cssi/SciSciGPT-SciSciNet huggingface dataset:
Exploring matrix isolated carbenes and bis‐carbenes with electronic spectroscopy as a guide

Singlet carbenes exhibit very informative electronic spectra, which vary as a sensitive function of substituents and geometries. In particular, the lowest energy σ–p type excitations for singlet carbenes range broadly from the short wavelength UV to the near IR. Substituent effects on the energy of this key electronic transition can be rationalized by very simple orbital mixing arguments, and parallel similar influences on singlet–triplet energies. Besides providing valuable electronic information on singlet carbenes and bis-carbenes which have been studied by low temperature matrix isolation methods, UV/Vis spectroscopy has often guided investigations of conformation-dependent photochemistry of these species. Insights learned from experimental and calculated UV/visible spectra of a broad range of matrix isolated singlet carbenes and bis-carbenes are described. Copyright © 2010 John Wiley & Sons, Ltd.
Performance of Markovian access protocols in satellite channels

The theory developed by J.-T. Lim and S.M. Meerkov (see ibid., vol.COM-35, p.1278-88, Dec. 1987) is extended to channels with long propagation delays. The performance characteristics of Markovian access control protocols in satellite channels are evaluated. It is shown that the channel propagation delay may lead to improvements in systems behavior, i.e. to elimination of the saturation effects and to stabilization of the network in a steady state with relatively high performance characteristics. >
Entry and competition effects in first-price auctions: theory and evidence from procurement auctions

Motivated by several interesting features of the highway mowing auction data from the Texas Department of Transportation (TDoT), we study three competing procurement auction models with endogenous entry. Our entry and bidding models provide several interesting implications. For the first time, we show that even within an independent private value paradigm, as the number of potential bidders increases, bidders' equilibrium bidding behaviour can become less aggressive, and the expected procurement cost may rise because the "entry effect" is always positive and may dominate the negative "competition effect". We then develop structural models of entry and bidding corresponding to the three models under consideration, controlling for unobserved auction heterogeneity, and use the recently developed semi-parametric Bayesian estimation method to analyse the data. We select the model that best fits the data, and use the corresponding structural estimates to quantify the "entry effect" and the "competition effect" with regard to the individual bids and the procurement cost. Copyright 2009, Wiley-Blackwell.
What Kids Get from Parents: Packages of Parental Involvement across Complex Family Forms.

Abstract While demographers continue to document the notable changes in family structure that have occurred in recent decades, little is known about the quality of parental investment that children receive across a range of contemporary family types. Employing data from a recent US urban birth cohort, we examine parental investment for children ages 1, 3, and 5 in two key domains: parent-child engagement (across three potential parent figures) and access to economic resources. Overall, we find that children living with their married biological parents are advantaged in both parental engagement and household income, while children living in other family types are less advantaged in one or both domains. Our research illuminates how changing family demography is related to parental investments in children, which has implications for public policies designed to support low-income families.
Organizations and economics

Judge Posner (2010) identifies organizational economics with the principal-agent problem and offers no definition of the crucial term organization, which leads him to force the principal-agent template on social formations that are not organizations and to neglect aspects of their operation that might be illuminated by alternative conceptions of organizational economics. This response offers an explicit characterization of organizations as central planning agencies, considers Posner's examples in light of the problems of purpose, information, and control faced by all central planners, and draws upon an emerging capabilities theory of organizations to extend the scope of Posner's analysis and suggest insights beyond those that flow from the principal-agent approach. Judge Posner (2010) treats organizational economics as a synonym for the principal-agent problem, as if the only issue arising in the design and evaluation of organizations was aligning the incentives of subordinates with the interests of their superiors. His perceptive discussion of a variety of private and public institutions through the lens of principal and agent illustrates not just the analytical power of this approach, but its limitations as well. Posner never defines thetermorganizationexplicitly,whichleadshimtoseeorganizationswherethere are none, and in forcing the principal-agent template on social formations that are not organizations, he neglects other important aspects of their operation and the insights that might be gained from alternative conceptions of organizational economics. More than 70 years ago, Ronald Coase and Friedrich Hayek, each in his own way, illuminated the contrasts between two kinds of social order, distinguished by the role in each of human purpose. Spontaneous orders, as Hayek called them, are created by the voluntary interaction of individuals in pursuit of their own purposes, constrained by rules of general application. Their hallmark is the sharp separation of individual purpose from systemic outcomes, epitomized by the process of efficient allocation that results, unintended by any buyer or seller, from their interaction in markets governed by the rule that every reallocation must be undertaken consensually. Especially when they are broadly beneficial to their participants, the intricate patterns of behavior and social institutions that emerge from these structured interactions often create the illusion of design,
Axioms for probability and belief-function propagation

