29 research outputs found
Study on the deformation mechanism and large deformation control method of a strongly weathered carbonaceous slate tunnel in western China
In response to the significant soft rock deformation challenges encountered during the construction of the Minxian Tunnel along the Lanzhou-Haikou Expressway (G75), this study conducted a comprehensive analysis of soft rock types and the underlying mechanical mechanisms governing the deformation of the surrounding rock. It presented tailored mechanical transformation strategies to address diverse mechanical mechanisms. Also, it introduced the application of anchor cable with high pre-tightening force, constant resistance and large deformation, a proven solution widely employed in mining and rock engineering. Furthermore, the research proposed a high-prestress and active and passive combined support technique, encompassing pre-reinforced retaining structure, optimally arranged active retaining structure with long and short NPR anchor cables, steel arches, and permanent retaining structure of shotcrete. By implementing numerical simulations and on-site monitoring, the results demonstrated a remarkable reduction in the maximum deformation of the surrounding rock in the test section to only 73 mm, and the pre-tightening forces applied to the anchor cable with constant resistance and large deformation ranged from 280 to 300 kN, underscoring the effectiveness of the optimized retaining technique in controlling surrounding rock deformation. This research highlights the pivotal role of retaining structure with constant resistance and yielding support, which significantly improves deformation control
Establishing CRISPRi for Programmable Gene Repression and Genome Evolution in Cupriavidus necator
Cupriavidus necator H16
is a “Knallgas”
bacterium with the ability to utilize various carbon sources and has
been employed as a versatile microbial cell factory to produce a wide
range of value-added compounds. However, limited genome engineering,
especially gene regulation methods, has constrained its full potential
as a microbial production platform. The advent of CRISPR/Cas9 technology
has shown promise in addressing this limitation. Here, we developed
an optimized CRISPR interference (CRISPRi) system for gene repression
in C. necator by expressing a codon-optimized
deactivated Cas9 (dCas9) and appropriate single guide RNAs (sgRNAs).
CRISPRi was proven to be a programmable and controllable tool and
could successfully repress both exogenous and endogenous genes. As
a case study, we decreased the accumulation of polyhydroxyalkanoate
(PHB) via CRISPRi and rewired the carbon fluxes to the synthesis of
lycopene. Additionally, by disturbing the expression of DNA mismatch
repair gene mutS with CRISPRi, we established CRISPRi-Mutator
for genome evolution, rapidly generating mutant strains with enhanced
hydrogen peroxide tolerance and robustness in microbial electrosynthesis
(MES) system. Our work provides an efficient CRISPRi toolkit for advanced
genetic manipulation and optimization of C. necator cell factories for diverse biotechnology applications
Vertical Orientation of Nanocylinders in Liquid-Crystalline Block Copolymers Directed by Light
The microphase-separated nanostructures
of block copolymers are
ideal nanotemplates for advanced fabrication, but they are greatly
limited by the rapid and precise manipulation especially at room temperature.
Here we report one method of light-directed regulation of nanostructures
in thin films of liquid-crystalline diblock copolymers containing
azobenzene units as photoresponsive mesogens. The in-plane orientated
nanocylinders in thin film can be light-directed into out-of-plane
on a time scale of seconds at room temperature. This fast regulation
is beneficial from the fast process of photoinduced phase transition
of the mesogenic block from liquid crystal to disordered isotropic
phase. Several influence factors like the molecular weight of polymer,
film thickness, light intensity, and relative humidity were studied
in the light-directed processes. In addition, the photoregulated nanostructures
demonstrate their capability of being photopatterned and further used
as nanotemplates for fabrication of nanoparticles. The light-directed
method shows noncontact, precise, and reversible features, enabling
it to find further applications in fast control of nanostructures
for nanofabrication and nanoengineering
Synthesis of a Novel Polymeric Material Folate-Poly(2-ethyl-2-oxazoline)-Distearoyl Phosphatidyl Ethanolamine Tri-Block Polymer for Dual Receptor and pH-Sensitive Targeting Liposome
