cssi/SciSciGPT-SciSciNet huggingface dataset:
Accuracy of smokers' risk perceptions

In response to disagreements about the extent to which smokers recognize the full risk of smoking-induced illness, an attempt was made to review all articles that have investigated smokers' risk perceptions. These diverse studies are grouped here into four categories, depending on the type of risk judgment solicited by researchers. This grouping shows that the apparent underestimation or overestimation of risk depends on how risk perceptions are assessed. No single conclusion about the accuracy of smokers' numerical risk estimates is possible since the accuracy depends entirely on the health outcome rated (e.g. lung cancer versus all deaths due to smoking). With other types of risk questions, smokers consistently acknowledge that smoking increases health risks, but they judge the size of these increases to be smaller and less well-established than do non-smokers. Finally, smokers minimize the personal relevance of the risks; they do not believe that they are as much at risk as other smokers of becoming addicted or suffering health effects. The accumulated data indicate that smokers continue to minimize their personal health risks.
Statistical theory for logistic mental test models with a prior distribution of ability

Abstract In previous work the logistic model of a mental test was introduced, and statistical inference methods were developed without the assumption of a prior distribution of ability. Such a distribution is assumed in the present paper, and corresponding statistical inference methods and distribution theory are developed. Results include detailed investigation of posterior distributions, given observed response patterns; point-estimation of ability, and its mean-squared error; and distributions of test scores and their moments. Some computational methods and detailed examples are given.
Quantum symmetries and stringy instantons

Abstract The quantum symmetry of many Landau-Ginzburg orbifolds appears to be broken by Yang-Mills instantons. However, isolated Yang-Mills instantons are not solutions of string theory: They must be accompanied by gauge anti-instantons, gravitational instantons, or topologically non-trivial configurations of the H field. We check that the configurations permitted in string theory do in fact preserve the quantum symmetry, as a result of non-trivial cancellations between symmetry breaking effects due to the various types of instantons. These cancellations indicate new constraints on Landau-Ginzburg orbifold spectra and require that the dilaton modulus mix with the twisted moduli in some Landau-Ginzburg compactifications. We point out that one can find similar constraints at all fixed points of the modular group of the moduli space of vacua.
Facile catalytic methods for intermolecular generation of allylic oxonium ylides and their stereoselective[2,3]-sigmatropic rearrangement

Abstract Allylic oxonium ylides, generated by rhodium(II) acetate-catalyzed decomposition of diazo carbonyl compounds in the presence of allyl methyl ethers, undergo the [2,3]-sigmatropic rearrangement with a high degree of diastereoselectivity.
On the chiral limit in lattice gauge theories with Wilson fermions

The chiral limit κ ≃ κc (β) in lattice gauge theories with Wilson fermions and problems related to near-to-zero (’exceptional’) eigenvalues of the fermionic matrix are studied. For this purpose we employ compact lattice QED in the confinement phase. A new estimator \(\tilde m_\pi\) for the calculation of the pseudoscalar mass mπ is proposed which does not suffer from ’divergent’ contributions at κ ≃ κc (β)We conclude that the main contribution to the pion mass comes from larger modes, and ’exceptional’ eigenvalues play no physical role. The behaviour of the subtracted chiral condensate \(\left\langle {\bar \psi \psi } \right\rangle _{subt}\) near κc(β) is determined. We observe a comparatively large value of \(\left\langle {\bar \psi \psi } \right\rangle _{subt} \cdot Z_P^{ - 1}\), which could be interpreted as a possible effect of the quenched approximation.
States of an ensemble of two-level atoms with reduced quantum uncertainty.

We generate entangled states of an ensemble of $5\ifmmode\times\else\texttimes\fi{}{10}^{4}$ $^{87}\mathrm{Rb}$ atoms by optical quantum nondemolition measurement. The resonator-enhanced measurement leaves the atomic ensemble, prepared in a superposition of hyperfine clock levels, in a squeezed spin state. By comparing the resulting reduction of quantum projection noise [up to 8.8(8) dB] with the concomitant reduction of coherence, we demonstrate a clock input state with spectroscopic sensitivity 3.0(8) dB beyond the standard quantum limit.
Unusual inorganic biradicals: a theoretical analysis.

Triatomic ions in the series FX2+, where X = O, S, Se, Te and Po are the terminal atoms, exhibit unusually high biradical characters (0.76 < β < 0.92), as measured from the analysis of Multi-Reference Configuration Interaction (MRCI) wavefunctions. Candidates in this series have the largest biradical character among the homologous, 18 valence electron CX22-, NX2-, X3 and OX2 (X = O, S, Se, Te and Po) systems. In the same scale the biradical character of ozone (O3) is just 0.19, whereas that of trimethylenemethane [C(CH2)3] is 0.97 (β=1 for an "ideal" biradical). For the 24 electron XO2 series, consisting of molecules with two oxygen atoms and a moiety X that is isoelectronic to oxygen, i.e. X= CH2, NH, O, F+, the singlet (S) state is lower than the triplet (T) one and the S-T splitting as well the barrier between their "open" and "ring" configurations was found to depend linearly with the inverse of the biradical character.
Higher Inductive Types as Homotopy-Initial Algebras