In this paper, we describe an abstract framework and axioms under which exact local computation of marginals is possible. The primitive objects of the framework are variables and valuations. The primitive operators of the framework are combination and marginalization. These operate on valuations. We state three axioms for these operators and we derive the possibility of local computation from the axioms. Next, we describe a propagation scheme for computing marginals of a valuation when we have a factorization of the valuation on a hypertree. Finally we show how the problem of computing marginals of joint probability distributions and joint belief functions fits the general framework.
Drift compression and final focus options for heavy ion fusion

Abstract A drift compression and final focus lattice for heavy ion beams should focus the entire beam pulse onto the same focal spot on the target. We show that this requirement implies that the drift compression design needs to satisfy a self-similar symmetry condition. For un-neutralized beams, the Lie symmetry group analysis is applied to the warm-fluid model to systematically derive the self-similar drift compression solutions. For neutralized beams, the 1D Vlasov equation is solved explicitly and families of self-similar drift compression solutions are constructed. To compensate for the deviation from the self-similar symmetry condition due to the transverse emittance, four time-dependent magnets are introduced in the upstream of the drift compression such that the entire beam pulse can be focused onto the same focal spot.
Catalytic Enantioselective Thioester Aldol Reactions That Are Compatible with Protic Functional Groups

This communication reports highly enantioselective and diastereoselective methyl malonic acid half thioester (MeMAHT) aldol reactions that are compatible with protic functional groups and enolizable aldehydes, affording syn S-phenyl thiopropionates.
Firm responses to social movement pressures: A competitive dynamics perspective

Why do firms respond to social movement pressures differently? This study investigates how the strategic motivation of firms, as captured by competitor activity and market dependence, influences the likelihood of their response to social movement demands. We examine this through a longitudinal analysis of wind power adoption by electric utilities in U.S. deregulated markets. We find that when either competitor actions aligned with movement demands or firm dependence on targeted markets increase, the positive effect of movement activism on firm response diminishes. In contrast, as strategic motivation declines, increases in movement activism become more influential at eliciting firm responses.
A globally applicable model of daily solar irradiance estimated from air temperature and precipitation data

Although not measured at many ground stations, the total daily solar irradiance (Rs) received at the earth’s surface is a critical component of ecosystem carbon, water and energy processes. Methods of estimating Rs from other meteorological data, particularly daily temperatures, have not worked as well in tropical and maritime areas. At Luquillo, Puerto Rico, the daily atmospheric transmittance for solar radiation was approximately equal to one minus the daily-average relative humidity (1 −rhave). From these observations, we developed a model (VP-RAD) for estimation of Rs with inputs of daily maximum and minimum air temperature, daily total precipitation, mean annual temperature, mean annual temperature range, site latitude, and site elevation. VP-RAD performed well over large areas; it showed a good agreement with the site data used for model development and for seven other warm, humid locations in the southeastern United States. Comparisons with a similar model revealed that predictions using VP-RAD had lower average errors and improved day-to-day correlation to measured solar irradiance. In a global comparison for the year 1987, VP-RAD-estimated and satellite-derived photosynthetically active radiation converged to within 1.0 MJ m −2 day − 1 at 72% of the 13072 1° latitude by 1° longitude vegetated grid cells. Although these comparisons revealed areas where VP-RAD may need improvement, VP-RAD should be a useful tool for applications globally. In addition, VP-RAD’s similarity in form to the Bristow–Campbell equation provides a convenient method to calculate the site-specific coefficients for this model that is widely used when solar irradiance data are not available. © 2001 Elsevier Science B.V. All rights reserved.
Why minimum wage increases are a poor way to help the working poor

Minimum wage increases are not a very effective mechanism for reducing poverty. They are not related to decreases in poverty rates. They can cost some low-income workers their jobs. And most minimum wage earners who gain from a higher minimum wage do not live in poor (or near-poor) families. A better tool for reducing poverty, and at lower cost, is the earned income tax credit. It is a much more targeted way to provide income to workers in poor families. It raises the wages of only workers in low-income families and rises with the number of dependent children in a family.
MATHEMATICAL ANALYSIS OF A MULTIPLE-LOOK CONCEPT IDENTIFICATION MODEL

The behaviour of focus samples, central to the multiple-look model of Trabasso & Bower (1968), is examined by three methods. First, exact probabilities of success conditional upon a certain brief history of stimulation are determined. Second, possible states of the organism during the experiment are defined and a transition matrix for those states determined, permitting prediction over all possible numbers of trials. Third, Fisher's (1971) generalizations and corrections of the Trabasso & Bower focus sample theory are examined. A general solution for the conditional probability of success is derived from Fisher's equation for the probability of n successes between any two errors. One very strong implication of the theory is given in Section 5.
1,5-Polyols: Challenging motifs for configurational assignment and synthesis

