cssi/SciSciGPT-SciSciNet huggingface dataset:
Multivariate lag-windows and group representations

Symmetries of the auto-cumulant function (a generalization of the auto-covariance function) of a kth-order stationary time series are derived through a connection with the symmetric group of degree k. Using the theory of group representations, symmetries of the auto-cumulant function are demystified and lag-window functions are symmetrized to satisfy these symmetries. A generalized Gabr-Rao optimal kernel is also derived through the developed theory.
Sunrunner: the engineering report

Abstract In November 1987, the first World Solar Challenge took place, a 3000 km (1860 miles) transcontinental solar powered vehicle race from Darwin to Adelaide across the Australian Outback. The race, held every three years, featured entries from various countries, including Switzerland, Japan, Australia, and the United States. The winning car, General Motors' Sunraycer, finished 970 km (600 miles) in front of its nearest competitor. Based on this outstanding performance, General Motors decided not to return to Australia in 1990, but to instead sponsor a solar car race of its own and send the top three finishers to the international competition. GM Sunrayce USA featured 32 cars from top engineering colleges throughout North America and took place from Florida to Michigan, covering 2660 km (1650 miles) during July 1990.
Guidance for test selection based on the cost of errors

A continual problem in the area of software testing is deciding if and where in a program additional testing should be done. Recent work by Cheung has indicated that the relative reliability of the individual nodes in a software flow graph, or modules in a software structure, can be used to guide the testing. This paper attempts to aid this process by suggesting a method for assigning a cost factor to the individual nodes in the software flow graph. This cost can be used to guide selection of additional tests.
Land use in a long narrow city

Abstract Most theoretical models of urban land use concentrate on residential density. Here we take up another important use of urban land, for roads, or, more generally, for transportation. We analyze, in the simplest possible setting, the optimal allocation of a given urban land area between the generation of traffic and the carrying of traffic. We show that, except in a limiting case, the proportion of land allocated to transportation is a decreasing, concave function of distance from the center of the city. We then analyze the competitive rent profile generated by any land-use pattern, on the assumptions that there are no congestion tolls for road use, and that commodities are sold at uniform delivered price with sellers absorbing transport cost. On these assumptions, we show that the market value of land may be a very poor guide to land-use decisions, and would lead to overallocation of land to transportation, especially near the center. Our model is one-dimensional because that is the best we can do now. We hope it will lead on to more realistic treatments of the problem.
Stochastic trajectory models for turbulent diffusion: Monte Carlo process versus Markov chains

Abstract Turbulent diffusion of passive scalars and particles is often simulated with either a Monte Carlo process or a Markov chain. Knowledge of the velocity correlation generated by either of these stochastic trajectory models is essential to their application. The velocity correlation for Monte Carlo process and Markov chain was studied analytically and numerically. A general relationship was developed between the Lagrangian velocity correlation and the probability density function for the time steps in a Monte Carlo process. The velocity correlation was found to be independent of the fluid velocity probability density function, but to be related to the time-step probability density function. For a Monte Carlo process with a constant time step, the velocity correlation is a triangle function; and the integral time scale is equal to one-half of the time-step length. When the time step was chosen randomly with an exponential pdf distribution, the resulting velocity correlation was an exponential function. Other time-step probability density functions, such as a uniform distribution and a half-Gaussian distribution, were also tested. A Markov chain, which presumes one-step memory, has a piecewise linear velocity correlation function with a finite time step. For a Markov chain with a short time step, only an exponential velocity correlation function can be realized. Thus, a Monte Carlo process with random time steps is more versatile than a Markov chain. Direct numerical calculation of the velocity correlation verified the analytical results. A new model which combines the ideas of the Monte Carlo process and the Markov chain was developed. By examining the long-time mean square dispersion, we found an exact solution for the Lagrangian integral time scale of the new model in terms of the intercorrelation parameter and the mean and the variance of the time steps. Using this new model, we can generate any velocity correlation, including one with a negative tail. Two approximate solutions that give upper and lower bounds for the Lagrangian velocity correlation are proposed.
Exceptional configurations with the clover action

Abstract We study exceptional modes of both the Wilson and the clover action in order to understand why quenched clover spectroscopy suffers so severely from exceptional configurations. We show that a large clover coefficient can make the exceptional modes extremely localized and thus very sensitive to short distance fluctuations. We contrast this with the case of the Wilson action where exceptional modes correspond to large instantons. These modes are broadly extended and suffer much less from discretization errors.
A model of disruptive surgeon behavior in the perioperative environment.