Homotopy Type Theory is a new field of mathematics based on the recently-discovered correspondence between Martin-Lof's constructive type theory and abstract homotopy theory. We have a powerful interplay between these disciplines - we can use geometric intuition to formulate new concepts in type theory and, conversely, use type-theoretic machinery to verify and often simplify existing mathematical proofs. Higher inductive types form a crucial part of this new system since they allow us to represent mathematical objects, such as spheres, tori, pushouts, and quotients, in the type theory. We investigate a class of higher inductive types called W-suspensions which generalize Martin-Lof's well-founded trees. We show that a propositional variant of W-suspensions, whose computational behavior is determined up to a higher path, is characterized by the universal property of being a homotopy-initial algebra. As a corollary we get that W-suspensions in the strict form are homotopy-initial.
Collusion, renegotiation and implementation

We study the implementation problem for exchange economies when agents can renegotiate the outcome assigned by the planner and can collude. We focus on the use of sequential mechanisms and present a simple sufficient condition for implementation with renegotiation in strong perfect equilibrium. We present an application to optimal risk sharing, showing that the possibility of collusion and renegotiation does not in general prevent the implementation of efficient allocations.
Compression bounds for wreath products

We show that if G and H are finitely generated groups whose Hilbert compression exponent is positive, then so is the Hilbert compression exponent of the wreath product G ? H. We also prove an analogous result for coarse embeddings of wreath products. In the special case G = Z, H = ℤ? ℤ our result implies that the Hilbert compression exponent of ℤ? (ℤ?ℤ) is at least 1/4, answering a question posed by several authors.
Statistical Analysis of Atmospheric Flight Gust Loads Analysis Data

To establish launch vehicle loads during atmospheric e ight, the statistical characteristics of the turbulence/gustinducedloadsneedtobedetermined.Recently,aMonteCarloanalysisprocedurewasdevelopedthatusesmeasured turbulence/gusts to establish launch-vehicle loads. The procedures developed to characterize the distribution of the data and to calculate tolerance bounds on these Monte Carlo loads are presented. Nomenclature C = cone dence level E = load enclosure FX or GX = cumulative distribution function of X FZ = cumulative distribution function of a standard normal random variable fX = probability density function of X n = sample size q X p = p-quantile of X s = sample standard deviation TX = tolerance bound for X tn,d , p = p-quantile of noncentral t distribution with n degrees of freedom and noncentrality parameter d X = random variable ¯ x = sample mean Z = standard normal random variable zp = standard normal p-quantile
Study of arpes data and d-wave superconductivity using electronic models in two dimensions

Abstract We review the results of an extensive investigation of photoemission spectral weight using electronic models for the high- T c superconductors. Here we show that some recently reported unusual features of the cuprates namely the presence of (i) flat bands, (ii) antiferromagnetically induced weight, and (iii) small quasiparticle bandwidths all have a natural explanation within the context of holes moving in the presence of robust antiferromagnetic correlations. Introducing interactions among the hole carriers, a model is constructed which has d x 2 − y 2 . superconductivity, an optimal doping of ~ 15% (caused by the presence of a large density of states at the top of the valence band), and a critical temperature ~ 100 K.
Reactivity and Microstructure of Rh and Rh-Ce in NO+CO

Changes in the activity and selectivity of Rh and Rh-Ce catalysts supported on Al[sub 2]O[sub 3] and SiO[sub 2] in the NO + CO reaction have been measured as a function of pretreatment. Rh-Ce/Al[sub 2]O[sub 3] had very low activity following a pretreatment in H[sub 2], which increased by a factor of [approximately]10 after heating in NO, and increased further in CO and in NO + CO. Rh-Ce catalysts also had very low N[sub 2] selectivity vs N[sub 2]O after treatments in H[sub 2], CO, and NO + CO, but not after heating in air or NO, and had a lower activation energy for NO reduction than Rh catalysts. The activities of Rh/Al[sub 2]O[sub 3] and Rh/SiO[sub 2] catalysts correlate well with changes in microstructures. An increased dispersion produced an increased activity at low temperatures except for the air pretreatment which oxidized the Rh and produced the lowest activity. Selectivity to N[sub 2] increased with increasing temperature below 300[degrees]C up to 100% for all pretreatments. All changes on alumina supported catalysts were reversible. The activity of Rh/SiO[sub 22] decreased after heating in NO + CO because of volatilization of Rh. 22 refs., 6 figs.
Tin-free reductive photochemical carboxymethylation of olefins with α-alkylthioacetates

Abstract An efficient tin-free reductive photochemical carboxymethylation of olefins with α-alkylthioacetates is developed, which (a) is an experimentally simple technique furnishing substituted derivatives of fatty acids in moderate to good yields, (b) is compatible with polar/protic functional groups and solvents, (c) does not require a special reducing reagent, (d) is fairly insensitive to the presence of dissolved oxygen and, generally, does not require degassing prior to irradiation. The critical feature of the mechanism in the “reluctance” of short-lived MeS • to group-transfer, resulting in hydrogen abstraction from the media.
Domino Tiling Congruence Modulo 4

