cssi/SciSciGPT-SciSciNet huggingface dataset:
Algebraic codes for Slepian-Wolf code design

Practical constructions of lossless distributed source codes (for the Slepian-Wolf problem) have been the subject of much investigation in the past decade. In particular, near-capacity achieving code designs based on LDPC codes have been presented for the case of two binary sources, with a binary-symmetric correlation. However, constructing practical codes for the case of non-binary sources with arbitrary correlation remains by and large open. From a practical perspective it is also interesting to consider coding schemes whose performance remains robust to uncertainties in the joint distribution of the sources. In this work we propose the usage of Reed-Solomon (RS) codes for the asymmetric version of this problem. We show that algebraic soft-decision decoding of RS codes can be used effectively under certain correlation structures. In addition, RS codes offer natural rate adaptivity and performance that remains constant across a family of correlation structures with the same conditional entropy. The performance of RS codes is compared with dedicated and rate adaptive multistage LDPC codes (Varodayan et al. '06), where each LDPC code is used to compress the individual bit planes. Our simulations show that in classical Slepian-Wolf scenario, RS codes outperform both dedicated and rate-adaptive LDPC codes under q-ary symmetric correlation, and are better than rate-adaptive LDPC codes in the case of sparse correlation models, where the conditional distribution of the sources has only a few dominant entries. In a feedback scenario, the performance of RS codes is comparable with both designs of LDPC codes. Our simulations also demonstrate that the performance of RS codes in the presence of inaccuracies in the joint distribution of the sources is much better as compared to multistage LDPC codes.
The dynamics of alternative pathways to compensatory substitution

The role of epistatic interactions among loci is a central question in evolutionary biology and is increasingly relevant in the genomic age. While the population genetics of compensatory substitution have received considerable attention, most studies have focused on the case when natural selection is very strong against deleterious intermediates. In the biologically-plausible scenario of weak to moderate selection there exist two alternate pathways for compensatory substitution. In one pathway, a deleterious mutation becomes fixed prior to occurrence of the compensatory mutation. In the other, the two loci are simultaneously polymorphic. The rates of compensatory substitution along these two pathways and their relative probabilities are functions of the population size, selection strength, mutation rate, and recombination rate. In this paper these rates and path probabilities are derived analytically and verified using population genetic simulations. The expected time durations of these two paths are similar when selection is moderate, but not when selection is weak. The effect of recombination on the dynamics of the substitution process are explored using simulation. Using the derived rates, a phylogenetic substitution model of the compensatory evolution process is presented that could be used for inference of population genetic parameters from interspecific data.
Mergers as Reallocation

We model merger waves as reallocation waves, and argue that mergers spread new technology in a way that is similar to that of entry and exit of firms. We focus on two periods: 1890-1930 during which electricity and the internal combustion engine spread through the U.S. economy, and 1970-2000 — the Information Age. The model’s main implication — that exits should lead mergers — is supported by data from both epochs.
Optimal linear dispersion codes for correlated MIMO channels

The design of space-time codes for frequency flat, spatially correlated MIMO fading channels is considered. The focus of the paper is on the class of space-time block codes known as linear dispersion (LD) codes, introduced by Hassibi and Hochwald. The LD codes are optimized with respect to the mutual information between the inputs to the space-time encoder and the output of the channel. The use of the mutual information as both a design criterion and a performance measure is justified by allowing soft decisions at the output of the space-time decoder. A spatial Fourier (virtual) representation of the channel is exploited to allow for the analysis of MIMO channels with quite general fading statistics. Conditions, known as generalized orthogonal conditions (GOC's), are derived for an LD code to achieve an upper bound on the mutual information, with the understanding that LD codes that achieve the upper bound, if they exist, are optimal. Explicit code constructions and properties of the optimal power allocation schemes are also derived. In particular, it is shown that optimal LD codes correspond to beamforming to a single virtual transmit angle at low SNR, and a necessary and sufficient condition for beamforming to be optimal is provided. Due to the nature of the code construction, it is further observed that the optimal LD codes can be designed to adapt to the statistics of different scattering environments. Finally, numerical results are provided to illustrate the optimal code design for three examples of sparse scattering environments. The performance of the optimal LD codes for these scattering environments is compared with that of LD codes designed assuming the i.i.d. Rayleigh fading (rich scattering) model, and it is shown that the optimal LD codes perform significantly better. The optimal LD codes are also compared to beamforming LD codes and it is shown that beamforming is nearly optimal over a range of SNR's of interest.
One Gravitational Potential or Two? Forecasts and Tests

