Silvicultural control of mechanical stresses in trees

1988 ◽  
Vol 18 (10) ◽  
pp. 1215-1225 ◽  
Author(s):  
Hans Kubler
Keyword(s):  
Spatial Distribution ◽  
Mechanical Stress ◽  
High Stress ◽  
Growth Conditions ◽  
Mechanical Stresses ◽  
Reaction Wood ◽  
Prevailing Wind ◽  
Growth Stresses ◽  
Stable Growth ◽  
Steep Slopes

Mechanical stress generated by growing wood cells causes heart checks in the ends of timber, while lumber end-splits and warps. It is not possible to prevent these growth stresses but they can be minimized. Trees generate relatively high stress in order to bend stems and branches into positions more favorable for the tree, as is known from reaction wood, whose growth stresses are extremely high. One controls the stresses by giving trees no reason to reorient themselves, that is, by providing stable growth conditions. To this end, trees should have sufficient, uniform light, and where light is scarce, as in understories, one-sided light changes have to be avoided. In particular, the spatial distribution of trees in the stand should be uniform; multistoried forests are preferable to single-storied, even-aged plantations. The stands should be thinned slightly, frequently, and uniformly, rather than haphazardly and severely after long periods. In areas with strong prevailing wind, close spacing may minimize the stresses, whereas on steep slopes wide spacing appears to be preferable.

scholarly journals Mechanosensitive binding of p120-Catenin at cell junctions regulates E-Cadherin turnover and epithelial viscoelasticity

2018 ◽  
Author(s):  
K. Venkatesan Iyer ◽  
Romina Piscitello-Gómez ◽  
Frank Jülicher ◽  
Suzanne Eaton
Keyword(s):  
Mechanical Stress ◽  
High Stress ◽  
Mechanical Stresses ◽  
Cell Junctions ◽  
Epithelial Tissue ◽  
Viscoelastic Deformation ◽  
P120 Catenin ◽  
Pupal Wing ◽  
Shape Changes ◽  
E Cadherin

AbstractStudying how epithelia respond to mechanical stresses is key to understanding tissue shape changes during morphogenesis. Here, we study the viscoelastic deformation of the Drosophila pupal wing epithelium in response to mechanical stress that evolves during morphogenesis. We show that wing epithelial tissue viscoelasticity depends on endocytic turnover of E-Cadherin. The fraction of ECadherin undergoing turnover depends on mechanical stress in the epithelium. We identified mechanosensitive binding of the endocytic regulator p120-Catenin (p120) as a mechanism to regulate E-Cadherin turnover. Under high stress, p120 is released into the cytoplasm, destabilizing E-Cadherin complexes and increasing its turnover. In p120 mutants, E-Cadherin turnover is insensitive to mechanical stress. Furthermore, we show that p120 is crucial for the viscoelastic deformation of the wing epithelium. Taken together, our findings reveal that mechanosensitive binding of p120-Catenin tunes epithelial tissue viscoelasticity during morphogenesis.

Erbium-Silicided Source/Drain Junction Formation by Rapid Thermal Annealing Technique for Decananometer-Scale Schottky Barrier Metal-Oxide-Semiconductor Field- Effect Transistors

2004 ◽  
Vol 810 ◽  
Author(s):  
Moongyu Jang ◽  
Yarkyeon Kim ◽  
Jaeheon Shin ◽  
Kyoungwan Park ◽  
Seongjae Lee
Keyword(s):  
Schottky Barrier ◽  
Annealing Temperature ◽  
Field Effect Transistors ◽  
Growth Conditions ◽  
Silicon On Insulator ◽  
Oxide Semiconductor ◽  
Oxide Interface ◽  
Silicide Growth ◽  
Stable Growth ◽  
Optimum Annealing Temperature

