Coal flotation using a biosurfactant from Pseudomonas aeruginosa as a frother

Mohammad Hassan Fazaelipoor,Hamid Khoshdast,Mohammad Ranjbar 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.5

A biosurfactant-producing bacterial species (Pseudomonas aeruginosa) was grown in a mineral solution with gas oil as the source of carbon and energy. The biosurfactant was recovered from the solution by collecting the foam on the surface and drying. It had critical micelle concentration of 100 ppm. Froth characterization showed that the biosurfactant was superior to methyl isobutyl carbinol (MIBC) in terms of froth height and stability. The biosurfactant was examined in coal flotation as a frother. The combustible matter recovery of 72-79% with 10-15.5% ash content supporting 55-57.5% separation efficiency seemed promising enough to introduce the biosurfactant from Pseudomonas aeruginosa as a new frother.

The Effect of Investment Risk and Macro-Economy Factors on Stock Return in D8 Member States based on a Dynamic Panel Approach

Mohammad Hossein Ranjbar,Nahid Sadeghi,Leila Sadeghi 대한산업공학회 2018 Industrial Engineeering & Management Systems Vol.17 No.3

Stock return, as a production factor, can play an effective role in growth but the problem that can influence the other variables in investment risk economy is the investigation of the causal relationship between the stock return and economic growth. On the other hand, one important factor regarding the economic growth is the attraction of the foreign capitals which is of a particular necessity in the developing countries featuring intermediate income levels for such a reason as the competition for rare resources and this is well indicative of the crucial significance of the causal relationship between the stock return, foreign direct investment and economic growth. The present study aims at investigating the relationship between the stock exchange market’s return rates, investment risks, growth in the formation of domestic gross capital, growth in per capita domestic gross production and growth in the net input rate of foreign direct investment in eight developing countries known as D8 countries during the years from 1990 to 2015. To do so, dynamic panel data approach has been adopted and generalized method of moment (GMM) estimator has been employed to propose a model for the abovementioned five variables. The estimations were evaluated in five separate models and the results indicated that the macroeconomic variables of exert a positive and significant effect on stock return rate as well as a negative effect on the investment risk.

Role of Organizational Climate in Organizational Commitment: The Case of Teaching Hospitals

Mohammad Amin Bahrami,Omid Barati,Malake-sadat Ghoroghchian,Razieh Montazer-alfaraj,Mohammad Ranjbar Ezzatabadi 질병관리본부 2016 Osong Public Health and Research Persptectives Vol.7 No.2

Objective: The commitment of employees is affected by several factors, including factors related to the organizational climate. The aim of this study was to investigate the relationship between organizational commitment of nurses and the organizational climate in hospital settings. Methods: A cross-sectional study was conducted in 2014 at two teaching hospitals in Yazd, Iran. A total of 90 nurses in these hospitals participated. We used stratified random sampling of the nursing population. The required data were gathered using two valid questionnaires: Allen and Meyer’s organizational commitment standard questionnaire and Halpin and Croft’s Organizational Climate Description Questionnaire. Data analysis was done through SPSS 20 statistical software (IBM Corp., Armonk, NY, USA). We used descriptive statistics and Pearson’s correlation coefficient for the data analysis. Results: The findings indicated a positive and significant correlation between organizational commitment and organizational climate (r = 0.269, p = 0.01). There is also a significant positive relationship between avoidance of organizational climate and affective commitment (r = 0.208, p = 0.049) and between focus on production and normative and continuance commitment (r = 0.308, p = 0.003). Conclusion: Improving the organizational climate could be a valuable strategy for improving organizational commitment.

Softening, Hardening, and Precipitation Evolution of the AA6082-T651 Heat-Affected Zone Caused by Thermal Cycles During and After Welding

Mohammad Jula,Reza Dehmolaei,Khalil Ranjbar 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.12

In this study, gas tungsten arc welding (GTAW) was used to weld AA6082-T651 plates using ER5335 and ER4340 fillermetals. Significant softening of the heat-affected zone (HAZ) was observed in the as-welded condition. An attempt wasmade to recover the softening by applying an appropriate heat treatment after welding. The thermal process consisted ofsolution annealing and then aging at 160 °C for 18 h. The HAZ properties were characterized in the as-welded and postweldheat-treated (PWHT) conditions using field emission scanning and high-resolution transmission electron microscopy,microhardness testing, thermal simulation, and differential scanning calorimetry techniques. The HAZ hardness profilerevealed four distinct regions: partially melted zone (PMZ), partial solution, over-aged zone, and partial transformation. APMZ with a hardness of about 90 Vickers was detected adjacent to the fusion line, which had been exposed to a sufficienttemperature to dissolve the Mg2Siphases completely. Accordingly, natural aging increased the hardness of PMZ after welding. The minimum HAZ hardness was found at a distance of about 7–9 mm from the fusion line, where the temperature wasin the range of β-Mg2Si formation and resulted in over-aging. In addition, dislocation density was reduced compared to theas-received base metal. The hardness after PWHT exhibited full recovery and improved to values higher than the as-receivedbase metal. The hardness recovery was attributed to the uniformly distributed fine coherent needle-shaped βꞌꞌ-Mg2Si afterPWHT. There were also coarse Al15(Fe,Mn)3Si2 intermetallic and submicron spherical Mn-rich dispersoids in all conditions.

