Effect of longitudinal joints on seismic response of the large shield tunnel in liquefiable soils

In view of the damages to shield tunnels in recent strong earthquakes, this paper focuses on the effect of longitudinal joints on the seismic response of the shield tunnel in liquefiable soils. First, the normal and shear behaviors of high-strength concrete interface at the joint were studied through direct shear tests under monotonic and cyclic loadings. The results show that the flatness rather than the roughness is the dominant factor influencing the behavior of the interface. As the confining stress and cyclic number increase, the total contact area increases, thus resulting in the increases of the normal stiffness and the friction coefficient. Based on the testing results, the seismic response of a shield tunnel in liquefiable soils was studied using numerical analysis. According to the results, the longitudinal joints have a significant effect on the seismic response of the shield tunnel. When neglecting the joints, the tensile stresses in concrete, the tunnel uplift and the surface deformation remarkably decrease, and the shield tunnel becomes less vulnerable to earthquakes. Due to the soil liquefaction, the joints located near the waist are more likely to get opened and corresponding bolts bear large tensile forces, which are the main reasons for the common damages to shield tunnels. Based on this experimental and numerical study, the effect of the joints and the seismic damages of the large shield tunnel are better understood, consisting an important step in the development of appropriate specifications for the seismic design of the large shield tunnel

Characterization of a cryptic plasmid pSM429 and its application for heterologous expression in psychrophilic Pseudoalteromonas

<p>Abstract</p> <p>Background</p> <p><it>Pseudoalteromonas </it>is an important genus widespread in marine environment, and a lot of psychrophilic <it>Pseudoalteromonas </it>strains thrive in deep sea and polar sea. By now, there are only a few genetic systems for <it>Pseudoalteromonas </it>reported and no commercial <it>Pseudoalteromonas </it>genetic system is available, which impedes the study of <it>Pseudoalteromonas</it>, especially for psychrophilic strains. The aim of this study is to develop a heterologous expression system for psychrophilic <it>Pseudoalteromonas</it>.</p> <p>Results</p> <p>A cryptic plasmid pSM429 isolated from psychrophilic <it>Pseudoalteromonas </it>sp. BSi20429 from the Arctic sea ice, was sequenced and characterized. The plasmid pSM429 is 3874 bp in length, with a G+C content of 28%. Four putative open reading frames (ORFs) were identified on pSM429. Based on homology, the ORF4 was predicted to encode a replication initiation (Rep) protein. A shuttle vector (<it>Escherichia coli, Pseudoalteromonas</it>), pWD, was constructed by ligating pSM429 and pUC19 and inserting a chloramphenicol acetyl transferase (CAT) cassette conferring chloramphenicol resistance. To determine the minimal replicon of pSM429 and to check the functionality of identified ORFs, various pWD derivatives were constructed. All derivatives except the two smallest ones were shown to allow replication in <it>Pseudoalteromonas </it>sp. SM20429, a plasmid-cured strain of <it>Pseudoalteromonas </it>sp. BSi20429, suggesting that the <it>orf4 </it>and its flanking intergenic regions are essential for plasmid replication. Although not essential, the sequence including some repeats between <it>orf1 </it>and <it>orf2 </it>plays important roles in segregational stability of the plasmid. With the aid of pWD-derived plasmid pWD2, the erythromycin resistance gene and the <it>cd </it>gene encoding the catalytic domain of a cold-adapted cellulase were successfully expressed in <it>Pseudoalteromonas </it>sp. SM20429.</p> <p>Conclusions</p> <p>Plasmid pSM429 was isolated and characterized, and the regions essential for plasmid replication and stability were determined, helping the development of pSM429-based shuttle vectors. The shuttle vectors pWD and its derivatives could be used as cloning vectors for <it>Pseudoalteromonas</it>, offering new perspectives in the genetic manipulation of <it>Pseudoalteromonas </it>strains. With the aid of pWD-derived vector and its host, the erythromycin resistance gene and the <it>cd </it>gene of a cold-adapted protein were successfully expressed, indicating that the potential use of this system for recombinant protein production, especially for cold-adapted proteins.</p

Extracellular Matrix Peptides of Artemia Cyst Shell Participate in Protecting Encysted Embryos from Extreme Environments