The metric of a perturbed Robertson–Walker space–time is characterized by three functions: a scale-factor giving the expansion history and two potentials that generalize the single potential of Newtonian gravity. The Newtonian potential induces peculiar velocities and, from these, the growth of matter fluctuations. Massless particles respond equally to the Newtonian potential and to a curvature potential. The difference of the two potentials, called the gravitational slip, is predicted to be very small in general relativity, but can be substantial in modified gravity theories. The two potentials can be measured, and gravity tested on cosmological scales, by combining weak gravitational lensing or the integrated Sachs–Wolfe effect with galaxy peculiar velocities or clustering.
Cosmology with galaxy clusters. III. Gravitationally lensed arc statistics as a cosmological probe

We calculate the expected number of gravitationally lensed optical, radio and sub-mm lensed sources on the whole sky due to foreground galaxy clusters for different cosmological models. We improve previous calculations of lensed arc statis- tics by including redshift information for background sources and accounting for the redshift evolution of the foreground lens- ing clusters. The background sources are described based on the redshift and optical magnitude or flux distribution for sources in the Hubble Deep Field (HDF). Using the HDF luminosity func- tion, we also account for the magnification bias in magnitude- limited observational programs to find lensed optical arcs. The foreground lensing clusters are modeled as singular isothermal spheres, and their number density and redshift distribution is calculated based on the Press-Schechter theory with normaliza- tions based on the local cluster temperature function. Based on the results from optical arc surveys, we find that the observed number of arcs can easily be explained in a flat universe (m + =1 ) with low values for cosmological mass density of the universe (m . 0:5). However, given the large systematic and statistical uncertainties involved with both the observed and predicted number of lensed arcs, more reli- able estimates of the cosmological parameters are not currently possible. We comment on the possibility of obtaining a much tighter constraint based on statistics from large area optical sur- veys. At radio wavelengths (1.4 GHz), we predict 1500 lensed radio sources with flux densities greater than 10 Jy, and with amplifications due to lensing greater than 2, in a flat cosmol- ogy with m =0 :3 and =0 :7. Given the recent detection of a sub-mm selected lensed Jy radio source towards A370, it is suggested that deep radio observations of clusters should contain such lensed sources. At sub-mm wavelengths (850m), the number of lensed sources expected towards the same fore- ground lens population and cosmology is 310 4 . We briefly consider the possibility of using the South Pole 10-m sub-mm telescope and the Planck surveyor to identify lensed sub-mm sources. A catalog of around 100 gravitationally lensed sources at 353 GHz may be a useful by-product of Planck.
Coherency identification for power system dynamic equivalents

Coherency-based approach to the problem of constructing power system dynamic equivalents has been very successful in applications. The key step in this approach is to identify groups of coherent generators. An analytic study of coherency is conducted. An algebraic characterization of coherency is given. An algorithm, based on the algebraic characterization, to identify coherent groups directly from system data is developed. A physical interpretation of the algebraic characterization of coherency is presented, where the condition for coherency is described in terms of generator inertia constants and their equivalent admittances to the bus of the disturbance.
The Effect of Adverse Housing and Neighborhood Conditions on the Development of Diabetes Mellitus among Middle-aged African Americans

The authors examined the associations of observed neighborhood (block face) and housing conditions with the incidence of diabetes by using data from 644 subjects in the African-American Health Study (St. Louis area, Missouri). They also investigated five mediating pathways (health behavior, psychosocial, health status, access to medical care, and sociodemographic characteristics) if significant associations were identified. The external appearance of the block the subjects lived on and housing conditions were rated as excellent, good, fair, or poor. Subjects reported about neighborhood desirability. Self-reported diabetes was obtained at baseline and 3 years later. Of 644 subjects without self-reported diabetes, 10.3% reported having diabetes at the 3-year follow-up. Every housing condition rated as fair-poor was associated with an increased risk of diabetes, with odds ratios ranging from 2.53 (95% confidence interval: 1.47, 4.34 for physical condition inside the building) to 1.78 (95% confidence interval: 1.03, 3.07 for cleanliness inside the building) in unadjusted analyses. No association was found between any of the block face conditions or perceived neighborhood conditions and incident diabetes. The odds ratios for the five housing conditions were unaffected when adjusted for the mediating pathways. Poor housing conditions appear to be an independent contributor to the risk of incident diabetes in urban, middle-aged African Americans.
Offshoring in a Knowledge Economy

How does the formation of cross-country teams affect the organization of work and the structure of wages? To study this question, we propose a theory of the assignment of heterogeneous agents into hierarchical teams, where less skilled agents specialize in production and more skilled agents specialize in problem solving. We first analyze the properties of the competitive equilibrium of the model in a closed economy, and show that the model has a unique and efficient solution. We then study the equilibrium of a two-country model (North and South), where countries differ in their distributions of ability, and in which agents in different countries can join together in teams. We refer to this type of integration as globalization. Globalization leads to better matches for all southern workers but only for the best northern workers. As a result, we show that globalization increases wage inequality among nonmanagers in the South, but not necessarily in the North. We also study how globalization affects the size distribution of firms and the patterns of consumption and trade in the global economy.
Fokker-Planck and Quasilinear Codes

Abstract The interaction of radio-frequency waves with a plasma is described by a Fokker-Planck equation with an added quasilinear term. Methods for solving this equation on a computer are discussed.
Blood clots are rapidly assembled hemodynamic sensors: flow arrest triggers intraluminal thrombus contraction.

