The mechanosorptive effect in Pinus radiata D. Don.

Holzforschung ◽  
2005 ◽  
Vol 59 (5) ◽  
pp. 552-558 ◽  
Author(s):  
Kenneth M. Entwistle
Keyword(s):  
Applied Stress ◽  
Pinus Radiata ◽  
Cell Walls ◽  
Cellulose Microfibril ◽  
Stress Component ◽  
Single Specimen ◽  
Shear Stress Component ◽  
Effect Analysis ◽  
Detailed Model ◽  
Valid Data

Abstract Measurements are reported of the mechanosorptive strain in Pinus radiata specimens stressed either in torsion or in bending. It is demonstrated that, to secure valid data, correction must be made for the moisture-induced distortion at zero load. A series of measurements can be made on a single specimen if two successive mechano-sorptive loading cycles are used and the sense of the stress is reversed for the second cycle. At the end of this procedure the specimen has reverted to its original dimensions. The mechanosorptive strain is shown to vary linearly with the applied stress; the ratio of the mechanosorptive strain to the initial elastic strain is therefore an appropriate way of quantifying the mechanosorptive effect. Analysis of torsion and bending data reveals that there is a strong correlation between the magnitude of the mechanosorptive strain and the shear stress component of the applied stress along the cellulose microfibril direction. It is suggested that the mechanosorptive effect arises from the effect of stress on the distribution of hydrogen bonds in hemicelluloses. A detailed model must await more information about the molecular structure of hemicelluloses in the cell walls.

scholarly journals β-tubulin affects cellulose microfibril orientation in plant secondary fibre cell walls

2007 ◽  
Vol 51 (4) ◽  
pp. 717-726 ◽  
Author(s):  
Antanas V. Spokevicius ◽  
Simon G. Southerton ◽  
Colleen P. MacMillan ◽  
Deyou Qiu ◽  
Siming Gan ◽  
...  
Keyword(s):  
Cell Walls ◽  
Cellulose Microfibril ◽  
Fibre Cell ◽  
Microfibril Orientation ◽  
Cellulose Microfibril Orientation ◽  
Β Tubulin ◽  
Secondary Fibre

Characterization of Thermally Induced Stress in IC Packages Using PiFETs Over a Temperature Range of −180°C to 80°C

2014 ◽  
Vol 2014 (1) ◽  
pp. 000500-000504 ◽  
Author(s):  
Francy J. Akkara ◽  
Uday S. Goteti ◽  
Richard C. Jaeger ◽  
Michael C. Hamilton ◽  
Michael J. Palmer ◽  
...  
Keyword(s):  
Shear Stress ◽  
Stress Component ◽  
Shear Stress Component ◽  
Thermally Induced ◽  
Temperature Changes ◽  
Temperature Range ◽  
Induced Stress ◽  
Highly Sensitive ◽  
Stress Components

In certain applications, IC packages may be exposed to extreme temperatures and knowledge of thermally induced stress aids the prediction of performance degradation or failure of the IC. In the devices that are used in extreme conditions, the stress is caused mainly by the mismatch in expansion of various materials triggered by the different coefficients of thermal expansion. This work performed in this study is conducted using NMOS current mirror circuits that are cycled through a wide temperature range of −180°C to 80°C. These circuits are highly sensitive to stress and provide well-localized measurements of shear stress. The sensors are fabricated in such a way that the effects of certain stress components are isolated. These sensors are also temperature compensated so that only the effect of mechanical stress components is observed and changes in device performance due to temperature changes are minimal. Current readings obtained from the sensors are used to extract the shear stress component. Finite element simulations, using expected materials performance parameter information were also performed for similar packages and these results are compared to the measured results.

Tracing cellulose microfibril orientation in inner primary cell walls

PROTOPLASMA ◽  
1993 ◽  
Vol 175 (3-4) ◽  
pp. 102-111 ◽  
Author(s):  
A. M. C. Wolters-Arts ◽  
T. van Amstel ◽  
J. Derksen
Keyword(s):  
Cell Walls ◽  
Cellulose Microfibril ◽  
Primary Cell ◽  
Microfibril Orientation ◽  
Cellulose Microfibril Orientation

scholarly journals Direct Measurement of Plant Cellulose Microfibril and Bundles in Native Cell Walls

2020 ◽  
Vol 11 ◽  
Author(s):  
Bo Song ◽  
Shuai Zhao ◽  
Wei Shen ◽  
Cynthia Collings ◽  
Shi-You Ding
Keyword(s):  
Direct Measurement ◽  
Cell Walls ◽  
Cellulose Microfibril ◽  
Native Cell

Detection and mapping of resin canals by image analysis in transverse sections of mechanically perturbed, young Pinus radiata trees

IAWA Journal ◽  
2017 ◽  
Vol 38 (2) ◽  
pp. 170-181 ◽  
Author(s):  
Jimmy Thomas ◽  
David A. Collings
Keyword(s):  
Pinus Radiata ◽  
Cell Walls ◽  
Compression Wood ◽  
Radiata Pine ◽  
Automated Detection ◽  
Flatbed Scanner ◽  
Pine Trees ◽  
Old Trees ◽  
Imagej Software ◽  
Resin Canals

