Assessing modulus of elasticity of wood-fiber cement (WFC) sheets using nondestructive evaluation (NDE)

This study evaluates whether the mechanical properties of modulus of rupture (MOR) and modulus of elasticity (MOE) of wood-fiber cement (WFC) sheets are correlated with the nondestructive parameters of stress wave velocity and density of the material. Longitudinal stress wave technique was used to evaluate WFC nondestructively using a total of 117 specimens (measuring each 241 x 51 mm) obtained from 39 WFC sheets. The aim was to establish the correlation between dynamic versus static MOE of the material for predicting the actual mechanical property. Even though short dimension specimens were used, results obtained were encouraging. A correlation coefficient (R) of 0.828 was found when the static MOE of the material was used as a function of nondestructive parameters. A multivariate linear regression analysis using the specimen's density, wave velocity, and dynamic MOE provided the strongest correlation to the static MOE. The correlation observed for MOR as a function of static MOE is within the normal range obtained for wood composites. A nondestructive evaluation (NDE) using full size WFC sheets is recommended and can probably improve the relationship between the static and the predicted MOE.     

Stiffness and checking of <Emphasis Type="Italic">Eucalyptus nitens</Emphasis> sawn boards: genetic variation and potential for genetic improvement

A trial was undertaken to assess the extent to which variation in sawn-board quality traits of plantation-grown Eucalyptus nitens is under genetic control and amenable to genetic improvement. Five hundred and sixty trees from 129 families and three central Victorian races were sampled from an open-pollinated progeny trial in Tasmania, Australia. Acoustic wave velocity (AWV) was assessed on standing trees and sawlogs. Wedges from disks extracted from sawlogs were assessed for basic density and checking. Processed boards from 496 of the trees were assessed for board stiffness (static modulus of elasticity, MOE), and internal and surface checking. Genetic differences among races were significant for AWV and MOE traits. The Southern race had the highest mean values for these traits. Significant additive genetic variation within races was observed in all traits, demonstrating that the quality of plantation-grown E. nitens boards could be improved through breeding. Estimated narrow-sense heritabilities were 0.85 for standing-tree AWV, 0.71 for log AWV, 0.37 for board MOE, and ranged from 0.20 to 0.52 for checking traits. A strongly positive genetic correlation (r _g = 1.05) was observed between standing-tree AWV and board MOE, indicating that AWV could be used as a selection trait to improve E. nitens board stiffness. The genetic correlation between basic density and board MOE was also positive (r _g = 0.62). However, a significant and adverse genetic correlation (r _g = 0.61) was identified between basic density and surface check length. Wood stiffness and checking traits were more-or-less genetically independent, and genetic correlations between surface and internal checking were positive but only moderate (r _g = 0.48–0.52).     

Rice straw-wood particle composite for sound absorbing wooden construction materials

In this study, rice straw-wood particle composite boards were manufactured as insulation boards using the method used in the wood-based panel industry. The raw material, rice straw, was chosen because of its availability. The manufacturing parameters were: a specific gravity of 0.4, 0.6, and 0.8, and a rice straw content (10/90, 20/80, and 30/70 weight of rice straw/wood particle) of 10, 20, and 30 wt.%. A commercial urea-formaldehyde adhesive was used as the composite binder, to achieve 140-290 psi of bending modulus of rupture (MOR) with 0.4 specific gravity, 700-900 psi of bending MOR with 0.6 specific gravity, and 1400-2900 psi of bending MOR with a 0.8 specific gravity. All of the composite boards were superior to insulation board in strength. Width and length of the rice straw particle did not affect the bending MOR. The composite boards made from a random cutting of rice straw and wood particles were the best and recommended for manufacturing processes. Sound absorption coefficients of the 0.4 and 0.6 specific gravity boards were higher than the other wood-based materials. The recommended properties of the rice straw-wood particle composite boards are described, to absorb noises, preserve the temperature of indoor living spaces, and to be able to partially or completely substitute for wood particleboard and insulation board in wooden constructions.     

