cssi/SciSciGPT-SciSciNet huggingface dataset:
Emerging Technologies in Physics Education

Three emerging technologies in physics education are evaluated from the interdisciplinary perspective of cognitive science and physics education research. The technologies—Physlet Physics, the Andes Intelligent Tutoring System (ITS), and Microcomputer-Based Laboratory (MBL) Tools—are assessed particularly in terms of their potential at promoting conceptual change, developing expert-like problem-solving skills, and achieving the goals of the traditional physics laboratory. Pedagogical methods to maximize the potential of each educational technology are suggested.
Differential Pathogenesis of Cowpox Virus Intranasal Infections in Mice Induced by Low and High Inoculum Volumes, and Effects of Cidofovir Treatment

Abstract The causes of death from intranasal cowpox virus infections in mice remain unclear. Hypotheses include severe pneumonitis, hepatitis and/or hyperproduction of cytokines and chemokines. This work explores these hypotheses by studying the influence of low- and high-volume virus inocula on viral pathogenesis. BALB/c mice were infected intranasally with a syncytium-forming variant of cowpox virus in 5 μL or 50 μL volumes containing the same infectious virus challenge dose. The 50 μL infection produced a more rapidly lethal disease associated with severe pneumonitis, high lung and nasal virus titres and increased cytokine and chemokine levels in the lungs and nasal tissue, whilst liver infection was minimal. The 5 μL inoculum infection was also lethal, but the infection was primarily confined to the upper respiratory tract and included elevated nasal cytokine and chemokine levels. Levels of the pro-inflammatory cytokine interleukin-6 were particularly high in both infections. Treatment of the infections with cidofovir (100 mg/kg/day for 2 days starting 24 h after virus exposure) led to survival and suppression of tissue virus titres. Treatment reduced pneumonitis in the 50 μL infection and lessened cytokine hyperproduction in both infections. We conclude that a 5 μL volume inoculum of cowpox virus causes a lethal upper respiratory tract infection, whilst the 50 μL inoculum targets both upper and lower respiratory tracts, with excessive release of systemic pro-inflammatory factors. Cidofovir effectively treated both infections and slowed viral replication sufficiently to subdue the exaggerated release of pro-inflammatory mediators.
PSEUDO-COLOR ENCODING OF PICTURES BY MEANS OF HALFTONE SCREENS AND COHERENT OPTICAL FILTERING*

Pseudo-coloring of a photograph in a coherent optical processing system can be achieved through the utiliza-tion of the newly advanced technique of halftone screens. The basic principle of the pseudo-coloring method is to mix the high diffraction order outputs of the halftone photograph generated by lasers of different wave-lengths in a coherent optical system. A discussion of the theory, the method, and its potential applications will be given.© (1977) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Physician factors in the timing of cancer patient referral to hospice palliative care

BACKGROUND Although physicians state that patients ideally should receive hospice care for 3 months before death, the majority of patients survive < 1 month in hospice care. In the current study, the authors attempted to determine whether the attributes of referring physicians were associated with the survival of terminally ill cancer patients in hospice. METHODS Using a prospective cohort study design, the authors observed the survival of 326 terminally ill cancer patients who were referred by 258 different physicians to 5 outpatient hospice programs in Chicago. The authors evaluated associations between patient, physician, and patient-physician relationship factors and patient survival. RESULTS Of the 326 participating patients, 313 (96%) had known dates of death. For these patients, the median survival was 26 days. Controlling for patient demographic and disease factors, there were several physician factors found to be associated with the length of patient survival after hospice referral. For example, when a physician had referred ≥ 2 patients to hospice care in the previous 3 months, the patient survived 17 days longer in hospice compared with those patients whose physician referred fewer patients to hospice. When a physician estimated patient survival accurately (estimate obtained at the time of referral), the patient lived 20 days longer in hospice compared with those patients whose physicians made inaccurate survival estimates. The practice specialty of the physician also was found to be associated with patient survival after hospice referral, with patients referred by general internists and geriatricians living 18 days longer in hospice compared with those patients who were referred by oncologists. CONCLUSIONS In the current study, referring physician factors were found to be associated with the survival of terminally ill cancer patients after referral to hospice. Cancer 2002; 94:2733–7. © 2002 American Cancer Society. DOI 10.1002/cncr.10530
Extreme Physics via X-rays from Black Holes and `Neutron' Stars

A combination of microchannel plate optics and a 32×32 pixel microcalorimeter would allow the successor to the Rossi XTE to explore new domains of spectroscopic timing in a MIDEX class mission. With ∼10 times the area and ∼100 times the spectral resolution of the PCA (and 10 times that of silicon detectors) such a mission would be able to explore redshifts and plasma conditions in weak line features over a wide range of celestial sources. This would allow several tests of basic physics, both QED/QCD and GR.
Synthesis of Sr2PrO4: a Pr4+-containing oxide in the Sr2PbO4 structure type

