cssi/SciSciGPT-SciSciNet huggingface dataset:
Learning mixtures of discrete product distributions using spectral decompositions

We study the problem of learning a distribution from samples, when the underlying distribution is a mixture of product distributions over discrete domains. This problem is motivated by several practical applications such as crowd-sourcing, recommendation systems, and learning Boolean functions. The existing solutions either heavily rely on the fact that the number of components in the mixtures is finite or have sample/time complexity that is exponential in the number of components. In this paper, we introduce a polynomial time/sample complexity method for learning a mixture of r discrete product distributions over {1,2,...,l} n , for general l and r. We show that our approach is statistically consistent and further provide finite sample guarantees. We use techniques from the recent work on tensor decompositions for higher-order moment matching. A crucial step in these moment matching methods is to construct a certain matrix and a certain tensor with low-rank spectral decompositions. These tensors are typically estimated directly from the samples. The main challenge in learning mixtures of discrete product distributions is that these low-rank tensors cannot be obtained directly from the sample moments. Instead, we reduce the tensor estimation problem to: a) estimating a low-rank matrix using only off-diagonal block elements; and b) estimating a tensor using a small number of linear measurements. Leveraging on recent developments in matrix completion, we give an alternating minimization based method to estimate the low-rank matrix, and formulate the tensor completion problem as a least-squares problem.
CaO-As2O5-H2O System at 23°± 1°C

The phase diagram for the ternary system CaO-As2O5-H2O at 23°± 1°C is plotted. The calcium arsenates represented are Ca(H2AsO4)2, CaHAsO4·H2O, Ca5H2(AsO4)4·9H2O, Ca3(AsO4)2·xH2O (x= 3⅔ and 4¼), Ca5(AsO4)3OH (apatite), and Ca4(OH)2(AsO4)2·4H2O. The solubility data indicate the following invariant points: Ca(H2AsO4)2–CaHAsO4·H2O–solution, CaHAsO4·H2O–Ca5H2(AsO4)4·9H2O–solution, Ca5H2(AsO4)4·9H2O–Ca3(AsO4)2·4¼H2O–solution, Ca3(AsO4)2·3⅔H2O–Ca4(OH)2(AsO4)2·4H2O–solution, and Ca4(OH)2(AsO4)2·4H2O–Ca(OH)2–solution. The tricalcium arsenate Ca3(AsO4)2·3⅔H2O is shown to be the only hydrate to dissolve congruently.
Five planets and an independent confirmation of HD 196885ab from lick observatory

We present time series Doppler data from Lick Observatory that reveal the presence of long-period planetary companions orbiting nearby stars. The typical eccentricity of these massive planets are greater than the mean eccentricity of known exoplanets. HD 30562b has Msin i = 1.29 M_(Jup), with semimajor axis of 2.3 AU and eccentricity 0.76. The host star has a spectral type F8V and is metal rich. HD 86264b has M sin i = 7.0 M_(Jup), ɑ_(rel) = 2.86 AU, an eccentricity e = 0.7 and orbits a metal-rich, F7V star. HD 87883b has M sin i = 1.78 M_(Jup), ɑ_(rel) = 3.6 AU, e = 0.53 and orbits a metal-rich K0V star. HD 89307b has M sin i = 1.78 M_(Jup), ɑ_(rel) = 3.3 AU, e = 0.24 and orbits a G0V star with slightly subsolar metallicity. HD 148427b has M sin i = 0.96 M_(Jup), ɑ_(rel) = 0.93 AU, eccentricity of 0.16 and orbits a metal rich K0 subgiant. We also present velocities for a planet orbiting the F8V metal-rich binary star, HD 196885A. The planet has M sin i = 2.58 M_(Jup), ɑ_(rel) = 2.37 AU, and orbital eccentricity of 0.48, in agreement with the independent discovery by Correia et al.
OLIGARCHIC VERSUS DEMOCRATIC SOCIETIES

This paper develops a model to analyze economic performance under different political regimes. An “oligarchic” society, where political power is in the hands of major producers, protects their property rights but also tends to erect significant entry barriers against new entrepreneurs. Democracy, where political power is more widely diffused, imposes redistributive taxes on producers, but tends to avoid entry barriers. When taxes in democracy are high and the distortions caused by entry barriers are low, an oligarchic society achieves greater efficiency. Because comparative advantage in entrepreneurship shifts away from the incumbents, the inefficiency created by entry barriers in oligarchy deteriorates over time. The typical pattern is one of rise and decline of oligarchic societies: An oligarchic society may first become richer, but later fall behind a similar democratic society. I also discuss how democracies may be better able to take advantage of new technologies, how within-elite conflict in oligarchies might cause a transition to democracy, and how the unequal distribution of income may keep inefficient oligarchic institutions in place. (JEL: P16, O10)
Group negative curvature for 3–manifolds with genuine laminations

