cssi/SciSciGPT-SciSciNet huggingface dataset:
Collision geometry fluctuations and triangular flow in heavy-ion collisions

We introduce the concepts of participant triangularity and triangular flow in heavy-ion collisions, analogous to the definitions of participant eccentricity and elliptic flow. The participant triangularity characterizes the triangular anisotropy of the initial nuclear overlap geometry and arises from event-by-event fluctuations in the participant-nucleon collision points. In studies using a multiphase transport model (AMPT), a triangular flow signal is observed that is proportional to the participant triangularity and corresponds to a large third Fourier coefficient in two-particle azimuthal correlation functions. Using two-particle azimuthal correlations at large pseudorapidity separations measured by the PHOBOS and STAR experiments, we show that this Fourier component is also present in data. Ratios of the second and third Fourier coefficients in data exhibit similar trends as a function of centrality and transverse momentum as in AMPT calculations. These findings suggest a significant contribution of triangular flow to the ridge and broad away-side features observed in data. Triangular flow provides a new handle on the initial collision geometry and collective expansion dynamics in heavy-ion collisions.
An Analysis of Bilateral Intra-Industry Trade in the Food Processing Sector

This paper analyses determinants of intra-industry trade in food processing for a 30-country sample over the period 1964–85. Previous studies have tested the hypothesis that imperfect competition is a major determinant of intra-industry trade (IIT) in the durable goods manufacturing sectors. This study is distinguised from the earlier studies of IIT by; the examination of the processed food sector (SIC=20), the use of a panel data set for 22 years and 30 countries available at the four-digit SIC level, the use of purchasing power parity measures of GDP, and the use of a weighted tobit model with fixed effects to account for the censored cross-section time-series nature of the date. The results indicate that ITI in food processing is a positive function of a country's GDP per capita and equality if GDP per capita between countries. In addition, it is also found that such trade is strongly influenced by distance between trading partners, membership in customs unions and free trade blocs, and also exchange r...
Occurrence and distribution of diverse populations of magnetic protists in a chemically stratified coastal salt pond

Abstract Chemical stratification occurs in the water columns and sediments of many aquatic habitats resulting in vertical chemical and redox gradients. Various types of microorganisms are often associated with specific depths and chemical parameters in these situations. For example, magnetite-producing magnetotactic bacteria are known to form horizontal “plates” of cells at the oxic/anoxic transition zone (OATZ) of such environments. Here, we report the presence of populations of diverse magnetic protists in a seasonally chemically stratified, coastal salt pond. The protistan types included several biflagellates, a dinoflagellate, and a ciliate that were each associated with specific depths and thus, specific chemical, microbiological and redox conditions in the water column. Most cells contained crystals of magnetite usually arranged in chains similar to the magnetosomes in the magnetotactic bacteria. The origin of the particles is unknown. There was no evidence of the presence of endosymbiotic magnetotactic bacteria within the protists nor were the protists observed to be engulfing magnetotactic bacteria despite the fact that high numbers of the latter were present at the same depths as the protists. However, this does not exclude ingestion of magnetotactic bacteria as a source of the magnetic particles while others may biomineralize magnetite. Because protists play an important role in the availability of iron for phytoplankton in marine waters by ingesting and reducing colloidal iron particles, the protists described here could play a significant role in iron cycling in chemically stratified anoxic basins, either through endogenous production of magnetic iron oxide and/or iron sulfide particles, or by ingestion of magnetotactic bacteria and the subsequent reduction and dissolution of iron oxide and/or sulfide particles in their magnetosomes.
A note on asymmetric and mixed strategy equilibria in the search-theoretic model of fiat money

The simple search-theoretic model of fiat money has three symmetric Nash equilibria: all agents accept money with probability 1; all agents accept money with probability 0; and all agents accept money with probability y in (0,1). Here I construct an asymmetric pure strategy equilibrium, payoff-equivalent to the symmetric mixed strategy equilibrium, where a fraction N in (0,1) of agents always accept money and 1-N never accept money. Counter to what has been conjectured previously, I find N > y. I also introduce evolutionary dynamics, and show that the economy converges to monetary exchange iff the initial proportion of agents accepting money exceeds N.
Correlations between O VI Absorbers and Galaxies at Low Redshift

We investigate the relationship between galaxies and metal-line absorption systems in a large-scale cosmological simulation with galaxy formation. Our detailed treatment of metal enrichment and nonequilibrium calculation of oxygen species allow us, for the first time, to carry out quantitative calculations of the cross-correlations between galaxies and O VI absorbers. We find the following: (1) The cross-correlation strength depends weakly on the absorption strength but strongly on the luminosity of the galaxy. (2) The correlation distance increases monotonically with luminosity from ~0.5-1 h−1 Mpc for 0.1L* galaxies to ~3-5 h−1 Mpc for L* galaxies. (3) The correlation distance has a complicated dependence on absorber strength, with a luminosity-dependent peak. (4) Only 15% of O VI absorbers lie near ≥Lz,* galaxies. The remaining 85%, then, must arise "near" lower luminosity galaxies; however, the positions of those galaxies is not well correlated with the absorbers. This may point to pollution of intergalactic gas predominantly by smaller galaxies. (5) There is a subtle trend that for 0.5Lz,* galaxies, there is a positive correlation between absorber strength and galaxy luminosity in the sense that stronger absorbers have a slightly higher probability of finding such a large galaxy at a given projection distance. For less luminous galaxies, there seems to be a negative correlation between luminosity and absorber strength.
Algorithms for intervector dependency utilization in variable-rate tree-structured vector quantization