Despite the well-established methods for stereochemical assignments and synthe- sis of 1,3-diols, the corresponding 1,5-diols and -polyols present specific challenges which remain unsolved. This article highlights some new strategies and methodologies specifically designed for the 1,5-diol motif.
Understanding preservation theorems, II

We present an exposition of much of Sections VI.3 and XVIII.3 from Shelah's book Proper and Improper Forcing. This covers numerous preservation theorems for countable support iterations of proper forcing, including preservation of the property “no new random reals over V ”, the property “reals of the ground model form a non-meager set”, the property “every dense open set contains a dense open set of the ground model”, and preservation theorems related to the weak bounding property, the weak ωω -bounding property, and the property “the set of reals of the ground model has positive outer measure” (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
The Surprise Examination or Unexpected Hanging Paradox

(1998). The Surprise Examination or Unexpected Hanging Paradox. The American Mathematical Monthly: Vol. 105, No. 1, pp. 41-51.
Financial contracting under extreme uncertainty:: an analysis of Brazilian corporate debentures

Abstract Economic volatility, high transaction costs, and fragile institutions hinder financial contracting in emerging markets. These conditions characterize the economy of Brazil, yet a nascent corporate bond market thrives. I analyze 50 Brazilian indenture agreements and find that sample debentures are characterized by (i) features that mitigate inflation risk for investors, (ii) contingent-maturity mechanisms that provide periodic opportunities for exit or renegotiation, (iii) a paucity of covenants that restrict the debtor's investment, financing, and dividend decisions, and (iv) self-enforcement mechanisms that avoid reliance on inefficient institutions. Analysis of these features enhances our understanding of contracting in emerging economies.
Intersection Alexander polynomials

By considering a (not necessarily locally-flat) PL knot as the singular locus of a PL stratified pseudomanifold, we can use intersection homology theory to define intersection Alexander polynomials, a generalization of the classical Alexander polynomial invariants for smooth or PL locally-flat knots. We show that the intersection Alexander polynomials satisfy certain duality and normalization conditions analogous to those of ordinary Alexander polynomials, and we explore the relationships between the intersection Alexander polynomials and certain generalizations of the classical Alexander polynomials that are defined for non-locally-flat knots. We also investigate the relations between the intersection Alexander polynomials of a knot and the intersection and classical Alexander polynomials of the link knots around the singular strata. To facilitate some of these investigations, we introduce spectral sequences for the computation of the intersection homology of certain stratified bundles.
Disposable PVDF ultrasonic transducers for nondestructive testing applications

Disposable ultrasonic contact transducers have been constructed with inexpensive PVDF films for nondestructive testing (NDT) applications. This paper reports the temperature-dependent ultrasonic performance of commercial polyvinylidene fluoride (PVDF) films and PVDF sensors. PVDF film was evaluated for its material properties of interest for ultrasonic transducer performance including the relative dielectric constant /spl epsi//sub r/, dielectric loss tangent tan /spl delta//sub e/, electromechanical coupling constant k/sub t/, mechanical quality factor Q/sub m/, and acoustic impedance Z. Disposable PVDF transducers were then coupled to both low and high acoustic impedance test panels and their ultrasonic insertion loss/sensitivity and frequency bandwidth measured as a function of temperature in both the pulse-echo and pitch-catch modes. The results yielded center frequencies in the 3.5-16 MHz range, with -6-dB fractional bandwidths for some of the transducers exceeding 100%. The temperature dependence of the transducers' performance is reported for the -40 to 80/spl deg/C range and shows an approximate linear decrease in center frequency and increase in fractional bandwidth with increasing temperature. These measured results are compared with predictions from computer simulations based on Mason's model. These tests showed that the same disposable transducers can be used for both ultrasonic and acoustic emission sensing NDT applications. This paper summarizes the quantitative ultrasonic and vibration sensing performance for all of the disposable PVDF film transducers which were tested.
Application of the 2-azaallyl anion cycloaddition method to syntheses of (±)-crinine and (±)-6-epicrinine

Transmetalation of the (2-azaallyl)stannane 9 with n-BuLi produced the 2-azaallyl anion 12 which underwent an intramolecular cycloaddition with an alkene to give the perhydroindole 10 in 80% yield as a single stereoisomer. Transformation of 10 to 6-epicrinine 2 and crinine 1 was readily accomplished.
Impact of biochar field aging on laboratory greenhouse gas production potentials.

