cssi/SciSciGPT-SciSciNet huggingface dataset:
THE DYNAMICS AND AFTERGLOW RADIATION OF GAMMA-RAY BURSTS. I. CONSTANT DENSITY MEDIUM

Direct multidimensional numerical simulation is the most reliable approach for calculating the fluid dynamics and observational signatures of relativistic jets in gamma-ray bursts (GRBs). We present a two-dimensional relativistic hydrodynamic simulation of a GRB outflow during the afterglow phase, which uses the fifth-order weighted essentially nonoscillatory scheme and adaptive mesh refinement. Initially, the jet has a Lorentz factor of 20. We have followed its evolution up to 150 years. Using the hydrodynamic data, we calculate synchrotron radiation based upon standard afterglow models and compare our results with previous analytic work. We find that the sideways expansion of a relativistic GRB jet is a very slow process and previous analytic works have overestimated its rate. In our computed light curves, a very sharp jet break is seen and the postbreak light curves are steeper than analytic predictions. We find that the jet break in GRB afterglow light curves is mainly caused by the missing flux when the edge of the jet is observed. The outflow becomes nonrelativistic at the end of the Blandford-McKee phase. But it is still highly nonspherical, and it takes a rather long time for it to become a spherical Sedov-von Neumann-Taylor blast wave. We find that the late-time afterglows become increasingly flatter over time. But we disagree with the common notion that there is a sudden flattening in light curves due to the transition into the Sedov-von Neumann-Taylor solution. We have also found that there is a bump in light curves at very late times (~1000 days) due to radiation from the counter jet. We speculate that such a counter jet bump might have already been observed in GRB 980703.
Small resolutions of SU(5)-models in F-theory

We provide an explicit desingularization and study the resulting fiber geometry of elliptically fibered four-folds defined by Weierstrass models admitting a split $\tilde{A}_4$ singularity over a divisor of the discriminant locus. Such varieties are used to geometrically engineer SU(5) grand unified theories in F-theory. The desingularization is given by a small resolution of singularities. The $\tilde{A}_4$ fiber naturally appears after resolving the singularities in codimension-one in the base. The remaining higher codimension singularities are then beautifully described by a four-dimensional affine binomial variety which leads to six different small resolutions of the elliptically fibered four-fold. These six small resolutions define distinct four-folds connected to each other by a network of flop transitions forming a dihedral group. The location of these exotic fibers in the base is mapped to conifold points of the three-folds that defines the type IIB orientifold limit of the F-theory. The full resolution has interesting properties, specially for fibers in codimension-three: the rank of the singular fiber does not necessary increase and the fibers are not necessary in the list of Kodaira and some are not even (extended) Dynkin diagrams.
A convenient route to spirocyclic C-glycosides. Demonstration that ring strain release can override normal operation of the ferrier rearrangement

Abstract The response of glycals substituted at C(1) with a tertiary cyclic carbinol is shown to vary strikingly as a function of ring size.
D-branes on Calabi-Yau spaces and their mirrors

We study the boundary states of D-branes wrapped around supersymmetric cycles in a general Calabi-Yau manifold. In particular, we show how the geometric data on the cycles are encoded in the boundary states. As an application, we analyze how the mirror symmetry transforms D-branes, and we verify that it is consistent with the conjectured periodicity and the monodromy of the Ramond-Ramond field configuration on a Calabi-Yau manifold. This also enables us to study open string worldsheet instanton corrections and relate them to closed string instanton counting. The cases when the mirror symmetry is realized as T-duality are also discussed.
The Expected Number of Nash Equilibria of a Normal Form Game

Fix finite pure strategy sets S1,..., S,,, and let S = S, x... x S-n. In our model of a random game the agents' payoffs are statistically independent, with each agent's payoff uniformly distributed on the unit sphere in R-A. For given nonempty T-1 subset of S-1,..., T-n subset of S-n we give a computationally implementable formula for the mean number of Nash equilibria in which each agent i's mixed strategy has support T-i. The formula is the product of two expressions. The first is the expected number of totally mixed equilibria for the truncated game obtained by eliminating pure strategies outside the sets Ti. The second may be construed as the "probability" that such an equilibrium remains an equilibrium when the strategies in the sets S-i\T-i become available.
VL2: a scalable and flexible data center network

To be agile and cost effective, data centers must allow dynamic resource allocation across large server pools. In particular, the data center network should provide a simple flat abstraction: it should be able to take any set of servers anywhere in the data center and give them the illusion that they are plugged into a physically separate, noninterfering Ethernet switch with as many ports as the service needs. To meet this goal, we present VL2, a practical network architecture that scales to support huge data centers with uniform high capacity between servers, performance isolation between services, and Ethernet layer-2 semantics. VL2 uses (1) flat addressing to allow service instances to be placed anywhere in the network, (2) Valiant Load Balancing to spread traffic uniformly across network paths, and (3) end system--based address resolution to scale to large server pools without introducing complexity to the network control plane. VL2's design is driven by detailed measurements of traffic and fault data from a large operational cloud service provider. VL2's implementation leverages proven network technologies, already available at low cost in high-speed hardware implementations, to build a scalable and reliable network architecture. As a result, VL2 networks can be deployed today, and we have built a working prototype. We evaluate the merits of the VL2 design using measurement, analysis, and experiments. Our VL2 prototype shuffles 2.7 TB of data among 75 servers in 395 s---sustaining a rate that is 94% of the maximum possible.
The Spectrum of the Neumann Matrix with Zero Modes

