cssi/SciSciGPT-SciSciNet huggingface dataset:
Proximity of galactic civilizations

Abstract Approximate expressions are derived for the number of civilizations within a few tens of light years of each other since intelligent life first evolved in the Galaxy. The number is proportional to the square of the usual selectivity factors and to the first power of the longevity. Arguments are presented for expecting intelligent life in certain multiple star systems, and the number of coexistent civilizations in such systems is estimated.
Traces on finite W-algebras

We compute the space of Poisson traces on a classical \( \mathcal{W} \)-algebra, i.e., linear functionals invariant under Hamiltonian derivations. Modulo any central character, this space identifies with the top cohomology of the corresponding Springer fiber. As a consequence, we deduce that the zeroth Hochschild homology of the corresponding quantum \( \mathcal{W} \)-algebra modulo a central character identifies with the top cohomology of the corresponding Springer fiber. This implies that the number of irreducible finite-dimensional representations of this algebra is bounded by the dimension of this top cohomology, which was established earlier by C. Dodd using reduction to positive characteristic. Finally, we prove that the entire cohomology of the Springer fiber identifies with the so-called Poisson-de Rham homology (defined previously by the authors) of the centrally reduced classical \( \mathcal{W} \)-algebra.
The Effect of Down Payment Assistance on Mortgage Choice

Lack of wealth for a down payment is one of the most recognized barriers to home ownership. In response to this barrier, state and federal government have implemented many programs that provide down payment assistance to potential home buyers. Numerous studies have shown that this assistance can increase homeownership rates, but few have measured how receiving assistance may alter borrowing behavior. Using data from a down payment assistance grant in the Midwest, this study compares the loan type and size of grant recipients to other borrowers that report similar income and buy homes in the same census tract. Results indicate grant recipients are more likely to use conventional loans, which are less expensive than other loan types that require a smaller down payment. Estimates also suggest that the grant may reduce loan size for borrowers who are on the margin of using a conventional loan.
An Atlas of Computed Equivalent Widths of Quasar Broad Emission Lines

We present graphically the results of several thousand photoionization calculations of broad emission-line clouds in quasars, spanning 7 orders of magnitude in hydrogen ionizing flux and particle density. The equivalent widths of 42 quasar emission lines are presented as contours in the particle density-ionizing flux plane for a typical incident continuum shape, solar chemical abundances, and cloud column density of N(H) = 1023 cm-2. Results are similarly given for a small subset of emission lines for two other column densities (1022 and 1024 cm-2), five other incident continuum shapes, and a gas metallicity of 5 Z☉. These graphs should prove useful in the analysis of quasar emission-line data and in the detailed modeling of quasar broad emission-line regions. The digital results of these emission-line grids and many more are available over the Internet.
Towards Strong Nonapproximability Results in the Lovász-Schrijver Hierarchy

Lovasz and Schrijver described a generic method of tightening the LP and SDP relaxation for any 0–1 optimization problem. These tightened relaxations were the basis of several celebrated approximation algorithms (such as for max-cut, max-3sat, and sparsest cut). We prove strong inapproximability results in this model for well-known problems such as max-3sat, hypergraph vertex cover and set cover. We show that the relaxations produced by as many as Ω(n) rounds of the LS + procedure do not allow nontrivial approximation, thus ruling out the possibility that the LS + approach gives even slightly subexponential approximation algorithms for these problems. We also point out why our results are somewhat incomparable to known inapproximability results proved using PCPs, and formalize several interesting open questions. We survey results that built upon this work.
On pricing kernels and finite-state variable Heath Jarrow Morton models

Once a pricing kernel is established, bond prices and all other interest rate claims can be computed. Alternatively, the pricing kernel can be deduced from observed prices of bonds and selected interest rate claims. Examples of the former approach include the celebrated Cox, Ingersoll, and Ross (1985b) model and the more recent model of Constantinides (1992). Examples of the latter include the Black, Derman, and Toy (1990) model and the Heath, Jarrow, and Morton paradigm (1992) (hereafter HJM). In general, these latter models are not Markov. Fortunately, when suitable restrictions are imposed on the class of volatility structures of forward rates, then finite-state variable HJM models do emerge. This article provides a linkage between the finite-state variable HJM models, which use observables to induce a pricing kernel, and the alternative approach, which proceeds directly to price after a complete specification of a pricing kernel. Given such linkages, we are able to explicitly reveal the relationship between state-variable models, such as Cox, Ingersoll, and Ross, and the finite-state variable HJM models. In particular, our analysis identifies the unique map between the set of investor forecasts about future levels of the drift of the pricing kernel and the manner by which these forecasts are revised, to the shape of the term structure and its volatility. For an economy with square root innovations, the exact mapping is made transparent.
Synchronous Byzantine quorum systems

Quorum systems have been used to implement many coordination problems in distributed systems such as mutual exclusion, data replication, distributed consensus, and commit protocols. Malkhi and Reiter recently proposed quorum systems that can tolerate Byzantine failures; they called these systems Byzantine quorum systems and gave some examples of such quorum systems. In this paper, we propose a new definition of Byzantine quorums that is appropriate for synchronous systems. We show how these quorums can be used for data replication and propose a general construction of synchronous Byzantine quorums using standard quorum systems. We prove tight lower bounds on the load of synchronous Byzantine quorums for various patterns of failures and we present synchronous Byzantine quorums that have optimal loads that match the lower bounds for two failure patterns.
Computerized instruction and the learning process.