Abstract Polycrystalline Sr2PrO4 was prepared from SrCO3 and Pr6O11 at 1000°C. The structure was solved by Rietveld refinement of synchrotron powder X-ray data. The structure was refined in space group Pbam, with a=6.12382(3) A, b=10.28083(5) A, and c=3.58963(2) A and is isostructural to Sr2PbO4. The structure consists of infinite chains of edge shared PrO6 octahedra connected by a perpendicular network of SrO6 trigonal prisms. Thermogravimetric analysis, diffuse reflectance measurements, and magnetic susceptibility measurements (1.20(4) μB) are all consistent with tetravalent praseodymium.
Neural cell adhesion molecule in aged mouse muscle

Expression of the neural cell adhesion molecule was compared in endplate and non-endplate regions of skeletal muscles of mature and old CBF-1 mice, in order to determine whether age-related changes in neuromuscular morphology were correlated with age changes in neural cell adhesion molecule expression. Three muscles were examined: two (soleus and sternomastoid) showed age-related regionalization of nerve terminals as one manifestation of increased synaptic remodelling while the third (diaphragm) did not. Relative neural cell adhesion molecule content in these muscles was measured by densitometry of immunoblots after concentration by affinity chromatography. Expression of the major 140,000 mol. wt form of neural cell adhesion molecule, which was most abundant in the endplate region, was increased in sternomastoid and soleus of old compared to adult mouse, but was unchanged with age in diaphragm. A 70,000-80,000 mol. wt presumably proteolytic polypeptide fragment of neural cell adhesion molecule was increased in immunoblots of all old muscles. Immunocytochemical studies of skeletal muscles showed no difference in neural cell adhesion molecule cellular distribution in mature vs old mice, but in motor nerve of sternomastoid, the number of neural cell adhesion molecule-positive nerve fibers was increased in old mice. Several lines of evidence indicated that partial denervation was rare in old CBF-1 mice, and therefore could not account for the findings above. Selective increase of 140,000 mol. wt neural cell adhesion molecule expression in the junctional regions of those muscles of old mice which show neuromuscular remodelling indicates that this adhesion molecule may play a role in the age-related instability of motor nerve terminals.
A New Approach to Two-View Motion Segmentation Using Global Dimension Minimization

We present a new approach to rigid-body motion segmentation from two views. We use a previously developed nonlinear embedding of two-view point correspondences into a 9-dimensional space and identify the different motions by segmenting lower-dimensional subspaces. In order to overcome nonuniform distributions along the subspaces, whose dimensions are unknown, we suggest the novel concept of global dimension and its minimization for clustering subspaces with some theoretical motivation. We propose a fast projected gradient algorithm for minimizing global dimension and thus segmenting motions from 2-views. We develop an outlier detection framework around the proposed method, and we present state-of-the-art results on outlier-free and outlier-corrupted two-view data for segmenting motion.
Molecular dynamics simulation of thermal and thermomechanical phenomena in picosecond laser material interaction

In recent years, short pulsed laser materials interaction has attracted considerable attention owing to the rapid development of short pulsed lasers and their potential applications in laser-material processing. In this work, molecular dynamics (MD) simulations are conducted to study the thermal and thermomechanical phenomena induced by picosecond laser heating. The generation and propagation of the stress wave are calculated and depicted in detail. Results of the MD simulation are compared with those obtained with an analytical solution. In addition, a temperature wave as a result of the coupling between temperature and the strain rate is observed, which propagates at the same speed as the stress wave.
Goby-Acomms version 2: extensible marshalling, queuing, and link layer interfacing for acoustic telemetry

Abstract We present the Goby-Acomms project version 2 (Goby2) which provides software for communication amongst autonomous marine vehicles over extremely bandwidth-constrained links. Goby2's modular design provides four discrete yet interoperable components: 1) physics-oriented marshalling via the Dynamic Compact Control Language (DCCL); 2) dynamic priority queuing; 3) time division multiple access (TDMA) medium access control (MAC); 4) and an extensible link-layer interface (ModemDriver).
Asymmetric currency exposure and currency risk pricing

Abstract Whether stock returns are linked to currency movements and whether currency risk is priced in a domestic context are less conclusive and thus still subject to a great debate. Based on a different approach, this paper attempts to provide new empirical evidence on these two inter-related issues, which are critical to investors and corporate risk management. In particular, this paper not only explores the possibility of asymmetric currency exposure that may explain why prior studies, which focus exclusively on linear exposure, have difficulty in detecting it, but also tests whether this asymmetric currency exposure is priced. The results show strong evidence of asymmetric currency exposure and currency risk pricing, suggesting that both asymmetry and conditional heteroskedasticity play important roles in testing currency exposure and its price.
Does Trade Liberalization Benefit Young and Old Alike

In an overlapping generations model, capital and labor produce two tradable goods. A kleptocratic government spends the tariff revenue. Trade liberalization benefits the retired generation if and only if the relative price of the capital-intensive good rises. Starting from autarky, a small liberalization benefits subsequent generations if and only if it hurts the retired one, a result reminiscent of the Stolper-Samuelson theorem. However, the terms-of-trade effect means a large liberalization may simultaneously raise the welfare of all generations.
A weak Galerkin mixed finite element method for second order elliptic problems