Hydraulic, biomechanical, and anatomical interactions of xylem from five species of Acer (Aceraceae)

Possible trade-offs between hydraulic conductivity and mechanical properties of woody stems from five species were assessed. Acer negundo is a ruderal tree, A. saccharinum, and A. rubrum are fast-growing and shade-intolerant soft maples, whereas A. nigrum and A. saccharum are slow-growing and shade-tolerant hard maples. It was hypothesized that the ruderal and soft maples would have lower modulus of elasticity (MOE) and modulus of rupture (MOR), but higher maximum specific conductivity (K(s max)) than hard maples. Many anatomical and general morphological characteristics were measured in an attempt to correlate them to water transport and/or mechanical strength differences between species. No difference was found between species in vessel diameter, fiber wall thickness, initial hydraulic conductivity (K(h initial)), specific conductivity (K(s max)), native percent embolism, or Huber value. Similarly, no trade-off was found between K(s max) and MOE or MOR across the genus. However, fiber lumen diameter was inversely correlated to MOE and MOR. Surprisingly, percentage of ray parenchyma was positively related to MOE. The results suggest transport/mechanical trade-offs do not occur in Acer and differences in mechanical properties may be due to fiber lumen differences that do not influence the efficient transport of water.     

Ensiling corn stover: effect of feedstock preservation on particleboard performance

Ensilage is a truncated solid-state fermentation in which anaerobically produced organic acids accumulate to reduce pH and limit microbial activity. Ensilage can be used to both preserve and pretreat biomass feedstock for further downstream conversion into chemicals, fuels, and/or fiber products. This study examined the ensilage of enzyme-treated corn stover as a feedstock for particleboard manufacturing. Corn stover at three different particle size ranges (<100, <10, and <5 mm) was ensiled with and without a commercial enzyme mixture having a cellulase:hemicellulase ratio of 2.54:1, applied at a hemicellulase rate of 1670 IU/kg dry mass. Triplicate 20 L mini-silos were destructively sampled and analyzed on days 0, 1, 7, 21, 63, and 189. Analysis included produced organic acids and water-soluble carbohydrates, fiber fractions, pH, and microorganisms, including Lactobacillus spp. and clostridia were monitored. On days 0, 21, and 189, the triplicate samples were mixed evenly and assembled into particleboard using 10% ISU 2 resin, a soy-based adhesive. Particleboard panels were subjected to industry standard tests for modulus of rupture (MOR), modulus of elasticity (MOE), internal bonding strength (IB), thickness swell (TS), and water absorption at 2 h boiling and 24 h soaking. Enzyme addition did improve the ensilage process, as indicated by sustained lower pH (P < 0.0001), higher water-soluble carbohydrates (P < 0.05), and increased lactic acid production (P < 0.0001). The middle particle size range (<10 mm) demonstrated the most promising results during the ensilage process. Compared with fresh stover, the ensilage process did increase IB of stover particleboard by 33% (P < 0.05) and decrease water adsorption at 2 h boiling and 24 h soaking significantly (P < 0.05). Particleboard panels produced from substrate ensiled with enzymes showed a significant reduction in water adsorption of 12% at 2 h boiling testing. On the basis of these results, ensilage can be used as a long-term feedstock preservation method for particleboard production from corn stover. Enzyme-amended ensilage not only improved stover preservation but also enhanced the properties of particleboard products.     

不同生态条件对人工林杨树木材物理力学性质的影响

在施肥与未施肥、淹水与未淹水两种生态条件下,以杨树人工林木材I-69杨为对象,对木材年轮宽度、基本密度、干缩性质、主要力学性质进行了测试,并对数据进行了统计、对比和分析.结果表明,施肥处理后,木材年轮宽度、静态抗弯弹性模量和顺纹抗压强度分别增大0.99%、2.73%和1.06%;全干时和气干时的径向、弦向、体积全干干缩率分别降低了4.2%、7.7%、6.6%、15.6%、6.3%和11.1%;木材密度、抗弯强度、动态抗弯弹性模量则分别降低了2%、1.79%、8.13%.与未淹水相比,季节性淹水对I-69杨木材密度、木材干缩率和力学性质的影响较大,二者差异显著(P＜0.05).其中木材密度、全干时和气干时的径向、弦向、体积干缩率、抗弯强度、抗弯弹性模量以及顺纹抗压强度分别降低了5.5%、11.1%、9.2%、9.6%、16.7%、10.9%、8.5%、24.29%、18.18%和16.81%.     

