cssi/SciSciGPT-SciSciNet huggingface dataset:
Holonomy limits of complex projective structures

Abstract We study the limits of holonomy representations of complex projective structures on a compact Riemann surface in the Morgan–Shalen compactification of the character variety. We show that the dual R -trees of the quadratic differentials associated to a divergent sequence of projective structures determine the Morgan–Shalen limit points up to a natural folding operation. For quadratic differentials with simple zeros, no folding is possible and the limit of holonomy representations is isometric to the dual tree. We also derive an estimate for the growth rate of the holonomy map in terms of a norm on the space of quadratic differentials.
Analytical Sensitivity Analysis of an Unsteady Vortex Lattice Method for Flapping Wing Optimization

This work considers the design optimization of a flapping wing in forward flight with active shape morphing, aimed at maximizing propulsive efficiency under lift and thrust constraints. This is done with an inviscid three-dimensional unsteady vortex lattice method, whose lack of fidelity is offset by a relatively inexpensive computational cost. The design is performed with a gradient-based optimization, where gradients are computed with an analytical sensitivity analysis. Wake terms provide the only connection between the forces generated at disparate time steps, and must be included to compute the derivative of the aerodynamic state at a time step with respect to the wing shape at all previous steps. The cyclic wing morphing, superimposed upon the flapping motions, is defined by a series of spatial and temporal approximations. The generalized coordinates of a finite number of twisting and bending modes are approximated by cubic splines. The amplitudes at the control points provide design variables; increasing the number of variables (providing the wing morphing with a greater degree of spatial and temporal freedom) is seen to provide increasingly superior designs, with little increase in computational cost. I. Introduction HE design and optimization of artificial flapping wing flyers presents considerable difficulties in terms of computational cost: the complex physical phenomena associated with the flight (unsteady low Reynolds number vortical flows in conjunction with a nonlinear elastic wing surface undergoing large prescribed rotations and translations) may require a high-fidelity computational tool. Furthermore, the search optimization process typically requires many function evaluations to converge to a relevant optimum. Lower fidelity numerical tools may help alleviate the burden, either used during the search process in conjunction with a higher-fidelity model 1
Enforcing smoothness and assessing uncertainty in non‐linear one‐dimensional prestack seismic inversion

Estimation of elastic properties of rock formations from surface seismic amplitude measurements remains a subject of interest for the exploration and development of hydrocarbon reservoirs. This paper develops a global inversion technique to estimate and appraise 1D distributions of compressional-wave velocity, shear-wave velocity and bulk density, from normal-moveout-corrected PP prestack surface seismic amplitude measurements. Specific objectives are: (a) to evaluate the efficiency of the minimization algorithm (b) to appraise the impact of various data misfit functions, and (c) to assess the effect of the degree and type of smoothness criterion enforced by the inversion. Numerical experiments show that very fast simulated annealing is the most efficient minimization technique among alternative approaches considered for global inversion. It is also found that an adequate choice of data misfit function is necessary for a reliable and efficient match of noisy and sparse seismic amplitude measurements. Several procedures are considered to enforce smoothness of the estimated 1D distributions of elastic parameters, including predefined quadratic measures of length, flatness and roughness. Based on the general analysis of global inversion techniques, we introduce a new stochastic inversion algorithm that initializes the search for the minimum with constrained random distributions of elastic parameters and enforces predefined autocorrelation functions (semivariograms). This strategy readily lends itself to the assessment of model uncertainty. The new global inversion algorithm is successfully tested on noisy synthetic amplitude data. Moreover, we present a feasibility analysis of the resolution and uncertainty of prestack seismic amplitude data to infer 1D distributions of elastic parameters measured with wireline logs in the deepwater Gulf of Mexico. The new global inversion algorithm is computationally more efficient than the alternative global inversion procedures considered here.
A fixed time performance evaluation of parallel CFD applications

The inviscid gas dynamics equations have been solved on the nCUBE 2s computer to better understand the challenges and opportunities that parallel processing presents. Two basic computational fluid dynamics (CFD) application problems representing different flow physics are used as test cases: supersonic internal flow and subsonic flow over an airfoil. Analysis of the parallel performance for these applications is presented following a fixed time measurement approach. Results from this study demonstrate that even though these flow simulation problems are communication-intensive, they are scalable. Parallel computing is shown to be an effective tool for future CFD challenges. >
Modeling free radical polymerization using dissipative particle dynamics

