cssi/SciSciGPT-SciSciNet huggingface dataset:
The Role of Mixing in Astrophysics

The role of hydrodynamic mixing in astrophysics is reviewed, emphasizing its connections with laser physics experiments and inertial confinement fusion. Computer technology now allows us to use two-dimensional simulations, with complex microphysics, of stellar hydrodynamics and evolutionary sequences, and it holds the promise of simulations in three dimensions. Careful validation of astrophysical methods by laboratory experiment, by the critical comparison of numerical and analytical methods, and by observation are necessary for the development of simulation methods with reliable predictive capabilities. The recent and surprising results from isotopic patterns in presolar grains, from two-dimensional hydrodynamic simulations of stellar evolution, and from laser tests and computer simulations of Richtmeyer-Meshkov and Rayleigh-Taylor instabilities will be discussed in relation to stellar evolution and supernovae.
The Surface-Pressure Signature of Atmospheric Tides in Modern Climate Models

Abstract Although atmospheric tides driven by solar heating are readily detectable at the earth’s surface as variations in air pressure, their simulations in current coupled global climate models have not been fully examined. This work examines near-surface-pressure tides in climate models that contributed to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC); it compares them with tides both from observations and from the Whole Atmosphere Community Climate Model (WACCM), which extends from the earth’s surface to the thermosphere. Surprising consistency is found among observations and all model simulations, despite variation of the altitudes of model upper boundaries from 32 to 76 km in the IPCC models and at 135 km for WACCM. These results are consistent with previous suggestions that placing a model’s upper boundary at low altitude leads to partly compensating errors—such as reducing the forcing of the tides by ozone heating, but also introducing spurious waves at the u...
Experience with approximate reliability-based optimization methods

Traditional reliability-based design optimization (RBDO) requires a double loop iteration process. The inner optimization loop is to find the most probable point (MPP) and the outer is the regular optimization loop to optimize the RBDO problem with reliability objectives or constraints. It is well known that the computation can be prohibitive when the associated function evaluation is expensive. As a result, many approximate RBDO methods, which convert the double loop to a single loop, have been developed. In this work, several approximate RBDO methods are coded, discussed, and tested against a double loop algorithm through four design problems.
Interfirm Collaboration Networks: The Impact of Large-Scale Network Structure on Firm Innovation

The structure of alliance networks influences their potential for knowledge creation. Dense local clustering provides information transmission capacity in the network by fostering communication and cooperation. Nonredundant connections contract the distance between firms and give the network greater reach by tapping a wider range of knowledge resources. We propose that firms embedded in alliance networks that exhibit both high clustering and high reach (short average path lengths to a wide range of firms) will have greater innovative output than firms in networks that do not exhibit these characteristics. We find support for this proposition in a longitudinal study of the patent performance of 1,106 firms in 11 industry-level alliance networks.
Differentiation of Physiologically Significant Coronary Artery Lesions by Coronary Blood Flow Measurements During Isoproterenol Infusion

At cardiac catheterization, the effect of isoproterenol on coronary blood flow was compared in six patients with normal coronary arteries and normal left ventricular function, and eight patients with angiographically defined coronary lesions. Coronary blood flow was measured by selective coronary artery injection of xenon-133 and external monitoring of disappearance curves with a dual probe, digital scintillation counter. Resting values did not differ in the two groups. In the normal group isoproterenol increased mean coronary blood flow 93 ml/100 g/min (152%) and cardiac output 2.3 liters/min (42%); coronary resistance/100 g decreased 60 ± 4% (sem), while total peripheral resistance decreased 29 ± 4%. In the coronary disease group coronary blood flow increased 20 ml/100 g/min (33%) and cardiac output increased 2.8 liters/min (62%); coronary resistance decreased 26 ± 9% and total peripheral resistance decreased 37 ± 4%. In all normal patients the percent increase in coronary blood flow markedly exceeded the percent increase in cardiac output and the percent fall in coronary resistance markedly exceeded the percent fall in total peripheral resistance. In six of the eight patients with coronary lesions the percent increase in coronary blood flow was less than the percent increase in cardiac output and the fall in coronary resistance was less than the fall in total peripheral resistance. Thus measurement of coronary blood flow, cardiac output, and aortic pressure before and during isoproterenol infusion may permit differentiation of those subjects with physiologically significant coronary obstructions.
Political entrepreneurship and the formation of special districts

Where general purpose governments provide a bundle of services within their boundaries, special district governments provide specific services inside the boundaries of general purpose governments. The alternative to forming a special purpose government is providing the service within a general purpose government. Formation of a special district represents the establishment of a new political enterprise, in contrast to the addition of a new product line to an existing government. We explore the formation of special districts as a particular form of the universal entrepreneurial search for gain or profit from exchange. Political entrepreneurship, like market entrepreneurship, operates inside some framework of rules, and the formation of special districts reflects the search for political gain within that framework of rules. We use an entrepreneurial framework to formulate several hypotheses concerning the formation and organization of special districts.
Special relations in automated deduction