Preparation and Evaluation of Cross-Linked Chitosan/Silver Sulfide Luminescence Nanocomposites by Using Green Capping Agent Against Some Pathogenic Microbial Strains

Mohammad hasan Moshafi,Mehdi Ranjbar,Neda Hedayatifar 한국고분자학회 2019 Macromolecular Research Vol.27 No.10

In this paper, different silver sulfide (Ag2S) nanoparticles were cross-linked with chitosan, as a biodegradable and bioactive polymer. Chitosan/Ag2S nanocomposites were synthesized for the first time, using multistage distillation, with the micellization-assisted ultrasonic method. The designed nanocomposites system was evaluated, for in vitro efficient antibacterial activity. Various factors, including concentration of surfactants, pulse time, power irradiation, and interaction between these factors, will directly affect different properties of the crosslinked chitosan/Ag2S nanocomposites. Results showed that cross-linked nanopolymer networks are capable of considerably inhibiting growth of antibiotic-resistant Escherichia coli, pseudomonas aeruginosa, and Serratia marcescens as gram-negative bacteria, and Bacillus subtilis and Micrococcus luteus as gram-positive bacteria, between 64 up and 32 μg/mL. Antibacterial activity was conducted against 7 Gram-negative and Gram-positive bacteria using agar well diffusion assay and minimum inhibitory concentration (MIC), was determined. Samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transition electron microscopy (TEM), atomic force microscopy (AFM), Fourier transformed infrared spectrum (FT-IR), thermo-gravimetric analysis (TGA), and dynamic light scattering (DLS).

In vitro Antibacterial Activity and Wound Healing Effects of Achillea millefolium Essential Oil in Rat

Ghasemi Mohammad Reza,Ranjbar Akram,Tamri Pari,Pourmoslemi Shabnam,Nourian Alireza,Dastan Dara 대한약침학회 2023 Journal of pharmacopuncture Vol.26 No.2

Objectives: In this study we aimed to evaluate the in vitro antibacterial activity and wound healing properties of Achillea millefolium essential oil (AMEO) in full-thickness wound model in rat. The antibacterial activity of AMEO was evaluated against Staphylococcus aureus and Pseudomonas aeruginosa using the broth dilution method. Methods: The 2 cm × 2 cm full-thickness excisional wounds were created on the back of animals. Topical therapy was applied twice a day using 1%, 2%, and 3% w/w AMEO ointments, and the measurement of the wounds area was carried out every 3 days, after that the wound closure percentage was calculated in these days. Hydroxyproline content and histopathological evaluation of wound tissue samples were carried out on day 7 and 14 post wounding. Eucerin was used for the treatment of vehicle control group and negative control group received no treatment. Results: Our results revealed the bacteriostatic activity of AMEO against S. aureus and P. aeruginosa. Wound healing activity evaluation of AMEO showed the significant increase (p < 0.05) in the wound closure percentages in rats treated with AMEO 1% and 2% comparing to those of non-treatment group. In addition, hydroxyproline contents of tissue significantly (p < 0.01) increased in AMEO 1% and 2% comparing to non-treatment group. Histopathological evaluations of wound tissue samples on day 7 and 14 demonstrated higher accumulation of collagen fibers, reduction of edema and inflammation and also formation of tissue appendages in 1% and 2% AMEO treated groups in comparison with non-treatment group. Conclusion: The results of this study indicated that AMEO has the potential to be used as a safe and effective wound healing agent.

Effect of Microstructure on the Mechanical Properties and Fracture Toughness of API X65 Pipeline Steel in the Presence of Hydrogen

Meysam Ranjbar,Reza Miresmaeili,Mohammad Reza Naimi‑Jamal,Majid Mirzaei 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.10

This study investigated the influence of microstructure on the mechanical properties and fracture toughness of API X65pipeline steel in the presence of hydrogen. In this study, electrochemical method was used for hydrogen charging and indentationtechnique was applied to obtain the fracture toughness. The results showed that in the presence of hydrogen, elongation(EL%), reduction of area (RA), ductile fracture percentage, and fracture toughness of all microstructures decreased. Themicrostructure of martensite (M) + bainite (B) + ferrite (F), had the highest hydrogen trapping and uptake (Capp) as 8.58 × 10–6 mol cm−3 and the lowest apparent hydrogen diffusivity (Dapp) as 5.68 × 10−10 m2 s−1; thus, the maximum decrements of33% in fracture toughness, 40% in ductile fracture percentage, 47% in RA, and 35% in EL% were observed. However, themicrostructure of ferrite (F) + degenerated perlite (DP) + martensite-austenite micro constituent (M/A), where the lowestvalue of 5.85 × 10–6 mol cm−3 for Cappand the highest value of 8.5 × 10–10 m2 s−1 for Dapphad the minimum decrements as2% in fracture toughness, 10% in ductile fracture percentage, 4% in RA, and 7% in El%. According to the obtained results,depending on the type of microstructures, hydrogen-induced work softening or hardening were observed by decreasing orincreasing the yield stress respectively.

