cssi/SciSciGPT-SciSciNet huggingface dataset:
Quasi-large sparse-sequence CDMA: Approach to single-user bound by linearly-complex LAS detectors

We have proposed a quasi-large random- sequence (QLRS) CDMA where K users access a point through a common channel with spectral spreading factor N. Each bit is extended by a temporal spreading factor B and hopped on a BN-chip random sequence that is spread in time and frequency. Each user multiplexes and transmits B extended bits and the total channel load is a = K/N bits/s/Hz. The linearly-complex LAS detectors detect the transmitted bits. We have obtained that as B rarr infin, if alpha < 1/2 - 1/(41n2), each transmitted bit achieves the single-bit bound in BER in high SNR regime as if there was no interference bit. In simulation, when bit number BK ges 500, each bit can approach the single-bit bound for alpha as high as 1 bit/s/Hz. In this paper, we further propose the quasi- large sparse-sequence (QLSS) CDMA by replacing the dense sequence in QLRS-CDMA with sparse sequence. Simulation results show that when the nonzero chips are as few as 16, the BER is already near that of QLRS- CDMA while the complexity is significantly reduced due to sequence sparsity.
Using a Clinical Data Repository to Estimate the Frequency and Costs of Adverse Drug Events

As a result of increased attention to medical errors, many institutions are contemplating increased use of information technology and clinical decision support. We conducted a retrospective analysis to estimate the frequency and cost of adverse drug events (ADEs) for inpatients at the University of Virginia. Applying published criteria for the detection of potential adverse events, we used a clinical data warehouse to identify patients and cases with potential ADEs. Again using published criteria, we then estimated the actual number of adverse drug events and preventable adverse drug events, as well as their attributable costs and excess length of stay. Our results showed a higher estimate (10.4–11.5 events per 100 admissions) for ADEs than seen in the ADE Prevention Study, highlighting the importance of considering the generalizability of published ADE studies to other settings. Our analysis demonstrates that retrospective analysis can be an efficient and powerful technique to evaluate rules and criteria used to detect ADEs and to assess their impact.
Coherence and Intermittency of Electron Density in Small-Scale Interstellar Turbulence

Spatial intermittency in decaying kinetic Alfven wave turbulence is investigated to determine if it produces non-Gaussian density fluctuations in the interstellar medium. Non-Gaussian density fluctuations have been inferred from pulsar scintillation scaling. Kinetic Alfven wave turbulence characterizes density evolution in magnetic turbulence at scales near the ion gyroradius. It is shown that intense localized current filaments in the tail of an initially Gaussian probability distribution function possess a sheared magnetic field that strongly refracts the random kinetic Alfven waves responsible for turbulent decorrelation. The refraction localizes turbulence to the filament periphery, and hence it avoids mixing by the turbulence. As the turbulence decays, these long-lived filaments create a non-Gaussian tail. A condition related to the shear of the filament field determines which fluctuations become coherent and which decay as random fluctuations. The refraction also creates coherent structures in electron density. These structures are not localized. Their spatial envelope maps into a probability distribution that decays as density to the power -3. The spatial envelope of density yields a Levy distribution in the density gradient.
USING ULTRA LONG PERIOD CEPHEIDS TO EXTEND THE COSMIC DISTANCE LADDER TO 100 Mpc AND BEYOND

We examine the properties of 18 long period (80-210 days) and very luminous (median absolute magnitude of MI = –7.86 and MV = –6.97) Cepheids to see if they can serve as a useful distance indicator. We find that these Ultra Long Period (ULP) Cepheids have a relatively shallow period-luminosity (PL) relation, so in fact they are more standard candle like than classical Cepheids. In the reddening-free Wesenheit index, the slope of the ULP PL relation is consistent with zero. The scatter of our sample about the WI PL relation is 0.23 mag, approaching that of classical Cepheids and Type Ia Supernovae. We expect this scatter to decrease as bigger and more uniform samples of ULP Cepheids are obtained. We also measure a nonzero period derivative for one ULP Cepheid (SMC HV829) and use the result to probe evolutionary models and mass loss of massive stars. ULP Cepheids' main advantage over classical Cepheids is that they are more luminous, and as such show great potential as stellar distance indicators to galaxies up to 100 Mpc and beyond.
Scalable Multicasting in One-Pump Parametric Amplifier

We report the experimental demonstration of all-optical wavelength multicasting of OC-768 (40 Gbps) channel using a single-pass, pump modulated parametric amplifier. The performances of 1-to-20 and 1-to-40 multicasting with excellent signal fidelity were observed. The impairment mechanisms were identified from cascaded filtering, linear and nonlinear crosstalk. It is shown that the parametric amplifier offers a wide range of operation characterized by minimal multicast penalty. We show that all multicast channels have an error free performance with Q factors well above the forward error correction (FEC) limit within the designed operating range.
Ionic Hydrogenation of Oxyallyl Intermediates: The Reductive Nazarov Cyclization

