cssi/SciSciGPT-SciSciNet huggingface dataset:
Subwavelength Nanopatch Cavities for Semiconductor Plasmon Lasers

We propose and analyze a family of nanoscale cavities for electrically pumped surface-emitting semiconductor lasers that use surface plasmons to provide optical mode confinement in cavities which have dimensions in the 100-300-nm range. The proposed laser cavities are in many ways nanoscale optical versions of micropatch antennas that are commonly used at microwave/RF frequencies. Surface plasmons are not only used for mode confinement but also for output beam shaping to realize single-lobe far-field radiation patterns with narrow beam waists from subwavelength size cavities. We identify the cavity modes with the largest quality factors and modal gain, and show that in the near-IR wavelength range (1.0-1.6 mum) cavity losses (including surface plasmon losses) can be compensated by the strong mode confinement in the gain region provided by the surface plasmons themselves and the required material threshold gain values can be smaller than 700 cm-1.
Interregional transfers and the smoothing of provincial expenditure in China

Abstract Interregional transfers can smooth shocks to regional revenue and prevent spending from varying across time. This paper estimates the amounts of expenditure smoothing provided by interregional net transfers to China's provinces over the 1952–2001 period. The findings indicate that net transfers minimized the volatility of provincial expenditure by cushioning a relatively large fraction of province-specific revenue shocks. However, aggregate shocks to revenue diminished the amount of smoothing, and extrabudgetary funds increased expenditure volatility. Rich provinces were better insured against province-specific revenue shocks than poor provinces. The cross-sectional disparity in expenditure smoothing widened dramatically after 1994.
How Talking Became Human Subjects Research: The Federal Regulation of the Social Sciences, 1965–1991

In universities across the United States, institutional review boards, or IRBs, claim that they have the moral and legal authority to control the work of researchers in the humanities and social sciences. While IRBs may claim powers independent of federal regulations, they invariably point to these regulations as a key source of their authority. This article draws on previously untapped manuscript materials in the National Archives to trace the history of the federal regulation of social science research. Officials raised sincere concerns about dangers to participants in social science research, especially the unwarranted invasion of privacy as a result of poorly planned survey and observational research. On the other hand, the application of the regulations to the social sciences was far less careful than was the development of guidelines for biomedical research. Regulators failed to define the problem they were trying to solve, then insisted on a protective measure borrowed from biomedical research without investigating alternatives.
Cooling rates in the lower crust of the Oman ophiolite: Ca in olivine, revisited

Debate over the mechanism of accretion of the lower oceanic crust has centered around the gabbro glacier and the sheeted sills models. The thermal profile of the crust, specifically the roles of hydrothermal circulation and cooling rate, is a key component in distinguishing between these two models. Results of this study show no systematic variation of cooling rate with depth in the lower crust of the Khafifah section in the Wadi Tayin massif of the Oman ophiolite. Additionally, very high rates recorded near the base of the crust suggest that hydrothermal circulation plays an important role in the removal of heat throughout the crust. While the conclusions presented here do not rule out the possibility of accretion by gabbro glacier, they do contradict the initial tenet of the gabbro glacier model – convective heat loss by hydrothermal circulation can penetrate to Moho depths and crystallization is not, by necessity, constrained to the upper crust. On the basis of these results it can be concluded that the sheeted sills model is a thermally viable mechanism for accretion of oceanic lower crust.
Assessing the relative power of structural break tests using a framework based on the approximate Bahadur slope

Abstract We compare the asymptotic relative efficiency of the Exp, Mean, and Sup functionals of the Wald, LM and LR tests for structural change analyzed by Andrews [Andrews, D.W.K., 1993. Tests for parameter instability and structural change with unknown change point. Econometrica 61, 821–856.] and Andrews and Ploberger [Andrews, D.W.K., Ploberger, W., 1994. Optimal tests when a nuisance parameter is present only under the alternative. Econometrica 62, 1383–1414.]. We derive the approximate Bahadur slopes of these tests using large deviations techniques. These show that tests based on the Mean functional are inferior to those based on the Sup and Exp when using the same base statistic. Also, for a given functional, the Wald-based test dominates the LR-based test, which dominates the LM-based one. We show that the Sup- and Mean-type tests satisfy Wieand’s [Wieand, H.S., 1976. A Condition under which the Pitman and Bahadur approaches to efficiency coincide. Annals of Statistics 4, 1003–1011.] condition so that their slopes yield the limiting (as the size tends to zero) asymptotic relative Pitman efficiency (whether this holds for the Exp-type tests still remains a conjecture). Using this measure of efficiency, the Mean-type tests are also inferior to the Sup. We also compare tests based on the Wald and LM statistics modified with a HAC estimator. In this case, the inferiority of the LM-based tests is especially pronounced. The relevance of our theoretical results in finite samples is assessed via simulations. Our results are in contrast to those obtained by the authors–in the second reference cited above–based on a local asymptotic framework, and our analysis thereby reveals its potential weaknesses in the context of structural change problems.
GUTZWILLER APPROXIMATION IN DEGENERATE HUBBARD MODELS

