cssi/SciSciGPT-SciSciNet huggingface dataset:
New results for fractal/wavelet image compression

In this research, we perform a multiresolution analysis of the mappings used in fractal image compression. We derive the transform-domain structure of the mappings and demonstrate a close connection between fractal image compression and wavelet transform coding using the Haar basis. We show that under certain conditions, the mappings correspond to a hierarchy of affine mappings between the subbands of the transformed image. Our analysis provides new insights into the mechanism underlying fractal image compression, leads to a non-iterative transform-domain decoding algorithm, and suggests a transform-domain encoding method with extensions to wavelets other than the Haar transform. As a result, we also propose a novel transform-domain encoding scheme whereby the image is hierarchically encoded starting with a coarse approximation and detail is added through a casual sequence of affine mappings between the subbands. This new approach is not only theoretically elegant, but also useful for embedded representation, i.e. images can be decoded to an intermediate resolution.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Time step size limitation introduced by the BSSN Gamma Driver

Many mesh refinement simulations currently performed in numerical relativity counteract instabilities near the outer boundary of the simulation domain either by changes to the mesh refinement scheme or by changes to the gauge condition. We point out that the BSSN Gamma Driver gauge condition introduces a time step size limitation in a similar manner as a Courant–Friedrichs–Lewy condition, but which is independent of the spatial resolution. We give a didactic explanation of this issue, show why, especially, mesh refinement simulations suffer from it, and point to a simple remedy.
Masculinity and Nationalism in East African Hip-Hop Music

Masculinity and Nationalism in East African Hip-Hop Music [English] East African music aligns itself with nationalistic desires while attempting to create a transnational and regional agenda that goes beyond individual nation-states. Hip-hop music appears at pains to define itself as different from the western art-forms with which it is hastily associated by instantiating localized forms and creating a different locution. This paper surveys East African hip-hop to demonstrate that the music is a productive site upon which the local, the national, and the global contest and negotiate. We demonstrate that central to the music's identity politics is the notion of masculinity, in which the construction of community is interpreted as a masculine enterprise. The audiences also invest the music with political and nationalist meanings that are fraught with sexualized readings. On the whole, the music rejects hostile nationalism but male artists tend to represent women negatively in their grand national, regional, and pan-African projects. Indirectly indicating the depth of the hegemonic masculinism they operate under, women artistes express a desire to deconstruct male constructs. At the same time they suggest that, in spite of themselves, their critique has to be cautious and subtle. Key Words: Masculinity, Nationalism, hip-hop music, East Africa Tydskrif vir letterkunde Vol. 41(2) 2004: 5-20
Do in-state tuition benefits affect the enrollment of non-citizens? Evidence from universities in Texas

Abstract In 2001, the Texas state legislature passed House Bill 1403. With the passage of the law, Texas became the first state to offer in-state tuition rates at public universities for non-citizens (including illegal immigrants) who attended high school in the state for three years. As a result of the policy change, the cost of attending college at public universities in Texas fell dramatically for non-citizens. Using administrative data from five universities in Texas, we employ a quasi-experimental design to identify the effects of the policy change on the probability of enrollment at each of the universities. The results demonstrate a large and significant positive effect of lowering tuition on the enrollment of non-citizens at the University of Texas at Pan American and the University of Texas at San Antonio.
Methods to calculate the response time of heat and smoke detectors installed below large unobstructed ceilings

Recently developed methods to calculate the time required for ceiling mounted heat and smoke detectors to respond to growing fires are reviewed. A computer program that calculates activation times for both fixed temperature and rate of rise heat detectors in response to fires that increase in heat release rate proportionally with the square of time from ignition is given. This program produces nearly equivalent results to the tables published in Appendix C, Guide for Automatic Fire Detector Spacing (NFPA 72E, 1984). A separate method and corresponding program are provided to calculate response time for fires having arbitrary heat release rate histories. This method is based on quasi-steady ceiling layer gas flow assumptions. Assuming a constant proportionality between smoke and heat released from burning materials, a method is described to calculate smoke detector response time, modeling the smoke detector as a low temperature heat detector in either of the two response time models.
Prediction of mutagenicity of aromatic and heteroaromatic amines from structure: a hierarchical QSAR approach.

