cssi/SciSciGPT-SciSciNet huggingface dataset:
The relaxation of the second moments in rapid shear flows of smooth disks

This paper compares the results of numerical simulations for two-dimensional, rapid, homogeneous shear flows of identical, smooth, inelastic disks with the predictions of Jenkins and Richman ((1988), J. Fluid Mech. 192, 313–328) for the relaxation of the second moments of the velocity distribution function following a homogeneous, but anisotropic disturbance of their steady values. For nearly elastic disks, the time-history of the relaxation is in excellent agreement with the theory in both its dense and dilute limits. However, deviations are observed in the case of inelastic particles.
Aproximaciones a la política exterior latinoamericana

El proceso de aprendizaje de la America Latina dentro del sistema internacional empieza a arrojar resultados, tanto conceptuales como practicos. Sin embargo, los paises latinoamericanos no se deciden a emplear su ya rico instrumento de politica exterior y no aprovechan plenamente su poder de negociacion y retroceden entre decisiones audaces.
Potential therapeutic advantage of strongly forward-directed beams for boron neutron capture therapy

The delivery of sufficient thermal neutrons selectively to the tumor is one of key requirements for the success of boron neutron capture therapy (BNCT). The authors implemented the design study of forward-directed beams and presented their therapeutic advantage in terms of physical dose and tumor control probability. A reactor-based BNCT facility was simulated for two cylindrical collimators that yield forward-directed beams (Collimator I of 10 cm-diameter/20 cm-length and Collimator II of 14 cm-diameter and 15 cm-length). The total tumor dose and theoretical tumor control probability were calculated for the forward-directed beams and a beam of a linear angular distribution. The normal brain tolerance dose of 1500 cGy-Eq and /sup 10/B-concentrations of 7.5 ppm in the brain, and 30 ppm in the tumor were applied for these calculations. The average values of directional cosine (/spl mu/) at the irradiation port were determined to be 0.90 and 0.86 for Collimator I and II, respectively. The total dose averaged over a 4cm-diameter tumor in the brain was shown to be 6096 cGy-Eq for Collimator I, 6140 cGy-Eq for Collimator II, and 5237 cGy-Eq for the beam with the linear angular distribution. The theoretical tumor control probability was determined to be 0.93 for Collimator I, 0.95 for Collimator II, and 0.48 for the linear distribution. Strongly forward-directed beams of /spl mu/>0.8 can be generated using a long cylindrical collimator made of thermal neutron absorbers. The therapeutic advantage would be even more significant for deep-seated tumor treatments.
Metabolic Engineering to Develop a Pathway for the Selective Cleavage of Carbon-Nitrogen Bonds

The objective of the project is to develop a biochemical pathway for the selective cleavage of C-N bonds in molecules found in petroleum. Specifically a novel biochemical pathway will be developed for the selective cleavage of C-N bonds in carbazole. The cleavage of the first C-N bond in carbazole is accomplished by the enzyme carbazole dioxygenase, that catalyzes the conversion of carbazole to 2-aminobiphenyl-2,3-diol. The genes encoding carbazole dioxygenase were cloned from Sphingomonas sp. GTIN11 and from Pseudomonas resinovorans CA10. The selective cleavage of the second C-N bond has been challenging, and efforts to overcome that challenge have been the focus of recent research in this project. Enrichment culture experiments succeeded in isolating bacterial cultures that can metabolize 2-aminobiphenyl, but no enzyme capable of selectively cleaving the C-N bond in 2-aminobiphenyl has been identified. Aniline is very similar to the structure of 2-aminobiphenyl and aniline dioxygenase catalyzes the conversion of aniline to catechol and ammonia. For the remainder of the project the emphasis of research will be to simultaneously express the genes for carbazole dioxygenase and for aniline dioxygenase in the same bacterial host and then to select for derivative cultures capable of using carbazole as the sole source of nitrogen.
Evidence of the Abnormal Accrual Anomaly Incremental to Operating Cash Flows

Recent research provides evidence that the operating cash flows‐to‐price ratio subsumes accruals in explaining future annual returns. This suggests that the accrual anomaly is part of the overall value‐glamour anomaly and does not represent the mispricing of earnings. We extend the literature by using multiple measures of abnormal accruals and separate analyses of future annual returns and future earnings announcement returns. The results reveal that the operating cash flows‐to‐price ratio does not subsume abnormal accruals in explaining future annual returns or future announcement returns. We also find that the operating cash flows‐to‐price ratio does not subsume total accruals in explaining future announcement returns. These results are not consistent with accruals being a manifestation of the value‐glamour anomaly. Our study contributes to the current debate on the existence and the extent of the (abnormal) accrual anomaly. Moreover, the methodology employed can help researchers in exploring mispricing...
Variations in relevance judgments and the measurement of retrieval effectiveness