Two deduction rules are introduced to give streamlined treatment to relations of special importance in an automated theorem-proving system. These rules, the relation replacement and relation matching rules, generalize to an arbitrary binary relation the paramodulation and E-resolution rules, respectively, for equality, and may operate within a nonclausal or clausal system. The new rules depend on an extension of the notion of polarity to apply to subterms as well as to subsentences, with respect to a given binary relation. The rules allow us to eliminate troublesome axioms, such as transitivity and monotonicity, from the system; proofs are shorter and more comprehensible, and the search space is correspondingly deflated.
A Monitor of the Focusing Strength of Plasma Lenses using MeV Synchrotron Radiation

The focusing strength of plasma lenses used with high energy electron or positron beams can give rise to synchrotron radiation with critical energies in the MeV range. A method is described for measuring the characteristic energy of this radiation as a way of monitoring the strength of the focus. The principle has been implemented in a plasma lens experiment with a 28.5 GeV positron beam.
The palladium-catalyzed trifluoromethylation of vinyl sulfonates.

A method for the palladium-catalyzed trifluoromethylation of cyclohexenyl sulfonates has been developed. Various cyclohexenyl triflates and nonaflates underwent trifluoromethylation under mild reaction conditions using a catalyst system composed of Pd(dba)2 or [(allyl)PdCl]2 and the monodentate biaryl phosphine ligand tBuXPhos. The trifluoromethyl anion (CF3–) or its equivalent for the process was generated in situ from TMSCF3 in combination with KF or TESCF3 in combination with RbF.
Multiwavelength Observations of Ultraluminous X-Ray Sources

Multiwavelength observations may help us understand the physical nature of the ultraluminous X-ray sources (ULXs) found in external galaxies. Enabled by the arcsecond X-ray source positions now available from Chandra, there has been significant recent progress in the identification of optical and radio counterparts to ULXs. Recent results are reviewed on the identification of optical stellar counterparts to ULXs, the relation between ULXs and regions of active star formation, the study of optical nebular counterparts to ULXs, and the estimation of the luminosity of an ULX via its influence on a surrounding nebula.
Streamline-Based Production Data Integration in Naturally Fractured Reservoirs

Streamline-Based Production Data Integration in Naturally Fractured Reservoirs. (May 2005) Mishal Habis Al Harbi, B.S., King Fahd University of Petroleum and Minerals, Saudi Arabia; M.S., Stanford University Chair of Advisory Committee: Dr. Akhil Datta-Gupta Streamline-based models have shown great potential in reconciling high resolution geologic models to production data. In this work we extend the streamline-based production data integration technique to naturally fractured reservoirs. We use a dualporosity streamline model for fracture flow simulation by treating the fracture and matrix as separate continua that are connected through a transfer function. Next, we analytically compute the sensitivities that define the relationship between the reservoir properties and the production response in fractured reservoirs. Finally, production data integration is carried out via the Generalized Travel Time inversion (GTT). We also apply the streamline-derived sensitivities in conjunction with a dual porosity finite difference simulator to combine the efficiency of the streamline approach with the versatility of the finite difference approach. This significantly broadens the applicability of the streamlinebased approach in terms of incorporating compressibility effects and complex physics. The number of reservoir parameters to be estimated is commonly orders of magnitude larger than the observation data, leading to non-uniqueness and uncertainty in reservoir parameter estimate. Such uncertainty is passed to reservoir response forecast which needs to be quantified in economic and operational risk analysis. In this work we sample parameter uncertainty using a new two-stage Markov Chain Monte Carlo (MCMC) that is very fast and overcomes much of its current limitations. The computational efficiency comes through a substantial increase in the acceptance rate during MCMC by using a fast linearized approximation to the flow simulation and the likelihood function, the critical link between the reservoir model and production data.
SHORT-LIVED RADIO BURSTS FROM THE CRAB PULSAR

Our high-time-resolution observations reveal that individual main pulses from the Crab pulsar contain one or more short-lived microbursts. Both the energy and duration of bursts measured above 1 GHz can vary dramatically in less than a millisecond. These fluctuations are too rapid to be caused by propagation through turbulence in the Crab Nebula or in the interstellar medium; they must be intrinsic to the radio emission process in the pulsar. The mean duration of a burst varies with frequency as {nu}{sup -2}, significantly different from the broadening caused by interstellar scattering. We compare the properties of the bursts to some simple models of microstructure in the radio emission region.
POPULATION AND THE ENVIRONMENT: POLLS, POLICIES, AND PUBLIC OPINION