We calculate the spectrum of the matrix M' of Neumann coefficients of the Witten vertex, expressed in the oscillator basis including the zero-mode a0. We find that in addition to the known continuous spectrum inside [−1/3,0) of the matrix M without the zero-modes, there is also an additional eigenvalue inside (0,1). For every eigenvalue, there is a pair of eigenvectors, a twist-even and a twist-odd. We give analytically these eigenvectors as well as the generating function for their components. Also, we have found an interesting critical parameter b0 = 8 ln 2 on which the forms of the eigenvectors depend.
Magnetic Rotator Winds and Keplerian Disks of Hot Stars

We set up equations and boundary conditions for magnetic rotator winds and disks in axially symmetric hot stars in a steady state. We establish a theorem stating that if a disk region has no meridional motion but its magnetic field has a normal component at a point Q on its shock boundary, the angular velocity of the disk region at Q is the same as the angular velocity of the star at the point P* at which the magnetic field line through Q is anchored. When there is equatorial symmetry, all points of the disk along the field line through Q will have the same angular velocity as P*. Also, we show that for a given value of the magnetic field strength, if the rotation rate is too high or the flow velocity into the shock boundary is too low, a Keplerian disk region will not be formed. We consider the formation of disks in magnetic rotators through the processes of fill-up and diffusion into Keplerian orbits. At the end of the fill-up stage the density of the disk increases significantly and the magnetic force in the disk becomes negligible. If the meridional component Bm of the field at the surface is larger than a minimum value Bm,min, a Keplerian disk can form. The radial extent of the Keplerian region is larger for larger values of Bm and is largest when Bm equals an optimal value Bm,opt. The extent does not increase when Bm is larger than Bm,opt. If α is the ratio of rotational speed to the critical rotation speed at the photosphere, the inner and outer radii of the maximal quasi-steady Keplerian disk region are given by α-2/3R and 24/3α-2/3R, respectively, where R is the stellar radius. For models with dipole-type fields, the values of Bm,min in B-type stars are of the order of 1-10 G, and in O-type stars they are about 500 G. Because the values of Bm required for disk formation in B-type stars are relatively small and the fill-up time is short, we suggest that meridional circulation may play a role in some of the time variation observed in disks of Be stars through its effect on the magnetic field near the photosphere.
Complex projective structures on Kleinian groups

Let M be a compact, oriented, irreducible, and boundary incompressible 3–manifold. Assume that its fundamental group is without rank two abelian subgroups and ∂M 6= ∅. We will show that every homomorphism θ: π1(M )→ PSL(2,C) which is not “boundary elementary” is induced by a possibly branched complex projective structure on the boundary of a hyperbolic manifold homeomorphic to M . AMS Classification 30F50; 30F45, 30F60, 30F99, 30C99
A generalization of dehn-sommerville relations to simple stratified spaces

We generalize the classical Dehn-Sommerville relations for simple, convex polytopes to compact, transverse intersections of arbitrary smooth manifolds with boundaries.
Validating Solar Wind Prediction Using the Current Sheet Source Surface Model

We have carried out a comparative study of the predicted solar wind based on the flux tube expansion factor computed using the current sheet source surface (CSSS) model and the potential field source surface (PFSS) model, with the aim of determining whether the CSSS model represents the solar wind sources better than the PFSS model. For this, we obtained the root mean square errors (RMSEs) and the correlation coefficients between the observed solar wind speed and that predicted by the models, the ratio of RMSEs between the two models, and a skill score. On average, the CSSS predictions are more accurate than the PFSS predictions by a factor of 1.6, taking RMSE as the metric of accuracy. The RMSEs increased as the solar cycle progressed toward maximum, indicating the difficulty in modeling the corona as the global field becomes more complex. We also compared the WSA/ENLIL predictions for a few Carrington rotations; the Wang-Sheeley-Arge (WSA) model makes use of the PFSS extrapolations to model the wind source. We found that the average value of RMSE ratio between the CSSS and the WSA/ENLIL predictions was about 1.9, implying that the CSSS predictions are nearly twice better than the WSA/ENLIL predictions, despite the simplicity of the CSSS model compared to ENLIL. We conclude, based on the present analysis, that the CSSS model is a valid proxy for solar wind measurements and that it improves upon existing commonly used methods of wind prediction or proxy analysis.
Intramolecular Additions of Alcohols and Carboxylic Acids to Inert Olefins Catalyzed by Silver(I) Triflate