Background Surgeons are the physicians with the highest rates of documented disruptive behavior. We hypothesized that a unified conceptual model of disruptive surgeon behavior could be developed based on specific individual and system factors in the perioperative environment. Study Design Semi-structured interviews were conducted with 19 operating room staff of diverse occupations at a single institution. Interviews were analyzed using grounded theory methods. Results Participants described episodes of disruptive surgeon behavior, personality traits of perpetrators, environmental conditions of power, and situations when disruptive behavior was demonstrated. Verbal hostility and throwing or hitting objects were the most commonly described disruptive behaviors. Participants indicated that surgical training attracts and creates individuals with particular personality traits, including a sense of shame. Interviewees stated this behavior is tolerated because surgeons have unchecked power, have strong money-making capabilities for the institution, and tend to direct disruptive behavior toward the least powerful employees. The most frequent situational stressors were when something went wrong during an operation and working with unfamiliar team members. Each factor group (ie, situational stressors, cultural conditions, and personality factors) was viewed as being necessary, but none of them alone were sufficient to catalyze disruptive behavior events. Conclusions Disruptive physician behavior has strong implications for the work environment and patient safety. This model can be used by hospitals to better conceptualize conditions that facilitate disruptive surgeon behavior and to establish programs to mitigate conduct that threatens patient safety and employee satisfaction.
Calculation of the mutual diffusion coefficient by equilibrium and nonequilibrium molecular dynamics.

A nonequilibrium molecular dynamics method for the calculation of the mutual diffusion coefficient for a mixture of hard spheres is described. The method is applied to a 50-50 mixture of equidiameter particles having a mass ratio of 0.1 for the two species, at a volume of three times close-packing. By extrapolating the results to the limit of vanishing concentration gradient and infinite system size, we obtain a value in statistical agreement with the result obtained using a Green-Kubo molecular dynamics procedure, which is also described. The non-equilibrium calculation yields a mutual diffusion coefficient which decreases slightly with increasing concentration gradient. The Green-Kubo timecorrelation function for mutual diffusion displays a slow decay with time, qualitatively similar to the long-time tail which has been predicted by the hydrodynamic theory of Pomeau.
ELEVEN NEWLY CHARACTERIZED XYLOGLUCAN OLIGOGLYCOSYL ALDITOLS : THE SPECIFIC EFFECTS OF SIDECHAIN STRUCTURE AND LOCATION ON 1H NMR CHEMICAL SHIFTS

Abstract Eleven previously uncharacterized oligosaccharides, each containing from seventeen to twenty glycosyl residues, were isolated from the xyloglucan produced by suspension-cultured Acer pseudoplatanus cells and characterized by 1 H NMR spectroscopy, fast-atom bombardment mass spectrometry, and matrix-assisted laser-desorption mass spectrometry. The complex mixture of xyloglucan oligosaccharides released by endo -(1 → 4)- β -glucanase ( Trichoderma reesei ) treatment of cell walls was similar to that released by digestion of the soluble xyloglucan present in the culture medium. The oligosaccharides were converted to oligoglycosyl alditols by borohydride reduction and purified by a combination of gel-permeation (Bio-Gel P-2) chromatography, normal-phase HPLC, reversed-phase HPLC, and high-performance anion-exchange (HPAE) chromatography. Eleven new oligoglycosyl alditols (along with several others that had been previously characterized) were isolated and characterized, allowing additional correlations between xyloglucan structure and specific chemical shift effects in the 1 H NMR spectra to be determined. The correlations between structural and spectral features deduced in this study will facilitate the structural determination of a wide range of xyloglucans and their subunit oligosaccharides.
Swallowing their pride: Indigenous and industrial beer in Peru and Bolivia

In this article, we examine the relations between food and social identity through an analysis of consumption in Peru and Bolivia, where food and drink are central components of many social gatherings. The key dimensions of social inequality in these countries are well known: a sharply skewed distribution of income and wealth along lines of social class, a separation between more dynamic urban areas and the more static countryside, regional differentials between more developed core areas and poorer interior and frontier zones, ethnic distinctions between national majority populations and indigenous minorities. In these countries, food systems also combine distinct and unequal elements. Indigenous and European crops are both widely consumed, though the latter are usually more prestigious. Moreover, simple peasant technologies of food preparation coexist with higher-status modern industrial technologies of food processing. What connections, then, exist between the sharp class, regional, and ethnic divisions on the one hand, and the composite food systems on the other? Does the patterning of food consumption simply reflect pre-existing social identities, or does food consumption play a more active role in forming and expressing these identities?
A theory of magnetization reversal in nanowires

Magnetization reversal in a ferromagnetic nanowire which is much narrower than the exchange length is believed to be accomplished through the thermally activated growth of a spatially localized nucleus, which initially occupies a small fraction of the total volume. To date, the most detailed theoretical treatments of reversal as a field-induced but noise-activated process have focused on the case of a very long ferromagnetic nanowire, i.e., a highly elongated cylindrical particle, and have yielded a reversal rate per unit length, due to an underlying assumption that the nucleus may form anywhere along the wire. But in a bounded-length (though long) cylindrical particle with flat ends, it is energetically favored for nucleation to begin at either end. We indicate how to compute analytically the energy of the critical nucleus associated with either end, i.e., the activation barrier to magnetization reversal, which governs the reversal rate in the low-temperature (Kramers) limit. Our treatment employs elliptic functions, and is partly analytic rather than numerical. We also comment on the Kramers prefactor, which for this reversal pathway does not scale linearly as the particle length increases, and tends to a constant in the low-temperature limit.
The Adult Respiratory Distress Syndrome: Clinical Features, Factors Influencing Prognosis and Principles of Management