Abstract Test collections have traditionally been used by information retrieval researchers to improve their retrieval strategies. To be viable as a laboratory tool, a collection must reliably rank different retrieval variants according to their true effectiveness. In particular, the relative effectiveness of two retrieval strategies should be insensitive to modest changes in the relevant document set since individual relevance assessments are known to vary widely. The test collections developed in the TREC workshops have become the collections of choice in the retrieval research community. To verify their reliability, NIST investigated the effect changes in the relevance assessments have on the evaluation of retrieval results. Very high correlations were found among the rankings of systems produced using different relevance judgment sets. The high correlations indicate that the comparative evaluation of retrieval performance is stable despite substantial differences in relevance judgments, and thus reaffirm the use of the TREC collections as laboratory tools.
Clinical Interventions Provided by Doctor of Pharmacy Students

OBJECTIVE:To assess the types, perceived benefit, and cost impact of the interactions provided by two-year post-B.S. Pharm.D. students on clerkship rotations.DESIGN:Information was obtained through voluntary reporting by students on a standardized data collection form. Cost analysis and peer review were performed on a subset of interventions.SETTING:The setting of the study included hospital clerkship sites (general medicine and specialty rotations) and an ambulatory care site (general medicine).PARTICIPANTS:Six second-year Pharm.D. students.RESULTS:Reports that were completed totaled 951, including 612 intervention, 335 information, and 4 unknown events. Most events were drug related and student initiated. Follow-up was predominantly to physicians. Intervention events primarily involved changes in drug therapy regimens (63.5 percent), changes in dose (29.5 percent), and identification of potential adverse drug reactions (7 percent). Acceptance rate of recommendations was 78.7 percent. Antibiotics, cardio...
Influence of Structural Variations in 1-Alkyl(aralkyl)-3-Methylimidazolium Hexafluorophosphates and Bis(trifluoromethylsulfonyl)imides on Physical Properties of the Ionic Liquids

A series of twenty four 1-alkyl(aralkyl)-3-methylimidazolium hexafluorophosphates and bis(trifluoromethyl-sulfonyl)imides are prepared and the influence of structural variations in the imidazolium cation and the identity of the anion on physical properties (phase transition, density, viscosity, and surface tension) of the ionic liquids is determined.
The Aharonov-Bohm Problem Revisited

Abstract Explicit solutions are constructed, and their properties investigated, for a nonrelativistic charged particle in two dimensions in the presence of an arbitrary number of nonquantized magnetic vortices in free space as well as in a uniform magnetic field. After eliminating the gauge potential, the vortices are represented as branch points in one of the complex coordinates. Multivortex solutions in free space can be obtained only if the vortices are treated as dynamical objects. But all the solutions suffer from some unphysical properties. The formulas may be generalized to describe a system of anyons.
Complex multipole beam approach to electromagnetic scattering problems

A novel approach to reducing the matrix size associated with the method of moments (MoM) solution of the problem of electromagnetic scattering from arbitrary shaped closed bodies is presented. The key step in this approach is to represent the scattered field in terms of a series of beams produced by multipole sources located in a complex space. On the scatterer boundary, the fields generated by these multipole sources resemble the Gabor basis functions. By utilizing the properties of the Gabor series, guidelines for selecting the orders as well as locations of the multipole sources are developed. It is shown that the present approach not only reduces the number of unknowns, but also generates a generalized impedance matrix with a banded structure and a low condition number. The accuracy of the proposed method is verified by comparing the numerical results with those derived by using the method of moments. >
Synthesis of novel fluorescently labeled sphingomyelin derivatives useful for sphingomyelinase assay

Abstract Substrates for the sphingomyelinase enzyme class have been prepared, which contain a fluorescent tag and a biotin moiety. These molecules are useful for development of rapid high throughput assays for sphingomyelinase activity. It was observed that retaining the choline ammonium group (as found in the native sphingomyelinase substrate) in synthetic substrates was critical to retain high cleavage rate by the enzyme.
Global limit theorems on the convergence of multidimensional random walks to stable processes

Symmetric heavily tailed random walks on Zd, d ≥ 1, are considered. Under appropriate regularity conditions on the tails of the jump distributions, global (i.e. uniform in x, t, ∣x∣ + t → ∞,) asymptotic behavior of the transition probability p(t, 0, x) is obtained. The examples indicate that the regularity conditions are essential.
Learning Trajectory Preferences for Manipulators via Iterative Improvement

We consider the problem of learning good trajectories for manipulation tasks. This is challenging because the criterion defining a good trajectory varies with users, tasks and environments. In this paper, we propose a co-active online learning framework for teaching robots the preferences of its users for object manipulation tasks. The key novelty of our approach lies in the type of feedback expected from the user: the human user does not need to demonstrate optimal trajectories as training data, but merely needs to iteratively provide trajectories that slightly improve over the trajectory currently proposed by the system. We argue that this co-active preference feedback can be more easily elicited from the user than demonstrations of optimal trajectories, which are often challenging and non-intuitive to provide on high degrees of freedom manipulators. Nevertheless, theoretical regret bounds of our algorithm match the asymptotic rates of optimal trajectory algorithms. We demonstrate the generalizability of our algorithm on a variety of grocery checkout tasks, for whom, the preferences were not only influenced by the object being manipulated but also by the surrounding environment.1
The Globular Cluster Systems of the Sculptor Group

