437 research outputs found
Cathodoluminescence of Recent biogenic carbonates: environmental and ontogenetic fingerprint
Cathodoluminescence (CL) examination of Recent biogenic carbonates shows that they are often luminescent regardless of their mineralogical composition (calcite v. aragonite), habitat (marine v. fresh water), way of life (sessile v. vagile) or environment (hyper- v. hyposaline water). Thus, the presence of luminescence in biogenic particles is not a reliable indicator of diagenetic alteration as some authors have suggested. In addition, CL can reveal variations in the mineralogy of shell material (e.g. regenerated calcitic v. primary aragonitic) and can highlight growth-related structures. Manganese (Mn2+) is the most likely activator of this luminescence, and its content in the shells of benthic organisms seems to be linked to growth rate, ontogeny, open sea conditions, bathymetry and salinity. In neritic environments the Mn2+ content and the CL of molluscs and foraminifera appear to increase with decreasing salinity. This study indicates that CL may be an important tool for the determination of environmental and ontogenetic parameters in biogenic carbonates in addition to its current use indiagenetic studie
Discussion of cathodoluminescence of Recent biogenic carbonates: an environmental and ontogenetic fingerprint
Goal: 5000-7500 words Currently: 6,465 words (including everything) Exclusive Dealing: Before Bork, and Beyond
Abstract: Antitrust scholars have come to accept the basic ideas about exclusive dealing that Bork articulated in The Antitrust Paradox. Indeed, they have even extended his list of reasons why exclusive dealing can promote economic efficiency. Yet they have also taken up his challenge to explain how exclusive dealing could possibly cause harm, and have modelled a variety of special cases where it does. Some (albeit not all) of these are sufficiently plausible to be useful to prosecutors and judges
Discussion of cathodoluminescence of Recent biogenic carbonates: an environmental and ontogenetic fingerprint
New Rotation Periods in the Pleiades: Interpreting Activity Indicators
We present results of photometric monitoring campaigns of G, K and M dwarfs in the Pleiades carried out in 1994, 1995 and 1996. We have determined rotation periods for 18 stars in this cluster. In this paper, we examine the validity of using observables such as X-ray activity and amplitude of photometric variations as indicators of angular momentum loss. We report the discovery of cool, slow rotators with high amplitudes of variation. This contradicts previous conclusions about the use of amplitudes as an alternate diagnostic of the saturation of angular momentum loss. We show that the X-ray data can be used as observational indicators of mass-dependent saturation in the angular momentum loss proposed on theoretical grounds
New rotation periods in the Pleiades: Interpreting activity indicators
We present results of photometric monitoring campaigns of G, K and M dwarfs
in the Pleiades carried out in 1994, 1995 and 1996. We have determined rotation
periods for 18 stars in this cluster. In this paper, we examine the validity of
using observables such as X-ray activity and amplitude of photometric
variations as indicators of angular momentum loss. We report the discovery of
cool, slow rotators with high amplitudes of variation. This contradicts
previous conclusions about the use of amplitudes as an alternate diagnostic of
the saturation of angular momentum loss. We show that the X-ray data can be
used as observational indicators of mass-dependent saturation in the angular
momentum loss proposed on theoretical grounds.Comment: 24 pages, LaTex (AASTeX); includes 8 postscript figures and 4 Latex
tables. To appear in ApJ, Feb. 1, 1998. Postscript version of preprint can be
obtained from http://casa.colorado.edu/~anitak/pubs.htm
Cyclotron Modeling Phase-Resolved Infrared Spectroscopy of Polars III: AM Herculis and ST Leo Minoris
We present phase-resolved low resolution infrared spectra of AM Her and ST
LMi, two low-field polars that we observed with SPEX on the IRTF. Optical/NIR
lightcurves are also published to help constrain the viewing geometry and
brightness of the objects at the time they were observed. Currently, only
limited IR spectra have been published for these objects, and none with the
phase-coverage presented here. In both cases, the resulting spectra are
dominated by emission from the secondary star in the NIR. However, the emission
regions are also self-eclipsed, allowing us to isolate the cyclotron emission
through subtraction of the dim-phase spectrum. We use a ``Constant Lambda''
prescription to model the changing cyclotron features seen in the resulting
data. For AM Her, we find a best fit model of: B = 13.6 MG, kT = 4.0 keV, and