Recent observations of decreased greenhouse gas (GHG) production from biochar amended soils have been used to further substantiate the environmental benefit of biochar production and soil incorporation strategies. However, the mechanisms behind this biochar-mediated response have not been fully elucidated. In addition, the duration of these GHG reductions is not known and is of pivotal importance for the inclusion of biochar into future bioenergy production and climate abatement strategies. In this study, the impacts of biochar field aging on the observed GHG production/consumption were evaluated. Two different wood-derived biochars and a macadamia nut shell biochar were weathered in an agricultural field in Rosemount, MN (2008–2011) and the impacts on net soil GHG production/consumption were assessed through laboratory incubations. For the three biochars evaluated here, weathering negated the suppression of N2O production that was originally observed from the fresh biochar in laboratory incubations. On the other hand, all three weathered biochars enhanced CO2 production (three- to tenfold compared with the fresh biochar amendments) in laboratory soil incubations, suggesting an enhanced microbial mineralization rate of the weathered biochar. This enhanced mineralization could be aided by the chemical oxidation of the biochar surfaces during weathering. Fresh biochar reduced observed soil methane oxidation rates, whereas the weathered biochars had no significant impacts on the observed soil methanotrophic activity. This study demonstrates that for these three biochars, weathering greatly alters the GHG response of the soil systems to biochar amendments.
Nox2 and p47phox Modulate Compensatory Growth of Primary Collateral Arteries

The role of NADPH oxidase (Nox) in both the promotion and impairment of compensatory collateral growth remains controversial because the specific Nox and reactive oxygen species involved are unclear. The aim of this study was to identify the primary Nox and reactive oxygen species associated with early stage compensatory collateral growth in young, healthy animals. Ligation of the feed arteries that form primary collateral pathways in rat mesentery and mouse hindlimb was used to assess the role of Nox during collateral growth. Changes in mesenteric collateral artery Nox mRNA expression determined by real-time PCR at 1, 3, and 7 days relative to same-animal control arteries suggested a role for Nox subunits Nox2 and p47phox. Administration of apocynin or Nox2ds-tat suppressed collateral growth in both rat and mouse models, suggesting the Nox2/p47phox interaction was involved. Functional significance of p47phox expression was assessed by evaluation of collateral growth in rats administered p47phox small interfering RNA and in p47phox−/− mice. Diameter measurements of collateral mesenteric and gracilis arteries at 7 and 14 days, respectively, indicated no significant collateral growth compared with control rats or C57BL/6 mice. Chronic polyethylene glycol-conjugated catalase administration significantly suppressed collateral development in rats and mice, implying a requirement for H2O2. Taken together, these results suggest that Nox2, modulated at least in part by p47phox, mediates early stage compensatory collateral development via a process dependent upon peroxide generation. These results have important implications for the use of antioxidants and the development of therapies for peripheral arterial disease.
Wireless Compressive Sensing Over Fading Channels With Distributed Sparse Random Projections

We address the problem of recovering a sparse signal observed by a resource constrained wireless sensor network with fading channels. Sparse random matrices are exploited to reduce the communication cost in forwarding information to a fusion center. The presence of channel fading leads to inhomogeneity and non-Gaussian statistics in the effective measurement matrix that relates the measurements collected at the fusion center and the sparse signal being observed. We analyze the impact of channel fading on recovery of a given sparse signal by leveraging the properties of heavy-tailed random matrices. We quantify the additional number of measurements required to ensure reliable signal recovery in the presence of nonidentical fading channels compared to that is required with identical Gaussian channels. Our analysis provides insights into how to control the probability of sensor transmissions at each node based on the channel fading statistics to minimize the number of measurements collected at the fusion center for reliable sparse signal recovery. We further discuss recovery guarantees of a given sparse signal with any random projection matrix where the elements are subexponential with a given subexponential norm. Numerical results are provided to corroborate the theoretical findings.
Equivalence classes of block Jacobi matrices

The paper contains two results on the equivalence classes of block Jacobi matrices: first, that the Jacobi matrix of type 2 in the Nevai class has A_n coefficients converging to 1, and second, that under an L^1-type condition on the Jacobi coefficients, equivalent Jacobi matrices of types 1, 2 and 3 are pairwise asymptotic.
Digital Signatures Today

To a lawyer, two issues stand out as critical impediments to the widespread acceptance of digital signatures in electronic commerce: the unresolved nature of liability issues and the looming uncertainty about the nature of the public key infrastructure. These issues are so closely related as to be almost intertwined.
A nonparametric empirical Bayes framework for large-scale multiple testing

S UMMARY We propose a flexible and identifiable version of the 2-groups model, motivated by hierarchical Bayes considerations, that features an empirical null and a semiparametric mixture model for the nonnull cases. We use a computationally efficient predictive recursion (PR) marginal likelihood procedure to estimate the model parameters, even the nonparametric mixing distribution. This leads to a nonparametric empirical Bayes testing procedure, which we call PRtest, based on thresholding the estimated local false discovery rates. Simulations and real data examples demonstrate that, compared to existing approaches, PRtest’s careful handling of the nonnull density can give a much better fit in the tails of the mixture distribution which, in turn, can lead to more realistic conclusions.
Testing the limits of quantum mechanics: motivation, state of play, prospects

