cssi/SciSciGPT-SciSciNet huggingface dataset:
Dynamics and control of a chain pendulum on a cart

A geometric form of Euler-Lagrange equations is developed for a chain pendulum, a serial connection of n rigid links connected by spherical joints, that is attached to a rigid cart. The cart can translate in a horizontal plane acted on by a horizontal control force while the chain pendulum can undergo complex motion in 3D due to gravity. The configuration of the system is in (S2)n×ℝ2. We examine the rich structure of the uncontrolled system dynamics: the equilibria of the system correspond to any one of 2n different chain pendulum configurations and any cart location. A linearization about each equilibrium, and the corresponding controllability criterion is provided. We also show that any equilibrium can be asymptotically stabilized by using a proportional-derivative type controller, and we provide a few numerical examples.
Theory of nodal s ± -wave pairing symmetry in the Pu-based 115 superconductor family

The spin-fluctuation mechanism of superconductivity usually results in the presence of gapless or nodal quasiparticle states in the excitation spectrum. Nodal quasiparticle states are well established in copper-oxide, and heavy-fermion superconductors, but not in iron-based superconductors. Here, we study the pairing symmetry and mechanism of a new class of plutonium-based high-Tc superconductors and predict the presence of a nodal s(±) wave pairing symmetry in this family. Starting from a density-functional theory (DFT) based electronic structure calculation we predict several three-dimensional (3D) Fermi surfaces in this 115 superconductor family. We identify the dominant Fermi surface "hot-spots" in the inter-band scattering channel, which are aligned along the wavevector Q = (π, π, π), where degeneracy could induce sign-reversal of the pairing symmetry. Our calculation demonstrates that the s(±) wave pairing strength is stronger than the previously thought d-wave pairing; and more importantly, this pairing state allows for the existence of nodal quasiparticles. Finally, we predict the shape of the momentum- and energy-dependent magnetic resonance spectrum for the identification of this pairing symmetry.
Piecewise linear approximations of fewest line segments

Schwerdtfeger has considered the problem of interpolation and curve fitting over a given partition by a sum of continuous sectionally linear functions. He showed how to construct an orthogonal system of these functions over a given partition and how to use this system to obtain an approximation of a given function which is best in the least square sense.
Graphene-coated Si mold for precision glass optics molding

Despite many attractive properties and well-developed micro/nano manufacturing technologies based on silicon (Si) wafers, severe adhesions between Si and glass at high temperature have limited its application as a mold material in precision glass molding. In this Letter, a coating using carbide-bonded graphene is introduced to build nonstick Si molds for glass molding. The coating has extraordinary mechanical properties and can effectively prevent Si-glass adhesion under high temperature. We demonstrated fabrications of a Fresnel lens and glass parts with micrometer pillars using graphene-coated Si molds. This newly developed process enables the use of Si as a mold material to fabricate sophisticated structures with high-precision dimensions that was not previously available. This technology will greatly improve precision glass molding process and allow high-precision low-cost glass optics to be manufactured in large quantity.
WISE Y DWARFS AS PROBES OF THE BROWN DWARF-EXOPLANET CONNECTION

We have determined astrometric positions for 15 WISE-discovered late-type brown dwarfs (six T8-9 and nine Y dwarfs) using the Keck-II telescope, the Spitzer Space Telescope, and the Hubble Space Telescope. Combining data from 8 to 20 epochs we derive parallactic and proper motions for these objects, which puts the majority within 15?pc. For ages greater than a few Gyr, as suggested from kinematic considerations, we find masses of 10-30 M Jup based on standard models for the evolution of low-mass objects with a range of mass estimates for individual objects, depending on the model in question. Three of the coolest objects have effective temperatures ~350?K and inferred masses of 10-15 M Jup. Our parallactic distances confirm earlier photometric estimates and direct measurements and suggest that the number of objects with masses below about 15 M Jup must be flat or declining, relative to higher mass objects. The masses of the coldest Y dwarfs may be similar to those inferred for recently imaged planet-mass companions to nearby young stars. Objects in this mass range, which appear to be rare in both the interstellar and protoplanetary environments, may both have formed via gravitational fragmentation?the brown dwarfs in interstellar clouds and companion objects in a protoplanetary disk. In both cases, however, the fact that objects in this mass range are relatively infrequent suggests that this mechanism must be inefficient in both environments.
On the Evans-Krylov theorem

We provide a short proof of the C 2,α interior estimate for convex fully nonlinear elliptic equations. This result was originally proved by L. C. Evans and N. Krylov. Our proof is based on the ideas from our work on integro-differential equations.
Priority pricing with application to time-shared computers

Where a commodity cannot be stored, the producer is generally unable to adjust the supply instantaneously to randomly fluctuating demands. When the demand is greater than the supply, some consumers can be put into queues. Since consumers can differ significantly in the urgency of their requests, important social costs may be involved if adequate procedures are not designed to favor the individuals whose requests are the most urgent.
SIS quasiparticle mixers with bow-tie antennas