Intramolecular additions of hydroxyl or carboxyl groups to inert olefins catalyzed by simple silver(I) triflate are described. Good to excellent yields can be obtained for a range of substrates und...
An Exact Jacobian SDP Relaxation for Polynomial Optimization

Given polynomials f (x), gi (x), hj (x), we study how to minimize f (x) on the set $$S = \left\{ x \in \mathbb{R}^n:\, h_1(x) = \cdots = h_{m_1}(x) = 0,\\ g_1(x)\geq 0, \ldots, g_{m_2}(x) \geq 0 \right\}.$$ Let fmin be the minimum of f on S. Suppose S is nonsingular and fmin is achievable on S, which are true generically. This paper proposes a new type semidefinite programming (SDP) relaxation which is the first one for solving this problem exactly. First, we construct new polynomials \({\varphi_1, \ldots, \varphi_r}\) , by using the Jacobian of f, hi , gj , such that the above problem is equivalent to $$\begin{gathered}\underset{x\in\mathbb{R}^n}{\min} f(x) \hfill \\ \, \, {\rm s.t.}\; h_i(x) = 0, \, \varphi_j(x) = 0, \, 1\leq i \leq m_1, 1 \leq j \leq r, \hfill \\ \quad \, \, \, g_1(x)^{\nu_1}\cdots g_{m_2}(x)^{\nu_{m_2}}\geq 0, \, \quad\forall\, \nu \,\in \{0,1\}^{m_2} .\hfill \end{gathered}$$ Second, we prove that for all N big enough, the standard N-th order Lasserre’s SDP relaxation is exact for solving this equivalent problem, that is, its optimal value is equal to fmin. Some variations and examples are also shown.
Trade Restrictiveness Benchmarks

Benchmark measures of trade restrictiveness uising the Trade Restrictiveness Index stand in sharp contrast to standard measures. For a 27 country sample, trade weighted average tariffs underestimate restrictiveness meastured by the 'uniform tariff equivalent' (the inverse of the TRI minus one) by an average of 50%. For a 7 case sample of changes in trade policy, the TRI and changes in average tariffs are uncorrelated. These concltusions appear to be robust with respect to missing data problems and to elasticity of substitution variation, but may be sensitive to the asstumptions uised to treat NTBs. Trade policies are often compared across countries and over time. For this purpose, analysts use such measures as trade-weighted average tariffs and NonTariff Barrier (NTB) coverage ratios, and dispersion measures such as the coefficient of variation of tariffs. All such measures are without theoretical foundation. The problem presented by the lack of theoretically based index numbers of trade policy stands out in two examples. First, the link between openness and growth can't be reliably examined without such indices (Edwards, 1993). Second, the World Bank routinely uses tariff mean and dispersion indices in the evaluation of loan conditionality. Anderson and Neary (1996) develop a theoretically consistent index of trade policy for both tariff and nontariff barriers, the Trade Restrictiveness Index (TRI). It is defined as the uniform price deflator which, applied to the new levels of distorted prices, yields the old level of utility of the representative agent. The inverse of the TRI minus one is equal to the uniform tariff equivalent of the tariff and NTB structure. The TRI provides a unified solution to two apparent defects of the atheoretic measures. First, the usual weights reflect the protected situation, hence are 'too small'. By treating the trade policy index number problem as an ideal price deflator problem, the TRI solves the problem of ideal weights. Second, and more subtly, the ideal weights are not ideal trade weights. The use of dispersion measures of tariffs is presumably motivated by the notion that the dead weight loss triangle due to tariffs (that is, a measure of the welfare cost of tariffs) is proportional to the square of the tariff. There is something right about this idea, as the TRI uses ideal marginal welfare weights. The TRI extends from tariffs only to include both tariffs and quotas and to include the trade restrictiveness impact of domestic measures such as production subsidies (Anderson et al.,
Stochastic Estimation of Conditional Structure: a Review

Mean square estimation methods can be applied to the approximation of conditionally averaged turbulent fields to educe mean structure of the fields. The mathematical procedure is reviewed, and the results obtained by selecting events of increasing complexity are summarized.
Designing and tuning properties of a three-dimensional porous quaternary chalcogenide built on a bimetallic tetrahedral cluster [M4Sn3S13]5− (M=Zn/Sn)

A multifunctional three-dimensional quaternary chalcogenide [Na{sub 5}Zn{sub 3.5}Sn{sub 3.5}S{sub 13}].6H{sub 2}O has been synthesized by solvothermal reactions. [Na{sub 5}Zn{sub 3.5}Sn{sub 3.5}S{sub 13}].6H{sub 2}O represents an interesting example of metal chalcogenides that combines semiconductivity, porosity, and light emission in a single structure. It crystallizes in the cubic space group Fm-3c, a=17.8630(3) A, V=5699.85(17) A{sup 3}, Z=8. The compound decomposes at {approx}450 deg. C. A band gap of 2.9 eV is estimated from the optical diffuse reflectance data. A strong photoluminescence peak is observed at 2.43 eV in Mn doped samples. The electronic and optical properties of this compound can be systematically tuned by substitution of metal and chalcogen elements. - Graphical abstract: A three-dimensional quaternary chalcogenide [Na{sub 5}Zn{sub 3.5}Sn{sub 3.5}S{sub 13}].6H{sub 2}O represents an interesting example of chalcogenide based semiconductor that combines semiconductivity, porosity, and light emission in a single structure. The electronic and optical properties of this compound can be systematically tuned by substitution of metal and chalcogen elements.
Compensation and performance: the case of Japanese managers and directors