Abstract. A new weak Galerkin (WG) method is introduced and analyzed for the second order elliptic equation formulated as a system of two first order linear equations. This method, called WG-MFEM, is designed by using discontinuous piecewise polynomials on finite element partitions with arbitrary shape of polygons/polyhedra. The WG-MFEM is capable of providing very accurate numerical approximations for both the primary and flux variables. Allowing the use of discontinuous approximating functions on arbitrary shape of polygons/polyhedra makes the method highly flexible in practical computation. Optimal order error estimates in both discrete H and L norms are established for the corresponding weak Galerkin mixed finite element solutions.
Linearity of Climate Response to Increases in Black Carbon Aerosols

AbstractThe impacts of absorbing aerosols on global climate are not completely understood. This paper presents the results of idealized experiments conducted with the Community Atmosphere Model, version 4 (CAM4), coupled to a slab ocean model (CAM4–SOM) to simulate the climate response to increases in tropospheric black carbon aerosols (BC) by direct and semidirect effects. CAM4-SOM was forced with 0, 1×, 2×, 5×, and 10× an estimate of the present day concentration of BC while maintaining the estimated present day global spatial and vertical distribution. The top-of-atmosphere (TOA) radiative forcing of BC in these experiments is positive (warming) and increases linearly as the BC burden increases. The total semidirect effect for the 1 × BC experiment is positive but becomes increasingly negative for higher BC concentrations. The global-average surface temperature response is found to be a linear function of the TOA radiative forcing. The climate sensitivity to BC from these experiments is estimated to be...
Effectiveness of temporary traffic control measures in highway work zones

In the United States, hundreds of people lose their lives each year and many more are injured due to vehicle crashes in the work zones. Over the years, temporary traffic control (TCC) measures have been developed and deployed in work zones. To continuously improve the safety, there is a need to identify the traffic control deficiencies in work zones by evaluating the effectiveness of existing TTC measures based on the real crash cases. In this study, researchers evaluated the effectiveness of several commonly used TTC methods using logistic regression techniques and various significance test methods including likelihood ratio test, score test, and Wald test. These TTC methods included flagger/officer, stop sign/signal, flasher, no passing zone control, and pavement center/edge lines. A total of 655 severe crashes in Kansas highway work zones between January 2003 and December 2004 were used for the evaluation, which included 29 fatal crashes and 626 injury crashes. Results indicated that flagger, flasher, and pavement center/edge lines were effective in reducing the probability of causing fatalities when severe crashes occurred. In addition, using these devices could prevent some common human errors, such as "disregarded traffic control", "inattentive driving", "followed too closely", and "exceeded speed limit or too fast for condition", from causing severe crashes. Language: en
French beans for the masses: a modern historical geography of food in Burkina Faso

Abstract Much of the literature on the modern history of food and diet in Africa focuses on material dearth and cultural loss, described in overarching terms such as ‘urbanization’ and ‘westernization’. Such generalizations do not capture the complexity of the dietary and culinary changes that have occurred there. This article shows how a geographic perspective enriches the historical analysis of food and foodways, by situating changing norms and practices in spatial and ecological contexts. It examines the twentieth-century history of food consumption in Burkina Faso, focusing on the region of Bobo-Dioulasso, the country's second largest city. It shows how the agricultural policies, dietary preferences, and health concerns of French colonials—all of which emphasized the need for fresh garden vegetables—helped to transform not just the regional diet but also the landscape and economy, and thus certain temporal and spatial patterns of daily life. The article also examines how, in recent history, Burkina Faso's incorporation into globalized markets and media networks has resulted in both unintended gluts of luxury food (French beans) as well as growing concerns about the safety and purity of everyday food.
The Sooner Lunar Schooner: Lunar engineering education

Abstract The Sooner Lunar Schooner is a multi-disciplinary ongoing project at the University of Oklahoma to plan, design, prototype, cost and (when funds become available) build/contract and fly a robotic mission to the Moon. The goal of the flight will be to explore a small section of the Moon; conduct a materials analysis of the materials left there by an Apollo mission thirty years earlier; and to perform a selenographic survey of areas that were too distant or considered too dangerous to be done by the Apollo crew. The goal of the Sooner Lunar Schooner Project is to improve the science and engineering educations of the hundreds of undergraduate and graduate students working on the project. The participants, while primarily from engineering and physics, will also include representatives from business, art, journalism, law and education. This project ties together numerous existing research programs at the University, and provides a framework for the creation of many new research proposals. The authors were excited and motivated by the Apollo missions to the Moon. When we asked what we could do to similarly motivate students we realized that nothing is as exciting as going to the Moon. The students seem to agree.
Invariant measures for the horocycle flow on periodic hyperbolic surfaces

We classify the ergodic invariant Radon measures for the horocycle flow on geometrically infinite regular covers of compact hyperbolic surfaces. The method is to establish a bijection between these measures and the positive minimal eigenfunctions of the Laplacian of the surface. Two consequences arise: if the group of deck transformations G is of polynomial growth, then these measures are classified by the homomorphisms from G 0 to ℝ where G 0 ≤ G is a nilpotent subgroup of finite index; if the group is of exponential growth, then there may be more than one Radon measure which is invariant under the geodesic flow and the horocycle flow. We also treat regular covers of finite volume surfaces.
INTEGRATED SACHS–WOLFE EFFECT FOR GRAVITATIONAL RADIATION