We have designed and evaluated planar lithographed W-band SIS mixers with bow-tie antennas and several different RF cou;ling structures. Both Pb-In-Au/Pb-Bi and Nb/Pb-In-Au junctions were used, each with ωRNC«1. Single junctions and series arrays of five junctions directly attached to bow-tie antennas with no additional coupling structure gave poor performance, as expected. Single junctions with inductive microstrips and five-junction arrays with parallel wire inductors gave good coupling over bandwidths of ∼5 and 25 percent respectively. Good agreement was found between design calculations based on a simple equivalent circuit and measurements of the frequency dependence of the mixer gain. When good coupling was achieved, typical values of mixer gain GM (DSB)≃0 dB, noise TM(DSB)≃150 K, and receiver noise ∼200 K were observed. These measurements are referred to the cryostat window. When corrected for the estimated loss between the cryostat window and the antenna terminals, these values of gain are comparable to those observed for W-band waveguide mixers with IF matching, but the noise is significantly higher. There is evidence that ∼100 K radiation surrounding the mixer reduces the gain and increases the noise. No systematic difference was observed between the performance of Pb-In-Au/Pb-Bi junctions and Nb/Pb-In-Au junctions when the area of the latter was made three times smaller and the current density three times larger so as to maintain the same capacitance and resistance.
Theory of normal and superconducting properties of fullerene-based solids

Abstract Recent experiments on the normal state and superconducting properties of fullerene-based solids are used to constrain the proposal theories of the electronic nature of these materials. In general, models of superconductivity based on electron pairing induced by phonons are consistent with electronic band theory and analyses of the measured normal state transport properties. The experiments on normal state transport properties also yield estimates of the parameters characterizing these type II superconductors. It is argued that, at this point, a ‘standard model’ of phonons interacting with itinerant electrons may be a good first approximation for explaining the properties of the metallic fullerenes.
Tuning of Metal−Metal Bonding by Counterion Size in Hypothetical AeTiO2 Compounds

In a theoretical study of a “defect perovskite” structure of stoichiometry AeTiO2 (AE = alkaline earth metal, Be, Mg, Ca, Sr, and Ba), we find substantial Ti−Ti bonding tuned by the size of the Ae2+ cation. The bonding is one-dimensional, partially σ, partially π. These formal d2 systems are expected to be nonmagnetic and metallic. A competing (for same Ae) structural alternative, an ordered rock-salt structure, is magnetic.
Emergent reduction of electronic state dimensionality in dense ordered Li-Be alloys.

The two lightest metallic elements, lithium and beryllium, do not interact with each other to form an alloy in ambient conditions. But the structure and also the reactivity of many compounds can be altered fundamentally by subjecting them to high pressure. A new computational study suggests that in the case of lithium and beryllium, four alloys — LiBe, LiBe2, LiBe4 and Li3Be — should be stable at readily accessible pressures. Intriguingly, two-dimensional layers of almost ideal free-electron-like states appear within the three-dimensional crystal environment of one of the alloys, which may also have interesting superconducting properties. A computational study identifies pressure-induced reactivity between the two lightest metals, lithium and beryllium. Although normally not even miscible, they form a number of ordered alloy compounds stable at high pressures. Intriguingly, quasi-two-dimensional electronic states emerge within the three-dimensional crystal environment of one of the alloys. This feature appears as the high pressure 'squeezes' electrons away from the lithium atoms and into layers of almost ideal free-electron like states that are close to the beryllium atoms. High pressure is known to influence electronic structure and crystal packing, and can in some cases even induce compound formation between elements that do not bond under ambient conditions1,2,3. Here we present a computational study showing that high pressure fundamentally alters the reactivity of the light elements lithium (Li) and beryllium (Be), which are the first of the metals in the condensed state and immiscible under normal conditions4,5. We identify four stoichiometric Li x Be1-x compounds that are stable over a range of pressures, and find that the electronic density of states of one of them displays a remarkable step-like feature near the bottom of the valence band and then remains almost constant with increasing energy. These characteristics are typical of a quasi-two-dimensional electronic structure, the emergence of which in a three-dimensional environment is rather unexpected. We attribute this observation to large size differences between the ionic cores of Li and Be: as the density increases, the Li cores start to overlap and thereby expel valence electrons into quasi-two-dimensional layers characterized by delocalized free-particle-like states in the vicinity of Be ions.
Boundary regularity, uniqueness and non-uniqueness for AH Einstein metrics on 4-manifolds

Abstract This paper studies several aspects of asymptotically hyperbolic (AH) Einstein metrics, mostly on 4-manifolds. We prove boundary regularity (at infinity) for such metrics and establish uniqueness under natural conditions on the boundary data. By examination of explicit black hole metrics, it is shown that neither uniqueness nor finiteness holds in general for AH Einstein metrics with a prescribed conformal infinity. We then describe natural conditions which are sufficient to ensure finiteness.
Exact solutions of exceptional gauge theories from toric geometry

