cssi/SciSciGPT-SciSciNet huggingface dataset:
Wide-Angle Wind-driven Bipolar Outflows: High-Resolution Models with Application to Source I of the Becklin-Neugebauer/Kleinmann-Low OMC-I Region

We carry out high-resolution simulations of the inner regions of a wide-angle wind-driven bipolar outflow using an adaptive mesh refinement code. Our code follows H-He gas with molecular, atomic, and ionic components and the associated time-dependent molecular chemistry and ionization dynamics with radiative cooling. Our simulations explore the nature of the outflow when a spherical wind expands into a rotating, collapsing envelope. We compare these with key observational properties of the outflow system of source I in the BN/KL region. Our calculations show that the wind evacuates a bipolar outflow cavity in the infalling envelope. We find the head of the outflow to be unstable and that it rapidly fragments into clumps. We resolve the dynamics of the strong shear layer, which defines the side walls of the cavity. We conjecture that this layer is the likely site of maser emission and examine its morphology and rotational properties. The shell of swept-up ambient gas that delineates the cavity edge retains its angular momentum. This rotation is roughly consistent with that observed in the source I SiO maser spots. The observed proper motions and line-of-sight velocity are approximately reproduced by the model. The cavity shell at the base of the flow assumes an X-shaped morphology that is also consistent with source I. We conclude that the wide opening angle of the outflow is evidence that a wide-angle wind drives the source I outflow and not a collimated jet.
A numerical method for the incompressible Navier-Stokes equations in three-dimensional cylindrical geometry

Abstract We describe a numerical method for solving the steady, three-dimensional, incompressible Navier-Stokes equations in cylindrical geometry. Also, we present results of computations in which this method is used to determine the flow in fluid-filled cylinders undergoing spinning and coning motion. Second-order accurate central finite difference formulas are used to approximate derivatives in the radial and axial directions and a Fourier method is used to approximate the angular derivatives. Nonuniform grids are used to improve the resolution of the velocity and pressure near the cylinder walls. The system of difference equations is solved using an iterative method based on successive-over-relaxation. The method has been found to be very efficient in terms of both computer time and storage. Results of the numerical method applied to the flow in spinning and coning cylinders are presented for several cases for which experimental data are available. In addition, perturbation methods are used to study the data at small coning speeds and small coning angles. Numerical results of this no-coning limit are compared with both the numerical data and experimental data at low coning conditions.
Optimal cover time for a graph-based coupon collector process

In this paper we study the following covering process defined over an arbitrary directed graph. Each node is initially uncovered and is assigned a random integer rank drawn from a suitable range. The process then proceeds in rounds. In each round, a uniformly random node is selected and its lowest-ranked uncovered outgoing neighbor, if such exists, is covered. We prove that if each node has in-degree @Q(d) and out-degree O(d), then with high probability, every node is covered within O(n+nlognd) rounds, matching a lower bound due to Alon. A special case of our result is that for any @Q(logn)-regular graph and a small rank range of @Q(logn), every node is covered within @Q(n) rounds. Alon has also shown that, for a certain class of d-regular expander graphs, the upper bound holds no matter what method is used to choose the uncovered neighbor. In contrast, we show that for arbitrary d-regular graphs, the method used to choose the uncovered neighbor can affect the cover time by more than a constant factor.
Hadrons in hot and dense matter

The description of excitations in hot and dense (hadronic) matter is discussed with emphasis on the use of correlation functions as a common framework for comparing different model (and QCD lattice) calculations with each other. Typical regimes of applicability of hadronic approaches are assessed, together with possibilities to confront them with experiment. We also elaborate on recent developments to relate baryonic in-medium effects to chiral-symmetry restoration.
Electrocatalysis of Anodic Oxygen Transfer Reactions: Comparison of Structural Data with Electrocatalytic Phenomena for Bismuth‐Doped Lead Dioxide

X‐ray structural data, evolution overpotentials , and rate constants are compared for anodic oxidation of Mn(II) and 2‐thiophene carboxylic acid (2‐TCA) at Bi‐doped in . It is concluded that the rutile structure of pure deposited anodically from containing Pb(II) is retained even as the Bi(III) content is increased to , i.e., mole fraction . There is no evidence of a new oxide phase being formed. Crystallites of the are deposited with an increasing preferential orientation of the 020‐plane parallel to the Au substrate surface as the ratio Bi/Pb is increased. Increasing values of and decreasing values of appear to be correlated with the increased preferential orientation. However, change in preferential orientation is concluded not to be the primary determining factor in the electrocatalytic phenomena. The kinetic results are discussed also on the basis of the so‐called "volcano plot" of as a function of the enthalpy of transition between the two highest oxide phases for metal oxide electrodes.
Long-Run Stock Returns Following Briloff's Analyses

