cssi/SciSciGPT-SciSciNet huggingface dataset:
Resolved Spectroscopy of M Dwarf/L Dwarf Binaries. I. DENIS J220002.05−303832.9AB

We present the discovery of the common proper motion M9+L0 binary DENIS J220002.05-303832.9AB, identified serendipitously with the SpeX near-infrared imager/spectrograph. Spectral types are derived from resolved near-infrared spectroscopy of the well-separated (109 ± 006) components and comparison to equivalent data for M and L dwarf spectral standards. Physical association is deduced from the angular proximity of the sources, their common proper motion, and their similar spectrophotometric distances (35 ± 2 pc). The estimated distance of this pair implies a projected separation of 38 ± 3 AU, wider than typical separations for other M dwarf/L dwarf binaries but consistent with the maximum separation/total system mass trend previously identified by Burgasser et al. We discuss the DENIS 2200-3038AB system in context with other low-mass binaries and its role in the study of dust formation processes and activity trends across the transition between the M and L dwarf spectral classes.
The turbulent magnetic prandtl number of mhd turbulence in disks

The magnetic Prandtl number PrM is the ratio of viscosity to resistivity. In astrophysical disks the diffusion of angular momentum (viscosity) and magnetic fields (resistivity) are controlled by turbulence. Phenomenological models of the evolution of large-scale poloidal magnetic fields in disks suggest that the turbulent magnetic Prandtl number PrM,T controls the rate of escape of vertical field from the disk; for PrM,T ≤ R/H vertical field diffuses outward before it can be advected inward by accretion. Here we measure field diffusion and angular momentum transport due to MHD turbulence in a shearing box, and thus PrM,T, by studying the evolution of a sinusoidal perturbation in the magnetic field that is injected into a turbulent background. We show that the perturbation is always stable, decays approximately exponentially, has decay rate k 2, and that the implied PrM,T ~ 1.
Stellar populations in bulges of spiral galaxies

We present line strengths in the bulges and inner discs of 38 galaxies in the local Universe, including several galaxies whose bulges were previously identified as being disc like in their colours or kinematics, to see if their spectral properties reveal evidence for secular evolution. We find that red bulges of all Hubble types are similar to luminous ellipticals in their central stellar populations. They have large luminosity-weighted ages, metallicities, and α/Fe ratios. Blue bulges can be separated into a metal-poor class that is restricted to late types with small velocity dispersion and a young, metal-rich class that includes all Hubble types and velocity dispersions. Luminosity-weighted metallicities and α/Fe ratios are sensitive to central velocity dispersion and maximum disc rotational velocity. Red bulges and ellipticals follow the same scaling relations. We see differences in some scaling relations between blue and red bulges and between bulges of barred and unbarred galaxies. Most bulges have decreasing metallicity with increasing radius; galaxies with larger central metallicities have steeper gradients. Where positive age gradients (with the central regions being younger) are present, they are invariably in barred galaxies. The metallicities of bulges are correlated with those of their discs. While this and the differences between barred and unbarred galaxies suggest that secular evolution cannot be ignored, our results are generally consistent with the hypothesis that mergers have been the dominant mechanism responsible for bulge formation.
Effect of flow pulsatility on modeling the hemodynamics in the total cavopulmonary connection

Total cavopulmonary connection is the result of a series of palliative surgical repairs performed on patients with single ventricle heart defects. The resulting anatomy has complex and unsteady hemodynamics characterized by flow mixing and flow separation. Although varying degrees of flow pulsatility have been observed in vivo, non-pulsatile (time-averaged) boundary conditions have traditionally been assumed in hemodynamic modeling, and only recently have pulsatile conditions been incorporated without completely characterizing their effect or importance. In this study, 3D numerical simulations with both pulsatile and non-pulsatile boundary conditions were performed for 24 patients with different anatomies and flow boundary conditions from Georgia Tech database. Flow structures, energy dissipation rates and pressure drops were compared under rest and simulated exercise conditions. It was found that flow pulsatility is the primary factor in determining the appropriate choice of boundary conditions, whereas the anatomic configuration and cardiac output had secondary effects. Results show that the hemodynamics can be strongly influenced by the presence of pulsatile flow. However, there was a minimum pulsatility threshold, identified by defining a weighted pulsatility index (wPI), above which the influence was significant. It was shown that when wPI<30%, the relative error in hemodynamic predictions using time-averaged boundary conditions was less than 10% compared to pulsatile simulations. In addition, when wPI<50, the relative error was less than 20%. A correlation was introduced to relate wPI to the relative error in predicting the flow metrics with non-pulsatile flow conditions.
A new genus and species of Amiidae (Holostei; Osteichthyes) from the Late Cretaceous of North America, with comments on the phylogeny of the Amiidae

