cssi/SciSciGPT-SciSciNet huggingface dataset:
Human hepatic cancer stem cells are characterized by common stemness traits and diverse oncogenic pathways

Epigenetic mechanisms play critical roles in stem cell biology by maintaining pluripotency of stem cells and promoting differentiation of more mature derivatives. If similar mechanisms are relevant for the cancer stem cell (CSC) model, then epigenetic modulation might enrich the CSC population, thereby facilitating CSC isolation and rigorous evaluation. To test this hypothesis, primary human cancer cells and liver cancer cell lines were treated with zebularine (ZEB), a potent DNA-methyltransferase1-inhibitor and putative CSCs were isolated by the Side Population (SP) approach. The CSC properties of ZEB-treated and untreated subpopulations were tested by standard in vitro and in vivo assays. Whole transcriptome profiling of isolated CSC was performed to generate CSC signatures. Clinical relevance of the CSC signatures was evaluated in diverse primary human cancers. Epigenetic modulation increased frequency of cells with CSC properties in the SP fraction isolated from human cancer cells as judged by self-renewal, superior tumor-initiating capacity in serial transplantations and direct cell tracking experiments. Integrative transcriptome analysis revealed common traits enriched for stemness-associated genes, although each individual CSC gene expression signature exhibited activation of different oncogenic pathways (e.g. EGFR, SRC and MYC). The common CSC signature was associated with malignant progression, enriched in poorly differentiated tumors and was highly predictive of prognosis in liver and other cancers patients. CONCLUSION Epigenetic modulation may provide a tool for prospective isolation and in-depth analysis of CSC. The liver CSC gene signatures are defined by a pernicious interaction of unique oncogene-specific and common stemness traits. These data should facilitate the identifications of therapeutic tools targeting both unique and common features of CSC.
Organ-specific shifts in mtDNA heteroplasmy following systemic delivery of a mitochondria-targeted restriction endonuclease

Most pathogenic mtDNA mutations are heteroplasmic and there is a clear correlation between high levels of mutated mtDNA in a tissue and pathology. We have found that in vivo double-strand breaks (DSBs) in mtDNA lead to digestion of cleaved mtDNA and replication of residual mtDNA. Therefore, if DSB could be targeted to mutations in mtDNA, mutant genomes could be eliminated and the wild-type mtDNA would repopulate the cells. This can be achieved by using mitochondria-targeted restriction endonucleases as a means to degrade specific mtDNA haplotypes in heteroplasmic cells or tissues. In this work, we investigated the potential of systemic delivery of mitochondria-targeted restriction endonucleases to reduce the proportion of mutant mtDNA in specific tissues. Using the asymptomatic NZB/BALB mtDNA heteroplasmic mouse as a model, we found that a mitochondria-targeted ApaLI (that cleaves BALB mtDNA at a single site and does not cleave NZB mtDNA) increased the proportion of NZB mtDNA in target tissues. This was observed in heart, using a cardiotropic adeno-associated virus type-6 (AAV6) and in liver, using the hepatotropic adenovirus type-5 (Ad5). No mtDNA depletion or loss of cytochrome c oxidase activity was observed in any of these tissues. These results show the potential of systemic delivery of viral vectors to specific organs for the therapeutic application of mitochondria-targeted restriction enzymes in mtDNA disorders.
Charged pion polarizability from the lattice

Direct evaluation of charged particle polarizabilities on the lattice is quite difficult. However, a short cut for charged pion polarizability - the Das, Mathur, Okubo Sum Rule - can readily be calculated using lattice techniques. A phenomenological model has been developed to fit the time behavior of the propagators in this expression. Numerical systematics are discussed and some preliminary results are presented.
A conceptual model for megaprogramming

"Currently, software is put together one statement at a time. What we need is to put software together one component at a time." --- Barry Boehm, at the Domain Specific Software Architecture (DSSA) Workshop, July 11--12, 1990.Megaprogramming, as defined at the first ISTO Software Technology Community Meeting, June 27-29, 1990, by Barry Boehm, director of DARPA/ISTO, is component-based software engineering and life-cycle management. The goal of this paper is to place megaprogramming in perspective with research in other areas of software engineering (i.e., formal methods and rapid prototyping) and to describe the author's experience developing a system to support megaprogramming.The paper, first, analyzes megaprogramming and its relationship to other DARPA research initiatives (CPS/CPL --- Common Prototyping System/Common Prototyping Language, DSSA --- Domain Specific Software Architectures, and SWU --- Software Understanding). Next, the desirable attributes of megaprogramming software components are identified and a software development model (The 3C Model) and resulting prototype megaprogramming system (LILEANNA --- Library Interconnection Language Extended by Annotated Ada) are described.
Structuring Innovation in the Knowledge Management Platform: Perceptions and Practices

This qualitative research study examined perceptions and current practices of structuring innovation in the knowledge management platform by questioning employees of companies in the greater New York metropolitan area. The 69 participants involved were enrolled in graduate-level distance learning courses offered by a fully-accredited higher education institution. Many participants in the study agreed with the premise of this paper that innovation policies can and should be structured into knowledge management systems. However, it was stated by a minority in the study group that officially setting up the innovation polices with the KM system is not truly feasible, although it is a worthy goal. Nevertheless, the concepts of innovation and knowledge are closely related, and within organisations today it is a tremendous missed opportunity if knowledge management systems are not developed and structured from the start with innovation in mind as a continual outcome.
Local anomaly cancellation, M-theory orbifolds and phase-transitions