The details of the Generalized-Gutzwiller-Approximation in degenerate Hubbard models are presented. It is found that the metal-insulator transition occurs at a finite correlation Uc when the average number of electrons per lattice site is an integer. A derivation is given for the general expression of Uc(x, N) which reproduces all previously known Gutzwiller solutions, including that of the boson Hubbard model. The Uc depends sensitively on both the band degeneracy N and the filling x. Effects of the lattice structure on the metal-insulator transition and the effective mass are discussed.
Magnetism of hexagonal Mn1.5X0.5Sn (X = Cr, Mn, Fe, Co) nanomaterials

Mn1.5X0.5Sn (X = Cr, Mn, Fe, Co) nanomaterials in the hexagonal Ni2In-type crystal structure have been prepared using arc-melting and melt spinning. All the rapidly quenched Mn1.5X0.5Sn alloys show moderate saturation magnetizations with the highest value of 458 emu/cm3 for Mn1.5Fe0.5Sn, but their Curie temperatures are less than 300 K. All samples except the Cr containing one show spin-glass-like behavior at low temperature. The magnetic anisotropy constants calculated from the high-field magnetization curves at 100 K are on the order of 1 Merg/cm3. The vacuum annealing of the ribbons at 550 °C significantly improved their magnetic properties with the Curie temperature increasing from 206 K to 273 K for Mn1.5Fe0.5Sn.
Analysis and control of a three-degree-of-freedom robot platform

Abstract This paper describes the analysis and design of a robot platform with two drive wheels, each with an independent steering mechanism resulting in three independent degrees of motion. The kinematic and inverse kinematic analyses are derived in detail. An adaptive controller is designed to compensate for large inertial variations and to satisfy the velocity (nonholonomic) constraints.
Variational splines on Riemannian manifolds with applications to integral geometry

We extend the classical theory of variational interpolating splines to the case of compact Riemannian manifolds. Our consideration includes in particular such problems as interpolation of a function by its values on a discrete set of points and interpolation by values of integrals over a family of submanifolds. The existence and uniqueness of interpolating variational spline on a Riemannian manifold is proven. Optimal properties of such splines are shown. The explicit formulas of variational splines in terms of the eigen functions of Laplace-Beltrami operator are found. It is also shown that in the case of interpolation on discrete sets of points variational splines converge to a function in C^k norms on manifolds. Applications of these results to the hemispherical and Radon transforms on the unit sphere are given.
Experimental Investigation of a Forced-Response Condition in a Multistage Compressor

It is nearly impossible to remove all resonant crossings from the operating range of a multistage compressor; thus, designers rely on models to predict the resonant response amplitude to determine if the crossing is acceptable. An accurate model can reduce unexpected forced-response problems encountered during engine testing. Although work has been done to improve such models, the confidence in these models comes from validation with quality test data including both the aerodynamic forcing function and the response of the blade row. Recent trends in turbomachinery, including higher blade loadings and use of integrally bladed rotors, lead to increased potential for forced-response issues. The Campbell diagram crossing for the excitation associated with the upstream and downstream vane rows on the embedded rotor first torsion vibratory mode is measured. The rotor response will be characterized with tip-timing measurements and the aerodynamic forcing functions measured. Unsteady casing pressures over the vib...
Bruhat order, smooth Schubert varieties, and hyperplane arrangements

The aim of this article is to link Schubert varieties in the flag manifold with hyperplane arrangements. For a permutation, we construct a certain graphical hyperplane arrangement. We show that the generating function for regions of this arrangement coincides with the Poincare polynomial of the corresponding Schubert variety if and only if the Schubert variety is smooth. We give an explicit combinatorial formula for the Poincare polynomial. Our main technical tools are chordal graphs and perfect elimination orderings.
Electromagnetic pair production in relativistic heavy-ion collisions

We survey the phenomenon of pair production by the transient electromagnetic fields produced in relativistic heavy-ion collisions, as it impinges upon atomic, nuclear, and particle physics, and the design of accelerators and detectors. The subject is naturally divided between coherent production in peripheral collisions, and incoherent production in central collisions. We discuss examples illustrating both regimes.
DEOXYGENATION OF 1,4-EPOXIDES BY GRIGNARD REAGENTS

Abstract Freshly prepared Grignard reagents in refluxing THF smoothly deoxygenate benzo-fused 1,4-dihydro-1,4-epoxides to afford the corresponding naphthalenes and anthracenes in good yields.
Mesmerism in New Orleans: 1845-1861.