The number of domino tilings of a region with reflective symmetry across a line is combinatorially shown to depend on the number of domino tilings of particular subregions, modulo 4. This expands upon previous congruency results for domino tilings, modulo 2, and leads to a variety of corollaries, including that the number of domino tilings of a k × 2k rectangle is congruent to 1 mod 4.
Risk Mitigation in Virtual Organizations

This paper examines the problem of risk mitigation in virtual organizations (VO's). We begin by discussing risk propensity in virtual organizations, and draw on a variety of research to suggest processes important in obtaining high levels of reliable performance in VO's. From this research we identify four processes we think are important: organizational structuring and design, communication, culture, and trust. Based on existing research done in conventional and high reliability organizations, we suggest how these processes may enhance reliability in VO's. We discuss how thoughtful management of these attributes can mitigate risk, and conclude with a theoretical and research agenda for future work.
Torons and D-brane bound states

Abstract We interpret instantons on a torus with twisted boundary conditions, in terms of bound states of branes. The interplay between the SU ( N ) and U (1) parts of the U ( N ) theory of N 4-branes allows the construction of a variety of bound states. The SU ( N ) and U (1) parts can contribute fractional amounts to the total instanton number which is integral. The geometry of non-self-intersecting 2-cycles in T 4 sheds some light on a number of properties of these solutions.
Diurnal tide in the upper atmosphere

Winds that have been revealed by sodium-vapor trails at heights of 90-130 km are analyzed to resolve the diurnal tidal component. An apparently significant component is discovered, whose variation with height is consistent with theoretical expectations and which may reasonably be attributed to the tide. Residual components, comprising a systematic prevailing wind and semidiurnal tide, and a rather irregular scatter, are also discussed.
A General Characterization of Interim Efficient Mechanisms for Independent Linear Environments

We consider the class of Bayesian environments with independent types, and utility functions which are both quasi-linear in a private good and linear in a one-dimensional private-value type parameter. We call these independent linear environments. For these environments, we fully characterize interim efficient allocation rules which satisfy interim incentive compatibility and interim individual rationality constraints. We also prove that they correspond to decision rules based on virtual surplus maximization, together with the appropriate incentive taxes. We illustrate these techniques with applications to auction design and public good provision.
The Mellin Transform and Spectral Properties of Toric Varieties

In this paper we apply the results of [W] on the twisted Mellin transform to problems in toric geometry. In particular, we use these results to describe the asymptotics of probability densities associated with the monomial eigenstates, zk, \( k \in \mathbb{Z}^{d} \), in Bargmann space and prove an “upstairs” version of the spectral density theorem of [BGU]. We also obtain for the zk’s, “upstairs” versions of the results of [STZ] on distribution laws for eigenstates on toric varieties.
Does sprawl reduce the black/white housing consumption gap?

Abstract Because unplanned suburban growth imposes social costs such as congestion, pollution, and reduction of open space, antisprawl policies are being adopted in fast‐growing metropolitan areas. This article explores one potential benefit of sprawl: It increases housing affordability, which may contribute to reducing the black/white housing consumption gap. The article uses 1997 American Housing Survey data to measure housing consumption for blacks and whites in metropolitan areas characterized by more and less sprawl. In sprawled areas, black households consume larger units and are more likely to own their homes than black households living in less sprawled areas.
Adaptive bandwidth control for efficient aggregate QoS provisioning

The paper proposes an adaptive bandwidth control algorithm that efficiently provides an aggregate loss guarantee to resolve the problem of inefficient bandwidth allocation due to incomplete, inaccurate traffic descriptors supplied by users. Because the control attempts to allocate only just enough bandwidth to meet the QoS requirement, the amount of bandwidth saving compared to static allocation can be substantial. Another distinct advantage of our control algorithm is that no a priori information on the traffic characteristics of the aggregate is required. From the simulation study, the proposed control can maintain the packet loss QoS while attaining very high utilization, and is robust against different system configurations and controller parameters.
Detecting changes in functional linear models

We observe two sequences of curves which are connected via an integral operator. Our model includes linear models as well as autoregressive models in Hilbert spaces. We wish to test the null hypothesis that the operator did not change during the observation period. Our method is based on projecting the observations onto a suitably chosen finite dimensional space. The testing procedure is based on functionals of the weighted residuals of the projections. Since the quadratic form is based on estimating the long-term covariance matrix of the residuals, we also provide some results on Bartlett-type estimators.
Trade Barriers as Bargaining Outcomes

Whether bilateral trade barrier data conform with the Grossman-Helpman (1995) model's predictions about ‘trade talks’ is examined in this article. A simple form of the prediction from the model is tested. Bilateral US-Japan and US-EU data from the 1990s are employed. The results are the first in the literature.
Solutions for Transient Heat Conduction With Solid Body Motion and Convective Boundary Conditions

