cssi/SciSciGPT-SciSciNet huggingface dataset:
Limits on Energy Storage in the Crusts of Accreting Neutron Stars

We have carried out a systematic study of the storage of nuclear and gravitational energy in the crusts of old neutron stars that are slowly accreting matter from the interstellar medium or distant binary companion stars. We considered neutron-star masses, radii, and accretion rates in the ranges 0.1-2.8 M☉, 7-150 km, and 1010-1016 g s-1, respectively. We also investigated the effects of variations in resulting from periodic passages of the neutron star through the Galactic midplane and/or occasional encounters with molecular clouds. We found, consistent with earlier work, that pycnonuclear reactions lead to the development of density inversions in the crust; the strongest inversions (of order 2% in density), which occur at the interface between 16C and heavier nuclei, store ~1041 ergs of gravitational potential energy. If an instability can trigger the overturn of such an inversion, the released energy would ignite a powerful thermonuclear flash, and the resulting starquake might result in magnetospheric effects that lead to the emission of a γ-ray burst or other energetic astrophysical phenomenon. Although the isotropy of the distribution of γ-ray burst sources, as determined by the BATSE experiment, precludes the possibility that all γ-ray bursts are associated with neutron stars in the Galactic disk, it remains possible that a subset of the observed bursts have their origin in events of this type. From our calculations, we determined that the total nuclear energy that can be stored in the crust of a neutron star is limited by the 16C +16C pycnonuclear reaction, which converts the accreted material at a density of ~5 × 1010 g cm-3 into nuclei substantially closer to nuclear equilibrium. As a result, the total (nuclear plus gravitational) energy, Etot, that can be stored is quite generally limited to less than ~1046 ergs, irrespective of neutron-star mass, radius, mean , or variations in . For =1010 g s-1, it takes ~1010 yr for maximum energy storage to be achieved; for higher accretion rates, the required time decreases very nearly as −1. For 3×1015 g s-1, thermonuclear flashes in the helium shell greatly reduce Etot. Irrespective of the γ-ray burst emission mechanism, the upper limit that we have obtained on Etot places a strong constraint on any model that ascribes a subset of γ-ray bursts to the emission of energy stored in the crusts of neutron stars. Our results are also relevant to any other energetic celestial phenomenon that might be associated with a Galactic-disk population of isolated neutron stars.
Demand and Supply in New Markets: Diffusion with Bilateral Learning

I explore the endogenous joint evolution of demand and supply in new markets. Firms and consumers learn, in a Bayesian fashion, by observing the behavior of other firms and consumers, respectively. As a result, endogenous information diffusion takes place on both sides of the market. In equilibrium, entry occurs in waves and its level depends on two distinct informational effects. The model identifies an externality that provides a natural explanation for S-shaped diffusion paths: entry reveals information to the consumers about the value of the new product, and thus early waves of entry affect the expected profitability of subsequent entry.
Initial stages of epitaxial growth of GaAs on (100) silicon

Direct observations of early stages of molecular‐beam epitaxial growth of GaAs on oriented and vicinal (100) Si surfaces are presented. Cross‐sectional transmission electron microscopy and plan view scanning electron microscopy images directly reveal three‐dimensional island growth for substrate temperatures above 300 °C. Island size, island spacing, surface morphology, and stacking fault defect spacing all increase with substrate temperature for fixed Ga and As fluxes. Below 300 °C, 7‐nm‐thick films are continuous and uniform. Films deposited on surfaces tilted from (100) coalesce anisotropically with respect to the tilt axis.
Dehn surgery on knots of wrapping number 2

Suppose K is a hyperbolic knot in a solid torus V intersecting a meridian disk D twice. We will show that if K is not the Whitehead knot and the frontier of a regular neighborhood of K[D is incompressible in the knot exterior, then K admits at most one exceptional surgery, which must be toroidal. Embedding V in S gives infinitely many knots Kn with a slope rn corresponding to a slope r of K in V . If r surgery on K in V is toroidal then either Kn.rn/ are toroidal for all but at most three n , or they are all atoroidal and nonhyperbolic. These will be used to classify exceptional surgeries on wrapped Montesinos knots in a solid torus, obtained by connecting the top endpoints of a Montesinos tangle to the bottom endpoints by two arcs wrapping around the solid torus.
Stock Price Synchronicity, Crash Risk, and Institutional Investors

Abstract Both stock price synchronicity and crash risk are negatively related to the firm's ownership by dedicated institutional investors, which have strong incentive to monitor due to their large stake holdings and long investment horizons. In contrast, the relations become positive for transient institutional investors as they tend to trade rather than monitor. These findings suggest that institutional monitoring limits managers' extraction of the firm's cash flows, which reduces the firm-specific risk absorbed by managers, thereby leading to a lower R 2 . Moreover, institutional monitoring mitigates managerial bad-news hoarding, which results in a stock price crash when the accumulated bad news is finally released.
Bounded size bias coupling: a Gamma function bound, and universal Dickman-function behavior