Abraham Briloff is well known for more than four decades of insightful analysis and criticism of the accounting practices of various companies. His critiques, in the form of articles published in Barron's, consist of detailed financial analyses of the questionable accounting practices of the companies he examines. Previous research has shown that the companies criticized by Briloff in Barron's experience significant negative abnormal returns around the article's publication date. To understand the valuation effect associated with his financial analyses, this article examines long-run abnormal returns following the publication date. In addition to the initial negative reaction on publication of the articles, the companies in the sample experienced further significant risk-adjusted returns for one and two years of, respectively, −15.51 percent and −22.88 percent. The results show that a decline in future operating performance appears to be an important reason for the poor stock market performance of the com...
Substrate control of diastereoselectivity in zirconium (II) mediated enyne cyclizations

Abstract The reductive cyclization of an extensive series of chiral enynes by Cp 2 Zr(II) complexes has been examined. In most instances excellent substrate control of cyclization stereochemistry was observed.
The intramolecular Diels-Alder cycloaddition of N-dienoyl acrylimidates. New methodology for the construction of nitrogen heterocycles.

Abstract N-(3,5-Hexadienoyl)-acrylimidates, which have been synthesized by acylation of 2-ethoxy-1-aza-1,3-butadienes with 3,5-hexadienoyl chloride, are found to undergo facile Intramolecular Diels-Alder cycloadditions to afford predominately cis -hexahydroisoquinolines in good yields.
Gravitational Lensing by Spiral Galaxies

We study gravitational lensing by spiral galaxies, using realistic models consisting of halo, disk, and bulge components combined to produce a flat rotation curve. Proper dynamical normalization of the models is critical because a disk has less (projected) mass than does a spherical halo with the same rotation curve—a face-on Mestel disk has a lensing cross section only 41% as large as that of a comparable singular isothermal sphere. Lensing cross sections are sensitive to inclination and are dominated by edge-on galaxies that, if very flattened, produce a large number of lenses with an unobserved image geometry consisting of 2 or 3 images off to one side of the galaxy center and straddling the projected disk. The absence of this "disk" image geometry among known lenses suggests that lens galaxies cannot be highly flattened. When averaged over inclination, disk+halo models predict 10% more lenses than do pure halo models, except in cases in which the disk is unreasonably massive, so including a disk does not significantly increase the expected number of spiral galaxy lenses. Models with an exponential disk and a central bulge are sensitive to the properties of the bulge. In particular, an exponential disk model normalized to our Galaxy but without a bulge cannot produce multiple images, and including a bulge reduces the net flattening of edge-on galaxies. The dependence of the lensing properties on the masses and shapes of the halo, disk, and bulge means that a sample of spiral galaxy lenses would provide useful constraints on galactic structure.
The Economics of Poverty Traps Part One: Complete Markets

This paper lists theoretical reasons why neoclassical models of one-sector growth imply that nations with identical economic structures need not converge to the same steady state or balanced growth path, and outlines the empirical significance and policy implications of conditional nonconvergence. We survey poverty traps in both convex and nonconvex economies with complete market structures. Among the potential causes of traps are subsistence consumption; distorted international trade in intermediate inputs; demographic transitions when fertility is endogenous; technological complementarities in the production of consumption goods, financial intermediation services, manufactures, or human capital; coordination failures among voters; various restrictions on borrowing; indivisibilities in human capital formation or child rearing; and monopolistic competition in product or factor markets.
A new iron(III)-salen catalyst for enantioselective Conia-ene carbocyclization.

A chiral iron(III)–salen complex based on a cis-2,5-diaminobicyclo[2.2.2]octane scaffold catalyzes asymmetric Conia-ene-type cyclization of α-functionalized ketones containing an unactivated terminal alkyne and produces an exo-methylenecycloalkane possessing a stereodefined quaternary center.
A simple derivation of the Gompertz law for human mortality

The Gompertz law of dependence of human mortality rate on age is derived from a simple model of death as a result of an exponentially rare escape of abnormal cells from immunological response.
A Gated Radiometer for Plasma Afterglow Study

In order to monitor the electron temperature during plasma afterglow experiments, a gated microwave radiometer has been developed. The radiometer differs from the usual Dicke type of radiometer in the input switching scheme and in the fact that a good time resolution is required. The radiometer to be described has a time resolution of one microsecond and a temperature sensitivity of about ten degrees Kelvin when measuring temperatures near room temperature. The response time when used with a repetitive afterglow is 20 seconds. Measurements of electron temperature in a decaying nitrogen plasma have been made duirng the initial 300 microseconds of the afterglow.
Computational geometry column 46

The old problem of determining the chromatic number of the plane is revisited.The question of the chromatic number of the Euclidean plane E2 has been unresolved for over fifty years. Informally, the question asks: How many colors are needed to paint the plane so that no two points a unit distance apart are painted the same color? If the same question is asked of the line, the answer is 2: Coloring [0,1) red, [1,2) blue, etc., ensures that no two unit-separated points have the same color. Here I report on a few new developments, and some related open problems that are perhaps easier.One can view the question as asking for the chromatic number X(E2) of the infinite unit-distance graph G, with every point in the plane a node, and an are between two nodes if they are separated by a unit distance. Erdos and de Bruijn showed [EdB51] that the chromatic number of the plane is attained for some finite subgraph of G. This result led to narrowing the answer to 4 ≤ X(E2) ≤7. For example, the lower bound of 4 is established by the "Moser graph" shown in Fig. 1, which needs 4 colors.
A portfolio balance model of the open economy