Although recent academic and popular attention has argued for a wedding between population and environmental problems and policies, the scientific knowledge base for these topics has grown separately and at differential rates. Environmental research has grown faster than population research, while the joint treatment of these topics remains in its infancy. International polls that have included many questions concerning environmental attitudes have included far fewer on population. The few surveys on population attitudes have ignored the environment. The World Fertility Survey and the Demographic and Health Survey are fertility, rather than population, surveys. They have been useful in precipitating national policies on family planning, but are poor models for needed attitudinal and cognitive research on population and the environment. Some contemporary polls, such as the UNDEP sponsored poll conducted by the Louis Harris Agency, have serious methodological defects. Others, such as the 1992 Gallup poll, contain valuable data from which future surveys could profit. The conclusion outlines the need for a new multinational survey of Population/Environment Knowledge, Attitude and Practice (PEKAP).
Reading Tomorrow’s Newspaper: Predictability in ETF Returns

We study the persistence of ETF premiums and discounts. Following a day of high or low premiums, or premiums or discounts over NAV, ETFs tend to maintain a premium or discount for as many as five days, though there is some regression to the mean. Premiums also predict distinct patterns of returns on the following day. Overnight prices drop following a high premium, but high-premium ETFs have significantly higher returns the next day. Surprisingly, the NAV returns over the next day also tend to be positive. Discounts show a similar but opposite pattern, with smaller magnitudes. We conclude that ETF premiums and discounts have some ability to predict future returns, including the fundamental returns of the underlying assets.
Planetary radar astronomy

Radar is a powerful technique that has furnished otherwise unavailable information about solar system bodies for three decades. The advantages of radar in planetary astronomy result from (1) the observer's control of all the attributes of the coherent signal used to illuminate the target, especially the wave form's time/frequency modulation and polarization; (2) the ability of radar to resolve objects spatially via measurements of the distribution of echo power in time delay and Doppler frequency; (3) the pronounced degree to which delay-Doppler measurements constrain orbits and spin vectors; and (4) centimeter-to-meter wavelengths, which easily penetrate optically opaque planetary clouds and cometary comae, permit investigation of near-surface macrostructure and bulk density, and are sensitive to high concentrations of metal or, in certain situations, ice. Planetary radar astronomy has primarily involved observations with Earth-based radar telescopes, but also includes some experiments with a spaceborne transmitter or receiver. In addition to providing a wealth of information about the geological and dynamical properties of asteroids, comets, the inner planets, and natural satellites, radar experiments have established the scale of the solar system, have contributed significantly to the accuracy of planetary ephemerides, and have helped to constrain theories of gravitation. This review outlines radar astronomical techniques and describes principal observational results.
On matroids and hierarchical graphs

We describe a hierearchical algorithm for computing optimum bases of certain matroids defined on graphs. Two families of matroids are introduced and polynomial-time algorithms for determining costs of their optimum bases are presented.
Feedback-Based Collaborative Secrecy Encoding Over Binary Symmetric Channels

In this paper, we propose a feedback scheme for transmitting secret messages between two legitimate parties, over an eavesdropped communication link. Relative to Wyner's traditional encoding scheme, our feedback-based encoding often yields larger rate-equivocation regions and achievable secrecy rates. More importantly, by exploiting the channel randomness inherent in the feedback channels, our scheme achieves a strictly positive secrecy rate even when the eavesdropper's channel is less noisy than the legitimate receiver's channel. All channels are modeled as binary and symmetric. We demonstrate the versatility of our feedback-based encoding method by using it in three different configurations: the stand-alone configuration, the mixed configuration (when it combines with Wyner's scheme), and the reversed configuration. Depending on the channel conditions, significant improvements over Wyner's secrecy capacity can be observed in all configurations.
Comet-solar wind interaction - Dynamical length scales and models

ICE magnetometer measurements at Comet Giacobini-Zinner and model simulations of comet-solar wind interactions are analyzed. The magnetometer data reveal the existence of intense hydromagnetic turbulence, a draping of the magnetic field lines to form a magnetotail, a weak shock, and a magnetic barrier region in the magnetosphere. The global models of the comet-solar wind interaction are described. The observed data and models are compared and good correlation is displayed.
The development of a smart distribution grid testbed for integrated information management systems

This paper presents a smart distribution grid testbed to test or compare designs of integrated information management systems (I2MSs). An I2MS extracts and synthesizes information from a wide range of data sources to detect abnormal system behaviors, identify possible causes, assess the system status, and provide grid operators with response suggestions. The objective of the testbed is to provide a modeling environment with sufficient data sources for the I2MS design. The testbed includes five information layers and a physical layer; it generates multi-layer chronological data based on actual measurement playbacks or simulated data sets produced by the physical layer. The testbed models random hardware failures, human errors, extreme weather events, and deliberate tampering attempts to allow users to evaluate the performance of different I2MS designs. Initial results of I2MS performance tests showed that the testbed created a close-to-real-world environment that allowed key performance metrics of the I2MS to be evaluated.
A Compartmental Model for Traffic Networks and Its Dynamical Behavior

