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

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.

Freeze fracture imaging and computer simulation of liposome structure: Membrane geometry and defects

1983 ◽  
Vol 41 ◽  
pp. 646-647
Author(s):  
Joseph A. Zasadzinski
Keyword(s):  
Liquid Crystalline ◽  
Freeze Fracture ◽  
Continuum Theory ◽  
Closed Surfaces ◽  
Straight Line ◽  
Low Weight ◽  
Concentric Spheres ◽  
Membrane Geometry ◽  
Dupin Cyclides ◽  
Limiting Case

At low weight fractions, many surfactant and biological amphiphiles form dispersions of lamellar liquid crystalline liposomes in water. Amphiphile molecules tend to align themselves in parallel bilayers which are free to bend. Bilayers must form closed surfaces to separate hydrophobic and hydrophilic domains completely. Continuum theory of liquid crystals requires that the constant spacing of bilayer surfaces be maintained except at singularities of no more than line extent. Maxwell demonstrated that only two types of closed surfaces can satisfy this constraint: concentric spheres and Dupin cyclides. Dupin cyclides (Figure 1) are parallel closed surfaces which have a conjugate ellipse (r1) and hyperbola (r2) as singularities in the bilayer spacing. Any straight line drawn from a point on the ellipse to a point on the hyperbola is normal to every surface it intersects (broken lines in Figure 1). A simple example, and limiting case, is a family of concentric tori (Figure 1b).To distinguish between the allowable arrangements, freeze fracture TEM micrographs of representative biological (L-α phosphotidylcholine: L-α PC) and surfactant (sodium heptylnonyl benzenesulfonate: SHBS)liposomes are compared to mathematically derived sections of Dupin cyclides and concentric spheres.

A Novel Approach: Trans-ascending Aorta Balloon Aortic Valvuloplasty via Sternotomy for Treating Severe Valvular Aortic Stenosis in a Low-Weight Infant

2014 ◽  
Vol 17 (1) ◽  
pp. 25 ◽  
Author(s):  
Lei Gao ◽  
Qin Wu ◽  
Xinhua Xu ◽  
Tianli Zhao ◽  
Wancun Jin ◽  
...  
Keyword(s):  
Aortic Stenosis ◽  
Transesophageal Echocardiography ◽  
Severe Aortic Stenosis ◽  
Ascending Aorta ◽  
Balloon Aortic Valvuloplasty ◽  
Congenital Aortic Stenosis ◽  
Novel Approach ◽  
Low Weight ◽  
Aortic Valvuloplasty ◽  
Peak Gradient

<p><b>Background:</b> Severe congenital aortic stenosis in infants is a life-threatening congenital heart anomaly that is typically treated using percutaneous balloon aortic valvuloplasty.</p><p><b>Methods:</b> The usual route is the femoral artery under radiographic guidance. However, this procedure may be limited by the small size of the femoral artery in low-weight infants. An infant weighing only 7 kg with severe aortic stenosis (peak gradient was 103 mmHg) was successfully treated with a novel approach, that is trans-ascending aorta balloon aortic valvuloplasty guided by transesophageal echocardiography.</p><p><b>Results:</b> The patient tolerated the procedure well, and no major complications developed. After the intervention, transesophageal echocardiography indicated a significant reduction of the aortic valvular peak gradient from 103 mmHg to 22 mmHg, no aortic regurgitation was found. Eighteen months after the intervention, echocardiography revealed that the aortic valvular peak gradient had increased to 38 mmHg and that still no aortic regurgitation had occurred.</p><p><b>Conclusions:</b> In our limited experience, trans-ascending aorta balloon aortic valvuloplasty for severe aortic stenosis under transesophageal echocardiography guidance effectively reduces the aortic peak gradient. As this is a new procedure, long-term follow up and management will need to be established. It may be an alternative technique to treat congenital aortic stenosis in low-weight patients.</p>

Updating structural dynamic models with emphasis on the damping properties

AIAA Journal ◽  
1998 ◽  
Vol 36 ◽  
pp. 1094-1099
Author(s):  
Amar T. Chouaki ◽  
Pierre Ladeveze ◽  
Laurent Proslier
Keyword(s):  
Dynamic Models ◽  
Damping Properties ◽  
Structural Dynamic

