cssi/SciSciGPT-SciSciNet huggingface dataset:
General techniques for constructing variational integrators

The numerical analysis of variational integrators relies on variational error analysis, which relates the order of accuracy of a variational integrator with the order of approximation of the exact discrete Lagrangian by a computable discrete Lagrangian. The exact discrete Lagrangian can either be characterized variationally, or in terms of Jacobi’s solution of the Hamilton-Jacobi equation. These two characterizations lead to the Galerkin and shooting constructions for discrete Lagrangians, which depend on a choice of a numerical quadrature formula, together with either a finite-dimensional function space or a one-step method. We prove that the properties of the quadrature formula, finite-dimensional function space, and underlying one-step method determine the order of accuracy and momentum-conservation properties of the associated variational integrators. We also illustrate these systematic methods for constructing variational integrators with numerical examples.
Global Well-Posedness for a Smoluchowski Equation Coupled with Navier-Stokes Equations in 2D

We prove global existence for a nonlinear Smoluchowski equation (a nonlinear Fokker-Planck equation) coupled with Navier-Stokes equations in 2d. The proof uses a deteriorating regularity estimate in the spirit of [5] (see also [1]).
The Physical Natures of Class I and Flat-Spectrum Protostellar Photospheres: A Near-Infrared Spectroscopic Study*

We present high-resolution (R 18,000), high signal-to-noise ratio, 2 ?m spectra of 52 IR-selected Class I and flat-spectrum young stellar objects in the Taurus-Auriga, ? Ophiuchi, Serpens, Perseus, and Corona Australis dark clouds. We detect key absorption lines in 41 objects and fit synthetic spectra generated from pre-main-sequence models to deduce the effective temperatures, surface gravities, near-IR veilings, rotation velocities, and radial velocities of each of these 41 sources. We find these objects to span ranges in effective temperature, surface gravity, and stellar luminosity that appear similar to those of late spectral type Class II sources and classical T Tauri stars. However, because of significant but uncertain corrections for scattering and extinction, the derived luminosities for the embedded protostellar objects must be regarded as being highly uncertain. We determine that the mean 2 ?m veiling of Class I and flat-spectrum objects is significantly higher than that of Class II objects in the same region where both types of objects are extensively observed (? Oph). We find that a significant fraction of our protostellar sample also exhibits emission lines. Twenty-three objects show H2 emission, which is usually indicative of the presence of energetic outflows. Thirty-four sources show H I Br? emission, and a number of these exhibit profile asymmetries consistent with infall. Eight sources show significant ?v = 2 CO emission suggestive of emission from a circumstellar disk. Overall, these observations indicate that Class I and flat-spectrum objects are self-embedded protostars undergoing significant mass accretion, although the objects appear to span a broad range of mass accretion activity.
Dielectric plastics as high exposure gamma-ray detectors

Abstract Dielectric plastics are being developed as high exposure dosimeters. The principle of operation is based on the relationship between the absorbed dose and the increased chemical reactivity of these dielectric solids. Polycarbonate plastics can be utilized in measuring absorbed dose in the range of about 107-109 rads. The advantages of the technique lie in the low cost of the detectors, ease of data readout, and high degree of reproducibility achievable. It is hoped that the method can be extended to include the dosimetry of massive doses of soft, low penetrating power X- or γ-radiations.
Spectral methods for matrices and tensors

While Spectral Methods have long been used for Principal Component Analysis, this survey focusses on work over the last 15 years with three salient features: (i) Spectral methods are useful not only for numerical problems, but also discrete optimization problems (Constraint Optimization Problems - CSP's) like the max. cut problem and similar mathematical considerations underlie both areas. (ii) Spectral methods can be extended to tensors. The theory and algorithms for tensors are not as simple/clean as for matrices, but the survey describes methods for low-rank approximation which extend to tensors. These tensor approximations help us solve Max-$r$-CSP's for $r>2$ as well as numerical tensor problems. (iii) Sampling on the fly plays a prominent role in these methods. A primary result is that for any matrix, a random submatrix of rows/columns picked with probabilities proportional to the squared lengths (of rows/columns), yields estimates of the singular values as well as an approximation to the whole matrix.
When different market concentration indices agree

Abstract The Herfindahl–Hirschman, entropy and N -firm indices may not agree when comparing market concentrations. For different oligopoly markets, the majorization pre-ordering is shown to be both necessary and sufficient for all to agree.
The depth distribution of hydrogen in lunar materials.

