cssi/SciSciGPT-SciSciNet huggingface dataset:
Transition-Metal-Mediated Cascade Reactions: C,C-Dicyclopropylmethylamines by Way of Double C,C-σ-Bond Insertion into Bicyclobutanes

The organometallic multicomponent reaction of alkenyl zirconocene, alkynyl imine, and zinc carbenoid in the presence of dimethylzinc leads to novel C,C-dicyclopropylmethylamines. The formation of intermediate bicyclo[1.1.0]butanes represents the first synthetically useful example of a double C,C-σ-bond insertion, and the increase in structural complexity from starting materials is highlighted by the formation of nine new C,C-bonds in the final product.
The Lorentz Force Law and its Connections to Hidden Momentum, the Einstein–Laub Force, and the Aharonov–Casher Effect

The Lorentz force of classical electrodynamics, when applied to magnetic materials, gives rise to hidden energy and hidden momentum. Removing the contributions of hidden entities from the Poynting vector, from the electromagnetic (EM) momentum density, and from the Lorentz force and torque densities simplifies the equations of the classical theory. In particular, the reduced expression of the EM force density becomes very similar (but not identical) to the Einstein-Laub expression for the force exerted by electric and magnetic fields on a distribution of charge, current, polarization, and magnetization. Examples reveal the similarities and differences among various equations that describe the force and torque exerted by EM fields on material media. An important example of the simplifications afforded by the Einstein-Laub formula is provided by a magnetic dipole moving in a static electric field and exhibiting the Aharonov-Casher effect.
Electromagnetic interference shielding by carbon fibre reinforced cement

Abstract The addition of short carbon fibres and chemical agents (triethanolamine, sodium sulphate and potassium aluminium sulphate) to Portland cement greatly increased the electromagnetic interference shielding effectiveness of the cement. For example, the attenuation of electromagnetic radiation of a frequency of 1.5 GHz increased from 0.5 dB for plain cement mortar (3.6 mm thick) to 10.2 dB for the same thickness of cement mortar containing chemical agents and 3 mm long carbon fibres (in the amount of 0.5% by weight of the cement or 0.21% by volume of cement mortar).
Properties of Free Baxter Algebras

Abstract The study of free Baxter algebras was started by Rota and Cartier 30 years ago. We continue this study by applying two recent constructions of free Baxter algebras. We investigate the basic structure of a free Baxter algebra and characterize in detail when a free Baxter algebra is a domain or a reduced algebra. We also describe the nilpotent radical of a free Baxter algebra when it is not reduced.
Interactive time-dependent tone mapping using programmable graphics hardware

Modern graphics architectures have replaced stages of the graphics pipeline with fully programmable modules. Therefore, it is now possible to perform fairly general computation on each vertex or fragment in a scene. In addition, the nature of the graphics pipeline makes substantial computational power available if the programs have a suitable structure. In this paper, we show that it is possible to cleanly map a state-of-the-art tone mapping algorithm to the pixel processor. This allows an interactive application to achieve higher levels of realism by rendering with physically based, unclamped lighting values and high dynamic range texture maps. We also show that the tone mapping operator can easily be extended to include a time-dependent model, which is crucial for interactive behavior. Finally, we describe the ways in which the graphics hardware limits our ability to compress dynamic range efficiently, and discuss modifications to the algorithm that could alleviate these problems.
Kinetically Controlled Nanostructure Formation in Self-Assembled Globular Protein–Polymer Diblock Copolymers

Aqueous processing of globular protein–polymer diblock copolymers into solid-state materials and subsequent solvent annealing enables kinetic and thermodynamic control of nanostructure formation to produce block copolymer morphologies that maintain a high degree of protein fold and function. When model diblock copolymers composed of mCherry-b-poly(N-isopropylacrylamide) are used, orthogonal control over solubility of the protein block through changes in pH and the polymer block through changes in temperature is demonstrated during casting and solvent annealing. Hexagonal cylinders, perforated lamellae, lamellae, or hexagonal and disordered micellar phases are observed, depending on the coil fraction of the block copolymer and the kinetic pathway used for self-assembly. Good solvents for the polymer block produce ordered structures reminiscent of coil–coil diblock copolymers, while an unfavorable solvent results in kinetically trapped micellar structures. Decreasing solvent quality for the protein improves...
On functions whose symmetric part of gradient agree and a generalization of Reshetnyak’s compactness theorem

