375 research outputs found
The use of accruals to manage reported earnings: theory and evidence
This paper develops a model in which firm managers maximize their own compensation by using accruals to manage reported earnings. The results of the model suggest that the form of the managerial compensation function and managerial time preferences may have an important influence on the relationship between accruals and latent earnings. Among the possible relationships suggested by the model are strategies we call Smooth Income, Occasional Big Bath, Live for Today, and Maximize Variability, each of which suggests a different reporting strategy pursued by managers. Most empirical tests of accruals are inconsistent with this and other theoretical models because they include a single earnings variable in a linear regression analysis. Instead, we document the reporting of accruals by two firms, Sunbeam and Citicorp, that is consistent with the “Live for Today” and “Occasional Big Bath” strategies.Investments
On the uniqueness of community banks
To the public, all banks seem alike. But banking insiders make important distinctions between community banks and all other banks. Policymakers worry that community banks’ unique characteristics threaten their survival in the face of industry consolidation. However, despite dramatic regulatory and technological changes in the industry in the past two decades, community banks have not only survived but often prospered. ; This article explores the differences between community banks and larger banks to discover what makes community banks unique. Large banks engage primarily in transactional banking—the provision of highly standardized intermediation services, such as gathering deposits and extending loans, that require little human input to manage. Community banks, in contrast, typically focus on relationship banking, which requires more human input, more detailed credit evaluation, and localized decision making. ; Examining profit and risk measures for the 1998–2002 period for both community banks and large banking organizations, the authors find evidence that small banks were generally profitable. In all but the smallest size category, community banks have performed as well as, and often better than, large banks in managing net interest margins, aggregate profits, and credit risk. Also, community banks are more likely to adopt Subchapter S tax status, which allows them to avoid direct federal income taxation and pass tax benefits on to shareholders. These institutions typically have relatively higher returns on both equity and assets than larger banks do. Whether community banks will be able to sustain this good performance will depend, the authors conclude, on how well managers find valuable relationship lending niches, invest bank capital, and balance asset quality with growth.Community banks
Kepler Input Catalog: Photometric Calibration and Stellar Classification
We describe the photometric calibration and stellar classification methods
used to produce the Kepler Input Catalog (KIC). The KIC is a catalog containing
photometric and physical data for sources in the Kepler Mission field of view;
it is used by the mission to select optimal targets. We derived atmospheric
extinction corrections from hourly observations of secondary standard fields
within the Kepler field of view. Repeatability of absolute photometry for stars
brighter than magnitude 15 is typically 2%. We estimated stellar parameters
Teff, log(g), log (Z), E_{B-V} using Bayesian posterior probability
maximization to match observed colors to Castelli stellar atmosphere models. We
applied Bayesian priors describing the distribution of solar-neighborhood stars
in the color-magnitude diagram (CMD), in log (Z)$, and in height above the
galactic plane. Comparisons with samples of stars classified by other means
indicate that in most regions of the CMD, our classifications are reliable
within about +/- 200 K and +/- 0.4 dex in log (g). It is difficult to assess
the reliability of our log(Z) estimates, but there is reason to suspect that it
is poor, particularly at extreme Teff. Of great importance for the Kepler
Mission, for Teff <= 5400 K, the distinction between main-sequence stars and
giants has proved to be reliable with better than 98% confidence. The KIC is
available through the MAST data archive.Comment: 77 pages, 12 figures, 1 Table. Accepted by Astronomical Journal 24
July 201
Turbulent CO2 Flux Measurements by Lidar: Length Scales, Results and Comparison with In-Situ Sensors
The vertical CO2 flux in the atmospheric boundary layer (ABL) is investigated with a Doppler differential absorption lidar (DIAL). The instrument was operated next to the WLEF instrumented tall tower in Park Falls, Wisconsin during three days and nights in June 2007. Profiles of turbulent CO2 mixing ratio and vertical velocity fluctuations are measured by in-situ sensors and Doppler DIAL. Time and space scales of turbulence are precisely defined in the ABL. The eddy-covariance method is applied to calculate turbulent CO2 flux both by lidar and in-situ sensors. We show preliminary mean lidar CO2 flux measurements in the ABL with a time and space resolution of 6 h and 1500 m respectively. The flux instrumental errors decrease linearly with the standard deviation of the CO2 data, as expected. Although turbulent fluctuations of CO2 are negligible with respect to the mean (0.1 %), we show that the eddy-covariance method can provide 2-h, 150-m range resolved CO2 flux estimates as long as the CO2 mixing ratio instrumental error is no greater than 10 ppm and the vertical velocity error is lower than the natural fluctuations over a time resolution of 10 s
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Kepler-4B: A Hot Neptune-Like Planet of A G0 Star Near Main-Sequence Turnoff
