Showing 257 results for Gas
Volume 0, Issue 0 (1-2024)
Abstract
Oil is one of the significant factors in promoting economic activities. Oil provides a considerable part of the government's revenue sources. The price of oil has always been fluctuating over the years for various reasons including political, social, and economic developments in countries. Since the price of oil affects different sectors of economy including the agricultural sector through the government budget and the revenue sources of the government, this study investigated the effect of positive and negative fluctuations in OPEC oil prices on the value added of the agricultural sector during 1990-2019. The new GAS method was used for estimating the OPEC oil price fluctuations and the NARDL method was used for estimating the long-term relationships between positive and negative OPEC oil price fluctuations on the value added of the agricultural sector. In addition to OPEC oil price fluctuations, other independent variables such as the consumer price index, employment in the agricultural sector, and the degree of trade openness were examined in the model. Based on the obtained results, the positive and negative fluctuations of OPEC oil prices in the long term had a negative effect on the value added of the agricultural sector. Furthermore, the degree of trade openness had a positive effect on the value added of the agricultural sector in a long term. results indicate that oil income is one of the most important issues that decline value added of agriculture sector and government should control this negative relation to develop agriculture as a vital sector of economic.
Volume 0, Issue 0 (1-2024)
Abstract
The insight of storage root formation mechanism under different soil compaction which is one of the vital factors affecting storage rot yield is crucial for the high and stable storage yield of sweet potato (Ipomoea batatas L.). Photosynthetic characters has been proved to be determining factor of crop yield. So field experiments were conducted with 2 varieties in control, loose, and compacted soil conditions, canopy apparent photosynthesis, gas exchange parameters and chlorophyll fluorescence parameters of the functional leaves, storage root yield were determined, and the relationship between yield and photosynthetic characters was studied as well. The results indicated compared to the control, the storage root yield was significantly increased in loose soil with the average increase of 27.03%~38.74%, but decreased in compacted soil with the average reduction of 17.87%~15.92%. The CAP got the similar change law. Loose soil also improved gas exchange parameters of functional leaves, overall performance and donor/recipient side properties of PSII, the reverse was found in compacted soil. The CAP was significantly positively correlated with storage root yield (r= 0.99, P<0.05) and single storage root weight (r= 0.90, P<0.05). As per statistical path analysis, the net photosynthetic rate (Pn) had the most total effect and higher direct effect on increasing CAP. That is, reduce the soil compaction increased Pn of functional leaves, brought higher CAP, resulted in high storage root yield.
Volume 0, Issue 0 (1-2024)
Abstract
Yogurt is a widely consumed fermented product celebrated for nutritional benefits and distinctive aroma, influenced by factors such as the type of probiotic bacteria, incubation methods, and the used milk type. Common bacteria in yogurt production include Lactobacillus bulgaricus and Streptococcus thermophilus. Aroma is crucial for consumers’ acceptance and varies according to the compounds formed during fermentation. Therefore, this study aimed to investigate the effect of different probiotic bacteria on aroma of yogurt through a unique incubation process. Probiotic bacteria examined were Lactobacillus, Streptococcus, and Bifidobacterium. Additionally, yogurt production process included sterilizing skim milk, introducing bacterial cultures, and incubating at specific temperatures. Aroma components of yogurt were analyzed using Gas Chromatography and Mass Spectrometry. The result showed that yogurt comprised various aroma compounds classified into four categories, namely acids, alcohols, ketones, and aldehydes. The dominant acid components found were acetic, octanoic, decanoic, and dodecanoic acids. Among the components, alcohol affected aroma despite being present in minimal quantities. Ketones such as acetoin and diacetyl were identified along with aldehydes including octadecanal and dodecanal in yogurt. This study provided valuable insights into the effect of probiotic bacteria on aroma profile of yogurt, assisting manufacturers in refining production processes to prepare product appealing to consumers.
Volume 2, Issue 2 (10-2014)
Abstract
Sohrab Sepehri and Abbas Kiarostami are artists who could express their thought in the form of another language using the myths and symbols. The most important considerations in their works are neutral symbols. In this paper, the authors tried to review the symbolic nature using comparative approach and Gaston Bachelard's theory. We analyzed Hasht Keteb and Kiarostami's movies, and found that the mythical structure and contents briefly express differences and commonalities in their works. The most applicant natural symbols widely used in these works consist water, air, soil and plants. The results of our study showed that Water and soil, in various forms, involve a dual role in poetry and cinema: both as a symbol of death and resurrection, and creation. Wind is the symbol of divine origin and evolution. Also it indicates the death and destruction. Plant is the symbol of cosmic tree. Symbolic imagery and mythical nature, in Kiarostami's films and Sepehri's poems, can affect the poetic spirit of two artists, which is result of thier familiarity with Eastern mysticism and also for being influenced by painting and photography skills.