We consider the following question: Given a connected open domain \({\Omega \subset \mathbb{R}^n}\), suppose \({u, v : \Omega \rightarrow \mathbb{R}^n}\) with det\({(\nabla u) > 0}\), det\({(\nabla v) > 0}\) a.e. are such that \({\nabla u^T(x)\nabla u(x) = \nabla v(x)^T \nabla v(x)}\) a.e. , does this imply a global relation of the form \({\nabla v(x) = R\nabla u(x)}\) a.e. in Ω where \({R \in SO(n)}\) ? If u, v are C1 it is an exercise to see this true, if \({u, v\in W^{1,1}}\) we show this is false. In Theorem 1 we prove this question has a positive answer if \({v \in W^{1,1}}\) and \({u \in W^{1,n}}\) is a mapping of Lp integrable dilatation for p > n − 1. These conditions are sharp in two dimensions and this result represents a generalization of the corollary to Liouville’s theorem that states that the differential inclusion \({\nabla u \in SO(n)}\) can only be satisfied by an affine mapping. Liouville’s corollary for rotations has been generalized by Reshetnyak who proved convergence of gradients to a fixed rotation for any weakly converging sequence \({v_k \in W^{1,1}}\) for which $$\int \limits_{\Omega} {\rm dist}(\nabla v_k, SO(n))dz \rightarrow 0 \, {\rm as} \, k \rightarrow \infty.$$ Let S(·) denote the (multiplicative) symmetric part of a matrix. In Theorem 3 we prove an analogous result to Theorem 1 for any pair of weakly converging sequences \({v_k \in W^{1,p}}\) and \({u_k \in W^{1,\frac{p(n-1)}{p-1}}}\) (where \({p \in [1, n]}\) and the sequence (uk) has its dilatation pointwise bounded above by an Lr integrable function, r > n − 1) that satisfy \({\int_{\Omega} |S(\nabla u_k) - S(\nabla v_k)|^p dz \rightarrow 0}\) as k → ∞ and for which the sign of the det\({(\nabla v_k)}\) tends to 1 in L1. This result contains Reshetnyak’s theorem as the special case (uk) ≡ Id, p = 1.
On the structure of glassy polymers. VI. Electron microscopy of polycarbonate, poly(ethylene terephthalate), poly(vinyl chloride), and polystyrene

High-resolution electron microscopy studies have been carried out on four glassy polymers examined in previous small-angle x-ray scattering (SAXS) investigations. The polymers include polycarbonate, poly(ethylene terephthalate), poly(vinyl chloride), and polystyrene. For all four polymers, both bright field and dark-field observations indicate the general absence of microstructural features of a size down to the resolution limit of the electron microscope. Only “pepper and salt” features on a scale ca. 5 A are seen as characteristic of the structures. These features reflect simple interferences as the resolution limit is approached, and are seen for single crystal and oxide glasses as well as for the polymers. The present results, taken together with structural information from light scattering, SAXS, and small-angle neutron scattering, indicate that glassy polymers should be regarded as having rendom structures. The combined results are inconsistent with heterogeneous microstructures having regions of locally high order present in large volume fractions.
Current status and future developments in radar remote sensing

Some of the major initiatives and directions of remote sensing using SAR (Synthetic Aperture Radar) data alone and in conjunction with other sensors for earth science investigations are outlined. Specific emphasis is on areas key to global monitoring using SAR data from spaceborne platforms: calibration, geophysical processing, and generation of digital elevation models. Calibration as used here encompasses end-to-end system characterization over the life of a sensor and characterization of data products relative to past and future sensors. Geophysical processing is defined here to include any processing which results in derived geophysical units. An additional data type, topography, which is required to complete the three-dimensional view of surface properties and correct for distortions inherent in SAR is discussed. Future challenges in radar remote sensing include development of strategies to extrapolate from regional to global scale models and development of new sensor technology.
Sink-to-sensors congestion control

The problem of congestion in sensor networks is significantly different from that of conventional ad-hoc networks and has not been studied to any great extent thus far. In this paper, we focus on providing congestion control from the sink to the sensors in a sensor field. We identify the different reasons for congestion from the sink to the sensors and show the uniqueness of the problem in sensor network environments. We propose a generic framework that addresses congestion from the sink to the sensors in a sensor network. Through ns2 based simulations, we evaluate the proposed approach and compare its performance with three baseline approaches.
PHYSICAL CONDITIONS IN THE FOREGROUND GAS OF REFLECTION NEBULAE: NGC 2023, VDB 102, AND NGC 7023

High-resolution optical spectra of HD 37903 and HD 147009, which illuminate the reflection nebulae NGC 2023 and vdB 102, were obtained for comparison with our results for HD 200775 and NGC 7023. Ground-based measurements of the molecules CH, C2, and CN and the atoms Na I and K I were analyzed to extract physical conditions in the foreground cloud. Estimates of the gas density, gas temperature, and flux of ultraviolet radiation were derived and were compared with the results from infrared and radio studies of the main molecular cloud. The conditions are similar to those found in studies of diffuse clouds. The foreground material is less dense than the gas in the molecular cloud behind the star(s). The gas temperature was set at 40 K, the temperature determined for the foreground gas in NGC 7023. The flux of ultraviolet radiation was found to be less intense than in the molecular material behind the star(s). The column densities of Na I and K I were reproduced reasonably well when the extinction curve for the specific line of sight was adopted. We obtained NEWSIPS data from the IUE archive for HD 37903 and HD 200775. The ultraviolet data on C I and CO allow extraction of the physical conditions by alternate methods. General agreement among the various diagnostics was found, leading to self-consistent pictures of the foreground photodissociation regions. An appendix describes checks on the usefulness of IUE NEWSIPS data for interstellar studies. Equivalent widths are compared with a previous analysis of IUE observations for interstellar gas toward 20 Aql. Excellent agreement is found with NEWSIPS results having smaller errors. A comparison of NEWSIPS data for C I toward X Per with data acquired with the Hubble Space Telescope shows similar levels of agreement in equivalent widths and that the derived column densities from IUE results are accurate to better than a factor of 2 for absorption lines of moderate strength.
Democratic performance in post-communist Bulgaria: election pledges and levels of fulfillment, 1997–2005

