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1.
Ultrasonics ; 138: 107271, 2024 Mar.
Article in English | MEDLINE | ID: mdl-38377829

ABSTRACT

Circumferential Shear Horizontal (CSH) guided waves provide an effective method for detecting defects like axial cracks and corrosion in pipes. Periodic Permanent Magnet Electromagnetic Acoustic Transducers (PPM EMATs) are typically used to generate CSH guided waves. However, there is an offset problem to which little attention has been paid. The offset problem refers to the offset of the center (position of maximum energy) of the operating region caused by the variation in the peak frequency of the spatial spectra of PPM with 2 or fewer cycles. Furthermore, the excitability of guided waves is one of the factors that needs to be considered when selecting the excitation parameters of EMATs, but there are still some studies that have not sufficiently addressed this issue. In this paper, the offset problem and the excitability of CSH guided waves were investigated. Firstly, by obtaining the operating regions corresponding to PPM with different cycles, the cause and influences of the offset problem were studied. The results show that the offset in the peak frequency of the spatial spectrum of PPM is the fundamental reason causing the offset problem, and it not only leads to incorrect prediction of the excitation efficiency of guided waves but also affects the selection of the excitation parameters of EMATs. Secondly, finite element simulations and experiments were performed to assess the influence of the excitability on the excitation efficiency of the CSH0 and CSH1 modes in pipes. By analyzing the simulation and experimental results of 2-cycle PPM, as well as the simulation results for PPM with 1 to 5 cycles, the impact of the excitability on the CSH1 mode was confirmed from two perspectives. The final conclusion indicates that an accurate prediction of the amplitudes of CSH guided waves with different modes is only possible through a comprehensively consideration of the operating region of EMAT and the excitability of guided waves.

2.
Nan Fang Yi Ke Da Xue Xue Bao ; 28(4): 576-8, 2008 Apr.
Article in Chinese | MEDLINE | ID: mdl-18495594

ABSTRACT

OBJECTIVE: To transfer human granulocyte-macrophage colony stimulating factor (hGM-CSF) gene into Actococcus lactis and obtain recombinant Lactococcus lactis highly expressing hGM-CSF (LL-CSF). METHODS: The optimized hGM-CSF gene sequence capable of expression in Lactococcus lactis was cloned into the vector pNBC1000, which contained P59 promoter, RBS, MCS, USP45 signal peptide and USP45 stop codon, to generate the recombinant plasmid pNCSF. pNCSF was subcloned into a shuttle vector pTR1001c to acquire the plasmid pTRCSF, which was transferred into Lactococcus lactis to obtain LL-CSF by means of electroporation. SDS-PAGE was used to verify the expression of hGM-CSF protein by the constructed LL-CSF. RESULTS: DNA sequencing and restriction enzyme digestion indicated the successful construction of the recombinant plasmid pNCSF, pTRCSF and the recombinant bacterium LL-CSF that was capable of steady and efficient expression of hGM-CSF as shown by SDS-PAGE. CONCLUSION: The recombinant Lactococcus lactis LL-CSF has been successfully constructed, which can be valuable for studying the biological activity of recombinant hGM-CSF and for evaluating the potential clinical application of the protein.


Subject(s)
Granulocyte-Macrophage Colony-Stimulating Factor/biosynthesis , Lactococcus lactis/genetics , Electrophoresis, Polyacrylamide Gel , Electroporation , Genetic Vectors/genetics , Granulocyte-Macrophage Colony-Stimulating Factor/genetics , Humans , Recombinant Proteins
3.
Nan Fang Yi Ke Da Xue Xue Bao ; 27(7): 951-4, 2007 Jul.
Article in Chinese | MEDLINE | ID: mdl-17666323

ABSTRACT

OBJECTIVE: To investigate the effect of short hairpin RNA (shRNA) targeting survivin on adhesion and invasion of human colon carcinoma cell line SW480 in vitro. METHODS: According to the sequence of the coding region of survivin gene, two strings of 19 nucleotides of inverted sequence flanking the loop sequence of two complementary 9-base oligonucleotides were designed and synthesized to prepare the hairpin construct as the DNA templates for the target shRNA. The shRNA templates were cloned into shRNA expression vector pRNAT-U6.1/Neo, and the resulted vector pRNAT-U6.1/Neo-survivin was transfected into SW480 cells using Lipofectamine 2000. Western blotting was performed to evaluate survivin gene silencing induced by shRNA transfection at the protein level, and the biological behaviors of the SW480 cells were investigated by cell-matrix adhesion, invasion and gelatin-zymography assays. RESULTS: Western blotting revealed significantly lowered survivin protein expression in transfected SW480 cells, and survivin gene silencing induced by shRNA significantly suppressed the metastatic potential of SW480 cells in association with suppressed MMPs activity. CONCLUSIONS: Survivin may play an important role in modulating human colorectal carcinoma cell invasion and metastasis, and survivin gene silencing can inhibit human colorectal cancer cell invasion and the production of MMP-2 and MMP-9. Survivin may affect invasion and metastasis of human colorectal carcinoma cells via regulating the production of MMPs.


Subject(s)
Colonic Neoplasms/pathology , Gene Silencing , Inverted Repeat Sequences , Microtubule-Associated Proteins/deficiency , Microtubule-Associated Proteins/genetics , Neoplasm Metastasis/genetics , RNA, Small Interfering/genetics , Animals , Blotting, Western , Cell Line, Tumor , Colonic Neoplasms/genetics , Humans , Inhibitor of Apoptosis Proteins , Matrix Metalloproteinases/metabolism , Neoplasm Invasiveness/genetics , Survivin
4.
Di Yi Jun Yi Da Xue Xue Bao ; 25(2): 195-7, 2005 Feb.
Article in Chinese | MEDLINE | ID: mdl-15699004

ABSTRACT

OBJECTIVE: To explore the method for in vitro gene assembly of apoptin-encoding DNA sequence, for instance, using a large number of oligodeoxyribonucleotides (oligos). METHODS: Based on the encoding sequence of apoptin gene (GeneBank accession number AY171617), a number of oligos were designed to assembly apoptin gene in pfu mix reaction system, and each oligo was 40 nucleotides (nt) in length, in which synonymous codon substitution was used to eliminate the restriction enzyme sites of Bgl II ( position 172, agatct-agatcc) and Hind III (position 306, aagctt-aatcct). The assembly mixture was further diluted and amplified with two end oligos. The targeting sequence was gel-purified, amplified for one more time, followed by the addition of T to the 3' end in the presence of Taq polymerase and dATP before cloning into pGEM-T easy vector. The positive clones were confirmed by restriction enzyme digestion and sequence analysis. RESULTS: The synthetic mixture presented obvious "tails" in the first PCR for assembly. After dilution of the mixture and amplification with two end oligos, clear DNA ladder bands with a clear targeted band were yielded. After PCR, the targeted gene was cloned into pGEM-T easy vector, and the positive clones were confirmed by sequence analysis with be identical to the designed coding sequence of apoptin gene. CONCLUSION: Gene assembly is a rapid and cost-effective approach for synthesis of genes or vectors, which allows simultaneous mutagenesis of several genes in vitro.


Subject(s)
Genes, Synthetic , Neoplasm Proteins/genetics , Oligodeoxyribonucleotides/genetics , Base Sequence , Capsid Proteins , Genetic Vectors , Humans , Molecular Sequence Data , Oligodeoxyribonucleotides/metabolism , Polymerase Chain Reaction
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