We propose a macroscopic traffic network flow model suitable for analysis as a dynamical system, and we qualitatively analyze equilibrium flows as well as convergence. Flows at a junction are determined by downstream supply of capacity as well as upstream demand of traffic wishing to flow through the junction. This approach is rooted in the celebrated Cell Transmission Model for freeway traffic flow. Unlike related results which rely on certain system cooperativity properties, our model generally does not possess these properties. We show that the lack of cooperativity is in fact a useful feature that allows traffic control methods, such as ramp metering, to be effective. Finally, we leverage the results of the technical note to develop a linear program for optimal ramp metering.
A compact Q-K-band dual frequency feed horn

A millimeter-wave dual frequency circularly polarized feed for an offset reflector antenna is being developed for a portable satellite ground terminal. The two frequency bands are Q - and K -bands for transmit and receive, respectively. A compact feed design consisting of a single corrugated horn with two circular waveguide concentric openings at the horn throat is described. Good aperture efficiency and low sidelobes in both of the frequency bands are achieved.
Genital and intestinal carriage of group B streptococci during pregnancy

To evaluate the relative importance of genital and gastrointestinal carriage of group B streptococci, repeated semiquantitative and quantitative cultures were obtained from 64 patients during pregnancy. Carriage was documented in 20% of the women at the first visit, in 41 % of the women cumulatively, and at 24% of 295 visits. Group B streptococci were isolated from 20% of genital, 17% of rectal, and 17% of stool cultures. Concordance of carriage among these body sites was high (87%-93%) for cultures collected simultaneously. Counts of streptococci ranged between 102 and 107 colony-forming units per gram of dry stool (geometric mean, 2.3 x 105) and varied widely among repeated samples from chronic carriers. The group B streptococci tended to appear, persist, and disappear simultaneously in genital, rectal, and stool cultures of individuals, although some women appeared to harbor the organism in the birth canal or lower bowel alone.
Weak convergence in applied probability

Abstract Weak convergence of probability measures on function spaces has been active area of research in recent years. While the theory has a somewhat abstract base, it is extremely useful in a wide variety of problems and we believe has much to offer to applied probability. Our aim in this survey paper is to discuss those aspects of the theory which are relevant to work in applied probability. After an introduction to the foundations of weak convergence, we shall discuss partial sum, point, Markov and extremal processes. These processes form the building blocks for many of the important models of applied probability.
First-order logical filtering

Logical filtering is the process of updating a belief state (set of possible world states) after a sequence of executed actions and perceived observations. In general, it is intractable in dynamic domains that include many objects and relationships. Still, potential applications for such domains (e.g., semantic web, autonomous agents, and partial-knowledge games) encourage research beyond intractability results. In this paper we present polynomial-time algorithms for filtering belief states that are encoded as First-Order Logic (FOL) formulas. Our algorithms are exact in many cases of interest. They accept belief states in FOL without functions, permitting arbitrary arity for predicates, infinite universes of elements, and equality. They enable natural representation with explicit references to unidentified objects and partially known relationships, still maintaining tractable computation. Previous results focus on more general cases that are intractable or permit only imprecise filtering. Our algorithms guarantee that belief-state representation remains compact for STRIPS actions (among others) with unbounded-size domains. This guarantees tractable exact filtering indefinitely for those domains. The rest of our results apply to expressive modeling languages, such as partial databases and belief revision in FOL.
An Extended Lagrangian Method

A unique formulation of describing fluid motion is presented. The method, referred to as "extended Lagrangian method," is interesting from both theoretical and numerical points of view. The formulation offers accuracy in numerical solution by avoiding numerical diffusion resulting from mixing of fluxes in the Eulerian description. The present method and the Arbitrary Lagrangian-Eulerian (ALE) method have a similarity in spirit?eliminating the cross-streamline numerical diffusion. For this purpose, we suggest a simple grid constraint condition and utilize an accurate discretization procedure. This grid constraint is only applied to the transverse cell face parallel to the local stream velocity, and hence our method for the steady state problems naturally reduces to the streamline-curvature method, without explicitly solving the steady streamline-coordinate equations formulated a priori. Unlike the Lagrangian method proposed by Loh and Hui which is valid only for steady supersonic flows, the present method is general and capable of treating subsonic flows and supersonic flows as well as unsteady flows, simply by invoking in the same code an appropriate grid constraint suggested in this paper. The approach is found to be robust and stable. It automatically adapts to flow features without resorting to clustering, thereby maintaining rather uniform grid spacing throughout and large time step. Moreover, the method is shown to resolve multi-dimensional discontinuities with a high level of accuracy, similar to that found in one-dimensional problems.
Mathematical models of graphics