We use CTIO 4 m Mosaic II images taken with the Washington CM and Harris R filters to identify candidate globular clusters in the six major galaxies of the Sculptor group: NGC 45, 55, 247, 254, 300, and 7793. From follow-up spectroscopy with Hydra-CTIO, we find 19 new globular clusters in NGC 55, 247, 253, and 300, bringing the total number of known Sculptor group globular clusters to 36. The newly discovered clusters have spectroscopic ages consistent with those of old Milky Way globular clusters, and the majority are metal-poor. Their luminosity function closely resembles that of the Milky Way's globular clusters; their metallicity distribution is somewhat more metal-rich, but this may be the result of our color selection of candidates. The mean [α/Fe] ratio in the clusters is -0.2 ± 0.3, which is lower than the Milky Way average. The specific frequencies SN are similar to those of other late-type galaxies. However, if we calculate the specific frequency using the K-band total magnitudes of the host galaxies, we find values that are more than a factor of 2 higher. The kinematics of the globular cluster systems are consistent with rotation with the H I disk in each of the four galaxies; however, only in NGC 253 is this result based on more than seven objects. We suggest that the Sculptor group galaxies add to evidence indicating that many of the first-generation globular clusters formed in disks, not halos.
Breaking Symmetry: Spontaneous Resolution of a Polyoxometalate

A chiral polyoxometalate [Hf(PW11O39)2]10- (1) has been prepared and structurally characterized. It crystallizes in the chiral space group P2(1)2(1)2, as a conglomerate of two enantiomerically pure crystals in the absence of any chiral source. The absolute configuration of 1 was determined from the Flack parameter by X-ray crystallography. The structure of 1 comprises two lacunary [PW11O39]7- units, each functioning as a tetra-dentate ligand sandwiching an 8-coordinate HfIV centre in a distorted square antiprismatic geometry. Optically active crystals of both enantiomers were spectroscopically distinguishable by means of solid state circular dichroism spectroscopy. This hafnium-substituted polyoxometalate (POM), 1, shows that spontaneous chiral resolution, a rare phenomenon, can be operable in POM systems.
Syntheses of 6-fluoro-meta-tyrosine and of its metabolites

Abstract 6-Fluoro- meta -tyrosine ( 1 ) was prepared from 2-fluoro-5-hydroxybenzaldehyde ( 6 ) based on an Erlenmeyer–Plochl azlactone strategy. Products of expected metabolism of the amino acid, including 6-fluoro- meta -tyramine ( 2 ) and its O -sulfate conjugate ( 3 ), (2-fluoro-5-hydrxoyphenyl)acetic acid ( 4 ), and 6-fluoro- meta -octopamine ( 5 ) also were prepared from 1 . The use of a recently reported ultrasound-catalyzed Henry reaction facilitated the preparation of the tyramine derivative 2 . The compounds synthesized are available for high performance liquid chromatography (HPLC) standards in positron emission tomography (PET) studies employing 6-[ 18 F]fluoro- meta -tyrosine and as reference samples for metabolic studies of the amino acid.
High-Reynolds number viscous flow computations using an unstructured-grid method

An unstructured grid method is presented to compute three-dimensional compressible turbulent flows for complex geometries. The Navier-Stokes equations, along with the one-equation turbulence model of Spalart-Allmaras are solved by the use of a parallel, matrix-free implicit method on unstructured tetrahedral grids. The developed method has been used to predict drags in the transonic regime for both DLR-F4 and DLR-F6 configurations to assess the accuracy and efficiency of the method
Reallocating wealth? Insecure property rights and agricultural investment in rural China

Abstract This paper evaluates the impact of village-level land reallocations in China on household economic outcomes. The primary objective is to analyze the effect of short-term differences in tenure security in the year of a reallocation, employing the past history of land shifts as a source of exogenous variation in current tenure security. The results show that a decrease in the probability of losing the current plot yields an increase in agricultural inputs and production with no change in non-agricultural investments, conditional on household fixed effects that control for any unobserved and time-invariant characteristics of the household. This suggests that even small increases in the security of tenure enjoyed by households could yield benefits in terms of greater agricultural output.
The Random Average Process and Random Walk in a Space-Time Random Environment in One Dimension

We study space-time fluctuations around a characteristic line for a one-dimensional interacting system known as the random average process. The state of this system is a real-valued function on the integers. New values of the function are created by averaging previous values with random weights. The fluctuations analyzed occur on the scale n1/4, where n is the ratio of macroscopic and microscopic scales in the system. The limits of the fluctuations are described by a family of Gaussian processes. In cases of known product-form invariant distributions, this limit is a two-parameter process whose time marginals are fractional Brownian motions with Hurst parameter 1/4. Along the way we study the limits of quenched mean processes for a random walk in a space-time random environment. These limits also happen at scale n1/4 and are described by certain Gaussian processes that we identify. In particular, when we look at a backward quenched mean process, the limit process is the solution of a stochastic heat equation.
Partitioning colored point sets into monochromatic parts

