scholarly journals The damping properties of the foam-filled shaft of primary feathers of the pigeon Columba livia

2021 ◽  
Vol 109 (1) ◽  
Author(s):  
K. Deng ◽  
A. Kovalev ◽  
H. Rajabi ◽  
C. F. Schaber ◽  
Z. D. Dai ◽  
...  
Keyword(s):  
Columba Livia ◽  
System Response ◽  
Damping Properties ◽  
Micro Computed Tomography ◽  
Fundamental Vibration ◽  
Low Weight ◽  
Noise Energy ◽  
Gradient Microstructure ◽  
Foam Filled ◽  
Relationship Of

AbstractThe avian feather combines mechanical properties of robustness and flexibility while maintaining a low weight. Under periodic and random dynamic loading, the feathers sustain bending forces and vibrations during flight. Excessive vibrations can increase noise, energy consumption, and negatively impact flight stability. However, damping can alter the system response, and result in increased stability and reduced noise. Although the structure of feathers has already been studied, little is known about their damping properties. In particular, the link between the structure of shafts and their damping is unknown. This study aims at understanding the structure-damping relationship of the shafts. For this purpose, laser Doppler vibrometry (LDV) was used to measure the damping properties of the feather shaft in three segments selected from the base, middle, and tip. A combination of scanning electron microscopy (SEM) and micro-computed tomography (µCT) was used to investigate the gradient microstructure of the shaft. The results showed the presence of two fundamental vibration modes, when mechanically excited in the horizontal and vertical directions. It was also found that the base and middle parts of the shaft have higher damping ratios than the tip, which could be attributed to their larger foam cells, higher foam/cortex ratio, and higher percentage of foam. This study provides the first indication of graded damping properties in feathers.

scholarly journals Unusual Deviation of the Main Foramen from the Root Apex

2016 ◽  
Vol 27 (5) ◽  
pp. 589-591 ◽  
Author(s):  
Marco Aurélio Versiani ◽  
Hany Mohamed Aly Ahmed ◽  
Manoel Damião de Sousa-Neto ◽  
Gustavo De-Deus ◽  
Paul Michael Howell Dummer
Keyword(s):  
Computed Tomography ◽  
Short Communication ◽  
Root Apex ◽  
Micro Computed Tomography ◽  
Tooth Type ◽  
The Subject ◽  
Relationship Of ◽  
The Relationship ◽  
Substantial Distance

Abstract The relationship of the main foramen to the anatomic root apex has been the subject of several studies. Although they are anatomically close, they rarely coincide, and their distance can vary according to age or tooth type, ranging from 0.2 to 3.0 mm. The aim of this short communication was to evaluate the distance between the main foramen of independent middle mesial canals (MMCs) and the anatomical mesial root apex of mandibular first molars using the micro-computed tomography. Twenty-five mandibular first molars with MMCs were scanned (resolution of 9.9 µm), and the distance from its main foramen to the anatomical apex was evaluated. Overall, the distance ranged from 0.2 to 2.4 mm; however, in 3 specimens the distance was greater than 3 mm. This report demonstrates that the exit of the main foramen of the MMC varies considerably and could approach a substantial distance from the anatomical apex greater than previously reported in the literature.

scholarly journals How pigeons couple three-dimensional elbow and wrist motion to morph their wings

2017 ◽  
Vol 14 (133) ◽  
pp. 20170224 ◽  
Author(s):  
Amanda K. Stowers ◽  
Laura Y. Matloff ◽  
David Lentink
Keyword(s):  
Three Dimensional ◽  
Columba Livia ◽  
Micro Computed Tomography ◽  
Wrist Motion ◽  
Motion Data ◽  
Morphing Wings ◽  
Computed Tomography Scans ◽  
Motion Paths ◽  
Wing Morphing ◽  
Planar Drawing