The adult respiratory distress syndrome (ARDS) is an important and common medical emergency and is likely to occur in all hospitals dealing in respiratory care. The syndrome occurs from a variety of diffuse pulmonary injuries which are either direct or indirect attacks on the lung parenchyma. Once lung damage occurs, exudation of fluid and loss of surfactant activity leads to impaired gas exchange and reduced pulmonary compliance. The syndrome presents clinically as marked respiratory distress, tachypnea, cyanosis, refractory hypoxemia, high inflation pressure requirements during ventilatory support, diffuse alveolar infiltrates on chest roentgenograms and postmortem pulmonary congestion, hyperemia and hyaline membrane formation. Principles of management include adequate support of oxygen transport, ventilation and circulation employing volume respirators with positive end-expiratory pressure (PEEP). During the support phase, further pulmonary injury in terms of fluid overload, oxygen toxicity or infection, must be prevented or treated. When these principles of management are followed, recovery often occurs in spite of severe pulmonary injury as indicated by the first two illustrative cases.
Goldstone theorem and diquark confinement beyond rainbow-ladder approximation

Abstract The quark Dyson-Schwinger equation and meson Bethe-Salpeter equation are studied in a truncation scheme that extends the rainbow-ladder approximation such that, in the chiral limit, the isovector, pseudoscalar meson remains massless. Repulsive contributions, which appear at higher order in the Bethe-Salpeter kernel, eliminate the bound state pole in the quark-quark (diquark) channel that is present in rainbow-ladder approximation. The net effect of higher order terms on the meson bound state masses is small.
Visible light-harvesting in covalently-linked porphyrin-cyanine dyes

Abstract We report the synthesis and properties of three members of a new class of photochemical model compounds containing a covalently-linked porphyrin and a cyanine dye. In compounds 1 and 2 the dye absorbs in the 450–570 nm region and energy transfer occurs with 80% efficiency from the dye to the free base porphyrin. In compound 3 the dye absorbs in the 650–780 nm region and energy transfer occurs with 80% efficiency from the free base porphyrin to the dye. The zinc-porphyrin-dyes exhibit both donor and acceptor quenching with only moderate yields of energy transfer. This work is a first step toward the development of an artificial phycobilisome.
Actinides: From heavy fermions to plutonium metallurgy

The actinide elements mark the emergence of 5f electrons. The f electrons possess sufficiently unuusual characteristics that their participation in atomic binding often results in dramatic changes in properties. This provides an excellent opportunity to study the question of localization of electrons; a question that is paramount in predicting the physical and chemical properties of d and f electron transition metals. The transition region between localized (magnetic) and itinerant (often superconducting) behavior provides for many interesting phenomena such as sctructural instabilities (polymorphism), spin fluctuations, mixed valences, charge density waves, exceptional catalyic activity and hydrogen storage. This region offers most interesting behavior such as that exhibited by the actinide compounds UBe13 and UPt3. Both compounds are heavy-fermion superconductors in which both magnetic and superconducting behavior exist in the same electrons. The consequences of f-electron bonding (which appears greatest at plutonium) show dramatic effects on phase stability, alloying behavior, phase transformations and mechanical behavior.
Ultrasonic Method for Aircraft Wake Vortex Detection

This paper describes the experimental proof of concept study for an ultrasonic method of wake vortex detection. This new acoustic method uses travel time of acoustic pulses around a closed path to measure the net circulation within the acoustic path. In this application the closed path encloses the vorticity shed from one side of a Piper PA-28 aircraft wing. Magnitude and sign of circulation detected is comparable to the expected circulation generated by the Piper PA-28 test aircraft. This study demonstrates the validity of the acoustic method in detecting aircraft wake vortices. Further investigations and applications using this technique are discussed.
To what extent does genealogical ancestry imply genetic ancestry

Abstract Recent statistical and computational analyses have shown that a genealogical most recent common ancestor (MRCA) may have lived in the recent past [Chang, J.T., 1999. Recent common ancestors of all present-day individuals. Adv. Appl. Probab. 31, 1002–1026. 1027–1038; Rohde, D.L.T., Olson, S., Chang, J.T., 2004. Modelling the recent common ancestry of all living humans. Nature 431, 562–566]. However, coalescent-based approaches show that genetic most recent common ancestors for a given non-recombining locus are typically much more ancient [Kingman, J.F.C., 1982a. The coalescent. Stochastic Process Appl. 13, 235–248; Kingman, J.F.C., 1982b. On the geneology of large populations. J. Appl. Probab. 19A, 27–43]. It is not immediately clear how these two perspectives interact. This paper investigates relationships between the number of descendant alleles of an ancestor allele and the number of genealogical descendants of the individual who possessed that allele for a simple diploid genetic model extending the genealogical model of [Chang, J.T., 1999. Recent common ancestors of all present-day individuals. Adv. Appl. Probab. 31, 1002–1026. 1027–1038].
Screening for Lung Cancer