Due to the lack of experimental data, there has been increasing use of theoretical structural descriptors in the hazard assessment of chemicals. We have used a hierarchical approach to develop class-specific quantitative structure−activity relationship (QSAR) models for the prediction of mutagenicity of a set of 95 aromatic and heteroaromatic amines. The hierarchical approach begins with the simplest molecular descriptors, the topostructural, which encode limited chemical information. The complexity is then increased, adding topochemical, geometric, and finally quantum chemical parameters. We have also added log P to the set of independent variables. The results indicate that the topological parameters, i.e., the topostructural and topochemical indices, explain the majority of the variance, and that the inclusion of log P, geometric, and quantum chemical parameters does not result in significantly improved predictive models.
Analysis of high resolution electron microscope images of the Pd2Si-Si interface

Abstract High resolution electron micrographs have been obtained from Pd 2 Si-Si(111) interfaces viewed edge on and a detailed analysis of the interface structure has been carried out using computer simulations of the images. Since the stacking sequence of hexagonal Pd 2 Si is AαAαAα…, the question whether the interface plane of Pd 2 Si is silicon rich, A, or silicon deficient, α, has been investigated. An advancing interface cannot be planar at all stages of growth; therefore the question of interface roughness along the direction of the electron beam and twinning orientations has been considered. This has been modeled by Fourier shift techniques incorporated into multislice dynamical theory and, of course, is complicated by the dynamical diffraction conditions of the structure and the contributions of high order Bragg reflections to image detail. It has been possible to access the image features present in Pd 2 Si/Si micrographs and to point out the difficulties which are encountered not only in this system but in a wide variety of interface structures by high resolution electron microscopy. Perhaps the most important finding of this study is that the interface region contains a mixture of silicon-rich and silicon-deficient Pd 2 Si planes adjacent to the silicon side of the interface.
The effect of industry consolidation and deposit insurance reform on the resiliency of the U.S. bank insurance fund

Abstract We examine the effects of structural change in the U.S. banking industry, as well as key regulatory changes, including recently enacted deposit insurance reform legislation, on the resiliency of the FDIC-administered bank insurance fund (BIF) by estimating and comparing the probability of BIF insolvency over time. We do this using a Markov-switching model that relies on historical patterns of BIF disbursements to define the probability of switching among three “states” of the banking industry's financial health. Monte Carlo simulations are then performed to project the financial condition of the BIF over a 50-year period. Our results indicate that the insolvency risk to the bank insurance fund has increased significantly due to industry consolidation, and is mainly due to the concentration of deposits in the 10 largest U.S. banking companies. We also find that recent deposit insurance reforms will cause only a marginal reduction in the risk of BIF insolvency. The increased risk associated with a more concentrated industry structure simply dominates the reform effect.
An introductory software engineering course that facilitates active learning

At the Rochester Institute of Technology, the undergraduate introductory software engineering course has been redesigned from a lecture-lab format to a project-centric studio format. The new format blends the lecture material with the project work. As a result, students drive their own learning experience based on scaffolding created by the course design. The challenges faced and the techniques and strategies utilized in the planning and delivery of the course will be discussed, including the utilization of online learning support infrastructure. This paper presents instructor experiences, analysis of student feedback, lessons learned and recommendations for other educators considering an active learning approach for their courses.
Investment dynamics with common and private values

Abstract We study a dynamic investment game with two-dimensional signals, where each firm observes its continuously distributed idiosyncratic cost of investment and a discrete signal correlated with common investment returns. We demonstrate that the one-step property holds and provide an equilibrium existence/characterization result. “Reversals” are possible, where a large number of firms investing in a given round becomes bad news about investment returns. Welfare is compared to static and rigid-timing benchmarks, and computed for large economies.
Affine and Toric Hyperplane Arrangements

We extend the Billera–Ehrenborg–Readdy map between the intersection lattice and face lattice of a central hyperplane arrangement to affine and toric hyperplane arrangements. For arrangements on the torus, we also generalize Zaslavsky’s fundamental results on the number of regions.
Temperature-Dependent Absorptances of Ceramics for Nd:YAG and CO2 Laser Processing Applications

The absorptance of material at the laser wavelength and as a junction of temperature, ranging from room temperature to the removal point, significantly affects the efficiency of the laser machining process. A priori predictions of a laser machining process, using either simplistic or sophisticated models, require knowledge of the material's absorptance behavior. An experimental apparatus for such measurements is described. The device consists of a specimen mounted inside an integrating sphere, heated rapidly by a CO 2 or a Nd:YAG laser. Reflectances are measured with a small focused probe laser (Nd:YAG or CO 2 ), while specimen surface temperatures are recorded by a high-speed pyrometer. Experimental results have been obtained for wavelengths of 1.06 μm (Nd:YAG) and 10.6 μm (CO 2 ) for graphite, alumina, hot-pressed silicon nitride, sintered α-silicon carbide, as well as two continous-fiber ceramic matrix composites (SiC-based). Data are presented for temperatures between room temperature and the ablation/decomposition points.
Thalamus of turtles and thalamic evolution

The nuclear masses in the thalamus and the midbrain region of turtles are described are illustrated with sections of the brain of the green turtle, Chelone midas.
Delayed feedback control near Hopf bifurcation

The stability of functional differential equations under delayed feedback is investigated near a Hopf bifurcation. Necessary and sufficient conditions are derived for the stability of the equilibrium solution using averaging theory. The results are used to compare delayed versus undelayed feedback, as well as discrete versus distributed delays. Conditions are obtained for which delayed feedback with partial state information can yield stability where undelayed feedback is ineffective. Furthermore, it is shown that if the feedback is stabilizing (respectively, destabilizing), then a discrete delay is locally the most stabilizing (resp., destabilizing) one among delay distributions having the same mean. The result also holds globally if one considers delays that are symmetrically distributed about their mean.
On the Integrated Spectrum of the X-Ray Binaries and the Origin of Soft X-Ray Emission from the Bulge of M31

