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Simple Extension (simple + extension)

Distribution by Scientific Domains

Business, Economics, Finance and Accounting	33%

Selected Abstracts

Evolution of morphogenesis in 360-million-year-old conodont chordates calibrated in days

EVOLUTION AND DEVELOPMENT, Issue 6 2008
Jerzy Dzik
SUMMARY Highly rhythmic increments of crown tissue are identifiable in conodont oral apparatus elements from the Late Devonian of the Holy Cross Mountains, Poland; individual laminae being of thickness comparable with daily increments of vertebrate tooth enamel and fish otoliths. Abundant occurrence of such specimens enables bed-by-bed (stratophenetic) studies of the process of evolution at the population level and quantitative presentation of the evolution of ontogeny in the sampled geological section covering several million years. The morphologic transformation is expressed as expansion of a juvenile asymmetry to later stages of the ontogeny and in decrease of the mature element width, which was due to a change of the mineral tissue secretion rate. It was not just a simple extension of a juvenile character into the later stage of the ontogeny (heterochrony) but rather a true developmental novelty. The evolution was gradual and very slow. The proposed quantitative approach to growth increments in the mineral skeleton of ancient chordates introduces real-time units to evolutionary developmental studies connected with direct paleontological evidence on the course of evolution. [source]

Temperature dependence of stress,lifetime fatigue curves

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 12 2000
J. Kohout
By analysing several finite-life fatigue curves obtained at various temperatures, a relation describing the temperature dependence of fatigue strength is proposed, based on the Basquin equation. Accordingly, an approximate inverse law between fatigue strength and the square root of absolute temperature is demonstrated. Moreover, a boundary temperature above which creep begins to play a significant role is estimated. A simple extension of the relationship to the low-cycle fatigue region, allows one to determine predictive curves describing fatigue behaviour at various temperatures, even in cases where only a single fatigue curve at a given temperature plus the temperature dependence of tensile strength are known. [source]

News Management in Monetary Policy: When Central Banks Should Talk to the Government

GERMAN ECONOMIC REVIEW, Issue 4 2000
Helge Berger
Central banks are often considered to be better informed about the present or future state of the economy than the government. A conservative central bank has an incentive to exploit this asymmetry by strategically managing its information policy. Strategic news management will keep the government uncertain about the state of the economy and increase the central bank's leeway for conducting a conservative monetary policy. We show that withholding information from the government is an equilibrium. However, there are also well-defined limits to strategic information policy as the central bank has to distort monetary policy to be in line with its news management. A simple extension of our findings is that, if the government on occasion learns about the bank's true information, it will then overrule the central bank's decision on monetary policy. [source]

Effects of head posture on the oral, pharyngeal and laryngeal axis alignment in infants and young children by magnetic resonance imaging

PEDIATRIC ANESTHESIA, Issue 6 2008
RENAUD VIALET MD
Summary Background:, Objective anatomical studies supporting the different recommendations for laryngoscopy in infants and young children are scarce. The objective of this study was to measure by magnetic resonance imaging (MRI) the consequences of head extension on the oral, pharyngeal and laryngeal axes in infants and young children. Methods:, Thirty patients (age: 33 ± 28 months; weight 14 ± 9 kg), under general inhalated anesthesia delivered via a laryngeal mask airway, were studied in two anatomic positions: head in the resting position and in simple extension. The following measurements were made on each scan: the face and the neck axes, the pharyngeal axis, the laryngeal axis, and the line of vision of glottis. The various angles between these axes were defined: , angle between line of vision and laryngeal axis, and , angle between pharyngeal axis and laryngeal axis. From an anatomical point of view, laryngoscopy and passage of a naso-tracheal tube would be facilitated if these angles are narrow. Results:, Placing the patient from the resting position into extension led to a narrowing of the angle , but a widening of the angle ,. Conclusions:, In infants and young children, under general anesthesia and with a laryngeal mask airway in place, just a slight head extension improves alignment of the line of vision of the glottis and the laryngeal axis (narrowing of angle ,) but worsened the alignment of the pharyngeal and laryngeal axes (widening of angle ,). [source]

The influence of stratospheric potential vorticity on baroclinic instability

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 644 2009
L. A. Smy
Abstract This article examines the dynamical coupling between the stratosphere and troposphere by considering the effect of direct perturbations to stratospheric potential vorticity on the evolution of midlatitude baroclinic instability in a simple extension of an Eady model. A simulation in which stratospheric potential vorticity is exactly zero is used as a control case, and both zonally symmetric and asymmetric perturbations to the stratospheric potential vorticity are then considered, the former representative of a strong polar vortex, the latter representative of the stratospheric state following a major sudden warming. Both types of stratospheric perturbation result in significant changes to the synoptic-scale evolution of surface temperature, as well as to zonally and globally averaged tropospheric quantities. In the case of a zonally symmetric perturbation, the linear growth rate of all unstable modes decreases with increasing perturbation amplitude. Initial growth rates in cases with significant asymmetric perturbations are also weaker than those of the control case, but final eddy kinetic energy values are much larger due to the growth of low zonal wavenumbers triggered by the initial stratospheric perturbation. A comparison of the zonally symmetric and asymmetric perturbations gives some insight into the possible influence of pre- or post-sudden-warming conditions on tropospheric evolution. Copyright © 2009 Royal Meteorological Society [source]

EXTENSIONS OF THE STANDARDIZED CROSS-SECTIONAL APPROACH TO SHORT-HORIZON EVENT STUDIES

THE JOURNAL OF FINANCIAL RESEARCH, Issue 4 2007
Ronald Bremer
Abstract Strong evidence indicates that short-horizon event-induced abnormal returns and volatility vary significantly over event days. Event-study methods that assume constant event-induced abnormal returns and volatility over event days have potentially inflated Type I error rates and poor test power. Our simple extensions of the Boehmer, Musumeci, and Poulsen (1991) approach scale abnormal returns with conditional variance, which is estimated with GARCH(1,1) and an indicator of the event in a two-stage estimation. Our method improves the Boehmer, Musumeci, and Poulsen approach on model specification and test power, even under challenging event-induced mean and volatility structures, and could standardize short-horizon event studies. [source]