The analytical solution for the problem of transient thermal conduction with solid body movement is developed for a parallelepiped with convective boundary conditions. An effective transformation scheme is used to eliminate the flow terms. The solution uses Green's functions containing convolution-type integrals, which involve integration over a dummy time, referred to as "cotime." Two types of Green's functions are used: one for short cotimes comes from the Laplace transform and the other for long cotimes from the method of separation of variables. A primary advantage of this method is that it incorporates internal verification of the numerical results by varying the partition time between the short and long components. In some cases, the long-time solution requires a zeroth term in the summation, which does not occur when solid body motion is not present. The existence of this zeroth term depends on the magnitude of the heat transfer coefficient associated with the convective boundary condition. An example is given for a two-dimensional case involving both prescribed temperature and convective boundary conditions. Comprehensive tables are also provided for the nine possible combinations of boundary conditions in each dimension.
A diacetate ketone-catalyzed asymmetric epoxidation of olefins

A fructose-derived diacetate ketone has been shown to be an effective catalyst for asymmetric epoxidation. High ee values have been obtained for a variety of trans and trisubstituted olefins including electron-deficient α,β-unsaturated esters as well as certain cis olefins.
ACCOUNTING STANDARDS AND VALUE RELEVANCE OF FINANCIAL STATEMENTS: AN INTERNATIONAL ANALYSIS

Abstract Using 17,743 firm-year observations of industrial companies in 21 countries from 1991 to 1997, this paper finds that the use of accrual accounting (versus cash accounting) negatively affects the value relevance of financial statements in countries with weak shareholder protection. This negative effect, however, does not exist in countries with strong shareholder protection. These findings are consistent with the belief that shareholder protection improves the effectiveness of accrual accounting, and suggest the importance of considering shareholder protection when formulating accounting policies related to accruals.
Nebular observations and stellar coronae

We examine the ways in which nebular observations of He II lambda4686 can be used to infer the existence of coronae or hot winds of early-type stars. The O VI lambdalambda3811, 3834 doublet is seen in the spectra of some central stars of planetary nebulae, and several authors have considered this to be evidence of a coronal wind. Observations of NGC 6751 reinforce this view by showing that radiative equilibrium model atmospheres cannot sufficiently photoexcite the O VI transitions without producing too much nebular emission at lambda4686. The hot gas in the coronal model produces a significant amount of radiation at energies above 54 eV; therefore, the He II Zanstra temperatures can be affected. Discrepancies between the He II Zanstra temperatures and effective temperatures derived from other methods may indicate coronal emission from planetary nebula central stars.Observations of diffuse nebulae about Population I early-type stars may also prove useful in detecting hot winds. The Lamers and Morton model of the wind of the O4f star xi Pup predicts a small amount of He/sup +/ ionizing radiation. If NGC 7635 is associated with the Of star BD +60/sup 0/2522, then the observation of nebular emission at lambda4686 may indicate coronal emission.
Asymmetric synthesis of S-(−)-cucurbitine

Abstract The asymmetric synthesis of (S)-(−)-cucurbitine in greater than 98 % ee is described. The key step of the synthesis involves 1,3-dipolar cycloaddition of azomethine ylide ( 1 ) 1 to α,β-dehydrolactone ( 3 ) to give pyrrolidine ( 6 ) as a single diastereomer.
Maximum energy traveltimes calculated in the seismic frequency band

Prestack Kirchhoff migration using first‐arrival traveltimes has been shown to produce poor images in areas of complex structure. To avoid this problem, I propose a new method for calculating traveltimes that estimates the traveltime of the maximum energy arrival, rather than the first arrival. This method estimates a traveltime that is valid in the seismic frequency band, not the usual high‐frequency approximation. Instead of solving the eikonal equation for the traveltime, I solve the Helmholtz equation to estimate the wavefield for a few frequencies. I then perform a parametric fit to the wavefield to estimate a traveltime, amplitude, and phase. The images created by using these parameters in a Kirchhoff imaging algorithm are comparable in quality to those created using full‐wavefield, finite‐difference, shot‐profile migration.
Random matrices, graphical enumeration and the continuum limit of toda lattices

In this paper we derive analytic characterizations for and explicit evaluations of the coefficients of the matrix integral genus expansion. The expansion itself arises from the large N asymptotic expansion of the logarithm of the partition function of N × N Hermitian random matrices. Its g th coefficient is a generating function for graphical enumeration on Riemann surfaces of genus g. The case that we particularly consider is for an underlying measure that differs from the Gaussian weight by a single monomial term of degree 2ν. Our results are based on a hierarchy of recursively solvable differential equations, derived through a novel continuum limit, whose solutions are the coefficients we want to characterize. These equations are interesting in their own right in that their form is related to partitions of 2g + 1 and joint probability distributions for conditioned random walks.
An IRAS survey of Galactic supernova remnants

A new independent survey of the IR emission for 161 Galactic supernova remnants are presented on the basis of Skyflux image data from the Infrared Astronomical Satellite. A new Galactic rotation curve with current IAU constants, R0 = 8.5 kpc and V0 = 220 km/s, is used to derive new kinematic distances for 11 of the 44 positively or possibly identified remnants. Temperature-sensitive flux ratio images are employed to help identify and define remnant emission structures and fluxes, particularly in complex regions. Of the 161 remnants examined, clear IR emission from 35 was found, with nine additional possible detections. Almost all young remnants (Tycho, Kepler, Cas A, Crab) were found to have a significant 12- and 25-micron flux, while older remnants are brightest at 60 and 100 microns. Correlations with mass and temperature indicate that older remnants are both colder and more massive, as expected from decreasing velocity. No radius-luminosity correlation was seen.
Phosphonamidate and phosphothioate dipeptides as potential inhibitors of VanX.