We show that if a closed atoroidal 3{manifold M contains a genuine lamination, then it is group negatively curved in the sense of Gromov. Specically, we exploit the structure of the non-product complementary regions of the genuine lamination and then apply the rst author’s Ubiquity Theorem to show that M satises a linear isoperimetric inequality.
Location decisions and nongovernmental organization motivation : evidence from rural Bangladesh

Nongovernmental organizations (NGOs) play an increasingly important role in development assistance, but little systematic evidence is available about their objectives and choices in developing countries. The authors develop two stylized accounts of NGO motivation: one in which donor contracts determine location decisions, and another in which altruistic motivations are the principal determinants. The authors then use data from the 1995 and 2000 rounds of the Bangladesh Households and Income and Expenditure Survey to analyze location decisions of NGO programs established between those two sample years. The data show that net change in a community's NGO program was unrelated to the community's need and that NGOs were ready to establish new programs in new areas without being concerned of duplicating the efforts of other NGOs. The findings suggest that contracts with donors, implicit or explicit, probably play a crucial role in determining the incentives that affect NGO program location choices.
Can You Recognize an Effective Teacher when You Recruit One

Research on the relationship between teacher characteristics and teacher effectiveness has been underway for over a century, yet little progress has been made in linking teacher quality with factors observable at the time of hire. To extend this literature, we administered an in-depth survey to new math teachers in New York City andcollectedinformationonanumberofnontraditional predictors of effectiveness, including teaching-specific content knowledge, cognitive ability, personality traits, feelings of self-efficacy, and scores on a commercially available teacher selection instrument. We find that only a few of these predictors have statistically significant relationships with student and teacher outcomes. However, the individual variables load onto two factors, which measure what one might describe as teachers’ cognitive and noncognitive skills. We find that both factors have a moderately large and statistically significant relationship with student and teacher outcomes, particularly with student test scores.
Time Versus Market Orientation in Product Concept Development: Empirically-Based Theory Generation

In collaboration with industry partners, a normative model of the product concept decision process was developed, supported with tools and techniques, and codified as a decision support process for product development teams. This process Concept Engineering was then introduced into a number of product development teams in different companies. A comparative analysis of actual product concept development activities, with and without the use of Concept Engineering, was conducted. All of the observed teams viewed time to market as a critical measure of their success. However, the development processes differed significantly depending on whether relatively more emphasis was placed on time or market considerations. Key variables associated with the product concept development decision process and time-to-market dynamics were identified and a theory of the concept development process was developed using the inductive system diagram technique, a research methodology developed in the course of this work. We believe this work contributes to the operations management literature in three ways. First, it introduces a very detailed, structured decision process for product concept development, enhancing the literature on Quality Function Deployment QFD. Second, it presents a theory of product concept development that can improve understanding of success and failure in product concept development. Third, this work develops new methodology Inductive Systems Diagrams for field work in operations management. This methodology marries the grounded theory methods familiar to sociologists with causal-loop modeling familiar to systems dynamicists, yielding a rigorous tool for systematically collecting, organizing, and distilling large amounts of field-based data.
Tax Bases, Tax Rates and the Elasticity of Reported Income

Abstract Tax reforms usually change both tax rates and tax bases. Using a panel of income tax returns spanning the two major U.S. tax reforms of the 1980s and a number of smaller tax law changes, I find that the elasticity of income reported on personal income tax returns depends on the available deductions. This highlights that this key behavioral elasticity is not an immutable parameter but rather that it can be to some extent controlled by policy makers. One implication is that base broadening reduces the marginal efficiency cost of taxation. The results are very similar for all income categories indicating that the rich are more responsive to tax rates because tax rules that apply to them are different (their tax base is narrower). The point estimates indicate that the Tax Reform Act of 1986 reduced the marginal cost of collecting a dollar of tax revenue, with roughly half of this reduction due to the base broadening and the other half due to the tax rate reduction. As a by-product, the analysis in this paper offers a reconciliation of disparate estimates obtained by previous studies of the tax responsiveness of income.
Endovascular and microsurgical treatment of cerebral arteriovenous malformations: Current recommendations

Background: Cerebral arteriovenous malformations (AVMs) can be a heterogeneous pathological entity whose management requires a complex decision-making process due to the risks associated with their treatment and natural history. Despite the recently published conclusions of the aborted Randomized Trial of Brain Unruptured AVMs (ARUBA) trial, the authors of this article believe multimodality intervention in general and microsurgical resection in particular continue to play a major role in the management of carefully selected ruptured or unruptured AVMs. Methods: The authors provide an overview of their methodology for endovascular intervention and microsurgical resection and share their technical nuances for successful embolization and microsurgical resection of AVMs with special emphasis on complication avoidance. Results: The authors have achieved successful outcomes in embolization and resection of cerebral AVMs when using their methodology. Conclusions: These lesions are among the most technically difficult pathological entities handled by the cerebrovascular specialist, and an overview of technical concepts to help systematize this challenging and variable endeavor can improve the safety of their treatment.
Nyquist stability criterion based ssr explanation for type 3 wind generators

