Number Of Barbs Research Articles

Numerical Study of Mitigating Cloud Cavitation Shedding Using Biomimetic Protuberant Stripes

Abstract Cloud cavitation usually appears on impeller blades of hydraulic machinery. When unsteady cloud cavitation travels downstream to a high-pressure region and collapses, performance drops and cavitation erosion appears. It is important to develop effective methods to mitigate the undesirable effects. By million years of natural selection, bird feather has presented excellent flow performance. As typical characteristic structure of bird feather, a number of barbs are supported by a central hollow shaft. Under inspiration of bird feathers, we presented a method of passive cavitation control. This method of passive cavitation control uses biomimetic protuberant stripes (PSs) mounted on a NACA66 hydrofoil. The effects of various biomimetic PS arrangements on the cavitation pattern, pressure fluctuation, and hydrodynamic load are numerically studied. Then, the cavitation control mechanism of the biomimetic PS is analyzed in detail. We observe that the biomimetic PSs not only inhibit the shedding of large-scale cloud cavitation but also reduce the cavitation size. Moreover, analysis shows that turbulence velocity fluctuation may be mitigated and boundary layer thickness is reduced with biomimetic PSs, which enhances the flow intensity in the main flow direction.

Comparative Morphology of the Stinger in Social Wasps (Hymenoptera: Vespidae).

Simple SummaryBoth solitary and social wasps have a fully functional venom apparatus and can deliver painful stings, which they do in self-defense. However, solitary wasps sting in subduing prey, while social wasps do so in defense of the colony. The structure of the stinger is remarkably uniform across the large family that comprises both solitary and social species. The most notable source of variation is in the number and strength of barbs at the tips of the slender sting lancets that penetrate the wound in stinging. These are more numerous and robust in New World social species with very large colonies, so that in stinging human skin they often cannot be withdrawn, leading to sting autotomy, which is fatal to the wasp. This phenomenon is well-known from honey bees.The physical features of the stinger are compared in 51 species of vespid wasps: 4 eumenines and zethines, 2 stenogastrines, 16 independent-founding polistines, 13 swarm-founding New World polistines, and 16 vespines. The overall structure of the stinger is remarkably uniform within the family. Although the wasps show a broad range in body size and social habits, the central part of the venom-delivery apparatus—the sting shaft—varies only to a modest extent in length relative to overall body size. What variation there is shows no apparent correlation with social habits. This is consistent with the hypothesis that stinger size is constrained by the demands of a flight-worthy body. The sting lancets bear distinct, acute barbs in all examined species except in members of the Stenogastrinae. Barbs vary considerably among species in number, their summed lengths, and the relative degree of serration (summed length relative to lancet width). Where they are numerous and strong, it increases the likelihood of the stinger remaining fatally embedded in the skin of a vertebrate adversary (sting autotomy). Although an index that combines the number and strength of barbs is a more natural measure of overall serration, the number of barbs alone is almost as good a predictor of the likelihood of sting autotomy. Across the family as a whole, the tendency to sting autotomy is concentrated in the swarm-founding New World polistines.

Determinants and constraints of feather growth.

During the periodic moult of the plumage of birds, a fast regrowth of feathers would shorten the time of reduced plumage functionality. However, it has long been known that feather growth-rate is limited and that long feathers take disproportionally longer to grow than small feathers, which has severe consequences on moult duration and the completeness of moult in large birds. The reasons for the limitations of feather-growth must be related to the size and/or functions of the feather follicle, but are largely unknown. Here we measured the size of the feather follicle (taking calamus width as a proxy) and related it to parameters of feather growth (feather growth-rate by mass and by length) and feather structure (feather length, mass, massiveness [mass of feather material per mm feather-length]). We used three independent datasets which allowed for interspecific analyses, and for intraspecific comparisons of differently structured feathers within the framework of biological scaling. We found that the cross-sectional area of the calamus (as a proxy of feather follicle size) was directly proportional to feather growth-rate by mass. Hence, factors acting at a two-dimensional scale (possibly nutrient supply to the growing feather) determines feather growth rate by mass, rather than the linear arrangement of stem cells (in a circular configuration) as had previously been assumed. Feather follicle size was correlated with both feather length and massiveness, hence it seems to be adapted to some extent to feather structure. Feather growth-rate by length was dependent on both the feather material produced per unit time (growth-rate by mass) and the amount of material deposited per unit feather-length. Follicle size not only determines feather growth-rate by mass, but also directly the structural design (shape, number of barbs, etc.) of a feather. Therefore, feather growth-rate is severely constrained by the requirements imposed by the structural feather design.

Long-term use of non-invasive sampling methods: does successful sampling of brown bears by hair snares and camera traps change over time?