logLambda = 5.0. The cyclotron derived accretion geometry is consistent with an
orbital inclination of 50 degrees and a magnetic co-latitude of 85 degrees. For
ST LMi, B = 12.1 MG, kT = 3.3 keV, and logLambda = 5.7 with an orbital
inclination of 55 degrees and a magnetic co-latitude of 128 degrees.Comment: 12 Pages, 9 figures. To Appear in 2008 August 1 issue of Ap
Reaching a Consensus: Terminology and Concepts Used in Coordination and Decision-Making Research
Research on coordination and decision-making in humans and nonhuman primates has increased considerably throughout the last decade. However, terminology has been used inconsistently, hampering the broader integration of results from different studies. In this short article, we provide a glossary containing the central terms of coordination and decision-making research. The glossary is based on previous definitions that have been critically revised and annotated by the participants of the symposium “Where next? Coordination and decision-making in primate groups” at the XXIIIth Congress of the International Primatological Society (IPS) in Kyoto, Japan. We discuss a number of conceptual and methodological issues and highlight consequences for their implementation. In summary, we recommend that future studies on coordination and decision-making in animal groups do not use the terms “combined decision” and “democratic/despotic decision-making.” This will avoid ambiguity as well as anthropocentric connotations. Further, we demonstrate the importance of 1) taxon-specific definitions of coordination parameters (initiation, leadership, followership, termination), 2) differentiation between coordination research on individual-level process and group-level outcome, 3) analyses of collective action processes including initiation and termination, and 4) operationalization of successful group movements in the field to collect meaningful and comparable data across different species
Sequential position readout from arrays of micromechanical cantilever sensors
Sequential position readout from a microfabricated array of eight cantilever-type sensors ~silicon technology! is demonstrated. In comparison with single sensors we find that mechanical disturbances from noise, such as from vibrations, turbulent gas flow, or abrupt pressure changes, can be effectively removed in array sensors by recording difference signals with respect to reference cantilevers. We demonstrate that chemically specific responses can be extracted in a noisy environment using a sensor to detect specific chemical interactions and an uncoated cantilever as reference
Quasi-periodic oscillations in accreting magnetic white dwarfs II. The asset of numerical modelling for interpreting observations
Magnetic cataclysmic variables are close binary systems containing a strongly
magnetized white dwarf that accretes matter coming from an M-dwarf companion.
High-energy radiation coming from those objects is emitted from the accretion
column close to the white dwarf photosphere at the impact region. Its
properties depend on the characteristics of the white dwarf and an accurate
accretion column model allows the properties of the binary system to be
inferred, such as the white dwarf mass, its magnetic field, and the accretion
rate. We study the temporal and spectral behaviour of the accretion region and
use the tools we developed to accurately connect the simulation results to the
X-ray and optical astronomical observations. The radiation hydrodynamics code
Hades was adapted to simulate this specific accretion phenomena. Classical
approaches were used to model the radiative losses of the two main radiative
processes: bremsstrahlung and cyclotron. The oscillation frequencies and
amplitudes in the X-ray and optical domains are studied to compare those
numerical results to observational ones. Different dimensional formulae were
developed to complete the numerical evaluations. The complete characterization
of the emitting region is described for the two main radiative regimes: when
only the bremsstrahlung losses and when both cyclotron and bremsstrahlung
losses are considered. The effect of the non-linear cooling in- stability
regime on the accretion column behaviour is analysed. Variation in luminosity
on short timescales (~ 1 s quasi-periodic oscillations) is an expected
consequence of this specific dynamic. The importance of secondary shock
instability on the quasi-periodic oscillation phenomenon is discussed. The
stabilization effect of the cyclotron process is confirmed by our numerical
simulations, as well as the power distribution in the various modes of
oscillation.Comment: 13 pages, 13 figures, 2 tables. Accepted for publication in A&
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