cssi/SciSciGPT-SciSciNet huggingface dataset:
V-V bond length fluctuations in VOx

We report a significantly stronger suppression of the phonon contribution to the thermal conductivity in VO x than can be accounted for by disorder of the 16% atomic vacancies present in VO. Since the transition from localized to itinerant electronic behavior is first order and has been shown to be characterized by bond length fluctuations in several transition-metal oxides with the perovskite structure, we propose that cooperative V–V bond length fluctuations play a role in VO similar to the M–O bond length fluctuations in the perovskites. This model is able to account for the strong suppression of the thermal conductivity, the existence of a pseudogap confirmed by thermoelectric power, an anomalously large Debye-Waller factor, the temperature dependence of the magnetic susceptibility, and the inability to order atomic vacancies in VO.
Reduced-order modeling for thermal recovery processes

Thermal recovery can entail considerably higher costs than conventional oil recovery, so the use of computational optimization techniques in designing and operating these processes may be beneficial. Optimization, however, requires many simulations, which results in substantial computational cost. Here, we implement a model-order reduction technique that aims at large reductions in computational requirements. The technique considered, trajectory piecewise linearization (TPWL), entails the representation of new solutions in terms of linearizations around previously simulated (and saved) training solutions. The linearized representation is projected into a low-dimensional space, with the projection matrix constructed through proper orthogonal decomposition of solution “snapshots” generated in the training step. Two idealized problems are considered here: primary production of oil driven by downhole heaters and a simplified model for steam-assisted gravity drainage, where water and steam are treated as a single “effective” phase. The strong temperature dependence of oil viscosity is included in both cases. TPWL results for these systems demonstrate that the method can provide accurate predictions relative to full-order reference solutions. Observed runtime speedups are very substantial, over 2 orders of magnitude for the cases considered. The overhead associated with TPWL model construction is equivalent to the computation time for several full-order simulations (the precise overhead depends on the number of training runs), so the method is only applicable if many simulations are to be performed.
Cholesterol autoxidation--current status

Several oxidation products of cholesterol have been reported to have biological activity in animals. Cholesterol oxidizes readily in solution, in aqueous dispersion and in foods when it is exposed to air, elevated temperatures, free radical initiators, light, or a combination of these. The main outline of the pathway for cholesterol oxidation is fairly well understood and involves initial formation of allylic hydroperoxides. HPLC and GC techniques are available for measuring the concentration of cholesterol oxides in animal-derived lipids. Biologically active cholesterol oxides have been reported to be present in egg products, dairy products, frying oils and other foods. Their concentration may be subject to process control.
The Argonne 60-in. scattering chamber

Abstract The 60-in. scattering chamber used with the external beam of the Argonne 60-in. cyclotron is described. The scattering chamber permits operation over an angular range from 4° to 176° with an accuracy of ±3 min of arc. The geometrical factors involved in the measurement of cross sections are known to ± 0.1% or better. The angular positions of the detectors, the target changer, and an absorber foil system in front of the detection units are operated by remote control so as to permit continuous operation of the cyclotron when these parameters are varied. It is possible to operate several detectors simultaneously; and in order to permit angular correlation studies, the angular position of one detector can be varied by remote control with respect to the other detector units.
Search for the optical counterpart to SGR 0418+5729

We report broadband Hubble Space Telescope imaging of the field of soft {gamma}-ray repeater SGR 0418+5729 with Advanced Camera for Surveys/Wide Field Channel and Wide Field Camera 3/IR. Observing in two wide filters, F606W and F110W, we find no counterpart within the positional error circle derived from Chandra observations, to limiting magnitudes m{sub F606W} > 28.6 and m{sub F110W} > 27.4 (Vega system), equivalent to reddening-corrected luminosity limits L{sub F606W} < 5 Multiplication-Sign 10{sup 28} and L{sub F110W} < 6 Multiplication-Sign 10{sup 28} erg s{sup -1} for a distance d = 2 kpc, at 3{sigma} confidence. This, in turn, imposes lower limits on the contemporaneous X-ray/optical flux ratio of {approx_equal}1100 and the X-ray/near-infrared flux ratio of {approx_equal}1000. We derive an upper limit on the temperature and/or size of any fall-back disk around the magnetar. We also compare the detection limits with observations of other magnetars.
Module theorem for the general theory of stable models