This paper develops a framework in which to investigate the effects of macroeconomic policies. The key building blocks are those of Metzler (1968, 1973) in the form of a wealth saving relation and the emphasis on portfolio considerations; the model in its dynamic aspects is extended in a manner suggested in the work of Foley/Sidrauski (1971) and Mussa (1973), where the asset accumulation implied by short-run equilibrium is pursued over time. A large body of literature on the implications of asset mobility for macroeconomic policy has been accumulated during the last decade. Following the work of Mundeli (1968) on capital mobility and the policy mix, that literature has primarily taken a perspective of stabilization policy and therefore espoused a shortrun view of the economy in describing it in terms of the IS-LM model – more or less appropriately modified – to accommodate the openness of the economy and the mobility of assets.1 Alternative routes with a longer time perspective, though still maintaining the assumption of a perfectly elastic supply of output at current prices, have been offered by McKinnon (1969), Tower (1972) and Branson (1972). The approach taken here assumes flexibility of relative prices, full employment and continuous market clearing, thereby assuming away a host of interesting short-run problems and substituting a set of issues that center on the time path of the economy, the endogeneity of asset supplies and the long-run effects of policies. In sections 2 and 3 of this paper the basic model and its equilibrium properties are developed. Section 4 considers three applications of the model, and in section 5 some observations on possible extensions and limitations of the model are offered. (This abstract was borrowed from another version of this item.)
Electrochemically Active Polymers for Electrochemical Energy Storage: Opportunities and Challenges

Polymers have a particularly important place in electrochemical energy storage (EES), not just as the electrolyte, as has been a large focus for solid-state batteries, but also as the electrode. This Viewpoint will introduce how electrochemically active polymers (EAPs) are utilized in electrochemical energy storage with an emphasis on battery cathodes. Recent advances in high capacity EAPs and selected challenges (high voltage stability and ion transport) are presented. Should these needs be met, the resulting electrode would bear a high capacity, energy, power, and cycle life. The low cost, potential application in flexible EES, and synthetic versatility of EAPs offer many unique aspects relative to conventional metal oxides. In composites with metal oxides, EAPs can be used as a means to boost ionic and electronic conductivity. Promising examples regarding high capacity polymeric sulfur electrodes, electrochemically stable polyaniline/polyacid complexes, porous polyaniline/V2O5 electrodes, and hydrogel-...
Threshold graphs, shifted complexes, and graphical complexes

We consider a variety of connections between threshold graphs, shifted complexes, and simplicial complexes naturally formed from a graph. These graphical complexes include the independent set, neighborhood, and dominance complexes. We present a number of structural results and relations among them including new characterizations of the class of threshold graphs.
Automatic Generation of Executable Communication Specifications from Parallel Applications

Portable parallel benchmarks are widely used and highly effective for (a) the evaluation, analysis and procurement of high-performance computing (HPC) systems and (b) quantifying the potential benefits of porting applications for new hardware platforms. Yet, past techniques to synthetically parametrized hand-coded HPC benchmarks prove insufficient for today's rapidly-evolving scientific codes particularly when subject to multi-scale science modeling or when utilizing domain-specific libraries. To address these problems, this work contributes novel methods to automatically generate highly portable and customizable communication benchmarks from HPC applications. We utilize ScalaTrace, a lossless, yet scalable, parallel application tracing framework to collect selected aspects of the run-time behavior of HPC applications. We subsequently generate benchmarks with identical run-time behavior from the collected traces in the CONCEPTUAL language, a domain-specific language that enables the expression of sophisticated communication patterns using a rich and easily understandable grammar yet compiles to ordinary C+MPI. Experimental results demonstrate that the generated benchmarks are able to preserve the run-time behavior of the original applications. This ability to automatically generate performance-accurate benchmarks from parallel applications is novel and without any precedence, to our knowledge.
The changing role of the state in the economy : a historical perspective

This paper discusses the role of the state from a historical perspective. It outlines how that role has changed over the past hundred years and discusses the forces that have promoted the changes. In the period between 1913 and 1980, there was a large increase in public spending in industrial countries and a considerable expansion in the role of the government in the economy in all countries. The paper also outlines the intellectual developments that, starting in the 1970s, have brought about a reaction to the large role that the state has come to play in the economy.
Communication Lower Bounds Using Directional Derivatives

We study the set disjointness problem in the most powerful model of bounded-error communication, the k-party randomized number-on-the-forehead model. We show that set disjointness requires Ω(√n/2kk) bits of communication, where n is the size of the universe. Our lower bound generalizes to quantum communication, where it is essentially optimal. Proving this bound was a longstanding open problem even in restricted settings, such as one-way classical protocols with k=4 parties [Wigderson 1997]. The proof contributes a novel technique for lower bounds on multiparty communication, based on directional derivatives of protocols over the reals.
Characteristics of Drivers Not Using Seat Belts in a High Belt Use State