Volume 2, Issue 2 (9-2018)
Abstract
Methyl Tert-butyl Ether(MTBE) has been used as a booster in gasoline octane numbers in many countries, but after a short time due to the high absorption in water and the possibility of entry into groundwater, its use in developed countries is prohibited. In this work, for the first time, to reduce the adverse environmental effects, MTBE was encapsulated, and release control was considered. For this purpose, the inverse mini-emulsion polymerization of monomer methylmethacrylate(MMA) was performed in the presence of MTBE and in the cyclohexane medium by oil/water/oil. Poly methyl methacrylate/MTBE nanocapsules were synthesized in 0.5, 1, 2 ratios of MTBE to methyl methacrylate (R = MTBE / MMA).
The effect of changing R values on conversion polymerization, on encapsulation efficiency of MTBE and on the morphology of capsules was investigated. For this purpose, TGA and TEM were used. Changing the R ratio from 0.5 to 2 allowed the capsule to be controlled in the range of 50-500 nm. The start of the MTBE degradation range of 130 ° C increased to 250 ° C due to the presence of the MTBE inside the capsule, and it was possible to start controlling the release of the nucleus by heating and starting at a temperature of 250 ° C. By addition of 1.5% of the capsules to the gasoline, the octane number increased by 5 units.
According to the results inverse mini-emulsion polymerization is a suitable method for encapsulating and reducing the environmental effects of MTBE by limiting its contact with the environment.
Volume 2, Issue 4 (3-2014)
Abstract
The effects of valerian, Valerian officinalis, and clove, Eugenia caryophylla, extracts as anesthetic chemicals were investigated on Panga siussutchi (12.95±0.92 mm, 16.85 ± 3.52 g). The fish were divided in 6 groups, each including 5 individuals and exposed to various concentrations (2, 3 and 4 g/lit) of clove and/or valerian extract. The mean time to induce sedition, the mean time to return and the mean number of opercular gill pulses to sedate and recover were measured. For both groups, the mean time to sedation was decreased by increasing the dose of the extract. In general, the mean time to onset of anesthesia for clove group was significantly lower than valerian. The mean number of opercular gill pulses during the sedation time was not significantly changed between different dose of clove, while it declined significantly by elevating the valerian doses (p<0.05). There was no mortality in both groups. Although V. officinalis extract could cause sedation in the fish, it needed relatively longer time to affect than clove, so it may not be a useful compound for sedation in P. siussutchi.
Volume 3, Issue 2 (10-2015)
Abstract
One of the most important characteristics of Iranian paintings is their connection and unity with Persian literature, which resulted in the formation of common language and similar subjects in these two art fields. However, since the Zands Dynasty, especially their late era, a certain divergence occurred between painting and poetry due to the weakness of literature and the fact that the painters were more influenced by the European art. While focusing on the benchmarks of the poems of the return era, and the Royal Court portrait paintings, this study strives to examine the common aesthetic connection between these two fields of art through performing historical, descriptive, analytical and comparative study, and achieve the response to this question that Which factors were effective in the formation and flourishing of the literature and painting during the reign of Fath Ali Shah Qajar and how and to what extent are their common aesthetic links? The painting and poetry of this era managed to achieve flourishing thanks to the supports granted by an art-lover king, i.e. Fath Ali Shah Qajar. Due to the policies of the Shah during his 37-year reign against the arts, a suitable basis was provided for the alignment of these two fields of art in a new and different manner (notwithstanding the occurred divergence) so that the painters act independently in choosing their subjects, and do not refer to poetry so often, while trying to take benefit from poetical descriptions and literature aesthetic criteria, and represent the same through a human-oriented vision.
Volume 3, Issue 2 (6-2017)
Abstract
The Evanioidea wasp fauna of Iran is reviewed. The study is based on literature as well as collecting research carried out during 2007-2015 in the East and West-Azarbaijan provinces. The total number of species recorded from Iran is 34 including: Aulacidae (Pristaulacus, 4 species), Evaniidae (Evania, 2 species and Brachygaster, one species) and Gasteruptiidae (Gasteruption, 27 species). Four new records from Iran are added: Brachygaster minutus (Olivier) (Evaniidae); Gasteruption goberti (Tournier), G. henseni van Achterberg and G. undulatum (AbeilledePerrin) (Gasteruptiidae).