We show that any two-colored set of n points in general position in the plane can be partitioned into at most $\lceil\frac{n+1}{2}\rceil$ monochromatic subsets, whose convex hulls are pairwise disjoint. This bound cannot be improved in general. We present an O(n log n) time algorithm for constructing a partition into fewer parts, if the coloring is unbalanced, i.e., the sizes of the two color classes differ by more than one. The analogous question for k-colored point sets (k > 2) and its higher dimensional variant are also considered.
Direct Conversion Pulsed UWB Transceiver Architecture

Ultra-wideband (UWB) communication is an emerging wireless technology that promises high data rates over short distances and precise locationing. The large available bandwidth and the constraint of a maximum power spectral density drives a unique set of system challenges. This paper addresses these challenges using two UWB transceivers and a discrete prototype platform.
Electron Affinities of Aln Clusters and Multiple-Fold Aromaticity of the Square Al42- Structure

The concept of aromaticity was first invented to account for the unusual stability of planar organic molecules with 4n + 2 delocalized π electrons. Recent photoelectron spectroscopy experiments on all-metal MAl4- systems with an approximate square planar Al42- unit and an alkali metal led to the suggestion that Al42- is aromatic. The square Al42- structure was recognized as the prototype of a new family of aromatic molecules. High-level ab initio calculations based on extrapolating CCSD(T)/aug-cc-pVxZ (x = D, T, and Q) to the complete basis set limit were used to calculate the first electron affinities of Aln, n = 0−4. The calculated electron affinities, 0.41 eV (n = 0), 1.51 eV (n = 1), 1.89 eV (n = 3), and 2.18 eV (n = 4), are all in excellent agreement with available experimental data. On the basis of the high-level ab initio quantum chemical calculations, we can estimate the resonance energy and show that it is quite large, large enough to stabilize Al42- with respect to Al4. Analysis of the calculate...
Impact of increased penetration of DFIG based wind turbine generators on transient and small signal stability of power systems

The targeted and current development of wind energy in various countries around the world reveals that wind power is the fastest growing power generation technology. Among the several wind generation technologies, variable speed wind turbines utilizing doubly fed induction generators (DFIGs) are gaining momentum in the power industry. With the increase in penetration of these wind turbines, the power system dominated by synchronous machines will experience a change in dynamics and operational characteristics. Given this assertion, the present paper develops an approach to analyze the impact of increased penetration of DFIG based wind turbines on transient and small signal stability of a large power system. The primary basis of the method is to convert the DFIG machines into equivalent conventional round rotor synchronous machines and then evaluate the sensitivity of the eigenvalues with respect to inertia. In this regard, modes that are both detrimentally and beneficially affected by the change in inertia are identified. These modes are then excited by appropriate disturbances and the impact of reduced inertia on transient stability performance is also examined. The proposed technique is tested on a large test system representing the Midwestern portion of the U.S. interconnection. The results obtained indicate that the proposed method effectively identifies both detrimental and beneficial impacts of increased DFIG penetration both for transient stability and small signal stability related performance.
Rituals alleviate grieving for loved ones, lovers, and lotteries.

Three experiments explored the impact of mourning rituals—after losses of loved ones, lovers, and lotteries—on mitigating grief. Participants who were directed to reflect on past rituals or who were assigned to complete novel rituals after experiencing losses reported lower levels of grief. Increased feelings of control after rituals mediated the link between use of rituals and reduced grief after losses, and the benefits of rituals accrued not only to individuals who professed a belief in rituals’ effectiveness but also to those who did not. Although the specific rituals in which people engage after losses vary widely by culture and religion—and among our participants—our results suggest a common psychological mechanism underlying their effectiveness: regained feelings of control.
Energy Conservation "Nudges" and Environmentalist Ideology: Evidence from a Randomized Residential Electricity Field Experiment

“Nudges” are being widely promoted to encourage energy conservation. We show that while the electricity conservation “nudge” of providing feedback to households on own and peers’ home electricity usage works with liberals, it can backfire with conservatives. Our regression estimates predict that a Democratic household that pays for electricity from renewable sources, that donates to environmental groups, and that lives in a liberal neighborhood reduces its consumption by 3 percent in response to this nudge. A Republican household that does not pay for electricity from renewable sources and that does not donate to environmental groups increases its consumption by 1 percent.
FOREIGN INVESTMENT POLICIES AND ENVIRONMENT

. We consider a North-South model of capital mobility in which foreign investment adversely impacts the environment in South. By focusing on the strategic aspects of environmental policies, among other things, we compare different policy regimes, i.e., different combinations of tax and quota. More specifically, we investigate the (non)equivalence of these policy regimes.
Gait recognition by two-stage principal component analysis