This study examines the nature of election promises made by political parties in Bulgaria during the 1997 and 2001 elections, and evaluates the factors that determine pledge fulfilment. The seven parties that took part in these elections made 792 pledges and fulfilled an average of 60% of them. A combination of institutional characteristics, i.e. size of the party, the nature of the pledges, as well as the agreement between pledges made by different parties, explains the probability of fulfilment. Election promises related to European Union accession are also more likely to be fulfilled than other types of pledges.
Shape and Orientation of Mercury from Radar Ranging Data

If Mercury's radius is expanded in Legendre functions to the second degree and order, the systematic error in radar ranging can be reduced significantly. We interpret the expansion coefficients in terms of a best-fit ellipsoid displaced with respect to the center of mass in the equatorial plane. The ellipsoid's principal axes are rotated in the equatorial plane such that the long axis is aligned with cartographic longitude 15.3 deg +/- 2.9 deg (west). The pole location is consistent with the IAU pole, normal to Mercury's orbital plane. There is a significant equatorial ellipticity (a - b)/a = (540 +/- 54) x 10(exp -6). The center of figure is offset from the center of mass (C.F.-C.M.) by 640 +/- 78 m in the equatorial plane in the direction of cartographic longitude 319.5 deg +/- 6.9 deg. The magnitude of the equatorial center of figure offset implies an excess crustal thickness of 12 km or less, comparable to the Moon's excess. By comparing the equatorial ellipticity with the Mariner 10 gravity coefficient C(sub 22) and assuming Airy isostatic compensation, we conclude that Mercury's crustal thickness is in the range from 100 to 300 km.
New developments in the treatment of chronic hepatitis B

Significant progress has been made during the last 2 years in the treatment of chronic hepatitis B (CHB). Treatment decisions differ significantly depending on whether patients are HBeAg+ or HBeAg-, treatment-naive or nucleoside/nucleotide-resistant, and in early or advanced stages of liver disease. Courses of finite duration, aiming to achieve sustained off-therapy responses, are practically restricted to HBeAg+ patients with compensated chronic liver disease, whereas long-term therapy aiming to achieve maintained on-therapy remission is mostly applicable to HBeAg- individuals either with early or advanced liver disease. A course of finite duration with pegylated (PEG)-IFN-α-2a offers the highest probability of sustained off-therapy response in HBeAg+ individuals, as well as in some HBeAg- individuals. Long-term therapy with nucleoside/nucleotide analogues, both in HBeAg+ and HBeAg- CHB, has most favourable effects on patient outcome, provided that virological and biochemical remission is maintained with...
Space-time noncommutative field theories and unitarity

Abstract We study the perturbative unitarity of noncommutative scalar field theories. Field theories with space–time noncommutativity do not have a unitary S-matrix. Field theories with only space noncommutativity are perturbatively unitary. This can be understood from string theory, since space noncommutative field theories describe a low energy limit of string theory in a background magnetic field. On the other hand, there is no regime in which space–time noncommutative field theory is an appropriate description of string theory. Whenever space–time noncommutative field theory becomes relevant massive open string states cannot be neglected.
Two enumerative results on cycles of permutations

Answering a question of Bona, it is shown that for n>=2 the probability that 1 and 2 are in the same cycle of a product of two n-cycles on the set {1,2,...,n} is 1/2 if n is odd and 12-2(n-1)(n+2) if n is even. Another result concerns the polynomial P"@l(q)=@?"wq^@k^(^(^1^,^2^,^...^,^n^)^@?^w^), where w ranges over all permutations in the symmetric group S"n of cycle type @l, (1,2,...,n) denotes the n-cycle 1->2->...->n->1, and @k(v) denotes the number of cycles of the permutation v. A formula is obtained for P"@l(q) from which it is deduced that all zeros of P"@l(q) have real part 0.
The Shimura-Taniyama conjecture and conformal field theory

Abstract The Shimura–Taniyama conjecture states that the Mellin transform of the Hasse–Weil L-function of any elliptic curve defined over the rational numbers is a modular form. Recent work of Wiles, Taylor–Wiles and Breuil–Conrad–Diamond–Taylor has provided a proof of this longstanding conjecture. Elliptic curves provide the simplest framework for a class of Calabi–Yau manifolds which have been conjectured to be exactly solvable. It is shown that the Hasse–Weil modular form determined by the arithmetic structure of the Fermat type elliptic curve is related in a natural way to a modular form arising from the character of a conformal field theory derived from an affine Kac–Moody algebra.
Is the Experimental Auction a Dynamic Market

Experimental auctions are generally thought of as static markets. This paper presents the results of an experimental auction designed to test whether participants’ perceptions regarding the relative difficulty of delaying or reversing a transaction outside the experimental market systematically affect their willingness-to-pay bids. The results show that auction participants’ perceptions significantly impact their bids in a manner that is consistent with real option theory. These results suggest that economists must be careful to consider the existence of outside markets when designing experimental auctions.
Gamma rays from colliding winds of massive stars

Colliding winds of massive binaries have long been considered as potential sites of non-thermal high-energy photon production. This is motivated by the detection of non-thermal spectra in the radio band, as well as by correlation studies of yet unidentified EGRET γ-ray sources with source populations appearing in star formation regions.
Eszopiclone improves insomnia and depressive and anxious symptoms in perimenopausal and postmenopausal women with hot flashes: a randomized, double-blinded, placebo-controlled crossover trial.