Abstract Mesmerism was generally rejected by the medical establishment in Europe and the United States until Jean-Martin Charcot introduced it at the Salpětriere in the 1870's. Nonetheless, a well-organized and active mesmer society flourished in New Orleans from 1845 to 1861. The origins of the society, composition of the membership, its activities, and its relationship with the established medical community are presented.
Ground States of Quantum Antiferromagnets in Two Dimensions

Abstract We explore the ground states and quantum phase transitions of two-dimensional, spin S=1/2, antiferromagnets by generalizing lattice models and duality transforms introduced by Sachdev and Jalabert (1990, Mod. Phys. Lett. B4, 1043). The minimal model for square lattice antiferromagnets is a lattice discretization of the quantum nonlinear sigma model, along with Berry phases which impose quantization of spin. With full SU(2) spin rotation invariance, we find a magnetically ordered ground state with Neel order at weak coupling and a confining paramagnetic ground state with bond charge (e.g., spin Peierls) order at strong coupling. We study the mechanisms by which these two states are connected in intermediate coupling. We extend the minimal model to study different routes to fractionalization and deconfinement in the ground state, and also generalize it to cases with a uniaxial anisotropy (the spin symmetry groups is then U(1)). For the latter systems, fractionalization can appear by the pairing of vortices in the staggered spin order in the easy-plane; however, we argue that this route does not survive the restoration of SU(2) spin symmetry. For SU(2) invariant systems we study a separate route to fractionalization associated with the Higgs phase of a complex boson measuring noncollinear, spiral spin correlations: we present phase diagrams displaying competition between magnetic order, bond charge order, and fractionalization, and discuss the nature of the quantum transitions between the various states. A strong check on our methods is provided by their application to S=1/2 frustrated antiferromagnets in one dimension: here, our results are in complete accord with those obtained by bosonization and by the solution of integrable models.
Double scaling limit in the random matrix model: The Riemann-Hilbert approach

We prove the existence of the double scaling limit in the unitary matrix model with quartic interaction, and we show that the correlation functions in the double scaling limit are expressed in terms of the integrable kernel determined by the ψ function for the Hastings-McLeod solution to the Painleve II equation. The proof is based on the Riemann-Hilbert approach, and the central point of the proof is an analysis of analytic semiclassical asymptotics for the ψ function at the critical point in the presence of four coalescing turning points. © 2003 Wiley Periodicals, Inc.
Computational leakage: Grover's algorithm with imperfections

We study the effects of dissipation or leakage on the time evolution of Grover's algorithm for a quantum computer. We introduce an effective two-level model with dissipation and randomness (imperfections), which is based upon the idea that ideal Grover's algorithm operates in a 2-dimensional Hilbert space. The simulation results of this model and Grover's algorithm with imperfections are compared, and it is found that they are in good agreement for appropriately tuned parameters. It turns out that the main features of Grover's algorithm with imperfections can be understood in terms of two basic mechanisms, namely, a diffusion of probability density into the full Hilbert space and a stochastic rotation within the original 2-dimensional Hilbert space.
Hirota quadratic equations for the extended Toda hierarchy

The extended Toda hierarchy (ETH) was introduced by E. Getzler [Ge] and independently by Y. Zhang [Z] in order to describe an integrable hierarchy that governs the Gromov-Witten invariants of CP1. The Lax-type presentation of the ETH was given in [CDZ]. In this article, we give a description of the ETH in terms of tau functions and Hirota quadratic equations (HQEs), also known as Hirota bilinear equations (HBEs). A new feature here is that the Hirota equations are given in terms of vertex operators taking values in the algebra of differential operators on the affine line
Low viscosity channels and the stability of long wavelength convection

Abstract Mantle convection simulations with a low viscosity channel, akin to the Earth's asthenosphere, are characterized by long wavelength flow structure. Boundary layer theory predicts that as the viscosity of the channel decreases, the wavelength that maximizes heat transfer increases. As a pattern selection criterion, this analysis is not complete. It provides no mechanism to relate the optimal heat transfer wavelength to the wavelength that is realized in nature. We present numerical simulation suites, for bottom and internally heated end-members, to demonstrate that the cell wavelengths that maximize heat transfer are also the most stable. This does not rule out the possibility of multiple wavelengths being realizable but it does imply that wavelengths near the stability peak will be preferred and, for the configurations we explore, the stability peak corresponds to the energetically most efficient flow configuration.
Cyanide-Melt Synthesis of Reduced Molybdenum Selenide Clusters

The tightly cross-linked Mo3nSe3n+2 (n = 2, 3, ...∞) cluster compounds react with alkali metal cyanide or cyanide salt mixtures at temperatures of 450−675 °C to yield cyanide-terminated molybdenum chalcogenide clusters, [Mo6Se8(CN)6]n- (1n-) (n = 6, 7) and [Mo4Se4(CN)12]8- (28-). The process by which discrete 1n- clusters are excised from a CN-linked intermediate chain compound, K6Mo6Se8(CN)5 (3), was investigated, and the cubane cluster 27- plays an essential role. An efficient one-step synthesis for Na8[28-] is presented. These clusters are stable in basic aqueous solutions. Cyclic voltammetric (CV) measurements in basic aqueous media show multiple reversible redox waves corresponding to 16-/7-, 17-/8-, and 18-/9- redox couples with half-wave potentials of E1/2 = −0.442, −0.876, and −1.369 V, respectively, versus SHE. Half-wave potentials (E1/2) for the [Mo4Se4(CN)12]6-/7- and [Mo4Se4(CN)12]7-/8- couples are 0.233 and −0.422 V, respectively, versus SHE. The 28- compounds are K7Na[28-]·5H2O·MeOH, Cs7Na4[...
Spectral Methods for Parameterized Matrix Equations

