Effect of Different Positions of Bordered Pit Torus in Yezo Spruce on Its Permeability

The green wood of yezo species (Picea jezoensis var. komarovii (V. Vassil.) Cheng et L. K. Fu) was treated with air drying and ethanol exchange drying and by soaking the air-dried wood in water followed by ethanol change drying. The results showed that the proportion of aspirated pits in the respective earlywood and latewood of the air-dried sapwood was increased to 99% and 81%, while that of heartwood was also as high as 97% and 86% because most of the bordered pits were aspirated at its green state. The permeability of air-dried sapwood and heartwood was as low as 0.114 and 0.045 darcy respectively. The proportion of aspirated pits in the earlywood and latewood of sapwood after ethanol exchange drying was very low (8% and 17% respectively), whereas that of heartwood was very high (97% and 86% respectively) since most of the pits in it were aspirated at its green state, so the ethanol exchange drying failed to prevent pit aspiration. The permeability of sapwood and heartwood after ethanol exchange drying was 11.713 and 0.074 darcy respectivly, which was increased 101.5 times and 62.0% over the permeability at air-dried state. t-test showed that the difference of permeability of ethanol exchange drying versus air drying for sapwood was very significant at the level of 0.1%, but was not significant for heartwood. The proportion of aspirated pits in earlywood and latewood of air-dried sapwood and heartwood after soaking in water followed by ethanol exchange drying was decreased by 18% and 22%, and 0 and 17%, respectively, while the permeability of sapwood and heartwood was 0.439 and 0.060 darcy respectively, which was increased by 85% and 49% respectively. The permeability difference of soaking sapwood and heartwood versus their controls was very significant at the 0.1% level by t-test.     

A biomechanical perspective on the role of large stem volume and high water content in baobab trees (Adansonia spp.; Bombacaceae)

The stems of large trees serve in transport, storage, and support; however, the degree to which these roles are reflected in their morphology is not always apparent. The large, water-filled stems of baobab trees (Adansonia spp.) are generally assumed to serve a water storage function, yet recent studies indicate limited use of stored water. Through an analysis of wood structure and composition, we examined whether baobab morphology reflects biomechanical constraints rather than water storage capacity in the six Madagascar baobab species. Baobab wood has a high water content (up to 79%), low wood density (0.09-0.17 g · cm(-3)), high parenchyma content (69-88%), and living cells beyond 35 cm into the xylem from the cambium. Volumetric construction cost of the wood is several times lower than in more typical trees, and the elastic modulus approaches that of parenchyma tissue. Safety factors calculated from estimated elastic buckling heights were low, indicating that baobabs are not more overbuilt than other temperate and tropical trees, yet the energy investment in stem material is comparable to that in temperate deciduous trees. Furthermore, the elastic modulus of the wood decreases with water content, such that excessive water withdrawal from the stem could affect mechanical stability.     

Preservation of hymenopteran specimens for subsequent molecular and morphological study

Some guidelines are presented for long-term preservation of insects for non-traditional systematic studies such as DNA sequencing and internal anatomical research. The main criteria for good DNA preservation appear to be the rapidity with which the DNA is protected from enzymatic and chemical breakdown, and subsequent storage conditions. The immediate post mortem treatment of specimens appears particularly important to the preservation of amplifiable DNA. For storage we recommend 70–100% ethanol at low temperature, deep freezing, and critical point or chemical drying direct from alcohol. For internal anatomy, traditional fixatives, 70% ethanol in a refrigerator, critical point drying or chemical drying are recommended. Cold-storage in 70% ethanol with or without subsequent critical point drying or chemical drying using hexamethyldisilazane allow both molecular and morphological study.     