We describe a methodology for classification of gait (walk, run, jog, etc.) and recognition of individuals based on gait using two successive stages of principal component analysis (PCA) on kinematic data. In psychophysical studies, we have found that observers are sensitive to specific "motion features" that characterize human gait. These spatiotemporal motion features closely correspond to the first few principal components (PC) of the kinematic data. The first few PCs provide a representation of an individual gait as trajectory along a low-dimensional manifold in PC space. A second stage of PCA captures variability in the shape of this manifold across individuals or gaits. This simple eigenspace based analysis is capable of accurate classification across subjects.
Payoff complementarities and financial fragility: Evidence from mutual fund outflows $

The paper provides empirical evidence that strategic complementarities among investors generate fragility in financial markets. Analyzing mutual fund data, we find that, consistent with a theoretical model, funds with illiquid assets (where complementarities are stronger) exhibit stronger sensitivity of outflows to bad past performance than funds with liquid assets. We also find that this pattern disappears in funds where the shareholder base is composed mostly of large investors. We present further evidence that these results are not attributable to alternative explanations based on the informativeness of past performance or on clientele effects. We analyze the implications for funds’ performance and policies.
A logic for reasoning about digital rights

We present a logic for reasoning about licenses, which are "terms of use" for digital resources. The logic provides a language for writing both properties of licenses and specifications that govern a client's actions. We discuss the complexity of checking properties and specifications written in our logic and propose a technique for verification. A key feature of our approach is that it is essentially parameterized by the language in which the licenses are written, provided that this language can be given a trace-based semantics. We consider two license languages to illustrate this flexibility.
The econometric analysis of transition data

Preface Part I. Model Building: 1. Some basic results 2. Covariates and the hazard function 3. Parametric families of duration distribution 4. Mixture models 5. Some important processes 6. Some structural transition models Part II. Inference: 7. Identifiability issues 8. Fully parametric inference 9. Limited information inference 10. Misspecification analysis 11. Residual analysis Appendix 1: The gamma function and distribution Appendix 2: Some properties of the Laplace transform Bibliography Index.
Water-soluble, self-assembling container molecules: an update

Over the past five years, an important development in the area of self-assembling containers has been the increase in interest in those containers that function in aqueous solution. This progress is a reflection of a similar trend within supramolecular chemistry in general, and is driven in part by the need to address issues and challenges within the biological sciences, as well as a desire to develop new strategies for greener chemistries carried out in water. It is also an opportunity to learn more about fundamental topics such as the hydrophobic effect. In this critical review we discuss progress in aqueous-based self-assembling container molecules since 2005 (177 references).
Molecular dynamics simulation of the SH3 domain aggregation suggests a generic amyloidogenesis mechanism.

Abstract We use molecular dynamics simulation to study the aggregation of Src SH3 domain proteins. For the case of two proteins, we observe two possible aggregation conformations: the closed form dimer and the open aggregation state. The closed dimer is formed by “domain swapping”—the two proteins exchange their RT-loops. All the hydrophobic residues are buried inside the dimer so proteins cannot further aggregate into elongated amyloid fibrils. We find that the open structure—stabilized by backbone hydrogen bond interactions—packs the RT-loops together by swapping the two strands of the RT-loop. The packed RT-loops form a β-sheet structure and expose the backbone to promote further aggregation. We also simulate more than two proteins, and find that the aggregate adopts a fibrillar double β-sheet structure, which is formed by packing the RT-loops from different proteins. Our simulations are consistent with a possible generic amyloidogenesis scenario.
A Simple Synthesis of 5-Amino-3-(2-dimethylaminoethyl) indole [5-Amino-N,N-dimethyltryptamine]

Abstract A short (three step) synthesis of 5-amino-3-(2-dimethylaminoethyl)indole [5-amino-N, N-dimethyltryptamine, 4] from commercially available starting materials is presented. Reaction of 5-nitroindole with oxalyl chloride followed by dimethylamine afforded N,N-dimethyl 5-nitroindole-3-glyoxamide (1), which was reduced by diborane to 5-nitro-3-(2-dimethylaminoethyl)indole (3). Catalytic reduction of (3) afforded the title compound in 19% overall yield from 5-nitroindole.
The Compact Nucleus of the Deep Silicate Absorption Galaxy NGC 4418

