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Search Results: 1 - 10 of 18411 matches for " Ali Pourakbar Saffar "
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Wettability and Surface Morphology Investigation of RGP Eye Contact Lens Irradiated by 193 nm Excimer Laser  [PDF]
Tayebeh Ariyafar, Ali Pourakbar Saffar, Peyman Tajalli, Habib Tajalli
Open Access Library Journal (OALib Journal) , 2015, DOI: 10.4236/oalib.1101463
Abstract: In this work, Rigid gas permeable (RGP) contact lenses based on Fluoro Silicone Acrylate, were irradiated by using 193 nm ArFexcimer laser, at 1 Hz pulse repetition rate with 75 mJ/pulse energy to improve surface wettability. We investigated the morphology of the ablated area by imaging the surface modification with Atomic force microscopy (AFM) with roughness analysis and Scanning electron microscopy (SEM). Characterization techniques were performed too via contact angle measurement in order to determine the surface wettability and Fourier transform infra-red spectroscopy (FTIR). The morphological appearance of samples reveals the effect of a photochemical and photothermal ablation mechanism. The laser irradiation without changing the chemical bonds has modified the lens surface properties and increased the surface hydrophilicity. Morphological surface changes with laser exposure and the water contact angle decreases as the surface of the fluorosilicone acrylate material is modified.
Surface Modification and Dielectric Response Investigation of Cellulose Acetate Membrane Treated by ArF Excimer Laser  [PDF]
Ali Pourakbar Saffar, Babak Jaleh, Parviz Parvin, Pikul Wanichapichart, Mahdi Farshchi-Tabrizi
Open Access Library Journal (OALib Journal) , 2014, DOI: 10.4236/oalib.1100488
Abstract:

Lasers are used to modify the surface morphology, crystallinity, chemical composition, reactivity and resistivity of polymer surfaces. In this work, several cellulose acetate membranes were exposed by ArF excimer laser, 193 nm, at 2 - 20 UV pulses, with 100 - 350 mJ/pulse energy, at 1 Hz pulse repetition rate. Characterization techniques viz. Fourier transform infrared spectroscopy (FTIR), Contact angle measurement, Scanning electron microscopy (SEM), Atomic force microscopy (AFM) with roughness analysis, Water Flux measurement was exploited to understand the induced changes in the surface properties of the polymer. The contact angle measurement was done here, to determine hydrophilicity of the irradiated polymer at various doses. The frequency dependent dielectric behavior was studied both in reference and irradiated samples in the frequency range from 75 KHz - 30 MHz. Results showed that the morphological surface changes with laser irradiation, and the water contact angle alters as the surface of the membrane is modified.

A Finite Element Study of Crack Behavior for Carbon Na-notube Reinforced Bone Cement  [PDF]
Kaveh PourAkbar Saffar, Ahmad Raeisi Najafi, Manssour H. Moeinzadeh, Leszek J. Sudak
World Journal of Mechanics (WJM) , 2013, DOI: 10.4236/wjm.2013.35A003
Abstract:

Polymethylmethacrylate (PMMA) bone cement is a polymeric material that is widely used as a structural orthopedic material. However, it is not an ideal material for bone grafting due to its fragility. Carbon nanotubes (CNTs) have been introduced in order to reinforce PMMA resulting in a composite material which exhibits improved tensile properties, increased fatigue resistance and fracture toughness. This improvement is potentially due to bridging and arresting cracks as well as absorption of energy. In this study, a two-dimensional finite element model is presented for the fracture analysis of PMMA-CNT composite material. Instead of the classical single fiber model, the present work considers an ensemble of CNTs interacting with a pre-existing crack. Casca is used to produce a two dimensional mesh and the fracture analysis is performed using Franc 2D. The model is subjected to uni-axial loading in the transverse plane and the interaction between the crack and CNTs is evaluated by determining the stress intensity factor in the vicinity of the crack tips. The effects of geometric parameters of the CNTs and the material structural heterogeneity on crack propagation trajectory are investigated. Furthermore, the effects of CNT diameter, wall thickness and elastic mismatch between the matrix and the nanotubes on crack growth are studied. The results illustrate that the CNTs repel cracks during loading as they act as barriers to crack growth. As a result, the incorporation of CNTs into PMMA reduces crack growth but more importantly increases the fracture resistance of bone cement.

