cssi/SciSciGPT-SciSciNet huggingface dataset:
Resistance of short pulses to self-focusing

We study the spatial and spectral modulation of the radiation produced by ultrashort pulse continuum generation. We show that the assumptions (1) that continuum radiation is generated at the location of the moving focus of a self-focusing pulse and (2) that the continuum radiation has the phase of the incident radiation allow us to predict the single-shot spectral and spatial modulation rather well. These assumptions could be valid only if self-focusing is halted by a simple process. On the basis of this evidence, we propose that spectral dispersion and other non-slowly-varying effects (which are absent from the usual self-focusing theory) are responsible for halting the self-focusing process.
Earnings Surprise Research: Synthesis and Perspectives

An investigation of the relation between earnings surprise and three empirical anomalies—the P/E effect, the size effect, and the Value Line enigma—indicates that the standardized unexpected earnings (SUE) effect appears to be separate and distinct from each of the three. The relations between the SUE phenomenon and firm risk, the appropriateness of the earnings expectations model, and the role of transaction costs are also investigated. The SUE phenomenon is not attributable to inappropriate risk adjustment, use of the “wrong” earnings expectations model, or ignoring transaction costs. The SUE effect may be partly explained by analysts' behavior and is both predictable and profitable. The SUE effect has also been observed in Japan.
Fast bit-reversal algorithms based on index representations in GF (2/sup b/)

The author proposes bit-reversal unscrambling algorithms based on representing array indices as elements in GF(2/sup b/). These elements are sequenced through by counters implemented with integer shifts and bitwise exclusive-OR. A very simple algorithm, developed by applying these counters in a structure similar to the Gold-Rader algorithm, is shown to be less complex and significantly faster than the Gold-Rader (1969) algorithm. A second algorithm, constructed by using counters in GF(2/sup b/) to adapt an algorithm proposed by Evans (1987), eliminates the lookup tables required by the Evans algorithm while maintaining its speed advantages. >
Synthesis of phenanthropyrroles and phenanthrolinopyrroles from isocyanoacetates: An extension of the barton-zard pyrrole condensation

Abstract 9-Nitrophenanthrene ( 1 ) and 5-nitro-1,10-phenanthroline ( 4 ) condensed with esters of isocyanoacetic acid in the presence of one equivalent of DBU to give the corresponding phenanthropyrroles 2 and phenantholinopyrroles 5 , respectively, in excellent yields.
Insulator-to-Metal Transition in Selenium-Hyperdoped Silicon: Observation and Origin

Hyperdoping has emerged as a promising method for designing semiconductors with unique optical and electronic properties, although such properties currently lack a clear microscopic explanation. Combining computational and experimental evidence, we probe the origin of sub-band-gap optical absorption and metallicity in Se-hyperdoped Si. We show that sub-band-gap absorption arises from direct defect-to-conduction-band transitions rather than free carrier absorption. Density functional theory predicts the Se-induced insulator-to-metal transition arises from merging of defect and conduction bands, at a concentration in excellent agreement with experiment. Quantum Monte Carlo calculations confirm the critical concentration, demonstrate that correlation is important to describing the transition accurately, and suggest that it is a classic impurity-driven Mott transition.
Stereospecific Cross-Coupling of Secondary Alkyl β-Trifluoroboratoamides

The stereospecific cross-coupling of enantioenriched nonbenzylic secondary alkyl boron compounds has been achieved. The high selectivity toward product formation over an undesired β-H elimination pathway is achieved via an intramolecular coordination of an ancillary carbonyl to the metal center in the diorganopalladium intermediate.
Weak expectations and the injective envelope

Given a unital C*-subalgebra of B(H), we study the set of all possible images of its injective envelope that are contained in B(H) and their position relative to the double commutant of the algebra in order to obtain more information about the existence or non-existence of weak expectations. We study the subset of B(H) that is the intersection of all possible images of the injective envelope and show that it is simultaneously a reflexive cover and a new type of order completion of the algebra.
Low temperature hydrogen production from methane on cerium nickel and zirconium based oxyhydrides

Hydrogen production from methane has been obtained at low temperature, in presence of O2, over cerium nickel and zirconium CeZrZNiXOY (z = 0 or 0.5 and 0 < x ´ 3) oxyhydrides. A H2 yield of 100% is obtained at high temperature (650°C), at 200°C a yield of 34 % is reached with a stable methane conversion at 53 % and selectivity in H2 at 64 % when the solid is previously in-situ treated in H2 at 200°C. Different physicochemical techniques have been used to characterize the catalysts. Depending on the composition and metal loading, a solid solution and/or a highly dispersed nickel oxide in ceria (or ceria-zirconia) can be obtained. Ion sputtering followed by XPS analysis has been very useful for estimating the size of small NiO clusters (10 – 15 A) present in the compounds. Correlations among the species present in the solid, and the catalytic performances are discussed, an active site based on the formation of anionic vacancies and a mechanism involving a heterolytic abstraction of a hydride species from methane are proposed.
Shuttle Navigation System for Entry and Landing Mission Phases