Abstract Context Non-invasive sampling methods are widely used by ecologists to collect animal hair, images, tissue or signs. Sampling devices are imperfect, and collection success may vary over time owing to behavioural changes in study organisms or other factors. If collection success decreases, the utility of non-invasive sampling devices for longitudinal studies that rely on consistency may be compromised. Aims Our primary objectives were to evaluate whether collection success of brown bear (Ursus arctos) hair by using hair snares and camera traps changed over time, and whether hair- and image-collection success was influenced by bear activity around the sampling site. Methods We paired non-invasive sampling by hair snares with motion-activated cameras at six streams in Alaska over 4–6 years, so as to evaluate how often brown bears left samples on wires or were photographed by cameras, and whether this sampling success changed over time. Changes in sampling success were evaluated in the context of bear activity per sampling period as determined by camera data (number of bear–wire encounters) or hair snare (number of barbs with hair); genetic analyses allowed us to evaluate whether the same bears were sampled repeatedly. Key results Overall, hair was collected in 78% and images in 73% of 2-day sampling periods when bears visited sites, and we observed no substantial change in the probability of successful sampling over time at 11 sites. The number of bear–wire encounters was positively correlated with the number of hair samples collected, as would be expected if sampling rates remained constant over time, and individual bears with previous wire experience were sampled in multiple years. Conclusions Overall, the results indicated that sampling success by using hair snare and camera trap showed substantial interannual variability, but changes over time were not consistently identified across sites. Among-site variation in sampling success highlighted the importance of accounting for site-specific differences in sampling success, and neither method sampled unfailingly. Implications Sampling by wires and cameras remained effective over time, suggesting that these non-invasive sampling methods may be successfully employed in long-term studies.

The Magdalenian harpoons from the Iberian Mediterranean, based on pieces from Cova de les Cendres (Teulada-Moraira, Valencian region)

Harpoons are one of the most characteristic implements of the Upper Magdalenian. However, morphologic differences in barbs and bases mark different regional traditions. This paper gives an account of the main features of harpoons in the Iberian Mediterranean, based on findings from Cova de les Cendres, and compares them with those found in other areas in Western Europe.The specificities of Mediterranean harpoons (a single range of barbs, variable length and number of barbs, and lack of hafting devices on the base) are considered in discussion of their potential functions and possible hafting systems.

Barbed Model–Driven Software Development: A Case Study

When thinking of MDE, the immediate understanding is that models drive software development, in the sense that the software is constructed by transforming models from higher levels of abstraction to the point where we reach a model which is executable with the desired degree of quality characteristics. What tends to be less evident, is that, precisely in order to reach the desired quality, many other models are used in the verification and assessment of the solutions under consideration at the various stages of development. That is, looking at the development process, besides a spine of model transformations moving from highly abstract, domain related models down to concrete platform related models (programs), we can see a number of barbs, relating models in the spine to specialized models that permit specific analysis of parts of the software.In this paper we report on some preliminary work on understanding Barbed Model–Driven Software Development. We are taking an experimental attitude, designing and implementing a barb, using specific technologies and verification tools. The goal is twofold: to get acquainted with the technologies, and to provide a first assessment of their suitability for subsequent explorations. In the experiment experiment the barb deals with the verification of properties of a SOA system modelled in UML.

Why do some traits show higher fluctuating asymmetry than others? A test of hypotheses with tail feathers of birds

Certain characters are more susceptible to increased fluctuating asymmetry (FA) than others. This trait-specific susceptibility has normally been attributed to different degrees of developmental stability, which could be caused by different modes of selection, functionality, or the stress experienced during the development process. Recently, it has also been suggested that the expression of FA not only depends on developmental stability, but also on the cost of growth of the trait, defined as the amount of structural components necessary to form a unit of length of a given character. In accordance with this argument, a trait with more structural components per unit of length should show lower asymmetry than a simpler one. To test this hypothesis, we examine the structure (number of barbs, barb length, and rachis width) and asymmetry of the longest tail feathers in 26 bird species. Regression analyses using phylogenetically independent contrasts show that FA is negatively correlated with the number of barbs and feather rachis width in males (including species with elongated tails subjected to sexual selection), and with rachis width in females, whose tails supposedly evolve by natural selection. Moreover, the negative correlation between FA and rachis width persisted when taking only the males of non-dimorphic species. These results confirm the hypothesis, suggesting that a trait's susceptibility to express developmental instability by fluctuating asymmetry depends on its structural composition.