We apply polynomial approximation methods—known in the numerical PDEs context as spectral methods—to approximate the vector-valued function that satisfies a linear system of equations where the matrix and the right-hand side depend on a parameter. We derive both an interpolatory pseudospectral method and a residual-minimizing Galerkin method, and we show how each can be interpreted as solving a truncated infinite system of equations; the difference between the two methods lies in where the truncation occurs. Using classical theory, we derive asymptotic error estimates related to the region of analyticity of the solution, and we present a practical residual error estimate. We verify the results with two numerical examples.
Investigating the Drivers of Consumer Cross-Category Learning for New Products Using Multiple Data Sets

Consumer new product adoption and preference evolution or learning may be influenced by intrinsic or internal factors (e.g., usage experiences, personal characteristics), external influences (e.g., social effects, media), and marketing activities of the firm. Moreover, the preference evolution in a certain category can spill over to other categories; i.e., consumers can exhibit cross-category learning. In this paper, we develop a multicategory framework to analyze the role of the above elements in the formation and evolution of consumer preferences across categories. We analyze these elements by employing multiple data sets, i.e., by combining revealed preference data (from scanner panel), stated data (from surveys measuring consumer lifestyle variables and demographics), and external influences (e.g., media mentions) in a completely heterogeneous framework while considering other facets of the learning process. By jointly estimating the model for organic purchases in six distinct food categories, we also explore the role of category differences. Results show that consumer new product adoption and learning is indeed impacted significantly and to various degrees by the aforementioned factors. We show how, by selectively encouraging purchases under various scenarios, firms can accelerate the learning process, not only for the focal category but also for other categories, thereby realizing considerable incremental profits. These results can be used by both manufacturers and retailers for more efficient allocation of marketing budgets across (new) products.
Free Parking at Christmas Is Not a Tragedy of the Commons

In his famous 1968 article, Garrett Hardin used the municipal practice of suspending the use of parking meters for Christmas shoppers as an example of how short-sighted politicians create a "Tragedy of the Commons." I argue that this example was not well chosen. Because shoppers spend more time in stores during December and because conventional parking meters are not easily recalibrated, free parking and the nonprice rationing that downtown organizations adopt are actually efficient responses to seasonal demand shifts.
Recognition-directed assembly of salt-binding [2]rotaxanes

Abstract This paper describes the synthesis of four isomeric [2]rotaxanes and includes the first example of a salt binding [2]rotaxane with the following key observations. In polar solvents the [2]rotaxane undergoes a relatively slow co-conformational exchange that produces broad signals in the 1H NMR spectrum. Upon complexation with K+, the NMR signals sharpen apparently because the rotaxane adopts a single co-conformation. In contrast, the binding of Cl− has no effect on the rotaxane's dynamic behavior. Although the binding of K+ induces a preorganization of the [2]rotaxane it does not change the rotaxane/Cl− association constant. The paper finishes with a discussion of the future directions of this work.
Analytic Results for Gaussian Wave Packets in Four Model Systems: II. Autocorrelation Functions

The autocorrelation function, A(t), measures the overlap (in Hilbert space) of a time-dependent quantum mechanical wave function, ψ(x, t), with its initial value, ψ(x, 0). It finds extensive use in the theoretical analysis and experimental measurement of such phenomena as quantum wave packet revivals. We evaluate explicit expressions for the autocorrelation function for time-dependent Gaussian solutions of the Schrodinger equation corresponding to the cases of a free particle, a particle undergoing uniform acceleration, a particle in a harmonic oscillator potential, and a system corresponding to an unstable equilibrium (the so-called ‘inverted’ oscillator.) We emphasize the importance of momentum-space methods where such calculations are often more straightforwardly realized, as well as stressing their role in providing complementary information to results obtained using position-space wavefunctions.
Arp 119: A High-Speed Galaxy Collision With Episodic Star Formation