Gravitational waves (GWs) are messengers carrying valuable information about their sources. For sources at cosmological distances, the waves will also contain the imprint left by the intervening matter. The situation is in close analogy with cosmic microwave photons, for which the large-scale structures the photons traverse contribute to the observed temperature anisotropies, in a process known as the integrated Sachs-Wolfe effect. We derive the GW counterpart of this effect for waves propagating on a Friedman-Robertson-Walker background with scalar perturbations. We find that the phase, frequency, and amplitude of the GWs experience Sachs-Wolfe-type integrated effects, in addition to the magnification effects on the amplitude from gravitational lensing. We show that for supermassive black hole binaries, the integrated effects could account for measurable changes on the frequency, chirp mass, and luminosity distance of the binary, thus unveiling the presence of inhomogeneities, and potentially dark energy, in the universe.
SELECTIVE DRY ETCHING OF GaN OVER AlGaN IN BCL3/SF6 MIXTURES

Inductively coupled plasma (ICP) etching of GaN with high selectivity over Al.22Ga.78N in BCl3/SF6 mixtures has been studied. Selectivity and surface morphology were investigated over a wide range of pressures (3.75–37.5mTorr), RF powers (30–120 W), ICP powers (100–400 W), and SF6/BCl3 ratios (0.1–0.7). Higher pressures, lower dc biases, and higher SF6/BCl3 ratios increased the GaN to AlGaN selectivity. Selectivities up to 25 were measured by laser interferometry. A root mean square (rms) surface roughness of 0.67 nm was measured by atomic force microscopy (AFM) after removal of 0.5 μm from a GaN template (process selectivity: 15, as-grown rms surface roughness: 0.56 nm). A degradation in surface morphology, with the gradual formation of pits, was observed for selectivities above 10.
Palladium-Catalyzed Conversion of Aryl and Vinyl Triflates to Bromides and Chlorides

The palladium-catalyzed conversion of aryl and vinyl triflates to aryl and vinyl halides (bromides and chlorides) has been developed using dialkylbiaryl phosphine ligands. A variety of aryl, heteroaryl, and vinyl halides can be prepared via this method in good to excellent yields.
What is the entropy of the universe

Standard calculations suggest that the entropy of our universe is dominated by black holes, whose entropy is of order their area in Planck units, although they comprise only a tiny fraction of its total energy. Statistical entropy is the logarithm of the number of microstates consistent with the observed macroscopic properties of a system, hence a measure of uncertainty about its precise state. Therefore, assuming unitarity in black hole evaporation, the standard results suggest that the largest uncertainty in the future quantum state of the universe is due to the Hawking radiation from evaporating black holes. However, the entropy of the matter precursors to astrophysical black holes is enormously less than that given by area entropy. If unitarity relates the future radiation states to the black hole precursor states, then the standard results are highly misleading, at least for an observer that can differentiate the individual states of the Hawking radiation.
Optimal Reconfigurations of Two-Craft Coulomb Formation in Circular Orbits

Optimal reconfigurations of a two-spacecraft Coulomb formation are determined by applying nonlinear optimal control techniques. The objective of these reconfigurations is to maneuver the two-craft formation between two charged equilibria configurations. The four optimality criteria considered are minimum time, minimum acceleration of the separation distance, minimum Coulomb and electric propulsion fuel usage, and minimum electrical power consumption. The reconfiguration between equilibra is first considered by varying the desired separation distance. In a radial relative equilibrium configuration, only the Coulomb force is required to control the in-plane motion and to steer the satellites from their initial to their final radial position. In this reconfiguration maneuver, the gravity gradient torque is exploited to stabilize the in-plane motion. For along-track and orbit normal equilibrium locations, the reconfiguration maneuver requires hybrid controls. Here the Coulomb force is varied to control the separation distance and inertial micro-thrusters are activated for control in the transverse directions. Second, a reconfiguration involving hybrid control is used to maneuver the crafts from any initial equilibrium position to a final one. The goal is to determine optimal maneuvers maximizing the use of Coulomb propulsion while minimizing the electric propulsion usage. The two-point boundary value problem optimization formulation is numerically solved via pseudo-spectral methods. Pontryagin’s Minimum Principle verifies the open loop solutions’ optimality.
Deep CCD Surface Photometry of the Edge-on Spiral NGC 4244

We have obtained deep surface photometry of the edge-on spiral galaxy NGC 4244. Our data reliably reach 27.5 R magnitude arcsec-2, a significant improvement on our earlier deep CCD surface photometry of other galaxies. NGC 4244 is a nearby Scd galaxy whose total luminosity is approximately 1 mag fainter than the peak of the Sc luminosity function. We find that it has a simple structure: a single exponential disk, with a scale height hZ = 246 ± 2 pc, a scale length hR = 1.84 ± 0.02 kpc, and a disk cutoff at a radius Rmax = 10.0 kpc (5.4 scale lengths). We confirm a strong cutoff in the stellar disk at Rmax, which happens over only 1 kpc. We do not see any statistically significant evidence for disk flaring with radius. Unlike the more luminous Sc galaxies NGC 5907 and M 33, NGC 4244 does not show any evidence for a second component, such as a thick disk or halo, at μR < 27.5 mag arcsec-2.
s -step iterative methods for (non)symmetric (in)definite linear systems