In an effort to prepare novel inhibitors of VanX, N-[(1-aminoethyl)hydroxyphosphinyl]-d-alanine 1 and S-[(aminoethyl)hydroxyphosphinyl]-thiolacetic acid 2 were synthesized and evaluated as inhibitors of VanX. Phosphonamidate 1 was shown to be a partial competitive inhibitor of VanX with a Ki of 36±3 μM, and phosphothioate 2 was shown not to inhibit VanX.
Turbulent convection in stellar interiors. I. Hydrodynamic simulation

We describe the results of 3D numerical simulations of oxygen shell burning and hydrogen core burning in a 23 M☉ stellar model. A detailed comparison is made to stellar mixing-length theory (MLT) for the shell-burning model. Simulations in 2D are significantly different from 3D, in terms of both flow morphology and velocity amplitude. Convective mixing regions are better predicted using a dynamic boundary condition based on the bulk Richardson number than by purely local, static criteria like Schwarzschild or Ledoux. MLT gives a good description of the velocity scale and temperature gradient for shell convection; however, there are other important effects that it does not capture, mostly related to the dynamical motion of the boundaries between convective and nonconvective regions. There is asymmetry between upflows and downflows, so the net kinetic energy flux is not zero. The motion of convective boundaries is a source of gravity waves; this is a necessary consequence of the deceleration of convective plumes. Convective overshooting is best described as an elastic response by the convective boundary, rather than ballistic penetration of the stable layers by turbulent eddies. The convective boundaries are rife with internal and interfacial wave motions, and a variety of instabilities arise that induce mixing through a process best described as turbulent entrainment. We find that the rate at which material entrainment proceeds at the boundaries is consistent with analogous laboratory experiments and simulation and observation of terrestrial atmospheric mixing. In particular, the normalized entrainment rate E = uE/σH is well described by a power-law dependence on the bulk Richardson number RiB = ΔbL/σ for the conditions studied, 20 RiB 420. We find E = ARi, with best-fit values log A = 0.027 ± 0.38 and n = 1.05 ± 0.21. We discuss the applicability of these results to stellar evolution calculations.
Metal-ceramic interfaces: Overlayer-induced reconstruction and magnetism of 4d transition-metal monolayers

Structural, electronic, and magnetic properties of metal-ceramic interfaces, M/MgO(001) (M=Pd, Rh, and Ru), have been investigated using the full potential linearized augmented-plane-wave method. Ru and Rh monolayers are found to be able to retain large spin magnetic moments on MgO(001) (1.95${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$ and 1.21${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$ for Ru and Rh, respectively)---indicating, in principle, the potential application of MgO(001) as a benign substrate for 4d monolayer magnetism. Significantly, according to our atomic-force determinations, the metal overlayers induce a sizable buckling reconstruction in the interfacial MgO layer, which enhances the M-MgO binding energy by 0.1 eV. The weak M-O interaction is mainly via tail effects; however, it affects the density of states at the Fermi level for Pd/MgO(001) significantly and completely eliminates the small magnetic moment of the free Pd monolayer (0.34${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$).
Spatial statistics of likely convective clouds in CloudSat data

[1] Spatial characteristics of cloud objects derived from 14 months of CloudSat data are analyzed with the aim of understanding global statistics for atmospheric convection. This study uses meteorological fields provided by NASA's Modern Era Reanalysis for Research and Applications (MERRA) and the European Center's ERA-Interim reanalysis to determine environmental conditions for the cloud objects. Width and aspect ratio statistics for clouds of likely convective origin are presented. Cloud object heights are compared with predictions from entraining plume models. A major finding of this study is that actual cloud depths are usually more than 50% smaller than those predicted by the plume models. This holds for a range of entrainment rate specifications, including rates based on observed cloud widths. A technique for isolating “mature” convective clouds based on their shape is proposed. When this technique is used to select objects, the comparison with the entraining plume model improves dramatically. Another result from this analysis is power law behavior in the cloud width distribution derived from CloudSat objects. After accounting for the difference between one-dimensional and two-dimensional sampling, the slope of the CloudSat distribution appears consistent with that found in earlier studies' cloud imagery. However, when clouds are selected using a minimum depth criterion, the resulting population is sharply peaked at widths close to this minimum depth. Finally, a weakly trimodal distribution of convective cloud depths is found, consistent with results from Johnson et al. (1999).
Effect of interface grading and lateral thickness variation on x-ray diffraction by InGaN/GaN multiple quantum wells

