Stratigraphic biases in the analysis of taxonomic survivorship

Paleobiology ◽  
1975 ◽  
Vol 1 (4) ◽  
pp. 343-355 ◽  
Author(s):  
J. John Sepkoski
Keyword(s):  
Simple Model ◽  
Lognormal Distribution ◽  
Fossil Record ◽  
The Other ◽  
Time Intervals ◽  
Survivorship Analysis ◽  
Other Hand ◽  
Incomplete Sampling ◽  
Biologic Factors

Taxonomic survivorship curves may reflect stratigraphic as well as biologic factors. The approximately lognormal distribution of lengths of Phanerozoic time intervals produces an error in the estimation of taxonomic durations that is also lognormally distributed. As demonstrated by several simulated examples, this error may cause concave taxonomic survivorship curves to appear linear, especially if the maximum durations involved are relatively short. The error of estimation also makes highly concave taxonomic survivorship curves virtually unrecognizable. Incomplete sampling of the fossil record, on the other hand, may not be a serious problem in survivorship analysis. Simulated paleontological sampling employing a simple model suggests that survivorship curves tend to retain their original shapes even when as few as 20% of the taxa have been discovered. However, concave taxonomic survivorship curves tend to lose their concavity as efficiency of sampling declines.

Did Ground Cover Change Over Geologic Time?

2000 ◽  
Vol 6 ◽  
pp. 171-182 ◽  
Author(s):  
Ben A. LePage ◽  
Hermann W. Pfefferkorn
Keyword(s):  
Fossil Record ◽  
Ground Cover ◽  
The Other ◽  
Detailed Account ◽  
Geologic Time ◽  
The Past ◽  
Other Hand ◽  
Plant Fossil

When one hears the term “ground cover,” one immediately thinks of “grasses.” This perception is so deep-seated that paleobotanists even have been overheard to proclaim that “there was no ground cover before grasses.” Today grasses are so predominant in many environments that this perception is perpetuated easily. On the other hand, it is difficult to imagine the absence or lack of ground cover prior to the mid-Tertiary. We tested the hypothesis that different forms of ground cover existed in the past against examples from the Recent and the fossil record (Table 1). The Recent data were obtained from a large number of sources including those in the ecological, horticultural, and microbiological literature. Other data were derived from our knowledge of Precambrian life, sedimentology and paleosols, and the plant fossil record, especially in situ floras and fossil “monocultures.” Some of the data are original observations, but many others are from the literature. A detailed account of these results will be presented elsewhere (Pfefferkorn and LePage, in preparation).

On the Legal and Illegal Behavior of the Regulated Firm

1986 ◽  
Vol 14 (4) ◽  
pp. 431-447
Author(s):  
Lawrence Martin
Keyword(s):  
Simple Model ◽  
Optimal Choice ◽  
Price Regulation ◽  
The Other ◽  
Production Plan ◽  
Illegal Activity ◽  
The Real ◽  
Illegal Behavior ◽  
Other Hand ◽  
Regulated Firm

This article develops a simple model of a firm's privately optimal choice of the degree to which it will abide with regulations. The model allows for the firm to disguise its illegal actions in order to avoid detection and to expend resources to mitigate possible punishment for violations. Both price and quantity type regulatory schemes are considered. Under quantity regulation noncompliance increases the total amount of the regulated activity and distorts efficiency in production. Price regulation, on the other hand, introduces a kind of dichotomy between the real production plan of the firm and its illegal activity. Even though price regulations are substantially evaded, the total amount of the regulated activity remains unchanged, and the firm continues to produce efficiently.

ORIGINATIONS AND EXTINCTIONS: ANALYSES OF FOSSIL DATA AND SIMULATIONS

2000 ◽  
Vol 11 (02) ◽  
pp. 277-285 ◽  
Author(s):  
TANE RAY ◽  
LEO MOSELEY ◽  
NAEEM JAN
Keyword(s):  
Fourier Transform ◽  
Frequency Dependence ◽  
Frequency Spectrum ◽  
Fossil Record ◽  
Trophic Levels ◽  
The Other ◽  
Simulation Data ◽  
The Past ◽  
Other Hand ◽  
Fossil Data

