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1.
PLoS One ; 19(6): e0304973, 2024.
Article in English | MEDLINE | ID: mdl-38838022

ABSTRACT

Cities are commonly recognized as the immediate hinterland of ports and play a crucial role in fostering the sustainable development of ports. Therefore, it is imperative to investigate the influence of cities on ports. By employing panel data from 2001 to 2021 for both ports and cities in the Bohai Rim region, this study examines the spatial spillover effect of urban economy on port efficiency using the spatial error model (SEM). The findings show that urban economies have a significant spatial spillover effect on port efficiency, but this effect diminishes across different spatial matrices. In particular, the geographical matrix demonstrates a stronger spatial spillover effect of the urban economy on port efficiency. These research findings help to establish a collaborative mechanism for port-city development and provide useful insights for government management decision-making.


Subject(s)
Cities , Humans , China , Sustainable Development/economics
2.
Front Psychol ; 15: 1366501, 2024.
Article in English | MEDLINE | ID: mdl-38770248

ABSTRACT

Introduction: Numerous studies within the school and academic contexts have underscored the profound impact of psychometric variables such as academic self-efficacy, self-esteem, and loneliness on academic achievement among children. Although physical activities and dance practices are known to bolster academic self-efficacy and enhance academic outcomes, the effect of Artistic Sports Activities on these psychological determinants among left-behind children (LBC) in rural schools remains underexplored. Method: This study was conducted from September 2020 to January 2022 among 405 LBCs aged 9 to 13 from six randomly selected primary schools in Hunan Province, China. Schools were chosen in collaboration with the Hunan Women and Children's Federation, ensuring informed consent through stakeholder informational sessions. The study employed rigorous sampling and data analysis methods, including the Shapiro-Wilk test for normal distribution and Cronbach's alpha for reliability, alongside Pearson correlation, independent and paired t-tests, and multiple linear regression analyses to investigate the effects of Artistic Sports Activities on psychometric variables and academic performance among LBCs. Data collection involved standardized questionnaires assessing academic self-efficacy, self-esteem, and loneliness before and after intervention. Results: Findings indicate that Artistic Sports Activities significantly improved academic self-efficacy and self-esteem and reduced loneliness, leading to enhanced academic performance. Notably, loneliness was identified as mediating the relationship between academic self-efficacy and self-esteem among LBCs. Discussion: The findings highlight the critical role of integrating Artistic Sports Activities in educational frameworks to bolster psychological and academic outcomes for LBCs. The study reveals the intricate interplay between loneliness, self-esteem, and academic self-efficacy, underscoring the necessity for targeted educational interventions.

3.
Nanotechnology ; 35(31)2024 May 13.
Article in English | MEDLINE | ID: mdl-38663370

ABSTRACT

The overuse of antibiotics currently results in the presence of various antibiotics being detected in water bodies, which poses potential risks to human health and the environment. Therefore, it is highly significant to remove antibiotics from water. In this study, we developed novel rod-like NiCo-phyllosilicate hybrid catalysts on calcined natural zeolite (NiCo@C-zeolite) via a facile one-pot process. The presence of the zeolite served as both a silicon source and a support, maintaining a high specific surface area of the NiCo@C-zeolite. Remarkably, NiCo@C-zeolite exhibited outstanding catalytic performance in antibiotic degradation under PMS activation. Within just 5 min, the degradation rate of metronidazole (MNZ) reached 96.14%, ultimately achieving a final degradation rate of 99.28%. Furthermore, we investigated the influence of catalyst dosage, PMS dosage, MNZ concentration, initial pH value, and various inorganic anions on the degradation efficiency of MNZ. The results demonstrated that NiCo@C-zeolite displayed outstanding efficacy in degrading MNZ under diverse conditions and maintained a degradation rate of 94.86% at 60 min after three consecutive cycles of degradation. Free radical quenching experiments revealed that SO•-4played a significant role in the presence of NiCo@C-zeolite-PMS system. These findings indicate that the novel rod-like NiCo-phyllosilicate hybrid catalysts had excellent performance in antibiotic degradation.