Objective— Blood clots form under flow during intravascular thrombosis or vessel leakage. Prevailing hemodynamics influence thrombus structure and may regulate contraction processes. A microfluidic device capable of flowing human blood over a side channel plugged with collagen (±tissue factor) was used to measure thrombus permeability (κ) and contraction at controlled transthrombus pressure drops. Methods and Results— The collagen (κcollagen=1.98×10−11 cm2) supported formation of a 20-µm thick platelet layer, which unexpectedly underwent massive platelet retraction on flow arrest. This contraction resulted in a 5.34-fold increase in permeability because of collagen restructuring. Without stopping flow, platelet deposits (no fibrin) had a permeability of κplatelet=5.45×10−14 cm2 and platelet-fibrin thrombi had κthrombus=2.71×10−14 cm2 for ΔP=20.7 to 23.4 mm Hg, the first ever measurements for clots formed under arterial flow (1130 s−1 wall shear rate). Platelet sensing of flow cessation triggered a 4.6- to 6.5-fold (n=3, P <0.05) increase in contraction rate, which was also observed in a rigid, impermeable parallel-plate microfluidic device. This triggered contraction was blocked by the myosin IIA inhibitor blebbistatin and by inhibitors of thromboxane A2 (TXA2) and ADP signaling. In addition, flow arrest triggered platelet intracellular calcium mobilization, which was blocked by TXA2/ADP inhibitors. As clots become occlusive or blood pools following vessel leakage, the flow diminishes, consequently allowing full platelet retraction. Conclusion— Flow dilution of ADP and thromboxane regulates platelet contractility with prevailing hemodynamics, a newly defined flow-sensing mechanism to regulate clot function.
Enantioselective Total Synthesis of (−)-Chlorothricolide via the Tandem Inter- and Intramolecular Diels−Alder Reaction of a Hexaenoate Intermediate

An enantioselective total synthesis of (−)-chlorothricolide (1) has been completed via a route involving the tandem inter- and intramolecular Diels−Alder (IMDA) reaction of hexaenoate 19 and the chiral dienophile (R)-12. This reaction, which establishes seven asymmetric centers in a single operation, is feasible only by virtue of the high diastereofacial and exo selectivity of dienophile 12. The C(9)-trimethylsilyl steric directing group of 19 also plays a key role by controlling the stereochemical course of the IMDA reaction leading to the bottom half octahydronaphthalene unit. Hexaenoate 19 was prepared in 32% overall yield by a 10-step sequence starting from the known acetylenic ketone 33. Key steps include the asymmetric reduction of 33 using Alpine Borane (up to 94% ee), the Suzuki cross coupling of α-iodo vinylsilane 20 with vinylboronic acid 21, and the Horner-type olefination of aldehyde 41 with dienylic phosphonate 22. The key tandem inter-intramolecular Diels−Alder reaction was performed by heat...
AlAs etch-stop layers for InGaAlAs/InP heterostructure devices and circuits

Wet chemical etching solutions were developed that allow the selective etching of InP lattice-matched InGaAs and InAlAs compounds using thin pseudomorphic AlAs layers as etch stop. Several dicarboxylic acids were found that allow the etching of indium compounds. The best results were obtained for etchants consisting of succinic acid, ammonia, and hydrogen peroxide. The etch rate in In/sub 0.53/Ga/sub 0.47/As is found to be over 1000 times the etch rate of AlAs, while the etch rate of In/sub 0.52/Ga/sub 0.48/As is over 500 times that of the AlAs. The dependences of the succinic acid based etch on pH and hydrogen concentration were also studied. Buffered HF can be used to remove the AlAs stop layer, while it does not etch InGaAlAs to any significant degree. >
Arylene–ethynylene macrocycles: Privileged shape-persistent building blocks for organic materials

This report details the advances in synthetic strategies toward arylene-ethynylene macrocycles (AEMs). After a brief description of traditional methods, we summarize recent advances based on dynamic covalent chemistry (DCC) whereby a highly active and func- tional group tolerant alkyne metathesis catalyst yields scalable quantities of AEMs under thermodynamic controlled reaction conditions.
Bar constructions for topological operads and the Goodwillie derivatives of the identity