Publisher Summary This chapter reviews some mathematical models for graphics as data sources and the interplay between these models and coding schemes. Graphics include the following three classes of images: (1) images that are nominally two tone, (2) binary images derived from continuous-tone images, (3) and binary images created in some continuous-tone image coding schemes. A majority of the current efficient coding schemes for two-tone images are based directly or indirectly on the concept of transmitting contours or boundary points. The chapter also discusses the application of contour tracing, for which one needs to store the entire image at the transmitting and the receiving end. The most optimal and efficient way of coding uses the idea of pattern recognition. This is particularly appealing in the case of typewritten and printed matter. An important comparison one can make among the various coding schemes is how their compression factors depend on image resolution or sampling density.
Dollarization and Trade

Abstract A series of papers by Andrew Rose and co-authors showing large and statistically significant effects of a currency union on bilateral trade supports the view that dollarization would promote trade between a country adopting the dollar and the United States. This paper presents results that cast doubt on the trade-enhancing effects of dollarization among those countries most likely to adopt this policy. Currency unions do not significantly promote bilateral trade of Western Hemisphere countries that have experience with dollarization, nor do they affect bilateral United States trade with non-industrial countries or with Western Hemisphere countries.
Simultaneous Design of Active Vibration Control and Passive Viscous Damping

Structural engineers have found that passive damping can reduce the amount of active damping required to control structural vibration. Conversely, improperly designed passive damping can inadvertently increase system reaction times, reducing control effectiveness. This paper presents several techniques for blending active vibration control and passive viscous damping. A closed-form optimal solution for minimizing a quadratic cost functional is derived, but it is shown to be dependent on the initial conditions and produces time-varying damping coefficients. To eliminate the dependence on initial conditions, solution techniques for suboptimal, state independent solutions are developed. The suboptimal solutions require less computation effort, but still give good estimates of the optimal solution. The advantages and disadvantages of the different solution techniques are discussed with respect to computation requirements and robustness. Methods of comparing competing designs are also discussed. Several numerical examples illustrate the similarities and differences of the various techniques. More importantly, the examples demonstrate the significant improvements achievable by simultaneously designing passive and active damping.
The Ground State Energy of Dilute Bose Gas in Potentials with Positive Scattering Length

The leading term of the ground state energy/particle of a dilute gas of bosons with mass m in the thermodynamic limit is \({2\pi \hbar^2 a \varrho/m}\) when the density of the gas is \({\varrho}\), the interaction potential is non-negative and the scattering length a is positive. In this paper, we generalize the upper bound part of this result to any interaction potential with positive scattering length, i.e, a > 0 and the lower bound part to some interaction potentials with shallow and/or narrow negative parts.
Images of Io's Sodium Cloud

The first direct images of Io's sodium cloud are reported and analyzed. The observed cloud extends for more than 100,000 kilometers along Io's orbit and is a somewhat 'banana-shaped' partial toroid. More sodium atoms precede Io than follow it. A model based on the escape of sodium from a specific localized area on Io provides a reasonable fit to the observed intensity distribution whereas isotropic escape does not.
Gating of a Molecular Transistor: Electrostatic and Conformational

We derive a general result that can be used to evaluate and compare the transconductance of different field-effect mechanisms in molecular transistors, both electrostatic and conformational. The electrostatic component leads to the well-known thermal limit in the absence of tunneling. We show that in a standard three-terminal geometry and in the absence of strong electron−phonon coupling, the conformational component can lead to significant advantages only if the molecular dipole moment μ is comparable to etox, tox being the thickness of the oxide. Surprisingly, this conclusion is independent of the “softness” of the conformational modes involved or other geometrical factors. Detailed numerical results for specific examples are presented in support of the analytical results.
Sample Selection and Biases in Local House Value Indices

Abstract Analysis of cross-sectional or intertemporal variations in house values among localities requires reliable house value indices. However, prior studies applying the hedonic method to transaction data have reported price series that may be biased. Our paper investigates a possible cause of bias and uses a censored regression technique extended to an intertemporal model to derive an unbiased index. We apply our method to 1971–1991 data from the Miami, Florida, MSA and find evidence in time varying amounts of bias. Our results suggest that prior studies using the hedonic method and samples consisting only of sold houses have understated the intertemporal variability of house prices.
Global Solutions to a Non-Local Diffusion Equation with Quadratic Non-Linearity

In this paper we prove the global in time well-posedness of the following non-local diffusion equation with α ∈ (0, 2/3): The initial condition u 0 is positive, radial, and non-increasing with u 0 ∈ L 1 ∩ L 2+δ(ℝ3) for some small δ > 0. There is no size restriction on u 0. This model problem appears of interest due to its structural similarity with Landau's equation from plasma physics, and moreover its radically different behavior from the semi-linear Heat equation: u t = ▵ u + αu 2.
Liouville theorems for stable Lane–Emden systems and biharmonic problems