Subject(s)
Anti-Bacterial Agents , Zeolites , Zeolites/chemistry , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/chemical synthesis , Catalysis , Water Pollutants, Chemical/chemistry , Metronidazole/chemistry , Water Purification/methods , Silicates/chemistry
4.
Heliyon ; 9(10): e20305, 2023 Oct.
Article in English | MEDLINE | ID: mdl-37800070

ABSTRACT

Recent studies have demonstrated that human maxillary sinus mesenchymal stem cells (hMSMSCs) have osteogenic potential and can be osteogenically induced. Here, we investigated pivotal molecular functions and candidates that contribute to the osteogenic differentiation of hMSMSCs. Human maxillary sinus membranes were harvested from 3 patients with jaw deformities. hMSMSCs from human maxillary sinus membranes were osteogenically induced for 0 or 21 days. Subsequently, their functional profiles were analysed by RNA sequencing and validated by quantitative PCR. Compared with control hMSMSCs, osteogenically induced hMSMSCs showed (1) osteogenic differentiation phenotype, as evidenced by the cell nodes, alizarin red staining, osteogenesis-related protein, and RNA expression; (2) accelerated osteogenic process of ossification and calcium signalling, as demonstrated by Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway; (3) enriched osteogenesis gene expression of SMOC2, OMD, IGF1, JUNB, BMP5, ADRA1A, and IGF2, which was validated by quantitative PCR. Based on by these results, we demonstrated that accelerated ossification process, calcium signalling, and upregulation of SMOC2, OMD, IGF1, JUNB, BMP5, ADRA1A and IGF2, may contribute to the osteogenic differentiation of hMSMSCs.

5.
Front Psychol ; 14: 1107233, 2023.
Article in English | MEDLINE | ID: mdl-37205070

ABSTRACT

Introduction: Although there is considerable research indicating that physical exercise and dance can strengthen children's self-efficacy, and children's self-efficacy can predict students' academic achievement at a wide range of academic levels. Few studies have been conducted using Latino Dance to improve self-efficacy in Left-Behind Children (LBC), especially the two aspects of student academic self-efficacy and general self-efficacy, while the mediator role of self-esteem between student academic self-efficacy and general self-efficacy has been less explored in previous research. Methods: This study proposed to examine Latino Dance interventions to improve general self-efficacy and students' academic self-efficacy among LBC students in rural areas to boost students' academic performance, and the research team hypothesised that general self-efficacy, students' academic self-efficacy and self-esteem would improve following the intervention and that outcomes will have a significant positive correlation as students' self-esteem can mediate both their academic self-efficacy and their general self-efficacy. Dates were collected from 305 LBCs children (160 boys and 145 girls) from 6 left-behind schools in Hunan province, China. Ralf Schwarzer's general self-efficacy scale, Morgan-Jinks Student academic Self-Efficacy Scale, and Rosenberg's self-esteem scale were administered to LBCs between September 2020 and January 2022. Results: The results revealed that the Latino Dance intervention significantly increased the LBC student' academic self-efficacy and general self-efficacy, which also involved a positive effect on the three sub-dimensions (talent, context, and effort) of students' academic self-efficacy. Further, multiple linear regression analysis confirmed that self-esteem (positive esteem/self-deprecation) acted as a partial mediator between student academic self-efficacy and general self-efficacy; perceived self-esteem played a mediating role between them. Discussion: This study filled a gap in the literature concerning the psychological reinforcement effect of Latino Dance on LBC groups and demonstrated that Latino Dance improved the student' academic self-efficacy and general self-efficacy among the LBCs. Our results suggest that Latino Dance can be beneficial for LBC in school by including Latino Dance in Physical Education or Art courses and improving students' self-esteem may lead to an increase in student academic self-efficacy as well as general self-efficacy, thereby improving and enhancing the learning of LBCs.