Abstract A study was undertaken in North Carolina to determine the characteristics of the minority of drivers who were not using seat belts following an extensive publicity/enforcement campaign, which had increased statewide use to 80%. Vehicles and drivers whose seat belt use was observed at sites across North Carolina were matched against Division of Motor Vehicles registration and driver history files for vehicle owners. The study file consisted of those observed drivers who matched the owners with respect to sex, race, and approximate age. The results of this investigation indicate that nonuse of seat belts was associated with males; younger age (
When Does Lack of Resources Make New Firms Innovative

We extend the resource-based perspective to explain innovation in new firms that have yet to develop resources. Using data on firms' efforts to commercialize technological inventions, we tested a m...
International DSM and DSM program evaluation: An indeep assessment☆

Abstract We discuss the current level of demand-side management (DSM) occurring in selected European countries and review the availability of information on DSM programs and program evaluation. Thirteen European DSM programs are compared by examining such factors as motivations for program implementation, marketing methods, participation rates, total energy savings and program costs. The transfer of DSM program results and experiences found in these case studies is also discussed, as well as the lessons learned during the design, implementation and evaluation of these programs. We find that these programs represent cost-effective resources and expect that these types of DSM programs will be useful for utilities and governments in emerging utility competition and restructuring, for both energy and non-energy reasons.
Thermotropic biaxial nematic liquid crystals.

We have synthesized liquid crystal (LC) mesogens based on a nonlinear oxadiazole unit that exhibit nematic phases near $200\text{ }\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$. Polarized microscopy and conoscopy indicate that these LCs are biaxial nematics. Unambiguous and quantitative evidence for biaxiality is achieved using $^{2}\mathrm{H}$ NMR spectroscopy. ``2D powder'' spectra, obtained by rotating $^{2}\mathrm{H}$-labeled samples about an axis perpendicular to the magnetic field at $\ensuremath{\sim}200\text{ }\text{ }\mathrm{Hz}$, yield phase biaxiality parameters of $\ensuremath{\sim}0.1$ when coupled with rigorous and proven simulations.
ECONOMICS OF NUCLEAR POWER

Publisher Summary This chapter discusses the general aspects of technological innovations and their criteria of introduction and also discusses some of the specific technological, organizational, and political factors that set nuclear power development apart from the problems encountered in the launching of other new products. The chapter further discusses the future development of conventional power as it affects the prospects of atomic energy and identifies the areas in nuclear power in which the major improvements may be expected. The results are undoubtedly favorable to much more extensive use of atomic power. Nuclear power must necessarily undergo that filtering mechanism that allows only few innovations to become commercial products. This mechanism of selection has a powerful economic component, which depends upon the interpretations of the cost structure made by the builder of the equipment. The prices for nuclear materials and processing services are established by government fiat. The commercial future of nuclear power will depend on the cost differential between it and conventional power.
A Philosophy of Management

Presents a condensed statement of the basis of management philosophy. Obligation of private enterprises emphasized by the philosophy; Information on the philosophy of conservatism; How the philosop...
Abstract Inference Structures to Support Variable Rule Structures for Expert Systems

Knowledge‐based systems have been successfully utilised in the develop‐ment of complex systems. In many cases, these systems have emphasised the need for techniques to integrate knowledge‐based processing with methods for managing both large amounts of data and knowledge. However, many potential applications for expert systems are precluded by limitations in the ability of conventional expert system technology to function in conjunction with data systems without manual intervention. The author focuses on the integration of knowledge‐bases and databases with the capability to: store and context select between parallel, competing expert system rule structures; cascade variable rule structures; allow an expert system to be interrupted and to be subsequently restarted by storing the state of the inference engine; handle simple data storage and retrieval.
Crisis in Infectious Diseases: Time for a New Paradigm?

Current practices in the treatment of infectious diseases are the result of two fundamental changes in antimicrobial therapy that occurred in the mid-20th century : the transition from pathogen-specific therapy to non-pathogen-specific therapy and the shift toward emphasis on antiinfective strategies that target microbial pathogens over those that enhance host immunity. The alarming rise in antimicrobial-resistant strains, the increasing frequency of serious infections in immunocompromised patients, and the paucity of new types of antibiotics suggest the need for reevaluation of the manner in which infections are treated. In the short term, the situation may be addressed-at least in part-by increased emphasis on improved diagnosis and, when possible, the use of specific or narrow-spectrum treatments. In the long term, a return to pathogen-specific therapy, possibly in combination with adjunctive immunotherapy, may be an attractive and desirable option provided that significant advances are made in diagnostic microbiology and drug discovery.
On diamond windows for high power synchrotron X-ray beams

