cssi/SciSciGPT-SciSciNet huggingface dataset:
The impact of risk and uncertainty on expected returns.

Abstract We study asset pricing in economies featuring both risk and uncertainty. In our empirical analysis, we measure risk via return volatility and uncertainty via the degree of disagreement of professional forecasters, attributing different weights to each forecaster. We empirically model the typical risk-return trade-off and augment these models with our measure of uncertainty. We find stronger empirical evidence for an uncertainty-return trade-off than for the traditional risk-return trade-off. Finally, we investigate the performance of a two-factor model with risk and uncertainty in the cross section.
Scalar Perturbations of Charged Dilaton Black Holes

We have studied the scalar perturbation of static charged dilaton black holes in 3+1 dimensions. The black hole considered here is a solution to the low-energy string theory in 3+1 dimensions. The quasinormal modes for the scalar perturbations are calculated using the WKB method. The dilaton coupling constant has a considerable effect on the values of quasi normal modes. It is also observed that there is a linear relation between the quasi normal modes and the temperature for large black holes.
Unraveling the Helix Nebula: Its Structure and Knots* **

Through Hubble Space Telescope (HST) imaging of the inner part of the main ring of the Helix Nebula, together with CTIO 4 m images of the fainter outer parts, we have a view of unprecedented quality of the nearest bright planetary nebula. These images have allowed us to determine that the main ring of the nebula is composed of an inner disk of about 499'' diameter (0.52 pc) surrounded by an outer ring (in reality a torus) of 742'' diameter (0.77 pc) whose plane is highly inclined to the plane of the disk. This outer ring is surrounded by an outermost ring of 1500'' (1.76 pc) diameter, which is flattened on the side colliding with the ambient interstellar medium. The inner disk has an extended distribution of low-density gas along its rotational axis of symmetry, and the disk is optically thick to ionizing radiation, as is the outer ring. Published radial velocities of the knots provide support for the two-component structure of the main ring of the nebula and for the idea that the knots found there are expanding along with the nebular material from which they recently originated. These velocities indicate a spatial expansion velocity of the inner disk of 40 and 32 km s-1 for the outer ring, which yields expansion ages of 6560 and 12,100 yr, respectively. The outermost ring may be partially ionized through scattered recombination continuum from the inner parts of the nebula, but shocks certainly are occurring in it. This outermost ring probably represents a third period of mass loss by the central star. There is one compact, outer object that is unexplained, showing shock structures indicating a different orientation of the gas flow from that of the nebula. There is a change in the morphology of the knots as a function of the distance from the local ionization front. This supports a scenario in which the knots are formed in or near the ionization front and are then sculpted by the stellar radiation from the central star as the ionization front advances beyond them.
Luteinizing hormone-releasing hormone (LHRH)-expressing cells do not migrate normally in an inherited hypogonadal (Kallmann) syndrome

Kallmann syndrome inherited hypogonadotropic hypogonadism with anosmia, is associated with an X-chromosome deletion at Xp 22.3. In a Kallmann fetus, we have found an absence of luteinizing hormone-releasing hormone (LHRH)-expressing cells in the brain despite dense clusters of LHRH cells and fibers in the nose. LHRH-containing cells and neurites end in a tangle beneath the forebrain, within the dural layers of the meninges, on the dorsal surface of the cribriform plate of the ethmoid bone. Normal fetal brains, matched for age and sex, had LHRH cells and fibers, as expected, in the hypothalamus and preoptic area. Since LHRH-expressing cells recently were discovered to migrate from the olfactory placode into the brain, it appears that the hypogonadotropism of the Kallmann syndrome can be accounted for by a failure of LHRH cells to migrate into the brain.
Collective sensing-capacity of bacteria populations

The design of biological networks using bacteria as the basic elements of the network is initially motivated by a phenomenon called quorum sensing. Through quorum sensing, each bacterium performs sensing the medium and communicating it to others via molecular communication. As a result, bacteria can orchestrate and act collectively and perform tasks impossible otherwise. In this paper, we consider a population of bacteria as a single node in a network. In our version of biological communication networks, such a node would communicate with one another via molecular signals. As a first step toward such networks, this paper focuses on the study of the transfer of information to the population (i.e., the node) by stimulating it with a concentration of special type of a molecules signal. These molecules trigger a chain of processes inside each bacteria that results in a final output in the form of light or fluorescence. Each stage in the process adds noise to the signal carried to the next stage. Our objective is to measure (compute) the maximum amount of information that we can transfer to the node. This can be viewed as the collective sensing capacity of the node. The molecular concentration, which carries the information, is the input to the node, which should be estimated by observing the produced light as the output of the node (i.e., the entire population of bacteria forming the node. The molecules are trapped in the bacteria receptors forming complexes inside the bacteria which affect the genes responsible for producing the light. We focus on the noise caused by the random process of trapping molecules at the receptors as well as the variation of outputs of different bacteria in the node. The optimal input distribution to maximize the mutual information between the output of the node, e.g., light, and the applied molecule concentration is derived. Further, the capacity variation with the number of bacteria in the node and the number of receptors per bacteria is obtained. Finally, we investigated the collective sensing capability of the node when a specific form of molecular signaling concentration (which resembles M-ary modulation) is used. The achievable sensing capacity and the corresponding error probabilities were obtained for such practical signaling techniques.
Using early data to illuminate the Pioneer anomaly

