A. Salimi | Islamic Azad University, Najafabad Branch (original) (raw)
Papers by A. Salimi
Sleep Medicine, 2015
Objective: The aim of this study was to evaluate whether high-frequency heart rate variability (H... more Objective: The aim of this study was to evaluate whether high-frequency heart rate variability (HF-HRV) during waking restfulness and during worry predicts increases in sleep disturbances in response to a stressful life event.
Frontiers in Human Neuroscience, 2015
Background and Aim: Predisposing factors place certain individuals at higher risk for insomnia, e... more Background and Aim: Predisposing factors place certain individuals at higher risk for insomnia, especially in the presence of precipitating conditions such as stressful life events. Sleep spindles have been shown to play an important role in the preservation of sleep continuity. Lower spindle density might thus constitute an objective predisposing factor for sleep reactivity to stress. The aim of this study was therefore to evaluate the relationship between baseline sleep spindle density and the prospective change in insomnia symptoms in response to a standardized academic stressor.
Polymer Testing, 2003
Poly vinylidene fluoride (PVDF) is a semi-crystalline polymer which shows polymorphism and is com... more Poly vinylidene fluoride (PVDF) is a semi-crystalline polymer which shows polymorphism and is commonly crystallized in non-polar crystalline a-phase. It has found various applications during the last decades and the most important applications lies in its pyro-and piezoelectric properties. The b-phase content is of prime importance in these applications so that increasing b-phase content of the polymer has always been of great concern in this field. Calorimetric studies and FTIR spectra show the appearance of b-phase in compression molded films of two different grades of PVDF resin. b-phase formation is more evident in stretched films by a transformation mechanism of a to b-phase via the formation of a necking region during stretching. By using FTIR techniques, a maximum content of 74% for bphase was calculated. This was achieved during stretching at 90°C and for a stretch ratio between 4.5 and 5. FTIR spectra offer a precise method for detecting the variations of b-phase in polymer films.
Journal of Polymer Science Part B: Polymer Physics, 2004
The supramolecular crystal structure in poly(vinylidene fluoride) (PVDF) solution-cast films is s... more The supramolecular crystal structure in poly(vinylidene fluoride) (PVDF) solution-cast films is studied through changing crystallization conditions in two solvents of different structures and polarities. The crystalline-state chain conformations of isothermally solution-crystallized PVDF in N, N-dimethylacetamide (DMAc), and cyclohexanone are studied through the specific FTIR absorption bands of ␣, , and ␥ phase crystals. There are no changes in the FTIR spectra of cyclohexanone solution-crystallized films in the temperature range of 50 -120°C. In the case of DMAc solutioncrystallized films, low temperature crystallization mainly results in formation of trans states ( and ␥ phases), whereas at higher temperatures gauche states become more populated (␣ phase). This is due to the variations in solvent polarity and ability to induce a specific conformation in PVDF chains, through the changes in chain coil dimensions. This indicates that in spite of cyclohexanone solutions, the intermolecular interactions between PVDF and DMAc are temperature-sensitive and more important in stabilizing conformations of PVDF in crystalline phase than temperature dependence of PVDF chain end-to-end distance Ͻr 2 Ͼ. The high-resolution 19 F NMR spectroscopy also showed little displacement in PVDF characteristic chemical shifts probably due to changes in PVDF chain conformation resulting from temperature variations. Upon uniaxial stretching of the prepared films under certain conditions, contribution of trans state becomes more prominent, especially for the originally higher ␣ phase-containing films. Due to formation of some kink bands during film stretching and phase transformation, ␣ phase absorption bands are still present in infrared spectra. Besides, uniaxial stretching greatly enhances piezoelectric properties of the films, maybe due to formation of oriented  phase crystals, which are of more uniform distribution of dipole moments.
Journal of Applied Polymer Science, 2009
Thermooxidation of polypropylene wax was investigated in the molten state under an air-flowing at... more Thermooxidation of polypropylene wax was investigated in the molten state under an air-flowing atmosphere. Calorimetric measurements were performed to investigate the effect of the inclusion of 1-dodecanol as an efficient primary alcohol and to reveal the typical outlines of thermooxidation, that is, the induction time and oxidation rate. The same parameters were obtained and compared on the basis of the Fourier transform infrared (FTIR) peaks of major oxidation products, such as ketones and hydroxyl groups. The results showed that 1-dodecanol caused a change in the shape of the calorimetric thermogram and also yielded oxidized products with more clarity in color. With the Arrhenius equation, the apparent activation energy was calculated on the basis of the induction time and oxidation rate for carbonyl and hydroxyl groups individually. The obtained apparent activation energy was in agreement with the proposed mechanism based on bimolecular hydroperoxide decomposition involving dodecanol. With FTIR spectroscopy, no changes in the chain helical conformation or double-bond concentration were observed during oxidation up to 500 min. An acid value of up to 6 mg of KOH per gram was obtained at this time.