In this paper we consider orbifold compactifications of M-theory on S1/Z2×T4/Z2. We discuss solutions of the local anomaly matching conditions by twisted vector, tensor and hypermultiplets confined on the local orbifold six-planes. In addition we consider phase-transitions among different solutions which are mediated by M-theory fivebranes which touch the local orbifold planes and are converted there to gauge instantons.
Dynamics and Microexplosion of High Energy Fuels Injected into a Combustor

Abstract The effects of microexploding fuel droplets injected into the shear layer in an axisymmelric dump combustor are studied numerically. The fuel droplets considered are multicomponent consisting of a solid high-energy fuel core surrounded by a liquid carrier. When droplets microexplode, pressure waves are generated that reverberate through the system and in some cases couple with the characteristic frequencies of the system. In a particular case, the low frequency quarter wave acoustic mode of the inlet is amplified, resulting in the formation of a large vortex structure near the combustor step. Periodic energy release associated with this large vortex structure sustains the low frequency oscillations even though droplets are injected continuously at a constant rate. By phase-coupling droplet injection to an external acoustic forcing frequency, it is demonstrated that pressure fluctuations at the forced frequency may be amplified or attenuated by the microexplosion of the fuel droplets.
Study of Lubricant Jet Flow Phenomena in Spur Gears—Out of Mesh Condition

An analysis was conducted for oil jet lubrication on the disengaging side of a gear mesh. Results of the analysis were computerized and used to determine the oil jet impingement depth for several gear ratios and oil jet to pitch line velocity ratios. An experimental program was conducted on the NASA gear test rig using high-speed photography to experimentally determine the oil jet impingement depth on the disengaging side of mesh. Impingement depth reaches a maximum at gear ratio near 1.5 where chopping by the leading gear tooth limits the impingement depth. The pinion impingement depth is zero above a gear ratio of 1.172 for a jet velocity to pitch time velocity ratio of 1.0 and is similar for other velocity ratios. The impingement depth for gear and pinion are equal and approximately one-half the maximum at a gear ratio of 1.0. Impingement depth on either the gear or pinion many be improved by relocation of the jet from the pitch line or by changing the jet angle. Results of the analysis were verified by experimental results using a high-speed camera and a well lighted oil jet.
Price dispersion, information and learning

Abstract We consider an economy where trade is decentralized and agents have incomplete information with respect to the value of money. Agents’ learning evolves from private experiences and we explore how the formation of prices interacts with learning. We show that multiple equilibria arise, and equilibria with price dispersion entail more learning than equilibria with one price. Price dispersion increases communication about private histories, which in turn increases the overall amount of information in the economy. We also compare ex ante welfare under price dispersion and one price. Our results show that, despite the existence of some meetings where no trade takes place, ex ante welfare under price dispersion may be higher than under one price.
Measures in wavelet decompositions

In applications, choices of orthonormal bases in Hilbert space H may come about from the simultaneous diagonalization of some specific abelian algebra of operators. This is the approach of quantum theory as suggested by John von Neumann; but as it turns out, much more recent constructions of bases in wavelet theory, and in dynamical systems, also fit into this scheme. However, in these modern applications, the basis typically comes first, and the abelian algebra might not even be made explicit. It was noticed recently that there is a certain finite set of non-commuting operators F"i, first introduced by engineers in signal processing, which helps to clarify this connection, and at the same time throws light on decomposition possibilities for wavelet packets used in pyramid algorithms. There are three interrelated components to this: an orthonormal basis, an abelian algebra, and a projection-valued measure. While the operators F"i were originally intended for quadrature mirror filters of signals, recent papers have shown that they are ubiquitous in a variety of modern wavelet constructions, and in particular in the selection of wavelet packets from libraries of bases. These are constructions which make a selection of a basis with the best frequency concentration in signal or data-compression problems. While the algebra A generated by the F"i-system is non-abelian, and goes under the name ''Cuntz algebra'' in C^*-algebra theory, each of its representations contains a canonical maximal abelian subalgebra, i.e., the subalgebra is some C(X) for a Gelfand space X. A given representation of A, restricted to C(X), naturally induces a projection-valued measure on X, and each vector in H induces a scalar-valued measure on X. We develop this construction in the general context with a view to wavelet applications, and we show that the measures that had been studied earlier for a very restrictive class of F"i-systems (i.e., the Lemarie-Meyer quadrature mirror filters) in the theory of wavelet packets are special cases of this. Moreover, we prove a structure theorem for certain classes of induced scalar measures. In the applications, X may be the unit interval, or a Cantor set; or it may be an affine fractal, or even one of the more general iteration limits involving iterated function systems consisting of conformal maps.
Enantioselective synthesis of hindered cyclic dialkyl ethers via catalytic oxa-Michael/Michael desymmetrization.