6.
Tissue Cell ; 79: 101948, 2022 Dec.
Article in English | MEDLINE | ID: mdl-36179452

ABSTRACT

Schneiderian membrane is an indispensable structure for osteogenesis under the sinus floor space after maxillary sinus floor elevation.Therefore,this study aimed to compare the Schneiderian membrane and palatine mucoperiosteum in various aspects to explore whether the Schneiderian membrane has a periosteal layer and osteogenic ability. Schneiderian membrane and palatine mucoperiosteum specimens were collected and stained with HE, Masson, and Sirius red. Immunofluorescence staining was used to observe the expression and localization of mesenchymal stem cells (MSCs). Then MSCs from two tissues were isolated,cultured, and identified. The expression of osteogenic markers OCN, RUNX2, and BMP2 ware detected by Western blotting and quantitative PCR after osteogenic differentiation.The morphological observations revealed both the Schneiderian membrane and palatine mucoperiosteum were composed of three layers.Immunofluorescence staining showed that the inner bone surface layer of the Schneiderian membrane was rich in MSCs, which was similar to the cambium layer of the palatine mucoperiosteum.In addition, MSCs from two tissues showed similar morphological phenotype. After further osteogenic induction of the two groups, the expression of BMP2, RUNX2, and OCN were significantly increased. This study provide a novel insight into that Schneiderian membrane is a mucoperiosteal membrane rich of MSCs, containing a periosteal layer and osteogenic ability similar to mucoperiosteum.


Subject(s)
Osteogenesis , Sinus Floor Augmentation , Osteogenesis/genetics , Core Binding Factor Alpha 1 Subunit/metabolism , Cell Differentiation/genetics , Nasal Mucosa/metabolism , Molecular Biology , Cells, Cultured
7.
Front Cardiovasc Med ; 9: 847163, 2022.
Article in English | MEDLINE | ID: mdl-35571218

ABSTRACT

Objective: Delayed enhancement cardiac CT is a reliable tool for the diagnosis of left atrial appendage thrombus but limited for scanning heterogeneity. We aimed to explore the improvement of the 1 and 3-min delay phase at the diagnostic level to detect left atrial appendage thrombus, in order to set up a reasonable CT scanning scheme. Materials and Methods: A total of 6,524 patients were continuously retrieved from January 2015 to September 2020 retrospectively. The patients had undergone Transesophageal echocardiography (TEE) and cardiac CT with complete period include the arterial enhancement phase, 1 and 3-min delay phase, TEE were used as the reference standard. The final study included 329 patients. Three experienced radiologists independently assessed each phase of the cardiac CT images for thrombus diagnosis. We explored the improvement of the diagnostic ability of different delayed contrast-enhanced phases for left atrial appendage thrombus detection. Multiple logistic regression analysis were used for further high-risk stratification to avoid an additional 1-min delayed scan. Results: In total, 29 thrombosis were detected at TEE. For all cardiac CT phases, sensitivity and negative predictive were 100%. The specificity were 0.54, 0.93, and 1.00, respectively; The positive predictive values (PPV) were 0.17, 0.57, and 1.00, respectively; Area under curve (AUC) were 0.75, 0.95, and 0.98, respectively. High risk factors that cannot be clearly diagnosed with 1-min delay phase included reduced cardiac function, increased CHA2DS2-VAScscore and left atrial enlargement. Compared with the arterial enhanced phase, increased radiation doses in the 1 and 3-min delay phases were 1.7 ± 1.3 msv and 1.5 ± 0.8 msv (mean ± standard deviation). Conclusion: Using TEE as the reference standard, early contrast-enhanced CT scanning with 1 and 3-min delay is necessary for the diagnosis of left appendage thrombus, which could significantly improve the diagnostic efficiency. Patients with high-risk stratification are suitable for direct 3-min delayed scanning.