A technique employing the resonant nuclear reaction ^1H(^(19)F, αγ) ^(16)O has been used to measure hydrogen concentration versus depth in selected coarse fine fragments from the Apollo 11 and Apollo 15 missions, and in glass coated surface chips from two Apollo 15 rocks. The highly variable hydrogen content in the coarse fine fragments is concentrated mainly in a layer extending from the surface to a depth of 2000 ± 500A˚. The hydrogen content of the surface region of the Apollo 15 rock chips is comparable to that of the coarse fine samples, but is concentrated mainly within a few hundred angstroms of the surface. The hydrogen depth distribution in a piece of platinum foil from the Apollo 16 Lunar surface Cosmic Ray Experiment was also measured in an attempt to place a limit on the flux of 10–40 keV protons associated with a solar flare event.
Integrated structural design and vibration suppression using independent modal space control

The integrated design of a structure and its control system is treated as a multiobjective optimization problem. Structural mass and a quadratic performance index constitute the vector objective function. The closed-loop performance index is taken as the time integral of the Hamiltonian. Constraints on natural frequencies, closed-loop damping, and actuator forces are also considered. Derivatives of the objective and constraint functions with respect to structural and control design variables are derived for a finite element beam model of the structure and constant feedback gains determined by independent modal space control. Pareto optimal designs generated for a simple beam demonstrate the benefit of solving the integrated structural and control optimization problem.
Application of Nuclear Microlocalization Techniques to Biomedical Problems

Ion beams at the Brookhaven 3.5 MV Research Van de Graaff accelerator have been used for elemental analysis and distribution in biomedical samples. This paper will present results from several collaborations. Both collimated and uncollimated charged particle beams are used for elemental analysis by measurement of characteristic x-rays (PIXE). A collimated proton beam, using a pinhole collimator (~20 ?m) has been used as a particle microprobe in the laboratory ambient. Thick, essentially unprepared, samples can be measured with general elemental sensitivities of ? 10 ppm. The spatial resolution and elemental sensitivity have proven adequate for many samples of tissue sections and cell clusters. Specimen damage by charged particle beams is discussed and results of cell irradiations by triton beams are presented. Deuterium localization has been carried out in cell uptake studies using the 2H(3H,n)4He reaction initiated by the triton beam at the accelerator. Alpha particles from the reaction register the deuterium distribution in a plastic track detector. This technique suggests that 3H may be replaced by the stable isotope H in tracer studies. Studies have included the detection of nonexchangeable 2H in oocytes and the uptake of deuterated thymidine in blood cells.
M-ary FSK Performance for Coherent Optical Communication Systems Using Semiconductor Lasers

This paper describes the design and performance of an M ary frequency shift keyed (FSK) signaling and demodulation scheme for an optical communication system using semiconductor lasers and heterodyne detection. Frequency or phase noise in semiconductor lasers causes spectral spreading, producing a nonzero linewidth laser signal. This degrades communication performance when compared to a system using an ideal laser with zero linewidth. We present estimates of the bit error rate (BER) performance of M -ary frequency shift keying (FSK) with noncoherent demodulation in the presence of white Gaussian frequency noise and additive channel noise. This is typical of an optical system using semiconductor lasers and heterodyne detection. Estimates use the union-Chernoff bound with a simplified channel model to predict the effects of frequency noise. Two effects of frequency noise are identified: signal attenuation or suppression, and crosstalk. These cause an offset in the BER curve from the BER in the absence of frequency noise, and an error rate floor, respectively. The error rate floor is lower than previously predicted. When performance is not crosstalk limited, M -ary FSK is found to perform better than binary FSK with the same system bandwidth constraints, as would be predicted if ideal lasers are used. Theoretical results are compared with Monte Carlo simulations of the system.
Peaked signals from dark matter velocity structures in direct detection experiments

In direct dark matter detection experiments, conventional elastic scattering of WIMPs results in exponentially falling recoil spectra. In contrast, theories of WIMPs with excited states can lead to nuclear recoil spectra that peak at finite recoil energies ER. The peaks of such signals are typically fairly broad, with ΔER/Epeak ~ 1. We show that in the presence of dark matter structures with low velocity dispersion, such as streams or clumps, peaks from up-scattering can become extremely narrow with FWHM of a few keV only. This differs dramatically from the conventionally expected WIMP spectrum and would, once detected, open the possibility to measure the dark matter velocity structure with high accuracy. As an intriguing example, we confront the observed cluster of 3 events near 42 keV from the CRESST commissioning run with this scenario. Inelastic dark matter particles with a wide range of parameters are capable of producing such a narrow peak. We calculate the possible signals at other experiments, and find that such particles could also give rise to the signal at DAMA, although not from the same stream. Over some range of parameters, a signal would be visible at xenon experiments. We show that such dark matter peaks are a very clear signal and can be easily disentangled from potential backgrounds, both terrestrial or due to WIMP down-scattering, by an enhanced annual modulation in both the amplitude of the signal and its spectral shape.
Statistical en-route filtering of injected false data in sensor networks

In a large-scale sensor network individual sensors are subject to security compromises. A compromised node can be used to inject bogus sensing reports. If undetected, these bogus reports would be forwarded to the data collection point (i.e., the sink). Such attacks by compromised nodes can result in not only false alarms but also the depletion of the finite amount of energy in a battery powered network. In this paper, we present a statistical en-route filtering (SEF) mechanism to detect and drop false reports during the forwarding process. Assuming that the same event can be detected by multiple sensors, in SEF each of the detecting sensors generates a keyed message authentication code (MAC) and multiple MACs are attached to the event report. As the report is forwarded, each node along the way verifies the correctness of the MAC's probabilistically and drops those with invalid MACs. SEF exploits the network scale to filter out false reports through collective decision-making by multiple detecting nodes and collective false detection by multiple forwarding nodes. We have evaluated SEF's feasibility and performance through analysis, simulation, and implementation. Our results show that SEF can be implemented efficiently in sensor nodes as small as Mica2. It can drop up to 70% of bogus reports injected by a compromised node within five hops, and reduce energy consumption by 65% or more in many cases.
Non-linear sigma model on the fuzzy supersphere