Analysis of the radio tracking data from the Pioneer 10/11 spacecraft at distances between about 20–70 AU from the Sun has consistently indicated the presence of an unmodelled, small, constant, Doppler blue shift drift of order 6 × 10−9 Hz s−1. After accounting for systematics, this drift can be interpreted as a constant acceleration of aP = (8.74 ± 1.33) × 10−8 cm s−2 directed towards the Sun, or perhaps as a time acceleration of at = (2.92 ± 0.44) × 10−18 s −2. Although it is suspected that there is a systematic origin to this anomaly, none has been unambiguously demonstrated. We review the current status of the anomaly, and then point out how the analysis of early data, which was never analysed in detail, could allow a clearer understanding of the origin of the anomaly, be it a systematic or a manifestation of unsuspected physics.
On the lack of density of Lipschitz mappings in Sobolev spaces with Heisenberg target

We study the question: when are Lipschitz mappings dense in the Sobolev space W (M, H)? Here M denotes a compact Riemannian manifold with or without boundary, while H denotes the nth Heisenberg group equipped with a sub-Riemannian metric. We show that Lipschitz maps are dense in W (M, H) for all 1 ≤ p < ∞ if dim M ≤ n, but that Lipschitz maps are not dense in W (M, H) if dim M ≥ n + 1 and n ≤ p < n + 1. The proofs rely on the construction of smooth horizontal embeddings of the sphere S into H. We provide two such constructions, one arising from complex hyperbolic geometry and the other arising from symplectic geometry. The nondensity assertion can be interpreted as nontriviality of the nth Lipschitz homotopy group of H. We initiate a study of Lipschitz homotopy groups for sub-Riemannian spaces.
Implementation of a Reverse Colocation Model: Lessons from Two Community Behavioral Health Agencies in Rural Pennsylvania

This qualitative study examined the implementation of a reverse colocation pilot program that sought to integrate medical care in two community behavioral health agencies. To accomplish this, each agency hired a registered nurse, provided training for its staff to function as wellness coaches, and implemented a web-based tool for tracking consumer outcomes. The findings from two rounds of stakeholder discussions and consumer focus groups suggested that agencies successfully trained their staffs in wellness coaching, integrated nurses into agency functions, developed integrated care planning processes, and increased awareness of wellness among staff and consumers. Similar to other complex interventions, the agencies experienced challenges including difficulty establishing new procedures and communication protocols, discomfort among staff in addressing physical health concerns, difficulty building collaborative relationships with primary care providers, and modest uptake of the web-based tool. The study offers insights into the practical aspects of integrating care and makes recommendations for future efforts.
A family of invariants of rooted forests

Abstract Let A be a commutative k-algebra over a field of k and Ξ a linear operator defined on A. We define a family of A-valued invariants Ψ for finite rooted forests by a recurrent algorithm using the operator Ξ and show that the invariant Ψ distinguishes rooted forests if (and only if) it distinguishes rooted trees T, and if (and only if) it is finer than the quantity α ( T )=|Aut( T )| of rooted trees T. We also consider the generating function U(q)=∑ n=1 ∞ U n q n with U n =∑ T∈ T n (1/α(T))Ψ(T) , where T n is the set of rooted trees with n vertices. We show that the generating function U ( q ) satisfies the equation Ξ exp U(q)=q −1 U(q) . Consequently, we get a recurrent formula for U n ( n ⩾1), namely, U 1 = Ξ (1) and U n = ΞS n −1 ( U 1 , U 2 ,…, U n −1 ) for any n ⩾2, where S n (x 1 ,x 2 ,…) (n∈ N ) are the elementary Schur polynomials. We also show that the (strict) order polynomials and two well-known quasi-symmetric function invariants of rooted forests are in the family of invariants Ψ and derive some consequences about these well-known invariants from our general results on Ψ . Finally, we generalize the invariant Ψ to labeled planar forests and discuss its certain relations with the Hopf algebra H P,R D in Foissy (Bull. Sci. Math. 126 (2002) 193) spanned by labeled planar forests.
Spectral classification of the brightest objects in the galactic star forming region W40