Abstract Recent advances in chemical vapor deposition (CVD) technology have made available thin, free-standing polycrystalline diamond foils that can be used as the window material on high heat load synchrotron X-ray beamlines. Diamond windows have many advantages that stem from the exceptionally attractive thermal, structural, and physical properties of diamond. Numerical simulations indicate that diamond windows can offer an attractive and at times the only alternative to beryllium windows for use on the third generation X-ray synchrotron radiation beamlines. Utilization, design, and fabrication aspects of diamond windows for high heat load X-ray beamlines are discussed, and analytical and numerical results are presented to provide a basis for the design and testing of such windows.
Detection of multiple faults using SSFTS in CMOS logic circuits

Abstract With the increasing density of CMOS VLSI circuits, it is necessary to test for the combinations of different multiple faults. This paper studies the possibility of using single stuck-at fault test set (SSFTS) to detect multiple faults and their combinations. The paper shows that a single stuck-at-fault test set can detect single and multiple self-feedback bridging faults, combinations of feedback bridging, input bridging and stuck-on faults when current monitoring is done. We also prove that a single stuck-at fault test set can detect the combination of single stuck-open fault and some other faults like bridging and stuck-on faults when both logic and current monitoring are done.
Quantification of model-form uncertainty in the correlated-k distribution method for radiation heat transfer

Abstract The full-spectrum correlated- k distribution method has been shown to be exact for thermal radiation in molecular gas-particulate mixtures which obey the correlation assumption. Unfortunately, this assumption breaks down for molecular gases with strong temperature or concentration gradients. There has previously been no way to effectively quantify the model-form uncertainty introduced by the failure of the correlation assumption. This paper examines the effect of temperature gradients in CO 2 and proposes a technique to generate probability density functions for the gray-gas absorption coefficients used in the full-spectrum correlated- k distribution method. The uncertainty in the absorption coefficients may then be propagated forward to ascertain confidence intervals for important quantities such as heat flux or intensity distributions.
Excited glue and the vibrating flux tube

Abstract Recent lattice results for the energy of gluonic excitations as a function of quark separation are shown to correspond to transverse relativistic flux tube vibration modes. For large quark separations all states appear to degenerate into a few categories which are predicted uniquely, given the ground state.
Designing new isomorphic fluorescent nucleobase analogues: the thieno[3,2-d]pyrimidine core

A convergent approach for a family of fluorescent nucleosides is described. It relies on thieno[3,2-d]pyrimidine-2,4(1H,3H)-dione that serves as a core heterocycle. This condensed pyrimidine is converted into an emissive pyrimidine nucleoside analogue by N-glycosylation and into an emissive purine nucleoside analogue by C-glycosidation at the thiophene's beta position. The design principles of this archetypical system are outlined together with the syntheses and photophysical properties of the resulting nucleosides.
A concise synthesis of enantiomerically pure taxane C-ring via the [2,3] wittig rearrangement

Abstract An efficient, stereoselective synthesis of an enantiomerically pure C-ring precursor 14-S of O-cinnamoyltaxicins-I and -II has been achieved from 3-methyl-2-cyclohexen-1-ol, using a [2,3] Wittig rearrangement as the key step.
A New Model for Boundary Layer Transition Using a Single-Point RANS Approach

This paper presents the development and implementation of a new model for bypass and natural transition prediction using Reynolds-averaged Navier-Stokes computational fluid dynamics (CFD), based on modification of two-equation, linear eddy-viscosity turbulence models. The new model is developed herein based on considerations of the universal character of transitional boundary layers that have recently been documented in the open literature, and implemented into a popular commercial CFD code (FLUENT) in order to assess its performance. Two transitional test cases are presented: (1) a boundary layer developing on a flat heated wall, with free-stream turbulence intensity (Tu∞) ranging from 0.2 to 6%; and (2) flow over a turbine stator vane, with chord Reynolds number 2.3 × 10 5 , and Tu∞ from 0.6 to 20%. Results are presented in terms of Stanton number, and compared to experimental data for both cases. Results show good agreement with the test cases and suggest that the new approach has potential as a predictive tool.
Wilson loop renormalization group flows

The locally BPS Wilson loop and the pure gauge Wilson loop map under AdS/CFT duality to string world-sheet boundaries with standard and alternate quantizations of the world-sheet fields. This implies an RG flow between the two operators, which we verify at weak coupling. Many additional loop operators exist at strong coupling, with a rich pattern of RG flows.
The Shapes of Galaxies in the Sloan Digital Sky Survey

We estimate the distribution of apparent axis ratios q for galaxies in the Sloan Digital Sky Survey Early Data Release. We divide the galaxies by profile type (de Vaucouleurs vs. exponential) as well as by color (u* - r* ≤ 2.22 vs. u* - r* > 2.22). The axis ratios found by fitting models to the surface photometry are generally smaller than those found by taking the second moments of the surface brightness distribution. Using the axis ratios found from fitting models, we find that galaxies with de Vaucouleurs profiles have axis ratio distributions that are inconsistent, at the 99% confidence level, with their being a population of randomly oriented oblate spheroids. Red de Vaucouleurs galaxies are slightly rounder, on average, than blue de Vaucouleurs galaxies. By contrast, red galaxies with exponential profiles appear very much flatter, on average, than blue galaxies with exponential profiles. The red exponential galaxies are primarily disk galaxies seen nearly edge-on, with reddening due to the presence of dust, rather than to an intrinsically red stellar population.
Automated synthesis of asynchronous interface circuits