An on-board filter is designed to efficiently process inertial-measurement-unit data in combination with data from other external navaids such as TAG AN, one-way Doppler, baro-altimeter, radar altimeter, and MLS. During the approach phase (altitude above 12,000 ft) a 13-state minimum-variance filter is recommended, with position (3), velocity (3), IMU alignment (3), and various navaid correlated errors (4) as state elements. The navaid errors are modeled as first-order Markov processes, with state (process) noise employed in the extrapolation procedure to account for unmodeled errors. A simple underweighting technique is employed to insure good navigation-system performance in the presence of large initial-condition errors. During the terminal phase (altitude below 12,000 ft) a 6-state filter is used, including as state elements only position (3) and velocity (3). Prestored weighting vectors are used here, based on the last computed values for the preceding approach phase.
Strategies to Identify Boosted Tops

We study techniques for identifying highly boosted top jets, where the subsequent top decay products are not isolated. For hadronic boosted tops, we consider variables which probe the jet substructure in order to reduce the background from QCD jets with large invariant mass. Substructure variables related to two-body kinematics are least sensitive to the modeling of parton shower, while those which involve multi-body kinematics may still have discrimination power. For leptonic boosted tops, we consider variables which characterize the separation between the lepton—although not isolated by conventional criterion—and the hadronic activity in the top jet. Such variables are useful in reducing the backgrounds both from heavy-flavor jets and from accidental jet-lepton overlap. We give numerical estimates of the top identification efficiency versus background rejection rate as a functions of cuts on these variables, and find that these variables offer additional useful information above invariant mass alone.
Alkylation Studies of N-Protected-5-substituted Morpholin-3-ones. A Stereoselective Approach to Novel Methylene Ether Dipeptide Isosteres

We have developed a versatile new synthesis of the Ψ[CH2O] pseudopeptides from N-protected-5-substituted morpholin-3-ones. The morpholin-3-ones are prepared in two steps from the corresponding amino alcohols by treatment with ethyl chloroacetate, followed by protection of the amide. We found that direct alkylation of the protected morpholin-3-ones gives the expected alkylation product where the electrophile approaches from the face opposite to the existing side chain (derived from the amino alcohol). If an S amino alcohol is used, this procedure results in the formation of the (S,R) Ψ[CH2O] dipeptide. Alternatively, the (S,S) Ψ[CH2O] dipeptide can be obtained if the protected morpholin-3-one enolate is quenched with an aldehyde and the aldol product is dehydrated and reduced. We have explored an alkylation/deprotonation/kinetic protonation scheme which is also amenable to the preparation of (S,S) pseudodipetides. It is, of course, possible to obtain the corresponding (R,R) and (S,R) Ψ[CH2O] dipeptides by ...
Detection of Pitting with Electrochemical Impedance Spectroscopy

Technique et resultats de la methode de detection des piqures par spectroscopie d'impedance electrochimique
Superhybrid Composite Blade Impact Studies

An investigation was conducted to determine the feasibility of superhybrid composite blades for meeting the mechanical design and impact resistance requirements of large fan blades for aircraft turbine engine applications. Two design concepts were evaluated: (1) leading edge spar (TiCom) and (2) center spar (TiCore), both with superhybrid composite shells. The investigation was both analytical and experimental. The results obtained show promise that superhybrid composites can be used to make light-weight, high-quality, large fan blades with good structural integrity. The blades tested successfully demonstrated their ability to meet steady-state operating conditions, overspeed, and small bird impact requirements.
Photoluminescence quenching in gold - MoS2 hybrid nanoflakes

Achieving tunability of two dimensional (2D) transition metal dichalcogenides (TMDs) functions calls for the introduction of hybrid 2D materials by means of localized interactions with zero dimensional (0D) materials. A metal-semiconductor interface, as in gold (Au) - molybdenum disulfide (MoS2), is of great interest from the standpoint of fundamental science as it constitutes an outstanding platform to investigate plasmonic-exciton interactions and charge transfer. The applied aspects of such systems introduce new options for electronics, photovoltaics, detectors, gas sensing, catalysis, and biosensing. Here we consider pristine MoS2 and study its interaction with Au nanoislands, resulting in local variations of photoluminescence (PL) in Au-MoS2 hybrid structures. By depositing monolayers of Au on MoS2, we investigate the electronic structure of the resulting hybrid systems. We present strong evidence of PL quenching of MoS2 as a result of charge transfer from MoS2 to Au: p-doping of MoS2. The results suggest new avenues for 2D nanoelectronics, active control of transport or catalytic properties.
Atomic electron correlation in nuclear electron capture

The effect of electron-electron Coulomb correlation on orbital electron capture by the nucleus was treated by the multiconfigurational Hartree-Fock approach. The theoretical Be-7 L/K capture ratio was found to be 0.086, and the Ar-37 M/L ratio, 0.102. Both ratios were smaller than the independent particle predictions. Measurements exist for the Ar M/L ratio, and agreement between theory and experiment was excellent.
Specializations of Ferrers ideals