Abstract Understanding the details of free radical polymerization (FRP) in multi-component mixtures and solutions is of great importance for the synthesis of polymeric functional materials. Using the framework of dissipative particle dynamics (DPD), we develop a new computational approach to model FRP that couples the reaction kinetics for the polymerization processes to the dynamics of the complex fluid. We specifically consider two mechanisms of chain termination: disproportionation and combination. We analyze the effects of initiation, propagation, and termination on the polymerization kinetics in three-dimensional bulk polymerization by varying the corresponding reaction probabilities. Our model not only allows us to capture the interplay between hydrodynamics and reaction kinetics, but also provides an effective means to model polymerization in the presence of solid inclusions. We demonstrate the latter feature by simulating the formation of polymer-clay nanocomposite gels by FRP in solution in the absence of organic cross-linking agents, where the exfoliated clay particles serve as multi-functional cross-linkers for the polymer network. We observe that increasing the volume fraction of clay particles can lead to an increase in the number of inter-particle cross-linking chains, which could improve the mechanical properties of the material. Our findings provide insight into the polymerization kinetics of the FRP, as well as potential guidelines for tailoring experimental conditions to achieve the desired polymerization products.
Gold and platinum catalysis of enyne cycloisomerization

This account provides a comprehensive overview of the development of gold and platinum catalysis of the enyne cycloisomerization. The use of these soft, alkynophilic metals enables mild, chemoselective and efficient transformations of a variety of readily available acyclic enynes to a wide range of synthetically useful carbocyclic and heterocyclic products. The review is organized according to diverse structural types of enynes that undergo skeletal cycloisomerizations. The account begins with an overview of transformations of primarily 1,6-enynes to 1-alkenylcyclopentenes, bicyclo[4.1.0]heptenes, methylenecycloalkenes, bicyclo[4.3.0]nonadienes and bicyclo[3.2.0]heptenes. This section is followed by the discussion of cycloisomerizations of 1,5-enynes, which enable a rapid access to a range of other cyclic products, including bicyclo[3.1.0]hexenes, cyclohexadienes, heterobicycloalkenes, methylenecyclopentenes, naphthalenes and methyleneindenes. In addition, the [3,3] rearrangement of 1,5-enynes provides efficient access to the corresponding allenes. The account concludes with an overview of the most recent studies on gold- and platinum-catalyzed cycloisomerizations of 1,4- and 1,3-enynes. Due to the rapidly increasing interest in this area during the past three to five years, we believe that this review provides a timely and comprehensive discussion of the development gold- and platinum-catalyzed cycloisomerization starting from the initial pioneering investigations to the latest advances in the field. A significant emphasis is placed on the mechanistic discussion of the observed manifolds of skeletal reorganizations.
Rapid solution casting under vacuum of very thick sheets of a segmented polyurethane elastomer

A technique has been developed for rapidly casting from solution under vacuum smooth, bubble-free, clear-white and uniformly thick (about 0.20 cm) sheets of a segmented polyurethane elastomer. The casting is carried out from dimethylformamide solutions inside temperature-controlled air-circulated ovens in order to minimize the establishment of thermal gradients throughout the casting solution. The technique produces quality sheets in 9 days, compared with 40-45 days for an inferior film produced in open pans.
PRIOR FLARING AS A COMPLEMENT TO FREE MAGNETIC ENERGY FOR FORECASTING SOLAR ERUPTIONS

From a large database of (1) 40,000 SOHO/MDI line-of-sight magnetograms covering the passage of 1300 sunspot active regions across the 30° radius central disk of the Sun, (2) a proxy of each active region's free magnetic energy measured from each of the active region's central-disk-passage magnetograms, and (3) each active region's full-disk-passage history of production of major flares and fast coronal mass ejections (CMEs), we find new statistical evidence that (1) there are aspects of an active region's magnetic field other than the free energy that are strong determinants of the active region's productivity of major flares and fast CMEs in the coming few days; (2) an active region's recent productivity of major flares, in addition to reflecting the amount of free energy in the active region, also reflects these other determinants of coming productivity of major eruptions; and (3) consequently, the knowledge of whether an active region has recently had a major flare, used in combination with the active region's free-energy proxy measured from a magnetogram, can greatly alter the forecast chance that the active region will have a major eruption in the next few days after the time of the magnetogram. The active-region magnetic conditions that, in addition to the free energy, are reflected by recent major flaring are presumably the complexity and evolution of the field.
Understanding spurious regressions in econometrics

Abstract This paper provides an analytical study of linear regressions involving the levels of economic time series. An asymptotic theory is developed for regressions that relate quite general integrated random processes. This includes the spurious regressions of Granger and Newbold (1974) and the recent cointegrating regressions of Granger and Engle (1985) . An asymptotic theory is developed for the regression coefficients and for conventional significance tests. It is shown that the usual t - and F -ratio test statistics do not possess limiting distributions in this context but actually diverge as the sample size T ↑ ∞. The limiting behavior of regression diagnostics such as the Durbin–Watson statistic, the coefficient of determination and the Box–Pierce statistic is also analyzed. The theoretical results that we present explain many of the earlier simulation findings of Granger and Newbold (1974, 1977) .
Course Bidding at Business Schools