Summary form only given. Type-3 wind generators in series-compensated networks could lead to subsynchronous resonance (SSR) oscillations- a phenomenon observed recently. In this letter, impedance-based Nyquist stability criterion is applied to explain the phenomenon. The resonance is not due to the shaft's torsional characteristics, but rather due to its slip related impedance, which can give rise to equivalent negative resistance. The explanation corroborates the authors' previous explanation of self-excitation using net negative resistance concept. Nyquist map is also able to demonstrate the impact of wind speed on SSR.
On the areas of cyclic and semicyclic polygons

We investigate the ''generalized Heron polynomial'' that relates the squared area of an n-gon inscribed in a circle to the squares of its side lengths. For a (2m+1)-gon or (2m+2)-gon, we express it as the defining polynomial of a certain variety derived from the variety of binary (2m-1)-forms having m-1 double roots. Thus we obtain explicit formulas for the areas of cyclic heptagons and octagons, and illuminate some mysterious features of Robbins' formulas for the areas of cyclic pentagons and hexagons. We also introduce a companion family of polynomials that relate the squared area of an n-gon inscribed in a circle, one of whose sides is a diameter, to the squared lengths of the other sides. By similar algebraic techniques we obtain explicit formulas for these polynomials for all n=<7.
Workplace Wellness Programs Can Generate Savings

Amid soaring health spending, there is growing interest in workplace disease prevention and wellness programs to improve health and lower costs. In a critical meta-analysis of the literature on costs and savings associated with such programs, we found that medical costs fall by about $3.27 for every dollar spent on wellness programs and that absenteeism costs fall by about $2.73 for every dollar spent. Although further exploration of the mechanisms at work and broader applicability of the findings is needed, this return on investment suggests that the wider adoption of such programs could prove beneficial for budgets and productivity as well as health outcomes.
Asymptotically Optimal Multiple-Access Communication Via Distributed Rate Splitting

We consider the multiple-access communication problem in a distributed setting for both the additive white Gaussian noise channel and the discrete memoryless channel. We propose a scheme called Distributed Rate Splitting to achieve the optimal rates allowed by information theory in a distributed manner. In this scheme, each real user creates a number of virtual users via a power/rate splitting mechanism in the M-user Gaussian channel or via a random switching mechanism in the M-user discrete memoryless channel. At the receiver, all virtual users are successively decoded. Compared with other multiple-access techniques, Distributed Rate Splitting (DRS) can be implemented with lower complexity and less coordination. Furthermore, in a symmetric setting, we show that the rate tuple achieved by this scheme converges to the maximum equal rate point allowed by the information-theoretic bound as the number of virtual users per real user tends to infinity. When the capacity regions are asymmetric, we show that a point on the dominant face can be achieved asymptotically. Finally, when there is an unequal number of virtual users per real user, we show that differential user rate requirements can be accommodated in a distributed fashion
DNS performance and the effectiveness of caching

This paper presents a detailed analysis of traces of domain name system (DNS) and associated TCP traffic collected on the Internet links of the MIT Laboratory for Computer Science and the Korea Advanced Institute of Science and Technology (KAIST). The first part of the analysis details how clients at these institutions interact with the wide-area domain name system, focusing on client-perceived performance and the prevalence of failures and errors. The second part evaluates the effectiveness of DNS caching. In the most recent MIT trace, 23% of lookups receive no answer; these lookups account for more than half of all traced DNS packets since query packets are retransmitted overly persistently. About 13% of all lookups result in an answer that indicates an error condition. Many of these errors appear to be caused by missing inverse (IP-to-name) mappings or NS records that point to nonexistent or inappropriate hosts. 27% of the queries sent to the root name servers result in such errors. The paper also presents the results of trace-driven simulations that explore the effect of varying time-to-live (TTL) and varying degrees of cache sharing on DNS cache hit rates. Due to the heavy-tailed nature of name accesses, reducing the TTL of address (A) records to as low as a few hundred seconds has little adverse effect on hit rates, and little benefit is obtained from sharing a forwarding DNS cache among more than 10 or 20 clients. These results suggest that client latency is not as dependent on aggressive caching as is commonly believed, and that the widespread use of dynamic low-TTL A-record bindings should not greatly increase DNS related wide-area network traffic.
On the marginal source of investment funds