Abstract Cyclization of tri- and tetrasubstituted dienones 1 under Lewis acidic conditions in the presence of triethylsilane led to formation of either silyl enol ethers 6 or cyclopentanones 7 in good to excellent yields, depending on work-up conditions. The proposed mechanism involves initial Nazarov cyclization to give oxyallyl intermediates 5 , which are intercepted via intermolecular transfer of hydride. The reactions proceeded cleanly with as little as 2 equiv. of silane and in most cases catalytic amounts of Lewis acid could be used. Trapping with Et 3 SiD occurs at the less substituted terminus in unsymmetrical cases.
On the Bilinear Equations for Fredholm Determinants Appearing in Random Matrices

It is shown how the bilinear differential equations satisfied by Fredholm determinants of integral operators appearing as spectral distribution functions for random matrices may be deduced from the associated systems of nonautonomous Hamiltonian equations satisfied by auxiliary canonical phase space variables introduced by Tracy and Widom. The essential step is to recast the latter as isomonodromic deformation equations for families of rational covariant derivative operators on the Riemann sphere and interpret the Fredholm determinants as isomonodromic τ -functions.
P(i-BuNCH2CH2)3N: An Efficient Ligand for the Direct α-Arylation of Nitriles with Aryl Bromides

A new catalyst system for the synthesis of α-aryl-substituted nitriles is reported. The bicyclic triaminophosphine P(i-BuNCH2CH2)3N (1b) serves as an efficient and versatile ligand for the palladium-catalyzed direct α-arylation of nitriles with aryl bromides. Using ligand 1b, ethyl cyanoacetate and primary as well as secondary nitriles are efficiently coupled with a wide variety of aryl bromides possessing electron-rich, electron-poor, electron-neutral, and sterically hindered groups.
Modulated coded zero-forcing decision feedback equalizer

Modulated codes (MC) are error correction codes (ECC) over the real/complex field, which are used for mitigating the intersymbol interference (ISI). The arithmetic operations of the MC encoder are the same as the ones of an ISI channel, therefore, an ISI channel and an MC can be naturally combined together. With the combination, the MC can be optimally designed for the mitigation of the ISI. In this paper, we propose a new coded zero-forcing decision feedback equalizer (ZF-DFE) using MC. For the MC coded ZF-DFE we present the performance analysis and the optimal MC design for a given ISI channel, where the coding gain based on the joint ZF-DFE is formulated comparing to the uncoded AWGN channel. Numerical results show that the MC coded ZF-DFE outperforms the conventional uncoded/coded ZF-DFE and the uncoded/coded Tomlinson-Harashima (TH) precoding at, at least, low channel SNR, where the BPSK is used.
Endoscopic transpedicular thoracic discectomy

Object. To reduce the invasiveness and risk of thoracic disc surgery, a transpedicular endoscopic approach has been created. The surgical technique and outcome of endoscopic transpedicular thoracic discectomy are reported. Methods. The surgical technique of posterior transpedicular thoracic discectomy was modified to endoscopic transpedicular surgery. A 1.5-cm trocar was placed in the interlaminar space via a 2-cm transverse paramedian skin incision. At the ventral aspect of the spinal cord discectomy was performed under direct visualization by using a 70°lens endoscope. This surgical technique was used in 25 patients. Twelve patients were men and 13 were women, aged 29 to 70 years (median 46 years). Myelopathy, with or without radiculopathy was present in 13 patients, radiculopathy in 10, and segmental pain in two. The follow-up periods ranged from 4 to 60 months (median 27 months). In 12 of the 13 patients with myelopathy excellent improvement was shown postoperatively; the remaining patient suffered recurrence of symptoms after a motor vehicle accident three months postoperatively. In nine of the 10 patients with radiculopathy, pain was resolved completely. In one patient with right-sided hypochondral pain and two patients with segmental pain, relief was not achieved despite excellent results of discectomy demonstrated on postoperative magnetic resonance imaging. The average length of hospital stay was one night. Conclusions. Endoscopic transpedicular thoracic discectomy was found to be a minimally invasive and effective surgical treatment.
Direct Mechanical Measurement of the Tensile Strength and Elastic Modulus of Multiwalled Carbon Nanotubes

We have conducted pulling and bending tests on individual carbon nanotubes in-situ in a transition electron microscope. Based on our observation of the force required to break the tube, a tensile strength of 0.15 TPa was computed. From corresponding bending studies on such nanotubes, the Young’s modulus was estimated to be 0.9 TPa (0.8 TPa after ‘sub continuum’ corrections). These results suggest a strength that is a large fraction of the elastic modulus, although previous measurements of their elastic stiffness have yielded higher modulus values, by as much as a factor of 2. The result does indicate that individual nanotubes can fail as essentially defect-free materials. Furthermore, we observed no obvious reduction in cross-sectional area prior to the failure. In addition, the bending experiments revealed a remarkable flexibility in these tubes. These unique properties support the potential of nanotubes as reinforcement fibers in structural materials. © 2002 Elsevier Science B.V. All rights reserved.
Symmetries of Toric Duality