In this paper a class of s-step methods for nonsymmetric linear systems of equations is introduced. These methods are obtained from nonsymmetric generalizations of the conjugate residual method, which apply to nonsymmetric definite systems [S. C. Eisenstat, H. C. Elmans and M. H. Schultz, SIAM J. Numer. Anal., 20 (1983), pp. 345–357]. The s-step methods are derived then in a way similar to obtaining the s-step conjugate gradient [G. E. Forsythe, Numer. Math., 11 (1968), pp. 57–76], [A. T. Chronopoulos and C. W. Gear, J. Comput. Math., 25 (1989), pp. 153–168], [A. T. Chronopoulos, Ph.D. thesis, Dept. of Computer Science, University of Illinois, Urbana, IL, 1986). It is proven that the s-step methods (with $s \geqq 2$) converge for all symmetric indefinite matrices, for nonsymmetric matrices with positive definite symmetric part and for a class of nonsymmetric indefinite problems. The s-step methods require less computational work but $s - 1$ more vectors of main memory storage than the standard ones. These...
Compilers and parallel computing systems

Increasing the delivered performance of computers by running programs in parallel is an old idea with a new urgency. Multi cores (multi processors) on chips have emerged as a way to increase performance wherever chips are used. The talk will focus on the role programming languages and compilers must play in delivering parallel performance to users and applications. The speakerpsilas personal experiences with languages and compilers for high performance systems will provide the basis for her observations. The talk is intended to encourage the exploration of new approaches.
Cosmogenesis and Collapse

Some possible benefits of dynamical collapse for a quantum theory of cosmogenesis are discussed. These are a possible long wait before creation begins, creation of energy and space, and choice of a particular universe out of a superposition.
Intermediate degree p-mode frequency splittings near solar maximum

We report on observations of global solar Ca K-line intensity oscillations taken in May 1991 from Mees Solar Observatory, Hawaii. We measurep-mode frequency splittings for modes of spherical harmonic degrees between 20 and 129 averaged over the radial order of the modes. Our measurement of the antisymmetric component of the splittings is comparable with previous measurements and thus indicates a decrease in the latitudinal differential rotation with depth into the convection zone and the upper radiative zone. We find evidence for a 1% variation in the rotation rate of the upper convection zone roughly in phase with the solar activity cycle. Our measurement of the symmetric component of the splittings is of the same order as was reported from the previous solar maximum and is an order of magnitude larger than has been measured near solar minimum. From the degree dependence of the symmetric component of the splittings, we find evidence for an aspherical fractional sound speed perturbation located at a depth of 0.85 ± 0.05 solar radii. This perturbation has a magnitude ofδc/c ≈ +9 × 10−4 at the equator relative to the poles. Additionally, there is evidence for a near-surface aspherical sound speed perturbation of smaller magnitudeδc/c ≈ +4 × 10−4 at the equator relative to the poles. If an intense global magnetic field were the dominant source of the observed symmetric component of the splittings, instead of latitudinal gradients in the sound speed, then global fields of order 105 G would be required in the convection zone.
A novel, stereoselective silyl-directed Stevens [1,2]-shift of ammonium ylides.

The silyl group of 2-silylpyrrolidines such as 1 plays several critical roles: a stereochemical control element in a facially selective carbenoid addition to the ring nitrogen, a stereochemical “p...
ON A NOTION OF MAPS BETWEEN ORBIFOLDS II: HOMOTOPY AND CW-COMPLEX

This is the second of a series of papers which is devoted to a comprehensive theory of maps between orbifolds. In this paper, we develop a basic machinery for studying homotopy classes of such maps. It contains two parts: (1) the construction of a set of algebraic invariants — the homotopy groups, and (2) an analog of CW-complex theory. As a corollary of this machinery, the classical Whitehead theorem (which asserts that a weak homotopy equivalence is a homotopy equivalence) is extended to the orbifold category.
Numerical solution of multiple nonlinear Volterra integral equations

Abstract We analyze a discretization method for solving nonlinear integral equations that contain multiple integrals. These equations include integral equations with a Volterra series, instead of a single integral term, on one side of the equation. We prove existence and uniqueness of solutions, and convergence and estimates of the order of convergence for the numerical methods of solution.
Experimental test of models of high-plasma-density, radio-frequency sheaths

Measurements of the rf-bias current and voltage applied to the substrate electrode of a high-density plasma reactor, combined with dc measurements of the ion current at the electrode and capacitive probe measurements of the plasma potential, enabled a rigorous, quantitative test of models of the electrical properties of the sheath adjacent to the electrode. The measurements were performed for argon discharges at 1.33 Pa (10 mTorr), ion current densities of 1.3--13 ${\mathrm{m}\mathrm{A}/\mathrm{c}\mathrm{m}}^{2}$, rf-bias frequencies of 0.1--10 MHz, and rf-bias voltages from less than 1 to more than 100 V. From the measurements, the current, voltage, impedance, and power of the sheath adjacent to the electrode were determined and were compared to model predictions. The properties of the opposing sheath, adjacent to grounded surfaces, were also determined. The behavior of the two sheaths ranged from nearly symmetric to very asymmetric. Changes in the symmetry are explained by models of the sheath impedance.
Russia's missing link? Social capital, entrepreneurialism, and economic performance in post-communist Russia