In this note we develop fuzzy versions of the supersymmetric non-linear sigma model on the supersphere S(2,2). In [1] Bott projectors have been used to obtain the fuzzy P1 model. Our approach utilizes the use of supersymmetric extensions of these projectors. Here we obtain these (super)-projectors and quantize them in a fashion similar to the one given in [1]. We discuss the interpretation of the resulting model as a finite dimensional matrix model.
Exploring node light-splitting capability for burst grooming in optical burst switched networks

Optical burst switching (OBS) is a switching concept which lies between optical circuit switching and optical packet switching. Both node switching time and burst size can impact the resource efficiency of an OBS network. To increase resource utilization, burst grooming has been proposed where numerous data bursts are coalesced to form a larger burst that will be switched as one unit in order to reduce the resource waste and switching penalty. In this article, assuming burst grooming can only be realized at edge nodes, we study the burst grooming problem where sub-bursts originating from the same source may be groomed together regardless of their destinations under certain conditions. We explore the capability that core nodes can split incoming light signals to support multicast to achieve more efficient burst grooming. Specifically, core nodes can transmit the groomed burst to multiple downstream nodes if the sub-bursts in the groomed burst have different destinations. The groomed burst will traverse a tree which spans the source and all the destinations of the sub-bursts in the groomed burst. The destination egress nodes recognize, de-burstify, and drop the sub-bursts destined to these nodes, i.e., the sub-bursts destined to these egress nodes are removed from the groomed burst. At the same time, the remaining sub-bursts may be groomed with sub-bursts at these egress nodes subject to burst grooming criteria. We propose two effective burst grooming algorithms, (1) a no over-routing waste approach (NoORW); and (2) a minimum relative total resource ratio approach (MinRTRR). Our simulation results have shown that the proposed algorithms are effective in terms of the burst blocking probability, the average burst end-to-end delay, the number of sub-bursts per groomed burst, as well as the resource waste.
Probabilistic management of OCR data using an RDBMS

The digitization of scanned forms and documents is changing the data sources that enterprises manage. To integrate these new data sources with enterprise data, the current state-of-the-art approach is to convert the images to ASCII text using optical character recognition (OCR) software and then to store the resulting ASCII text in a relational database. The OCR problem is challenging, and so the output of OCR often contains errors. In turn, queries on the output of OCR may fail to retrieve relevant answers. State-of-the-art OCR programs, e.g., the OCR powering Google Books, use a probabilistic model that captures many alternatives during the OCR process. Only when the results of OCR are stored in the database, do these approaches discard the uncertainty. In this work, we propose to retain the probabilistic models produced by OCR process in a relational database management system. A key technical challenge is that the probabilistic data produced by OCR software is very large (a single book blows up to 2GB from 400kB as ASCII). As a result, a baseline solution that integrates these models with an RDBMS is over 1000x slower versus standard text processing for single table select-project queries. However, many applications may have quality-performance needs that are in between these two extremes of ASCII and the complete model output by the OCR software. Thus, we propose a novel approximation scheme called Staccato that allows a user to trade recall for query performance. Additionally, we provide a formal analysis of our scheme's properties, and describe how we integrate our scheme with standard-RDBMS text indexing.
Mutual fund theorems when minimizing the probability of lifetime ruin

Abstract We show that the mutual fund theorems of Merton [1971. Journal of Economic Theory 3, 373–413] extend to the problem of optimal investment to minimize the probability of lifetime ruin. We obtain two such theorems by considering a financial market both with and without a riskless asset for random consumption. The striking result is that we obtain two-fund theorems despite the additional source of randomness from consumption.
Propagation of Stress Waves in Fiber-Reinforced Composite Rods

The mechanical behavior of fiber-reinforced composite materials subject to dynamic loadings is investigated. The elastic moduli and damping coefficients of glass-epoxy and boronepoxy beams were determined from the frequencies and bandwidths of their resonances during lateral forced vibrations. Longitudinal stress pulses were generated in the composites by impact of lead pellets fired from a pneumatic rifle. Measured values of the velocity and attenuation of the pulses agree favorably with those based upon the vibration data and the assumption of linear viscoelastic behavior. Results of an exploratory study on the propagation of highfrequency waves in composites using an ultrasonic technique are also reported.
Restoring Natural Resources with Destination-Driven Costs