ABSTRACT Melvius thomasi, new genus and new species, from the Late Cretaceous Hell Creek Formation of northeastern Montana and Wyoming, is one of the largest known amiids (standard length 160 cm or more). It is based on disarticulated elements of the skull and axial skeleton. Additional isolated elements probably referable to this species are known from North and South Dakota, Utah, Texas and New Mexico. All known specimens occur below the Cretaceous-Tertiary boundary. Specimens of large amiids from the Early Cretaceous Trinity Formation, Texas, may also be referable to this or a related taxon. Detailed comparison with other amiids, described from more complete material, is not yet possible, but some features of the new taxon appear to relate it to Enneles and Pachyamia. Melvius lived in estuaries and large rivers along the western margin of the Western Interior Sea.
Financial Crisis and Credit Crunch in the Housing Market

We investigate the recent financial crisis with an emphasis on the interlock among housing, mortgage, and credit markets. Following Geanakoplos (Econometric Society Monographs 2:170–205, 2003, 2010), we develop a model in which both prices of the mortgage and its collateral are simultaneously and endogenously determined. Our empirical tests confirm the model’s prediction that an adverse change in the risk free rate or the loan recovery rate can trigger the financial crisis as we observed. Finally, we discuss how the pro-cyclical leveraging practice by financial intermediaries can magnify their losses in mortgage-related assets and consequently cause significant contraction in the balance sheets of these firms.
Comovement, information production, and the business cycle

Abstract Recent theoretical research suggests that information production is a positive externality of aggregate economic activity ( Veldkamp, 2005 ). Both the quantity and quality of information increase during periods of economic expansion and decrease during periods of contraction. Based on this insight, we hypothesize and confirm that time-varying information production drives the comovement patterns observed in stock returns. We examine stock return comovement in 36 countries from 1980 to 2007 and show that, consistent with the theory, comovement patterns are countercyclical; that is, when information production is high (low), comovement is low (high). We also find that the relation between comovement and the business cycle is stronger in countries that experience large intertemporal swings in information production. Finally, we show that the relation between business cycle and comovement is stronger in poor countries, countries with less developed financial markets, and countries with weaker accounting and transparency standards. These results suggest that financial development and transparency are conducive to a steady flow of financial information over the business cycle.
The Housing Price Impact of Covenant Restrictions and Other Subdivision Characteristics

Private land-use restrictions at the subdivision level, commonly called covenant or deed restrictions, have the potential to reduce housing consumption and investment risk and existing empirical evidence has shown a positive marginal housing price for covenant restrictions. However, some commentators have charged that covenant restrictions are full of boilerplate and mostly unenforced, thus any positive marginal price measurement captures other unobserved aspects of the subdivision. Indeed newly published estimates report zero or negative marginal price for deed-restricted subdivisions (DRS). This paper reviews these claims using a hedonic model of housing and a unique dataset that includes covenant restrictions, by-laws, and club goods. Results show a positive marginal price of deed restrictions even when controlling for several subdivision characteristics; however, the marginal price of restrictions falls to zero if a covenant is not updated after 25 years.
A Posteriori Error Estimates for Finite Element Exterior Calculus: The de Rham Complex

Finite element exterior calculus (FEEC) has been developed over the past decade as a framework for constructing and analyzing stable and accurate numerical methods for partial differential equations by employing differential complexes. The recent work of Arnold, Falk, and Winther includes a well-developed theory of finite element methods for Hodge---Laplace problems, including a priori error estimates. In this work we focus on developing a posteriori error estimates in which the computational error is bounded by some computable functional of the discrete solution and problem data. More precisely, we prove a posteriori error estimates of a residual type for Arnold---Falk---Winther mixed finite element methods for Hodge---de Rham---Laplace problems. While a number of previous works consider a posteriori error estimation for Maxwell's equations and mixed formulations of the scalar Laplacian, the approach we take is distinguished by a unified treatment of the various Hodge---Laplace problems arising in the de Rham complex, consistent use of the language and analytical framework of differential forms, and the development of a posteriori error estimates for harmonic forms and the effects of their approximation on the resulting numerical method for the Hodge---Laplacian.
Development of an eco‐tourism strategy for Texas

This paper deals with the development of a nature tourism strategy for Texas. As opposed to many states and countries Texas is unique in terms of private land ownership. In fact 97 percent of land belongs to private sector owners leaving 3 percent to the public domain. Private ownership makes it very difficult to maneuver in developing a strategy. This paper gives the history and methodology that was used in developing a nature tourism strategy. The process involved a number of private and public interests and focused on the obstacles that make it difficult for tourism development.
Study of the Flow Over Wind Turbine Blade

This paper presents the comparison of the performance between two different designs of wind turbine blades; one is a straight and the other with a backward swept blade. The straight edge blade was constructed so that it is optimal on coming wind and rotation speeds with 7m/s and 20rpm. The blade has a length of 20m and uses a constant airfoil cross section NACA 4412. The swept edge blade has the same characteristics as the straight edge except for the trajectory of the edge. Each cross section has the same dimensions and has at the same distance from the hub as its corresponding section in the straight edge blade. To test this new design the performance of both blades were measured using CFD at a wind speeds ranging 0 to 20m/s. Comparisons were made for power generation and acoustic noise for both designs of the blades.Copyright © 2011 by ASME
Continuity of spectral averaging