Colliding galaxies are excellent laboratories for studying galactic evolution and global star formation. Computer simulations of galaxy collisions, in which at least one galaxy has a significant gaseous component, show the production of density enhancements and shock waves in the interstellar medium. These high-density regions coincide with the locations of recent, large-scale star formation in observations of some real colliding galaxies. Thus, combined n-body/hydrodynamic computer simulations can be used to explore the history and conditions of star-forming regions in colliding galaxies. We compare multiwavelength observations of the Arp 119 system with a combined n-body/SPH simulation of colliding galaxies. Most of the observations used here are gleaned from the literature. Additionally, we obtained new near-infrared (J- and H-band) observations of this system, using the NIRIM camera at the Mount Laguna observatory. These new data add information about the underlying, old stellar population. Arp 119 (CPG 29) is comprised of a southern member, Arp 119S (Mrk 984), which has an extremely disturbed appearance, and a northern member, Arp 119N, a gas-poor elliptical. The morphology of both members can be fitted well by a simulation in which a gas-rich disk galaxy has been impacted by an equal-mass elliptical that had a trajectory approximately perpendicular to the plane of the disk and passed through the disk slightly off-center. From our comparison, we find that the progression of recent large-scale star formation in this galaxy can be accounted for by a single outwardly propagating collision-induced density wave in the gas. We deduce that the star formation rate in this density wave was not a smooth function of time but that, so far, three major episodes of star formation have occurred at roughly 25-30 Myr intervals. An initial burst took place very soon after the peak of the collision between the two galaxies, and the latest burst is still ongoing. The fit of the simulations to the observations indicates that this collision occurred approximately 71 Myr ago. At the current, projected separation of 53 kpc (assuming H0 = 75 km s-1 Mpc-1), we obtain a current relative space velocity between the two galaxies of approximately 850 km s-1. This is strong evidence that the collision partner was Arp 119N and not some currently more distant galaxy. Furthermore, the high relative velocity of the pair and the paucity of gas currently to be found in the elliptical may explain the very high velocity gas observed in the greatly disturbed disk galaxy, Arp 119S.
Velocity field of a cylinder in the wake of a rotor in forward flight

The rotor and the airframe of a rotorcraft can have severe effects on each other because of flowfield interactions. Data on flowfield characteristics have been obtained using laser velocimetry in an attempt to identify and interpret the features of such interactions. This paper summarizes previous results on the flowfield of the rotor and then describes the effects of the rotor wake on the flowfield around an airframe model. A circular cylinder with a hemispherical nose is used as the airframe model and is instrumented with static pressure taps and flush-mounted microphones. A two-bladed teetering rotor is suspended above it in a wind tunnel. The periodic and time-averaged velocity fields are measured along lines parallel to the airframe axis at a rotor advance ratio of 0.1 and a rotor tip Mach number of 0.29. The dominant features in the velocity distribution over the airframe are seen to be linked to vortex interactions with the airframe surface. The tip vortex and the trailing vortex sheet are seen to be displaced in opposite directions by the airframe. Secondary vortex generation phenomena are observed near the airframe surface during vortex interaction.
A Krull–Schmidt theorem for one-dimensional rings of finite Cohen–Macaulay type

Abstract This paper determines when the Krull–Schmidt property holds for all finitely generated modules and for maximal Cohen–Macaulay modules over one-dimensional local rings with finite Cohen–Macaulay type. We classify all maximal Cohen–Macaulay modules over these rings, beginning with the complete rings where the Krull–Schmidt property is known to hold. We are then able to determine when the Krull–Schmidt property holds over the non-complete local rings and when we have the weaker property that any two representations of a maximal Cohen–Macaulay module as a direct sum of indecomposables have the same number of indecomposable summands.
Device Concepts Based on Spin-Dependent Transmission in Semiconductor Heterostructures

We examine zero-magnetic-field spin-dependent transmission in nonmagnetic semiconductor heterostructures with structural inversion asymmetry (SIA) and bulk inversion asymmetry (BIA), and report spin devices concepts that exploit their properties. Our modeling results show that several design strategies could be used to achieve high spin filtering efficiencies. The current spin polarization of these devices is electrically controllable, and potentially amenable to high-speed spin modulation, and could be integrated in optoelectronic devices for added functionality.
Heat Transfer Mechanisms During Flow Boiling in Microchannels

The forces due to surface tension and momentum change during evaporation, in conjunction with the forces due to viscous shear and inertia, govern the two-phase flow patterns and the heat transfer characteristics during flow boiling in microchannels. These forces are analyzed in this paper, and two new nondimensional groups, K1 and K2 , relevant to flow boiling phenomenon are derived. These groups are able to represent some of the key flow boiling characteristics, including the CHF. In addition, a mechanistic description of the flow boiling phenomenon is presented. The small hydraulic dimensions of microchannel flow passages present a large frictional pressure drop in single-phase and two-phase flows. The small hydraulic diameter also leads to low Reynolds numbers, in the range 100‐1000, or even lower for smaller diameter channels. Such low Reynolds numbers are rarely employed during flow boiling in conventional channels. In these low Reynolds number flows, nucleate boiling systematically emerges as the dominant mode of heat transfer. The high degree of wall superheat required to initiate nucleation in microchannels leads to rapid evaporation and flow instabilities, often resulting in flow reversal in multiple parallel channel configuration. Aided by strong evaporation rates, the bubbles nucleating on the wall grow rapidly and fill the entire channel. The contact line between the bubble base and the channel wall surface now becomes the entire perimeter at both ends of the vapor slug. Evaporation occurs at the moving contact line of the expanding vapor slug as well as over the channel wall covered with a thin evaporating film surrounding the vapor core. The usual nucleate boiling heat transfer mechanisms, including liquid film evaporation and transient heat conduction in the liquid adjacent to the contact line region, play an important role. The liquid film under the large vapor slug evaporates completely at downstream locations thus presenting a dryout condition periodically with the passage of each large vapor slug. The experimental data and high speed visual observations confirm some of the key features presented in this paper. @DOI: 10.1115/1.1643090#
Social security reforms and poverty among older dual-earner couples.