We introduce a specialization technique in order to study monomial ideals that are generated in degree two by using our earlier results about Ferrers ideals. It allows us to describe explicitly a cellular minimal free resolution of various ideals including any strongly stable and any squarefree strongly stable ideal whose minimal generators have degree two. In particular, this shows that threshold graphs can be obtained as specializations of Ferrers graphs, which explains their similar properties.
Macroeconomic Expectations of Households and Professional Forecasters

Economists have long emphasized the importance of expectations in determining macroeconomic outcomes. Yet there has been almost no recent effort to model actual empirical expectations data; instead ,m acroeconomists usually simply assume that expectations are ‘rational.’ This paper shows that while empirical household expectations are not rational in the usual sense, expectational dynamics are well captured by a model in which households’ views derive from news reports of the views of professional forecasters, which in turn may be rational. The model’s estimates imply that people only occasionally pay attention to news reports; this inattention generates ‘stickyness’ in aggregate expectations, with important macroeconomic consequences.
Disconnected electromagnetic form factors

Abstract Preliminary results of a calculation of disconnected nucleon electromagnetic factors factors on the lattice are presented. The implementation of the numerical subtraction scheme is outlined. A comparison of results for electric and magnetic disconnected form factors on two lattice sizes with those of the Kentucky group is presented. Unlike previous results, the results found in this calculation are consistent with zero in these sectors.
High Resolution Mid-Infrared Imaging of the Nucleus of NGC 1068

We interpret the faint optical counterpart to the mid-infrared southern extension as being due to partial obscuration by the intervening disk of the host galaxy.
Intramolecular Diels-Alder reactions of unsaturated acylcyclopentadienes and cyclopentadienecarboxylates

Abstract The dimers of unsaturated acylcyclopentadienes and cyclopentadienecarboxylates have been synthesized. Pyrolyses provide monomers which undergo the intramolecular cycloadditions. Three types of adducts are obtained.
Exact Expressions for Some Randomness Tests

For a computable probability distribution P over the set of infinite binary sequences Martin-Lof defined a test d(x|P) measuring the degree of nonrandomness of the sequence x with respect of P. We give some expressions in terms of Kolmogorov's and other complexities of the initial segments of x whose difference from d(x|P) is bounded by a constant.
Accurate measurement of scattering and absorption loss in microphotonic devices

We present a simple measurement and analysis technique to determine the fraction of optical loss due to both radiation (scattering) and linear absorption in microphotonic components. The method is generally applicable to optical materials in which both nonlinear and linear absorption are present and requires only limited knowledge of absolute optical power levels, material parameters, and the structure geometry. The technique is applied to high-quality-factor (Q=1×10^6 to Q=5×10^6) silicon-on-insulator (SOI) microdisk resonators. It is determined that linear absorption can account for more than half of the total optical loss in the high-Q regime of these devices.
Bio/chemical sensors heterogeneously integrated with Si-CMOS circuitry

Sensor arrays for bio/chemical sensing generally incorporate different types of sensors with different substrate coatings, enabling increased sensor sensitivity and selectivity. However, a challenge in using multiple sensor systems is integration with RF electronic circuitry. This work presents the development of flexural plate wave (FPW) acoustic devices implemented in a sensor array and co-integrated on a Si-CMOS circuit. FPWs are highly sensitive to surface perturbations and indirectly sense analytes by detecting mass changes on the sensing plate surface. The sensors are placed in an oscillating circuit, where changes in the oscillation frequency are used to determine changes in the wave velocity due to mass loading by the analyte [1, 2]. Since FPWs are generated in thin plates, these devices are highly sensitive to loading and exhibit the highest mass sensitivities of any acoustic wave device [1, 2]. In the work presented, FPWs are fabricated on Si/SiO 2 /Si native substrates, with the interdigitated transducers (IDTs) isolated from the active sensing surface. This innovative design enables the sensors to be fabricated and then separated from the native substrate, transferred, and bonded to the host Si-CMOS circuit. Thus, a new approach for the heterogeneous integration of FPW sensors and circuitry is provided. Following integration, the FPWs can be customized with either chemical membranes or biological functionalization. Moreover, this novel approach allows each sensor to be optimized independently before being connected to the host substrate. This paper presents the design, development, and integration process of an FPW sensor on Si-CMOS circuitry.
Synthesis of Shuttle Vehicle Damping Using Substructure Test Results

An empirical method is developed for predicting the modal damping of a combined parallel-stage shuttle model by means of damping measurements performed on the individual substructures. Correlations are first determined for each component in terms of damping energy as a function of peak kinetic energy and modal amplitude. The results are then used to predict component damping energies corresponding to the respective kinetic energies and amplitudes that occur for the new modes of the combined system. Modal characteristics for the system, other than damping, are obtained by a real eigenvalue solution of dynamic equations developed by Hurty's procedure of substructures. System equations, which include component modal damping, are also solved by a complex eigenvalue approach for comparison with results of the empirical method.
Verdier specialization via weak factorization

