cssi/SciSciGPT-SciSciNet huggingface dataset:
Elucidation of structural relationships and assignment of 1H NMR spectra of transition-metal cyclidene complexes by 2-D NMR techniques

The complete /sup 1/H NMR spectra of five nickel cyclidene macrocyclic complexes are assigned by using DEPT (distortionless enhancement by polarization transfer) and 2-D NMR techniques: /sup 1/H-/sup 13/C shift correlation, COSY (correlated shift), and NOESY (nuclear Overhauser enhanced correlated shift). The /sup 1/H NMR assignments are consistent with the complexes having an overall saddle shape with the two saturated six-membered rings (composed of nickel, two nitrogens, and a trimethylene chain) adopting a chair and a boat configuration similar to those observed in the X-ray crystal structures of these complexes. The /sup 1/H NMR spectra can distinguish between two possible configurations for the bridging moiety (lid-off and lid-on). The vinyl methyl groups, labeled as O and N, have a chemical shift separation greater the 0.35 ppm for a lid-off configuration and less than 0.15 ppm for a lid-on configuration. The complex (2,9,10,17,19,25,33,34-octamethyl-3,6,13,16,20,24,27,31-octaazapentacyclo(16.7.7.2/sup 8,11/.2/sup 3,6/.2/sup 13,16/)- octatriaconta-1,8,10,17,19,24,26,31,33-nonaene-K/sup 4/N)nickel(II) hexafluorophosphate (V) has a bridge that consists of durene(tetramethylbenzene) supported by two piperazine rings. Those protons on the piperazine rings that are in close proximity to the arene ring are shifted upfield due to shielding contributions of the ring currents. 23 references, 9 figures, 1 table.
Office Building Capitalization Rates: The Case of Downtown Chicago

This paper is an empirical study of the capitalization rates for 132 office building sales in downtown Chicago from 1996 to 2007. The capitalization rate is hypothesized to be a function of the classic capital asset pricing model variable and variables intended to capture the expectation that the real market value of the building will change. The results show that the capitalization rate for office buildings incorporates a very low value for “beta.” A lower capitalization rate was associated with a smaller risk-free rate, a lower borrowing rate, class A buildings, newer buildings, buildings that had been renovated, a reduction in the vacancy rate in the downtown Chicago office market, and an increase in employment in the financial sector of the metropolitan area.
Numerical modeling of unsteady flame propagation

Abstract The problem of the numerical modeling of unsteady flame propagation with large amounts of exothermic heat release has been addressed through the use of a model equation which contains many of the important nonlinearities and difficulties in the problem. The model equation has been solved for a significant variation in Damkohler number with a variety of conventional and new finite-difference procedures. One of the new procedures used was an adaptive grid method which places node points in the region of large temperature gradients where they are necessary for a proper simulation of the phenomena. This adaptive grid procedure does have significant advantages over conventional second and fourth order uniform grid methods for many aspects of the problem. It has been found that conventional methods with relatively few node points are inadequate for flames with high Damkohler number, because of the fact that too few nodes are located in the flame. Further refinement of the adaptive grid method seems feasible, but even in the present form it represents a significant improvement over conventional techniques.
Power spectra of extinction in the fossil record

Recent Fourier analyses of fossil extinction data have indicated that the power spectrum of extinction during the Phanerozoic may take the form of 1/f noise, a result which, it has been suggested, could be indicative of the presence of `critical dynamics' in the processes giving rise to extinction. In this paper we examine extinction power spectra in some detail, using family-level data from two widely available compilations. We find that although the average form of the power spectrum roughly obeys the 1/f law, the spectrum can be represented more accurately by dividing it into two regimes: a low-frequency one which is well fit by an exponential, and a high-frequency one in which it follows a power law with a 1/f2 form. We give explanations for the occurrence of each of these behaviours and for the position of the crossover between them.
COMPREHENSIVE PHOTOMETRIC HISTORIES OF ALL KNOWN GALACTIC RECURRENT NOVAE

I collect virtually all photometry of the 10 known galactic recurrent novae (RNe) and their 37 known eruptions. This consists of my modern measures of nearly all archival plates (providing the only data for half of 37 known eruptions), my own 10,000 CCD magnitudes from 1987 to present (providing virtually all of the magnitudes in quiescence for seven RNe), over 140,000 visual magnitude estimates recorded by amateur astronomers (who discovered half the known eruptions), and the small scattering of magnitudes from all the literature. From this, I produce various uniform products: (1) BVRIJHK comparison star magnitudes and BV comparison star sequences to cover the entire range of eruption; (2) complete light curves for all eruptions; (3) best-fit B and V light curve templates; (4) orbital periods for all but one RN; (5) exhaustive searches for all missed eruptions; (6) measured discovery efficiencies since 1890; (7) true recurrence time scales; (8) predicted next eruption dates; (9) variations on time scales of minutes, hours, days, months, years, decades, and century; (10) uniform distances and extinctions to all RNe; (11) BV colors at peak and UBVRIJHK colors at minimum, all with extinction corrections; and (12) the spectral energy distributions over UBVRIJHK. Highlights of this work include the discoveries of one new RN, six previously unknown eruptions, and the orbital periods for half the RNe. The goal of this work is to provide uniform demographics for answering questions like the What is the death rate of RNe in our Galaxy? and Are the white dwarfs gaining or losing mass over each eruption cycle?. An important use of this work is for the question of whether RNe can be the progenitors of Type Ia supernovae.
Rise time and recovery of GaAs photoconductive semiconductor switches