This paper serves to elucidate the nature of toric duality dubbed in hep-th/0003085 in the construction for world volume theories of D-branes probing arbitrary toric singularities. This duality will be seen to be due to certain permutation symmetries of multiplicities in the gauged linear sigma model fields. To this symmetry we shall refer as ``multiplicity symmetry.'' We present beautiful combinatorial properties of these multiplicities and rederive all known cases of torically dual theories under this new light. We also initiate an understanding of why such multiplicity symmetry naturally leads to monodromy and Seiberg duality. Furthermore we discuss certain ``flavor'' and ``node'' symmetries of the quiver and superpotential and how they are intimately related to the isometry of the background geometry, as well as how in certain cases complicated superpotentials can be derived by observations of the symmetries alone.
Air-Stable Bifunctional Allylation Reagents for the Asymmetric Synthesis of Differentiated syn- and anti-1,3-Diols

Turning the diols: Enantiomerically pure bifunctional reagents I and ent-I undergo asymmetric aldehyde allylation followed by Ir(I)-catalyzed enantioselective decarboxylative allylic etherification to give differentiated syn- and anti-1,3-diols with complete control of the absolute and relative stereochemistry (see scheme; PMP = para-methoxyphenyl, dbcot = dibenzo[a,e]cyclooctatetraene, DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene).
F-regularity does not deform

We show that the property of F-regularity does not deform, and thereby settle a long- standing open question in the theory of tight closure. Specifically, we construct a three dimensional -graded domain R which is not F-regular (or even F-pure), but has a quotient R tR which is F-regular. Examples are constructed over fields of characteristic p 0, as well as over fields of characteristic zero. 1. Introduction. Throughout this paper, all rings are commutative, Noethe- rian, and have an identity element. The theory of tight closure was developed by Melvin Hochster and Craig Huneke in (HH2) and draws attention to rings which have the property that all their ideals are tightly closed, called weakly F-regular rings. The term F-regular is reserved for rings all of whose localizations are weakly F-regular. A natural question that arose with the development of the the- ory was whether the property of F-regularity deforms, i.e., if (R, m, K) is a local ring such that R tR is F-regular for some nonzerodivisor t m ,m ustR be F- regular? (See the Epilogue of (Ho).) Hochster and Huneke showed that this is indeed true if the ring R is Gorenstein, (HH3), and their work has been followed by various attempts at extending this result, see (AKM), (Si), (Sm3). Our pri- mary goal here is to settle this question by constructing a family of examples to show that F-regularity does not deform. We shall throughout be considering -graded rings, but local examples can be obtained, in all cases, by localizing at the homogeneous maximal ideals. Our main result is: THEOREM 1.1. There exists an -graded ring R of dimension three (finitely generated over a field R 0 = K of characteristic p 2) which is not F-pure, but has an F-regular quotient R tR where t m is a homogeneous nonzerodivisor. Specifically, for positive integers m and n satisfying m m n 2, consider the ring R = K(A, B, C, D, T) I where I is generated by the size two minors of the
Damping Reduction in Structures Using Piezoelectric Circuitry With Negative Resistance

As damping reduction can potentially lead to performance enhancement in certain applications, a scheme based upon the concept of piezoelectric circuitry that yields reduced damping effect in a structural system is developed. The piezoelectric circuitry consists of an inductor and a negative resistance circuit serially connected to the piezoelectric transducer. By using the negative resistance element to make the overall resistance of the circuitry to be negative, the vibratory response becomes higher. The stability boundary of the negative resistance is derived for both ideal piezoelectric transducer and actual transducer with energy loss. The results are validated via experimental investigations.Copyright © 2010 by ASME
Reflectivity Spectra for Commonly Used Reflectors

Monte Carlo simulations play an important role in developing and evaluating the performance of radiation detection systems. To accurately model a reflector in an optical Monte Carlo simulation, the reflector's spectral response has to be known. We have measured the reflection coefficient for many commonly used reflectors for wavelengths from 250 nm to 800 nm. The reflectors were also screened for fluorescence and angular distribution changes with wavelength. The reflectors examined in this work include several polytetrafluoroethylene (PTFE) reflectors, Spectralon, GORE diffuse reflector, titanium dioxide paint, magnesium oxide, nitrocellulose filter paper, Tyvek paper, Lumirror, Melinex, ESR films, and aluminum foil. All PTFE films exhibited decreasing reflectivity with longer wavelengths due to transmission. To achieve >;0.95 reflectivity in the 380 to 500 nm range, the PTFE films have to be at least 0.5 mm thick-nitrocellulose is a good alternative if a thin diffuse reflector is needed. Several of the reflectors have sharp declines in reflectivity below a cut-off wavelength, including TiO2 (420 nm), ESR film (395 nm), nitrocellulose (330 nm), Lumirror (325 nm), and Melinex (325 nm). PTFE-like reflectors were the only examined reflectors that had reflectivity above 0.90 for wavelengths below 300 nm. Lumirror, Melinex, and ESR film exhibited fluorescence. Lumirror and Melinex are excited by wavelengths between 320 and 420 nm and have their emission peaks located at 440 nm, while ESR film is excited by wavelengths below 400 nm and the emission peak is located at 430 nm. Lumirror and Melinex also exhibited changing angular distributions with wavelength.
Health awareness campaigns and diagnosis rates: Evidence from National Breast Cancer Awareness Month