The module theorem by Janhunen et al. demonstrates how to provide a modular structure in answer set programming, where each module has a well-defined input/output interface which can be used to establish the compositionality of answer sets. The theorem is useful in the analysis of answer set programs, and is a basis of incremental grounding and reactive answer set programming. We extend the module theorem to the general theory of stable models by Ferraris et al. The generalization applies to non-ground logic programs allowing useful constructs in answer set programming, such as choice rules, the count aggregate, and nested expressions. Our extension is based on relating the module theorem to the symmetric splitting theorem by Ferraris et al. Based on this result, we reformulate and extend the theory of incremental answer set computation to a more general class of programs.
Why an informatics degree

i M a g E S c o U r t E S y o F i N D i a N a U N i V E r S i t y S c h o o L o F i N F o r M a t i c S a N D c o M P U t i N g auction technology, computer scientists found that they needed to understand how humans would select bidding strategies given the system design, and indeed how to design the system to motivate certain types of behavior (truthful value revelation, for example). This co-design problem led to fruitful interdisciplinary collaborations between computer scientists, economists and, increasingly, social psychologists. Likewise, designing successful technology for trust, privacy, reputation, and sharing in social computing environments requires both computer science and behavioral science. These interactions between problem domain context and computational design are characteristic of the maturing of computer science. Computing is no longer owned solely by computer science, any more than statistics is owned solely by faculty in statistics departments. Computing and computational thinking have become ubiquitous, and embedded in all aspects of science, research, industry, government, and social interaction. Consider the flurry of excitement about “e-commerce” in the late 1990s. Quickly e-commerce moved from being seen as a new field to being absorbed in “commerce”: the study of business communications, logistics, fulfillment, and strategy, for which the Internet and computing were just two technologies in a complex infrastructure. How then does computing education need to change to respond to the new reality, and more importantly, to be equipped to respond to future developments? We must embrace the diversity of ways in which problems DOI:10.1145/1646353.1646364 Dennis P. Groth and Jeffrey K. MacKie-Mason
Trauma Severity and Defensive Emotion-Regulation Reactions as Predictors of Forgetting Childhood Trauma

Using a retrospective survey, we studied a sample of 1,679 college women to determine whether reports of prior forgetting of childhood sexual abuse, physical abuse, and other traumas could be explained by trauma severity and individual differences in the use of defensive emotion-regulation reactions (i.e., repressive coping, dissociation, and fantasy proneness). Among victims of physical abuse (but not sexual abuse or other types of trauma), those who experienced severe abuse and used defensive reactions were sometimes more likely to report temporary forgetting of abuse but other times less likely to report forgetting. We also found unanticipated main effects of trauma severity on temporary forgetting. Our results provide an understanding of victims' experiences of forgetting by demonstrating the importance of considering unique effects of trauma type, different aspects of trauma severity, and victims' defensive reactions to trauma.
Elected Leaders, Community and Development: Evidence on Distribution and Agency from a Case in India

Abstract Although democratic decentralisation or community development by elected leaders is hypothesised to broaden development, there is little evidence on just how elected leaders make distributional decisions and far less on how communities in turn shape their leaders' decisions. This study combines structural equation modelling with ethnography in India to investigate how leaders of elected local bodies called panchayats distribute development. While quantitative findings reveal that democratic decentralisation mitigates elite capture, ethnography gives insight into the role of political brokers in brokering development for votes, widening distribution to non elite groups.
The Elusive p-air Cross Section

For the $$\bar pp$$ and pp systems, we have used all of the extensive data of the Particle Data Group [K. Hagiwara et al. (Particle Data Group), Phys. Rev. D 66, 010001 (2002)]. We then subject these data to a screening process, the “Sieve” algorithm [M. M. Block, physics/0506010], in order to eliminate “ outliers” that can skew a χ2 fit. With the “Sieve” algorithm, a robust fit using a Lorentzian distribution is first made to all of the data to sieve out abnormally high Δχ 2 , the individual ith point’s contribution to the total χ2. The χ2 fits are then made to the sieved data. We demonstrate that we cleanly discriminate between asymptotic ln s and ln2 s behavior of total hadronic cross sections when we require that these amplitudes also describe, on average, low energy data dominated by resonances. We simultaneously fit real analytic amplitudes to the “sieved” high energy measurements of $$\bar pp$$ and pp total cross sections and ρ-values for $$\sqrt s $$ ≥ GeV, while requiring that their asymptotic fits smoothly join the the σ pp and σpp total cross sections at $$\sqrt s $$ = 4.0 GeV—again both in magnitude and slope. Our results strongly favor a high energy ln2 s fit, basically excluding a ln s fit. Finally, we make a screened Glauber fit for the p-air cross section, using as input our precisely-determined pp cross sections at cosmic ray energies.
A decoupling pole placement self‐tuning controller for a class of multivariable processes