I present the motivation for experiments which attempt to generate, and verify the existence of, quantum superpositions of two or more states which are by some reasonable criterion `macroscopically' distinct, and show that various a priori objections to this programme made in the literature are flawed. I review the extent to which such experiments currently exist in the areas of free-space molecular diffraction, magnetic biomolecules, quantum optics and Josephson devices, and sketch possible future lines of development of the programme.
Thermal sensation and comfort in transient non-uniform thermal environments

Most existing thermal comfort models are applicable only to steady-state, uniform thermal environments. This paper presents summary results from 109 human tests that were performed under non-uniform and transient conditions. In these tests, local body areas were independently heated or cooled while the rest of the body was exposed to a warm, neutral or cool environment. Skin temperatures, core temperature, thermal sensation and comfort responses were collected at 1- to 3-min intervals. Based on these tests, we have developed predictive models of local and overall thermal sensation and comfort.
Law in the Development of Dynastic Families Among American Business Elites: The Domestication of Capital and the Capitalization of Family

American dynastic business families as descent groups constitute a category of social organization with which anthropologists have been traditionally familiar, but in the unlikely setting of a complex, bureaucratized society. This paper examines aspects of such groups and argues that law has been a critical organizational resource in their development. Law does not merely impinge at times on family concerns, but becomes an integral dimension of extended family relations in the arrangements for perpetuating collective wealth as business capital, and in distributing individual entitlements to that wealth among descendants. A general model of family/ business formations is presented, supported by a comparative discussion of two dynastic families of Galveston, Texas.
Severance payments in equilibrium unemployment

Abstract Under the insider wage model of Mortensen and Pissarides [Mortensen, D.T., Pissarides, C.A., 1994. Job creation and job destruction in the theory of unemployment. Review of Economic Studies 61, 397–415], this paper shows that (1) severance pay negatively affects market tightness (vacancy to unemployment ratio) and (2) the amount of severance pay is limited thereby insuring the employer a rational bargaining outcome.
Quadrupole ion trap studies of fundamental organic reactions

Over the past several decades, quadrupole ion traps have become important instruments in the study of gas phase ion/molecule reactions. As a part of this work, they have been employed in a number of studies focused on fundamental organic reaction mechanisms. In this review, the general features and limitations of quadrupole ion traps are discussed followed by a description of representative ion trap studies of organic reaction mechanisms such as substitution, elimination, and acyl transfer reactions.
Unsupervised methods for determining object and relation synonyms on the web

The task of identifying synonymous relations and objects, or synonym resolution, is critical for high-quality information extraction. This paper investigates synonym resolution in the context of unsupervised information extraction, where neither hand-tagged training examples nor domain knowledge is available. The paper presents a scalable, fully-implemented system that runs in O(KN log N) time in the number of extractions, N, and the maximum number of synonyms per word, K. The system, called RESOLVER, introduces a probabilistic relational model for predicting whether two strings are co-referential based on the similarity of the assertions containing them. On a set of two million assertions extracted from the Web, RESOLVER resolves objects with 78% precision and 68% recall, and resolves relations with 90% precision and 35% recall. Several variations of RESOLVER's probabilistic model are explored, and experiments demonstrate that under appropriate conditions these variations can improve F1 by 5%. An extension to the basic RESOLVER system allows it to handle polysemous names with 97% precision and 95% recall on a data set from the TREC corpus.
Introduction to first-principles electronic structure methods: Application to actinide materials

This paper provides an introduction for non-experts to first-principles electronic structure methods that are widely used in condensed-matter physics. Particular emphasis is placed on giving the appropriate background information needed to better appreciate the use of these methods to study actinide and other materials. Specifically, the underlying theory is described in sufficient detail to enable an understanding of the relative strengths and weaknesses of the methods. In addition, the meaning of commonly used terminology is explained, including density functional theory (DFT), local density approximation (LDA), and generalized gradient approximation (GGA), as well as linear muffin-tin orbital (LMTO), linear augmented plane wave (LAPW), and pseudopotential methods. Methodologies that extend the basic theory to address specific limitations are also briefly discussed. Finally, a few illustrative applications are presented, including quantum molecular dynamics (QMD) simulations and studies of surfaces, impurities, and defects. The paper concludes by addressing the current controversy regarding magnetic calculations for actinide materials.
MULTI-ZONE MODELING OF THE PULSAR WIND NEBULA HESS J1825−137