Still rethinking the value of high wood density

? Premise of the study: In a previous paper, we questioned the traditional interpretation of the advantages and disadvantages of high wood density (Functional Ecology 24: 701-705). Niklas and Spatz (American Journal of Botany 97: 1587-1594) challenged the biomechanical relevance of studying properties of dry wood, including dry wood density, and stated that we erred in our claims regarding scaling. ? Methods: We first present the full derivation of our previous claims regarding scaling. We then examine how the fresh modulus of rupture and the elastic modulus scale with dry wood density and compare these scaling relationships with those for dry mechanical properties, using almost exactly the same data set analyzed by Niklas and Spatz. ? Key results: The derivation shows that given our assumptions that the modulus of rupture and elastic modulus are both proportional to wood density, the resistance to bending is inversely proportional to wood density and strength is inversely proportional with the square root of wood density, exactly as we previously claimed. The analyses show that the elastic modulus of fresh wood scales proportionally with wood density (exponent 1.05, 95% CI 0.90-1.11) but that the modulus of rupture of fresh wood does not, scaling instead with the 1.25 power of wood density (CI 1.18-1.31). ? Conclusions: The deviation from proportional scaling for modulus of rupture is so small that our central conclusion remains correct: for a given construction cost, trees with lower wood density have higher strength and higher resistance to bending.     

Elucidation of extracellular matrix mechanics from muscle fibers and fiber bundles

The importance of the extracellular matrix (ECM) in muscle is widely recognized, since ECM plays a central role in proper muscle development (Buck and Horwitz, 1987), tissue structural support (Purslow, 2002), and transmission of mechanical signals between fibers and tendon (Huijing, 1999). Since substrate biomechanical properties have been shown to be critical in the biology of tissue development and remodeling (Engler et al., 2006; Gilbert et al., 2010), it is likely that mechanics are critical for ECM to perform its function. Unfortunately, there are almost no data available regarding skeletal muscle ECM viscoelastic properties. This is primarily due to the impossibility of isolating and testing muscle ECM. Therefore, this note presents a new method to quantify viscoelastic ECM modulus by combining tests of single muscle fibers and fiber bundles. Our results demonstrate that ECM is a highly nonlinearly elastic material, while muscle fibers are linearly elastic.     

Biomechanics of isolated tomato (Solanum lycopersicum L.) fruit cuticles: the role of the cutin matrix and polysaccharides

The mechanical characteristics of the cuticular membrane (CM), a complex composite biopolymer basically composed of a cutin matrix, waxes, and hydrolysable polysaccharides, have been described previously. The biomechanical behaviour and quantitative contribution of cutin and polysaccharides have been investigated here using as experimental material mature green and red ripe tomato fruits. Treatment of isolated CM with anhydrous hydrogen fluoride in pyridine allowed the selective elimination of polysaccharides attached to or incrusted into the cutin matrix. Cutin samples showed a drastic decrease in elastic modulus and stiffness (up to 92%) compared with CM, which clearly indicates that polysaccharides incorporated into the cutin matrix are responsible for the elastic modulus, stiffness, and the linear elastic behaviour of the whole cuticle. Reciprocally, the viscoelastic behaviour of CM (low elastic modulus and high strain values) can be assigned to the cutin. These results applied both to mature green and red ripe CM. Cutin elastic modulus, independently of the degree of temperature and hydration, was always significantly higher for the ripe than for the green samples while strain was lower; the amount of phenolics in the cutin network are the main candidates to explain the increased rigidity from mature green to red ripe cutin. The polysaccharide families isolated from CM were pectin, hemicellulose, and cellulose, the main polymers associated with the plant cell wall. The three types of polysaccharides were present in similar amounts in CM from mature green and red ripe tomatoes. Physical techniques such as X-ray diffraction and Raman spectroscopy indicated that the polysaccharide fibres were mainly randomly oriented. A tomato fruit CM scenario at the supramolecular level that could explain the observed CM biomechanical properties is presented and discussed.     

