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There are certain limitations when empirical formulas are used to predict the ship hull vertical vibration. Natural frequency of ship's vertical vibration is predicted by support vector machine (SVM), which possesses many characteristics such as small sample learning, global optimization and strong generalization. Considering the parameters that influence the natural frequency of ship's vertical vibration are much more, a grey relation model between ship's main parameters and natural frequency of ship's vertical vibration is established by grey relational analysis theory to get the grey correlation degree of each parameter. The parameters with greater correlation degree are used as input data and the measured values of natural frequency of vertical vibration are used as output data in SVM to build the nonlinear regression model of the natural frequency of vertical vibration. Natural frequencies of eight ships' vertical vibration are predicted by the nonlinear regression model, and the results are coincident with the measured values. The proposed method in this paper is proved to be accurate and feasible, which provides a new idea to the prediction of natural frequency of ship's overall vertical vibration. [ABSTRACT FROM AUTHOR]

Abstract: Marek''s disease virus (MDV) is a highly oncogenic alphaherpesvirus that induces rapid-onset T-cell lymphoma in poultry. The complete genome of the avirulent vaccine strain MDV-814 was cloned as an infectious bacterial artificial chromosome (BAC) using an 8.8-kb fragment containing the self-designed selective marker guanosine phosphoriboxyl transferase. The recombinant virus MDV-814-BAC was generated by co-transfection of a BAC transfer vector and MDV-814 total DNA, and was purified by eight rounds of selective passaging. The infectivity of the BAC DNA clone was validated by MDV reconstitution from chicken embryo fibroblasts transfected with MDV-BAC DNA, which was extracted from electroporated Escherichia coli DH10B cells. In vitro, the BAC-derived virus had similar biological characteristics and growth kinetics as the wild-type parental and recombinant viruses, and chickens immunized with BAC derivatives by various delivery mechanisms acquired protection against virulent MDV challenge. Construction of this MDV-BAC may aid the development of recombinant vaccines-containing multiple antigens. [Copyright &y& Elsevier]

Despite highly effective vaccines, Marek's disease (MD) causes great economic loss to the poultry industry annually, largely due to the continuous emergence of new MD virus (MDV) strains. To explore the pathogenic characteristics of newly emerged MDV strains, we selected two strains (AH/1807 and DH/18) with clinically different pathotypes. We studied each strain's infection process and pathogenicity and observed differences in immunosuppression and vaccine resistance. Specific pathogen-free chickens, unvaccinated or vaccinated with CVI988, were challenged with AH/1807 or DH/18. Both infections induced MD damage; however, differences were observed in terms of mortality (AH/1807: 77.8%, DH/18: 50%) and tumor rates (AH/1807: 50%, DH/18: 33.3%). The immune protection indices of the vaccine also differed (AH/1807: 94.1, DH/18: 61.1). Additionally, while both strains caused interferon-β and interferon-γ expression to decline, DH/18 infection caused stronger immunosuppression than AH/1807. This inhibition persisted even after vaccination, leading to increased replication of DH/18 that ultimately broke through vaccine immune protection. These results indicate that both strains have different characteristics, and that strains such as DH/18, which cause weaker pathogenic damage but can break through vaccine immune protection, require further attention. Our findings increase the understanding of the differences between epidemic strains and factors underlying MD vaccination failure in China. [ABSTRACT FROM AUTHOR]