An asymmetric oxa-Michael/Michael cascade reaction of p-quinols and α,β-unsaturated aldehydes provides access to hindered dialkyl ethers. A highly enantioselective oxa-Michael addition of a tertiary alcohol precedes an intramolecular cyclohexadienone desymmetrization, which allows for the concomitant formation of four contiguous stereocenters in a single step. The highly functionalized bicyclic frameworks are rapidly obtained from simple starting materials with good diastereoselection and serve as valuable precursors for further manipulation.
SOLID STATE DETHIOACETALIZATION USING CLAYFEN

Abstract Thio acetals and ketals derived from aldehydes and ketones are readily deprotected by clayfen within seconds under solvent-free conditions. This rapid and environmentally benign method avoids the use of excess solvents and toxic oxidants usually employed in the dethioacetalization process.
The LMO-invariant of 3-manifolds of rank one and the Alexander polynomial

We prove that the LMO-invariant of a 3-manifold of rank one is determined by the Alexander polynomial of the manifold, and conversely, that the Alexander polynomial is determined by the LMO-invariant. Furthermore, we show that the Alexander polynomial of a null-homologous knot in a rational homology 3-sphere can be obtained by composing the weight system of the Alexander polynomial with the Arhus invariant of knots.
Topology in physics—A perspective

This article, written in honor of Fritz Rohrlich, briefly surveys the role of topology in physics.
Chiral perturbation theory for hadrons containing a heavy quark. The sequel

Abstract Charm and bottom mesons and baryons are incorporated into a low energy chiral lagrangian. Interactions of the heavy hadrons with light octet Goldstone bosons are studied in a framework which represents a synthesis of chiral perturbation theory and the heavy quark effective theory. The differential decay rate for the semileptonic process Λ b 0 →Σ c ++ + œ − + ν e + π − is calculated at the zero recoil point using this hybrid formalism.
A Statistical Study of Threshold Rotation Rates for the Formation of Disks around Be Stars

This paper presents a detailed statistical determination of the equatorial rotation rates of classical Be stars. The rapid rotation of Be stars is likely to be linked to the ejection of gas that forms dense circumstellar disks. The physical origins of these disks are not understood, although it is generally believed that the ability to spin up matter into a Keplerian disk depends on how close the stellar rotation speed is to the critical speed at which the centrifugal force cancels gravity. There has been recent disagreement between the traditional idea that Be stars rotate between 50% and 80% of their critical speeds and new ideas (inspired by the tendency for gravity darkening to mask rapid rotation at the equator) that their rotation may be very nearly critical. This paper utilizes Monte Carlo forward modeling to simulate distributions of the projected rotation speed (v sin i), taking into account gravity darkening, limb darkening, and observational uncertainties. A χ2 minimization procedure was used to find the distribution parameters that best reproduce observed v sin i distributions from R. Yudin's database. Early-type (O7e-B2e) Be stars were found to exhibit a roughly uniform spread of intrinsic rotation speed that extends from 40%-60% up to 100% of critical. Late-type (B3e-A0e) Be stars exhibit progressively narrower ranges of rotation speed as the effective temperature decreases; the lower limit rises to reach critical rotation for the coolest Be stars. The derived lower limits on equatorial rotation speed represent conservative threshold rotation rates for the onset of the Be phenomenon. The significantly subcritical speeds found for early-type Be stars represent strong constraints on physical models of angular momentum deposition in Be star disks.
Dense granular flow at the critical state: maximum entropy and topological disorder

After extensive quasi-static shearing, dense dry granular flows attain a steady-state condition of porosity and deviatoric stress, even as particles are continually rearranged. The paper considers two-dimensional flow and derives the probability distributions of two topological measures of particle arrangement—coordination number and void valence—that maximize topological entropy. By only considering topological dispersion, the method closely predicts the distribution of void valences, as measured in discrete element (DEM) simulations. Distributions of coordination number are also derived by considering packings that are geometrically and kinetically consistent with the particle sizes and friction coefficient. A cross-entropy principle results in a distribution of coordination numbers that closely fits DEM simulations.
Evaluating accumulo performance for a scalable cyber data processing pipeline

Streaming, big data applications face challenges in creating scalable data flow pipelines, in which multiple data streams must be collected, stored, queried, and analyzed. These data sources are characterized by their volume (in terms of dataset size), velocity (in terms of data rates), and variety (in terms of fields and types). For many applications, distributed NoSQL databases are effective alternatives to traditional relational database management systems. This paper considers a cyber situational awareness system that uses the Apache Accumulo database to provide scalable data warehousing, real-time data ingest, and responsive querying for human users and analytic algorithms. We evaluate Accumulo's ingestion scalability as a function of number of client processes and servers. We also describe a flexible data model with effective techniques for query planning and query batching to deliver responsive results. Query performance is evaluated in terms of latency of the client receiving initial result sets. Accumulo performance is measured on a database of up to 8 nodes using real cyber data.
Ultrafast polyene dynamics: the ring opening of 1,3-cyclohexadiene derivatives

