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Long Tail (long + tail)
Selected AbstractsMeasuring dispersal and detecting departures from a random walk model in a grasshopper hybrid zoneECOLOGICAL ENTOMOLOGY, Issue 2 2003R. I. Bailey Abstract. 1. The grasshopper species Chorthippus brunneus and C. jacobsi form a complex mosaic hybrid zone in northern Spain. Two mark,release,recapture studies were carried out near the centre of the zone in order to make direct estimates of lifetime dispersal. 2. A model framework based on a simple random walk in homogeneous habitat was extended to include the estimation of philopatry and flying propensity. Each model was compared with the real data, correcting for spatial and temporal biases in the data sets. 3. All four data sets (males and females at each site) deviated significantly from a random walk. Three of the data sets showed strong philopatry and three had a long dispersal tail, indicating a low propensity to move further than predicted by the random walk model. 4. Neighbourhood size estimates were 76 and 227 for the two sites. These estimates may underestimate effective population size, which could be increased by the long tail to the dispersal function. The random walk model overestimates lifetime dispersal and hence the minimum spatial scale of adaptation. 5. Best estimates of lifetime dispersal distance of 7,33 m per generation were considerably lower than a previous indirect estimate of 1344 m per generation. This discrepancy could be influenced by prezygotic isolation, an inherent by-product of mosaic hybrid zone structure. [source] Spatial distributions of mean age and higher moments in steady continuous flowsAICHE JOURNAL, Issue 10 2010M. Liu Abstract Transport equations and boundary conditions for spatial distribution of age moments in steady continuous flows are derived. Mean age is the first moment. The coefficient of variation is obtained from the second moment. Mixing-cup averaged mean age and higher moments across the exit plane are identical to the corresponding moments of the residence-time distribution. Numerical solutions for a 2-D (two-dimensional) reactor are studied and compared with those from a transient tracer equation. Agreement is excellent. Local tracer distribution function curves reveal that mean age is located on the long tail for both convection dominated short circuiting paths and diffusion dominated dead zones. Computing cost for the mean age and higher moment equations is orders of magnitude lower than that for the transient tracer concentration equation, making this mean age method an efficient tool to study mixing in steady continuous flow systems. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Evolution of the spermatozoon in muroid rodentsJOURNAL OF MORPHOLOGY, Issue 3 2005William G. Breed Abstract In the rodent superfamily Muroidea, a model for the evolution of sperm form has been proposed in which it is suggested that a hook-shaped sperm head and long tail evolved from a more simple, nonhooked head and short tail in several different subfamilies. To test this model the shape of the sperm head, with particular emphasis on its apical region, and length of sperm tail were matched to a recent phylogeny based on the nucleotide sequence of several protein-coding nuclear genes from 3 families and 10 subfamilies of muroid rodents. Data from the two other myomorph superfamilies, the Dipodoidea and kangaroo rats in the Geomyoidea, were used for an outgroup comparison. In most species in all 10 muroid subfamilies, apart from in the Murinae, the sperm head has a long rostral hook largely composed of acrosomal material, although its length and cross-sectional shape vary across the various subfamilies. Nevertheless, in a few species of various lineages a very different sperm morphology occurs in which an apical hook is lacking. In the outgroups the three species of dipodid rodents have a sperm head that lacks a hook, whereas in the heteromyids an acrosome-containing apical hook is present. It is concluded that, as the hook-shaped sperm head and long sperm tail occur across the muroid subfamilies, as well as in the heteromyid rodents, it is likely to be the ancestral condition within each of the subfamilies with the various forms of nonhooked sperm heads, that are sometimes associated with short tails, being highly derived states. These findings thus argue against a repeated evolution in various muroid lineages of a complex, hook-shaped sperm head and long sperm tail from a more simple, nonhooked sperm head and short tail. An alternative proposal for the evolution of sperm form within the Muroidea is presented in the light of these data. J. Morphol. © 2005 Wiley- Liss, Inc. [source] Trichotillomania ± trichobezoar: revisitedJOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 8 2006VN Sehgal Abstract Trichotillomania is an intriguing psychosomatic entity in which there is an irresistible desire to pull out the hair from the scalp, eyelashes, eyebrows and other parts of the body. The process results in an instant release of tension, a sense of relief and security. However, non-scaring alopecia is its clinical presentation. The development of trichobezoar following