We consider averages κ of spectral measures of rank one perturbations with respect to a σ-finite measure ν. It is examined how various degrees of continuity of ν with respect to α-dimensional Hausdorff measures (0 < α ≤ 1) are inherited by κ. This extends Kotani's trick where ν is simply the Lebesgue measure.
A simple, convenient, general procedure for the synthesis of 2-alkyn-1-ylboronates

Abstract Representative 2-alkyn-1-ylboronates have been synthesized in good to excellent yields using the reaction of the newly available diisopropyl iodomethylboronate with alkynyllithiums generated in situ. Comparable yields are obtained from both acyclic and cyclic boronates. However, 2-(iodomethyl)-1,3,2-dioxa-4,4,5,5-tetramethylborolane gave superior yields with a wide variety of alkynyllithiums. This procedure offers a simple and convenient alternative route to existing methodologies in terms of the milder reaction condition and the ease of the operation.
Database metatheory: asking the big queries

Is “database theory” an oxymoron? Or is ata platitude? What is the fitness measure that decides the surviva! of ideas (and areas) in mathematics, in applted science, and in computer science? Which ideas from database theory during the past twenty-five years have influenced research in other fields of computer science? How many were encapsulated in actual products? Was the relational model the on[y true paradigm sh@ m computer science ? Is applicability the only and ultimate justification of theoretical research in an applied science? Are applicability pressures rea!ly exogenous and unwelcome? Are negattve results appropriate goals of theoretical research in an appiied science —or are they the on[y possibie such research goals? If scientific theories must be refutab!e, what are the “hard facts” that provide the possibility of refutation in the case of database theory?
Universal Graphs with Forbidden Subgraphs and Algebraic Closure

We apply model theoretic methods to the problem of existence of countable universal graphs with finitely many forbidden connected subgraphs. We show that to a large extent the question reduces to one of local finiteness of an associated “algebraic closure” operator. The main applications are new examples of universal graphs with forbidden subgraphs and simplified treatments of some previously known cases.
Control of exocytosis from adrenal chromaffin cells

1. Calcium-dependent exocytosis of catecholamines from intact and digitonin-permeabilized bovine adrenal chromaffin cells was investigated. 2. 45Ca2+ uptake and secretion induced by nicotinic stimulation or depolarization in intact cells were closely correlated. The results provide strong support for Ca2+ entry being the trigger for exocytosis. 3. Experiments in which the H+ electrochemical gradient across the intracellular secretory granule (chromaffin granule) membrane was altered indicated that the gradient does not play an important role in exocytosis. 4. Ca2+ entry into the cells is associated with activation of phospholiphase C and a rapid translocation of protein kinase C to membranes. 5. The plasma membrane of chromaffin cells was rendered permeable to Ca2+, ATP, and proteins by the detergent digitonin without disruption of the intracellular secretory granules. In this system in which the intracellular milieu can be controlled, micromolar Ca2+ directly stimulated catecholamine secretion. 6. Treatment of the cells with phorbol esters and diglyceride, which activate protein kinase C, enhanced phosphorylation and subsequent Ca2+-dependent secretion in digitonin-treated cells. 7. Phorbol ester-induced secretion could be specifically inhibited by trypsin. The experiments indicate that protein kinase C modulates but is not necessary for Ca2+-dependent secretion.
VLBA Imaging of NGC 4261: Symmetric Parsec-scale Jets and the Inner Accretion Region

Dual frequency VLBA observations of the nucleus of NGC 4261 (3C270) reveal highly symmetric radio structures at both 1.6 and 8.4 GHz. Analysis of these images shows that the central 10 pc of this source is not significantly affected by free-free absorption, even though the nucleus of the galaxy is known to contain a nearly edge-on disk of gas and dust. The lack of detectable absorption implies that the density of ionized gas in the central 10 pc is less than (is similar to) 10(sup 3) cm (sup -3), assuming a temperature of (is similar to) 10(sup 4)K.
Trajectory and control optimization for flexible space robots

This paper is concerned with a flexible space robot whose mission is to ferry some payload in space and to dock smoothly with an orbiting target. Using a perturbation approach, the problem is divided into one for the rigidbody maneuvering of the robot and one for the feedback control of elastic vibrations and perturbations from the rigid-body maneuvering motions. The procedure involves optimization of the robot trajectory, inverse dynamics for the determination of the maneuvering forces and torques, and the use of the linear quadratic regulator (LQR) theory for a time-varying system for the determination of an optimal control law for the elastic motions and the perturbation from the rigid-body maneuvering motions. A numerical example demonstrates the approach.
Might Dark Matter and Energy be Intrinsic Properties of Space

