cssi/SciSciGPT-SciSciNet huggingface dataset:
DC coronal heating and the nonlinear evolution of current sheets

Abstract Recent theoretical developments have re-awakened interest in the role of electric current sheets in DC coronal heating [Parker. Astrophys. J. 330, 474, 1988; Priest et al. Astrophys. J. 576, 522, 2002] . Dahlburg et al. [Dahlburg et al. Adv. Space Res. 32, 1029, 2003; Dahlburg et al. Astrophys. J. 622, 1191, 2005] reported the existence of a “secondary instability” that could explain the required “switch-on” effect required for adequate energy storage. This ideal, three-dimensional instability also provided a straightforward explanation for the subsequent fast release of energy, as the rapid growth of the mode eventually results in a state of turbulent magnetic reconnection. Earlier studies of the secondary instability were limited to systems with relatively simple perturbations, viz., resistive stability eigenmodes. A current sheet in the Sun is likely to be subject to much more complex perturbations involving a waves of various wavelengths and amplitudes. We describe the evolution of three-dimensional electric current sheets disturbed by random 3D perturbations. We find that the significant characteristics of secondary instability are also observed in this case. The numerical results are compared to solar observations.
Hedging GNMA Mortgage‐Backed Securities with T‐Note Futures: Dynamic versus Static Hedging

This article proposes a dynamic hedging model for Government National Association Mortgage-Backed Securities (GNMA MBSs) that is free of the drawbacks associated with the static hedging strategies currently used. The simultaneity bias of the regression approach is dealt with by modeling the joint distribution of price changes of GNMA MBSs and 10-year Treasury-note futures. Error correction (EC) terms from cointegrating relationships are included in the conditional mean equations to preserve the long-term equilibrium relationship of the two markets. The time-varying variance–covariance structure of the two markets is modeled via a version of the bivariate generalized autoregressive conditionally heteroskedastic model (bivariate GARCH), which assures that the time-varying variance–covariance matrix is positive semidefinite for all time periods. This dynamic error-correction GARCH model is estimated using daily data on six different coupon GNMA MBSs. Dynamic cross-hedge ratios are obtained from the time-varying variance–covariance matrix using the 10-year Treasury-note futures contract as the hedging instrument. These ratios are evaluated in terms of both overall risk reduction and expected utility maximization. There is overwhelming evidence that dynamic hedge ratios are superior to static ones even when transaction costs are incorporated into the analysis. This conclusion holds for all six different coupon GNMA MBSs under investigation.
Kinetics of the alkaline hydrolysis of cis- and trans-diacetatobis(1,2-propanediamine)cobalt(III) cations

Abstract The alkaline hydrolysis of cis -and trans -diacetatobis(1,2-propanediamine)cobalt(III) cations appears to follow a substitution nucleophilic unimolecular conjugate base mechanism. In these cations, the acetate ligands are replaced by hydroxide ion in a stepwise manner. Both isomers undergo complete hydrolysis without configurational change.
Eulerian–Eulerian simulation of dense solid–gas cylindrical fluidized beds: Impact of wall boundary condition and drag model on fluidization

Abstract Modeling the hydrodynamics of dense-solid gas flows is strongly affected by the wall boundary condition and in particular, the specularity coefficient ϕ which characterizes the tangential momentum transfer from the particles to the wall. The focus of this study is to investigate the impact of ϕ on the fluidization hydrodynamics using a fully Eulerian description of the solid and gas phases in 3D cylindrical coordinates. In order to quantify this impact, tools for characterizing the bubbling dynamics and solids circulation are developed and applied to both lab-scale (diameters 10 cm and 14.5 cm) and pilot-scale (diameter 30 cm) cylindrical beds. Comparison of simulation predictions with experimental data for different fluidization regimes and particle properties suggests that values of ϕ in the range [0.01,0.3] are suitable for simulating most dense solid–gas flows of practical interest. It is also shown that for this range of ϕ , the fluidization hydrodynamics are not significantly dependent on the choice of ϕ especially as the bed diameter is increased. Additionally, 3D validation of the variable ϕ model by Li and Benyahia [1] shows the bubble diameter predictions to be in excellent agreement with experiment and the average value of ϕ predicted within the range [0.01,0.3]. Quantifying the impact of ϕ and establishing an appropriate range is not only important for accurate simulations at both lab and pilot scales but also validation of models and sub-models for a better understanding of the fluidization phenomenon. Finally, a comparison of the Gidaspow and Syamlal–O'Brien gas–solids drag model shows that the former is more applicable to homogeneous bubbling fluidization (U/U mf mf
Protecting Group-Free Synthesis of 1,2-Azaborines: A Simple Approach to the Construction of BN-Benzenoids