We examine the elliptic system given by for 1?<?p???? and the fourth order scalar equation where 1?<??. We prove various Liouville type theorems for positive stable solutions. For instance we show there are no positive stable solutions of (1) (respectively, (2)) provided N???10 and 2???p???? (respectively, N???10 and 1?<??). Results for higher dimensions are also obtained. These results regarding stable solutions on the full space imply various Liouville theorems for positive (possibly unstable) bounded solutions of with u?=?v?=?0 on . In particular there is no positive bounded solution of (3) for any 2???p???? if N???11. Higher dimensional results are also obtained.
How can economic stochasticity promote or prevent corporate defaults

Purpose – The purpose of this paper is to theoretically examine under what circumstances economic cycles advance or deter corporate defaults.Design/methodology/approach – The theoretical inferences are authenticated through Monte Carlo simulations.Findings – It is found that an ongoing catastrophe dominates other macroeconomic conditions and forces corporate failures. In contrast, when a catastrophe is unlikely, a constant economy permits no‐defaults merely as an unstable equilibrium, yet a stochastic economy allows rival firms to remain operational within a stable general disequilibrium and under a wide range of economic conditions.Research limitations/implications – This topic can only be theoretically examined.Practical implications – The paper's findings assert that moderate economic variability typically discourages corporate defaults. These inferences convey high significance for regulators and policy makers.Originality/value – The paper shows that in a perfect competition, economic waves can change...
Analytical Bethe Ansatz for quantum algebra invariant spin chains

Abstract We have recently constructed a large class of open quantum spin chains which have quantum-algebra symmetry and which are integrable. We show here that these models can be exactly solved using a generalization of the analytical Bethe Ansatz (BA) method. In particular, we determine in this way the spectrum of the transfer matrices of the Uq[su(2)]-invariant spin chains associated with A1(1) and A2(2) in the fundamental representation. The quantum-algebra invariance of these models plays an essential role in obtaining these results. The BA equations for these open chains are “doubled” with respect to the BA equations for the corresponding closed chains.
Divalent titanium chemistry. Synthesis, reactivity, and X-ray and neutron diffraction studies of Ti(BH4)2(dmpe)2 and Ti(CH3)2(dmpe)2

Low valent organotitanium complexes have been implicated as Ziegler-Natta olefin polymerization catalysts and as stoichiometric reagents in organic synthesis. However, very few low-valent alkyls of titanium have been reported, and, in particular, the divalent oxidation state of titanium is virtually unexplored. The authors now report the synthesis and characterization of the unusual divalent tetrahydroborate complex Ti(BH/sub 4/)/sub 2/(dmpe)/sub 2/, 1, and its conversion to the methyl compound Ti(CH/sub 3/)/sub 2/(dmpe)/sub 2/, 2. Complex 2 is unique among octahedral complexes of the 3d metals in being low-spin within the t/sub 2g/ manifold and exhibits very unusual NMR features for the titanium methyl group.
Proton–proton scattering lengths from effective field theory

Abstract Using a recently developed effective field theory for the interactions of nucleons at non-relativistic energies, we calculate the Coulomb corrections to proton–proton scattering. Including the dimension-eight derivative interaction in PDS regularization scheme, we obtain a modified Jackson-Blatt relation for the scattering lengths which is found to be phenomenologically satisfactory. The effective range is not modified by Coulomb effects to this order in the calculation.
Building and Rebuilding Trust with Promises and Apologies

Using trust games, we study how promises and messages are used to build new trust where it did not previously exist and to rebuild damaged trust. In these games, trustees made non-binding promises of investment-contingent returns, then investors decided whether to invest, and finally trustees decided how much to return. After an unexpected second game was announced, but before it commenced, trustees could send a one-way message. This design allowed us to observe the endogenous emergence and natural distribution of trust-relevant behaviors and focus on naturally occurring remedial strategies used by promise-breakers and distrusted trustees, their effects on investors, and subsequent outcomes. In the first game 16.6% of trustees were distrusted and 18.8% of trusted trustees broke promises. Trustees distrusted in the first game used long messages and promises closer to equal splits to encourage trust in the second game. To restore damaged trust, promise-breakers used apologies and upgraded promises. On average, investments in each game paid off for investors and trustees, suggesting that effective use of cheap signals fosters profitable trust-based exchange in these economies.
The Probable Optical Counterpart of the Luminous X-Ray Source in NGC 6441*