Using ROSAT PSPC data, we have performed several tests aimed at understanding the origin of the soft X-ray spectral component detected from the bulge of M31. We find that a significant soft component in the spectrum of the bulge is spatially correlated with the unresolved X-ray emission near the core of M31, which is probably a hot interstellar medium or perhaps a population of multiple faint sources. For the first time, we extracted the spectrum of this unresolved emission, by removing point sources dominating the integral spectrum of the bulge, and found it to be responsible for most of the soft excess. A soft spectral component is not at all needed to fit the point-source spectrum that remains after subtracting the unresolved emission. The integral spectra of bright point sources, both inside and outside of the M31 bulge, can be fitted with a single power law in the ROSAT band. Our analysis rules out the previous suggestion that all bulge emission in M31 may be generated by low-mass X-ray binaries (Irwin & Bregman).
Lattice trends in Ti5Si3Zx (Z=B,C,N,O and 0<x<1)

Abstract Several Ti5Si3Zx compositions (Z=boron, carbon, nitrogen and oxygen) were synthesized by arc-melting. Powder X-ray diffraction indicates the materials maintain the Mn5Si3-type structure of the binary compound Ti5Si3. Calculated cell constants were correlated to ternary composition based on chemical analysis. Nitrogen and oxygen additions to Ti5Si3 promote a cell volume decrease, while boron additions promote a cell volume increase. Carbon additions cause a decrease in the a-cell constant and an increase in the c-cell constant with a concomitant cell volume increase. Room temperature X-ray single crystal structural analysis was performed on one composition for each ternary addition. Each analyzed composition has the P63/mcm space group (No. 193) with the Mn5Si3-type structure. The ternary addition occupies the normally vacant interstitial site at the center of the trigonal antiprisms of titanium (Ti2) atoms (Ti6Z polyhedra), located in chains at the corners of the hexagonal unit cell. Bonding between the interstitial atoms and the titanium (Ti2) atoms in the Ti6Z polyhedra is indicated by a decrease in the Ti2–Ti2 and Ti2–Z atomic separations.
Laminar Natural Convection in Shallow Open Cavities

Etude experimentale realisee par anemometrie laser Doppler. La cavite est rectangulaire avec une paroi laterale ouverte
Modeling the hydroclimatology of the midwestern United States. Part 1: current climate

An ensemble of six 22-year numerical experiments was conducted to evaluate the ability of Regional Climate Model version 3 (RegCM3) to simulate the energy and water budgets of the midwestern United States. RegCM3 was run using two surface physics schemes: Integrated Biosphere Simulator (IBIS) and Biosphere-Atmosphere Transfer Scheme 1e (BATS1e), and two convective closure assumptions: Fritsch & Chappell (FC80) and Arakawa & Schubert (AS74). Boundary conditions were provided by the National Centers for Environmental Prediction-Department of Energy Reanalysis 2 dataset and the ECHAM5 general circulation model. A companion paper examines the American Midwest under future climate scenarios. Overall, the model that reproduces the observed seasonal cycles of the midwestern United States climate system best is RegCM3 using IBIS and the AS74 convective closure assumption. IBIS simulates shortwave radiation more accurately, while BATS1e simulates longwave radiation more accurately. Summer two-meter air temperature is overestimated by the combination of IBIS and the FC80 convective closure assumption. All models contain a wet bias and overestimate evapotranspiration during the spring. Total runoff, surface runoff, groundwater runoff, and root zone soil moisture are best simulated by RegCM3 using IBIS and the AS74 convective closure assumption. While BATS1e does capture the seasonal cycle of total runoff, gross errors in the partitioning of total runoff between surface runoff and groundwater runoff exist. The seasonal cycle of root zone soil moisture simulated by RegCM3 using IBIS and the AS74 convective closure assumption is dry, but agrees with observations during the summer. The rest of the models underestimate root zone soil moisture.
Comparing the Economic Impact of an Export Shock in Two Modeling Frameworks

Because of more restrictive assumptions on regional input-output (IO) models compared to computable general equilibrium (CGE) models, IO results are thought to be consistent with long-run equilibrium but otherwise overestimated. We compare IO and CGE models' response to a shock to Washington crop exports under various labor market and capital closures. Contrary to conventional wisdom, we find that the positive secondary impacts are larger in the CGE models than in the IO model. Also contrary to conventional wisdom, we find that the closest match between direct effects is when the CGE model has short run, rather than long run restrictions.
Reliability Analysis of Ceramic Matrix Composite Laminates

