistic nucleus-nucleus collisions

Calculations are presented for electric quadrupole excitations in relativistic nucleus-nucleus collisions. The theoretical results are compared to an extensive data set and it is found that electric quadrupole effects provide substantial corrections to cross sections, especially for heavier nuclei.
Bragg Resonances for Tunneling Between Edges of a 2D Quantum Hall System.

A theory is presented for tunneling between compressible regions on the sides of a narrow incompressible Quantum Hall strip. Assuming that electron interactions lead to formation of a Wigner crystal on the edges of the compressible regions, we consider the situation when the non-conservation of electron momentum required for transport is provided, in the absence of disorder, by umklapp scattering on the crystal. The momentum given to the crystal is quantized due to the Bragg condition, which leads to resonances in tunneling conductivity as a function of the incompressible strip width, similar to those reported recently by N. Zhitenev, M. Brodsky, R. Ashoori, and M. Melloch.
Design of minimally invasive all-pole analog lowpass filters

In this paper, a new design technique for designing higher order minimally invasive lowpass filters is proposed. The proposed fully differential filter has been simulated in TSMC 130 nm technology for third and fourth orders. When compared with the conventional filter implementations such as a Tow-Thomas architecture, the proposed third order solution achieves a total in-band input-referred integrated noise of $$44.09\,\upmu V$$44.09μV compared to $$78.83\,\upmu V$$78.83μV, achieved by a Tow-Thomas implementation. The proposed solution offers higher tolerance to blockers along with lesser number of active devices required. Though, the total capacitance used is increased from 23.82 pF to 89.82 pF, from third order Tow-Thomas filter to its minimally invasive filter counterpart, the power consumption reduces by $$77\,\%$$77% from third order Tow-Thomas to the third order minimally invasive filter.
Characterization and catalytic studies of Y-zeolites coexchanged with iron and a second polyvalent cation

Abstract Y-zeolites exchanged with both Fe and either Ca, La, Eu, Cr, Mn, Co, Ni, or Cu were characterized by magnetic susceptibility measurements and Mossbauer spectroscopy. In addition, these zeolites were studied as catalysts for the oxidation of CO with NO and for the decomposition of N 2 O into N 2 and O 2 . The results showed that Ca, La, and Eu cations in FeCaY, FeLaY, and FeEuY occupy primarily site I, forcing a large fraction of Fe cations to sites I′, II, and/or II′. Such zeolites exhibited higher reaction rates than FeY for both reactions. Coexchanged, first-row transition metals had a different effect on the Fe. For example, Mn, Ni, and Cu cations in FeMnY, FeNiY, and FeCuY were found to make the Fe more oxidizable and less reducible. Reaction rates measured over CrY, MnY, FeY, CoY, NiY, and CuY showed that the oxidizability of these cations decreases in the order Cr(III) > Fe(II), Cu(I) > Co(II) > Mn(II), Ni(II). Finally, the Fe in FeEuY was found to enhance the reducibility of the Eu.
New technologies for chemical genetics

Chemical genetics, in which small molecules are used in lieu of mutations to study biological processes, requires large and diverse chemical libraries to specifically perturb different biological pathways. Here we describe a suite of technologies that enable chemical libraries prepared by split-pool solid phase synthesis to be screened in a diverse range of chemical genetic assays. Compounds are synthesized on 500 micron high-capacity polystyrene beads, and arrayed into individual wells of 384-well plates using a hand-held bead arrayer. Compounds are cleaved from synthesis beads using a chemically-resistant ceramic dispensing system, producing individual stock solutions of single compounds. Nanoliter volumes of these solutions are then transferred into assay plates using an array of stainless steel pins mounted on a robotic arm. We have designed reusable 1536- and 6144-well assay plates made of silicone rubber that can be cast in the laboratory and filled by hand. This integrated technology platform enables hundreds of biological assays to be performed from the product of a single synthesis bead, enabling the results of different chemical genetic experiments to be directly compared.
Particle-phase chemistry of secondary organic material: modeled compared to measured O:C and H:C elemental ratios provide constraints.