Abstract Economics typically assumes that injured natural resources are restored along a fixed path of increasing marginal costs. By contrast, many restoration efforts—such as cleaning a contaminated aquifer or replacing the sand on an oil-tarnished beach—are characterized by destination-driven costs , which depend mainly on final quality, not the prerestoration quality. Given the resulting nonconvexities in cost, the optimal level of restoration may be a discontinuous and nonmonotonic function of post-injury quality. Regulatory rules should reflect these patterns, as should liability rules, since restoration plans and costs determine the expected cost of putting a resource at risk.
Radio Properties of Infrared-selected Galaxies in the IRAS 2 Jy Sample

The radio counterparts to the IRAS Redshift Survey galaxies are identified in the NRAO VLA Sky Survey (NVSS) catalog. Our new catalog of the IR flux-limited (S60 μm ≥ 2 Jy) complete sample of 1809 galaxies lists accurate radio positions, redshifts, and 1.4 GHz radio and IRAS fluxes. This sample is 6 times larger in size and 5 times deeper in redshift coverage (to z ≈ 0.15) than those used in earlier studies of the radio and far-IR (FIR) properties of galaxies in the local volume. The well-known radio-FIR correlation is obeyed by the overwhelming majority (≥98%) of the IR-selected galaxies, and the radio AGNs identified by their excess radio emission constitute only about 1% of the sample, independent of the IR luminosity. These FIR-selected galaxies can account for the entire population of late-type field galaxies in the local volume, and their radio continuum may be used directly to infer the extinction-free star formation rate in most cases. Both the 1.4 GHz radio and 60 μm IR luminosity functions are reasonably well described by linear sums of two Schechter functions, one representing normal, late-type field galaxies and the other representing starbursts and other luminous IR galaxies. The integrated FIR luminosity density for the local volume is (4.8 ± 0.5) × 107 L☉ Mpc-3, less than 10% of which is contributed by the luminous IR galaxies with LFIR ≥ 1011 L☉. The inferred extinction-free star formation density for the local volume is 0.015 ± 0.005 M☉ yr-1 Mpc-3.
Practical in-place merging

We present a novel, yet straightforward linear-time algorithm for merging two sorted lists in a fixed amount of additional space. Constant of proportionality estimates and empirical testing reveal that this procedure is reasonably competitive with merge routines free to squander unbounded additional memory, making it particularly attractive whenever space is a critical resource.
Anode Sputtering Characteristics of the Berkeley 2.5 MV Source

This paper reports an investigation of a number of parameters affecting the performance of the SuperHILAC 2.5 MV Adam injector source. The description will emphasize anode sputtered materials, and will discuss in some detail calcium and gold ion production. Parameters varied include electrode geometry, support gas type and electrode bias, to optimize beam intensity and electrode consumption. A factor of three improvement with high n+ gold ions appears evident with a new displaced electrode geometry. The source is operated in cold mode, is pulsed and operates usually at less than 0.6 amperes average current. Under these conditions source life has been measured to be sixteen hours at 25% duty factor, when generating calcium ions, with neon support gas.
U.S. science parks: the diffusion of an innovation and its effects on the academic missions of universities

The paper is an exploratory study of science parks in the United States. It models the history of science parks as the diffusion of an innovation that was adopted at a rapid and increasing rate in the early 1980s, and since then at a decreased rate. It models the growth of a science park once established, showing significant effects on growth for the proximity to universities and other resources. The paper also reports university administrators’ perceptions about the impact of their science parks on the academic missions of their universities. Statistical analyses show there is a direct relationship between the proximity of the science park to the university and the probability that the academic curriculum will shift from basic toward applied research.
Iterative Soft-Input Soft-Output Decoding of Reed&#8211;Solomon Codes by Adapting the Parity-Check Matrix

An iterative algorithm is presented for soft-input soft-output (SISO) decoding of Reed-Solomon (RS) codes. The proposed iterative algorithm uses the sum-product algorithm (SPA) in conjunction with a binary parity-check matrix of the RS code. The novelty is in reducing a submatrix of the binary parity-check matrix that corresponds to less reliable bits to a sparse nature before the SPA is applied at each iteration. The proposed algorithm can be geometrically interpreted as a two-stage gradient descent with an adaptive potential function. This adaptive procedure is crucial to the convergence behavior of the gradient descent algorithm and, therefore, significantly improves the performance. Simulation results show that the proposed decoding algorithm and its variations provide significant gain over hard-decision decoding (HDD) and compare favorably with other popular soft-decision decoding methods
An alternative approach to fundamental analysis: The asset side of the equation

A standard approach for determining the fundamental value of financial claims is to compute the discounted value of the expected dividend stream. This paper discusses an alternative approach that estimates fundamental value as the discounted value of the cash flows expected from underlying real assets. Illustrative empirical estimates indicate that the ratio of market to fundamental value varies over time and across industries. Downloadable document available at: https://jpm.pm-research.com/content/17/2/6
Celebrity diplomacy and global citizenship

‘Heal a rape victim’: This possibility is one of many that Oprah Winfrey's ‘For All Women Registry’ offers to those who are willing to donate ‘$5 or 5 minutes’. Such appeals on Oprah's website repr...
Optimal estimation of rain-rate profiles from single-frequency radar echoes