Fast rise time applications have encouraged us to look at the rise time dependences of lockon switching. Our tests have shown rise time and delay effects which decrease dramatically with increasing electric field across the switch and/or optical energy used in activating lockon. Interest in high repetition rate photoconductive semiconductor switches (PCSS) which require very little trigger energy (our 1 . 5cm long switches have been triggered with as little as 20 J) has also led us to investigate recovery from lock-on. Several circuits have been used to induce fast recovery the fastest being 30 ns. The most reliable circuit produced a 4-pulse burst of +/- 10-kY pulses at 7 MHz with lOO-jtJ trigger energy per pulse.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Neutrino Mass Models: circa 2008

We review recent developments in theoretical models for neutrino masses and mixing. Emphases are given to models based on finite group family symmetries. In particular, we describe one recent model based on SU(5), in which both the tri-bimaximal neutrino mixing and realistic CKM matrix are generated. We also discuss two models based on a non-anomalous U(1)F family symmetry in which the gauge anomalies are cancelled due to the presence of the right-handed neutrinos. In one of these models, the seesaw scale can be as low as a TeV; in the other model, which is based on SUSY SU(5), the U(1)F symmetry forbids Higgs-mediated proton decays.
The prediction of jet noise ground effects using an acoustic analogy and a tailored Green's function

Abstract An assessment of an acoustic analogy for the mixing noise component of jet noise in the presence of an infinite surface is presented. The reflection of jet noise by the ground changes the distribution of acoustic energy and is characterized by constructive and destructive interference patterns. The equivalent sources are modeled based on the two-point cross-correlation of the turbulent velocity fluctuations and a steady Reynolds-Averaged Navier–Stokes (RANS) solution. Propagation effects, due to reflection by the surface and refraction by the jet shear layer, are taken into account by calculating the vector Green's function of the linearized Euler equations (LEE). The vector Green's function of the LEE is written in relation to that of Lilley's equation; that is, it is approximated with matched asymptotic solutions and Green's function of the convective Helmholtz equation. The Green's function of the convective Helmholtz equation in the presence of an infinite flat plane with impedance is the Weyl–van der Pol equation. Predictions are compared with measurements from an unheated Mach 0.95 jet. Microphones are placed at various heights and distances from the nozzle exit in the peak jet noise direction above an acoustically hard and an asphalt surface. The predictions are shown to accurately capture jet noise ground effects that are characterized by constructive and destructive interference patterns in the mid- and far-field and capture overall trends in the near-field.
Remarkably chemoselective indium-mediated coupling en route to the C21–C40 acyclic portion of the azaspiracids

Abstract A densely functionalized acyclic intermediate representing the C21–C40 portion of the novel marine natural product azaspiracid was prepared via a chemoselective indium-mediated coupling between C21–C27 and C28–C40 intermediates. Although the coupling partners contained aldehyde, azide, ketone, enone, and lactone functionalities, the C21–C27 allylic species added selectively to the aldehyde of a C28–C40 intermediate under aqueous indium-mediated conditions. The C21–C27 and C35–C40 fragments were prepared in a divergent fashion from a common syn-1,3-dimethyl synthon 9 .
Dendron-Mediated Self-Assembly, Disassembly, and Self-Organization of Complex Systems

Dendron-mediated self-assembly, disassembly, and self-organization of complex systems have been investigated. The most ideal building blocks would need to display shape persistence in solution and in the solid state, since only this feature provides access to the use of complementary methods of structural analysis. Most supramolecular dendrimers are chiral even when they are constructed from nonchiral building blocks and are equipped with mechanisms that amplify chirality. This poses additional challenges associated with the understanding of the structural origin of chirality in different supramolecular structures through combinations of structural analysis methods. While many supramolecular structures assembled from dendrimers and dendrons resemble some of the related morphologies generated from block-copolymers, they are much more complex and are not determined by the volume ratio between the dissimilar parts of the molecule.
Charge transfer processes at the interface between plasmas and liquids