The light activated ring-opening reaction of the 1,3-cyclohexadiene chromophore finds application in optical control, optical switching, optical memory, light activated molecular machines, photobiology, photochromic materials, and conformation-specific photocatalysts. The development of ultrafast spectroscopic methods and powerful computational methods have accelerated the understanding and facilitated the application of this important chromophore in a wide range of systems. Here we look at the current state of theoretical and experimental understanding for the ring-opening reaction of the isolated cyclohexadiene molecule and the ring-opening reactions of substituted cyclohexadienes, including fulgides, diarylethenes, and provitamin D.
Simulating the X-Ray Forest

Numerical simulations predict that a large number of baryons reside in intergalactic space at temperatures between 105 and 107 K. Highly ionized metals, such as O VII and O VIII, are good tracers of this "warm-hot intergalactic medium," or WHIM. For collisionally ionized gas, the ionization fraction of each ion peaks at some particular temperature ("peak temperatures"), so different ions can therefore trace the intergalactic medium (IGM) at different temperatures. We performed a hydrodynamic simulation to study the metal distributions in the IGM. We then draw random lines of sight across the simulated region and synthesize resonance absorption line spectra in a similar way to simulating the Lyα forest. By studying the distribution functions of H- and He-like O, Si, and Fe in a collisionally ionized IGM and comparing with semianalytic results based on the Press-Schechter formalism, we find the following: (1) ions with higher peak temperatures (e.g., Fe XXVI) tend to concentrate around virialized halos, which can be well described by the Press-Schechter distribution, and ions with lower peak temperatures are found both in small halos (such as groups of galaxies) and in filaments; (2) lower peak temperature ions are more abundant and should be easily observed; and (3) peculiar velocities contribute a significant part to the broadening of the resonant absorption lines.
Relaxation-compensated difference spin diffusion NMR for detecting 13C-13C long-range correlations in proteins and polysaccharides.

The measurement of long-range distances remains a challenge in solid-state NMR structure determination of biological macromolecules. In 2D and 3D correlation spectra of uniformly 13C-labeled biomolecules, inter-residue, inter-segmental, and intermolecular 13C–13C cross peaks that provide important long-range distance constraints for three-dimensional structures often overlap with short-range cross peaks that only reflect the covalent structure of the molecule. It is therefore desirable to develop new approaches to obtain spectra containing only long-range cross peaks. Here we show that a relaxation-compensated modification of the commonly used 2D 1H-driven spin diffusion (PDSD) experiment allows the clean detection of such long-range cross peaks. By adding a z-filter to keep the total z-period of the experiment constant, we compensate for 13C T1 relaxation. As a result, the difference spectrum between a long- and a scaled short-mixing time spectrum show only long-range correlation signals. We show that one- and two-bond cross peaks equalize within a few tens of milliseconds. Within ~200 ms, the intensity equilibrates within an amino acid residue and a monosaccharide to a value that reflects the number of spins in the local network. With T1 relaxation compensation, at longer mixing times, inter-residue and inter-segmental cross peaks increase in intensity whereas intra-segmental cross-peak intensities remain unchanged relative to each other and can all be subtracted out. Without relaxation compensation, the difference 2D spectra exhibit both negative and positive intensities due to heterogeneous T1 relaxation in most biomolecules, which can cause peak cancellation. We demonstrate this relaxation-compensated difference PDSD approach on amino acids, monosaccharides, a crystalline model peptide, a membrane-bound peptide and a plant cell wall sample. The resulting difference spectra yield clean multi-bond, inter-residue and intermolecular correlation peaks, which are often difficult to resolve in the parent 2D spectra.
Kinetic studies on the oxidation of cellulose and its model compounds by Mn(III)

Abstract Oxidation of cellulose and model compounds, including d -glucose, ethanol, 2,3-butanediol, and propanal in HClO 4 solutions with Mn(III) as an oxidant found to be of first order with respect to Mn(III). A general rate expression was derived to explain the effects of the reactant concentrations and the acidity, with the roles played by Mn 3+ , MnOH 2+ , and their complexes being taken into account. Rate and equilibrium constants were determined under simplified experimental conditions. From the relative rate constants of oxidation for the model compounds, the reaction sites of glucose have been deduced. Cellulose was oxidized by electrogenerated Mn(III), which acts as an electron transfer mediator for the reaction. Its oxidation products show a new IR band at 1729 cm −1 , which was assigned primarily to the ketone group produced during the oxidation.
Approximate solution to radiative transfer in two-dimensional cylindrical media

The development of an approximate solution to radiative transfer in two-dimensional, absorbing, emitting, scattering, cylindrical media is presented. The approach is based on an isolation of the discontinuities of the intensity prior to specifying the set of discrete ordinates. The discontinuities in the intensity or its slope at any point within the medium or at the bounding wall may be because of property variation along a bounding wall or at a corner, or the bounding geometry. The chosen set of discrete ordinates is based on Gaussian quadratures, and integrations are performed over solid angles over which the intensity is continuous and possesses continuous derivatives. Results for the incident radiation and radiative heat flux are presented for different physical configurations, and they are in good agreement with those available in the literature. In particular, approximately an order-of-magnitude fewer unknown intensities are involved in the solution to obtain results of accuracy comparable to the discrete-ordinates method.
The strength of ceramics bonded with metals

