Mixed mode I/II fracture criterion to anticipate cracked composite materials based on a reinforced kinked crack along maximum shear stress path

Sadra Shahsavar,Mahdi Fakoor,Filippo Berto 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.39 No.6

In this paper, a fracture criterion for predicting the failure of the cracked composite specimens under mixed mode I/II loading is provided. Various tests performed on composite components reveal that cracks always grow along the fibers in the isotropic media. Using a new material model called reinforcement isotropic solid (RIS) concept, it is possible to extend the isotropic mixed mode fracture criteria into composite materials. In the proposed criterion, maximum shear stress (MSS) theory which is widely used for failure investigation of un-cracked isotropic materials will be extended to composite materials in combination with RIS concept. In the present study, cracks are oriented along the fibers in the isotropic material. It is assumed that at the onset of fracture, crack growth will be in a path where the shear stress has the highest value according to the MSS criterion. Investigating the results of this criterion and comparing with the available experimental data, it is shown that, both the crack propagation path and the moment of crack growth are well predicted. Available mixed mode I/II fracture data of various wood species are used to evaluate and verify the theoretical results.

Catalytic dehydration of glucose to 5-HMF using heterogeneous solid catalysts in a biphasic continuous-flow tubular reactor

Sadra Souzanchi,Laleh Nazari,Kasanneni Tirumala Venkateswara Rao,Zhongshun Yuan,Zhongchao Tan,Chunbao Charles Xu 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.101 No.-

This work aimed to produce 5-hydroxymethylfurfural (5-HMF) from glucose in a biphasic continuousflowtubular reactor with various heterogeneous solid acid catalysts or combined solid acid-base catalysts. Among the catalysts tested, niobium phosphate (NbP) was found to be the most active catalystfor glucose dehydration with a maximum 5-HMF yield of 45% at 150 C. The higher activity of NbPwas attributed to its higher total number of acid sites and BET surface area, as well as the presence of bothLewis acid and Brønsted acid sites. The effects of different operating conditions such as aqueous toorganic (A/O) phase ratio, reaction temperature and feeding flow rate on the activity of some selected catalystswere studied. Reducing A/O ratio by increasing the extracting organic phase flow rate and increasingthe reaction temperature (up to 150 C) were found to positively affect 5-HMF production fromglucose in the presence of NbP. Kinetics study demonstrated that the overall reaction of glucose dehydrationto 5-HMF over the NbP catalyst is a first-order reaction with the reaction rate constants (k) determinedas 0.06, 0.21 and 0.6 min 1 at 110, 130 and 150 C, respectively, and the apparent activationenergy (Ea) calculated to be 77 kJ/mol.

HeLa E-Box Binding Protein, HEB, Inhibits Promoter Activity of the Lysophosphatidic Acid Receptor Gene Lpar1 in Neocortical Neuroblast Cells

김남호,Ali Sadra,박희영,오성민,Jerold Chun,윤정교,허성오 한국분자세포생물학회 2019 Molecules and cells Vol.42 No.2

Lysophosphatidic acid (LPA) is an endogenous lysophospholipid with signaling properties outside of the cell and it signals through specific G protein-coupled receptors, known as LPA1–6. For one of its receptors, LPA1 (gene name Lpar1), details on the cis-acting elements for transcriptional control have not been defined. Using 5′RACE analysis, we report the identification of an alternative transcription start site of mouse Lpar1 and characterize approximately 3,500 bp of non-coding flanking sequence 5′ of mouse Lpar1 gene for promoter activity. Transient transfection of cells derived from mouse neocortical neuroblasts with constructs from the 5′ regions of mouse Lpar1 gene revealed the region between −248 to +225 serving as the basal promoter for Lpar1. This region also lacks a TATA box. For the region between −761 to −248, a negative regulatory element affected the basal expression of Lpar1. This region has three E-box sequences and mutagenesis of these E-boxes, followed by transient expression, demonstrated that two of the E-boxes act as negative modulators of Lpar1. One of these E-box sequences bound the HeLa E-box binding protein (HEB), and modulation of HEB levels in the transfected cells regulated the transcription of the reporter gene. Based on our data, we propose that HEB may be required for a proper regulation of Lpar1 expression in the embryonic neocortical neuroblast cells and to affect its function in both normal brain development and disease settings.

Diagnostic performance of stitched and non-stitched cross-sectional cone-beam computed tomography images of a non-displaced fracture of ovine mandibular bone

Farzane Ostovarrad,Sadra Masali Markiyeh,Zahra Dalili Kajan Korean Academy of Oral and Maxillofacial Radiology 2023 Imaging Science in Dentistry Vol.53 No.-

Purpose: This study assessed the diagnostic performance of stitched and non-stitched cross-sectional cone-beam computed tomography (CBCT) images of non-displaced ovine mandibular fractures. Materials and Methods: In this ex vivo study, non-displaced fractures were artificially created in 10 ovine mandibles (20 hemi-mandibles) using a hammer. The control group comprised 8 hemi-mandibles. The non-displaced fracture lines were oblique or vertical, <0.5 mm wide, 10-20 mm long, and only in the buccal or lingual cortex. Fracture lines in the ramus and posterior mandible were created to be at the interface or borders of the 2 stitched images. CBCT images were obtained from the specimens with an 80 mm×80 mm field of view before and after fracture induction. OnDemand software (Cybermed, Seoul, Korea) was used for stitching the CBCT images. Four observers evaluated 56 (28 stitched and 28 non-stitched) images to detect fracture lines. The diagnostic performance of stitched and non-stitched images was assessed by calculating the area under the receiver operating characteristic curve (AUC). Sensitivity and specificity values were also calculated (alpha=0.05). Results: The AUC was calculated to be 0.862 and 0.825 for the stitched and non-stitched images, respectively (P=0.747). The sensitivity and specificity were 90% and 75% for the non-stitched images and 85% and 87% for the stitched images, respectively. The inter-observer reliability was shown by a Fleiss kappa coefficient of 0.79, indicating good agreement. Conclusion: No significant difference was found in the diagnostic performance of stitched and non-stitched cross-sectional CBCT images of non-displaced fractures of the ovine mandible.