Abstract This paper argues that there is a spurious correlation between social capital and economic development in the regions of post-communist Russia. This argument rejects Robert Putnam's collectivist hypothesis that social capital is the ubiquitous cause of economic growth. Rather, the data presented in this paper indicates that individualistic behavior in the form of entrepreneurialism, has been the prerequisite for growth in post-communist Russia. While social capital may slow or accelerate economic growth, it will not cause it. Without entrepreneurialism, social capital cannot be harnessed for economic development. In essence, social capital does not create wealth, entrepreneurs do.
Enhancement of Ambipolar Diffusion Rates through Field Fluctuations

Previous treatments of ambipolar diffusion in star-forming molecular clouds do not consider the effects of fluctuations in the fluid fields about their mean values. This paper generalizes the ambipolar diffusion problem in molecular cloud layers to include such fluctuations. Because magnetic diffusion is a nonlinear process, fluctuations can lead to an enhancement of the ambipolar diffusion rate. In addition, the stochastic nature of the process makes the ambipolar diffusion time take on a distribution of different values. In this paper, we focus on the case of long-wavelength fluctuations and find that the rate of ambipolar diffusion increases by a significant factor Λ ~ 1-10. The corresponding decrease in the magnetic diffusion time helps make ambipolar diffusion more consistent with observations.
The interactive multimedia jukebox (IMJ): a new paradigm for the on-demand delivery of audio/video

Abstract Straightforward, one-way delivery of video programming through television sets has existed for many decades. In the 1980s, new services like Pay-Per-View and Video-on-Demand were touted as the “killer application” for next-generation Internet and TV services. However, the hype has quickly died away leaving only hard technical problems and costly systems. As an alternative, and what we propose, is a new paradigm offering flexibility in how programs are requested and scheduled for playout, ranging from complete viewer control (true VoD), to complete service provider control (traditional broadcast or cable TV). In this paper, we describe our proposed jukebox paradigm and relate it to other on-demand paradigms. Our new paradigm presents some challenges of its own, including how to best schedule viewer requests, how to provide VCR-style interactive functions, and how to track viewer usage patterns. In addition to addressing these issues we also present our implementation of a jukebox-based service called the Interactive Multimedia Jukebox (IMJ). The IMJ provides scheduling via the World Wide Web (WWW) and content delivery via the Multicast Backbone (MBone). We discuss the challenges of building a functioning system and our ongoing efforts to improve the jukebox paradigm.
Small satellites and the DARPA/Air Force FALCON program

Abstract The FALCON program is a technology demonstration effort with three major components: a Small Launch Vehicle (SLV), a Hypersonic Technology Vehicle (HTV), and a Hypersonic Cruise Vehicle (HCV). Sponsored by the Defense Advanced Research Projects Agency (DARPA) and executed jointly by the United States Air Force and DARPA with NASA participation, the objectives are to develop and demonstrate technologies that will enable both near-term and far-term capability to execute time-critical, global reach missions. The focus of this paper is on the SLV as it relates to small satellites and the implications of lower cost to orbit for small satellites. The target recurring cost for placing 1000 pounds payloads into a circular reference orbit of 28 . 5 ∘ at 100 nautical miles is $5,000,000 per launch. This includes range costs but not the payload or payload integration costs. In addition to the nominal 1000 pounds to low earth orbit (LEO), FALCON is seeking delivery of a range of orbital payloads from 220 to 2200 pounds to the reference orbit. Once placed on ‘alert’ status, the SLV must be capable of launch within 24 h.
Cool Customers in the Stellar Graveyard. II. Limits to Substellar Objects around Nearby DAZ White Dwarfs

Results from a concerted Hubble Space Telescope (HST) survey of nearby white dwarfs for substellar objects are presented. A total of seven DAZ white dwarfs with distances of 18MJ. The lack of significant near-IR excesses for our targets limits any kind of unresolved companions present to be substellar. In light of these results we make several comments on the possibility of determining the origin of metals in the atmospheres of these white dwarfs.
The C. elegans MicroRNA mir-71 Acts in Neurons to Promote Germline-Mediated Longevity through Regulation of DAF-16/FOXO

The life span of Caenorhabditis elegans is controlled by signaling between the germline and the soma. Germ cell removal extends life span by triggering the activation of the DAF-16/FOXO transcription factor in the intestine. Here we analyze microRNA function in C. elegans aging and show that the microRNA mir-71 functions to mediate the effects of germ cell loss on life span. mir-71 is required for the life span extension caused by germline removal, and overexpression of mir-71 further extends the life span of animals lacking germ cells. mir-71 functions in the nervous system to facilitate the localization and transcriptional activity of DAF-16 in the intestine. Our findings reveal a microRNA-dependent mechanism of life span regulation by the germline and indicate that signaling among the gonad, the nervous system, and the intestine coordinates the life span of the entire organism.
Vickrey-Clarke-Groves mechanisms and perfect competition