Abstract We develop a method for simulating the effects of interface grading and lateral variation in layer thickness on x-ray diffraction by InGaN/GaN multiple quantum wells (MQWs). Using the resulting simulation scheme, we perform detailed fitting of symmetric (0002) ω/2θ scans measured for a selection of typical InGaN/GaN MQW heterostructures. We find that incorporation of the combined effects of interface grading and thickness variation substantially improves the goodness of fit relative to a conventional model that assumes ideal MQW structure. The improved simulations of experiments reveal that the examined In x Ga 1 −x N/GaN MQWs (0.17≤ x ≤0.24) grown on the basal plane of GaN have graded heterointerface widths, w , in the range 0.5≤ w ≤1.1 nm concomitant with lateral variations in total MQW thickness of 0.7–6.3 nm rms. Atomic force microscopy of 10×10 μm 2 areas of the as-grown MQWs finds surface roughnesses of 1.0–5.6 nm rms in agreement with corresponding rms thickness variations found by simulating the XRD measurements. For samples with smaller thickness variations, higher order MQW satellites are observed in high-dynamic-range diffraction experiments and best-fit simulations find evidence for asymmetric MQW interface widths. The lower interfaces are narrower than the upper interfaces in agreement with recent transmission electron microscopy and atom-probe studies of MQW interfaces by other groups. These under-recognized structural features—heterointerface grading and lateral film-thickness variation—will influence not only x-ray diffraction, but also polarization, bandstructure, and carrier localization within InGaN-based MQW heterostructures.
Toe Spreading Ability in Men With Chronic Pelvic Pain Syndrome

We examined toe-spreading ability in subjects with chronic pelvic pain syndrome (CPPS) to test the hypothesis that subjects with CPPS could have deficiencies in lower extremity functions innervated by sacral spinal roots. Seventy two subjects with CPPS and 98 volunteer controls were examined as part of a larger study on CPPS. All the subjects underwent a detailed urologic and neurological examination including a toe-spreading examination with a quantitative scoring system. We compared the groups in terms of ability of toe-spreading as either "complete" (all toes spreading) or "incomplete" (at least one interdigital space not spreading) and also by comparing the number of interdigital spaces. For CPPS subjects only, we also analyzed the variation of the National Institutes of Health Chronic Prostatitis Symptom Index (NIH-CPSI) scales by toe-spreading categories. CPPS subjects were less often able to spread all toes than subjects without CPPS (p = 0.005). None of the NIH-CPSI sub-scales (pain, urinary symptoms, and quality of life), nor the total score showed an association with toe spreading ability. We found toe spreading to be diminished in subjects with CPPS. We hypothesize that incomplete toe spreading in subjects with CPPS may be related to subtle deficits involving the most caudal part of the spinal segments.
Symmetry-enhanced supertransfer of delocalized quantum states

Coherent hopping of excitation relies on quantum coherence over physically extended states. In this work, we consider simple models to examine the effect of symmetries of delocalized multi-excitation states on the dynamical timescales, including hopping rates, radiative decay and environmental interactions. While the decoherence (pure dephasing) rate of an extended state over N sites is comparable to that of a non-extended state, superradiance leads to a factor of N enhancement in decay and absorption rates. In addition to superradiance, we illustrate how the multi-excitonic states exhibit 'supertransfer' in the far-field regime—hopping from a symmetrized state over N sites to a symmetrized state over M sites at a rate proportional to MN. We argue that such symmetries could play an operational role in physical systems based on the competition between symmetry-enhanced interactions and localized inhomogeneities and environmental interactions that destroy symmetry. As an example, we propose that supertransfer and coherent hopping play a role in recent observations of anomalously long diffusion lengths in nano-engineered assembly of light-harvesting complexes.
Geometric compression with predictable compression ratio

Due to the proliferation of 3D objects, which are often expensive to manipulate in computers and to transmit across the Internet, techniques of geometric oppression are becoming increasingly important. Based on the parallelogram coordinate prediction and connectivity compression, this paper presents a near-lossless, two-pass, triangular mesh compression algorithm that achieves a compression ratio ranging from 15:1 to 40:1. An average compression ratio better than 20:1 has also been derived form a large collection of 3D objects ranging from simple man-made shapes to complex natural objects. Several derived compression algorithms, taking advantage of fold angles, have been implemented as part of the compression ratio and algorithm comparison. A linear predictive formula has been derived that effectively foretells the compression ratio from a derivable parameter of the fold-angle histogram of any given 3D-object model. The parameter x is defined as x= df/(tf- df), where df is the frequency of a dominant fold angle and tf is the total non-zero frequency. Experiments show that the predictive formula holds for most high-resolution models ($GTR1000 points). This predictability of compression ratio allows users to effectively predetermine the transmission time and the computing time requirements for any post-processing. Thus, the results presented here not only contribute algorithms for geometric compression by achieving good compression ratios but also provide valuable predictability for those dynamic or online applications.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Automated Modeling and Rapid Solution of Robot Dynamics Using the Symbolic Polynomial Technique

Fast and accurate solutions of the dynamic equations of a robot arm are required for real time on-line control. In this paper we present a new method for rapidly evaluating the exact dynamic state of a robot. This method uses a combination of symbolic and numerical computations on the equations of motion, which are developed in the form of polynomials—hence the name, the symbolic polynomial technique.
Deformations of large fundamental groups

A projective variety has a large fundamental group if its universal covering has no compact subvarieties. In this paper we investigate whether the property of a variety having a large fundamental groups is stable under K\"{a}hler deformations.
Kinetic vs. thermodynamic control in intramolecular diene cyclozirconation: Synthesis of elemol.