8.
Tissue Cell ; 72: 101592, 2021 Oct.
Article in English | MEDLINE | ID: mdl-34303282

ABSTRACT

Yes-associated protein (YAP) is essential in maintaining tissue size. Aberrant epithelial remodeling is a key pathological alteration in both inflammation and benign tumors in nasal mucosa. We sought to investigate the expression and localization patterns of YAP in remodeled nasal epithelium of basal cell hyperplasia, goblet cell metaplasia and squamous metaplasia. YAP expression patterns were evaluated in tissues obtained from patients with NP (n = 45) and IP (n = 27), and control subjects with septal deviation (n = 17) and tissue-derived primary cell cultures. Compared to the normal epithelium, expressions of YAP were significantly higher in basal cell hyperplasia (NP, 11.4-fold; IP, 19.6-fold), followed by squamous metaplasia (8.2-fold) and mild to moderate goblet cell metaplasia (2.9-fold); while their expression was lower in severe goblet cell metaplasia (3.3-fold). Our resultsshowed that: 1) ectopic nuclear YAP expression associated with p63+ basal cell hyperplasia and the high proliferative potential epithelial cells; 2) increase of cytoplasmic YAP correlated with mild to moderate goblet cell metaplasia; 3) increase of cytoplasmic YAP correlated with squamous cell metaplasia. The in vitro cell model also demonstrated almost concordant changes of YAP with the mucosa findings. Different YAP expression and localization patterns should play critical but differential roles in the nasal epithelial remodeling processes under mucosal inflammation and benign tumor formation.


Subject(s)
Nasal Mucosa/metabolism , YAP-Signaling Proteins/metabolism , Adult , Cell Differentiation , Cell Proliferation , Cells, Cultured , Epithelial Cells/cytology , Epithelial Cells/metabolism , Female , Humans , Keratin-8/metabolism , Male , Middle Aged , Nasal Mucosa/cytology , Proliferating Cell Nuclear Antigen/metabolism , Subcellular Fractions/metabolism , Transcription Factors/metabolism , Tumor Suppressor Proteins/metabolism
9.
Quant Imaging Med Surg ; 11(1): 328-340, 2021 Jan.
Article in English | MEDLINE | ID: mdl-33392032

ABSTRACT

BACKGROUND: Extramural venous invasion (EMVI) has been found to be related to poor prognosis in gastric cancer. Preoperative diagnosis of EMVI is challenging, as it can only be detected by surgical pathology. The present study aimed to investigate the value of quantitative dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and diffusion-weighted imaging (DWI) in predicting EMVI preoperatively, and to determine the relationship between prediction results and prognosis in patients with locally advanced gastric cancer (LAGC). METHODS: Between January, 2015, and June, 2017, 79 LAGC patients underwent MRI preoperatively were enrolled in this study. Pathological EMVI (pEMVI) was used as the gold standard for diagnosis. The differences in quantitative DCE-MRI and DWI parameters between groups with different pEMVI status were analyzed. Multivariate logistic regression was used to build the combined prediction model for pEMVI with statistically significant quantitative parameters. The performance of the model for predicting pEMVI was evaluated using receiver operating characteristic (ROC) analysis. Patients were grouped based on MRI-predicted EMVI (mrEMVI). Kaplan-Meier analysis was used to investigate the relationship between mrEMVI and 2-year recurrence-free survival (RFS). RESULTS: Of the 79 LAGC patients who underwent MRI, 29 were pEMVI positive and 50 were pEMVI negative. Among the patients' clinical and pathological characteristics, only postoperative staging showed a significant difference between the 2 groups (P=0.015). The pEMVI-positive group had higher volume transfer constant (Ktrans) and rate constant (kep), and lower apparent diffusion coefficient (ADC) values than the negative group (0.189 vs. 0.082 min-1, 0.687 vs. 0.475 min-1, and 1.230×10-3 vs. 1.463×10-3 mm2/s, respectively; P<0.05). Quantitative parameters, Ktrans and kep, and ADC values, were independently associated with pEMVI which odds ratio values were 3.66, 2.65, and 0.30 (P<0.05), respectively, using multivariate logistic regression. ROC analysis showed that the area under the curve, sensitivity, specificity, positive predictive value, and negative predictive value in predicting pEMVI using combined Ktrans, kep, and ADC values were 0.879, 72.4%, 96%, 91.3%, and 85.7%, respectively. A total of 23 cases were considered to be mrEMVI positive, and 56 cases were considered to be mrEMVI negative, according to the predictive results. The median RFS of the mrEMVI-positive group was significant lower than the negative group (21.7 vs. 31.2 months), and the 2-year RFS rate in the mrEMVI-positive group was significantly lower than that of the negative group (43.6% vs. 72.5%, P=0.010). CONCLUSIONS: The quantitative DCE-MRI parameters, Ktrans and kep, and DWI parameter, ADC, are independent predictors of pEMVI in LAGC; mrEMVI was confirmed to be a poor prognostic predictor for RFS.