We present high signal-to-noise, moderate resolution (R ≈ 2000) near-infrared spectra, as well as 10 μm imaging, for the brightest members of the central stellar cluster in the W40 H II region, obtained using the SpeX and MIRSI instruments at NASA's Infrared Telescope Facility. Using these observations combined with archival Spitzer Space Telescope data, we have determined the spectral classifications, extinction, distances, and spectral energy distributions (SEDs) for the brightest members of the cluster. Of the eight objects observed, we identify four main-sequence (MS) OB stars (one late-O, three early-B), two Herbig Ae/Be stars, and two low-mass young stellar objects (Class II). Strong He I absorption at 1.083 μm in the MS star spectra strongly suggests that at least some of these sources are in fact close binaries. Two out of the four MS stars also show significant infrared excesses typical of circumstellar disks. Extinctions and distances were determined for each MS star by fitting model stellar atmospheres to the SEDs. We estimate a distance to the cluster of between 455 and 535 pc, which agrees well with earlier (but far less precise) distance estimates. We conclude that the late-O star we identify is the dominant source of Lyman continuum luminosity needed to power the W40 H II region and is the likely source of the stellar wind that has blown a large (≈4 pc) pinched-waist bubble observed in wide-field mid-IR images. We also suggest that 3.6 cm radio emission observed from some of the sources in the cluster is likely not due to emission from ultracompact H II regions, as suggested in other work, due to size constraints based on our derived distance to the cluster. Finally, we also present a discussion of the curious source IRS 3A, which has a very strong mid-IR excess (despite its B3 MS classification) and appears to be embedded in a dusty envelope roughly 2700 AU in size.
On Disjoint Borel Uniformizations

Abstract Larman showed (1973, Mathematika 20 , 233–246) that any closed subset of the plane with uncountable vertical cross-sections has ℵ 1 disjoint Borel uniformizing sets. Here we show that Larman's result is best possible: there exist closed sets with uncountable cross sections which do not have more than ℵ 1 disjoint Borel uniformizations, even if the continuum is much larger than ℵ 1 . This negatively answers some questions of Mauldin (1990, “Open Problems in Topology” (J. van Mill and G. M. Reed, Eds.), 617–629). The proof is based on a result of Stern, stating that certain Borel sets cannot be written as a small union of low-level Borel sets (1978, C. R. Acad. Sci. Pan's Ser. A–B 286 , A855–A857). The proof of the latter result uses Steel's method of forcing with tagged trees (1978, Ann. Math. Logic 15 , 55–74); a full presentation of this method, written in terms of Baire category rather than forcing, is given here.
Jean Gebser and the spirit of cooperation

Epochs of great confusion and general uncertainty in a given world contain the slumbering, not-yet-manifest seeds of clarity and certainty. The manifestations of the aperspectival world... show that these seeds are already pressing toward realization. This means that we are approaching the "zenith" of confusion and are thus nearing the necessary breakthrough. Jean Gebser, 1953 The Ever-Present Origin1
The Universality of Seesaws

I discuss how the ideas associated with Seesaws, first introduced in the context of neutrino masses, are generally useful for understanding the very disparate scales one encounters in particle physics. From this point of view, the energy scale characterizing the Universe's dark energy presents a real challenge. A natural Seesaw explanation for this scale ensues if one imagines tying the dark energy sector to the neutrino sector, but this idea requires bold new dynamics.
A Radio Polarimetric Study of the Galactic Center Threads

The Very Large Array has been used to carry out a multifrequency, polarimetric study of the non-thermal filaments (NTF’s), G0.08+0.15, and G359.96+0.09, also known as the Northern and Southern Threads (Morris & Yusef-Zadeh 1985). These linear structures have been observed at �=20, 6, 3.6 and 2 cm, with high enough spatial resolution to be resolved for the first time at �6 and �3.6 cm. The �20 cm image reveals a wealth of new detail in the radio sources lying within the inner 60 pc of the Galaxy. The Southern Thread has a prominent split along its length, similar to splitting at the ends of previously studied NTF’s. In addition to the prominent Northern and Southern Threads, there are several elongated features that resemble NTF’s, but extend for only 5 7 pc. With resolutions as fine as 2 ′′ , the �3.6 and �6 cm images reveal a high degree of continuity and little substructure internal to the filament. However, the width of the Northern Thread varies along its length between �4 ′′ and �12 ′′ (0.15 0.5 pc), and becomes markedly diffuse at its NW extremity. The spectral index of the Northern Thread has been determined over a broad range of frequencies. Its flux density falls with frequency, (�= 0.5) between �90 and �6 cm (where S� / � � ), and becomes much steeper (�= 2.0) between �6 and �2 cm. The spectral index does not vary significantly along the length of the Northern Thread, which implies either that the diffusion timescale for the emitting electrons is less than their synchrotron lifetime, or that the emitting electrons are reaccelerated continuously at multiple positions along the filament. Because of the lack of spectral index variation, we have not located the source of relativistic electrons. Polarization observations at �6 and �3.6 cm confirm the non-thermal nature of the emission from the Northern Thread. The fractional polarization in the Northern Thread reaches 70% in some regions, although the polarized emission is patchy. Large rotation measures (RM � 2000 rad m −2 ) have been observed with irregular variations across the filament; typical values of RM are 100 2000 rad m −2 . The lack of any apparent pattern in the distribution of RM suggests that the Faraday rotating medium is not physically assocated with the Northern Thread since the filament itself is so highly ordered. The intrinsic magnetic field in the Northern Thread is predominantly aligned along its long axis. The data on the Southern Thread were less conclusive: the Southern Thread was not detected in total intensity at �6 or �3.6 cm, while the polarized emission at �3.6 cm arising from the Southern Thread is evident, with a bifurcated structure similar to that detected in total �20 cm intensity.
Chaotic oscillations in mechanical systems