It is shown that if a volume element V, of space is assumed to have intrinsic energy E, then basic principles of mechanics, thermodynamics and special relativity lead to the equation of state: E=pV, where p is the pressure. When this equation of state is incorporated in the Einstein equations it leads to the prediction that the orbital speed of matter circling a visible galaxy embedded in a spherical galactic halo should be relativistic, in disagreement with observations. However, it also leads directly to the interesting notion that the inertial mass of such a medium can be understood as a resistance to being compressed via Lorentz contraction. It is then shown that the mathematical structure of thermodynamics suggests another plausible definition of pressure if we allow for the possibility that the intrinsic energy of spacetime may not be described by the same work-energy relationship as ordinary matter. This additional possibility leads to the equation of state: E=−pV. While both of these equations of state describe forms of energy that are quite unlike ordinary energy, neither alone is able to account for observed rotational velocity curves of matter orbiting visible galaxies. Therefore, the possibility that space has two distinct components of energy is investigated. This results in a plausible, two-component equation of state in which the former equation of state is tentatively identified as the “dark matter” (DM) component, the latter as the “dark energy” (DE) component. The effective equation of state of space, accounting for the presence of both components, may then be written in the form: p=w e, where e is the total energy density, p the total pressure, and w represents the fractional excess of DM over DE (and therefore satisfies: −1≤w≤+1). Given the wide range of possible spacetime properties implied by this equation it appears to be a viable candidate for explaining observations presently attributed to the presence of both DM and DE. Specifically, the static, spherically symmetric solution of Einstein’s field equations, neglecting effects of ordinary matter, predicts the inverse r 2 distribution of intrinsic space energy required to explain observed constant rotational velocity curves for matter in circular orbits around visible galaxies embedded within spherically symmetric galactic halos. The proposed equation of state is also capable of describing regions of space undergoing accelerated expansion as regions where DE is dominant (i.e., w<−1/3).
Skewless network clock synchronization without discontinuity: convergence and performance

This paper examines synchronization of computer clocks connected via a data network and proposes a skewless algorithm to synchronize them. Unlike existing solutions, which either estimate and compensate the frequency difference (skew) among clocks or introduce offset corrections that can generate jitter and possibly even backward jumps, our solution achieves synchronization without these problems. We first analyze the convergence property of the algorithm and provide explicit necessary and sufficient conditions on the parameters to guarantee synchronization. We then study the effect of noisy measurements (jitter) and frequency drift (wander) on the offsets and synchronization frequency, and further optimize the parameter values to minimize their variance. Our study reveals a few insights, for example, we show that our algorithm can converge even in the presence of timing loops and noise, provided that there is a well-defined leader. This marks a clear contrast with current standards such as NTP and PTP, where timing loops are specifically avoided. Furthermore, timing loops can even be beneficial in our scheme as it is demonstrated that highly connected subnetworks can collectively outperform individual clients when the time source has large jitter. The results are supported by experiments running on a cluster of IBM BladeCenter servers with Linux.
Is Environmentally-Friendly Agriculture Less Profitable for Farmers? Evidence on Integrated Pest Management in Bangladesh

Concerns about the sustainability of conventional agriculture have prompted widespread introduction of integrated pest management (IPM), an ecologically-based approach to control of harmful insects and weeds. IPM is intended to reduce ecological and health damage from chemical pesticides by using natural parasites and predators to control pest populations. Since chemical pesticides are expensive for poor farmers, IPM offers the prospect of lower production costs and higher profitability. However, adoption of IPM may reduce profitability if it also lowers overall productivity, or induces more intensive use of other production factors. On the other hand, IPM may actually promote more productive farming by encouraging more skillful use of available resources. Data scarcity has hindered a full accounting of IPM's impact on profitability, health, and local ecosystems. Using new survey data, the authors attempt such an accounting for rice farmers in Bangladesh. They compare outcomes for farming with IPM and conventional techniques, using input-use accounting, conventional production functions, and frontier production estimation. All of their results suggest that the productivity of IPM rice farming is not significantly different from the productivity of conventional farming. Since IPM reduces pesticide costs with no countervailing loss in production, it appears to be more profitable than conventional rice farming. The interview results also suggest substantial health and ecological benefits. However, externality problems make it difficult for farmers to adopt IPM individually. Without collective adoption, neighbors' continued reliance on chemicals to kill pests will also kill helpful parasites and predators, as well as exposing IPM farmers and local ecosystems to chemical spillovers from adjoining fields. Successful IPM adoption may therefore depend on institutional support for collective action.
Instability, turbulence, and enhanced transport in accretion disks