Abstract The strength of Al2O3 materials bonded using thin Pt layers is investigated. The measured strength levels are interpreted by conducting elastic/plastic stress analysis in conjunction with weakest link statistics. Comparisons between theory and experiment includes bond thickness effects, coupled with the role of interfacial flaws and the flow stress of the Pt.
A NEW CHIRAL TITANIUM SPECIES FOR THE RING OPENING REACTIONS OF MESO EPOXIDES

Abstract The synthesis of a new chiral ligand 1 based on the conformationally defined 1,7-dioxaspiro[5.5]undecane ring system is reported. Generation of the corresponding ligand 1 -Ti(OiPr) 4 complex as a catalyst and its use in the enantioselective ring opening reaction of cyclohexene oxide with TMSN 3 is described.
The radiation environment of the local interstellar medium

Abstract The heliosphere and the very local interstellar medium are closely connected. Understanding the photoionization of the Local Interstellar Cloud (LIC) is essential to both areas of study. The nature of the interstellar radiation field in the LIC is largely determined by the density, temperature and morphology of the local interstellar medium (LISM). The LISM is dominated by the large, low density region known as the Local Cavity or Local Bubble. Despite the low HI density extending 50–250 pc in all directions, no O stars have low enough absorption to contribute significantly to the ionizing radiation field in the LIC. The brightest stellar sources of ionizing radiation are two B stars ( ϵ CMa and β CMa) and several white dwarf stars. Most of the H ionizing photons, however, appear to be contributed by emission from the hot ( T ∼10 6 K) gas that fills the Local Bubble. An additional possible source is EUV emission generated at the interface of the hot gas and the LIC. Understanding the ionization of the LIC requires knowledge of the diffuse EUV radiation field, which remains very uncertain. I discuss the nature of all of these contributors to the radiation environment of local interstellar medium.
The Most Luminous Starbursts in the Universe

A summary of starburst luminosities based on polycyclic aromatic hydrocarbon (PAH) features is given for 243 starburst galaxies with 0 < z < 2.5, observed with the Spitzer Infrared Spectrograph. Luminosity ν Lν(7.7 μm) for the peak luminosity of the 7.7 μm PAH emission feature is found to scale as log [ ν Lν(7.7 μm) ] = 44.63(± 0.09) + 2.48(± 0.28) log (1 + z) for the most luminous starbursts observed. Empirical calibrations of ν Lν(7.7 μm) are used to determine bolometric luminosity LIR and the star formation rate (SFR) for these starbursts. The most luminous starbursts found in this sample have log LIR = 45.4(± 0.3) + 2.5(± 0.3) log (1 + z) , in ergs s−1, and the maximum star formation rates for starbursts in units of M☉ yr−1 are log (SFR) = 2.1(± 0.3) + 2.5(± 0.3) log (1 + z) , up to z = 2.5. The exponent for pure luminosity evolution agrees with optical and radio studies of starbursts but is flatter than previous results based in infrared source counts. The maximum star formation rates are similar to the maxima determined for submillimeter galaxies; the most luminous individual starburst included within the sample has log LIR = 46.9, which gives an SFR = 3.4 × 103 M☉ yr−1.
Location-allocation algorithms for land use plan design with fixed and substitutable interactions

Many attempts have been made to formalize the problem of designing land use plans (Brotchie, Sharpe, and Toakley [2], Gordon and MacReynolds [3], Karlqvist and Lundqvist [6], Mills [lo], Schlager [ 111, Southeastern Wisconsin Regional Planning Commission [El). Few of these have successfully handled the complexity of the real problem; none has handled this complexity for a problem of large size. This paper first formalizes as a mathematical program a complex version of the land use plan design problem. The formalized problem is of interest not only as a land use plan design model, but also as a general model for complex location-allocation problems that involve more than one type of spatial interaction. A realistic data set for a large land use problem is used to test alternative solution methods. Decomposition is required to handle large problems. The three solution methods presented are combinations of a particular decomposition approach and three different heuristic algorithms. 1. FORMALIZING THE LAND USE PLAN DESIGN PROBLEM
Mean Motion Resonances from Planet-Planet Scattering

Planet-planet scattering is the leading mechanism to explain the large eccentricities of the observed exoplanet population. However, scattering has not been considered important to the production of pairs of planets in mean motion resonances (MMRs). We present results from a large number of numerical simulations of dynamical instabilities in three-planet systems. We show that MMRs arise naturally in about 5% of cases. The most common resonances we populate are the 2:1 and 3:1 MMRs, although a wide variety of MMRs can occur, including high-order MMRs (up to 11th order). MMRs are generated preferentially in systems with uneven mass distributions: the smallest planet is typically ejected after a series of close encounters, leaving the remaining, more massive planets in resonance. The distribution of resonant planets is consistent with the phase-space density of resonant orbits, meaning that planets are randomly thrown into MMRs rather than being slowly pulled into them. It may be possible to distinguish between MMRs created by scattering versus convergent migration in a gaseous disk by considering planetary mass ratios: resonant pairs of planets beyond ~1 AU with more massive outer planets are likely to have formed by scattering. In addition, scattering may be responsible for pairs of planets in high-order MMRs (3:1 and higher) that are not easily populated by migration. The frequency of MMRs from scattering is comparable to the expected survival rate of MMRs in turbulent disks. Thus, planet-planet scattering is likely to be a major contributor to the population of resonant planets.
Effect of Acoustic Perturbations on Liquid Jet Atomization