Effect of mineral dissolution from bone specimens on the viscoelastic properties of cortical bone

Although physiological saline (0.15 M NaCl aqueous solution) has been used as a storage solution to prevent bone specimens from drying, there have been reports that Ca²⁺ ions dissolve from bone specimens during the storage in saline. In order to determine whether such storage has a marked effect on mechanical properties, the relaxation modulus of bovine cortical bone stored in physiological saline was compared with that stored in a buffer solution containing a sufficient amount of Ca²⁺ ions. After storage in saline, the modulus value of specimens was significantly reduced from that before storage. On the other hand, the modulus value of specimens soaked in the solution containing sufficient Ca²⁺ ions did not change after storage. The relaxation rate of a bone specimen stored in physiological saline was larger than that of a specimen stored in Ca²⁺-buffered saline solution and that of the control specimens. The results suggest that by the dissolution of Ca²⁺ ions from a bone specimen during storage in physiological saline, percolated paths of mineral phase and of reinforced matrix phase are disjoined, resulting in reduction in the elastic modulus and change in the viscoelastic properties of bone.     

Utilizing peanut husk (Arachis hypogaea L.) in the manufacture of medium-density fiberboards

The main objective of this study was to investigate the potential of peanut husk (Arachis hypogaea L.) as a fiber–peanut mixture to produce fiberboards for general purposes. For panel production, the addition of peanut husk at various percentages to the wood fiber was the only variable. Panels produced utilizing peanut husk were compared to panels produced using 100% wood fiber. The chemical properties of peanut husk; holocellulose and lignin content, alcohol–benzene, hot and cold water, and dilute alkali (1% NaOH) solubility, were also determined. Results indicated that panels could be produced utilizing up to 30% peanut husk without affecting the usability of the panels. It was not possible to meet the minimum IB strength standards when peanut husk was added to the mixture. Higher additions resulted in panels having lower elastic and rupture moduli than the minimum requirements according to TS-EN standards.     

Effects of tissue preservation on murine bone mechanical properties

Murine bone specimens are used extensively in skeletal research to assess the effects of environmental, physiologic and pathologic factors on their mechanical properties. Given the destructive nature of mechanical testing, it is normally performed as a terminal procedure, where specimens must be preserved without affecting their mechanical properties. To this end, we aimed to study the effects of tissue preservation (freezing and formalin fixation) on the elastic and viscoelastic mechanical properties of murine femur and vertebrae. A total of 120 femurs and 180 vertebral bodies (L3–L5) underwent non-destructive cyclic loading to assess their viscoelastic properties followed by mono-cyclic loading to failure to assess their elastic properties. All specimens underwent re-hydration in 0.9% saline for 30 min prior to mechanical testing. Analysis indicated that stiffness, modulus of elasticity, yield load, yield strength, ultimate load and ultimate strength of frozen and formalin-fixed femurs and vertebrae were not different from fresh specimens. Cyclic loading of both femurs and vertebrae indicated that loss, storage and dynamic moduli were not affected by freezing. However, formalin fixation altered their viscoelastic properties. Our findings suggest that freezing and formalin fixation over a 2-week period do not alter the elastic mechanical properties of murine femurs and vertebrae, provided that specimens are re-hydrated for at least half an hour prior to testing. However, formalin fixation weakened the viscoelastic properties of murine bone by reducing its ability to dissipate viscous energy. Future studies should address the long-term effects of both formalin fixation and freezing on the mechanical properties of murine bone.     

Biomechanics and transgenic wood

Wood, or secondary xylem, is composed mostly of three components-cellulose, hemicelluloses, and lignin. Yet this apparent simplicity is deceiving because the sophisticated arrangement of the components on various structural levels, ranging from intricate molecular architecture to defined cellular arrangements to tissue morphology, makes wood a challenging and interesting subject of biomechanical investigation. Recent advances in genetic transformation, providing easier access to wood of specifically altered composition or structure, have opened new opportunities for research on the intricate relation between material structure and composition and mechanical properties. At the same time, investigations into the mechanical properties have provided new information regarding the structural configuration of wood. The present paper reviews the work conducted in this field and outlines future perspectives and prospects for research.     