The protecting group-free synthesis of a versatile 1,2-azaborine synthon 5 is described. Previously inaccessible 1,2-azaborine derivatives, including the BN isostere of phenyl phenylacetate and BN1 triphenylmethane were prepared from 5 and characterized. The structural investigation of BN phenyl phenylacetate revealed the presence of a unique NH-carbonyl hydrogen bond that is not present in the corresponding carbonaceous analogue. The methyne CH in BN triphenylmethane was found to be less acidic than the corresponding proton in triphenylmethane. The gram-quantity synthesis of the parent 1,2-azaborine 4 was demonstrated, which enabled the characterization of its boiling point, density, refractive index, and its polarity on the ET(30) scale.
COARSE EMBEDDINGS INTO A HILBERT SPACE, HAAGERUP PROPERTY AND POINCARÉ INEQUALITIES

We prove that a metric space does not coarsely embed into a Hilbert space if and only if it satisfies a sequence of Poincare inequalities, which can be formulated in terms of (generalized) expanders. We also give quantitative statements, relative to the compression. In the equivariant context, our result says that a group does not have the Haagerup Property if and only if it has relative property T with respect to a family of probabilities whose supports go to infinity. We give versions of this result both in terms of unitary representations, and in terms of affine isometric actions on Hilbert spaces.
Variable long-term trends in mineral prices: The ongoing tug-of-war between exploration, depletion, and technological change

Abstract This paper explores the use of low-frequency band-pass filters for describing long-run trends in real mineral commodity prices. This approach has the advantage of allowing long-run trend rates to evolve gradually over time, rather than assuming that they are constant (perhaps with occasional structural breaks) over time. This is a flexible way of capturing the ongoing ‘tug of war’ between exploration, depletion, and technological change. Over 100 mineral and commodities, stretching back to the late 19th or early 20th century, are considered. The variety of LR trends is astonishing, but very few increase monotonically, contrary to the prediction of the basic Hotelling model. Some decline monotonically (as predicted by Prebisch and Singer); some have the U-shaped pattern predicted by Pindyck (1978), Heal (1981) and Slade (1982). Others have changed direction up to three times in the period since 1900. The tug of war continues with exhaustion nowhere in sight.
Extragalactic X-ray Sources

A review is given of the physical properties of extragalactic X-ray sources. The generation of X-rays as thermal bremsstrahlung, by the synchrotron mechanism or by Compton Scattering, is discussed. It is shown that each may be important depending on the circumstances. Only more detailed observations will enable us to decide which process dominates in any given source.
MCFM for the Tevatron and the LHC

A summary is given of the current status of the next-to-leading order (NLO) parton-level integrator MCFM. Some details are given about the Higgs + 2-jet process and the production and decay of t t ¯ , both of which have recently been added to the code. Using MCFM, comparisons between the Tevatron running at s = 2 TeV and the LHC running at s = 7 TeV are made for standard model process including the production of Higgs bosons. The case for running the Tevatron until 16 fb − 1 are accumulated by both detectors is sketched.
Commutative partial differential operators

In one variable, it is possible to describe explicitly the differential operators that commute with a given one, at least when the centralizer of the given operator has rank 1. So far, a generalization of the theory to several variables has been developed (inexplicitly) only for matrices, whose size increases with the number of variables. We propose to develop an algebraic theory of commuting partial differential operators (PDOs) by formulating a generalization of the one-variable techniques, in particular Darboux transformations and differential resultants. In this paper, we present a counter example to a one-variable feature of maximal-commutative rings and some facts, examples and questions on differential resultants.
Diethylaluminum Chloride Mediated Vinylsilane Synthesis: Comparison of Different Solvent Systems

Abstract Aromatic ketones were converted to one‐carbon elongated‐vinylsilanes in a convenient one‐pot operation via the Peterson protocol. Reactions were conducted in two different solvents for comparison: pentane and triethylamine. Results indicate that triethylamine appeared to be a more suitable solvent for such a transformation producing vinylsilanes with great chemo‐ and stereo‐selectivity than pentane.
The curve complex has dead ends

It is proved that the curve graph $${\mathcal {C}^1(\Sigma )}$$ of a surface $$\Sigma _{g,n}$$ has a local pathology that had not been identified as such: there are vertices $$\alpha ,\beta \in {\mathcal {C}^1(\Sigma )}$$ such that $$\beta $$ is a dead end of every geodesic joining $$\alpha $$ to $$\beta $$ . There are also double dead-ends. Every dead end has depth 1.
Hot quarks and gluons at an electron-ion collider

The nuclear wave-function is dominated at low- and medium-x by gluons. As the rapid growth of the gluon distribution towards low x, as derived from current theoretical estimates, would violate unitarity, there must be a mechanism that tames this explosive growth. This is most efficiently studied in colliders running in e+A mode, as the nucleus is an efficient amplifier of saturation effects occurring with high gluon densities. In fact, large A can lead to these effects manifesting themselves at energies a few orders of magnitude lower than in e+p collisions. In order to study these effects, there are proposals to build an e+A machine in the USA, operating over a large range of masses and energies. These studies will allow for an in-depth comparison to A+A collisions where results have given tantalising hints of a new state of matter with partonic degrees of freedom. In order to explain these results quantitatively, the gluons and their interactions must be understood fully as they are the dominant source of hard probes at both RHIC and LHC energies.
An improved model of direct gauge mediation