Let X⊂V be a closed embedding, with V∖X nonsingular. We define a constructible function ψ X,V on X, agreeing with Verdier’s specialization of the constant function 1 V when X is the zero-locus of a function on V. Our definition is given in terms of an embedded resolution of X; the independence of the choice of resolution is obtained as a consequence of the weak factorization theorem of Abramovich–Karu–Matsuki–Wlodarczyk. The main property of ψ X,V is a compatibility with the specialization of the Chern class of the complement V∖X. With the definition adopted here, this is an easy consequence of standard intersection theory. It recovers Verdier’s result when X is the zero-locus of a function on V. Our definition has a straightforward counterpart Ψ X,V in a motivic group. The function ψ X,V and the corresponding Chern class c SM(ψ X,V ) and motivic aspect Ψ X,V all have natural ‘monodromy’ decompositions, for any X⊂V as above. The definition also yields an expression for Kai Behrend’s constructible function when applied to (the singularity subscheme of) the zero-locus of a function on V.
Asymmetric synthesis of the antibiotic (+)-thiamphenicol using cis-N-(p-toluenesulfinyl)aziridine 2-carboxylic acids

Abstract A concise, highly efficient asymmetric synthesis of aminopropanediol (1R,2R)-(−)-3, precursor to the broad spectrum antibiotics thiamphenicol/florfenicol 1 2 , was prepared in two steps from cis-aziridine 2-carboxylic acid (2S,3S)-(−)-5.
Maximal Ball Packings of Symplectic-Toric Manifolds

Let (M, σ, ψ) be a symplectic-toric manifold of dimension at least four. This article investigates the symplectic ball packing problem in the toral equivariant setting. We show that the set of toric symplectic ball packings of M admits the structure of a convex polytope.Previous work of the first author shows that up to equivalence, only (ℂℙ 1 ) 2 and ℂℙ 2 admit density one packings when n = 2 and only ℂℙ n admits density one packings when n > 2. In contrast, we show that for a fixed n ≥ 2 and each δ ∈ (0, 1), there are uncountably many genuinely inequivalent 2n-dimensional symplectic-toric manifolds with a maximal toric packing of density δ. This result follows from a general analysis of how the densities of maximal packings change while varying a given symplectic-toric manifold through a family of symplectic-toric manifolds that are equivariantly diffeomorphic but not equivariantly symplectomorphic.
Wear of seal materials used in aircraft propulsion systems

A review of various types of seal locations in a gas turbine engine and the significance of wear for each type are presented. Material selection guidelines and the PV (contact pressure times sliding velocity) criteria for seal materials are discussed, and examples of wear mechanisms in positive contact seals are given. It is suggested that improved wear, erosion, and oxidation resistant materials will be required for improved seal durability; finally, a correlation is proposed between wear characteristics and a factor that includes material strength, ductility, specific heat and hot-working temperature to attain low porosity metallic gas path seal materials.
The predictive value of symptoms in diagnosing childhood tinea capitis.

Objective To determine which sign, symptom, or combination thereof best predicts cultures positive for fungi in children with possible tinea capitis. Design Convenience survey. Setting Urban hospital-based general pediatric practice. Patients Results were obtained on 100 consecutive children presenting with at least 1 sign or symptom (scalp pruritus, scaling, diffuse or circumscribed alopecia, or occipital adenopathy). Intervention All enrolled children had samples for scalp cultures taken. Demographic information and clinical findings were verified by the author. Main Outcome Measure Whether detected clinical findings can predict the outcome of fungal cultures. Results Cultures positive for fungi were found in 68 children. There was a significant relationship (Fisher exact test; P Conclusions In children who are suspected of having tinea capitis, there is a high likelihood of cultures positive for fungi in those with adenopathy. A fungal infection is rarely the cause when neither adenopathy nor alopecia is present. Attention to signs and symptoms in children with suspected tinea capitis can result in better diagnostic and treatment precision.
Equiangular tight frames from complex Seidel matrices containing cube roots of unity

We derive easily verifiable conditions which characterize when complex Seidel matrices containing cube roots of unity have exactly two eigenvalues. The existence of such matrices is equivalent to the existence of equiangular tight frames for which the inner product between any two frame vectors is always a common multiple of the cube roots of unity. We also exhibit a relationship between these equiangular tight frames, complex Seidel matrices, and highly regular, directed graphs. We construct examples of such frames with arbitrarily many vectors.
Angular photonic band gap

We present detailed numerical simulations of a class of material systems that strongly discriminate light based primarily on the angle of incidence, over a broad range of frequencies, and independent of the polarization. Unique properties of these systems emerge from exploring photonic crystals whose constituents have an anisotropic dielectric response.
High-tech R&D subsidies Estimating the effects of Sematech