The biomechanical effects of limb lengthening and botulinum toxin type A on rabbit tendon

Numerous studies have examined the effects of distraction osteogenesis (DO) on bone, but relatively fewer have explored muscle adaptation, and even less have addressed the concomitant alterations that occur in the tendon. The purpose herein was to characterize the biomechanical properties of normal and elongated rabbit (N=20) tendons with and without prophylactic botulinum toxin type A (BTX-A) treatment. Elastic and viscoelastic properties of Achilles and Tibialis anterior (TA) tendons were evaluated through pull to failure and stress relaxation tests.All TA tendons displayed nonlinear viscoelastic responses that were strain dependent. A power law formulation was used to model tendon viscoelastic responses and tendon elastic responses were fit with a microstructural model. Distraction-elongated tendons displayed increases in compliance and stress relaxation rates over undistracted tendons; BTX-A administration offset this result. The elastic moduli of distraction-lengthened TA tendons were diminished (p=0.010) when distraction was combined with gastrocnemius (GA) BTX-A administration, elastic moduli were further decreased (p=0.004) and distraction following TA BTX-A administration resulted in TA tendons with moduli not different from contralateral control (p>0.05). Compared to contralateral control, distraction and GA BTX-A administration displayed shortened toe regions, (p=0.031 and 0.038, respectively), while tendons receiving BTX-A in the TA had no differences in the toe region (p>0.05). Ultimate tensile stress was unaltered by DO, but stress at the transition from the toe to the linear region of the stress–stretch curve was diminished in all distraction-elongated TA tendons (p<0.05). The data suggest that prophylactic BTX-A treatment to the TA protects some tendon biomechanical properties.     

Viscoelastic nature of isolated tomato (Solanum lycopersicum) fruit cuticles: a mathematical model

Viscoelastic behaviour of isolated tomato fruit cuticle (CM) is well known and extensively described. Temperature and hydration conditions modify the mechanical properties of CM. Mechanical data from previous transient‐creep analysis developed in tomato fruit cuticle under different temperature and hydration conditions have been used to propose a rheological model that describes the viscoelastic nature of CM. As a composite material, the biomechanical behaviour of the plant cuticle will depend not only on the mechanical characteristics of the individual components by themselves but also on the sum of them. Based on this previous information, we proposed a two‐element model to describe the experimental behaviour: an elastic hookean element connected in parallel to a viscous element or Voigt element that will describe the mechanical behaviour of the isolated CM and cutin under the studied conditions. The main parameters of the model, E₁ and E₂ will reflect the elastic and viscoelastic behaviour of the cuticle. Relationship between these physical parameters and the change in CM properties were discussed in order to elucidate the rheological processes taking place in CM. This model describes both the influence of temperature and hydration and the behaviour of the isolated cutin and the inferred contribution of the cuticle fraction of polysaccharides when the whole cuticle is tested.     

Mechanical Properties of Black Locust (Robinia pseudoacacia) Wood: Correlations among Elastic and Rupture Moduli,Proportional Limit,and Tissue Density and Specific Gravity

The purpose of this paper is to determine the extent to which the physical and mechanical properties of dry and green wood samples are correlated. Samples of green (fresh) sap- and heartwood differing in density (ρ) were removed from the trunk of a black locust (Robinia pseudoacaciaL.) tree 30 years old and measuring 15 m in height. These samples were mechanically tested to determine their Young's elastic modulus (E), proportional (elastic) limit (σ_p), and modulus of rupture (σ_R). The Young's elastic modulus of green wood samples increased in magnitude to a limit with increasing cross-sectional area of the sample tested. The values of all three mechanical parameters measured for sapwood samples were consistently lower than those measured for heartwood samples with equivalent cross-sectional areas.Ewas linearly and positively correlated with the σ_pand σ_Rof heartwood tissue samples. All mechanical properties were highly correlated with the density of green heartwood. Likewise, these properties were highly correlated with the specific gravity of wood samples. Based on these results, it is concluded that either the density of fresh wood or the specific gravity of air-dried wood can be used to estimate the mechanical properties of black locust wood based on simple regression curves in the absence of extensive mechanical tests.     