At a macroscopic level, a composite lamina may be considered as a homogeneous orthotropic solid whose directional strengths are random variables. Incorporation of these random variable strengths into failure models, either interactive or non-interactive, allows for the evaluation of the lamina reliability under a given stress state. Using a non-interactive criterion for demonstration purposes, laminate reliabilities are calculated assuming previously established load sharing rules for the redistribution of load as the failure of laminae occur. The matrix cracking predicted by ACK theory is modeled to allow a loss of stiffness in the fiber direction. The subsequent failure in the fiber direction is controlled by a modified bundle theory. Results using this modified bundle model are compared with previous models which did not permit separate consideration of matrix cracking, as well as to results obtained from experimental data.
Dynamo action in a thin slab

We consider the dynamo action produced by convection of a partially ionized, electrically conducting gas in a magnetic field. The model consists of two thin, Cartesian unipolar inductors connected in series by the magnetic field. For the case of a uniform magnetic field we compute the total current system generated by an arbitrary gas flow; for the case of a nonuniform field, we compute only the field-aligned coupling current. Application is made to the solar atmosphere.
Minimum-Time Control of a Two-Link Robot Arm

Abstract Minimum time paths for a two-link robot arm are determined so that the tip moves a specified distance, starting from rest and ending at rest. Two torquers are used, one at the shoulder and one at the elbow, each having bounded torque. The optimal locations of the two end points in the robot coordinate system are determined as part of the solution. The paths are found to be “bang-bang” in both controls. For distances that are small compared to the reach of the arm, the minimum time paths are asymmetric, changing to symmetric paths when the distance is just slightly less than the maximum reach of the arm. A new gradient algorithm for systems with multiple bounded controls was developed to solve the problem.
Mammary collective cell migration involves transient loss of epithelial features and individual cell migration within the epithelium

Normal mammary morphogenesis involves transitions between simple and multilayered epithelial organizations. We used electron microscopy and molecular markers to determine whether intercellular junctions and apico-basal polarity were maintained in the multilayered epithelium. We found that multilayered elongating ducts had polarized apical and basal tissue surfaces both in three-dimensional culture and in vivo. However, individual cells were only polarized on surfaces in contact with the lumen or extracellular matrix. The basolateral marker scribble and the apical marker atypical protein kinase C zeta localized to all interior cell membranes, whereas PAR3 displayed a cytoplasmic localization, suggesting that the apico-basal polarity was incomplete. Despite membrane localization of E-cadherin and β-catenin, we did not observe a defined zonula adherens connecting interior cells. Instead, interior cells were connected through desmosomes and exhibited complex interdigitating membrane protrusions. Single-cell labeling revealed that individual cells were both protrusive and migratory within the epithelial multilayer. Inhibition of Rho kinase (ROCK) further reduced intercellular adhesion on apical and lateral surfaces but did not disrupt basal tissue organization. Following morphogenesis, segregated membrane domains were re-established and junctional complexes re-formed. We observed similar epithelial organization during mammary morphogenesis in organotypic culture and in vivo. We conclude that mammary epithelial morphogenesis involves a reversible, spatially limited, reduction in polarity and intercellular junctions and active individualistic cell migration. Our data suggest that reductions in polarity and adhesion during breast cancer progression might reflect partial recapitulation of a normal developmental program.
Catalytic activity of Pd(II) and Pd(II)/DAB-R systems for the Heck arylation of olefins

Abstract Palladium-catalyzed reactions of aryl bromides with various olefins involving Pd(II)/diazabutadiene (DAB-R) systems have been investigated. The scope of a coupling process using Pd(II) sources and an α-diimine as ligand in the presence of Cs2CO3 as base was tested using various substrates. The Pd(OAc)2/DAB-Cy (1, DAB-Cy=1,4-dicyclohexyl-diazabutadiene) system presents the highest activity with respect to electron-neutral and electron-deficient aryl bromides in coupling with electron rich olefins. The synthesis and X-ray characterization of a Pd(II)-diazabutadiene ligand is reported. Extensive optimization experiments showed that another Pd(II) source, Pd(acac)2 (acac=acetylacetonate), proved to activate aryl bromides at high temperatures, low catalyst loadings when the appropriate concentration of nBu4NBr additive was employed. The effect of the DAB-Cy ligand is important at very low catalyst loadings and high temperatures. Pd(acac)2 and Pd(acac)2/DAB-Cy precatalysts were very effective for the arylation of various olefins with aryl bromides with respect to reaction rate, catalyst loadings, and functional group tolerance.
Creative self-expression in socio-technical systems

Massive networked communities, from Wikipedia contributors to amateur multimedia producers, have demonstrated enormous creativity and productivity in recent years. The dissertation research I discuss in this paper theorizes the creative products of these communities as acts of self-expression that exist within unique socio-technical contexts. Further, my work motivates the study of these creative acts as a new avenue for designing creativity support tools in CSCW.
Manipulating kondo temperature via single molecule switching