Abstract We investigate empirically the nature of Japanese executives' compensation contracts. The principal issues examined are: the extent Japanese executives are rewarded for performance in the short and long term, the role of unique Japanese governance and control mechanisms such as cross-shareholdings and main banks on the design of the executive compensation contract and the importance of non share value related goals in compensation. Our results indicate that only a relatively small percentage of the group of Japanese executives/directors receives increased compensation from short-term share increases. In the long term, the reward to share performance relationship is more prominent thus providing some indication of the existence of implicit contracts to pursue long-term share value maximization goals. Bonuses, on the other hand, are more related to short-term performance, although their importance diminishes in the long term. This feature of compensation is reasonable given the often transitory nature of short-term performance. However, some surprising results are: (1) the dominant role of sales maximization in setting executive contracts, even in the long term; (2) the highly asymmetric nature of Japanese executive compensation, where increased compensation is given in both years when the firm's market value increases and in years when market value decreases, but sales increase; and (3) lower compensation and market value alignment in recent years when the stock market was declining.
Optimum coherent imaging of a limited field of view in the presence of angular and aperture noise

The question of image distribution reconstruction for coherent illumination of an object located in the aperture far zone is considered from first principles without postulating any particular optical spread function. The object function is mathematically modeled as a complex random function of angular coordinates, and it is assumed that the object distribution of interest is angularly limited to a certain a priori assigned field of view (FOV). A linear reconstruction procedure that is uniformly optimal in the FOV is established by using the methods of statistical estimation. Two special cases are examined: imaging a limited sector of a wide-angle random scene and objects in the FOV immersed in a wide-angle background of angular noise. It is noted that the domain of application of the reconstruction method is restricted to microwave frequencies.
The Pervasive Impact of Moral Judgment

: A series of recent studies have shown that people's moral judgments can affect their intuitions as to whether or not a behavior was performed intentionally. Prior attempts to explain this effect can be divided into two broad families. Some researchers suggest that the effect is due to some peculiar feature of the concept of intentional action in particular, while others suggest that the effect is a reflection of a more general tendency whereby moral judgments exert a pervasive influence on folk psychology. The present paper argues in favor of the latter hypothesis by showing that the very same effect that has been observed for intentionally also arises for deciding, in favor of, opposed to, and advocating.
Geometry-Based Parametric Modeling For Single-Pursuer Multiple Evader Problems

In this paper we examine the situation where a single pursuer must develop an optimal strategy with respect to multiple evaders. The pursuers' objective is to capture an evader, while each evaders' objective is to avoid capture. We assume that the evaders are all of equal value to the pursuer and that the pursuer can capture no more than one evader. We also assume that the pursuer has incomplete information on the evader states and no information on the evaders' strategies (which could be, but is not required to be, cooperative) and vise vers a. This problem is unique in that previous pursuit -evasion problems studied in the literature address one -on-one engagements. Current techniques for solving pursuit -evasion games rely on the construction of trajectories in space -time by applying either a minmax strategy at each time -step or through evolutionary/simulation techniques. However, even for one-on-one pursuit -evasion problems, differential game theoretic models with incomplete information result in intractable formulations without saddle point solutions. Evolutionary and simulation -based methods require extensive computational time and resources to arrive at strategies that may not even be provably optimal. By adding multiple evaders to the mix, these "construction -based" methods are severely handicapped. The approach taken in this study is to rapidly develop bounds on the pursuer's capture (evader's escape) possibilities for use in an optimization program.
Advances in nonlinear programming concepts for process control

Abstract Some recent advances in nonlinear programming concepts and methods for nonlinear model predictive control are described and surveyed. These areas include the importance of: tailoring the nonlinear programming (NLP) algorithm to nonlinear model predictive control; a reliable NLP formulation to deal with open loop unstable control systems; efficient, large-scale algorithms for quadratic programming (QP) and NLP for on-line application of model predictive control (MPC); constraint handling for large-scale problems using interior point formulations. These concepts are illustrated by numerous examples. Open questions and future research directions are also discussed. In particular, the need to handle nominal and robust stability motivates more innovative NLP formulations and more powerful algorithms. The final section briefly mentions applications of NLP sensitivity analysis and nonconvex optimization to address these questions.
Developing mechanism-based methods for estimating hypersonic boundary-layer transition in flight: The role of quiet tunnels