Abstract We predicted (ZINDO) that the major diastereomer from the equilibrating cyclozirconation of the α-terpineol derived diene 1 should be, after oxygenation, the diol 2 . We have confirmed this by converting 2 to (+)-elemol 8 . The diastereomeric control of the cyclozirconation under kinetic conditions is also striking, providing diol 3 .
Ultraviolet Emission-line Ratios of Cataclysmic Variables*

We present a statistical analysis of the ultraviolet emission lines of cataclysmic variables (CVs) based on ≈ 430 ultraviolet spectra of 20 sources extracted from the International Ultraviolet Explorer Uniform Low Dispersion Archive. These spectra are used to measure the emission-line fluxes of N V, Si IV, C IV, and He II and to construct diagnostic flux ratio diagrams. We investigate the flux ratio parameter space populated by individual CVs and by various CV subclasses (e.g., AM Her stars, DQ Her stars, dwarf novae, nova-like variables). For most systems, these ratios are clustered within a range of ~1 decade for log Si IV/C IV ≈ -0.5 and log He II/C IV ≈ -1.0 and ~1.5 decades for log N V/C IV ≈ -0.25. These ratios are compared to photoionization and collisional ionization models to constrain the excitation mechanism and the physical conditions of the line-emitting gas. We find that the collisional models do the poorest job of reproducing the data. The photoionization models reproduce the Si IV/C IV line ratios for some shapes of the ionizing spectrum, but the predicted N V/C IV line ratios are simultaneously too low by typically ~0.5 decades. Worse, for no parameters are any of the models able to reproduce the observed He II/C IV line ratios; this ratio is far too small in the collisional and scattering models and too large by typically ~0.5 decades in the photoionization models.
Bond additivity corrections for quantum chemistry methods

New bond additivity correction (BAC) methods have been developed for the G2 method, BAC-G2, as well as for a hybrid density functional theory (DFT) Moller−Plesset (MP)2 method, BAC−hybrid. These BAC methods use a new form of BAC corrections, involving atomic, molecular, and bond-wise additive terms. These terms enable one to treat positive and negative ions as well as neutrals. The BAC-G2 method reduces errors in the G2 method due to nearest-neighbor bonds. The parameters within the BAC-G2 method only depend on atom types. Thus the BAC-G2 method can be used to determine the parameters needed by BAC methods involving lower levels of theory, such as BAC−hybrid and BAC-MP4. The BAC−hybrid method is expected to scale well for large molecules. The BAC−hybrid method uses the differences between the DFT and MP2 predictions as an indication of the method's accuracy, whereas the BAC-G2 method uses its internal methods (G1 and G2MP2) to accomplish this. A statistical analysis of the error in each of the methods is ...
Photoemission of Electrons from Silicon into Silicon Dioxide

Electron transport in thermally grown layers of Si${\mathrm{O}}_{2}$ has been studied. Electrons are introduce into the oxide by photoemission from the adjoining silicon crystal. Specimens consist of a silicon crystal covered with an Si${\mathrm{O}}_{2}$ layer about 2 microns thick and, over this, a semitransparent gold electrode. On illuminating, light passes through the gold electrode and the oxide and is absorbed by the silicon. With appropriate voltage applied between gold and silicon, there is a steady photocurrent for light of wavelengths shorter than 2900 \AA{}. Various possible origins of the photocurrent were investigated, and it is concluded that the current is due to photoemission of electrons from the silicon into the Si${\mathrm{O}}_{2}$ conduction band. By analysis of the spectral response of the photocurrent a photoemission threshold of 4.25 eV is obtained, independent of whether the silicon is $n$-type or $p$-type. This is roughly 0.9 eV smaller than the threshold for photoemission from silicon into vacuum. Using the vacuum photoemission threshold and the known optical absorption edge for Si${\mathrm{O}}_{2}$, a diagram of the energy relations at the Si-Si${\mathrm{O}}_{2}$ interface is constructed. It is found that deep electron traps are present in concentrations around 3\ifmmode\times\else\texttimes\fi{}${10}^{14}$/${\mathrm{cm}}^{3}$. Trapped electrons are stable against thermal ionization for hours at room temperature in the dark but may be ionized by visible light. From the spectral response for ionization of traps it is found that the trap levels lie 2 eV below the conduction-band edge. Measurements of the kinetics of trapping give a capture cross section or 1.3\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}12}$ ${\mathrm{cm}}^{2}$, indicating that the trap is a Coulomb attractive center with a positive charge. Comparison of the magnitude of the capture cross section with a current model for capture by a Coulomb attractive center gives an estimate for the microscopic mobility $\ensuremath{\mu}$ of electron in the Si${\mathrm{O}}_{2}$ conduction band. The estimated value of $\ensuremath{\mu}$ is either 34 or 17 ${\mathrm{cm}}^{2}$/Vsec depending on whether the trapping center is singly or doubly charged.
Possibility of Coexistence of Bulk Superconductivity and Spin Fluctuations in UPt3