Recent years have witnessed dramatic progress in our understanding of how turbulence arises and transports angular momentum in astrophysical accretion disks. The key conceptual point has its origins in work dating from the 1950s, but its implications have been fully understood only in the last several years: the combination of a subthermal magnetic field (any nonpathological configuration will do) and outwardly decreasing differential rotation rapidly generates magnetohydrodynamic (MHD) turbulence via a remarkably simple linear instability. The result is a greatly enhanced effective viscosity, the origin of which had been a long-standing problem. The MHD nature of disk turbulence has linked two broad domains of magnetized fluid research: accretion theory and dynamos. The understanding that weak magnetic fields are not merely passively acted upon by turbulence, but actively generate it, means that the assumptions of classical dynamo theory break down in disks. Paralleling the new conceptual understanding has been the development of powerful numerical MHD codes. These have taught us that disks truly are turbulent, transporting angular momentum at greatly enhanced rates. We have also learned, however, that not all forms of disk turbulence do this. Purely hydrodynamic turbulence, when it is imposed, simply causes fluctuations without a significant increase in transport. The interplay between numerical simulation and analytic arguments has been particularly fruitful in accretion disk theory and is a major focus of this article. The authors conclude with a summary of what is now known of disk turbulence and mention some knotty outstanding questions (e.g., what is the physics behind nonlinear field saturation?) for which we may soon begin to develop answers.
The rewriting logic semantics project: A progress report

Rewriting logic is an executable logical framework well suited for the semantic definition of languages. Any such framework has to be judged by its effectiveness to bridge the existing gap between language definitions on the one hand, and language implementations and language analysis tools on the other. We give a progress report on how researchers in the rewriting logic semantics project are narrowing the gap between theory and practice in areas such as: modular semantic definitions of languages; scalability to real languages; support for real time; semantics of software and hardware modeling languages; and semantics-based analysis tools such as static analyzers, model checkers, and program provers.
The signal estimator limit setting method

Abstract A new technique is presented for determining confidence limits in searches with low statistics. Recognizing that the physicist wishes to set limits on the signal hypothesis, the technique defaults to a confidence limit on signal only when zero events are observed. In order to accomplish this, the method overcovers, but much less so than methods using conditioning techniques. As a result, this technique gives more powerful frequentist confidence limits than conditioning techniques while still avoiding some unpleasant features of classical confidence limits.
The Nanoscience Revolution: Merging of Colloid Science, Catalysis and Nanoelectronics

The incorporation of nanosciences into catalysis studies has become the most powerful approach to understanding reaction mechanisms of industrial catalysts and designing new-generation catalysts with high selectivity. Nanoparticle catalysts were synthesized via controlled colloid chemistry routes. Nanostructured catalysts such as nanodots and nanowires were fabricated with nanolithography techniques. Catalytic selectivity is dominated by several complex factors including the interface between active catalyst phase and oxide support, particle size and surface structure, and selective blocking of surface sites, etc. The advantage of incorporating nanosciences into the studies of catalytic selectivity is the capability of separating these complex factors and studying them one by one in different catalyst systems. The role of oxide–metal interfaces in catalytic reactions was investigated by detection of continuous hot electron flow in catalytic nanodiodes fabricated with shadow mask deposition technique. We found that the generation mechanism of hot electrons detected in Pt/TiO2 nanodiode is closely correlated with the turnover rate under CO oxidation. The correlation suggests the possibility of promoting catalytic selectivity by precisely controlling hot electron flow at the oxide–metal interface. Catalytic activity of 1.7–7.2 nm monodispersed Pt nanoparticles exhibits particle size dependence, demonstrating the enhancement of catalytic selectivity via controlling the size of catalyst. Pt–Au alloys with different Au coverage grown on Pt(111) single crystal surface have different catalytic selectivity for four conversion channels of n-hexane, showing that selective blocking of catalytic sites is an approach to tuning catalytic selectivity. In addition, presence and absence of excess hydrogen lead to different catalytic selectivity for isomerization and dehydrocyclization of n-hexane on Pt(111) single crystal surface, suggesting that modification of reactive intermediates by the presence of coadsorbed hydrogen is one approach to shaping catalytic selectivity. Several challenges such as imaging the mobility of adsorbed molecules during catalytic reactions by high pressure STM and removing polymeric capping agents from metal nanoparticles remain.
The dynamic range of ultra-high-resolution cryogenic gamma-ray spectrometers

Abstract We are developing high-resolution cryogenic gamma-ray spectrometers for nuclear science and non-proliferation applications. The gamma-ray detectors are composed of a bulk superconducting Sn foil absorber attached to a multilayer Mo/Cu transition-edge sensor (TES). The energy resolution of a detector with a 1×1×0.25 mm 3 Sn absorber is 50–90 eV FWHM for γ-rays up to 100 keV, and it decreases for larger absorbers. Here, we present the detector performance for different absorber volumes, and discuss the trade-offs between energy resolution and dynamic range.
Synthesis of offset dual shaped subreflector antennas for control of Cassegrain aperture distributions