Under the assumption that the distribution of a nonnegative random variable $$X$$ admits a bounded coupling with its size biased version, we prove simple and strong concentration bounds. In particular the upper tail probability is shown to decay at least as fast as the reciprocal of a Gamma function, guaranteeing a moment generating function that converges everywhere. The class of infinitely divisible distributions with finite mean, whose Levy measure is supported on an interval contained in $$[0,c]$$ for some $$c < \infty $$ , forms a special case in which this upper bound is logarithmically sharp. In particular the asymptotic estimate for the Dickman function, that $$\rho (u) \approx u^{-u}$$ for large $$u$$ , is shown to be universal for this class. A special case of our bounds arises when $$X$$ is a sum of independent random variables, each admitting a 1-bounded size bias coupling. In this case, our bounds are comparable to Chernoff–Hoeffding bounds; however, ours are broader in scope, sharper for the upper tail, and equal for the lower tail. We discuss bounded and monotone couplings, give a sandwich principle, and show how this gives an easy conceptual proof that any finite positive mean sum of independent Bernoulli random variables admits a 1-bounded coupling with the same conditioned to be nonzero.
Theoretical Spectra and Light Curves of Close-in Extrasolar Giant Planets and Comparison with Data

We present theoretical atmosphere, spectral, and light-curve models for extrasolar giant planets (EGPs) undergoing strong irradiation for which Spitzer planet/star contrast ratios or light curves have been published (circa 2007 June). These include HD 209458b, HD 189733b, TrES-1, HD 149026b, HD 179949b, and υ And b. By comparing models with data, we find that a number of EGP atmospheres experience thermal inversions and have stratospheres. This is particularly true for HD 209458b, HD 149026b, and υ And b. This finding translates into qualitative changes in the planet/star contrast ratios at secondary eclipse and in close-in EGP orbital light curves. Moreover, the presence of atmospheric water in abundance is fully consistent with all the Spitzer data for the measured planets. For planets with stratospheres, water absorption features invert into emission features and mid-infrared fluxes can be enhanced by a factor of 2. In addition, the character of near-infrared planetary spectra can be radically altered. We derive a correlation between the importance of such stratospheres and the stellar flux on the planet, suggesting that close-in EGPs bifurcate into two groups: those with and without stratospheres. From the finding that TrES-1 shows no signs of a stratosphere, while HD 209458b does, we estimate the magnitude of this stellar flux breakpoint. We find that the heat redistribution parameter, Pn, for the family of close-in EGPs assumes values from ~0.1 to ~0.4. This paper provides a broad theoretical context for the future direct characterization of EGPs in tight orbits around their illuminating stars.
A lightweight, robust P2P system to handle flash crowds

An Internet flash crowd (also known as hot spots) is a phenomenon that results from a sudden, unpredicted increase in an on-line object's popularity. Currently, there is no efficient means within the Internet to deliver Web objects scalably under hot spot conditions to all clients that desire the object. We present peer-to-peer (P2P) randomized overlays to obviate flash-crowd symptoms (PROOFS), a simple, lightweight, P2P approach that uses randomized overlay construction and randomized, scoped searches to locate and deliver objects efficiently under heavy demand to all users that desire them. We evaluate PROOFS' robustness in environments in which clients join and leave the P2P network, as well as in environments in which clients are not always fully cooperative. Through a mix of simulation and prototype experimentation in the Internet, we show that randomized approaches like PROOFS should effectively relieve flash crowd symptoms in dynamic, limited-participation environments.
Formation of the First Supermassive Black Holes

We consider the physical conditions under which supermassive black holes could have formed inside the first galaxies. Our smoothed particle hydrodynamics simulations indicate that metal-free galaxies with a virial temperature of ~104 K and suppressed H2 formation (due to an intergalactic UV background) tend to form a binary black hole system that contains a substantial fraction (10%) of the total baryonic mass of the host galaxy. Fragmentation into stars is suppressed without substantial H2 cooling. Our simulations follow the condensation of ~5 × 106 M☉ around the two centers of the binary down to a scale of 0.1 pc. Low-spin galaxies form a single black hole instead. These early black holes lead to quasar activity before the epoch of reionization. Primordial black hole binaries lead to gravitational radiation emission at redshifts z 10 that would be detectable by Laser Interferometer Space Antenna.
KHOVANOV HOMOLOGY AND THE TWIST NUMBER OF ALTERNATING KNOTS

In A Volumish Theorem for the Jones Polynomial, by O. Dasbach and X. S. Lin, it was shown that the sum of the absolute value of the second and penultimate coefficient of the Jones polynomial of an alternating knot is equal to the twist number of the knot. Here we give a new proof of this result using Khovanov homology. The proof is by induction on the number of crossings using the long exact sequence in Khovanov homology corresponding to the Kauffman bracket skein relation.
Higher-Frequency Analysis of Low-Frequency Data

