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Longer Tails (longer + tail)
Selected AbstractsThe cluster abundance in cosmic string models for structure formationMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2000P. P. Avelino We use the present observed number density of large X-ray clusters to constrain the amplitude of matter density perturbations induced by cosmic strings on the scale of 8 h,1 Mpc (,8), in both open cosmologies and flat models with a non-zero cosmological constant. We find a slightly lower value of ,8 than that obtained in the context of primordial Gaussian fluctuations generated during inflation. This lower normalization of ,8 results from the mild non-Gaussianity on cluster scales, where the one-point probability distribution function is well approximated by a ,2 distribution and thus has a longer tail than a Gaussian distribution. We also show that ,8 normalized using cluster abundance is consistent with the COBE normalization. [source] Spectroscopic Ellipsometry as a Tool for Damage Profiling in Very Shallow Implanted SiliconPLASMA PROCESSES AND POLYMERS, Issue 2 2006Iordan Karmakov Abstract Summary: Ion implantation is still one of the key steps in Si integrated circuit technology. Spectroscopic Ellipsometry (SE) detects the defects created in the implanted Si. The successful application of SE for damage profiling depends on the quality of the algorithm used for evaluating the damage profile from SE data. In this work, we present retrieved SE damage depth profiles by our previously published algorithm in the as-implanted Si with very low energies Ge+ ions- from 2 keV to 20 keV and 1 keV B+ ions (1,×,1015 cm,2). The comparisons of the SE retrieved damage depth profiles with experimental atomic concentration depth profiles, or simulated by the state-of-the-art computer ATHENA code of Silvaco TCAD suits were made. The functional relation was obtained by proper fitting of measured by SE a/c depths, and the depths named "ends of damage" with the experimental or simulated ions concentration depth profiles. For reasons not understood, the damage profile of 5 keV Ge+ in c-Si is smoother in shape beyond the a/c depth, with a longer tail. The damage profiles measured by SE for 5 keV Ge+ in c-Si with two different doses: curve 1 - for 6,×,1013 cm,2 and curve 2 - for 1,×,1015 cm,2. Curve 3 - presents the damage profile simulated by ATHENA for Ge+ ions with 5 keV; 1,×,1015 cm,2. [source] Robust Joint Modeling of Longitudinal Measurements and Competing Risks Failure Time DataBIOMETRICAL JOURNAL, Issue 1 2009Ning Li Abstract Existing methods for joint modeling of longitudinal measurements and survival data can be highly influenced by outliers in the longitudinal outcome. We propose a joint model for analysis of longitudinal measurements and competing risks failure time data which is robust in the presence of outlying longitudinal observations during follow-up. Our model consists of a linear mixed effects sub-model for the longitudinal outcome and a proportional cause-specific hazards frailty sub-model for the competing risks data, linked together by latent random effects. Instead of the usual normality assumption for measurement errors in the linear mixed effects sub-model, we adopt a t -distribution which has a longer tail and thus is more robust to outliers. We derive an EM algorithm for the maximum likelihood estimates of the parameters and estimate their standard errors using a profile likelihood method. The proposed method is evaluated by simulation studies and is applied to a scleroderma lung study (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Adaptive Offspring Sex Ratio Depends on Male Tail Length in the GuppyETHOLOGY, Issue 11 2006Kenji Karino A biased sex ratio in a brood is considered to be an adaptive strategy under certain circumstances. For example, if the expected reproductive success of one sex is greater than that of the other, parents should produce more offspring of the former sex than the latter. A previous study has documented that in the guppy, Poecilia reticulata, the female offspring of males possessing proportionally longer tails exhibit smaller body sizes and show decreased reproductive outputs than those of males having shorter tails. On the other hand, the total lengths of the male offspring of the long-tailed males are larger because of their longer tails; consequently, they exhibit greater sexual attractiveness to females. Therefore, it has been hypothesized that this asymmetry in the expected reproductive success between the male and female offspring of long-tailed males may result in a biased sex ratio that is dependent on the tail lengths of their fathers. This hypothesis was tested in the present study. The results showed that the females that mated with long-tailed males produced more male offspring than those that mated with short-tailed males. Logistic regression analysis showed that the ratio of tail length to the standard length of the fathers is a determinant factor of the sex of their offspring. These results suggest that the manipulation of the offspring sex ratios by parents enhances the overall fitness of the offspring. [source] NATURAL SELECTION ALONG AN ENVIRONMENTAL GRADIENT: A CLASSIC CLINE IN MOUSE PIGMENTATIONEVOLUTION, Issue 7 2008Lynne M. Mullen We revisited a classic study of morphological variation in the oldfield mouse (Peromyscus polionotus) to estimate the strength of selection acting on pigmentation patterns and to identify the underlying genes. We measured 215 specimens collected by Francis Sumner in the 1920s from eight populations across a 155-km, environmentally variable transect from the white sands of Florida's Gulf coast to the dark, loamy soil of southeastern Alabama. Like Sumner, we found significant variation among populations: mice inhabiting coastal sand dunes had larger feet, longer tails, and lighter pigmentation than inland populations. Most striking, all seven pigmentation traits examined showed a sharp decrease in reflectance about 55 km from the coast, with most of the phenotypic change occurring over less than 10 km. The largest change in soil reflectance occurred just south of this break in pigmentation. Geographic analysis of microsatellite markers shows little interpopulation differentiation, so the abrupt change in pigmentation is not associated with recent secondary contact or reduced gene flow between adjacent populations. Using these genetic data, we estimated that the strength of selection needed to maintain the observed distribution of pigment traits ranged from 0.0004 to 21%, depending on the trait and model used. We also examined changes in allele frequency of SNPs in two pigmentation genes, Mc1r and Agouti, and show that mutations in the cis -regulatory region of Agouti may contribute to this cline in pigmentation. The concordance between environmental variation and