We describe a cooperad structure on the simplicial bar construction on a reduced operad of based spaces or spectra and, dually, an operad structure on the cobar construction on a cooperad. We also show that if the homology of the original operad (respectively, cooperad) is Koszul, then the homology of the bar (respectively, cobar) construction is the Koszul dual. We use our results to construct an operad structure on the partition poset models for the Goodwillie derivatives of the identity functor on based spaces and show that this induces the ‘Lie’ operad structure on the homology groups of these derivatives. We also extend the bar construction to modules over operads (and, dually, to comodules over cooperads) and show that a based space naturally gives rise to a left module over the operad formed by the derivatives of the identity.
Broadband exterior cloaking

It is shown how a recently proposed method of cloaking is effective over a broad range of frequencies. The method is based on three or more active devices. The devices, while not radiating significantly, create a "quiet zone" between the devices where the wave amplitude is small. Objects placed within this region are virtually invisible. The cloaking is demonstrated by simulations with a broadband incident pulse.
Host galaxies of luminous quasars: population synthesis of optical off-axis spectra

There is increasing evidence of a connection between AGN activity and galaxy evolution. To obtain further insight into this potentially important e volutionary phase, we analyse the properties of quasar host galaxies. In this paper, we presen t a population synthesis modeling technique for off-axis spectra, the results of which con strain host colour and the stellar ages of luminous quasars (MV (nuc) < 23). Our technique is similar to well established quiescent-galaxy models, modified to accommodate scattere d nuclear light (a combination of atmospheric, instrumental and host galaxy scattered light) observed off axis. In our model, subtraction of residual scattered quasar light is performe d, while simultaneously modeling the constituent stellar populations of the host galaxy. The rel iability of this technique is tested via a Monte-Carlo routine in which the correspondence between synthetic spectra with known parameters and the model output is determined. Application of this model to a preliminary sample of 10 objects is presented and compared to previous studies. Spectroscopic data was obtained via long-slit and integral-field unit observations o n the Keck and WIYN telescopes. We confirm that elliptical quasar hosts are distinguishable (b luer) from inactive ellipticals in rest frame B-V colour. Additionally, we note a trend for radio luminous (L5GHz & 10 40 erg s 1 ) quasars to be located in redder host galaxies in comparison to their less luminous radio counterparts. While the host colour and age of our radio luminous sample is in close proximity to the green valley, our radio faint sample is consistent wit h quiescent star-forming galaxies. However, further observations are needed to confirm these re sults. Finally, we discuss future applications for our technique on a larger sample of objects being obtained via SALT and WIYN telescope observing campaigns.
Binding energy effects in cascade evolution and sputtering

Abstract The marlowe model was extended to include a binding energy dependent on the local crystalline order: atoms are bound less strongly to lattice sites near surfaces or damage. Sputtering and cascade evolution were studied in self-ion irradiations of Cu and Au monocrystals. In cascades, the mean binding energy is reduced ∼8% in Cu with little dependence on the initial energy; in Au, it is reduced ∼9% at 1 keV and ∼15% at 100 keV. In sputtering, the mean binding energy is reduced ∼8% in Cu and ∼15% in Au with little energy dependence; the yields are increased less, averaging about half as much. Most sites from which atoms are sputtered are isolated in both metals. Small clusters of sites occur in Cu, but there are some large clusters in Au, especially in {111} targets. There are always more large clusters with damage-dependent binding than with a constant binding energy, but only a few clusters are compact enough to be regarded as pits.
High-temperature behavior of grain boundaries from embedded atom method molecular dynamics simulation

The behavior of a metallic grain boundary at high temperatures is studied using an embedded atom potential. A recently developed molecular dynamics code is used which allows the simulation of an isolated grain boundary at temperatures as high as the bulk melting point. The stability of the boundary below the melting point is studied and compared with earlier investigations which have suggested the existence of a ''premelting'' transition. It is found that the boundary migrates at high temperature but remains well defined up to the bulk melting point. In contrast to simulations of ideal crystals, it was not possible to superheat the grain boundary due to the nucleation of bulk melting at the boundary. 14 refs., 4 figs.
Exact solution for the Green's function describing time-dependent thermal Comptonization

We obtain an exact, closed-form expression for the time-dependent Green's function solution to the Kompaneets equation. The result, which is expressed as the integral of a product of two Whittaker functions, describes the evolution in energy space of a photon distribution that is initially monoenergetic. Effects of spatial transport within a homogeneous scattering cloud are also included within the formalism. The Kompaneets equation that we solve includes both the recoil and energy diffusion terms, and therefore our solution for the Green's function approaches the Wien spectrum at large times. This was not the case with earlier analytical solutions that neglected the recoil term and were therefore applicable only in the soft-photon limit. We show that the Green's function can be used to generate all of the previously known steady-state and time-dependent solutions to the Kompaneets equation. The new solution allows the direct determination of the spectrum, without the need to solve the partial differential equation numerically. It is therefore much more convenient for data analysis purposes. Based upon the Green's function, we derive a new, exact solution for the variation of the inverse-Compton temperature of an initially monoenergetic photon distribution. Furthermore, we also obtain a new time-dependent solution for the photon distribution resulting from the reprocessing of an optically thin bremsstrahlung initial spectrum with a low-energy cut-off. Unlike the previously known solution for bremsstrahlung injection, the new solution possesses a finite photon number density, and therefore it displays proper equilibration to a Wien spectrum at large times. The relevance of our results for the interpretation of emission from variable X-ray sources is discussed, with particular attention to the production of hard X-ray time lags and the Compton broadening of narrow features such as iron lines.
Harmonic analysis with respect to heat kernel measure