Lung cancer is the commonest cause of death from cancer in both men and women, with approximately 152,000 new cases and 139,000 deaths in 1988. The incidence and mortality rates are increasing rapidly in women. Two main tests have been used to screen for lung cancer: chest roentgenography and sputum cytology. Four recent controlled trials and one case-control study failed, however, to show that screening reduces lung cancer mortality even in high-risk persons (smokers). In the Mayo Lung Project, for example, the lung cancer death rate in high-risk men offered sputum cytology and chest roentgenogram every 4 months was 3.1 per 1000 person-years, compared with 3.0 per 1000 person-years in a control group. Chest roentgenograms and sputum cytology lead to false-positive test results in smokers of approximately 5% and 0.5%, respectively. Because of the lack of evidence of benefit and because of its potential harms and costs, screening for lung cancer is not recommended.
Hints for the scale of new CP-violating physics from B-CP anomalies

We consider several hints for new physics involving CP-asymmetries in B-decays and interpret them in terms of generic contributions to effective Wilson coefficients. The effects we focus on are: the differences in the fitted value of sin 2β versus the ones directly measured via the time dependent CP asymmetries in B → J/ψK or via B → (,η')K; the difference between the direct CP asymmetries in B− → K−π0 and 0 → K−π+ and the ≈ 2.2σ indications for the CP-asymmetry in Bs → J/ψ. To alleviate concerns regarding the disagreement between inclusive and exclusive Vub, we show that our results hold even without the inclusion of Vub in the analysis. We find that no matter what kind of new physics (NP) is invoked to explain these effects, its effective scale is bounded from above from a few hundred GeV to a few TeV depending on specific assumptions regarding the type of new physics. The only exception to this is when the NP contribution is assumed to reside entirely in LR operators in K mixing, then the scale of NP can be as high as around 24 TeV; however, this case cannot account for CP asymmetry in Bs → J/ψ or a difference in sin 2β from penguin modes compared to that from J/ψK or for that matter the large difference seen between direct CP asymmetries in K−π+ and in K−π0.
Oxazoline-mediated synthesis of the Gossypium sesquiterpene lacinilene C-7 methyl ether and a structurally Related HIV-1 Reverse Transcriptase Inhibitor

Abstract An efficient synthesis of the phytoalexin, lacinilene C-7 methyl ether, via its probable biosynthetic precursor, 2-hydroxy-7-methoxycadalene is described. A related synthesis of a HIV-1 reverse-transcriptase inhibitor is briefly discussed.
G-Modes and the Solar Neutrino Problem

We show that low-order g-modes with large enough amplitudes to affect significantly the solar neutrino fluxes would produce surface velocities that are 10 exp 4 times larger than the observed upper limits and hence are ruled out by existing data. We also demonstrate that any large-amplitude, short-period oscillations that grow on a Kelvin-Helmholtz time scale will require, to affect solar neutrino fluxes, a large amount of energy (for g-modes, 10 exp 9 times the energy in the observed p-mode oscillations) and a tiny amount of dissipation (for g modes, 10 exp -8 the fractional dissipation rate of the p-modes).
INFLUENCES AND TRENDS IN MUTUAL FUND EXPENSE RATIOS

A common question for the mutual fund industry, which has experienced a fivefold increase in assets over the last few years, is whether it shows declining production costs. Prior studies on fund expenses give conflicting results because several factors, from asset size to management style to share class, affect costs. Controlling for these and other factors shows the average stock fund expense ratio declined 1 basis point per year and bond fund ratios decreased 1 to 3 basis points per year, depending on the investment objective, from 1994 to 1998. Funds participating in no-transaction-fee supermarkets are more expensive than equivalent nonparticipants. JEL classification: G20, G28
Velocity peaks and caustic rings.

The late infall of cold dark matter onto an isolated galaxy produces flows with definite velocity vectors at any physical point in the galactic halo. It also produces caustic rings, which are places in space where the dark matter density is very large. The self-similar model of galactric halo formation predicts that the caustic ring radii an follow the approximate law an ≅ 1n. Bumps in the rotation curves of NGC 3198 and of our own galaxy are interpreted as due to caustic rings of dark matter.
Thermal, non-catalyzed Huisgen cycloaddition for the preparation of 4,5-bis(trimethylsilyl)-1H-1,2,3-triazoles

The 1,2,3-triazole scaffold is an important pharmacophore and a versatile, increasingly leveraged, substructure in biochemical, materials, polymer, and metal-coordinating applications. Continuing advances in 1,2,3-triazole construction, by either non-catalyzed or metal-catalyzed azide/alkyne cycloaddition, foster further creative use. The work reported here establishes a general protocol for the synthesis of 4,5-bis(trimethylsilyl)-1H-1,2,3-triazoles via thermal Huisgen cycloaddition between azides and bis(trimethylsilyl)acetylene.
The Massive Pulsar PSR J1614?2230: Linking Quantum Chromodynamics, Gamma-ray Bursts, and Gravitational Wave Astronomy