ABSTRACTThe stable growth conditions of erbium-silicide on silicon-on-insulator (SOI) are investigated considering annealing temperature, SOI and sputtered erbium thickness. From the sheet resistance measurement, X-ray diffraction and Auger electron spectroscopy analysis, the optimum annealing temperature is determined as 500°C. Also, for the stable growth of erbium- silicide on SOI, the sputtered erbium thickness should be less than 1.5 times of SOI thickness. As the SOI thickness decreases below this critical thickness, erbium-rich region is formed at the erbium-silicide and buried-oxide interface. By applying the optimized erbium-silicide growth conditions, 50-nm-gate-length n-type SB-MOSFET is manufactured, which shows the possible usage of erbium-silicide as the source and drain material in the n-type Schottky barrier MOSFETs for decananometer regime applications.

scholarly journals The analysis of landslide vulnerability level distribution in the Labuhanbatu Utara Regency, North Sumatera Province, Indonesia

2021 ◽  
Vol 912 (1) ◽  
pp. 012063
Author(s):  
A S Thoha ◽  
B Slamet ◽  
M M Harahap ◽  
T Y Sari ◽  
D L N Hulu
Keyword(s):  
Spatial Distribution ◽  
Agricultural Land ◽  
Forest Degradation ◽  
Disaster Risk ◽  
Index Method ◽  
Study Objective ◽  
Community Activities ◽  
Steep Slopes ◽  
The Impact ◽  
Very High

Abstract Forest degradation can increase the level of disaster risk, particularly landslides. The impact of landslides, especially in Labuhanbatu Utara Regency, North Sumatera Province, socio-economic, physical and environmental losses that are directly perceived by the community in the disaster site. The study objective was to analyze the distribution of landslide vulnerability levels in the Labuhanbatu Utara Regency. The spatial distribution of landslide vulnerability level used spatial modeling with the Storie Index method with four variables, including rainfall, slope, soil type, and land cover type. The spatial distribution of landslide vulnerability level was mostly at a very low – low level with a percentage of 57.6% of the area of Labuhanbatu Utara Regency. Areas that occupied high – very high of landslide vulnerability level with the largest area were in three districts, including Na IX-X, Aek Natas, and Kualuh Selatan. Landslide prone areas are generally located on plantation and agricultural land use and also distribute on steep slopes. Various parties need to reorganize community activities in areas of high – very high landslide vulnerability to reduce disaster risk.

scholarly journals Magneto- and Tensoresistance of the p Ge Compensated Crystals in the Range of Weak, Intermediate and Classically Strong Magnetic Fields

2016 ◽  
Vol 17 (1) ◽  
pp. 43-47 ◽  
Author(s):  
G.P. Gaidar
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Mechanical Stress ◽  
Elastic Deformation ◽  
Crystallographic Orientation ◽  
Longitudinal Axis ◽  
Mechanical Stresses ◽  
Strong Magnetic Fields ◽  
Compensation Factor

On the crystalsof compensatedp‑Ge (with the compensation factor of k = NSb/NGa = 0.5) the transverse (Н ^ (J // X)) magnetoresistance (within the magnetic fields of 0 < Н £ 22.3 kOe) at fixed values of the mechanical stresses Хі = 0; 0.2; 0.4; 0.6; 0.9; 1.1; 1.5 GPa were measured at 77 K. These mechanical stresses X created the elastic deformation along the samples, the crystallographic orientation of which coincided with the direction of [100]. Also at fixed magnetic field intensities Ні = 2; 4; 8; 10; 15; 20; 22.3 kOe the dependencies of resistivity  on the mechanical stress X, which coincides with the longitudinal axis of the crystal (X // J // [100]) and changes in the range of 0 £ Х £ 1.5 GPa, were measured. Last dependences characterized by the presence of a minimum in the range of X ~ 0.5 ¸ 0.6 GPa at the minimal magnetic field intensities Н = 2 kOe, which was shifted to the values of X ~ 0.2 ¸ 0.3 GPa with increasing Н up to 22.3 kOe.