Volume 3, Issue 3 (9-2017)
Abstract
Background: Helicobacter pylori infection is generally acquired in childhood. Algeria is a country with a high prevalence of H. pylori infection. The aim of this work was to take stock of H. pylori infection in Algerian children.
Materials and Methods: About 31antral biopsies were cultured, and then antibiotic susceptibility testing was performed. The statuses of cagPAI and vacA s, m, I, and d regions were determined as well as geographical typing was done by MultiLocus Sequence Typing (MLST) method.
Results: Culture was H. pylori positive in 12 children. Only one resistance to clarithromycin and one to metronidazole were detected. Four out of six strains possessed cagPAI, and five out of six strains were identified as vacA s2m2i2d2. The five strains tested by MLST were of the hpEurope type.
Conclusion: This study revealed high prevalence of H. pylori infection and low resistance to antibiotics and reported for the first time in Algeria a genetic typing of H. pylori strains isolated from Pediatrics.
Volume 3, Issue 3 (9-2017)
Abstract
The subfamily Microgastrinae Foerster, 1862 (Hymenoptera, Ichneumonoidea, Braconidae) is a challenging and the most diverse groups of braconids that has significant importance in biological control programs. They are koinobiont endoparasitoids of lepidopteran larvae and generally attack and develop in early instars and exit from the host larvae to pupate. In current paper, the findings of primary taxonomic investigations on these valuable biocontrol agents is presented and for each genus, the general habitus of a represented species is illustrated. Also, the proportion of known hosts for some genera was provided. The purpose of this paper is to provide a preliminary information of the Microgastrinae in Iran to serve as a starting point for future studies on the group and to encourage further study of more species in other regions of Iran, on various aspects of taxonomic, ecological, host associations, conservation, DNA barcoding and bio-control.
Volume 3, Issue 3 (12-2019)
Abstract
In this study, the three phase mixed matrix membranes comprising Pebax®1657, PEG-200 and MIL-53(AL) nanoparticles were evaluated for CO2 gas separation. The effect of various PEG-200 and MIL-53(AL) concentration within the pebax polymeric matrix on the structure, gas permeability, and selectivity of the membranes was investigated. To study the cross-sectional morphology, crystallinity and thermal properties of the synthesized membranes, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were utilized, respectively. Fourier transform infrared (FT-IR), was also carried out to identify the formation of the chemical bonds in the membrane. SEM images demonstrated a uniform cross-section and admissible dispersion of nanoparticles. The results of the thermal analyses indicated an increase in crystallinity and Tg in presence of MIL-53 particles. Permeation of pure gases (i.e., CO2, CH4) through the prepared neat Pebax®1657, the blended Pebax/PEG-200 and the Pebax/PEG-200/MIL-53(AL) mixed matrix membrane was measured at the pressure of 2–10 bar and temperature of 30 °C. The results showed that at the pressure 10 bar, the CO2 gas permeation from 133.36 barrer in pure membrane increased to 311.7 barrer (134%) in a membrane containing 10%wt MIL-53.
Volume 3, Issue 4 (12-2014)
Abstract
Chrysoperla carnea is a voracious predator. It is currently mass-reared and released for biological control programs. This study was aimed at finding out the effect of different diets on biological characteristics of adult predator, and to introduce a better and cheaper artificial diet for its mass-rearing. In order to obtain a pure and physiologically homogenous population, the predator was reared for seven successive generations in laboratory conditions. The effect of six different diets [a mixture of 30% concentrations of glucose, fructose and sucrose (1: 1: 1);, glucose, fructose, sucrose plus extract of Sitotroga cerealella eggs (1: 1); glucose, fructose, sucrose plus extract of Anagasta kuehniella eggs (1: 1);, a mixture of honey, yeast and distilled water (1: 1: 1);, honey, yeast plus extract of S. cerealella eggs (1: 1: 1) and honey, yeast plus extract of A. kuehniella eggs (1: 1: 1)] was studied on biological parameters (Pre-oviposition, oviposition and post-oviposition period,longevity of males and females, fecundity, egg hatchability and eggs remained in the ovary of females after death) of the seventh generation. Experiments were conducted under laboratory conditions (25 ± 2ºC, 60 ± 10% RH and 16L: 8Dh) with four replications and five observations. Results revealed that the mixture of honey, yeast and extract of A. kuehniella eggs (1: 1: 1), influenced the biological traits of the predator more effectively and favorably than all other diets, considering the average longevity, oviposition period and fecundity of female (37.73 ± 0.59, 28.57 ± 1.09 days, 795.0 ± 23.05 eggs, respectively), and egg hatchability (84.98 ± 0.71 %) compared to those of other diet treatments. Minimum pre-oviposition period (6.66 ± 0.49 days) was also found in adults fed by this diet.