We analyse the fossil data of Benton1 with and without interpolation schemes. By Fourier transform analysis, we find a frequency dependence of the amplitude of 1/f for the various interpolation schemes used in the past. We illustrate that shuffling the interpolated data changes the spectra only slightly. On the other hand, an identical analysis performed on the raw (uninterpolated) fossil data gives a flat frequency spectrum. We conclude that the 1/f behavior is an artifact of the interpolation schemes. We next introduce a simulation of extinctions driven only by interactions between two trophic levels. Fourier transform analysis of the simulation data shows a frequency dependence of 1/f. When the data are grouped into a form resembling the fossil record the frequency dependence vanishes, giving a flat spectrum. Our simulation produces a frequency spectrum that agrees with the observed fossil record.

Who Uses Interest Arbitration? The Case of British Columbia's Teachers, 1947–1981

ILR Review ◽  
1989 ◽  
Vol 42 (3) ◽  
pp. 363-379 ◽  
Author(s):  
Janet Currie
Keyword(s):  
British Columbia ◽  
Simple Model ◽  
Empirical Finding ◽  
The Other ◽  
Principal Agent ◽  
Data Set ◽  
Unique Data ◽  
Other Hand ◽  
Previous Round

Several researchers have attempted to identify the circumstances under which parties subject to compulsory interest arbitration will actually push a contract dispute to arbitration. In this paper, a simple model that incorporates elements of the leading hypotheses is tested using a unique data set spanning 35 years of compulsory conventional arbitration experience among teachers in British Columbia. The strongest empirical finding is that bargaining units that used arbitration in the previous round of negotiations were at least ten percent more likely than other units to use it in the current round. On the other hand, variables intended to capture attitudes toward risk, changes in the degree of uncertainty associated with arbitral outcomes, differing beliefs about likely arbitral outcomes, and principal-agent problems were found to have little impact on the estimated probability of using arbitration.

The contractile vacuole of Amoeba proteus. Some of the consequences of the microcoalescence hypothesis

1983 ◽  
Vol 61 (12) ◽  
pp. 2669-2673 ◽  
Author(s):  
Pierre Couillard ◽  
Marc Bourdeau
Keyword(s):  
Simple Model ◽  
Amoeba Proteus ◽  
Surface Growth ◽  
The Other ◽  
Contractile Vacuole ◽  
Other Hand

A simple model describing the contractile vacuole cycle in the freshwater protozoan Amoeba proteus is used to compute coalescence frequencies of submicroscopic vesicles needed to account for the growth of the vacuole. With this model, microvesicles were first considered as the source of volume and then as contributing the surface for the growing vacuole. Results show that vacuole growth by microvesicle accretion entails excessive fusion frequencies, thus generating a huge surplus of membrane. It is thus unlikely that microvesicle accretion is the only process involved in the growth of the contractile vacuole. On the other hand, vacuolar surface growth through vesicle accretion is much more plausible. The consequences of these facts are discussed.

scholarly journals Sharks eating mosasaurs, dead or alive?

2005 ◽  
Vol 84 (3) ◽  
pp. 335-340 ◽  
Author(s):  
B.M. Rothschild ◽  
L.D. Martin ◽  
A.S. Schulp
Keyword(s):  
Fossil Record ◽  
The Other ◽  
Bite Marks ◽  
Other Hand ◽  
Type Area

AbstractShark bite marks on mosasaur bones abound in the fossil record. Here we review examples from Kansas (USA) and the Maastrichtian type area (SE Netherlands, NE Belgium), and discuss whether they represent scavenging and/or predation. Some bite marks are most likely the result of scavenging. On the other hand, evidence of healing and the presence of a shark tooth in an infected abscess confirm that sharks also actively hunted living mosasaurs.

Theory of Optimum Tire Contour and Its Application

1996 ◽  
Vol 24 (3) ◽  
pp. 184-203 ◽  
Author(s):  
Y. Nakajima ◽  
T. Kamegawa ◽  
A. Abe
Keyword(s):  
Simple Model ◽  
Objective Function ◽  
The Other ◽  
New Approach ◽  
The Past ◽  
Other Hand

Abstract A new approach to determine an optimum tire contour was developed and was applied to improve various tire performances following the corresponding objective function and constraints. Although several tire contour theories have been proposed in the past, some of them were based on a simple model and could not be used to improve tire performances effectively. On the other hand, others were not described by an equation and their application was limited. In the new approach, the optimization technology was applied to efficiently obtain the optimum contour by minimizing an objective function, while satisfying the constraints. The new approach was verified to be able to improve various tire performances.