ingestion of the pulled hair is its salient complication in a few cases. Subsequently, it may cause symptoms pertaining to the gastrointestinal tract culminating in intestinal obstruction, perforation, pancreatitis and obstructive jaundice. The Rapunzel syndrome (trichobezoar) may occur when gastrointestinal obstruction is produced by a rare manifestation of a trichobezoar with a long tail that extends to or beyond the ileocecal valve. In most cases in children, trichotillomania ± trichobezoar is a habit disorder and thus has a better prognosis. However, in adults the psychopathology is usually deeper and thus entails a poor prognosis. The diagnosis is made after taking a thorough history, noting the clinical features and evaluating a hair-root examination, where telogen hair is (almost) completely lacking, which distinguish trichotillomania from other hair disorders. Treatment modalities vary in childhood and adult varieties. Apart from psychotherapy, the drug treatment involves several agents including selective serotonin reuptake inhibitors (SSRIs) and domipramine. Trichobezoar/Rapunzel syndrome requires surgical intervention. [source] Homology modeling and molecular dynamics simulations of lymphotactinPROTEIN SCIENCE, Issue 11 2000Buyong Ma Abstract We have modeled the structure of human lymphotactin (hLpnt), by homology modeling and molecular dynamics simulations. This chemokine is unique in having a single disulfide bond and a long C-terminal tail. Because other structural classes of chemokines have two pairs of Cys residues, compared to one in Lpnt, and because it has been shown that both disulfide bonds are required for stability and function, the question arises how the Lpnt maintains its structural integrity. The initial structure of hLpnt was constructed by homology modeling. The first 63 residues in the monomer of hLpnt were modeled using the structure of the human CC chemokine, RANTES, whose sequence appeared most similar. The structure of the long C-terminal tail, missing in RANTES, was taken from the human muscle fatty-acid binding protein. In a Protein Data Bank search, this protein was found to contain a sequence that was most homologous to the long tail. Consequently, the modeled hLpnt C-terminal tail consisted of both ,-helical and ,-motifs. The complete model of the hLpnt monomer consisted of two ,-helices located above the five-stranded ,-sheet. Molecular dynamics simulations of the solvated initial model have indicated that the stability of the predicted fold is related to the geometry of Pro78. The five-stranded ,-sheet appeared to be preserved only when Pro78 was modeled in the cis conformation. Simulations were also performed both for the C-terminal truncated forms of the hLpnt that contained one or two (CC chemokine-like) disulfide bonds, and for the chicken Lpnt (cLpnt). Our MD simulations indicated that the turn region (T30-G34) in hLpnt is important for the interactions with the receptor, and that the long C-terminal region stabilizes both the turn (T30-G34) and the five-stranded ,-sheet. The major conclusion from our theoretical studies is that the lack of one disulfide bond and the extension of the C-terminus in hLptn are mutually complementary. It is very likely that removal of two Cys residues sufficiently destabilizes the structure of a chemokine molecule, particularly the core ,-sheet, to abolish its biological function. However, this situation is rectified by the long C-terminal segment. The role of this long region is most likely to stabilize the first ,-turn region and ,-helix H1, explaining how this chemokine can function with a single disulfide bond. [source] Cones perform a non-linear transformation on natural stimuliTHE JOURNAL OF PHYSIOLOGY, Issue 3 2010D. Endeman Visual information in natural scenes is distributed over a broad range of intensities and contrasts. This distribution has to be compressed in the retina to match the dynamic range of retinal neurons. In this study we examined how cones perform this compression and investigated which physiological processes contribute to this operation. M- and L-cones of the goldfish were stimulated with a natural time series of intensities (NTSI) and their responses were recorded. The NTSI displays an intensity distribution which is skewed towards the lower intensities and has a long tail into the high intensity region. Cones transform this skewed distribution into a more symmetrical one. The voltage responses of the goldfish cones were compared to those of a linear filter and a non-linear biophysical model of the photoreceptor. The results show that the linear filter under-represents contrasts at low intensities compared to the actual cone whereas the non-linear biophysical model performs well over the whole intensity range used. Quantitative analysis of the two approaches indicates that the non-linear biophysical model can capture 91 ± 5% of the coherence rate (a biased measure of information rate) of the actual cone, where the linear filter only reaches 48 ± 8%. These results demonstrate that cone photoreceptors transform an NTSI in a non-linear fashion. The comparison between current clamp and voltage clamp recordings and analysis of the behaviour of the