IN recent years there has been a tremendous number of articles and news releases dealing with computer-assisted instruction, or as it has been abbreviated, CAT. One might conjecture that this proliferation is an indicant of rapid progress in the field. Unfortunately, I doubt that it is. A few of the reports about CAT are based on substantial experience and research, but the majority are vague speculations and conjectures with little if any data or real experience to back them up. I do not want to denigrate the role of speculation and conjecture in a newly developing area like CAT. However, of late it seems to have produced little more than a repetition of ideas that were exciting in the 1950s but, in the absence of new research, are simply well-worn cliches in the late 1960s. These remarks should not be misinterpreted. Important and significant research on CAT is being carried on in many laboratories around the country, but certainly not as much as one is led to believe by the attendant publicity. The problem for someone trying to evaluate developments in the field is to distinguish between those reports that are based on fact and those that are disguised forms of science fiction. In my paper, I shall try to stay very close to data and actual experience. My claims will be less grand than many that have been made for CAI, but they will be based on a substantial research effort. In 1964 Patrick Suppes and I initiated a project under a grant from the Office of Education to develop and implement a CAI program in initial reading and mathematics. Because of our particular research interests, Suppes has taken responsibility for the mathematics curriculum and I have been responsible for the initial reading program. At the beginning of the project, two major hurdles had to be overcome. There was no lesson material in either mathematics or reading suitable
Pull-in of a pre-stressed thin film by an electrostatic potential: A 1-D rectangular bridge and a 2-D circular diaphragm

Abstract A one-dimensional (1-D) rectangular pre-stressed thin film clamped at two opposite ends is actuated by an electrostatic voltage applied to a pad directly underneath. The pre-stress is allowed to be either tensile or compressive in nature. At a critical applied voltage, the film becomes unstable and makes direct contact with the pad, leading to “pull-in”. An elastic model is constructed to account for the phenomenon over ranges of film–pad gap and residual stress. The results compare favorably with finite element analysis (FEA) in literature and experimental data, and possess distinct advantages over other available closed-form solutions. The model is further extended to a two-dimensional (2-D) axisymmetric diaphragm clamped at the periphery. Interrelationship between bridge–pad gap, residual membrane stress, critical voltage, and pull-in central deflection is derived such that new design criteria can be derived for micro-/nano-electromechanical devices. Implications for nano-structures are also discussed.
A NEW SPIN ON QUANTUM GRAVITY

We suggest that the (small but nonvanishing) cosmological constant, and the holographic properties of gravitational entropy, may both reflect unconventional quantum spin statistics at a fundamental level. This conjecture is motivated by the nonlocality of quantum gravity and the fact that spin is an inherent property of space–time. As an illustration we consider the "quon" model, which interpolates between Fermi and Bose statistics, and show that this can naturally lead to an arbitrarily small cosmological constant. In addition to laboratory tests, we briefly discuss the possible observable imprint on cosmological fluctuations from inflation.
Another clue about particle acceleration in impulsive hard X-ray/microwave bursts

In a sample of impulsive bursts with rise times less than 30 s, a correlation between burst rise times and the frequency of maximum microwave emission has been found. The immplications for source structure and dynamics are discussed. Previously evidence was found that such bursts are caused by some propagating disturbance such as a shock wave or thermal conduction front. Combining that evidence with the microwave and hard X-ray spectral information suggests that the most rapid bursts are emitted from the most compact and intensely magnetized sources. The most rapid bursts also exhibited the hardest X-ray spectra, as published previously. These facts are important clues to understanding the physical process responsible for impulsive bursts. A model for the bursts is suggested, based on the observations and inferences described.
Direct observation of vortex decoupling in synthetic MoGe/Ge multilayers

Abstract Interlayer vortex decoupling is directly observed as a function of temperature and applied magnetic field via electronic transport perpendicular to the layers in synthetic MoGe/Ge multilayers. Below the decoupling temperature TD, the resistivity anisotropy collapses and striking nonlinearities appear in the perpendicular transport. In contrast, no corresponding nonlinearities appear for the in-plane transport, and the in-plane resistance remains finite below TD. The observed behavior at TD is inconsistent with a vortex melting transition.
Lithography-free fabrication of high quality substrate-supported and freestanding graphene devices