Abstract We derive four-dimensional gauge theories with the exceptional groups F 4 , E 8 , E 7 , and E 7 with matter, by starting from the duality between the heterotic string on K 3 and F-theory on a elliptically fibered Calabi-Yau 3-fold. This configuration is compactified to four dimensions on a torus, and by employing toric geometry, we compute the type IIB mirrors of the Calabi-Yaus of the type IIA string theory. We identify the Seiberg-Witten curves describing the gauge theories as ALE spaces fibered over a P 1 base.
A symmetry problem

Consider the Newtonian potential of a homogeneous bounded body DR 3 with known constant density and connected complement. If this potential equals c/|x| in a neighborhood of infinity, where c > 0 is a constant, then the body is a ball. This known result is now proved by a different simple method. The method can be applied to other problems.
The Extended Fe Distribution in the Intracluster Medium and the Implications Regarding AGN Heating

We present a systematic analysis of XMM-Newton observations of eight cool-core clusters of galaxies and determine the Fe distribution in the intracluster medium relative to the stellar distribution in the central dominant galaxy (CDG). Our analysis shows that the Fe is significantly more extended than the stellar mass in the CDG in all of the clusters in our sample, with a slight trend of increasing extent with increasing central cooling time. The excess Fe within the central 100 kpc in these clusters can be produced by Type Ia supernovae from the CDG over the past 3-7 Gyr. Since the excess Fe primarily originates from the CDG, it is a useful probe for determining the motion of the gas and the mechanical energy deposited by AGN outbursts over the past ~5 Gyr in the centers of clusters. We explore two possible mechanisms for producing the greater extent of the Fe relative to the stars in the CDG, bulk expansion of the gas and turbulent diffusion of the Fe. Assuming that the gas and Fe expand together, we find that a total energy of 1060-1061 erg s−1 must have been deposited into the central 100 kpc of these clusters in order to produce the currently observed Fe distributions. Since the required enrichment time for the excess Fe is approximately 5 Gyr in these clusters, this gives an average AGN mechanical power over this time of 1043-1044 erg s−1. The extended Fe distribution in cluster cores can also arise from turbulent diffusion. Assuming a steady state (i.e., the outward mass flux of Fe across a given surface is equal to the mass injection rate of Fe within that surface), we find that diffusion coefficients of 1029-1030 cm2 s−1 are required in order to maintain the currently observed Fe profiles. We find that heating by both turbulent diffusion of entropy and dissipation are important heating mechanisms in cluster cores. In half of the clusters with central cooling times greater than 1 Gyr, we find that heating by turbulent diffusion of entropy alone can balance radiative losses. In the remaining clusters, some additional heating by turbulent dissipation, with turbulent velocities of 150-300 km s−1, is required in order to balance radiative cooling. We also find that the average Type Ia supernova fraction within the central 100 kpc of these clusters is 0.53 (roughly twice the solar value), on the basis of the Si-to-Fe mass ratio. This implies a total (Type Ia plus core-collapse) supernova heating rate of less than 10% of the bolometric X-ray luminosity within the centers of clusters.
Zirconium Bis(Amido) Catalysts for Asymmetric Intramolecular Alkene Hydroamination

In situ combination of diphosphinic amides and Zr(NMe(2))(4) results in the formation of chiral zirconium bis(amido) complexes. The complexes are competent catalysts for intramolecular asymmetric alkene hydroamintion, providing piperidines and pyrrolidines in up to 80% ee and high yield. This system utilizes an inexpensive zirconium precatalyst and readily prepared ligands and is the first asymmetric alkene hydroamination catalyst based upon a neutral zirconium bis(amido) complex.
CARGuide: on-board computer for automobile route guidance

This paper describes the Computer for Automobile Route Guidance (CARGuide), a prototype system designed and built at Carnegie-Mellon University. CARGuide is a portable, microcomputer-based system to aid drivers in route finding and navigation in city streets. Given starting and destination intersections, CARGuide calculates an optimum route to the destination, displays portions of the street map containing the route, and highlights the streets on the route by flashing them on a display. It provides automatic or manual zooming into the map picture and speaks driving directions along the route. Both hardware and software design is explained in the paper. The hardware consists of a 68000 processor on a Multibus, bubble memories for secondary storage, a 128 x 128 dot matrix fluorescent display, a speech synthesizer, RAM, control and interface logic for the components, and a keyboard. A total of six circuit boards are used, four of them designed at CMU. A compact street map database is constructed from a regular street map and is stored in CARGuide's half megabyte secondary storage. An efficient optimum route-finding scheme was implemented, which uses a divide and conquer method and precomputed routes to improve the performance of a shortest-path algorithm. For optimum route calculations, streets are given weights estimating the travel time, and penalties are introduced for turns and crossing intersections. CARGuide has been tested by implementing a portion of the Pittsburgh street map.
Noise correlations of hard-core bosons: quantum coherence and symmetry breaking