The effect of unsteady chamber characteristics on the atomization process is investigated using nonlinear free-surface models based on boundary element methods. Two separate scenarios are considered. In the e rst case, a liquid column is subjected to transverse oscillations from the gas phase. The second calculation addresses dynamic orie ce mass e ow caused by the presence of longitudinal acoustic perturbations. Results indicate that the atomization process can be strongly affected by these perturbations. As expected, the most prominent coupling occurs at driving frequencies that are at (or near) the natural frequency of oscillation of the liquid. Nomenclature a = orie ce radius Im = modie ed Bessel function of the e rst kind, order m Km = modie ed Bessel function of the second kind, order m k = wave number n = mode number for column excitation, Eq. (5) P = pressure q = velocity normal to local surface r = radial coordinate t = time U = velocity We = Weber number, rgU 2 a/s = rU 2 a/s in Figs. 8 ‐ 12 x = horizontal coordinate y = vertical coordinate z = axial coordinate « = density ratio, rg/r k = surface curvature r = density s = surface tension f = velocity potential v = oscillation frequency Subscript g = gas phase Superscript ˆ = perturbation quantity
Smith-Purcell radiation from a 50 MeV beam

Abstract A 50 MeV electron beam and a 1 mm period, 5° blaze, echelle grating have been used to produce radiation in the mid-infrared spectral region. The emission is highly collimated and forward-directed. The intensity level in the few ps pulse (2 nJ/sr) indicates a degree of coherent enhancement.
Managerial Entrenchment and Payout Policy

Building on the managerial entrenchment literature, we develop and test a novel perspective on payout policy that integrates the influence of internal governance mechanisms, investment opportunities, management compensation, and monitoring by large shareholders. Our study incorporates both dividend payments and share repurchases, and examines the determinants of the likelihood and the level of payouts. Our model performs well in both in-sample and out-of-sample predictions on a sample of 2,081 firms during 1992–2000. We find that both the likelihood and the level of payouts are significantly and positively (negatively) related to factors that increase (decrease) executive entrenchment levels, even when controlling for size, leverage, and the proportion of tangible to total assets. We identify factors that significantly affect the likelihood but not the level of payouts (or vice versa), and show that entrenchment has an asymmetric influence on dividend vs. shares repurchase policy.
Unconstrained Spherical Parameterization

We introduce a novel approach for the construction of spherical parameterizations based on energy minimization. The energies are derived in a general manner from classic formulations well known in the planar parameterization setting (e.g., conformal, Tutte, area, stretch energies, etc.), based on the following principles: the energy should (1) be a measure of spherical triangles; (2) treat energies independently of the triangle location on the sphere; and (3) converge to the continuous energy from above under refinement. Based on these considerations, we give a very simple nonlinear modification of standard formulas that fulfills all these requirements. The method avoids the usual collapse of flat energies when they are transferred to the spherical setting without additional constraints (e.g., fixing three or more vertices). Our unconstrained energy minimization problem is amenable to the use of standard solvers. Consequently, the implementation effort is minimal while still achieving excellent robustness...
Acid-catalyzed conjugate additions to 3-fluorobutenone

3-Fluorobutenone (2) reacts under Zn(II) catalysis in ethanol solution with active methylene compounds such as anthrone and aromatic phenols to give products of the addition of one unit of 3-fluorobutenone.
Three pregnane-10,2-carbolactones from a sponge, Strongylophora sp.

Abstract Three pregnanes, 3,4-dihydroxypregna-5,17-diene-10,2-carbolactone (1), 3,4-dihydroxypregna-5,20-diene-10,2-carbolactone (2) and 3,4-dihydroxypregna-5,15-dien-20-one-10,2-carbolactone (3) were isolated from a sponge, Strongylophora sp. The structures were assigned on the basis of spectral data and confirmed by X-ray crystallography of 1.
Uniform minimal full-access networks

Abstract Minimal Full-Access (MFA) networks are the class of all interconnection networks for N = 2n inputs and outputs that require a minimum number of switching elements and provide full access capability. In this paper, MFA networks with 2 × 2 switching elements that use the same interconnection pattern between the stages are studied; such networks are called uniform MFA (UMFA) networks. Most of the known networks, including the Omega, the binary n-cube, and the regular (2, 2)-banyan, belong to this class. A graph-theoretic approach is used to study the class of UMFA networks, and a procedure is described to derive topologically nonequivalent networks from the Omega network. It is shown that the number of UMFA networks grow exponentially with N, and a lower bound of about 2N/32 is obtained for N ⩾ 32. We also outline an extension of our methods to derive similar bounds for networks using k × k switches, for k ⩾ 3.
Characterizations of metric trees and Gromov hyperbolic spaces

