scholarly journals A Comparative Analysis of the Mechanical Role of Leaf Sheaths of Poaceae, Juncaceae, and Cyperaceae

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Andreas Kempe ◽  
Martin Sommer ◽  
Christoph Neinhuis
Keyword(s):  
Mechanical Properties ◽  
Flexural Rigidity ◽  
Shoot Elongation ◽  
Tissue Formation ◽  
Meristematic Tissue ◽  
Three Point Bending ◽  
Relative Contribution ◽  
Before And After ◽  
Bromus Erectus

Similarities in structural organization of the culm in Poaceae, Juncaceae, and Cyperaceae such as leaf sheaths and the presence of intercalary meristems at every node suggest the same mechanical properties and, accordingly, the same functionality. Meristems are zones of tissue formation, which constitute areas of weakness along the entire culm and provide the basis for rapid shoot elongation. Leaf sheaths clasp the culm preventing the shoot from breaking, ensuring the rigidity to grow erectly and to avoid damage of the meristematic tissue. The mechanical influence of leaf sheaths was investigated in members of Poaceae, Juncaceae, and Cyperaceae in the flowering stage. Mechanical properties of Poa araratica, Bromus erectus, Arrhenatherum elatius (Poaceae), Luzula nivea (Juncaceae), and Carex arctata (Cyperaceae) were determined in three-point bending before and after the removal of leaf sheaths. The presence of leaf sheaths results in smoothing the distribution of flexural rigidity and therefore avoids stress peaks. The achieved maxima of relative contribution of leaf sheaths to entire flexural rigidity ranged from 55% up to 81% for Poaceae, 72% for C. arctata, and 40% for L. nivea. Across the investigated families, the mechanical role of leaf sheaths could be verified as essential for culm stability during development and beyond.

Synthesis of a Core-Shell Acrylate Elastomer with UV Stabilization and its Application in Polyoxymethylene

2011 ◽  
Vol 239-242 ◽  
pp. 2431-2434 ◽  
Author(s):  
Fan Yang ◽  
Gui Bo Wu ◽  
Shi Ling Zhang ◽  
Xian Cheng Ren
Keyword(s):  
Mechanical Properties ◽  
Methyl Methacrylate ◽  
Uv Irradiation ◽  
Butyl Acrylate ◽  
Core Shell ◽  
Visible Absorption ◽  
Transmission Electron ◽  
Before And After ◽  
Uv Stabilization

In this study, a core-shell structure acrylate elastomer with UV stabilization core–shell poly[methyl methacrylate-butyl acrylate-2-hydroxy-4-(3-methacryloxy-2-hydroxylproroxy) benzophenone] [poly(MMA-BA-BPMA)] was synthesized by methyl methacrylate (MMA), butyl acrylate (BA) and a polymerizable UV-stabilizer 2-hydroxy-4-(3-methacryloxy-2-hydroxylproroxy) benzophenone (BPMA) via semicontinuous seeding emulsion polymerization. The composition and characteristics of core-shell Poly (MMA-BA-BPMA) were determined by using Fourier transform infrared spectroscopy (FTIR), Ultraviolet-visible absorption spectroscopy (UV-vis) and transmission electron microscope (TEM). Further, the obtained core-shell poly (MMA-BA-BPMA) was blended with polyoxymethylene (POM) to modify its photostabilization. The mechanical properties of POM composite were tested before and after UV-irradiation. The result showed that core-shell poly (MMA-BA-BPMA) can be dispersed well in the POM matrix, which could play a role of improving compatibility with POM and the mechanical properties of modified POM were kept well, which leaded higher impact strength and elongation at break after UV-irradiation.

scholarly journals Mechanical Properties of FDM Printed PLA Parts before and after Thermal Treatment

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1239
Author(s):  
Ali Chalgham ◽  
Andrea Ehrmann ◽  
Inge Wickenkamp
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Process Parameters ◽  
Fused Deposition Modeling ◽  
Poly Lactic Acid ◽  
Three Point Bending ◽  
Fused Deposition ◽  
Before And After ◽  
Deposition Modeling ◽  
3D Printed