Abstract We present a game theoretic-mechanism characterization of perfect competition: we prove the perfectly competitive mechanism is the only Pareto optimal, individually rational, dominant strategy allocation mechanism. Thus, perfect competition is uniquely capable of efficiently and non-coercively solving the incentive/bargaining problem when there is incomplete information, i.e., when each individual knows his own tastes and production possibilities better than anyone else. We also show one can interpret any dominant strategy, demand-revealing mechanism as “working” because it mimics the reward scheme that characterizes the perfectly competitive market, namely, the marginal product reward scheme.
Semilattices of bisimple orthodox semigroups

A structure theorem for bisimple orthodox semigroups was given by Clifford [2]. In this paper we determine all homomorphisms of a certain type from one bisimple orthodox semigroup into another, and apply the results to give a structure theorem for any semilattice of bisimple orthodox semigroups with identity in which the set of identity elements forms a subsemigroup. A special case of these results is indicated for bisimple left unipotent semigroups.
Density of cubic field discriminants

In this paper we give a conjectural refinement of the Davenport- Heilbronn theorem on the density of cubic field discriminants. We explain how this refinement is plausible theoretically and agrees very well with computa- tional data. Let an be the number of isomorphism classes of abelian cubic fields with discrim- inant n. Let bn be the number of isomorphism classes of non-abelian cubic fields with discriminant n. The numbers an are very well understood. The numbers bn have been the subject of extensive theoretical and computational study for at least sixty years, but are less well understood. The object of this note is to contribute to the study of these bn, by bringing together the theoretical and computational literature. For � ∈ {−,+}, define g�(x) =
Calorie Posting in Chain Restaurants

We study the impact of mandatory calorie posting on consumers' purchase decisions using detailed data from Starbucks. We find that average calories per transaction fall by 6 percent. The effect is almost entirely related to changes in consumers' food choices—there is almost no change in purchases of beverage calories. There is no impact on Starbucks profit on average, and for the subset of stores located close to their competitor Dunkin Donuts, the effect of calorie posting is actually to increase Starbuc ks revenue. Survey evidence and analysis of commuters suggests the mechanism for the effect is a combination of learning and salience. (JEL D12, D18, D83, L83)
An Experimental Investigation of Hard and Soft Price Ceilings in Emissions Permit Markets

Tradable emissions permits have been implemented to control pollution levels in various markets and represent a major component of legislative efforts to control greenhouse gas emissions. Because permits are supplied for a fixed level of pollution, allowing the market for permits to determine the price, price control mechanisms may be needed to protect firms from price spikes caused by fluctuations in the demand for permits. We test permit markets in an experimental laboratory setting to determine the effectiveness of several price control mechanisms, with special attention on the soft price ceiling. We focus on a static setting similar to some of the earliest experimental work focused on price ceilings. Results indicate that both permit supply adjustments and price ceilings (hard ceilings) effectively limit elevated prices in this setting. By contrast, reserve auctions to implement soft ceilings do not consistently control prices, especially when a minimum reserve permit price is applied. Furthermore, the grandfathering of permits allows permit sellers to realize significant welfare gains at the expense of buyers under a soft ceiling policy. Our results thus highlight several advantages of hard ceilings for controlling short term price increases.
A cytotoxic decahydronaphthalenylpropenal derivative and tetrahydrofuran lignans from the stems of Cameraria latifolia

Abstract A new decahydronaphthalenylpropenal derivative, (+)-camerarialdehyde (1), a new tetrahydrofuran lignan, (−)-diepiolivil (2), and two known lignans were isolated from a methanol-soluble extract of the stems of Cameraria latifolia, which was obtained from a repository donated to IHVR by Merck Research Laboratories. The structures of compounds 1 and 2 were determined by interpretation of their spectroscopic data, with the absolute configuration of 1 being established by analysis of its CD spectrum. The absolute configuration of the 1,3-diol moiety of 2 was proposed from the CD spectrum induced with dimolybdenum tetraacetate in DMSO solution. All compounds isolated were evaluated against HT-29 human colon cancer cells, and compound 1 was found to show cytotoxicity toward this cell line.
Gauge Fields and Scalars in Rolling Tachyon Backgrounds

We investigate the dynamics of gauge and scalar fields on unstable D-branes with rolling tachyons. Assuming an FRW metric on the brane, we find a solution of the tachyon equation of motion which is valid for arbitrary tachyon potentials and scale factors. The equations of motion for a U(1) gauge field and a scalar field in this background are derived. These fields see an effective metric which differs from the original FRW metric. The field equations receive large corrections due to the curvature of the effective metric as well as the time variation of the gauge coupling. The equations of state for these fields resemble those of nonrelativistic matter rather than those of massless particles.
Characterization of Thin‐Film Rechargeable Lithium Batteries with Lithium Cobalt Oxide Cathodes