Chemical mechanisms for the production of secondary organic material (SOM) are developed in focused laboratory studies but widely used in the complex modeling context of the atmosphere. Given this extrapolation, a stringent testing of the mechanisms is important. In addition to particle mass yield as a typical standard for model-measurement comparison, particle composition expressed as O:C and H:C elemental ratios can serve as a higher dimensional constraint. A paradigm for doing so is developed herein for SOM production from a C5 C10 C15 terpene sequence, namely isoprene, R-pinene, and β-caryopyhllene. The model MCM-SIMPOL is introduced based on the Master Chemical Mechanism (MCM v3.2) and a group contribution method for vapor pressures (SIMPOL). The O:C and H:C ratios of the SOM are measured using an Aerosol Mass Spectrometer (AMS). Detailed SOM-specific AMS calibrations for the organic contribution to the H2Oþ and COþ ions indicate that published O:C and H:C ratios for SOM are systematically too low. Overall, the measurement-model gap was small for particle mass yield but significant for particle-average elemental composition. The implication is that a key chemical pathway is missing from the chemical mechanism. The data can be explained by the particle-phase homolytic decomposition of organic hydroperoxides and subsequentmore » alkyl-radical-promoted oligomerization.« less
Roll Call Voting in the NCAA

view of the NCAA as an organization. In fact, the NCAA's wide authority over all aspects of the athletic side of major colleges and universities has not been limited to issues that are solely related to the financial returns of its members In this article, we use data on NCAA convention roll call votes between 1986 and 1994, to investigate the mtraorganizational decision-making process. A spatial model of voting decisions, which is similar to models used previously to analyze voting in Congress, is used to analyze the votes. We can explain variation in the decisions of schools on restructuring issues quite well. This is consistent with an economic view of NCAA voting, since restructuring of the NCAA rank and file can be thought of as an exercise in raising entry barriers. However, the same estimation procedure is only moderately successful for other issues It thus seems unlikely that decisions on academic reform are motivated solely by economic considerations.
Asymmetric Synthesis of Bicyclo[4.3.1]decadienes and Bicyclo[3.3.2]decadienes via [6 + 3] Trimethylenemethane Cycloaddition with Tropones

The cyanosubstituted trimethylenemethane donor undergoes palladium-catalyzed [6 + 3] cycloaddition with a variety of tropones to yield bicyclo[4.3.1]decadienes in excellent regio-, diastereo-, and ...
Do students like the flipped classroom? An investigation of student reaction to a flipped undergraduate IT course

The flipped classroom pedagogy has achieved significant mention in academic circles in recent years. "Flipping" involves the reinvention of a traditional course so that students engage with learning materials via recorded lectures and interactive exercises prior to attending class and then use class time for more interactive activities. Proper implementation of a flipped classroom is difficult to gauge, but combines successful techniques for distance education with constructivist learning theory in the classroom. While flipped classrooms are not a novel concept, technological advances and increased comfort with distance learning have made the tools to produce and consume course materials more pervasive. Flipped classroom experiments have had both positive and less-positive results and are generally measured by a significant improvement in learning outcomes. This study, however, analyzes the opinions of students in a flipped sophomore-level information technology course by using a combination of surveys and reflective statements. The author demonstrates that at the outset students are new — and somewhat receptive — to the concept of the flipped classroom. By the conclusion of the course satisfaction with the pedagogy is significant. Finally, student feedback is provided in an effort to inform instructors in the development of their own flipped classrooms.
A UBVR CCD Survey of the Magellanic Clouds

We present photometry and a preliminary interpretation of a UBVR survey of the Large and Small Magellanic Clouds, which covers 14.5 deg2 and 7.2 deg2, respectively. This study is aimed at obtaining well-calibrated data on the brighter, massive stars, complementing recent, deeper CCD surveys. Our catalog contains 179,655 LMC and 84,995 SMC stars brighter than V ~ 18.0, and is photometrically complete to U ~ B ~ V ~ 15.7 and R ~ 15.2, although stars in crowded regions are selectively missed. We compare our photometry to that of others, and describe the need for gravity-dependent corrections to our CCD U-band photometry. We provide a preliminary cross-reference between our catalog stars and the stars with existing spectroscopy. We discuss the population of stars seen toward the two Clouds, identifying the features in the color-magnitude diagram, and using existing spectroscopy to help construct H-R diagrams. We derive improved values for the blue-to-red star ratios in the two Clouds, emphasizing the uncertainties involved in this before additional spectroscopy. We compare the relative number of red supergiants and Wolf-Rayet stars in the LMC and SMC with that of other galaxies in the Local Group, demonstrating a very strong, tight trend with metallicity, with the ratio changing by a factor of 160 from the SMC to M31. We also reinvestigate the initial mass function of the massive stars found outside of the OB associations. With the newer data, we find that the initial mass function (IMF) slope of this field population is very steep, with Γ ~ -4 ± 0.5, in agreement with our earlier work. This is in sharp contrast to the IMF slope found for the massive stars with OB associations (Γ ~ -1.3). Although much more spectroscopy is needed to make this result firm, incompleteness can no longer be invoked as an explanation.