Abstract Under the ‘new view’ of dividend taxation developed by Auerbach (Quarterly Journal of Economics 1979;93:433–446), Bradford (Journal of Public Economics 1981;15:1–22) and King ( Public Policy and the Corporation , Chapman & Hall, London, 1977), the marginal source of finance for new investment projects is retained earnings. In this case, the tax advantage of retaining earnings precisely offsets the double taxation of subsequent dividends: taxes on dividends have no impact on the investment incentives of firms using retentions as a marginal source of funds and paying dividends with residual cash flows. We show that the same invariance with respect to dividend taxes may hold under weaker conditions with respect to the source of funds, if the use of funds follows the same pattern. We find evidence that there is significant heterogeneity in our sample of US firms, with some firms exhibiting dividend behavior consistent with this expanded version of the new view, and others exhibiting behavior consistent with the traditional view that retained earnings are not an important marginal source of funds.
Classical transitions for flux vacua

We present the simplest model for classical transitions in flux vacua. A complex field with a spontaneously broken U(1) symmetry is embedded in M2 S1. We numerically construct dierent winding number vacua, the vortices interpolating between them, and simulate the collisions of these vortices. We show that classical transitions are generic at large boosts, independent of whether or not vortices miss each other in the compact S1.
Unique structural topology and reactivities of the ABD tricycle in phomactin A

Stereoselective and transannular reactivities are described for the ABD tricyclic manifold of phomactin A that possesses a unique structural topology.
Trilepton signatures of light charged and CP-odd Higgs bosons in top quark decays

In singlet extensions of the two Higgs doublet model, a light CP-odd Higgs boson (A) can significantly modify decay modes of the charged Higgs, without necessarily affecting decay modes of the standard model-like Higgs boson. These effects can be sizable even if the doublet component of the light CP-odd Higgs is small, so that constraints from Upsilon decays and direct CP-odd Higgs production do not apply. We study a scenario in which the charged Higgs is produced in top quark decays, t → H ± b, with dominant H ± → W ± A. We focus on the CP-odd Higgs mass range below the $ b\overline{b} $ threshold. We summarize all current experimental constraints and find that, as a result of H ± → W ± A dominance, this scenario is not constrained in a large region of tan β, m H ± , and CP-odd Higgs doublet component. We discuss search strategies based on A → τ + τ −, with both taus decaying leptonically, and on the subleading decay mode A → μ + μ −. We show that a search for t → H + b, H + → W + A, A → μ + μ − in 20 fb−1 of 8 TeV LHC data can constrain most of the currently allowed parameter space. Existing trilepton searches are not sensitive to this signal due to the adopted isolation criteria.
Mapping brain maturation.

Human brain maturation is a complex, lifelong process that can now be examined in detail using neuroimaging techniques. Ongoing projects scan subjects longitudinally with structural magnetic resonance imaging (MRI), enabling the time-course and anatomical sequence of development to be reconstructed. Here, we review recent progress on imaging studies of development. We focus on cortical and subcortical changes observed in healthy children, and contrast them with abnormal developmental changes in early-onset schizophrenia, fetal alcohol syndrome, attention-deficit‐hyperactivity disorder (ADHD) and Williams syndrome. We relate these structural changes to the cellular processes that underlie them, and to cognitive and behavioral changes occurring throughout childhood and adolescence.
Symplectomorphism groups and isotropic skeletons

The symplectomorphism group of a 2-dimensional surface is homotopy equiv- alent to the orbit of a filling system of curves. We give a generalization of this statement to dimension 4. The filling system of curves is replaced by a decomposition of the symplectic 4-manifold (M, ω) into a disjoint union of an isotropic 2-complex L and a disc bundle over a symplectic surfacewhich is Poincare dual to a multiple of the form ω. We show that then one can recover the homotopy type of the symplectomorphism group of M from the orbit of the pair (L,�). This allows us to compute the homotopy type of certain spaces of Lagrangian submanifolds, for example the space of Lagrangian RP 2 ⊂ CP 2
Instability in a generalized Keller–Segel model

We present a generalized Keller–Segel model where an arbitrary number of chemical compounds react, some of which are produced by a species, and one of which is a chemoattractant for the species. To investigate the stability of homogeneous stationary states of this generalized model, we consider the eigenvalues of a linearized system. We are able to reduce this infinite dimensional eigenproblem to a parametrized finite dimensional eigenproblem. By matrix theoretic tools, we then provide easily verifiable sufficient conditions for destabilizing the homogeneous stationary states. In particular, one of the sufficient conditions is that the chemotactic feedback is sufficiently strong. Although this mechanism was already known to exist in the original Keller–Segel model, here we show that it is more generally applicable by significantly enlarging the class of models exhibiting this instability phenomenon which may lead to pattern formation.
A Phosphine‐Mediated Conversion of Azides into Diazo Compounds

N2 the mild: Diazo compounds are extremely versatile intermediates for synthetic organic chemistry, but their synthesis can be challenging in the presence of delicate functional groups. The Staudinger ligation has inspired a mild method for the conversion of a broad range of azides into their diazo compound derivatives through an acyl triazene intermediate.
Noncausal nonminimum phase ARMA modeling of non-Gaussian processes

