Dispersion of waves in FG porous nanoscale plates based on NSGT in thermal environment

Ebrahimi, Farzad,Seyfi, Ali,Dabbagh, Ali Techno-Press 2019 Advances in nano research Vol.7 No.5

In the present study, nonlocal strain gradient theory (NSGT) is developed for wave propagation of functionally graded (FG) nanoscale plate in the thermal environment by considering the porosity effect. $Si_3N_4$ as ceramic phase and SUS304 as metal phase are regarded to be constitutive material of FG nanoplate. The porosity effect is taken into account on the basis of the newly extended method which considers coupling influence between Young's modulus and mass density. The motion relation is derived by applying Hamilton's principle. NSGT is implemented in order to account for small size effect. Wave frequency and phase velocity are obtained by solving the problem via an analytical method. The effects of different parameters such as porosity coefficient, gradient index, wave number, scale factor and temperature change on phase velocity and wave frequency of FG porous nanoplate have been examined and been presented in a group of illustrations.

Synergistic Effect of Cold Plasma Treatment and RGD Peptide Coating on Cell Proliferation over Titanium Surfaces

Ozan Karaman,Seyfi Kelebek,Emine Afra Demirci,Fatma Ibis,Murat Ulu,Utku Kursat Ercan 한국조직공학과 재생의학회 2018 조직공학과 재생의학 Vol.15 No.1

The aim of this study was to investigate the synergistic effect of cold atmospheric plasma (CAP) treatment and RGD peptide coating for enhancing cellular attachment and proliferation over titanium (Ti) surfaces. The surface structure of CAP-treated and RGD peptide-coated Ti discs were characterized by contact angle goniometer and atomic force microscopy. The effect of such surface modification on human bone marrow derived mesenchymal stem cells (hMSCs) adhesion and proliferation was assessed by cell proliferation and DNA content assays. Besides, hMSCs’ adhesion and morphology on surface modified Ti discs were observed via fluorescent and scanning electron microscopy. RGD peptide coating following CAP treatment significantly enhanced cellular adhesion and proliferation among untreated, CAP-treated and RGD peptide-coated Ti discs. The treatment of Ti surfaces with CAP may contribute to improved RGD peptide coating, which enables increased cellular integrations with the Ti surfaces.

Eringen's nonlocal elasticity theory for wave propagation analysis of magneto-electro-elastic nanotubes

Ebrahimi, Farzad,Dehghan, M.,Seyfi, Ali Techno-Press 2019 Advances in nano research Vol.7 No.1

In this article, wave propagation characteristics in magneto-electro-elastic (MEE) nanotube considering shell model is studied in the framework nonlocal theory. To account for the small-scale effects, the Eringen's nonlocal elasticity theory of is applied. Nonlocal governing equations of MEE nanotube have been derived utilizing Hamilton's principle. The results of this investigation have been accredited by comparing them of previous studies. An analytical solution of governing equations is used to obtain phase velocities and wave frequencies. The influences of different parameters, such as different mode, nonlocal parameter, length parameter, geometry, magnetic field and electric field on wave propagation responses of MEE nanotube are expressed in detail.

Wave dispersion characteristics of porous graphene platelet-reinforced composite shells

Farzad Ebrahimi,Ali Seyfi,Ali Dabbagh,Francesco Tornabene 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.71 No.1

Wave propagation analysis of a porous graphene platelet reinforced (GPLR) nanocomposite shell is investigated for the first time. The homogenization of the utilized material is procured by extending the Halpin-Tsai relations for the porous nanocomposite. Both symmetric and asymmetric porosity distributions are regarded in this analysis. The equations of the shell’s motion are derived according to Hamilton’s principle coupled with the kinematic relations of the first-order shear deformation theory of the shells. The obtained governing equations are considered to be solved via an analytical solution which includes two longitudinal and circumferential wave numbers. The accuracy of the presented formulations is examined by comparing the results of this method with those reported by former authors. The simulations reveal a stiffness decrease in the cases which porosity influences are regarded. Also, one must pay attention to the effects of longitudinal wave number on the wave dispersion curves of the nanocomposite structure.

Propofol with and without Midazolam for Diagnostic Upper Gastrointestinal Endoscopies in Children

Ulas Emre Akbulut,Seyfi Kartal,Ufuk Dogan,Gulgun Elif Akcali,Serap Kalayci,Hulya Kirci 대한소아소화기영양학회 2019 Pediatric gastroenterology, hepatology & nutrition Vol.22 No.3

Purpose: Various publications on the use of sedation and anesthesia for diagnostic procedures in children have demonstrated that no ideal agent is available. Although propofol has been widely used for sedation during esophagogastroduodenoscopy in children, adverse events including hypoxia and hypotension, are concerns in propofol-based sedation. Propofol is used in combination with other sedatives in order to reduce potential complications. We aimed to analyze whether the administration of midazolam would improve the safety and efficacy of propofol-based sedation in diagnostic esophagogastroduodenoscopies in children. Methods: We retrospectively reviewed the hospital records of children who underwent diagnostic esophagogastroduodenoscopies during a 30-month period. Demographic characteristics, vital signs, medication dosages, induction times, sedation times, recovery times, and any complications observed, were examined. Results: Baseline characteristics did not differ between the midazolam-propofol and propofol alone groups. No differences were observed between the two groups in terms of induction times, sedation times, recovery times, or the proportion of satisfactory endoscopist responses. No major procedural complications, such as cardiac arrest, apnea, or laryngospasm, occurred in any case. However, minor complications developed in 22 patients (10.7%), 17 (16.2%) in the midazolam-propofol group and five (5.0%) in the propofol alone group ( p =0.010). Conclusion: The sedation protocol with propofol was safe and efficient. The administration of midazolam provided no additional benefit in propofol-based sedation.