The recent measurement of the Shapiro delay in the radio pulsar PSR J1614–2230 yielded a mass of 1.97 ± 0.04 M ☉, making it the most massive pulsar known to date. Its mass is high enough that, even without an accompanying measurement of the stellar radius, it has a strong impact on our understanding of nuclear matter, gamma-ray bursts (GRBs), and the generation of gravitational waves from coalescing neutron stars. This single high-mass value indicates that a transition to quark matter in neutron-star cores can occur at densities comparable to the nuclear saturation density only if the quarks are strongly interacting and are color superconducting. We further show that a high maximum neutron-star mass is required if short-duration GRBs are powered by coalescing neutron stars and, therefore, this mechanism becomes viable in the light of the recent measurement. Finally, we argue that the low-frequency (≤500 Hz) gravitational waves emitted during the final stages of neutron-star coalescence encode the properties of the equation of state because neutron stars consistent with this measurement cannot be centrally condensed. This will facilitate the measurement of the neutron star equation of state with Advanced LIGO/Virgo.
A worldsheet description of planar Yang–Mills theory☆

Abstract We extend previous work by developing a worldsheet description of non-Abelian gauge theory (Yang–Mills). This task requires the introduction of Grassmann variables on the world sheet analogous to those of the Neveu–Schwarz–Ramond formulation of string theory. A highlight of our construction is that once the three gluon vertices of Yang–Mills Feynman diagrams are given a worldsheet description, the worldsheet formalism automatically produces all of the quartic vertices.
Sensors for measuring combustibles in the absence of oxygen

Calorimetric and semiconductor types of sensors for combustibles generally require the presence of oxygen in the measurement gas. This paper describes sensors incorporating at least one ZrO2 electrochemical cell together with a combustibles-sensing element that are capable of measuring combustibles even in the absence of oxygen. The ZrO2 cell is used as an oxygen pump to introduce into the sensor structure the amount of oxygen necessary for the proper operation of the sensing element. Devices of this type can also be used to determine the composition of simple fuel mixtures. Results of experimental investigation of these devices concepts are presented.
Irreducible representations of groupoid $C^*$-algebras

If G is a second countable locally compact Hausdorff groupoid with Haar system, we show that every representation induced from an irreducible representation of a stability group is irreducible.
Wealthy, healthy and wise: does money compensate for being born into difficult conditions?

Recent studies have linked transfers from Mexican conditional cash transfer programme Oportunidades (formerly PROGRESA) to improvements in child development (Fernald et al., 2008, 2009), but this work has been criticized as failing to account for endogeneity of the transfers. We create an exogenous instrument for the amount of transfers and use it to test programme and transfer effects. Applying the new instrument confirms that improvements in child development are more linked to the transfers themselves than to other portions of the programme, which involve medical check-ups as well as educational sessions for mothers.
Efficiency rents: A new theory of the natural vacancy rate for rental housing

Abstract This paper adapts the theory of efficiency wages to explain the natural vacancy rate in rental housing markets. A positive vacancy rate provides landlords an incentive to invest in maintenance because if they fail to do so, some tenants will leave and the unit will sit vacant for a finite period of time. The resulting foregone rent will penalize landlords’ failure to maintain. Habitability laws, which have been enacted by states since the 1960s, provide a non-market penalty which lessens the need for market enforcement. Variation in these laws by state offers an opportunity to test the theory.
Mitochondria in heart failure

This review focuses on the evidence accumulated in humans and animal models to the effect that mitochondria are key players in the progression of heart failure (HF). Mitochondria are the primary source of energy in the form of adenosine triphosphate that fuels the contractile apparatus, and are thus essential for the pumping activity of the heart. We evaluate changes in mitochondrial morphology and alterations in the main components of mitochondrial energetics, such as substrate utilization and oxidative phosphorylation coupled with the level of respirasomes, in the context of their contribution to the chronic energy deficit and mechanical dysfunction in HF.
Dynamic simulation of carbonate fuel cell-gas turbine hybrid systems

Hybrid fuel cell/gas turbine systems provide an efficient means of producing electricity from fossil fuels with ultra low emissions. However, there are many significant challenges involved in integrating the fuel cell with the gas turbine and other components of this type of system. The fuel cell and the gas turbine must maintain efficient operation and electricity production while protecting equipment during perturbations that may occur when the system is connected to the utility grid or in stand-alone mode. This paper presents recent dynamic simulation results from two laboratories focused on developing tools to aid in the design and dynamic analyses of hybrid fuel cell systems. The simulation results present the response of a carbonate fuel cell/gas turbine, or molten carbonate fuel cell/gas turbine, (MCFC/GT) hybrid system to a load demand perturbation. Initial results suggest that creative control strategies will be needed to ensure a flexible system with wide turndown and robust dynamic operation. Copyright © 2006 by ASME.
The Hot Interstellar Medium of Normal Elliptical Galaxies. I. A Chandra Gas Gallery and Comparison of X-Ray and Optical Morphology