pigmentation in the face of high levels of interpopulation gene flow strongly implies that natural selection is maintaining a steep cline in pigmentation and the genes underlying it. [source] TRITURUS NEWTS DEFY THE RUNNING-SWIMMING DILEMMAEVOLUTION, Issue 10 2006Lumíl Gl Abstract Conflicts between structural requirements for carrying out different ecologically relevant functions may result in a compromise phenotype that maximizes neither function. Identifying and evaluating functional trade-offs may therefore aid in understanding the evolution of organismal performance. We examined the possibility of an evolutionary trade-off between aquatic and terrestrial locomotion in females of European species of the newt genus Triturus. Biomechanical models suggest a conflict between the requirements for aquatic and terrestrial locomotion. For instance, having an elongate, slender body, a large tail, and reduced limbs should benefit undulatory swimming, but at the cost of reduced running capacity. To test the prediction of an evolutionary trade-off between swimming and running capacity, we investigated relationships between size-corrected morphology and maximum locomotor performance in females of ten species of newts. Phylogenetic comparative analyses revealed that an evolutionary trend of body elongation (increasing axilla-groin distance) is associated with a reduction in head width and forelimb length. Body elongation resulted in reduced maximum running speed, but, surprisingly, also led to a reduction in swimming speed. The evolution of longer tails was associated with an increase in maximal swimming speed. We found no evidence for an evolutionary trade-off between aquatic and terrestrial locomotor performance, probably because of the unexpected negative effect of body elongation on swimming speed. We conclude that the idea of a design conflict between aquatic and terrestrial locomotion, mediated through antagonistic effects of body elongation, does not apply to our model system. [source] Deficit Targeting Strategies: Fiscal Consolidation and the Probability Distribution of Deficits under the Stability PactJCMS: JOURNAL OF COMMON MARKET STUDIES, Issue 3 2003A.J. Hughes Hallett Using stochastic simulations, this article analyses the probability distribution of a country's deficit ratio under fixed exchange rates and a variety of monetary and fiscal policy rules. The purpose is to show how the probability of an ,excessive deficit', defined by Europe's Stability Pact as a deficit to GDP ratio above 3 per cent, varies with different deficit targets and policy rules. Using a macro model, we find that when subject to historically consistent shocks, these fiscal ratios typically have a wide distribution, with fat tails and significantly longer tails on the upper side. That means fiscal targets may have to be country-specific and conservative, and that fiscal policy has to be forward-looking to keep the probability of excessive deficits below acceptable limits. [source] Escape behaviour and ultimate causes of specific induced defences in an anuran tadpoleJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 1 2005C. Teplitsky Abstract Induced defences, such as the predator avoidance morphologies in amphibians, result from spatial or temporal variability in predation risk. One important component of this variability should be the difference in hunting strategies between predators. However, little is known about how specific and effective induced defences are to different types of predators. We analysed the impact of both pursuing (fish, Gasterosteus aculeatus) and sit-and-wait (dragonfly, Aeshna cyanea) predators on tadpole (Rana dalmatina) morphology and performance (viz locomotive performance and growth rate). We also investigated the potential benefits of the predator-induced phenotype in the presence of fish predators. Both predators induced deeper tail fins in tadpoles exposed to threat of predation, and stickleback presence also induced longer tails and deeper tail muscles. Morphological and behavioural differences resulted in better escape ability of stickleback-induced tadpoles, leading to improved survival in the face of stickleback predation. These results clearly indicate that specific morphological responses to different types of predators have evolved in R. dalmatina. The specific morphologies suggest low correlations between the traits involved in the defence. Independence of traits allows prey species to fine-tune their response according to current predation risk, so that the benefit of the defence can be maximal. [source] Ease and effectiveness of costly autotomy vary with predation intensity among lizard populationsJOURNAL OF ZOOLOGY, Issue 3 2004William E. Cooper Jr Abstract Costly anti-predatory defences are used in ecological time and maintained in evolutionary time by natural selection favouring individuals that survive through their use. Autotomy of expendable body parts is a striking example of a defence having multiple substantial costs, including loss of ability to use the same defence, loss of energy, and decreased growth, reproductive success and survival following autotomy, plus the energetic cost of replacing the lost body part in species capable of regenerating them. Our study shows that autotomy in the lacertid lizard Podarcis lilfordi reduces sprint speed, indicating decreased capacity to escape as well as the loss of energy. Autotomy carries substantial cost, and thus should be avoided except as a last resort. Ease of autotomy and post-autotomic movements were studied in three populations of lacertid lizards. Two were islet populations of P. lilfordi from Aire (lowest predation pressure) and Colom (intermediate predation pressure) off Minorca. The third was a mainland population of Podarcis hispanica, a closely related species from the mainland of the Iberian Peninsula where predation pressure is higher than on the islets. As predicted, a suite of autotomic traits increases the effectiveness of autotomy as a defence as predation pressure increases. With increasing predation pressure, the frequency of voluntary autotomy increases, latency to autotomy decreases, pressure on the tail needed to induce autotomy decreases, vigour of post-autotomic tail movements increases, and distance moved by the shed tail increases. Additional changes that might be related to predation pressure, but could have other causes, are the presence of tail coloration contrasting with body coloration except under the lowest predation pressure (Aire) and longer tails in the mainland species P. hispanica. Correspondence between predation pressure and the suite of autotomic traits suggests that autotomy is an important defence that responds to natural selection. Comparative data are needed to establish the generality of relationships suggested in our study of only three populations. [source] | ||||||||||