ABSTRACT In this paper we improve and extend our previous results in finite- state variable rate tree-structured vectorquantization (FSVRTSVQ)1 by developing two new algorithms to increase its coding efficiency. The twonew algorithms are derived to utilize the inter-codeword dependency and the tree structure property ofthe codebook so as to achieve bit rate reduction. The evaluation of both algorithms on various synthesisand real sources has shown that as many as 32.3% of bit rate savings has been obtained over the prunedtree- structured vector quantization (PTSVQ)3.Keywords: source compression, vector quantization, tree-structured vector quantization, finite state vec-tor quantization 1 INTRODUCTION In vector quantization (VQ) of sources with memory, such as video and audio signals, there will exist correlation in the quantizer outputs. On the other hand, the structural design of the tree-structured codebooks determines that highly correlated source vectors will be encoded either by the same codevectoror by the codevectors within a small subtree. It implies that if two source vectors are highly correlated,one can expect that a great portion of their path maps will be the same. Therefore, we may utilize thecodevector correlation to improve the coding efficiency of variable rate tree-structured vector quantization
Long-Term Light Induced Changes in Dark Conductivity of Kapton.

The light-induced increase in dark conductivity of Kapton in space and simulated space environments has been investigated. It was found that a long-term increase in conductivity is caused by an accumulation of electrically active centers generated by solar radiation in the bulk of the material if maintained in vacuum. An analysis of the increase in conductivity as a function of light exposure time indicates that the dark conductivity of Kapton can be raised to a level at which the film can become sufficiently conductive to be antistatic simply by exposing it to solar radiation in orbit.
Evaluation of Weld Root Failure Using Battelle Structural Stress Method

Weld related fatigue failure is one of the most common concerns in welded structures. From the fatigue design point of view, weld toe failure is preferable to weld root failure. Base plate thickness is a controlling parameter for weld toe failure, while weld metal size is a controlling parameter for weld root failure. However, controlling the weld metal size is not easy because the actual weld penetration and weld leg size vary along a weld and from weld to weld. Therefore, analyzing fatigue test data for weld root failure tends to enlarge scatter band due to variability in weld penetration and weld leg size when the nominal weld size is considered. The structural stress based weld fatigue master S-N curve adopted by 2007 ASME section VIII Div. 2 and new API 579/ASME FFS-1 was constructed by incorporating only clearly defined weld toe fatigue data. In this article, a simplified structural stress procedure was developed and a design master S-N curve for weld root failure was established based on the published fatigue test data. Consequently, the mean design master S-N curve for weld root failure is downshifted relative to the mean master S-N curve for weld toe failure, and has a wider scatter band. To be conservative, a crack path along weld throat is recommended for structural stress calculation. Also, the transverse shear stress effects on structural stress calculation can be ignored.
Multiplication Operators on the Bloch Space of Bounded Homogeneous Domains

In this paper, we study the multiplication operators on the Bloch space of a bounded homogeneous domain in ℂn. Specifically, we characterize the bounded and the compact multiplication operators, establish estimates on the operator norm, and determine the spectrum. We prove that the only bounded multiplication operators on the Bloch space of the polydisk are those whose symbol is constant. Furthermore, we prove that for a large class of bounded symmetric domains, the isometric multiplication operators are those whose symbol is a constant of modulus one.
Extension dimension for paracompact spaces

Abstract We prove existence of extension dimension for paracompact spaces. Here is the main result of the paper: Theorem. Suppose X is a paracompact space. There is a CW complex K such that (a) K is an absolute extensor of X up to homotopy, (b) If a CW complex L is an absolute extensor of X up to homotopy, then L is an absolute extensor of Y up to homotopy of any paracompact space Y such that K is an absolute extensor of Y up to homotopy. The proof is based on the following simple result (see Theorem 1.2). Theorem. Let X be a paracompact space. Suppose a space Y is the union of a family {Ys}s∈S of its subspaces with the following properties: (a) Each Ys is an absolute extensor of X, (b) For any two elements s and t of S there is u∈S such that Ys∪Yt⊂Yu. If f :A→Y is a map from a closed subset A to Y such that A=⋃s∈SIntA(f−1(Ys)), then f extends over X. That result implies a few well-known theorems of classical theory of retracts which makes it of interest in its own.
The finite temperature phase diagram of a U (1) Higgs-Yukawa model

