Size Effect on the Elastic Mechanical Properties of Beech and Its Application in Finite Element Analysis of Wood Structures

Elastic constants of wood are fundamental parameters used in finite element analysis of wood structures. However, few studies and standards regulate the dimensions of sample used to measure elastic constants of wood. The size effect on mechanical properties (i.e., elastic constants and proportional limit stresses) of European beech (Fagus sylvatica L.) wood was studied with five different sizes samples. The data of experiments were inputted into a finite element model of self-designed chair and the loading capacity of chair was investigated by finite element method (FEM) and experiment. The results showed that nonlinear relationships were found between proportional limit stresses, cross-sectional area, and height of specimen by response surface method with R2 greater than 0.72 in longitudinal, radial, and tangential directions. Elastic moduli and shear moduli increased with the height of specimen when cross-sectional area was kept constant, and decreased with an increased cross-sectional area of specimen, when the height was a constant, while the trends of Poisson’s ratio were not as expected. The comparisons between experiment and FEM suggested that the accuracy of FEM simulation increase with the raise of width-height ratio (≤1) of specimens used to determine the elastic constants. It is recommended to use small cubic wood specimen to determine the elastic mechanical properties used for finite element analysis of beech wood structures. Further research to find optimized wood specimen dimensions to get mechanical properties for FEM is quite necessary

Stem segments of apple microcuttings take up auxin predominantly via the cut surface and not via the epidermal surface

Abstract In conventional cuttings, auxin applied to achieve rooting is taken up predominantly via the cut surface and not via the epidermal surface of the stem. Even though in tissue-cultured plants the cuticle is poorly developed and the stomata do not function properly, stem segments of apple microcuttings took up labelled indoleacetic acid also predominantly via the cut surface. Stem segments with an epidermis with gaps caused by excision of the petioles required a lower exogenous concentration of auxin to achieve rooting than segments with an intact epidermis, indicating that the gaps facilitated uptake of auxin from the medium. This was con®rmed in an experiment on uptake of labelled indoleacetic acid.

Research on Ecosystem Security and Restoration Pattern of Urban Agglomeration in the Yellow River Basin

Reasonable identification of the ecosystem security space and pattern restoration for the Yellow River Basin will be significant for facilitating future ecological protection and restoration projects. This study employs ecosystem services and landscape connectivity to discern ecological source areas and conducts an optimization evaluation method of resistance surfaces and the minimum cumulative resistance (MCR) model to identify the ecosystem security pattern of urban agglomeration. Then, restoration measures are proposed. The results indicate that: (1) There are 46 ecological source areas in the ecosystem security patterns of the Lanxi urban agglomeration, with a total area of 8199.249 km2. Moreover, in terms of spatial distribution, ecological source areas are sparse in the east while crowded in the west of the Lanxi urban agglomeration and are mainly composed of natural reserves, forest parks, and farmlands. (2) The ecosystem security patterns contain 914 ecological corridors with a total length of 62,970.181 km, most of which are short-distance corridors, being dense in the part of the northwest with a webbed feature. (3) The study adds 10 ecological source areas to restore the ecosystem security pattern and ecological corridors to improve the rationality of the ecosystem security pattern. Meanwhile, this study proposes restoration measures to protect the ecological environment by defining the levels of ecological security in order to provide a reference for the government to formulate policies and regulations

Stem segments of apple microcuttings take up auxin predominantly via the cut surface and not via the epidermal surface

In conventional cuttings, auxin applied to achieve rooting is taken up predominantly via the cut surface and not via the epidermal surface of the stem. Even though in tissue-cultured plants the cuticle is poorly developed and the stomata do not function properly, stem segments of apple microcuttings took up labelled indoleacetic acid also predominantly via the cut surface. Stem segments with an epidermis with gaps caused by excision of the petioles required a lower exogenous concentration of auxin to achieve rooting than segments with an intact epidermis, indicating that the gaps facilitated uptake of auxin from the medium. This was confirmed in an experiment on uptake of labelled indoleacetic acid.</p

FINITE ELEMENT ANALYSIS OF TENSILE LOAD RESISTANCE OF MORTISE-AND-TENON JOINTS CONSIDERING TENON FIT EFFECTS

Effects of tenon fit in its width direction on the tensile load-deflection behavior of T-shaped, round-end, mortise-and-tenon joints were investigated experimentally and analytically. Finite element method (FEM) 3D modeling technique as an analytical tool was used to model the tensile load-deformation behavior of T-shaped, round-end, mortise-and-tenon joints. Experimental results indicated that mean ultimate tensile loads and stiffness of evaluated mortise-and-tenon increased significantly as tenon fit increased from 0 to 0.2 mm with an increment of 0.1 mm. The measured glue-line thickness between mortise-andtenon contact surface was found to be a good indicator of tensile load resistance performance of mortise-andtenon joints evaluated in this study. FEM modeling technique was verified as a valid analytical tool for prediction of tensile load resistances of T-shaped, round-end, mortise-and-tenon joints

Research on Ecosystem Security and Restoration Pattern of Urban Agglomeration in the Yellow River Basin

