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Search Results: 1 - 10 of 13562 matches for " Mohammad Sadeghi "
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Pectin-Based Biodegradable Hydrogels with Potential Biomedical Applications as Drug Delivery Systems  [PDF]
Mohammad Sadeghi
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2011, DOI: 10.4236/jbnb.2011.21005
Abstract: In this work, synthesis and swelling behavior of a superabsorbent hydrogel based on Pectin (Pc) and polyacrylonitrile (PAN) were investigated. A mechanism for hydrogel formation was proposed and the structure of the product was es-tablished using FTIR spectroscopy. The Pc-poly (sodium acrylate-co-acrylamide) hydrogel exhibited a pH-responsive swelling-deswelling behavior at pH’s 2 and 8. This on-off switching behavior provides the hydrogel with the potential to control delivery of bioactive agents. Release profiles of ibuprofen (IBU), a poor water-soluble drug, from the hydro-gels were studied under both simulated gastric and intestinal pH conditions.
Synthesis of pH-Sensitive Hydrogel Based on Starch-Polyacrylate Superabsorbent  [PDF]
Mohammad Sadeghi, Fatemeh Soleimani
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2012, DOI: 10.4236/jbnb.2012.322038
Abstract: In this article, we synthesize of a novel starch-based superabsorbent hydrogel via graft copolymerization of mixtures of acrylic acid (AA) and 2-Hydroxy ethyl methacrylate (HEMA) onto starch backbones. The polymerization reaction was carried out in an aqueous medium and in the presence of ammonium persulfate (APS) as an initiator and N,N’-methylene bisacrylamide (MBA) as a crosslinker. The hydrogel structures were confirmed by FTIR spectroscopy. Furthermore, the swelling of superabsorbing hydrogels was examined in solutions with pH values ranging between 1 and 13. It showed a reversible pH-responsive behavior at pHs 2 and 8. This on-off switching behavior makes the synthesized hydrogels as an excellent candidate for controlled delivery of bioactive agents. A proposed mechanism for hydrogel formation was suggested and the structure of the product was established using FTIR and SEM spectroscopies.
Effect of Neurofeedback on Visual-Spatial Attention in Male Children with Reading Disabilities: An Event-Related Potential Study  [PDF]
Neda Sadeghi, Mohammad Ali Nazari
Neuroscience & Medicine (NM) , 2015, DOI: 10.4236/nm.2015.62013
Abstract:
Recent studies describe a number of difficulties associated with attention deficit in children with reading disabilities. Information about visual-spatial attention mainly arises from studies using event-related potentials (ERPs) during Posner’s spatial cueing paradigm. This study aims to use neurofeedback with a special protocol for treating children with reading disabilities, and moreo-ver, to evaluate visual-spatial attention ability by means of Posner paradigm task and ERPs. The study was conducted in a single subject design in 20 sessions. Participants were 2 male children, aged between 10 - 12 years old, who completed twelve 30-min neurofeedback sessions. Repeated measurements were performed during the baseline, treatment, and post treatment phases. Results showed some improvement in Posner paradigm parameters (correct response, valid and invalid reaction times). Furthermore, grand average ERPs for both of the participants in each of the four conditions (Valid-right, Invalid-right, Valid-left and Invalid-left) were analyzed. The analysis of P3 component showed a reduction in latency, indicating an improvement in the timing of cognitive processes. In addition, the graphs showed a decrease in amplitude level, which meant easier processing than before.
Paleoceanography and Paleobiogeography Patterns of the Turonian-Campanian Foraminifers from the Abderaz Formation, North Eastern Iran  [PDF]
Meysam Shafiee Ardestani, Mohammad Vahidinia, Abbas Sadeghi
Open Journal of Geology (OJG) , 2013, DOI: 10.4236/ojg.2013.31003
Abstract:

In this research, the Turonian-early Campanian sedimentary succession of the Abderaz Formation with 510 mthick (comprising: light grey shale and marls) was studied in the type section in eastern Kopeh-Dagh basin. The statistical analysis of the morphotype groups of the identified planktonic foraminifers shows that most of them are shallow water forms (SWF) and deep water forms (DWF). The high planktonic to benthic ratio indicates particular oligotrophic conditions and sedimentation in relatively deeper zones of a marine environment. The salinity of sea water during Coniacian was in the minimum level, whereas it reached maximum in Coniacian-Santonian boundary. Comparing Planktonic assemblages from the study formation with those from the Cretaceous biogeographical provinces reflects a close relationship between the identified species and the planktonic forms of the Tethyan provinces.