This paper surveys developments over the last decade in harmonic analysis on Lie groups relative to a heat kernel measure. These include analogs of the Hermite expansion, the Segal-Bargmann transform, and the Taylor ex- pansion. Some of the results can be understood from the standpoint of geo- metric quantization. Others are intimately related to stochastic analysis.
Assume-guarantee abstraction refinement for probabilistic systems

We describe an automated technique for assume-guarantee style checking of strong simulation between a system and a specification, both expressed as non-deterministic Labeled Probabilistic Transition Systems (LPTSes). We first characterize counterexamples to strong simulation as stochastic trees and show that simpler structures are insufficient. Then, we use these trees in an abstraction refinement algorithm that computes the assumptions for assume-guarantee reasoning as conservative LPTS abstractions of some of the system components. The abstractions are automatically refined based on tree counterexamples obtained from failed simulation checks with the remaining components. We have implemented the algorithms for counterexample generation and assume-guarantee abstraction refinement and report encouraging results.
The effect of tether substituents on the selectivity of Pd catalyzed enyne cyclizations. A total synthesis of chokol C

Abstract In the context of the palladium catalyzed cycloisomerization of enynes, two of the most important tether substituents, the carbonyl group because of its general synthetic versatility and the ketal because of its prospect to induce absolute stereochemistry by employing the ketal from a chiral diol, are probed within the context of a synthesis of chokol C, an antifungal compound produced by Phleum pratense when infected by a pathogenic fungus Epichloe typhina .
Computational test of the infinite order sudden approximation for excitation of linear rigid rotors by collisions with atoms

Abstract The infinite order sudden approximation for excitation of linear rigid rotors by collisions with atom is tested by comparing integral state-to-state cross sections with accurate close coupling and coupled states results. The systems studied are HClAr, HClHe, COHe, HCNHe, CSH 2 and OCSH 2 . With the exception of diatomic hydrides (e.g., HCl) which have atypically large rotational constants the method is found to be very accurate to remarkably low collision energies. This approximation should generally be extremely useful for thermal energy collisions.
Temperature dependence of the crystal structures of nylon 11

Abstract : Careful examination of the X-ray diffraction patterns from melt-crystallized Nylon ll films showed significant discrepancies with the proposed alpha-form structure. These discrepancies did not disappear after annealing the samples. The temperature dependence of the d-spacings of the two strongest peaks showed further evidence that the melt-crystallized and solution cast films (alpha-form) possess different crystal structures. These results suggest a different crystal structure for the melt-crystallized films, and this would help explain the rather low piezoelectric response of these films and also the failure to observe a rapid decrease in polarization at the transition temperature.
Copper oxide nanoparticles inhibit the metabolic activity of Saccharomyces cerevisiae

Copper oxide nanoparticles (CuO NPs) are used increasingly in industrial applications and consumer products and thus may pose risk to human and environmental health. The interaction of CuO NPs with complex media and the impact on cell metabolism when exposed to sublethal concentrations are largely unknown. In the present study, the short-term effects of 2 different sized manufactured CuO NPs on metabolic activity of Saccharomyces cerevisiae were studied. The role of released Cu2+ during dissolution of NPs in the growth media and the CuO nanostructure were considered. Characterization showed that the 28 nm and 64 nm CuO NPs used in the present study have different primary diameter, similar hydrodynamic diameter, and significantly different concentrations of dissolved Cu2+ ions in the growth media released from the same initial NP mass. Exposures to CuO NPs or the released Cu2+ fraction, at doses that do not have impact on cell viability, showed significant inhibition on S. cerevisiae cellular metabolic activity. A greater CuO NP effect on the metabolic activity of S. cerevisiae growth under respiring conditions was observed. Under the tested conditions the observed metabolic inhibition from the NPs was not explained fully by the released Cu ions from the dissolving NPs. Environ Toxicol Chem 2016;35:134–143. © 2015 SETAC
Development of finite element procedures for fluid-structure interaction.