We present a lithography-free technique for fabrication of clean, high quality graphene devices. This technique is based on evaporation through hard Si shadow masks, and eliminates contaminants introduced by lithographical processes. We demonstrate that devices fabricated by this technique have significantly higher mobility values than those obtained by standard electron beam lithography. To obtain ultra-high mobility devices, we extend this technique to fabricate suspended graphene samples with mobilities as high as 120 000 cm 2 /(V·s).
Solid-state NMR study of metastable immiscibility in alkali borosilicate glasses

In several series of lithium, sodium, and potassium borosilicate glasses whose compositions traverse known regions of liquid–liquid phase separation, we have applied triple-quantum magic-angle spinning (3QMAS) 11B and 17O NMR to obtain high-resolution information about short-range structure and connections among various network structural units, and their variation with composition and thermal history. Oxygen-17 3QMAS spectra reveal changes in connectivities between silicate and BO3 ([3]B) and BO4 ([4]B) units, by quantifying populations of bridging oxygens such as B–O–B, Si–O–B and Si–O–Si, and of non-bridging oxygens. [3]B–O–Si and [4]B–O–Si as well as [3]B–O–[3]B and [4]B–O–[3]B linkages can be distinguished. 11B MAS and 3QMAS at a magnetic field of 14.1 T allow proportions of several borate units to be determined, including [3]B in boroxol ring and non-ring sites and [4]B with 3 versus 4 Si neighbors. By combining the 11B and 17O NMR results, detailed information on Si/B mixing in sodium borosilicates can be derived, showing, for example, that [4]B and non-ring [3]B tend to mix with silicate units, while ring [3]B is mainly connected to borate groups. In a preliminary study of the effects of varying alkali cation, potassium-containing glasses are similar to those in the sodium borosilicate system, but a lithium borosilicate seems to exhibit considerably greater chemical heterogeneity. In annealing experiments that converted an optically clear to obviously phase-separated glasses, the ratio of [3]B to [4]B does not change significantly, but part of the non-ring [3]B converts to ring [3]B as the degree of unmixing increases.
Inductive Constructions for Frameworks on a Two-Dimensional Fixed Torus

An infinite periodic framework in the plane can be represented as a framework on a torus, using a $${\mathbb {Z}}^2$$Z2-labelled gain graph. We find necessary and sufficient conditions for the generic minimal rigidity of frameworks on the two-dimensional fixed torus $${\mathcal {T}}_0^2$$T02. It is also shown that every minimally rigid periodic orbit framework on $${\mathcal {T}}_0^2$$T02 can be constructed from smaller frameworks through a series of inductive constructions. These are fixed torus adapted versions of the results of Laman and Henneberg, respectively, for finite frameworks in the plane. The proofs involve the development of inductive constructions for $${\mathbb {Z}}^2$$Z2-labelled graphs.
High-Efficiency, Thin-Film GaAs Solar Cells

The present research is directed toward demonstrating the feasibility of producing high-efficiency GaAs solar cells with high power-to-weight ratio by organo-metallic chemical vapor deposition (OM-CVD) growth of thin epi-layers on suitable substrates. Antireflection-coated, metal-oxide-semiconductor (AMOS), GaAs solar cells grown on bulk polycrystalline Ge substrates were initially studied, with the best efficiency achieved being about 9 percent AM1 (7 percent AM0). Subsequently, a new direct deposition method for fabricating ultra-thin top layer, epitaxial n/sup +//p shallow homojunction solar cells on (100) GaAs substrates (without anodic thinning) was developed by means of which large area (1 cm/sup 2/) cells were produced with about 19 percent AM1 (15 percent AM0) conversion efficiency. An AM1 conversion efficiency of about 18 percent (14 percent AM0), or about 17 percent (13 percent AM0) with 5 percent grid coverage, was achieved for a single-crystal, GaAs, n/sup +//p cell grown by OM-CVD on a Ge wafer. These achievements led to the fabrication, for the first time, of thin GaAs epi-layers OMCVD grown with good crystallographic quality, using a (100) Si-substrate on which a thin Ge epi-interlayer was first deposited by CVD from GeH/sub 4/ and processed for improved surface morphology.
A new theory for rotational isomeric states: polysilanes lead the way

Abstract Conformational studies of polysilanes have led to a new model for rotational isomerism. The new model applies to most linear polymers and oligomers other than hydrocarbons, for which the familiar anti and gauche minima are valid. According to the model, the permitted rotational minima, their symbols and their approximate intrachain torsional angles ω are: transoid , T , ±165°; deviant , D , ±150°; ortho , O , ±90°; gauche , G , ±55°; and cisoid , C , ±40°.
Evaluation of a data warehouse in an academic health sciences center