DAMPING PROPERTIES OF SEISMIC PROTECTIVE SYSTEMS

2019 ◽  
pp. 96-98
Author(s):  
B. T. Ibragimov ◽  
S. V. Mirzaev ◽  
D. R. Raupov ◽  
A. R. Raupov ◽  
Z. Ilashov
Keyword(s):  
Damping Properties ◽  
Protective Systems

Dimeric NGF Mimetic Attenuates Hyperglycaemia and DNA Damage in Mice with Streptozotocin-Induced Early-Stage Diabetes

2020 ◽  
Vol 20 (3) ◽  
pp. 453-463
Author(s):  
Svetlana Yagubova ◽  
Aliy Zhanataev ◽  
Rita Ostrovskaya ◽  
Еlena Anisina ◽  
Тatiana Gudasheva ◽  
...  
Keyword(s):  
Dna Damage ◽  
Comet Assay ◽  
Early Stage ◽  
Alkaline Comet Assay ◽  
Β Cells ◽  
Ghost Cells ◽  
Low Weight

Background: NGF deficiency is one of the reasons for reduced β-cells survival in diabetes. Our previous experiments revealed the ability of low-weight NGF mimetic, GK-2, to reduce hyperglycaemia in a model of advanced diabetes. The increase in DNA damage in advanced diabetes was repeatedly reported, while there were no data about DNA damage in the initial diabetes. Aim: The study aimed to establish whether DNA damage occurs in initial diabetes and whether GK-2 is able to overcome the damage. Methods: The early-stage diabetes was modelled in Balb/c mice by streptozotocin (STZ) (130 mg/kg, i.p.). GK-2 was administered at a dose of 0.5 mg/kg, i.p., subchronically. The evaluation of DNA damage was performed using the alkaline comet assay; the percentage of DNA in the tail (%TDNA) and the percentage of the atypical DNA comets (“ghost cells”) were determined. Results: STZ at this subthreshold dose produced a slight increase in glycemia and MDA. Meanwhile, pronounced DNA damage was observed, concerning mostly the percentage of “ghost cells” in the pancreas, the liver and kidneys. GK-2 attenuated the degree of hyperglycaemia and reduced the % of “ghost cells” and %TDNA in all the organs examined; this effect continued after discontinuation of the therapy. Conclusion: Early-stage diabetes is accompanied by DNA damage, manifested by the increase of “ghost cells” percentage. The severity of these changes significantly exceeds the degree of hyperglycaemia and MDA accumulation. GK-2 exerts an antihyperglycaemic effect and attenuates the degree of DNA damage. Our results indicate that the comet assay is a highly informative method for search of antidiabetic medicines.

scholarly journals Evaluating the results of long tubular bone distraction with an advanced rod monolateral external fixator for achondroplasia

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bolatbek Dossanov ◽  
Vitaliy Trofimchuk ◽  
Vassiliy Lozovoy ◽  
Sergey Khmyzov ◽  
Assem Dossanova ◽  
...  
Keyword(s):  
External Fixator ◽  
Limb Lengthening ◽  
Tubular Bone ◽  
High Durability ◽  
Low Weight ◽  
Classical Technique ◽  
Orthopedic Care ◽  
Monolateral External Fixator ◽  
Experimental Group ◽  
Tubular Bones

AbstractThe work aimed to evaluate the effectiveness of the developed distraction system based on the rod external monolateral fixation mechanisms by comparing it with the classical technique of long tubular bones distraction based on the circular multi-axial system. The study included patients with a genetically confirmed diagnosis of achondroplasia. The experimental group consisted of 14 patients who underwent surgical limb lengthening by the rod monolateral external fixator with a distraction system developed by the authors. The lengthening was performed on 28 segments of tubular bones. The majority of the experimental group patients achieved the lengthening value close to the planned one and the deformation correction. The fixation period was averagely 83.8 ± 3.7 days, the regenerate length was 8.5 ± 0.6 cm, and the mechanical strength of the distraction regenerate was 10.3° ± 2.18°. The rod external fixator with a control distraction system developed by the authors has small dimensions and low weight of the external supporting elements of high durability. It is reported to provide a good psychological tolerance of the treatment process and significantly outperforms the circular multi-axis system. Considering the aforementioned, the proposed apparatus can grant good orthopedic care to patients with achondroplasia.

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