Evaluation of Unsaturated Layer Effect on Seismic Analysis of Unbraced Sheet Pile Wall  [PDF]
Mohammad Hossein Jahangir, Hadis Soleymani, Saeideh Sadeghi
Open Journal of Marine Science (OJMS) , 2017, DOI: 10.4236/ojms.2017.72022
Abstract: This paper is built upon the previous developments on lateral earth pressure by providing a series of analytical expressions that may be used to evaluate vertical profiles of the effective stress and the corresponding suction stress under steady-state flow conditions. Suction stress profile is modeled for one layer sand near the ground above the water level under hydrostatic conditions. By definition, the absolute magnitude of suction stress depends on both the magnitude of the effective stress parameter and matric suction itself. Thus, by developing the Rankine’s relations in seismic state, the composing method of active and passive surfaces in sides of unbraced sheet pile is examinated and the effects of soil parameter on those surfaces are evaluated by a similar process. The relations described the quantitative evaluation of lateral earth pressure on sheet pile and the effects of unsaturated layer on bending moment and embedded depth of sheet pile in soil.
Experimental and Theoretical Studies on the Effect of Die Temperature on the Quality of the Products in High-Pressure Die-Casting Process
Mohammad Sadeghi,Jafar Mahmoudi
Advances in Materials Science and Engineering , 2012, DOI: 10.1155/2012/434605
Abstract: Die temperature in high-pressure die casting of A380 alloy is optimized by experimental observation and numerical simulation. Ladder frame (one part of the new motor EF7) with a very complicated geometry was chosen as an experimental sample. Die temperature and melt temperature were examined to produce a sound part. Die temperatures at the initial step and the final filling positions were measured and the difference between these values was calculated. ProCAST software was used to simulate the fluid flow and solidification step of the part, and the results were verified by experimental measurements. It is shown that the proper die temperature for this alloy is above 200°C. 1. Introduction High-pressure die-casting (HPDC) process has been widely used to manufacture a large variety of products with high dimensional accuracy and productivities. It has a much faster production rate in comparison to other methods and it is an economical and efficient method for producing components with low surface roughness and high-dimensional accuracy. All major aluminum automotive components can be processed with this technology [1–7]. In this process, the metal is injected into the die at high speeds (30–100?m/s and typically 40–60?m/s for aluminum alloys [2]) and under high pressure through complex gate and runner systems [3]. Although HPDC has a considerably higher speed than other metal forming processes, due to complexity of the process and the number of variables, optimization of the process is essential. In particular, there are issues related to control of die temperature, solidification of the components, quality control of the castings, and more important, development or use of a coherent and integrated system. The mechanical properties of a die-cast product are principally related to the die temperature, the metal velocity at the gate, and the applied casting pressure [4]. Combination of die temperature, fluidity of the molten metal, geometrical complexity of the parts, and cooling rate during die casting affect the integrity of a cast component. If these parameters are not adequately controlled, various defects within the finished component will be expected [6, 7]. Thermal profile of the die during operation is another important factor in the production of high-quality components. Too high temperature of the die will lead to longer solidification which consequently prolongs the cycle time, while a cold die will contribute to a number of surface defects [3, 8, 9]. Kermanpur et al. [10] used FLOW-3D software to simulate the filling and solidification sequences
Crosslinked Graft Copolymer of Methacrylic Acid and Gelatin as a Novel Hydrogel with pH-Responsiveness Properties
Mohammad Sadeghi,Behrouz Heidari
Materials , 2011, DOI: 10.3390/ma4030543
Abstract: In this paper, a novel gelatin-based hydrogel was synthesized through crosslinking graft copolymerization of methacrylic acid (MAA) onto gelatin, using ammonium persulfate (APS) as a free radical initiator in the presence of methylenebisacrylamide (MBA) as a crosslinker. A proposed mechanism for hydrogel formation was suggested and the structure of the product was established using FTIR spectroscopy and gravimetric analysis of the products. Moreover, morphology of the samples was examined by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA/DTG). The effect of reaction variables such as concentration of APS and MBA were systematically optimized to achieve a hydrogel with swelling capacity as high as possible. The gelatin-g-PMAA hydrogel exhibited a pH-responsiveness character so that a swelling-deswelling pulsatile behavior was recorded at pHs 2 and 8. This on-off switching behavior makes the hydrogel as a good candidate for controlled delivery of bioactive agents.