In this thesis the development of finite element procedures for fluid-structure interaction problems is presented. The areas upon which attention is focused are: numerical transient algorithms which emphasize implicit-explicit finite element concepts; finite element kinematical descriptions for modelling fluid subdomains in fluidstructure interaction problems; finite element methodology for nearly incompressible fluids and solids, and beam, plate and shell structures based upon theories which include transverse shear deformations; and finite rotation effects in numerical integration of rate constitutive equations arising in large-deformation analysis. All these nonlinear methodologies have been integrated into a working finite element computer code. A number of numerical examples are presented to demonstrate the effectiveness of these approaches.
Birthing a Nation: The Effect of Fertility Control Access on the 19th Century Demographic Transition

During the 19th century, the US birthrate fell by half. While previous economic literature has emphasized demand-side explanations for this decline--that rising land prices and literacy caused a decrease in demand for children--historians and others have emphasized changes in the supply of technologies to control fertility, including abortion and birth control. In this paper I exploit the introduction during the 19th century of state laws governing American women's access to abortion to measure the effect of changes in the supply of fertility technologies on the number of children born. I estimate an increase in the birthrate of 4 to 12% when abortion is restricted, which lies within the ranges of estimates found for the effect of fertility control supply restrictions on birthrates today. The importance of legal abortion in reducing 19th-century birthrates helps to account for a previously unexplained portion of the demographic transition. This paper posits that there has long been a demand, often unmet, for fertility control that should be considered in future demographic research as well as in policy formulation.
Greed in resource scheduling

We examine the worst-case performance of a class of heuristic scheduling algorithms commonly referred to as priority-driven or list-scheduling algorithms. It is well known that these algorithms have anomalous, unpredictable performance when used to schedule nonpreemptive tasks with precedence constraints. We present a general method for deriving the worst-case performance of these algorithms. This method is easy to use, yet powerful enough to yield tight performance bounds for many classes of scheduling problems. We demonstrate the method for several problems to show it has wide applicability. We also present several task systems for which list-scheduling algorithms exhibit unavoidable worst-case performance and discuss the general characteristics of these task systems. These task systems are sometimes overlooked in simulation studies; consequently, the results of these studies may be overly optimistic.
Object data models to support source code queries: implementing SCA within REFINE

The REFINE object base is being used widely for code analysis and reverse engineering. From the perspective of program querying and interactive program analysis however, REFINE-like object bases offer only general-purpose programming languages in which users must code their program queries. In contrast, Source Code Algebra (SCA) is an object algebra designed to serve as an applicative source code query language. We are currently implementing an SCA-based query processor within the REFINE environment. This paper provides insights into some object data model features which are currently absent in the REFINE framework, and argues that their incorporation will enable certain source code queries to be handled more efficiently. We also argue that the inclusion of these features will greatly simplify the implementation of the SCA query processor. >
The request reply family of group routing protocols

We present a family of group routing protocols for a network of processes. The task of these protocols is to route data messages to each member of a process group. To this end, a tree of processes is constructed in the network, ensuring that each group member is included in the tree. No processing or storage overhead is required for processes not included in the tree. The overhead of processes in the tree consists solely of the periodic exchange of request/reply messages with their parent. To choose the processes that constitute the tree, we take advantage of the existing unicast routing protocol in the network. In addition, our family of group routing protocols distinguishes itself from other group routing protocols in three ways. First, the protocols are proven correct. Second, the protocols preserve the integrity of the group tree as it adapts to changes in the unicast routing tables, even in the presence of temporary unicast routing loops. Third, data messages are propagated along the entire group tree, even while the tree adapts to changes in the unicast routing tables.
Investigating Bimodal Clustering in Human Mobility

We apply a simple clustering algorithm to a large dataset of cellular telecommunication records, reducing the complexity of mobile phone users' full trajectories and allowing for simple statistics to characterize their properties. For the case of two clusters, we quantify how clustered human mobility is, how much of a user's spatial dispersion is due to motion between clusters, and how spatially and temporally separated clusters are from one another.
Distances and Riemannian Metrics for Multivariate Spectral Densities

The paper is concerned with the practical problem of how to compare power spectral densities of multivariable time-series. For scalar time-series several notions of distance (divergences) have been proposed and studied starting from the early 1970s while multivariable ones have only recently began to receive any attention. In the paper, two classes of divergence measures inspired by classical prediction theory are introduced. These divergences naturally induce Riemannian metrics on the cone of multivariable densities. The metrics amount to the quadratic term in the divergence between “infinitesimally close to each other” power spectra. For one of the two we provide explicit formulae for the corresponding geodesics and geodesic distance. A close connection between the geometry of power spectra and the geometry of the Fisher-Rao metric is noted.
Severe left ventricular systolic dysfunction increases atrial fibrillation after ablation of atrial flutter.