Fused deposition modeling (FDM) is one of the most often-used technologies in additive manufacturing. Several materials are used with this technology, such as poly(lactic acid) (PLA), which is most commonly applied. The mechanical properties of 3D-printed parts depend on the process parameters. This is why, in this study, three-point bending tests were carried out to characterize the influence of build orientation, layer thickness, printing temperature and printing speed on the mechanical properties of PLA samples. Not only the process parameters may affect the mechanical properties, but heat after-treatment also has an influence on them. For this reason, additional samples were printed with optimal process parameters and characterized after pure heat treatment as well as after deformation at a temperature above the glass transition temperature, cooling with applied deformation, and subsequent recovery under heat treatment. These findings are planned to be used in a future study on finger orthoses that could either be printed according to shape or in a flat shape and afterwards heated and bent around the finger.

scholarly journals Mechanical Properties of Flexible TPU-Based 3D Printed Lattice Structures: Role of Lattice Cut Direction and Architecture

Polymers ◽  
2021 ◽  
Vol 13 (17) ◽  
pp. 2986
Author(s):  
Victor Beloshenko ◽  
Yan Beygelzimer ◽  
Vyacheslav Chishko ◽  
Bogdan Savchenko ◽  
Nadiya Sova ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Lattice Structure ◽  
Pore Space ◽  
Thermoplastic Polyurethane ◽  
Bending Tests ◽  
Three Point Bending ◽  
Lattice Materials ◽  
3D Printed ◽  
Anisotropy Of Mechanical Properties

This study addresses the mechanical behavior of lattice materials based on flexible thermoplastic polyurethane (TPU) with honeycomb and gyroid architecture fabricated by 3D printing. Tensile, compression, and three-point bending tests were chosen as mechanical testing methods. The honeycomb architecture was found to provide higher values of rigidity (by 30%), strength (by 25%), plasticity (by 18%), and energy absorption (by 42%) of the flexible TPU lattice compared to the gyroid architecture. The strain recovery is better in the case of gyroid architecture (residual strain of 46% vs. 31%). TPUs with honeycomb architecture are characterized by anisotropy of mechanical properties in tensile and three-point bending tests. The obtained results are explained by the peculiarities of the lattice structure at meso- and macroscopic level and by the role of the pore space.

Effect of High-Temperature Heat Treatment on Mechanical Property of Cr-Geopolymer Composite

2011 ◽  
Vol 399-401 ◽  
pp. 469-473
Author(s):  
Mei Rong Wang ◽  
Yi Zheng ◽  
De Chang Jia ◽  
Yu Zhou
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Mechanical Property ◽  
Treatment Temperature ◽  
Bending Test ◽  
Chromium Powder ◽  
Three Point Bending ◽  
High Temperature Heat Treatment ◽  
Micro Cracks ◽  
Before And After

Chromium powder reinforced geopolymer composite (Cr/geopolymer) was prepared in order to enhance its thermal conductivity and mechanical properties. The phase composition, microstructure and mechanical properties of Cr/geopolymer before and after heat treatment at 900, 1000, 1100 and 1200°C were investigated by the X–ray diffraction (XRD), scanning electron microscopy (SEM) and three–point bending test. With increasing heat treatment temperature from 900 to 1100°C, mechanical property of Cr/geopolymer increased gradually and at 1100°C flexural strength got the peak value, which was 325% higher than that of specimens without heat treatment. Cr/geopolymer treated at 900°C did not completely transform into crystalline phase, and many micro cracks around the chromium particles were observed. Cr/geopolymer treated at 1000–1100°C completely crystallized into leucite phase, and the metal chromium remained its original state. Meanwhile, most of the micro cracks were closed. When the temperature further increased to 1200°C, many visible defects were observed in Cr/geopolymer, and chromium oxide appeared in the interface of Cr/geopolymer, which had detrimental effect on the heat conduction and mechanical property of the composite.

scholarly journals Variation of the modulus of elasticity of aligner foil sheet materials due to thermoforming

2021 ◽  
Author(s):  
Bijan Golkhani ◽  
Anna Weber ◽  
Ludger Keilig ◽  
Susanne Reimann ◽  
Christoph Bourauel
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Modulus Of Elasticity ◽  
Young's Modulus ◽  
The Other ◽  
Bending Tests ◽  
Three Point Bending ◽  
Sheet Materials ◽  
Before And After ◽  
Lateral Walls