A method is presented for the estimation of the parameters of a noncausal nonminimum phase ARMA model for non-Gaussian random processes. Using certain higher order cepstra slices, the Fourier phases of two intermediate sequences (h/sub min/(n) and h/sub max/(n)) can be computed, where h/sub min/(n) is composed of the minimum phase parts of the AR and MA models, and h/sub max/(n) of the corresponding maximum phase parts. Under the condition that there are no zero-pole cancellations in the ARMA model, these two sequences can be estimated from their phases only, and lead to the reconstruction of the AR and MA parameters, within a scalar and a time shift. The AR and MA orders do not have to be estimated separately, but they are by product of the parameter estimation procedure. Through simulations it is shown that, unlike existing methods, the estimation procedure is fairly robust if a small order mismatch occurs. Since the robustness of the method in the presence of additive noise depends on the accuracy of the estimated phases of h/sub min/(n) and h/sub max/(n), the phase errors due to finite length data are studied and their statistics are derived. >
Nature of roll to spiral-defect-chaos transition

We investigate the nature of the parallel-roll to spiral-defect-chaos (SDC) transition in Rayleigh-Benard convection, based on the generalized Swift-Hohenberg model. We carry out extensive, systematic numerical studies by, on one branch, increasing the control parameter gradually from the parallel roll regime to the SDC regime and, on the other branch, decreasing it in the opposite manner. We find that the data of several time-averaged global quantities all form hysteretic loops from the two branches. We also discuss several possible scenarios for the transition and analyze our data for SDC accordingly. We conclude that the roll-to-SDC transition is first-order in character and that the correlation length diverges at the conduction to convection onset. We further postulate that this transition can be understood somewhat similar to the hexagon-to-roll transition in non-Boussinesq fluids. Finally we comment on the differences between our conclusion and those in two experiments.
Nonlinear dynamics, spillovers and growth in the G7 economies: an empirical investigation

This paper proposes an empirical growth model which is consistent with a stochastic steady-state labour productivity level varying over time and across countries, where the disequilibrium mechanism leading to long-run equilibrium follows a nonlinear equilibrium correction model. Using data for the G7 economies during the postwar period since 1950, the empirical analysis yields a long-run model which implies plausible estimates of the production function parameters. Postwar economic growth in each of the G7 countries appears to be well characterized by a nonlinear equilibrium correction model where the dynamic adjustment towards long-run equilibrium is governed by a logistic function, while also capturing spillover effects in growth dynamics.
Sensor-Actuator Placement for Flexible Structures with Actuator Dynamics

A novel approach for placement of sensors and actuators in control of flexible space structures is developed. Using an approximation of the control forces and output measurements by spatially continuous functions, the approach follows a nonlinear programming technique to determine optimal locations for sensors and actuators. Two different criteria are considered for the placement of sensors and actuators. The first criterion optimizes the location of the sensors and actuators in order to move the transmission zeros of the system farther to the left of the imaginary axis. The second criterion, however, places the sensors and actuators to optimize a function of the singular values of the Hankel matrix, which includes both measures of controllabili ty and observability. Moreover, the effect of actuator dynamics in the placement of sensors and actuators is investigated. ENSOR and actuator placement is an integral part of a control design, particularly in the control of flexible struc- tures. Although engineering judgment and trial-and-error analysis are quite often used to determine the optimal locations of sensors and actuators, there have been various attempts to develop systematic means of achieving it. Among a few of these, Chen and Seinfeld1 used an optimization- based ap- proach wherein optimal locations of measurement outputs are computed from a finite set of possible locations with the aid of integer programming. Skelton and Chiu2 have considered an order reduction approach such that the inputs and outputs are reduced from a large set so as to make the smallest possible perturbation in a performance metric. Horta and Juang3 pro- posed a sequential linear programming approach for truss structures in which optimal numbers as well as locations of actuators are obtained from a large set of actuators. A com- mon point of reference in most of these approaches is the use of a performance metric. To date, various measures of con- trollability and observability,4"5'7 controllability and spill- over,6 and energy-based metrics2 have been considered as per- formance metrics in the literature. Of recent efforts, Maghami and Joshi8 provide a method in which the discrete nature of the sensor and actuator placement problem is transformed into a continuous nonlinear programming problem with the aid of functional approximation of the control forces and output measurements. Lim9 proposes an approach for placing actua- tors and sensors that is based on projecting eigenvectors into the intersection subspace of the controllability and observabil- ity subspaces for each sensor-actuator pair. In this paper, a new approach for sensor and actuator place- ment in the control of flexible space structures is developed. The approach follows the development of Ref. 8, which re- duces the problem of sensor-actuator positioning to a solution of a nonlinear programming optimization. The discrete con- trol forces and output measurements are approximated by spatially continuous functions in order to avoid the disconti- nuity problems caused when actuators and sensors are recon-
Carbopalladation of Nitriles: Synthesis of 2,3-Diarylindenones and Polycyclic Aromatic Ketones by the Pd-Catalyzed Annulation of Alkynes and Bicyclic Alkenes by 2-Iodoarenenitriles