Abstract This paper describes a design methodology for asynchronous interface circuits through an example, a VMEbus master interface. The circuit and the environment where it operates are described using a formalization of timing diagrams, the signal transition graph. A standard cell implementation of the circuit is automatically derived from the specification. Then the implementation is automatically analysed for potential hazards, and information on the internal gate delays and external environment delays is used to verify that the circuit is hazard-free. If such hazard verification fails (e.g. due to tolerances in the delay information), then delay buffers are automatically inserted, producing a hazard-free, albeit slower, circuit.
Steady-state ab initio laser theory for N-level lasers

We show that Steady-state Ab initio Laser Theory (SALT) can be applied to find the stationary multimode lasing properties of an N-level laser. This is achieved by mapping the N-level rate equations to an effective two-level model of the type solved by the SALT algorithm. This mapping yields excellent agreement with more computationally demanding N-level time domain solutions for the steady state.
The Light-Front Vacuum and Dynamics

I give a quantum-theoretical description of kinematically invariant vacuua on the algebra of free fields restricted to a light front and discuss the relation between the light-front Hamiltonian, P−, the vacuum, and Poincare invariance. This provides a quantum-theoretical description of zero modes.
Shapes of polyhedra and triangulations of the sphere

The space of shapes of a polyhedron with given total angles less than 2\pi at each of its n vertices has a Kaehler metric, locally isometric to complex hyperbolic space CH^{n-3}. The metric is not complete: collisions between vertices take place a finite distance from a nonsingular point. The metric completion is a complex hyperbolic cone-manifold. In some interesting special cases, the metric completion is an orbifold. The concrete description of these spaces of shapes gives information about the combinatorial classification of triangulations of the sphere with no more than 6 triangles at a vertex.
Square function/non-tangential maximal function estimates and the Dirichlet problem for non-symmetric elliptic operators

A. We consider divergence form elliptic operators L = − div A(x)∇, defined in the half space Rn+1 + , n ≥ 2, where the coefficient matrix A(x) is bounded, measurable, uniformly elliptic, t-independent, and not necessarily symmetric. We establish square function/non-tangential maximal function estimates for solutions of the homogeneous equation Lu = 0, and we then combine these estimates with the method of “!-approximability” to show that L-harmonic measure is absolutely continuous with respect to surface measure (i.e., n-dimensional Lebesgue measure) on the boundary, in a scale-invariant sense: more precisely, that it belongs to the class A∞ with respect to surface measure (equivalently, that the Dirichlet problem is solvable with data in Lp, for some p < ∞). Previously, these results had been known only in the case n = 1.
Approximation Algorithms for Degree-Constrained Minimum-Cost Network-Design Problems

We study network-design problems with two different design objectives: the total cost of the edges and nodes in the network and the maximum degree of any node in the network. A prototypical example is the degree-constrained node-weighted Steiner tree problem: We are given an undirected graph G(V,E), with a non-negative integral function d that specifies an upper bound d(v) on the degree of each vertex v∈V in the Steiner tree to be constructed, nonnegative costs on the nodes, and a subset of k nodes called terminals. The goal is to construct a Steiner tree T containing all the terminals such that the degree of any node v in T is at most the specified upper bound d(v) and the total cost of the nodes in T is minimum. Our main result is a bicriteria approximation algorithm whose output is approximate in terms of both the degree and cost criteria—the degree of any node v∈V in the output Steiner tree is O(d(v)log k) and the cost of the tree is O(log k) times that of a minimum-cost Steiner tree that obeys the degree bound d(v) for each node v. Our result extends to the more general problem of constructing one-connected networks such as generalized Steiner forests. We also consider the special case in which the edge costs obey the triangle inequality and present simple approximation algorithms with better performance guarantees.
Molecular Theory of Rubber Elasticity

Once the existence of polymer chains as covalent structures became established a half century ago, the understanding of the molecular basis of the high elasticity characteristic of rubber-like substances presented itself as a foremost challenge. The first attempts1, 2 to explain this remarkable property may be said to date from the beginning of molecular theory as applied to polymers. Although the subject today is old, it is of continuing interest and one in which much remains to be done before an acceptable state of completion will have been attained.
Asymmetric Cell Kinetics Genes: The Key to Expansion of Adult Stem Cells in Culture