The effect of temperature on mechanical properties of standing lodgepole pine trees

To estimate strength parameters of living lodgepole pine stems over a range of temperatures (-16 to +17°C), trees were winched near or past the point of breakage, during which the applied force and deflection of the stem were measured. Trees were 43 years old, 10 m tall, and since the experiments were conducted in the late winter and early spring, when the soil was frozen and the roots were held rigid, the resistance of the stem to deflection could be isolated from the resistances of the root and soil. Static flexure theory for cantilever beams was used to estimate stress, strain, Young's modulus (E), and modulus of rupture (MOR) of the stem. Trees were stiffer and stronger in the winter when wood was frozen, with a nearly 50% increase in E and MOR compared with the spring, when wood was thawed. In winter stems failed on the tension side, while in spring stems buckled on the compression side. Compared with strength estimations reported in the literature from small samples of clear green wood at standard temperatures, modulus of elasticity (MOE) estimates of the whole stem were 35% lower in spring, and in winter MOR exceeded published values by 53%. This suggests that the sway behavior of trees is probably temperature dependent in northern forests and whole-tree strength characteristics should be considered in wind sway models used in these regions.     

Genetic variation in basic density and modulus of elasticity of coastal Douglas-fir

Douglas-fir trees from 39 open-pollinated families at four test locations were assessed to estimate heritability of modulus of elasticity (MOE) and basic density. After trees were felled, sound velocity was measured on 4-m logs with the Director HM200. Disks were taken to estimate dry and green wood density; dynamic MOE was estimated as green density × (sound velocity)². Heritability estimates of MOE (across-site h ²=0.55) were larger than those for total height (0.15) and diameter at breast height (DBH; 0.29), and similar to those for density (0.59). Negative genetic correlations were found for MOE with height (r _A=−0.30) and DBH (r _A=−0.51), and were similar to those found for density with height (r _A=−0.52) and DBH (r _A=−0.57). The partial correlations of height with MOE and density, while holding DBH constant, were positive, implying that the observed negative correlations between height and the wood properties were a function of the high positive correlation between height and DBH and the strong negative correlations between DBH and the wood properties. Taper [DBH/(height−1.4)] was found to be negatively associated with MOE. Selection for MOE may produce greater gains than selection for density because MOE had a larger coefficient of additive variation (9.6%) than density (5.1%). Conversely, selection for growth may have a more negative impact on MOE than density because of the greater genetic variation associated with MOE. Family mean correlations of the wood quality traits with stem form and crown health were mostly nonsignificant.     

Studies on thermal degradation and termite resistant properties of chemically modified wood

A series of experiments were carried out to examine the resistant capacity of a chemically treated hard wood, Anthocephalus cadamba (Roxb) Miq. to thermal and termite degradation. The treatment with thermosetting resins viz. urea formaldehyde (UF), melamine formaldehyde (MF) and phenol formaldehyde (PF) at 31-33 levels of weight percent gain (WPG) increased the strength property i.e. modulus of rupture (MOR) by 7.50-21.02% and stiffness i.e. modulus of elasticity (MOE) by 9.50-12.18% over the untreated one with no remarkable effect on specific gravity. The treated samples were found resistant to termite attack, while the untreated one was badly damaged by termites on 12 months' exposure to a termite colony. The thermal degradations of untreated and treated wood samples were studied using thermogravimetric (TGA) and differential thermogravimetric (DTG) techniques at heating rates 20 and 30 degrees C min(-1) in temperature range 30-650 degrees C. The treated wood was found to be thermally more stable than the untreated one.     

Mechanical and water soaking properties of medium density fiberboard with wood fiber and soybean protein adhesive

Soybean protein is a renewable and abundant material that offers an alternative to formaldehyde-based resins. In this study, soybean protein was modified with sodium dodecyl sulfate (SDS) as an adhesive for wood fiber medium density fiberboard (MDF) preparation. Second-order response surface regression models were used to study the effects and interactions of initial moisture content (IMC) of coated wood fiber, press time (PT) and temperature on mechanical and water soaking properties of MDF. Results showed that IMC of coated fiber was the dominant influencing factor. Mechanical and soaking properties improved as IMC increased and reached their highest point at an IMC of 35%. Press time and temperature also had a significant effect on mechanical and water soaking properties of MDF. Second-order regression results showed that there were strong relationships between mechanical and soaking properties of MDF and processing parameters. Properties of MDF made using soybean protein adhesive are similar to those of commercial board.     