This paper describes a new multivariable self-tuning controller that specifically handles different time delays between each of the input-output pairs (multiple delays), and deals with unknown or varying time delay (variable dead time compensation) without requiring an explicit estimate of each delay. The new algorithm can control unstable and/or non-minimum phase processes; it eliminates both set-point and load offsets without having to maintain integral action continuously; it decouples the loops, both dynamically and at steady state. The effective decoupling algorithm not only minimizes significant interactions among the control loops, it permits the use of a very simple design criterion, namely the approximate assignment of the primary closed-loop poles to prespecified locations. A straightforward autotuning technique locates the closed-loop poles on-line so as to optimize the system set-point step responses. One desirable side-effect is to account for inexact decoupling. The controller is demonstrated using a simulated paper machine head box having an unusually large amount of (off-diagonal) interaction, a simulated two-input, two-output distillation column with time-varying parameters (varying gains and time delays), and a highly interacting unstable and non-minimum phase system on which the autotuning technique is demonstrated. These three processes place stringent requirements on any control method, and two of them have been used extensively in the literature to test various multivariable and/or self-tuning algorithms. Hence, the success of the new technique indicates that it is a very promising candidate to deal with intransigent processes, i.e. those characterized as unstable, non-minimum phase, time-varying (non-linear), and interacting.
Catalytic ketyl-olefin cyclizations enabled by proton-coupled electron transfer.

Concerted proton-coupled electron transfer is a key mechanism of substrate activation in biological redox catalysis. However, its applications in organic synthesis remain largely unexplored. Herein, we report the development of a new catalytic protocol for ketyl-olefin coupling and present evidence to support concerted proton-coupled electron transfer being the operative mechanism of ketyl formation. Notably, reaction outcomes were correctly predicted by a simple thermodynamic formalism relating the oxidation potentials and pKa values of specific Bronsted acid/reductant combinations to their capacity to act jointly as a formal hydrogen atom donor.
Compact quantum metric spaces and ergodic actions of compact quantum groups

We show that for any co-amenable compact quantum group A=C(G) there exists a unique compact Hausdorff topology on the set EA(G) of isomorphism classes of ergodic actions of G such that the following holds: for any continuous field of ergodic actions of G over a locally compact Hausdorff space T the map T→EA(G) sending each t in T to the isomorphism class of the fibre at t is continuous if and only if the function counting the multiplicity of γ in each fibre is continuous over T for every equivalence class γ of irreducible unitary representations of G. Generalizations for arbitrary compact quantum groups are also obtained. In the case G is a compact group, the restriction of this topology on the subset of isomorphism classes of ergodic actions of full multiplicity coincides with the topology coming from the work of Landstad and Wassermann. Podleś spheres are shown to be continuous in the natural parameter as ergodic actions of the quantum SU(2) group. We also introduce a notion of regularity for quantum metrics on G, and show how to construct a quantum metric from any ergodic action of G, starting from a regular quantum metric on G. Furthermore, we introduce a quantum Gromov–Hausdorff distance between ergodic actions of G when G is separable and show that it induces the above topology.
The evolution of manufacturing technology and its impact on industrial structure: An international study

This paper shows that plant and firm size in manufacturing, and especially in engineering industry, in several Western industrial countries has declined since the early 1970s. Two hypotheses explaining the decline are advanced. One is “de-glomeration” or specialization: the divestiture of non-core businesses in order to free up scarce resources (particularly management time) to defend and nurture core business activities. The second hypothesis is that the emergence of new computer-based technology has improved the quality and productivity of small and medium scale production relative to standardized mass-production techniques which dominated previously.
ASYMPTOTIC INFRARED FRACTAL STRUCTURE OF THE PROPAGATOR FOR A CHARGED FERMION

It is well known that the long-range nature of the Coulomb interaction makes the definition of asymptotic "in" and "out" states of charged particles problematic in quantum field theory. In particular, the notion of a simple particle pole in the vacuum charged particle propagator is untenable and should be replaced by a more complicated branch cut structure describing an electron interacting with a possibly infinite number of soft photons. Previous work suggests a Dirac propagator raised to a fractional power dependent upon the fine structure constant, however the exponent has not been calculated in a unique gauge-invariant manner. It has even been suggested that the fractal "anomalous dimension" can be removed by a gauge transformation. Here, a gauge-invariant non-perturbative calculation will be discussed yielding an unambiguous fractional exponent. The closely analogous case of soft graviton exponents is also briefly explored.
Thermo-Optical Analysis Of Two Long-Focal-Length Aerial Reconnaissance Lenses

A 36-inch f/5.0 lens and a 24-inch f/3.5 lens used for aerial reconnaissance missions are described. During design, these lenses were analyzed over t heir full operating temperautre range of 20 to 60 C. Their performance at ambient conditions and at the maximum operating temperature is reported. The results indicate that at steady state the performance of each lens is affeted only modestly over the operating temperature range when the image is held in focus by a thermal comensating lens mount.
Degradation of Structural Ceramics by Erosion

Materials wastage by solid-particle erosion can be severe and limit lifetimes. This paper will review the theoretical description of solid-particle erosion in brittle materials, which is well-developed for monolithic ceramics. The models can usually account for effects from the principal projectile properties: size, impact velocity, and impact angle. Materials parameters such as fracture toughness and hardness can be included. Steady-state erosion measurements on a wide variety of ceramics, ranging from Si single crystals to SiC-whisker-reinforced A12O3 are reviewed and compared to the models. It is believed thatR-curve behavior and/or particle fragmentation is responsible for discrepancies between the theory and experimental results for composite ceramics. Additionally, the theories make no attempt to describe threshold or incubation effects.
Polarization filtering of SAR data