An experimental investigation on PZT behavior under mechanical and cycling loading

2013 ◽  
Vol 22 (3-4) ◽  
pp. 129-136
Author(s):  
Haim Abramovich ◽  
Eugeny Tsikchotsky ◽  
Gregory Klein
Keyword(s):  
Electric Power ◽  
Mechanical Stress ◽  
Electrical Power ◽  
Electrical Energy ◽  
Mechanical Stresses ◽  
Cyclic Loads ◽  
Present Test ◽  
Static Mechanical ◽  
The Right ◽  
Cycling Loading

AbstractThe drive to produce electrical energy by directly compressing piezoceramic material using mechanical stress stands behind the present test series. To be able to correctly choose the right material, PZT disks manufactured by three different manufacturers have been tested under static mechanical compressive and cyclic loads. It was shown that although the disks can withstand high mechanical stresses (up to 100 MPa) without any visible damage, their transduction is confined to much lower stresses (50–75 MPa), a range in which the electrical output is a function of the square of the applied stress. This range is further reduced, when the PZT is subjected to cyclic mechanical loading, yielding an applicable mechanical stress in the range of 30–40 MPa, from which electrical power can be produced without further deterioration. To compensate for the low electric power, due to relatively low mechanical stresses applied on the PZT disks, one can increase the volume of the material used by placing layers of piezoelectric material one on top of the other, each subjected to the same mechanical stress. This will yield the required electric power from a safe given mechanical stress without reduction in its output.

scholarly journals Methods for evaluation of mechanical stress condition of materials

2018 ◽  
Vol 145 ◽  
pp. 05008 ◽  
Author(s):  
Yordan Mirchev ◽  
Pavel Chukachev ◽  
Mitko Mihovski
Keyword(s):  
Surface Waves ◽  
Mechanical Stress ◽  
Ultrasonic Method ◽  
Mechanical Stresses ◽  
Principal Stresses ◽  
Small Depth ◽  
Type Size ◽  
Cylindrical Holes ◽  
The One ◽  
First Time

Primary attention is given to the following methods: method by drilling cylindrical holes (drill method) and integrated ultrasonic method using volume (longitudinal and transverse), surface, and sub-surface waves. Drill method allows determination of residual mechanical stress in small depth of material surfaces, assessing type, size, and orientation of principal stresses. For the first time, parallel studies are carried out of mechanical stress in materials using the electroacoustic effect of volume, surface and sub-surface waves on the one hand, and effective mechanical stresses on the other. The experimental results present electroacoustic coefficients for different types of waves in the material of gas pipeline tube of 243 mm diameter and 14 mm thickness. These are used to evaluate mechanical stresses in pipelines, according to active GOST standards.

Dentin Erosion Simulation by Cantilever Beam Fatigue and pH Change

2005 ◽  
Vol 84 (4) ◽  
pp. 371-375 ◽  
Author(s):  
M. Staninec ◽  
R.K. Nalla ◽  
J.F. Hilton ◽  
R.O. Ritchie ◽  
L.G. Watanabe ◽  
...  
Keyword(s):  
Mechanical Stress ◽  
High Stress ◽  
Load Ratio ◽  
Maximum Load ◽  
Cyclic Fatigue ◽  
Ph Change ◽  
Material Loss ◽  
Dimensional Changes ◽  
Before And After ◽  
Human Dentin

Exposed root surfaces frequently exhibit non-carious notches representing material loss by abrasion, erosion, and/or abfraction. Although a contribution from mechanical stress is often mentioned, no definitive proof exists of a cause-effect relationship. To address this, we examined dimensional changes in dentin subjected to cyclic fatigue in two different pH environments. Human dentin cantilever-beams were fatigued under load control in pH = 6 (n = 13) or pH = 7 (n = 13) buffer, with a load ratio ( R = minimum load/maximum load) of 0.1 and frequency of 2 Hz, and stresses between 5.5 and 55 MPa. Material loss was measured at high- and low-stress locations before and after cycling. Of the 23 beams, 7 withstood 1,000,000 cycles; others cracked earlier. Mean material loss in high-stress areas was greater than in low-stress areas, and losses were greater at pH = 6 than at pH = 7, suggesting that mechanical stress and lower pH both accelerate erosion of dentin surfaces.