Anaerobic digestion of saline creeping wild ryegrass for biogas production and pretreatment of particleboard material

The objective of this research was to develop an integrated process to produce biogas and high-quality particleboard using saline creeping wild ryegrass (CWR), Leymus triticoides through anaerobic digestion (AD). Besides producing biogas, AD also serves as a pretreatment method to remove the wax layer of CWR for improving binding capability and then the residue is used to produce high-quality particleboard. CWR was digested for three time periods, 15, 22, and 33 days with the volatile solid (VS) loading of 10 g-VS/L-sludge and the food to microorganism (F/M) ratio of 1.41. The highest biogas yield after digestion for 33 days was 251 mL/g-VS, which is corresponded to energy of 8419BTU/kg-dry CWR. The highest methane content of biogas was 63%. Compared with particleboards manufactured from urea formaldehyde (UF) and untreated CWR, the mechanical and long-term (24 h) water resistance properties of particleboards made from UF and 33-day AD CWR residue were statistically significantly improved, except for modulus of elasticity (MOE). For example, the modulus of rupture (MOR) was increased by 39%. The results indicated that the integrated process could be a cost-effective and environmentally friendly method for producing bioenergy and particleboard with agricultural residues.     

Selection perspectives for genetic improvement of wood stiffness in hybrid larch (<Emphasis Type="Italic">Larix</Emphasis> x <Emphasis Type="Italic">eurolepis</Emphasis> Henry)

Genetic variability of modulus of elasticity (MOE) was investigated in three genetic trials, including two progeny (16 years old) and one clonal (19 years old) trials of hybrid larch (Larix x eurolepis Henry). MOE was directly assessed on standing trees using the Rigidimeter, a bending device, and related to other traits including height, BH diameter and wood density. Mean MOE ranged from 5,183 to 9,228 MPa among families in the progeny trials and from 4,591 to 11,486 MPa in the clonal trial. Among traits studied, MOE was one of the most variable traits. It was strongly and positively related to wood density at both the individual and genotype mean levels. Interestingly too, wood stiffness did not seem, or only weakly, unfavourably linked to stem diameter at the phenotypical level, but it was negatively or not correlated to diameter at the genetic level. As well, MOE showed a high GxE stability over the two progeny trial sites. Narrow-sense heritabilities for MOE were moderate (around 0.36). In all three trials, they were lower than those for wood density or total height, and of the same level as for diameter. Improvement of wood stiffness of hybrid larch using the Rigidimeter seems possible and promising genetic gains are expected. Impacts of selection for growth traits on MOE are also discussed.     

Inheritance of growth and solid wood quality traits in a large Norway spruce population tested at two locations in southern Sweden

Unfavorable genetic correlations between growth and wood quality traits are one of the biggest challenges in advanced conifer breeding programs. To examine and deal with such correlation, increment cores were sampled at breast height from 5,618 trees in 524 open-pollinated families in two 21-year-old Norway spruce progeny trials in southern Sweden, and age trends of genetic variation, genetic correlation, and efficiency of selection were investigated. Wood quality traits were measured on 12-mm increment cores using SilviScan. Heritability was moderate (~0.4–0.5) for wood density and modulus of elasticity (MOE) but low (~0.2) for microfibril angle (MFA). Different age trends were observed for wood density, MFA, and MOE, and the lower heritability of MFA relative to wood density and MOE in Norway spruce contrasted with general trends of the three wood quality traits in pine. Genetic correlations among growth, wood density, MFA, and MOE increased to a considerably high value from pith to bark with unfavorable genetic correlations (?0.6 between growth and wood density, ?0.74 between growth and MOE). Age–age genetic correlations reached 0.9 after ring 4 for diameter at breast height (DBH), wood density, MFA, and MOE traits. Early selections at ring 10 for diameter and at ring 6 or 7 for wood quality traits had similar effectiveness as selection conducted at reference ring 15. Selection based on diameter alone produced 19.0 % genetic gain in diameter but resulted in 4.8 % decrease in wood density, 9.4 % decrease in MOE, and 8.0 % increase in MFA. Index selection with a restriction of no change in wood density, MOE, and MFA, respectively, produced relatively lower genetic gains in diameter (16.4, 12.2, and 14.1 %, respectively), indicating such index selection could be implemented to maintain current wood density. Index selection using economic weights is, however, recommended for maximum economic efficiency.     