Abstract Sparked by concerns about their shrinking market share, 14 leading U.S. semiconductor producers, with the financial assistance of the U.S. government in the form of $100 million in annual subsidies, formed a joint R&D consortium — Sematech — in 1987. Using Compustat data on all U.S. semiconductor firms, we estimate the effects of Sematech on members' R&D spending, profitability, investment, and productivity. In so doing we examine two hypotheses: the ‘commitment’ hypothesis that Sematech obligates member firms to spend more on high-spillover R&D, and the ‘sharing’ hypothesis that Sematech reduces duplication of member R&D spending. Whereas the commitment hypothesis provides a rationale for the government subsidies, the sharing hypothesis does not. We find that Sematech induced members to cut their overall R&D spending on the order of $300 million per year, providing support for the sharing hypothesis.
Comparing classical and quantum probability distributions for an asymmetric infinite well

We compare the classical and quantum mechanical position-space probability densities for a particle in an asymmetric infinite well. In an idealized system with a discontinuous step in the middle of the well, the classical and quantum probability distributions agree fairly well, even for relatively small quantum numbers, except for anomalous cases which arise due to the unphysical nature of the potential. We are able to derive upper and lower bounds on the differences between the quantum and classical results. We also qualitatively discuss the momentum-space probability densities for this system using intuitive ideas about the amount of time a classical particle spends in various parts of the well. This system provides an excellent example of a non-trivial, but tractable, quantum mechanical bound state problem where the correlations between the amplitude and curvature of quantum mechanical wavefunctions can be easily compared to classical intuition about particle motion, with quantitative success, but also warning of possible surprises in non-physical limiting cases.
Fractional charge and quantized current in the quantum spin Hall state

Quantum spin Hall insulators are new states of matter that were recently predicted and observed. A theoretical work now explores distinct experimental manifestations resulting from the exotic behaviour that characterizes these structures.
Mott transition of the f-electron system in the periodic Anderson model with nearest neighbor hybridization

We show analytically that, under certain assumptions, the periodic Anderson model and the Hubbard model become equivalent within the dynamical mean field theory for quasiparticle weight Z → 0. A scaling relation is derived which is validated numerically using the numerical renormalization group at zero temperature and quantum Monte Carlo simulations at finite temperatures. Our results show that the ƒ-electrons of the half-filled periodic Anderson model with nearest neighbor hybridization get localized at a finite critical interaction strength U c, also at zero temperature. This transition is equivalent to the Mott-transition in the Hubbard model.
The Response of Stock Prices to Permanent and Temporary Shocks to Dividends

This paper investigates the response of stock prices to dividend shocks in a bivariate model of stock prices and price-dividend spreads. Dividend process is modeled as the sum of a permanent component and a temporary component. By using the stock price valuation (present value) model, the two components are related to stock prices. The stock market responds significantly not only to permanent shocks to dividends, but also to temporary shocks to dividends. Furthermore, initial responses of stock prices to the temporary shocks are as strong as those to the permanent shocks. As a result, substantial variation in stock prices is due to the temporary shocks. This finding provides empirical support for the imperfect information hypothesis that emphasizes the failure of investors to clearly dis? tinguish between the two components of dividends, and also suggests that the observed mean-reverting behavior of stock returns should be explained by incorporating a significant temporary component into stock prices. The price-dividend spreads are primarily accounted for by the temporary shocks to dividends, and respond strongly to them, suggesting that, in response to the temporary shocks to dividends, stock prices respond excessively relative to dividends.
The Photospheric Energy and Helicity Budgets of the Flux-injection Hypothesis

The flux-injection hypothesis for driving coronal mass ejections (CMEs) requires the transport of substantial magnetic energy and helicity flux through the photosphere concomitant with the eruption. Under the magnetohydrodynamics approximation, these fluxes are produced by twisting magnetic field and/or flux emergence in the photosphere. A CME trajectory, observed 2000 September 12 and fitted with a flux-rope model, constrains energy and helicity budgets for testing the flux-injection hypothesis. Optimal velocity profiles for several driving scenarios are estimated by minimizing the photospheric plasma velocities for a cylindrically symmetric flux-rope magnetic field subject to the flux budgets required by the flux-rope model. Ideal flux injection, involving only flux emergence, requires hypersonic upflows in excess of the solar escape velocity 617 km s–1 over an area of 6 × 108 km2 to satisfy the energy and helicity budgets of the flux-rope model. These estimates are compared with magnetic field and Doppler measurements from Solar and Heliospheric Observatory/Michelson Doppler Imager on 2000 September 12 at the footpoints of the CME. The observed Doppler signatures are insufficient to account for the required energy and helicity budgets of the flux-injection hypothesis.
MULTISCALE ALGORITHMS FOR EIGENVALUE PROBLEMS