Objectives: The Clinical data repository (CDR) at the University of Virginia Health System is a data warehouse that provides direct access to data for clinical research and effective decision making. We undertook an evaluation of the CDR to understand factors affecting its adoption. Design: We used a theoretical framework that is based on diffusion of innovation theory. Building on validated survey instruments, we developed a questionnaire and conducted interviews of key executive leaders. Fifty-three individuals with logon ids to the CDR completed our questionnaire. Twelve executive leaders were interviewed. Measurements: The outcome variables were the initial and continued use of the CDR. Independent variables included attributes suggested by diffusion theory (i.e. relative advantage, complexity), knowledge and skills expected to correlate with computer usage, and the influence of communication channels. Results: Our overall response rate was 82%. We identified characteristics of users associated with the initial decision to use the CDR. Compatibility with an individual's skills and work style was associated strongly with satisfaction and continued use. Secondly, the importance of organizational culture and the need for data was illuminated by management interviews. Conclusions: We have shown that diffusion of innovation theory can be used to help understand factors contributing to the success of a data warehouse in a healthcare setting. Our results suggest areas for future research and inquiry as the CDR evolves.
An Air Coplanar Wafer Probe

A new wafer probe is presented based on using coplanar waveguide in air. The transmission line is called air coplanar waveguide, and the probe an air coplanar probe (ACP). The probe consists of a coaxial connector, a short piece of coaxial cable and finally the air coplanar waveguide which is formed into a probe tip. This air coplanar tip is made of beryllium copper (BeCu) and allows in excess of 500,000 contact cycles. Both the coaxial cable and air coplanar waveguide are very low loss allowing the ACP to have less than 1 dB insertion loss at 40 GHz. The flexible air coplanar waveguide exhibits high mechanical compliance and repeatable measurements for non planar DUT surfaces. For example either surface irregularities up to 25 um high, or 10 degrees of surface non-planarity cause less than -30 dB error in measured data up to 40 GHz. The air coplanar waveguide also allows better viewing of the contact pads of the DUT than previously attainable with wafer probes. A discussion will be included on the development of the probe and examples of it in use.
The nominative object in finnish

predictable from the surface grammatical relations of a sentence. Thus the grammatical subject is the NP directly dominated by the S node, and it is specified as nominative; the object is the NP directly domi-, nated by the VP node, and it is specified as accusative (Chomsky 1965: 221-2). When the semantic object is in fact specified as nominative, it must first have become the grammatical subject through the operation of a transformation which modifies grammatical relations, as for example the passive or raising. Finnish contradicts these assumptions in an interesting way, by using the nominative to specify the object in certain environments. This unexpected use of the nominative for object is the topic of this paper.*
The impossibility of implementing reliable communication in the face of crashes

Abstract : An important function of communication networks is to implement reliable data transfer over an unreliable underlying network. Formal specifications are given for reliable and unreliable communication layers, in terms of I/O automata. Based on these specifications, it is proved that no reliable communication protocol can tolerate crashes of the processors on which the protocol runs.
Venture capital investment cycles: The impact of public markets

Abstract It is well documented that the venture capital industry is highly volatile and that much of this volatility is associated with shifting valuations and activity in public equity markets. This paper examines how changes in public market signals affected venture capital investing between 1975 and 1998. We find that venture capitalists with the most industry experience increase their investments the most when public market signals become more favorable. Their reaction to an increase is greater than the reaction of venture capital organizations with relatively little industry experience and those with considerable experience but in other industries. The increase in investment rates does not affect the success of these transactions adversely to a significant extent. These findings are consistent with the view that venture capitalists rationally respond to attractive investment opportunities signaled by public market shifts.
The computational complexity of truthfulness in combinatorial auctions

One of the fundamental questions of Algorithmic Mechanism Design is whether there exists an inherent clash between truthfulness and computational tractability: in particular, whether polynomial-time truthful mechanisms for combinatorial auctions are provably weaker in terms of approximation ratio than non-truthful ones. This question was very recently answered for universally truthful mechanisms for combinatorial auctions [4], and even for truthful-in-expectation mechanisms [12]. However, both of these results are based on information-theoretic arguments for valuations given by a value oracle, and leave open the possibility of polynomial-time truthful mechanisms for succinctly described classes of valuations.This paper is the first to prove computational hardness results for truthful mechanisms for combinatorial auctions with succinctly described valuations. We prove that there is a class of succinctly represented submodular valuations for which no deterministic truthful mechanism provides an m1/2-∈-approximation for a constant ∈>0, unless NP=RP (m denotes the number of items). Furthermore, we prove that even truthful-in-expectation mechanisms cannot approximate combinatorial auctions with certain succinctly described submodular valuations better than within nγ, where n is the number of bidders and γ>0 some absolute constant, unless NP ⊆ P/poly. In addition, we prove computational hardness results for two related problems.
Sound Production Due to Large-Scale Coherent Structures