Abstract Objective Investigate and compare the mechanical properties of different aligner materials before and after deep drawing and determine differences in the mechanical properties after thermoforming. Materials and methods Four aligner film sheets from three manufacturers (Duran Plus® [Scheu Dental, Iserlohn, Germany]; Zendura® [ClearCorrect, Bay Materials LLC, Fremont, CA, USA]; Essix ACE® and Essix® PLUS™ [Dentsply Sirona Deutschland, Bensheim, Germany]) were tested in 3‑point bending with support distances of 8, 16, and 24 mm. Dimension of the specimens was 10 × 50 mm2. Two groups each were tested: (1) 10 specimens were investigated in the as-received state (before thermoforming), (2) 10 specimens were deep drawn on a master plate with cuboids of the dimension 10 × 10 × 50 mm3. Then, specimens were cut out of the upper side and lateral walls and were measured in 3‑point bending. Forces and reduction in thickness were measured and corrected theoretical forces of drawn sheets after thickness reduction as well as Young’s modulus were calculated. Results At a support distance of 8 mm and a displacement of 0.25 mm Essix® PLUS™, having the highest thickness in untreated state, showed highest forces of 28.2 N, followed by Duran Plus® (27.3 N), Essix ACE® (21.0 N) and Zendura® (19.7 N). Similar results were registered for the other distances (16, 24 mm). Thermoforming drastically reduced thickness and forces in the bending tests. Forces decreased to around 10% or less for specimens cut from the lateral walls. Young’s modulus decreased significantly for deep drawn foil sheets, especially for Essix® PLUS™. Conclusions Three-point bending is an appropriate method to compare different foil sheet materials. Young’s modulus is significantly affected by thermoforming.

Child and Adolescent Suicides in Bosnia and Herzegovina Before and After the War (1992–1995)

Crisis ◽  
2010 ◽  
Vol 31 (3) ◽  
pp. 160-164 ◽  
Author(s):  
Almir Fajkic ◽  
Orhan Lepara ◽  
Martin Voracek ◽  
Nestor D. Kapusta ◽  
Thomas Niederkrotenthaler ◽  
...  
Keyword(s):  
Bosnia And Herzegovina ◽  
Age Differences ◽  
Suicide Risk ◽  
Child And Adolescent ◽  
Youth Suicide ◽  
Southeastern Europe ◽  
Suicide Rates ◽  
Before And After ◽  
Sex And Age Differences

Background: Evidence on youth suicides from Southeastern Europe is scarce. We are not aware of previous reports from Bosnia and Herzegovina, which experienced war from 1992 to 1995. Durkheim’s theory of suicide predicts decreased suicide rates in wartime and increased rates afterward. Aims: To compare child and adolescent suicides in Bosnia and Herzegovina before and after the war. Methods: Data on youth suicide for prewar (1986–90) and postwar (2002–06) periods were analyzed with respect to prevalence, sex and age differences, and suicide methods. Suicide data from 1991 through 2001 were not available. Results: Overall youth suicide rates were one-third lower in the postwar than in the prewar period. This effect was most pronounced for girls, whose postwar suicide rates almost halved, and for 15–19-year-old boys, whose rates decreased by about a one-fourth. Suicides increased among boys aged 14 or younger. Firearm suicides almost doubled proportionally and were the predominant postwar method, while the most common prewar method had been hanging. Conclusions: The findings from this study indicate the need for public education in Bosnia and Herzegovina on the role of firearm accessibility in youth suicide and for instructions on safe storage in households. Moreover, raising societal awareness about suicide risk factors and suicide prevention is needed.

Role of putrescine in enhancing shoot elongation in Scirpus mucronatus under submergence

1996 ◽  
Vol 96 (3) ◽  
pp. 419-424
Author(s):  
Tse-Min Lee ◽  
Yuh-Jang Shieh ◽  
Chang-Hung Chou
Keyword(s):  
Shoot Elongation

Strategic Role of Zakat in Multidimensional Quality of Life in Sijunjung, Indonesia

2018 ◽  
Vol 15 (1) ◽  
pp. 55-72
Author(s):  
Herlin Hamimi ◽  
Abdul Ghafar Ismail ◽  
Muhammad Hasbi Zaenal
Keyword(s):  
Quality Of Life ◽  
Positive Impact ◽  
Wealth Distribution ◽  
Absolute Poverty ◽  
Before And After ◽  
The Status ◽  
Being There ◽  
The Impact