Investigating the Effects of Graphene Content and Application Method on Surface Properties of Vinyl Ester/Silica Aerogel Coatings

Kiyoumars Labani Motlagh,Javad Seyfi,Hossein Ali Khonakdar,Saeed Mortazavi 한국고분자학회 2022 Macromolecular Research Vol.30 No.5

Vinyl ester (VE) based nanocomposite coatings, loaded with an optimum content of silica aerogels, were fabricated on aluminum. Different graphene contents (1, 2, and 3% w/w) were applied via one-step and two-step spraying methods. Surface properties exhibited pronounced changes for the two-step coatings but remained nearly unchanged for the one-step coatings. Graphene was localized in the bulk of one-step coatings whereas the two-step method led to the aggregation of graphene nanoplatelets on the coating surface. Depending on the graphene content, small stacks (2 μm) to large agglomerations (20 μm) were detected on the surface of two-step coatings. The water contact angle was essentially increased from 61° for the pure VE coating to 96° and 115° upon the incorporation of silica aerogel and induction of an individual graphene layer, respectively. Such enhanced hydrophobicity was the major reason for the improved corrosion protection properties as found by Tafel polarization plots. The maximum protection efficiency was obtained for the two-step coating loaded by 2% graphene (η=99.5%). In conclusion, vinyl ester resin was found to be a great candidate for applications where high-performance coatings with improved corrosion resistance are needed. Moreover, the use of graphene, as an individual layer on the coating surface, and the utilization of silica aerogel, as a corrosion protective additive, were demonstrated to be a promising approach in real-life corrosion protection applications.

Propofol with and without Midazolam for Diagnostic Upper Gastrointestinal Endoscopies in Children

Akbulut, Ulas Emre,Kartal, Seyfi,Dogan, Ufuk,Akcali, Gulgun Elif,Kalayci, Serap,Kirci, Hulya The Korean Society of Pediatric Gastroenterology 2019 Pediatric gastroenterology, hepatology & nutrition Vol.22 No.3

Purpose: Various publications on the use of sedation and anesthesia for diagnostic procedures in children have demonstrated that no ideal agent is available. Although propofol has been widely used for sedation during esophagogastroduodenoscopy in children, adverse events including hypoxia and hypotension, are concerns in propofol-based sedation. Propofol is used in combination with other sedatives in order to reduce potential complications. We aimed to analyze whether the administration of midazolam would improve the safety and efficacy of propofol-based sedation in diagnostic esophagogastroduodenoscopies in children. Methods: We retrospectively reviewed the hospital records of children who underwent diagnostic esophagogastroduodenoscopies during a 30-month period. Demographic characteristics, vital signs, medication dosages, induction times, sedation times, recovery times, and any complications observed, were examined. Results: Baseline characteristics did not differ between the midazolam-propofol and propofol alone groups. No differences were observed between the two groups in terms of induction times, sedation times, recovery times, or the proportion of satisfactory endoscopist responses. No major procedural complications, such as cardiac arrest, apnea, or laryngospasm, occurred in any case. However, minor complications developed in 22 patients (10.7%), 17 (16.2%) in the midazolam-propofol group and five (5.0%) in the propofol alone group (p=0.010). Conclusion: The sedation protocol with propofol was safe and efficient. The administration of midazolam provided no additional benefit in propofol-based sedation.

Assessment of Surface, Structural, and Viscoelastic Properties of Immiscible Polylactic Acid/Polyvinylidene Fluoride Blends

Ali Hadian Rasanani,Babak Kaffashi,Shervin Ahmadi,Javad Seyfi 한국고분자학회 2022 Macromolecular Research Vol.30 No.5

In this study, polylactic acid (PLA)/polyvinylidene fluoride (PVDF) blends were fabricated via solution casting. To eliminate the adverse effect of moistureinduced phase separation, the samples were dried at 60℃. The accelerated drying also reduced the phase separation between the blend components leading to a smaller size of the dispersed phase, i.e., increased interfacial area. Morphology results revealed that, in contrast to PVDF, PLA exhibits a more uniform distribution once used as the dispersed phase. The ratio of β to α crystals in PVDF was increased upon the introduction of PLA. On the other hand, the crystallized PVDF domains improved the PLA crystallinity. Rheological analysis indicated that the viscoelastic response of the 50/ 50 blend was governed by the PVDF phase, which agreed with the fact that PVDF became the matrix phase in that composition. The samples with PVDF as the matrix exhibited a shear-thinning behavior instead of the partial Newtonian behavior of blends with PLA as the matrix. The dynamic mechanical analysis results, further proved our claims from rheological measurements. The damping curves suggested that PVDF as the dispersed phase caused a higher restricting effect on the macromolecular motions, attributed to its dispersion quality. The wettability results showed an increasing trend in the hydrophobicity as the PVDF content increased in the blends. Due to the enhanced β phase content and improved compatibility, PLA/PVDF blends with 30/70 and 50/ 50 compositions show a promising potential to be used in piezoelectric devices.