We report results from Hubble Space Telescope (HST)WFPC2 imaging of the field of the luminous, bursting X-ray source in the globular cluster NGC 6441. Although the X-ray position is known to a precision of a few arcseconds, this source is only ~6'' from the cluster center, and the field contains hundreds of stars within the 3'' X-ray error circle, making it difficult to isolate the optical counterpart. Nevertheless, our multicolor images reveal a single, markedly UV-excess object with m336 = 19.0, m439 = 19.3, within the X-ray error circle. Correcting for substantial reddening and bandpass differences, we infer B0 = 18.1, (U-B)0 = -1.0, clearly an unusual star for a globular cluster. Furthermore, we observe an ultraviolet intensity variation of 30% for this object over 0.5 hr, as well as an even greater variation in m439 between two HST observations taken approximately 1 yr apart. The combination of considerable UV excess and significant variability strongly favors this object as the optical counterpart to the low-mass X-ray binary X1746-370. With a group of five optical counterparts to high-luminosity globular cluster X-ray sources now known, we present a homogeneous set of HST photometry on these objects and compare their optical properties with those of field low-mass X-ray binaries. The mean (U-B)0 color of the cluster sources is identical to that of the field sources, and the mean MB0 is similar to bursters in the field. However, the ratio of optical to X-ray flux of cluster sources seems to show a significantly larger dispersion than that of the field sources.
Facile synthesis of N-10 flavin disulfides

A facile, high yield route to N-10 flavin disulfides is described. The key feature is catalytic reduction of the nitro group to an amine function in an organic sulfide using platinum sulfide on charcoal.
The GM-CPHD applied to the corrected TNO-Blind, adjusted SEABAR07 and Metron multi-static sonar datasets

The Gaussian Mixture CardinalizedPHD (GM-CPHD) Tracker was applied to the corrected TNO-Blind dataset, the SNR adjusted datasets in SEABAR07 and to the Metron dataset generated for the MSTWG (Multistatic TrackingWorking Group). The increasing difficulty of the datasets is handled by improvements on the tracker. The tracking results (plots and metrics of performance) are included.
On black hole singularities in quantum gravity

Abstract We show that the absence of space-like boundaries in 1+1 dimensional dilaton-gravity implies a catastrophic event at the end point of black hole evaporation. The proof is completely independent of the physics at Planck scales. We argue that the same will occur in any theory of quantum gravity in 3+1 dimensions that only admits trivial space-time topologies
On the Gap Conjecture concerning group growth

We discuss some new results concerning Gap Conjecture on group growth and present a reduction of it (and its \(*\)-version) to several special classes of groups. Namely we show that its validity for the classes of simple groups and residually finite groups will imply the Gap Conjecture in full generality. A similar type reduction holds if the Conjecture is valid for residually polycyclic groups and just-infinite groups. The cases of residually solvable groups and right orderable groups are considered as well.
Gauge-Fermion unification and flavour symmetry

After we study the 6-dimensional = (1,1) supersymmetry breaking and R symmetry breaking on M4 × T2/Zn, we construct two = (1,1) supersymmetric E6 models on M4 × T2/Z3 where E6 is broken down to SO(10) × U(1)X by orbifold projection. In Model I, three families of the Standard Model fermions arise from the zero modes of bulk vector multiplet, and the R symmetry U(1)FI × SU(2)4− can be considered as flavour symmetry. This may explain why there are three families of fermions in the nature. In Model II, the first two families come from the zero modes of bulk vector multiplet, and the flavour symmetry is similar. In these models, the anomalies can be cancelled, and we have very good fits to the SM fermion masses and mixings. We also comment on the = (1,1) supersymmetric E6 models on M4 × T2/Z4 and M4 × T2/Z6, SU(9) models on M4 × T2/Z3, and SU(8) models on T2 orbifolds.
Towards realizing dynamical SUSY breaking in heterotic model building

We study a new mechanism to dynamically break supersymmetry in the E8 × E8 heterotic string. As discussed recently in the literature, a long-lived, meta-stable non-supersymmetric vacuum can be achieved in an = 1 SQCD whose spectrum contains a sufficient number of light fundamental flavors. In this paper, we present, within the context of the hidden sector of the weakly and strongly coupled heterotic string, a slope-stable, holomorphic vector bundle on a Calabi-Yau threefold for which all matter fields are in the fundamental representation and are massive at generic points in moduli space. It is shown, however, that near certain subvarieties in the moduli space a sufficient number of light matter fields can occur, providing an explicit heterotic model realizing dynamical SUSY breaking. This is demonstrated for the low-energy gauge group Spin(10). However, our methods immediately generalize to Spin(Nc), SU(Nc), and Sp(Nc), for a wide range of color index Nc. Moduli stabilization in vacua with a positive cosmological constant is briefly discussed.
Antithrombotic Therapy in Peripheral Arterial Disease

The management of elderly patients with peripheral arterial disease requires a multidisciplinary and individualized approach, especially for patients requiring intervention and for those on antithrombotic therapy. Communication between the patient's primary physician, consulting medical specialists, and vascular surgeon is essential because all may contribute synergistically to deliver optimal care to the patient. This article reviews the pathophysiology of peripheral arterial disease and data regarding the use of antiplatelet and anticoagulant agents.
Creep Damage Development in Structural Ceramics