Charge transfer processes at the interface of plasmas and liquid electrolytes have been studied for over 100 years. Both plasmas and liquid electrolytes contain charged species, and interactions between the two phases represent a unique combination of physics, chemistry, and materials science that is fundamentally different than that between solid electrodes and liquid electrolytes. Unfortunately, scientific progress over the last century has been slow because of several key challenges including the inability to stabilize nonthermal plasmas at atmospheric pressure, and the lack of fundamental understanding of the mechanisms for charge transfer. Within the last decade, significant strides have been made to overcome these challenges. Here, the authors review this fascinating area of study, highlighting the history, development of experimental systems, mechanistic aspects, and emerging applications.
Synthesis of archaebacterial lipid C20 chirons

Abstract Archaebacterial lipid C 20 chirons were synthesized by cross-coupling optically active C 10 “dimer” units prepared from hydroxyester 7 . Vitamin E (C 15 ) side chain was similarly constructed.
Skew loops in flat tori

We produce skew loops—loops having no pair of parallel tangent lines—homotopic to any loop in a flat torus or other quotient of R n . The interesting case here is n = 3. More subtly for any n, we characterize the homotopy classes that will contain a skew loop having a specified loop $$\tau\subset{\bf S}^{n-1}$$ as tangent indicatrix.
Specific heat variations in oil energy storage media and their economic implications

Hydrocarbon oils have been considered for use as thermal energy storage media in solar thermal electric systems. In systems storing the energy as sensible heat, the energy storage capacity is determined by the specific heat of the oil. Among the oils proposed is Caloria HT-43, a product of Exxon Corporation. Previously reported specific heat data on Caloria HT-43 show values differing by as much as 25 percent. An attempt was made to resolve this discrepancy by measuring the specific heat from 77 to 327/sup 0/C. Results show values from four samples varying by as much as 11 percent. The variations are correlated with differences in average molecular weights and inhomogeneity of the samples. The impact on cost of an 11 percent variation in specific heat is less than 1 percent for oil/rock systems and less than 2 percent for an all-oil system.
Earnings Informativeness and Strategic Disclosure: An Empirical Examination of “Pro Forma” Earnings

This paper provides evidence on the characteristics of firms that include “pro forma” earnings information in their press releases, whether the usefulness of pro forma earnings to investors varies systematically with these characteristics, and whether the investor response to pro forma earnings is consistent with market efficiency or mispricing. Using a sample of 249 press releases from 1997–99, we find that firms with low GAAP earnings informativeness are more likely to disclose pro forma earnings than other firms. We also find that strategic considerations, measured using the direction of GAAP earnings surprises, are an important determinant of pro forma reporting. In addition, our examination of the relative and incremental information content of pro forma earnings shows that investors find pro forma earnings to be more useful when GAAP earnings informativeness is low or when strategic considerations are absent. Tests of the predictive ability of pro forma earnings for future profitability and returns ...
Machine learning for science and society

The special issue on "Machine Learning for Science and Society" showcases machine learning work with influence on our current and future society. These papers address several key problems such as how we perform repairs on critical infrastructure, how we predict severe weather and aviation turbulence, how we conduct tax audits, whether we can detect privacy breaches in access to healthcare data, and how we link individuals across census data sets for new insights into population changes. In this introduction, we discuss the need for such a special issue within the context of our field and its relationship to the broader world. In the era of "big data," there is a need for machine learning to address important large-scale applied problems, yet it is difficult to find top venues in machine learning where such work is encouraged. We discuss the ramifications of this contradictory situation and encourage further discussion on the best strategy that we as a field may adopt. We also summarize key lessons learned from individual papers in the special issue so that the community as a whole can benefit.
Efficient equilibrium convergence: Heterogeneity and growth

Abstract An endogenous growth model arising from task specialization is used to examine the effects of differing initial human capital distributions. Two macroeconomic phenomena are produced: income convergence and leapfrogging of living standards. Income convergence occurs for all countries in the same market, arising from diminishing returns to individual human capital. Leapfrogging occurs by comparing countries in two separate markets. Income leapfrogging can occur because the stationary growth rate increases with market size, and human capital heterogeneity reduces growth. The introduction of coordination costs of task assignment can produce gains in welfare and growth from human capital heterogeneity.
Bayesian Quickest Change Point Detection with Sampling Right Constraints

In this paper, Bayesian quickest change detection problems with sampling right constraints are considered. Specifically, there is a sequence of random vari ables whose probability density function will change at an unknown time. The goal is to detect such a change in a way such that a linear combination of the average detection delay and the false alarm probability is minimized. Two types of sampling right constrains are discussed. The first one is a li mited sampling right constraint, in which the observer can take at most N observations from this random sequence. Under this setup, we show that the cost function can be written as a set of iterative fun ctions, which can be solved by Markov optimal stopping theory. The optimal stopping rule is shown to be a threshold rule. An asymptotic upper bound of the average detection delay is developed as the false alarm probability goes to zero. This upper bound indicates that the performance of the limited sampling right problem is close to that of the classic Bayesian quickest detection for several scenar ios of practical interest. The second constraint discussed in this paper is a stochastic sampling right const raint, in which sampling rights are consumed by taking observations and are replenished randomly. The observer cannot take observations if there are no sampling rights left. We characterize the optimal solution, which has a very complex structure. For practical applications, we propose a low complexity algorithm, in which the sampling rule is to take observations as long as the observer has sampling rights left and the detection scheme is a threshold rule. We show that this low complexity scheme is first order as ymptotically optimal as the false alarm probability goes to zero.
First-order Resonance Overlap and the Stability of Close Two-planet Systems