Objective Menopause-associated insomnia is commonly associated with other symptoms (hot flashes, depression, anxiety). Given frequent symptom cooccurrence, therapies targeting sleep may provide an important approach to treatment during midlife. Study Design Peri/postmenopausal women (40-65 years old) with sleep-onset and/or sleep-maintenance insomnia cooccurring with hot flashes and depressive and/or anxiety symptoms were randomized to eszopiclone 3 mg orally or placebo in a double-blinded, crossover 11 week trial. Changes in the Insomnia Severity Index (ISI) scale and secondary outcomes (diary-based sleep parameters, depression/anxiety, hot flashes, quality of life) were analyzed using repeated-measure linear models. Results Of 59 women, 46 (78%) completed the study. Eszopiclone reduced ISI scores by 8.7 ± 1.4 more points than placebo ( P P Conclusion Eszopiclone treats insomnia and cooccurring menopause-related symptoms. Our results provide evidence that hypnotic therapies may improve multiple domains of well-being during midlife.
Diffusion of Wave Packets in a Markov Random Potential

We consider the evolution of a tight binding wave packet propagating in a time dependent potential. If the potential evolves according to a stationary Markov process, we show that the square amplitude of the wave packet converges, after diffusive rescaling, to a solution of a heat equation.
A simple, vertically resolved model of tropical disturbances with a humidity closure

A vertically resolved linear model for large-scale motions in an equatorial non-rotating atmosphere is presented. Precipitation is forced by tropospheric precipitable water, cloud–radiation interactions (CRI), and wind-induced surface heat exchange (WISHE). The dynamics of the model are based on the assumption that the vertical heating profile has the shape of the first baroclinic mode. The vertical profiles of vertical velocity, temperature perturbation, etc. are calculated using an upward radiation boundary condition. The modelled modes are of three types: fast gravity waves that resemble adiabatic modes with the vertical wavelength twice the depth of the troposphere; convectively coupled gravity modes that are damped and move with a phase speed of ≈17 m s −1 ; and the unstable moisture mode. The value of the model is that under a single dynamical assumption it yields the observed phase speed for the convectively coupled gravity waves that map to Kelvin waves in the equatorial beta plane case while still producing the unstable moisture mode. However, the model lacks the precipitation physics needed to produce the observed destabilization of the gravity mode.
Thiomethylation of indole and haloindole zinc salts

Abstract Thiomethylation of indole and haloindoles has been achieved via their zinc salts. This one-pot reaction uses methyl disulfide as electrophile. Isolation of thiomethylated indole products in moderate yields requires the addition of a thiol (e.g., cysteine hydrochloride) during aqueous workup, facilitating the displacement of the thiomethylated product from a water-insoluble zinc salt.
Exotic hybrid mesons from improved Kogut-Susskind fermions

Abstract We summarize our measurement of the mass of the exotic 1−+ hybrid meson using an improved Kogut-Susskind action. We show results from both quenched and dynamical quark simulations and compare with results from Wilson quarks. Extrapolation of these results to the physical quark mass allows comparison with experimental candidates for the 1−+ hybrid meson.
(1‐Methoxyvinyl)boronic and (1‐chlorovinyl)boronic esters

(s)-Pinanediol (1-methoxyvinyl)boronate (1) was prepared from (1-methoxyvinyl)-lithium and triisopropyl borate followed by (s)-pinanediol. Attempted reaction with (dichloromethyl)lithium failed, and reaction with butylmagnesium chloride followed by acetic acid yielded a mixture of diastereomers of (s)-pinanediol (1-methoxy-1-methyl-pentyl)boronate (2). (s)-Pinanediol (1-chlorovinyl)boronate (4) has been prepared by dehydrochlorination of (s)-pinanediol 1,1-dichloroethylboronate (3) with lithium chloride in dimethylformamide. Reaction of 4 with (dichloromethyl)lithium yielded (s)-pinanediol (1S)-(1,2-dichloroallyl)boronate (5) in 92% diastereomeric excess. Reaction of 5 with RMgX resulted in a 3 : 1 ratio of displacement of the 1-Cl from carbon by R to displacement of the entire 1,2-dichloroallyl group from boron by R. With lithium benzyl oxide, displacement of the 1-Cl from 5 failed entirely. Reaction of 4 with (dibromomethyl)lithium was inefficient and yielded a gross mixture of diastereomers.
Charged black holes in two-dimensional string theory