Low-frequency data present significant challenges to investors because infrequent observations lead to imperfect intra-period understandings of market behavior, which in turn frustrate risk management and portfolio monitoring. Nowhere is this phenomenon more vexing than in portfolios that include both liquid and illiquid investments, whose low-frequency reporting compromises an investor’s ability to form a holistic portfolio perspective. The authors examine the consequences of this issue and evaluate two methodologies for interpolating low-frequency data to facilitate use in higher-frequency settings. Through a numerical study, they determine that the decision to use one methodology over another—or whether to interpolate at all—is context-dependent, and illustrate the effect of higher-frequency interpolation on risk evaluation, attribution, and other common risk measures.
Should the stagnant homeownership rate be a source of concern

Abstract The homeownership rate in the United States was essentially stagnant during the 1980s. This stagnation should be a source of concern if the rate reflects stagnant economic conditions and ownership opportunities; not if it simply reflects changing demographic conditions or preferences. Using a series of affordability measures, we find that homeownership opportunities improved almost everywhere during the 1980s, suggesting that the cause of the stagnant rate was something other than economic conditions. In fact, we found that both demographics and changes in preferences led to an increase in the proportion of households headed by single people; all else being equal, this would tend to push the owner-occupancy rate downward. We also found that, while homeownership opportunities improved during the 1980s, the ex ante user cost of owning a home increased almost everywhere, reducing the financial attractiveness of owning a home. The combination of improving affordability conditions and worsening financial appeal had an overall neutral effect on the aggregate ownership rate.
Vectorization of an applicative language: current results and future directions

It is shown that applicative programs do not require special hardware for efficient execution, and with little effort can automatically exploit concurrent and vector processors. The author praises applicative languages for their semantic aesthetics, describes their potential inefficiencies, and highlights some important optimizations. In particular, he compares the performances of Sisal and Fortran. It is demonstrated that the applicative paradigm is a powerful tool for scientific computation. One can reap the benefits of side-effect-free semantics and at the same time acquire a performance edge. The results are better maintenance, increased portability, enhanced productivity, and guaranteed confidence and security. >
Relativistic transport theory of fluctuating fields for hadrons

We analyze the physics of relativistic nuclear collisions, and demonstrate that an adequate treatment of pions must include the quantum time-energy uncertainty principle and non-sequential 3-body collisions. We apply relativistic quantum field theory to obtain exact equations determining the time evolution of hadronic fields and their fluctuations in terms of the effective interactions describing scattering in matter. These equations relate the main physical observables to the sought-after properties of nuclear matter, and involve only these quantities and the corresponding properties of free-space 1- and 2-body processes. We show how to regularize the singularities by employing the internal structure of the mesons, while maintaining causality and unitarity. We show that, in a very good approximation, the dynamic quantities reduce to functions of 8 variables — those of the Boltzmann equation, supplemented by the energy of the hadron. Our method appears capable of deducing the properties of hot dense nuclear matter from data already measured in experiments on the collisions of heavy nuclei.
Testing linear-theory predictions of galaxy formation

The angular momentum of galaxies is routinely ascribed to a process of tidal torques acting during the early stages of gravitational collapse, and is predicted from the initial mass distribution using second-order perturbation theory and the Zel’dovich approximation. We test this theory for a flat hierarchical cosmogony using a large N-body simulation with sufficient dynamic range to include tidal fields, allow resolution of individual galaxies, and thereby expand on previous studies. The predictions of linear collapse, linear tidal torque, and biased-peaks galaxy formation are applied to the initial conditions and compared with results for evolved bound objects. We find relatively good correlation between the predictions of linear theory and actual galaxy evolution. Collapse is well described by an ellipsoidal model within a shear field, which results primarily in triaxial objects that do not map directly to the initial density field. While structure formation from early times is a complex history of hierarchical merging, salient features are well described by the simple spherical-collapse model. Most notably, we test several methods for determining the turnaround epoch, and find that turnaround is successfully described by the spherical-collapse model. The angular momentum of collapsing structures grows linearly until turnaround, as predicted, and continues quasi-linearly until shell crossing. The predicted angular momentum for well-resolved galaxies at turnaround overestimates the true turnaround and final values by a factor of ∼3, with a scatter of ∼70 per cent, and only marginally yields the correct direction of the angular momentum vector. We recover the prediction that final angular momentum scales as mass to the 5/3 power. We find that mass and angular momentum also vary proportionally with peak height. In view of the fact that the observed galaxy collapse is a stochastic hierarchical and non-linear process, it is encouraging that the linear theory can serve as an effective predictive and analytic tool.
Quantum Information Processing with Trapped Neutral Atoms