Motivated by the population of observed multi-planet systems with orbital period ratios 1 < P 2/P 1 2, we study the long-term stability of packed two-planet systems. The Hamiltonian for two massive planets on nearly circular and nearly coplanar orbits near a first-order mean motion resonance can be reduced to a one-degree-of-freedom problem. Using this analytically tractable Hamiltonian, we apply the resonance overlap criterion to predict the onset of large-scale chaotic motion in close two-planet systems. The reduced Hamiltonian has only a weak dependence on the planetary mass ratio m 1/m 2, and hence the overlap criterion is independent of the planetary mass ratio at lowest order. Numerical integrations confirm that the planetary mass ratio has little effect on the structure of the chaotic phase space for close orbits in the low-eccentricity (e 0.1) regime. We show numerically that orbits in the chaotic web produced primarily by first-order resonance overlap eventually experience large-scale erratic variation in semimajor axes and are therefore Lagrange unstable. This is also true of the orbits in this overlap region which satisfy the Hill criterion. As a result, we can use the first-order resonance overlap criterion as an effective stability criterion for pairs of observed planets. We show that for low-mass ( 10 M ?) planetary systems with initially circular orbits the period ratio at which complete overlap occurs and widespread chaos results lies in a region of parameter space which is Hill stable. Our work indicates that a resonance overlap criterion which would apply for initially eccentric orbits likely needs to take into account second-order resonances. Finally, we address the connection found in previous work between the Hill stability criterion and numerically determined Lagrange instability boundaries in the context of resonance overlap.
Epoxides derived from pyranosyl dienes: Unusually stable glycosyl donors

Abstract A pyranosyl diene appropriately substituted for use in a total synthesis of staurosporine has been synthesized. The mono-epoxides and bis-epoxides obtained from treatment of this diene with dimethyldioxirane are unusually stable.
Predictors and financial outcomes of corporate entrepreneurship: An exploratory study

Abstract Today, there is considerable scholarly and managerial interest in corporate entrepreneurship; that is, those activities that enhance a company's ability to innovate, take risk, and seize opportunities in its markets. Corporate entrepreneurship centers on creating new business by penetrating new markets, pursuing new business, or both. Despite the growing recognition and use of corporate entrepreneurship, little empirical research has been done on its antecedents and potential association with company financial performance. To fill this gap in the literature, this study proposes a model that identifies potential environmental, strategic, and organizational factors that may spur or stifle corporate entrepreneurship. The model also highlights the potential associations between corporate entrepreneurship and corporate financial performance. Building on the existing literature, the study advances five hypotheses that operationalize the model. The hypotheses are tested using data from 119 of the Fortune 500 industrial firms, covering the period 1986 to 1989. This exploratory study's results indicate that: (1) environmental dynamism, hostility, and heterogeneity (multiplicity and complexity of environmental components) intensify corporate entrepreneurship; (2) growth-oriented strategies are associated with increased corporate entrepreneurship, whereas a strategy of stability is not conducive to corporate entrepreneurship; (3) the scanning, formal communication, and integration components of formal organizational structure are positively related to corporate entrepreneurship—increased differentiation and extensive controls stifle corporate entrepreneurship; (4) clearly defined organizational values, whether relating to competitors or employees, are positively associated with corporate entrepreneurship; and (5) corporate entrepreneurship activities are associated with company financial performance and reduced systematic risk.
Professional psychology and the control of human behaviour

This paper is a discussion of ethical and psychological issues connected with the involvement of professional psychologists in the control or modification of human behaviour‐especially in therapeut...
When Is the Right Time to Refresh Knowledge Discovered from Data

Knowledge discovery in databases KDD techniques have been extensively employed to extract knowledge from massive data stores to support decision making in a wide range of critical applications. Maintaining the currency of discovered knowledge over evolving data sources is a fundamental challenge faced by all KDD applications. This paper addresses the challenge from the perspective of deciding the right times to refresh knowledge. We define the knowledge-refreshing problem and model it as a Markov decision process. Based on the identified properties of the Markov decision process model, we establish that the optimal knowledge-refreshing policy is monotonically increasing in the system state within every appropriate partition of the state space. We further show that the problem of searching for the optimal knowledge-refreshing policy can be reduced to the problem of finding the optimal thresholds and propose a method for computing the optimal knowledge-refreshing policy. The effectiveness and the robustness of the computed optimal knowledge-refreshing policy are examined through extensive empirical studies addressing a real-world knowledge-refreshing problem. Our method can be applied to refresh knowledge for KDD applications that employ major data-mining models.
Design for shape memory alloy rotatory joint actuators using shape memory effect and pseudoelastic effect