We discuss two dimensional string theories containing gauge fields, introduced either via coupling to open strings, in which case we get a Born-Infeld type action, or via heterotic compactification. The solutions of the modified background field equations are charged black holes which exhibit interesting space time geometries. We also compute their masses and charges.
The Molecular Disk in the Cloverleaf Quasar

We propose a new interpretation for the CO-emitting region of the Cloverleaf (H1413+1143), a gravitationally lensed quasi-stellar object. We fitted a two-galaxy lensing model directly to the Institut de Radioastronomie Millimetrique CO (7-6) data rather than to the optical Hubble Space Telescope image, and from the fit we infer that the CO (7-6) source is a disklike structure with a characteristic radius of 785 pc, a size similar to that of the CO-emitting regions present in nearby starburst ultraluminous infrared galaxies. We therefore suggest that the Cloverleaf contains both an extended rotating molecular starburst disk and a central quasar.
Effects of freeze-drying on the glass temperature of cyclic polystyrenes

Abstract The calorimetric glass temperature was measured for three cyclic polystyrenes with apparent molecular weights ranging from 4.0×10 3 to 195.5×10 3 g/mol for both bulk material and for samples freeze-dried from dilute solution. Freeze-drying from dilute solution was found to reduce the glass temperature by 7–14 K depending on the sample. These T g depressions are 5–12 K greater than those found previously for freeze-dried linear polystyrene. Annealing at 403.2 and 443.2 K (130 and 170 °C) resulted in recovery of the T g back to the bulk value with the time scales depending on both temperature and the magnitude of the T g reduction; the low apparent activation energy dependence of the recovery of T g precludes its being due to viscous flow.
Analytic continuation of Liouville theory

Correlation functions in Liouville theory are meromorphic functions of the Liouville momenta, as is shown explicitly by the DOZZ formula for the three-point function on S2. In a certain physical region, where a real classical solution exists, the semiclassical limit of the DOZZ formula is known to agree with what one would expect from the action of the classical solution. In this paper, we ask what happens outside of this physical region. Perhaps surprisingly we find that, while in some range of the Liouville momenta the semiclassical limit is associated to complex saddle points, in general Liouville’s equations do not have enough complex-valued solutions to account for the semiclassical behavior. For a full picture, we either must include “solutions” of Liouville’s equations in which the Liouville field is multivalued (as well as being complex-valued), or else we can reformulate Liouville theory as a Chern-Simons theory in three dimensions, in which the requisite solutions exist in a more conventional sense. We also study the case of “timelike” Liouville theory, where we show that a proposal of Al. B. Zamolodchikov for the exact three-point function on S2 can be computed by the original Liouville path integral evaluated on a new integration cycle.
An on-line performance visualization technology

A new software technology for on-line performance analysis and the visualization of complex parallel and distributed systems is presented. Often heterogeneous, these systems need capabilities for the flexible integration and configuration of performance analysis and visualization. Our technology is based on an object-oriented framework for the rapid prototyping and development of distributable visual objects. The visual objects consist of two levels, a platform/device-specific low level and an analysis- and visualization-specific high level. We have developed a very high-level markup language called VOML and a compiler for the component-based development of high-level visual objects. The VOML is based on a software architecture for on-line event processing and performance visualization called EPIRA. The technology lends itself to constructing high-level visual objects from globally distributed component definitions. Details of the technology and tools used, as well as how an example visual object can be rapidly prototyped from several reusable components, are presented.
The Impacts of Land Use Change on Malaria Vector Abundance in a Water-Limited, Highland Region of Ethiopia

Changes in land use and climate are expected to alter the risk of malaria transmission in areas where rainfall limits vector abundance. We use a coupled hydrology-entomology model to investigate the effects of land use change on hydrological processes impacting mosquito abundance in a highland village of Ethiopia. Land use affects partitioning of rainfall into infiltration and runoff that reaches small-scale topographic depressions, which constitute the primary breeding habitat of Anopheles arabiensis mosquitoes. A physically based hydrology model isolates hydrological mechanisms by which land use impacts pool formation and persistence, and an agent-based entomology model evaluates the response of mosquito populations. This approach reproduced observed interannual variability in mosquito abundance between the 2009 and 2010 wet seasons. Several scenarios of land cover were then evaluated using the calibrated, field-validated model. Model results show variation in pool persistence and depth, as well as in mosquito abundance, due to land use changes alone. The model showed particular sensitivity to surface roughness, but also to root zone uptake. Scenarios in which land use was modified from agriculture to forest generally resulted in lowest mosquito abundance predictions; classification of the entire domain as rainforest produced a 34% decrease in abundance compared to 2010 results. This study also showed that in addition to vegetation type, spatial proximity of land use change to habitat locations has an impact on mosquito abundance. This modeling approach can be applied to assess impacts of climate and land use conditions that fall outside of the range of previously observed variability.
Country Resource Environments, Firm Capabilities, and Corporate Diversification Strategies*