In this note we give new characterizations of metric trees and Gromov hyperbolic spaces and generalize recent results of Chatterji and Niblo. Our results have a purely metric character, however, their proofs involve two classical tools from analysis: Stokes' formula in $\R^2$ and a Rademacher type differentiation theorem for Lipschitz maps.
Irregular oscillations of the West Antarctic ice sheet

Model simulations of the West Antarctic ice sheet suggest that sporadic, perhaps chaotic, collapse (complete mobilization) of the ice sheet occurred throughout the past one million years. The irregular behaviour is due to the slow equilibration time of the distribution of basal till, which lubricates ice-sheet motion. This nonlinear response means that predictions of future collapse of the ice sheet in response to global warming must take into account its past history, and in particular whether the present basal till distribution predisposes the ice sheet towards rapid change.
UNIQUENESS OF REFLECTIONLESS JACOBI MATRICES AND THE DENISOV-RAKHMANOV THEOREM

If a Jacobi matrix J is reectionless on ( 2; 2) and has a single an0 equal to 1, then J is the free Jacobi matrix an 1, bn 0. I'll discuss this result and its generalization to arbitrary sets and present several applications, including the following: if a Jacobi matrix has some portion of its an's close to 1, then one assumption in the Denisov-Rakhmanov Theorem can be dropped.
Counting Colorings of a Regular Graph

At most how many (proper) q-colorings does a regular graph admit? Galvin and Tetali conjectured that among all n-vertex, d-regular graphs with 2d|n, none admits more q-colorings than the disjoint union of n/2d copies of the complete bipartite graph K d,d . In this note we give asymptotic evidence for this conjecture, showing that for each q ? 3 the number of proper q-colorings admitted by an n-vertex, d-regular graph is at most $$\begin{array}{ll}(q^2/4)^\frac{n}{2}\binom{q}{q/2}^\frac{n(1+o(1))}{2d} &{\rm if}\; q \; {\rm is}\; {\rm even}\\((q^2-1)/4)^\frac{n}{2}\binom{q+1}{(q+1)/2}^\frac{n(1+o(1))}{2d} & {\rm if}\; q\; {\rm is}\; {\rm odd,}\end{array}$$ ( q 2 / 4 ) n 2 q q / 2 n ( 1 + o ( 1 ) ) 2 d if q is even ( ( q 2 - 1 ) / 4 ) n 2 q + 1 ( q + 1 ) / 2 n ( 1 + o ( 1 ) ) 2 d if q is odd , where $${o(1)\rightarrow 0}$$ o ( 1 ) ? 0 as $${d \rightarrow \infty}$$ d ? ? ; these bounds agree up to the o(1) terms with the counts of q-colorings of n/2d copies of K d,d . Along the way we obtain an upper bound on the number of colorings of a regular graph in terms of its independence number. For example, we show that for all even q ? 4 and fixed ? > 0 there is $${\delta=\delta(\varepsilon,q)}$$ ? = ? ( ? , q ) such that the number of proper q-colorings admitted by an n-vertex, d-regular graph with no independent set of size $${n(1-\varepsilon)/2}$$ n ( 1 - ? ) / 2 is at most $$(q^2/4-\delta)^\frac{n}{2},$$ ( q 2 / 4 - ? ) n 2 , with an analogous result for odd q.
Peculiarities in low temperature properties of doped manganites A1-xBxMnO3

The phase diagram and low temperature properties of the doped manganites A1-xBxMnO3 are discussed for the concentrations $$x \le 0.4$$ . The transition from insulating antiferromagnetic to metallic ferromagnetic state at $${x_{cr}} \simeq 0.16$$ is treated by means of percolation theory. The unifying description of insulating and metallic states is presented. The undoped manganite is a band insulator consisting of ferromagnetic layers, which are coupled antiferromagnetically along the c direction with a low Neel temperature. The metallic phase can be described by the two-band Fermi liquid picture. The behavior of conductivity, spin wave excitations, etc. is analyzed and the comparison with experimental data is carried out.
Highly potent and selective chiral inhibitors of PDE5: An illustration of Pfeiffer’s rule

A series of potent chiral PDE5 inhibitors are described that are based on the sildenafil architecture but exhibit much greater selectivity over PDE6. Eudismic analysis of the SAR in this series provided a clear illustration of Pfeiffer's rule and indicated that the chiral motif was involved in a highly-stereoselective interaction with PDE5. This PDE5 specificity translated to levels of selectivity over PDE6 that were hitherto unprecedented in the sildenafil scaffold. UK-371,800 (compound 8) was identified as a development candidate from this series that married sildenafil-like molecular properties with high selectivity over PDE6. Clinical data confirm that UK-371,800 has markedly superior human pharmacokinetics to a previously-described higher molecular weight achiral analogue in this template (compound 1).
Impacts of programmable manufacturing technology: A review of recent studies and contingency formulation