Creep rupture of structural ceramics occurs by either the nucleation, growth, and coalescence of grain-boundary cavities throughout the material or the growth of a dominant flaw. Recent experimental results obtained with small-angle neutron scattering (SANS) and stereoimaging strain analysis are reviewed and used to answer a number of critical questions pertaining to both damage mechanisms. The nucleation and growth processes of grain-boundary cavities are examined using the SANS results and pertinent results from other studies. The stochastic nature of cavitation is demonstrated and discussed. Creep-crack growth is described as either a direct mass transport process or a damage zone growth process. New stereoimaging strain results pertinent to the damage zone growth process are presented and used to elucidate the crack growth process and the growth threshold.
Dosimetric evaluation of a variable energy superficial X-ray machine with applications for endocavitary radiotherapy techniques.

Abstract This investigation presents the beam characteristics of a newly-marketed variable energy superficial X ray machine for radiotherapy. The X ray system hardware, including a high voltage generator, and console software allow for nine independent operator-selected X ray beams from 10–150 kVp. Filament current values are also independently variable; 1.0–13.0 mA for 90–150 kVp, and 1.0–30.0 mA for 10–90 kVp. The HVL's, effective energies, and radiation outputs for the nine combinations of kVp and mA are presented. In addition, percentage depth dose and beam uniformity results are presented as a function of cone size. Radiation output stability and reproducibility results are included. Discussion of adaption of this X ray system to the Papillon technique for the treatment of rectal cancers is presented.
Production of Positive Ion Beams from Solids

We have recently reported a technique for making metal ions for cyclotrons. Metal and non-metal ions from solids are produced in a Penning ion source by a process that involves ions that are unable to cross the first acceleration gap between the ion source and dee and are accelerated back into the ion source where they sputter charge material into the arc. This material is ionized and extracted from the ion source and accelerated. We have now used this technique for a large variety of ions, both metal and non-metal, including most recently aluminum from the metal and boron from boron nitride charge materials. We have also calculated the efficiency for making iron ions with different ion support gases and have experimentally checked these results. We are presently designing a dual ion source for our dc Penning ion source test stand which we believe will make an excellent source for producing ions from solids for dc extracted Penning ion sources.
Chandra View of the Dynamically Young Cluster of Galaxies A1367. I. Small-Scale Structures

The 40 ks Chandra ACIS-S observation of A1367 provides new insights into small-scale structures and point sources in this dynamically young cluster. Here we concentrate on small-scale extended structures. A ridgelike structure around the center ("the ridge") is significant in the Chandra image. The ridge, with a projected length of ~8' (or 300 h kpc), is elongated from northwest to southeast, as is the X-ray surface brightness distribution on much larger scales (~2 h Mpc). The ridge is cooler than its western and southern surroundings, while the differences from its eastern and northern surroundings are small. We also searched for small-scale structures with sizes of about an arcminute. Nine extended features, with sizes from ~05 to 15, were detected at significance levels above 4 σ. Five of the nine features are located in the ridge and form local crests. The nine extended features can be divided into two types. Those associated with galaxies (NGC 3860B, NGC 3860, and UGC 6697) are significantly cooler than their surroundings (0.3-0.9 keV vs. 3-4.5 keV). The masses of their host galaxies are sufficient to bind the extended gas. These extended features are probably related to thermal halos or galactic superwinds of their host galaxies. The existence of these relatively cold halos implies that galaxy coronae can survive in a cluster environment (e.g., Vikhlinin and coworkers in 2001). Features of the second type are not apparently associated with galaxies. Their temperatures may not be significantly different from those of their surroundings. This class of extended features may be related to the ridge. We consider several possibilities for the ridge and the second type of extended features. The merging scenario is preferred.
Laser radar angular tracking

This paper deals with the theory of monopulse angle tracking with a laser radar employing heterodyne detection. The detector is assumed to be of the quadrant type. The target's angular location is inferred from the location of its diffraction pattern in the detector plane. A generalized gain characteristic for the detector can be used to relate the strength of the matched filter outputs, which correspond to the spatial regions (halves) of the detector surface, to the corresponding angular location of the target. The maximum likelihood angle estimator is derived for a speckle target. The performance of an approximation to the maximum likelihood angle estimator is evaluated for both the speckle and glint targets. The angle estimator performance is also evaluated in the presence of atmospheric turbulence and beam jitter.
Extruded monolithic catalyst supports

Abstract Extruded monolithic catalyst substrates are widely used in automotive and stationary emissions control reactors. They are increasingly being used, developed, and evaluated in many other reactor applications such as for the chemical processing industries, for catalytic combustion, for ozone abatement, and others. This paper will compare the variety of extruded monoliths used for these applications and will review the forming and characterization of them. Emphasis is on the materials used for automotive substrates, catalysts for selective catalytic reduction of NOx and for new high surface area substrates.