A new design for shape memory alloy rotatory joint actuators using shape memory effect and pseudoelastic effect is presented. In this design, one SMA wire works with its shape memory effect, while the other SMA wire works with its pseudoelastic effect. The pseudoelastic type of SMA wire provides the shape memory type of SMA wire with bias force, and therefore, the bias spring in a bias force type of SMA actuator can be eliminated. A quasi-static analysis of this type of actuators is performed which incorporates a varying load torque. General stress-strain relation and stress- temperature relation of the shape memory effect wire and a formula for an equivalent spring rate of the pseudoelastic wire are derived. Liang and Rogers' model for shape memory materials is used for the analysis. An experimental method to obtain the equivalent spring rate is also described. Design formulas for a simplified design are derived based on the quasi-static analysis of the actuator.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Infrared spectrum of Hg(OH)2 in solid neon and argon.

Mercury(II) hydroxide molecules have been prepared upon mercury arc lamp irradiation of Hg, H2, and O2 mixtures in solid neon and argon. The strongest three infrared absorptions are identified through isotopic substitution (D2, HD, 18O2, 16O18O) and comparison to frequencies from DFT calculations. The isolated Hg(OH)2 molecule is stable and has a linear O−Hg−O linkage in a C2 structure with an 86° dihedral angle. However, in aqueous solution Hg2+ and 2OH- may form an Hg(OH)2 intermediate, which eliminates water and precipitates solid HgO: The solid Hg(OH)2 compound is not known.
Electrochemical Synthesis of Ba2Ag8S7, a Quasi‐One‐Dimensional Barium Silver(I) Sulfide Containing Mixed S2−/S22− Ligands

A stingray pattern is adopted by Ba(2)Ag(8)S(7). Crystals of this compound were grown in a two-electrode chemical cell from a BaS(3)/ethylenediamine solution. In the pseudo-one-dimensional structure columns of (1)(infinity)[Ag(8)S(7)] (shown in the picture) are stacked head-to-tail to create voids where the barium atoms reside. The coexistence of S(2-) and S(2)(2-) indicates a reductive decomposition [Eq. (1)].
New Entry and the Rate of Return to Education: The Case of Registered Nurses

In the 1970s, the percentage of high school graduates completing RN training increased with little change in the rate of return to training. During the 1980s, this percentage declined, despite large increases in the rate of return. The national data employed here examine long-run trends (with emphasis on the 1970s and 1980s) in financial incentives and entry into the nursing profession and suggest that broader professional career opportunities in the 1980s exerted a large impact vis-a-vis the 1970s, among other factors. Rates of return remain high in the 1990s with modest signs of the market stabilizing. Successful policies to ensure stability in health care service delivery must incorporate these varying trends in the RN market.
Optimal Transit Routing with Partial Online Information

Abstract This paper studies the routing strategy in a transit network with partial online information at stops. By partial online information, we mean that the arrival time of the incoming transit vehicles is available for a subset of the lines serving a stop. To cope with the partial information assumption, a new routing strategy is proposed and closed form formulae for computing expected waiting times and line boarding probabilities are derived. The proposed strategy unifies existing hyperpath-based transit route choice models that assume either no information or full information. Like many existing models, it ensures optimality when all information is available or the headway is exponentially distributed. The problem of determining the attractive set is discussed for each of the three information cases. In particular, a new heuristic algorithm is developed to generate the attractive set in the partial information case, which will always yield a solution no worse than that obtained without any information. The paper also reveals that, when information is available, an optimal hyperpath may contain cycles. Accordingly, the cause of such cycles is analyzed, and a sufficient condition that excludes cycles from optimal hyperpaths is proposed. Finally, numerical experiments are conducted to illustrate the impact of information availability on expected travel times and transit line load distributions. Among other findings, the results suggest that it is more useful to have information on faster lines than on slower lines.
Cometary impact and the magnetization of the Moon

Abstract Collisions of comets with planetary bodies are capable of impressing patterns of magnetization onto them that match those observed for the Moon and possibly for Mercury. The ambient solar wind magnetic field is briefly but strongly enhanced as the large partially ionized cometary atmosphere is compressed against the planetary surface. Just at the time of peak field enhancement, the solid part of the comet collides with the surface and the compressed fields are permanently imprinted by shock magnetization.
EFFECT OF SURFACE ROUGHNESS ON EMITTANCE OF NONMETALS

It has been observed experimentally, both at NBS and elsewhere, that the emittance of polished metals can be markedly increased by roughening the surface, by as much as a factor of 2 or 3. For nonmetals and particularly white ceramic materials, on the other hand, the emittance appears to be essentially independent of surface roughness, at least for wavelengths below 7 or 8 μ. This apparant anomaly is explained on the basis of the differences in the optical properties of the two types of materials.
Variational bounds on Darcy's constant