The pulsar wind nebula associated with PSR J1826−1334, HESS J1825−137, is a bright very high energy source with an angular extent of ∼ 1 ◦ and spatially-resolved spectroscopic TeV measurements. The gammaray spectral index is observed to soften with increasing dis tance from the pulsar, likely the result of cooling losses as electrons traverse the nebula. We describe analys is of X-ray data of the extended nebula, as well as 3-D time-dependent spectral energy distribution modeling, with emphasis on the spatial variations within HESS J1825−137. The multi-wavelength data places significant constrai nts on electron injection, transport, and cooling within the nebula. The large size and high nebular energy budget imply a relatively rapid initial pulsar spin period of 13 ± 7 ms and an age of 40 ± 9 kyr. The relative fluxes of each VHE zone can be explained by advective particle transport with a radially d ecreasing velocity profile with v(r) ∝ r −0.5 . The evolution of the cooling break requires an evolving magnetic field which also decreases radially from the pulsar, B(r,t) ∝ r −0.7 u E(t) 1/2 . Detection of 10 TeV flux ∼ 80 pc from the pulsar requires rapid diffusion of high energy particles with τesc ≈ 90(R/10pc) 2 (Ee/100TeV) −1 year, contrary to the common assumption of toroidal magnetic fields with strong magnetic confinement . The model predicts a rather uniform Fermi LAT surface brightness out to ∼ 1 ◦ from the pulsar, in good agreement with the recently discovered LAT source centered 0.5 ◦ southwest of PSR J1826−1334 with extension 0.6 ± 0.1 ◦ . Subject headings:pulsars: individual (PSR J1826−1334) ‐ X-rays: general
On the optimal number of advertising slots in a generalized second-price auction

In search advertising, a search engine uses a generalized second-price auction to sell advertising slots adjacent to search results on its webpage. In this paper, we study an interesting question related to the design of the generalized second-price auction: how should a search engine strategically decide on the number of advertising slots? To answer this question, we analyze the implication of varying the number of slots in a base model in which the click-through rates are assumed to be independent of the number of slots. When deciding the number of slots, we find that a search engine’s profit is based on two counteracting factors: the incremental clicks from an extra slot and the influence of the extra slot on advertisers’ payments per click. Our analysis characterizes the conditions for optimality of the number of slots and the implications of different distributions for advertiser valuations. We also extend the base model to allow for attraction and cannibalization of clicks from existing slots by new ad slots and show how such effects affect the optimal number of slots. Our overall results show that search engines need to optimize the number of ad slots offered for auction in order to maximize profit.
On the Fundamental Limits of Adaptive Sensing

Suppose we can sequentially acquire arbitrary linear measurements of an n -dimensional vector x resulting in the linear model y = A x + z, where z represents measurement noise. If the signal is known to be sparse, one would expect the following folk theorem to be true: choosing an adaptive strategy which cleverly selects the next row of A based on what has been previously observed should do far better than a nonadaptive strategy which sets the rows of A ahead of time, thus not trying to learn anything about the signal in between observations. This paper shows that the folk theorem is false. We prove that the advantages offered by clever adaptive strategies and sophisticated estimation procedures-no matter how intractable-over classical compressed acquisition/recovery schemes are, in general, minimal.
A more direct representation for complex relativity

An alternative to the representation of complex relativity by self-dual complex 2-forms on the spacetime manifold is presented by assuming that the bundle of real 2-forms is given an almost-complex structure. From this, one can define a complex orthogonal structure on the bundle of 2-forms, which results in a more direct representation of the complex orthogonal group in three complex dimensions. The geometrical foundations of general relativity are then presented in terms of the bundle of oriented complex orthogonal 3-frames on the bundle of 2-forms in a manner that essentially parallels their construction in terms of self-dual complex 2-forms. It is shown that one can still discuss the Debever-Penrose classification of the Riemannian curvature tensor in terms of the representation presented here.
Estimation of Sq variation by means of multiresolution and principal component analyses

Abstract A wavelet based method of deconvoluting the solar quiet variation from the low and mid-latitude H-component records is proposed. The resulting daily variation is non-constant, and its day-to-day variability is quantified by functional principal component scores. The procedure removes the signature of an enhanced ring current by comparing the scores at different stations. The method is fully algorithmic and is implemented in the statistical software R .
Rapid identification of linear and nonlinear systems.