Two conformations of isolated single TBrPP-Co molecules on a Cu(111) surface are switched by applying +2.2 V voltage pulses from a scanning tunneling microscope tip at 4.6 K. The TBrPP-Co has a spin-active cobalt atom caged at its center, and the interaction between the spin of this cobalt atom and free electrons from the Cu(111) substrate can cause a Kondo resonance. Tunneling spectroscopy data reveal that switching from the saddle to a planar molecular conformation enhances spin-electron coupling, which increases the associated Kondo temperature from 130 to 170 K. This result demonstrates that the Kondo temperature can be manipulated just by changing molecular conformation without altering chemical composition of the molecule.
Hamiltonian Formulation of Quantum Hall Skyrmions with Hopf Term

We study the nonrelativistic nonlinear sigma model with Hopf term in this letter. This is an important issue because of its relation to the currently interesting studies in skyrmions in quantum Hall systems. We perform the Hamiltonian analysis of this system in CP1 variables. When the coefficient of the Hopf term becomes zero we get the Landau–Lifshitz description of the ferromagnets. The addition of Hopf term dramatically alters the Hamiltonian analysis. The spin algebra is modified giving a new structure and interpretation to the system. We point out momentum and angular momentum generators and new features they bring into the system.
M 2 ocean tide parameters and the deceleration of the Moon's mean longitude from satellite orbit data

An estimation is made of the principal long-period spherical harmonic parameters in the representation of the M2 ocean tide from the orbital histories of the three satellites 1967-92A, Starlette, and GEOS 3. The data used are primarily the evolution of the orbital inclinations of the satellites in conjunction with the longitude of the ascending node from GEOS 3. Analysis procedure and analytic formulation, as well as ocean tidal parameter estimation and deceleration of the lunar mean longitude are outlined. The credibility of the M2 ocean tide solution is further enhanced by the close accord between the computed value for the deceleration of the lunar mean longitude and other recently reported estimates. It is evident from the results presented that studies of close earth satellite orbits are able to provide important information about the tidal forces acting on the earth.
Rate constants for reactions of perfluorobutylperoxyl radical with alkenes

Perfluorobutylperoxyl radicals were produced by radiolytic reduction of perfluorobutyl iodide in aerated methanol solutions. Rate constants for the reactions of this peroxyl radical with various organic compounds were determined by kinetic spectrophotometric pulse radiolysis. The rate constants for alkanes and alkenes were determined by competition kinetics using chlorpromazine as a reference. The results indicate that hydrogen abstraction from aliphatic compounds takes place with a rate constant that is too slow to measure in our system (<105 M−1 s−1), and that abstraction of allylic and doubly allylic hydrogens is slow compared with addition. Addition to alkenes takes place with rate constants of the order of k = 106 − 108 M−1 s−1. Good correlation was obtained between log k and the Taft substituent constants σ* for the various substituents on the double bond. Perfluorobutylperoxyl radical is found to be more reactive than trichloromethylperoxyl and other peroxyl radicals.
STABILITY AND PARADOX IN ALGORITHMIC LOGIC

There is significant interest in type-free systems that allow flexible self-application. Such systems are of interest in property theory, natural language semantics, the theory of truth, theoretical computer science, the theory of classes, and category theory. While there are a variety of proposed type-free systems, there is a particularly natural type-free system that we believe is prototypical: the logic of recursive algorithms. Algorithmic logic is the study of basic statements concerning algorithms and the algorithmic rules of inference between such statements. As shown in [1], the threat of paradoxes, such as the Curry paradox, requires care in implementing rules of inference in this context. As in any type-free logic, some traditional rules will fail. The first part of the paper develops a rich collection of inference rules that do not lead to paradox. The second part identifies traditional rules of logic that are paradoxical in algorithmic logic, and so should be viewed with suspicion in type-free logic generally.
Thermodynamics of the two-component Fermi gas with unequal masses at unitarity

We consider mass-imbalanced two-component Fermi gases for which the unequal-mass atoms interact via a zero-range model potential with a diverging $s$-wave scattering length ${a}_{s}$, that is, with $1/{a}_{s}=0$. The high-temperature thermodynamics of the harmonically trapped and homogeneous systems are examined using a virial expansion approach up to third order in the fugacity. We find that the universal part of the third-order virial coefficient associated with two light atoms and one heavy atom is negative, while that associated with two heavy and one light atom changes sign from negative to positive as the mass ratio $\ensuremath{\kappa}$ increases and diverges when Efimov physics sets in at $\ensuremath{\kappa}=13.61$. By examining the Helmholtz free energy, we find that the equilibrium polarization of the trapped and homogeneous systems is 0 for $\ensuremath{\kappa}=1$, but finite for $\ensuremath{\kappa}\ensuremath{\ne}1$ (with a majority of heavy particles). Compared to the equilibrium polarization of the noninteracting system, the equilibrium polarization at unitarity is increased for the trapped system and decreased for the homogeneous system. We find that unequal-mass Fermi gases are stable for all polarizations.
Dopamine-secreting glomus vagale: a case report and histopathologic correlation.