The significant ambiguities inherent in the determination of a particular vertical rain intensity profile from a given time profile of radar echo powers measured by a downward-looking (spaceborne or airborne) radar at a single attenuating frequency are well documented. Indeed, one already knows that by appropriately varying the parameters of the reflectivity-rain rate (Z-R) and/or attenuation-rain rate (k- R) relationships one can produce several substantially different rain-rate profiles that would produce the same radar power profile. Imposing the additional constraint that the path-averaged rain rate be a given fixed number does reduce the ambiguities but falls far short of eliminating them. While formulas to generate all mutually ambiguous rain-rate profiles from a given profile of received radar reflectivities have already been derived, there remains to be produced a quantitative measure to assess how likely each of these profiles is, what the appropriate "average" profile should be, and what the "variance" of these multiple solutions is. To do this, one needs to spell out the stochastic constraints that can allow us to make sense of the words "average" and "variance" in a mathematically rigorous way. Such a quantitative approach would be particularly well suited for such systems as the planned precipitation radar of the Tropical Rainfall Measuring Mission (TRMM). Indeed, one would then be able to use the radar reflectivities measured by the TRMM radar to estimate the rain-rate profile that would most likely have produced the measurements, as well as the uncertainty in the estimated rain rates as a function of range. Such an optimal approach is described in this paper.
An Accurate Solution of the Gas Lubricated, Flat Sector Thrust Bearing

A flat sector shaped pad geometry for gas lubricated thrust bearings is analyzed considering both pitch and roll angles of the pad and the true film thickness distribution. Maximum load capacity is achieved when the pad is tilted so as to create a uniform minimum film thickness along the pad trailing edge. Performance characteristics for various geometries and operating conditions of gas thrust bearings are presented in the form of design curves. A comparison is made with the rectangular slider approximation. It is found that this approximation is unsafe for practical design, since it always overestimates load capacity.
Short Neuropeptide F Is a Sleep-Promoting Inhibitory Modulator

To advance the understanding of sleep regulation, we screened for sleep-promoting cells and identified neurons expressing neuropeptide Y-like short neuropeptide F (sNPF). Sleep induction by sNPF meets all relevant criteria. Rebound sleep following sleep deprivation is reduced by activation of sNPF neurons, and flies experience negative sleep rebound upon cessation of sNPF neuronal stimulation, indicating that sNPF provides an important signal to the sleep homeostat. Only a subset of sNPF-expressing neurons, which includes the small ventrolateral clock neurons, is sleep promoting. Their release of sNPF increases sleep consolidation in part by suppressing the activity of wake-promoting large ventrolateral clock neurons, and suppression of neuronal firing may be the general response to sNPF receptor activation. sNPF acutely increases sleep without altering feeding behavior, which it affects only on a much longer time scale. The profound effect of sNPF on sleep indicates that it is an important sleep-promoting molecule.
Debt Financing in Asset Markets

Short-term debt, such as overnight repurchase agreements and commercial paper, was heavily used by financial institutions to fund their investment positions during the asset market boom preceding the financial crisis of 2007– 2008, and later played a major role in leading to the distress of these institutions during the crisis. What explains the popularity of short-term debt in financing asset market investments? Geanakoplos (2010) presents a dynamic model of the joint equilibrium of asset markets and credit markets, in which optimistic buyers of a risky asset use the asset as collateral to raise debt financing from less optimistic creditors. The asset’s collateral value depends on the marginal creditor’s asset valuation, and determines the buyers’ purchasing capacity to bid up the asset price. Geanakoplos posits that short-term debt allows the asset buyers to maximize riskless leverage. 1 Short-term debt, however, exposes the asset buyers to rollover risk (e.g., Acharya, Gale, and Yorulmaker 2011; and He and Xiong 2012, forthcoming), which is reflected in the fact that the asset buyers in Geanakoplos’ model may not be able to obtain refinancing after a negative fundamental shock. As a result, they are forced to transfer their asset holdings to the
Defect Structure and Electrical Properties of Single‐Crystal Ba0.03Sr0.97TiO3

The electrical conductivity and thermoelectric power of single-crystalline Ba0.03Sr0.97TiO3 were measured over a wide temperature (800° to 1100°C) and oxygen partial pressure (105 to 10-15 Pa) range. Our experimental data, like those of previous workers on nominally undoped BaTiO3 or SrTiO3, support a defect model based on doubly ionized oxygen vacancies, electrons, holes, and accidental acceptor impurities. The simultaneous measurement of electrical conductivity and thermoelectric power, together with precise experimental data obtained with an advanced thermoectric power measurement technique, enabled us to determine for the first time reliable values for the preexponential factors and the activation energies which characterize the defect equilibrium constants. These calculated values, together with the defect model, were found to give an excellent fit to the experimental data, and were used to generate the boundaries, in Po2-1/T space, of the various defect regimes.
A Simply Stabilized Running Model

The spring-loaded inverted pendulum (SLIP), or monopedal hopper, is an archetypal model for running in numerous animal species. Although locomotion is generally considered a complex task requiring sophisticated control strategies to account for coordination and stability, we show that stable gaits can be found in the SLIP with both linear and "air" springs, controlled by a simple fixed-leg reset policy. We first derive touchdown-to-touchdown Poincare maps under the common assumption of negligible gravitational effects during the stance phase. We subsequently include and assess these effects and briefly consider coupling to pitching motions. We investigate the domains of attraction of symmetric periodic gaits and bifurcations from the branches of stable gaits in terms of nondimensional parameters.
Adsorption on carbon nanotubes: quantum spin tubes, magnetization plateaus, and conformal symmetry.