Abstract We present a new, improved model of gauge mediation of dynamical SUSY Breaking: the model does not have gauge messengers or ∼10 TeV scalars charged under the Standard Model (SM), thus avoiding the problem of negative (mass)2 for supersymmetric SM (SSM) scalars faced by some earlier models. The gauge mediation is direct, i.e., the messengers which communicate SUSY breaking to the SSM fields carry quantum numbers of the gauge group which breaks SUSY. These messenger fields couple to a modulus field. The model has a very simple particle content: the modulus and the messengers are the only chiral superfields (other than the SSM fields) in the model. The inverted hierarchy mechanism is used to generate a local SUSY breaking minimum for the modulus field in a perturbative regime thus making the model calculable.
Underwriter learning about unfamiliar firms: Evidence from the history of biotech IPOS

Abstract This study examines the ability of underwriters to properly value unfamiliar firms prior to issuance. I use a sample of IPOs in biotechnology, a relatively new but thriving industry. The first American biotech IPO was in 1980. Through the end of 2004, almost 500 biotech IPOs have appeared in the public market. I find that biotechnology differs from other industries in the attributes of individual firms valued by the market. In particular, RD in those cases, first-day market returns were predictable by firm attributes not used by underwriters to establish IPO issue prices. I also find that underwriters have learned over time, albeit slowly. Over the 20+ years of biotech history, IPO issue prices have become more dependent on firm attributes unique to biotechs while first-day market returns have become less predictable.
SOME LESSONS FROM SIXTY YEARS OF THEORIZING

It gives me great pleasure that so many distinguished colleagues, many of you old friends, have gathered here for a conference associated with my near-centennial, my reaching the age of fourscore years. It is a pleasure to see all of you and to listen to what you have to say. I have been asked to make some remarks too, and I thought hard about what would be appropriate. The result was a decision not to present a paper on some of the research that I'm carrying out, but rather to mention a few of the things I have learned about doing research in theoretical science, things I wish someone had explained to me around 60 years ago. The one I should like to emphasize particularly has to do with the frequently encountered need to go against certain received ideas. Sometimes these ideas are taken for granted all over the world and sometimes they prevail only in some broad region or in certain institutions. Often they have a negative character and they amount to prohibitions of thinking along certain lines. Now we know that most challenges to scientific orthodoxy are wrong and many are crank. Now and then, however, the only way to make progress is to defy one of those prohibitions that are uncritically accepted without good reason.
Spacer effects on lateral heat transfer in multilayer insulation

Lateral heat transfer along parallel conducting and radiating plates spaced by absorbing and isotropically scattering dielectric
NRQCD and static systems — A general variational approach

We present initial results from Monte Carlo simulations of NRQCD-light, static-light, and NRQCD-NRQCD mesons, using a variational technique (MOST), as part of our ongoing calculation of the ƒB decay constant. The basis states for the variational calculation are quark-antiquark operators separated by all possible relative distances not equivalent under the cubic group (for example, for a 203 lattice there are 286 operators). The efficacy of the method is demonstrated by the good plateaus obtained for the ground state and the clean extraction of the wave functions of the ground and first radially excited state.
Kirbac 1.1 activity in liposomes is suppressed by cholesterol

Inwardly rectifying potassium channels (Kir) are responsible for regulating diverse processes including: cellular excitability, vascular tone, heart rate, renal salt flow, and insulin release. Our earlier studies have shown that inwardly-rectifying K channels from Kir2 family are strongly suppressed by the elevation of cellular cholesterol. Little is known, however, about the mechanism responsible for cholesterol modulation of Kir channels. The goal of this study is to test whether cholesterol-induced suppression of Kir channels is observed when purified channels are incorporated into liposomes. To achieve this goal, we reconstituted a bacterial channel Kirbac 1.1, a structural homolog of mammalian Kir channels, into liposomes of defined composition consisting of 3:1 phosphatidyl ethanolamine: phosphatidyl glycerol ratio and variable concentrations of cholesterol. The activity of the channels was assayed using 86Rb+ uptake. Our results show that 86Rb+ flux through the Kirbac 1.1 is strongly inhibited by incorporating cholesterol. Incorporation of 5% (mass Cho/PL) cholesterol into the liposome suppresses more then 50% 86Rb+ flux, and the activity is completely inhibited at 12-15% (mass Cho/PL). No effect was observed at cholesterol levels below 1% (mass Cho/PL). Furthermore, epicholesterol, a stereo isomer of cholesterol that has physical properties similar to those of cholesterol, also suppresses 86Rb+ flux but its effect is significantly less pronounced. Purified KcsA, structurally similar K+ ion channel from Streptomyces lividans was not at all inhibited by cholesterol when incorporated into the liposomes instead of Kirbac 1.1.These observations demonstrate that cholesterol suppresses Kir channels in a non-cellular environment and suggest that it may interact with the Kirbac 1.1 channels directly.
Difficulties of transferring risk-based capital requirements to developing countries