Quantum information can be processed using large ensembles of ultracold and trapped neutral atoms, building naturally on the techniques developed for high-precision spectroscopy and metrology. This article reviews some of the most important protocols for universal quantum logic with trapped neutrals, as well as the history and state-of-the-art of experimental work to implement these in the laboratory. Some general observations are made concerning the different strategies for qubit encoding, transport and interaction, including trade-offs between decoherence rates and the likelihood of two-qubit gate errors. These trade-offs must be addressed through further refinements of logic protocols and trapping technologies before one can undertake the design of a general-purpose neutral-atom quantum processor.
Role of metal–oxo complexes in the cleavage of C–H bonds

The functionalization of C-H bonds has yet to achieve widespread use in synthetic chemistry in part because of the lack of synthetic reagents that function in the presence of other functional groups. These problems have been overcome in enzymes, which have metal-oxo active sites that efficiently and selectively cleave C-H bonds. How high-energy metal-oxo transient species can perform such difficult transformations with high fidelity is discussed in this tutorial review. Highlighted are the relationships between redox potentials and metal-oxo basicity on C-H bond activation, as seen in a series of bioinspired manganese-oxo complexes.
Rationale for a posttraumatic stress spectrum disorder

An understanding of PTSD and stress-related conditions is in its infancy. This is not surprising given the fact PTSD was not recognized as a distinct diagnostic entity until 1980. Since that time, the diagnostic classification has undergone continuous change as our understanding of PTSD is refined. The authors believe that PTSD can be best understood through a dimensional conceptualization viewed along at least three spectra: (1) symptom severity, (2) the nature of the stressor, and (3) responses to trauma. Along the severity spectrum, studies that review diagnostic thresholds reveal significant prevalence of PTSD symptoms and impairment that results from subthreshold conditions. Comorbidity patterns suggest that when PTSD is associated with other psychiatric illness, diagnosis is more difficult and the overall severity of PTSD is considerably greater. With regard to a stressor criteria spectrum, the diagnostic nomenclature initially only recognized severe forms of trauma personally experienced. More recently, however, the person's subjective response and events occurring to loved ones were included. This has greatly broadened the stressor criteria by leading to an appreciation of the range of precipitating stressors and the potential impact of "low-magnitude" events. Given that responses to trauma vary considerably, another possible spectrum includes trauma-related conditions. Traumatic grief, somatization, acute stress disorder and dissociation, personality disorders, depressive disorders, and other anxiety disorders all have significant associations with PTSD. Further research is needed to clarify and expand the current understanding of PTSD and other trauma-related conditions. Consideration of the severity of symptoms and the range of stressors coupled with the various disorders precipitated by trauma should greatly influence scientific research. The future undoubtedly will bring a refinement of the current understanding of PTSD and improved treatments.
Evidence for braggoriton excitations in opal photonic crystals infiltrated with highly polarizable dyes

We studied angle-dependent reflectivity spectra of opal photonic crystals infiltrated with cyanine dye aggregates, which are highly polarizable media with very large Rabi frequency. We show that, at resonance condition between the exciton-polariton of the dye aggregate and the Bragg gap, the Bragg stop band decomposes into two reflectivity bands with a semitransparent spectral range in between, that is due to propagation of braggoritons inside the gap.
Efficient distributed SAT and SAT-based distributed Bounded Model Checking

SAT-based Bounded Model Checking (BMC), though a robust and scalable verification approach, still is computationally intensive, requiring large memory and time. Even with the recent development of improved SAT solvers, the memory limitation of a single server rather than time can become a bottleneck for doing deeper BMC search for large designs. Distributing computing requirements of BMC over a network of workstations can overcome the memory limitation of a single server, albeit at increased communication cost. In this paper, we present (a) a method for distributed SAT over a network of workstations using a Master/Client model where each Client workstation has an exclusive partition of the SAT problem and uses knowledge of partition topology to communicate with other Clients, (b) a method for distributing SAT-based BMC using the distributed SAT. For the sake of scalability, at no point in the BMC computation does a single workstation have all the information. We experimented on a network of heterogeneous workstations interconnected with a standard Ethernet LAN. To illustrate, on an industrial design with ∼13 K FFs and ∼0.5 million gates, the non-distributed BMC on a single workstation (with 4 GB memory) ran out of memory after reaching a depth of 120; on the other hand, our SAT-based distributed BMC over 5 similar workstations was able to go up to 323 steps with a communication overhead of only 30%.
Ranking and tradeoffs in sponsored search auctions

In a sponsored search auction, decisions about how to rank ads impose tradeoffs between objectives, such as revenue and welfare. In this article, we examine how these tradeoffs should be made. We begin by arguing that the most natural solution concept to evaluate these tradeoffs is the lowest symmetric Nash equilibrium (SNE). As part of this argument, we generalise the well-known connection between the lowest SNE and the VCG outcome. We then propose a new ranking algorithm, loosely based on the revenue-optimal auction, that uses a reserve price to order the ads (not just to filter them) and give conditions under which it raises more revenue than simply applying that reserve price. Finally, we conduct extensive simulations examining the tradeoffs enabled by different ranking algorithms and show that our proposed algorithm enables superior operating points by a variety of metrics.
The Canopy Graph and Level Statistics for Random Operators on Trees