Physical and mechanical properties of European Hophornbeam (Ostrya carpinifolia Scop.) wood

The main purpose of the study was to determine some physical and mechanical properties of European Hophornbeam (Ostrya carpinifolia Scop.) wood of which is not any detailed previous research in the literature. The sample trees harvested from a mixed beech-oak-hornbeam stand in the Zonguldak Forest Enterprises, north western part of Turkey. Conventional methods followed and the test procedures were performed on small clean specimens. European Hophornbeam wood's air dry and over dry densities were determined as 890 and 853 kg m(-3); density value in volume (basic density) was determined as 671 kg m(-3); volumetric shrinkage and swelling were determined as 23.02% and 24.94%; Fiber saturation point (FSP) was found 34.21%; MOR, MOE, compression strength parallel to grain, impact bending, tensile strength parallel and perpendicular to grain, and Janka hardness values (parallel and perpendicular to grain) were determined as 131.50 N/mm2, 11501.06 N/mm2, 66.94 N/mm2, 18.66 N/mm2, 105.49 N/mm2, 7.11 N/mm2, 6.89 and 5.63 kN, respectively.     

Anti-Analgesic Effect of the Mu/Delta Opioid Receptor Heteromer Revealed by Ligand-Biased Antagonism

Delta (DOR) and mu opioid receptors (MOR) can complex as heteromers, conferring functional properties in agonist binding, signaling and trafficking that can differ markedly from their homomeric counterparts. Because of these differences, DOR/MOR heteromers may be a novel therapeutic target in the treatment of pain. However, there are currently no ligands selective for DOR/MOR heteromers, and, consequently, their role in nociception remains unknown. In this study, we used a pharmacological opioid cocktail that selectively activates and stabilizes the DOR/MOR heteromer at the cell surface by blocking its endocytosis to assess its role in antinociception. We found that mice treated chronically with this drug cocktail showed a significant right shift in the ED₅₀ for opioid-mediated analgesia, while mice treated with a drug that promotes degradation of the heteromer did not. Furthermore, promoting degradation of the DOR/MOR heteromer after the right shift in the ED₅₀ had occurred, or blocking signal transduction from the stabilized DOR/MOR heteromer, shifted the ED₅₀ for analgesia back to the left. Taken together, these data suggest an anti-analgesic role for the DOR/MOR heteromer in pain. In conclusion, antagonists selective for DOR/MOR heteromer could provide an avenue for alleviating reduced analgesic response during chronic pain treatment.     

响应面法优化深层发酵樟芝总三萜的提取工艺(英文)

采用响应面法对樟芝深层培养中总三萜的提取工艺进行优化。根据Box-Benhnken的中心组合实验设计原理,在单因素实验的基础上,选取溶剂浓度、提取温度和液固比为变量,应用响应面法进行三因素三水平的实验设计。以总三萜得率作为响应值,建立了樟芝总三萜提取的回归模型,对其提取条件进行进一步优化。结果表明,优化的总三萜提取条件为乙醇浓度86%,提取温度75℃,液固比37。进一步的实验也验证了该模型的有效性。     

Food, density, and microhabitat: factors affecting growth and recruitment potential of juvenile saltmarsh fishes