Abstract The finite temperature phase diagram of a U(1) Higgs-Yukawa model at a finite value of the scalar self coupling λ is investigated by means of a large-Nf calculation and numerical simulations. The phase diagrams is similar to the one at zero temperature and shows a ferromagnetic, two symmetric and an antiferromagnetic phase. However, the phase transition lines are shifted to larger values of the Yukawa coupling demonstrating the occurence of the finite temperature symmetry restoration.
Photoproduction in Ultra-Peripheral Relativistic Heavy Ion Collisions with STAR

We present a summary of recent photoproduction results in ultra peripheral relativistic heavy ions collisions with STAR. These collisions have impact parameters larger then twice the nuclear radius; the nuclei do not physically collide, but interact via long-range electromagnetic fields. We observe exclusive ρ0 production as well as AuAu → Au*Au*ρ0 with accompanying mutual nuclear excitation at s N N = 200 GeV. We report the ρ0 production cross section for both coherent and incoherent coupling accompanied by mutual nuclear excitation. We have studied the cross section as a function of pT, y ρ 0 and Mππ and compared it to theoretical models. In addition, we measured the ρ0 helicity matrix elements. They are found to be consistent with s-channel helicity conservation. The ratio of coherent ρ0 and direct π+π− pair photoproduction has been measured and found to be consistent with earlier measurements. The 4-pion final state AuAu → π+π−π+π− state has also been observed.
Octahedral and Tetrahedral Coinage Metal Clusters: Is Three-Dimensional d-Orbital Aromaticity Viable?

The first quantitative evidence for the viability of three-dimensional aromatic clusters involving d-orbitals in pseudo-octahedral coinage metal cages M6Li2 (M = Cu, Ag, Au) as well as in tetrahedral coinage metal cages M‘4Li4 (M‘ = Cu, Ag) was obtained computationally. These cages exhibit many features similar to those of their square planar M4Li2 analogues. The large negative nucleus-independent chemical shifts (NICS) at the cage centers indicate three-dimensional delocalization. This diatropic character arises mostly from d-orbital delocalization combined with substantial contributions from the lowest-valence orbitals. The bonding molecular orbitals of the pseudo-octahedral clusters M6Li2 (M = Cu, Ag, Au) are analogous to those in similar octahedral clusters involving p-orbital delocalization (e.g., B6H62-). The M‘4Li4 clusters exhibit two isomeric forms: metal tetrahedral cages tetracapped by lithium cations on the outside [(M‘4)·4Li] and lithium tetrahedra on the inside capped by coinage metal atoms...
Energetics of a strongly correlated Fermi gas

Abstract The energy of the two-component Fermi gas with the s-wave contact interaction is a simple linear functional of its momentum distribution: E internal = ℏ 2 Ω C / 4 π am + ∑ k σ ( ℏ 2 k 2 / 2 m ) ( n k σ - C / k 4 ) where the external potential energy is not included, a is the scattering length, Ω is the volume, n k σ is the average number of fermions with wave vector k and spin σ , and C ≡ lim k → ∞ k 4 n k ↑ = lim k → ∞ k 4 n k ↓ . This result is a universal identity . Its proof is facilitated by a novel mathematical idea, which might be of utility in dealing with ultraviolet divergences in quantum field theories. Other properties of this Fermi system, including pair correlations and the dimer–fermion scattering length, are also studied.
Electrical Conductivity in Lead Zirconate‐Titanate Ceramics

Electrical conductivity was investigated in polycrystalline lead zirconate-titanate ceramics, with and without various dopants and stoichiometry, fabricated from chemical solutions and mixed-oxide powders. A multiphase packing-powder technique was used to control the stoichiometry of the system during sintering. The dc resistivity was measured by using a guard-ring method. Electrical conduction follows typical semiconductor behavior. Thermoelectric power measurements showed that hole conduction was dominant. Impurity ions which can serve as acceptors or donors significantly affect the conduction process. For undoped PZT the activation energy was 3.6 eV from 650° to 800°C and 1.4 eV at <650°C.
SYNTHESIS OF 2'-DEOXY- AND 2',5'-DIDEOXY-ADENOSINE-3'-DI- AND 3'-TRIPHOSPHATE

Abstract The synthesis of a number of adenine nucleotide-3′-polyphosphates has been devised, via a phosphotriester approach that combines the method of alkoxide activation with the use of 2,2,2-tribromoethyl phosphoromorpholinochloridate 2 as phosphorylating agent.
Integral invariants for 3D curves: an inductive approach

In this paper we obtain, for the first time, explicit formulae for integral invariants for curves in 3D with respect to the special and the full affine groups. Using an inductive approach we first compute Euclidean integral invariants and use them to build the affine invariants. The motivation comes from problems in computer vision. Since integration diminishes the effects of noise, integral invariants have advantage in such applications. We use integral invariants to construct signatures that characterize curves up to the special affine transformations.
Resource Letter TF-1: Turbulence in fluids