10.
Inflamm Res ; 70(1): 139-149, 2021 Jan.
Article in English | MEDLINE | ID: mdl-33226450

ABSTRACT

OBJECTIVE AND DESIGN: IL-17 plays essential roles in neutrophilic inflammation in the lower respiratory tract, however, the characteristics of local IL-17+ T cells in nasal inflammatory mucosa are not fully understood. We investigated the roles of IL-17+ T cells in regulating neutrophil infiltration and the effect of the mucosal microenvironment in modulating IL-17+ T cell differentiation in CRSwNP tissues. SUBJECTS: 47 polyp tissues from chronic rhinosinusitis with nasal polyps (CRSwNP) patients without corticosteroid therapy and 26 tissues from healthy mucosa were obtained. METHODS: Immunohistochemistry and flow cytometry were used to analyze the neutrophil infiltration, local IL-17+ T cell subsets, as well as cytokine producing profiles of IL-17+ T cell; tissue homogenates were used to study neutrophil migration and IL-17+ T cell differentiation. RESULTS: Increase of IL-17+ cells and IL-17+ T cell subsets was significant in polyp tissues versus controls, IL-17+ cell number was positively correlated with neutrophil infiltration; while homogenates from polyp tissues with high IL-17 promoted neutrophil migration in vitro. IL-17 response was found in polyp-derived T cells upon Staphylococcus aureus infection. IL-17+ T cells were also down-regulated in polyps from patients treated with glucocorticoid steroids, and exhibited poly-functionality patterns in polyp tissues. Finally, IL-17+ T cell differentiation could be induced by IL-23, and homogenates from polyps could enhance IL-17+ T cell development. CONCLUSIONS: This study determined a functional association of IL-17+ T cells with neutrophils in CRSwNP, and revealed that polyp microenvironment could promote IL-17+ T cell differentiation, suggesting a potential feedback role for IL-17+ T cell development and local neutrophilic inflammation.


Subject(s)
Interleukin-17/immunology , Nasal Mucosa/immunology , Nasal Polyps/immunology , Neutrophil Infiltration , Rhinitis/immunology , Sinusitis/immunology , T-Lymphocytes/immunology , Adolescent , Adult , Chronic Disease , Enterotoxins , Female , Humans , Male , Middle Aged , Staphylococcus aureus , Young Adult
11.
Differentiation ; 116: 1-8, 2020.
Article in English | MEDLINE | ID: mdl-33065511

ABSTRACT

Osteogenic differentiation of dental pulp stem cells (DPSCs) is considered as a promising strategy in posterior maxilla tooth implantation. Information on the function and mechanisms of long non-coding RNAs (lncRNAs) in osteogenic differentiation of DPSCs is growing, however, the mechanism of LINC00968 and miR-3658 in regulating osteogenic differentiation of DPSCs still needs to be explored. In this study, the LINC00968 and miR-3658 expression level was upregulated and downregulated in DPSCs and peri-implantitis DPSCs (pDPSCs) treated with bone morphogenic protein (BMP)2, respectively. Moreover, the effects of LINC00968 and miR-3658 on BMP2-induced osteogenic differentiation of DPSCs in vitro using Alizarin Red S staining, alkaline phosphatase (ALP) activity, quantitative real time PCR and Western blot assays showed that overexpression of LINC00968 significantly promoted mineralized bone matrix, alkaline phosphatase (ALP), runt-related transcription factor 2 (RUNX2), and osterix (OSX) expression levels for osteogenic differentiation of DPSCs and pDPSCs; and overexpression of miR-3658 showed an opposite result that inhibited osteogenic differentiation of DPSCs and pDPSCs. Luciferase reporter assay showed that luciferase activities of LINC00968-WT reporter and RUNX2-WT reporter were strongly suppressed by miR-3658 overexpression. In addition, the miR-3658 upregulation interfered ectopic bone formation in vivo stimulated by LINC00968. In general, we had identified a novel molecular pathway involving LINC00968/miR-3658/RUNX2 during DPSCs and pDPSCs differentiation into osteoblasts, which might facilitate bone anabolism.