In this paper, a systematic theoretical analysis of polarization filtering for a bistatic system is developed for two applications: maximization of signal to noise ratio and discrimination between two target types. The described method finds the optimum receive antenna polarization analytically but relies on a numerical approach to find the optimum transmit antenna polarization. The method uses the Stokes matrix representation, and therefore applies to analyze the partially polarized scattered field from extended targets. Examples of the technique are presented for the NASA CV990 polarimetric L-band radar. Image enhancement filters maximizing the signal-to-noise ratio are developed for different noise characteristics and different target types (urban and forest). A filter is also developed to maximize the power ratio between urban and natural targets. Results show that the filter maximizing the contrast between urban and forest area is essentially the same as the one maximizing the contrast between urban and ocean areas.
Antibody-functionalized fluid-permeable surfaces for rolling cell capture at high flow rates.

Adhesion-based cell capture on surfaces in microfluidic devices forms the basis of numerous biomedical diagnostics and in vitro assays. However, the performance of these platforms is partly limited by interfacial phenomena that occur at low Reynolds numbers. In contrast, cell homing to porous vasculature is highly effective in vivo during inflammation, stem cell trafficking, and cancer metastasis. Here, we show that a porous, fluid-permeable surface functionalized with cell-specific antibodies promotes efficient and selective cell capture in vitro. This architecture is advantageous due to enhanced transport as streamlines are diverted toward the surface. Moreover, specific cell-surface interactions are promoted due to reduced shear, allowing gentle cell rolling and arrest. Together, these synergistic effects enable highly effective cell capture at flow rates more than an order of magnitude larger than those provided by existing devices with solid surfaces.
Impeller flow field measurement and analysis

A series of experiments are performed to investigate and quantify the three-dimensional mean flow field in centrifugal compressor flow passages and to evaluate contemporary internal flow models. The experiments include the acquisition and analysis of LDV data in the impeller passages of a low-speed moderate-scale research mixed-flow centrifugal compressor operating at its design point. Predictions from a viscous internal flow model are then correlated with these data. The LDV data show the traditional jet-wake structure observed in many centrifugal compressors, with the wake observed along the shroud 70 percent of the length from the pressure to suction surface. The viscous model predicts the major flow phenomena. However, the correlations of the viscous predictions with the LDV data were poor.
There and (Slowly) Back Again: Entropy-Driven Hysteresis in a Model of DNA Overstretching

When pulled along its axis, double-stranded DNA elongates abruptly at a force of ∼65 pN. Two physical pictures have been developed to describe this overstretched state. The first proposes that strong forces induce a phase transition to a molten state consisting of unhybridized single strands. The second picture introduces an elongated hybridized phase called S-DNA. Little thermodynamic evidence exists to discriminate directly between these competing pictures. Here we show that within a microscopic model of DNA we can distinguish between the dynamics associated with each. In experiment, considerable hysteresis in a cycle of stretching and shortening develops as temperature is increased. Since there are few possible causes of hysteresis in a system whose extent is appreciable in only one dimension, such behavior offers a discriminating test of the two pictures of overstretching. Most experiments are performed upon nicked DNA, permitting the detachment (unpeeling) of strands. We show that the long-wavelength progression of the unpeeled front generates hysteresis, the character of which agrees with experiment only if we assume the existence of S-DNA. We also show that internal melting can generate hysteresis, the degree of which depends upon the nonextensive loop entropy of single-stranded DNA.
Fusobacterial Infections in Children

Fusobacteria are members of the oral and gastrointestinal flora and are important potential pathogens in children. They are increasingly recognized as a cause of infections in children. These include infections of the head and neck (Lemierre syndrome, acute and chronic mastoiditis, chronic otitis and sinusitis, tonsillitis, peritonsillar and retropharyngeal abscesses, postanginal cervical lymphadenitis, periodontitis), brain, lungs, abdomen, pelvis, bones, joints, and blood. This review describes the clinical spectrum of fusobacterial infection in children and their management.
Discrete Miura Opers and Solutions of the Bethe Ansatz Equations

Solutions of the Bethe ansatz equations associated to the XXX model of a simple Lie algebra Open image in new window come in families called the populations. We prove that a population is isomorphic to the flag variety of the Langlands dual Lie algebra Open image in new window The proof is based on the correspondence between the solutions of the Bethe ansatz equations and special difference operators which we call the discrete Miura opers. The notion of a discrete Miura oper is one of the main results of the paper.
ArtNova: touch-enabled 3D model design