上海中心城区绿地土壤水库特征

以上海中心城区典型公园和公共绿地土壤为研究对象,通过实地调查,分析上海中心城区绿地土壤水库库容、常数特征及影响因子.结果表明: 上海中心城区绿地土壤总库容偏低,但就整个中心城区绿地,土壤蓄积水量可观,达1.88×10⁷ m³;土壤水分现存量较高,占总库容的75.7%,土壤剩余蓄水空间偏低;绿地土壤滞洪库容和有效库容分别占土壤总库容的31.6%和27.2%;而土壤死库容占总库容的44.5%.不同植被类型土壤水库存在差异:其中,乔木和灌木地土壤总库容、剩余蓄水空间均显著高于草地;灌木地土壤滞洪库容、有效库容均显著高于乔木地、草地;但各植被类型土壤水分现存量、死库容差异不显著.建议通过降低土壤压实、增加土壤有机质含量、改善土壤物理性质和优化绿地植物配置来提高城市绿地土壤水库库容.     

Effect of sample treatment on biomechanical properties of insect cuticle

Experimental limitations often prevent to perform biomechanical measurements on fresh arthropod cuticle samples. Hence, in many cases short- or long-term storage of samples is required. So far, it is not known whether any of the standard lab-techniques commonly used to fix or store insect cuticle samples in any way affects the biomechanical properties of the respective samples.In this paper we systematically address this question for the first time, with a focus on practical, easily accessible and common lab-methods including storage in water, ethanol, glutaraldehyde, freezing and desiccation. We performed a comprehensive and sensitive non-destructive Dynamic Mechanical Analysis (DMA) on locust hind leg tibiae using a three-point-bending setup. Our results show that from all tested treatments, freezing samples at −20 °C was the best option to maintain the original values for Young's modulus and damping properties of insect cuticle. In addition, our results indicate that the damping properties of locust hind legs might be mechanically optimized in respect to the jumping and kicking direction.     

Studies of the structural change during deformation in Cryptomeria japonica by time-resolved synchrotron small-angle X-ray scattering

A definite proportional limit which has been observed typically in metallic materials during the transition from elastic deformation into plastic one was also detected in the load-displacement curve of the compression wood with the water content about 100% from Cryptomeria japonica D. Don. Time-resolved small-angle X-ray scattering studies demonstrated a large structural change, that is, a strong decrease in the microfibril angle in the cell wall occurring with increasing the displacement beyond the proportional limit for the compression wood loaded in uniaxial tension. Correspondingly, the mechanical properties are changed and high elongations begin to be seen. For the dried normal wood, on the other hand, only a weak decrease in the microfibril angle was observed with increasing the elongation until the fracture is initiated, where the elastic behavior was maintained.     

Effects of Hasten Drying and Storage Conditions on Properties and Microstructure of Konjac Glucomannan-Whey Protein Isolate Blend Films

Impact of drying process and storage conditions on properties of konjac glucomannan (KGM) and whey protein isolate (WPI) blend films was investigated. Hundred grams of film solution contained 0.4 g KGM, 3.8 g WPI and 1.5 g glycerol. During drying process, air velocity was varied to produce fast drying (3 h) and slow drying (15 h) in tray dryers under 50 °C. The high air velocity resulted in a significant higher drying rate in fast drying than low air velocity in slow drying. Drying curves from both processes were well-fitted with Page model and Henderson and Pabis model (R² ≥ 0.98). Fast drying improved transparency and mechanical properties without impairing color, solubility or water vapor permeability (WVP). Fast-dried film had less surface roughness and contained larger protein clusters. It also had greater melting enthalpy of protein aggregates, implying stronger networks. For stability study, fast-dried film was stored at 4-35 °C for 24 days. Transparency decreased over time. Overall mechanical properties have improved during storage. Color, solubility and WVP did not significantly change over time at all conditions (p?>?0.05). Microstructure of aged films was relatively similar to that of the freshly prepared film. Overall, the fast-dried KGM-WPI film exhibited reasonable storage stability.     