Mechanisms that rely on course bidding are widely used at Business Schools in order to allocate seats at oversubscribed courses. Bids play two key roles under these mechanisms: Bids are used to infer student preferences and bids are used to determine who have bigger claims on course seats. We show that these two roles may easily consict and preferences induced from bids may signiÞcantly differ from the true preferences. Therefore while these mechanisms are promoted as market mechanisms, they do not necessarily yield market outcomes. The two consicting roles of bids is a potential source of efficiency loss part of which can be avoided simply by asking students to state their preferences in addition to bidding and thus “separating” the two roles of the bids. While there may be multiple market outcomes under this proposal, there is a market outcome which Pareto dominates any other market outcome.
Deposition and immersion-mode nucleation of ice by three distinct samples of volcanic ash

Abstract. Ice nucleation of volcanic ash controls both ash aggregation and cloud glaciation, which affect atmospheric transport and global climate. Previously, it has been suggested that there is one characteristic ice nucleation efficiency for all volcanic ash, regardless of its composition, when accounting for surface area; however, this claim is derived from data from only two volcanic eruptions. In this work, we have studied the depositional and immersion freezing efficiency of three distinct samples of volcanic ash using Raman microscopy coupled to an environmental cell. Ash from the Fuego (basaltic ash, Guatemala), Soufriere Hills (andesitic ash, Montserrat), and Taupo (Oruanui eruption, rhyolitic ash, New Zealand) volcanoes were chosen to represent different geographical locations and silica content. All ash samples were quantitatively analyzed for both percent crystallinity and mineralogy using X-ray diffraction. In the present study, we find that all three samples of volcanic ash are excellent depositional ice nuclei, nucleating ice from 225 to 235 K at ice saturation ratios of 1.05 ± 0.01, comparable to the mineral dust proxy kaolinite. Since depositional ice nucleation will be more important at colder temperatures, fine volcanic ash may represent a global source of cold-cloud ice nuclei. For immersion freezing relevant to mixed-phase clouds, however, only the Oruanui ash exhibited appreciable heterogeneous ice nucleation activity. Similar to recent studies on mineral dust, we suggest that the mineralogy of volcanic ash may dictate its ice nucleation activity in the immersion mode.
Managerial use of metrics for object-oriented software: an exploratory analysis

With the increasing use of object-oriented methods in new software development, there is a growing need to both document and improve current practice in object-oriented design and development. In response to this need, a number of researchers have developed various metrics for object-oriented systems as proposed aids to the management of these systems. In this research, an analysis of a set of metrics proposed by Chidamber and Kemerer (1994) is performed in order to assess their usefulness for practising managers. First, an informal introduction to the metrics is provided by way of an extended example of their managerial use. Second, exploratory analyses of empirical data relating the metrics to productivity, rework effort and design effort on three commercial object-oriented systems are provided. The empirical results suggest that the metrics provide significant explanatory power for variations in these economic variables, over and above that provided by traditional measures, such as size in lines of code, and after controlling for the effects of individual developers.
Noisy Directional Learning and the Logit Equilibrium

We specify a dynamic model in which agents adjust their decisions toward higher payoffs, subject to normal error. This process generates a probability distribution of players' decisions that evolves over time according to the Fokker-Planck equation. The dynamic process is stable for all potential games, a class of payoff structures that includes several widely studied games. In equilibrium, the distributions that determine expected payoffs correspond to the distributions that arise from the logit function applied to those expected payoffs. This "logit equilibrium" forms a stochastic generalization of the Nash equilibrium and provides a possible explanation of anomalous laboratory data.
Discovery of Bright Galactic R Coronae Borealis and DY Persei Variables: Rare Gems Mined from ACVS

We present the results of a machine-learning (ML)-based search for new R Coronae Borealis (RCB) stars and DY Persei-like stars (DYPers) in the Galaxy using cataloged light curves from the All-Sky Automated Survey (ASAS) Catalog of Variable Stars (ACVS). RCB stars—a rare class of hydrogen-deficient carbon-rich supergiants—are of great interest owing to the insights they can provide on the late stages of stellar evolution. DYPers are possibly the low-temperature, low-luminosity analogs to the RCB phenomenon, though additional examples are needed to fully establish this connection. While RCB stars and DYPers are traditionally identified by epochs of extreme dimming that occur without regularity, the ML search framework more fully captures the richness and diversity of their photometric behavior. We demonstrate that our ML method can use newly discovered RCB stars to identify additional candidates within the same data set. Our search yields 15 candidates that we consider likely RCB stars/DYPers: new spectroscopic observations confirm that four of these candidates are RCB stars and four are DYPers. Our discovery of four new DYPers increases the number of known Galactic DYPers from two to six; noteworthy is that one of the new DYPers has a measured parallax and is m ≈ 7 mag, making it the brightest known DYPer to date. Future observations of these new DYPers should prove instrumental in establishing the RCB connection. We consider these results, derived from a machine-learned probabilistic classification catalog, as an important proof-of-concept for the efficient discovery of rare sources with time-domain surveys.
Models of steroid binding based on the minimum deviation of structurally assigned 13C NMR spectra analysis (MiDSASA).