2-Iodobenzonitrile, its derivatives, and various heterocyclic analogues undergo palladium(0)-catalyzed annulation onto diarylacetylenes or bicyclic alkenes to afford 2,3-diarylindenones and polycyclic aromatic ketones in very good to excellent yields. This reaction represents one of the first examples of the addition of an organopalladium moiety to the carbon−nitrogen triple bond of a nitrile. The reaction is compatible with a number of functional groups. A reaction mechanism, as well as a model accounting for the electronic effects of substituents on the aromatic ring of the nitrile, is proposed.
AI knowledge bases and databases

In which the author expresses general scepticism about proposals for a trouble free marriage of AI Knowledge Bases and Databases (narrowly and tendentiously construed.) The author argues, as well, against a shotgun wedding.
A fluorinated masked o-benzoquinone

Abstract A fluorinated masked o -benzoquinone has been prepared by oxidation 4-fluoro-2-methoxyphenol in methanol with phenyliodine diacetate. The fluorinated diene reacts in situ in normal Diels–Alder reactions with various dienophiles. The sequence provides new fluorinated building blocks for the synthesis of a variety of fluorinated compounds.
P. ACNES: A HIDDEN MENACE

Infection after shoulder surgery is an infrequent but devastating complication with a reported incidence from 0 to 4%. A careful history is critical because many patients have a history of a “stitch abscess” or “superficial wound infection”. Prop. Acnes is the most common organism responsible for infection following rotator cuff surgery, instability surgery, ORIF proximal humerus fractures, and shoulder arthroplasty. This organism typically does not start to grow until Day 5, therefore it is critical to keep cultures a minimum of 10 to 14 days. The diagnosis can be challenging, principally among patients undergoing revision surgery. The majority of patients with a low grade infection do not have blatant signs of infection such as erythema or sinus tracts. Pre-operative lab values as well as intra-operative pathology have been shown to be unreliable in predicting who will have positive cultures at the time of revision surgery. There is an assortment of options for treating a patient with a post-operative infection. Important variables include the timing of infection, status of the host, the specific organism, status of implant fixation, and the status of the rotator cuff and deltoid. One of the most frequently employed options for treating the infected shoulder arthroplasty is two stage re-implantation. However, the rate of complications with this technique as well as residual infection remains high.
Zygosporamide, a cytotoxic cyclic depsipeptide from the marine-derived fungus Zygosporium masonii

Abstract Zygosporamide ( 1 ), a new cyclic pentadepsipeptide, was isolated from the seawater-based fermentation broth of a marine-derived fungus identified as Zygosporium masonii . The structure of 1 , which is composed of α-hydroxyleucic acid and both d - and l -amino acids, was determined by combined spectral and chemical methods. Despite a simple structure, zygosporamide illustrated significant cytotoxicity in the NCI’s 60 cell line panel (median GI 50 = 9.1 μM), with highly enhanced selectivity against the CNS cancer cell line SF-268 (GI 50 = 6.5 nM) and the renal cancer cell line RXF 393 (GI 50 ⩽ 5.0 nM).
Highly enantioselective catalytic asymmetric hydrogenation of β-keto esters in room temperature ionic liquids

Polar phosphonic acid-derived Ru-BINAP systems were used to catalyze asymmetric hydrogenation of β-keto esters in room temperature ionic liquids (RTILs) with complete conversions and ee values higher than those obtained from homogeneous reactions in MeOH (up to 99.3%), and were recycled by simple extraction and used for four times without the loss of activity and enantioselectivity.
Synthesis of para-alkyl aryl amide analogues of sphingosine-1-phosphate: discovery of potent S1P receptor agonists.

Abstract Sphingosine-1-phosphate (S1P) is a biologically active lysophospholipid with the capacity to induce a broad range of cellular responses via its interaction with the S1P family of G-protein coupled receptors. This report describes the synthesis of several potent S1P receptor agonists. For instance, compound 9c displayed an EC 50 =8.6 nM at the S1P 1 receptor using a [γ- 35 S]GTP binding assay as compared to an EC 50 =4.5 nM for the endogenous ligand. We also report the effects associated with introduction of a phenyl ring between the ‘linker’ and ‘lipophilic tail’ regions of the analogues, for example total loss of activity at S1P 2 and increased agonism at S1P 5 .
Cephalosporin-derived inhibitors of β-Lactamase. Part 4: The C3 substituent