We present a system, ArtNova, for 3D model design with a haptic interface. ArtNova offers the novel capability of interactively applying textures onto 3D surfaces directly by brush strokes, with the orientation of the texture determined by the stroke. Building upon the framework of inTouch [GEL00], it further provides an intuitive physically-based force response when deforming a model. This system also uses a user-centric viewing technique that seamlessly integrates the haptic and visual presentation, by taking into account the user's haptic manipulation in dynamically determining the new viewpoint locations. Our algorithm permits automatic placement of the user viewpoint to navigate about the object. ArtNova has been tested by several users and they were able to start modeling and painting with just a few minutes of training. Preliminary user feedback indicates promising potential for 3D texture painting and modeling.
Pollution abatement activities and traditional productivity

Abstract This study models the joint production of good and bad output production and calculates traditional productivity when bad output production is regulated and when it is unregulated. We apply this model to data for U.S. coal-fired electric power plants for 1985–1995 and compare rates of productivity and technical change to gain an understanding of the association between pollution abatement activities and traditional rates of productivity and technical change. While traditional productivity and technical change associated with abatement activities decline, we conclude they are not statistically significant.
Industrial fatigue Redux

Abstract This paper presents a gift-exchange labor market model in which workers are prone to exhaustion. Although norms of reciprocity and fairness indicate that firms and workers must exchange ‘gifts’ in the form of higher wages and higher effort respectively, these incentives are mitigated by the evolution of fatigue and, therefore, the dynamic efficiency wage is lower than its static counterpart.
Is deidentification sufficient to protect health privacy in research

The revolution in health information technology has enabled the compilation and use of large data sets of health records for genomic and other research. Extensive collections of health records, esp...
The synthesis and antifungal activity of nitrogen containing hemiaminal ethers of LY303366.

LY303366 (Fig. 1), currently in phase II clinical trials, is a semisynthetic, broad spectrum, fungicidal agent derived through extensive structure-activity relationship (SAR) studies based on the echinocandin B (ECB) nucleus 1∼3) . Possession of such potent activity against clinically important fungi such as Aspergillus fumigatus, Candida albicans and Candida parapsilosis has prompted subsequent SAR studies focused on two major properties. First, improving the water solubility (<0.1 mg/ml) associated with the molecule and secondly, addressing the instability which is observed under strongly basic conditions. This instability is attributed to the hemiaminal group and results in a ring opened, inactive product as shown previously 4) . To this end, derivatization of the hemiaminal to form an ether linkage with amino alcohols would address both areas via formation of a stable hemiaminal ether possessing a pendant basic amine for salt formation. A similar approach has been taken in the pneumocandin B 0 class of antifungal agents 5) .
Leveled Fully Homomorphic Signatures from Standard Lattices

In a homomorphic signature scheme, a user Alice signs some large dataset x using her secret signing key and uploads the signed data to an untrusted remote server. The server can then run some computation y=f(x) over the signed data and homomorphically derive a short signature σf,y certifying that y is the correct output of the computation f. Anybody can verify the tuple (f, y, σf,y) using Alice's public verification key and become convinced of this fact without having to retrieve the entire underlying data. In this work, we construct the first leveled fully homomorphic signature} schemes that can evaluate arbitrary {circuits} over signed data. Only the maximal {depth} d of the circuits needs to be fixed a-priori at setup, and the size of the evaluated signature grows polynomially in d, but is otherwise independent of the circuit size or the data size. Our solution is based on the (sub-exponential) hardness of the small integer solution (SIS) problem in standard lattices and satisfies full (adaptive) security. In the standard model, we get a scheme with large public parameters whose size exceeds the total size of a dataset. In the random-oracle model, we get a scheme with short public parameters. In both cases, the schemes can be used to sign many different datasets. The complexity of verifying a signature for a computation f is at least as large as that of computing f, but can be amortized when verifying the same computation over many different datasets. Furthermore, the signatures can be made context-hiding so as not to reveal anything about the data beyond the outcome of the computation.These results offer a significant improvement in capabilities and assumptions over the best prior homomorphic signature schemes, which were limited to evaluating polynomials of constant degree.As a building block of independent interest, we introduce a new notion called homomorphic trapdoor functions (HTDF) which conceptually unites homomorphic encryption and signatures. We construct HTDFs by relying on the techniques developed by Gentry et al. (CRYPTO '13) and Boneh et al. (EUROCRYPT '14) in the contexts of fully homomorphic and attribute-based encryptions.
High performance liquid chromatographic analysis of St. John’s Wort with photodiode array detection

An RP-HPLC method with photodiode array detection was established for the determination of major constituents (rutin, hyperoside, isoquercitrin, quercitrin, quercetin, pseudohypericin, hyperforin and hypericin) in St. John's Wort dietary supplements. The samples were extracted with methanol by means of sonication in low temperature. The extraction was rapid, with two steps of sonication (30 min each) recovering more than 99% of the major constituents in St. John's Wort samples. The major components were separated by RP-18 chromatography column using a 60-min water-acetonitrile-methanol-trifluoroacetic acid gradient. The quantification was performed by using external standards. Sample preparation and stability of methanolic extract of St. John's Wort were extensively explored. It is worth noting that the major constituents in the methanolic extract of St John's Wort, especially hypericin and pseudohypericin, might be retained by some filter cartridges during the filtration. The current method may serve as a valuable tool for the QA/QC of St. John's Wort dietary supplements.
Total synthesis of (+)-asperlin