This paper develops a quantitative k-nearest neighbors modeling technique. The technique is used to demonstrate that a compound's biological binding activity to a receptor can be calculated from the minimum of the square root of the sum of squared deviations (SSSD) of a structurally assigned chemical shift on a template between the unknown compound to be predicted and a set of known compounds with known activities. When building models of biological activity, nonlinear relationships are built into the input training data. If a model is developed by selecting only compounds with minimum structurally assigned chemical shift deviations from the unknown compound, some of the nonlinear relationships can be removed. The smaller the total chemical shift deviation between a compound with known activity and another compound with unknown activity, the more likely it will have similar biological, chemical, and physical properties. This means that a model can be produced without rigorous statistics or neural networks...
Projectile transverse motion and stability in electromagnetic induction launchers

The transverse motion of a projectile in an electromagnetic induction launcher is considered. The equations of motion for translation and rotation are derived assuming a rigid projectile and a flyway restoring force per unit length that is proportional to the local displacement. Linearized transverse forces and torques due to energized coils are derived for displaced or tilted armature elements based on a first order perturbation method. The resulting equations of motion for a rigid projectile composed of multiple elements in a multi-coil launcher are analyzed as a coupled oscillator system of equations and a simple linear stability condition is derived. The equations of motion are incorporated into the 2-D Slingshot circuit code and numerical solutions for the transverse motion are obtained. >
Pd0/PR3-Catalyzed Arylation of Nicotinic and Isonicotinic Acid Derivatives

The first example of C-H functionalizations of pyridine rings at the 3- and 4-positions is developed using Pd(0)/PR3/ArBr. This reaction provides a powerful method for the preparation of structurally diverse nicotinic and isonicotinic acids that are of tremendous importance in drug discovery.
Hot Electron Transport in AlN

The energy distribution of electrons that were transported through a thin intrinsic AlN film was directly measured as a function of the applied field. The measurements were realized by extracting the electrons into vacuum through a semitransparent Au contact and measuring their energy using an electron spectrometer. At moderate applied fields (350 kV/cm), the energy distribution followed a Maxwellian model corresponding to an electron temperature of 2700 K and a drift component below the spectrometer resolution. At higher fields, intervalley scattering was evidenced by the presence of a second peak at 0.7 eV. This coincides well with the energy position of the L-M valley in AlN. To the best of our knowledge, these are the first measurements that offer direct evidence of intervalley scattering in any solid system.
Mutually unbiased bases, generalized spin matrices and separability

Abstract A collection of orthonormal bases for a complex d-dimensional Hilbert space is called mutually unbiased (MUB) if for any two vectors v and w from different bases the square of the inner product equals 1/d:|〈v,w〉| 2 = 1 d . The MUB problem is to prove or disprove the existence of a maximal set of d+1 bases. It has been shown in [Ann. Phys. 191 (1989) 363] that such a collection exists if d is a power of a prime number p. We revisit this problem and use d×d generalizations of the Pauli spin matrices to give a constructive proof of this result. Specifically we give explicit representations of commuting families of unitary matrices whose eigenvectors solve the MUB problem. Additionally we give formulas from which the orthogonal bases can be readily computed. We show how the techniques developed here provide a natural way to analyze the separability of the bases. The techniques used require properties of algebraic field extensions, and the relevant part of that theory is included in the appendix.
Cation Ordering and Electrochemical Properties of the Cathode Materials LiZnxMn2-xO4, 0 < x ≤ 0.5: A 6Li Magic-Angle Spinning NMR Spectroscopy and Diffraction Study

The local and long-range structures of LiZnxMn2-xO4 (x = 0.1, 0.2, 0.3, 0.5) have been studied by using 6Li magic-angle spinning (MAS) NMR spectroscopy and X-ray and neutron powder diffraction. For all the samples, a 6Li resonance at approximately 2000 ppm is observed due to the presence of Li in the octahedral sites of the spinel structure, indicating that Zn substitutes for lithium in the tetrahedral sites. For low doping levels (x = 0.1 and 0.2), several resonances at 500−700 ppm are seen, which are assigned to lithium cations in tetrahedral sites with local environments such as Li(OMn3.5+)12-y(OMn4+)y, Mn3.5+ indicating a Mn ion with an average oxidation state of 3.5. The x = 0.3 sample is not obtained as a single phase; instead, two phases with Zn-doping levels corresponding to x = 0.2 and 0.5 are observed. Different cation-ordering schemes are observed for the x = 0.5 sample, depending on the condition of synthesis: slow cooling from 700 °C to room temperature results in cation ordering in both tet...
Cyclic Combustion Variations in Dual Fuel Partially Premixed Pilot-Ignited Natural Gas Engines