In principle, financial regulation seeks to remedy recognized deficiencies in a nation's economic, political, and bureaucratic incentive structures. But the social urgency of particular financial policy problems differ according to a country's stage of development. Regulatory strategies that make sense for industrial countries are unlikely to work the same way in developing countries. The author examines opportunities for transferring the framework of risk-based capital requirements negotiated by the G-10 countries under the auspices of the Bank for International Settlements in Basle. He finds that an unchanged transfer of the Basle framework to developing countries is economically inappropriate and politically infeasible. And its voluntary adapation is difficult because the long-run economic appropriateness of the Basle framework of solvency regulations directly opposes their short-run political embraceability. The author believes that what most urgently needs to be transferred to developing countries are elements of supervisory technology: methods of information collection and management, legal processes for prompt and equitable default resolution, and mechanisms for controlling the incentive conflicts that lead bankers and government supervisors to resist the healthy exit or recapitalization of damaged institutions. As a first step, the author recommends that the World Bank and the Bank for International Settlements promote economically beneficial reforms in information collection and management, reforms that do not preclude flexibility in current prudential standards in individual countries.
Split attractor flows and the spectrum of BPS D-branes on the quintic

We investigate the spectrum of type-IIA BPS D-branes on the quintic from a four-dimensional supergravity perspective and the associated split attractor flow picture. We obtain some very concrete properties of the (quantum corrected) spectrum, mainly based on an extensive numerical analysis, and to a lesser extent on exact results in the large radius approximation. We predict the presence and absence of some charges in the BPS spectrum in various regions of moduli space, including the precise location of the lines of marginal stability and the corresponding decay products. We explain how the generic appearance of multiple basins of attraction is due to the presence of conifold singularities and give some specific examples of this phenomenon. Some interesting space-time features of these states are also uncovered, such as a non trivial, moduli independent lower bound on the area of the core of arbitrary BPS solutions, whether they are black holes, empty holes, or more complicated composites.
SEARCH FOR SQUARKS IN R-PARITY VIOLATING SUPERSYMMETRY IN ep COLLISIONS AT HERA

The search for squarks in R-parity violating supersymmetry in ep collisions at HERA is reviewed. In the full data sample used by the H1 collaboration corresponding to about 0.5 fb-1 no deviation from Standard Model predictions was observed and limits were set in phenomenological models. For example, for a R-parity violating coupling of electromagnetic strength λ′11k = 0.3(k ∈ {1, 2}), the mass bound on the corresponding right-handed down-type squark is . The results are compared to other searches for supersymmetry. In particular, they are put in context with more recent results from the Large Hadron Collider (LHC). An outlook is given on search opportunities at a future ep collider.
Delegating Power to Bureaucracies: Evidence from the States

Empirical analysis has lagged behind theoretical advancement in the study of legislative delegation of power to bureaucracies. This article analyzes why state legislatures delegated advisory and policy-forming powers to bureaucracies for the Aid to Families with Dependent Children (AFDC) program from 1935 through 1996. The analysis supports various theories of bureaucratic discretion, while painting a complex political picture of delegation decisions. Legislators rely on bureaucrats to resolve uncertainty, especially when internal legislative information is scarce. Contrary to recent wisdom, however, delegation is not found to be associated with the general condition of unified government. Rather, delegation occurs under both divided and unified government, but the procedures chosen and appointment powers granted vary under these two conditions.
A chemoselective, one-pot transformation of aldehydes to nitriles

This paper describes a procedure for direct conversion of aldehydes to nitriles using O-(diphenylphosphinyl)hydroxylamine (DPPH). Aldehydes are smoothly transformed to their corresponding nitriles by heating with DPPH in toluene. The reaction can be accomplished in the presence of alcohol, ketone, ester, or amine functionality.
Binary vector multiplications with nonlinear optical interfaces.

Bistable nonlinear optical interfaces have potential advantages of lower absorption and higher switching speed over resonator-based bistable optical gates. The design of parallel vector multipliers based on all-optical logic gates on a nonlinear optical interface is proposed in this letter. These schemes can be extended to parallel multiplications of matrices and to photonic switching.© (1987) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Forward scattering of neutrons from polymeric and magnetic multilayers

Abstract Grazing incidence neutrons are not only reflected and refracted from imperfect layers, but also partially scattered by lateral dishomogeneities. In general, scattering may take place both in the reflection plane (“forward scattering”) and out of it. The forward scattering from multilayers is highly structured in ridges, whose maxima can be indexed in terms of the multilayer spacings. In experiments on diverse diblock copolymers, two kinds of ridges were found, either at constant-kz loci or else at constant-qz loci. The relative intensity of the ridges appears to be related to the type and size of imperfections of the lamellar structure. Constant-qz streaks of magnetic nature were also found in the forward scattering of metallic superlattices (Fe/Cr, Co/Ru, Fe/Nb) in the antiferromagnetic state. Here the diffuse scattering appears around the antiferromagnetic peaks while they are absent from the structural peaks, as if the crystalline superlattice were to partition into antiferromagnetic domains of limited lateral extension and columnar character.
Concise Synthesis of Iminocyclitols via Petasis-Type Aminocyclization