Background: Atrial fibrillation (Afib) that occurs after a successful atrial flutter (AFL) ablation may negate the potential benefits of the ablation. Afib occurs more often when severe left ventricular systolic dysfunction (LVSD) is present. We hypothesized that even after a successful AFL ablation, the incidence of postablation Afib is increased when severe LVSD is present. Methods: Ninety consecutive patients with LVSD who underwent ablation for AFL at Montefiore Medical Center from August 2001 to January 2005 were classified according to the severity of LVSD. Group 1 (n = 36) consisted of patients with EF ≤ 35%, and group 2 (n = 54) consisted of patients with EF 36–55%. There were no statistically significant differences in baseline patient characteristics between the two groups. Results: During a mean follow up of 350 days, Afib occurred in 31% (n = 11; 8 with prior history of AFib) in group 1, and 7.4% (n = 4; all with prior history of Afib) in group 2. Cumulative probability of remaining Afib-free in group 1 versus group 2 was 75% versus 96% at 365 days, and 69% versus 91% at 600 days (P = 0.01). A prior history of Afib did not interact with EF when analyzed with a logistic regression analysis. Conclusion: After an AFL ablation, the incidence of Afib is increased, and the probability of remaining free of Afib is decreased, when severe LVSD is present, independent of a prior history of Afib. This finding may have implications for optimal patient selection for AFL ablation, and the use of adjunctive therapies.
Reduced-order dynamic compensator design for stability robustness of linear discrete-time systems

A reduced-order dynamic compensator design is presented with stability robustness for linear discrete systems, by including a stability robustness component in addition to the standard quadratic state and control terms in the performance criterion. The robustness component is based on an unstructured perturbation stability bound for time varying perturbations. The controller design is developed by the parameter optimization technique and involves the solution of five algebraic matrix equations, four of which are discrete-time Lyapunov matrix equations. >
Fourier plasmonics: Diffractive focusing of in-plane surface plasmon polariton waves

An in-plane Fresnel zone plate for focusing surface plasmon polariton (SPP) fields has been designed, fabricated and tested. Diffractive SPP fields from each Fresnel zone constructively interfere and focus at the designed focal point.
Refining and Extending the Business Model With Information Technology: Dell Computer Corporation

The exceptional performance of Dell Computer in recent years illustrates an innovative response to a fundamental competitive factor in the personal computer industry - the value of time. This article shows how Dell's strategies of direct sales and build-to-order production have proven successful in minimizing inventory and bringing new products to market quickly, enabling it to increase market share and achieve high returns on investment. The Dell case illustrates how one business model may have inherent advantages under particular market conditions, but it also shows the importance of execution in exploiting those advantages. In particular, Dell's use of information technology (IT) has been vital to executing both elements of its business model - direct sales and build-to-order - and provides valuable insights into how IT can be applied to achieve speed and flexibility in an industry in which time is critical. Many of the insights gained from this case can be applied more generally to other time-dependen...
A Theory of Equity Carve-Outs and Negative Stub Values under Heterogeneous Beliefs

We develop a theory of new-project financing and equity carve-outs under heterogeneous beliefs. In our model, an employee of a firm generates an idea for a new project that can be financed either by issuing equity against the cash flows of the entire firm (‘‘integration’’), or by undertaking an equity carve-out of the new project alone (‘‘non-integration’’). While the patent underlying the new project is owned by the firm, the employee generating the idea needs to be motivated to exert optimal effort for the project to be successful. The firm’s choice between integration and non-integration is driven primarily by heterogeneity in beliefs among outside investors (each of whom has limited wealth to invest in the equity market) and between firm insiders and outsiders: if the marginal outsider financing the new project is more optimistic about the prospects of the project than firm insiders, and this incremental optimism of the marginal outsider over firm insiders is greater regarding new-project cash flows than that about assets-in-place cash flows, then the firm will implement the project under non-integration rather than integration. Two other ingredients driving the firm’s financing choice are the cost of motivating the employee to exert optimal effort, and the potential synergies between the new project and assets in place. We derive a number of testable predictions regarding a firm’s equilibrium choice between integration and non-integration. We also provide a rationale for the ‘‘negative stub values’’ documented in the equity carve-outs of certain firms (e.g., the carve-out of Palm from 3Com) and develop predictions for the magnitude of these stub values.
Acid catalyzed rearrangements of 4-methyl-4-cyanocyclohexadienone

Abstract Acid-catalyzed dienone-phenol rearrangement reactions of 4-methyl-4-cyanocyclohexadienone occur very slowly and give either fragmentation or methyl group migration, not cyano group migration, under non-nucleophilic strongly acidic conditions.
Estimating demographic parameters using a combination of known‐fate and open N‐mixture models