The acoustic pressure fluctuations due to large-scale finite amplitude disturbances in a free turbulent shear flow are calculated. The flow is decomposed into three component scales; the mean motion, the large-scale wave-like disturbance, and the small-scale random turbulence. The effect of the large-scale structure on the flow is isolated by applying both a spatial and phase average on the governing differential equations and by initially taking the small-scale turbulence to be in energetic equilibrium with the mean flow. The subsequent temporal evolution of the flow is computed from global energetic rate equations for the different component scales. Lighthill's theory is then applied to the region with the flowfield as the source and an observer located outside the flowfield in a region of uniform velocity. Since the time history of all flow variables is known, a minimum of simplifying assumptions for the Lighthill stress tensor is required, including no far-field approximations. A phase average is used to isolate the pressure fluctuations due to the large-scale structure, and also to isolate the dynamic process responsible. Variation of mean square pressure with distance from the source is computed to determine the acoustic far-field location and decay rate, and, in addition, spectra at various acoustic field locations are computed and analyzed. Also included are the effects of varying the growth and decay of the large-scale disturbance on the sound produced.
Hydrogen in polar intermetallics: Syntheses and structures of the ternary Ca5Bi3D0.93, Yb5Bi3Hx, and Sm5Bi3H~1 by powder neutron or single crystal X-ray diffraction

The syntheses of the title compounds are described in detail. Structural characterizations from refinements of single crystal X-ray diffraction data for Yb{sub 5}Bi{sub 3}H{sub x} and Sm{sub 5}Bi{sub 3}H{sub 1} and of powder neutron diffraction data for Ca{sub 5}Bi{sub 3}D{sub 0.93(3)} are reported. These confirm that all three crystallize with the heavy atom structure type of {beta}-Yb{sub 5}Sb{sub 3}, and the third gives the first proof that the deuterium lies in the center of nominal calcium tetrahedra, isostructural with the Ca{sub 5}Sb{sub 3}F-type structure. These Ca and Yb phases are particularly stable with respect to dissociation to Mn{sub 5}Si{sub 3}-type product plus H{sub 2}. Some contradictions in the literature regarding Yb{sub 5}Sb{sub 3} and Yb{sub 5}Sb{sub 3}H{sub x} phases are considered in terms of adventitious hydrogen impurities that are generated during reactions in fused silica containers at elevated temperatures.
Graphite Fluoride Lubrication: The Effect of Fluorine Content, Atmosphere, and Burnishing Technique

Eight different graphite fluoride (CFx)n compounds with fluorine to carbon ratios varying from x = 0.25 to 1.1 were evaluated as burnished films in order to determine the effect of fluorine content on the solid lubricant properties of graphite fluoride. For comparison, similar experiments were conducted on graphite burnished films. It was found that even a small amount of fluorine in graphite fluoride (CF0.25)n improved the lubricating Properties of graphite. However, such factors as burnishing atmosphere, burnishing technique, test atmosphere, and specimen temperature affected the results as much as varying the fluorine to carbon ratio of the compound. Best life was found for films that were machine-burnished in moist air and tested in moist air. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference held in Miami Beach, Florida, October 21–23, 1975
Aligned vertical fractures, HTI reservoir symmetry and Thomsen seismic anisotropy parameters for polar media

Certain crack-influence parameters of Sayers and Kachanov are shown to be directly related to Thomsen's weak-anisotropy seismic parameters for fractured reservoirs when the crack/fracture density is small enough. These results are then applied to the problem of seismic wave propagation in polar reservoirs, i.e., those anisotropic reservoirs having two axes that are equivalent but distinct from the third axis), especially for horizontal transversely isotropic seismic wave symmetry due to the presence of aligned vertical fractures and resulting in azimuthal seismic wave symmetry at the Earth's surface. The approach presented suggests one method of inverting for fracture density from wave speed data. A significant fraction of the technical effort in the paper is devoted to showing how to predict the angular location of the true peak (or trough) of the quasi-SV-wave for polar media and especially how this peak is related to another angle that is very easy to compute. The axis of symmetry is always treated here as the x 3 -axis for either vertical transversely isotropic symmetry (due, for example, to horizontal cracks), or horizontal transversely isotropic symmetry (due to aligned vertical cracks). Then, the meaning of the stiffnesses is derived from the fracture analysis in the same way for vertical transversely isotropic and horizontal transversely isotropic media, but for horizontal transverse isotropy the wave speeds relative to the Earth's surface are shifted by 90° in the plane perpendicular to the aligned vertical fractures. Skempton's poroelastic coefficient B is used as a general means of quantifying the effects of fluids inside the fractures. Explicit Biot-Gassmann-consistent formulas for Thomsen's parameters are also obtained for either drained or undrained fractures resulting in either vertical transversely isotropic or horizontal transversely isotropic symmetry of the reservoir.
Application of a High Performance Parallel Eigensolver to Electronic Structure Calculations

In this paper we report the development of a very high performance parallel eigensolver based on the portable ScaLAPACK library, and its application to electronic structure calculations in the MP-Quest code. This work was done on ASCI-Red, a supercomputer based on over 4600 dual-processor Pentium Pro1 nodes at Sandia National Laboratories. We report sustained performance in the code of 605GFlops and peak performance in the eigensolver of 684GFlops. This is comparable to performance obtained from MP-Linpack on a similar sized problem. For a smaller problem we have sustained performance of 420GFlops in the application and peak performance in the eigensolver of 563GFlops. Impact of this work on the specific application is important, but the development of significant improvements to a portable eigensolver and other libraries will also benefit a number of applications.
EUV impurity study of the Alcator Tokamak