INFLUENCE OF MECHANICAL STRESS IN A MULTILAYER STRUCTURE ON SPATIAL DISTRIBUTION OF DOPANTS IN IMPLANTED-JUNCTION AND DIFFUSION-JUNCTION RECTIFIERS

2010 ◽  
Vol 24 (09) ◽  
pp. 867-895 ◽  
Author(s):  
E. L. PANKRATOV
Keyword(s):  
Diffusion Coefficient ◽  
Spatial Distribution ◽  
Mechanical Stress ◽  
Multilayer Structure ◽  
Spatial Dimensions ◽  
Dopant Redistribution ◽  
Additional Reduction ◽  
And Diffusion ◽  
Junction Rectifiers

The influence of mechanical stress in a multilayer structure on spatial distribution of dopants in implanted-junction and diffusion-junction rectifiers, which was produced in the structure has been analyzed. It is shown that the stress leads to additional reduction of spatial dimensions of the p–n junction in comparison with the reduction — a result of inhomogeneity — of the diffusion coefficient of dopant and other parameters of dopant redistribution (see, for example, Refs. 1–3).

scholarly journals Emphysema and Mechanical Stress-Induced Lung Remodeling

Physiology ◽  
2013 ◽  
Vol 28 (6) ◽  
pp. 404-413 ◽  
Author(s):  
Béla Suki ◽  
Susumu Sato ◽  
Harikrishnan Parameswaran ◽  
Margit V. Szabari ◽  
Ayuko Takahashi ◽  
...  
Keyword(s):  
Mechanical Stress ◽  
Transpulmonary Pressure ◽  
Mechanical Stresses ◽  
Lung Remodeling ◽  
Cell Functions ◽  
New Directions ◽  
Mechanical Factors ◽  
Mechanical Rupture

Transpulmonary pressure and the mechanical stresses of breathing modulate many essential cell functions in the lung via mechanotransduction. We review how mechanical factors could influence the pathogenesis of emphysema. Although the progression of emphysema has been linked to mechanical rupture, little is known about how these stresses alter lung remodeling. We present possible new directions and an integrated multiscale view that may prove useful in finding solutions for this disease.

Branches versus stems in woody plants: control of branch diameter growth and angle

1998 ◽  
Vol 76 (11) ◽  
pp. 1852-1856 ◽  
Author(s):  
Brayton F Wilson
Keyword(s):  
Acer Rubrum ◽  
Growth Stress ◽  
Diameter Growth ◽  
Reaction Wood ◽  
Differential Growth ◽  
Lateral Shoot ◽  
Branch Diameter ◽  
Growth Stresses ◽  
Branch Angle ◽  
Apical Control

The results of three studies at different stages of branch development demonstrated the importance of apical control of diameter growth in both stem formation and branch angle. Diameter growth is controlled by competition between branches and the stem for branch-produced photosynthate. Apical control of branch angle occurs only in species that can produce differential growth stresses. In those species, upward bending is largely regulated by the amount of branch diameter growth. The first study followed stem formation from current shoots in Kalmia latifolia L., a shrub without terminal buds or apical control of branch angle. When several current or older shoots were competing, the longest, most distal lateral shoot usually became the stem. Shoot angle was poorly correlated with eventual dominance. A more proximal lateral shoot on the underside of a leaning parent became the longest, dominant lateral in 24% of the parent shoots. The second study used stem girdles to test the hypothesis that the subjacent stem competes with the branch for branch-produced photosynthate. Results from Pinus strobus L. supported the hypothesis, but results from Betula lenta L. and Acer rubrum L. did not. The third study removed apical control from branches of six forest-shrub species by cutting off the stem above the branch. Branches of all species increased diameter growth after cutting the stem, but only branches of Ilex verticillata (L.) Gray, Hamamelis virginiana L., and Cornus amomum Mill. developed differential growth stress and bent upward. Treated branches of Gaylusaccia baccata (Wang.) K. Koch, Viburnum cassinoides L., and K. latifolia sagged as much as controls.Key words: apical control, diameter growth, branch angle, growth stress, reaction wood.

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