Thin-film rechargeable lithium batteries with amorphous and crystalline LiCoO{sub 2} cathodes were investigated. The lithium cobalt oxide films were deposited by radio-frequency (RF) magnetron sputtering of an LiCoO{sub 2} target in a 3:1 Ar/O{sub 2} mixture gas. From proton-induced {gamma}-ray emission analysis (PIGE) and Rutherford backscattering spectrometry (RBS), the average composition of these films was determined to be Li{sub 1.15}CoO{sub 2.16} or, within experimental uncertainty, LiCoO{sub 2} + 0.08 Li{sub 2}O. The X-ray powder diffraction patterns of films annealed in air at 500 to 700 C were consistent with the regular hexagonal structure observed for crystalline LiCoO{sub 2}. The discharge curves of the cells with amorphous LiCoO{sub 2} cathodes showed no obvious structural transition between 4.2 and 2.0 V, while the discharge curves of the cells with polycrystalline cathodes were consistent with a two-phase potential plateau at {approximately}3.9 V with a relatively large capacity. Two lower capacity plateaus were observed at {approximately} 4.2 and 4.1 V with the 600 and 700 C annealed cathodes; the {minus}dq/dV peaks were broader and weaker for the 600 C annealed cathodes and were not present at all with the 500 C annealed films. The chemical diffusion coefficients of Li{sup +} in the cathodes obtainedmore » from ac impedance measurements at cell potentials of {approximately} 4 V ranged from {approximately} 10{sup {minus}12} cm{sup 2}/s for the as-deposited amorphous cathodes to {approximately} 10{sup {minus}9} cm{sup 2}/s for the films annealed at 700 C. The capacity loss on extended cycling of the thin-film cells varied with the crystallinity and thickness of the cathodes and with temperature. With the highly crystalline, 700 C annealed material, losses on cycling between 4.2 and 3.8 V at 25 C ranged from 0.0001%/cycle (> 10{sup 4} cycles) to 0.002%/cycle for cells with cathodes form 0.05 to 0.5 {micro}m thick.« less
Enabling diffusion: How complementary inputs moderate the response to environmental policy

Abstract While policies encouraging diffusion of new technologies provide incentives for adopting the focal good, they typically ignore the ecosystem of complementary goods and services. Based on existing literature on indirect network effects, we argue that when there is less availability of complementary goods, policies have a smaller impact on diffusion. Using a natural experiment based on the establishment of state-level solar carve-out policies, we demonstrate that solar power installations increased substantially more after the policy in cities where a critical complementary good – qualified installers – was more available.
REVIEW OF TOP QUARK PHYSICS RESULTS

As the heaviest known fundamental particle, the top quark has taken a central role in the study of fundamental interactions. Production of top quarks in pairs provides an important probe of strong interactions. The top quark mass is a key fundamental parameter which places a valuable constraint on the Higgs boson mass and electroweak symmetry breaking. Observations of the relative rates and kinematics of top quark final states constrain potential new physics. In many cases, the tests available with study of the top quark are both critical and unique. Large increases in data samples from the Fermilab Tevatron have been coupled with major improvements in experimental techniques to produce many new precision measurements of the top quark. The first direct evidence for electroweak production of top quarks has been obtained, with a resulting direct determination of Vtb. Several of the properties of the top quark have been measured. Progress has also been made in obtaining improved limits on potential anomalous production and decay mechanisms. This review presents an overview of recent theoretical and experimental developments in this field. We also provide a brief discussion of the implications for further efforts.
New perspective on fermion mass matrices

Abstract It is shown that any n × n Dirac fermion mass matrix may be written as the sum of n states of equal “mass”. However, these states are in general not orthogonal. Thus the texture of any such fermion mass matrix may be understood as the nonzero overlap among these states.
A mixed methods approach to assess the likelihood of testing for STI using self-collected samples among behaviourally bisexual women.

Objectives Behaviourally bisexual women (women who have sex with women and men (WSWM)) are more likely to report a history of sexually transmitted infections (STI) than women who have sex exclusively with men or exclusively with women. Barriers to care may prohibit WSWM from seeking STI testing. The present study investigated participant willingness to self-collect oral, vaginal and anal samples for STI testing. Methods Eighty WSWM were recruited from two midwestern locations. After completing an online questionnaire, a subset of the participants were interviewed (n=54) and provided the option to self-collect oral, vaginal and/or anal samples to screen for Chlamydia trachomatis , Neisseria gonorrhoeae and Trichomonas vaginalis . Results Over two-thirds (67.5%, n=54) of the participants completed the baseline scheduled and attended the interview. The majority of these participants provided vaginal (87.0%, n=47), oral (85.2%, n=46) and/or anal (61.1%, n=33) samples. Participants with a history of anal play were significantly more likely to provide an anal sample. C. trachomatis infection was identified in the samples of 6.8% (n=3) of the participants including 4.5% (n=2) of the vaginal samples and 3.3% (n=1) of the anal samples. None of the samples were positive for N. gonorrhoeae or T. vaginalis . Participants who reported a recent history of anal sexual behaviour with a male partner were significantly more likely to self-collect an anal sample. Conclusions Given the comparatively high STI rates among WSWM, self-sampling in non-traditional settings may present a unique opportunity to provide needed care to this underserved population of women.