New C3-substituted β-lactamase inhibitors were prepared and evaluated against representative class A and class C enzymes. It was possible to improve simultaneous inhibitory activity of both classes of serine hydrolase. Other inhibitors showed high selectivity for either the class C cephalosporinases or the class A penicillinases. This represents the first time that cephalosporin-derived inhibitors have demonstrated selectivity for the class A β-lactamases.
New two-inductor boost converter with auxiliary transformer

A new, two-inductor, two-switch boost converter topology and its variations suitable for applications with a large difference between the input and output voltage are described. The output voltage regulation of the proposed converters is achieved in a wide load and input-voltage range with constant-frequency control by employing an auxiliary transformer that couples the current paths of the two boost inductors.
System structure at infinity

On utilise l'algorithme de structure pour le calcul de la structure a l'infini d'un systeme lineaire
Intent to Use Technology: Facilitation Effect of Group Presence

Although there has been much empirical attention on studying groups and ones intention to adopt new technology, almost no research has focused on how this adoption is influenced by the collective nature of the implementation. The purpose of this study was to study an important contextual factor, whether group versus individual adoption of technology influences ones intention to adopt new technology. We utilized two different methodological approaches: ANOVA (study 1) and Conjoint (study 2) to assess, not only the importance of product usefulness but also group presence. We found that group presence facilitated intent to use a new technology. Future research and practical implications are then discussed.
A dynamic theory of electoral competition

We present a dynamic theory of electoral competition to study the determinants of fiscal policy. In each period, two parties choose electoral platforms to maximize the expected number of elected representatives. The platforms include public expenditure, redistributive transfers, the tax rate, and the level of public debt. Voters cast their vote after seeing the platforms and elect representatives according to a majoritarian winner take all system. The level of debt, by affecting the budget constraint in future periods, creates a strategic linkage between electoral cycles. We characterize the Markov equilibrium of this game when public debt is the state variable and study how Pareto efficiency depends on the electoral rule and the underlying fundamentals of the economy.
Height, Health, and Cognitive Function at Older Ages

Research across a number of disciplines has highlighted the role of early life health and circumstance in determining health and economic outcomes at older ages. Nutrition in utero and in infancy may set the stage for the chronic disease burden that an individual will face in middle age (David J. Barker, 1998; Barker et al. 1989; Johann Eriksson et al. 2001). Childhood health may also have significant effects on economic outcomes in adulthood. Collectively, a set of childhood health measures can account for a large fraction of the explained variance in employment and social status observed among a British cohort followed from birth into adulthood (Anne Case, Angela Fertig and Christina Paxson 2005).
Floer cohomology and geometric composition of Lagrangian correspondences

Abstract We prove an isomorphism of Floer cohomologies under geometric composition of Lagrangian correspondences in exact and monotone settings.
A continuous-time model of centrally coordinated motion with random switching

This paper considers differential problems with random switching, with specific applications to the motion of cells and centrally coordinated motion. Starting with a differential-equation model of cell motion that was proposed previously, we set the relaxation time to zero and consider the simpler model that results. We prove that this model is well-posed, in the sense that it corresponds to a pure jump-type continuous-time Markov process (without explosion). We then describe the model’s long-time behavior, first by specifying an attracting steady-state distribution for a projection of the model, then by examining the expected location of the cell center when the initial data is compatible with that steady-state. Under such conditions, we present a formula for the expected velocity and give a rigorous proof of that formula’s validity. We conclude the paper with a comparison between these theoretical results and the results of numerical simulations.
Complexity and directional entropy in two dimensions

We study the directional entropy of a dynamical system associated to a Z2 configuration in a finite alphabet. We show that under local assumptions on the complexity, either every direction has zero topological entropy or some direction is periodic. In particular, we show that all nonexpansive directions in a Z2 system with the same local assumptions have zero directional entropy.
A Higher-Order Abstract Syntax Approach to Verified Transformations on Functional Programs

We describe an approach to the verified implementation of transformations on functional programs that exploits the higher-order representation of syntax. In this approach, transformations are specified using the logic of hereditary Harrop formulas. On the one hand, these specifications serve directly as implementations, being programs in the language $$\lambda $$λProlog. On the other hand, they can be used as input to the Abella system which allows us to prove properties about them and thereby about the implementations. We argue that this approach is especially effective in realizing transformations that analyze binding structure. We do this by describing concise encodings in $$\lambda $$λProlog for transformations like typed closure conversion and code hoisting that are sensitive to such structure and by showing how to prove their correctness using Abella.
Lack of Selection and Limits to Delegation: Firm Dynamics in Developing Countries