Dual fuel pilot ignited natural gas engines are identified as an efficient and viable alternative to conventional diesel engines. This paper examines cyclic combustion fluctuations in conventional dual fuel and in dual fuel partially premixed low temperature combustion (LTC). Conventional dual fueling with 95% (energy basis) natural gas (NG) substitution reduces NOx emissions by almost 90%t relative to straight diesel operation; however, this is accompanied by 98% increase in HC emissions, 10 percentage points reduction in fuel conversion efficiency (FCE) and 12 percentage points increase in COVimep. Dual fuel LTC is achieved by injection of a small amount of diesel fuel (2-3 percent on an energy basis) to ignite a premixed natural gasAÂAÂAÂAÂ¢AÂAÂAÂAÂAÂAÂAÂAÂair mixture to attain very low NOx emissions (less than 0.2 g/kWh). Cyclic variations in both combustion modes were analyzed by observing the cyclic fluctuations in start of combustion (SOC), peak cylinder pressures (Pmax), combustion phasing (Ca50), and the separation between the diesel injection event and Ca50 (termed AÂAÂAÂAÂ¢AÂAÂAÂAÂAÂAÂAÂAÂrelative combustion phasingAÂAÂAÂAÂ¢AÂAÂAÂAÂAÂAÂAÂAÂ). For conventional dual fueling, as % NG increases, Pmax decreases, SOC and Ca50 are delayed, and cyclic variations increase. For dual fuel LTC, as diesel injection timing is advanced from 20AÂAÂAÂAÂAÂAÂAÂAÂ° to 60AÂAÂAÂAÂAÂAÂAÂAÂ°BTDC, the relative combustion phasing is identified as an important combustion parameter along with SoC, Pmax, and CaPmax. For both combustion modes, cyclic variations were characterized by alternating slow and more » fast burn cycles, especially at high %NG and advanced injection timings. Finally, heat release return maps were analyzed to demonstrate thermal management strategies as an effective tool to mitigate cyclic combustion variations, especially in dual fuel LTC. « less
Current Directions in Violence Risk Assessment

Over recent years, a variety of instruments that improve clinicians' ability to forecast the likelihood that an individual will behave violently have been published. Increasingly, these instruments are being applied in response to laws that require specialized risk assessments. In this article, we present a framework that goes beyond the “clinical” and “actuarial” dichotomy to describe a continuum of structured approaches to risk assessment. Despite differences among validated instruments, there is little evidence that one predicts violence better than another. We believe that these group-based instruments are useful for assessing an individual’s risk and that an instrument should be chosen based on an evaluation’s purpose (i.e., risk assessment vs. risk reduction). The time is ripe to shift attention from predicting violence to understanding its causes and preventing its (re)occurrence.
Are Federal Labor‐Management Partnerships Decreasing Conflict? Evidence from the Last Eight Years of Reported Data

In December 2009, President Obama signed Executive Order 13522, initiating a formal period during which the federal government has been acting under a declared labor-management partnership. Researchers and practitioners believe these partnerships can result in substantial benefits to the organization. However, this article's analysis of an original data set containing agency data on labor-management collaboration and conflict over time indicates that partnerships are not associated with changes in conflict. Instead, participation in labor-management pilot projects weakly predicts a decrease in conflict. Qualitative data from union officials suggest that this finding could be because the partnerships do not represent true labor-management collaboration.
Measuring Welfare for Small but Vulnerable Groups: Poverty and Disability in Uganda

When vulnerable population groups are numerically small -as is often the case, obtaining representative welfare estimates from non-purposive sample surveys becomes an issue. Building on a method developed by Elbers, Lanjouw and Lanjouw (2003) it is shown how, for census years, estimates of income poverty for small vulnerable populations can be derived by combining sample survey and population census information. The approach is illustrated for Uganda, for which poverty amongst households with disabled heads is determined. This is possibly the first time that, for a developing country, statistically representative information on income poverty amongst disabled people is generated.
Set-valued risk measures for conical market models

Set-valued risk measures on $${L^p_d}$$ with 0 ≤ p ≤ ∞ for conical market models are defined, primal and dual representation results are given. The collection of initial endowments which allow to super-hedge a multivariate claim are shown to form the values of a set-valued sublinear (coherent) risk measure. Scalar risk measures with multiple eligible assets also turn out to be a special case within the set-valued framework.
Partial-MDS Codes and Their Application to RAID Type of Architectures

A family of codes with a natural 2-D structure is presented, inspired by an application of redundant arrays of independent disks (RAID) type of architectures whose units are solid-state drives (SSDs). Arrays of SSDs behave differently from arrays of hard disk drives, since hard errors in sectors are common and traditional RAID approaches (like RAID 5 or RAID 6) may be either insufficient or excessive. An efficient solution to this problem is given by the new codes presented, called partial maximum distance separable (PMDS) codes.
Thermal energy storage for cooling of commercial buildings