We present an X-ray analysis of 54 normal elliptical galaxies in the Chandra archive and isolate their hot gas component from the contaminating point-source emission, allowing us to conduct, for the first time, a morphological analysis on the gas alone. A comparison with optical images and photometry shows that the hot gas morphology has surprisingly little in common with the shape of the stellar distribution. We observe no correlation between optical and X-ray ellipticities in the inner regions where stellar mass dominates over dark matter. A shallow correlation would be expected if the gas had settled into hydrostatic equilibrium with the gravitational potential. Instead, observed X-ray ellipticities exceed optical ellipticities in many cases. We exclude rotation as the dominant factor to produce the gas ellipticities. The gas appears disturbed, and hydrostatic equilibrium is the exception rather than the rule. Nearly all hydrostatic models can be ruled out at 99% confidence, based on their inability to reproduce the optical-X-ray correlation and large X-ray ellipticities. Hydrostatic models not excluded are those in which dark matter either dominates over stellar mass inside the inner half-light radius or has a prominently cigar-shaped distribution, both of which can be ruled out on other grounds. We conclude that, even for rather X-ray-faint elliptical galaxies, the gas is at least so far out of equilibrium that it does not retain any information about the shape of the potential, and that X-ray-derived radial mass profiles may be in error by factors of order unity.
Chemical fractionation and abundances in coronal plasma

Abstract Much of modern. astrophysics is grounded on the observed chemical compositions of stars and the diffuse plasma that pervades the space between stars, galaxies and clusters of galaxies. X-ray and EUV spectra of the hot plasma in the outer atmospheres of stars have demonstrated that these environments are subject to chemical fractionation in which the abundances of elements can be enhanced and depleted by an order of magnitude or more. These coronal abundance anomalies are discussed and some of the physical mechanisms that might be responsible for producing them are examined. It is argued that coronal abundances can provide important new diagnostics on physical processes at work in solar and stellar coronae. It seems likely that other hot astrophysical plasmas will be subject to similar effects.
Transition metal-catalyzed C–H activation reactions: diastereoselectivity and enantioselectivity

This critical review discusses historical and contemporary research in the field of transition metal-catalyzed carbon–hydrogen (C–H) bond activation through the lens of stereoselectivity. Research concerning both diastereoselectivity and enantioselectivity in C–H activation processes is examined, and the application of concepts in this area for the development of novel carbon–carbon and carbon–heteroatom bond-forming reactions is described. Throughout this review, an emphasis is placed on reactions that are (or may soon become) relevant in the realm of organic synthesis (221 references).
Numerical study of phase conjugation in stimulated backscatter with pump depletion

Abstract Two-dimensional numerical simulations are presented of phase conjugation in stimulated backscatter of a focused aberrated beam, including the effects of pump depletion. In all cases, pump depletion significantly improved the conjugation fidelity H . As expected, the far field distribution of light scattered back through the aberrator exhibited a prominent axial spike closely matching that of the incident beam; however, the near field distribution had large and rapid spatial inhomogeneities, even for H ≈ 90%. In spite of such structure, the backscatter was able to reproduce a rough image of large scale modulation in the incident beam.
Sensitivity of Two-Sample Permutation Inferences in Observational Studies

Abstract In observational studies, subjects are not randomly assigned to treatment or control, so they may differ in their chances of receiving the treatment. A simple method is developed and demonstrated for displaying the sensitivity of conventional two-group permutation inferences to departures from random assignment of treatments. The unmatched case, discussed here, differs in certain technical and computational details from the matched case, discussed previously; however, the underlying model and the method for quantifying departures from randomization are the same. The method may be applied to Wilcoxon's rank sum test, the Gehan and log-rank tests for censored outcomes, Mantel's test for scored categories, and Fisher's exact test for binary responses. The method embeds the usual randomization reference distribution in a one-parameter family of departures involving an unobserved covariate that would have been controlled by adjustments had it been observed. As this parameter is varied, the sensitivity...
Contrast-negation and texture synthesis differentially disrupt natural texture appearance

Natural textures have characteristic image statistics that make them discriminable from unnatural textures. For example, both contrast-negation and texture synthesis alter the appearance of natural textures even though each manipulation preserves some features while disrupting others. Here, we examined the extent to which contrast-negation and texture synthesis each introduce or remove critical perceptual features for discriminating unnatural textures from natural textures. We find that both manipulations remove information that observers use for distinguishing natural textures from transformed versions of the same patterns, but do so in different ways. Texture synthesis removes information that is relevant for discrimination in both abstract patterns and ecologically valid textures, and we also observe a category-dependent asymmetry for identifying an “oddball” real texture among synthetic distractors. Contrast negation exhibits no such asymmetry, and also does not impact discrimination performance in abstract patterns. We discuss our results in the context of the visual system’s tuning to ecologically relevant patterns and other results describing sensitivity to higher-order statistics in texture patterns.
Tidal Dissipation in the Solid Cores of the Major Planets

Abstract If the orbital resonances in the Jovian and Saturnian satellite systems are the result of orbital evolution due to tidal dissipation then the present rates of energy dissipation ( E dot ) are >2 × 1020 ergs sec−1 (Jupiter) and ≳2 × 1016 ergs sec−1 (Saturn). These values of E dot can be accounted for if the planets have rocky cores with volumes equal to those suggested by current models of the interiors and if the material of these cores is both solid and imperfectly elastic (Qe ∼ 34). The calculated values of Qe are not strongly dependent on either the rigidity of the core or the densities of the core and the mantle. Thus, these quantities need not be known precisely. It may be significant that approximately the same value of Qe is needed for all the major planets (Jupiter, Saturn, and Uranus) even though the values of E dot for these planets differ by a factor greater than 104.
Scaling of structure functions.