The intensity of resonance line radiation from oxygen, nitrogen, carbon and molybdenum impurities has been measured in the high-field (80 kG), high-density (6 × 1014 cm−3) discharges of the Alcator Tokamak, using a 0.4-m normal-incidence monochromator (300–1300 A) with its line of sight fixed along a major radius. Total light-impurity concentrations of a few tenths of a percent have been estimated by using both a simple model and a computer code which included Pfirsch-Schluter impurity diffusion. The resulting values of Zeff, including the contributions due to both the light impurities and molybdenum, were close to one. The power lost through the impurity line radiation from the lower ionization states accounted for ~10% of the total Ohmic input power at high densities.
12 C/ 13 C Ratio in Planetary Nebulae from the IUE Archives

We investigated the abundance ratio of 12C/13C in planetary nebulae by examining emission lines arising from C III 2s2p 3P → 2s2 1S0. Spectra were retrieved from the International Ultraviolet Explorer archives, and multiple spectra of the same object were co-added to achieve improved signal-to-noise ratio. The 13C hyperfine structure line at 1909.6 A was detected in NGC 2440. The 12C/13C ratio was found to be ~4.4 ± 1.2. In all other objects, we provide an upper limit for the flux of the 1910 A line. For 23 of these sources, a lower limit for the 12C/13C ratio was established. The impact on our current understanding of stellar evolution is discussed. The resulting high-signal-to-noise ratio C III spectrum helps constrain the atomic physics of the line formation process. Some objects have the measured 1907/1909 A flux ratio outside the low-electron density theoretical limit for 12C. A mixture of 13C with 12C helps to close the gap somewhat. Nevertheless, some observed 1907/1909 A flux ratios still appear too high to conform to the currently predicted limits. It is shown that this limit, as well as the 1910/1909 A flux ratio, are predominantly influenced by using the standard partitioning among the collision strengths for the multiplet 1S0-3P according to the statistical weights. A detailed calculation for the fine-structure collision strengths between these individual levels would be valuable.
Hypervelocity launch dynamics

Abstract The launch dynamics from a generic hypervelocity cannon are considered over the velocity range from 1500 through 3500 m/s. Both fin and flare stabilized projectiles are examined for the influence of in-bore dynamics, muzzle blast, sabot discard, and free flight aerodynamics upon their trajectory. Computations are performed using codes developed and validated for conventional cannon with ordnance muzzle velocities (approximately 1700 m/s). While the extension into the hypervelocity regime is not supported by experimental data, this initial study is intended to aid in defining potential problem areas.
Solving topological 2D quantum gravity using Ward identities

Abstract A topological procedure for computing correlation functions for any (1, q ) model is presented. Our procedure can be used to compute any correlation function on the sphere as well as some correlation functions at higher genus. We derive new and simpler recursion relations that extend previously known results based on W -constraints. In addition, we compute an effective contact algebra with multiple contacts that extends Verlindes' algebra. Computational techniques based on the KdV approach are developed and used to compute the same correlation functions. A simple and elegant proof of the puncture equation derived directly from the KdV equations is included. We hope that this approach can lead to a deeper understanding of D = 1 quantum gravity and non-critical string theory.
The Spiritual: Soul of Black Religion

My subject is the religion of the black American and my thesis is twofold: that the black man's religion is a religion of soul and that the soul of the black man's religion is his music. My concentration is on the spirituals. The paragraphs that follow are in part an abstract of my paper and in part a bibliographical essay indicating some studies or interpretations on which I draw or to which I am indebted. I
Location of Incenters and Fermat Points in Variable Triangles.

(2001). Location of Incenters and Fermat Points in Variable Triangles. Mathematics Magazine: Vol. 74, No. 2, pp. 123-129.
Comparisons of an Evolutionary Chemical Model with Other Models

We compare an evolutionary chemical model with simple empirical models of the abundance and with static chemical models. We focus on the prediction of molecular line profiles that are commonly observed in low-mass star forming cores. We show that empirical models can be used to constrain evaporation radii and infall radii using lines of some species. Species with more complex abundance profiles are not well represented by the empirical models. Static chemical models produce abundance profiles different from those obtained from an evolutionary calculation, because static models do not account for the flow of matter inward from the outer regions. The resulting profiles of lines used to probe infall may differ substantially.
A new one step synthesis of maleimides by condensation of glyoxylate esters with acetamides

Bisphenyl, Bisheteroaryl, indolylaryl and indolylcycloalkyl maleimides are prepared in one step and 67–99% yield by condensation of glyoxylate esters with acetamides using a 1.0 M solution of potassium tert-butoxide in THF. The mechanism of the reaction is discussed.
A VERSION OF FABRY'S THEOREM FOR POWER SERIES WITH REGULARLY VARYING COEFFICIENTS