Abstract For more than half a century, researchers have been aware that freestream fluctuations have an important effect on laminar-turbulent transition. A century of effort has also been devoted to the development of theory and experiment for the instability mechanisms that lead to transition, in order to develop more reliable prediction methods. Both these long efforts are now beginning to bear fruit in the subarea of hypersonic transition. At hypersonic speeds, it was necessary to develop quiet tunnels with laminar nozzle-wall boundary layers in order to achieve low fluctuation levels that are comparable to flight; three such tunnels are now in operation, worldwide. Hypersonic instability mechanisms are also more complex than at low speeds, and the computer resources and computational tools necessary to compute them are only now becoming fairly widely available, along with the instrumentation necessary to measure these mechanisms in a reasonably affordable way. The present review begins to show how these two steps are aiding in the development of physics-based methods for estimating transition in flight.
Complexity Analysis of Pipeline Mapping Problems in Distributed Heterogeneous Networks

Largescale scientific applications require using various system resources to execute complex computing pipelines in distributed networks to support collaborative research. System resources are typically shared in the Internet or over dedicated connections based on their location, availability, capability, and capacity. Optimizing the network performance of computing pipelines in such distributed environments is critical to the success of these applications. We consider two types of largescale distributed applications: interactive applications where a single dataset is sequentially processed along a pipeline; and streaming applications where a series of datasets continuously flow through a pipeline. The computing pipelines of these applications consist of a number of modules executed in a linear order in network environments with heterogeneous resources under different constraints. Our goal is to find an efficient mapping scheme that allocates the modules of a pipeline to network nodes for minimum endtoend delay or maximum frame rate. We formulate the pipeline mappings in distributed environments as optimization problems and categorize them into six classes with different optimization goals and mapping constraints: Minimum Endtoend Delay with No Node Reuse (MEDNNR), Minimum Endtoend Delay with Contiguous Node Reuse (MEDCNR), Minimum Endtoend Delay with Arbitrary Node Reuse (MEDANR), Maximum Frame Rate with No Node Reuse or Share (MFRNNRS), Maximum Frame Rate with Contiguous Node Reuse and Share (MFRCNRS), and Maximum Frame Rate with Arbitrary Node Reuse and Share (MFRANRS). Here, “contiguous node reuse” means that multiple contiguous modules along the pipeline may run on the same node and “arbitrary node reuse” imposes no restriction on node reuse. Note that in interactive applications, a node can be reused but its resource is not shared. We prove that MEDANR is polynomially solvable and the rest are NP-complete. MEDANR, where either contiguous or noncontiguous modules in the pipeline can be mapped onto the same node, is essentially the Maximum n-hop Shortest Path problem, and can be solved using a dynamic programming method. In MEDNNR and MFRNNRS, any network node can be used only once, which requires selecting the same number of nodes for onetoone onto mapping. We show its NP-completeness by reducing from the Hamiltonian Path problem. Node reuse is allowed in MEDCNR, MFRCNRS and MFRANRS, which are similar to the Maximum n-hop Shortest Path problem that considers resource sharing. We prove their NP-completeness by reducing from the Disjoint-Connecting-Path Problem and Widest path with the Linear Capacity Constraints problem, respectively.
CLIENTELE TRADING IN RESPONSE TO PUBLISHED INFORMATION: EVIDENCE FROM THE DARTBOARD COLUMN

We present an analysis of clientele trading effects in response to the widespread dissemination of public information. Employing analyst recommendations published in the Wall Street Journal's Dartboard column as the informational stimulus and the NYSE's trades and quotes (TAQ) transactions database as the data resource, we document that investors in different trading clienteles exhibit dramatically different trading responses to identical innovations in the informational environment.
THE INFRARED CONTINUUM SIZES OF Be STAR DISKS

We present an analysis of the near-infrared continuum emission from the circumstellar gas disks of Be stars using a radiative transfer code for a parameterized version of the viscous decretion disk model. This isothermal gas model creates predicted images that we use to estimate the half-width at half-maximum emission radius along the major axis of the projected disk and the spatially integrated flux excess at wavelengths of 1.7, 2.1, 4.8, 9, and 18 μm. We discuss in detail the effect of the disk base density, inclination angle, stellar effective temperature, and other physical parameters on the derived disk sizes and color excesses. We calculate color excess estimates relative to the stellar V-band flux for a sample of 130 Be stars using photometry from the Two Micron All Sky Survey and the AKARI infrared camera all-sky survey. The color excess relations from our models make a good match of the observed color excesses of Be stars. We also present our results on the projected size of the disk as a function of wavelength for the classical Be star ζ Tauri and show that the model predictions are consistent with interferometric observations in the H, K', and 12 μm bands.
Basin Structure beneath the Santa Rosa Plain, Northern California: Implications for Damage Caused by the 1969 Santa Rosa and 1906 San Francisco Earthquakes