Existing retirement studies have, in the main, focused only on labor supply decisions of couples in which the husband has been the sole earner. This paper extends the focus of analysis to examine retirement among dual-earner couples. It further develops a framework for assessing how several past and prospective Social Security reforms might be expected to affect older working couples' retirement ages and retirement incomes. Two questions are addressed in some detail: (1) What are the likely effects of various changes in Social Security rules on the retirement decisions of older working women and their husbands? and (2) How might these changes alter the incidence of poverty among retired dual-earner couples? Empirical evidence from the United States suggests that many benefit reforms currently being discussed in policy circles will enhance Social Security system revenues, but will also worsen the economic status of an important segment of dual-earner couples.
Quantifying Uncertainty for Coherent Structures

Abstract Field Alignment is a useful and often necessary preprocessing step in contemporary geophysical state and parameter estimation of coherent structures. In an advance, we introduce a new framework for using Field Alignment to quantify uncertainty from an ensemble of coherent structures. Our method, called Coalescence , discovers the mean field under non-trivial misalignments of fields with complex shapes, which is especially diffcult to calculate in the presence of sparse observations. We solve the associated Field Alignment problem using novel constraints derived from turbulent displacement spectra. In conjunction with a continuation method called Scale Cascaded Alignment (SCA), we are able to extract simpler explanations of the error between fields before cascading to more complex deformation solutions. For coherent structures, SCA and Coalescence have the potential to change the way uncertainty is quantified and data is assimilated. We illustrate utility here in a Nowcasting application.
Mechanisms to explain damage growth in optical materials

Damage growth in optical materials used in large aperture laser systems is an issue of great importance when determining component lifetime and therefore cost of operation. Understanding the mechanisms and photophysical processes associated with damage growth are important in order to devise mitigation techniques. In this work we examined plasma-modified material and cracks for their correlation to damage growth on fused silica and DKDP samples. We employ an in-situ damage testing optical microscope that allows the acquisition of light scattering and fluorescence images of the area of interest prior to, and following exposure to a high fluence, 355-nm, 3-ns laser pulse. In addition, high-resolution images of the damage event are recorded using the associated plasma emission. Experimental results indicate that both aforementioned features can initiate plasma formation at fluences as low as 2 J/cm{sup 2}. The intensity of the recorded plasma emission remains low for fluences up to approximately 5 J/cm{sup 2} but rapidly increases thereafter. Based on the experimental results, we propose as possible mechanisms leading to damage growth the initiation of avalanche ionization by defects at the damage modified material and presence of field intensification due to cracks.
THE SOURCE OF FIVE-MINUTE PERIOD PHOTOSPHERIC UMBRAL OSCILLATIONS

Many types of velocity oscillations are observed in the umbrae and penumbrae of sunspots. We describe a project aimed at determining the source of one type of oscillation, the five-minute period photospheric umbra oscillations. The project uses imaging spectroscopy of spot umbrae, measuring the Doppler shift of pure umbral absorption lines to study the temporal and spatial properties of these oscillations. The Mees CCD (MCCD) instrument is an imaging spectroscopy device which uses the 25-cm coronagraph telescope and the 3.0-m coude spectrograph at Mees Solar Observatory (MSO) on Haleakala, Maui. The instrument works with resolving power up to R ~ 200,000 with significant throughput from lambda-3934 A (Ca II K) to lambda ~ 10,000 A. A fast guiding active mirror stabilizes the image during observations. A rapidly writing magnetic tape storage system allows observations to be recorded at 256 kbytes s-1. We observed the oscillations in the umbrae of two sunspots using the MCCD imaging spectrograph. We observed the Doppler shifts of 18 molecular lines in the umbrae for roughly 50 hours in each spot during the interval of 11 to 16 May 1991. We find no simple correlation between the velocity measured with molecular lines and the velocity measured using two iron lines. We remove solar rotation, image drift, and interpolate all the data onto an even time grid. We perform four spatial analyses of the umbral velocity and find (1) there is more power traveling toward the center of the umbrae than leaving the center of the umbrae (this provides a direct measure of the absorption of p-modes by the sunspot umbrae) (2) the umbral oscillations have spatial and temporal characteristics indistinguishable from the quiet-sun oscillations, (3) a Fourier-Bessel analysis shows no obvious resonant frequencies which might represent natural oscillation modes of the sunspot umbrae, and (4) the centers of the umbrae have less RMS velocity than the edge of the umbrae. >From these analyses we conclude that the photospheric umbral oscillations are driven by an external source and that source is the global p-mode oscillations.
Synthesis of N(3‐dimethylaminopropyl)‐6‐substituted naphtho[2,1‐b]thiophene‐4‐carboxamides

A series of N-(3-dimethylaminopropyl)-6-substituted naphtho[2,1-b]thiophenes-4-carboxamides have been synthesized. 6-Substituted naphtho[2,1-b]thiophene-4-carboxylic acids were obtained upon oxidative-photo-cyclization of α-(2-thienyl)-β-arylacrylic acids. The naphtho[2,1-b]thiophene carboxylic acids were converted to the corresponding amides through their acid chlorides or, in one case, by use of 1,1-carbonyldiimidazole coupling of the amine and the acid.
Results from laser sheet visualization of a periodic rotor wake