STUDIES ON GRAFT COPOLYMERIZATION OF 2-HYDROXYETHYLMETHACRYLATE ONTO KAPPA-CARRAGEENAN INITIATED BY CERIC AMMONIUM NITRATE
SADEGHI,MOHAMMAD; HOSSEINZADEH,HOSSEIN;
Journal of the Chilean Chemical Society , 2010, DOI: 10.4067/S0717-97072010000400019
Abstract: the polysaccharide, kappa-carrageenan (kc), has been chemically modified by graft copolymerization of 2-hydroxyethylmethacrylate (hema) in an aqueous medium using ceric ammonium nitrate (can) as an initiator under argon atmosphere. a plausible reaction mechanism of grafting has been suggested. evidence of grafting was obtained by comparison of ftir spectra of kc and homopolymer-free kc-g-poly(hema) as well as solubility characteristics and gravimetric analysis of the products. the optimum reaction conditions affording maximum grafting ratio and add-on value have been determined. the grafting parameters have been found to increase with increasing in kc, can, and hema concentrations as well as polymerization time and temperature, up to a certain value, but these parameters decrease on further increasing in reaction conditions.
STUDIES ON GRAFT COPOLYMERIZATION OF 2-HYDROXYETHYLMETHACRYLATE ONTO KAPPA-CARRAGEENAN INITIATED BY CERIC AMMONIUM NITRATE
MOHAMMAD SADEGHI,HOSSEIN HOSSEINZADEH
Journal of the Chilean Chemical Society , 2010,
Abstract: The polysaccharide, kappa-carrageenan (kC), has been chemically modified by graft copolymerization of 2-hydroxyethylmethacrylate (HEMA) in an aqueous medium using ceric ammonium nitrate (CAN) as an initiator under argon atmosphere. A plausible reaction mechanism of grafting has been suggested. Evidence of grafting was obtained by comparison of FTIR spectra of kC and homopolymer-free kC-g-poly(HEMA) as well as solubility characteristics and gravimetric analysis of the products. The optimum reaction conditions affording maximum grafting ratio and add-on value have been determined. The grafting parameters have been found to increase with increasing in kC, CAN, and HEMA concentrations as well as polymerization time and temperature, up to a certain value, but these parameters decrease on further increasing in reaction conditions.
Depression among Resident Doctors in Tehran, Iran
Majid Sadeghi,Mohammad Navidi,Amir Ebrahim Sadeghi
Iranian Journal of Psychiatry , 2007,
Abstract: : "nIn developing countries, little evidence is available on the mental health status of health care providers, especially doctors. Therefore, the aim of this study is to obtain an estimation on the prevalence of depression amongresident doctors of medical universities in Tehran, Iran. "n "n "nMethod: "nThe study population consisted of 2251 resident doctors who worked in the hospitals of 3 medical universities located in Tehran.Beck Depression Inventory (BDI) was used as the main instrument of thisresearch "n "n "nResults: "nThe response rate was 68.28%.31.2% of the total study population had symptoms of depression (26% of the males and 39% of the females).Symptoms of depression were 2.3 times more frequent in females. Mostdepressed physicians did not have a history of psychiatric visit or treatment.Conclusion: "n "nThis study demonstrates that depression is common among Iranian residents(particularly in females); however, most of them do not seek any treatment. This may lead to serious impacts on health behavior of the community in general.Moreover, depression may seriously affect physicians' professional function.
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