A two-step method has been developed to synthesize several biologically important iminocyclitols in ca. 44−60% yields by using Petasis-type condensation. The method is very general and operationally simple, affording a series of iminocyclitols from easily available sugar derivatives. Unexpected diastereoselectivities are observed, suggesting that the condensation may proceed through a five- or six-membered cyclic iminium ion intermediate.
Reverse mathematics and infinite traceable graphs

We analyze three applications of Ramsey’s Theorem for 4-tuples to infinite traceable graphs and finitely generated infinite lattices using the tools of reverse mathematics. The applications in graph theory are shown to be equivalent to Ramsey’s Theorem while the application in lattice theory is shown to be provable in the weaker system RCA0.
ON INDECOMPOSABLE SETS WITH APPLICATIONS

In this note we show the characteristic function of every indecomposable set F in the plane is BV equivalent to the characteristic function a closed set F, i.e. � 11F − 11FBV (IR2) =0 . We show by example this is false in dimension three and above. As a corollary to this result we show that for every �> 0 a set of finite perimeter S can be approximated by a closed subset Swith finitely many inde- composable components and with the property that H 1 (∂ M S� \∂ M S )=0a nd� 11S − 11S� � BV(IR2) <� . We apply this corollary to give a short proof that locally quasiminimizing sets in the plane are BVl extension domains.
Drag reduction in flow over a flat plate using active feedback control

Abstract This paper focuses on two-dimensional incompressible Newtonian fluid flow over a flat plate and studies the problem of reducing the frictional drag exerted on the plate using active feedback control. Several alternative control configurations, including both pointwise and spatially uniform control actuation and sensing, are developed and tested through computer simulations. All control configurations use control actuation in the form of blowing/suction on the plate and measurements of shear stresses along the plate. The simulation results indicate that the use of active feedback control, which employs reasonable control effort, can significantly reduce the frictional drag exerted on the plate compared to the open-loop values.
Novel Physical Consequences of the Extended Relativity in Clifford Spaces

Novel physical consequences of the Extended Relativity Theory in C-spaces (Clifford spaces) are explored. The latter theory provides a very different physical explanation of the phenomenon of “relativity of locality” than the one described by the Doubly Special Relativity (DSR) framework. Furthermore, an elegant nonlinear momentum-addition law is derived in order to tackle the “soccer-ball” problem in DSR. Neither derivation in C-spaces requires a curved momentum space nor a deformation of the Lorentz algebra. While the constant (energy-independent) speed of photon propagation is always compatible with the generalized photon dispersion relations in C-spaces, another important consequence is that these generalized photon dispersion relations allow also for energy-dependent speeds of propagation while still retaining the Lorentz symmetry in ordinary spacetimes, while breaking the extended Lorentz symmetry in C-spaces. This does not occur in DSR nor in other approaches, like the presence of quantum spacetime foam. We conclude with some comments on the quantization program and the key role that quantum Clifford-Hopf algebras might have in the future developments since the latter q-Clifford algebras naturally contain the κ-deformed Poincare algebras which are essential ingredients in the formulation of DSR.
“Weather” Variability of Close-in Extrasolar Giant Planets

Shallow-water numerical simulations show that the atmospheric circulation of the close-in extrasolar giant planet (EGP) HD 209458b is characterized by moving circumpolar vortices and few bands/jets (in contrast to ~10 bands/jets and the absence of polar vortices on cloud-top Jupiter and Saturn). The large spatial scales of moving circulation structures on HD 209458b may generate detectable variability of the planet's atmospheric signatures. In this Letter, we generalize these results to other close-in EGPs, by noting that shallow-water dynamics is essentially specified by the values of the Rossby (Ro) and Burger (Bu) dimensionless numbers. The range of likely values of Ro (~10-2 to 10) and Bu (~1-200) for the atmospheric flow of known close-in EGPs indicates that their circulation should be qualitatively similar to that of HD 209458b. This results mostly from the slow rotation of these tidally synchronized planets.
Propulsion Theory of Flapping Airfoils: Comparison with Computational Fluid Dynamics

It is shown that the time-dependent aerodynamic forces acting on a flapping airfoil in forward flight are functions of both axial and normal reduced frequencies. The axial reduced frequency is based on the chord length, and the normal reduced frequency is based on the plunging amplitude. Furthermore, the time-dependent aerodynamic forces are related to two Fourier coefficients, which are evaluated here from computational results. Correlation equations for these Fourier coefficients are obtained from a large number of grid- and time-step-resolved inviscid computational-fluid-dynamics solutions, conducted over a range of both axial and normal reduced frequencies. The correlation results can be used to predict the thrust, required power, and propulsive efficiency for airfoils in forward flight with sinusoidal pitching and plunging motion. Within the range of parameters typically encountered in the efficient forward flight of birds, results obtained from the correlation equations match the computational-fluid...
SILICA GEL SUPPORTED JONES REAGENT (SJR): A SIMPLE, VERSATILE, AND EFFICIENT REAGENT FOR OXIDATION OF ALCOHOLS IN NON-AQUEOUS MEDIA