This Resource Letter provides a guide to the literature on fully developed turbulence in fluids. It is restricted to mechanically driven turbulence in an incompressible fluid described by the Navier–Stokes equations of hydrodynamics, and places greatest emphasis on fundamental physical questions. Journal articles and books are cited for the following topics: the Navier–Stokes equations, qualitative aspects of turbulence, the 1941 Kolmogorov theory, intermittency and small scale structure, time correlations and pressure; with brief mention of two-dimensional turbulence, passive scalars in turbulence, and the turbulent boundary layer. Turbulent fluid flows are ubiquitous in the atmosphere, the oceans, and the stars. They also occur in a wide variety of engineering applications. Most studies of turbulence have an applied objective, whether this application be to engineering, to geophysics, to astrophysics, or to weather predicition. But there is a basic problem in physics underlying all of these applications...
Equivalence of the information structure with unawareness to the logic of awareness

This paper proves the Li (2009) [13] unawareness structure equivalent to the single-agent propositionally generated logic of awareness of Fagin and Halpern (1988) [4]. For any model of one type one can construct a model of the other type describing the same belief and awareness. Li starts from an agent unable to perceive aspects of the world and distinguish states, modeled with subjective state spaces coarser than the objective state space. Fagin and Halpern limit the agentʼs language or cognitive ability to reasoning only about a subset of the primitive propositions describing the world. Equivalence of these approaches suggests they capture a natural notion of unawareness in a minimal way.
Pricing access in network competition

We compare various access pricing rules in the two-way access model. We show that the Generalized Efficient Component Pricing Rule (TECPR) leads to a lower equilibrium price than does the Efficient Component Pricing Rule, (ECPR) marginal cost pricing, (MCP) and any non-negative fixed access charges.
21 Centimeter Fluctuations from Cosmic Gas at High Redshifts

The relatively large Thomson optical depth, ?es, inferred recently from the WMAP observations suggests that the universe was reionized in a more complex manner than previously believed. However, the value of ?es provides only an integral constraint on the history of reionization and, by itself, cannot be used to determine the nature of the sources responsible for this transition. Here we show that the evolution of the ionization state of the intergalactic medium (IGM) at high redshifts can be measured statistically using fluctuations in 21 cm radiation from neutral hydrogen. By analogy with the mathematical description of anisotropies in the cosmic microwave background, we develop a formalism to quantify the variations in 21 cm emission as a function of both frequency and angular scale. Prior to and following reionization, fluctuations in the 21 cm signal are mediated by density perturbations in the distribution of matter. Between these epochs, pockets of gas surrounding luminous objects become ionized, producing large H II regions. These bubbles of ionized material imprint features into the 21 cm power spectrum that make it possible to distinguish them from fluctuations produced by the density perturbations. The variation of the power spectrum with frequency can be used to infer the evolution of this process. As has been emphasized previously by others, the absolute 21 cm signal from neutral gas at high redshifts is difficult to detect as a result of contamination by foreground sources. However, we argue that this source of noise can be suppressed by comparing maps closely spaced in frequency, i.e., redshift, so that 21 cm fluctuations from the IGM can be measured against a much brighter, but smoothly varying (in frequency), background.
Covariant and local field theory on the world sheet

In earlier work, using the light cone picture, a world sheet field theory that sums planar ϕ3 graphs was constructed and developed. Since this theory is both non-local and not explicitly Lorentz invariant, it is desirable to have a covariant and local alternative. In this paper, we construct such a covariant and local world sheet field theory, and show that it is equivalent to the original non-covariant version.
Analysis of running coupling constant unification in string theory

Abstract We use recently obtained two-loop string coupling constants to analyze a class of string models based on orbifold compactification. Assuming weak coupling at the string scale m s and single-scale unification leads to restrictions on the spectrum of massive ( M z ⪡ M ⩽ m s ) matter supermultiplets and/or on the Kac-Moody algebra level.
Asymptotically tight steady-state queue length bounds implied by drift conditions

The Foster---Lyapunov theorem and its variants serve as the primary tools for studying the stability of queueing systems. In addition, it is well known that setting the drift of the Lyapunov function equal to zero in steady state provides bounds on the expected queue lengths. However, such bounds are often very loose due to the fact that they fail to capture resource pooling effects. The main contribution of this paper is to show that the approach of "setting the drift of a Lyapunov function equal to zero" can be used to obtain bounds on the steady-state queue lengths which are tight in the heavy-traffic limit. The key is to establish an appropriate notion of state-space collapse in terms of steady-state moments of weighted queue length differences and use this state-space collapse result when setting the Lyapunov drift equal to zero. As an application of the methodology, we prove the steady-state equivalent of the heavy-traffic optimality result of Stolyar for wireless networks operating under the MaxWeight scheduling policy.
The integral Chow ring of the stack of at most 1-nodal rational curves

We give a presentation for the stack of rational curves with at most 1 node as the quotient by GL3 of an open set in a 6-dimensional irreducible representation. We then use equivariant intersection theory to calculate the integral Chow ring of this stack.
Stereocontrolled synthesis of substituted tetrahydropyrans from 1,3-dioxan-4-ones