Volume 3, Issue 4 (3-2020)
Abstract
Research subject: In recent years, there are so many attractions in the field of effective detection and discrimination of volatile organic compounds (VOCs). Detection of VOCs compounds, are very important in many applications and industries such as air pollution control, air quality control, food packaging, food quality control, disease diagnostic, agriculture etc. The sensitivity and selectivity of the prepared sensors to detect of VOCs needs to improve.
Research approach: A conductive polymer composite sensitive layer based on poly (lactic acid) as polymer matrix and multiwall carbon nanotubes as conductive filler was prepared to detect of volatile organic compounds (VOCs). For this purpose the porous sensitive layer was prepared by non-solvent induced phase separation (NIPS) method. In this structure, chloroform (low boiling point temperature) was used as the solvent and ethanol (high boiling point temperature) was used as a non-solvent. The sensitive layer was used to detect of toluene, methanol, and chloroform. The structure and morphology of synthesized layer was investigated by means of scanning electron microscopy (SEM) and BET test.
Main results: The investigation indicated that the phase separation method induced the open cell morphology into the conductive composite. The BET results showed that the specific surface area of composite increased to 22.3 m2/gr. The experimental results showed that the response properties of porous layers was improved dramatically in comparison with dense layers. It was related to the increase of specific surface area of polymer composite and therefore the increase of diffusion coefficient of analyte molecules into the polymer matrix. Finally the sensitivity and selectivity of porous sensitive layers was investigated based on Flory-Huggins interaction parameter.
Volume 4, Issue 1 (3-2018)
Abstract
During the collecting of Hypogastruridae (Collembola) in Mazandaran province, Xenylla mediterranea da Gama, 1964 was reported for the first time from Iran. With the new record in this study, the number of Xynella species known from Iran increased to four. Information for specie including material examined, description, ecology, distribution, and illustrations are given.
Volume 4, Issue 1 (6-2020)
Abstract
Research subject:
Methane hydrate reservoirs as an unconventional resource of natural gas can secure demand of energy in the world for many years. Efficient production prom this resources is the subject of concern. CO2-Methane replacement is a novel method for production from naturally occurring methane hydrate deposits such that methane production and CO2 storage take occur simultaneously.
Research approach: In this study a new kinetic model is proposed for CO2-Methane replacement in hydrate structure. This kinetic model is developed based on the mechanism proposed for replacement in the hydrate structure in the presence of excess water in a slurry phase of methane hydrate. According to this mechanism partial breakage of methane hydrate cages, methane-CO2 substitution and formation of CO2 hydrate proceed simultaneously. Methane hydrate dissociation and CO2 hydrate formation kinetic parameters are evaluated experimentally and fitted on polynomials as function of pressure and temperature.
Main results: Evaluation of the effects of pressure and temperature on the replacement efficiency show that higher replacement efficiency is obtained at higher temperatures and lower pressures. It means that replacement kinetic is controlled by methane hydrate dissociation step. Since, higher temperature and lower pressure favor dissociation of methane hydrate. At 278.15 K the replacement efficiency decreased from 15.78 to 8.80 as total pressure increased from 55 bar to 65 bar, at 280.15 K it decreased from 26.98 to 15.91 by decreasing total pressure from 60 bar to 70 bar. At same pressure 60 bar for 280.15 K and 278.15 K the replacement efficiency is 20.96 and 11.59 respectively.
Volume 4, Issue 1 (6-2020)
Abstract
Research subject: In recent years, researchers have proposed various methods for gas separation because of rising greenhouse gases in the atmosphere and causing enormous environmental problems. One of the newest and emerging methods is membrane gas separation. In the last decade, mixed matrix membranes (MMMs) have received much attention due to their ability to successful separation of polar gases from mixtures.
Research approach: In this study, a novel two-component mixed matrix membrane was prepared by incorporating the nickel zinc iron oxide nanoparticles into the Pebox polymer matrix. This is owing to combination the unique features of Pebax copolymer such as high mechanical strength and gas permeability, with nanoparticle properties as considerable permeability and selectivity, and appropriate mechanical and thermal stability. The gas permeability test was performed for pristine membrane and MMMs at 35 °C and pressure range from 2 to 10 bar. Fabricated membranes were also evaluated by FESEM, FTIR-ATR, DSC and XRD tests
Main results: Results demonstrated that in the case of the optimum membrane with 1 wt.% of filler loading and at 10 bar, the CO2 permeability was increased about 128% and reached to 278 Barrer, compared to pristine membrane. However, the CO2/CH4 and CO2/N2 selectivities were improved by 175 and 183 percent, respectively. This superior results was due to the presence of iron, nickel, and zinc atoms in the filler structure, which resulted in a better interaction with CO2. On the other hand, the presence of CO2-friendly segments in the Pebax structure caused much higher CO2 permeability in comparison with other light gases.