Iterative multiscale methods for electronic structure calculations offer several advantages for large-scale problems. Here we examine a nonlinear full approximation scheme (FAS) multigrid method for solving fixed potential and self-consistent eigenvalue problems. In principle, the expensive orthogonalization and Ritz projection operations can be moved to coarse levels, thus substantially reducing the overall computational expense. Results of the nonlinear multiscale approach are presented for simple fixed potential problems and for self-consistent pseudopotential calculations on large molecules. It is shown that, while excellent efficiencies can be obtained for problems with small numbers of states or well-defined eigenvalue cluster structure, the algorithm in its original form stalls for large-molecule problems with tens of occupied levels. Work is in progress to attempt to alleviate those difficulties.
Combinatorics of the Springer correspondence for classical Lie algebras and their duals in characteristic 2

Abstract We give a combinatorial description of the Springer correspondence for classical Lie algebras of type B , C or D and their duals in characteristic 2. The combinatorics used here is of the same kind as those appearing in the description of (generalized) Springer correspondence for unipotent case of classical groups by Lusztig in odd characteristic and by Lusztig and Spaltenstein in characteristic 2.
Noise-tolerant learning, the parity problem, and the statistical query model

We describe a slightly subexponential time algorithm for learning parity functions in the presence of random classification noise, a problem closely related to several cryptographic and coding problems. Our algorithm runs in polynomial time for the case of parity functions that depend on only the first O(log n log log n) bits of input, which provides the first known instance of an efficient noise-tolerant algorithm for a concept class that is not learnable in the Statistical Query model of Kearns [1998]. Thus, we demonstrate that the set of problems learnable in the statistical query model is a strict subset of those problems learnable in the presence of noise in the PAC model.In coding-theory terms, what we give is a poly(n)-time algorithm for decoding linear k × n codes in the presence of random noise for the case of k = c log n log log n for some c > 0. (The case of k = O(log n) is trivial since one can just individually check each of the 2k possible messages and choose the one that yields the closest codeword.)A natural extension of the statistical query model is to allow queries about statistical properties that involve t-tuples of examples, as opposed to just single examples. The second result of this article is to show that any class of functions learnable (strongly or weakly) with t-wise queries for t = O(log n) is also weakly learnable with standard unary queries. Hence, this natural extension to the statistical query model does not increase the set of weakly learnable functions.
Symplectic embeddings of polydisks

If P and P′ are symplectic polydisks of radii R1≤...≤Rn and R1′≤...≤Rn′, respectively, then we prove that P symplectically embeds in P′ provided that C(n)R1≤R1′ and C(n)R1...Rn≤R1′...Rn′. Up to a constant factor, these conditions are optimal.
Detection of Functional Ovarian Hyperandrogenism in Women With Androgen Excess

Abstract Background. Distinguishing between ovarian and adrenal causes of androgen excess may be difficult. We have found that women with the polycystic ovary syndrome have supranormal plasma 17-hydroxyprogesterone responses to the gonadotropin-releasing hormone agonist nafarelin. We determined the usefulness of testing with nafarelin to distinguish ovarian causes of hyperandrogenism in women. Methods. We studied 40 consecutive women with hyperandrogenism who had oligomenorrhea, hirsutism, or acne. All 40 underwent testing with nafarelin, dexamethasone, and corticotropin with measurement of circulating concentrations of gonadotropins and steroid hormones, and 19 underwent ovarian ultrasonography. Results. The plasma 17-hydroxyprogesterone response to nafarelin was supranormal in 23 of the 40 women (58 percent), and the plasma androgen response to corticotropin was elevated in 23; 13 women had both abnormalities. Only one woman had conclusive evidence of a steroidogenic block; she had nonclassic adrenal 21...
A direct second-variational method for unconstrained optimal control problems

A direct second-variational algorithm is proposed for the iterative solution of optimal control problems in continuous, as well as discrete, systems. While the classical method using the Riccati transformation is shown to follow from the direct method, the latter has certain promising features in terms of structural simplicity, ease of programming, and substantial reduction in computation time. The process involves a predictor-corrector algorithm for a forward sweep in the state equations, followed by a backwards sweep in the adjoint equations. Applied to discrete systems, this method functions under conditions less stringent than in the classical scheme. Linearized quasioptimal feedback control is examined from the point of view of the direct method and a scheme for successive improvement in quasi-optimal policy is proposed for systems that suffer small perturbations from a given optimal trajectory.
Thermal fluctuations and validity of the 1-loop effective potential

Abstract We examine the validity of the 1-loop approximation to the effective potential at finite temperatures and present a simple test for its reliability. As an application we study the standard electroweak potential, showing that for a Higgs mass above 70 GeV, and fairly independently of the top mass (with m t⩾90 GeV), the 1-loop approximation is no longer valid for temperatures in the neighborhood of the critical temperature.
Thermo-Mechanical Response of Patched Plates