For real power series whose non-zero coefficients satisfy|am| 1/m → 1, we prove a stronger version of Fabry’s theorem relating the frequency of sign changes in the coefficients and analytic continuationof the sum of the power series.
Partition Equilibrium Always Exists in Resource Selection Games

We consider the existence of Partition Equilibrium in Resource Selection Games. Super-strong equilibrium, where no subset of players has an incentive to change their strategies collectively, does not always exist in such games. We show, however, that partition equilibrium (introduced in (Feldman and Tennenholtz in SAGT, pp. 48–59, 2009) to model coalitions arising in a social context) always exists in general resource selection games, as well as how to compute it efficiently. In a partition equilibrium, the set of players has a fixed partition into coalitions, and the only deviations considered are by coalitions that are sets in this partition. Our algorithm to compute a partition equilibrium in any resource selection game (i.e., load balancing game) settles the open question from (Feldman and Tennenholtz in SAGT, pp. 48–59, 2009) about existence of partition equilibrium in general resource selection games. Moreover, we show how to always find a partition equilibrium which is also a Nash equilibrium. This implies that in resource selection games, we do not need to sacrifice the stability of individual players when forming solutions stable against coalitional deviations. In addition, while super-strong equilibrium may not exist in resource selection games, we show that its existence can be decided efficiently, and how to find one if it exists.
Evolution of Nuclear Spectra with Nuclear Forces

We first define a series of $NN$ interaction models ranging from very simple to fully realistic. We then present Green's function Monte Carlo calculations of light nuclei to show how nuclear spectra evolve as the nuclear forces are made increasingly sophisticated. We find that the absence of stable five- and eight-body nuclei depends crucially on the spin, isospin, and tensor components of the nuclear force.
Efficient and Nearly-Efficient Partnerships

This paper shows in two ways that the degree to which free-riding diminishes the performance of deterministic partnerships may be less than has been generally thought. First, a necessary and sufficient condition is provided for a partnership to sustain full efficiency. It implies that many non-trivial partnerships sustain efficiency, such as generic ones with finite action spaces, and neoclassical ones with Leontief technologies. Second, approximate efficiency is shown to be achievable in a large class of partnerships, including ones with smooth and monotonic production and disutility functions. Approximate efficiency is achieved by mixed-strategy equilibria: one partner takes, with small probability, an inefficient action. The degree to which efficiency is approximated is restricted only by the amount of liability the partners can bear. Nonetheless, their equilibrium payments are not arbitrarily large.
Atomic data related to X and XUV radiation

Abstract An attempt was made to locate relevant tables published in books, journals, and reports. Various indexes and listings were of great assistance. In the selection of items to be presented the policy was not to give a complete historical overview, but to offer the titles most helpful (and available) to today's researcher, whether experimental or theoretical. In a few soses some of the older and less obtainable work was mentioned in order to make comments on the new work understandable. Information about omissions or errors will be welcome.
Local and global analysis: complementary activities for increasing the effectiveness of requirements verification and validation

This paper presents a unique approach to connecting requirements engineering activities into a process framework that can be employed to obtain quality requirements with reduced expenditures of effort and cost. It is well understood that early detection and correction of errors offers the greatest potential for improving requirements quality and avoiding cost overruns in the development of software systems. To realize the maximum benefits of this ideology, we propose a two-phase model that is novel in that it introduces the concept of verification and validation (VV the corresponding focus is on the quality of linkages between requirements sets rather than on the requirements within the sets. Consequently, this approach reduces the effort in verification and enhances the focus on the verification task. The second phase also addresses the business concerns collectively, and thereby produces requirements that are not only quality adherent, but are also business compliant. Our approach, unlike other models, has a minimal time delay between the elicitation of requirements and the execution of the VV this enhances the feedback during the V&V activities. Furthermore, our model includes activities that closely align with the effective requirements engineering processes employed in the software industry. Thus, our approach facilitates a better understanding of the flow of requirements, and provides guidance for the implementation of the requirements engineering process.This paper describes a well-defined, two-phase requirements engineering approach that incorporates the principles of early V&V to provide the benefits of reduced costs and enhanced quality requirements.
Cosmic-ray modulation and the anomalous component.