Chaotic oscillations have now been observed in nonlinear mechanical systems by analytical, numerical, and experimental methods. Nevertheless, a more fundamental understanding of why and when such oscillations occur is of great importance. This goal will be pursued here by considering the relationship between chaos induced by forced oscillations vs self-excited oscillations, the relationship of indeterminancy of the final equilibrium state in the initial value problem to chaos in the sustained oscillation problem, comparison of theory to physical experiment, necessary and sufficient conditions for chaos to occur, and the question of convergence of systems of modal ordinary differential equations that derive from partial differential equations.
So-called “dual emission” for 3MLCT luminescence in ruthenium complex ions: What is really happening?

Dual emission is a reality in many, but not all, ruthenium complex ions, even at room temperature and in fluid solution. It requires significantly different ligands and is more obvious in rigid media such as glasses at low temperature and crystalline powders. However, there are not just two unique lifetimes. Rather, there is a continuum of similar but slightly different lifetimes drawn from a bimodal distribution. In some of the cases that do not show dual emission, there still seems to be a continuum within a unimodal distribution. After reviewing a wide range of data, we describe possible interpretations. Most novel, but in our view most attractive, is a major role for ion pairing. If one admits that ions near charge transfer orbitals should have a stabilizing effect, and if one doubts that there would be any unique configuration for ion pairs, then it would seem that a continuous variation of excited state behavior is mandatory. This mechanism accounts for the fact that highly asymmetric substitutions at the 4-position of the phen ligand that most affects charge transfer always show dual emission and offer the most exaggerated differences between the two emissions. Other possibilities remain, given the data available at this time.
A structurally perfect S = 1/2 Kagomé antiferromagnet

The syntheses and magnetic susceptibilities of a pure series of rare copper minerals from the atacamite family with general formula ZnxCu4-x(OH)6Cl2 (0 ≤ x ≤ 1) are reported. The structure of these compounds features a corner-sharing triangular kagome lattice of antiferromagnetically coupled Cu(II) ions. We correlate the onset of magnetic ordering with the mole fraction of paramagnetic Cu(II) ions located between kagome layers and demonstrate that the fully Zn-substituted compound shows no magnetic ordering down to 2 K, resulting in a highly spin-frustrated S = 1/2 lattice.
Merging Photoredox and Nickel Catalysis: Decarboxylative Cross-Coupling of Carboxylic Acids with Vinyl Halides

Decarboxylative cross-coupling of alkyl carboxylic acids with vinyl halides has been accomplished through the synergistic merger of photoredox and nickel catalysis. This new methodology has been successfully applied to a variety of α-oxy and α-amino acids, as well as simple hydrocarbon-substituted acids. Diverse vinyl iodides and bromides give rise to vinylation products in high efficiency under mild, operationally simple reaction conditions.
Network Analyzer Calibrations - Yesterday, Today and Tomorrow

From the very beginning, network analyzers were calibrated manually. Grease pencils were used to mark the reference level on a CRT display or meter display. Such calibration methods were able to remove some of the measurement scalar errors. Full real time vector error correction wasn't possible until the introduction of the hp8540A automatic vector network analyzer. It also allowed imperfect standards, i.e. an open, to be defined by a device model. The short-open-load-through calibration method was fully enabled. Since then, a surge in research on vna calibration methods brought us the through-reflect-line family of calibrations. Electronic calibration was invented to simplify calibration. Multi-port, differential and non-linear calibration methods and standards are the current and future challenges.
Enantioselective α-Alkenylation of Aldehydes with Boronic Acids via the Synergistic Combination of Copper(II) and Amine Catalysis

The enantioselective α-alkenylation of aldehydes has been accomplished using boronic acids via the synergistic combination of copper and chiral amine catalysis. The merger of two highly utilized and robust catalytic systems has allowed for the development of a mild and operationally trivial protocol for the direct formation of α-formyl olefins employing common building blocks for organic synthesis.
Heat Mirrored Solar Energy Receivers

RANSPARENT heat mirrors are thin films that transmit visible light but reflect infrared radiation. This paper investigates the potential utilization of this wavelength selective property in the process of trapping incident solar energy and its conversion to heat in a high-temperature (5401650°C) windowed cavity. The heat mirror film permits the solar energy to enter the cavity but reflects part or all of the internally generated blackbody (heat) radiation as it attempts to escape. The characteristics and durability of a number of transparent heat mirror films developed at the MIT Lincoln Laboratory for solar energy applications have been reported. l'3 These transparent heat mirror film types include metal films1 (e.g., Au and Ag), semiconductors2 (e.g., Sn-doped In2O3), composite layer films2 (e.g., TiO2/Ag/TiO2), and thin-film conducting microgrids.3 From a simplistic viewpoint, heat mirror films pass nearly all of the radiation below a given wavelength and reflect nearly all of the radiation above it; the separation point (transmission vs reflection) edge wavelength being determined by the materials and construction methods used to fabricate the heat mirror. Although in the early development stage, heat mirror films offer the potential advantage of reducing the window heat load because of their reflective properties. A simplified model of a heat mirrored cavity receiver is considered herein and used to predict cavity operating efficiency as a function of incident sun level, cavity operating temperature, and heat mirror reflectance edge position. The results are compared with those for a windowed receiver where escape of reradiated energy is prevented by a process of radiation absorption in the window, rather than by reflection back to the cavity interior as in the case of the heat mirror. Experimental data on some existing heat mirrors are summarized, and achievable performance improvements with existing heat mirror films are calculated and compared with idealized predictions. The results reported here should be considered as an initial inquiry into the usefulness of the heat mirror approach in a cavity receiver with the objective of determining whether the use of such films is sufficiently promising to warrant more detailed investigations. Though evaluations are made for three experimental heat mirrors, these heat mirrors have not been optimized for the cavity receiver application, and
Taking rights seriously in Chile