Awareness campaigns are often used to encourage medical screening that allows for early detection of health problems, but much remains unknown about the effectiveness of these programs. This paper evaluates whether National Breast Cancer Awareness Month (NBCAM) has led to increased diagnosis of breast cancer. The analysis examines the number of diagnoses made in November (1 month after NBCAM) during years before and after NBCAM was initiated. We find that from 1993 to 1995, the period when breast cancer advocacy was expanding rapidly into a nationwide movement, NBCAM led to an increase in the number of November diagnoses. During earlier periods (from the mid-1980s to the early-1990s), when breast cancer advocacy was still a nascent grassroots movement, and in later periods, when breast cancer advocacy had become a well-established nationwide cause, there is little evidence that October NBCAM events had an effect on November diagnoses.
Parameter governors for discrete-time nonlinear systems with pointwise-in-time state and control constraints

Parameter governors are add-on control schemes that adjust parameters (such as gains or offsets) in the nominal control laws to avoid violation of pointwise-in-time state and control constraints and to improve the overall system transient performance via the receding horizon minimization of a cost functional. As compared to more general model predictive controllers, parameter governors tend to be more conservative but the computational effort needed to implement them on-line can be relatively modest because the few parameters to be optimized remain constant over the prediction horizon. In this paper, we discuss the properties of several classes of parameter governors which have a common property in that the governed parameters do not shift the steady-state equilibrium of the states on which the incremental cost function explicitly depends on. This property facilitates the application of meaningful cost functionals. An example, together with simulation results, is reported to provide additional insights into the operation of the proposed parameter governor schemes.
Nonlinear Laplacian spectral analysis: capturing intermittent and low-frequency spatiotemporal patterns in high-dimensional data

We present a technique for spatiotemporal data analysis called nonlinear Laplacian spectral analysis NLSA, which generalizes singular spectrum analysis SSA to take into account the nonlinear manifold structure of complex datasets. The key principle underlying NLSA is that the functions used to represent temporal patterns should exhibit a degree of smoothness on the nonlinear data manifold M; a constraint absent from classical SSA. NLSA enforces such a notion of smoothness by requiring that temporal patterns belong in low-dimensional Hilbert spaces Vl spanned by the leading l Laplace--Beltrami eigenfunctions on M. These eigenfunctions can be evaluated efficiently in high ambient-space dimensions using sparse graph-theoretic algorithms. Moreover, they provide orthonormal bases to expand a family of linear maps, whose singular value decomposition leads to sets of spatiotemporal patterns at progressively finer resolution on the data manifold. The Riemannian measure of M and an adaptive graph kernel width enhances the capability of NLSA to detect important nonlinear processes, including intermittency and rare events. The minimum dimension of Vl required to capture these features while avoiding overfitting is estimated here using spectral entropy criteria.
Do Oncologists Believe New Cancer Drugs Offer Good Value

Background. Substantial debate centers on the high cost and relative value of new cancer therapies. Oncologists play a pivotal role in treatment decisions, yet it is unclear whether they perceive high-cost new treatments to offer good value or how therapeutic costs factor into their treatment recommendations. Methods. We surveyed 139 academic medical oncologists at two academic hospitals in Boston. We asked respondents to provide estimates for the cost and effectiveness of bevacizumab and whether they believed the treatment offered “good value.” We also asked respondents to judge how large a gain in life expectancy would justify a hypothetical cancer drug that costs $70,000 a year. Using this information, we calculated implied costeffectiveness thresholds. Finally, we explored respondents’ views on the role of cost in treatment decisions. Results. Ninety academic oncologists (65%)
Who gets credit? The behavior of bureaucrats and state banks in allocating credit to Chinese state-owned enterprises

Abstract Using a sample of Chinese state-owned enterprises spanning 1980 to 1994, we investigate the factors that determine the sources of finance for firm-level fixed investment, including retained earnings, bank finance, and government transfers. Direct government transfers were not significantly associated with profitability throughout the period. In contrast, bank finance was positively linked to both profitability and some types of reform. Reforms that enabled managers to self-select, and thus expose themselves (and their employees) to greater risk, were positively associated with acquiring bank finance. The association between bank finance and profitability weakened in the 1990s as banks increasingly assumed bailout responsibility.
Scheduling nonuniform traffic in a packet-switching system with small propagation delay

A new model of nonuniform traffic is introduced for a single-hop packet-switching system. This traffic model allows arbitrary traffic streams subject only to a constraint on the number of data packets which can arrive at any, individual source in the system or for any individual destination in the system over time periods of specified length. The nonuniform traffic model is flexible enough to cover integrated data networks carrying diverse classes of data. The system model is rather general, and includes passive optical star wavelength-division networks. Transmission algorithms are introduced for a single-hop packet-switching system with such nonuniform traffic and with propagation delay that is negligible relative to the packet length. The algorithms are based on collision-free scheduling of packets using graph-matching algorithms since the global state of the system is known to all stations at any time.
The Rise of School-Supporting Nonprofits.