Background Catecholamine secretion by head and neck paragangliomas is uncommon. Dopamine secretion by these tumors has not routinely been assessed. This case report describes a dopamine-secreting glomus vagale and evaluates seven other paragangliomas immunohistochemically for their ability to synthesize dopamine. Methods Light microscopic and immunohistochemical studies were performed on eight tumors, and biochemical testing for serum/urine catecholamines was performed on two patients. Results One patient (case report) had elevated serum dopamine which corrected following surgery. Five tumors stained strongly positive for the presence of tyrosine hydroxylase, the critical enzyme in the biosynthesis of dopamine. Conclusion This case report describes the ability of a glomus vagale to secrete dopamine. Other paragangliomas express the enzymatic machinery necessary to begin catecholamine synthesis. Now that dopamine is routinely screened during catecholamine determination, other cases may be identified. © 1998 John Wiley & Sons, Inc. Head Neck 20: 753–757, 1998.
The synthesis of attrition resistant slurry phase iron Fischer–Tropsch catalysts

Abstract We describe the evolution of catalyst microstructure as a precipitated Fe–Cu catalyst precursor is transformed into an attrition resistant Fischer–Tropsch (F–T) catalyst. The precipitated Fe–Cu catalyst, as-prepared, is weak compared to the same catalyst that was spray-dried, but without a binder. Spray-drying improves the attrition resistance of the catalyst. Ultrasonic fragmentation was used in this work to measure the attrition resistance of the slurry phase catalysts. Both catalysts, after ultrasonication, produce fine particles below 5 μm, which could cause filtration problems in slurry F–T reactors. The addition of silica as the binder improved the catalyst’s attrition resistance with negligible generation of fine particles below 5 μm. Cross-section TEM of the SiO2-containing Fe F–T catalyst shows that the crystallized Fe particles with an average particle diameter of 80 nm are uniformly distributed within a silica binder. This study provides insight into the catalyst microstructure that leads to improved attrition resistance in Fe F–T catalysts.
Efficient asymmetric synthesis of biologically important tryptophan analogues via a palladium-mediated heteroannulation reaction.

A novel and concise synthesis of optically active tryptophan derivatives was developed via a palladium-catalyzed heteroannulation reaction of substituted o-iodoanilines with an internal alkyne. The required internal alkyne 14a or 25 was prepared in greater than 96% de via alkylation of the Schollkopf chiral auxiliary 19 employing diphenyl phosphate as the leaving group. The Schollkopf chiral auxiliary was chosen here for the preparation of l-tryptophans would be available from d-valine while the d-isomers required for natural product total synthesis would originate from the inexpensive l-valine (300-g scale). Applications of the palladium-catalyzed heteroannulation reaction were extended to the first asymmetric synthesis of l-isotryptophan 38 and l-benz[f]tryptophan 39. More importantly, the optically pure 6-methoxy-d-tryptophan 62 was prepared by this protocol on a large scale (>300 g). This should permit entry into many ring-A oxygenated indole alkaloids when coupled with the asymmetric Pictet−Spengler ...
The Role of Agriculture in Development

A longstanding question in economics is why some countries are so much richer than others. Today, for example, income per capita in the world's richest countries is roughly thirty-five times greater than it is in the world's poorest countries. Recent work argues that the proximate cause of the disparity is that today's poor countries began the process of industrialization much later and that this process is slow. In this paper we argue that a model of structural transformation provides a useful theory of both why industrialization occurs at different dates, and why it proceeds slowly. A key implication of this model is that growth in agricultural productivity is central to development, a message that also appears prominently in the traditional development literature.
On Ohtsuki's invariants of integral homology 3-spheres, I

We provide some more explicit formulae to facilitate the computation of Ohtsuki’s rational invariants λ n of integral homology 3-spheres extracted from Reshetikhin-TuraevSU(2) quantum invariants. Several interesting consequences will follow from our computation of λ2. One of them says that λ2 is always an integer divisible by 3. It seems interesting to compare this result with the fact shown by Murakami that λ1 is 6 times the Casson invariant. Other consequences include some general criteria for distinguishing homology 3-spheres obtained from surgery on knots by using the Jones polynomial.
Failure Semantics for Modal Transition Systems

With the aim to preserve deadlock freedom, we define a new refinement preorder for modal transition systems (MTSs), using an MTS-specific variant of testing inspired by De Nicola and Hennessy. We characterize this refinement with a kind of failure semantics and show that it “supports itself,” for example, in the sense of thoroughness—in contrast to standard modal refinements. We present a conjunction operator with respect to our new refinement, which is quite different from existing ones. It always returns an MTS—again in contrast to the case of modal refinement. Finally, we also consider De Nicola’s and Hennessy’s may- and must-testing, where the latter leads to a semantics that is also compositional for hiding.
Synthesis of the angular furanoxanthone, deoxydehydropsorospermin methyl ether (5,10-dimethoxy-2-isopropenyl-6H-furo[2,3-c]xanthen-6-one)