In a recent paper, Benzi et al. [ Universit\`a di Roma, Report No. ROM 2F/92/54 (unpublished)] proposed that an extensive scaling region can be observed---even at moderate Reynolds numbers---when the structure functions of arbitrary order are plotted against the third-order structure function, and that the scaling region in such plots encompasses both inertial and dissipative ranges. This notion of extended self-similarity is analyzed here, and it is found that the concept is valid when it entails low-order structure functions, but that the scaling in the inertial and dissipation regions differs clearly for high orders. The same is true also for moments of the absolute value of velocity increments.
Dynamic modeling of gas springs

Linear dynamic modeling of gas springs is important for basic design of free piston Stirling engines. The conventional gas spring model, a dashpot in parallel with an ideal spring, gives poor prediction of gas spring performance. The anelastic model presented here consists of two parallel springs, one of which is in series with a dashpot. With proper selection offspring and damping constants, it gives improved prediction of gas spring dynamics
SDSS J141624.08+134826.7: Blue L dwarfs and Non-equilibrium Chemistry

We present an analysis of the recently discovered blue L dwarf SDSS J141624.08+134826.7. We extend the spectral coverage of its published spectrum to {approx}4 {mu}m by obtaining a low-resolution L-band spectrum with SpeX on the NASA IRTF. The spectrum exhibits a tentative weak CH{sub 4} absorption feature at 3.3 {mu}m but is otherwise featureless. We derive the atmospheric parameters of SDSS J141624.08+134826.7 by comparing its 0.7-4.0 {mu}m spectrum to the atmospheric models of Marley and Saumon which include the effects of both condensate cloud formation and non-equilibrium chemistry due to vertical mixing and find the best-fitting model has T{sub eff} = 1700 K, log g = 5.5 (cm s{sup -2}), f{sub sed} = 4, and K{sub zz} = 10{sup 4} cm{sup 2} s{sup -1}. The derived effective temperature is significantly cooler than previously estimated but we confirm the suggestion by Bowler et al. that the peculiar spectrum of SDSS J141624.08+134826.7 is primarily a result of thin condensate clouds. In addition, we find strong evidence of vertical mixing in the atmosphere of SDSS J141624.08+134826.7 based on the absence of the deep 3.3 {mu}m CH{sub 4} absorption band predicted by models computed in chemical equilibrium. Finally, this result suggests that observations ofmore » blue L dwarfs are an appealing way to quantitatively estimate the vigor of mixing in the atmospheres of L dwarfs because of the dramatic impact such mixing has on the strength of the 3.3 {mu}m CH{sub 4} band in the emergent spectra of L dwarfs with thin condensate clouds.« less
The Present State of Geothermal Investigations

At present, the emphasis in geothermal studies in non‐volcanic areas is on the flow of heat to the surface, a quantity of much theoretical importance. The number of reliable determinations of heat flow is still small, with few of the oil‐producing regions represented. While thermal gradients range from about 5 to 70°C/km, most of the measurements of heat flow fall within the range 1.2⋅10-6cal/cm2‐sec±50%, including the recent values for the deep ocean basins. There are suggestions of regional variations, but many more measurements reliable to 10% or better will be needed for further progress. The study of regions or provinces, rather than single localities, is especially desirable, and should be feasible in areas extensively drilled for oil. The principal requirements, which are difficult to meet, are: 1) approximate thermal equilibrium, which may require an undisturbed period of many months, and 2) availability for laboratory study of cores representing the major formations penetrated by the well. A rene...
Diversity and Origin of 2:1 Orbital Resonances in Extrasolar Planetary Systems

A diversity of 2 : 1 resonance configurations can be expected in extrasolar planetary systems, and their geometry can provide information about the origin of the resonances. Assembly during planet formation by the differential migration of planets due to planet-disk interaction is one scenario for the origin of mean-motion resonances in extrasolar planetary systems. The stable 2 : 1 resonance configurations that can be reached by differential migration of planets with constant masses and initially coplanar and nearly circular orbits are (1) antisymmetric configurations with the mean-motion resonance variables θ1 = λ1 - 2λ2 + 1 and θ2 = λ1 - 2λ2 + 2 (where λj and j are the mean longitudes and the longitudes of periapse, respectively) librating about 0° and 180°, respectively (as in the Io-Europa pair), (2) symmetric configurations with both θ1 and θ2 librating about 0° (as in the GJ 876 system), and (3) asymmetric configurations with θ1 and θ2 librating about angles far from either 0° or 180°. There are, however, stable 2 : 1 resonance configurations with symmetric (θ1 ≈ θ2 ≈ 0°), asymmetric, and antisymmetric (θ1 ≈ 180° and θ2 ≈ 0°) librations that cannot be reached by differential migration of planets with constant masses and initially coplanar and nearly circular orbits. If real systems with these configurations are ever found, their origin would require (1) a change in the planetary mass ratio m1/m2 during migration, (2) a migration scenario involving inclination resonances, or (3) multiple-planet scattering in crowded planetary systems. We find that the asymmetric configurations with large e2 and the θ1 ≈ 180° and θ2 ≈ 0° configurations have intersecting orbits and that the θ1 ≈ θ2 ≈ 0° configurations with e1 > 0.714 have prograde periapse precessions.
Recent progress with the DNA repair mutants of Chinese hamster ovary cells