Regional gravity data in the northern San Francisco Bay region reflect a complex basin configuration beneath the Santa Rosa plain that likely contributed to the significant damage to the city of Santa Rosa caused by the 1969 M 5.6, 5.7 Santa Rosa earthquakes and the 1906 M 7.9 San Francisco earthquake. Inversion of these data indicates that the Santa Rosa plain is underlain by two sedimentary basins about 2 km deep separated by the Trenton Ridge, a shallow west-northwest-striking bedrock ridge west of Santa Rosa. The city of Santa Rosa is situated above the 2- km-wide protruding northeast corner of the southern basin where damage from both the 1969 and 1906 earthquakes was concentrated. Ground-motion simulations of the 1969 and 1906 earthquakes, two events with opposing azimuths, using the gravity- defined basin surface, show enhanced ground motions along the northeastern edge of this corner, suggesting that basin-edge effects contributed to the concentration of shaking damage in this area in the past and may also contribute to strong shaking during future earthquakes.
Atmosphere, Interior, and Evolution of the Metal-rich Transiting Planet HD 149026b

We investigate the atmosphere and interior of the new transiting planet HD 149026b, which appears to be very rich in heavy elements. We first compute model atmospheres at metallicities ranging from solar to 10 times solar and show how for cases with high metallicity or inefficient redistribution of energy from the dayside, the planet may develop a hot stratosphere due to absorption of stellar flux by TiO and VO. The spectra predicted by these models are very different than cooler atmosphere models without stratospheres. The spectral effects are potentially detectable with the Spitzer Space Telescope. In addition, the models with hot stratospheres lead to a large limb brightening, rather than darkening. We compare the atmosphere of HD 149026b to other well-known transiting planets, including the recently discovered HD 189733b, which we show has a planet-to-star flux ratio twice that of HD 209458 and TrES-1. The methane abundance in the atmosphere of HD 189733b is a sensitive indicator of atmospheric temperature and metallicity and can be constrained with Spitzer IRAC observations. We then turn to interior studies of HD 149026b and use a grid of self-consistent model atmospheres and high-pressure equations of state for all components to compute thermal evolution models of the planet. We estimate that the mass of heavy elements within the planet is in the range of 60-93 M⊕. Finally, we discuss trends in the radii of transiting planets with metallicity in light of this new member of the class.
Equidistribution of singular measures on nilmanifolds and skew products

We prove that for a minimal rotation T on a two-step nilmanifold and any measure μ , the push-forward T n ⋆ μ of μ under T n tends toward Haar measure if and only if μ projects to Haar measure on the maximal torus factor. For an arbitrary nilmanifold we get the same result along a sequence of uniform density one. These results strengthen Parry’s result [Ergodic properties of affine transformations and flows on nilmanifolds. Amer. J. Math. 91 (1968), 757–771] that such systems are uniquely ergodic. Extending the work of Furstenberg [Strict ergodicity and transformations of the torus. Amer. J. Math. 83 (1961), 573–601], we get the same result for a large class of iterated skew products. Additionally we prove a multiplicative ergodic theorem for functions taking values in the upper unipotent group. Finally we characterize limits of T n ⋆ μ for some skew product transformations with expansive fibers. All results are presented in terms of twisting and weak twisting, properties that strengthen unique ergodicity in a way analogous to that in which mixing and weak mixing strengthen ergodicity for measure-preserving systems.
Does the stock market underreact to going concern opinions? Evidence from the U.S. and Australia

Abstract We examine 12-month returns following disclosure of first-time going concern (GC) opinions in the U.S. and Australia. We find no evidence of significant negative abnormal returns associated with GC opinions in Australia. In the U.S., negative abnormal returns subsequent to GC opinions are sensitive to choice of expected returns—notably, there are no significant negative abnormal returns when using factor models or after controlling for momentum. Overall, contrary to Taffler, Lu, Kausar's [2004. In denial? Stock market underreaction to going-concern audit report disclosures. Journal of Accounting and Economics 38, 263–285.] U.K. results, we are unable to document a market anomaly in the U.S. or Australia associated with GC opinions.
Intramolecular [4 + 2]-cycloadditions of vinylnitrosonium cations with olefins

Les α,β-epoxycetonitrones sont des precurseurs viables des cations vinylnitrosonium par traitement avec le triflate de trimethylsilyle. L'heterodiene N=O genere subit une cycloaddition [4+2] intramoleculaire avec l'olefine non activee. Le cours de la reaction depend fortement de la geometrie de la nitrone de depart. Un certain nombre d'α,β-epoxyaldonitrones est prepare, dans les memes conditions ces substrats generent des cations vinylnitrosonium a −30°C et subissent une cycloaddition analogue
Catalytic Carbonyl Z-Dienylation via Multicomponent Reductive Coupling of Acetylene to Aldehydes and α-Ketoesters Mediated by Hydrogen: Carbonyl Insertion into Cationic Rhodacyclopentadienes