Birds change the shape and area of their wings to an exceptional degree, surpassing insects, bats and aircraft in their ability to morph their wings for a variety of tasks. This morphing is governed by a musculoskeletal system, which couples elbow and wrist motion. Since the discovery of this effect in 1839, the planar ‘drawing parallels’ mechanism has been used to explain the coupling. Remarkably, this mechanism has never been corroborated from quantitative motion data. Therefore, we measured how the wing skeleton of a pigeon ( Columba livia ) moves during morphing. Despite earlier planar assumptions, we found that the skeletal motion paths are highly three-dimensional and do not lie in the anatomical plane, ruling out the ‘drawing parallels’ mechanism. Furthermore, micro-computed tomography scans in seven consecutive poses show how the two wrist bones contribute to morphing, particularly the sliding ulnare. From these data, we infer the joint types for all six bones that form the wing morphing mechanism and corroborate the most parsimonious mechanism based on least-squares error minimization. Remarkably, the algorithm shows that all optimal four-bar mechanisms either lock, are unable to track the highly three-dimensional bone motion paths, or require the radius and ulna to cross for accuracy, which is anatomically unrealistic. In contrast, the algorithm finds that a six-bar mechanism recreates the measured motion accurately with a parallel radius and ulna and a sliding ulnare. This revises our mechanistic understanding of how birds morph their wings, and offers quantitative inspiration for engineering morphing wings.

Dynamics of Deformable Fractal Surface in Contact with Harmonically Excited Rigid Flat

2017 ◽  
Vol 7 (2) ◽  
pp. 38-62
Author(s):  
Tamonash Jana ◽  
Anirban Mitra ◽  
Prasanta Sahoo
Keyword(s):  
Rough Surface ◽  
Dynamic Properties ◽  
Element Model ◽  
Harmonic Excitation ◽  
System Response ◽  
Fractal Surface ◽  
Fractal Rough Surface ◽  
Mass Damper ◽  
Relationship Of ◽  
Force Displacement

Dynamics of contact between a deformable fractal rough surface and a rigid flat is studied under harmonic excitation to the flat surface. Fractal surface is generated from the modified Weierstrass-Mandelbrot function and is imported to ANSYS to construct the finite element model of the same. A parameter called ‘nonlinearity exponent', is obtained from the force-displacement relationship of the rough surface and is used to find out the dynamic properties of the contacting interface using single spring-mass-damper model. The effect of variation in surface roughness and material properties on the system response is analyzed. The system exhibits superharmonic responses for different values of the nonlinearity exponent. The phase plot and time-displacement plots for the system are also furnished.

Pummelos as Concept Generators for Biomimetically Inspired Low Weight Structures with Excellent Damping Properties

2010 ◽  
Vol 12 (12) ◽  
pp. B658-B663 ◽  
Author(s):  
Sebastian F. Fischer ◽  
Marc Thielen ◽  
Ruth R. Loprang ◽  
Robin Seidel ◽  
Claudia Fleck ◽  
...  
Keyword(s):  
Damping Properties ◽  
Low Weight ◽  
Weight Structures

Comparative effects of mites and lice on the reproductive success of rock doves (Columba livia)

Parasitology ◽  
1995 ◽  
Vol 110 (2) ◽  
pp. 195-206 ◽  
Author(s):  
D. H. Clayton ◽  
D. M. Tompkins
Keyword(s):  
Reproductive Success ◽  
Body Mass ◽  
Growth Rates ◽  
Columba Livia ◽  
Nestling Growth ◽  
Adult Body Mass ◽  
Evolution Of Virulence ◽  
Relationship Of ◽  
The Impact ◽  
The Relationship