SUMMARY Repair-deficient mutants of Chinese hamster ovary (CHO) cells are being used to identify human genes that correct the repair defects and to study mechanisms of DNA repair and mutagenesis. Five independent tertiary DNA transformants were obtained from the EM9 mutant, which is noted for its very high sister-chromatid exchange frequencies. In these clones a human DNA sequence was identified that correlated with the resistance of the cells to chlorodeoxyuridine (CldUrd). After EcoRI digestion, Southern transfer, and hybridization of transformant DNAs with the BLUR-8 Alu family sequence, a common fragment of 25–30 kilobases (kb) was present. Since the DNA molecules used to produce these transformants were sheared to Using drug-resistance markers to select for hybrids after fusion, we have done complementation experiments with ultraviolet light (u.v.)-sensitive mutants and have identified a sixth complementation group, line UV61. Additionally, CHO mutants UV27-1 and MMC-2, isolated in other laboratories, were found to belong to UV group 3, which is represented by line UV24. To study the behaviour of transfected DNA molecules in repair-deficient cells, we treated plasmid pSV2gpt with either u.v. radiation or cis-diamminedichloroplatinum(II) (cis-DDP) and introduced the damaged DNA into normal CHO cells (AA8) and mutants UV4 and UV5. Unrepaired damage to the plasmid was indicated by loss of colony-forming ability of the transfected cells in selective medium containing mycophenolic acid. With u.v. damage, the differential survival of the cell lines was similar to that seen when whole cells are treated with u.v. However, with cis-DDP damage, mutant UV4 did not exhibit the extreme hypersensitivity (50-fold) that occurs when cells are treated. This result suggests that UV4 cells may be able to repair cross-links in transfected DNA.
Improving the fine tuning in models of low energy gauge mediated supersymmetry breaking

The fine tuning in models of low energy gauge mediated supersymmetry breaking required to btain the correct Z mass is quantified. To alleviate the fine tuning problem, a model with split (5 + 5) messenger fields is presented. This model has additional triplets in the low energy theory which get a mass of O(500) GeV from a coupling to a singlet. The improvement in fine tuning is quantified and the spectrum in this model is discussed. The same model with the above singlet coupled to the Higgs doublets to generate the μ term is also discussed. A Grand Unified version of the model is constructed and a known doublet-triplet splitting mechanism is used to split the messenger (5 + 5)'s. A complete model is presented and some phenomenological constraints are discussed.
Call establishment overload in large ATM networks

Abstract The call establishment process in asynchronous transfer mode (ATM) networks can constitute a source of overload in the switches of the network. The purpose of this paper is to use analytic modeling and simulation to investigate this effect. The call establishment overload can be particularly significant when the network will contain a relatively large number of switches, due to the inaccuracy of the information available to the switch accepting or rejecting the call, and because of the multiple paths which need to be assessed and then utilized to establish the call. We simulate the call set-up phase of an ATM connection, including path selection, bandwidth reservation and call rejection, and simulate the flow of call establishment messages to estimate by simulation and analytically the queue lengths of call establishment processing at the input, output and intermediate switches. Average usage of bandwidth at the links, and the probability that a call request is rejected due to insufficient capacity at some link, are measured via simulation and also predicted using an analytical model. Simulation results show that if bandwidth is not reserved at input nodes, very large queues of call establishment jobs can build up in the switches of the network. A simplified analytical model is derived to estimate the queue lengths of call establishment jobs at each node of the network when advanced reservation with perfect information is implemented. Simulation results are compared to approximate model predictions for each individual switching node in a 100-node (switch) ATM network model. It is shown that the analytical model dealing with a large ATM network can qualitatively predict the locations of queue build-up of jobs for call establishment processing, with accurate queue length predictions for being made in the case of light traffic load. The analytical model provides a lower bound to queue lengths, and remains within the same order of magnitude when the call request traffic is high.
An Improved Procedure for the Synthesis of 1-Alkyladenines : Removal of the Ribofuranosyl Group from 1-Benzyl-, 1-(3-Methyl-2-butenyl)-, and 1-Allyladenosine Hydrobromide in Acetic Acid

1-Benzyl- (IIIa), 1-(3-methyl-2-butenyl)-(IIIb), and 1-allyladenine (IIIc) were prepared in 77, % 44%, and 69% yield, respectively, by alkylation of adenosine (I) followed by heating the resulting 1-substituted adenosine hydrobromides (IIa, b, c) in acetic acid.
The Effects of Active and Passive Recovery on Short-Term, High Intensity Power Output

The advantage of active over passive recovery from long and intermediate duration exercise is well documented. Success has been attributed to metabolite washout and/or lactate (La) utilization by t...