We formulate the problem of adsorption onto the surface of a carbon nanotube as a lattice gas on a triangular lattice wrapped around a cylinder. This model is equivalent to an $\mathrm{XXZ}$ Heisenberg quantum spin tube. We find density plateau structures for armchair, zigzag, and chiral nanotubes. The zigzags are special and have extensive zero temperature entropy plateaus in the classical limit. Quantum effects lift the degeneracy, leaving gapless excitations described by a $c\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$ conformal field theory with compactification radius quantized by the tube circumference.
Establishing wireless conference calls under delay constraints

A prevailing feature of mobile telephony systems is that the cell where a mobile user is located may be unknown. Therefore, when the system is to establish a call between users, it may need to search, or page, all the cells that it suspects the users are located in, to find the cells where the users currently reside. The search consumes expensive wireless links and so it is desirable to develop search techniques that page as few cells as possible.We consider cellular systems with c cells and m mobile users roaming among the cells. The location of the users is uncertain as given by m probability distribution vectors. Whenever the system needs to find specific users, it conducts a search operation lasting some number of rounds (the delay constraint). In each round, the system may check an arbitrary subset of cells to see which users are located there. In this setting the problem of finding one user with minimum expected number of cells searched is known to be solved optimally in polynomial time.In this paper we address the problem of finding several users with the same optimization goal. This task is motivated by the problem of establishing a conference call between mobile users. We first show that the problem is NP-hard. Then we prove that a natural heuristic is an e/(e - 1 )-approximation solution.
Maximizing the efficiency of ferritin as a photocatalyst for applications in an artificial photosynthesis system

ABSTRACT Alternate fuel sources are becoming increasingly important as the reserve of fossil fuels decrease. We describe a photosynthesis mimic that is capable of extracting electrons from sacrificial electron donors. This model is based on the bio-photo-catalyst ferritin. Ferritin is an iron storage protein that naturally sequesters ferrihydrite inside a spherical 12 nm protein shell. Ferrihydrite is a semi-conductor that functions as a photo-catalyst in aqueous solvents. Ferritin has been shown to photoreduce Au 3+ to form Au(0) nanoparticles. Citrate acts as a sacrificial electron donor to supply electrons for the photoreduction. We describe studies designed to understand the mechanism of this catalyst in order to improve the efficiency of the reaction. We have developed a spectrophotometric assay to simultaneously illuminate the sample and kinetically monitor the formation of products of Au 3+ reduction. We report that buffers containing sulfur significantly increase the rate of the r eactions. Control reactions with colloidal ferrihydrite nanoparticles do not catalyze the photochemical reaction, but produce a black precipitate indicating that the protein shell has an important function in nanoparticle formation. Keywords: ferritin, ferrihydrite, gold nanoparticles, photor eduction, artificial photosynthesis, photosystem II
A SIEVE M-THEOREM FOR BUNDLED PARAMETERS IN SEMIPARAMETRIC MODELS, WITH APPLICATION TO THE EFFICIENT ESTIMATION IN A LINEAR MODEL FOR CENSORED DATA.

In many semiparametric models that are parameterized by two types of parameters – a Euclidean parameter of interest and an infinite-dimensional nuisance parameter, the two parameters are bundled together, i.e., the nuisance parameter is an unknown function that contains the parameter of interest as part of its argument. For example, in a linear regression model for censored survival data, the unspecified error distribution function involves the regression coefficients. Motivated by developing an efficient estimating method for the regression parameters, we propose a general sieve M-theorem for bundled parameters and apply the theorem to deriving the asymptotic theory for the sieve maximum likelihood estimation in the linear regression model for censored survival data. The numerical implementation of the proposed estimating method can be achieved through the conventional gradient-based search algorithms such as the Newton-Raphson algorithm. We show that the proposed estimator is consistent and asymptotically normal and achieves the semiparametric efficiency bound. Simulation studies demonstrate that the proposed method performs well in practical settings and yields more efficient estimates than existing estimating equation based methods. Illustration with a real data example is also provided.
Cell-Surface Adhesive Interactions in Microchannels and Microvessels

Adhesive interactions between white blood cells and the interior surface of the blood vessels they contact is important in inflammation and in the progression of heart disease. Parallel-plate microchannels have been useful in characterizing the strength of these interactions, in conditions that are much simplified over the complex environment these cells experience in the body. Recent computational and experimental work by several laboratories have attempted to bridge this gap between behavior observed in flow chamber experiments and cell-surface interactions observed in the microvessels of anesthetized animals.
Theory of Surface Polaritons in n-Type Silicon in the Presence of a DC Current.