Abstract A stereochemically unambiguous synthesis of (+)-asperlin from L-rhamnose establishes the configuration of the antibiotic as 4S, 5S, 6S, 7R.
Evolution of Rotating Supermassive Stars to the Onset of Collapse

We launch a fully relativistic study of the formation of supermassive black holes via the collapse of supermassive stars. Here we initiate our investigation by analyzing the secular evolution of supermassive stars up to the onset of dynamical instability and collapse. We focus on the effects of rotation, assumed uniform, and general relativity. We identify the critical configuration at which radial instability sets in and determine its structure in detail. We show that the key nondimensional ratios R/M, T/|W|, and J/M2 (T is the rotational kinetic energy, and W is the gravitational potential energy) for this critical configuration are universal numbers, independent of the mass, spin, radius, or history of the star. We compare results from an approximate, analytic treatment with a fully relativistic, numerical calculation and find good agreement. We solve analytically for the time evolution of these parameters up to the onset of instability. Cooling by photon radiation drives the evolution, which is accompanied by mass, angular momentum, and entropy loss. The critical configuration serves as initial data for a future relativistic, hydrodynamical, three-dimensional simulation of the collapse of an unstable supermassive star. Since this implosion starts from a universal critical configuration, the collapse is also uniquely determined and should produce a universal gravitational waveform. In this paper we briefly speculate on the possible outcome of this collapse and assess to what extent it offers a promising route to forming a supermassive black hole.
Entropy and the variational principle for actions of sofic groups

Recently Lewis Bowen introduced a notion of entropy for measure-preserving actions of a countable sofic group on a standard probability space admitting a generating partition with finite entropy. By applying an operator algebra perspective we develop a more general approach to sofic entropy which produces both measure and topological dynamical invariants, and we establish the variational principle in this context. In the case of residually finite groups we use the variational principle to compute the topological entropy of principal algebraic actions whose defining group ring element is invertible in the full group C∗-algebra.
Mixed wino dark matter: Consequences for direct, indirect and collider detection

In supersymmetric models with gravity-mediated SUSY breaking and gaugino mass unification, the predicted relic abundance of neutralinos usually exceeds the strict limits imposed by the WMAP collaboration. One way to obtain the correct relic abundance is to abandon gaugino mass universality and allow a mixed wino-bino lightest SUSY particle (LSP). The enhanced annihilation and scattering cross sections of mixed wino dark matter (MWDM) compared to bino dark matter lead to enhanced rates for direct dark matter detection, as well as for indirect detection at neutrino telescopes and for detection of dark matter annihilation products in the galactic halo. For collider experiments, MWDM leads to a reduced but significant mass gap between the lightest neutralinos so that 2 two-body decay modes are usually closed. This means that dilepton mass edges– the starting point for cascade decay reconstruction at the CERN LHC– should be accessible over almost all of parameter space. Measurement of the m2−m1 mass gap at LHC plus various sparticle masses and cross sections as a function of beam polarization at the International Linear Collider (ILC) would pinpoint MWDM as the dominant component of dark matter in the universe.
ON THE INDEX AND DILATIONS OF COMPLETELY POSITIVE SEMIGROUPS

It is known that every semigroup of normal completely positive maps P = {Pt:t≥ 0} of ℬ(H), satisfying Pt(1) = 1 for every t ≥ 0, has a minimal dilation to an E0 acting on ℬ(K) for some Hilbert space K⊇H. The minimal dilation of P is unique up to conjugacy. In a previous paper a numerical index was introduced for semigroups of completely positive maps and it was shown that the index of P agrees with the index of its minimal dilation to an E0-semigroup. However, no examples were discussed, and no computations were made. In this paper we calculate the index of a unital completely positive semigroup whose generator is a bounded operator \[ L: {\mathcal B} (H)\to {\mathcal B} (H) \] in terms of natural structures associated with the generator. This includes all unital CP semigroups acting on matrix algebras. We also show that the minimal dilation of the semigroup P={exp tL:t≥ 0} to an E0-semigroup is is cocycle conjugate to a CAR/CCR flow.
External Adjustment and the Strong Yen: Recent Japanese Experience

The parameters of a conventional model of Japan's current account were found to be stable in the period of the steeply rising yen, end-1985 to end-1987. Thus, Japan's current account has been adjusting to the strengthening yen in accordance with established historical relationships--a conclusion substantiated by the model's reasonably accurate tracking of the current account in this period. Simulations of the model show that the rise in the yen has already made a substantial contribution to correcting Japan's external imbalance.
THE SLOAN DIGITAL SKY SURVEY DATA RELEASE 7 SPECTROSCOPIC M DWARF CATALOG. III. THE SPATIAL DEPENDENCE OF MAGNETIC ACTIVITY IN THE GALAXY