The relationships among microhabitat use, food habits, conspecific density and recent growth rate for estuarine-dependent juvenile spotted seatrout, Cynoscion nebulosus, and red drum, Sciaenops ocellatus, were studied to determine how nursery habitat influences early growth. Juvenile spotted seatrout and red drum were quantified along the marsh-edge ecotone from multiple drop samples, and their immediate environments characterized by a suite of physical and chemical variables along with substrate type and Spartina stem density. Recent daily growth of individual fish was modeled in a series of multiple regression analyses that considered the relative contributions of food, microhabitat, and conspecific density. The spotted seatrout model (p < 0.0001) included four independent variables, otolith radius, prey diversity, salinity, and a salinity-DO interaction term, and explained 67.9% of the variation in daily growth. All variables were significant (p < 0.05), and regression slopes were positive for all variables except salinity. The red drum model (p > 0.0001) included five independent variables, otolith radius, temperature, salinity, depth and substrate, and explained 63.3% of the variation in daily growth. All variables were significant (p > 0.05), and all regression slopes were positive. Fish size (as estimated by otolith radius) accounted for most of the variance in the spotted seatrout (60.2%) and red drum (44.8%) models, while the remaining environmental variables were significant and responsible for 7.7 and 18.5%, respectively. Density variables were not selected for either model, suggesting that density-dependence was not an important influence on recent daily growth. Generally, physico-chemical variables such as temperature, salinity, and dissolved oxygen contributed more to growth than diet or extrinsic factors such as grass stem density.     

Mechano-acoustic determination of Young's modulus of articular cartilage

The compressive stiffness of an elastic material is traditionally characterized by its Young's modulus. Young's modulus of articular cartilage can be directly measured using unconfined compression geometry by assuming the cartilage to be homogeneous and isotropic. In isotropic materials, Young's modulus can also be determined acoustically by the measurement of sound speed and density of the material. In the present study, acoustic and mechanical techniques, feasible for in vivo measurements, were investigated to quantify the static and dynamic compressive stiffness of bovine articular cartilage in situ. Ultrasound reflection from the cartilage surface, as well as the dynamic modulus were determined with the recently developed ultrasound indentation instrument and compared with the reference mechanical and ultrasound speed measurements in unconfined compression (n=72). In addition, the applicability of manual creep measurements with the ultrasound indentation instrument was evaluated both experimentally and numerically. Our experimental results indicated that the sound speed could predict 47% and 53% of the variation in the Young's modulus and dynamic modulus of cartilage, respectively. The dynamic modulus, as determined manually with the ultrasound indentation instrument, showed significant linear correlations with the reference Young's modulus (r(2)=0.445, p<0.01, n=70) and dynamic modulus (r(2)=0.779, p<0.01, n=70) of the cartilage. Numerical analyses indicated that the creep measurements, conducted manually with the ultrasound indentation instrument, were sensitive to changes in Young's modulus and permeability of the tissue, and were significantly influenced by the tissue thickness. We conclude that acoustic parameters, i.e. ultrasound speed and reflection, are indicative to the intrinsic mechanical properties of the articular cartilage. Ultrasound indentation instrument, when further developed, provides an applicable tool for the in vivo detection of cartilage mechano-acoustic properties. These techniques could promote the diagnostics of osteoarthrosis.     

Heterotrophy mitigates the response of the temperate coral Oculina arbuscula to temperature stress

Anthropogenic increases in atmospheric carbon dioxide concentration have caused global average sea surface temperature (SST) to increase by approximately 0.11°C per decade between 1971 and 2010 – a trend that is projected to continue through the 21st century. A multitude of research studies have demonstrated that increased SSTs compromise the coral holobiont (cnidarian host and its symbiotic algae) by reducing both host calcification and symbiont density, among other variables. However, we still do not fully understand the role of heterotrophy in the response of the coral holobiont to elevated temperature, particularly for temperate corals. Here, we conducted a pair of independent experiments to investigate the influence of heterotrophy on the response of the temperate scleractinian coral Oculina arbuscula to thermal stress. Colonies of O. arbuscula from Radio Island, North Carolina, were exposed to four feeding treatments (zero, low, moderate, and high concentrations of newly hatched Artemia sp. nauplii) across two independent temperature experiments (average annual SST (20°C) and average summer temperature (28°C) for the interval 2005–2012) to quantify the effects of heterotrophy on coral skeletal growth and symbiont density. Results suggest that heterotrophy mitigated both reduced skeletal growth and decreased symbiont density observed for unfed corals reared at 28°C. This study highlights the importance of heterotrophy in maintaining coral holobiont fitness under thermal stress and has important implications for the interpretation of coral response to climate change.