Firm dynamics in poor countries show striking dierences to those of rich countries. While few rms indeed experience growth as they age, most rms are simply stagnant in that they neither exit nor expand. We interpret this fact as a lack of selection, whereby producers with little growth potential survive because innovative entrepreneurs do not expand enough to force them out of the market. To explain these dierences, we develop a theory whereby rms require managerial inputs for production and countries dier in their managerial delegation possibilities. If delegation of managerial tasks to outside managers is dicult in poor countries, entrepreneurs are forced to rely on their own time to supply managerial services. Improvements in the eciency of delegation will raise the returns to growing large, induce innovative rms to expand, and thereby force stagnant entrepreneurs out of the market. We prove the existence and uniqueness of the dynamic equilibrium and show analytically how the degree of selection depends on some of the key structural parameters. To discipline the quantitative importance of this mechanism, we calibrate our model to micro data from the US and India. Dierences in the eciency of managerial delegation can explain an important fraction of the dierences in plants’ life-cycles.
Atomistic Mechanisms and Diameter Selection during Nanorod Growth

We study in this paper the atomic mechanisms of nanorod growth and propose the mechanism of diameter selection of nanorods. A characteristic radius is demonstrated to be crucial in nanorod growth. If the critical size of the two-dimensional nucleus is assumed to be 1, the characteristic radius increases proportional to 1/5 power of the ratio of the interlayer hopping rate of adatoms across the monolayer steps to the deposition rate. When the radius of the initial island is larger than this characteristic radius, a screening effect is important for nanorod growth. The growth morphology evolves from a taper-like structure to a nanorod with a radius equal to the characteristic radius after some transient layers, depending on the screening strength. When the radius of the initial island is smaller than this characteristic radius, the nanorod morphology can be maintained during the growth, with the stable radius being limited by both the radius of the initial island and the threedimensional Ehrlich-Schwoebel barrier. Therefore, different growth modes and the diameter of nanorod can be selected by changing the characteristic radius, via controlling the growth condition. The theoretical predictions are in good agreement with experimental observations of ZnO growth.
Atelier: Repurposing Expert Crowdsourcing Tasks as Micro-internships

Expert crowdsourcing marketplaces have untapped potential to empower workers' career and skill development. Currently, many workers cannot afford to invest the time and sacrifice the earnings required to learn a new skill, and a lack of experience makes it difficult to get job offers even if they do. In this paper, we seek to lower the threshold to skill development by repurposing existing tasks on the marketplace as mentored, paid, real-world work experiences, which we refer to as micro-internships. We instantiate this idea in Atelier, a micro-internship platform that connects crowd interns with crowd mentors. Atelier guides mentor-intern pairs to break down expert crowdsourcing tasks into milestones, review intermediate output, and problem-solve together. We conducted a field experiment comparing Atelier's mentorship model to a non-mentored alternative on a real-world programming crowdsourcing task, finding that Atelier helped interns maintain forward progress and absorb best practices.
A Global Game with Strategic Substitutes and Complements: Note

In a 2007 paper, “A global game with strategic substitutes and complements”, by Karp, L., I.H. Lee, and R. Mason, Games and Economic Behavior, 60(1), 155-175, an argument is made to show existence of Bayesian-Nash equilibrim in global games that may include both strategic substitutes and complements. This note documents a gap in the proof of that statement and presents an alternative proof for a finite player version of their model.
Design of truss-like cellular structures using relative density mapping method

Abstract Truss-like cellular structures have great potential to be applied in light-weight design applications. However, determining the appropriate designs for these truss-like cellular structures can be a challenging task due to their geometric complexities and prohibitive computational costs in the design process. In this research, a new design method is proposed which can drastically reduce computational costs and design parameters, while maintaining the performance of the targeted outcome. Furthermore, the proposed method facilitates cellular structure designs that can handle multiple loading conditions. The proposed method utilizes the relative density information obtained from a solid topology optimization to automatically determine the diameter of each individual strut in the structure, which collectively represent the set of design variables. This allows the method to produce lattice structures that can perform reliably under multiple loading conditions and also reduce the computational cost associated with the design of these structures. The efficacy of the developed method is compared to existing methods including the size matching and scaling method that combines solid-body analysis and a predefined unit–cell library.
US Natural Gas Price Determination: Fundamentals and the Development of Shale

This paper uses a structural vector autoregression (SVAR) to model the US natural gas market. Domestic natural gas production has dramatically increased in the late 2000’s as producers implemented improved horizontal drilling and hydraulic fracturing techniques to extract natural gas from shale deposits. This paper applies techniques developed in the crude-oil literature that incorporate time-varying parameters (TVP), which more realistically model a changing market. Results suggest the supply curve associated with aggregate demand shocks, residential demand shocks, and other natural gas market demand shocks has become more elastic during the latter part of the sample. This latter period corresponds to the recent rapid expansion in shale gas production. By contrast, the curvature of the supply curve associated with precautionary inventory demand shocks has remained at a stable level for most of the sample since 2000, and has not changed significantly even with the rapid growth of shale gas production. Furthermore, it appears that in the new era of ample natural gas supply, the demand curve has also become more elastic, partly reflecting greater flexibility in fuel use substitution.