According to development scholars, legal reforms should provide litigants with new rights, enhance efficiency, and increase citizen trust in legal institutions. I investigate whether some of these normative claims have been realized through Chile's landmark criminal law reforms occurring after its transition to democracy. I find that Chile's criminal law reforms have improved defendants' rights by reducing the percentage of individuals incarcerated prior to sentence. This reduction signals a significant change in the treatment of criminals who once languished in jail for long periods without adequate due process and in violation of international human rights standards. Although the reforms have been viewed positively by citizens, opinions about Chile's judiciary have not changed significantly since Chile's return to democracy. While the Chilean government's focus on criminal law reform has not been misplaced, similar reforms with substantial government support are needed to significantly change citizens' ...
The automorphism group of a domain with an exponentially flat boundary point

Abstract We study the automorphisms group action on a bounded domain in C n having a boundary point that is exponentially flat. Such a domain typically has a compact automorphism group. Our results enable us to generate many new examples.
Logarithm laws and shrinking target properties

We survey some of the recent developments in the study of logarithm laws and shrinking target properties for various families of dynamical systems. We discuss connections to geometry, diophantine approximation and probability theory.
Simulations of ultrarelativistic magnetodynamic jets from gamma‐ray burst engines

Long-duration gamma-ray bursts (GRBs) require an engine capable of driving a jet of plasma to ultrarelativistic bulk Lorentz factors of up to several hundred and into narrow opening angles of a few degrees. We use global axisymmetric stationary solutions of magnetically dominated (force-free) ultrarelativistic jets to test whether the popular magnetic-driving paradigm can generate the required Lorentz factors and opening angles. Our global solutions are obtained via time-dependent relativistic ideal magnetodynamical numerical simulations which follow the jet from the central engine to beyond six orders of magnitude in radius. Our model is primarily motivated by the collapsar model, in which a jet is produced by a spinning black hole or neutron star and then propagates through a massive stellar envelope. We find that the size of the pre-supernova progenitor star and the radial profile of pressure inside the star determine the terminal Lorentz factor and opening angle of the jet. At the radius where the jet breaks out of the star, our well-motivated fiducial model generates a Lorentz factor γ ∼ 400 and a half-opening angle Oj ∼ 2°, consistent with observations of many long-duration GRBs. Other models with slightly different parameters give y in the range 100-5000 and θ j from 0°1 to 10°, thus reproducing the range of properties inferred for GRB jets. A potentially observable feature of some of our solutions is that the maximum Poynting flux in the jet is found at 0 ∼ θ j with the jet power concentrated in a hollow cone, while the maximum in the Lorentz factor occurs at an angle 0 substantially smaller than θ j also in a hollow cone. We derive approximate analytical formulae for the radial and angular distribution of y and the radial dependence of θ j . These formulae reproduce the simulation results and allow us to predict the outcome of models beyond those simulated. We also briefly discuss applications to active galactic nuclei, X-ray binaries and short-duration GRBs.
Some examples of Mahler measures as multiple polylogarithms

The Mahler measures of certain polynomials of up to five variables are given in terms of multiple polylogarithms. Each formula is homogeneous and its weight coincides with the number of variables of the corresponding polynomial.
Steady Viscous Flow in a Triangular Cavity

Steady recirculating viscous flow inside an equilateral triangular cavity is generated by translating one side. The Navier-Stokes equations are solved numerically using finite differences on a transformed geometry. Alternative numerical approaches, and associated numerical difficulties, are also discussed. The results show a primary eddy and a series of secondary eddies at the stagnant corner. For high Reynolds numbers the interior of the primary eddy has constant vorticity, but its value cannot be predicted by the mean-squared law.
Chemical Solution Routes to Single-Crystal Thin Films

Epitaxial thin films of inorganic single crystals can be grown on single-crystal substrates with a variety of different solution chemistries. This review emphasizes chemical solution deposition, in which a solution is used to deposit a layer of precursor molecules that decompose to low-density, polycrystalline films during heating. Ways to control film cracking during deposition and heat treatment and why many precursors synthesize metastable crystalline structures are discussed, and the different mechanisms that convert the polycrystalline film into a single crystal are reviewed. Hydrothermal epitaxy, in which single crystal thin films are directly synthesized on templating substrates in an aqueous solution at temperatures <150°C, is also discussed.
A FACILE ONE-POT SYNTHESIS OF SYMMETRICAL AND UNSYMMETRICAL ACETALDEHYDE ACETALS FROM PRIMARY ALCOHOLS