Experimental and theoretical studies of cosmic-ray-modulation phenomena reported in the open literature by US researchers during the 1979-1982 period are reviewed. Areas covered include microscopic diffusion theory, gradient and curvature drift, global modulation theory, the anomalous component, and general modulation observations (such as the Pioneer-10 Forbush-decrease-propagation observations and studies on the time variation of the electron-to-proton ratio). An impressionistic overview of current and future trends in this area of study is also provided.
Regioselective syntheses and structural characterizations of 2,3-dibromo- and 2,3,7,8,12,13-hexabromo-5,10,15,20- tetraphenylporphyrins

Abstract The title dibromoporphyrins 4 5 and hexabromoporphyrins 11 12 are prepared from H2(2-NO2TPP) 1 and Cu(2-NO2TPP) 8, respectively. The β-nitro group confines the 18-π-annulene system of a tetraphenylporphyrin to its N22H-N24H aromatic delocalization pathway which induces the localization of an antipodal double bond on the porphyrin periphery and enhances its susceptibility to electrophilic attack. Dibromination of H2-NO2TPP) 1 occurs regioselectively affording the 12,13-dibromo-2- nitroporphyrin 2 which, upon Michael addition of NaBH4 and re-aromatization of the resulting nitrochlorin 3, provides an entry to 2,3-dibromoTPP 4 5 as well as an improved route to 2,3- dicyanoporphyrins 6 7 . Perbromination of Cu(2-NO2TPP) 8 and denitration of 9 gave, after demetalation, 2,3,7,8,12,13-hexabromoTPP 12. Both 4 and 12 are structurally characterized by X-ray crystallography.
CLEO results on tau Michel parameters

We present measurements of the tau Michel Parameters made by the CLEO experiment. Three different analyses are performed: a spin-independent lepton spectrum analysis and a second spin-dependent analysis using l^± vs. π^‡π^0 events, and a third spin-dependent analysis using π^+ vs. π^− events. the results are used to derive limits on the general four-fermion couplings, the mass of the charged Higgs in the MSSM, and a right-handed W in left-right models. Many of these measurements are more precise than the PDG world averages.
Two-loop diagrammatics in a self-dual background

Diagrammatic rules are developed for simplifying two-loop QED diagrams with propagators in a constant self-dual background field. This diagrammatic analysis, using dimensional regularization, is used to explain how the fully renormalized two-loop Euler-Heisenberg effective lagrangian for QED in a self-dual background field is naturally expressed in terms of one-loop diagrams. The connection between the two-loop and one-loop vacuum diagrams in a background field parallels a corresponding connection for free vacuum diagrams, without a background field, which can be derived by simple algebraic manipulations. It also mirrors similar behavior recently found for two-loop amplitudes in N = 4 SUSY Yang-Mills theory.
Global Aerodynamic Modeling for Stall/Upset Recovery Training Using Efficient Piloted Flight Test Techniques

Flight test and modeling techniques were developed for efficiently identifying global aerodynamic models that can be used to accurately simulate stall, upset, and recovery on large transport airplanes. The techniques were developed and validated in a high-fidelity fixed-base flight simulator using a wind-tunnel aerodynamic database, realistic sensor characteristics, and a realistic flight deck representative of a large transport aircraft. Results demonstrated that aerodynamic models for stall, upset, and recovery can be identified rapidly and accurately using relatively simple piloted flight test maneuvers. Stall maneuver predictions and comparisons of identified aerodynamic models with data from the underlying simulation aerodynamic database were used to validate the techniques.
Identification Problems in the Social Sciences

The aim of methodological research in the social sciences is to learn what conclusions can and cannot be drawn given empirically relevant combinations of assumptions and data. Methodologists have long found it useful to separate inferential problems into statistical and identification components. Studies of identification seek to characterize the conclusions that could be drawn if the researcher had available a sample of unlimited size. Studies of statistical inference seek to characterize the generally weaker conclusions that can be drawn given a sample of positive butfinite size. Statistical and identification problems limit in distinct ways the conclusions that may be drawn in empirical research. Statistical problems are most severe when the available sample is small. Identification problems are most severe when the researcher knows little about the population under study and the sampling process yields only weak data on the population. This chapter synthesizes some of my recent research and thinking on identification problems in the social sciences. Four problems are discussed: extrapolation of regressions, the selection problem, identification of endogenous social effects, and identification of subjective phenomena. These problems arise regularly in social science research and are the source of many substantive disputes.
Coincidence lattice model for the structure and energy of grain boundaries

Abstract The Coincidence Site Lattice (CSL) model of grain boundaries is developed on a simple physical basis. We propose that, to a good approximation, the construction of a boundary can be described in terms of three basic steps:(1) a rigid body joining of two perfect crystals along the boundary plane (Step I); (2) a primary relaxation (Step II) consisting of relaxations in the boundary centered on 0-Lattice elements which act to improve lattice matching in these regions; and (3) a possible secondary relaxation (Step III) which produces the final structure composed of patches of a low ∑ boundary and secondary grain boundary dislocations. The energy after Step I is obtained by summing pairwise interactions across the boundary and is found to be relatively low for a number of low ∑ boundaries and to approach a larger constant value for all large ∑ boundaries. The energy decrease due to Step II varies monotonically with crystal misorientation according to a Read-Shockley function, and the energy decrease associated with Step III produces cusps in the energy versus misorientation curve at misorientations corresponding to low ∑ boundaries. The model appears to be consistent with our present knowledge of boundary structure and energy, and its general applicability is discussed.