Multi-scale analysis of the effect of loading conditions on monotonic and fatigue behavior of a glass fiber reinforced polyphenylene sulfide (PPS) composite

In this paper, two kinds of PPS/GF composite samples (PPS-0°, PPS-90°) were prepared with two different fiber main orientations related to the injection direction. A wide range of their properties were discussed. Using DMTA analysis, it was shown that the PPS/GF composite under study obeyed the time-temperature equivalence principle. Moreover, Perez model was verified and gave a good estimation of the viscoelastic properties of the PPS/GF. Monotonic and fatigue behaviors and fatigue life of PPS/GF were investigated. Fiber's orientation, applied amplitude and loading frequency effects were emphasized. Self-heating effect on fatigue strength was also analyzed. SEM fracture surface observations allowed analyzing, at the local scale, the main deformation mechanisms occurring during mechanical loading. No evident damage development was observed for both monotonic and fatigue loading. PPS matrix plasticity appeared to be the predominant deformation mechanism until a semi-ductile or semi-brittle final failure depending on the loading conditions and local microstructure

The effects of poly L-lactic acid nanofiber scaffold on mouse spermatogonial stem cell culture

Introduction: A 3D-nanofiber scaffold acts in a similar way to the extracellular matrix (ECM)/basement membrane that enhances the proliferation and self-renewal of stem cells. The goal of the present study was to investigate the effects of a poly L-lactic acid (PLLA) nanofiber scaffold on frozen-thawed neonate mouse spermatogonial stem cells (SSCs) and testis tissues. Methods: The isolated spermatogonial cells were divided into six culture groups: (1) fresh spermatogonial cells, (2) fresh spermatogonial cells seeded onto PLLA, (3) frozen-thawed spermatogonial cells, (4) frozen-thawed spermatogonial cells seeded onto PLLA, (5) spermatogonial cells obtained from frozen-thawed testis tissue, and (6) spermatogonial cells obtained from frozen-thawed testis tissue seeded onto PLLA. Spermatogonial cells and testis fragments were cryopreserved and cultured for 3 weeks. Cluster assay was performed during the culture. The presence of spermatogonial cells in the culture was determined by a reverse transcriptase polymerase chain reaction for spermatogonial markers (Oct4, GFRα-1, PLZF, Mvh(VASA), Itgα6, and Itgβ1), as well as the ultrastructural study of cell clusters and SSCs transplantation to a recipient azoospermic mouse. The significance of the data was analyzed using the repeated measures and analysis of variance. Results: The findings indicated that the spermatogonial cells seeded on PLLA significantly increased in vitro spermatogonial cell cluster formations in comparison with the control groups (culture of SSCs not seeded on PLLA) (P�0.001). The viability rate for the frozen cells after thawing was 63.00 ± 3.56. This number decreased significantly (40.00 ± 0.82) in spermatogonial cells obtained from the frozen-thawed testis tissue. Both groups, however, showed in vitro cluster formation. Although the expression of spermatogonial markers was maintained after 3 weeks of culture, there was a significant downregulation for some spermatogonial genes in the experimental groups compared with those of the control groups. Furthermore, transplantation assay and transmission electron microscopy studies suggested the presence of SSCs among the cultured cells. Conclusion: Although PLLA can increase the in vitro cluster formation of neonate fresh and frozen-thawed spermatogonial cells, it may also cause them to differentiate during cultivation. The study therefore has implications for SSCs proliferation and germ cell differentiation in vitro. © 2013 Eslahi et al

Experimental study of PLA thermal behavior during fused filament fabrication

Fused filament fabrication (FFF) is an additive manufacturing technique that is used to produce prototypes and a gradually more important processing route to obtain final products. Due to the layer-by-layer deposition mechanism involved, bonding between adjacent layers is controlled by the thermal energy of the material being printed, which strongly depends on the temperature development of the filaments during the deposition sequence. This study reports experimental measurements of filament temperature during deposition. These temperature profiles were compared to the predictions made by a previously developed model. The two sets of data showed good agreement, particularly concerning the occurrence of reheating peaks when new filaments are deposited onto previously deposited ones. The developed experimental technique is shown to demonstrate its sensitivity to changing operating conditions, namely platform temperature and deposition velocity. The data generated can be valuable to predict more accurately the bond quality achieved in FFF parts

Psychometric Properties of the Persian Adaptation of Mini-Cog Test in Iranian Older Adults

The aim of this study was to assess the psychometric properties of the Mini-Cog in Iranian older adults. It was a cross-sectional study; 50 older people with dementia and 50 without dementia who matched for age, gender, and education entered the study. The diagnostic and statistical manual of mental disorders criteria for dementia were used as gold standard. A battery of scales included the abbreviated mental test score (AMTS), the Geriatric Depression Scale, and the Mini-Cog was performed. Validity and reliability of the Mini-Cog determined using the Pearson product-moment correlation coefficient (Pearson�s r), Cronbach�s alpha, and Receiver Operating Characteristic (ROC) curve analysis. The Persian version of Mini-Cog showed a good inter-rater reliability (K = 0.76, p <.01) and a positive concurrent validity (r = 0.39, p <.01) with the AMTS. The sensitivity and specificity were 88 and 62.8, respectively, using the original cutoff point of 2. The findings showed that the Persian version of Mini-Cog have an acceptable sensitivity, specificity, and substantial overall agreement with the AMTS. © 2017, © The Author(s) 2017

Psychometric Properties of the Persian Adaptation of Mini-Cog Test in Iranian Older Adults

The aim of this study was to assess the psychometric properties of the Mini-Cog in Iranian older adults. It was a cross-sectional study; 50 older people with dementia and 50 without dementia who matched for age, gender, and education entered the study. The diagnostic and statistical manual of mental disorders criteria for dementia were used as gold standard. A battery of scales included the abbreviated mental test score (AMTS), the Geriatric Depression Scale, and the Mini-Cog was performed. Validity and reliability of the Mini-Cog determined using the Pearson product-moment correlation coefficient (Pearson�s r), Cronbach�s alpha, and Receiver Operating Characteristic (ROC) curve analysis. The Persian version of Mini-Cog showed a good inter-rater reliability (K = 0.76, p <.01) and a positive concurrent validity (r = 0.39, p <.01) with the AMTS. The sensitivity and specificity were 88 and 62.8, respectively, using the original cutoff point of 2. The findings showed that the Persian version of Mini-Cog have an acceptable sensitivity, specificity, and substantial overall agreement with the AMTS. © 2017, © The Author(s) 2017