A review, unie cation, and extension of the analysis and results pertaining to patched beam plates subjected to a uniform temperature e eld (heating and cooling ) and in-plane edge force (compressive or tensile ), is presented. A self-consistent nonlinear formulation has been derived, which lends itself to an exact analytical solution, to within the context of the model. Three nondimensional parameters are seen to characterize the response of the composite system. These are 1 ) a loading parameter, 2 ) a critical temperature, and 3 ) a critical membrane force. Critical behavior includes bifurcation buckling, asymptotic buckling, and sling-shot buckling, nontrivial ground states, and demarcation and transition in dee ection direction. Results for both heating and cooling are consolidated and presented in a unie ed manner, yielding a broader understanding of the problem of interest. UMEROUS aerospace, mechanical, and electronic structural components consist of a primary base structure with a secondary element bonded to it for the purpose of strengthening, stiffening, or providing thermal or electrical contact. Specie c examples are bonded sensors or repair patches on aircraft wings and fuselages or the attachment of electronic components to printed circuit boards. The combination of the primary and secondary structures forms a composite system. Because the structure has been changed with regard to its geometry and structural properties, the structural response canchangesignie cantly with theintroduction ofthepatch, with sometimes unanticipated performance as a result. In particular, the local stiffness has been changed, the neutral axis has been moved, and a thermal mismatch between the base structure and the patch may have been introduced. The last two will independently cause local bending, and together can induce novel behavior of the structure.
Aggravating and Mitigating Sentencing Factors at the ICTR—An Exploratory Analysis

The International Criminal Tribunal for Rwanda (ICTR) has been operating for nearly two decades now and has sentenced over sixty defendants. While the sentencing guidelines from the official Tribunal statute and rules of procedure are vague and indefinite, the court has established a sentencing jurisprudence of its own, especially when it comes to aggravating and mitigating factors. The use of these factors in sentencing have been questioned, so an exploratory analysis of what factors the court has considered and how they have done so was constructed. The results show a wide ranging list of both aggravating and mitigating factors without providing a strict sentencing structure. These sentencing factors may set a standard for future international courts sentencing defendants for the most heinous of crimes.
Perturbative QCD and tau decay

Sufficiently inclusive observables in the decay of the tau lepton can be calculated using the methods of perturbative QCD. These include the asymmetry parameter A τ that determines that angular distribution of the total hadron momentum in the decay of a polarized tau. It should be possible to measure A τ accurately using existing data from LEP. Reliable estimates of theoretical errors are essential in order to determine whether a given observable is sufficiently inclusive to be calculated using perturbative methods. The theoretical uncertainties due to higher orders in α s can be estimated using recent calculations to all orders in the large—(33 − 2 N f ) limit. These estimates indicate that tau decay data can be used to determine α s ( M Z ) to a precision of 2% or better.
Organocatalysis in biorefining for biomass conversion and upgrading

Organocatalysis using small-molecule organic compounds as catalysts has risen to prominence in organic synthesis and polymer synthesis. However, its application in biorefining for catalytic biomass conversion and upgrading into sustainable chemicals, materials, and biofuels has come to light only recently. This emergence of applying organocatalysis for biorefining has not only broadened the scope of organocatalysis and offered metal-free “greener” alternatives for biomass conversion and upgrading, it has also showed some unique activity and selectivity in such transformations as compared to metal-mediated processes. This review captures highlights of this emerging area by focusing on utilization of organocatalytic means for catalytic conversions of cellulose, glucose and fructose, upgrading of furaldehydes, and organocatalytic polymerization of biomass feedstocks.
Nonuniform Line Coverage From Noisy Scalar Measurements

We study the problem of distributed coverage control in a network of mobile agents arranged on a line. The goal is to design distributed dynamics for the agents to achieve optimal coverage positions with respect to a scalar density field that measures the relative importance of each point on the line. Unlike previous work, which implicitly assumed the agents know this density field, we only assume that each agent can access noisy samples of the field at points close to its current location. We provide a simple randomized protocol wherein every agent samples the scalar field at three nearby points at each step and which guarantees convergence to the optimal positions. We further analyze the convergence time of this protocol and show that, under suitable assumptions, the squared distance to the optimal coverage configuration decays as $O(1/t)$ with the number of iterations $t$ , where the constant scales polynomially with the number of agents $n$ . We illustrate these results with simulations.
The capital structure of hospitals and reimbursement policy

Abstract Empirical research has shown that hospitals have higher than average leverage, the extent of leverage is related to the extent of cost-based reimbursement, and not-for-profit hospitals are not as highly levered as their for-profit counterparts. Previous theoretical work does not unambiguously predict all of these results. This article develops a model of reimbursement policy and proves that, if reimbursement follows the indicated pattern, the Modigliani-Miller capital structure irrelevance theorem fails to hold and, given reasonable restrictions upon the utility functions of not-for-profit donor/investors, each of the empirically observed results would be expected ex ante.
Geometric control of failure behavior in perforated sheets