Many existing large ground reflector antennas have been designed as Cassegrain systems-i.e., paraboloid/hyperboloid combinations. Other large ground antennas are simply paraboloid designs. Upgrading the gain of these systems to a gain comparable to that obtainable with a dual shaped reflector antenna system has been an important and costly objective of many such ground stations. A potentially economic method for such an antenna upgrade is presented herein. It involves a redesign of only the subreflector portion of a Cassegrain antenna or the introduction of a subreflector feed system for a parabaloid. A pair of offset subreflectors are synthesized which will give a controllable high gain amplitude distribution in the aperture of the large paraboloid. The synthesis method that is used is based on an approximate formulation for an offset dual shaped high gain antenna that was first presented by Galindo-Israel and Mittra in 1977. In that approximate formulation, the geometrical optics (GO) energy was scattered from a subreflector and then from a second large reflector which reflected a uniform phase distribution. In the present offset dual shaped subreflector (DSS) antenna, the second reflection is from a smaller (sub) reflector and it scatters a spherical wave that feeds a hyperboloid or feeds a large paraboloid directly. Excellent results are shown for the approximate synthesis of the DSS.
Structural Parameters of Thin and Thick Disks in Edge-on Disk Galaxies

We analyze the global structure of 34 late-type, edge-on, undisturbed, disk galaxies spanning a wide range of mass. We measure structural parameters for the galaxies using two-dimensional least-squares fitting to our R-band photometry. The fits require both a thick and a thin disk to adequately fit the data. The thick disks have larger scale heights and longer scale lengths than the embedded thin disks by factors of ~2 and ~1.25, respectively. The observed structural parameters agree well with the properties of thick and thin disks derived from star counts in the Milky Way and from resolved stellar populations in nearby galaxies. We find that massive galaxies' luminosities are dominated by the thin disk. However, in low-mass galaxies (Vc 120 km s-1) thick disk stars contribute nearly half the luminosity and dominate the stellar mass. Thus, although low-mass dwarf galaxies appear blue, the majority of their stars are probably quite old. Our data are most easily explained by a formation scenario in which the thick disk is assembled through direct accretion of stellar material from merging satellites while the thin disk is formed from accreted gas. The baryonic fraction in the thin disk therefore constrains the gas richness of the merging pregalactic fragments. If we include the mass in H I as part of the thin disk, the thick disk contains 10% of the baryons in high-mass galaxies and ~25%–30% of the baryons in low-mass galaxies. Our data, therefore, indicate that the fragments were quite gas rich at the time of merging (fgas = 75%–90%). However, because low-mass galaxies have a smaller fraction of baryons in their thin disks, the pregalactic fragments from which they assembled must have been systematically more gas poor. We believe this trend results from increased outflow due to supernova-driven winds in the lower mass pregalactic fragments. We estimate that ~60% of the total baryonic mass in these systems was lost due to outflows. Pushing the episode of significant winds to early times allows the mass-metallicity relationship for disks to be established early, before the main disk is assembled, and obviates the difficulty in driving winds from diffuse disks with low star formation efficiencies. We discuss other implications of this scenario for solving the G dwarf problem, for predicting abundance trends in thick disks, and for removing discrepancies between semianalytic galaxy formation models and the observed colors of low-mass galaxies.
Lie group variational integrators for the full body problem

We develop the equations of motion for full body models that describe the dynamics of rigid bodies, acting under their mutual gravity. The equations are derived using a variational approach where variations are defined on the Lie group of rigid body configurations. Both continuous equations of motion and variational integrators are developed in Lagrangian and Hamiltonian forms, and the reduction from the inertial frame to a relative frame is also carried out. The Lie group variational integrators are shown to be symplectic, to preserve conserved quantities, and to guarantee exact evolution on the configuration space. One of these variational integrators is used to simulate the dynamics of two rigid dumbbell bodies.
Correlations in the Far-Infrared Background

We compute the expected angular power spectrum of the cosmic far infrared background (FIRB). We find that the signal due to source correlations dominates the shot noise for l 1000 and results in anisotropies with rms amplitudes [l(l + 1)Cl/2?]1/2 between 5% and 10% of the mean for l 150. The angular power spectrum depends on several unknown quantities, such as the UV flux density evolution, optical properties of the dust, biasing of the sources of the FIRB, and cosmological parameters. However, when we require our models to reproduce the observed direct current level of the FIRB, we find that the anisotropy is at least a few percent in all cases. This anisotropy is detectable with proposed instruments, and its measurement will provide strong constraints on models of galaxy evolution and large-scale structure at redshifts up to at least z ~ 5.
A Tunable Snapshot Imaging Spectrometer

Replacement of current etched CGH dispersing elements with an electronically tunable liquid crystal element adds the ability to change the configuration of the Computed Tomographic Imaging Spectrometer (CTIS). The adaptation of the CGH design algorithm for the tunable disperser is presented.
Efficient Algorithms for Implementation of Hysteresis Models

The homogenized energy model characterizes hysteresis in ferroelectric, ferromagnetic and ferroelastic compounds through a combination of energy analysis at the lattice level and stochastic homogenization techniques to provide macroscopic constitutive relations. Whereas this framework can characterize the frequency, stress and temperature dependent dynamics of these compounds for a variety of operating regimes, the direct implementation of the model is often not sufficiently efficient for applications requiring high speed simulation, model identification, or control implementation. Here we discuss techniques to increase the efficiency of algorithms for forward simulations and parameter identification. This significantly enhances the capability of the model for uncertainty analysis, sensitivity analysis, model calibration, device design, and model-based control implementation.
Rapid determination of mycophenolic acid in plasma by reversed-phase high-performance liquid chromatography