Cool storage technology has been first applied more than a half century ago. However, widespread use of the technology has been limited because of the increased efficiency and reliability of conventional cooling systems and the decreasing cost of producing electricity. As fossil fuel resources become increasingly less available and more expensive, many energy conservation strategies become more viable. (Although nuclear power plants are available for electricity production, their future, at this time, is uncertain due to higher risks involved during nuclear reactor accidents, as demonstrated by the most recent accident in Cheronobyl, USSR, 1986.) Even though energy conservation is highly publicized and studied, peak load energy conservation is not addressed until recently [1–3]. Peak demand is important because utilities are faced to either invest in new generation capacity or purchase electricity from neighboring utilities or even from neighboring countries to accommodate expected increases in peak demand. Peak load energy is also more expensive to generate owing to the use of older and less efficient generators which use more expensive fuels (e.g., oil or gas).
Relative importance of sectoral and aggregate sources of price changes

This paper estimates a dynamic common factor model to assess relative importance of the aggregate and the sector-specific factors that determine changes in the prices of individual products. It also examines how aggregate price changes are affected by these factors. Two different specifications of the model are estimated: the baseline model with one aggregate factor, and a second specification with two aggregate factors. In the one-actor model, the aggregate factor contributes little to the movements of changes in prices, mostly of nondurable goods whereas it seems to have important contributions to the movements of changes in prices of commodity groups mainly used as intermediate or capital goods. In the specification with two aggregate factors, the additional factor has significant effects on changes in prices of ‘farm products’ and ‘processed foods and feeds’ only. Forecast-error variance decompositions of both aggregate and disaggregate price changes suggest that sectoral factors account for most of t...
Validating a web service security abstraction by typing

An XML web service is, to a first approximation, an RPC service in which requests and responses are encoded in XML as SOAP envelopes, and transported over HTTP. We consider the problem of authenticating requests and responses at the SOAP-level, rather than relying on transport-level security. We propose a security abstraction, inspired by earlier work on secure RPC, in which the methods exported by a web service are annotated with one of three security levels: none, authenticated, or both authenticated and encrypted. We model our abstraction as an object calculus with primitives for defining and calling web services. We describe the semantics of our object calculus by translating to a lower level language with primitives for message passing and cryptography. To validate our semantics, we embed correspondence assertions that specify the correct authentication of requests and responses. By appeal to the type theory for cryptographic protocols of Gordon and Jeffrey's Cryptyc, we verify the correspondence assertions simply by typing. Finally, we describe an implementation of our semantics via custom SOAP headers.
Design of Adjoint-Based Laws for Wing Flutter Control

An airplane, by its nature of being, is constructed so that it is as light as possible. The structural design is guided by static and dynamic factors. The more stringent constraints on the structural design are due to dynamic loads, caused by aero-elastic interactions. One of the most commonly encountered problems in aeroelasticity is flutter, a term that is used to recognize the transfer of energy from unsteady aerodynamics associated with the surrounding fluid to the wing structure, resulting in rapidly divergent behaviour. If flutter can be controlled at cruise speeds, we can design lighter wings and consequently more efficient airplanes. It is therefore, in the aircraft designer’s best interest to design innovative ways in which flutter can be controlled without making the resulting structure too heavy. There are three important choices to make while designing active control strategies for suppressing flutter. The first is the choice of actuator. In this paper, the actuators we use are jets in the walls through which there is a small mass flow, either by way of blowing or suction. The second is to define a clear control objective. Finally, we need to design a control law that will make suitable state measurements and drive the actuators so that the desired control objective is achieved. The concept of Active Flow Control is fast gaining popularity in Fluid Mechanics circles. Indeed, it is important to realize that adding or removing fluid at the wing surface is equivalent to effecting a shape modification. Flow control using surface jets should, in principle, have an effect very similar to that of morphing surfaces. The capability to directly alter the flow field offers a huge realm of possibilities. Seifert, Theofilis and Joslin categorize the problems that are amenable to using Active Flow Control:
Stochastic balancing and approximation-stability and minimality

A new method of stochastic model reduction has recently been introduced by Desai et al. [1], [2]. The stability of the reduced order model has not previously, been considered. In this paper, we show that the stability of the reduced order model follows directly from the results of Pernebo and Silverman [3]. It is also shown that the reduced order model is minimal, in the controllability/observability sense. The relevance of this notion of minimality to stochastic minimality is made clear.
Synthesis of Substituted Biaryls through Gold‐Catalyzed Petasis–Ferrier Rearrangement of Propargyl Ethers

Au-catalyzed cycloisomerization of aryl propargyl ethers provides controlled transition from alkyne to carbonyl chemistry followed up by a Petasis–Ferrier rearrangement/aromatization cascade leading to substituted biaryls with functionalized naphthalene cores.
Global stability of relay feedback systems