biophysical model indicates that both the calcium feedback loop in the outer segment and the hydrolysis of cGMP are the major components that introduce the specific non-linear response properties found in the goldfish cones. [source] Genetic structure and differentiation of the Japanese extremely long-tailed chicken breed (Onagadori), associated with plumage colour variation: suggestions for its management and conservationANIMAL GENETICS, Issue 6 2009R. Tadano Summary The Onagadori is a distinguished chicken breed that is characterized by an extremely long tail in the male. In this breed, three different plumage colour varieties have been developed (black-breasted white, black-breasted red and white) in which the black-breasted white is believed to be the original colour of the Onagadori, based on historical records. To establish a conservation strategy, 176 birds were genotyped for autosomal microsatellites. Significant genetic distinctness was found between the original (black-breasted white) and two derivative varieties (FST = 0.091 and 0.093). At the same time, a Bayesian model-based clustering revealed that the majority of individuals belonging to the black-breasted red and white varieties had an extremely low proportion of the genome shared with the original type (black-breasted white). This suggests that derivative varieties were created by crossing with other breeds, with low introgression of the original-type genome. We propose that the three plumage colour varieties should be treated as separate genetic units in a conservation programme. [source] Experimental evidence for female choice and energetic costs of male tail elongation in red-collared widowbirdsBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2005SARAH R. PRYKE The black nuptial plumage of the highly polygynous male red-collared widowbird (Euplectes ardens) comprises a red carotenoid-based collar patch and a long graduated tail (c. 22 cm). Tail length was the strongest predictor of male mating success in a previous selection analysis, motivating this experimental test of the relative importance of tail plumes in male contest competition and female choice. Males were assigned to either a short (12.5 cm) or control (20 cm) tail manipulation prior to territory establishment. Male contest competition was unaffected by the tail treatments as the shortened- and control-tailed males were equally successful in acquiring territories of similar size and quality. In contrast, however, although the longer-tailed control males spent less time in flight and courtship displays, they attracted significantly more prospecting and nearly three times as many nesting females to their territories compared to the short-tailed males. In further support of tail length as the primary mate choice cue, none of the other measured and potential female cues (e.g. body size, collar colorimetrics, territorial behaviours or territory quality) influenced male reproductive success. In addition to potentially increasing detectability (,signal efficacy'), the long tail is also a likely indicator of male quality (,signal content'). Despite the higher activities of short-tailed males, control-tailed males showed a steeper decline in condition (relative body mass) during the breeding season. Furthermore, both short- and control-tailed residents lost more condition than did the short- and control-treated floaters (males not establishing territories), suggesting an interaction between tail length and the costs of territory acquisition, defence and courtship displays. These results confirm the role of mate choice and honest quality advertising as the main selection pressures behind elongated tails in widowbirds. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 86, 35,43. [source] An Early Cretaceous Avialian Bird, Shenzhouraptor sinensis from Western Liaoning, ChinaACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 1 2003Ji Qiang Abstract, This paper describes an avialian bird from the Early Cretaceous Jiufotang Formation in Yixian county, western Liaoning, China, which is named as Shenzhouraptor sinensis by Ji et al. on July 15,2002. Shenzhouraptor sinensis is characterized by no teeth in its mouth, the forelimbs longer than the hindlimbs, a long tail with more than 23 caudal vertebrae, U-shaped wishbone, and remiges longer than the total length of ulna and manus. It is certain that the new avialian bird is really capable of powerful flight, representing a missing link between theropod dinosaurs and birds. [source] Multiple pathology and tails of disability: Space,time structure of disability in longevityGERIATRICS & GERONTOLOGY INTERNATIONAL, Issue 4 2003Satoru Matsushita Disability and the resulting lowered quality of life are serious issues accompanying increased longevity. Curiously, despite its potential contribution to aging theory, complete statistical and etiological structures of this common and unwelcome aging phenotype before death have not been well identified. Another neglected issue in aging and disability is the principles of phylogenesis and morphogenesis, which contemporary life science invariably starts with. In the present review these two related subjects are addressed, with an introduction