Fatigue resistance under extreme stress conditions is an important indicator to evaluate industrial application potential of Al-Si-Mg alloys, but their fatigue resistance is inherently weakened by large grain size, long-needle Si phases and coarse precipitates. This work reports significantly optimized microstructure configuration and fatigue resistance of hypoeutectic Al-Si composite optimized by the nanocrystallization products of a NiNbTi metallic glass. It was proved the in-situ NiTi (B2) nanocrystals can serve as the heterogeneous nucleation sites of α-Al and β-Mg 2 Si and the growth retarder of eutectic Si. Particularly, the optimized composite exhibited nearly 5 times and 6 times longer fatigue life than the unoptimized alloy at 120 MPa (60 Hz) and 240 MPa (20 Hz), respectively. The fatigue strength (N = 107) was increased by 21.7 % and 25.9 % at 60 Hz and 20 Hz, respectively. The α-Al refinement enhanced the resistance to fatigue crack initiation. The refinement and spheroidization of eutectic Si phases reduced stress concentration. Also, the austenite-martensite phase transformation of NiTi afforded more energy for precipitation. Refined β-Mg 2 Si and β'' phases were facilitated to interact with dislocations, improving the resistance to dislocation slip during cyclic strain through the dislocation shearing effect. This work provides a theoretical basis for the future development of Al-Si alloys and composites with excellent fatigue resistance for expanding their industrial application scope. [Display omitted] • The microstructure was fully manipulated by trace in-situ nanocrystals. • The σ b , ε l , a k , and U T were improved by 20.4 %, 29.1 %, 13.3 % and 58.7 %. • The mean fatigue strengths were 21.7 % (60 Hz) and 25.9 % (20 Hz) improved. • Refined α-Al, eutectic Si and precipitates enhanced fatigue life. [ABSTRACT FROM AUTHOR]

• We studied IFN mRNA/protein expression in MDV-infected hosts for the first time. • MDV inhibited type Ⅰ IFN expression in the thymus and bursa of infected chickens. • Inhibition of type I IFNs by MDV strains of varying pathogenicity differed. Marek's disease virus (MDV), an α -herpesvirus targeting avian species, causes fatal Marek's disease (MD) in chickens. The host interferon (IFN) responses play a key role in resisting viral infection. However, host IFN responses following MDV infection in the chicken central immune organs (thymus and bursa of Fabricius), which contain numerous MDV target cells, is poorly understood. In this study, we performed animal experiments in specific pathogen-free chickens infected with two virulent MDV strains (BS/15 and Md5) or without infection as negative controls. Specifically, the type I IFN (IFN-α and IFN-β) transcriptional and proteomic expression levels at 7, 10, 14, 17, and 21 days post infection (dpi) were detected and analyzed. Our results indicated that the mRNA and protein expression levels of IFN-α and IFN-β in the thymus and bursa of Fabricius were mainly downregulated in cytolytic infection (such as 10 dpi) and reactivation (such as 17 dpi) stages, but not the latent (such as 14 dpi) stage of MDV infection, which was determined by comprehensively analyzing the MDV viral load and immune organ damage caused by MDV infection. These data suggest that MDV could inhibit the expression of host type I IFNs, which may be involved in the MDV-induced host immunosuppression and contribute to the immune escape of MDV from host immunity. Furthermore, we found that the downregulated expression of the host type I IFNs induced by BS/15 and Md5 infection was significantly different, which we speculated may be related to the diverse virulence and pathogenicity of MDV strains. In conclusion, our study demonstrated that MDV mostly inhibited the expression of type I IFNs in infected hosts, which may be associated to its pathogenesis. [ABSTRACT FROM AUTHOR]

The virulence of Marek's disease virus (MDV) is continuously evolving, and more virulent MDV pathotypes are emerging, thereby reducing the effectiveness of the existing vaccines. In this study, feather pulps were collected from diseased chickens in commercial chicken flocks in China that presented significant MD visceral tumors in 2011 and were inoculated into a monolayer of duck embryo fibroblasts (DEFs). Three field isolates of MDV were obtained by plaque cloning and identified as MDV via PCR and designated strains LCC, LLY, and LTS. Unvaccinated and CVI988 vaccine-vaccinated specific pathogen-free chickens were challenged at 7 days post vaccination (dpv) with 1000 plaque forming units of each of the respective MDV isolates. These strains induced gross MD lesions in all (100%) of the unvaccinated chickens, and the mortality rates of the unvaccinated chickens were 42.9%, 46.7%, and 23.1% by 60 days post challenge (dpc), respectively. The CVI988 vaccine induced protective indices (PIs) of 85.7, 92.3, and 66.7, respectively. These results showed that the pathogenic characteristics of the Chinese isolates were diverse and that vaccine CVI988 provided different levels of protection against them. These data indicated that the existence of variant MDV strains was a possible reason of immunity failure in China. [ABSTRACT FROM AUTHOR]