Subject(s)
Core Binding Factor Alpha 1 Subunit/genetics , Dental Pulp/cytology , MicroRNAs/genetics , Osteogenesis/genetics , RNA, Long Noncoding/genetics , Bone Morphogenetic Protein 2/therapeutic use , Cell Line , Core Binding Factor Alpha 1 Subunit/metabolism , HEK293 Cells , Humans , MicroRNAs/metabolism , Peri-Implantitis/drug therapy , Peri-Implantitis/pathology
12.
ACS Synth Biol ; 9(6): 1418-1425, 2020 06 19.
Article in English | MEDLINE | ID: mdl-32379964

ABSTRACT

Microbial fermentation was widely explored to produce malic acid. Previously, Aspergillus niger has been successfully engineered, and a high titer of malic acid was achieved with strain S575, but it also produced a high level of byproduct citric acid. Here, the capability of A. niger in malic acid biosynthesis was further improved by eliminating the accumulation of citric acid and enhancing glycolytic flux. Characterization of variant mutants suggested that disruption of cexA, a gene encoding citric acid transporter located on cell membrane, abolished citric acid accumulation. However, cexA-deficient strain S895 showed significantly decreased malic acid production. Further analysis of S895 indicated that the transcription level of genes involved in glucose transportation and glycolytic pathway was significantly reduced, and the corresponding enzyme activity was also lower than those of S575. Individual overexpression of genes encoding glucose transporter MstC and key enzymes (hexokinase HxkA, 6-phosphofructo-2-kinase PfkA, and pyruvate kinase PkiA) involved in irreversible reactions of glycolic pathway increased malic acid production. Accordingly, genes of mstC, hxkA, pfkA, and pkiA were overexpressed altogether in S895, and the resultant strain S1149 was constructed. The titer of malic acid in fed-batch fermentation with S1149 reached 201.13 g/L. Compared with S575, the byproduct of citric acid was completely abolished in S1149, and the ratio of malic acid/glucose was increased from 1.27 to 1.64 mol/mol, the highest yield reported so far, and the fermentation period was shortened from 9 to 8 days. Thus, a strain with great industrial application potential was developed by engineering nine genes in A. niger, and a pilot fermentation technology was exploited.


Subject(s)
Aspergillus niger/metabolism , Glycolysis/genetics , Malates/metabolism , Batch Cell Culture Techniques , Citric Acid/metabolism , Fungal Proteins/genetics , Fungal Proteins/metabolism , Glucose/metabolism , Metabolic Engineering/methods , Multigene Family
13.
Appl Microbiol Biotechnol ; 103(19): 8105-8114, 2019 Oct.
Article in English | MEDLINE | ID: mdl-31392377

ABSTRACT

The filamentous fungus Aspergillus niger is widely used in the biotechnology industry for the production of chemicals and enzymes. Engineering of this valuable organism to improve its productivity is currently hampered by the lack of efficient genetic tools. Here, a Cre-loxP-based system for gene editing in A. niger was developed and its application in construction of A. niger cell factories to produce various organic acids was explored. Two established inducible systems, the xylanase A gene promoter Pxln and Tet-on system, were examined for driving cre expression and thus selection marker hyh deletion. Under inducing conditions, the efficiency of loxP site-specific recombination in the strain with cre driven by Pxln is about 2%, while cre driven by Tet-on system is about 34% which was used as the platform strain for further genetic engineering. As a proof of application of this system, strains containing different copies of oxaloacetate acetylhydrolase-encoding gene (oahA) were constructed, and the resultant strain S428 showed as high as 3.1-fold increase in oxalic acid production. Furthermore, an efficient malate-producing strain was generated through four-step genetic manipulation (oahA deletion, pyc, mdh3 and C4-dicarboxylate transporter gene c4t318 insertion). The resultant strain S575 achieved a titer 120.38 g/L malic acid with the flask culture, and a titer 201.24 g/L malic acid in fed-batch fermentation. These results demonstrated that this modified Cre-loxP system is a powerful tool for genetic engineering in A. niger, which has the potential to be genetically modified as a viable aciduric platform strain to produce high levels of various organic acids.