Exposure of aldehydes or alpha-ketoesters to equal volumes of acetylene and hydrogen gas at ambient temperature and pressure in the presence of cationic rhodium catalysts provides products of carbonyl Z-butadienylation, which arise via multicomponent coupling of four molecules: two molecules of acetylene, a molecule of vicinal dicarbonyl compound, and a molecule of elemental hydrogen. The collective data suggest a catalytic mechanism involving carbonyl insertion into a cationic rhodacyclopentadiene intermediate derived via oxidative dimerization of acetylene. Hydrogenolytic cleavage of the resulting oxarhodacycloheptadiene via formal sigma-bond metathesis provides the product of carbonyl addition and cationic rhodium(I) to close the catalytic cycle. Studies involving the hydrogenation of 1,6-diyne 14a in the presence of alpha-ketoester 6a corroborate the proposed catalytic mechanism. These multicomponent couplings represent the first use of acetylene gas, a basic chemical feedstock, in metal-catalyzed reductive C-C bond formation.
Simulation and Analyses of Stage Separation of Two-Stage Reusable Launch Vehicles

*† ‡ § ** †† ‡‡ NASA has initiated the development of methodologies, techniques and tools needed for analysis and simulation of stage separation of next generation reusable launch vehicles. As a part of this activity, ConSep simulation tool is being developed which is a MATLAB‐based front-and-back-end to the commercially available ADAMS ® solver, an industry standard package for solving multi-body dynamic problems. This paper discusses the application of ConSep to the simulation and analysis of staging maneuvers of two-stage-to-orbit (TSTO) Bimese reusable launch vehicles, one staging at Mach 3 and the other at Mach 6. The proximity and isolated aerodynamic database were assembled using the data from wind tunnel tests conducted at NASA Langley Research Center. The effects of parametric variations in mass, inertia, flight path angle, altitude from their nominal values at staging were evaluated. Monte Carlo runs were performed for Mach 3 staging to evaluate the sensitivity to uncertainties in aerodynamic coefficients.
Collapsing D-branes in one-parameter models and small/large radius duality

Abstract We finalize the study of collapsing D-branes in one-parameter models by completing the analysis of the associated hypergeometric hierarchy. This brings further evidence that the phenomenon of collapsing 6-branes at the mirror of the ‘conifold’ point in IIA compactifications on one-parameter Calabi–Yau manifolds is generic. It also completes the reduction of the study of higher periods in one-parameter models to a few families which display characteristic behaviour. One of the models we consider displays an exotic form of small–large radius duality, which is a consequence of an “accidental” discrete symmetry of its moduli space. We discuss the implementation of this symmetry at the level of the associated type II string compactification and its action on D-brane states. We also argue that this model admits two special Lagrangian fibrations and that the symmetry can be understood as their exchange.
Measurement of the optical properties of solid biomedical phantoms at the National Institute of Standards and Technology

Solid phantoms that serve as a proxy for human tissue provide a convenient test subject for optical medical imaging devices. In order to determine the quantitative performance of a given system, the absolute optical properties of the test subject must be known. Currently there is no national scale applicable to the scattering and absorption properties of solid diffuse tissue phantoms that would provide traceability and estimated measurement uncertainties for optical imaging applications. This paper describes progress in the development of a facility dedicated to the determination of the optical properties of solid biomedical phantoms. A brief description of the system, data analysis, Graphical User Interface (GUI), and measurement uncertainties is presented. The design is based on a double-integrating sphere, steady-state domain approach. The initial evaluation of the system includes the measurement of solid phantoms and a comparison to the manufacturer’s values that were determined by a time resolved approach. The initial results indicate that measurement agreement is within the estimated uncertainties with the coverage factor k =2.
Irreversibility and the behavior of aggregate stochastic growth models

Abstract This paper examines the effects of capital restrictions on aggregate stochastic growth models. In a one-sector model, irreversibility of investment reduces the response of investment to positive shocks to the economy. In real business cycle models irreversibility lowers the variation of output, investment, and hours worked. The magnitude of the effects depends on the variance and autocorrelation of productivity shocks. In a two-sector model, constraints on the movement of capital across sectors are more important than depreciation constraints. There is evidence that immobility of capital has a significant impact on the sectoral variability of production and hours worked.
Low-altitude turbulence model for estimating gust loads on aircraft.

The development of a low-altitude turbulence model for estimating aircraft gust loads within the friction layer of the atmosphere Is described. The development of the model is based largely on the gust data obtained from the B-66 low-level gust program arid climatological wind data provided by the National Weather Records Center, Asheville, N. C. In developing the model, the B-66 vertical gust spectra are used to determine a spectrum function relating spectrum shape to the height above ground arid terrain roughness. From the standard deviations of the vertical gust velocities and mean wind speed estimates, empirical standard deviation vs mean wind speed functions are estimated for smooth and rough terrain conditions. Climatological wind data analyses for both smooth arid rough terrains are used to provide wind probability density distribution characteristics. From these results, estimates of the standard deviation of vertical gust velocity probability density distribution functions are obtained on the basis of specified confidence limits for the empirical standard deviation gust velocity functions. Finally, the procedure for obtaining probability estimates of the vertical gust velocity is presented for assumed climatic mean wind speed conditions for both smooth and rough terrains. Application of the model to estimating aircraft gust loads is also discussed.
Modeling high-pressure chemical oxygen-iodine lasers