This paper examines voluntary contributions to public education via charitable school foundations, booster clubs, parent teacher associations, and parent teacher organizations. We use panel data on school-supporting charities with national coverage from 1995 to 2010, which we geocode and match to school districts. We document the meteoric rise of school-supporting nonprofits during this panel, and then estimate a series of regression models to examine the distributional consequences of voluntary contributions. We find relatively large districts have higher probabilities of receiving revenues from a school-supporting nonprofit but the level of per-pupil voluntary contributions declines with student enrollment. In addition, we find school districts with higher endowments have higher probabilities of being served by at least one school-supporting nonprofit and higher levels of per-pupil contributions. Finally, we find no evidence that impressive recent growth in the number and financial size of these school-supporting charities relates to reductions in the public financing of schools.
Velocity adaptive handoff algorithms for microcellular systems

Fast velocity adaptive handoff algorithms for microcellular systems capable of providing consistent and near optimal performance are presented and characterized. Guidelines are first developed for the amount of spatial averaging required for local mean estimation in microcellular systems. Afterwards, three different velocity estimators are introduced and compared with respect to their sensitivity to Rice factors, non-isotropic scattering, additive Gaussian noise, and performance in a adaptive handoff algorithm. >
Design of Multistage Decimation Filters Using Cyclotomic Polynomials: Optimization and Design Issues

This paper focuses on the design of multiplier-less decimation filters suitable for oversampled digital signals. The aim is twofold. On one hand, it proposes an optimization framework for the design of constituent decimation filters in a general multistage decimation architecture. The basic building blocks embedded in the proposed filters belong, for a simple reason, to the class of cyclotomic polynomials (CPs): the first 104 CPs have a z-transfer function whose coefficients are simply {-1, 0, +1}. On the other hand, the paper provides a bunch of useful techniques, most of which stem from some key properties of CPs, for designing the proposed filters in a variety of architectures. Both recursive and non-recursive architectures are discussed by focusing on a specific decimation filter obtained as a result of the optimization algorithm. Comparisons are given with respect to classical comb filters and some recently proposed techniques. Design guidelines are provided with the aim to simplify the design of the constituent decimation filters in the multistage chain.
Subsidized Vehicle Acquisition and Earned Income in the Transition from Welfare to Work

Availability and affordability of reliable transportation – either through public transportation or individual ownership of automobiles – appears necessary to support a successful transition from welfare to work. One approach adopted by state and local governments is to subsidize vehicle acquisition by welfare recipients in transition. To date there are no empirical studies that analyze the impacts or effectiveness of these vehicle subsidy programs. The objective of this study is to examine the extent to which participation in a small-scale vehicle donation-and-sales program in Vermont increases earned income by individuals in transition from welfare to work. Using reduced-form random effects and censored regression models to account for the simultaneity of decisions to work and participate in welfare programs, we examine the impacts of this vehicle acquisition program for a small group of individuals. Our analyses indicate that the program results in a statistically significant increase in both earned income and the probability of employment.
A combinatorial description of knot Floer homology

Given a grid presentation of a knot (or link) K in the three-sphere, we describe a Heegaard diagram for the knot complement in which the Heegaard surface is a torus and all elementary domains are squares. Using this diagram, we obtain a purely combinatorial description of the knot Floer homology of K.
Structure of Heterogeneous Networks

Heterogeneous networks play a key role in the evolution of communities and the decisions individuals make. These networks link different types of entities, for example, people and the events they attend. Network analysis algorithms usually project such networks unto simple graphs composed of entities of a single type. In the process, they conflate relations between entities of different types and loose important structural information.We develop a mathematical framework that can be used to compactly represent and analyze heterogeneous networks that combine multiple entity and link types.We generalize Bonacich centrality, which measures connectivity between nodes by the number of paths between them, to heterogeneous networks and use this measure to study network structure. Specifically, we extend the popular modularity-maximization method for community detection to use this centrality metric. We also rank nodes based on their connectivity to other nodes. One advantage of this centrality metric is that it has a tunable parameter we can use to set the length scale of interactions. By studying how rankings change with this parameter allows us to identify important nodes in the network.We apply the proposed method to analyze the structure of several heterogeneous networks. We show that exploiting additional sources of evidence corresponding to links between, as well as among, different entity types yields new insights into network structure.
Model checking with probabilistic tabled logic programming