For operators with homogeneous disorder, it is generally expected that there is a relation between the spectral characteristics of a random operator in the infinite setup and the distribution of the energy gaps in its finite volume versions, in corresponding energy ranges. Whereas pure point spectrum of the infinite operator goes along with Poisson level statistics, it is expected that purely absolutely continuous spectrum would be associated with gap distributions resembling the corresponding random matrix ensemble. We prove that on regular rooted trees, which exhibit both spectral types, the eigenstate point process has always Poissonian limit. However, we also find that this does not contradict the picture described above if that is carefully interpreted, as the relevant limit of finite trees is not the infinite homogenous tree graph but rather a single-ended ‘canopy graph.’ For this tree graph, the random Schrodinger operator is proven here to have only pure-point spectrum at any strength of the disorder. For more general single-ended trees it is shown that the spectrum is always singular – pure point possibly with singular continuous component which is proven to occur in some cases.
Probabilistically safe control of noisy Dubins vehicles

We address the problem of controlling a stochastic version of a Dubins vehicle such that the probability of satisfying a temporal logic specification over a set of properties at the regions in a partitioned environment is maximized. We assume that the vehicle can determine its precise initial position in a known map of the environment. However, inspired by practical limitations, we assume that the vehicle is equipped with noisy actuators and, during its motion in the environment, it can only measure its angular velocity using a limited accuracy gyroscope. Through quantization and discretization, we construct a finite approximation for the motion of the vehicle in the form of a Markov Decision Process (MDP). We allow for task specifications given as temporal logic statements over the environmental properties, and use tools in Probabilistic Computation Tree Logic (PCTL) to generate an MDP control policy that maximizes the probability of satisfaction. We translate this policy to a vehicle feedback control strategy and show that the probability that the vehicle satisfies the specification in the original environment is bounded from below by the maximum probability of satisfying the specification on the MDP.
Advanced Control to Reduce the Likelihood of Cobbles in the Tandem Rolling of Hot Metal Strip

The performance of our state-dependent Riccati equation-based controller in the face of various extended uncertainties and disturbances was shown in our previous work to be highly successful. In our previous investigation, we have taken the material of the workpiece to be of one phase (austenite) and of medium and low carbon equivalents. However, it is recognized that a disturbance such as a greater decrease in temperature while processing a material of extra-low carbon equivalent could result in a change in the phase of the workpiece. Such a change in phase can result in a wreck (a cobble) in the mill, with resulting downtime and the possibility of equipment damage. In this paper, we expand our previous work to examine the effects of changes in the temperature of a workpiece of extra-low carbon equivalent and show that any resulting changes in the phase of the workpiece are effectively handled by our controller to reduce the likelihood of cobbles in the mill.
Increasing Statistical Power in Mediation Models Without Increasing Sample Size

Inadequate statistical power to detect treatment effects in health research is a problem that is compounded when testing for mediation. In general, the preferred strategy for increasing power is to increase the sample size, but there are many situations where additional participants cannot be recruited, necessitating the use of other methods to increase statistical power. Many of these other strategies, commonly applied to analysis of variance and multiple regression models, can be applied to mediation models with similar results. Additional predictors or blocking variables will increase or decrease statistical power, however, depending on whether these variables are related to the mediator, the outcome, or both. The effect of these two methods on the power for tests of mediation is illustrated through the use of simulations. Implications for health researchers using these methods are discussed.
A statistical framework for efficient monitoring of end-to-end network properties

Network service providers and customers are often concerned with aggregate performance measures that span multiple network paths. Unfortunately, forming such network-wide measures can be difficult, due to the issues of scale involved. As a result, it is of interest to explore the feasibility of methods that dramatically reduce the number of paths measured in such situations while maintaining acceptable accuracy.In previous work [4] we have proposed a statistical framework for efficiently addressing this problem. The key to our method lies in the observation and exploitation of the fact that network paths show significant redundancy (sharing of common links).We now make three contributions in [3]: (1) we generalize the framework to make it more immediately applicable to network measurements encountered in practice; (2) we demonstrate that the observed path redundancy upon which our method is based is robust to variation in key network conditions and characteristics, including the presence of link failures; and (3) we show how the framework may be applied to address three practical problems of interest to network providers and customers, using data from an operating network.
Characterizing the Delaunay decompositions of compact hyperbolic surfaces

Given a Delaunay decomposition of a compact hyperbolic surface, one may record the topological data of the decomposition, together with the intersection angles between the \empty disks" circumscribing the regions of the decompo- sition. The main result of this paper is a characterization of when a given topological decomposition and angle assignment can be realized as the data of an actual Delaunay decomposition of a hyperbolic surface.
The equation of motion of an electron

