MECHANICAL PROPERTIES AND RESISTANT MECHANISM AROUND BEARING JOINT BETWEEN PLYWOOD AND BOLT OF BUILDING STRUCTURES

The authors have suggested a structural sandwich panel, in which a steel column is sandwiched between thick plywood connected by bolt joints. In a previous study the horizontal resistance mechanism and destructive properties of sandwich panels using structural plywood were clarified. This resistance mechanism is affected by the bolt layout of the sandwich panel. In this study, the bearing test of structural plywood was performed as a parameter with fiber anisotropy to investigate the bearing resistance, destructive properties, and stress transfer mechanism of structural plywood by the bearing joint between plywood and bolt. From the test result, the bearing resistance and destructive properties were clarified, and an analysis method was proposed to calculate the bearing strength. The destructive properties and stress transfer mechanism of structural plywood differ according to the fiber anisotropy. During the installation of the sandwich panel, it was found that the fiber direction of the plywood due to the bearing resistance was related to the destructive properties.

Genetic Analysis of a Horizontal Resistance Locus BLMR2 in Brassica napus

Leptosphaeria maculans causes blackleg disease in Brassica napus. The blackleg disease is mainly controlled by resistance genes in B. napus. Previous studies have shown that the blackleg resistant BLMR2 locus that conferred horizontal resistance under field conditions, is located on chromosome A10 of B. napus. The purpose of this study is to fine map this locus and hence identify a candidate gene underlying horizontal resistance. The spectrum of resistance to L. maculans isolates of the resistance locus BLMR2 was analyzed using near isogenic lines, resistant, and susceptible cultivars. The results showed that this locus was horizontally resistant to all isolates tested. Sequence characterized amplified regions (SCAR), simple sequence repeats (SSR), and single nucleotide polymorphism (SNP) markers were developed in the chromosome region of BLMR2 and a fine genetic map was constructed. Two molecular markers narrowed BLMR2 in a 53.37 kb region where six genes were annotated. Among the six annotated genes, BnaA10g11280D/BnaA10g11290D encoding a cytochrome P450 protein were predicted as the candidate of BLMR2. Based on the profiling of pathogen induced transcriptome, three expressed genes in the six annotated genes were identified while only cytochrome P450 showed upregulation. The candidate corresponds to the gene involved in the indole glucosinolate biosynthesis pathway and plant basal defense in Arabidopsis thaliana. The molecular markers identified in this study will allow the quick incorporation of the BLMR2 allele in rapeseed cultivars to enhance blackleg resistance.

Commensal Escherichia coli Antimicrobial Resistance and Multidrug-Resistance Dynamics during Broiler Growing Period: Commercial vs. Improved Farm Conditions

New measures applied to reduce antimicrobial resistances (AMR) at field level in broiler production are focused on improving animals’ welfare and resilience. However, it is necessary to have better knowledge of AMR epidemiology. Thus, the aim of this study was to evaluate AMR and multidrug resistance (MDR) dynamics during the rearing of broilers under commercial (33 kg/m2 density and max. 20 ppm ammonia) and improved (17 kg/m2 density and max. 10 ppm ammonia) farm conditions. Day-old chicks were housed in two poultry houses (commercial vs. improved), and no antimicrobial agents were administered at any point. Animals were sampled at arrival day, mid-period and at slaughter day. High AMR rates were observed throughout rearing. No statistical differences were observed between groups. Moreover, both groups presented high MDR at slaughter day. These results could be explained by vertical or horizontal resistance acquisition. In conclusion, AMR and MDR are present throughout rearing. Moreover, although a lower level of MDR was observed at mid-period in animals reared under less intensive conditions, no differences were found at the end. In order to reduce the presence of AMR bacteria in poultry, further studies are needed to better understand AMR acquisition and prevalence in differing broiler growing conditions.

Evaluation of horizontal resistance of sunflower (Helianthus annuus L.) to downy mildew (Plasmopara halstedii)

Downy mildew is one of the most important diseases of sunflower crop around the world caused by Plasmopara halstedii (Farl.) Berl.et de Toni. The aim of our study was to evaluate the horizontal resistance of elite and prospective lines to downy mildew in field conditions. Experiments were conducted at All-Russia Research Institute of Oil Crops (VNIIMK) in 2016–2020. Released and prospective sunflower lines bred at VNIIMK were studied, divided into four groups on the base of their race-specific resistance in laboratory tests. Experimental design was randomized blocks with two replications. Evaluation was made by recording all the recognizable symptoms of downy mildew from emergence till flowering. The results obtained allowed us to identify the lines with the highest race non-specific resistance to downy mildew: VK 678 (5.3%), VK 653 (7.3%), VA 760 (3.3%), VA 93 (2.0%) and VK 732 (6.3%). The final aim is the development of sunflower hybrids with the most durable resistance to downy mildew, combining one parental line with the major gene (Pl15) most effective for the specific location and the second parental line with a high level of horizontal resistance to downy mildew.