Journal of Adhesion Science and Technology, 2010
International Journal of Adhesion and Adhesives, 2014
ABSTRACT The effect of acrylic acid deposition in the plasma-treated polypropylene surface was in... more ABSTRACT The effect of acrylic acid deposition in the plasma-treated polypropylene surface was investigated on the surface adhesion properties. The PP sheets were examined by low frequency LF plasma treatments of the oxygen and argon gas discharge individually followed by acrylic acid dipping. The PP surface topography and hydrophilicity were characterized using surface energy measurement, attenuated total reflection spectroscopy ATR and the atomic force microscopy AFM. An evident improvement in surface energy and the coating adhesion was attributed to the creation of polar groups on PP surface in oxygen and argon plasma treatments. In comparison with argon gas plasma, the AFM images of oxygen plasma-treated specimen revealed the peak and valley structure on the PP surface. The deposition of the plasma-treated surfaces into different acrylic acid solutions resulted to surface water repellency and smoothness. Based on the AFM images, the roughness profile of the plasma treated surface changed by the concentration of acrylic acid solution. The lower surface hydrophilicity may be due to acrylic acid effect in dissolving and then removing off the formed polar groups on PP surface. However, the scanning electron microscopy SEM showed distinct regions of acrylic acid grafting on PP surface. Then, the surface adhesion properties were evaluated in pull-off adhesion test after dipping the modified sheets into an acrylic–urethane coating. The adhesion test indicated for the higher adhesion strength in oxygen plasma treatment than argon treatment and an adverse effect of acrylic acid deposition. The addition of aqueous solution of sodium hydroxide into the acrylic acid solution improved the efficiency of acrylic acid grafting on the plasma-treated PP surface. The results of ATR, water contact angle and the pull-off adhesion test showed increasing degree of acrylic acid grafting on PP surface.
Polymer Testing, 2003
Poly vinylidene fluoride (PVDF) is a semi-crystalline polymer which shows polymorphism and is com... more Poly vinylidene fluoride (PVDF) is a semi-crystalline polymer which shows polymorphism and is commonly crystallized in non-polar crystalline α-phase. It has found various applications during the last decades and the most important applications lies in its pyro-...
AIChE Journal, 1996
... It only requires a somewhat larger memory usage than the method of characteristics ... In the... more ... It only requires a somewhat larger memory usage than the method of characteristics ... In the hypothesis that the extraction time is much larger than the residence time (Vpe/W) it is ... Modeling Results and Discussion A value of the partition factor of essential oil between phases (k,) is ...
2006 International Conference on Power System Technology, 2006
ABSTRACT
Sleep Medicine, 2015
Objective: The aim of this study was to evaluate whether high-frequency heart rate variability (H... more Objective: The aim of this study was to evaluate whether high-frequency heart rate variability (HF-HRV) during waking restfulness and during worry predicts increases in sleep disturbances in response to a stressful life event.
Frontiers in Human Neuroscience, 2015
Background and Aim: Predisposing factors place certain individuals at higher risk for insomnia, e... more Background and Aim: Predisposing factors place certain individuals at higher risk for insomnia, especially in the presence of precipitating conditions such as stressful life events. Sleep spindles have been shown to play an important role in the preservation of sleep continuity. Lower spindle density might thus constitute an objective predisposing factor for sleep reactivity to stress. The aim of this study was therefore to evaluate the relationship between baseline sleep spindle density and the prospective change in insomnia symptoms in response to a standardized academic stressor.
Polymer Testing, 2003
Poly vinylidene fluoride (PVDF) is a semi-crystalline polymer which shows polymorphism and is com... more Poly vinylidene fluoride (PVDF) is a semi-crystalline polymer which shows polymorphism and is commonly crystallized in non-polar crystalline a-phase. It has found various applications during the last decades and the most important applications lies in its pyro-and piezoelectric properties. The b-phase content is of prime importance in these applications so that increasing b-phase content of the polymer has always been of great concern in this field. Calorimetric studies and FTIR spectra show the appearance of b-phase in compression molded films of two different grades of PVDF resin. b-phase formation is more evident in stretched films by a transformation mechanism of a to b-phase via the formation of a necking region during stretching. By using FTIR techniques, a maximum content of 74% for bphase was calculated. This was achieved during stretching at 90°C and for a stretch ratio between 4.5 and 5. FTIR spectra offer a precise method for detecting the variations of b-phase in polymer films.