The angular isopropenylfuranoxanthone heterocyclic system, on which the anti-leukemic natural product psorospermin is based, is synthesized by the reaction of cuprous isopropenylacetylide with 4-bromo-1,5-dimethoxy-3-hydroxyxanthone.
Effects of fluoride concentration and temperature of milk on caries lesion rehardening

Abstract Objectives The aim of the present in vitro study was to investigate the effects of fluoride concentration and temperature of milk on caries lesion rehardening under pH cycling conditions. Methods Incipient caries-like lesions were formed in human enamel specimens, characterized using Vickers surface microhardness (VHN) and assigned to seven treatment groups ( n = 18 per group): fluoride was tested at five levels (0, 2.5, 5, 10, 20 mg/l, all 22 °C) and milk temperature at three levels (4, 22, 60 °C), but only for 10 mg/l F. Lesions were pH cycled for 15d (4×/daily 10 min milk treatments, 1×/daily 4 h acid challenge, remineralization in human/artificial saliva mixture). VHN of specimens were measured again and changes from lesion baseline were calculated. Subsequently, enamel fluoride uptake (EFU) was determined using the micro drill technique. Results Lesions responded to fluoride in a dose–response manner with higher fluoride concentrations resulting in more lesion rehardening (20 > 10 ≥ 5 ≥ 2.5 > 0 mg/l F). Furthermore, fluoridated milk at 60 °C was found to be more efficacious than at 4 °C (60 ≥ 22 > 4 °C). EFU results were similar (20 > 10 > 5 > 2.5 ≥ 0 mg/l F; 60 > 22 ≥ 4 °C). Conclusions Both fluoride concentration and milk temperature are likely to contribute to the anti-caries potential of fluoridated milk.
Mating‐induced loss of sex pheromone and sexual receptivity in insects with emphasis on Helicoverpa zea and Lymantria dispar

Mating in most species of insects leads to a transient or permanent loss in sexual receptivity of the females. Among moths, this loss of receptivity is often accompanied with a loss of the sex pheromone in the absence of calling, which also could be temporary or permanent. Most of the earlier work on changes in reproductive behavior after mating was done with Diptera in which sperm and/or male accessory gland secretions were shown to be responsible for termination of receptivity. In the corn earworm moth, Helicoverpa zea, mated females become depleted of pheromone and become nonreceptive to further mating attempts, but only for the remainder of the night of mating. A pheromonostatic peptide isolated from the accessory glands of males may be responsible for the depletion of pheromone, while the termination of receptivity is independently controlled. In the gypsy moth, Lymantria dispar, the changes in behavior following mating are permanent. In this species, the switch from virgin to mated behavior involves three steps: a physical stimulation associated with mating, transfer of viable sperm to the spermatheca, and commencement of oviposition. Signals generated by these factors operate through neural pathways and, unlike in H. zea, accessory gland factors seem not to be involved. © 1994 Wiley-Liss, Inc.1
Vortices, instantons and branes

The purpose of this paper is to describe a relationship between the moduli space of vortices and the moduli space of instantons. We study charge vortices in Yang-Mills-Higgs theories and show that the moduli space is isomorphic to a special lagrangian submanifold of the moduli space of instantons in non-commutative Yang-Mills theories. This submanifold is the fixed point set of a action on the instanton moduli space which rotates the instantons in a plane. To derive this relationship, we present a D-brane construction in which the dynamics of vortices is described by the Higgs branch of a gauge theory with 4 supercharges which is a truncation of the familiar ADHM gauge theory. We further describe a moduli space construction for semi-local vortices, lumps in the and grassmannian sigma-models, and vortices on the non-commutative plane. We argue that this relationship between vortices and instantons underlies many of the quantitative similarities between quantum field theories in two and four dimensions.
Network Characteristics for Server Selection in Online Games

Online gameplay is impacted by the network characteristics of players connected to the same server. Unfortunately, the network characteristics of online game servers are not well-understood, particularly for groups that wish to play together on the same server. As a step towards a remedy, this paper presents analysis of an extensive set of measurements of game servers on the Internet. Over the course of many months, actual Internet game servers were queried simultaneously by twenty-five emulated game clients, with both servers and clients spread out on the Internet. The data provides statistics on the uptime and populations of game servers over a month long period an an in-depth look at the suitability for game servers for multi-player server selection, concentrating on characteristics critical to playability--latency and fairness. Analysis finds most game servers have latencies suitable for third-person and omnipresent games, such as real-time strategy, sports and role-playing games, providing numerous server choices for game players. However, far fewer game servers have the low latencies required for first-person games, such as shooters or race games. In all cases, groups that wish to play together have a greatly reduced set of servers from which to choose because of inherent unfairness in server latencies and server selection is particularly limited as the group size increases. These results hold across different game types and even across different generations of games. The data should be useful for game developers and network researchers that seek to improve game server selection, whether for single or multiple players.
Inelastic dissipation in wobbling asteroids and comets