Abstract Conversion of aldehydes to 1,3-dioxan-4-ones, followed by methylenation with dimethyl titanocene gave the corresponding vinyl acetals which could undergo a stereocontrolled aluminum-mediated rearrangement to afford substituted tetrahydropyrans.
Hypersonic Shock/Boundary-Layer Interaction Database

Turbulence modeling is generally recognized as the major problem obstructing further advances in computational fluid dynamics (CFD). A closed solution of the governing Navier-Stokes equations for turbulent flows of practical consequence is still far beyond grasp. At the same time, the simplified models of turbulence which are used to achieve closure of the Navier-Stokes equations are known to be rigorously incorrect. While these models serve a definite purpose, they are inadequate for the general prediction of hypersonic viscous/inviscid interactions, mixing problems, chemical nonequilibria, and a range of other phenomena which must be predicted in order to design a hypersonic vehicle computationally. Due to the complexity of turbulence, useful new turbulence models are synthesized only when great expertise is brought to bear and considerable intellectual energy is expended. Although this process is fundamentally theoretical, crucial guidance may be gained from carefully-executed basic experiments. Following the birth of a new model, its testing and validation once again demand comparisons with data of unimpeachable quality. This report concerns these issues which arise from the experimental aspects of hypersonic modeling and represents the results of the first phase of an effort to develop compressible turbulence models.
Complementarity of representations in quantum mechanics

We show that Bohr's principle of complementarity between position and momentum descriptions can be formulated rigorously as a claim about the existence of representations of the CCRs. In particular, in any representation where the position operator has eigenstates, there is no momentum operator, and vice versa. Equivalently, if there are nonzero projections corresponding to sharp position values, all spectral projections of the momentum operator map onto the zero element.
Fourier finite-difference wave propagation

We introduce a novel technique for seismic wave extrapolation in time. The technique involves cascading a Fourier transform operator and a finite-difference operator to form a chain operator: Fourier finite differences (FFD). We derive the FFD operator from a pseudoanalytical solution of the acoustic wave equation. Two-dimensional synthetic examples demonstrate that the FFD operator can have high accuracy and stability in complex-velocity media. Applying the FFD method to the anisotropic case overcomes some disadvantages of other methods, such as the coupling of qP-waves and qSV-waves. The FFD method can be applied to enhance accuracy and stability of seismic imaging by reverse time migration.
Mass spectrometry-based proteomics: existing capabilities and future directions

Mass spectrometry (MS)-based proteomics is emerging as a broadly effective means for identification, characterization, and quantification of proteins that are integral components of the processes essential for life. Characterization of proteins at the proteome and sub-proteome (e.g., the phosphoproteome, proteoglycome, or degradome/peptidome) levels provides a foundation for understanding fundamental aspects of biology. Emerging technologies such as ion mobility separations coupled with MS and microchip-based-proteome measurements combined with MS instrumentation and chromatographic separation techniques, such as nanoscale reversed phase liquid chromatography and capillary electrophoresis, show great promise for both broad undirected and targeted highly sensitive measurements. MS-based proteomics increasingly contribute to our understanding of the dynamics, interactions, and roles that proteins and peptides play, advancing our understanding of biology on a systems wide level for a wide range of applications including investigations of microbial communities, bioremediation, and human health.
An IRAS-Based Search for New Dusty Late-Type WC Wolf-Rayet Stars

I have examined all Infrared Astronomical Satellite (IRAS) data relevant to the 173 Galactic Wolf-Rayet (W-R) stars in an updated catalog, including the 13 stars newly discovered by Shara and coworkers. Using the W-R coordinates in these lists, I have examined the IRAS Point Source Catalog (PSC), the Faint Source Catalog, and the Faint Source Reject Catalog, and have generated one-dimensional spatial profiles, 'ADDSCANs', and two-dimensional full-resolution images, 'FRESCOS'. The goal was to assemble the best set of observed IRAS color indices for different W-R types, in particular for known dusty late-type WC Wolf-Rayet (WCL) objects. I have also unsuccessfully sought differences in IRAS colors and absolute magnitudes between single and binary W-R stars. The color indices for the entire ensemble of W-R stars define zones in the IRAS color-color ([12] - [25], [25] - [60])-plane. By searching the PSC for otherwise unassociated sources that satisfy these colors, I have identified potential new W-R candidates, perhaps too faint to have been recognized in previous optical searches. I have extracted these candidates' IRAS low-resolution spectrometer (LRS) data and compared the spectra with the highly characteristic LRS shape for known dusty WCL stars. The 13 surviving candidates must now be ex amined by optical spectroscopy. This work represents a much more rigorous and exhaustive version of the LRS study that identified IRAS 17380 - 3031 (WR98a) as the first new W-R (WC9) star discovered by IPAS. This search should have detected dusty WCL stars to a distance of 7.0 kpc from the Sun, for l is greater than 30 degrees, and to 2.9 kpc even in the innermost galaxy. For free-free-dominated W-R stars the corresponding distances are 2.5 and 1.0 kpc, respectively.
Expensive Speech, Illegitimate Power: Corporations and Free Expression