ABSTRACT Environmental differences among countries are often assumed away in strategy research. In particular, the unique contexts of the emerging economies have not been considered adequately in extant research. I bring country environmental contexts to the foreground and conceptualize various types of economies (developed economies, emerging economies, institution-driven high growth emerging economies, and factor-driven high growth emerging economies) as dissimilar types of country resource environments that provide firms with country resources: factors and institutions. To compete successfully, firms will find it more optimal to emphasize appropriate firm capabilities (market capabilities and non-market capabilities) and corporate diversification strategy (product and international diversification). By integrating insights from institutional economics and resource-based view, this paper offers a conceptual framework to examine the multifaceted relationships linking firm capabilities and corporate diversification across dissimilar country resource environments.
The Dust Opacity of Star‐forming Galaxies

ABSTRACT The presence of dust in galaxies removes one‐half or more of the stellar energy from the UV‐optical budget of the universe and has a profound impact on our understanding of how galaxies evolve. Measures of opacity in local galaxies are reviewed together with widely used theoretical and empirical methods for quantifying its effects. Existing evidence shows that the dust content of nearby galaxies depends not only on their morphology but also on their luminosity and activity level. A digression is devoted to starbursts in view of their potential relevance for measures of opacity in distant galaxies. Scarcity of coherent multiwavelength data sets hampers our ability to derive reliable obscuration estimates in intermediate‐ and high‐redshift galaxies. This, in turn, limits the reliability of inferred physical quantities, such as star formation rates, stellar population ages, galaxy luminosity functions, and others.
Registry request: Intestinal ulcers, Malabsorption, celiac disease, ulcerative ileojejunitis

Excerpt To the editor: At least 20 cases of multiple small-intestinal ulcers and malabsorption have been reported in the literature. Some of these were diagnosed as "non-granulomatous ulcerative il...
The Last Word on Science

While I was growing up, history was presented as a succession of political events stretched on a matrix of dates, elections, battles, and diplomatic coups. I found it all rather boring, so it is somewhat ironic that I find myself now a professional historian. My own views began to change when I discovered that some people studied the evolution of things other than politics: of ideas and concepts, of the social institutions that affected and were affected by those ideas, of the relationship in general between society and (for the case in point) the sciences. I had always been interested in science but rather more in the process of scientific validation of concepts than in assimilating the currently accepted world view. I was therefore delighted to discover the field of history of science and was fortunate to have several excellent teachers to introduce me to it.
Strongly Polarized Optical Afterglows of Gamma-Ray Bursts.

The optical afterglows of the gamma-ray bursts can be strongly polarized, in principle up to tens of percents, if (1) the afterglow is synchrotron radiation from an ultrarelativistic blast, (2) the blast is beamed during the afterglow phase, i.e., the shock propagates within a narrow jet, (3) we observe at the right time from the right viewing angle, and (4) magnetic fields parallel and perpendicular to the jet have different proper strengths.
Optimal Quasi-Steady Plasma Thruster System Characteristics

The overall characteristics of a generalized Quasi-steady Plasma Thruster (QPT) system consisting of thruster head, power conditioning network, propellant supply subsystem are studied. Energy balance equations for the system are coupled with component mass relationships in order to determine overall system mass and performance. Power supply power levels varying from 100 to 10,000 watts with thruster power levels ranging from 300 kw to 30 Mw employing argon as the propellant are considered. The manner in which overall system mass, average thrust, and burn time vary as a function power supply power level, quasi-steady power level, and pulse time are studied. Results indicate the existence of optimum pulse times when system mass is employed as an optimization criterion.
Totally geodesic surfaces and homology

Let M D H= ,  PSL2.C/ be an orientable hyperbolic 3–manifold, and let f W F ! M be a proper immersion of a connected, orientable surface of genus at least 2 such that f W 1.F /!  is injective. F (or more precisely .f;F /) is said to be totally geodesic if f . 1.F //  is conjugate into PSL2.R/. Thurston and Bonahon have described the geometry of surface groups in hyperbolic 3–manifolds as falling into three classes: doubly degenerate groups, quasi-Fuchsian groups and groups with accidental parabolics. The class of totally geodesic surface groups is a “positive codimension” subclass of the quasi-Fuchsian groups, so one may expect that hyperbolic 3–manifolds containing totally geodesic surface groups are special.
A common origin for quasar extended emission-line regions and their broad-line regions

We present a correlation between the presence of luminous extended emission-line regions (EELRs) and the metallicity of the broad-line regions (BLRs) of low-redshift quasars. The result is based on ground-based [O III] λ5007 narrowband imaging and Hubble Space Telescope UV spectra of 12 quasars at 0.20 ≤ z ≤ 0.45. Quasars showing luminous EELRs have low-metallicity BLRs (Z 0.6 Z☉), while the remaining quasars show typical metal-rich gas (Z > Z☉). Previous studies have shown that EELRs themselves also have low metallicities (Z 0.5 Z☉). The correlation between the occurrence of EELRs and the metallicity of the BLRs, strengthened by the subsolar metallicity in both regions, indicates a common external origin for the gas, almost certainly from the merger of a gas-rich galaxy. Our results provide the first direct observational evidence that the gas from a merger can indeed be driven down to the immediate vicinity (<1 pc) of the central black hole.
An Observational and Modeling Study of an Atmospheric Internal Bore during NAME 2004