Zakat is one of the five pillars of Islam which has a function of faith, social and economic functions. Muslims who can pay zakat are required to give at least 2.5 per cent of their wealth. The problem of poverty prevalent in disadvantaged regions because of the difficulty of access to information and communication led to a gap that is so high in wealth and resources. The instrument of zakat provides a paradigm in the achievement of equitable wealth distribution and healthy circulation. Zakat potentially offers a better life and improves the quality of human being. There is a human quality improvement not only in economic terms but also in spiritual terms such as improving religiousity. This study aims to examine the role of zakat to alleviate humanitarian issues in disadvantaged regions such as Sijunjung, one of zakat beneficiaries and impoverished areas in Indonesia. The researcher attempted a Cibest method to capture the impact of zakat beneficiaries before and after becoming a member of Zakat Community Development (ZCD) Program in material and spiritual value. The overall analysis shows that zakat has a positive impact on disadvantaged regions development and enhance the quality of life of the community. There is an improvement in the average of mustahik household incomes after becoming a member of ZCD Program. Cibest model demonstrates that material, spiritual, and absolute poverty index decreased by 10, 5, and 6 per cent. Meanwhile, the welfare index is increased by 21 per cent. These findings have significant implications for developing the quality of life in disadvantaged regions in Sijunjung. Therefore, zakat is one of the instruments to change the status of disadvantaged areas to be equivalent to other areas.

Tire Treadwear — A Comprehensive Evaluation of the Factors: Generic Type, Aspect Ratio, Tread Pattern, and Tread Composition Part IV: Laboratory Measurement of Mechanical Properties and Mechanical Actions of Tires Relating to Treadwear

1986 ◽  
Vol 14 (4) ◽  
pp. 264-291
Author(s):  
K. L. Oblizajek ◽  
A. G. Veith
Keyword(s):  
Mechanical Properties ◽  
Shear Stress ◽  
Contact Zone ◽  
Flexural Rigidity ◽  
Comprehensive Evaluation ◽  
Shear Stiffness ◽  
Shear Stresses ◽  
Lateral Shear ◽  
Band Bending ◽  
Tread Rubber

Abstract Treadwear is explained by specific mechanical properties and actions of tires. Rubber shear stresses in the contact zone between the tire and the road become large at large slip angles. When normal stresses are insufficient to prevent sliding at the rear of the footprint, wear occurs at a rate that depends on test severity. Two experimental approaches are described to relate treadwear to tire characteristics. The first uses transducers imbedded in a simulated road surface to obtain direct measurements of contact stresses on the loaded, freely-rolling, steered tires. The second approach is developed with the aid of a simple carcass, tread-band, tread-rubber tire model. Various tire structural configurations; characterized by carcass spring rate, edgewise flexural band stiffness, and tread rubber shear stiffness; are simulated and lateral shear stress response in the contact zone is determined. Tires featuring high band stiffness and low carcass stiffness generate lower lateral shear stress levels. Furthermore, coupling of tread-rubber stiffness and band flexural rigidity are important in determining level of shear stresses. Laboratory measurements with the described apparatus produced values of tread-band bending and carcass lateral stiffness for several tire constructions. Good correlation is shown between treadwear and a broad range of tire stiffness and test course severities.

SUBLINGUAL VITAMIN D3 DRUG THERAPY IN VITAMIN D DEFICIENCY PATIENTS AT PRAVARA RURAL HOSPITAL

2019 ◽  
pp. 18-20
Author(s):  
Sanjeeva Kumar Goud T ◽  
Rahul Kunkulol
Keyword(s):  
Vitamin D ◽  
Vitamin D Deficiency ◽  
Vitamin D3 ◽  
Serum Vitamin ◽  
Cross Sectional ◽  
Serum Vitamin D ◽  
Significant Difference ◽  
Before And After

The present study was aimed to study the effect of Sublingual Vitamin D3 on Serum Vitamin D level in Vitamin D deficiency patients. This was a cross-sectional and interventional study. All the Vitamin D deficiency patients of age 18-60years and either gender, willing to participate in the study were included. Patients who had greater than 20 ng/ml were excluded from the study. The total number of participants in our study was 200, out of these 111 males and 89 females, the mean age in our study was 51.07 ± 7.39Yrs. All volunteers were given sublingual vitamin D3 (60,000IU) in six doses every fifteen days of follow up for 3 months. The subject’s serum 25(OH)D levels were estimated before and after the treatment of sublingual vitamin D3. There was a statistically significant difference in serum vitamin D3 level before 16.61±6.71 ng/ml and after 35.80±7.80 ng/ml after treatment with Sublingual Vitamin D3. Six doses of 60,000IU of Vitamin D3 sublingual route having improved the role of serum 25(OH)D levels in the treatment of Vitamin D3 deficiency patients.Keywords: Vitamin D3; Sublingual route

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