We present a formulation of the problem of probabilistic model checking as one of query evaluation over probabilistic logic programs. To the best of our knowledge, our formulation is the first of its kind, and it covers a rich class of probabilistic models and probabilistic temporal logics. The inference algorithms of existing probabilistic logic-programming systems are well defined only for queries with a finite number of explanations. This restriction prohibits the encoding of probabilistic model checkers, where explanations correspond to executions of the system being model checked. To overcome this restriction, we propose a more general inference algorithm that uses finite generative structures (similar to automata) to represent families of explanations. The inference algorithm computes the probability of a possibly infinite set of explanations directly from the finite generative structure. We have implemented our inference algorithm in XSB Prolog, and use this implementation to encode probabilistic model checkers for a variety of temporal logics, including PCTL and GPL (which subsumes PCTL*). Our experiment results show that, despite the highly declarative nature of their encodings, the model checkers constructed in this manner are competitive with their native implementations.
Generic regularity of conservative solutions to a nonlinear wave equation

Abstract The paper is concerned with conservative solutions to the nonlinear wave equation u t t − c ( u ) ( c ( u ) u x ) x = 0 . For an open dense set of C 3 initial data, we prove that the solution is piecewise smooth in the t–x plane, while the gradient u x can blow up along finitely many characteristic curves. The analysis is based on a variable transformation introduced in [7] , which reduces the equation to a semilinear system with smooth coefficients, followed by an application of Thom's transversality theorem.
Dynamics of two van der Pol oscillators coupled via a bath

Abstract In this work we study a system of two van der Pol oscillators, x and y , coupled via a “bath” z : x −ϵ(1−x 2 ) x +x=k(z−x) y −ϵ(1−y 2 ) y +y=k(z−y) z =k(x−z)+k(y−z) We investigate the existence and stability of the in-phase and out-of-phase modes for parameters ϵ >0 and k >0. To this end we use Floquet theory and numerical integration. Surprisingly, our results show that the out-of-phase mode exists and is stable for a wider range of parameters than the in-phase mode. This behavior is compared to that of two directly coupled van der Pol oscillators, and it is shown that the effect of the bath is to reduce the stability of the in-phase mode. We also investigate the occurrence of other periodic motions by using bifurcation theory and the AUTO bifurcation and continuation software package. Our motivation for studying this system comes from the presence of circadian rhythms in the chemistry of the eyes. We present a simplified model of a circadian oscillator which shows that it can be modeled as a van der Pol oscillator. In our model although there is no direct connection between the two eyes, they can influence each other by affecting the concentration of melatonin in the bloodstream, which is represented by the bath.
Size-Based Separation of Microparticles in a Multilayered Microfluidic Device

The current analysis of microbial populations in diverse environments is stymied by the inability to culture the vast majority of microbes in a laboratory setting. Consequently, considerable work is currently underway to identify new microbes based on genetic characterizations, and one limitation is that the majority of sequencing schemes will miss rare populations of microbes as large numbers are pooled for analysis. One approach to overcome this obstacle is to presort the microbes from a heterogeneous field sample based on size, as many microbes live in small clusters, and then analyze the various strains using in situ hybridization. In this paper, a multilayered microfluidic device has been developed for the size-based separation of heterogeneous microbial samples as a first step toward this goal. This device is fabricated using polydimethylsiloxane and soft lithographic techniques. The device includes three successive constrictions with reducing heights and was employed to successfully separate a heterogeneous population of microparticles and field samples obtained from Lake Michigan. The device was found to trap the microparticles and environmental samples with efficiency between 89% and 98% when the particles were larger than the constrictions and 97% for the unknown environmental sample.
Do Cross‐Border Listing Firms Manage Earnings or Seize a Window of Opportunity?

Firms raising new equity capital at cross-listing (IPO) and those cross- listing existing home-country public shares (non-IPO) benefit from earnings that are high when they cross-list on U.S. stock exchanges. IPO firms have greater benefits than non-IPO firms because they receive cash infusion at listing. I find that performance (ROA) and cash flows peak at cross-listing period for all cross-border firms. Using a matched-firm research design to control for industry and performance, the results sug- gest that both IPO and non-IPO firms time cross-listing when performance is peaking (seize a window of opportunity). Further tests investigate whether IPO and non-IPO firms differ in their incentives to engage in earnings management at the time of cross- listing. The results suggest that both appear to engage in the same level of earnings management at the time of cross-listing. This suggests that incentives to boost earn- ings to obtain higher cash infusion are not the main motivation for the earnings man- agement observed. Other incentives, such as greater investor recognition could be a stronger motivation.
In-flight wing deformation characteristics during limit-cycle oscillations