Noise correlations, such as those observable in the time of flight images of a released cloud, are calculated for hard-core bosonic (HCBs) atoms. These second-order correlations are used to explore quantum coherence of strongly correlated bosons in the fermionized regime with and without external parabolic confinement. Our analysis points to distinctive new experimental signatures of the Mott phase. We also calculate noise correlations for the corresponding spin-1/2 XY model onto which the HCB system is standardly mapped. Our study shows important differences between the two systems due to the contribution of multiply occupied virtual states in HCBs. Such states do not exist in spin models. An interesting manifestation of such states is the breaking of particle–hole symmetry in HCB systems.
Employer size and compensation: the role of worker characteristics

The substantial effect of employer size on wages, health insurance and pension coverage is examined. Much of the size-related variation in compensation is shown to result from the types of jobs and workers hired by large employers. While firm and establishment size have similar effects on wages, firm-size effects clearly dominate in the provision of fringe benefits, particularly for pensions. Worker and job types explain a larger share of the size-related variation for wages than for health insurance or pension coverage. Possible explanations for these patterns are provided.
Job satisfaction, expectations, and gender: beyond the European Union

Purpose – Do gender differences in expected rewards contribute to gender differences in job satisfaction?Design/methodology/approach – This paper utilizes data collected from over 9,400 employees in five economically and culturally diverse former socialist economies, first, to determine whether there are gender differences in desired and expected rewards, and second, to assess whether the link between job satisfaction and expected reward varies by gender or reward desirability.Findings – This paper finds that for women, job satisfaction is positively linked to both extrinsic and intrinsic rewards, but for men, job satisfaction tends to be positively linked to extrinsic rewards. When reward desirability is included, more often for women than for men, non‐monetary rewards are positively linked to job satisfaction regardless of whether they are viewed as desirable. Among men, the link between job satisfaction and a particular reward tends to be stronger if the reward is desired, although for job security thi...
News on strangeness at ultrarelativistic energies—review of microscopic models

We review recent developments in the field of microscopic transport model calculations for ultrarelativistic heavy ion collisions. In particular, we focus on the strangeness production, for example, the -meson and its role as a messenger of the early phase of the system evolution. Moreover, we discuss the important effects of the (soft) field properties on the multiparticle system. We outline some current problems of the models as well as possible solutions to them.
Effect of Capillary Heterogeneity on Buckley-Leverett Displacement

The Buckley-Leverett (BL) equation has been routinely used for the description of immiscible displacement in laboratory operations and for parameter estimation and prediction. Recent advances, however, have led to a serious challenge of the validity of many of the traditional theories. For the case of BL displacement, most studies have examined heterogeneity effects as they relate to viscous fingering. In this paper, the authors investigate the effects of capillary heterogeneity induced by variations in permeability in the direction of displacement. The authors study a variety of heterogeneity profiles, both uncorrelated and correlated spatially. The authors find that capillary heterogeneity significantly affects the saturation distributions, which closely follow the heterogeneity variation. The saturation response is stronger at lower rates, at more unfavorable mobility, under drainage conditions, and for smaller spatial correlations. The results are in agreement with available experimental data for primary drainage and secondary imbibition. They may be useful in the interpretation of saturation profiles and the identification of heterogeneity.
Stability characteristics for flows of the vortex-sheet type

Calcul des conditions interfaciales pour une nappe tourbillonnaire cylindrique ou une couche de fluide cylindrique avec des distributions de densite et vitesse et un champ magnetique dependants du rayon pour des ecoulements tourbillonnaires compressibles isentropiques soumis a des perturbations arbitraires. La deformation de la nappe ou de la couche affecte l'ecoulement de deux manieres: perturbation du champ de pression total et perturbation du champ de force centrifuge cree par les composantes azimutales de la vitesse et du flux magnetique. Etude des conditions interfaciales et de leurs caracteristiques de stabilite pour une classe generale d'ecoulements incompressibles soumis a des perturbations temporelles
A Bayesian significance test of the stationarity of regression parameters

This paper presents a Bayesian significance test for stationarity of a regression equation using the highest posterior density credible set. In addition, a solution to the BehrensFisher problem is provided. From a Monte Carlo simulation study, it has been shown that the Bayesian significance test has stronger power than the Cusum and the Cusum of squares tests. The Bayesian significance test may be useful in detecting individual parameter nonstationarity.
Atmospheric compensation for WorldView-2 satellite and in-water component retrieval