For a large class of relay feedback systems (RFS) there will be limit cycle oscillations. Conditions to check existence and local stability of limit cycles for these systems are well known. Global stability conditions, however, are practically nonexistent. The paper presents conditions in the form of linear matrix inequalities (LMIs) that, when satisfied, guarantee global asymptotic stability of limit cycles induced by relays with hysteresis in feedback with linear time-invariant (LTI) stable systems. The analysis consists in finding quadratic surface Lyapunov functions for Poincare maps associated with RFS. These results are based on the discovery that a typical Poincare map induced by an LTI flow between two hyperplanes can be represented as a linear transformation analytically parametrized by a scalar function of the state. Moreover, level sets of this function are convex subsets of linear manifolds. The search for quadratic Lyapunov functions on switching surfaces is done by solving a set of LMIs. Although this analysis methodology yields only a sufficient criterion of stability, it has proved very successful in globally analyzing a large number of examples with a unique locally stable symmetric unimodal limit cycle. In fact, it is still an open problem whether there exists an example with a globally stable symmetric unimodal limit cycle that could not be successfully analyzed with this new methodology. Examples analyzed include minimum-phase systems, systems of relative degree larger than one, and of high dimension. Such results lead us to believe that globally stable limit cycles of RFS frequently have quadratic surface Lyapunov functions.
Rigorous Estimates of the Tails of the Probability Distribution Function for the Random Linear Shear Model

In previous work Majda and McLaughlin, and Majda computed explicit expressions for the 2Nth moments of a passive scalar advected by a linear shear flow in the form of an integral over R N . In this paper we first compute the asymptotics of these moments for large moment number. We are able to use this information about the large-N behavior of the moments, along with some basic facts about entire functions of finite order, to compute the asymptotics of the tails of the probability distribution function. We find that the probability distribution has Gaussian tails when the energy is concentrated in the largest scales. As the initial energy is moved to smaller and smaller scales we find that the tails of the distribution grow longer, and the distribution moves smoothly from Gaussian through exponential and “stretched exponential.” We also show that the derivatives of the scalar are increasingly intermittent, in agreement with experimental observations, and relate the exponents of the scalar derivative to the exponents of the scalar.
Trafficking and fragility in West Africa

Trafficking is an emerging concern in West Africa that is gaining increasing attention from the international community. This paper examines the relationship between trafficking and fragility in the region through a meta-analysis of existing knowledge and data on the subject. Given the scope of this paper, we will not attempt to provide any primary empirical or qualitative analysis, but instead focus on offering a comprehensive, unbiased overview of the recent policy and academic literature on the subject, which we hope will assist development practitioners working in the region and help the World Bank identify possible programmatic responses. The authors start this paper by defining trafficking to frame our analysis, and then provide an overview of the trafficking economy across the region. Next, authors outline the potential channels between trafficking and fragility, discussing the actors involved (organized criminal groups, rebels, local or national level politicians, the military, and civilians) and their relevance to specific countries. Finally, the authors present our suggestions on possible policy and programmatic responses, based on identifying both regional and external dimensions to the problems.
Zernike expansions for non-Kolmogorov turbulence

We investigate the expression of non-Kolmogorov turbulence in terms of Zernike polynomials. Increasing the power-law exponent of the three-dimensional phase power spectrum from 2 to 4 results in a higher proportion of wave-front energy being contained in the tilt components. Closed-form expressions are given for the variances of the Zernike coefficients in this range. For exponents greater than 4 a von Karman spectrum is used to compute the variances numerically as a function of exponent for different outer-scale lengths. We find in this range that the Zernike-coefficient variances depend more strongly on outer scale than on exponent and that longer outer-scale lengths lead to more energy in the tilt terms. The scaling of Zernike-coefficient variances with pupil diameter is an explicit function of the exponent.
Gas transport properties of liquid crystalline poly (ethylene terephthalate‐co‐p‐oxybenzoate)

Gas transport properties are reported for a series of films prepared from thermotropic poly (ethylene terephthalate-co-p-oxybenzoate), or PET/PHB, having compositions of 60 and 80 mol % PHB. The mesomorphic and crystalline morphology of the copolyester films was examined by cross-polarized light microscopy, differential scanning calorimetry (DSC), and x-ray diffraction. Melt-processed films of both compositions appeared to exhibit an entirely anisotropic morphology with low levels of conventional crystallinity. Solution-cast films prepared from the 60 mol % material were found to contain a large fraction of isotropic regions, which become ordered upon annealing above the glass transition. Permeability measurements were made for He, H2, O2, N2, and CO2 at 35°C and the diffusivities were computed from time-lag data. The largely anisotropic films exhibit good barrier properties resulting from very low solubility coefficients. The partially isotropic 60 mol % films show much higher permeability coefficients driven primarily by increased solubility coefficients, while diffusivity is affected to a lesser extent. These results appear to contrast with what is observed in semicrystalline systems where increased crystalline order results in more dramatic reductions in penetrant mobility.
Propellant-Free Control of Tethered Formation Flight, Part 2: Nonlinear Underactuated Control