The claim by Rohrlich that the Abraham–Lorentz–Dirac equation is not the correct equation for a classical point charge is shown to be incorrect and it is pointed out that the equation which he proposes is the equation derived by Ford and O’Connell for a charge with structure. The quantum-mechanical case is also discussed.  2003 Elsevier B.V. All rights reserved.
Dispersion cancellation with phase-sensitive Gaussian-state light

Franson's paradigm for nonlocal dispersion cancellation [J. D. Franson, Phys. Rev. A 45, 3126 (1992)] is studied using two kinds of jointly Gaussian-state signal and reference beams with phase-sensitive cross correlations. The first joint signal-reference state is nonclassical, with a phase-sensitive cross correlation that is at the ultimate quantum-mechanical limit. It models the outputs obtained from continuous-wave spontaneous parametric down-conversion. The second joint signal-reference state is classical--it has a proper P representation--with a phase-sensitive cross correlation that is at the limit set by classical physics. Using these states we show that a version of Franson's nonlocal dispersion cancellation configuration has essentially identical quantum and classical explanations except for the contrast obtained, which is much higher in the quantum case than it is in the classical case. This work bears on Franson's recent article [J. D. Franson, Phys. Rev. A 80, 032119 (2009)], which asserts that there is no classical explanation for all the features seen in quantum nonlocal dispersion cancellation.
Optimization in Online Content Recommendation Services: Beyond Click-Through-Rates

A new class of online services allows Internet media sites to direct users from articles they are currently reading to other content they may be interested in. This process creates a “browsing path” along which there is potential for repeated interaction between the user and the provider, giving rise to a dynamic optimization problem. A key metric that often underlies this recommendation process is the click-through rate (CTR) of candidate articles. Whereas CTR is a measure of instantaneous click likelihood, we analyze the performance improvement that one may achieve by some lookahead that accounts for the potential future path of users. To that end, by using some data of user path history at major media sites, we introduce and derive a representation of content along two key dimensions: clickability, the likelihood to click to an article when it is recommended; and engageability, the likelihood to click from an article when it hosts a recommendation. We then propose a class of heuristics that leverage bo...
Cancer treatment using an optically inert Rose Bengal derivative combined with pulsed focused ultrasound

Abstract Pulsed high intensity focused ultrasound (HIFU) has been combined with a photo-insensitive Rose Bengal derivative (RB2) to provide a synergistic cytotoxicity requiring the presence of both ultrasonic cavitation and drug. In vitro tests have shown that a short treatment (less than 30 s) of pulsed HIFU with peak negative pressure > 7 MPa (~ 27 W acoustic power at 1.4 MHz) destroys > 95% of breast cancer cells MDA-MB-231 in suspension with > 10 μM of the compound. Neither the pulsed HIFU nor the RB2 compound was found to have any significant impact on the viability of the cells when used alone. Introducing an antioxidant (N-acetylcysteine) reduced the effectiveness of the treatment. In vivo tests using these same cells growing as a xenograft in nu/nu mice were also done. An ultrasound contrast agent (Optison) and lower frequency (1.0 MHz) was used to help initiate cavitation at the tumor site. We were able to demonstrate tumor regression with cavitation alone, however, addition of RB2 compound injected i.v. yielded a substantial synergistic improvement.
An authentication scheme based on the twisted conjugacy problem

The conjugacy search problem in a group G is the problem of recovering an x ∈ G from given g ∈ G and h = x-1gx. The alleged computational hardness of this problem in some groups was used in several recently suggested public key exchange protocols, including the one due to Anshel, Anshel, and Goldfeld, and the one due to Ko, Lee et al. Sibert, Dehornoy, and Girault used this problem in their authentication scheme, which was inspired by the Fiat-Shamir scheme involving repeating several times a three-pass challenge-response step. In this paper, we offer an authentication scheme whose security is based on the apparent hardness of the twisted conjugacy search problem which is: given a pair of endomorphisms (i.e., homomorphisms into itself) θ, ψ of a group G and a pair of elements ω, t ∈ G, find an element s ∈ G such that t = ψ(s-1)ωθ(s) provided at least one such s exists. This problem appears to be very non-trivial even for free groups. We offer here another platform, namely, the semigroup of all 2 × 2 matrices over truncated one-variable polynomials over F2, the field of two elements, with transposition used instead of inversion in the equality above.
Semiconductor Nanowires for Subwavelength Photonics Integration