Oxidation of alcohols to carbonyl compounds has been carried out by utilization of Jones reagent supported on silica gel (SJR). The SJR procedure has advantages over traditional Jones oxidation procedure. This procedure is safer to carry out and simplified workup by allowing organic media.
Numerical simulation of delta-wing roll

Abstract This paper presents computations of the flowfield around an 80° sweep delta wing undergoing a constant roll-rate manoeuver from 0° to 45°. The governing equations for the problem are the unsteady, three-dimensional Navier-Stokes equations. The equations are solved using the implicit, approximately-factored algorithm of Beam-Warming. Fixed roll angle results are also presented and compared with experimental measurements to demonstrate the ability of the numerical technique to accurately capture the flowfield around a rolled delta wing. The dynamical behavior of the vortex position and strength, as well as its corresponding effect on surface pressure, lift and roll moment are described. A simple, quasi-static explanation of this vortex behavior based on effective angle of attack and sideslip angle is proposed.
Techniques for reducing thermal conduction and natural convection heat losses in annular receiver geometries

An effective device for the collection of solar energy which has received widespread attention is the so called parabolic-cylindrical solar collector. In this design a circular receiver tube, with a suitable selective coating, is enclosed by a concentric glass envelope and situated along the focal line of a parabolic trough reflector. The heat transfer processes which occur in the annular space between the receiver tube and the glass envelope are important in determining the overall heat loss from the receiver tube. In typical high temperature receiver tube designs the rate of energy loss by combined thermal conduction and natural convection is of the same order of magnitude as that due to thermal radiation, and can amount to approximately 6 percent of the total rate at which energy is absorbed by the solar collector. The elimination of conduction and natural convection losses can significantly improve the performance of a large collector field. Several techniques useful for the reduction of energy loss by thermal conduction and natural convection are considered. The receiver configuration chosen for study is typical of those used in the Solar Total Energy System at Sandia Laboratories. The receiver tube has a ''black chrome'' selective coating and is 2.54 more » cm in outside diameter. The inside diameter of the glass envelope is approximately 4.4 cm. Typical operating temperatures of the receiver tube and glass envelope are approximately 300/sup 0/C and 100/sup 0/C, respectively. « less
Polynomial Basins of Infinity

We study the projection \({\pi : \mathcal{M}_d \rightarrow \mathcal{B}_d}\) which sends an affine conjugacy class of polynomial \({f : \mathbb{C} \rightarrow \mathbb{C}}\) to the holomorphic conjugacy class of the restriction of f to its basin of infinity. When \({\mathcal{B}_d}\) is equipped with a dynamically natural Gromov–Hausdorff topology, the map π becomes continuous and a homeomorphism on the shift locus. Our main result is that all fibers of π are connected. Consequently, quasiconformal and topological basin-of-infinity conjugacy classes are also connected. The key ingredient in the proof is an analysis of model surfaces and model maps, branched covers between translation surfaces which model the local behavior of a polynomial.
Kinetics of the reaction of OH radicals with t‐amyl methyl ether revisited

The kinetics of the reaction of OH radicals with t-amyl methyl ether (TAME) have been reinvestigated using both absolute (flash photolysis resonance fluorescence) and relative rate techniques. Relative rate experiments were conducted at 295 K in 99 kPa (740 torr) of synthetic air using ethyl t-butyl ether, cyclohexane, and di-isopropyl ether as reference compounds. Absolute rate experiments were performed over the temperature range 240–400 K at a total pressure of 4.7 kPa (35 torr) of argon. Rate constant determinations from both techniques are in good agreement and can be represented by k1=(6.32 ± 0.72) × 10−12 exp[(−40 ± 70)/T] cm3 molecule−1 s−1. Quoted errors represent 2σ from the least squares analysis and do not include any estimate of systematic errors. We show that results from the previous kinetic study of reaction (1) are in error due to the presence of a reactive impurity. Results are discussed in terms of the atmospheric chemistry of TAME. © 1993 John Wiley & Sons, Inc.
Analyzing motoric and physiological data in describing upper extremity movement in the aged

Cognitive functions, motoric expression, and changes in physiology are often studied separately, with little attention to the relationships or correlations among them. The study presented in this paper implements an integrated approach by combining motion capture (action) and EMG (physiological) parameters as synchronized data streams resulting from the action and associated physiological data. The reported experiments were designed to measure the preparatory movement capabilities of the upper extremities. In particular, measurement of changes in preparatory activity during the aging process is of interest in this context, as the attempt is to develop means to compensate for loss of adaptive capabilities that aging entails. To achieve this goal, it is necessary to quantify preparation phases (timing and intensity). Motion capture and EMG parameters were measured when subjects raised their arms without constraint (condition one) and raised their arms while holding a ball (second condition). Furthermore, on comparing aging and young participants, it was confirmed that with aging the temporal relationships between actual movement and the preceding EMG signal change.
On the lower bound for the Higgs boson mass

Abstract We derive an alternative lower bound on the mass of the Higgs boson of the Standard Model. For one TeV cutoff, the result is numerically the same as obtained in conventional effective potential approach. For high scale cutoff, the lower bound is increased by slightly more than the expected uncertainty in the calculation. We also indicate how two extant effective potential calculations which are in disagreement may be reconciled.
Gd5(SixGe1–x)4: An Extremum Material