A simple, accurate and sensitive high-performance liquid chromatographic method with UV detection was carried out to measure plasma concentrations of mycophenolic acid. Following a simplified acid hydrolysis of the sample, the separation was carried out in 4 min using a Zorbax Eclipse C(8) reversed-phase column with a flow-rate of 1.5 ml/min, and monitoring the absorbance at 250 nm. Throughput was up to 100 samples in 24 h. Within the investigated concentration ranges of mycophenolic acid (0-100 mg/l), good linearity (r>0.99) was obtained. The method is sensitive (the limit of detection was about 20 microg/l) and precise (for 0.49 mg/l added to plasma, within-run C.V. was 2% and between-run was 4.2%; for 2.88 mg/l, within-run C.V. was 0.35% and between-run C.V. was 0.69%; for 24.38 mg/l, within-run C.V. was 0.77% and between-run C.V. was 3.1%). Analytical recoveries were 96% for 0.5 mg/l mycophenolic acid added to plasma, 100% for 12 mg/l and 102.5% for 24 mg/l.
FISCAL SHOCKS AND THEIR CONSEQUENCES

This paper investigates the response of hours worked and real wages to fiscal policy shocks in the post-World-War II US. We identify these shocks with exogenous changes in military purchases and argue that they lead to a persistent increase in government purchases and tax rates on capital and labor income, and a persistent rise in aggregate hours worked as well as declines in real wages. The shocks are also associated with short lived rises in aggregate investment and small movements in private consumption. We describe and implement a methodology for assessing whether standard neoclassical models can account for the consequences of a fiscal policy shock. Simple versions of the neoclassical model can account for the qualitative effects of a fiscal shock. Once we allow for habit formation and investment adjustment costs, the model can also account reasonably well for the quantitative effects of a fiscal shock.
Effects of frequent information disclosure: the case of daily net asset value reporting for closed-end investment companies

There are two competing hypotheses regarding the effects of increased financial disclosure. One states that increased disclosure leads to decreased information asymmetry and more efficient pricing resulting in reduced bid-ask spreads, volatility and illiquidity. The other says that increased disclosure places additional burdens on traders leading to increased transactions costs and volatility. This paper examines the effects of more-frequent reporting for the case of closed-end funds that voluntarily changed their net-asset-value reporting from weekly to daily beginning in 1998. Multivariate analyses indicate a decrease in asymmetric information following initiation of daily reporting as evidenced by lower spreads, greater transactions volume, reduced volatility and decreased illiquidity. We conclude that closed-end fund daily net-asset-value reporting provides an example of information disclosure that provides useful information to investors and reduces information asymmetry.
Chandra measurements of non-thermal-like X-ray emission from massive, merging, radio halo clusters

We report the discovery of spatially extended, non-thermal-like emission components in Chandra X-ray spectra for five of a sample of seven massive, merging galaxy clusters with powerful radio haloes. The emission components can be fitted by power-law models with mean photon indices in the range 1.5 < r < 2.0. A control sample of regular, dynamically relaxed clusters, without radio haloes but with comparable mean thermal temperatures and luminosities, shows no compelling evidence for similar components. Detailed X-ray spectral mapping reveals the complex thermodynamic states of the radio halo clusters. Our deepest observations, of the Bullet Cluster 1E 0657-56, demonstrate a spatial correlation between the strongest power-law X-ray emission, highest thermal pressure and brightest 1.34 GHz radio halo emission in this cluster. We confirm the presence of a shock front in the IE 0657-56 and report the discovery of a new, large-scale shock front in Abell 2219. We explore possible origins for the power-law X-ray components. These include inverse-Compton scattering of cosmic microwave background photons by relativistic electrons in the clusters; bremsstrahlung from suprathermal electrons energized by Coulomb collisions with an energetic, non-thermal proton population; and synchrotron emission associated with ultrarelativistic electrons. Interestingly, we show that the power-law signatures may also be due to complex temperature and/or metallicity structure in clusters particularly in the presence of metallicity gradients. In this case, an important distinguishing characteristic between the radio halo clusters and control sample of predominantly cool-core clusters is the relatively low central X-ray surface brightness of the former. Our results have implications for previous discussions of soft excess X-ray emission from clusters and highlight the importance of further deep X-ray and radio mapping, coupled with new hard X-ray, y-ray and TeV observations, for improving our understanding of the non-thermal particle populations in these systems.
The nature of the agricultural firm