We analyze the magnetic activity of 59,318 M dwarfs from the Sloan Digital Sky Survey (SDSS) Data Release 7. This analysis explores the spatial distribution of M dwarf activity as a function of both vertical distance from the Galactic plane (Z) and planar distance from the Galactic center (R). We confirm the established trends of decreasing magnetic activity (as measured by Hα emission) with increasing distance from the mid-plane of the disk and find evidence for a trend in Galactocentric radius. We measure a non-zero radial gradient in the activity fraction in our analysis of stars with spectral types dM3 and dM4. The activity fraction increases with R and can be explained by a decreasing mean stellar age with increasing distance from the Galactic center.
Altered Luminosity Functions of Relativistically Beamed Jet Populations

The intrinsic luminosity functions of extremely fast jets found in many active galaxies and gamma-ray bursts are difficult to measure since their apparent luminosities are strongly affected by relativistic beaming. Past studies have only provided analytical predictions for the beamed characteristics of populations in which all jets have the same Lorentz factor. However, the jets found in active galaxies are known to span a large range of speeds. Here we derive analytical expressions for the expected Doppler factor distributions and apparent (beamed) luminosity functions of randomly oriented, two-sided jet populations that have bulk Lorentz factors distributed according to a simple power law over a range [γ1, γ2]. We find that if a jet population has a uniform or inverted Lorentz factor distribution, its Doppler factor distribution and beamed luminosity function will be very similar to that of a jet population with Lorentz factors all equal to γ2. In particular, the beamed and intrinsic luminosity functions will have the same slope at high luminosities. In the case of a steep Lorentz factor distribution, the slopes at high luminosities will also be identical, but only up to an apparent luminosity equivalent to the upper cutoff of the intrinsic luminosity function. In addition, at very high apparent luminosities, the slope will be proportional to the power-law slope of the Lorentz factor distribution. At very low luminosities, the form of the apparent luminosity function is very sensitive to the lower cutoff and steepness of the Lorentz factor distribution. We discuss how it should be possible to recover useful information about the intrinsic luminosity functions of relativistic jets by studying flux-limited samples selected on the basis of beamed jet emission.
Core formation in terrestrial planets

Calculations of the radial distribution of the energy released in core formation indicate that the cores of all the terrestrial planets may be expected to receive a disproportionate share of the gravitational energy released. Since the model of the process used in these calculations favors transfer of energy to the mantle, it is likely that other reasonable models of the process will result in even more energy being deposited in the cores of the early planets. The calculations also show that it is necessary for a certain amount of core phase to separate and accumulate, before the energy released by gravitational settling is sufficient to supply the latent heat of fusion of the core phase. The amount of melting required to reach this point varies according to the total mass of the planet, and mass fraction of core, but is not particularly great (<5% for the Earth to ∼ 37% for the Moon). In the case of the Moon, this amount of segregation, although large, amounts to a surface layer about 260 km thick, similar to the proposed depth of early wholesale melting. Core separation in terrestrial planets appears to be a self-sustaining process even for fairly small bodies, provided that a small amount of a dense potential core phase is present. Although it seems likely to occur rapidly (within 106–107 years) even for small (Moon-size) bodies, detailed kinetic models will be necessary to specify the time scale.
Aspects of (0,2) orbifolds and mirror symmetry

Abstract We study orbifolds of (0,2) models and their relation to (0,2) mirror symmetry. In the Landau-Ginzburg phase of a (0,2) model the superpotential features a whole bunch of discrete symmetries, which by quotient action lead to a variety of consistent (0,2) vacua. We study a few examples in very much detail. Furthermore, we comment on the application of (0,2) mirror symmetry to the calculation of Yukawa couplings in the space-time superpotential.
Generalized activity equations for spiking neural network dynamics

Much progress has been made in uncovering the computational capabilities of spiking neural networks. However, spiking neurons will always be more expensive to simulate compared to rate neurons because of the inherent disparity in time scales - the spike duration time is much shorter than the inter-spike time, which is much shorter than any learning time scale. In numerical analysis, this is a classic stiff problem. Spiking neurons are also much more difficult to study analytically. One possible approach to making spiking networks more tractable is to augment mean field activity models with some information about spiking correlations. For example, such a generalized activity model could carry information about spiking rates and correlations between spikes self-consistently. Here, we will show how this can be accomplished by constructing a complete formal probabilistic description of the network and then expanding around a small parameter such as the inverse of the number of neurons in the network. The mean field theory of the system gives a rate-like description. The first order terms in the perturbation expansion keep track of covariances.
On the Stability of Vortex Motions in Compressible Stratified Fluids