Abstract Initial formation of a vinyl ether 2 by treatment of a primary alcohol 1 with ethyl vinyl ether in the presence of mercury (11) acetate followed by treatment with the same or a different alcohol in the presence of p-toluenesulfonic acid affords the symmetrical and unsymmetrical acetaldehyde acetals 3 in good overall yield. The method is easily scaled up and represents a significant improvement over currently available procedures.
Efficient and guaranteed rank minimization by atomic decomposition

Recht, Fazel, and Parrilo provided an analogy between rank minimization and l 0 -norm minimization. Subject to the rank-restricted isometry property, nuclear norm minimization is a guaranteed algorithm for rank minimization. The resulting semidefinite formulation is a convex problem but in practice the algorithms for it do not scale well to large instances. Instead, we explore missing terms in the analogy and propose a new algorithm which is computationally efficient and also has a performance guarantee. The algorithm is based on the atomic decomposition of the matrix variable and extends the idea in the CoSaMP algorithm for l 0 -norm minimization. Combined with the recent fast low rank approximation of matrices based on randomization, the proposed algorithm can efficiently handle large scale rank minimization problems.
The impact of scanners on employment in supermarkets

A brief review is given of the early estimates of the rate at which scanners would be installed in supermarkets and the resulting labor and consumer responses. The actual situation in 1979 is then discussed and detailed labor savings achieved by one supermarket chain are given. A fully scanner-equipped supermarket is estimated to have a 5 percent lower labor requirement than an unautomated store with the same volume. It is projected that 50 percent of the 23,000 large supermarkets will install scanners by 1984 with the remainder doing so by 1988. At full penetration, scanners will reduce total industry employment by approximately 50,000. Few actual layoffs will occur because of the high turnover in the industry. Furthermore, the stores that install scanners may attract customers from nonautomated stores leaving those stores to handle the job losses.
DESIGN AND EVALUATION OF A COMPUTER-BASED TOEFL TUTORIAL

In order to train examinees whose native language is not English to take a computerized Test of English as a Foreign Language (TOEFL®), a special set of tutorials was designed and developed. The TOEFL tutorials were field tested as part of a computer familiarity study in 1996. This report describes the development of the tutorials. Also, the experiences of the 1,169 individuals who participated in the computer familiarity study are characterized in terms of timing and performance data, as well as self-reported attitudes. These analyses took into account computer familiarity and English ability, which both proved to be important in explaining some differences in time to complete the tutorials and perception of the tutorials' usefulness. Most examinees were successful in completing the practice items in the tutorials and thought that the tutorials were helpful. Some changes were subsequently made before operational implementation of the computerized TOEFL test in order to reduce the time needed to complete the TOEFL tutorials.
Biological activity and phosphorylation of 2'-azido-2'-deoxyuridine and 2'-azido-2'-deoxycytidine

2'-Azido-2'-deoxyuridine and 2'-azido-2'-deoxycytidine were evaluated for their inhibitory activity against ribonucleotide reductase and for subsequent cell growth inhibition. Their mono- and di-phosphates were synthesized and their inhibitory activities against the reductase were also determined in a permeabilized cell system, along with the two nucleosides. The results of the present study identify the first phosphorylation step involved in the conversion of the two azidonucleosides to the corresponding diphosphates to be rate-limiting in the overall activation.
Predication, fiction, and artificial intelligence

This paper describes the SNePS knowledge-representation and reasoning system. SNePS is an intensional, propositional, semantic-network processing system used for research in AI. We look at how predication is represented in such a system when it is used for cognitive modeling and natural-language understanding and generation. In particular, we discuss issues in the representation of fictional entities and the representation of propositions from fiction, using SNePS. We briefly survey four philosophical ontological theories of fiction and sketch an epistemological theory of fiction (implemented in SNePS) using a story operator and rules for allowing propositions to “migrate” into and out of story “spaces”.
Selective tight binding inhibitors of trypanosomal glyceraldehyde-3-phosphate dehydrogenase via structure-based drug design.