We describe a novel, semi-automatic method for the detection, visualisation and quantification of axially oriented resin canals in transverse sections of Pinus radiata D. Don (radiata pine) trees. Sections were imaged with a flatbed scanner using circularly polarised transmitted light, with the resin canals that contained only primary cell walls appearing dark against a bright background of highly-birefringent tracheids. These images were analysed using ImageJ software and allowed for a non-biased, automated detection of resin canals and their spatial distribution across the entire stem. We analysed 8-month-old trees that had been subjected to tilting to induce compression wood and rocking to simulate the effects of wind. These experiments showed that both rocking and tilting promoted the formation of wood and confirmed that resin canals were most common adjacent to the pith. Both the rocking and tilting treatments caused a decrease in the number of resin canals per unit area when compared to vertical controls, but this change was due to the increased formation of wood by these treatments. In tilted samples, however, analysis of resin canal distribution showed that canals were more common on the lower sides of stems but these canals were excluded from regions that formed compression wood.

scholarly journals Resonant soft X-ray scattering reveals cellulose microfibril spacing in plant primary cell walls

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
Dan Ye ◽  
Sarah N. Kiemle ◽  
Sintu Rongpipi ◽  
Xuan Wang ◽  
Cheng Wang ◽  
...  
Keyword(s):  
Cell Walls ◽  
Cellulose Microfibril ◽  
Primary Cell ◽  
X Ray ◽  
X Ray Scattering ◽  
Plant Primary Cell Walls ◽  
Ray Scattering

The Influence of Turbulence Memory on Idealized Tornado Simulations

2020 ◽  
Vol 148 (12) ◽  
pp. 4875-4892
Author(s):  
Aaron Wang ◽  
Ying Pan ◽  
Paul M. Markowski
Keyword(s):  
Boundary Condition ◽  
Shear Stress ◽  
Stress Component ◽  
Lower Boundary ◽  
Surface Friction ◽  
Surface Shear Stress ◽  
Normal Surface ◽  
Shear Stress Component ◽  
Surface Shear ◽  
Lower Boundary Condition

AbstractSurface friction contributes to tornado formation and maintenance by enhancing the convergence of angular momentum. The traditional lower boundary condition in atmospheric models typically assumes an instant equilibrium between the unresolved stress and the resolved shear. This assumption ignores the physics that turbulent motions are generated and dissipated at finite rates—in effect, turbulence has a memory through its lifetime. In this work, a modified lower boundary condition is proposed to account for the effect of turbulence memory. Specifically, when an air parcel moves along a curved trajectory, a normal surface-shear-stress component arises owing to turbulence memory. In the accompanying large-eddy simulation (LES) of idealized tornadoes, the normal surface-shear-stress component is a source of additional dynamic instability, which provides an extra pathway for the development of turbulent motions. The influence of turbulence memory on the intensity of quasi-steady-state tornadoes remains negligible as long as assumptions employed by the modified lower boundary condition hold over a relatively large fraction of the flow region of interest. However, tornadoes in a transient state may be especially sensitive to turbulence memory.Significance StatementFriction between the wind and the ground can influence atmospheric phenomena in important ways. For example, surface friction can be a significant source of rotation in some thunderstorms, and it can also help to intensify rotation when rotation is already present. Unfortunately, the representation of friction’s effects in atmospheric simulations is especially error-prone in phenomena characterized by rapid temporal evolution or strong spatial variations. Our work explores a new framework for representing friction to include the effect of the so-called turbulence memory. The approach is tested in idealized tornado simulations, but it may be applied to a wide range of atmospheric vortices.

scholarly journals Experimental study on granite acoustic emission and micro-fracture behavior with combined compression and shear loading: phenomenon and mechanism

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yue Cao ◽  
Jinhai Xu ◽  
Liang Chen ◽  
Peng Wu ◽  
Faiz Shaikh
Keyword(s):  
Shear Stress ◽  
Acoustic Emission ◽  
Fracture Mode ◽  
Inclination Angle ◽  
Fracture Behavior ◽  
Shear Failure ◽  
Stress Component ◽  
Shear Loading ◽  
Shear Stress Component ◽  
Microcrack Initiation

AbstractOne element that is essential to consider in underground mining engineering applications is the possibility of pillar failure, which can result in deadly geological disasters, including earthquakes and surface subsidence. Pillars are commonly present under an inclined state and are significantly dependent upon combined compression and shear loading. However, many scholars regard the pure uniaxial compression strength (UCS) of rock as the main evaluation index of pillar strength, which is inconsistent with the field practice. Hence, the present study developed a novel combined compression and shear test (C-CAST) system, which was applied in the investigative acoustic emission (AE) experiments to characterize the failure mechanism and micro-fracture behavior of granite specimens at different inclination angles. The experimental results presented the exponential decrease of UCS of inclined specimens with increase in the shear stress component. Changes in the inclination angle with a range of 0°–10° produced a splitting-shear failure fracture mode from the initial splitting failure. In comparison, an increase in the inclination angle from 10° to 20° produced a single shear failure fracture mode from the initial combined splitting-shear failure. The specimens exhibited nonlinearly reduced microcrack initiation (CI) and damage (CD) thresholds following an increase in the inclination angle, suggesting the dependence of the microcrack initiation and propagation on the shear stress component. The ratio of CI and CD thresholds to inclined UCS varies within a certain range, indicating that the ratio may be an inherent property of granite specimens and is not affected by external load conditions. Additionally, the rock fracture behavior was largely dependent upon the mechanism of shear stress component, as validated by the microcrack initiation and growth. Finally, a modified empirical formula for pillar strength is proposed to investigate the actual strength of inclined pillar. Results of a case study show that the modified formula can be better used to evaluate the stability of inclined pillars.

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