Convincing evidence has been discovered for bulk superconductivity in UPt3 at 0.54 K based on specific-heat, resistance, and ac susceptibility measurements. In addition, new evidence is presented that indicates that UPt3 is a spin-fluctuation system. If true, this is the first coexistent superconductor-spin-fluctuation system.
Measurement of the 6S → 7S Transition Polarizability in Atomic Cesium and an Improved Test of the Standard Model

The ratio of the off-diagonal hyperfine amplitude to the tensor transition polarizability $({M}_{\mathrm{hf}}/\ensuremath{\beta})$ for the $6S\ensuremath{\rightarrow}7S$ transition in cesium has been measured. The value of $\ensuremath{\beta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}27.024(43{)}_{\mathrm{expt}}(67{)}_{\mathrm{theor}}{a}_{0}^{3}$ is then obtained using an accurate semiempirical value of ${M}_{\mathrm{hf}}$. This is combined with a previous measurement of parity nonconservation in atomic cesium and previous atomic structure calculations to determine the value of the weak charge. The uncertainties in the atomic structure calculations are updated (and reduced) in light of new experimental tests. The result ${Q}_{W}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}72.06(28{)}_{\mathrm{expt}}(34{)}_{\mathrm{theor}}$ differs from the prediction of the standard model of elementary particle physics by 2.5 $\ensuremath{\sigma}$.
Computation of supersonic jet mixing noise for an axisymmetric CD nozzle using k-epsilon turbulence model

The turbulent mixing noise of a supersonic jet is calculated for a round convergent-divergent nozzle at the design pressure ratio. Aerodynamic computations are performed using the PARC code with a k-epsilon turbulence model. Lighthill's acoustic analogy combined with Ribner's assumption is adopted. The acoustics solution is based upon the methodology followed by GE in the MGB code. The source correlation function is expressed as a linear combination of second-order tensors. Assuming separable second-order correlations and incorporating Batchelor's isotropic turbulence model, the source term was calculated from the kinetic energy of turbulence. A Gaussian distribution for the time-delay of correlation was introduced. The computational fluid dynamics (CFD) solution was used to obtain the source strength as well as the characteristic time-delay of correlation. The effect of sound/flow interaction was incorporated using the high frequency asymptotic solution to Lilley's equation for axisymmetric geometries. Acoustic results include sound pressure level directivity and spectra at different polar angles. The aerodynamic and acoustic results demonstrate favorable agreement with experimental data.
An Analysis of the Necessary Decoder Corrections for Color Receiver Operation with Non-Standard Receiver Primaries

A method of color error correction for the Sulphide green and blue phosphors is developed. The method is general in nature and may be used to develop a correction matrix for phosphors with arbitrary color coordinates. A linear matrix is used to obtain an exact coordinate transformation and exact color reproduction within the capabilities of the new phosphors. A non-linear matrix, which gives approximate correction, can be simlated by adjusting the demodulating gains and angles of the color decoder.
Recent advances in free electron laser theory

Abstract Free electron lasers (FELs) have advanced to the stage where the experiments may be considered to have verified the essential FEL theories. The future research in FELs will be strongly tied to applications. There exist many types of lasers and optical techniques to obtain the required laser characteristics in the optical regime. FELs can make significant impact in the IR, UV and X-ray regimes, where conventional lasers are limited. Competition with other sources also requires FELs to be compact and user oriented. The theory developments addressing some of these issues will be presented in this article.
Multiagent control of self-reconfigurable robots

Abstract We demonstrate how multiagent systems provide useful control techniques for modular self-reconfigurable (metamorphic) robots. Such robots consist of many modules that can move relative to each other, thereby changing the overall shape of the robot to suit different tasks. Multiagent control is particularly well-suited for tasks involving uncertain and changing environments. We illustrate this approach through simulation experiments of Proteo, a metamorphic robot system currently under development.
Intrinsic Finite Element Modeling of Nonlinear Dynamic Response in Helical Springs

This paper presents an efficient intrinsic finite element approach for modeling and analyzing the forced dynamic response of helical springs. The finite element treatment employs intrinsic curvature (and strain) interpolation and vice rotation (and displacement) interpolation and, thus, can accurately and efficiently represent initially curved and twisted beams with a sparse number of elements. The governing equations of motion contain nonlinearities necessary for large curvatures. In addition, a constitutive model is developed, which captures coupling due to nonzero initial curvature and strain. The method is employed to efficiently study dynamically-loaded helical springs. Convergence studies demonstrate that a sparse number of elements accurately capture spring dynamic response, with more elements required to resolve higher frequency content, as expected. Presented results also document rich, amplitude-dependent frequency response. In particular, moderate loading amplitudes lead to the presence of secondary resonances (not captured by linearized models), while large loading amplitudes lead to complex dynamics and transverse buckling.