The large shear displacements of atomic layers in Gd5(SixGe1–x)4 materials, coupled with the change of crystallographic symmetry and magnetic order, characterizes these transformations as magnetic–martensitic, which are extremely rare. The start and the end of the magnetic–martensitic transitions depends strongly on the direction of change (i.e., increasing or decreasing) of either or both the temperature and magnetic field. These profound bonding, structural, electronic, and magnetic changes, which occur in the Gd5(SixGe1–x)4 system, bring about some extreme changes of the materials' behavior resulting in a rich variety of unusually powerful magneto-responsive properties, such as the giant magnetocaloric effect, colossal magnetostriction, and giant magnetoresistance.
How Accurate Is Poisson-Boltzmann Theory for Monovalent Ions near Highly Charged Interfaces?

Surface sensitive synchrotron X-ray scattering studies were performed to obtain the distribution of monovalent ions next to a highly charged interface. A lipid phosphate (dihexadecyl hydrogen-phosphate) was spread as a monolayer at the air−water interface to control surface charge density. Using anomalous reflectivity off and at the L3 Cs+ resonance, we provide spatial counterion (Cs+) distributions next to the negatively charged interfaces. Five decades in bulk concentrations are investigated, demonstrating that the interfacial distribution is strongly dependent on bulk concentration. We show that this is due to the strong binding constant of hydronium H3O+ to the phosphate group, leading to proton-transfer back to the phosphate group and to a reduced surface charge. The increase of Cs+ concentration modifies the contact value potential, thereby causing proton release. This process effectively modifies surface charge density and enables exploration of ion distributions as a function of effective surface ...
Small-scale structures in three-dimensional magnetohydrodynamic turbulence.

We investigate using direct numerical simulations with grids up to ${1536}^{3}$ points, the rate at which small scales develop in a decaying three-dimensional MHD flow both for deterministic and random initial conditions. Parallel current and vorticity sheets form at the same spatial locations, and further destabilize and fold or roll up after an initial exponential phase. At high Reynolds numbers, a self-similar evolution of the current and vorticity maxima is found, in which they grow as a cubic power of time; the flow then reaches a finite dissipation rate independent of the Reynolds number.
A convexity theorem for the real part of a Borel invariant subvariety

M. Brion proved a convexity result for the moment map image of an irreducible subvariety of a compact integral Kahler manifold preserved by the complexification of the Hamiltonian group action. V. Guillemin and R. Sjamaar generalized this result to irreducible subvarieties preserved only by a Borel subgroup. In another direction, L. O'Shea and R. Sjamaar proved a convexity result for the moment map image of the submanifold fixed by an antisymplectic involution. Analogous to Guillemin and Sjamaar's generalization of Brion's theorem, in this paper we generalize O'Shea and Sjamaar's result, proving a convexity theorem for the moment map image of the involution fixed set of an irreducible subvariety preserved by a Borel subgroup.
Hearing versus Listening: Attention to Speech and Its Role in Language Acquisition in Deaf Infants with Cochlear Implants

The advent of cochlear implantation has provided thousands of deaf infants and children access to speech and the opportunity to learn spoken language. Whether or not deaf infants successfully learn spoken language after implantation may depend in part on the extent to which they listen to speech rather than just hear it. We explore this question by examining the role that attention to speech plays in early language development according to a prominent model of infant speech perception – Jusczyk's WRAPSA model – and by reviewing the kinds of speech input that maintains normal-hearing infants’ attention. We then review recent findings suggesting that cochlear-implanted infants’ attention to speech is reduced compared to normal-hearing infants and that speech input to these infants differs from input to infants with normal hearing. Finally, we discuss possible roles attention to speech may play on deaf children's language acquisition after cochlear implantation in light of these findings and predictions from Jusczyk's WRAPSA model.
Combustion-Generated Turbulence in Practical Combustors

There are many fundamental as well as practical factors that produce combustion-generated turbulence in propulsion systems. For simple flames, turbulent dilatation and viscous dissipation processes suppress turbulence, whereas advection and shear gradient effects generate additional flame turbulence. In practical combustors, four principal factors (combustion zone structure, fluctuating reaction and heat release rates, recirculating and swirling motion, and two-phase combustion) are responsible for combustion-generated turbulence. In this investigation, available experimental data on combustion-ge nerated turbulence in practical combustors are analyzed. This reveals that a moderate to appreciable level of turbulence is produced by the combustion process. Measurements show a dominating influence of small-scale turbulence consistent with mean gradient transport modeling. Axial mean pressure gradient, scalar fluctuations, recirculation zone size, swirl number, and mean mixture fraction variation are found to affect combustion-generated turbulence in a significant way.
The Generalized Weierstrass System for Nonconstant Mean Curvature Surfaces and the Nonlinear Sigma Model