All legitimate democratic governments must remain responsive to the interests of their citizens. Such responsiveness depends, in turn, on the right of free expression, without which citizens cannot make their interests and grievances known. When citizens must compete for attention and influence with powerful private corporations, however, unregulated expression can become a danger to democracy. Drawing ideas from the republican tradition of political thought, this essay argues that political speech funded by business corporations—not just during election campaigns but in all political seasons—threatens the legitimacy of American government. The essay advances an egalitarian, democratic theory of free expression and uses the theory to clarify the relationship between free speech and vibrant democracy. It then defends ambitious restrictions on corporate political speech that extend far beyond campaign-finance reform.
Complex Behavior in “Old” and “Young” Rats

A group of albino rats aged 600 to 640 days was compared with four animals aged 90 to 130 days with regard to their performance on a sequential three-lever chain. The older animals gave significantly more total responses than the younger rats. Mean number of correct responses as well as percentage of accurate responses, on the other hand, favored the younger animals. Increased deprivation did not enhance performance of older animals.
Resolving the Dusty Circumstellar Structure of the Enigmatic Symbiotic Star CH Cygni with the MMT Adaptive Optics System

We imaged the symbiotic star CH Cyg and two PSF calibration stars using the unique 6.5 m MMT deformable secondary adaptive optics system. Our high-resolution (FWHM = 03), very high Strehl (98% ± 2%), mid-infrared (9.8 and 11.7 μm) images of CH Cyg allow us to probe finer length scales than ever before for this object. CH Cyg is significantly extended compared to our unresolved PSF calibration stars (μ UMa and α Her) at 9.8 and 11.7 μm. We estimated the size of the extension by convolving a number of simple Gaussian models with the μ UMa PSF and determining which model provided the best fit to the data. Adopting the Hipparcos distance for this object of 270 pc, we found a nearly Gaussian extension with a FWHM at 9.8 μm of ~40.5 ± 2.7 AU (015 ± 001) and a FWHM at 11.7 μm of 45.9 ± 2.7 AU (017 ± 001). After subtracting out the Gaussian component of the emission (convolved with our PSF), we found a faint ~ 07 asymmetric extension, which peaks in flux ~05 north of the stars. This extension is roughly coincident with the northern knotlike feature seen in HST WFPC2 images obtained in 1999.
Stochastic Acceleration of Solar Flare Protons.

The acceleration of solar flare protons is considered by cyclotron damping of intense Alfven wave turbulence in a magnetic trap. The energy diffusion coefficient is computed for a near-isotropic distribution of super-Alfvenic protons and a steady-state solution for the particle spectrum is found for both transit-time and diffusive losses out of the ends of the trap. The acceleration time to a characteristic energy approximately 20 Mev/nucl can be as short as 10 sec. On the basis of phenomenological arguments an omega/2 frequency dependence for the Alfven wave spectrum is inferred. The correlation time of the turbulence lies in the range .0005 less than tau/corr less than .05s.
Relativistic and Classical Doppler Electronic Tracking Accuracies

The first-order Doppler effect has, in general, been used in electronic tracking, but for the greater accuracies now desired in velocity measurements, this approach is no longer satisfactory. A fundamental study of the Doppler effect is presented in this paper. Five steps are developed which enable the exact derivation of the Doppler equations for any system. Six different configurations of transmitter, receiver, and vehicle are investigated, and the results are applied to a number of Doppler systems. It is determined that, for velocity inaccuracies <1.0 fps, the second-order relativistic or classical equations must be used. The receipt of a zero Doppler shift has also been investigated, and it does not necessarily imply zero line-ofsight velocity. Nomenclature a = proportional frequency shift factor produced by a beacon 6 = constant frequency shift factor produced by a beacon c = velocity of light / = frequency h = factor relating the constant frequency shift to the proportional shift produced by a beacon N = wave normal of a plane wave t = time parameter v = velocity magnitude V = velocity relative to the earth w = phase velocity X = position vector Subscripts i = receiver-fixed reference system when subscript 0 refers to transmitter d = Doppler received by a beacon r = receiver reference system t = transmitter reference system v = vehicle 0 = fixed reference system (receiver or transmitter as the case may be)
Design of Optimum Structures to Impulse Type Loading

The purpose of this paper is to present the results of an analytical study on optimization problems involving large structures subjected to impulse type loading. The impact due to aircraft landing, aerodynamic gust, and the effect of blast waves are a few examples of impulse-type loadings on aerospace structures. The method of optimization presented in this paper is called designing in the dynamic mode. The dynamic mode may be a single natural mode of the structure or a combination of a set of natural modes depending on the spatial distribution and dynamic characteristics of the forcing function. The aperiodic forcing function is represented by Fourier integral in determining the dynamic response. A procedure for determining the participating modes in the dynamic response is discussed. The illustrative examples are a wing structure and a circular arch.
Creep of Intersecting Equal Diameter Cylindrical Shells Under Internal Pressure