Asteroids and comets dissipate energy when they rotate about any axis different from the axis of the maximal moment of inertia. We show that the most efficient internal relaxation happens at twice the frequency of the precession of the body. Therefore earlier estimates that ignore the double frequency input underestimate the internal relaxation in asteroids and comets. We suggest that seismological data of the Earth may poorly represent the acoustic properties of asteroids and comets as internal relaxation increases in the presence of moisture. At the same time, owing to the non-linearity of inelastic relaxation, small angle nutations can persist for very long time spans, but our ability to detect such precessions is limited by the resolution of the radar-generated images. Wobbling may provide valuable information on the composition and structure of asteroids and on their recent history of external impacts.
A New Design Tool: The Matched Characteristic Method of Nonlinear Analysis

The analytical method presented here simplifies problems associated with transmitting transistor and diode characteristics from the semiconductor manufacturer to the electronic designer. This novel approach permits the base and collector characteristics of any individual transistor of a given type to be derived from the nominal characteristics of that type by use of a set of matching factors and terms that modify the nominal characteristics to suit that individual. Availability of complete characteristics allows the designer to accurately simulate the nonlinear behavior of the device in a circuit by means of a convergent iterative process.
Biases in Virial Black Hole Masses: An SDSS Perspective

We compile black hole (BH) masses for ~60,000 quasars in the redshift range 0.1 z 4.5 included in the Fifth Data Release of the Sloan Digital Sky Survey, using virial BH mass estimators based on the Hβ, Mg II, and C IV emission lines. Within our sample, the widths of the three lines follow lognormal distributions, with means and dispersions that do not depend strongly on luminosity or redshift. The Mg II- and Hβ-estimated BH masses are consistent with one another, but there is a positive bias between the C IV- and Mg II-estimated BH masses correlated with the C IV-Mg II blueshift, suggesting that the C IV estimator is more severely affected by a disk wind. If the underlying BH mass distribution decreases with mass and the Eddington ratio distribution at fixed true BH mass has nonzero width, we show that the measured virial BH mass and Eddington ratio distributions within finite luminosity bins are subject to Malmquist bias. We present a model that reproduces the observed virial mass distribution, quasar luminosity function, and line width distribution of our sample; it has an underlying BH mass distribution dN/dlog M ∝ M−2.6 and a lognormal true Eddington ratio distribution at fixed true mass with dispersion 0.4 dex and mean dependent on BH mass. In this model, the observed virial mass (Eddington ratio) distribution for the SDSS sample is biased high (low) by ~0.6 dex within finite luminosity bins. Finally, we compare virial BH masses of radio and broad absorption line quasars with ordinary quasars matched in redshift and luminosity.
Investigations on the development of a mixed displacement-pressure formulation for an anelastic displacement-field finite element

Space and weapon delivery systems contain guidance components and payload that need to be protected from the extremely harsh acoustic excitation present during launch operations. The above example represents just one application where high-damping viscoelastic materials are used in the design of shock and vibration isolation components. The shock transients generally encountered are characterized by a broad frequency spectrum. Widely available finite element codes do not offer the proper tools to model the frequency- dependent mechanical properties of viscoelastic materials over the frequency domain of interest. An added difficulty is the large Poissson's ratio exhibited by some of these materials, which indicates that previously developed displacement-based finite element formulations should be complemented with mixed pressure-displacement finite element formulations. A pure displacement-based finite element generally predicts the displacements well, if the mesh used is fine enough, but the same thing may not be said about the values of the predicted stresses. The Anelastic Displacement Fields (ADF) method is employed herein to model frequency-dependence of material properties within a time-domain finite element framework and using a mixed displacement-pressure finite element formulation. Finite elements based on this new formulation are developed.
Development progress on the atmospheric fluidized bed coal combustor for cogeneration gas turbine system for industrial cogeneration plants

The Atmospheric Fluidized Bed Coal Combustor Program will develop the technology for a fluidized bed coal combustion system to provide a source of high temperature air for process heating and power generation with gas turbines in industrial plants. The gas turbine has the advantages of a higher ratio of electric power output to exhaust heat load and a higher exhaust temperature than do steam turbines in cogeneration applications. The program is directed toward systems in the size range of 5 to 50 MW(e) and is sponsored by the Department of Energy. Conceptual design studies have been done for typical industrial installations, and some of these results are presented. The conceptual design of a 300 kW(e) test unit has been completed. A number of furnace design firms have been invited to submit their own designs for a 1500 kW(t) (5*10/sup 6/ Btu/hr) combustor, from which a final selection will be made. 7 refs.
Orthogonal sulfation strategy for synthetic heparan sulfate ligands.

An orthogonal sulfation strategy involving six different protecting groups has been developed for generating sulfated carbohydrate libraries based on heparan. Chemoselective cleavage conditions (optimized for a heparan disaccharide) can be performed in the presence of sulfate esters as well as the remaining protecting groups.