In the present work, the WorldView-2 (WV2) capability for retrieving Case 2 water components is analyzed. In the Case 2 water problem, the sensor-reaching signal due to water is very small when compared to the signal due to the atmospheric effects. Therefore, adequate atmospheric compensation becomes an important first step to accurately retrieve water parameters. The problem becomes more difficult when using multispectral imagery as there are typically only a handful of bands suitable for performing atmospheric compensation. In this work, we test atmospheric compensation techniques for the WV2 satellite, enabling it to be used for water constituent retrieval in both deep and shallow water. A look-up-table (LUT) methodology is implemented to retrieve the water parameters for a simulated case study. The in-water radiative transfer code HydroLight is used to simulate reflectance data in this study while the MODTRAN code is used to simulate atmospheric effects. This data is used to test the proposed methodology. Finally, a sensitivity analysis is performed to evaluate how sensitive the constituent retrieval process is to adequate atmospheric compensation.
Incentive schemes for Internet congestion management: Raffles versus time-of-day pricing

The Internet is plagued with congestion problems of growing severity which are worst at peak periods. In this paper, we compare two schemes that incentivize users to shift part of their usage from the peak-time to the off-peak time. The traditional time-of-day pricing scheme gives a fixed reward per unit of shifted usage. Conversely, the raffle-based scheme provides a random reward distributed in proportion of each user's fraction of the total shifted usage. Using a game-theoretic model, we show that both schemes can achieve an optimal level of decongestion at a unique Nash equilibrium. We provide a comparison of the schemes' sensitivity to uncertainty of the users' utilities.
Recent Observations of Plasma and Alfvénic Wave Energy Injection at the Base of the Fast Solar Wind

We take stock of recent observations that identify the episodic plasma heating and injection of Alfvenic energy at the base of fast solar wind (in coronal holes). The plasma heating is associated with the occurrence of chromospheric spicules that leave the lower solar atmosphere at speeds of order 100 km/s, the hotter coronal counterpart of the spicule emits radiation characteristic of root heating that rapidly reaches temperatures of the order of 1 MK. Furthermore, the same spicules and their coronal counterparts (“Propagating Coronal Disturbances”; PCD) exhibit large amplitude, high speed, Alfvenic (transverse) motion of sufficient energy content to accelerate the material to high speeds. We propose that these (disjointed) heating and accelerating components form a one-two punch to supply, and then accelerate, the fast solar wind. We consider some compositional constraints on this concept, extend the premise to the slow solar wind, and identify future avenues of exploration.
Smoothed and iterated bootstrap confidence regions for parameter vectors

The construction of confidence regions for parameter vectors is a difficult problem in the nonparametric setting, particularly when the sample size is not large. We focus on bootstrap ellipsoidal confidence regions. The bootstrap has shown promise in solving this problem, but empirical evidence often indicates that the bootstrap percentile method has difficulty in maintaining the correct coverage probability, while the bootstrap percentile- t method may be unstable, often resulting in very large confidence regions. This paper considers the smoothed and iterated bootstrap methods to construct the bootstrap percentile method ellipsoidal confidence region. The smoothed bootstrap method is based on a multivariate kernel density estimator. An optimal bandwidth matrix is established for the smoothed bootstrap procedure that reduces the coverage error of the bootstrap percentile method. We also provide an analytical adjustment to the nominal level to reduce the computational cost of the iterated bootstrap method. Simulations demonstrate that the methods can be successfully applied in practice.
Enantioselective Selenocyclization via Dynamic Kinetic Resolution of Seleniranium Ions by Hydrogen-Bond Donor Catalysts

Highly enantioselective selenocyclization reactions are promoted by the combination of a new chiral squaramide catalyst, a mineral acid, and an achiral Lewis base. Mechanistic studies reveal that the enantioselectivity originates from the dynamic kinetic resolution of seleniranium ions through anion-binding catalysis.
Chemical synthesis of the tumor-associated globo H antigen

A derivative of the tumor-associated globo H antigen, a complex hexasaccharide, was synthesized by a convergent and efficient [3+2+1] strategy using various glycosylation methods. All glycosylation reactions afforded good to excellent yields and outstanding stereoselectivity, including the installation of cis α-linked D-galactose and L-fucose. The longest linear sequence for this synthesis was 11 steps from a galactose derivative 11 to give an overall yield of 2.6%. The synthetic target had a free and reactive amino group at the glycan reducing end, facilitating its conjugation with other molecules for various applications.
Edit distance with move operations

The traditional edit-distance problem is to find the minimum number of insert-character and delete-character (and sometimes change character) operations required to transform one string into another. Here we consider the more general problem of a string represented by a singly linked list (one character per node) and being able to apply these operations to the pointer associated with a vertex as well as the character associated with the vertex. That is, in O(1) time, not only can characters be inserted or deleted, but substrings can be moved or deleted. We limit our attention to the ability to move substrings and leave substring deletions for future research. Note that O(1) time substring move operation implies O(1) substring exchange operation as well, a form of transformation that has been of interest in molecular biology. We show that this problem is NP-complete, and that a ''recursive'' sequence of moves can be simulated with at most a constant factor increase by a non-recursive sequence. Although a greedy algorithm is known to have poor (a polynomial factor) worst case performance, we present a polynomial time greedy algorithm for non-recursive moves which on a subclass of instances of a problem of size n achieves an approximation factor to optimal of at most O(logn). The development of this greedy algorithm shows how to reduce moves of substrings to moves of characters, and how to convert moves of characters to only inserts and deletes of characters.
Differential systems with Fuchsian linear part: Correction and linearization, normal forms and multiple orthogonal polynomials