Oscillatory wing response data were measured on an F-16C aircraft during limit-cycle-oscillation (LCO) testing of an external store configuration. The configuration tested exhibited typical LCO response in the transonic flight regime. Deformation characteristics were measured at 11 locations on the wing and missile launchers during various LCO events. These measurements allowed viewing of the aeroelastic mode of instability for various flight conditions. Details of a linear flutter analysis model are presented, and the predicted eigenmode from the linear flutter analysis is compared to the in-flight measured mode. The measured LCO modes are also compared for level flight vs elevated load factor flight and subcritical LCO vs critical LCO conditions. At the onset of LCO, the mode shape bears a strong resemblance to the flutter mode predicted by linear flutter analysis. Further, the wing deformation characteristics during LCO vary significantly with respect to Mach number and load factor. The nonsynchronous motion of the LCO diminishes and becomes more synchronous as the Mach number increases beyond 0.90. This contradicts the trends predicted by linear flutter analyses and suggests that a change in the oscillation bounding mechanism occurs over the flight region examined.
Azidotris(diethylamino)phosphonium bromide : a self-catalyzing diazo transfer reagent

Abstract Acidic methylene compounds are conveniently converted to diazo compounds in high yields by azidotris(diethylamino)phosphonium bromide, 1 , in diethyl ether using only a catalytic amount of base. The product diazo compounds are easily separated from the co-product hexaethylphosphorimidic triamide hydrobromide.
A water conservation digital library using ontologies

New technologies are emerging that assist in organizing and retrieving knowledge stored in a variety of forms (books, papers, models, decision support systems, databases), but they can only be evaluated through real world applications. Ontology has been used to manage the Water Conservation Digital Library holding a growing collection of various types of digital resources in the domain of urban water conservation in Florida, USA. The ontology based back-end powers a fully operational web interface, available at http://library.conservefloridawater.org . The system has already demonstrated numerous benefits of the ontology application, including: easier and more precise finding of resources, information sharing and reuse, and proved to effectively facilitate information management.
Fast Capitalism, School Reform, and Second Language Literacy Practices

This 2-year qualitative study explores the ironies of educational reform in the United States as experienced by three second language learners attending a school attempting to transform itself into a high-performance elementary school in California's Silicon Valley. Drawing on the concept of “fast capitalism” in a globalized economic work order (Gee, Hull, & Lankshear, 1996) and the tools of critical discourse analysis (Fairclough, 1989), the findings from this investigation reveal that the discourses of school reform in the United States visibly and invisibly placed second language learners in new highly vulnerable positions. In what follows I provide an analysis of this vulnerability by relating the experiences of three families and their attempts to enrol and stay enrolled in the school of their choice. Next, I provide a critical analysis of the discourses of reading and writing instruction and of a text produced by a focal student named Alma in this context. This analysis highlights the ways in which classroom literacy practices inadvertently constrained the efforts of second language learners to acquire academic literacies and ultimately legitimated the school's decision to declare Alma “not Web material.” The implications of this study relate to better understanding classroom SLA from a historical, institutional perspective and to supporting teachers and policy makers in addressing the needs of second language learners in a time of rapid social and economic change.
A unified force control approach to autonomous underwater manipulation

A unified force control scheme for an autonomous underwater robotic system is proposed in this paper. This robotic system is composed of a six degree-of-freedom autonomous underwater vehicle (AUV) and a robotic arm that is mounted on the AUV. A unified force control approach, which combines impedance control with hybrid position/force control by means of fuzzy switching to perform autonomous underwater manipulation, is presented in this paper. This controller requires a dynamic model of the underwater vehicle-manipulator system. However, it does not require any model of the environment and therefore will have the potential to be useful in underwater tasks where the environment is generally unknown. The proposed approach combines the advantages of impedance control with hybrid control so that both smooth contact transition and force trajectory tracking can be achieved. In the absence of any functional autonomous underwater vehicle-manipulator system that can be used to verify the proposed controller, extensive computer simulations are performed and the results are presented in the paper.
Seasonal Variability of the Polar Stratospheric Vortex in an Idealized AGCM with Varying Tropospheric Wave Forcing

The seasonal variability of the polar stratospheric vortex is studied in a simplified AGCM driven by specified equilibrium temperature distributions. Seasonal variations in equilibrium temperature are imposed in the stratosphere only, enabling the study of stratosphere‐troposphere coupling on seasonal time scales, without the complication of an internaltropospheric seasonalcycle. The model is forced with different shapes andamplitudesofsimplebottomtopography,resultinginarangeofstratosphericclimates.Theeffectofthese differentkindsoftopographyontheseasonalvariabilityofthestrengthofthepolarvortex,theaveragetiming andvariability intimingofthefinalbreakupofthevortex(final warmingevents),theconditionsofoccurrence and frequency of midwinter warming events, and the impact of the stratospheric seasonal cycle on the troposphere are explored. The inclusion of wavenumber-1 and wavenumber-2 topographies results in very different stratospheric seasonal variability. Hemispheric differences in stratospheric seasonal variability are recovered in the model with appropriate choices of wave-2 topography. In the model experiment with a realistic Northern Hemisphere‐like frequency of midwinter warming events, the distribution of the intervals between these events suggests that the model has no year-to-year memory. When forced with wave-1 topography, the gross features of seasonalvariabilityaresimilartothoseforcedwith wave-2topography,butthedependenceonforcingmagnitude is weaker. Further, the frequency of major warming events has a nonmonotonic dependence on forcing magnitude and never reaches the frequency observed in the Northern Hemisphere.
Why we can't be bothered to read privacy policies models of privacy economics as a lemons market