Abstract Observations from the 2004 North American Monsoon Experiment (NAME) have been used to identify an atmospheric internal bore that occurred over the Gulf of California (GoC) on 31 July 2004. This bore disturbance was identified at Bahia Kino along the northwest coast of Mexico during the late evening of 31 July. It was hypothesized to have originated from the interaction of a gravity current from a large mesoscale convective system (MCS), which formed along the western slopes of the Sierra Madre Occidental during the afternoon, and a surface stable layer that developed from a sea-breeze circulation. It is suggested that the bore’s energy was trapped at low levels by an elevated stable layer. The vertical structure and undular nature of the bore was initially identified from 915-MHz wind profiler data at Bahia Kino. Results show a series of waves along the bore’s leading edge and turbulent mixing of air from above the stable layer to the surface on the downstream face of the leading undulation. The ...
Noncontemporaneous cointegration and the importance of timing

Abstract It is well known that in standard I(1) cointegration, the timing of variables in the cointegrating relation does not interfere with the cointegration property, whereas in an I(2) framework, it may. We show that, in a general (fractional) CI(d,b) model, it is the reduction in integration orders, b, implied by cointegration that determines whether timing matters, and not the integration order of the observed variables. We also derive implications of noncontemporaneous cointegration in both the time and frequency domains.
Multiple mechanisms of spiral wave breakup in a model of cardiac electrical activity

It has become widely accepted that the most dangerous cardiac arrhythmias are due to reentrant waves, i.e., electrical wave(s) that recirculate repeatedly throughout the tissue at a higher frequency than the waves produced by the heart's natural pacemaker (sinoatrial node). However, the complicated structure of cardiac tissue, as well as the complex ionic currents in the cell, have made it extremely difficult to pinpoint the detailed dynamics of these life-threatening reentrant arrhythmias. A simplified ionic model of the cardiac action potential (AP), which can be fitted to a wide variety of experimentally and numerically obtained mesoscopic characteristics of cardiac tissue such as AP shape and restitution of AP duration and conduction velocity, is used to explain many different mechanisms of spiral wave breakup which in principle can occur in cardiac tissue. Some, but not all, of these mechanisms have been observed before using other models; therefore, the purpose of this paper is to demonstrate them using just one framework model and to explain the different parameter regimes or physiological properties necessary for each mechanism (such as high or low excitability, corresponding to normal or ischemic tissue, spiral tip trajectory types, and tissue structures such as rotational anisotropy and periodic boundary conditions). Each mechanism is compared with data from other ionic models or experiments to illustrate that they are not model-specific phenomena. Movies showing all the breakup mechanisms are available at http://arrhythmia.hofstra.edu/breakup and at ftp://ftp.aip.org/epaps/chaos/E-CHAOEH-12-039203/ INDEX.html. The fact that many different breakup mechanisms exist has important implications for antiarrhythmic drug design and for comparisons of fibrillation experiments using different species, electromechanical uncoupling drugs, and initiation protocols. (c) 2002 American Institute of Physics.
Block multigrid implicit solution of the Euler equations of compressible fluid flow

A multigrid diagonal implicit algorithm has been developed to solve the Euler equations of inviscid compressible flow on block structured grids. Two model of advancing the multigrid cycle have been examined with respect to convergence rates, accuracy, and efficiency. The algorithm has been designed to run on parallel computers. Results are computed for transonic flows past airfols and include pressure distributions to verify the accuracy of the scheme and convergence histories to demonstrate the efficiency of the method.
A hybrid density functional cluster study of the bulk and surface electronic structures of plutonium monoxide

Abstract A hybrid density functional theory with Becke's three-parameter functional and the correlation functional of Lee, Yang and Parr (B3LYP) and relativistic effective core potentials has been applied to investigate the electronic structures of both the bulk and the (1 0 0) surface of plutonium monoxide. The bulk and the surface have been represented by a set of molecular clusters embedded in large arrays of point charges. A large overlap between the Pu 5f bands and O 2p bands and a significant covalent nature in the chemical bonding are found in the monoxide. The highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) gaps and the density of states (DOS) of the clusters tend to support the idea that PuO is a semiconductor. The valence bandwidth is found to increase with the cluster size and tends to be saturated.
The Lusternik-Schnirelmann category of a Lie groupoid

We propose a new homotopy invariant for Lie groupoids which generalizes the classical Lusternik-Schnirelmann category for topological spaces. We use a bicategorical approach to develop a notion of contraction in this context. We propose a notion of homotopy between generalized maps given by the 2-arrows in a certain bicategory of fractions. This notion is invariant under Morita equivalence. Thus, when the groupoid defines an orbifold, we have a well-defined LS-category for orbifolds. We prove an orbifold version of the classical Lusternik-Schnirelmann theorem for critical points.
Titanium(IV)-Promoted Mukaiyama Aldol−Prins Cyclizations