High-resolution Hubble Space Telescope (HST) near-infrared and Keck mid-infrared images of the heavily extinguished infrared-luminous galaxy NGC 4418 are presented. These data make it possible to observe the imbedded near-infrared structure on scales of 10–20 pc and to constrain the size of the mid-infrared–emitting region. The 1.1–2.2 μm data of NGC 4418 show no clear evidence of nuclear star clusters or of a reddened active galactic nucleus. Instead, the nucleus of the galaxy consists of a ~100–200 pc linear structure with fainter structures extending radially outward. The near-infrared colors of the linear feature are consistent with a 10–300 Myr starburst suffering moderate levels (a few magnitudes) of visual extinction. At 7.9–24.5 μm NGC 4418 has estimated size upper limits in the range of 30–80 pc. These dimensions are consistent with the highest-resolution radio observations obtained to date of NGC 4418, as well as the size of 50–70 pc expected for a blackbody with a temperature derived from the 25, 60, and 100 μm flux densities of the galaxy. Further, a spectral energy distribution constructed from the multiwavelength mid-infrared observations shows the strong silicate absorption feature at 10 μm, consistent with previous mid-infrared observations of NGC 4418. An infrared surface brightness of ~2.1 × 10^(13) L_⊙ kpc^(-2) is derived for NGC 4418. Such a value, though consistent with the surface brightness of warm ultraluminous infrared galaxies [L_(IR)(8–1000 μm) ≥ 10^(12) L_⊙], such as IRAS 05189-2524 and IRAS 08572+3915, is not large enough to distinguish NGC 4418 as a galaxy powered by an active galactic nucleus, as opposed to a lower surface brightness starburst.
On Stable Factor Structures in the Pricing of Risk: Do Time‐Varying Betas Help or Hurt?

There is now considerable evidence suggesting that estimated betas of unconditional capital asset pricing models (CAPMs) exhibit statistically significant time variation. Therefore, many have advocated the use of conditional CAPMs. If we succeed in capturing the dynamics of beta risk, we are sure to outperform constant beta models. However, if the beta risk is inherently misspecified, there is a real possibility that we commit serious pricing errors, potentially larger than with a constant traditional beta model. In this paper we show that this is indeed the case, namely that pricing errors with constant traditional beta models are smaller than with conditional CAPMs. LINEAR FACTOR MODELS such as the unconditional capital asset pricing model (CAPM) and the arbitrage pricing theory (APT) have been the cornerstone of theoretical and empirical finance for decades now. Supported by seminal papers, like those of Sharpe (1964), Lintner (1965), Merton (1973), and Ross (1976), they are the most widely used tools to value the return on risky assets. Although the theory maintains a linear and stable relationship between risk factors and returns, there is now considerable empirical evidence documenting time variation in market betas and other factor payoffs. This is perhaps not so surprising because the theoretical underpinnings of the unconditional arbitrage-pricing theory reveal that timeinvariant linear factor structures are only obtained when one imposes strong assumptions on the underlying probability distributions and investors’ attitudes toward risk. 1 In practice, many portfolio managers constantly update and reestimate factor returns, and indeed Harvey (1989), Ferson and Harvey (1991, 1993),
The Mass Assembly Histories of Galaxies of Various Morphologies in the GOODS Fields

We present an analysis of the growth of stellar mass with cosmic time partitioned according to galaxy morphology. Using a well-defined catalog of 2150 galaxies based, in part, on archival data in the Great Observatories Origins Deep Survey (GOODS) fields, we assign morphological types in three broad classes (ellipticals, spirals, peculiar/irregulars) to a limit of zAB = 22.5 and make the resulting catalog publicly available. Utilizing 893 spectroscopic redshifts, supplemented by 1013 determined photometrically, we combine optical photometry from the GOODS catalog and deep Ks-band imaging to assign stellar masses to each galaxy in our sample. We find little evolution in the form of the galaxy stellar mass function from z ~ 1 to z = 0, especially at the high-mass end where our results are most robust. Although the population of massive galaxies is relatively well established at z ~ 1, its morphological mix continues to change, with an increasing proportion of early-type galaxies at later times. By constructing type-dependent stellar mass functions, we show that in each of three redshift intervals, E/S0 galaxies dominate the higher mass population, while spirals are favored at lower masses. This transition occurs at a stellar mass of (2-3) × 1010 M☉ at z ~ 0.3 (similar to local studies), but there is evidence that the relevant mass scale moves to higher mass at earlier epochs. Such evolution may represent the morphological extension of the downsizing phenomenon, in which the most massive galaxies stop forming stars first, with lower mass galaxies becoming quiescent later. We infer that more massive galaxies evolve into spheroidal systems at earlier times, and that this morphological transformation may only be completed 1-2 Gyr after the galaxies emerge from their active star-forming phase. We discuss several lines of evidence suggesting that merging may play a key role in generating this pattern of evolution.
A three-mass tethered system for micro-g/variable-g applications

This paper describes a Space-Station attached tethered system for micro-g/variable-g applications. The system consists of three platforms: the Space Station, an end mass anchored at the end of a 10 km long kevlar tether and a micro-g/variable-g laboratory with the capability of crawling along the tether. Control strategies are devised for performing both the deployment and the station-keeping maneuvers of the system. Effective algorithms are identified for damping out the major vibrational modes.
Network rupture and the flow of concentrated polymer solutions

Network rupture hypothesis and molecular structure considerations used in obtaining constitutive equations for flow of polymer melts and solutions
An algorithm to estimate unsteady and quasi-steady pressure fields from velocity field measurements