Subject(s)
Aspergillus niger/genetics , Aspergillus niger/metabolism , Carboxylic Acids/metabolism , Gene Editing/methods , Metabolic Engineering/methods , Metabolic Networks and Pathways/genetics , Recombination, Genetic
14.
Soft Matter ; 14(45): 9175-9184, 2018 Nov 21.
Article in English | MEDLINE | ID: mdl-30398509

ABSTRACT

Stress oscillation has been observed in a number of linear thermoplastic polymers during the cold-drawing process, where the polymers exhibit periodic self-excited oscillatory neck propagation. However, the origin of the mechanical stress oscillation process and its relationship with the crystalline morphology of the polymer are still under debate. In this work, we revisit the stress oscillation behavior by studying a semi-crystalline polyester, poly(butylene succinate) (PBS), a biodegradable polymer suitable for biomedical and packaging applications. Stress oscillation of PBS is observed when deformed at a range of elongation rates from 10 to 200 mm min-1, and the fluctuation magnitude decays as the deformation temperature increases from 23 to 100 °C. Periodic transparent/opaque bands form during necking of PBS, which consists of alternating regions of highly oriented crystalline zones and microcavities due to crazing and voiding, although the degree of crystallinity did not change significantly in the bands. Simultaneous small- and wide-angle X-ray scattering confirms that the alternating stress increases, as shown in the stress-strain curves, correspond to the appearance of the transparent bands in the sample, and the abrupt drop of the stress is the result of voiding during the neck propagation. The voiding and cavitation are ultimately responsible for the stress oscillation process in PBS. The in-depth analysis of this work is important in understanding and controlling the occurrence of instabilities/cavitation during polymer processing such as film blowing, biaxial stretching and injection moulding of biodegradable polymer materials.

15.
Materials (Basel) ; 11(9)2018 Sep 13.
Article in English | MEDLINE | ID: mdl-30217019

ABSTRACT

The characteristics and formation mechanisms of intragranular acicular ferrite (IAF) in steel with MgO nanoparticle additions were systematically investigated for different isothermal heat-treatment temperatures, and its influence on mechanical properties was also clarified. The results indicate that the inclusions were finely dispersed and refined after adding MgO nanoparticles. In addition, with decreasing heat-treatment temperature, the microstructure changed from grain boundary ferrite (GBF) and polygonal ferrite (PF) to intragranular acicular ferrite. Moreover, the steel with MgO additions had excellent mechanical properties in the temperature range of 973 to 823 K and an average Charpy absorbed energies value of around 174 J at 873 K due to the significant refinement of the microstructure and nucleation of intragranular acicular ferrite.

16.
J Biomater Appl ; 19(4): 303-22, 2005 Apr.
Article in English | MEDLINE | ID: mdl-15788427

ABSTRACT

Chitosan-gelatin (Cs-Gel) scaffolds are modified with poly (DL-lactic acid) (PDLLA) dichloromethane solution of different concentrations (0.1, 0.5, and 1.0%) and immersed in water after the evaporation of the solvent. The swollen scaffolds are freeze dried. The concentration of PDLLA has significant effects on both the physicomechanical properties and the cytocompatibility. Data reveal that only the 0.1% concentration could increase the tensile strength fourfold in comparison with the pristine Cs-Gel scaffold, while maintaining the human fibroblast adhesion, migration, and proliferation just like the Cs-Gel scaffold.


Subject(s)
Cell Culture Techniques/methods , Chitosan/chemistry , Fibroblasts/cytology , Fibroblasts/physiology , Gelatin/chemistry , Lactic Acid/chemistry , Polymers/chemistry , Tissue Engineering/methods , Absorption , Biocompatible Materials/chemistry , Cell Adhesion/physiology , Cell Movement/physiology , Cell Proliferation , Cells, Cultured , Elasticity , Humans , Materials Testing , Polyesters , Tensile Strength , Water/chemistry
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