Abstract A theoretical investigation has been carried out on the effect of a drift current on surface polaritons in n-type silicon. The current direction is taken to be parallel to the direction of propagation of the surface polaritons. From the dispersion curves, there is evidence that an interaction takes place between the current and the polaritons which gives rise to polariton instability or amplification for certain frequency ranges. These instabilities are believed to be due to the presence of the surface.
An Asymptotic, Probabilistic Analysis of a Routing Problem

Certain “Bus Problems” are defined as generalizations of the traveling salesman problem. The simplest result concerns the length of the tour required by a single bus to pick up and deliver n passengers from random locations to random destinations in a bounded region of the plane. It is shown that the length of the tour divided by the square root of n converges almost surely to the square root of slightly more than twice the area of the region as n goes to infinity. When several buses are available, the length of the tour is simply divided by the number of buses. The bus problems have been motivated by the practical problem of scheduling dial-a-ride transportation systems.
Synthesis of lithium dialuminate by salt imbibition

Synthese de LiAl 2 (OH) 7 •2H 2 O par reaction a temperature ordinaire de Li(OH) solide, Al(OH) 3 polycristallin et de vapeur d'eau. Etude RX. L'ion OH et 2 molecules d'eau se situent entre les couches
Acoustic vortical interaction in a complex turbulent flow

Abstract This investigation is concerned with the interaction between vortical structures and an externally applied acoustic field in a complex turbulent flow field. The flow field is produced by a flow of air over a backward-facing step in a rectangular section duct. The purposes of this investigation are to (a) demonstrate the existence of somewhat organized vortical structures in the shear layer, (b) demonstrate that the vortical structures are influenced (organized) by an applied acoustic field, and (c) determine if the vortical structures in turn affect the applied acoustic field. By anemometry and acoustic pressure measurement, together with aeroacoustic theory, the first demonstrations are made. However, in the flow field used, without strong downstream constrictions, there is no discernible feedback into the acoustic field.
An Improved Synthesis of 4-Methylene-2-cyclohexen-1-one

Abstract An improved synthesis of 4-methylene-2-cyclohexen-1-one (1) is described, which involves four steps from commercially available starting materials and proceeds in 65–75% overall yield.
Resolving the Mystery of X-Ray-faint Elliptical Galaxies: Chandra X-Ray Observations of NGC 4697

Chandra observations of the X-ray-faint elliptical galaxy NGC 4697 resolve much of the X-ray emission (61% within one effective radius) into ~80 point sources, of which most are low-mass X-ray binaries (LMXBs). These LMXBs provide the bulk of the hard emission and much of the soft emission as well. Of the remaining unresolved emission, it is likely that about half is from fainter LMXBs, while the other half (~23% of the total emission) is from interstellar gas. Three of the resolved sources are supersoft sources. In the outer regions of NGC 4697, eight of the LMXBs (about 25%) are coincident with candidate globular clusters, indicating that globulars have a high probability of containing X-ray binaries compared with the normal stellar population. The X-ray luminosities (0.3-10 keV) of the resolved LMXBs range from ~5 × 1037 to ~2.5 × 1039 ergs s-1. The luminosity function of the LMXBs has a "knee" at 3.2 × 1038 ergs s-1, which is roughly the Eddington luminosity of an 1.4 M☉ neutron star (NS); this knee might be useful as a distance indicator. The highest luminosity source has the Eddington luminosity of an ~20 M☉ black hole (BH). The presence of this large population of NS and massive BH stellar remnants in this elliptical galaxy shows that it (or its progenitors) once contained a large population of massive main-sequence stars.
A Bipolar Model of the Passivity of Stainless Steel: The Role of Mo Addition

The passive films formed on the surface of and alloys in have been characterized by AES and variable angle XPS. It is found that additions of Mo to results in the formation of a passive film with a more highly developed interfacial barrier film composed mainly of , containing in solid solution which forms a glassy phase. In addition, the passive films were found to contain more Fe. Molybdenum appears to be present as Mo4+ and Mo6+ identified as hydrated and , apparently as . It is proposed that anions are formed in the solid state along with , which together are responsible for producing, in , a bipolar film consisting of a cation selective outer layer containing and and an intrinsically anion selective inner layer. The ion selective property of this duplex film is considered to be largely responsible for the development of the barrier layer and resisting Cl− and OH− ingress. Both of these properties provide greater resistance to break down of passivity in Cl− ion media.
Interest-rate risk factor and stock returns: a time-varying factor-loadings model

We extend the Fama–French three-factor model to include a risk factor that proxies for interest-rate risk faced by firms in an attempt to reduce the pricing errors that the three-factor model cannot explain. These pricing errors are observed especially in small size and low book-to-market ratio firms, which are in general more sensitive to interest-rate risk. In addition, the factor loadings are modelled as time-varying so that the investors’ learning process can be taken into account. The results show that our Time-Varying-Loadings Four-Factor (TVL4) model significantly reduces the pricing errors.
The first acidity constant of carbon dioxide in solutions of ammonium chloride from e.m.f. measurements at 278.15 to 318.15 K