We describe and characterize a method for estimating the pressure field corresponding to velocity field measurements such as those obtained by using particle image velocimetry. The pressure gradient is estimated from a time series of velocity fields for unsteady calculations or from a single velocity field for quasi-steady calculations. The corresponding pressure field is determined based on median polling of several integration paths through the pressure gradient field in order to reduce the effect of measurement errors that accumulate along individual integration paths. Integration paths are restricted to the nodes of the measured velocity field, thereby eliminating the need for measurement interpolation during this step and significantly reducing the computational cost of the algorithm relative to previous approaches. The method is validated by using numerically simulated flow past a stationary, two-dimensional bluff body and a computational model of a three-dimensional, self-propelled anguilliform swimmer to study the effects of spatial and temporal resolution, domain size, signal-to-noise ratio and out-of-plane effects. Particle image velocimetry measurements of a freely swimming jellyfish medusa and a freely swimming lamprey are analyzed using the method to demonstrate the efficacy of the approach when applied to empirical data.
Corporate Share Repurchases in the 1990s: What Role Do Stock Options Play?

This paper investigates how the growth of stock option programs has affected corporate payout policy. Given that earnings per share (EPS) is widely used in equity valuation, some corporations may opt to repurchase shares to avoid the dilution of EPS that results from past stock option grants. Executives may also prefer distributing cash by repurchasing shares or retaining more earnings, as opposed to increasing dividends, to enhance the value of their own stock options. This paper tests the importance of these two hypotheses using crosssectional and panel data on stock option programs. I find that stock options granted to top executives affect payout policy differently than do stock options granted to other employees. Option grants in general are associated with increased share repurchases and increased total payouts. However, the larger is the executives’ holding of stock options, the more apt the firm is to retain more earnings and curtail cash distributions. Analysis of panel data for a sample of large firms suggests that firms conduct an ongoing repurchase of shares over the life of an option that undoes much of the dilution to EPS that results from past stock option grants.
Embedding a Field Experiment in Contingent Valuation to Measure Context-Dependent Risk Preferences: An Application to Wildfire Risk

This paper contributes towards the development of an approach that would generate welfare measures that accommodate non-expected utility risk preferences. Combining the merits of elicitation approaches used in field experiments with contingent valuation, we embed an experimental design that systematically varies probabilities and losses across a survey sample in a willingness to pay elicitation format, where a hypothetical situation is described that closely resembles the actual policy context. We apply the proposed elicitation and estimation approaches to estimate the risk preferences of a representative homeowner who faces probabilistic wildfire risks and an investment option that reduces losses due to wildfire. Based on prospect theory, we estimate parameters of probability weighting, risk preferences and use individual characteristics as covariates for these parameters and as utility shifters. We find that risk preferences are consistent with non-expected utility theory. We also find that the use of individual characteristics as utility shifters, as is standard non-market valuation, attenuates some of the effects of the probability weights. Prior experience with wildfire is associated with risk preferences that are closer to expected utility theory.
Shark: SQL and rich analytics at scale

Shark is a new data analysis system that marries query processing with complex analytics on large clusters. It leverages a novel distributed memory abstraction to provide a unified engine that can run SQL queries and sophisticated analytics functions (e.g. iterative machine learning) at scale, and efficiently recovers from failures mid-query. This allows Shark to run SQL queries up to 100X faster than Apache Hive, and machine learning programs more than 100X faster than Hadoop. Unlike previous systems, Shark shows that it is possible to achieve these speedups while retaining a MapReduce-like execution engine, and the fine-grained fault tolerance properties that such engine provides. It extends such an engine in several ways, including column-oriented in-memory storage and dynamic mid-query replanning, to effectively execute SQL. The result is a system that matches the speedups reported for MPP analytic databases over MapReduce, while offering fault tolerance properties and complex analytics capabilities that they lack.
The Outbursts and Orbit of the Accreting Pulsar GS 1843-02=2S 1845-024

We present observations of a series of 10 outbursts of pulsed hard X-ray flux from the transient 10.6 mHz accreting pulsar GS 1843-02, using the Burst and Transient Source Experiment on the Compton Gamma Ray Observatory. These outbursts occurred regularly every 242 days, coincident with the ephemeris of the periodic transient GRO J1849-03, which has recently been identified with the SAS 3 source 2S 1845-024. Our pulsed detection provides the first clear identification of GS 1843-02 with 2S 1845-024. We present a pulse timing analysis that shows that the 2S 1845-024 outbursts occur near the periastron passage of the neutron star's highly eccentric (e=0.88 ± 0.01) 242.18 ± 0.01 day period binary orbit about a high-mass (M_c>7 M_☉) companion. The orbit and transient outburst pattern strongly suggest that the pulsar is in a binary system with a Be star. Our observations show a long-term spin-up trend, with most of the spin-up occurring during the outbursts. From the measured spin-up rates and inferred luminosities we conclude that an accretion disk is present during the outbursts.
Smekal-Raman Type Modified X-Ray Scattering

With the help of a bent mica Cauchois spectrograph and a bent quartz spectrograph, and using K alpha and K beta radiations of Cu and Mo from the sealed-off x-ray tubes with graphite, polystyrene, and Be as scattering specimens, the modified lines of Smekal-Raman type were observed in calculated positions using the spectrographs for each of the scattering specimens. Tracings of the original microphotometer records are given, clearly showing Rayleigh lines, Compton bands, and Smekal-Raman type modified lines in x-ray scattering. (W.D.M.)
Evaluation of Longitudinal Desired Dynamics for Dynamic-Inversion Controlled Generic Reentry Vehicles