Photosonochemical catalytic ring opening of α-epoxyketones
Memarian Hamid R,Saffar-Teluri Ali
Beilstein Journal of Organic Chemistry , 2007, DOI: 10.1186/1860-5397-3-2
Abstract: The combination of ultrasound and photochemical methods has been used for the catalytic ring opening of α-epoxyketones by 1-benzyl-2,4,6-triphenylpyridinium tetrafluoroborate (NBTPT) as photocatalyst in methanol. Sonication of these compounds in the presence of NBTPT did not result in the opening of epoxide ring, but the use of ultrasound increased the rate of photoreaction.
Increasing antibiotic resistance among uropathogens isolated during years 2006-2009: impact on the empirical management
Mohammad-Jafari, Hamid;Saffar, Mohammed Jafar;Nemate, Ibrahim;Khalilian, Hana Saffar Ali-Reza;
International braz j urol , 2012, DOI: 10.1590/S1677-55382012000100004
Abstract: urinary tract infections (uti) are one of the most common infections with an increasing resistance to antimicrobial agents. purpose: empirical initial antibiotic treatment of uti must rely on susceptible data from local studies. materials and methods: retrospective analysis of isolated bacteria from children with utis was performed at the university hospital during years 2006-2009. the findings were compared with data collected in a similar study carried out in 2002- 2003. results: a total of 1439 uropathogens were isolated. escherichia coli (e.coli) was the leading cause, followed by enterobacter, and other gram negative bacilli. it was observed resistance of e.coli to ceftriaxone, cefexime, amikacin, gentamycin, and nalidixic acid; enterobacter to cefexime; and the resistance of gram negative bacilli to gentamicin and cefexime increased significantly. the highest effective antibiotic was imipenem, ciprofloxacin, and amikacin with 96.7%, 95% and 91% sensitivity rates , respectively, followed by ceftriaxone 77.2%, gentamicin 77%, nitrofurantoin 76.4%, nalidixic acid 74.3% and cefexime with 70%. conclusion: the use of nitrofurantoin or nalidixic acid as initial empirical antibacterial therapy for cystitis seems appropriate. for cases of simple febrile uti, the use of initial parenteral therapies with amikacin or ceftriaxone followed by an oral third generation cephalosporin also seemed appropriated, and in cases of severely ill patients or complicated uti, imipenem as monotherapy or, a combination of ceftriaxone with an aminoglycoside, are recommended.
Viral hepatitis and prevention-current status and future prospects
Mohammad Jafar Saffar,Hiva Saffar,Hana Saffar
Journal of Mazandaran University of Medical Sciences , 2008,
Abstract: (Received 12 Aug, 2008; Accepted 3 Dec, 2008) Abstract Viral hepatitis is the most common cause of liver disease in the world. In the past 30 years, highly effective vaccines have become available for two of the five hepatitis viruses, and where implemented, vaccination has become a key component of hepatitis prevention. To provide a current review and critical analysis of the viral hepatitis, A (HAV) and B (HBV) prevention by immunization has been presented in this article.Review of medical articles obtained from Medline 2000 to 2007 and Iran Medix (1377 to 1386) database. There are signitificant differences regarding epidemiology of hepatitis A and B viruses’ infection between countries. A zero prevalence rate was highly correlated with sanitation and socio-economic conditions. Dramatic vaccine-induced declines in the incidence of both hepatitis A and B and have occurred in countries where HAV and HBV vaccines were integrated into universal childhood immunization. Improved sanitation and living conditions leads to a decline in the average HAV zero prevalence rates. Planning for large-scale immunization programs against HAV should involve careful analysis of the cost-benefit and sustainability in different appropriate hepatitis A prevention strategies. Due to the grave impact of universal infant HB vaccination on prevalence of HBV infections, continued universal infant HB vaccination is recommended. Moreover, this is to ensure continued success of hepatitis B immunization. The need for booster doses to preserve vaccine-induced immunity should be evaluated regularly as vaccinated cohort age. J Mazand Univ Med Sci 2008; 18(67): 133-144 (Persian)
Exposure of Satureia hortensis L seeds to magnetic fields: effect on germination, growth characteristics and activity of some enzymes
Pourakbar L.,Hatami S.
Journal of Stress Physiology & Biochemistry , 2012,
Abstract: The objective of the present study investigated on the effects Satureia hortensis L seeds exposure to magnetic fields on seed germination, early growth and enzyme activity, under laboratory conditions Satureia hortensis seeds (dry and wet) were studied after treating with different intensities of magnetic field (0, 25, 50 and 75 mT) and exposure time (0, 30 and 60 min). There were significant effects among treatments for germination percentage, root length, shoot length, seedling dry mass and seedling vigor index in Satureia hortensis seeds under different magnetic intensity. In the germinating seeds enzyme activities of α-amylase, dehydrogenase and protease were significantly higher in treated seeds in contrast to control.
The construction of a short gene by a very fast, modified, and simplified gene synthesis and the analysis of various effects on this synthesis
Hajjari, Mohammadreza;Saffar, Behnaz;
Brazilian Archives of Biology and Technology , 2011, DOI: 10.1590/S1516-89132011000100007
Abstract: we have constructed a short gene with a single step assembly pcr without any additional amplification primers with taq and pfu polymerases. since the taq polymerase is a common and conventional enzyme for pcr reactions, we have analyzed various effects on its efficiency. eventually, we have been able to synthesize the gene in less than 40 minutes by taq polymerase.
Effect of Abiotic Stresses on Histidine kinases Gene Expression in Zea mays L. cv. SC. 704
Javadmanesh, Susan,Rahmani, Fatemeh,Pourakbar, Latifeh
Journal of Stress Physiology & Biochemistry , 2013,
Abstract: UV-B radiation and osmotic stress (like drought and salinity) have a significant effect on physiology, morphology, biochemistry and molecular biology. To cope with such stimuli, plants must be able to effectively sense, respond to and adapt to changes in their biological activities. Hence, signal transduction pathways play important role in response to environmental stimuli. In this study, the expression of three Histidine Kinases including ZmHK1, ZmHK2 and ZmHK3a was studied in maize plants exposed to 8 days drought, salinity and UV-B stresses applying transcript approach. The semi-quantitative RT-PCR analyses of ZmHKs showed up-regulation of ZmHK1 and ZmHK3 agenes after 8 days exposure to applied stresses except salinity in leaves, although, their regulation was more prominent during drought stress. Astonishingly, exposure to these stresses showed down-regulation of all genes in maize roots. However, the ZmHK1 behavior was quite different from two other homologues and showed up-regulation in combined stresses. We suggest that ZmHK1 and ZmHK3a, as cytokinin transmembrane receptors, sense osmolarity changes in cells caused by dehydration. Our data supports the involvement of ZmHK homologues under these stresses in maize and provides a gene expression dynamics during the stress which will be valuable for further studies of the molecular mechanisms of stress tolerance in maize.
Leukotriene inhibition in hamster periodontitis. A histochemical and morphometric study
B. Baroukh,J. L. Saffar
Mediators of Inflammation , 1992, DOI: 10.1155/s0962935192000504
Abstract:
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