The creep behavior in the crotch region of two normally intersecting cylindrical shells of equal diameter and thickness is treated with the aid of an axisymmetric shell model. The edge and pressure loads on this model, which has already proved to be useful in the case of elastic and elastic-plastic analysis, are chosen to simulate the loading in the crotch region. The model is used to calculate the redistribution of stress from the elastic state to the stationary state. By taking into account the wall thinning, which occurs as creep takes place, the critical elapsed time to rupture of a ductile vessel is estimated.
Dynamic properties of the welfare caseload

The welfare caseload evolves through a process of flows onto and off of welfare that can be described with a Markov Chain model. Using formal results for Markov models, this paper examines the dynamic properties of the welfare caseload. In particular, we examine steady states, the speed of convergence, and the relative importance of entry and exit for changes in the caseload. Implementing these models with administrative data for California, we find that the welfare caseload has considerable momentum and that adjustments are far from instantaneous. In addition, we find that changes in the entry rate are empirically more important than changes in the exit rate for explaining changes in the overall caseload. These findings have several implications for the conventional methods that are used to study the changing caseload.
Biophysical aspects of microsphere engulfment by human neutrophils

A quantitative investigation into the mechanism of neutrophil phagocytosis of opsonized microspheres possessing well defined dimensions was undertaken. Three aspects were documented: membrane conservation, cell adhesion to the spheres, and active cell cytoplasmic projection around the microspheres. The physical act of internalizing a particle by a cell involves a reduction in its plasma membrane area and an increase in its volume. As a consequence, a cell can internalize only a finite number of particles. A store of membrane area exists on cytoplasmic granules and may be recruited during phagocytosis. Previous measurements of neutrophil membrane area and volume served as a basis for estimates of the maximum number of internalized microspheres. A comparison with experimental prediction based on membrane conservation and degranulation agrees within 10% for a range of microsphere diameters, from 0.5 to 8 microns. This suggests that the limitation for additional particle uptake in the population of engorged neutrophils is the lack of excess plasma membrane area. In a random population of neutrophils, there was a sub-group, approximately 40%, which could no longer phagocytose before depleting their membrane stores. Several aspects of the engulfment process were investigated to elucidate the cause of this phagocytosis deficiency. It could be shown by single cell observation that these cases were associated with a lack of pseudopod projection, although adhesion was still evident between the cell membrane and the microspheres.
Developing an Application for Refractory Open Cell Metal Foams in Jet Engines

The thermodynamic efficiency of the Brayton cycle, upon which all gas turbines (aeropropulsion and power generation) are based on scales with the peak operating temperature. However, the peak temperature is limited by the turbine blades and the temperature they can withstand. The highest temperatures in the gas turbine occur in the combustor region but these temperatures are often too high for turbine blades. As a result, the combustion products must be diluted with relatively cooler air from the compressor to reduce the temperature to tolerable levels for the turbine blades. This research suggests placing a ring of high temperature open cell metal foam between the combustors and turbine sections of the jet engine to mix and average the difference in temperatures resulting from the cooling schemes in combustor cans. Temperature mixing effect was tested using a special setup with the application of an infrared camera and streams of hot and cold air passing through the foam. High speed flow pressure drop around Mach 1 (340 m/s) was done on the same foam samples to understand pressure drop in the compressible regime of air. Infrared imaging showed that open cell metal foams successfully mixed and averaged the difference in temperatures of the hot and cold gasses thus creating a more uniform temperature profile while pressure drop testing revealed that open cell metal foams result in minimal pressure drop at high flows especially when the increase in temperature in taken into consideration.
Visualizing reference patterns for solving memory leaks in Java

Many Java programmers believe they do not have to worry about memory management because of automatic garbage collection. In fact, many Java programs run out of memory unexpectedly after performing a number of operations. A memory leak in Java is caused when an object that is no longer needed cannot be reclaimed because another object is still referring to it. Memory leaks can be difficult to solve, since the complexity of most programs prevents us from manually verifying the validity of every reference. In this paper we show a new methodology for finding the causes of memory leaks. We have identified a basic memory leak scenario which fits many important cases. In this scenario, we allow the programmer to identify a period of time in which temporary objects are expected to be created and released. Using this information we are able to identify objects that persist beyond this period and the references which are holding on to them. Scaling this methodology to real-world systems brings additional challenges. We propose a novel combination of visual syntax and reference pattern extraction to manage this additional complexity. We also describe how these techniques can be applied to a wider class of memory problems, including the exploration of large data structures. These techniques have been implemented and have been proven successful on large projects.
Thermonuclear X-ray bursts: theory vs. observations

Abstract I review our theoretical understanding of thermonuclear flashes on accreting neutron stars, concentrating on comparisons to observations. Sequences of regular Type I X-ray bursts from GS 1826-24 and 4U 1820-30 are very well described by the theory. I discuss recent work which attempts to use the observed burst properties in these sources to constrain the composition of the accreted material. For GS 1826-24, variations in αwith accretion rate indicate that the accreted material has solar metallicity; for 4U 1820-30, future observations should constrain the hydrogen fraction, testing evolutionary models. I briefly discuss the global bursting behavior of burst sources, which continues to be a major puzzle. Finally, I turn to superbursts, which naturally fit into the picture as unstable carbon ignition in a thick layer of heavy elements. I present new time-dependent models of the cooling tails of superbursts, and discuss the various interactions between superbursts and normal Type I bursts, and what can be learned from them.
Solar calibration of stellar rotation tracers