A singular challenge in stem cell research today is the expansion and propagation of functional adult stem cells. Unlike embryonic stem cells, which are immortal in culture, adult stem cells are notorious for the difficulty encountered when attempts are made to expand them in culture. One overlooked reason for this difficulty may be the inherent asymmetric cell kinetics of stem cells in postnatal somatic tissues. Senescence is the expected fate of a culture whose growth depends on adult stem cells that divide with asymmetric cell kinetics. Therefore, the bioengineering of strategies to expand adult stem cells in culture requires knowledge of cellular mechanisms that control asymmetric cell kinetics. The properties of several genes recently implicated to function in a cellular pathway(s) that regulates asymmetric cell kinetics are discussed. Understanding the function of these genes in asymmetric cell kinetics mechanisms may be the key that unlocks the adult stem cell expansion problem.
A preparation of 3-aryl-2,5-dihydrothiophene-1,1-dioxides from aryl iodides

Abstract As part of our synthetic program we sought an efficient preparation of 1-aryl-4-substituted-1-cyclohexenes that would provide flexibility in both the nature of the aryl and cyclohexenyl substituents. An ideal approach would involve [4+2] cycloaddition if a versatile synthesis of the requisite 2-aryl-1,3-butadienes were available. Several syntheses of 2-phenyl-1,3-butadiene have been reported. There are two general approaches: 1) classical methods involved a pyrolysis of an alcohol or alcohol derivative as a final step [1,2]; 2) more recent methods utilize a transition metal-mediated coupling of a preformed diene [3,4]. The coupling with chloroprene grignard [3] would appear to provide greatest flexibility. However, prompted by the low catalyst activity with aryl halides as well as the probable carcinogenicity and cost of chloroprene, we sought a more convenient method.
Tu lui les as donnés ? Variation dans l'ordre des pronoms multiples en phrases déclaratives

Tuaillon (1983) claims that variation in the order of third-person multiple object pronouns is a “clear regionalism” from the lower Rhone valley. To investigate this phenomenon in Briancon, a small town in southeastern France, 41 participants from this area filled out an acceptability judgment questionnaire, evaluating sentences with such pronouns in different orders. The results of statistical tests show that, even though participants prefer the standard French order, they also accept the reversed order (standard ‘le lui’ vs. reversed ‘lui le’). The analysis also suggests a change in apparent time (which seems to coincide with economic and social changes in the region since WWII) as well as age grading.
Optimal Conjunctive Use of Surface and Groundwater with Recharge and Return Flows: Dynamic and Spatial Patterns

This paper derives the efficiency price patterns for a comprehensive spatial and dynamic model of conjunctive water use incorporating conveyance losses, canal return flows, and groundwater recharge. The first-best shadow price of surface water is composed of a charge for water that flows into the farm and differential credits for water that flows to other uses. The shadow prices can be used as the basis of water pricing schemes or for exchange rates to facilitate water trading. We show that farmers near the headworks use irrigation water in the optimal program, and only farmers more distant from the headworks extract groundwater. We also illustrate the possibility of reswitching in the sequence of resource use. It may be efficient for some farms to switch from one source to another and then switch back again, e.g. groundwater to surface water to groundwater.
Understanding the impact of churn in dynamic oligopoly markets

We incorporate the effects of churn, which refers to customers switching to competing brands, in a dynamic model of advertising for oligopoly markets. Each firm's market share depends not only on its own and competitors' advertising decisions, but also on market churn. Applying differential game theory, we derive a feedback Nash equilibrium under symmetric and asymmetric competition. We obtain explicit solutions and discover the counter-intuitive result that, as market churn increases, firms should decrease advertising rather than increase it to counteract the impact of churn.
Rhapsamine, a Cytotoxin from the Antarctic Sponge Leucetta leptorhapsis

Abstract Bioassay guided fractionation of the cytotoxic crude extract from the antarctic sponge Leucetta leptorhapsis has resulted in the isolation of rhapsamine ( 1 ), a linear C28 polyene terminally substituted by 1,3-diaminoglycerol groups. © 1997 Elsevier Science Ltd.
Offset-polygon annulus placement problems

The @d-annulus of a polygon P is the closed region containing all points in the plane at distance at most @d from the boundary of P. An inner (resp., outer) @d-offset polygon is the polygon defined by the inner (resp., outer) boundary of its @d-annulus. In this paper we address three major problems of covering a given point set S by an offset version or a polygonal annulus of a polygon P. First, the Maximum Cover objective is, given a value of @d, to cover as many points from S as possible by the @d-offset (or by the @d-annulus) of P, allowing translation and rotation. Second, the Containment problem is to minimize the value of @d such that there is a rigid transformation of the @d-offset (or the @d-annulus) of P that covers all points from S. Third, in the Partial Containment problem we seek the minimum offset of P covering k=<|S| points. These problems arise in many applications where one needs to match a given polygonal figure (a known model) to a set of points (usually, obtained measures). We address several variants of these problems, including convex and simple polygons, as well as polygons with holes and sets of polygons, and obtain algorithms with low-degree polynomial running times in all cases.
The specification of visual language syntax

Visual programming languages use pictures as programs. One approach to building a visual programming environment is to parameterize a generic environment with a language specification. We describe a mechanism for specifying visual languages that can be used as the basis of a language-independent visual programming environment. Our mechanism is a new type of grammar, called a picture layout grammar. We show how this type of grammar can describe the two-dimensional syntax of a visual language and give an example of its use. A picture layout grammar permits the syntactic structure of visual program to be recovered by parsing. The parsing ability provides the basis of our visual programming environment.
Megakaryocytes derived from human embryonic stem cells: a genetically tractable system to study megakaryocytopoiesis and integrin function.