Abstract: A recombinant fowlpox virus (rFPV-IFNγS1) that co-expressed the infectious bronchitis virus (IBV) S1 gene and the chicken interferon-γ gene has been constructed. To evaluate the efficacy of the recombinant fowlpox virus vaccine against heterotypic IBV strains, 60 4-week-old Specific-Pathogen-Free (SPF) chickens were inoculated with this vaccine and 3 weeks post inoculation challenged with the homotypic IBV strain LX4 and the heterotypic IBV strains LHB, LHLJ04XI, LTJ95I and LSC99I. Antibodies against IBV were detected in vaccinated chickens 1-week post inoculation. The number of CD4+ and CD8+ T-lymphocytes in the peripheral blood increased rapidly in the vaccinated groups challenged with strains LX4, LHB and LHLJ04XI. There were significant differences in the number of CD4+ and CD8+ T-lymphocytes between the vaccinated groups challenged with strains LTJ95I and LSC99I and all the control groups. The morbidity was below 30% in vaccinated groups challenge with strains LX4, LHB and LHLJ04XI, but was 40% greater than that in the other groups. In addition, the lesions and the amount of virus shedding were less severe in the vaccinated groups challenged by strains LX4, LHB and LHLJ04XI when compared with the other groups, but there was no significant difference in the average body weight of the chickens in all groups (all p >0.05). These results indicate that the rFPV-IFNγS1 protected chickens against challenge with homotypic IBV strain LX4 and heterotypic strains LHLJ04XI and LHB. [Copyright &y& Elsevier]

• Approximately 50% of detected tumor chickens in Chinese flocks were GaHV-2 positive. • Co-infection of REV occurred in 13% of GaHV-2-positive samples. • Co-infection increased mortality and tumor formation in experimental infection. • REV/GaHV-2 co-infection may contribute to persistent neoplastic disease in poultry. The prevalence of Marek's disease (MD) caused by Gallid herpesvirus-2 (GaHV-2) has been increasing in chickens in China despite universal vaccination. Among the possible reasons for this trend, of Reticuloendotheliosis virus (REV) contamination in vaccines could lead to co-infection and reduce the vaccine efficacy. Here, we report the epidemiological findings of our continuous surveillance of MD, and an examination of the effects of REV and/or GaHV-2 co-infection. A total of 1230 samples were collected between 2011 and 2015 from 305 flocks covering many of the chicken-raising regions of China. Among these, 606 samples were determined to be GaHV-2-positive, 13.0% of which were found to be co-infected with REV from 18.8% of the flocks. One GaHV-2 strain (HS/1412), a REV strain (HS/1412R), and a GaHV-2 and REV-co-infected strain (HS/1412 GR) were isolated from different chickens of a GaHV-2 and REV co-infected flock. Pathogenicity tests showed that HS/1412 and HS/1412 GR caused disease in all chickens and that HS/1412R induced morbidity in 84.6% of the infected chickens. HS/1412 GR induced 100% mortality and 76.9% tumor formation, which were significantly higher frequencies than those observed with strain HS/1412 (38.5% and 15.4%, respectively) and HS/1412R (0% and 0%). These results indicate that co-infection with GaHV-2 and REV might explain the persistent, sporadic outbreaks of neoplastic disease in some commercial flocks, resulting in a significant economic burden to the poultry industry of China. [ABSTRACT FROM AUTHOR]