A laser sheet has been applied to the visualization of a periodic rotor wake produced by a model rotorcraft in forward flight. A stiff, two-bladed teetering rotor is mounted independently of an idealized airframe consisting of an instrumented circular cylinder with a hemispherical nose. The model was installed in a wind tunnel, and tests were carried out at three different advance ratios (forward flight speeds) at one value of rotor collective pitch angle. The laser sheet technique enables detailed flow visualization to be carried out. Quantitative data regarding the location of the rotor tip vortex can be obtained. Results from the flow visualization confirm that the rotor wake is a complex flowfield not amenable to simple analysis. However, the details of the tip vortex geometry are both periodic and repeatable. The motion of the rotor wake in close proximity to the airframe is examined. The behavior of the tip vortex is strongly affected by the presence of the airframe. In particular, the interaction of the rotor tip vortex with the airframe results in the destruction of the vortex core; apparently the vorticity is diffused, and the vortex loses its definition. No vortex filaments appear below the airframe as identifiable flow features. Examples of airframe surface pressure data are presented and are seen to correlate well with the results from the flow visualization.
Vibration Signature Analysis of a Faulted Gear Transmission System

A comprehensive procedure in predicting faults in gear transmission systems under normal operating conditions is presented. Experimental data were obtained from a spiral bevel gear fatigue test rig at NASA/Lewis. Time-synchronous-averaged vibration data were recorded throughout the test as the fault progressed from a small single pit to severe pitting over several teeth, and finally tooth fracture. A numerical procedure based on the Wigner-Ville distribution was used to examine the time-averaged vibration data. Results from the Wigner-Ville procedure are compared to results from a variety of signal analysis techniques that include time-domain analysis methods and frequency analysis methods. Using photographs of the gear tooth at various stages of damage, the limitations and accuracy of the various techniques are compared and discussed. Conclusions are drawn from the comparison of the different approaches as well as the applicability of the Wigner-Ville method in predicting gear faults.
Acid strength of silica-supported oxide catalysts studied by microcalorimetric measurements of pyridine adsorption

Microcalorimetric measurements of the differential heat of pyridine adsorption were used to probe the distribution of acid strength on a series of silica-supported oxide catalysts. Depositing oxides of the following cations onto silica increased the acid strength of the catalyst: Ga{sup 3{plus}}, Zn{sup 2{plus}}, Al{sup 3{plus}}, Fe{sup 3{plus}}, Fe{sup 2{plus}}, Mg{sup 2{plus}}, and Sc{sup 3{plus}}. The acid strength distribution curves for the supported oxide samples showed either two or three regions of constant heat of adsorption while silica had an energetically homogeneous surface. The Ga, Al, and Sc samples were found to have both Bronsted and Lewis acidity while the remaining samples showed only Lewis acidity. Incremental adsorption of pyridine indicated that the initial region of highest heat corresponds to strong Lewis acidity while intermediate heats seemed to be due to weaker Lewis acid sites or a combination of Lewis and Bronsted acid sites. The final region of lowest heat was due to H-bonded pyridine on silica. Estimates of the entropies of adsorption were determined, providing information about the mobility of the adsorbed pyridine molecules. The initial differential heat of adsorption increases proportionally to the Sanderson electronegativity of the added oxide.
Effect of natural convection on growth velocity and morphology of dendritic ice crystals

Quantitative measurements were made of the growth rate and dimensions of ice crystals growing in pure water unencumbered by container walls. The structures which were photographed changed sequentially from disks, to perturbed disks, to disk-dendrites, to partially developed dendrites, and finally to fully developed dendrites. Therefore, the morphology of ice crystals depends on the subcooling and time elapsed from the start of free growth. Fully developed dendrites were shown by double exposure photographs to grow in a shape preserving manner with the tip propagating at constant velocity. The shape of a fully developed ice dendrite was determined by photographing it from its various planes. An elliptic paraboloid with an aspect ratio 30<R2/R1<100 most closely approximates the shape in the vicinity of the tip region. The growth velocity of the tip is invariant with time, but side branches constantly adjust their growth directions. Natural convection was found to affect the growth velocity, the overall morphology, and morphological stability.
On the Nature of Angular Momentum Transport in Nonradiative Accretion Flows