Effects of Intrabony Length and Cortical Bone Density on the Primary Stability of Orthodontic Miniscrews

Miniscrews have gained recent popularity as temporary anchorage devices in orthodontic treatments, where failure due to sinus perforations or damage to the neighboring roots have increased. Issues regarding miniscrews in insufficient interradicular space must also be resolved. This study aimed to evaluate the primary stability of miniscrews shorter than 6 mm and their feasibility in artificial bone with densities of 30, 40, and 50 pounds per cubic foot (pcf). The primary stability was evaluated by adjusting the intrabony miniscrew length, based on several physical properties: maximum insertion torque (MIT), maximum removal torque (MRT), removal angular momentum (RAM), horizontal resistance, and micromotion. The MIT and micromotion results demonstrated that the intrabony length of a miniscrew significantly affected its stability in low-density cortical bone, unlike cases with a higher cortical bone density (p < 0.05). The horizontal resistance, MRT, and RAM were affected by the intrabony length, regardless of the bone density (p < 0.05). Thus, the primary stability of miniscrews was affected by both the cortical bone density and intrabony length. The effect of the intrabony length was more significant in low-density cortical bone, where the implantation depth increased as more energy was required to remove the miniscrew. This facilitated higher resistance and a lower risk of falling out.

Calculative Width of Pile Foundation on Slope Based on Particle Image Velocimetry (PIV)

The calculative width directly affecting the horizontal bearing capacity of the pile is an important parameter of the horizontal loaded pile foundation and its effective value will change with the variation of slope angle. In order to research the effect of slope on calculative width, 4 groups of model test under static lateral loading with different slope angles were carried out indoor. Based on the PIV system, the horizontal diffusion angle was obtained by the quantitative analysis of the vectorial displacement field of soil around the pile. The calculative width of pile under 4 slopes was then calculated based on the Horizontal Diffusion Principle. Compared with numerical simulation and full-scale test, calculative width based on Horizontal Diffusion Principle is greater than that based on the code of China (JGJ94-2008) and it decreases by about 3.3 m by every 10° increase of slope. After correcting the calculative width based on Horizontal Diffusion Principle, m-value that can characterize the horizontal resistance of the pile is greater than that based on the code of China (JGJ94-2008); the average difference of two m-values is about 75 MN/m4. Slope has a strong weakening effect on m-value. These conclusions provide a certain reference for the selection of calculative width in engineering.

Primary Stability of Orthodontic Titanium Miniscrews due to Cortical Bone Density and Re-Insertion

The increasing demand for orthodontic treatment over recent years has led to a growing need for the retrieval and reuse of titanium-based miniscrews to reduce the cost of treatment, especially in patients with early treatment failure due to insufficient primary stability. This in vitro study aimed to evaluate differences in the primary stability between initially inserted and re-inserted miniscrews within different cortical bone densities. Artificial bone was used to simulate cortical bone of different densities, namely 20, 30, 40, and 50 pound per cubic foot (pcf), where primary stability was evaluated based on maximum insertion torque (MIT), maximum removal torque (MRT), horizontal resistance, and micromotion. Scanning electron microscopy was used to evaluate morphological changes in the retrieved miniscrews. The MIT, MRT, horizontal resistance, and micromotion was better in samples with higher cortical bone density, thereby indicating better primary stability (P < 0.05). Furthermore, a significant reduction of MIT, MRT, and horizontal resistance was observed during re-insertion compared with the initial insertion, especially in the higher density cortical bone groups. However, there was no significant change in micromotion. While higher cortical bone density led to better primary stability, it also caused more abrasion to the miniscrews, thereby decreasing the primary stability during re-insertion.

Evaluation of Variation in Switchgrass (Panicum virgatum L.) Cultivars for Rust (Puccinia emaculata) Resistance1

Eleven switchgrass cultivars (eight ornamental and three agronomic) were inoculated with 40 switchgrass rust isolates collected from the southeastern U.S. to study host resistance, rust virulence and host/pathogen interactions by measuring urediniospore germination percentage, latent period, and the number of uredia and urediniospores produced per cm2 of leaf surface. In general, ornamental switchgrass cultivars had reduced number of uredia and urediniospores produced per cm2 than did agronomic cultivars. Rust isolates were variable for virulence in culture (on grass blades in petri dishes); however they could not be segregated into groups based on collection locations or years. The results of this study will provide information concerning durable horizontal resistance in switchgrass for the ornamental industry. Index words:, Switchgrass, leaf rust, resistance. Species used in the study: switchgrass (Panicum virgatum L., rust (Puccinia emaculata).

Experimental study on horizontal bearing capacity of enlarged cap-group pile composite foundation

In order to provide reference for the engineering design in the area with large wind, water flow and other horizontal loads, the experimental study on the horizontal bearing capacity of composite foundation under three different working conditions was carried out in this paper, which includes cap-single pile, cap-9 piles and enlarged cap-9 piles. The results show that under the condition of cap-9 piles, the group pile effect coefficient is 1.17, and the load sharing ratio of the back piles is the largest, and the middle and front piless decrease sequentially. Also, with the increase of horizontal load, the load sharing ratio of the back pile increases while the middle and front piless is decremented. Under the condition of enlarged cap-9 piles, the group pile effect coefficient is 1.36, which is 16.24% higher than that of the cap-9 piles, which means the horizontal resistance is obviously enhanced. At the same time, compared with the cap-9 piles, the load sharing ratio of the back pile is reduced while the middle and front piless is increased, which means the stress of pile body tends to be more uniform.