Influence of Low Acyl and High Acyl Gellan Gums on Pasting and Rheological Properties of Rice Starch Gel

The pasting, viscoelastic, morphological and retrogradation properties of rice starch as affected by low acyl (LA) and high acyl (HA) gellan gums were studied. The additions of both LA and HA gums increased the peak and trough viscosities, while decreased the final and setback viscosities of rice starch paste. The starch-HA mixed pastes exhibited superior viscoelastic properties to the starch-LA pastes as evidenced by their higher storage modulus and lower loss tangent values. The starch-HA system exhibited higher resistance to the stress and more pronounced recovery rate in in-shear structural recovery test. The creep recovery data were well fitted by a 4-element Burger’s model. The shrinkage measurements showed that the addition of both hydrocolloids, especially the HA gellan gum retarded the retrogradation of rice starch gel during cold storage. It was concluded that the addition of LA and HA gellan gums modified the rheology and textural properties of rice starch gel in different ways and interacted under different mechanisms based on their molecular structures.     

Worldwide correlations of mechanical properties and green wood density

? Premise of the study: The density of wood is highly correlated with the ability of stems and roots to resist bending or twisting, which is important for evaluating the mechanical behavior of trees. It also provides a measure of carbon storage, which is an important variable in modeling ecosystem processes and tree construction costs. However, most measurements of the density and mechanical properties of wood have little direct bearing on understanding the biomechanics of living plants because they are based on kiln- or air-dried samples. ? Methods: Here, we present and analyze the relationships between four important mechanical properties (Young's modulus, the modulus of rupture, and the maximum strength in shearing and in compression) and the density of green wood (i.e., wood at 50% moisture content) from a worldwide, taxonomically broad spectrum of 161 species. ? Key results: These data indicate that each of the mechanical properties disproportionately increases across species with increasing green wood density, i.e., stems composed of denser green wood are disproportionately stiffer and stronger than stems with equivalent cross-sections composed of less dense green wood. ? Conclusions: Although denser wood may have a higher carbon construction cost, the mechanical benefits of denser woods likely outweigh the extra cost.     

Systematic review and meta-analysis of the biomechanical properties of the human dura mater applicable in computational human head models

Accurate biomechanical properties of the human dura mater are required for computational models and to fabricate artificial substitutes for transplantation and surgical training purposes. Here, a systematic literature review was performed to summarize the biomechanical properties of the human dura mater that are reported in the literature. Furthermore, anthropometric data, information regarding the mechanically tested samples, and specifications with respect to the used mechanical testing setup were extracted. A meta-analysis was performed to obtain the pooled mean estimate for the elastic modulus, ultimate tensile strength, and strain at maximum force. A total of 17 studies were deemed eligible, which focused on human cranial and spinal dura mater in 13 and 4 cases, respectively. Pooled mean estimates for the elastic modulus (n?=?448), the ultimate tensile strength (n?=?448), and the strain at maximum force (n?=?431) of 68.1 MPa, 7.3 MPa and 14.4% were observed for native cranial dura mater. Gaps in the literature related to the extracted data were identified and future directions for mechanical characterizations of human dura mater were formulated. The main conclusion is that the most commonly used elastic modulus value of 31.5 MPa for the simulation of the human cranial dura mater in computational head models is likely an underestimation and an oversimplification given the morphological diversity of the tissue in different brain regions. Based on the here provided meta-analysis, a stiffer linear elastic modulus of 68 MPa was observed instead. However, further experimental data are essential to confirm its validity.