The principles underlying a proposed class of black hole accretion models are examined. The flows are generally referred to as "convection-dominated" and are characterized by inward transport of angular momentum by thermal convection and outward viscous transport, vanishing mass accretion, and vanishing local energy dissipation. In this paper, we examine the viability of these ideas by explicitly calculating the leading-order angular momentum transport of axisymmetric modes in magnetized, differentially rotating, stratified flows. The modes are destabilized by the generalized magnetorotational instability, including the effects of angular velocity and entropy gradients. It is explicitly shown that modes that would be stable in the absence of a destabilizing entropy gradient transport angular momentum outward. There are no inward-transporting modes at all, unless the magnitude of the (imaginary) Brunt-Vaisala frequency is comparable to the epicyclic frequency, a condition requiring substantial levels of dissipation. When inward-transporting modes do exist, they appear at long wavelengths, unencumbered by magnetic tension. Moreover, very general thermodynamic principles prohibit the complete recovery of irreversible dissipative energy losses, a central feature of convection-dominated models. Dissipationless flow is incompatible with the increasing inward entropy gradient needed for the existence of inward-transporting modes. Indeed, under steady conditions, dissipation of the free energy of differential rotation inevitably requires outward angular momentum transport. Our results are in good agreement with global MHD simulations, which find significant levels of outward transport and energy dissipation, whether or not destabilizing entropy gradients are present.
Selective oxidation of sulfides to sulfoxides and sulfones by microwave thermolysis on wet silica-supported sodium periodate

Abstract A variety of symmetrical and unsymmetrical sulfides have been selectively and expeditiously oxidized to either sulfoxides or sulfones in good yields using wet silica-supported sodium periodate under microwave thermolysis conditions.
Search parameters for the remote detection of extraterrestrial life

Abstract Direct consequences of biological activity (biosignatures) and alterations of the geological environment due to biological processes (geosignatures) are currently known only for the planet Earth. However, geoindicators remotely detectable by robotic technology have revealed a number of sites in the solar system where conditions compatible with the support of life may exist. By focusing on a search for energy gradients, complex chemistry, liquids that may act as solvents, atmospheres, and indicators of geological differentiation, robotic exploration of the solar system and beyond should lead to fruitful targets in the search for extraterrestrial life. An analysis of all major solar system bodies for these parameters suggests that Mars, Titan, and the Galilean satellites should be given the highest priority in the search for extraterrestrial life in our solar system. Extending them to other bodies in the solar system, however, draws attention to Io, Triton, Titania, Enceladus, and Iapetus, among others, as worthy of greater attention.
Nonlinear development of speaking rate in child-directed speech

Abstract This study investigates the role of child-directed speech (CDS) in language acquisition by re-evaluating the old claim that mothers adapt their speech over the course of child language development. The specific hypothesis tested is that there may be quantal changes in certain properties of CDS such as speaking rate around the time children reach major linguistic milestones. The developmental path of CDS speaking rate was analyzed in 25 mother–child pairs from longitudinal corpora in CHILDES database ( MacWhinney, 2000 ). A parallel analysis was also made on the development of speaking rate in the child as well as the mean length of utterance (MLU) in mother and child. The total number of utterances analyzed approximates one million. The findings reveal that CDS speaking rate changes nonlinearly with a shift occurring early in the multiword stage. There is also some indication that another breakpoint might be present around the onset of child speech production. A parallel pattern of nonlinearity is also observed in the speaking rate of the child and the MLU of both mother and child. The results support the notion that CDS is adapted to the changing needs of the language-learning child, which could reflect its facilitative role in child language acquisition.
Benefits of Power Electronic Interfaces for Distributed Energy Systems

With the increasing use of distributed energy (DE) systems in industry and its technological advancement, it is becoming more important to understand the integration of these systems with the electric power systems. New markets and benefits for DE applications include the ability to provide ancillary services, improve energy efficiency, enhance power system reliability, and allow customer choice. Advanced power electronic (PE) interfaces will allow DE systems to provide increased functionality through improved power quality and voltage/volt-ampere reactive (VAR) support, increase electrical system compatibility by reducing the fault contributions, and flexibility in operations with various other DE sources, while reducing overall interconnection costs. This paper will examine the system integration issues associated with DE systems and show the benefits of using PE interfaces for such applications.
The Real Value of Money under Endogenous Beliefs

Abstract We study an overlapping generations model where the level of confidence in money evolves endogenously as a function of aggregate real money balances. The economy can display multiple stationary equilibria where the aggregate bubble on money is stochastic and the level of confidence is partial. Steady states can be ranked by the degree of confidence, with more inefficiency being associated with less confidence. It is only under certain restrictions that the Golden Rule constitutes a steady state for the system. Autarky becomes unstable and complex dynamics such as cycles and chaos can emerge even under gross substitutability. Journal of Economic Literature Classification Numbers: D50, E10, E40.
Synthesis of an elaborated heliquinomycin isocoumarin moiety

Synthesis of a fully functionalized isocoumarin moiety 2 of DNA helicase inhibitor heliquinomycin (1) is reported. The key step is a modified condensation reaction of diethyl bromomalonate with readily accessible phthalaldehydic acid derivative 3. Introduction of an allyl side chain is accomplished by Claisen rearrangement of allyl phenyl ether 8.
Room temperature aryl trifluoromethylation via copper-mediated oxidative cross-coupling.

A method for the room temperature copper-mediated trifluoromethylation of aryl and heteroaryl boronic acids has been developed. This protocol is amenable to normal benchtop setup and reactions typically require only 1−4 h. Proceeding under mild conditions, the method tolerates a range of functional groups, allowing access to a variety of trifluoromethylarenes.