Abstract Differential systems with a Fuchsian linear part are studied in regions including all the singularities in the complex plane of these equations. Such systems are not necessarily analytically equivalent to their linear part (they are not linearizable) and obstructions are found as a unique nonlinear correction after which the system becomes formally linearizable. More generally, normal forms are found. The corrections and the normal forms are found constructively. Expansions in multiple orthogonal polynomials and their generalization to matrix-valued polynomials are instrumental to these constructions.
Bicyclist safety performance functions for a U.S. city

Efforts have intensified to apply a more evidence-based approach to traffic safety. One such effort is the Highway Safety Manual, which provides typical safety performance functions (SPFs) for common road types. SPFs model the mathematical relationship between frequency of crashes and the most significant causal factors. Unfortunately, the manual provides no SPFs for bicyclists, despite disproportionately high fatalities among this group. In this paper, a method for creating city-specific, bicycle SPFs is presented and applied to Boulder, Colorado. This is the first time a bicycle SPF has been created for a U.S. city. Such functions provide a basis for both future investigations into safety treatment efficacy and for prioritizing intersections to better allocate scarce funds for bicycle safety improvements. As expected, the SPFs show that intersections with higher bicyclist traffic and higher motorist traffic have higher motorist-cyclist collisions. The SPFs also demonstrate that intersections with more cyclists have fewer collisions per cyclist, illustrating that cyclists are safer in numbers. Intersections with fewer than 200 entering cyclists have substantially more collisions per cyclist.
Efficacy of the Flutter device for airway mucus clearance in patients with cystic fibrosis

The Flutter is a handheld device designed to facilitate clearance of mucus in hypersecretory lung disorders. Exhalation through the Flutter results in oscillations of expiratory pressure and airflow, which vibrate the airway walls (loosening mucus), decrease the collapsibility of the airways, and accelerate airflow, facilitating movement of mucus up the airways. We studied 18 patients with cystic fibrosis and mild to moderate lung disease to determine the efficacy of the Flutter in clearing mucus from the airways. The amount of sputum expectorated (measured by weight) when the Flutter was used was compared with the amount expectorated with vigorous voluntary coughing and with postural drainage (chest percussion and vibration). The amount of sputum expectorated by subjects using the Flutter was more than three times the amount expectorated with either voluntary cough or postural drainage (p < 0.001). There were no adverse effects. The Flutter is simple to use, inexpensive, and fully portable, and once the patient and family are instructed in its use, it does not require the assistance of a caregiver. For hospitalized patients, elimination of the need for a therapist could reduce health care costs. Long-term studies of the use of the Flutter seem justified to determine its effects on pulmonary function and outcome.
Nonsingular surface quasi-geostrophic flow

Abstract The dynamics of large eddies in the atmosphere and oceans is described by the surface quasi-geostrophic equation, which is reminiscent of the Euler equations. Thermal fronts build up rapidly. Two different numerical methods combined with analytical criteria are used to show there are no singularities in finite time.
Time-Varying Expected Small Firm Returns and Closed-End Fund Discounts

This article describes the relation between closed-end fund discounts and time-varying expected excess returns on small firms. The results indicate that closed-end fund discounts forecast future excess returns on small firms. The information in discounts is independent of that in other commonly used forecasting variables such as the dividend yield on the market, the default spread, and the term spread. Furthermore, the closed-end fund discount forecasts only the small firm factor return and is the only variable that forecasts the small firm factor return. Additional tests indicate that the information in discounts is related to expectations of future earnings growth and expectations of future inflation. These results provide significant support for a rational explanation of the time-series relationship between discounts and expected returns on small firms. Article published by Oxford University Press on behalf of the Society for Financial Studies in its journal, The Review of Financial Studies.
S Matrix in semiclassical approximation

Abstract It is shown that the tree approximation currently utilized in connection with phenomenological chiral Lagrangians corresponds to a semiclassical approximation applied to the S-matrix in quantum field theory. Some invariance properties of the S-matrix are derived in this framework.
Chaotic mixing in noisy Hamiltonian systems