BACKGROUND: Many species of the brine shrimp Artemia are found in various severe environments in many parts of the world where extreme salinity, high UV radiation levels, high pH, anoxia, large temperature fluctuations, and intermittent dry conditions are often recorded. To withstand adverse environments, Artemia undergoes an oviparous developmental pathway to release cysts whereas, under favorable conditions, swimming nauplius larvae are formed directly via an ovoviviparous pathway. In the former case these cysts have an extraordinary ability to keep the embryos protected from the harsh environment for long periods. This is achieved through the protection by a complex out-wrapping cyst shell. However, the formation and function of the cyst shell is complex; the details remain largely unclear. PRINCIPAL FINDING: A shell gland-specific gene (SGEG2) was cloned and identified from a suppression subtractive hybridization library. Western blot analysis showed that SGEG2 presumably requires post-translational proteolysis in order to be processed into two mature peptides (SGEG2a and 2b). The three matrix peptides (SGEG1 reported previously, 2a, and 2b) were found to distribute throughout the cyst shell. The results of gene knockdown by RNAi and subsequent resistance to environmental stresses assays indicated that these matrix peptides are required for cyst shell formation and are involved in protecting the encysted embryos from environmental stress. CONCLUSIONS/SIGNIFICANCE: This study revealed that extracellular matrix peptides participate in protecting embryos from extreme salinity, UV radiation, large temperature fluctuations and dry environments, thereby facilitating their survival. The cyst shell provides an excellent opportunity to link the ecological setting of an organism to the underlying physiological and biochemical processes enabling its survival. The cyst shell material has also a high potential to become an excellent new biomaterial with a high number of prospective uses due, specifically, to such biological characteristics

Structure of cryptophyte photosystem II-light-harvesting antennae supercomplex.

Cryptophytes are ancestral photosynthetic organisms evolved from red algae through secondary endosymbiosis. They have developed alloxanthin-chlorophyll a/c2-binding proteins (ACPs) as light-harvesting complexes (LHCs). The distinctive properties of cryptophytes contribute to efficient oxygenic photosynthesis and underscore the evolutionary relationships of red-lineage plastids. Here we present the cryo-electron microscopy structure of the Photosystem II (PSII)-ACPII supercomplex from the cryptophyte Chroomonas placoidea. The structure includes a PSII dimer and twelve ACPII monomers forming four linear trimers. These trimers structurally resemble red algae LHCs and cryptophyte ACPI trimers that associate with Photosystem I (PSI), suggesting their close evolutionary links. We also determine a Chl a-binding subunit, Psb-γ, essential for stabilizing PSII-ACPII association. Furthermore, computational calculation provides insights into the excitation energy transfer pathways. Our study lays a solid structural foundation for understanding the light-energy capture and transfer in cryptophyte PSII-ACPII, evolutionary variations in PSII-LHCII, and the origin of red-lineage LHCIIs

An anoikis-related gene signature predicts prognosis and reveals immune infiltration in hepatocellular carcinoma

BackgroundHepatocellular carcinoma (HCC) is a global health burden with poor prognosis. Anoikis, a novel programmed cell death, has a close interaction with metastasis and progression of cancer. In this study, we aimed to construct a novel bioinformatics model for evaluating the prognosis of HCC based on anoikis-related gene signatures as well as exploring the potential mechanisms.Materials and methodsWe downloaded the RNA expression profiles and clinical data of liver hepatocellular carcinoma from TCGA database, ICGC database and GEO database. DEG analysis was performed using TCGA and verified in the GEO database. The anoikis-related risk score was developed via univariate Cox regression, LASSO Cox regression and multivariate Cox regression, which was then used to categorize patients into high- and low-risk groups. Then GO and KEGG enrichment analyses were performed to investigate the function between the two groups. CIBERSORT was used for determining the fractions of 22 immune cell types, while the ssGSEA analyses was used to estimate the differential immune cell infiltrations and related pathways. The “pRRophetic” R package was applied to predict the sensitivity of administering chemotherapeutic and targeted drugs.ResultsA total of 49 anoikis-related DEGs in HCC were detected and 3 genes (EZH2, KIF18A and NQO1) were selected out to build a prognostic model. Furthermore, GO and KEGG functional enrichment analyses indicated that the difference in overall survival between risk groups was closely related to cell cycle pathway. Notably, further analyses found the frequency of tumor mutations, immune infiltration level and expression of immune checkpoints were significantly different between the two risk groups, and the results of the immunotherapy cohort showed that patients in the high-risk group have a better immune response. Additionally, the high-risk group was found to have higher sensitivity to 5-fluorouracil, doxorubicin and gemcitabine.ConclusionThe novel signature of 3 anoikis-related genes (EZH2, KIF18A and NQO1) can predict the prognosis of patients with HCC, and provide a revealing insight into personalized treatments in HCC