Consumers want to interact with web sites, but they also want to keep control of their private information. Asymmetric information about whether web sites will sell private information or not leads to a lemons market for privacy. We discuss privacy policies as signals in a lemons market and ways in which current realizations of privacy policies may fail to be effective signals. As a result of these shortcomings, we consider a "lemons market with testing," where consumers have a cost of determining whether a site meets their privacy requirement. Our model explains empirical data concerning privacy policies and privacy seals. We end by discussing cyclic instability in the number of web sites that sell consumer information.
Lattice QCD and String Theory

Bosonic string formation in gauge theories is reviewed with particular attention to the confining flux in lattice QCD and its string theory description. Recent results on the Casimir energy of the ground state and the string excitation spectrum are analyzed in the Dirichlet string limit of large separation between static sources. The closed string-soliton (torelon) with electric flux winding around a compact dimension is also discussed.
Beyond Border Barriers: The Liberalisation of Services Trade in Tunisia and Egypt

Tunisia and Egypt have both recently undertaken significant steps toward trade reform. They have committed to a partnership agreement with the European Union. Both countries have also joined the WTO and are participating in Doha Round discussions on the liberalisation of non-tariff barriers on both goods and services trade. These developments provide an interesting context within which to investigate not only the changes in welfare associated with reforms affecting the trade in goods, but also the impacts of services liberalisation. Using open-economy computable general equilibrium models for both Tunisia and Egypt, this paper explores the reasons why structural differences in these two economies imply different opportunities and challenges with trade reform and services liberalisation. The gains from eliminating barriers at the border for goods trade are significantly greater for Tunisia than Egypt. Both countries, however, gain substantially from liberalisation of foreign direct investment in services. Furthermore, economic growth is more evenly distributed across sectors than with liberalisation of trade in goods alone. In addition to reporting on the impact of alternative policies on income, output, employment and trade, sector-level effects are also considered.
Mobile robot localization using landmarks

We describe an efficient method for localizing a mobile robot in an environment with landmarks. We assume that the robot can identify these landmarks and measure their bearings relative to each other. Given such noisy input, the algorithm estimates the robot's position and orientation with respect to the map of the environment. The algorithm makes efficient use of our representation of the landmarks by complex numbers. The algorithm runs in time linear in the number of landmarks. We present results of simulations and propose how to use our method for robot navigation.
MicroSCALE Screening Reveals Genetic Modifiers of Therapeutic Response in Melanoma

Cell microarrays are a promising tool for performing large-scale functional genomic screening in mammalian cells at reasonable cost, but owing to technical limitations they have been restricted for use with a narrow range of cell lines and short-term assays. Here, we describe MicroSCALE (Microarrays of Spatially Confined Adhesive Lentiviral Features), a cell microarray-based platform that enables application of this technology to a wide range of cell types and longer-term assays. We used MicroSCALE to uncover kinases that when overexpressed partially desensitized B-RAFV600E-mutant melanoma cells to inhibitors of the mitogen-activated protein kinase kinase kinase (MAPKKK) RAF, the MAPKKs MEK1 and 2 (MEK1/2, mitogen-activated protein kinase kinase 1 and 2), mTOR (mammalian target of rapamycin), or PI3K (phosphatidylinositol 3-kinase). These screens indicated that cells treated with inhibitors acting through common mechanisms were affected by a similar profile of overexpressed proteins. In contrast, screens involving inhibitors acting through distinct mechanisms yielded unique profiles, a finding that has potential relevance for small-molecule target identification and combination drugging studies. Further, by integrating large-scale functional screening results with cancer cell line gene expression and pharmacological sensitivity data, we validated the nuclear factor κB pathway as a potential mediator of resistance to MAPK pathway inhibitors. The MicroSCALE platform described here may enable new classes of large-scale, resource-efficient screens that were not previously feasible, including those involving combinations of cell lines, perturbations, and assay outputs or those involving limited numbers of cells and limited or expensive reagents.
UHF propagation in indoor hallways

A new model for UHF propagation in large buildings is presented. This model relies on knowledge of the interior arrangement of the building without requiring much detail. The guiding of radiation along hallways is the most significant propagation process at distances of more than 10 m from the transmitter. The waveguide model predicts the power loss rate along the hallways, which is affected by the coupling among the propagating modes. The coupling results from the roughness of the surfaces in the building; it is predicted in an average manner using the average deviation of the walls from perfect smoothness. The model predictions are compared to measurements in an office building and to ray tracing predictions.
Low-crosstalk and low-loss multi-core fiber utilizing fiber bend

We designed and fabricated a multi-core fiber whose attenuation is less than 0.18 dB/km and effective area is about 80 µm2. Crosstalk was observed be less than −55.5 dB after 17.6 km propagation.