Kinetics, Microstructure And Mechanisms of Ion Beam Induced Epitaxial Crystallization of Semiconductors.

1985 ◽  
Vol 51 ◽  
Author(s):  
R.G. Elliman ◽  
J.S. Williams ◽  
D.M. Maher ◽  
W.L. Brown
Keyword(s):  
Activation Energy ◽  
Simple Model ◽  
Epitaxial Growth ◽  
Ion Beam ◽  
The Other ◽  
Thermally Induced ◽  
Substrate Orientation ◽  
Epitaxial Crystallization ◽  
Temperature Range ◽  
Other Hand

ABSTRACTIon-beam induced epitaxy is shown to be essentially athermal over the temperature range 200-400°C, and to exhibit no dependence on substrate orientation and little dependence on doping in this regime. On the other hand, the formation and propagation of defects during growth and the interaction of the advancing crystal-amorphous interface with implanted impurities is essentially identical for both thermally induced and ion-beam induced epitaxy. These observations lead to a simple model for ion-beam induced epitaxial crystallization in which epitaxial growth is nucleated by defects generated at, or near, the crystal-amorphous interface by the ion beam. Comparisons of ion-beam induced epitaxy and thermally induced epitaxy suggest that the 2.7 eV activation energy associated with the latter process is dominated by a 2.0 eV nucleation step.

Party Responsibility in the States: Some Causal Factors

1964 ◽  
Vol 58 (1) ◽  
pp. 60-71 ◽  
Author(s):  
Thomas A. Flinn
Keyword(s):  
Simple Model ◽  
Policy Process ◽  
Party Systems ◽  
Party Competition ◽  
The Other ◽  
Causal Factors ◽  
Other Hand ◽  
Rigorous Test ◽  
The Subject ◽  
Rational Organization

Pleas and programs for party responsibility are not new. It is remarkable, however, how little the discussion has advanced. I do not mean that I am surprised that the path of reform has been hard but that knowledge of the subject has not grown in proportion to the length of the discussion. Proponents believe party responsibility introduces desired qualities into the policy process and makes possible rational organization of the electorate in terms of policy. Not much has been done to provide adequate support for either of these propositions. In fact, it is hard to discover a serious effort to put these propositions in some form which would permit a partial but rigorous test. Opponents on the other hand conjure up visions of polarized parties, downtrodden minorities, and multipartyism as the fruits of party responsibility. They are able to make these improbable inferences by working with an exceedingly simple model, by ignoring the functions of party competition and the complex of factors which seem to shape party systems. Some observers less involved in the argument allow that the debate may have some value since it leads to notice of important realities. But, for them, proposed reforms are not to be taken seriously because they are Utopian in two senses: (1) sweeping and incalculable; and (2) out of reach. This view seems to overlook the fact that party responsibility is a matter of degree and that incremental reform is, at least, possible in principle. Finally, very little attention has been paid to factors which may promote or inhibit party responsibility.

A study of cometary eruptions through OH radio-lines

1999 ◽  
Vol 173 ◽  
pp. 249-254
Author(s):  
A.M. Silva ◽  
R.D. Miró
Keyword(s):  
Short Duration ◽  
Growth Curves ◽  
The Other ◽  
Initial Mass ◽  
Radio Lines ◽  
Other Hand ◽  
Sudden Rise

AbstractWe have developed a model for theH2OandOHevolution in a comet outburst, assuming that together with the gas, a distribution of icy grains is ejected. With an initial mass of icy grains of 108kg released, theH2OandOHproductions are increased up to a factor two, and the growth curves change drastically in the first two days. The model is applied to eruptions detected in theOHradio monitorings and fits well with the slow variations in the flux. On the other hand, several events of short duration appear, consisting of a sudden rise ofOHflux, followed by a sudden decay on the second day. These apparent short bursts are frequently found as precursors of a more durable eruption. We suggest that both of them are part of a unique eruption, and that the sudden decay is due to collisions that de-excite theOHmaser, when it reaches the Cometopause region located at 1.35 × 105kmfrom the nucleus.

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