SUMMARYWe report experimental data comparing the effects of Mesostigmatid mites and Ischnoceran lice on the reproductive performance of a single group of captive rock doves (Columba livia). Several components of host reproductive success were compared for the two groups, including number of eggs laid, hatching success, nestling growth rates, fledging success, post-fledging body mass and survival. Adult body mass and survival were also compared. There was a dramatic difference in the effects of the mites and lice. The former drove host reproductive success to zero, mainly by agitating adults and causing them to incubate eggs less faithfully. Nestling growth rates and post-fledging survival were also significantly reduced by mites. Lice showed no effect on reproductive success whatsoever, even though the feather damage they cause is known to have energetic consequences (Booth, Clayton & Block, 1993). Neither parasite had a significant effect on adult birds. Although Ischnocera are found on most species of birds, our results for lice constitute the first experimental test of the impact of Ischnocera on avian reproductive success (preliminary report by Clayton & Tompkins, 1994). We discuss reasons for the different effects of mites and lice, including the relationship of horizontal (mites) and vertical (lice) transmission to the evolution of virulence.

scholarly journals Femoral mechanical performance of precocial and altricial birds: a simulation study

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Xinsen Wei ◽  
Zihui Zhang
Keyword(s):  
Mechanical Performance ◽  
Axial Loading ◽  
Columba Livia ◽  
Ontogenetic Changes ◽  
Micro Computed Tomography ◽  
Erect Posture ◽  
Element Analysis ◽  
Lower Strain ◽  
Altricial Birds ◽  
Radial Loading

AbstractBackgroundAs the major load-bearing structures, bones exhibit various properties related to mechanical performance to adapt to different locomotor intensities. The habits and ontogenetic changes of locomotion in animals can, thus, be explored by assessing skeletal mechanical performance.MethodsIn this study, we investigated the growing femoral mechanical performance in an ontogenetic series of Cabot’s Tragopans (Tragopan caboti) and Pigeons (Columba livia domestica). Micro-computed tomography-based finite element analysis was conducted to evaluate the stress, strain, and strain energy density (SED) of femora under axial and radial loading.ResultsFemora deflected medio-laterally and dorso-ventrally under axial and radial loading, respectively. Femora deformed and tensed more severely under radial loading than axial loading. In adult individuals, Cabot’s Tragopans had lower strain and SED than pigeons. During ontogeny, the strain and SED of pigeons decreased sharply, while Cabot’s Tragopans showed moderately change. The structural properties of hatchling pigeons are more robust than those of hatchling Cabot’s Tragopans.ConclusionsLimb postures have dominant effect on skeletal deformation. The erect posture is preferred by large mammals and birds to achieve a high safety factor of bones during locomotion. Adult Cabot’s Tragopans have stronger femora than pigeons, reflecting a better bone adaption to the terrestrial locomotion of the studied pheasant species. Changes in strain and SED during growth reflect the marked difference in locomotor ability between precocial and altricial hatchlings. The femora of hatchling Cabot’s Tragopans were built with better energy efficiency than deformation resistance, enabling optimized mechanical performance. In contrast, although weak in mechanical function at the time of hatching, pigeon femora were suggested to be established with a more mature structural design as a prerequisite for rapid growth. These results will be helpful for studies regarding developmental patterns of fossil avian species.

Growth and conception in continuously underfed Brahman heifers

1991 ◽  
Vol 53 (1) ◽  
pp. 45-50 ◽  
Author(s):  
R. R. Vera
Keyword(s):  
Weight Gain ◽  
Live Weight ◽  
Proportional Hazard ◽  
Proportional Hazard Model ◽  
Subsequent Growth ◽  
Target Weight ◽  
Dummy Variable ◽  
Low Weight ◽  
Gompertz Growth Model ◽  
Relationship Of

ABSTRACTThe objective of the experiment was to determine the effects of different, sustained levels of undernutrition on the reproductive performance of Brahman heifers, and on their subsequent growth to adulthood, when reared exclusively on a low-quality tropical pasture.Irrespective of the live-weight gains realized between weaning and the target weight of 270 kg, heifers on all treatments conceived at a similar mean weight of 290 kg. Nevertheless, heifers on the low weight-gain treatment had a significantly different relationship of cumulative conceptions to weight, which was confirmed when Cox's proportional hazard model was fitted to the data, using a dummy variable to represent treatment effect.A Gompertz growth model was fitted to the live weight of each individual animal. A significantly larger mean asymptotic weight was observed for the low weight-gain treatment, which was unrelated to the number of calvings or weanings, or to the total weight of calves weaned per animal. Asymptotic weights were positively correlated with first conception weight and age, both within and across treatments.The implications of drastic post-weaning undernutrition and continued suboptimal feeding are discussed briefly.