Rapid parameter identification system for linear time-invariant plant with only input and output measurable
Electronic Markets, Search Costs, and Firm Boundaries

We study how interorganizational systems (IOS) such as electronic markets and other enabling information technologies that facilitate broader interfirm transactions affect the extent of outsourcing in firms. We do so by modeling firms in a three-tier value chain consisting of buyers, intermediaries, and suppliers, who can interact using IOS that lower the procurement search costs associated with finding appropriate trading partners. In the context of complex business-to-business (B2B) search, we study how decreasing search costs affect a firm's decision to insource or outsource the procurement function, depending on whether the search process is information intensive or communication intensive. Variation in search costs changes the transaction costs of interaction between firms, as well as the contracting costs associated with outsourcing, owing to changes in the costs of moral hazard for delegated search. We study these effects in a new model that integrates search theory into the principal-agent framework, and establish that the optimal outsourcing contract has a simple “all or nothing” performance-based structure under fairly general assumptions. Our model predicts that when B2B search is information intensive, IOS will facilitate an increase in outsourcing, market-based transactions, and a reduction in the vertical scope of extended enterprises. In contrast, when B2B search is primarily communication intensive, IOS will lead to tighter integration and an increase in the vertical scope of the extended enterprise. Our research suggests that the nature of the information technologies and of the business activities supported by IOS are crucial determinants of the organizational and industry changes they induce, and our results have important implications for a variety of industries in which both technological and agency issues will influence the eventual success of global IT-facilitated extended enterprise initiatives.
ON METAPHOR: Reciprocity and Immunity

My reading of David Napier’s article foregrounds or highlights (1) a key scientific “discovery” or observation; (2) the history of shifting high level metaphors as key new biological mechanisms are apprehended; (3) three key contemporary problems in immunological biology identified by Napier (transplantation, tumor immunology, autoimmune diseases); and (4) the ways in which popular culture takes up new scientific terminologies as folk “philosophemes” or cultural components for apprehending sociocultural change. In this sequencing, I remain in the anthropological tradition recognized by Polish bacteriologist, virologist, and immunologist Ludwik Fleck (1962) in his 1935 nowcanonical text on changing explanations for syphilis, and how the Wasserman test became the stabilizing diagnostic. Fleck positioned himself between the Durkheimians and the logical positivists (pragmatists). He argued “no epistemology without history,” and that every good diagnostician understood that the warfare metaphor for illness (self–nonself in Napier’s terms) was not how biology works and cannot explain why some infected people fall ill and others do not. Emily Martin (2004) made a similar argument, shifting attention also the circuits of how understandings and metaphors circulate among general clinicians, specialists, the media, and patients. Among the problems of communication is not just the failure to unpack metaphors, but allowing metaphors to function as premature closure of explanation.
Universal codes for the Gaussian MAC via spatial coupling

We consider transmission of two independent and separately encoded sources over a two-user binary-input Gaussian multiple-access channel. The channel gains are assumed to be unknown at the transmitter and the goal is to design an encoder-decoder pair that achieves reliable communication for all channel gains where this is theoretically possible. We call such a system universal with respect to the channel gains. Kudekar et al. recently showed that terminated low-density parity-check convolutional codes (a.k.a. spatially-coupled low-density parity-check ensembles) have belief-propagation thresholds that approach their maximum a-posteriori thresholds. This was proven for binary erasure channels and shown empirically for binary memoryless symmetric channels. It was conjectured that the principle of spatial coupling is very general and the phenomenon of threshold saturation applies to a very broad class of graphical models. In this work, we derive an area theorem for the joint decoder and empirically show that threshold saturation occurs for this problem. As a result, we demonstrate near-universal performance for this problem using the proposed spatially-coupled coding system.
A nonlinear stability analysis of the freezing of a dilute binary alloy

An investigation is made of the stability of the shape of a moving planar interface between the liquid and solid phases in the freezing of a dilute binary alloy. A nonlinear model is used to describe an experimental situation in which solidification is controlled so that the mean position of the interface moves with constant speed. The model postulates two-dimensional diffusion of solute and heat such that: 1. Convection in the liquid is negligible. 2. Diffusion of the solute in the solid is negligible. 3. Solute concentration in the liquid is small. 4. The effects of interface attachment kinetics are negligible. 5. The extent of the liquid and solid phases is infinite. 6. c8=c1 where c8(c1) is the specific heat per unit volume of the solid (liquid). 7. (D/Dth) 1, , where D is the diffusion coefficient of the solute in the liquid and Dth is the thermal diffusivity in the liquid. 8. G= G where G is the imposed temperature gradient in the liquid and Gcis the critical value of G at which linear theory predicts the onset of instability. The analysis is expected to be asymptotically valid as G-Gc. It is found that the interface can be unstable to finite amplitude disturbances even when linear stability theory predicts stability to infinitesimal disturbances. Further, cellular structure can be anticipated for certain ranges of parameter values. These results are in accord with relevant experimental evidence.
View synthesis by trinocular edge matching and transfer