Adding perforations to a continuum sheet allows new modes of deformation, and thus modifies its elastic behavior. The failure behavior of such a perforated sheet is explored, using a model experimental system: a material containing a one-dimensional array of rectangular holes. In this model system, a transition in failure mode occurs as the spacing and aspect ratio of the holes are varied: rapid failure via a running crack is completely replaced by quasistatic failure, which proceeds via the breaking of struts at random positions in the array of holes. I demonstrate that this transition can be connected to the loss of stress enhancement, which occurs as the material geometry is modified.
Ni-Catalyzed Ketene Cycloaddition: A System That Resists the Formation of Decarbonylation Side Products

Ni-phosphine complexes were used as catalysts for the cycloaddition of various ketenes and diynes. In general, 2,4-cyclohexadienones were formed instead of products arising from decarbonylation of the ketenes.
A Positive Semidefinite Approximation of the Symmetric Traveling Salesman Polytope

For a convex body B in a vector space V, we construct its approximation Pk, k =1 , 2, . . ., using an intersection of a cone of positive semidefinite quadratic forms with an affine subspace. We show that Pk is contained in B for each k. When B is the Symmetric Traveling Salesman Polytope on n cities Tn, we show that the scaling of Pk by n/k + O(1/n) contains Tn for $k \leq \lfloor n/2 \rfloor$. Membership for Pk is computable in time polynomial in n (of degree linear in k). We also discuss facets of Tn that lie on the boundary of Pk and we use eigenvalues to evaluate our bounds.
Machomatics in egonomics

Abstract Mathematics, like medieval Latin, is a medium of disputation in economics wherein those skillful in its use can subdue those who are not, independent of any substantive economic meaning. In so using mathematics, economics has shut itself off from much of the richness of economic activity that is impossible to express in the language of mathematics and from the contributions of economists, many of whom may be women, whose understanding is better communicated in the vernacular.
Triple-Coincidence with Automatic Chance Coincidence Correction

The chance coincidences in a triple-coincidence circuit are of two types - partially correlated and entirely uncorrelated. Their relative importance depends on source strength and source and detector geometry so that the total chance correction cannot, in general, be calculated. The system to be described makes use of several delays and straightforward integrated circuit logic to provide independent evaluation of the two components of the chance coincidence rate.
Turbulent Cooling Flows in Molecular Clouds

We propose that inward, subsonic flows arise from the local dissipation of turbulent motions in molecular clouds. Such "turbulent cooling flows" may account for recent observations of spatially extended inward motions toward dense cores. These pressure-driven flows may arise from various types of turbulence and dissipation mechanisms. For the example of MHD waves and turbulence damped by ion-neutral friction, sustained cooling flow requires that the outer gas be sufficiently turbulent, that the inner gas have marginal field-neutral coupling, and that this coupling decrease sufficiently rapidly with increasing density. These conditions are most likely met at the transition between outer regions ionized primarily by UV photons and inner regions ionized primarily by cosmic rays. If so, turbulent cooling flows can help form dense cores, with speeds faster than expected for ambipolar diffusion. Such motions could reduce the time needed for dense core formation and could precede and enhance the motions of star-forming gravitational infall.
The First Direct Observation of the Trifluoride Anion (F3-) in the Gas Phase

Numerous theoretical calculations predict that F{sub 3}{sup {minus}} is a stable anion; however, there has been no reported observation of this species in the gas phase. The authors now report the formation and detection of F{sub 3}{sup {minus}} by electron-capture mass spectrometry, suggest a mechanism for its formation, and present a preliminary investigation of its collision-induced dissociation (CID).
Ellipsometric surface analysis of wear tracks produced by different lubricants

Ellipsometric analyses of wear tracks in berings of M-50 steel were carried out after operation under severe conditions with different lubricant additives. The base lubricant was a synthetic ester. It was found that the surface and wear additives benzotirazole and tricresylyphosphate produced very patchy oxide layers. Dioctyldiphenylamine, a common antioxidant, on the other hand produced smoother films. The analyses were performed with a specially designed and constructed ellipsometer of very high (20 micron) spatial resolution. The results are consistent with data obtained by Auger electron spectroscopy.
Implications of Atmospheric Differential Refraction for Adaptive Optics Observations

Many adaptive optics systems operate by measuring the distortion of the wave front in one wavelength range and performing the scientific observations in a second, different wavelength range. One common technique is to measure wave front distortions at wavelengths less than ~1 μm while operating the science instrument at wavelengths greater than ~1 μm. The index of refraction of air decreases sharply from shorter visible wavelengths to near-infrared wavelengths. Therefore, because the adaptive optics system is measuring the wave front distortion in one wavelength range and the science observations are performed at a different wavelength range, residual image motion occurs and the maximum exposure time before smearing of the image can be significantly limited. We demonstrate the importance of atmospheric differential refraction, present calculations to predict the effect of atmospheric differential refraction, and finally discuss the implications of atmospheric differential refraction for several current and proposed observatories.
The effect of entry and information costs on oral versus sealed-bid auctions

Abstract At equilibrium with respect to bids, entry and information acquisition, oral auctions can generate significantly more revenue than sealed-bid auctions even in the case of independently-distributed privately-known values.