HeLa E-Box Binding Protein, HEB, Inhibits Promoter Activity of the Lysophosphatidic Acid Receptor Gene Lpar1 in Neocortical Neuroblast Cells

Kim, Nam-Ho,Sadra, Ali,Park, Hee-Young,Oh, Sung-Min,Chun, Jerold,Yoon, Jeong Kyo,Huh, Sung-Oh Korean Society for Molecular and Cellular Biology 2019 Molecules and cells Vol.42 No.2

Lysophosphatidic acid (LPA) is an endogenous lysophospholipid with signaling properties outside of the cell and it signals through specific G protein-coupled receptors, known as $LPA_{1-6}$. For one of its receptors, $LPA_1$ (gene name Lpar1), details on the cis-acting elements for transcriptional control have not been defined. Using 5'RACE analysis, we report the identification of an alternative transcription start site of mouse Lpar1 and characterize approximately 3,500 bp of non-coding flanking sequence 5' of mouse Lpar1 gene for promoter activity. Transient transfection of cells derived from mouse neocortical neuroblasts with constructs from the 5' regions of mouse Lpar1 gene revealed the region between -248 to +225 serving as the basal promoter for Lpar1. This region also lacks a TATA box. For the region between -761 to -248, a negative regulatory element affected the basal expression of Lpar1. This region has three E-box sequences and mutagenesis of these E-boxes, followed by transient expression, demonstrated that two of the E-boxes act as negative modulators of Lpar1. One of these E-box sequences bound the HeLa E-box binding protein (HEB), and modulation of HEB levels in the transfected cells regulated the transcription of the reporter gene. Based on our data, we propose that HEB may be required for a proper regulation of Lpar1 expression in the embryonic neocortical neuroblast cells and to affect its function in both normal brain development and disease settings.

Oxyresveratrol activates parallel apoptotic and autophagic cell death pathways in neuroblastoma cells

Rahman, Md.A.,Bishayee, K.,Sadra, A.,Huh, S.O. Elsevier/North-Holland 2017 Biochimica et biophysica acta, General subjects Vol.1861 No.2

Background: Drug resistance from apoptosis is a challenging issue with different cancer types, and there is an interest in identifying other means of inducing cytotoxicity. Here, treatment of neuroblastoma cells with oxyresveratrol (OXYRES), a natural antioxidant, led to dose-dependent cell death and increased autophagic flux along with activation of caspase-dependent apoptosis. Methods: For cell viability, we performed the CCK-8 assay. Protein expression changes were with Western blot and immunocytochemistry. Silencing of proteins was with siRNA. The readouts for cell cycle, mitochondria membrane potential, caspase-3, autophagy and apoptosis were performed with flow cytometry. Results: Phosphorylation of p38 MAPK increased with OXYRES treatment and inhibition of p38 reduced autophagy and cell death from OXYRES. In contrast, PI3K/AKT/mTOR signaling decreased in the target cells with OXYRES and inhibition of PI3K or mTOR enhanced OXYRES-mediated cytotoxicity with increased levels of autophagy. Modulation of either of the apoptosis and autophagy flux pathways affected the extent of cell death by OXYRES, but did not affect the indicators of these pathways with respect to each other. Both pathways were independent of ROS generation or p53 activation. Conclusion: OXYRES led to cell death from autophagy, which was independent of apoptosis induction. The OXYRES effects were due to changes in the activity levels of p38 MAPK and PI3K/AKT/mTOR. General significance: With two independent and parallel pathways for cytotoxicity induction in target cells, this study puts forward a potential utility for OXYRES or the pathways it represents as novel means of inducing cell death in neuroblastoma cells.

Polyether sulfone-graphite nanocomposite for nanofiltration membrane with enhanced separation, antifouling and antibacterial properties

Sayed Mohsen Hosseini,Sima Mohammadianfar,Samaneh Koudzari Farahani,Sadra Solhi 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.1

Mixed matrix polyether sulfone based-graphite nanoparticle nanofiltration membranes were prepared by phase inversion technique. SEM, SOM, 3D surface analysis, water content, water contact angle, tensile strength, salt rejection, water flux, porosity, antifouling measurements as well as antibacterial activity were used in membrane characterization. SOM images showed graphite nanoparticle distribution in the structure of membranes relatively. The cross section SEM showed that incorporation of graphite nanoparticles into the casting solution had significant effect on the appearance structural properties of the membrane. The water flux of modified membranes was higher than the amount for unmodified membrane obviously. Salt rejection also increased from 82% for unmodified membrane to 91.79% for the membrane containing 0.5 wt% graphite nanoparticles. The water content and porosity increased at 0.05 wt% and 0.5 wt% concentration of graphite nanoparticle, and showed decreasing manner at 0.1 wt% and 1 wt% additives ratios. Utilizing 0.05 wt% G-nanoparticles into the polymeric solution made a membrane with smoother and hydrophilic surface that tended to improved anti-fouling properties. The 0.05 wt% G-nanoparticles/PES membrane showed more suitable behavior than other membranes. Moreover, blended membranes showed antibacterial activity against E-coli.