Dynamic inversion is a control synthesis technique in which the inherent dynamics of a dynamical system are canceledoutandreplacedbydesireddynamics,selectedbythedesigner.Theoutputofsuchaninner-loopcontroller isthecontrol input, whichproducesthedesiredclosed-loop response.Thedesireddynamicsessentially form aloopshaping compensator that affects the closed-loop response of the entire system. This paper attempts to quantify the effect of different forms of desired dynamics on the closed-loop performance and robustness of a dynamicinversion e ight controllerfor reentry vehicles. Proportional, proportional-integral, e ying-quality, and ride-quality forms of desired dynamics are evaluated using time-domain specie cations, robustness requirements on singular values, quadratic cost, and a passenger ride comfort index. Longitudinal controllers are synthesized for a generic X-38 type crew return vehicle, using a set of linear models at subsonic, transonic, and hypersonic e ight conditions. For the candidate forms of desired dynamics and inversion controller structures evaluated here, results indicate that the form used impacts closed-loop performance and robustness and more so for some inversion controller structures more than others. The ride-quality dynamics used with a two-loop angle-of-attack inversion controller provide the best overall system performance, in terms of both time-domain and frequency-domain specie cations, and the evaluation criteria.
Multiway Spectral Clustering: A Margin-based Perspective

Spectral clustering is a broad class of clustering procedures in which an intractable combinatorial optimization formulation of clustering is “relaxed” into a tractable eigenvector problem, and in which the relaxed solution is subsequently “rounded” into an approximate discrete solution to the original problem. In this paper we present a novel margin-based perspective on multiway spectral clustering. We show that the margin-based perspective illuminates both the relaxation and rounding aspects of spectral clustering, providing a unified analysis of existing algorithms and guiding the design of new algorithms. We also present connections between spectral clustering and several other topics in statistics, specifically minimum-variance clustering, Procrustes analysis and Gaussian intrinsic autoregression.
Annonaceous Acetogenins: Recent Progress

The Annonaceous acetogenins are promising new antitumor and pesticidal agents that are found only in the plant family Annonaceae. Chemically, they are derivatives of long-chain fatty acids. Biologically, they exhibit their potent bioactivities through depletion of ATP levels via inhibiting complex I of mitochondria and inhibiting the NADH oxidase of plasma membranes of tumor cells. Thus, they thwart ATP-driven resistance mechanisms. This review presents the progress made in the chemistry, biology, and development of these compounds since December 1995.
Adaptive channel allocation spectrum etiquette for cognitive radio networks

In this work, we propose a game theoretic framework to analyze the behavior of cognitive radios for distributed adaptive channel allocation. We define two different objective functions for the spectrum sharing games, which capture the utility of selfish users and cooperative users, respectively. Based on the utility definition for cooperative users, we show that the channel allocation problem can be formulated as a potential game, and thus converges to a deterministic channel allocation Nash equilibrium point. Alternatively, a no-regret learning implementation is proposed for both scenarios and it is shown to have similar performance with the potential game when cooperation is enforced, but with a higher variability across users. The no-regret learning formulation is particularly useful to accommodate selfish users. Non-cooperative learning games have the advantage of a very low overhead for information exchange in the network. We show that cooperation based spectrum sharing etiquette improves the overall network performance at the expense of an increased overhead required for information exchange.
MISR Stereo Heights of Grassland Fire Smoke Plumes in Australia

Plume heights from wildfires are used in climate modeling to predict and understand trends in aerosol transport. This paper examines whether smoke from grassland fires in the desert regions of western and central Australia ever rises above the atmospheric boundary layer. Three methods for deriving plume heights from the Multi-angle Imaging SpectroRadiometer (MISR) instrument were utilized: (1) the MISR standard stereo-height algorithm; (2) the MISR enhanced stereo product; and (3) the MISR INteractive eXplorer (MINX) v.1 tool. To provide context and to search for correlative factors, stereo heights were combined with fire radiant energy flux from the Moderate Resolution Imaging Spectroradiometer instrument, atmospheric structure information from the National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis project model, surface cover from the Australia National Vegetation Information System, and forward and backward trajectories from the National Oceanic and Atmospheric Administration Hybrid Single-Particle Lagrangian Integrated Trajectory model. Although most smoke plumes concentrate in the near-surface boundary layer as expected, some appear to rise higher. Smoke that gets above the boundary layer will travel farther, remain in the atmosphere longer, and therefore have a larger environmental impact. It was previously thought unlikely for grassland fires to inject smoke above the boundary layer. Our findings suggest that climate modelers should reevaluate common assumptions about the heights of smoke plumes when producing aerosol transport models involving grassland fires. A closer examination of grassland fire energetics may also be warranted.