Abstract The equilibrium constant K1o of the reaction: CO2 + H2O = HCO3− + H+, was determined from the e.m.f. of the cell: Pt/H2, CO2/NH4HCO3(m1), NH4Cl(m2), CO2(m3)/AgCl/Ag. The activity coefficients of NH4HCO3 in NH4Cl(aq) and in pure water at 278.15, 288.15, 198.15, 308.15, and 318.15 K were calculated. The values of m 1 m 2 were approximately 1, 2, 3, and 6. The molality of NH4Cl ranged from 0.02 to 0.3 mol·kg−1, whereas the molality of NH4HCO3 was varied from 0.04 to 0.73 mol·kg−1. Values of −lgK1o were calculated by means of the Harned extrapolation method. The average value (pK1o = 6.355) for all different ratios of m 1 m 2 agreed well with the adopted value (pK1o = 6.360) for (sodium bicarbonate + sodium chloride + water) and (potassium bicarbonate + potassium chloride + water) at 298.15 K. The values of lg γ were interpreted by the mixed-electrolyte equations of Pitzer and Kim to yield Pitzer's ion-interaction parameters for NH4+ and HCO3tt-. With these results, the stoichiometric and equilibrium activity coefficients and the osmotic coefficient of pure NH4HCO3, as well as the trace activity coefficients of NH4HCO3 in NH4Cl are calculated at various temperatures and selected molalities.
Sliding mode control of electric power system comprised of fuel cells, DC-DC boost converters and ultracapacitors

The paper deals with controlling an autonomous electric power system that comprises Proton Exchange Membrane fuel cell (PEMFC) that is considered as a primary source of electrical energy, the DC-DC boost power converter, and the ultracapacitor. System's PEMFC/ultracapacitor/DC-DC boost power converter zero dynamics are analyzed and appeared to be stable. Relative degree approach is applied for direct control of the output load voltage as well as the fuel cell and ultracapacitor current in the presence of the model uncertainties. The adaptive gain super-twisting sliding mode controller controls the current in PEMFC. The decoupled SMCs are designed for controlling the output voltage and the fast component of the load current that is commanded to the ultracapacitor. The efficacy and robustness of the proposed three-fold SMC and 2-SM adaptive-gain controllers are confirmed via computer simulations.
Application of gaseous sphere injection method for modeling under-expanded H2 injection

A methodology for modeling gaseous injection has been refined and applied to recent experimental data from the literature. This approach uses a discrete phase analogy to handle gaseous injection, allowing for addition of gaseous injection to a CFD grid without needing to resolve the injector nozzle. This paper focuses on model testing to provide the basis for simulation of hydrogen direct injected internal combustion engines. The model has been updated to be more applicable to full engine simulations, and shows good agreement with experiments for jet penetration and time-dependent axial mass fraction, while available – radial mass fraction data is less well predicted.
A Pulsational Model for the Orthogonal Polarization Modes in Radio Pulsars

In an earlier paper we introduced a model for pulsars in which nonradial oscillations of high spherical degree (l ) aligned to the magnetic axis of a spinning neutron star were able to reproduce subpulses like those observed in single-pulse measurements of pulsar intensity. The model did not address polarization, which is an integral part of pulsar emission. Observations show that many pulsars emit radio waves that appear to be the superposition of two linearly polarized emission modes with orthogonal polarization angles. In this paper we extend our model to incorporate linear polarization. As before, we propose that pulsational displacements of stellar material modulate the pulsar emission, but now we apply this modulation to a linearly polarized mode of emission, as might be produced by curvature radiation. We further introduce a second polarization mode, orthogonal to the first, that is modulated by pulsational velocities. We combine these modes in superposition to model the observed Stokes parameters in radio pulsars.
Diagram rigidity for geometric amalgamations of free groups.

In this paper, we show that a class of 2-dimensional locally CAT(-1) spaces is topologically rigid: isomorphism of the fundamental groups is equivalent to the spaces being homeomorphic. An immediate application of this result is a diagram rigidity theorem for certain amalgamations of free groups. The direct limits of two such amalgamations are isomorphic if and only if there is an isomorphism between the respective diagrams.
Persistence of invariant manifolds for nonlinear PDEs

We prove that under certain stability and smoothing properties of the semi-groups generated by the partial differential equations that we consider, manifolds left invariant by these flows persist under 1 perturbation. In particular, we extend well-known finite-dimensional results to the setting of an infinite-dimensional Hilbert manifold with a semi-group that leaves a submanifold invariant. We then study the persistence of global unstable manifolds of hyperbolic fixed points, and as an application consider the two-dimensional Navier–Stokes equation under a fully discrete approximation.Finally, we apply our theory to the persistence of inertial manifolds for those PDEs that possess them.