Prager’s variational method of obtaining upper bounds on the fluid permeability (Darcy’s constant) for slow flow through porous media is reexamined. By exploiting the freedom one has in choosing the trial stress distributions, several new results are derived. One result is a phase interchange relation for permeability; when the fluid-phase and particle-phase are interchanged for a fixed geometry, we find an upper bound on a linear combination of the complementary permeabilities. Another result is a proof of the monotone properties of the bounds. The optimal two-point bounds from this class of variational principles are evaluated numerically and compared to exact results of low density expansions for assemblages of spheres.
Hardware support for address mapping in PGAS languages: a UPC case study

The Partitioned Global Address Space (PGAS) programming model strikes a balance between the explicit, locality-aware, message-passing model and locality-agnostic, but easy-to-use, shared memory model (e.g. OpenMP). However, the PGAS memory model comes at a performance cost which limits both scalability and performance. Compiler optimizations are often not sufficient and manual optimizations are needed which considerably limit the productivity advantage. This paper proposes a hardware architectural support for PGAS, which allows the processor to efficiently handle shared addresses through new instructions. A prototype compiler is realized allowing to use the support with unmodified code, preserving the PGAS productivity advantage. Speedups of up to 5.5x are demonstrated on the unmodified NAS Parallel Benchmarks using the Gem5 full system simulator.
Integration, Cointegration and the Forecast Consistency of Structural Exchange Rate Models

Abstract We propose an alternative set of criteria for evaluating forecast rationality: the forecast and the actual series (1) have the same order of integration, (2) are cointegrated and (3) have a cointegrating vector consistent with long-run unitary elasticity of expectations. We denote forecasts that meet these criteria as `consistent'. Forecasts generated from monetary models generally pass (1). However, using the Johansen procedure, cointegration fails to hold the longer the horizon. Of the cointegrated pairs, (3) is not generally rejected. Using the Horvath–Watson procedure, imposing the unitary coefficient restriction, we find fewer instances of consistency, although a higher proportion of the cases of consistency are found at the longer horizons.
Design of decentralized observation schemes for large-scale interconnected systems: some new results

Abstract A new algorithm for the design of decentralized observation schemes for large-scale interconnected systems is presented. This algorithm offers a constructive procedure based on a stability result that employs the notion of block diagonal dominance in matrices, and is shown to improve considerably upon the existing results for the decentralized observer design problem. A principal contribution of this paper is the demonstration of how the observer gains can be tailored systematically to the existing interconnection pattern within the overall system. Although the present results are developed in the context of decentralized observation, they can be extended to the design of decentralized stabilization algorithms and to the design of decentralized model reference adaptive identification schemes.
Matrix-Based Image Reconstruction Methods for Tomography

Matrix methods of image reconstruction have not been used, in general, because of the large size of practical matrices, ill condition upon inversion and the success of Fourier-based techniques. An exception is the work that has been done at the Lawrence Berkeley Laboratory for imaging with accelerated radioactive ions. An extension of that work into more general imaging problems shows that, with a correct formulation of the problem, positron tomography with ring geometries results in well behaved matrices which can be used for image reconstruction with no distortion of the point response in the field of view and flexibility in the design of the instrument. Maximum Likelihood Estimator methods of reconstruction, which use the system matrices tailored to specific instruments and do not need matrix inversion, are shown to result in good preliminary images. A parallel processing computer structure based on multiple inexpensive microprocessors is proposed as a system to implement the matrix-MLE methods.
Aircraft automatic flight control system with model inversion

A simulator study was conducted to verify the advantages of a Newton-Raphson model-inversion technique as a design basis for an automatic trajectory control system in an aircraft with highly nonlinear characteristics. The simulation employed a detailed mathematical model of the aerodynamic and propulsion system performance characteristics of a vertical-attitude takeoff and landing tactical aircraft. The results obtained confirm satisfactory control system performance over a large portion of the flight envelope. System response to wind gusts was satisfactory for various plausible combinations of wind magnitude and direction.
Pascal program for generating tables of SU(3) Clebsch-Gordan coefficients

Abstract Pascal routines are provided that generate representations of the group SU (3) and tabulate the Clebsch-Gordan coefficients in the products of representations.
Unearthing the Infrastructure: Humans and Sensors in Field-Based Scientific Research

Distributed sensing systems for studying scientific phenomena are critical applications of information technologies. By embedding computational intelligence in the environment of study, sensing systems allow researchers to study phenomena at spatial and temporal scales that were previously impossible to achieve. We present an ethnographic study of field research practices among researchers in the Center for Embedded Networked Sensing (CENS), a National Science Foundation Science & Technology Center devoted to developing wireless sensing systems for scientific and social applications. Using the concepts of boundary objects and trading zones, we trace the processes of collaborative research around sensor technology development and adoption within CENS. Over the 10-year lifespan of CENS, sensor technologies, sensor data, field research methods, and statistical expertise each emerged as boundary objects that were understood differently by the science and technology partners. We illustrate how sensing technologies were incompatible with field-based environmental research until researchers "unearthed" their infrastructures, explicitly reintroducing human skill and expertise into the data collection process and developing new collaborative languages that emphasized building dynamic sensing systems that addressed human needs. In collaborating around a dynamic sensing model, the sensing systems became embedded not in the environment of study, but in the practices of the scientists.
Experimental evaluation of psychophysical distortion metrics for JPEG-encoded images

