Structures, or Why Things Don’t Fall Down

Gordon, James; Stewart, Maurice Bruce

doi:10.1119/1.12007

Cited by 103 publications

(40 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…For example, pre-stressed material components are found within bone and teeth. These stresses not only allow for the structure of bone to perform in its preferred mode of loading [59], but also protect the microstructure from cracking [60]. Collagen dehydration upon mineralisation has been found to be at the origin of the compressive pre-strains commonly observed in bone mineral [61].…”

Section: Discussionmentioning

confidence: 99%

Towards new material biomarkers for fracture risk

Greenwood

Clement

Dicken

et al. 2016

Bone

View full text Add to dashboard Cite

Osteoporosis is a prevalent bone condition, characterised by low bone mass and increased fracture risk. Currently, the gold standard for identifying osteoporosis and increased fracture risk is through quantification of bone mineral density (BMD) using dual energy X-ray absorption (DEXA). However, the risk of osteoporotic fracture is determined collectively by bone mass, architecture and physicochemistry of the mineral composite building blocks. Thus DEXA scans alone inevitably fail to fully discriminate individuals who will suffer a fragility fracture. This study examines trabecular bone at both ultrastructure and microarchitectural levels to provide a detailed material view of bone, and therefore provides a more comprehensive explanation of osteoporotic fracture risk. Physicochemical characterisation obtained through X-ray diffraction and infrared analysis indicated significant differences in apatite crystal chemistry and nanostructure between fracture and non-fracture groups.Further, this study, through considering the potential correlations between the chemical biomarkers and microarchitectural properties of trabecular bone, has investigated the relationship between bone mechanical properties (e.g. fragility) and physicochemical material features.

show abstract

Section: Discussionmentioning

confidence: 99%

Towards new material biomarkers for fracture risk

Greenwood

Clement

Dicken

et al. 2016

Bone

View full text Add to dashboard Cite

show abstract

“…[6] Thanks to the large longitudinal tensile strength of wood, such stress distribution contributes significantly to bending strength of stems. It allows them to sustain much higher wind loading as compared to the case of a stress-free wooden column of similar mechanical properties [3]. It is in this sense that growth stress contributes to the skeletal function of wood in the standing tree [2].…”

Section: Biomechanical Functions Of Growth Stress Typical Growth Strementioning

confidence: 99%

“…Whereas in animals, the muscles would not be effective without bones, in trees, the wood itself fulfills the supporting function of a skeleton. It will be shown in next section that in addition to the ''muscular'' function, the stress distribution by itself contributes to the ''skeletal'' function through enhanced bending strength [2,3].…”

Section: Introductionmentioning

confidence: 99%

Tree growth stress and related problems

et al. 2017

View full text Add to dashboard Cite

Tree growth stress, resulted from the combined effects of dead weight increase and cell wall maturation in the growing trees, fulfills biomechanical functions by enhancing the strength of growing stems and by controlling their growth orientation. Its value after new wood formation, named maturation stress, can be determined by measuring the instantaneously released strain at stem periphery. Exceptional levels of longitudinal stress are reached in reaction wood, in the form of compression in gymnosperms or higher-than-usual tension in angiosperms, inspiring theories to explain the generation process of the maturation stress at the level of wood fiber: the synergistic action of compressive stress generated in the amorphous ligninhemicellulose matrix and tensile stress due to the shortening of the crystalline cellulosic framework is a possible driving force. Besides the elastic component, growth stress bears viscoelastic components that are locked in the matured cell wall. Delayed recovery of locked-in components is triggered by increasing temperature under high moisture content: the rheological analysis of this hygrothermal recovery offers the possibility to gain information on the mechanical conditions during wood formation. After tree felling, the presence of residual stress often causes processing defects during logging and lumbering, thus reducing the final yield of harvested resources. In the near future, we expect to develop plantation forests and utilize more wood as industrial resources; in that case, we need to respond to their large growth stress. Thermal treatment is one of the possible countermeasures: green wood heating involves the hygrothermal recovery of viscoelastic locked-in growth strains and tends to counteract the effect of subsequent drying. Methods such as smoke drying of logs are proposed to increase the processing yield at a reasonable cost.

show abstract

“…Additionally, because the maximum buckling load depends on the unsupported shoot length (i.e. between the seed and any overlying leaf if the surrounding soil does not limit bucking) and also on whether either end of the shoot is rigidly fixed, free to swivel, or free to move sideways (Gordon 1978), the boundary between shoots that buckle before they can reach their maximum thrust and those that do not will not only be dependent on shoot diameter. Nevertheless, shoot diameter and stiffness are the only seed-specific factors controlling shoot thrust, with diameter being the dominant factor.…”

Section: Discussionmentioning

confidence: 99%

“…1. The Euler buckling load of a cylindrical column is proportional to Er /I (Gordon 1978), whereas shoot thrust is proportional only to r (where E is the shoot's Young's modulus or stiffness, r its radius and / the unsupported shoot length). Thus, starting with small shoots that fail by buckling, as shoot diameter increases we expect thrust to increase in proportion to r 4 until it matches the maximum thrust due to turgor -if other factors remain constant.…”

Section: Discussionmentioning

confidence: 99%

Allometric relationships between seed mass and seedling characteristics reveal trade-offs for neotropical gap-dependent species

et al. 2007

View full text Add to dashboard Cite

A seed size-seed number trade-off exists because smaller seeds are produced in greater number but have a lower probability of establishment. This reduced establishment success of smaller-seeded species may be determined by biophysical constraints imposed by scaling rules. Root and shoot diameter, root growth extension rate (RGER) and shoot length at death for dark-grown seedlings are predicted to scale with the cube root of seed embryo and endosperm mass (m). We confirmed this expectation for ten neotropical gap-dependent tree species with an embryo and endosperm dry mass >1 mg. However, for nine smaller seeded species (m < 1 mg) with photoblastic germination, root and shoot diameters were larger than expected, and consequently, RQER was slower than expected. The maximum shoot thrust of seedlings from seeds with masses >1 mg was comparable to the estimated force required to displace overlying litter, supporting the hypothesis that photoblastic behaviour only occurs in seeds with insufficient shoot thrust to displace overlying leaves. Using the model soil water, energy and transpiration to predict soil drying in small and large gaps, we showed that: (1) gaps that receive a significant amount of direct sunlight will dry more quickly than small gaps that do not, (2) compared to the wet-season, soil that is already dry at depth (i.e. the dry-season) will dry faster after rainfall (this drying would most likely kill seedlings from small seeds) and (3) even during the wet-season, dry periods of a few days in large gaps can kill shallow-rooted seedlings. We conclude that the smaller the seed, the more vulnerable its seedling would be to both covering by litter and soil drying because it can only emerge from shallow depths and has a slow RGER-Consequently, we suggest that these allometrically related factors contribute to the reduced establishment success of smaller-seeded species that underpins the seed size-seed number trade-off.

show abstract

Structures, or Why Things Don’t Fall Down

Cited by 103 publications

References 0 publications

Towards new material biomarkers for fracture risk

Towards new material biomarkers for fracture risk

Tree growth stress and related problems

Allometric relationships between seed mass and seedling characteristics reveal trade-offs for neotropical gap-dependent species

Contact Info

Product

Resources

About