Abstract : Necessary conditions for stability of a general class of compressible vortex flows are obtained using the method of generalized progressing wave expansion. The vortex motion and its density are assumed to vary in both the radial and axial directions. These conditions, representing a state of statically stable distribution for the steady flow, require that the flow be stable in the centrifugal force field created by the rotation of the fluids, in the gravitational force field arised from the density variation in the vertical direction, and in the pressure field constraining the density stratification in both directions. These results also suggest the likely behavior of the Richardson criterion for stability of the flow yet to be derived. (Author)
Beyond Moulin mechanisms

Abstract The only known general technique for designing truthful and approximately budget-balanced cost-sharing mechanisms with good efficiency or computational complexity properties is due to Moulin [1999. Incremental cost sharing: Characterization by coalition strategy-proofness. Soc. Choice Welfare 16 (2), 279–320]. For many fundamental cost-sharing applications, however, Moulin mechanisms provably suffer from poor budget-balance, poor economic efficiency, or both. We propose acyclic mechanisms , a new framework for designing truthful and approximately budget-balanced cost-sharing mechanisms. Acyclic mechanisms strictly generalize Moulin mechanisms and offer three important advantages. First, it is easier to design acyclic mechanisms than Moulin mechanisms: many classical primal-dual algorithms naturally induce a non-Moulin acyclic mechanism with good performance guarantees. Second, for important classes of cost-sharing problems, acyclic mechanisms have exponentially better budget-balance and economic efficiency than Moulin mechanisms. Finally, while Moulin mechanisms have found application primarily in binary demand games, we extend acyclic mechanisms to general demand games, a multi-parameter setting in which each bidder can be allocated one of several levels of service.
Finding sparse systems of parameters

Abstract For several computational procedures such as finding radicals and Noether normalizations, it is important to choose as sparse as possible a system of parameters in a polynomial ideal or modulo a polynomial ideal. We describe new strategies for these tasks, thus providing solutions to problems (1) and (2) posed by D. Eisenbud et al. [Invent. Math. 110 (1992) 207-236]. To accomplish the first task we introduce a notion of “setwise complete intersection”. We prove that a set of monomials generating an ideal of codimension c in a polynomial ring can be partitioned into c disjoint sets forming a setwise complete intersection, although the corresponding result is false for arbitrary sets of polynomials. We reduce the general case to the monomial case by a deformation argument. For homogeneous ideals the output is homogeneous. Our analysis of the second task is based on a concept of Noether complexity for homogeneous ideals and its characterization in terms of Chow forms.
Reliable predictions of the thermochemistry of boron-nitrogen hydrogen storage compounds: BxNxHy, x = 2, 3.

Thermochemical data calculated using ab initio molecular orbital theory are reported for 16 BxNxHy compounds with x = 2, 3 and y ≥ 2x. Accurate gas-phase heats of formation were obtained using coupled cluster with single and double excitations and perturbative triples (CCSD(T)) valence electron calculations extrapolated to the complete basis set (CBS) limit with additional corrections including core/valence, scalar relativistic, and spin−orbit corrections to predict the atomization energies and scaled harmonic frequencies to correct for zero point and thermal energies and estimate entropies. Computationally cheaper calculations were also performed using the G3MP2 and G3B3 variants of the Gaussian 03 method, as well as density functional theory (DFT) using the B3LYP functional. The G3MP2 heats of formation are too positive by up to ∼6 kcal/mol as compared with CCSD(T)/CBS values. The more expensive G3B3 method predicts heats of formation that are too negative as compared with the CCSD(T)/CBS values by up t...
Wide Area Technical Report Service: technical reports online

Wide Area Technical Report Service (WATERS) is a distributed database of computer science technical reports. Contributors are departments of computer science that make their reports, stored locally at their sites, available through World-Wide Web and a WAIS search engine. By using WATERS, anyone with access to the Internet can, using a client such as Mosaic browse, search, obtain abstract and bibliographic information, and retrieve technical reports online. The latter assumes that the user's WWW client is set up to launch viewers such as ghostview for Postscript files, xdvi for dvi files, and xtiff for TIFF page images.
The noncommutative Choquet boundary II: Hyperrigidity

A (finite or countably infinite) set G of generators of an abstract C*-algebra A is called hyperrigid if for every faithful representation of A on a Hilbert space A ⊆ B(H) and every sequence of unital completely positive linear maps ϕ 1, ϕ 2,... from B(H) to itself, $$\mathop {\lim }\limits_{n \to \infty } ||{\phi _n}(g) - g|| = 0,{\forall _g} \in G \Rightarrow \mathop {\lim }\limits_{n \to \infty } {\phi _n}(a) - a|| = 0,{\forall _a} \in A.$$ We show that one can determine whether a given set G of generators is hyperrigid by examining the noncommutative Choquet boundary of the operator space spanned by G ∪ G*. We present a variety of concrete applications and discuss prospects for further development.