The in vivo distribution of antitumor drugs is usually lack of selectivity, and thus, leading to a low efficacy of chemotherapy on cancers and high toxicity to normal cells. Receptor-mediated targeting liposome with pH-sensitivity as a dual drug delivery system is one of the efficient approaches to overcome the disadvantages. The study was to synthesize a novel smart polymeric material (folate-poly(2-ethyl-2-oxazoline)-distearoyl phosphatidyl ethanolamine, F-PEOz-DSPE), which can combine with the folate-receptor (FR) over-expressed on cancer cells and respond to pH changes in endosome lysosome system in cancer cells to rapidly release drug simultaneously. The F-PEOz-DSPE was synthesized by the method of asymmetric synthesis of organic polymer and characterized by IR, H-1-NMR, electrospray ionization (ESI)-MS and gel permeation chromatography (GPC). To investigate the properties of targeting and pH-sensitivity of F-PEOz-DSPE, blank liposomes, blank fluorescently labeled liposomes and doxorubicin (DOX)-loaded liposomes containing F-PEOz-DSPE or PEOz-DSPE or DSPE were prepared. The cytotoxicity, cellular uptake and drug cumulative release in vitro were investigated. Blank liposomes modified with PEOz block had little cytotoxicity in vitro. The liposomes containing F-PEOz-DSPE showed a higher affinity to human ovarian cancer cell SKOV3, a FR+ cancer cells, than those with PEOz-DSPE. A higher drug cumulative release from DOX-loaded liposomes containing F-PEOz-DSPE or PEOz-DSPE in vitro was found in phosphate buffered saline at pH 5.0 medium than at pH 7.4. These results indicate that F-PEOz-DSPE exhibits selective targeting, pH-sensitivity and little cytotoxicity, and may be a promising polymeric material for dual receptor and pH-sensitive targeting liposome.Chemistry, MedicinalChemistry, MultidisciplinaryPharmacology & PharmacySCI(E)5ARTICLE4390-3986
Association between tumor necrosis factor alpha-238G/a polymorphism and tuberculosis susceptibility: a meta-analysis study
Abstract Background Tumor necrosis factor alpha (TNF-α) plays a key role in the containment of tuberculosis. The relationship between the TNF -238G/A polymorphism and tuberculosis susceptibility remains inconclusive. A comprehensive meta-analysis was made to provide a more precise estimate of the relationship between them. Methods Multiple search strategies were used. A fixed effect model was takentook to estimate pooled OR with 95% confidence interval (CI) for the association between the TNF -238G/A polymorphism and tuberculosis susceptibility. The Chi-squared-based Q-test and I-squaredI2 statistic were calculated to examine heterogeneity. Begg’s funnel plot and Egger’s test were used to assess publication bias. Results 9 case-control studies were included in this meta-analysis. No significant heterogeneity was demonstrated, and no obvious publication bias was detected among the included studies. The meta-analysis indicated that there was no significant association between the TNF -238G/A polymorphism and tuberculosis susceptibility (GA+AA versus GG model: OR=1.005, 95% CI: 0.765-1.319; A versus G model: OR=1.000, 95% CI: 0.769-1.300). In the subgroup analyses by ethnicity, types of TB and human immunodeficiency virus (HIV) status, no significant association were identified. Conclusions The meta-analysis involving 2723 subjects did not detect any association between the TNF -238G/A polymorphism and tuberculosis susceptibility.</p
Vertical Orientation of Nanocylinders in Liquid-Crystalline Block Copolymers Directed by Light
The microphase-separated nanostructures
of block copolymers are
ideal nanotemplates for advanced fabrication, but they are greatly
limited by the rapid and precise manipulation especially at room temperature.
Here we report one method of light-directed regulation of nanostructures
in thin films of liquid-crystalline diblock copolymers containing
azobenzene units as photoresponsive mesogens. The in-plane orientated
nanocylinders in thin film can be light-directed into out-of-plane
on a time scale of seconds at room temperature. This fast regulation
is beneficial from the fast process of photoinduced phase transition
of the mesogenic block from liquid crystal to disordered isotropic
phase. Several influence factors like the molecular weight of polymer,
film thickness, light intensity, and relative humidity were studied
in the light-directed processes. In addition, the photoregulated nanostructures
demonstrate their capability of being photopatterned and further used
as nanotemplates for fabrication of nanoparticles. The light-directed
method shows noncontact, precise, and reversible features, enabling
it to find further applications in fast control of nanostructures
for nanofabrication and nanoengineering
Characterization of a Carbapenem-Resistant Kluyvera Cryocrescens Isolate Carrying Blandm-1 from Hospital Sewage
Carbapenem-resistant Enterobacteriaceae have been a global public health issue in recent years. Here, a carbapenem-resistant Kluyvera cryocrescens strain SCW13 was isolated from hospital sewage, and was then subjected to whole-genome sequencing (WGS). Based on WGS data, antimicrobial resistance genes were identified. Resistance plasmids were completely circularized and further bioinformatics analyses of plasmids were performed. A conjugation assay was performed to identify a self-transmissible plasmid mediating carbapenem resistance. A phylogenetic tree was constructed based on the core genome of publicly available Kluyvera strains. The isolate SCW13 exhibited resistance to cephalosporin and carbapenem. blaNDM-1 was found to be located on a ~53-kb self-transmissible IncX3 plasmid, which exhibited high similarity to the previously reported pNDM-HN380, which is an epidemic blaNDM-1-carrying IncX3 plasmid. Further, we found that SCW13 contained a chromosomal blaKLUC-2 gene, which was the probable origin of the plasmid-born blaKLUC-2 found in Enterobacter cloacae. Phylogenetic analysis showed that K. cryocrescens SCW13 exhibited a close relationship with K. cryocrescens NCTC10483. These findings highlight the further dissemination of blaNDM through clonal IncX3 plasmids related to pNDM-HN380 among uncommon Enterobacteriaceae strains, including Kluyvera in this case