Accurate estimates of demographic parameters are required to infer appropriate ecological relationships and inform management actions. Known-fate data from marked individuals are commonly used to estimate survival rates, whereas N-mixture models use count data from unmarked individuals to estimate multiple demographic parameters. However, a joint approach combining the strengths of both analytical tools has not been developed. Here we develop an integrated model combining known-fate and open N-mixture models, allowing the estimation of detection probability, recruitment, and the joint estimation of survival. We demonstrate our approach through both simulations and an applied example using four years of known-fate and pack count data for wolves (Canis lupus). Simulation results indicated that the integrated model reliably recovered parameters with no evidence of bias, and survival estimates were more precise under the joint model. Results from the applied example indicated that the marked sample of wolves was biased toward individuals with higher apparent survival rates than the unmarked pack mates, suggesting that joint estimates may be more representative of the overall population. Our integrated model is a practical approach for reducing bias while increasing precision and the amount of information gained from mark-resight data sets. We provide implementations in both the BUGS language and an R package.
A passive soft-switching snubber for PWM inverters

This paper presents a regenerative passive snubber circuit for pulse-width modulation (PWM) inverters to achieve soft-switching purposes without significant cost and reliability penalties. This passive soft-switching snubber (PSSS) employs a diode/capacitor snubber circuit for each switching device in an inverter to provide low dv/dt and low switching losses to the device. The PSSS further uses a transformer-based energy regenerative circuit to recover the energy captured in the snubber capacitors. All components in the PSSS circuit are passive, thus leading to reliable and low-cost advantages over those soft-switching schemes relying on additional active switches. The snubber has been incorporated into a 150 kVA PWM inverter. Simulation and experimental results are given to demonstrate the validity and features of the snubber circuit.
Open modules: modular reasoning about advice

Advice is a mechanism used by advanced object-oriented and aspect-oriented programming languages to augment the behavior of methods in a program. Advice can help to make programs more modular by separating crosscutting concerns more effectively, but it also challenges existing ideas about modularity and separate development. We study this challenge using a new, simple formal model for advice as it appears in languages like AspectJ. We then add a module system designed to leave program functionality as open to extension through advice as possible, while still enabling separate reasoning about the code within a module. Our system, Open Modules, can either be used directly to facilitate separate, component-based development, or can be viewed as a model of the features that certain AOP IDEs provide. We define a formal system for reasoning about the observational equivalence of programs under advice, which can be used to show that clients are unaffected by semantics-preserving changes to a module's implementation. Our model yields insights into the nature of modularity in the presence of advice, provides a mechanism for enforceable contracts between component providers and clients in this setting, and suggests improvements to current AOP IDEs.
Digital-to-voice conversion

For the past two years Motorola has maintained a program to study and develop digital-to-voice conversion techniques. This program has examined the needs for digital-to-voice conversion and has, through feasibility experiments, studied some of the promising techniques. This paper reports on this work.
Sloppy models, parameter uncertainty, and the role of experimental design

Computational models are increasingly used to understand and predict complex biological phenomena. These models contain many unknown parameters, at least some of which are difficult to measure directly, and instead are estimated by fitting to time-course data. Previous work has suggested that even with precise data sets, many parameters are unknowable by trajectory measurements. We examined this question in the context of a pathway model of epidermal growth factor (EGF) and neuronal growth factor (NGF) signaling. Computationally, we examined a palette of experimental perturbations that included different doses of EGF and NGF as well as single and multiple gene knockdowns and overexpressions. While no single experiment could accurately estimate all of the parameters, experimental design methodology identified a set of five complementary experiments that could. These results suggest optimism for the prospects for calibrating even large models, that the success of parameter estimation is intimately linked to the experimental perturbations used, and that experimental design methodology is important for parameter fitting of biological models and likely for the accuracy that can be expected from them.
On detecting discrete Cheshire charge

We analyze the charges carried by loops of string in models with non-abelian local discrete symmetry. The charge on a loop has no localized source, but can be detected by means of the Aharonov-Bohm interaction of the loop with another string. We describe the process of charge detection, and the transfer of charge between point particles and string loops, in terms of gauge-invariant correlation functions.
Phase properties of Hurwitz polynomials

Rantzer (1992) established a fundamental bound on the rate of change of phase of a Hurwitz polynomial. An inductive proof given in Bose (1994) has stated that this fundamental bound can be derived from Tellegen's theorem in network theory, the purpose of this paper is to give a direct proof of the fundamental bound using the Hermite-Bieler theorem which, in turn, follows from the monotonic phase property and total phase change properties of a Hurwitz polynomial, this is instructive because control engineers are, by and large, unfamiliar with Tellegen's theorem, and the authors' direct proof makes transparent the central role played by these phase properties.
Long-term growth and short-term economic instability

When learning by doing is at the origin of growth the long-run growth rate should be negatively related to the amplitude of the business cycle if human capital accumulation is increasing and concave in the cyclical component of production. Empirical evidence strongly supports this "nding for industrialized countries and European regions. Using the standard control variables, we "nd that countries and regions that have a higher standard deviation of growth and of unemployment have lower growth rates. The result does not come from an e!ect of instability on investment. The negative relation, however, does not hold for non-industrialized countries, for which learning by doing may not to be the main engine of growth. ( 2000 Elsevier Science B.V. All rights reserved. JEL classixcation: O40; E32