of an analysis on patients and published data. Statistically rigorous log,normal and normal distributions distinguish disability for its duration and age-wise distribution, respectively. Multiple pathology and diverse effects of various endogenous diseases on disability are confirmed. The robust long-tailed log,normal distribution for various phases of disability validates the fact that patients in disability undergo series of stochastic subprocesses of many independent endogenous diseases until death. For 60% of patients, the log,normal distribution is mimicked by a random walk model. Diseases of core organs are major causes of the long tails. A declining force of natural selection after reproduction and trade-off of life history through pleiotropy of the genes are considered to be the roots of aging. The attenuated selection pressure and the resulting decrease of genetic constraints produce an increased opportunity for chance and stochastics. Elucidated stochastic behaviors of disability underscore the key role of chance in aging. Evolutionary modifications in the development of the structure tend to favor developmentally later stages first. Distal parts are developmentally last, therefore most subject to modification. The rate of molecular evolution of the genes is also found to be relatively slow at the core and rapid at the edge of cells and organs. Therefore, systems at the core must be relatively slow and inactive to comply with pleiotropy and trade-offs in comparison with systems at the edge. Hence, against flat and probabilistic aging, the core organs must be moulded to be more robust with a lower threshold for dysfunction, to age relatively slowly, and should have less of a disease quota in aging. The principle of core protective aging assures possibilities not only to reduce disability but also to accomplish the Third Age as well. Finally, it must also be acknowledged that the principle is a double-edged sword. Paradoxically, the developed biological and societal organization provides protection for the injured core, and so develops long tails of disability. The principle of core protective aging re-emphasizes the key role of prevention in order to reduce the amount of disability. [source] Intraspecific differences in benefits from feeding in mixed-species flocksJOURNAL OF AVIAN BIOLOGY, Issue 4 2000Teruaki Hino The Madagascar Paradise Flycatcher Terpsiphone mutata and Common Newtonia Newtonia brunneicauda frequently form two-species flocks in the deciduous dry forest of western Madagascar. In T. mutata, some males have long tails, while other males and females have short tails. When foraging in mixed flocks, each type of bird captured prey more rapidly than otherwise, but the degree of increase in feeding rate was smaller in long-tailed males. When in mixed flocks, all T. mutata caught prey on leaves in the canopy where N.brunneicauda foraged. Long-tailed males changed feeding habits from sallying when not in mixed flocks, whereas short-tailed birds showed no change of feeding habit. The elongated tails of long-tailed males may have made their foraging less efficient owing to decreased agility in the canopy. N. brunneicauda is monomorphic and often formed groups of three to five individuals. In monospecific flocks, subordinates fed at low rates on branches owing to frequent hostile encounters. When foraging in mixed flocks, however, subordinates foraged among leaves, and their feeding rates increased because the frequency of intraspecific interference decreased greatly. Dominants did not show any difference in feeding pattern with social situation. Thus, heterospecific flocking was more advantageous for subordinates. [source] On the robustness of the h -indexJOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, Issue 10 2007Jerome K. Vanclay The h -index (Hirsch, 2005) is robust, remaining relatively unaffected by errors in the long tails of the citations-rank distribution, such as typographic errors that short-change frequently cited articles and create bogus additional records. This robustness, and the ease with which h -indices can be verified, support the use of a Hirsch-type index over alternatives such as the journal impact factor. These merits of the h -index apply both to individuals and to journals. [source] The non-Gaussian nature of bibliometric and scientometric distributions: A new approach to interpretationJOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, Issue 13 2001Ludmila E. Ivancheva An attempt has been made to give an answer to the question: Why do most bibliometric and scientometric laws reveal characters of Non-Gaussian distributions, i.e., have unduly long "tails"? We tried to apply the approach of the so-called "Universal Law," discovered by G. Stankov (1997, 1998). The basic principle we have used here is that of the reciprocity of energy and space. A new "wave concept" of scientific information has been propounded, in which terms the well-known bibliometric and scientometric distributions find a rather satisfactory explanation. One of the made corollaries is that , = 1 is the most reasonable value for the family of Zipf laws, applied to information or social phenomena. [source] | ||||||||||||||||