SNAIL SPEARS AND SCIMITARS: A CHARACTER ANALYSIS OF CONUS RADULAR TEETH

Knowledge of the attributes of the venom-injecting radular teeth of Conus can enhance understanding of the functional biology of feeding and the systematics of this large and taxonomically difficult genus of gastropods. We define and provide a scheme for coding the states of Conus radular tooth characters, in order to facilitate their use in taxonomic and phylogenetic studies. To exemplify these characters, we describe and illustrate teeth of putatively primitive species and of species representing generalized, vermivorous, molluscivorous and piscivorous feeding groups within the genus. We define and address the intraspecific and interspecific variation of ten presence-absence characters and 15 continuous characters, of which at least five and ten, respectively, are present in most species. Some continuous characters are bimodally distributed among the species sampled. If this distribution still obtains when additional species are examined, these characters could also be coded unambiguously as having two states. We also review the several previously proposed classification schemes of Conus radular teeth and of species according to tooth characters. As Troschel suggested in 1866, a tooth length:width ratio greater than or less than 20 separates the genus into two distinct species groups, now known to comprise the molluscivorous and piscivorous species in the former, and vermivorous and generalized species in the latter. Important subsidiary characters are the number of barbs, presence/absence of blade, cusp, and spur, length of serrations, relative width of base, and tooth length:shell length ratio.

Structural Changes in the Main Rectrices of the Superb Lyrebird Menura novaehollandiae in the Development of the Filamentary Feathers

SummaryThe development of the tail plumage of the female and male Superb Lyrebird Menura novaehollandiae proceeds through a number of moults during which the feathers formed undergo structural changes. The number of barbs in successive 50 mm lengths of the main rectrices (plain and filamentary feathers) (designated ‘barb density’) were counted, starting at the distal end. As the bird grows older, the relevant barb densities decrease. The paper identifies the changes in structure of a feather during the growing process. The case histories of several identifiable subjects are given, illustrating the independent behaviour of the individual follicles within the tail plumage of particular birds and between different birds.

Nye harpunfund

Nye harpunfund

Pattern Analysis in Plumage. III. Action of Thyroxin in High Concentrations

The sequence of response of the components of the definitive feather to increasing thyroxin concentrations—blanching of barbs, barbule formation, and pigment deposition—and the manner of estimating barb growth in the germ by observation of the order of appearance of pigment following injection of thyroxin have been established by Lillie and Juhn. An examination of definitive feathers subjected to heavy thyroxin dosages (10 mg., single injection) during development shows that both barb frequency and barb lengths are markedly altered. Barb frequency increases to a level around twice the barb frequency of a normal feather; a sudden drop then occurs to a level below that characteristic of barb frequency for the same region of the control feather. Barb length decreases following injection of thyroxin, then gradually returns to normal or possibly greater than normal length. These relations are shown in the accompanying graph. The curves are for single longitudinal vane-halves of modified and control neck feathers. Distances from origin of rhachis are given in centimeters on the horizontal axis. Figures on the left ordinate refer to barb frequency, i. e., the number of barbs per millimeter rhachis length. Figures on the right ordinate apply to barb lengths.

The Radiographic Detection of the Catfish Spur as a Foreign Body

Some time ago I was asked to attempt the radiographic determination of a foreign body of a rather unusual nature. This foreign body was supposed to have been the spur of a catfish.1 Being unfamiliar with the composition of this spur, I secured one and was rather surprised to find it dense enough to cast an excellent shadow through the flesh or bones of a man's foot. As the wounds from this fish are of frequent occurrence in this region, I felt that the matter might be of some interest. The catfish is often caught by those who fish along the beaches of the South Carolina coast and since it is not regarded as edible except by the colored people, it is felt to be a nuisance and is left to die on the shore, where it is frequently stepped upon. The spur (Figs. 1 and 2) has a number of barbs which make it very difficult of withdrawal from the wound and there is some chance that small fragments may be broken off. While it is commonly believed that the slime from this fish is poisonous, there is no real foundation to that idea; but at least the wound gives pain out of all proportion to a clean wound. In this particular instance a woman stepped on a catfish which had been recently caught. The spur penetrated through the sole of her shoe, obliquely through the second toe, and into the great toe. The spur was examined by some one in the party and pronounced whole but it is doubtful if the examination was very carefully made. For about five days the patient was able to walk, but with difficulty, following which the pain became so severe that she had to remain in bed for a week. Discharge continued from the wound for about one month. A radiographic examination made about two weeks after the injury showed a minute foreign body in the soft tissue of the great toe, just medial to the base of the proximal phalanx. This body, which was triangular in shape, was seen in the same position on five films of different densities. It seems reasonable to believe that this was the point of the spur. No attempt was made to remove the fragment, as it could hardly have been found. Another series of films made two months later showed that it had disappeared, either by discharge from the wound or absorption. This piece of spur was so small that it could not be reproduced in a magazine illustration, so a similar spur was procured, placed beneath a foot, and a test film made. This spur, which is shown in Figure 3, is seen to be quite dense, showing well through the metatarsal bones. This case is reported because, so far as I know, no mention has been made of a similar one in any previous writings. I am indebted to Mr. E. Milby Burton, Acting Director of the Charleston Museum, for the in formation about this fish.