This paper summarizes an investigation of the effects of low-amplitude noise and periodic driving on phase-space transport in three-dimensional Hamiltonian systems, a problem directly applicable to systems like galaxies, where such perturbations reflect internal irregularities and/or a surrounding environment. A new diagnostic tool is exploited to quantify the extent to which, over long times, different segments of the same chaotic orbit evolved in the absence of such perturbations can exhibit very different amounts of chaos. First-passage-time experiments are used to study how small perturbations of an individual orbit can dramatically accelerate phase-space transport, allowing ‘sticky’ chaotic orbits trapped near regular islands to become unstuck on surprisingly short time-scales. The effects of small perturbations are also studied in the context of orbit ensembles with the aim of understanding how such irregularities can increase the efficacy of chaotic mixing. For both noise and periodic driving, the effect of the perturbation scales roughly logarithmically in amplitude. For white noise, the details are unimportant: additive and multiplicative noise tend to have similar effects and the presence or absence of friction related to the noise by a fluctuation–dissipation theorem is largely irrelevant. Allowing for coloured noise can significantly decrease the efficacy of the perturbation, but only when the autocorrelation time, which vanishes for white noise, becomes so large that there is little power at frequencies comparable with the natural frequencies of the unperturbed orbit. This suggests strongly that noise-induced extrinsic diffusion, like modulational diffusion associated with periodic driving, is a resonance phenomenon. Potential implications for galaxies are discussed.
Calculating fermion masses in superstring derived standard-like models

One of the intriguing achievements of the superstring derived standard-like models in the free fermionic formulation is the possible explanation of the top quark mass hierarchy and the successful prediction of the top quark mass. An important property of the superstring derived standard-like models, which enhances their predictive power, is the existence of three and only three generations in the massless spectrum. Up to some motivated assumptions with regard to the light Higgs spectrum, it is then possible to calculate the fermion masses in terms of string tree level amplitudes and some VEVs that parameterize the string vacuum. I discuss the calculation of the heavy generation masses in the superstring derived standard-like models. The top quark Yukawa coupling is obtained from a cubic level mass term while the bottom quark and tau lepton mass terms are obtained from nonrenormalizable terms. The calculation of the heavy fermion Yukawa couplings is outlined in detail in a specific toy model. The dependence of the effective bottom quark and tau lepton Yukawa couplings on the flat directions at the string scale is examined. The gauge and Yukawa couplings are extrapolated from the string unification scale to low energies. Agreement with {alpha}{sub strong}, sin{sup 2}more » {theta}{sub W} and {alpha}{sub em} at M{sub Z} is imposed, which necessitates the existence of intermediate matter thresholds. The needed intermediate matter thresholds exist in the specific toy model. The effect of the intermediate matter thresholds on the extrapolated Yukawa couplings is studied. It is observed that the intermediate matter thresholds help to maintain the correct b/{tau} mass relation. It is found that for a large portion of the parameter space, the LEP precision data for {alpha}{sub strong}, sin{sup 2} {theta}{sub W} and {alpha}{sub em}, as well as the top quark mass and the b/{tau} mass relation can all simultaneously be consistent with the superstring derived standard-like models.« less
Planetesimal Disk Evolution Driven by Planetesimal-Planetesimal Gravitational Scattering

We investigate the process of inhomogeneous planetesimal disk evolution caused by planetesimal-planetesimal gravitational scattering. We develop a rather general approach based on kinetic theory that self-consistently describes the evolution in time and space of both the disk's surface density and its kinematic properties—dispersions of eccentricity and inclination. The gravitational scattering of planetesimals is assumed to be in the dispersion-dominated regime, which considerably simplifies the analytical treatment. The resultant equations are of the advection-diffusion type. Distance-dependent scattering coefficients entering these equations are calculated analytically under the assumption of two-body scattering to leading order in the Coulomb logarithm. They are essentially nonlocal in nature. Our approach allows one to explore the dynamics of nonuniform planetesimal disks with arbitrary mass and random-velocity distributions. It can also naturally include other physical mechanisms that are important for the evolution of such disks—gas drag, migration, and so on.
Mars global atmospheric oscillations - Annually synchronized, transient normal-mode oscillations and the triggering of global dust storms

Transient events of an unusual character have been discovered in the daily pressure variations of the Mars atmosphere's pressure at the planetary surface which last only a few Martian days, appear to repeat on an annual basis, cover a large part of the given day's hemisphere, occur in pairs separated by 20-days in some cases, and coincide with the annual pressure minimum. They also consist of spectral components nearly identical in frequency with diurnal and semidiurnal harmonics. It is presently suggested that these events are Kelvin, normal-mode, transient, global oscillations. An almost-diurnal and an almost-semidiurnal high-frequency global oscillation distinct from solar-driven tides may be common on Mars.
Information transmission under conditions of sensory shielding

WE present results of experiments suggesting the existence of one or more perceptual modalities through which individuals obtain information about their environment, although this information is not presented to any known sense. The literature1–3 and our observations lead us to conclude that such abilities can be studied under laboratory conditions.
Is Japan's trade (still) different?