Summary. Background: The platelet fibrinogen receptor, a heterodimer consisting of integrin subunits αIIb and β3, is required for platelet aggregation, spreading, and hemostasis. Platelet agonists such as thrombin and adenosine diphosphate (ADP) lead to the activation of αIIbβ3, thereby enhancing its affinity and avidity for binding fibrinogen (inside-out signaling). Furthermore, fibrinogen binding to αIIbβ3 triggers cytoskeletal changes and granule release (outside-in signaling).Aim: Genetic approaches to characterize the molecular pathways involved in αIIbβ3 signaling are not possible with anucleate blood platelets. Therefore, we have established an OP9 stromal cell co-culture system to generate megakaryocytes from human embryonic stem cells (hESCs).Results: αIIbβ3 activation, measured by soluble fibrinogen binding to hESC-derived megakaryocytes, /GPIbα+ cells, is readily detectable following stimulation with known platelet agonists. Dose–response curves for peptide agonists specific for the two platelet thrombin receptors, protease-activated receptor 1 (PAR1) and PAR4, show a relative responsiveness that mirrors that of human platelets, and sub-maximal ADP responses are augmented by epinephrine. Moreover, hESC-derived megakaryocytes undergo lamellipodia formation, actin filament assembly, and vinculin localization at focal adhesions when plated on a fibrinogen-coated surface, characteristic of αIIbβ3 outside-in signaling. Undifferentiated hESCs genetically modified by lentiviral infection can be cloned and maintained in an undifferentiated state and then differentiated into megakaryocytes capable of αIIbβ3 activation.Conclusion: Using hESCs, we have developed a renewable source of human megakaryocytes, and a genetically tractable system for studying megakaryocytopoiesis and αIIbβ3 signaling in the native cellular environment.
Surface roughness studies with DALLAS-detector array for laser light angular scattering

An instrument has been developed to study surface roughness by measuring the angular distributions of scattered light. In our instrument, a beam from a He-Ne laser illuminates the surface at an angle of incidence which may be varied. The scattered li,.ght'distribution is detected by an array of 87 fiber optic sensors positioned in a semicircular yoke which can be rotated about its axis so that the scattered radiation may be sampled over an entire hemisphere. The output from the detector array is digitized, stored, and analyzed in a laboratory computer. The initial experiments have concentrated 'on measurements of stainless steel surfaces which are highly two-dimensional and which yield scattering distributions that are localized in the plane of incidence. The results are analyzed by comparing the angular scattering data with theoretical angular scattering distributions computed from digitized roughness profiles measured by a stylus instrument. The theoretical distributions are calculated by substituting the roughness profiles into the operand of an integral equation for electromagnetic scattering developed by Beckmann and Spizzichino. This approach directly tests the accuracy of the basic optical theory.
PMOS NBTI-induced circuit mismatch in advanced technologies

Abstract PMOS transistor degradation due to negative bias temperature instability (NBTI) has proven to be a significant concern to present CMOS technologies. This is of particular importance for analog applications where the ability to match device characteristics to a high precision is critical. Analog circuits use larger than minimum device dimensions to minimize the effects of process variation, leaving PMOS NBTI as a possible performance limiter. This paper examines the effect of PMOS-NBTI induced mismatch on analog circuits in a 90 nm technology.
Star formation in QSO host galaxies

Many of the conditions that are necessary for starbursts appear to be important in the triggering of QSOs. However, it is still debatable whether starbursts are ubiquitously present in galaxies harboring QSOs. In this paper we review our current knowledge from observations of the role of starbursts in different types of QSOs. Post-starburst stellar populations are potentially present in a majority of QSO hosts. QSOs with far-infrared colors similar to those of ultraluminous infrared galaxies invariably reside in merging galaxies that have interaction-induced starbursts of a few hundred Myr or less. Similar, but dramatically more luminous post-starburst populations are found in the recently discovered class of QSOs known as post-starburst QSOs, or Q + A’s. Both of these classes, however, comprise only a small fraction (10–15%) of the total QSO population. The so-called ‘‘red’’ QSOs generally suffer from strong extinction at optical wavelengths, making them ideal candidates for the study of hosts. Their stellar populations typically show a post-starburst component as well, though with a larger range of ages. Finally, optical "classical" QSO hosts show traces of major star formation episodes (typically involving >10% of the mass of the stellar component) in the more distant past (1–2 Gyr). These starbursts appear to be linked to past merger events. It remains to be determined whether these mergers were also responsible for triggering the QSO activity that we observe today.