Two experiments for evaluating psychophysical distortion metrics in Joint Photographic Experts Group (JPEG) encoded images are described. The first is a threshold experiment, in which subjects determined the bit rate or level of distortion at which distortion was just noticeable. The second is a suprathreshold experiment in which subjects ranked image blocks according to perceived distortion. The results of these experiments were used to determine the predictive value of a number of computed image distortion metrics. It was found that mean-square-error is not a good predictor of distortion thresholds or suprathreshold perceived distortion. Some simple pointwise measures were in good agreement with psychophysical data; other more computationally intensive metrics involving spatial properties of the human visual system gave mixed results. It was determined that mean intensity, which is not accounted for in the JPEG algorithm, plays a significant role in perceived distortion.
Chandra Grating Spectroscopy of the X-Ray Binary 4U 1700–37 in a Flaring State

Chandra X-Ray Observatory grating spectra of the supergiant X-ray binary 4U 1700� 37 reveal emission lines from hydrogen- and helium-like S, Si, Mg, and Ne in the 4-13 Arange. The spectrum also shows fluorescent lines from S and Si and a prominent Fe Kline at 1.94 A ˚ . The lines contribute to the previously unaccounted '' soft excess '' in the flux in this range at orbital � � 0:7. The X-ray source was observed during intermittent flaring, and the strengths of the lines vary with the source state. The widths of the lines (FWHM � 1000 2000 km s � 1 ) can result from either Compton scattering or Doppler shifts. Power spectra of the hard X-rays show red noise, and the soft X-rays and lines show in addition quasi-periodic oscillations and a power spectral break. Helium-like triplets of Si and Mg suggest that the gas is not in a pure photo- ionization equilibrium. We discuss whether resonant scattering could affect the line ratios or whether a portion of the wind may be heated to temperatures T � 10 6 K. Subject headings: binaries: close — stars: individual (4U 1700� 37) — X-rays: binaries — X-rays: individual (4U 1700� 37)
Gas-phase velocimetry by nearly degenerate four-wave mixing

We demonstrate a new velocimetry technique for gas flows based on Nearly Degenerate Four-Wave Mixing (NDFWM). Measurements were performed on nitric oxide in a free-jet expansion using helium and argon as carrier gases, at flow velocities on the order of 1000 m/s. We obtained velocities by analyzing experimental spectra from the jet using a perturbative treatment of NDFWM that we extended to include an arbitrary bulk velocity. The results agreed with independent velocity measurements based on Laser-Induced Fluorescence (LIF), as well as with theoretical flow-field velocities, to better than 5% in all cases studied.
Properties of Synergies Arising from a Theory of Optimal Motor Behavior

Studies of the motor synergies reveal several interesting findings. First, optimal motor actions can be generated by summing a small number of scaled and time-shifted motor synergies, indicating that optimal movements can be planned in a low-dimensional space by using optimal motor synergies as motor primitives or building blocks. Second, some optimal synergies are task independent—they arise regardless of the task context—whereas other synergies are task dependent—they arise in the context of one task but not in the contexts of other tasks. Biological organisms use a combination of task-independent and task-dependent synergies. Our work suggests that this may be an efficient combination for generating optimal motor actions from motor primitives. Third, optimal motor actions can be rapidly acquired by learning new linear combinations of optimal motor synergies. This result provides further evidence that optimal motor synergies are useful motor primitives. Fourth, synergies with similar properties arise regardless if one uses an arm controlled by torques applied at the joints or an arm controlled by muscles, suggesting that synergies, when considered in “movement space,” are more a reflection of task goals and constraints than of fine details of the underlying hardware.
Variability in the Thermal Emission from Accreting Neutron Star Transients

The composition of the outer 100 m of a neutron star sets the heat flux that flows outward from the core. For an accreting neutron star in an X-ray transient, the thermal quiescent flux depends sensitively on the amount of hydrogen and helium remaining on the surface after an accretion outburst and on the composition of the underlying ashes of previous H/4He burning. Because H/4He has a higher thermal conductivity, a larger mass of H/4He implies a shallower thermal gradient through the low-density envelope and hence a higher effective temperature for a given core temperature. The mass of residual H and 4He varies from outburst to outburst, so the thermal quiescent flux is variable even though the core temperature is constant for timescales 104 yr. Heavy elements settle from an H/4He envelope in a few hours; we therefore model the quiescent envelope as two distinct layers, H/4He over heavier elements, and treat the mass of H/4He as a free parameter. We find that the emergent thermal quiescent flux can vary by a factor of 2-3 between different quiescent epochs. The variation is more pronounced at lower interior temperatures, making systems with low quiescent luminosities and frequent outbursts, such as SAX J1808.4-3658, ideal candidates from which to observe this effect. Because the ashes of H/4He burning are heavier than 56Fe, their thermal conductivity is greatly reduced. This increases the inferred crust temperature beyond previous estimates for a given effective temperature. We survey this effect for different ash compositions and apply our calculations to Cen X-4, Aql X-1, and SAX J1808.4-3658. In the case of Aql X-1, the inferred high interior temperature suggests that neutrino cooling contributes to the neutron star's thermal balance.
The point in weak semiprojectivity and AANR compacta