Abstract Does Japanese trade in manufactured goods differ from the rest-of-the world average and from the US? We use a simple industry-level gravity model and 1981–1998 data to answer this question. We construct a measure of normalized imports by dividing bilateral industry-level imports by the importer's aggregate absorption and the exporter's industry output. We find that Japan imports less than other countries, but also exports less than other countries. Relative to the US, Japanese export performance is half as strong today as it was in the mid-1980s. Bilaterally, Japan is more open to imports from the US than the US is to imports from Japan. This means that the US runs a trade surplus with Japan in normalized imports of manufactured goods. J. Japanese Int. Economies 17 (4) (2003) 507–519.
The joint demand for health care, leisure, and commodities: Implications for health care finance and access in Vietnam

Abstract This paper explores linkages between the demand for health care providers and the consumption of food, non-food goods, and leisure in Vietnam, using a mixed continuous/discrete dependent variable model. Cross-price elasticities calculated from the model suggest there are strong substitution effects between health care, leisure, and certain commodities. The model allows us to explore the implications of replacing user fees with alternative forms of health care finance, such as commodity taxes. In particular, the results suggest financing public health care services with a non-food sales tax rather than user fees would be more progressive and would improve access to care.
Short-duration Gamma-ray Bursts From Off-axis Collapsars

We present two-dimensional (2D) high-resolution hydrodynamic simulations of the relativistic outflows of long-duration gamma-ray burst (GRB) progenitors. We analyze the properties of the outflows at wide off-axis angles, produced by the expansion of the hot cocoon that surrounds the jet inside the progenitor star. We find that the cocoon emission at wide angles may have properties similar to those of the subclass of short-duration GRBs with persistent X-ray emission. We compute the predicted duration distribution, redshift distribution, and afterglow brightness, and we find that they are all in agreement with the observed properties of short GRBs with persistent emission. We suggest that a supernova component, the properties of the host galaxies, and late afterglow observations can be used as a crucial test to verify this model.
Mechanistic studies on the hydroxylation of methane by methane monooxygenase.

Methanotrophs are bacteria that live on methane as their only source of carbon.1 The first step in their utilization of this simplest of all hydrocarbons is its selective conversion to methanol. Subsequent biochemical pathways transform methanol to formaldehyde, which in turn is processed into biomass. Further oxidation of formaldehyde to carbon dioxide provides energy that is stored for later use as NADH.2 The conversion of methane to methanol is catalyzed at the active site of a metalloenzyme known as methane monooxygenase, or MMO.3-9
Metal oxidation kinetics and the transition from thin to thick films.

We report an investigation of growth kinetics and transition from thin to thick films during metal oxidation. In the thin film limit ( 1 μm) and leads to parabolic growth kinetics dl/dt ∝ 1/l, where l is the oxide film thickness. Theory presented here unifies the two models and provides a complete description of oxidation including the transition from thin to thick film. The range of validity of Cabrera and Mott's theory and Wagner's theory can be well defined in terms of the Debye–Huckel screening length. The transition from drift-dominated ionic transport for thin film to diffusion-dominated transport for thick film is found to strictly follow the direct logarithmic law log(dl/dt) ∝ −l that is frequently observed in many experiments.
A less dusty future

[1] Atmospheric desert dust is potentially highly sensitive to changes in climate, carbon dioxide and human land use. In this study we use 6 different scenarios of the processes responsible for changes in source areas and explore changes in desert dust loading in pre-industrial and future climates, although all the scenario results are likely to be sensitive to the climate model simulations used for this study. Simulations suggest that future dust may be 20 to 60% lower than current dust loadings. The anthropogenic portion of the current dust loading may be as large as 60%, or humans may have caused a 24% decrease in desert dust, depending on the relative importance of land use, carbon dioxide and human induced climate change. These results suggest there may be a high sensitivity of ‘natural aerosols’ to human intervention, which has enormous implications for climate and biogeochemistry in the future.
SCALING OF THE TRANSMISSION AND REFLECTION COEFFICIENTS NEAR THE MOBILITY EDGE

The behavior of the optical transmission and reflection coefficients near the mobility edge of a disordered medium which elastically scatters light are discussed using a scaling theory. The transmission coefficient shows an interesting dependence on slab thickness. The coherent back scattering peak has a width determined by the correlation length and a height which also depends on this length. Both become small near the mobility edge. The effects of absorption are found to be important.
Alcohol consumption and risky sexual behavior among young adults: evidence from minimum legal drinking age laws

This paper exploits the discrete jump in alcohol consumption at the minimum legal drinking age (MLDA) in the USA and uses a regression discontinuity design to investigate the relationship between drinking and risky sexual behaviors among young adults. Using confidential data from the National Longitudinal Survey of Youth (1997 Cohort), we document that young adults tend to drink up to 2.1 days more once they are granted legal access to alcohol at age 21. Although the discrete jump in alcohol consumption at the MLDA is associated with an increase in the probability of having sex by up to 7.8 percentage points, it does not have a significant impact on the probability of engaging in risky sexual behaviors among young adults. We also document that the effect of the MLDA on the probability of using several different birth control methods is not significant for those who had sex in the past 4 weeks. These results are robust under alternative specifications and imply that although the MLDA law is quite effective in reducing alcohol consumption among young adults, spillover effects of this law on risky sexual behaviors are relatively limited.