This article focuses on one-dimensional (1D) semiconductor subwavelength optical elements and assesses their potential use as active and passive components in photonic devices. An updated overview of their optical properties, including spontaneous emission, ultrafast carrier dynamics, cavity resonance feedback (lasing), photodetection, and waveguiding, is provided. The ability to physically manipulate these structures on surfaces to form simple networks and assemblies is the first step toward integrating chemically synthesized nanomaterials into photonic circuitry. These high index semiconductor nanowires are capable of efficiently guiding light through liquid media, suggesting a role for such materials in microfluidics-based biosensing applications.
Design and Evaluation of a 42-V Automotive Alternator With Integrated Switched-Mode Rectifier

This paper presents techniques for the design of high-power Lundell alternators with integrated switched-mode rectifiers. A multisection stator winding and interleaved rectifier arrangement is introduced that enables high power levels to be achieved using small semiconductor devices, and which greatly reduces the output filter capacitor requirements. We also demonstrate control methods suited for this interleaved system. In addition to accurate closed-loop output voltage control, we introduce methods to provide (partial) synchronous rectification for reduced loss, and to provide tight load-dump transient control. The proposed technology is validated in the design and experimental evaluation of a 42-V, 3.4-kW alternator with fully integrated power electronics and controls. The prototype alternator achieves approximately a factor of 2.1 increase in power and 1.6 increase in power density as compared to a conventional diode-rectified alternator.
Controllability of complex networks

The ultimate proof of our understanding of natural or technological systems is reflected in our ability to control them. Although control theory offers mathematical tools for steering engineered and natural systems towards a desired state, a framework to control complex self-organized systems is lacking. Here we develop analytical tools to study the controllability of an arbitrary complex directed network, identifying the set of driver nodes with time-dependent control that can guide the system's entire dynamics. We apply these tools to several real networks, finding that the number of driver nodes is determined mainly by the network's degree distribution. We show that sparse inhomogeneous networks, which emerge in many real complex systems, are the most difficult to control, but that dense and homogeneous networks can be controlled using a few driver nodes. Counterintuitively, we find that in both model and real systems the driver nodes tend to avoid the high-degree nodes.
Fast beam stacking using RF barriers

Two barrier RF systems were fabricated, tested and installed in the Fermilab Main Injector. Each can provide 8 kV rectangular pulses (the RF barriers) at 90 kHz. When a stationary barrier is combined with a moving barrier, injected beams from the Booster can be continuously deflected, folded and stacked in the Main Injector, which leads to doubling of the beam intensity. This paper gives a report on the beam experiment using this novel technology.
On optimal message assignments for interference channels with CoMP transmission

The degrees of freedom (DoF) number of the fully connected K-user Gaussian interference channel is known to be K over 2 (see [3]). In [4], the DoF for the same channel model was studied while allowing each message to be available at its own transmitter as well as M − 1 successive transmitters. In particular, it was shown that the DoF gain through cooperation does not scale with the number of users K for a fixed value of M, i.e., the per user DoF number is 1 over 2. In this work, we relax the cooperation constraint such that each message can be assigned to M transmitters without imposing further constraints on their location. Under the new constraint, we study properties for different message assignments in terms of the gain in the per user DoF number over that achieved without cooperation. In particular, we show that a local cooperation constraint that confines the transmit set of each message within a o(K) radius cannot achieve a per user DoF number that is greater than 1 over 2. Moreover, we show that the same conclusion about the per user DoF number holds for any assignment of messages such that each message cannot be available at more than two transmitters. Finally, for the case where M > 2, we do not know whether a per user DoF number that is greater than 1 over 2 is achievable. However, we identify a candidate class of message assignments that could potentially lead to a positive answer.
Are Chinese Growth and Inflation Too Smooth? Evidence from Engel Curves

China has experienced remarkably stable growth and ination in recent years according to ocial statistics. We construct alternative estimates using detailed information on Chinese household purchasing patterns. As households become richer, a smaller fraction of total expenditures are spent on necessities such as grain and a larger fraction on luxuries such as eating out. We use systematic discrepancies between cross-sectional and time-series Engel curves to construct alternative estimates of Chinese growth and ination. Our estimates suggest that ocial statistics present a smoothed version of reality. Ocial ination rose in the 2000’s, but our estimates indicate that true ination was still higher and consumption growth was overstated over this period. In contrast, ination was overstated and growth understated during the lowination 1990’s. Similar patterns emerge from the data whether we base our estimates on major categories such as food or clothing as a fraction of total expenditures or subcategories such as grain as a fraction of food expenditures or garments as a fraction of clothing expenditures.
Estimating Tax Agency Efficiency

Empirical work on a tax agency's production process has been plagued by the absence of comparable tax administrative data across countries and years. Such data are now available from the Organisation of Economic Co-operation and Development. This paper uses these data for the years 2007 to 2011, together with an estimation strategy that utilizes data envelopment analysis and stochastic frontier analysis, to determine the relative efficiency of tax agencies in their use of inputs. Overall, the average efficiency scores indicate that countries should be able to collect their current level of revenues with approximately 10 to 16 percent less inputs.
How Does Retiree Health Insurance Influence Public Sector Employee Saving