This is the second in a series of papers that exploit the physical coupling of tethered spacecraft to derive a propellant-free spin-up and attitude control strategy. We take a nonlinear control approach to underactuated tethered formation flying spacecraft, whose lack of full state feedback linearizability, along with their complex nonholonomic behavior, characterizes the difficult nonlinear control problem. We introduce several nonlinear control laws that are more efficient in tracking time-varying trajectories than linear control. We also extend our decentralized control approach to underactuated tethered systems, thereby eliminating the need for any intersatellite communication. To our knowledge, this work reports the first nonlinear control results for underactuated tethered formation flying spacecraft. This article further illustrates the potential of the proposed strategy by providing a new momentum dumping method that does not use torque-generating thrusters.
RADIO CONSTRAINTS ON HEAVILY OBSCURED STAR FORMATION WITHIN DARK GAMMA-RAY BURST HOST GALAXIES

Highly dust-obscured starbursting galaxies (submillimeter galaxies and their ilk) represent the most extreme sites of star formation in the distant universe and contribute significantly to overall cosmic star formation beyond z > 1.5. Some stars formed in these environments may also explode as gamma-ray bursts (GRBs) and contribute to the population of "dark" bursts. Here we present Very Large Array wideband radio-continuum observations of 15 heavily dust-obscured Swift GRBs to search for radio synchrotron emission associated with intense star formation in their host galaxies. Most of these targets (11) are not detected. Of the remaining four objects, one detection is marginal, and for two others we cannot yet rule out the contribution of a long-lived radio afterglow. The final detection is secure, but indicates a star formation rate (SFR) roughly consistent with the dust-corrected UV-inferred value. Most galaxies hosting obscured GRBs are therefore not forming stars at extreme rates, and the amount of optical extinction seen along a GRB afterglow sightline does not clearly correlate with the likelihood that the host has a sufficiently high SFR to be radio-detectable. While some submillimeter galaxies do readily produce GRBs, these GRBs are often not heavily obscured—suggesting that the outer (modestly obscured) parts of these galaxies overproduce GRBs and the inner (heavily obscured) parts underproduce GRBs relative to their respective contributions to star formation, hinting at strong chemical or initial mass function gradients within these systems.
Enantioselective α-amination enabled by a BINAM-derived phase-transfer catalyst

Chiral anion phase-transfer of aryldiazonium cations was utilized to achieve highly enantioselective α-amination of carbonyl compounds. A broad scope of indanone- and benzosuberone-derived substrates was amenable to this strategy. Critical to obtaining high levels of enantioselectivity was the use of BINAM-derived phosphoric acids. The utility of this transformation was demonstrated through facile conversion of diazene products to valuable α-amino acid derivatives.
Consistency of local density matrices is QMA-Complete

Suppose we have an n-qubit system, and we are given a collection of local density matrices ρ1,...,ρm, where each ρi describes a subset Ci of the qubits. We say that the ρi are “consistent” if there exists some global state σ (on all n qubits) that matches each of the ρi on the subsets Ci. This generalizes the classical notion of the consistency of marginal probability distributions. We show that deciding the consistency of local density matrices is QMA-complete (where QMA is the quantum analogue of NP). This gives an interesting example of a hard problem in QMA. Our proof is somewhat unusual: we give a Turing reduction from Local Hamiltonian, using a convex optimization algorithm by Bertsimas and Vempala, which is based on random sampling. Unlike in the classical case, simple mapping reductions do not seem to work here.
Preparation of Tertiary Alkyl Carbinamines, Propargylamines, and α-Heteroarylamines by Ketone-Based Aminoalkylation

Ketones 6a−i were converted into their benzotriazolylamine adducts 8a−i either directly from the corresponding ketone 6a or via enamines 7b−i. Adducts 8a−i on treatment with Grignard reagents, lithium phenylacetylide, or heteroaryllithiums gave tertiary alkyl carbinamines 9a−h (47−61%), propargylamines 10a−i (30−98%), and α-heteroarylamines 11a−k (44−85%), respectively.
Modeling the Formation of Clouds in Brown Dwarf Atmospheres

Because the opacity of clouds in substellar mass object (SMO) atmospheres depends on the composition and distribution of particle sizes within the cloud, a credible cloud model is essential for accurately modeling SMO spectra and colors. We present a one-dimensional model of cloud particle formation and subsequent growth based on a consideration of basic cloud microphysics. We apply this microphysical cloud model to a set of synthetic brown dwarf atmospheres spanning a broad range of surface gravities and effective temperatures (gsurf ¼ 1:78 � 10 3 3 � 10 5 cm s � 2 and Teff ¼ 600 1600 K) to obtain plausible particle sizes for several abundant species (Fe, Mg2SiO4, and Ca2Al2SiO7). At the base of the clouds, where the particles are largest, the particle sizes thus computed range from � 5 to over 300 lm in radius over the full range of atmospheric conditions considered. We show that average particle sizes decrease significantly with increasing brown dwarf surface gravity. We also find that brown dwarfs with higher effective temperatures have characteristically larger cloud particles than those with lower effective temperatures. We therefore conclude that it is unrealistic when modeling SMO spectra to apply a single particle size distribution to the entire class of objects. Subject headings: stars: atmospheres — stars: low-mass, brown dwarfs