We initiate the study of pointed approximative absolute neighborhood retracts. Our motivation is to generate examples of C⁎-algebras that behave in unexpected ways with respect to weak semiprojectivity. We consider both weak semiprojectivity (WSP) and weak semiprojectivity with respect to the class of unital C⁎-algebras (WSP1). For a non-unital C⁎-algebra, these are different properties. One example shows a C⁎-algebra A can fail to be WSP while its unitization A˜ is WSP. Another example shows WSP1 is not closed under direct sums.
Hyperbolic geometry of multiply twisted knots

We investigate the geometry of hyperbolic knots and links whose diagrams have a high amount of twisting of multiple strands. We find information on volume and certain isotopy classes of geodesics for the complements of these links, based only on a diagram. The results are obtained by finding geometric information on generalized augmentations of these links.
Total Synthesis of Clavepictines A and B. Diastereoselective Cyclization of δ-Aminoallenes

The stereocontrolled total synthesis of (−)-clavepictine A (1A) and (+)-clavepictine B (1B) has been accomplished in an enantioselective fashion, which has unequivocally established the absolute configuration of 1A and 1B. The pivotal step in the synthesis is diastereoselective silver(I)-promoted cyclization of δ-amino allenes. Another key method includes cross-coupling of enol triflates of N-acyl lactams, which allows stereocontrolled functionalization of otherwise unreactive lactams under mild conditions. The utility of Beak's α-lithiation-substitution chemistry of N-BOC piperidines involving a functionalized aldehyde as the electrophile is demonstrated in the preparation of highly substituted nitrogen heterocycles. These new synthetic strategies should be of general synthetic utility in the stereoselective syntheses of quinolizidines, indolizidines, and related aza-heterocylces. Also included is the unique conformational preference of the highly substituted cis-quinolizidine core of clavepictines; the ...
Synthesis of 2′-β-fluoro-substituted nucleosides by a direct approach

Abstract Recent research activities directed toward the synthesis of 2′-β-fluoro-substitutednucleosides by nucleophilic displacement of an activated 2′-hydroxy group of preformedribonucleosides are reviewed. In the pyrimidine- C -nucleoside area, direct fluorination ofa 4,5′-anhydro- C -nucleoside triflate with TASF afforded the desired 2′-β-fluoro-1-methyl-ψ-uridine (C-FMAU). A similar strategy in regular pyrimidine series by using the corresponding2,5′- O -, 2,3′- O - and 5′,6-anhydro nucleoside derivatives did not give thedesired fluoro-containing products. An interesting triflyl migration was discovered whena triflate nucleoside was treated with LiCl in HMPA. The carbocyclic analog of theadenosine containing a fluorine in the 2′-β configuration was prepared from O 5′ , O 3′ , N 6 -tribenzoylaristeromycin in reaction with DAST. A similar treatment of purine nucleosidesled to decomposition. When, however, inosine, adenosine and guanosine were tritylatedat the 3′,5′ positions of the sugar moiety and suitably protected at the base, thecorresponding 2′-β-fluoro-substituted arabino -nucleosides were obtained by treatmentwith DAST in moderate to good yields. Deprotection afforded the desired F- ara -H,F- ara -A and F- ara -G. The role of the bulky trityl groups at the 3′,5′ positions of thesugar and the effect of C-3′- endo to C-2′- endo conformational shift on the reaction courseof 2′-hydroxyl group with DAST is discussed.
Capital-Intensive Software Technology

Each section of this four-part article deals with a different aspect of capital-intensive software technology. Together, they present an integrated view of the subject.
Remote Measurement of Gases Using Discretely Tunable Infrared Lasers

Single-ended laser radars using discretely tunable infrared gas lasers have been demonstrated to be capable of high-sensitivity remote measurement of gases. Two systems have been investigated: (1) a deuterium fluoride laser was used for remote measurement of the integrated concentration of HC1, CH4, and N20 between the lidar system and a topographic target; and (2) a CO2 laser was used for range-resolved measurement of water vapor using radiation backscattered from naturally occurring aerosols in the atmosphere. Calculations indicate that range-resolved concentration profiles can be obtained for many gases at a range of 10 km using commercially available components.