This paper reviews the literature on the social impacts of programmable manufacturing technology (PMT). Several perspectives on the social impact of technology are identified ranging from simple additive models that view technology as having a set of individual and independent causal impacts to a contingency perspective which views the impact of technology as dependent on technical and organizational characteristics. The paper statistically summarizes 30 empirical studies within the 1986-1990 period and finds common trends in findings as well as contradictory evidence. The common trends are that PMT tends to lead to more organic organizations, but also meets with negative employee attitudes, stress, and perceptions of reduced job security and mobility. The contradictory evidence is that most studies report simple, additive effects, while a substantial portion find that the impacts depend on a wide range of contingency variables. The authors argue that simplistic views of PMT as being a homogeneous set of technologies with unidirectional, non-contingent social impacts is neither realistic nor useful. A number of future research directions in this area are suggested.
Supernovae, grains and the formation of the Solar System

An investigation is conducted concerning the possibility that observed Mg-26 anomalies in meteorites may be related to a nucleosynthetic event which preceded the formation of the solar system by at most a few million years. The Al-26, which decayed to form the observed excess Mg-26, could have been produced in either explosive carbon burning or in a high temperature carbon burning shell source immediately preceding the explosion. The results of supernova grain condensation calculations are presented and related to the hypothesis that a 'last event' supernova was indeed related to the formation of the solar system and thus might have created the observed isotopic anomalies in magnesium, oxygen, neon, and xenon.
The dipole picture in DIS: saturation and heavy quarks

We discuss the description of the proton structure function within the dipole factorization framework. We parameterize the forward dipole amplitude to account for saturation as predicted by the small-x QCD evolution equations. Contrarily to previous models, the saturation scale does not decrease when taking heavy quarks into account. We show that the same dipole amplitude also allows to reproduce diffractive data and exclusive vector meson production.
A Note on the Ultimatum Paradox, Bounded Rationality, and Uncertainty

The ultimatum game is a sequential-move bargaining game in which a giver offers a taker a share of a monetary pie. The predicted subgame perfect equilibrium in the ultimatum game is for purely rational givers who act in their own narrow self-interest to offer the smallest possible share of a monetary price, and for purely rational takers to accept. Experimental trials suggest, however, that givers make generous offers because they have a taste for fairness. The analysis presented in this paper argues that it is in the best interest of givers of any type to make offers that will not be rejected, and that offers become more generous as a giver’s uncertainty about the taker’s reservation offer increases.
Methods for investigating the strength characteristics of a lunar soil simulant

A lunar soil simulant was used in research on predicting the performance of the Lunar Roving Vehicle (LRV) on the moon. The simulant was prepared from ground basaltic rock whose grain size distribution was matched to the lunar soil samples collected by Apollo 11 and 12. The strength characteristics of the simulant, i.e., internal friction angle, cohesion, and cone penetration resistance, were tested in triaxial tests, trenching tests, and cone penetration resistance tests. Subsequent soil tests and LRV performance on the moon proved that the lunar soil strength characteristics could be successfully simulated.-
Deductive synthesis of sorting programs

Using the deductive synthesis framework developed by Manna and Waldinger we have derived a wide variety of recursive sorting programs. These derivations represent the first application of the deductive framework to the derivation of nontrivial algorithms. While the programs given were derived manually, we ultimately hope that a computer implementation of the system (of which none currently exists) will find similar programs automatically. Our derivations are intended to suggest this possibility; the proofs are short in relation to program complexity (on the order of 40 steps per program) and individual derivation steps are uncontrived. We also present a new rule for the generation of auxiliary procedures, a common ''eureka'' step in program construction.
Combustion response to compositional fluctuations

A mechanism involving compositional fluctuations at certain frequencies is examined by which the heterogeneity of a composite solid propellant may contribute directly to the combustion response function of combustion instability theory. A combustion model appropriate to ammonium perchlorate (AP) is used to derive the combustion response to compositional fluctuations, and the properties of the combustion response are discussed in terms of the theoretical results obtained. The concentration exponent, i.e., the dependence of the burn rate on AP concentration, is found to be a signficant combustion parameter and to have a tremendous range of variability. It is suggested that the combustion response to compositional fluctuations may be a dominating factor in driving combustion instability.
A Practical, Secure, and Verifiable Cloud Computing for Mobile Systems

Abstract Cloud computing systems, in which clients rent and share computing resources of third party platforms, have gained widespread use in recent years. Furthermore, cloud computing for mobile systems (i.e., systems in which the clients are mobile devices) have too been receiving considerable attention in technical literature. We propose a new method of delegating computations of resource-constrained mobile clients, in which multiple servers interact to construct an encrypted program known as garbled circuit. Next, using garbled inputs from a mobile client, another server executes this garbled circuit and returns the resulting garbled outputs. Our system assures privacy of the mobile client's data, even if the executing server chooses to collude with all but one of the other servers. We adapt the garbled circuit design of Beaver et al. and the secure multiparty computation protocol of Goldreich et al. for the purpose of building a secure cloud computing for mobile systems. Our method incorporates the novel use of the cryptographically secure pseudo random number generator of Blum et al. that enables the mobile client to efficiently retrieve the result of the computation, as well as to verify that the evaluator actually performed the computation. We analyze the server-side and client-side complexity of our system. Using real-world data, we evaluate our system for a privacy preserving search application that locates the nearest bank/ATM from the mobile client. We also measure the time taken to construct and evaluate the garbled circuit for varying number of servers, demonstrating the feasibility of our secure and verifiable cloud computing for mobile systems.