Abstract This paper presents a novel automatic method for view synthesis (or image transfer) from a triplet of uncalibrated images based on trinocular edge matching followed by transfer by interpolation, occlusion detection and correction and finally rendering. The edge-based technique proposed here is of general practical relevance because it does not rely upon dense correspondences and is computationally efficient. Applications range from immersive media and teleconferencing, image interpolation for fast rendering and compression.
Vector Autoregressions, Policy Analysis, and Directed Acyclic Graphs: An Application to the U.S. Economy

The paper considers the use of directed acyclic graphs (DAGs), and their construction from observational data with PC-algorithm TETRAD II, in providing over-identifying restrictions on the innovations from a vector autoregression. Results from Sims’ 1986 model of the US economy are replicated and compared using these data-driven techniques. The directed graph results show Sims’ six-variable VAR is not rich enough to provide an unambiguous ordering at usual levels of statistical significance. A significance level in the neighborhood of 30 % is required to find a clear structural ordering. Although the DAG results are in agreement with Sims’ theory-based model for unemployment, dif ferences are noted for the other five variables: income, money supply, price level, interest rates, and investment. Overall the DAG results are broadly consistent with a monetarist view with adaptive expectations and no hyperinflation.
From non-local gap solitary waves to bound states in periodic media

Solitary waves in one-dimensional periodic media are discussed by employing the nonlinear Schrodinger equation with a spatially periodic potential as a model. This equation admits two families of gap solitons that bifurcate from the edges of Bloch bands in the linear wave spectrum. These fundamental solitons may be positioned only at specific locations relative to the potential; otherwise, they become non-local owing to the presence of growing tails of exponentially small amplitude with respect to the wave peak amplitude. Here, by matching the tails of such non-local solitary waves, high-order locally confined gap solitons, or bound states, are constructed. Details are worked out for bound states comprising two non-local solitary waves in the presence of a sinusoidal potential. A countable set of bound-state families, characterized by the separation distance of the two solitary waves, is found, and each family features three distinct solution branches that bifurcate near Bloch-band edges at small, but finite, amplitude. Power curves associated with these solution branches are computed asymptotically for large solitary-wave separation, and the theoretical predictions are consistent with numerical results.
Exact Solution of the Six-Vertex Model with Domain Wall Boundary Conditions. Disordered Phase

The six-vertex model, or the square ice model, with domain wall boundary conditions (DWBC) has been introduced and solved for finite N by Korepin and Izergin. The solution is based on the Yang–Baxter equations and it represents the free energy in terms of an N × N Hankel determinant. Paul Zinn–Justin observed that the Izergin– Korepin formula can be re-expressed in terms of the partition function of a random matrix model with a nonpolynomial interaction. We use this observation to obtain the large N asymptotics of the six-vertex model with DWBC in the disordered phase. The solution is based on the Riemann–Hilbert approach and the Deift–Zhou nonlinear steepest descent method. As was noticed by Kuperberg, the problem of enumeration of alternating sign matrices (the ASM problem) is a special case of the six-vertex model. We compare the obtained exact solution of the six-vertex model with known exact results for the 1, 2, and 3 enumerations of ASMs, and also with the exact solution on the so-called free fermion line. We prove the conjecture of Zinn–Justin that the partition function of the six-vertex model with DWBC has the asymptotics, $$Z_N\sim CN^\kappa e^{N^{2}f}$$ as N → ∞, and we find the exact value of the exponent κ.
Age-related differences in spatiotemporal markers of gait stability during dual task walking

Abstract Increased stride-to-stride variability during walking characterizes gait instability and predicts falling in older adults. Walking while performing cognitive tasks (dual task walking) is also associated with increased risk of falling. The purpose of the study was to examine whether gait velocity and stride-to-stride variability in gait velocity differ in older adults compared with middle-aged and younger adults during normal and dual task walking conditions. Sixty older ( n =20, mean age=81 years), middle-aged ( n =20, mean age=48 years), and young adults ( n =20, mean age=25 years) participated in the study. Gait parameters were quantified with GAITRite ® instrumentation. In the dual task condition, participants spelled five-letter words in reverse while walking across the walkway. Across groups, gait velocity was slower ( p p =0.001) in dual task walking. Older subjects walked more slowly than did middle-aged and younger subjects and the difference in gait velocity was greatest in the dual task condition ( p p
The Neurocognitive Effects of Sleep Disruption in Children and Adolescents

Sleep problems in children and adolescents are common, and sleep disruption is associated with a wide range of behavioral, cognitive, and mood impairments, including hyperactivity, reduced school grades, and depression. Insufficient or fragmented sleep may induce sleepiness, which is associated with problematic behavior, impaired learning, and/or negative mood. Furthermore, treatment of sleep disruption, by improving sleep hygiene or treating specific sleep disorders, is often associated with improvements in daytime performance, suggesting a common mechanism for the behavioral manifestations. This article reviews the daytime manifestations of sleep disruption.