Abstract Models explaining the choice between rent, wage, and share contracts in agriculture abstract from the large variations within the classes of rent, share, and owner-managed forms of organization regarding the extent to which a specific form accommodates specialization between labor and management. As a result, modern explanations of agricultural organizations are misleadingly dependent on risk aversion or the assumption that landowners have an absolute advantage in production decisions. Viewing the agricultural firm as a constitution instead of as a nexus of contracts facilitates an agency explanation of alternative organizational forms and their amenability to specialization.
Ergodic theoretic proof of equidistribution of Hecke points

We prove the equidistribution of Hecke points for any connected non-compact , generalizing a theorem of Clozel, Oh and Ullmo. The main tool is a theorem of Mozes and Shah on unipotent flows.
SUSY-based variational method for the anharmonic oscillator

Using a newly suggested algorithm of Gozzi, Reuter and Thacker for calculating the excited states of one-dimensional systems, we determine approximately the eigenvalues and eigenfunctions of the anharmonic oscillator, described by the Hamiltonian H=12p2+gx4. We use ground state post-Gaussian trial wave functions of the form Ψ(x)=N exp(−b|x|2n), where n and b are continuous variational parameters. This algorithm is based on the hierarchy of Hamiltonians related by supersymmetry (SUSY) and the factorization method. We find that our two-parameter family of trial wave functions yields excellent energy eigenvalues and wave functions for the first few levels of the anharmonic oscillator.
Interstellar Absorption Lines in the Spectrum of the Starburst Galaxy NGC 1705

A Goddard High Resolution Spectrograph archival study of the interstellar absorption lines in the line of sight to the H I–rich, starburst dwarf galaxy NGC 1705 in the 1170 to 1740 A range at ~120 km s-1 resolution is presented. The absorption features arising because of photospheric lines are distinctly different from the interstellar lines: the photospheric lines are weak, broad (equivalent widths >1 A), asymmetric, and centered around the systemic LSR velocity of NGC 1705 (~610 km s-1). The interstellar lines consist of three relatively narrow components at LSR velocities of -20, 260, and 540 km s-1, and include absorption by neutral atoms (N I λ1200 triplet and O I λ1302), singly ionized atoms (Si II λλ1190, 1193, 1260, 1304, and 1526, S II λ1253, C II λ1334, C II* λ1336, Fe II λ1608, and Al II λ1670), and atoms in higher ionization states (Si III λ1206, Si IV λλ1393, 1402, and C IV λλ1548, 1550). The Si IV and C IV absorption features have both interstellar and photospheric contributions. In an earlier study, Sahu & Blades identified the absorption system at -20 km s-1 with Milky Way disk/halo gas, and the 260 km s-1 system with a small, isolated high-velocity cloud HVC 487, which is probably associated with Magellanic Stream gas. The 540 km s-1 absorption system is associated with a kiloparsec-scale expanding, ionized supershell centered on the super–star cluster NGC 1705-1. The analysis presented in this paper consists of (1) a list of all interstellar absorption features with greater than 3 σ significance and their measured equivalent widths, (2) plots of the lines in the various atomic species together with the results of nonlinear least-squares fit profiles to the observed data, and (3) unpublished 21 cm maps from the Wakker & van Woerden survey showing the large-scale H I distribution in the region near the NGC 1705 sight line and HVC 487. Furthermore, weak N I λ1200 triplet absorption for the supershell component is reported, which in the absence of dust depletion and ionization corrections implies a low N abundance. A low N abundance for the supershell is consistent with an interpretation of nucleosynthetic enrichment by time-delayed primary nitrogen production, the age estimate of (10–20) × 106 yr for the central super–star cluster NGC 1705-1 of Heckman & Leitherer, and the underabundance of Fe reported by Sahu & Blades. However, using the N I λ1200 triplet alone to estimate the total N abundance could result in a severe underestimation of this quantity: although N does not deplete onto interstellar dust grains, photoionization and collisional ionization effects could increase the fraction of N found in higher ionization stages. Uncertainties in the total N abundance caused by photoionization and collisional ionization effects can only be addressed by future observations of the higher ionization lines, namely, N II λ1084 and N III λ989.
Sex ratios and marital status.

One common characteristic of populations throughout the world is the preponderance of women at older ages. Women are the majority of the elderly population in the vast majority of countries, and their share of the population increases with age. This gender imbalance at older ages has many implications for population and individual aging, perhaps the most important of which involve marital status and living arrangements. Family members are the main source of emotional and economic support for the elderly (see Note 1 at the end of text), although in some developed countries the state has assumed a larger share of the economic responsibilities. Marital status strongly affects many aspects of one’s life. Studies in developed countries (see Note 2 at the end of text) show that married people, particularly married men, are healthier and live longer than their non-married counterparts (1-4). Older married couples tend to be more financially secure than non-married people. Changes in marital status at older ages can affect pension potential, retirement income, and an individual’s social support network; many older widowed men, in particular, may lose contact with much of their support network after their wife dies (5). In contrast, widowed women tend to maintain their support network after the death of a spouse (6). Marital status also influences one’s living arrangements and affects the nature of caregiving that is readily available in case of illness or disability.