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from the sleeping sickness parasite Trypanosoma brucei is a rational target for anti-trypanosomatid drug design because glycolysis provides virtually all of the energy for the bloodstream form of this parasite. Glycolysis is also an important source of energy for other pathogenic parasites including Trypanosoma cruzi and Leishmania mexicana. The current study is a continuation of our efforts to use the X-ray structures of T. brucei and L. mexicana GAPDHs containing bound NAD+ to design adenosine analogues that bind tightly to the enzyme pocket that accommodates the adenosyl moiety of NAD+. The goal was to improve the affinity, selectivity, and solubility of previously reported 2‘-deoxy-2‘-(3-methoxybenzamido)adenosine (1). It was found that introduction of hydroxyl functions on the benzamido ring increases solubility without significantly affecting enzyme inhibition. Modifications at the previously unexploited N6-position of the purine not only lead to a su...
Propagation of transients in a random medium

The propagation of transient scalar waves in a three−dimensional random medium is considered. The analysis is based on the smoothing method. An integro−differential equation for the coherent (or average) wave is derived and solved for the case of a statistically homogeneous and isotropic medium and a delta−function source. This yields the coherent Green’s function of the medium. It is found that the waveform of the coherent wave depends generally on the distance from the source measured in terms of a certain dimensionless parameter. Based on the magnitude of this parameter, three propagation zones, called the near zone, the far zone, and the intermediate zone, are defined. In the near zone the evolution of the waveform is determined primarily by attenuation of the high−frequency components of the wave, whereas in the far zone it is determined mainly by dispersion of the low−frequency components. The intermediate zone is a region of transition between the near and far zones. The results show that, in gener...
The complexity of constructing pseudorandom generators from hard functions

We study the complexity of constructing pseudorandom generators (PRGs) from hard functions, focussing on constant-depth circuits. We show that, starting from a function f : {0,1}l --> {0,1} computable in alternating time O(l) with O(1) alternations that is hard on average (i.e. there is a constant e > 0 such that every circuit of size 2el failes to compute f on at elast a 1/poly(l) fraction of inputs) we can construct a PRG : {0,1}O(log n) --> {0,1}n computable be DLOGTIME-uniform constant deptg circuits of size polunomial in n. Such a PRG implies BP . ACO = ACO under DLOGTIME-uniformity. On the negative side, we prove that starting from a worst-case hard function f : {0,1}l --> {0,1} (i.e. there is a constant e > 0 such that every circuit size of 2el fails to compute f on some input) for evey positive constant &$948; {0,1}n computable by constant-depth circuits of size polynomial in n. We also study worst-case hardness amplification, which is the related problem of producing an average-case hard function starting from a worst-case hard one. In particular, we deduce that there is no blackbox worst-case hardness amplification within the polynomial time hierarchy. These negative results are obtained by showing that polynomialsize constant-depth circuits cannot compute good extractors and listdecodable codes.
Quantitative schlieren visualization.

Using a closed circuit television camera (CCTV), a method is developed to obtain quantitative sound pressure measurements directly from the sound field imaged in a schlieren system. By using the exact time format of the composite video signal and a series of time delay circuits, it is possible to take vertical intensity scans of a schlieren image at any position on the TV raster. The method uses the camera's horizontal blanking pulse to trigger a broadband, high-speed sample–hold amplifier. This amplifier is triggered to sample each horizontal scan line at a selected time in the horizontal scan sweep and to feed this value into a transient recorder. The signal is digitized, and a continuous analog voltage signal corresponding to the black–white information from a schlieren image is displayed on a scope. The same analog signal is also plotted on an X-Y recorder. The schlieren system can be operated using only a single calibration curve at each frequency. The curves plotted applied transducer voltage against the video output level. Thus, by comparing the video output levels for several vertical image intensity scans on a schlieren image, relative sound pressure measurements are routinely obtained.
H ∞ static output feedback control for discrete-time switched linear systems with average dwell time

This study investigates the problem of H∞ static output feedback (SOF) control for discrete-time switched linear systems with average dwell time. By the aid of multiple Lyapunov functions combined with Finsler's lemma, a switched SOF controller is designed such that the closed-loop switched system is exponentially stable and achieves a weighted L2-gain. Sufficient conditions for SOF control are derived and formulated in terms of linear matrix inequalities (LMIs). The minimal average dwell time and the corresponding SOF controller are obtained from the LMI conditions for a given system decay degree. The proposed method is less conservative than the existing ones, which is validated by a numerical example.
A residue theorem for Malcev--Neumann series

In this paper, we establish a residue theorem for Malcev-Neumann series that requires few constraints, and includes previously known combinatorial residue theorems as special cases. Our residue theorem identifies the residues of two formal series (over a field of characteristic zero) which are related by a change of variables. We obtain simple conditions for when a change of variables is possible, and find that the two related formal series in fact belong to two different fields of Malcev-Neumann series. The multivariate Lagrange inversion formula is easily derived and Dyson's conjecture is given a new proof and generalized.
Exchange rate volatility and Spanish-American commodity trade flows

Abstract A number of recent studies have tested the impact of exchange rate volatility on trade flows, particularly for individual commodities, for various country pairs. These have found that risk can increase as well as decrease trade, but that oftentimes industries are not affected. This study examines trade between the United States and Spain over the period from 1962 to 2009, for 131 U.S. export industries and 88 import industries. We find that exchange rate volatility has short-run and long-run effects in only a fraction of the cases, but that exports respond more to increased uncertainty than imports do. In all, only 35 of the 74 U.S. export industries are affected (11 positive, 24 negative), whilst only three out of 37 import industries have positive coefficients and 11 have negative ones. We find no evidence that durable or nondurable goods are more likely to respond to volatility, whilst small industries or specialized goods might show more of a positive response.
A FRAMEWORK FOR A CRYPTOGRAPHIC PROTOCOL EVALUATION WORKBENCH