Effects of Herbal combination (Melissa officinalis L. and Nepeta menthoides Boiss. & Buhse) on insomnia severity, anxiety and depression in insomniacs: Randomized placebo controlled trial

Maryam Ranjbar,Ali Firoozabadi,Alireza Salehi,Zahra Ghorbanifar,Mohammad M. Zarshenas,Khosro Sadeghniiat-Haghighi,Hossein Rezaeizadeh 한국한의학연구원 2018 Integrative Medicine Research Vol.7 No.4

Background: Insomnia is a prevalent disorder leading to psychological problems such as anxiety and depression. Methods: This study investigates the effect of a combination of herbs (Melissa officinalis L. and Nepeta menthoides Boiss. & Buhse) on anxiety and depression for insomniacs and on insomnia severity. This study is a double-blind randomized placebo-controlled clinical trial. A total number of 67 participants met the inclusion criteria who were diagnosed as cases of insomnia. The patients were randomized into the herbal treatment or placebo groups. The herbal treatment group received a combination of Melissa officinalis and Nepeta menthoides Boiss. & Buhse. The primary outcomes were insomnia, depression and anxiety. We used per-protocol analysis. Results: The all outcomes of herbal treatment were significantly improved compared with placebo in the ISI, BAI and BDI scores after four weeks’ treatment (p value: 0.008, 0.005 and <0.001 respectively). Conclusion: A combination of Melissa officinalis L. and Nepeta menthoides Boiss. & Buhse may improve insomnia and its comorbid depression and anxiety.

Numerical fluid structural interface analysis in condenser microphone design

Akbar Ranjbar,Mohammad-Ali Saeimi-Sadigh,Bashir Behjat 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.3

Condenser microphones are widely used in electronic and acoustic applications. Although, various mechanical and electro-mechanical methods have been developed to design and analyze these sensors. However, due to the difficulty of fluid-structural-electrical couplings,none of them can introduce a method that consider all parameters of the design together. This research concerns the effects of four main parameters: a) Air gap size; b) Number of holes on the back-plate; c) holes radius size and d) location of the holes in back plate, on the response of the microphones. This analysis have been carried out based on coupled finite element and finite volume method using ANSYS-CFX software to simulate fluid-structure interaction between the diaphragm and air in the air-gap region. By using this method,the effects of the geometric parameters on the response of the microphone have been investigated. Results show that, increasing air gap size, holes radius, and holes number decrease the damping effects of the air between diaphragm and back plate. On the other hand, increasing the distance between the holes has the opposite effect. In addition, results reveal that among these four parameters, increasing the number of holes on back plate is the most efficient method in reducing air-gap damping effects.

Effect of Brace Treatment on Craniovertebral to Lumbopelvic Sagittal Parameters in Adolescents with Idiopathic Scoliosis: A Systematic Review

Ghorbani Faezeh,Ranjbar Hadi,Kamyab Mojtaba,Babaee Taher,Kamali Mohammad,Razavi Hiva,Sharifi Pouya,Janani Leila 대한척추외과학회 2023 Asian Spine Journal Vol.17 No.2

The current study was carried out systematically by conducting a review of the literature. The purpose of this study was to conduct a systematic review of the literature to determine the effects of brace wearing on sagittal parameters in adolescents with idiopathic scoliosis (AIS). In this study, PubMed/MEDLINE (National Library of Medicine), Scopus, Ovid, CINAHL, PEDro, Google Scholar, and the Cochrane Library were accessed and searched using the patient, intervention, comparison, outcome, and study design model. We included studies that looked at the effects of brace treatment on sagittal spinopelvic parameters in AIS patients over the age of 18. The studies were chosen for their cross-sectional, retrospective, or prospective observational designs, and they were published in English. Review articles, case reports, case study designs, and conference abstracts were excluded from consideration. The methodological quality of the remaining articles was assessed using the Newcastle Ottawa Scale. A total of 12 studies were chosen, and 995 participants were evaluated, with 3 (25%) and 9 (75%) having high and moderate quality, respectively. The studies were classified based on the length of follow-up. Long-term, short-term, and immediate effects of brace wearing on sagittal spinopelvic parameters were reported in four, five, and three studies, respectively. The results of nine studies showed a significant decrease in Cobb angle after wearing the brace, which contradicted the findings of the other two. The cervical and sagittal pelvic parameters, thoracic kyphosis (TK), lumbar lordosis (LL), spinopelvic parameters, and sagittal balance were all evaluated in the intended studies, yielding varying results. According to the available literature, wearing a brace flattens the TK and LL. According to this systematic review, brace treatment may affect sagittal spinopelvic parameters in adolescents with AIS, particularly in TK and LL. The cervical and pelvic parameters yielded inconclusive results. This study backs up the idea that brace design and structure can influence sagittal parameter changes. The limitations of this study include different methods of parameter measurement, variations in the brace types and wear time, varying follow-up duration, and differences in participant characteristics.