The Blaze II chemical laser model was baselined to existing oxygen-iodine research assessment and device improvement chemical laser (RADICL) data. Mixing calculations for the RADICL nozzle indicate that higher iodine flow rates are necessary to maintain a significant fraction of the nominal performance as the helium flow rate is increased to raise the total pressure of the flow; this agrees with RADICL experimental data. Overall, the model is in very good qualitative and quantitative agreement with RADICL data as a function of increased He flow rate over a total pressure range of 70-130 Torr. This was accomplished only after the nominal I * 2 + He → I 2 + He rate constant was increased by an order of magnitude. To determine the set of five unknown parameters which best matched Blaze II model predictions with experimental data, a genetic algorithm technique was implemented to efficiently search the parameter space. This is the first known application of the genetic algorithm technique for modeling lasers, chemically reacting flows, and chemical lasers. Different reduced reaction/species sets were investigated; a 13-reaction, 10-species set gave excellent agreement and an 8-reaction, 8-species set gave very good agreement with the full reaction set.
Doppler-Free Laser Polarization Spectroscopy

We have demonstrated a sensitive new method of Doppler-free spectroscopy, monitoring the nonlinear interaction of two monochromatic laser beams in an absorbing gas via changes in light polarization. The signal-to-background ratio can greatly surpass that of saturated absorption. Polarization spectra of the hydrogen Balmer-$\ensuremath{\beta}$ line, recorded with a cw dye laser, reveal the Stark splitting of single fine-structure components in a Wood discharge.
PARTITION FUNCTIONS, DUALITY AND THE TUBE METRIC

Abstract The partition function of type IIA and B strings on R 6 × K3 , in the T 4 / Z 2 orbifold limit, is explicitly computed as a modular invariant sum over spin structures required by perturbative unitarity in order to extend the analysis to include type II strings on R 6 × W4 , where W4 is associated with the tube metric conformal field theory, given by the degrees of freedom transverse to the Neveu-Schwarz fivebrane solution. This generates partition functions and perturbative spectra of string theories in six space-time dimensions, associated with the modular invariants of the level-k affine SU(2) Kac-Moody algebra. These theories provide a conformal field theory (i.e. perturbative) probe of non-perturbative (fivebrane) vacua. We contrast them with theories whose N = (4, 4) sigma-model action contains nH = k + 2 hypermultiplets as well as vector supermultiplets, and where k is the level just mentioned. In Appendix B we also give a D = 6, N = (1, 1) ‘free fermion’ string model which has. a different moduli space of vacua from the 81-parameter space relevant to the above examples.
The Fate of Stellar Mass Loss in Central Cluster Galaxies

Star formation within the central galaxies of galaxy clusters is often interpreted as being fueled by cooling of the hot intracluster medium. However, the star-forming gas is dusty, and Spitzer spectra show that the dust properties are similar to those in more normal star-forming environments, in which the dust has come from the winds of dying stars. Here we consider whether the primary source of the star-forming gas in central cluster galaxies could be normal stellar mass loss. We show that the overall stellar mass-loss rate in a large central galaxy (~4-8 M ☉ yr–1) is at least as large as the observed star formation rates in all but the most extreme cases and must be included in any assessment of the gas-mass budget of a central cluster galaxy. We also present arguments suggesting that the gas shed by stars in galaxy clusters with high core pressures and short central cooling times may remain cool and distinct from its hot surroundings, thereby preserving the dust within it.
L Dwarf Variability: I-Band Observations

We report on the results of an I-band photometric variability survey of 18 L dwarfs. We find that seven exhibit statistically significant variations above the 95.4% confidence level with rms scatter (including photometric errors) between 0.010 and 0.083 mag. Another five targets have variability probabilities ≈80%, suggesting that these are likely variable objects. Two objects display significant peaks in a CLEAN periodogram that are several times higher than the noise. The periods found for 2MASS 0746+20AB and 2MASS 1300+19 are longer than those periods likely from rotation velocity measurements, and they do not represent periodic behavior in the light curve that persists through the entire data set. These observations suggest that we are not observing the rotation modulation of a long-lived albedo feature. Instead, rapid evolution of atmospheric features is likely causing the nonperiodic variability. The remaining variable objects show no prominent features in their light curves, suggesting even more rapid evolution of atmospheric features. We argue against the existence of magnetic spots in these atmospheres and favor the idea that nonuniform condensate coverage is responsible for these variations. The magnetic Reynolds number in the atmospheres of L dwarfs is too small to support the formation of magnetic spots. In contrast, silicate and iron clouds are expected to form in the photospheres of L dwarfs. Inhomogeneities in such cloud decks and the evolution of the inhomogeneities can plausibly produce the observed photometric variations.
Hypergammaglobulinemia in Swine Infected with African Swine Fever Virus

SummaryMarked hypergammaglobulinemia appeared in swine which became carriers after inoculation with moderately attenuated African swine fever virus. It may have been induced by persistent viral infection. Swine given highly attenuated virus had normal gamma globulin levels.