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Mahdieh Namvar-Mahboub,Majid Pakizeh 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.2
Separation performance of polyamide composite membranes is affected by several parameters during formationof thin upper layer via interfacial polymerization. We investigated the effect of various polyamide synthesisconditions on the performance of organic solvent resistant polyamide composite membranes through the model equationsdesigned by 2-level fractional factorial design. The dewaxing solvent recovery was selected as separation process. Fivefactors were changed in two level includin; TMC concentration (0.05-0.1%), MPD concentration (1-2%), support immersiontime in organic solution (2-4 min), support immersion time in aqueous solution (1-2 min), and curing temperature(70-80 oC). The resultant equations showed 93.48% and 94.82% of the variability (R2adj) in data used to fit oilrejection and permeate flux models, respectively. The analysis of variance revealed that both models were high significant. It was also observed that TMC concentration, MPD concentration and immersion time in TMC have morepronounced effect on the oil rejection and permeate flux than other factors and interactions. Optimal polyamide preparationconditions were obtained using multiple response method for 94% oil rejection as target value. According tothe results, the best value of permeate flux (8.86 l/(m2·h)) was found at TMC concentration of 0.1%, MPD concentrationof 1.94%, immersion time in TMC of 3.88 min, immersion time in MPD of 1.95 min and curing temperature of71.96 oC with desirability factor of 1.
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Neonatal Acute Epidural Hematoma: A Case Report and Literature Review
Arad Iranmehr,Milad Rashidbeygi,Mohammad Namvar,Khadivi Ayda,Ehsan Hoseynzadeh,Abolfazl Payinmahalli 대한신경손상학회 2020 Korean Journal of Neurotrauma Vol.16 No.2
We present a rare case of an acute epidural hematoma (EDH) in a neonate. The EDH was caused by a fall during natural vaginal delivery. The clinical fndings were normal afer fall and the frst ultrasonographic study did not show any hematomas. A computed tomography scan on the second day afer delivery showed an EDH with 20 mm thickness extending through a skull fracture into subgaleal space. We performed a craniotomy and removed the EDH and subgaleal hematoma. Afer the surgery we performed follow-up twice ultrasonographic study for seeking probable hematoma recurrence. The patient was discharged afer postoperative 3 days without any neurological defcits.
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Sub-lattice polarization states in anti-ferroelectrics and their relaxation process
M.M. Vopson,X. Tan,E. Namvar,M. Belusky,S.P. Thompson,V. Kuncser,F. Plazaola,I. Unzueta,C.C. Tang 한국물리학회 2019 Current Applied Physics Vol.19 No.4
We report studies of quasi-remanent polarization states in Pb0.99Nb0.02[(Zr0.57Sn0.43)0.94Ti0.06]0.98O3 (PNZST) anti-ferroelectric ceramics and investigation of their relaxation effects using unique in-situ electrically activated time-resolved Synchrotron X-ray powder diffraction (SXPD) and 119Sn Mössbauer Spectroscopy (MS). The SXPD patterns are consistent with a phase transition from quasi-tetragonal perovskite in 0 V relaxed anti-ferroelectric state to rhombohedral distortion in ferroelectric state under saturating applied voltages of±2 kV. The observed quasi-remanent polarization relaxation processes are due to the fact that tetragonal to rhombohedral distortion does not occur at the applied voltage required to access the quasi-remanent polarization states, and the tetragonal symmetry restored after the removal of the applied electric field is preserved. Since these quasi-remanent polarization states were seen as possibly suitable for memory applications, the implications of this study are that anti-ferroelectrics are more feasible for multi-state dynamic random access memories (DRAM), while their application to non-volatile memories requires development of more sophisticated “read-out” protocols, possibly involving dc electrical biasing.
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Bahram Jalaei,Ayub Valadbeigi,Rasool Panahi,Morteza Hamidi Nahrani,Hossein Namvar Arefi,Maryam Zia,Nastaran Ranjbar 대한청각학회 2019 Journal of Audiology & Otology Vol.23 No.2
Background and Objectives: Mild cognitive impairment (MCI) is a disorder that usually occurs in the elderly, leading to dementia in some progressive cases. The purpose of this study is to examine the utility of central auditory processing tests as early diagnostic tools for identifying the elderly with MCI. Subjects and Methods: This study was conducted on 20 elderly patients with MCI and 20 healthy matched peers. The speech perception ability in a quiet environment and in the presence of background noise and also temporal resolution were assessed by using Speech Perception in Noise (SPIN) and Gap in Noise (GIN) tests, respectively. Results: The results indicated that the ability to understand speech in a quiet environment did not differ significantly between the two groups. However, SPIN at the three signal-tonoise ratios and the temporal resolution scores were significantly different between the two groups (p<0.001). Conclusions: Individuals with MCI appear to have poorer speech comprehension in noise and a lower temporal resolution than those of the same age, but without cognitive defects. Considering the utility of these tests in identifying cognitive problems, we propose that since the GIN test seems to be less influenced by intervening factors, this test can therefore, be a useful tool for the early screening of elderly people with cognitive problems.
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Preparation and characterization of dimethyldichlorosilane modified SiO2/PSf nanocomposite membrane
Majid Pakizeh,Amir Neghad Moghadam,Mohammad Reza Omidkhah,Mahdieh Namvar-Mahboub 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.3
Investigations on nanocomposite membranes imply that these hybrid materials recommend promising newgeneration membranes for gas separation in future. In this study, to investigate the effects of preparation parameters on the morphology and gas transport, various parameters including nanofiller content, surface modification and polymer concentration were considered. Two types of fumed silica nanoparticles (nonmodified and modified) were used to study the surface modification effect on agglomeration, void formation and gas separation properties of prepared membranes. Prepared nanocomposite membranes were characterized by scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and tensile strength techniques. The gas permeabilities of hydrogen, methane, and carbon dioxide through pure PSf and nanocomposites were measured as a function of silica volume fraction, and permeability coefficients were determined using a variable pressure/constant volume experimental setup. Results showed that gas permeabilities increase with silica content, and proper H2/CH4 and H2/CO2selectivities can be achieved with modified type of silica nanoparticles due to inhibition of particle agglomeration and bonding with polymer network. Hydrogen selectivity was improved by using 15 wt% polymer content instead of 9 wt%in preparation of nanocomposite membrane with same silica content. Gas permeation results indicated that increasing of feed pressure from 3 bar to 6 bar has a positive effect on selectivity of H2/CH4 but negligible effect on that of H2/CO2for modified silica/PSf membrane.
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