Cutting Force Fluctuation Suppression and Error Homogenization of Noncircular Gear Hobbing Based on the Tool Shifting Method

The current research on noncircular hobbing mainly focuses on the linkage model and motion realization.However,the intermittent cutting characteristics of hobbing would increase uncertainties in the manufacturing process.In this paper,a hobbing machining model with tool-shifting characteristics was proposed to solve the problems of cutting force fluctuation and inconsistency of tooth profile envelope accuracy at different positions of the pitch curve in noncircular gear hobbing.Based on the unit cutting force coefficient method,the undeformed chip volume generated by interrupted cutting was used to characterize the fluctuation trend of the hobbing force.The fluctuation characteristics of the cutting force generated by different hobbing models were compared and analyzed.Using the equivalent gear tooth and hob slotting numbers,an analysis model of the tooth profile envelope error of the noncircular gear was constructed.Subsequently,the tooth profile envelope errors at different positions of the pitch curve were compared and analyzed based on the constructed model.The transmission structure of the electronic gearbox was constructed based on the proposed hobbing model,and the hobbing experiment was conducted based on the selfdeveloped noncircular gear CNC hobbing system.This paper proposes a hobbing method that can effectively suppress the fluctuation of the peak and whole circumference cutting force and reduce the maximum envelope error of the whole circumference gear teeth.

Genome-Wide Identification, Evolution and Expression Analyses of GA2ox Gene Family in Brassica napus L.

Gibberellin 2-oxidases(GA2ox)are important enzymes that maintain the balance of bioactive GAs in plants.GA2ox genes have been identified and characterized in many plants,but these genes were not investigated in Brassica napus.Here,we identified 31 GA2ox genes in B.napus and 15 of these BnaGA2ox genes were distributed in the A and C subgenomes.Subcellular localization predictions suggested that all BnaGA2ox proteins were localized in the cytoplasm,and gene structure analysis showed that the BnaGA2ox genes contained 2–4 exons.Phylogenetic analysis indicated that BnGA2ox family proteins in monocotyledons and dicotyledons can be divided into four groups,including two C_(19)-GA2ox and two C_(20)-GA2ox clades.Group 4 is a C_(20)-GA2ox Class discovered recently.Most BnaGA2ox genes had a syntenic relationship with AtGA2ox genes.BnaGA2ox genes in the C subgenome had experienced stronger selection pressure than genes in the A subgenome.BnaGA2ox genes were highly expressed in specific tissues such as those involved in growth and development,and most of them were mainly involved in abiotic responses,regulation of phytohormones and growth and development.Our study provided a valuable evolutionary analysis of GA2ox genes in monocotyledons and dicotyledons,as well as an insight into the biological functions of GA2ox family genes in B.napus.

Biodiversity of the Symbiotic Bacteria Associated with Toxic Marine Dinoflagellate Alexandrium tamarense

Paralytic shellfish poisoning (PSP) toxins are potent neurotoxins mainly produced by dinoflagellates and being concentrated in bivalves through food web transfer. Increasing number of findings of toxin-producing bacteria in the cells of dinoflagellate such as Alexandriumtamarense supports the hypothesis of the bacterial origin of PSP toxins. Evidence that there are specific symbiosis bacterial taxa associated with the phytoplankton indicates the presence of specific selective mechanisms between them, and implies that the symbiosis bacteria have some vital function to the benefit of the dinoflagellates. Studies on the role of toxin-producing symbiosis bacteria in the marine ecosystem are considered to be becoming more important. Although toxigenic bacteria could be isolated from toxic dinoflagellates, it was not clearly proven whether the isolated bacterial strains based on culture-dependent manner and the corresponding intracellular bacteria were the same because of microbial unculturability. This paper aims to demonstrate the biodiversity of the symbiotic bacteria associated with toxic dinoflagellate A. tamarense using the culture-indepen- dent high-throughput pyrosequencing method, as well as the phylogenetic analysis based on 16S rDNA sequences of the symbiotic cultivable bacteria strains isolated from toxic Alexander tamarense.

Diversity of Secondary Metabolites from Two Antarctic Microbes Rhodococcus sp. NJ-008 and <i>Pseudomonas</i>sp. NJ-011

Diversity analysis on secondary metabolites of Antarctic microbes, Rhodococcus sp. NJ-008 and Pseudomonas sp. NJ-011, together with the structural elucidation of some purified compounds, has been carried out for understanding of their chemical constituents. The methanol extracts of Rhodococcus sp. NJ-008 and Pseudomonas sp. NJ-011 were subjected to HPLC-TOF MS test for diversity analysis on secondary metabolites, respectively. The chemical constituents of NJ-011 are mainly N-containing compounds including some alkaloids and short polypeptides, while those of NJ-008 are not N-containing ones. Three compounds were also isolated and identified from extract of NJ011 by different column chromatography and preparative HPLC, and their structures were elucidated as b-carboline (1), 3-benzylhexahydropyrrolo[1,2-a]pyrazine-1,4-dione (2) and 3-isobutylhexahydropyrrolo[1,2-a]pyrazine-1,4-dione (3) by comparison of TOF MS, 1Hand 13C-NMR data with those reported. More microbial material of Pseudomonas sp. NJ-011 should be needed for exploration of the minor constituents with complicated structures.

A two-year(2020–2021)observation of marine phycotoxins in phytoplankton in typical mariculture areas of East China Sea

To learn the marine phycotoxins(MPTs)contamination status in mariculture areas in the East China Sea(ECS),from May 2020 to October 2021,80 net-concentrated phytoplankton samples were collected from 12 stations in three typical areas with high incidence of red tides,namely,Gouqi Island,Sandu’ao-Lianjiang,and Zhangzhou-Dongshan Island in ECS,and MPTs of the samples were detected.Six types of toxins were detected in 24 samples from 9 stations.Lipophilic marine toxins(LMTs)were more common and diverse in these areas.Pectenotoxin 2(PTX2)was the main lipophilic marine toxin(LMT)in the concentrated phytoplankton samples and the occurrence showed seasonal differences from north to south.According to the potential risks of pectenotoxin(PTXs)to seafood safety,it is suggested to execute regular monitoring on PTXs in ECS and a mandatory standard should be formulated based on the comprehensive analysis of in-situ monitoring and lab research.Meanwhile,contamination risks of cyclic imine toxins in the north and domoic acid(DA)in the south of ECS should also be paid with attention to.Only 2 paralytic shellfish toxins(PSTs),N-sulfocarbamoyl toxin C2(C2),and decarbamoyl gonyatoxin 3(dcGTX3),were found from spring samples in the north of ECS.As the biggest mussel culture county of China,Gouqi Island showed higher toxin diversity and the toxin detection rate was higher than the other two areas.In Gouqi Island area,PSTs were a serious potential threat in spring,and LMTs instead of PSTs became the main risk in summer-autumn seasons.To ensure the safety of seafood and marine environmental health,it is recommended to conduct long-term targeted tracking and monitoring of MPTs in this and similar mariculture areas.

An Effective Extract Method of Phospholipids from Antarctic Krill <em>Euphausea superba</em>

Phospholipids are one of the major bioactive ingredients of Antarctic krill Euphausea superba. A feasible and effective extraction method of Antarctic krill oil was investigated and modified by orthogonal test which the ratio of solid to liquid was 1:2.5, extraction time was 5 min, ratio of ethyl acetate (EA) and n-butanol (BuOH) was 1:1. With this method, the extract of krill oil has a higher phospholipids content of 27.7% - 42.3%, together with total oil yields of 4.15% - 6.18%.