Journal of Polymer Science Part B: Polymer Physics, 2004
The supramolecular crystal structure in poly(vinylidene fluoride) (PVDF) solution-cast films is s... more The supramolecular crystal structure in poly(vinylidene fluoride) (PVDF) solution-cast films is studied through changing crystallization conditions in two solvents of different structures and polarities. The crystalline-state chain conformations of isothermally solution-crystallized PVDF in N, N-dimethylacetamide (DMAc), and cyclohexanone are studied through the specific FTIR absorption bands of ␣, , and ␥ phase crystals. There are no changes in the FTIR spectra of cyclohexanone solution-crystallized films in the temperature range of 50 -120°C. In the case of DMAc solutioncrystallized films, low temperature crystallization mainly results in formation of trans states ( and ␥ phases), whereas at higher temperatures gauche states become more populated (␣ phase). This is due to the variations in solvent polarity and ability to induce a specific conformation in PVDF chains, through the changes in chain coil dimensions. This indicates that in spite of cyclohexanone solutions, the intermolecular interactions between PVDF and DMAc are temperature-sensitive and more important in stabilizing conformations of PVDF in crystalline phase than temperature dependence of PVDF chain end-to-end distance Ͻr 2 Ͼ. The high-resolution 19 F NMR spectroscopy also showed little displacement in PVDF characteristic chemical shifts probably due to changes in PVDF chain conformation resulting from temperature variations. Upon uniaxial stretching of the prepared films under certain conditions, contribution of trans state becomes more prominent, especially for the originally higher ␣ phase-containing films. Due to formation of some kink bands during film stretching and phase transformation, ␣ phase absorption bands are still present in infrared spectra. Besides, uniaxial stretching greatly enhances piezoelectric properties of the films, maybe due to formation of oriented  phase crystals, which are of more uniform distribution of dipole moments.
Journal of Applied Polymer Science, 2009
Thermooxidation of polypropylene wax was investigated in the molten state under an air-flowing at... more Thermooxidation of polypropylene wax was investigated in the molten state under an air-flowing atmosphere. Calorimetric measurements were performed to investigate the effect of the inclusion of 1-dodecanol as an efficient primary alcohol and to reveal the typical outlines of thermooxidation, that is, the induction time and oxidation rate. The same parameters were obtained and compared on the basis of the Fourier transform infrared (FTIR) peaks of major oxidation products, such as ketones and hydroxyl groups. The results showed that 1-dodecanol caused a change in the shape of the calorimetric thermogram and also yielded oxidized products with more clarity in color. With the Arrhenius equation, the apparent activation energy was calculated on the basis of the induction time and oxidation rate for carbonyl and hydroxyl groups individually. The obtained apparent activation energy was in agreement with the proposed mechanism based on bimolecular hydroperoxide decomposition involving dodecanol. With FTIR spectroscopy, no changes in the chain helical conformation or double-bond concentration were observed during oxidation up to 500 min. An acid value of up to 6 mg of KOH per gram was obtained at this time.
Journal of Adhesion Science and Technology, 2010
International Journal of Adhesion and Adhesives, 2014
ABSTRACT The effect of acrylic acid deposition in the plasma-treated polypropylene surface was in... more ABSTRACT The effect of acrylic acid deposition in the plasma-treated polypropylene surface was investigated on the surface adhesion properties. The PP sheets were examined by low frequency LF plasma treatments of the oxygen and argon gas discharge individually followed by acrylic acid dipping. The PP surface topography and hydrophilicity were characterized using surface energy measurement, attenuated total reflection spectroscopy ATR and the atomic force microscopy AFM. An evident improvement in surface energy and the coating adhesion was attributed to the creation of polar groups on PP surface in oxygen and argon plasma treatments. In comparison with argon gas plasma, the AFM images of oxygen plasma-treated specimen revealed the peak and valley structure on the PP surface. The deposition of the plasma-treated surfaces into different acrylic acid solutions resulted to surface water repellency and smoothness. Based on the AFM images, the roughness profile of the plasma treated surface changed by the concentration of acrylic acid solution. The lower surface hydrophilicity may be due to acrylic acid effect in dissolving and then removing off the formed polar groups on PP surface. However, the scanning electron microscopy SEM showed distinct regions of acrylic acid grafting on PP surface. Then, the surface adhesion properties were evaluated in pull-off adhesion test after dipping the modified sheets into an acrylic–urethane coating. The adhesion test indicated for the higher adhesion strength in oxygen plasma treatment than argon treatment and an adverse effect of acrylic acid deposition. The addition of aqueous solution of sodium hydroxide into the acrylic acid solution improved the efficiency of acrylic acid grafting on the plasma-treated PP surface. The results of ATR, water contact angle and the pull-off adhesion test showed increasing degree of acrylic acid grafting on PP surface.
Polymer Testing, 2003
Poly vinylidene fluoride (PVDF) is a semi-crystalline polymer which shows polymorphism and is com... more Poly vinylidene fluoride (PVDF) is a semi-crystalline polymer which shows polymorphism and is commonly crystallized in non-polar crystalline α-phase. It has found various applications during the last decades and the most important applications lies in its pyro-...
AIChE Journal, 1996
... It only requires a somewhat larger memory usage than the method of characteristics ... In the... more ... It only requires a somewhat larger memory usage than the method of characteristics ... In the hypothesis that the extraction time is much larger than the residence time (Vpe/W) it is ... Modeling Results and Discussion A value of the partition factor of essential oil between phases (k,) is ...
2006 International Conference on Power System Technology, 2006
ABSTRACT