A new version of the Mukaiyama aldol−Prins (MAP) cyclization has been developed. Unsaturated enol ethers such as 3 were found to couple with aldehydes in the presence of TiBr4 to give 4-bromotetrahydropyran products. This cascade reaction sequence leads to the formation of two new carbon−carbon bonds, a ring, and three new stereogenic centers. We expect this reaction to be a powerful new tool in synthesis.
Synthesis and antiviral activity of cyclopropyl-spirocarbocyclic adenosine, (4R,5S,6R,7R)-4-(6-amino-9H-purin-9-yl)-7-(hydroxymethyl)spiro[2.4]heptane-5,6-diol against hepatitis C virus

An efficient method was developed for the synthesis of 6-exocyclic methylene carbocyclic intermediate 4. The Simmons-Smith cyclopropanation protocol was applied on the 6-exocyclic methylene of intermediate 4 and demonstrated its utility for the synthesis of novel class of a spiro-carbocyclic nucleoside analog 8. The titled compound 8 demonstrated a significant antiviral activity against HCV with EC(50) values of 0.273 and 0.368 μM in genotypes 1A and 1B, respectively.
High-resolution topography and albedo of the south polar layered deposits on Mars

Using a new photoclinometric technique with high-resolution Mariner 9 images, maximum slopes of 10°–20° are found to occur on an exposure of layered deposits within the south polar residual cap of Mars. Stereophotogrammetry is used to constrain the photoclinometric solutions, which resolve layer thicknesses of 100–300 m. Albedo variations are correlated with slope, indicating that frost is present on level areas. There is evidence for temporal changes in frost distribution in the 7 days (4° of L_S) between the two images used in this study. The magnitude of the slopes derived here and consideration of the stability of water ice at the surface of the layered deposits strongly suggest the presence of a competent weathering rind. The weathered surface may be composed of dark filamentary sublimation residue particles that protect the underlying ice from solar heating. This hypothesis is consistent with previous studies of the regional color and albedo of the layered deposits, which indicate that the deposits are slightly darker and less red than the bright dust that mantles much of the south polar region. Furthermore, the proposed weathering mechanism provides a plausible source of dark, saltating material for the Martian polar dune fields.
CLASSICAL ELECTRON THEORY AND CONSERVATION LAWS

Abstract It is shown that the traditional conservation laws for total charge, energy, linear and angular momentum, hold jointly in classical electron theory if and only if classical electron spin is included as dynamical degree of freedom.
Synthesis of carbamate-containing cyclodextrin analogues.

The one-pot cyclooligomerization of a saccharide-derived p-nitrophenyl carbamate monomer was developed to generate a series of novel carbamate-containing cyclodextrin analogues. The “transcarbamoylation” occurs by initial base-induced activation to the isocyanate, followed by polycondensation/cyclization of the isocyanato alcohol. In the presence of NaH, only cyclized oligomers were observed, suggesting the importance of Na+ in promoting the efficiency of the cyclization process. The facile deprotection of the oligomers was achieved.
Some Surprising Properties of Power Indices

Abstract While it is troubling when power-index values change with the index, the problem is more severe: Different indices can generate radically different rankings. For example, a 15-player game exists with over a trillion different strict index rankings of the players. In contrast, with a fixed number of players certain indices always share the same ranking: e.g., the Shapley and Banzhaf rankings agree with three players, but they can have opposite rankings with more players. It is explained why index outcomes can be sensitive to assumptions and to when players leave a game. Journal of Economic Literature Classification Numbers: C71, D71.
Constrained minimum-energy optimal control of the dissipative Bloch equations

Abstract In this letter, we apply optimal control theory to design minimum-energy π / 2 and π pulses for the Bloch system in the presence of relaxation with constrained control amplitude. We consider a commonly encountered case in which the transverse relaxation rate is much larger than the longitudinal one so that the latter can be neglected. Using Pontryagin’s maximum principle, we derive optimal feedback laws which are characterized by the number of switches, depending on the control bound and the coordinates of the desired final state.
Logic programming and constraint logic programming

Logic programming is a language paradigm based on logic, more specifically on resolution theorem proving in the predicate calculus as proposed in Robinson [1965]. Robinson had the foresight to distinguish the importance of two components in automatic theorem proving: a single inference rule called resolution and the testing for equality of trees called unification. Resolution is an inference step used to prove the validity of predicate calculus formulas expressed as clauses. In its simplest version: P ~ Q and -P ~ R imply Q ~ R, which is called the resolvant. Unification is the matching of terms used in a resolution step. It consists of testing the satisfiability of the equality of terms (i.e., labeled trees) whose leaves may contain variables. For example, the unification of the terms p(X, q(Z, a)) and p(b, q(a, Y)) succeeds, yielding the bindings X 5 b, Z 5 a, and Y 5 a. Prolog, the main representative of LP, consists of a sequence of Horn clauses. A Horn clause is one containing (at most) one positive literal. The term definite clause is used to denote a clause with exactly one positive literal. Prolog programs can be viewed as a set of definite clauses in which the positive literal is the head of the rule and the negative literals constitute the body or tail of the rule. From a procedural point of view, a head corresponds to the definition of a Boolean function whose body consists of conjunctions of calls to the Boolean functions representing the tail [Kowalski 1979]. A quintessential example of a Prolog program is that of append. It consists of two Horn clauses specifying that list L3 is the concatenation of two lists, L1 and L2: