cssi/SciSciGPT-SciSciNet huggingface dataset:
Dynamical Simulations of Magnetically Channeled Line-driven Stellar Winds. I. Isothermal, Nonrotating, Radially Driven Flow

We present numerical magnetohydrodynamic (MHD) simulations of the effect of stellar dipole magnetic fields on line-driven wind outflows from hot, luminous stars. Unlike previous fixed-field analyses, the simulations here take full account of the dynamical competition between field and flow and thus apply to a full range of magnetic field strength and within both closed and open magnetic topologies. A key result is that the overall degree to which the wind is influenced by the field depends largely on a single, dimensionless wind magnetic confinement parameter η* (= BR/v∞), which characterizes the ratio between magnetic field energy density and kinetic energy density of the wind. For weak confinement, η* ≤ 1, the field is fully opened by the wind outflow, but nonetheless, for confinements as small as η* = 1/10 it can have a significant back-influence in enhancing the density and reducing the flow speed near the magnetic equator. For stronger confinement, η* > 1, the magnetic field remains closed over a limited range of latitude and height about the equatorial surface, but eventually is opened into a nearly radial configuration at large radii. Within closed loops, the flow is channeled toward loop tops into shock collisions that are strong enough to produce hard X-rays, with the stagnated material then pulled by gravity back onto the star in quite complex and variable inflow patterns. Within open field flow, the equatorial channeling leads to oblique shocks that are again strong enough to produce X-rays and also lead to a thin, dense, slowly outflowing disk at the magnetic equator. The polar flow is characterized by a faster-than-radial expansion that is more gradual than anticipated in previous one-dimensional flow tube analyses and leads to a much more modest increase in terminal speed (less than 30%), consistent with observational constraints. Overall, the results here provide a dynamical groundwork for interpreting many types of observations—e.g., UV line profile variability, redshifted absorption or emission features, enhanced density-squared emission, and X-ray emission—that might be associated with perturbation of hot-star winds by surface magnetic fields.
Searching for the Higgs boson(s)

Abstract The ability of LEP-200, the Tevatron, the Di-Tevatron, the LHC, and a next linear e+e− collider (NLC) to probe the Higgs sectors of the minimal Standard Model (SM) and the Minimal Supersymmetric Model (MSSM) is reviewed. Emphasis is placed on newly developed detection modes and on predictions for supersymmetric particle Higgs decay channels when the MSSM is constrained using boundary conditions motivated by supergravity/superstring models.
Preparation of azidoaryl- and azidoalkyloxazoles for click chemistry

A series of azidoaryl- and azidoalkyl(diphenyl)oxazole scaffolds were warranted for biofilm inhibition studies. Cyclization of azidoaryl- or azidoalkyl esters of benzoin with ammonium acetate in acetic acid gives 2-azidoaryl- or 2-azidoalkyl-4,5-diphenyloxazoles. The azidoaryl esters are prepared from the corresponding azidocarboxylic acids/acid chlorides while the azidoalkyl esters are prepared from the corresponding haloalkyl esters.
STP: Skills, tactics, and plays for multi-robot control in adversarial environments:

AbstractIn an adversarial multi-robot task, such as playing robot soccer, decisions for team and single-robot behaviour must be made quickly to take advantage of short-term fortuitous events. When no such opportunities exist, the team must execute sequences of coordinated team action that increases the likelihood of future opportunities. A hierarchical architecture, called STP, has been developed to control an autonomous team of robots operating in an adversarial environment. STP consists of skills for executing the low-level actions that make up robot behaviour, tactics for determining what skills to execute, and plays for coordinating synchronized activity among team members. The STP architecture combines each of these components to achieve autonomous team control. Moreover, the STP hierarchy allows for fast team response in adversarial environments while carrying out actions with longer goals. This article presents the STP architecture for controlling an autonomous robot team in a dynamic adversarial t...
Counting edge-Kempe-equivalence classes for 3-edge-colored cubic graphs

Abstract Two n -edge colorings of a graph are edge-Kempe equivalent if one can be obtained from the other by a series of edge-Kempe switches. In this work we show every planar bipartite cubic graph has exactly one edge-Kempe equivalence class, when 3 = χ ′ ( G ) colors are used. In contrast, we also exhibit infinite families of nonplanar bipartite cubic (and thus 3-edge colorable) graphs with a range of numbers of edge-Kempe equivalence classes when using 3 colors. These results address a question raised by Mohar.
Codes for Deletion and Insertion Channels With Segmented Errors

We consider deletion channels and insertion channels under an additional segmentation assumption: the input consists of disjoint segments of b consecutive bits, with at most one error per segment. Under this assumption, we demonstrate simple and computationally efficient deterministic encoding and decoding schemes that achieve a high provable rate even under worst case errors. We also consider more complex schemes that experimentally achieve higher rates under random error.
Some Experimental Results of Two Concepts Designed to Increase Turbine Blade Loading

Turbine blade designs considered for increasing load capacity covering tandem, jet-blade and base plain blade configurations and test results
Numerical optimization design of advanced transonic wing configurations

A computationally efficient and versatile technique for use in the design of advanced transonic wing configurations has been developed. A reliable and fast transonic wing flow-field analysis program, TWING, has been coupled with a modified quasi-Newton method, unconstrained optimization algorithm, QNMDIF, to create a new design tool. Fully three-dimensional wing designs utilizing both specified wing pressure distributions and drag-to-lift ration minimization as design objectives are demonstrated. Because of the high computational efficiency of each of the components of the design code, in particular the vectorization of TWING and the high speed of the Cray X-MP vector computer, the computer time required for a typical wing design is reduced by approximately an order of magnitude over previous methods. In the results presented here, this computed wave drag has been used as the quantity to be optimized (minimized) with great success, yielding wing designs with nearly shock-free (zero wave drag) pressure distributions and very reasonable wing section shapes.
Has Internet Access Taxation Affected Internet Use

Most arguments in favor of the Internet Tax Freedom Act (ITFA) assume that taxing Internet access would reduce Internet use. The authors investigate this possibility empirically, making use of panel data covering all U.S. states for the years 1998, 2000, and 2001. Statutory variation in the taxation of Internet access occurs because 10 states were permitted to continue their existing Internet access taxes as of the initial passage of the ITFA in 1998. None of the econometric analyses provides any evidence that Internet access taxes have had an effect on Internet access rates.
Simulations of XUV Disks with a Star Formation Density Threshold

The outer regions of disk galaxies show a drop-off in optical and Hα emission, suggesting a star formation threshold radius, assumed to owe to a critical surface density below which star formation does not take place. Signs of filamentary star formation beyond this threshold radius have been observed in individual galaxies in the Hα, and recent GALEX surveys have discovered that 30% of disk galaxies show UV emission out to 2-3 times the optical radius of the galaxy. We run smooth particle hydrodynamics simulations of disk galaxies with constant-density extended gas disks to test whether overdensities owing to spiral structure in the outer disk can reproduce the observed star formation. We indeed find that spiral density waves from the inner disk propagate into the outer gas disk and raise local gas regions above the star formation density threshold, yielding features similar to those observed. Because the amount of star formation is low, we expect to see little optical emission in outer disks, as observed. Our results indicate that XUV disks can be simulated simply by adding an extended gas disk with a surface density near the threshold density to an isolated galaxy and evolving it with fiducial star formation parameters.
The Natural Right to Intervene The Evolution of the Concepts of Justification and Excuse for Both State and Individual

One can draw a parallel between the restrictions states place on their soldiers’ use of force and the manner in which the United Nations restricts a state's use of force under Article 2(4) of the Charter. This parallel is useful in showing how both the ‘sovereigns’ limitations on the use of force are, in turn, limited by rule of law principles of natural justice that go beyond self-defence and into the realm of the defence of duress, necessity and coercion, giving rise to a justification or an excuse. The United Nations' absolute restriction on the use of force, therefore, should be limited by more than just the self-defence provision of Article 51 and would potentially allow unilateral humanitarian intervention in extreme circumstances. The US military courts, in dicta, have implied a balancing test in which the order to not use force can be trumped by the imminence and severity of the threat to the innocent; therefore, continued obedience would no longer be mandated. This conclusion, as highlighted by George Fletcher and Jens Ohlin in their book, Defending Humanity, is rooted in the evolution of both law and philosophy.
Evolution of resonant wave triads in three-dimensional boundary layers

An analysis is presented that examines the modulation of different instability modes that satisfy the triad resonance conditions in time and space in a three‐dimensional, boundary‐layer flow. Detuning parameters are used for the wavenumbers and frequencies. The nonparallelism of the mean flow is taken into account in the analysis. At the leading‐edge region of an infinite swept wing, different resonant triads comprised of traveling cross‐flow, stationary cross‐flow, vertical vorticity, and Tollmien–Schlichting modes are investigated. The spatial evolution of the resonating triad components are studied.
Search for relativistic curvature effects in gamma-ray burst pulses

We analyze the time profiles of individual gamma-ray burst (GRB) pulses that are longer than 2 s by modeling them with analytical functions that are based on physical first principles and well-established empirical descriptions of GRB spectral evolution. These analytical profiles are independent of the emission mechanism and can be used to model both the rise and decay profiles, allowing for the study of the entire pulse light curve. Using this method, we have studied a sample of 77 individual GRB pulses, allowing us to examine the fluence, pulse width, asymmetry, and rise and decay power-law distributions. We find that the rise phase is best modeled with a power law of average index r = 1.48 ± 0.07 and that the average decay phase has an index of d = 2.44 ± 0.12. We also find that the ratio between the rise and decay times (the pulse asymmetry) exhibited by the GRB pulse shape has an average value of 0.47, which varies little from pulse to pulse and is independent of pulse duration or intensity. Although this asymmetry is largely uncorrelated to other pulse properties, a statistically significant trend is observed between the pulse asymmetry and the decay power-law index, possibly hinting at the underlying physics. We compare these parameters with those predicted to occur if individual pulse shapes are created purely by relativistic curvature effects in the context of the fireball model, a process that makes specific predictions about the shape of GRB pulses. The decay index distribution obtained from our sample shows that the average GRB pulse fades faster than the value predicted by curvature effects, with only 39% of our sample being consistent with the curvature model. We discuss several refinements of the relativistic curvature scenario that could naturally account for these observed deviations, such as symmetry breaking and varying relative timescales within individual pulses.
Do external sources generate greater investor awareness that can affect a firm's value and cost of capital?

Purpose – The purpose of this paper is to examine whether focused attention on a firm by an external organization, group, or influential analyst generates greater investor awareness that can affect a firm's value and cost of capital. This study is motivated by contemporary research that provides support for the hypothesis that investors have limited attention. Prior studies have focused on how investors' limited attention has influenced their analysis of firm‐specific financial data. The studies have shown that investors may have limited attention and hence pay more attention to the more salient financial statement items. This paper extends this stream of research by empirically testing to determine if external sources attract investors' limited attention to a firm.Design/methodology/approach – The paper examines the published monthly Center for Financial Research and Analysis (CFRA) research reports from 1998 through 2004 that identify firms experiencing operational problems and/or using unusual or aggre...
Twistor space structure of one-loop amplitudes in gauge theory

We analyze the twistor space structure of certain one-loop amplitudes in gauge theory. For some amplitudes, we find decompositions that make the twistor structure manifest; for others, we explore the twistor space structure by finding differential equations that the amplitudes obey.
Restricted volumes and base loci of linear series

We introduce and study the restricted volume of a divisor along a subvariety. Our main result is a description of the irreducible components of the augmented base locus by the vanishing of the restricted volume.
Hypersonic Buckshot: Astrophysical Jets as Heterogeneous Collimated Plasmoids

Herbig-Haro jets are commonly thought of as homogeneous beams of plasma traveling at hypersonic velocities. Structure within jet beams is often attributed to periodic or 'pulsed' variations of conditions at the jet source. Simulations based on this scenario result in knots extending across the jet diameter. Observations and recent high energy density laboratory experiments shed new light on structures below this scale and indicate they may be important for understanding the fundamentals of jet dynamics. In this paper, we offer an alternative to 'pulsed' models of protostellar jets. Using direct numerical simulations we explore the possibility that jets are chains of subradial clumps propagating through a moving interclump medium. Our models explore an idealization of this scenario by injecting small (r {rho}{sub jet}) spheres embedded in an otherwise smooth interclump jet flow. The spheres are initialized with velocities differing from the jet velocity by {approx}15%. We find that the consequences of shifting from homogeneous to heterogeneous flows are significant as clumps interact with each other and with the interclump medium in a variety of ways. Structures which mimic what is expected from pulsed-jet models can form, as can be previously unseen, 'subradial' behaviors including backwardmore » facing bow shocks and off-axis working surfaces. While these small-scale structures have not been seen before in simulation studies, they are found in high-resolution jet observations. We discuss implications of our simulations for the interpretation of protostellar jets with regard to characterization of knots by a 'lifetime' or 'velocity history' approach as well as linking observed structures with central engines which produce the jets.« less
On the Production and Survival of Carbon Fuel for Superbursts on Accreting Neutron Stars: Implications for Mass Donor Evolution

We have investigated the physical conditions under which accreting neutron stars in low-mass X-ray binaries can both produce and preserve sufficient quantities of carbon fuel to trigger superbursts. Our theoretical models span the plausible ranges of neutron star thermal conductivities, core neutrino emission mechanisms, and areal radii, as well as the CNO abundances in the accreted material. We find that neutron stars that accrete hydrogen-rich material with CNO mass fractions ZCNO ZCNO,☉ will not exhibit superbursts under any circumstances. Neutron stars that accrete material with CNO mass fractions 4ZCNO,☉ will exhibit superbursts at accretion rates in the observed range. On this basis, we suggest that the mass donors of superburst systems must have enhanced CNO abundances. The accreted CNO acts only as a catalyst for hydrogen burning via the hot CNO cycle, and therefore it is the sum of the three elements' mass fractions, not the individual mass fractions themselves, that is important. Systems that exhibit superbursts are observed to differ from those that do not exhibit superbursts in the nature of their helium-triggered type I X-ray bursts: the bursts have shorter durations and much greater α-values. Increasing the CNO abundance of the accreted material in our models reproduces both of these observations, thus once again suggesting enhanced CNO abundances in the mass donors. Many compact binary systems have been observed in which the abundances of the accreting material are distinctly nonsolar. Although abundance analyses of the systems that exhibit superbursts currently do not exist, Bowen fluorescence blend profiles of 4U 1636-536 and Ser X-1 suggest that the mass donor stars may indeed have nonsolar CNO metallicities. More detailed abundance analyses of the accreting matter in systems that exhibit superbursts are needed to verify our assertion that the matter is rich in CNO elements.
Efficient Nazarov cyclizations of 2-alkoxy-1,4-pentadien-3-ones.

Expeditious and high-yielding Nazarov cyclizations of 2-alkoxy-1,4-pentadien-3-ones are described. An example of a catalytic asymmetric Nazarov cyclization is presented.
Principal-component analysis of RR Lyrae light curves

In this paper, we analyse the structure of RRab starlight curves using principal-component analysis. We find this to be a very efficient way of describing many aspects of RRab light-curve structure: in many cases, a principal-component fit with nine parameters can describe a RRab light curve including bumps, whereas a 17-parameter Fourier fit is needed. Consequently, we show statistically why the amplitude is also a good summary of the structure of these RR Lyrae light curves. We also use our analysis to derive an empirical relation relating absolute magnitude to light-curve structure. In comparing this formula with those derived from exactly the same data set but using Fourier parameters, we find that the principal-component analysis approach has distinct advantages. These advantages are, firstly, that the errors on the coefficients multiplying the fitted parameters in such formulae are much smaller, and secondly, that the correlation between the principal components is significantly smaller than the correlation between Fourier amplitudes. These two factors lead to reduced formal errors, in some cases estimated to be a factor of 2, on the eventual fitted value of the absolute magnitude. This technique will prove very useful in the analysis of data from existing and new large-scale survey projects concerning variable stars.
Fronts in Reactive Convection: Bounds, Stability, and Instability

This paper examines a simplified active combustion model in which the reaction influences the flow. We consider front propagation in a reactive Boussinesq system in an infinite vertical strip. Nonlinear stability of planar fronts is established for narrow domains when the Rayleigh number is not too large. Planar fronts are shown to be linearly unstable with respect to long-wavelength perturbations if the Rayleigh number is sufficiently large. We also prove uniform bounds on the bulk burning rate and the Nusselt number in the KPP reaction case. © 2003 Wiley Periodicals, Inc.
Strong equivalence made easy: nested expressions and weight constraints

Logic programs $P$ and $Q$ are strongly equivalent if, given any program $R$, programs $P \cup R$ and $Q \cup R$ are equivalent (that is, have the same answer sets). Strong equivalence is convenient for the study of equivalent transformations of logic programs: one can prove that a local change is correct without considering the whole program. Lifschitz, Pearce and Valverde showed that Heyting's logic of here-and-there can be used to characterize strong equivalence for logic programs with nested expressions (which subsume the better-known extended disjunctive programs). This note considers a simpler, more direct characterization of strong equivalence for such programs, and shows that it can also be applied without modification to the weight constraint programs of Niemela and Simons. Thus, this characterization of strong equivalence is convenient for the study of equivalent transformations of logic programs written in the input languages of answer set programming systems dlv and SMODELS. The note concludes with a brief discussion of results that can be used to automate reasoning about strong equivalence, including a novel encoding that reduces the problem of deciding the strong equivalence of a pair of weight constraint programs to that of deciding the inconsistency of a weight constraint program.
Contraction Analysis of Nonlinear Distributed Systems

Contraction theory is a comparatively recent dynamic analysis and non-linear control system design tool based on an exact differential analysis of convergence. This paper extends contraction theory to local and global stability analysis of important classes of non-linear distributed dynamics, such as convection-diffusion-reaction processes, Lagrangian and Hamilton–Jacobi dynamics, and optimal controllers and observers. By contrast with stability proofs based on energy dissipation, stability and convergence can be determined for energy-based systems excited by time-varying inputs. The Hamilton–Jacobi–Bellman controller and a similar optimal non-linear observer design are studied based on explicitly computable conditions on the convexity of the cost function. These stability conditions extend the well-known conditions on controllability and observability Grammians for linear time-varying systems, without requiring the unknown transition matrix of the underlying differential dynamics.
Using assertions to improve language translators

New enhancement techniques for language translators based on work in program verification are developed. Assertions are normally added to a program in order to verify the program is correct. Once verified, the assertions are usually ignored. This paper shows that verified assertions often contain information which can improve certain object code characteristics when the program is translated: execution time, storage requirements, and program style. The latter quality is especially important if the object code is itself in a "high-level" language. The techniques developed fall into three categories: early binding, using complementary constructs, and noting restricted cases.
Toward a bias corrected currency equivalent index

Measuring the economic stock of money, defined to be the present value of current and future monetary service flows, is a difficult asset pricing problem, because most monetary assets yield interest. Thus, an interest yielding monetary asset is a joint product: a durable good providing a monetary service flow and a financial asset yielding a return. The currency equilivant index provides an elegant solution, but it does so by making strong assumptions about expectations of future monetary service flows. These assumptions cause the currency equivalent index to exhibit significant downward bias. In this paper, we propose an extension to the currency equivalent index that will correct for a significant amount of this bias.
Where Is My Bus? Impact of mobile real-time information on the perceived and actual wait time of transit riders

Abstract In order to attract more choice riders, transit service must not only have a high level of service in terms of frequency and travel time but also must be reliable. Although transit agencies continuously work to improve on-time performance, such efforts often come at a substantial cost. One inexpensive way to combat the perception of unreliability from the user perspective is real-time transit information. The OneBusAway transit traveler information system provides real-time next bus countdown information for riders of King County Metro via website, telephone, text-messaging, and smart phone applications. Although previous studies have looked at traveler response to real-time information, few have addressed real-time information via devices other than public display signs. For this study, researchers observed riders arriving at Seattle-area bus stops to measure their wait time while asking a series of questions, including how long they perceived that they had waited. The study found that for riders without real-time information, perceived wait time is greater than measured wait time. However, riders using real-time information do not perceive their wait time to be longer than their measured wait time. This is substantiated by the typical wait times that riders report. Real-time information users say that their average wait time is 7.5 min versus 9.9 min for those using traditional arrival information, a difference of about 30%. A model to predict the perceived wait time of bus riders was developed, with significant variables that include the measured wait time, an indicator variable for real-time information, an indicator variable for PM peak period, the bus frequency in buses per hour, and a self-reported typical aggravation level. The addition of real-time information decreases the perceived wait time by 0.7 min (about 13%). A critical finding of the study is that mobile real-time information reduces not only the perceived wait time, but also the actual wait time experienced by customers. Real-time information users in the study wait almost 2 min less than those arriving using traditional schedule information. Mobile real-time information has the ability to improve the experience of transit riders by making the information available to them before they reach the stop.
Volatile element chemistry during metamorphism of ordinary chondritic material and some of its implications for the composition of asteroids

We used chemical equilibrium calculations to model thermal metamorphism of ordinary chondritic material as a function of temperature, pressure, and trace element abundance and use our results to discuss volatile mobilization during thermal metamorphism of ordinary chondrite parent bodies. We compiled trace element abundances in H-, L-, and LL-chondrites for the elements Ag, As, Au, Bi, Br, Cd, Cs, Cu, Ga, Ge, I, In, Pb, Rb, Sb, Se, Sn, Te, Tl, and Zn, and identified abundance trends as a function of petrographic type within each class. We calculated volatility sequences for the trace elements in ordinary chondritic material, which differ significantly from the solar nebula volatility sequence. Our results are consistent with open-system thermal metamorphism. Abundance patterns of Ag and Zn remain difficult to explain.
Decreased response to inhaled steroids in overweight and obese asthmatic children.

Background The mechanisms and consequences of the observed association between obesity and childhood asthma are unclear. Objectives We sought to determine the effect of obesity on treatment responses to inhaled corticosteroids in asthmatic children. Methods We performed a post hoc analysis to evaluate the interaction between body mass index (BMI) and treatment with inhaled budesonide on lung function in the Childhood Asthma Management Program trial. Participants were then stratified into overweight/obese and nonoverweight groups, and their response to inhaled budesonide was analyzed longitudinally over the 4 years of the trial. Results There was a significant interaction between BMI and budesonide for prebronchodilator FEV 1 /forced vital capacity (FVC) ratio ( P = .0007) and bronchodilator response (BDR; P = .049) and a nonsignificant trend for an interaction between BMI and budesonide on prebronchodilator FEV 1 ( P = .15). Nonoverweight children showed significant improvement with inhaled budesonide in lung function (FEV 1 , FEV 1 /FVC ratio, and BDR) during the early (years 1-2) and late (years 3-4) stages of the trial. Overweight/obese children had improved FEV 1 and BDR during the early but not the late stage of the trial and showed no improvement in FEV 1 /FVC ratio. When comparing time points at which both groups showed a significant response, the degree of improvement among nonoverweight children was significantly greater than in overweight/obese children at most visits. Nonoverweight children had a 44% reduction in the risk of emergency department visits or hospitalizations throughout the trial ( P = .001); there was no reduction in risk among overweight/obese children ( P = .97). Conclusions Compared with children of normal weight, overweight/obese children in the Childhood Asthma Management Program showed a decreased response to inhaled budesonide on measures of lung function and emergency department visits/hospitalizations for asthma.
Stereospecific Cross-Coupling of Secondary Organotrifluoroborates: Potassium 1-(Benzyloxy)alkyltrifluoroborates

Potassium 1-(alkoxy/acyloxy)alkyltrifluoroborates have been synthesized through a copper-catalyzed diboration of aldehydes and subsequent conversion of the resulting potassium 1-(hydroxy)alkyltrifluoroborates. The palladium-catalyzed Suzuki–Miyaura reaction employing the potassium 1-(benzyloxy)alkyltrifluoroborates with aryl and heteroaryl chlorides provides access to protected secondary alcohols in high yields. The β-hydride elimination pathway is avoided through use of the benzyl protecting group, which is proposed to stabilize the diorganopalladium intermediate by coordination of the arene to the metal center. This cross-coupling is stereospecific with complete retention of stereochemistry.
Molecular Recognition of DNA by Hoechst Benzimidazoles: Exploring Beyond the Pyrrole-Imidazole-Hydroxypyrrole Polyamide-Pairing Code

A series of three-ring analogs of the minor-groove-binding molecule Hoechst 33258 (1), consisting of benzimidazole (B), imidazopyridine (P), and hydroxybenzimidazole (H) monomers, have been synthesized in order to investigate both their sequence specificity and binding modes. MPE⋅FeII Footprinting has revealed the preference of both PBB and BBB ligands for 5′-WGWWW-3′ and 5′-WCWWW-3′ tracts, as well as A⋅T-rich sequences. Affinity-cleavage titrations show no evidence for a 2 : 1 binding mode of these Hoechst analogs. Importantly, all derivatives are oriented in one direction at each of their binding sites. The implications of these results for the design of minor-groove-binding small molecules is discussed.
Pulmonary complications of HIV infection.

Abstract: The AIDS epidemic has had a devastating global impact in the last two decades; although prevalence rates are low in Asia and the Pacific, their enormous population is associated with an estimated 1 million people infected with HIV in 2006 alone. Survival from what had been a uniformly fatal illness has improved markedly with combination antiretroviral therapy and restoration of the immune system, but these treatments are expensive and difficult to distribute to the millions who need them around the world. In addition, millions more do not know they are infected with HIV until they develop an opportunistic infection. The lungs are the most frequent sites of these infections, and in different geographic regions, tuberculosis, bacterial pneumonia and Pneumocystis jiroveci are the dominant pathogens. The incidences of lung cancer and HIV-associated pulmonary arterial hypertension are also increasing in patients with HIV infection, and with the use of antiretrovirals, inflammatory disorders associated with immune restoration are being recognized.
Modeling the timing of business firm exits

The previous theoretical studies of the timing of business exits have employed two different approaches. They have either developed sequential decision-making models or models based on gambler's ruin. The purpose of this paper is to evaluate both approaches. For this task some simple models of the exit process are developed and it is shown that both types of models are capable of generating the observed patterns of firm mortality. The reasonableness of the assumptions and the importance of key variables in the two models are tested using a case study of restaurant exits. We find that the sequential decision-making model would have to be rather complex to serve as a realistic descriptive model of the exit process. Gambler's ruin models, on the other hand, provide a realistic descriptive model not only of the environment in which a large portion of this industry operates, but of the decision process as well. Models based on gambler's ruin may, therefore, provide a potentially useful approach for modeling exit process in other industries dominated by small firms.
Mariner 9: An instrument of dynamical science☆

We review and evaluate the contributions of Mariner 9 in improving our knowledge of the dynamical characteristics of Mars and its two satellites, Phobos and Deimos. Primary results include the discovery of the large gravitational and topographical bulge in the Tharsis region, the development of a detailed gravity model representable as coefficients in a spherical harmonic expansion, the development of a topographic model exhibiting a three kilometer displacement of the center of figure from the center of mass, and the determination of the size, shape and motion of Phobos and Deimos.
A practical equation of state

To use the Peng-Robinson equation of state (PREOS) to predict the phase and volumetric behavior of hydrocarbon mixtures, one needs to know the critical pressure, p{sub c}, critical temperature, T{sub c}, and acentric factor, {omega}, for each component present in the mixture. for pure compounds, the required properties are well-defined, but nearly all naturally occurring gas and crude oil fluids contain some heavy fractions that are not well-defined and are not mixtures of discretely identified components. These heavy fractions often are lumped and called the plus fraction (e.g., C{sub 7+} fraction). Adequately characterizing these undefined plus fractions in terms of their critical properties and acentric factors has long been a problem. Changing the characterization of the plus fraction can have a significant effect on the volumetric and phase behavior of a mixture predicted by the PREOS. This limitation of the PREOS results from an improper procedure of determining coefficients a, b, and {alpha} for the plus fraction and for hydrocarbon components with critical temperatures less than the system temperature (i.e., methane and nitrogen). This paper presents a practical approach to calculating the parameters of the PREOS for the undefined fractions to improve the predictive capability of the equation. use ofmore » the modified equation is illustrated by matching laboratory data on several crude oil and gas-condensate systems.« less
The random-field potts model in three dimensions

Abstract We perform a 1/ q expansion for the q -state Potts model in a random field. The expansion parameter is z = 1/q 1 3 in three dimensions and we calculate to ¢O( z 12 ) using the Pade method for resumation. A phase diagram is constructed and a transition into an ordered phase is found. For q ⩾ 3 the transition is of first order and for q = 2 (Ising model) we find the location of the tricritical point.
Lower Bounds on Nodal Sets of Eigenfunctions via the Heat Flow

We study the size of nodal sets of Laplacian eigenfunctions on compact Riemannian manifolds without boundary and recover the currently optimal lower bound by comparing the heat flow of the eigenfunction with that of an artificially constructed diffusion process. The same method should apply to a number of other questions; we use it to prove a sharp result saying that a nodal domain cannot be entirely contained in a small neighborhood of a “reasonably flat” surface and recover an older result of Cheng. The arising concepts can be expected to have many more connections to classical theory and we pose some conjectures in that direction.
Synthesis, Structure, and Physical Properties of a Novel Quaternary Niobium Telluride, Nb2FeCu0.35Te4

Nb 2 FeCu 0.35 Te 4 , the first solid-state quaternary niobium telluride, was prepared via chemical vapor transport reactions. The structure of this compound was determined by single-crystal X-ray diffraction methods. It crystallizes in the orthorhombic system, space group Pmmn (No. 59). The unit cell dimensions are a=12.576(1) A, b=3.8395(6) A, c=7.3012(9) A, Z=2, and V=352.54(8) A 3 . Structural refinement with 433 observed reflections (I>3σ(I)) and 40 variable parameters results in R=4.0% and R w =4.8%. Nb 2 FeCu 0.35 Te 4 represents a novel three-dimensional structure type with interesting structural features and one-dimensional extended metal-metal bonds
Synthetic approaches for the preparation of cyclic polymers

Despite decades of studies devoted to the unique physical properties and potential applications of cyclic polymer topologies, their exploration has remained limited because of synthetic inefficiencies and acyclic impurities. Many recently developed synthetic techniques offer efficient routes to well-defined cyclic macromolecules to answer this need. This tutorial review aims to provide a concise overview of the most significant synthetic contributions in this field, and highlight the relative advantages and disadvantages of each approach.
Global biodiversity and the ancient carbon cycle

Abstract Paleontological data for the diversity of marine animals and land plants are shown to correlate significantly with a concurrent measure of stable carbon isotope fractionation for approximately the last 400 million years. The correlations can be deduced from the assumption that increasing plant diversity led to increasing chemical weathering of rocks and therefore an increasing flux of carbon from the atmosphere to rocks, and nutrients from the continents to the oceans. The CO2 concentration dependence of photosynthetic carbon isotope fractionation then indicates that the diversification of land plants led to decreasing CO2 levels, while the diversification of marine animals derived from increasing nutrient availability. Under the explicit assumption that global biodiversity grows with global biomass, the conservation of carbon shows that the long-term fluctuations of CO2 levels were dominated by complementary changes in the biological and fluid reservoirs of carbon, while the much larger geological reservoir remained relatively constant in size. As a consequence, the paleontological record of biodiversity provides an indirect estimate of the fluctuations of ancient CO2 levels.
Quantum moduli spaces of linear and ring mooses

Abstract Quantum moduli spaces of four-dimensional SU (2) r linear and ring moose theories with N =1 supersymmetry and link chiral superfields in the fundamental representation are produced starting from simple pure gauge theories of disconnected nodes.
Extremal of Log Sobolev inequality and W entropy on noncompact manifolds

Abstract Let M be a complete, connected noncompact manifold with bounded geometry. Under a condition near infinity, we prove that the Log Sobolev functional (1.1) has an extremal function decaying exponentially near infinity. We also prove that an extremal function may not exist if the condition is violated. This result has the following consequences. 1. It seems to give the first example of connected, complete manifolds with bounded geometry where a standard Log Sobolev inequality does not have an extremal. 2. It gives a negative answer to the open question on the existence of extremal of Perelmanʼs W entropy in the noncompact case, which was stipulated by Perelman (2002) [22, p. 9, 3.2 Remark] . 3. It helps to prove, in some cases, that noncompact shrinking breathers of Ricci flow are gradient shrinking solitons.
Hydrogen in the seaward advancement of industrial societies

Abstract Since the initial impetus of Derek Gregory's landmark analysis of the Hydrogen Economy in 1972, most concepts for producing hydrogen offshore have assumed that the entire product utilization will be onshore. Although delivery to shore is undoubtedly one option, there is another, which is use at sea at or near the site of hydrogen generation. While many of us strive toward the development of hydrogen as tomorrow's fuel, another evolutionary bud is sprouting: our industry is beginning to move seaward. At the same time most signs point to a realization that we are on the threshold of a new social order; a society that is growth-limited by finite energy resources and one that may have to modify its techno-demographic patterns. Existing onshore energy infrastructures must convert to hydrogen at considerable expense and the conversion must be incremental and non-disruptive—no mean challenge. Offshore urban/industrial complexes, on the other hand, could be based upon hydrogen from the beginning. They could thus serve as test and demonstration beds for the eventual adoption of hydrogen as the storable, transportable and ecologically sound fuel base of highly efficient urban/industrial complexes everywhere. This paper explores this option and offers glimpses of future possibilities.
A renormalization group for dynamical triangulations in arbitrary dimensions

Abstract A block spin renormalization group approach is proposed for the dynamical triangulation formulation of quantum gravity in arbitrary dimensions. Renormalization group flow diagrams are presented for the three-dimensional and four-dimensional theories near their respective transitions.
Spin-dependent Cyclotron Decay Rates in Strong Magnetic Fields

Cyclotron decay and absorption rates have been well studied in the literature, focusing primarily on spectral, angular, and polarization dependence. Astrophysical applications usually do not require retention of information on the electron spin state, and these are normally averaged in obtaining the requisite rates. In magnetic fields, higher order quantum processes such as Compton scattering become resonant at the cyclotron frequency and its harmonics, with the resonances being formally divergent. Such divergences are usually eliminated by accounting for the finite lifetimes of excited Landau states. This practice requires the use of spin-dependent cyclotron rates in order to obtain accurate determinations of process rates very near cyclotronic resonances, the phase-space domain most relevant for certain applications to pulsar models. This paper develops previous results in the literature to obtain compact analytic expressions for cyclotron decay rates/widths in terms of a series of Legendre functions of the second kind; these expressions can be used expediently in astrophysical models. The rates are derived using two popular eigenstate formalisms, namely, that due to Sokolov & Ternov and that due to Johnson & Lippmann. These constitute two sets of eigenfunctions of the Dirac equation that diagonalize different operators and accordingly yield different spin-dependent cyclotron rates. This paper illustrates the attractive Lorentz transformation characteristics of the Sokolov & Ternov formulation, which is another reason why it is preferable when electron spin information must be explicitly retained.
Comparative molecular field analysis (CoMFA) of a series of symmetrical bis-benzamide cyclic urea derivatives as HIV-1 protease inhibitors.

A 3D-QSAR study using CoMFA methodology was conducted on a series of 29 symmetrical bis-benzamide cyclic urea derivatives having anti-HIV-1-protease activities. Active site minimization of the ligands was used to exclude conformations which are not sterically accessible within the active site. A significant cross-validated correlation coefficient q2 (0.724) was obtained indicating the predictive potential of the model for untested compounds of this class. A significant non-cross-validated correlation coefficient (r2) of 0.971 with a low standard error estimate (S) of 0.119 was obtained indicating that the model reliably predicted the anti-protease activities of poorly to highly active compounds. The model was used to predict the anti-protease activities of eight test-set compounds, and the predicted values were in good agreement with the experimental values. The CoMFA coefficient contour plots identified several key features which explain the wide range of activities. The already reported 2D-QSAR along wi...
Parallel implementation of the PHOENIX generalized stellar atmosphere program. II. Wavelength parallelization

We describe an important addition to the parallel implementation of our generalized nonlocal thermodynamic equilibrium (NLTE) stellar atmosphere and radiative transfer computer program PHOENIX. In a previous paper in this series we described data and task parallel algorithms we have developed for radiative transfer, spectral line opacity, and NLTE opacity and rate calculations. These algorithms divided the work spatially or by spectral lines, that is, distributing the radial zones, individual spectral lines, or characteristic rays among different processors and employ, in addition, task parallelism for logically independent functions (such as atomic and molecular line opacities). For finite, monotonic velocity fields, the radiative transfer equation is an initial value problem in wavelength, and hence each wavelength point depends upon the previous one. However, for sophisticated NLTE models of both static and moving atmospheres needed to accurately describe, e.g., novae and supernovae, the number of wavelength points is very large (200,000-300,000) and hence parallelization over wavelength can lead both to considerable speedup in calculation time and the ability to make use of the aggregate memory available on massively parallel supercomputers. Here, we describe an implementation of a pipelined design for the wavelength parallelization of PHOENIX, where the necessary data from the processor working on a previous wavelength point is sent to the processor working on the succeeding wavelength point as soon as it is known. Our implementation uses a MIMD design based on a relatively small number of standard message passing interface (MPI) library calls and is fully portable between serial and parallel computers.
Electric Impedance of Marine Egg Membranes

ALTERNATING current impedance measurements were made during the past summer on unfertilized and fertilized Arbacia punctulata eggs to determine whether or not an interpretation which has been given1,2 for the low-frequency increase of capacity on fertilization is correct. The earlier data on Hipponoe3 (Tripneustes) esculentus and Arbacia1 egg suspensions showed the presence of two capacity elements, and it was suggested that the plasma membrane capacities of about 0·8 µf./cm.2 remained unchanged on fertilization and that the fertilization membranes appeared with capacities of about 2 and 3µf./cm.2 respectively. The capacity element of the fertilized egg suspensions which was attributed to the plasma membrane has been much less pronounced in the recent measurements on both suspensions4 and single eggs5, and it has also been found, for both unfertilized and fertilized eggs, that the relatively non-conducting membrane lies either at or very close to the plasma membrane. Thus the increase in capacity on fertilization is probably due entirely to a change in the plasma membrane. It is possible that the second capacity element shown by the older measurements was due to unfertilized eggs in the fertilized suspensions.