Abstract Economic theory predicts that employer-provided retiree health insurance (RHI) benefits have a crowd-out effect on household wealth accumulation, not dissimilar to the effects reported elsewhere for employer pensions, Social Security, and Medicare. Nevertheless, we are unaware of any similar research on the impacts of retiree health insurance per se. Accordingly, the present paper utilizes a unique data file on respondents to the Health and Retirement Study, to explore how employer-provided retiree health insurance may influence net household wealth among public sector employees, where retiree healthcare benefits are still quite prevalent. Key findings include the following: - Most full-time public sector employees anticipate having employer-provided health insurance coverage in retirement, unlike most private sector workers. - Public sector employees covered by RHI had substantially less wealth than similar private sector employees without RHI. In our data, Federal workers had about $82,000 (18%) less net wealth than private sector employees lacking RHI; state/local workers with RHI accumulated about $69,000 (or 15%) less net wealth than their uninsured private sector counterparts. - After controlling on socioeconomic status and differences in pension coverage, net household wealth for Federal employees was $116,000 less than workers without RHI and the result is statistically significant; the state/local difference was not.
The NASA Astrophysics Data System: Data holdings

Since its inception in 1993, the ADS Abstract Service has become an indispensable research tool for as- tronomers and astrophysicists worldwide. In those seven years, much eort has been directed toward improving both the quantity and the quality of references in the database. From the original database of approximately 160 000 astronomy abstracts, our dataset has grown al- most tenfold to approximately 1.5 million references cov- ering astronomy, astrophysics, planetary sciences, physics, optics, and engineering. We collect and standardize data from approximately 200 journals and present the resulting information in a uniform, coherent manner. With the co- operation of journal publishers worldwide, we have been able to place scans of full journal articles on-line back to the rst volumes of many astronomical journals, and we are able to link to current version of articles, abstracts, and datasets for essentially all of the current astronomy liter- ature. The trend toward electronic publishing in the eld, the use of electronic submission of abstracts for journal articles and conference proceedings, and the increasingly prominent use of the World Wide Web to disseminate in- formation have enabled the ADS to build a database un- paralleled in other disciplines. The ADS can be accessed at: http://adswww.harvard.edu
Cost-sensitive classification: empirical evaluation of a hybrid genetic decision tree induction algorithm

This paper introduces ICET, a new algorithm for cost-sensitive classification. ICET uses a genetic algorithm to evolve a population of biases for a decision tree induction algorithm. The fitness function of the genetic algorithm is the average cost of classification when using the decision tree, including both the costs of tests (features, measurements) and the costs of classification errors. ICET is compared here with three other algorithms for cost-sensitive classification -- EG2, CS-ID3, and IDX -- and also with C4.5, which classifies without regard to cost. The five algorithms are evaluated empirically on five real-world medical datasets. Three sets of experiments are performed. The first set examines the baseline performance of the five algorithms on the five datasets and establishes that ICET performs significantly better than its competitors. The second set tests the robustness of ICET under a variety of conditions and shows that ICET maintains its advantage. The third set looks at ICET's search in bias space and discovers a way to improve the search.
Cooperative agent systems: artificial agents play the ultimatum game

We explore computational approaches for artificial agents to play the ultimatum game. We compare our agents' behavior with that predicted by classical game theory, as well as behavior found in experimental (or behavioral) economics investigations. In particular, we study the following questions: How do artificial agents perform in playing the ultimatum game against fixed rules, dynamic rules, and rotating rules? How do coevolving artificial agents perform? Will learning software agents do better? What is the value of intelligence? What will happen when smart learning agents play against dumb (no-learning) agents? What will be the impact of agent memory size on performance? We provide some initial experimental results pertaining to these questions.
Optimal Control of Two-Stage Discrete Event Systems with Real-Time Constraints

We consider discrete event systems (DES) involving tasks with real-time constraints and seek to control processing times so as to minimize a cost function subject to each task meeting its own constraint. When tasks are processed over a single stage, it has been shown that there are structural properties of the optimal sample path that lead to very efficient solutions of such problems. When tasks are processed over multiple stages and are subject to end-to-end real-time constraints, these properties no longer hold and no obvious extensions are known. We consider a two-stage problem with homogeneous cost functions over all tasks at each stage and derive several new optimality properties. These properties lead to the idea of introducing "virtual" deadlines at the first stage, thus partially decoupling the stages so that the known efficient solutions for single-stage problems can be used. We prove that the solution obtained by an iterative virtual deadline algorithm (VDA) converges to the global optimal solution of the two-stage problem and illustrate the efficiency of the VDA through numerical examples.
Supersymmetry and gravity in noncommutative field theories

Abstract We discuss the renormalization properties of noncommutative supersymmetric theories. We also discuss how the gauge field plays a role similar to gravity in noncommutative theories.