Reasonable identification of the ecosystem security space and pattern restoration for the Yellow River Basin will be significant for facilitating future ecological protection and restoration projects. This study employs ecosystem services and landscape connectivity to discern ecological source areas and conducts an optimization evaluation method of resistance surfaces and the minimum cumulative resistance (MCR) model to identify the ecosystem security pattern of urban agglomeration. Then, restoration measures are proposed. The results indicate that: (1) There are 46 ecological source areas in the ecosystem security patterns of the Lanxi urban agglomeration, with a total area of 8199.249 km2. Moreover, in terms of spatial distribution, ecological source areas are sparse in the east while crowded in the west of the Lanxi urban agglomeration and are mainly composed of natural reserves, forest parks, and farmlands. (2) The ecosystem security patterns contain 914 ecological corridors with a total length of 62,970.181 km, most of which are short-distance corridors, being dense in the part of the northwest with a webbed feature. (3) The study adds 10 ecological source areas to restore the ecosystem security pattern and ecological corridors to improve the rationality of the ecosystem security pattern. Meanwhile, this study proposes restoration measures to protect the ecological environment by defining the levels of ecological security in order to provide a reference for the government to formulate policies and regulations

Experimental and numerical study on a novel bamboo joint for furniture considering effect of loading type on mechanical parameters used in finite element method

The effect of loading type (tension, compression and bolt-bearing) on mechanical properties (elastic modulus, Poisson’s ratio and ultimate strength) of Moso bamboo (Phyllostachys heterocycla var. pubescens) in longitudinal direction was evaluated in this study. In addition, experimental and numerical tests were conducted to evaluate withdrawal force capacity and bending moment resistances of a novel demountable bamboo-bolt joint considering effect of loading type on mechanical parameters used in finite element method. The results showed that 1) loading type had significant effect on mechanical properties of Moso bamboo, especially, for ultimate strength; 2) the values of mechanical properties evaluated in this study measured in tension were all much higher than those measured in bolt-bearing state and followed by compression accordingly; 3) in tension, the tensile elastic modulus and Poisson’s ratio measured at outer surface were bigger than those at inner surface, respectively; 4) finite element method got more accurate results using the mechanical parameters measured in compression than those in tension and bolt-bearing states; 5) the bamboo-bolt joint proposed in this study can be used in lightweight bamboo structures through improving the embedding strength of beech wood in bamboo culm. In conclusion, one should consider the loading type used to obtain the mechanical parameters inputted in finite element method. In addition, further studies will focus on effect of size and geometry of samples used to determine mechanical properties used in finite element method, and the method of improving embedding strength of beech wood in bamboo culm to increase withdrawal force capacity and bending moment resistances of the demountable bamboo-bolt joint proposed in this stud

Rooting of apple stem slices in vitro is affected by indoleacetic-acid depletion of the medium

We have studied rooting of 1-mm thick apple stem slices in relation to indoleacetic acid (IAA) depletion of the medium. When slices were cultured in the dark close to one another on a 3-mm thick medium (20 ml in a 9-cm Petri dish), the IAA concentration in the medium beneath the slices dropped to 20 % of the initial concentration during the first day of culture. This was due to uptake, enzymatic oxidation and slow replenishment from medium in other areas of the Petri dish. Because of depletion, the rate of IAA uptake decreased with time. When medium was renewed daily, the rate of IAA uptake remained the same. When the slices were cultured scattered over the Petri dish or on a thick layer of medium (6-mm instead of 3-mm thick), they took up more IAA. As could be expected, differences in uptake amongst the various conditions (slices cultured scattered or close to one another; 20 or 40 ml of medium) were small during the first day of culture but large after that. Because the rhizogenic action of IAA occurs not immediately at the start of culture but later (viz., from 24 to 72 h after the start of culture; DE KLERK et al., 1995; J. Exp. Bot. 46, 965-972), rooting at the various conditions corresponded closely to the amount of IAA taken up from 24 to 72h. Since the various incubation conditions resulted in the same maximal root number (but at different IAA concentrations), there was only depletion of the medium with respect to IAA.</p

Clinical characteristics of liver injury in SARS-CoV-2 Omicron variant- and Omicron subvariant-infected patients

Introduction and Objectives: Liver injury in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant- and Omicron subvariant-infected patients is unknown at present, and the aim of this study is to summarize liver injury in these patients. Patients and Methods: In this study, 460 SARS-CoV-2-infected patients were enrolled. Five severe or critical patients were excluded, and 34 patients were also excluded because liver injury was not considered to be related to SARS-CoV-2 infection. Liver injury was compared between Omicron and non-Omicron variants- and between Omicron subvariant-infected patients; additionally, the clinical data related to liver injury were also analyzed. Results: Among the 421 patients enrolled for analysis, liver injury was detected in 76 (18.1%) patients, including 46 Omicron and 30 non-Omicron variant-infected patients. The ratios did not differ between Omicron and non-Omicron variant-, Omicron BA.1, BA.2 and BA.5 subvariant-infected patients (P>0.05). The majority of abnormal parameters of liver function tests were mildly elevated (1-3 × ULN), the most frequently elevated parameter of liver function test was γ-glutamyl transpeptidase (GGT, 9.5%, 40/421), and patients with cholangiocyte or biliary duct injury markers were higher than with hepatocellular injury markers. Multivariate analysis showed that age (>40 years old, OR=1.898, 95% CI=1.058–3.402, P=0.032), sex (male gender, OR=2.031, 95% CI=1.211–3.408, P=0.007), serum amyloid A (SAA) level (>10 mg/ml, OR=3.595, 95% CI=1.840–7.026, P<0.001) and vaccination status (No, OR=2.131, 95% CI=1.089–4.173, P=0.027) were independent factors related to liver injury. Conclusions: Liver injury does not differ between Omicron and non-Omicron variants or between Omicron subvariant-infected patients. The elevations of cholangiocyte or biliary duct injury biomarkers are dominant in SARS-CoV-2-infected patients