Tools to evaluate Cryptographic Protocols (CPs) exploded into the literature after development of BAN Logic.2,3 Many of these were created to repair weaknesses in BAN Logic. Unfortunately, these tools are all complex and difficult to implement individually, with little or no effort available to implement multiple tools in a workbench environment. We propose a framework that allows a protocol analyst to exercise multiple CP evaluation tools in a single environment. Moreover, this environment exhibits characteristics that will enhance the effectiveness of the CP evaluation methods themselves.
Some Remarks on Singular Solutions of Nonlinear Elliptic Equations III: Viscosity Solutions Including Parabolic Operators

The paper concerns singular solutions of nonlinear elliptic equations, which include removable singularities for viscosity solutions, a strengthening of the Hopf Lemma including parabolic equations, Strong maximum principle and Hopf Lemma for viscosity solutions including also parabolic equations.
Transition Metal-Catalyzed Oxidative Carbonylation of Amines to Ureas

The synthesis of ureas from amines has traditionally been accomplished with stoichiometric reactions of phosgene or its derivatives, which are associated with environmental and waste disposal issues. Because of the prevalence of urea moieties in molecules of interest for several applications, alternative catalytic routes for the oxidative conversion of amines to ureas using CO as the carbonyl source have been developed. This microreview discusses recent developments in transition metal-catalyzed oxidative carbonylation of amines to ureas as an alternative to phosgene and its derivatives. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Plasmons localized at point charges in semiconductor quantum wells

Abstract The plasmon excitations of inhomogeneous carrier gases in semiconductor quantum wells in the presence of point charge impurities are investigated. The random phase approximation for the carrier gas yields an integral equation which expresses the condition that plasmons may be self-consistently localized in the vicinity of the impurity. The localized plasmon is a density wave trapped at the impurity site and exists in the electron (hole) gas only for negative (positive) impurity charge. Bound states of the intersubband plasmon are found for all densities of the carrier gas in a quantum well, a result which differs qualitatively from the bulk case. Numerical results for the binding energies are given for a range of relevant parameters.
On the Fourier coefficients of 2-dimensional vector-valued modular forms

Let $\rho: SL(2,\mathbb{Z})\to GL(2,\mathbb{C})$ be an irreducible representation of the modular group such that $\rho(T)$ has finite order $N$. We study holomorphic vector-valued modular forms $F(\tau)$ of integral weight associated to $\rho$ which have \emph{rational} Fourier coefficients. (These span the complex space of all integral weight vector-valued modular forms associated to $\rho$.) As a special case of the main Theorem, we prove that if $N$ does \emph{not} divide 120 then every nonzero $F(\tau)$ has Fourier coefficients with \emph{unbounded denominators}.
33.8 GHz CCS Survey of Molecular Cores in Dark Clouds

We have conducted a survey of the CCS JN = 32-21 line toward 11 dark clouds and star-forming regions at 30'' spatial resolution and 0.054 km s-1 velocity resolution. CCS was detected only in quiescent clouds, not in active star-forming regions. The CCS distribution shows remarkable clumpy structure, and 25 clumps are identified in seven clouds. Seven clumps with extremely narrow nonthermal line widths (<0.1 km s-1) are among the most quiescent clumps ever found. The CCS clumps tend to exist around the higher density regions traced by NH3 emission or submillimeter continuum sources, and the distribution is not spherically symmetric. Variation of the CCS abundance was suggested as an indicator of the evolutionary status of star formation. However, we can only find a weak correlation between N(CCS) and n. The velocity distributions of CCS clouds reveal that a systematic velocity pattern generally exists. The most striking feature in our data is a ring structure in the position-velocity diagram of L1544 with an well-resolved inner hole of 0.04 pc × 0.13 km s-1 and an outer boundary of 0.16 pc × 0.55 km s-1. This position-velocity structure clearly indicates an edge-on disk or ring geometry, and it can be interpreted as a collapsing disk with an infall velocity 0.1 km s-1 and a rotational velocity less than our velocity resolution. Nonthermal line width distribution is generally coherent in CCS clouds, which could be evidence for the termination of Larson's Law at small scales, ~0.1 pc.
Chromatic control in coextruded layered polymer microlenses

We describe the formation, characterization and theoretical understanding of microlenses comprised of alternating polystyrene and polymethylmethacrylate layers produced by multilayer coextrusion. These lenses are fabricated by photolithography, using a grayscale mask followed by plasma etching, so that the refractive index alternation of the bilayer stack appears across the radius of the microlens. The alternating quarter-wave thick layers form a one-dimensional photonic crystal whose dispersion augments the material dispersion, allowing one to sculpt the chromatic dispersion of the lens by adjusting the layered structure. Using Huygen’s principle, we model our experimental measurements of the focal length of these lenses across the reflection band of the multilayer polymer film from which the microlens is fashioned. For a 56 μm diameter multilayered lens of focal length 300 μm, we measured a ∼ 25% variation in the focal length across a shallow, 50 nm-wide reflection band.