scholarly journals Endurance of Damping Properties of Foam-Filled Tubes

Materials ◽  
2015 ◽  
Vol 8 (7) ◽  
pp. 4061-4079 ◽  
Author(s):  
Matteo Strano ◽  
Alessandro Marra ◽  
Valerio Mussi ◽  
Massimo Goletti ◽  
Philippe Bocher
Keyword(s):  
Damping Properties ◽  
Foam Filled

Association between Dental Caries and Delayed Growth in Korean Children

2017 ◽  
Vol 52 (1-2) ◽  
pp. 71-77 ◽  
Author(s):  
Su-Hyun Shim ◽  
Dong-Hun Han ◽  
Young-Ho Khang
Keyword(s):  
Dental Caries ◽  
Sociodemographic Factors ◽  
Nutritional Deficiency ◽  
Korean Children ◽  
Health And Nutrition ◽  
Low Weight ◽  
Relationship Of ◽  
The Relationship ◽  
Delayed Growth ◽  
Height For Age

The purpose of this study was to assess the relationship of dental caries with anthropometric outcomes in 4- to 6-year-old children participating in the Korean National Health and Nutrition Examination Survey (KNHANES). The sample size was 1,910 children from the 4th and 5th KNHANES. The caries status was assessed with the decayed and filled teeth index in primary dentition (dft score). We employed height for age, body weight for age, and body mass index for age as outcome variables. Age, gender, region, and income were confounders. Nutritional deficiency as a mediator in the association between dental caries and delayed growth was also examined. A series of logistic regression analyses estimated the magnitude of association between dental caries and unfavorable growth after adjustment of the confounders and the mediator. Those with a high dft score were more likely to be deficient in nutrition (OR 1.77, 95% CI 1.14-2.74). After adjusting for sociodemographic factors and nutritional deficiency, we also found that a high dft score was associated with low weight (OR 1.70, 95% CI 1.15-2.51). The influence of dental caries on delayed growth was found in Korean representative children.

scholarly journals Association of Toll-Like Cell Receptors TLR2 (p.Arg753GLN) and TLR4 (p.Asp299GLY) Polymorphisms with Indicators of General and Local Immunity in Patients with Atopic Dermatitis

2017 ◽  
Vol 2017 ◽  
pp. 1-6 ◽  
Author(s):  
Yury A. Tyurin ◽  
Anton F. Shamsutdinov ◽  
Nikolay N. Kalinin ◽  
Alsou A. Sharifullina ◽  
Irina D. Reshetnikova
Keyword(s):  
Atopic Dermatitis ◽  
Immune Responses ◽  
System Response ◽  
Immunological Parameters ◽  
Local Immunity ◽  
Innate And Adaptive Immunity ◽  
Immune System Response ◽  
Relationship Of ◽  
The Relationship ◽  
Control Study

A whole group of polymorphisms of genes involved in the formation of the epidermal barrier, immune responses, and their regulation is important in the formation of atopic phenotype. The purpose of the study is to determine the relationship of polymorphisms of genes of Toll-like receptors TLR2 and TLR4 with clinical and immunological parameters in atopic dermatitis patients in a “case-control” study. Polymorphisms of genes TLR2 (p.Arg753Gln) and TLR4 (Asp299Gly) were detected by PCR. Parameters of the state of innate and adaptive immunity were assessed by the level of local production of sIgA, cytokine profile of blood serum for IL-4, IL-10, and IFN-γ. Biological samples from 50 people with allergic pathology, aged 4.5 to 35 years, and 100 healthy individuals (controls) were analyzed. Observed dysregulation of cytokine production (IL-4, IL-10) in patients with heterozygous polymorphic genotypes probably reflects an imbalance of Th1/Th2/Th17 regulation of immune system response in these individuals.

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