A study of the generalized Weierstrass system which can be used to induce mean curvature surfaces in three-dimensional Euclidean space is presented. A specific transformation is obtained which reduces the initial system to a two-dimensional Euclidean nonlinear sigma model. Some aspects of integrability are discussed, in particular, a connection with a version of the sinh-Gordon equation is established. Finally, some specific solutions are given and a systematic way of calculating multisoliton solutions is presented.
Dynamic vacuum analysis for APS high heat flux beamline front ends using optical ray-tracing simulation methods

The high-power and high-flux x-ray beams produced by third generation synchrotron radiation sources such as the Advanced Photon Source (APS) can cause significantly high gas desorption rates on beamline front-end components if beam missteering occurs. The effect of this gas desorption needs to be understood for dynamic vacuum analysis. To simulate beam missteering conditions, optical ray-tracing methods have been employed. The results of the ray-tracing analysis have been entered into a system-oriented vacuum program to provide dynamic vacuum calculations for determination of pumping requirements for the beamline front-ends. The APS will provide several types of synchrotron radiation sources, for example, undulators, wigglers, and bending magnets. For the purpose of this study, the wiggler source was chosen as a ``worst case`` scenario due to its high photon flux, high beam power, and relatively large beam cross section.
Neuropsychologic deficits in schizophrenia : Relation to social function and effect of antipsychotic drug treatment

Cognitive impairment is present in the majority of schizophrenic patients, even at the onset of psychosis. It is a relatively stable characteristic in most patients, usually with little progression over the course of illness, but sometimes progresses to severe dementia. The results of studies of the effects of typical neuroleptic drugs on cognitive functioning in schizophrenia are conflicting. Clozapine, which has superior antipsychotic effects compared to typical neuroleptic drugs, has been reported to improve executive function, verbal fluency, attention, and recall memory in two of three studies. Cognitive measures predict work function and overall outcome on clozapine as assessed by the Global Assessment Scale and Quality-of-Life Scale in neuroleptic—resistant schizophrenia. Improvement in cognitive function by clozapine may be a major reason for expanding its currently limited utilization.
Lewis Acid Promoted Annulation of p-Quinoneimines by Allylsilanes: A Facile Entry into Benzofused Heterocycles†

Lewis acid promoted addition of allyltriisopropylsilane to p-quinoneimines afforded different benzofused heterocycles in moderate to good yields depending on the conditions employed.
The Effect of Proton Temperature Anisotropy on the Solar Minimum Corona and Wind

A semiempirical, axisymmetric model of the solar minimum corona is developed by solving the equations for conservation of mass and momentum with prescribed anisotropic temperature distributions. In the high-latitude regions, the proton temperature anisotropy is strong and the associated mirror force plays an important role in driving the fast solar wind; the critical point where the outflow velocity equals the parallel sound speed (v = c∥) is reached already at 1.5 R☉ from Sun center. The slow wind arises from a region with open-field lines and weak anisotropy surrounding the equatorial streamer belt. The model parameters were chosen to reproduce the observed latitudinal extent of the equatorial streamer in the corona and at large distance from the Sun. We find that the magnetic cusp of the closed-field streamer core lies at about 1.95 R☉. The transition from fast to slow wind is due to a decrease in temperature anisotropy combined with the nonmonotonic behavior of the nonradial expansion factor in flow tubes that pass near the streamer cusp. In the slow wind, the plasma β is of order unity and the critical point lies at about 5 R☉, well beyond the magnetic cusp. The predicted outflow velocities are consistent with O5+ Doppler dimming measurements from UVCS/SOHO. We also find good agreement with polarized brightness (pB) measurements from LASCO/SOHO and H I Lyα images from UVCS/SOHO.
Supersonic interference flow along the corner of intersecting wedges

Abstract : An experimental investigation of the inviscid supersonic flow field in a corner formed by two intersecting wedges is reported. The study includes measurements of the distribution of the surface pressure and the wave structure of the flow field in the corner region both for a symmetrical corner configuration (e. e., equal wedge angles) in the Mach-number range between 2.5 and 4 and for an asymmetrical model at one Mach number as a function of the incidence angle of one wedge. A clearly identifiable shock structure is discovered that divides the interference field into four zones. The total extent of the disturbance near the surfaces of the model is approximately twice the extent indicated by available small-perturbation analyses. The highest pressure rise occurs in the inner zone near the corner; the magnitude of this rise is related successfully to the second-order linearized theory. The inviscid flow field is shown to involve strong cross-stream pressure and entropy gradients both at the corner proper and away from it, which cannot be disregarded in analyses of the viscous boundary layer. (Author)
Bragg reflection of ocean waves from sandbars

[1] Resonant Bragg reflection of ocean surface waves by a field of natural shore-parallel sandbars was observed in Cape Cod Bay, MA. Waves transmitted through the bars were reflected strongly from the steep shoreline, and the observed cross-shore variations in the onshore- and offshore-directed energy fluxes are consistent with theory for resonant Bragg reflection, including a 20% decay of the incident wave energy flux that is an order of magnitude greater than expected for wave-orbital velocity induced bottom friction. Bragg reflection was observed for a range of incident wave conditions, including storms when sediment transported toward and away from nodes and antinodes caused by the reflecting waves might result in growth and maintenance of the sandbars.