A study of the time variability of the disk-integrated solar magnetic flux, with a view to the behavior of emission-line intensity variations observed in lower main sequence stars, has determined that solar rotation modulation of the integrated flux is present in 75% of all rotations. For observing intervals of more than twice the lifetime of the features causing rotational modulation, the correct rotation period is identified in more than 90% of all cases. The optimum time for measuring rotational modulation is the decay phase of the activity cycle, and the solar rotation period is measured with an accuracy of a few percent. The lifetime of a rotational modulation period is approximately five rotations, and a sensitivity limit of Delta S= 0.005 is found for the Vaughan et al (1981) stellar rotation measures.
The shielding of muons around high energy electron accelerators: Theory and measurement

Abstract The muon flux density and the absorbed dose rate that is produced when a high energy electron beam is completely attenuated in matter is calculated by integrating the muon pair production cross section over the photon distribution in the electromagnetic shower. Several cross section and photon track lenght formulae are examined. The Fermi-Eyges theory of multiple scattering is applied to the case of 1 to 20 GeV muons penetrating thick shields, and the results are folded into the production theory. An 18 GeV electron beam was used to produce muons in order to verify the theory. The results indicate that the theory, even with multiple scattering included, does not correctly predict the shape of the angular dose rate distribution, although integration over the theoretical and experimental curves gives agreement within experimental error.
Long time behavior of solutions to the mKdV

ABSTRACTIn this paper we consider the long time behavior of solutions to the modified Korteweg-de Vries equation on ℝ. For sufficiently small, smooth, decaying data we prove global existence and derive modified asymptotics without relying on complete integrability. We also consider the asymptotic completeness problem. Our result uses the method of testing by wave packets, developed in the work of Ifrim and Tataru on the 1d cubic nonlinear Schrodinger and 2d water wave equations.
Arcjet Anode Plasma Measurements Using Electrostatic Probes

A 1-kW hydrazine arcjet thruster has been modie ed for internal probing of the anode sheath boundary layer with an array of 14 electrostatic microprobes e ush mounted into the anode body. Axial and azimuthal distributions of the plasma properties e oating potential, anode sheath potential, wall current density, electron number density, and electron temperature have been obtained for arc currents between 7.8 and 10.6 A and propellant e ow rates of 40 ‐60 mg/s. The specie c power ranged from 18.8 to 27.4 MJ/ kg. Azimuthal symmetry has been verie ed for all arcjet operating conditions. The electron temperature data show that the near-anode plasma is highly nonequilibrium. Most of the current density and anode heating is located within 2 ‐4 mm of the constrictor exit, with the location affected more by mass e ow rate than by arc current. The axial anode heating distribution is closely coupled to current density and accounts for ;18‐24% of the total input power. Reasonable agreement between a numerical model and experimental results is found for a constant value of the electron inelastic energy-loss factor.
Synthesis and Biological Evaluation of 9-Substituted Tetracycline Derivatives.

The synthesis of 9-substituted tetracycline derivatives has been accomplished by the reaction of C9 diazonium tetrafluoroborate tetracycline salts with organotin reagents under modified Stille coupling conditions. Several of these unreported derivatives show promising in vitro biological activity against tetracycline resistant and antibiotic resistant bacteria.
Almost All Palindromes Are Composite

First published in Mathematical Research Letters 11 (2004) nos.5-6, pp.853-868, published by International Press. ©International Press.
A New Approach to Probing Large-Scale Power with Peculiar Velocities

We propose a new strategy for probing the power spectrum on large scales using galaxy peculiar velocities. We explore the properties of surveys that cover only two small fields in opposing directions on the sky. Surveys of this type have several advantages over those that attempt to cover the entire sky; in particular, by concentrating on galaxies in narrow cones, these surveys are able to achieve the density needed to measure several moments of the velocity field with only a modest number of objects, even for surveys designed to probe scales 100 h-1 Mpc. We construct mock surveys with this geometry and analyze them in terms of the three moments to which they are most sensitive. We calculate window functions for these moments and construct a χ2 statistic that can be used to put constraints on the power spectrum. In order to explore the sensitivity of these surveys, we calculate the expectation values of the moments and their associated measurement noise as a function of the survey parameters such as density and depth for several popular models of structure formation. In addition, we have studied how well these kinds of surveys can distinguish between different power spectra and found that, for the same number of objects, cone surveys are as good as or better than full-sky surveys in distinguishing between popular cosmological models. We find that a survey with 200-300 galaxy peculiar velocities with distance errors of 15% in two cones with an opening angle of ~10° could put significant constraints on the power spectrum on scales of 100-300 h−1 Mpc, where few other constraints exist. We believe that surveys of the kind we describe here could provide a valuable tool for the study of large-scale structure on these scales and present a viable alternative to full-sky surveys.