The hypothesis was tested that upper limits to height growth in trees are the result of the increasing bending moment of trees as they grow in height. The increasing bending moment of tall trees demands increased radial growth at the expense of height growth to maintain mechanical stability. In this study, the bending moment of large lodgepole pine (Pinus contorta Dougl. Ex Loud. var. latifolia Engelm.) was reduced by tethering trees at 10 m height to counter the wind load. Average bending moment of tethered trees was reduced to 38% of control trees. Six years of tethering resulted in a 40% increase in height growth relative to the period before tethering. By contrast, control trees showed decreased height growth in the period after tethering treatment. Average radial growth along the bole, relative to height growth, was reduced in tethered trees. This strongly suggests that mechanical constraints play a crucial role in limiting the height growth of tall trees. Analysis of bending moment and basal area increment at both 10 m and 1.3 m showed that the amount of wood added to the stem was closely related to the bending moment produced at these heights, in both control and tethered trees. The tethering treatment also resulted in an increase in the proportion of latewood at the tethering height, relative to 1.3 m height. For untethered control trees, the ratio of bending stresses at 10 m versus 1.3 m height was close to 1 in both 1998 and 2003, suggesting a uniform stress distribution along the outer surface of the bole.

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The silk fibroin/sodium alginate scaffolds were prepared using lyophilization method. And then, the blend scaffolds were treated with calcium ions. The morphology of the blend scaffolds exhibited a thin layer structure before calcium ions treatment, and much more rod-like structure appeared at the layer surface with adding the increase content of sodium alginate in the blend scaffolds. After calcium ions treatment, much more rod-like structure disappeared after adding 30% sodium alginate or more in the blend scaffolds. Wide angle X-ray diffraction and Fourier transform infrared analysis results confirmed the crystal structure of silk fibroin was not influenced by adding the different content of sodium alginate, exhibiting the silk I and silk II structure co-existed in the blend scaffolds. And the same time, the average mass loss value of the blend scaffolds was higher than the pure silk fibroin scaffold, reaching 9.884%, 11.2%, and 8.626%, respectively, when the blend scaffolds contained 10%, 30%, and 50% sodium alginate, respectively. Thus, the silk fibroin/sodium alginate scaffolds should be a useful biomaterial applicable for a wide range of tissue engineering.

Abstract. Ultraviolet aging of B.mori silk fabric was studied under natural and artificial weathering conditions. Exposed samples were removed periodically and characterized by several analytical techniques. During both types of weathering, the results showed that yellowness index presented a rising trend with the extension of aging time; breaking strength of B.mori silk fabric decreased approximately 93.62%, 43.30% under natural aging 150 days and artificial accelerated aging 80 h, respectively; the peak intensity of amide I, and amide II, etc. significantly declined, even disappeared. At the same time, the conformation transition of B.mori silk was from random coil to β-pleated sheet following the prolonging of ultraviolet aging time. What's more, the content of amino acid obviously declined especially histidine, tyrosine, and lysine etc. In addition, the results evidenced that during natural and artificial weathering, various performances of B.mori silk fabric changed similarly. So artificial weathering can be used to substitute for natural weathering for its weathering evaluation, which is helpful to understand the aging behavior and take measures to avoid aging and elongate its service life.

The effect of particle sedimentation on the evaporation rate of nanofluid droplets on a heated substrate is studied numerically. A two-dimension model of droplet evaporation and deposition using Arbitrary Lagrangian-Eulerian (ALE) method is developed, considering evaporation cooling, two-phase heat transfer, mass diffusion, nanoparticle transport and free surface evolution. The effects of temperature and particle concentration distribution on the total and local evaporation rate of millimeter-sized sessile nanofluid droplets with varying substrate temperature are numerically analyzed. It is shown that the nanoparticle concentration nearby the droplet edge is much higher than that nearby droplet center, and also the sedimentation at droplet edge is much more than that at droplet center. The non-uniform nanoparticle concentration inside droplets leads to a greater temperature difference along the free surface.