Early time-series photometry from NASA's Kepler spacecraft has revealed a planet transiting the star we term Kepler-4, at R.A. = 19(h)02(m)27.(s)68, delta = +50 degrees 08'08 '' 7. The planet has an orbital period of 3.213 days and shows transits with a relative depth of 0.87 x 10(-3) and a duration of about 3.95 hr. Radial velocity (RV) measurements from the Keck High Resolution Echelle Spectrometer show a reflex Doppler signal of 9.3(-1.9)(+1.1) m s(-1), consistent with a low-eccentricity orbit with the phase expected from the transits. Various tests show no evidence for any companion star near enough to affect the light curve or the RVs for this system. From a transit-based estimate of the host star's mean density, combined with analysis of high-resolution spectra, we infer that the host star is near turnoff from the main sequence, with estimated mass and radius of 1.223(-0.091)(+0.053) M(circle dot) and 1.487(-0.084)(+0.071) R(circle dot).We estimate the planet mass and radius to be {M(P), R(P)} = {24.5 +/- 3.8 M(circle plus), 3.99 +/- 0.21 R(circle plus)}. The planet's density is near 1.9 g cm(-3); it is thus slightly denser and more massive than Neptune, but about the same size.W. M. Keck FoundationNASA's Science Mission DirectorateAstronom
White-light flares on cool stars in the Kepler Quarter 1 Data
We present the results of a search for white light flares on the ~23,000 cool
dwarfs in the Kepler Quarter 1 long cadence data. We have identified 373
flaring stars, some of which flare multiple times during the observation
period. We calculate relative flare energies, flare rates and durations, and
compare these with the quiescent photometric variability of our sample. We find
that M dwarfs tend to flare more frequently but for shorter durations than K
dwarfs, and that they emit more energy relative to their quiescent luminosity
in a given flare than K dwarfs. Stars that are more photometrically variable in
quiescence tend to emit relatively more energy during flares, but variability
is only weakly correlated with flare frequency. We estimate distances for our
sample of flare stars and find that the flaring fraction agrees well with other
observations of flare statistics for stars within 300 pc above the Galactic
Plane. These observations provide a more rounded view of stellar flares by
sampling stars that have not been pre-selected by their activity, and are
informative for understanding the influence of these flares on planetary
habitability.Comment: 42 pages, 10 figures, 2 tables; Accepted for publication in the
Astronomical Journa
The Association Between Persistent White-Matter Abnormalities and Repeat Injury After Sport-Related Concussion
Objective: A recent systematic review determined that the physiological effects of concussion may persist beyond clinical recovery. Preclinical models suggest that ongoing physiological effects are accompanied by increased cerebral vulnerability that is associated with risk for subsequent, more severe injury. This study examined the association between signal alterations on diffusion tensor imaging following clinical recovery of sport-related concussion in athletes with and without a subsequent second concussion. Methods: Average mean diffusivity (MD) was calculated in a region of interest (ROI) in which concussed athletes (n = 82) showed significantly elevated MD acutely after injury (<48 h), at an asymptomatic time point, 7 days post-return to play (RTP), and 6 months relative to controls (n = 69). The relationship between MD in the identified ROI and likelihood of sustaining a subsequent concussion over a 1-year period was examined with a binary logistic regression (re-injured, yes/no). Results: Eleven of 82 concussed athletes (13.4%) sustained a second concussion within 12 months of initial injury. Mean MD at 7 days post-RTP was significantly higher in those athletes who went on to sustain a repeat concussion within 1 year of initial injury than those who did not (p = 0.048; d = 0.75). In this underpowered sample, the relationship between MD at 7 days post-RTP and likelihood of sustaining a secondary injury approached significance [χ2 (1) = 4.17, p = 0.057; B = 0.03, SE = 0.017; OR = 1.03, CI = 0.99, 1.07]. Conclusions: These preliminary findings raise the hypothesis that persistent signal abnormalities in diffusion imaging metrics at RTP following concussion may be predictive of a repeat concussion. This may reflect a window of cerebral vulnerability or increased susceptibility following concussion, though understanding the clinical significance of these findings requires further study
Pulsar scintillation through thick and thin: Bow shocks, bubbles, and the broader interstellar medium
Observations of pulsar scintillation are among the few astrophysical probes of very small-scale (≲ au) phenomena in the interstellar medium (ISM). In particular, characterization of scintillation arcs, including their curvature and intensity distributions, can be related to interstellar turbulence and potentially overpressurized plasma in local ISM inhomogeneities, such as supernova remnants, H II regions, and bow shocks. Here we present a survey of eight pulsars conducted at the Five-hundred-metre Aperture Spherical Telescope (FAST), revealing a diverse range of scintillation arc characteristics at high sensitivity. These observations reveal more arcs than measured previously for our sample. At least nine arcs are observed toward B1929+10 at screen distances spanning ~90 per cent of the pulsar’s 361 pc path length to the observer. Four arcs are observed toward B0355+54, with one arc yielding a screen distance as close as ∼105 au (<1 pc) from either the pulsar or the observer. Several pulsars show highly truncated, low-curvature arcs that may be attributable to scattering near the pulsar. The scattering screen constraints are synthesized with continuum maps of the local ISM and other well-characterized pulsar scintillation arcs, yielding a three-dimensional view of the scattering media in context
Discovery of the Transiting Planet Kepler-5B
We present 44 days of high duty cycle, ultra precise photometry of the 13th magnitude star Kepler-5 (KIC 8191672, T(eff) = 6300 K, log g = 4.1), which exhibits periodic transits with a depth of 0.7%. Detailed modeling of the transit is consistent with a planetary companion with an orbital period of 3.548460 +/- 0.000032 days and a radius of 1.431(-0.052)(+0.041) R(J). Follow-up radial velocity measurements with the Keck HIRES spectrograph on nine separate nights demonstrate that the planet is more than twice as massive as Jupiter with a mass of 2.114(-0.059)(+0.056) M(J) and a mean density of 0.894 +/- 0.079 g cm(-3).NASA's Science Mission DirectorateAstronom
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