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  • Author: Yang Yang x
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Damage and Fracture Analysis of Bolted Joints of Composite Materials Based on Peridynamic Theory

Abstract

It is clear that the advantages of fibre glass-reinforced plastics surpass those of steel, but the failure analysis of composite structures is much more complex than that of isotropic materials as composite materials may fail in a variety of ways. In order to simulate the damage and fracture of bolted joints of fibre reinforced composite, the bond-based peridynamic method suitable for elastic, brittle and anisotropic characteristics of composite material is used. The peridynamic model for composite laminate is validated by the finite element method. Then a peridynamic program of composite damage is applied to calculating the damage of bolted joint structure and the damage propagation process and failure mode of the structure is obtained.

Open access
Morphological and molecular characterization of two isolates of Paratrichodorus porosus from Shenzhen, China

Abstract

Studies were conducted to characterize morphological and molecular profiles of two isolates of Paratrichodorus porosus (SZ1 and SZ2) which were recovered from Acacia mangium in Tianxinshan and Gleichenia linearis in Yangmeikeng environmental monitoring sites in Shenzhen, China, respectively. Analysis of morphometric, morphological and molecular characters revealed these two Shenzhen isolates are identical to P. porosus. Measurements of both study isolates lie within the ranges for P. porosus. It is typologically characterized by possessing a clearly swollen body cuticle after fixation, an onchiostyle ventrally curved, 46–58 μm long, a pharyngeal bulb usually with a well developed anterior-dorsal intestinal overlap, a secretoryexcretory pore opening between the nerve ring and anterior end of pharyngeal bulb, 90–110 μm from the anterior end, a reproductive system with didelphic, amphidelphic, without spermathecae, a pore-like vulva in ventral view and occupying 52.0 %–59.5 % of total body length from anterior end, a short and barrel-shaped vagina with small sclerotizations, a pair of ventromedian advulvar body pores located prevulvar and postvulvar, a rounded tail and a subterminal anus in females. The sequence analysis based on partial rDNA 18S gene and 28S D2/D3 expansion segment confirm its identity as P. porosus. This is the first report of P. porosus associated with A. mangium and G. linearis.

Open access
Histopathological and cytopathological findings in minipigs infected with Streptococcus suis serotype 2

Abstract

Five pathogen-free miniature pigs (minipigs) were infected with the virulent strain SH08 of Streptococcus suis 2 (SS2) by intramuscular injection. The pigs died consecutively within 72 h after the challenge. An additional five non-infected pigs were euthanised and used as controls. Microstructural observations showed that degeneration, bleeding, congestion, cellular necrosis, and an increase in inflammatory cells were present in all organs and tissues except the brain. Ultrastructural observations revealed mitochondrial vacuolation and malformed or missing cristae, indicating that infection of minipigs with strain SH08 of SS2 can lead to extensive lesions in major internal organs and tissues. The findings also demonstrated that the minipig is a useful model for the study of SS2 infection.

Open access
Cloning and differential expression analyses of Cdc42 from sheep

Abstract

Introduction

Serological diagnosis of brucellosis is still a great challenge due to the infeasibility of discriminating infected animals from vaccinated ones, so it is necessary to search for diagnostic biomarkers for differential diagnosis of brucellosis.

Material and Methods

Cell division cycle 42 (Cdc42) from sheep (Ovis aries) (OaCdc42) was cloned by rapid amplification of cDNA ends (RACE), and then tissue distribution and differential expression levels of OaCdc42 mRNA between infected and vaccinated sheep were analysed by RT-qPCR.

Results

The full-length cDNA of OaCdc42 was 1,609 bp containing an open reading frame (ORF) of 576 bp. OaCdc42 mRNAs were detected in the heart, liver, spleen, lung, kidneys, rumen, small intestine, skeletal muscles, and buffy coat, and the highest expression was detected in the small intestine. Compared to the control, the levels of OaCdc42 mRNA from sheep infected with Brucella melitensis or sheep vaccinated with Brucella suis S2 was significantly different (P < 0.01) after 40 and 30 days post-inoculation, respectively. However, the expression of OaCdc42 mRNA was significantly different between vaccinated and infected sheep (P < 0.05 or P < 0.01) on days: 14, 30, and 60 post-inoculation, whereas no significant difference (P > 0.05) was noted 40 days post-inoculation. Moreover, the expression of OaCdc42 from both infected and vaccinated sheep showed irregularity.

Conclusion

OaCdc42 is not a good potential diagnostic biomarker for differential diagnosis of brucellosis in sheep.

Open access
Exploration of the main sites for the transformation of normal prion protein (PrPC) into pathogenic prion protein (PrPsc)

Abstract

Introduction: The functions and mechanisms of prion proteins (PrPC) are currently unknown, but most experts believe that deformed or pathogenic prion proteins (PrPSc) originate from PrPC, and that there may be plural main sites for the conversion of normal PrPC into PrPSc. In order to better understand the mechanism of PrPC transformation to PrPSc, the most important step is to determine the replacement or substitution site.

Material and Methods: BALB/c mice were challenged with prion RML strain and from 90 days post-challenge (dpc) mice were sacrificed weekly until all of them had been at 160 dpc. The ultra-structure and pathological changes of the brain of experimental mice were observed and recorded by transmission electron microscopy.

Results: There were a large number of pathogen-like particles aggregated in the myelin sheath of the brain nerves, followed by delamination, hyperplasia, swelling, disintegration, phagocytic vacuolation, and other pathological lesions in the myelin sheath. The aggregated particles did not overflow from the myelin in unstained samples. The phenomenon of particle aggregation persisted all through the disease course, and was the earliest observed pathological change.

Conclusion: It was deduced that the myelin sheath and lipid rafts in brain nerves, including axons and dendrites, were the main sites for the conversion of PrPC to PrPSc, and the PrPSc should be formed directly by the conversion of protein conformation without the involvement of nucleic acids.

Open access
Effect and Mechanism of High-Pressure Processing: A Case Study of Flue-Cured Tobacco

Summary

After a high-pressure processing (HPP) treatment sensory evaluation of flue-cured tobacco showed modifications. There was no significant difference (P > 0.05) between the routine chemical components (total sugar, reducing sugar, nicotine, and total nitrogen) of flue-cured tobacco after high-pressure processing treatment (HPP sample) and that of an untreated control group (CG). An overall judgement, which can be made from the observations of scanning electron microscopy (SEM), X-ray computed microtomography (micro-CT) and transmission electron microscopy (TEM), is that HPP could compress the inner tunnel and tissue gap in a flue-cured tobacco leaf. However, the ultrastructure, such as the cellular cytoskeleton, would not be changed. Compared with CG, the apparent density of the HPP sample rose by 19.3%, while the true density only rose by 1.4%. This also explained that the main effect of high-pressure processing on flue-cured tobacco was microstructure compression rather than compression on the ultrastructure level. The differences between the lamina (leaf-shaped) sample, which were caused by high-pressure processing, were reflected in terahertz time-domain spectroscopy (THz-TDS), simultaneous thermal analysis (STA), and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). When the same tests were carried out using a sample that was milled to a powder, however, these differences were nearly removed. The milling process destroyed most of the microstructure of the flue-cured tobacco lamina; therefore, the results of THz-TDS, STA, and Py-GC/MS confirmed the hypothesis: That 400 MPa high-pressure processing treatment minimally changes the ultrastructure of flue-cured tobacco and only changes its relatively larger microstructure.

Open access