Volume 4, Issue 2 (10-2020)
Abstract
Research subject: Regarding to temperature effect on the rate of corrosion in absorption tower of gas refineries, it is very useful to examine and invest on new methods to decrease the temperature in mentioned towers.
Research approach: By studying different types of corrosion in amine processes and the influence of different variables on them, the dominant effect of temperature on the rate of corrosion in absorption towers was determined. Due to decreasing temperature in the absorption tower the surface tension of amine solvent and corrosion rate decrease. The reduction in surface tension reduces the foaming and flooding in the tower, which reduces the concentration of sour gases CO2 and H2S from the natural gas outlet. Various methods of reducing temperature in the absorption tower such as increasing flow rate of circulation amine solvent, opening the insulated tower wall and injecting amines into the middle of the tower have been studied. Aspen- HYSYS software was used to investigate the effects of amine injection into the middle of the tower.
Main result: According to the simulation results, the maximum temperature in the two-feed absorption tower was reduced to about 3°C and in the three feedstocks the maximum temperature was reduced to about 10°C. Also, as the CO2 and H2S concentration of the gas outlet decreases, the amount of Spent Caustic and catalyst in the lower part of the tower will decrease. Finally, it was found that among the above methods, injection of amine into the middle of the tower had the highest efficiency in decreasing the temperature of it. However, a combination of the above methods can be used to further reduce the temperature in the tower.
Volume 4, Issue 3 (9-2016)
Abstract
The effects of plant growth promoting rhizobacteria (PGPR) on growth and physiological characteristics of seedlings Corylus avellana were determined in a forest nursery. For this purpose, in a completely randomized design (CRD) and four replicates, three putative bacteria, including Pseudomonas putida, Bacillus subtilis and Enterobacter cloacae, as alone and mixed, were examined. The greatest height (26.88 cm), collar diameter (7.11 mm), leaf area (23.87 cm2)net photosynthesis (17.23μmol CO2 m−2s−1), transpiration rate (3.22 mmol H2O m−2s−1(, stomatal conductance (0.189 mol CO2 m−2s−1), water use efficiency (5.33 μmol CO2 mmol−1 H2O) and chlorophyll content (26.16 SPAD) allocated to seedlings inoculated with a combination of three bacteria. The greatest root dry weight (3.98 g), root volume (10.87 cm3), total plant dry weight (9.91g) was detected in seedlings inoculated with P. putida. In total, for the beneficial effects of PGPR on growth and physiological traits of C. avellana seedlings, all three bacteria either as individual or as mixed were found suitable for seedling inoculation. In fact, it is affirmed that inoculation of root with PGPR can be a proper approach to produce healthy and strong seedlings in nursery.
Volume 5, Issue 0 (0-2005)
Abstract
Gas sensitive metal oxide layers used in fabrication of resistive gas sensors are prepared by different deposition techniques. The technical data reported on some basic and practically important specifications of these devices, although fabricated based on the same gas sensitive oxide, are anomalously different. The influence of the fabrication technique used for the deposition of the gas sensitive layer on determination of the significant specifications of the transient response of a resistive gas sensor is experimentally investigated for the first time. ZnO and SnO2 layers were prepared by LPCVD, PVD, EPD and powder pressing techniques. Prototype gas sensors based on these layers were fabricated. The transient responses of these devices to a step change in the composition of the surrounding atmosphere were recorded and compared. It was shown that the thickness, porosity and pore micro-structure of the gas sensitive layer are the most effective parameters in determination of the transient response. The relationship between these parameters and the temporal variation of the electrical conductivity of the gas sensitive layer was qualitatively analyzed. Oxide layers of higher porosity resulted in gas sensors of faster response, but response time increased with the thickness of these gas sensitive layers. The sensors produced by EPD technique demonstrated the fastest responses while those produced by CVD were the slowest among the samples investigated.
Volume 5, Issue 1 (6-2016)
Abstract
In this study surimi was produced from big head (Hypophtalmichthys nobilis) carp and the effects of three independent factors including microbial transglutaminase (0.5%, 0.75% and 1%), salt (0%, 1.25% and 2.5%) and temperature (35 ̊C, 40 ̊C and 45 ̊C), were examined on textural properties and color parameters of produced surimi was examined. The results showed that enzyme concentration of 0.5 % and 1.25 % of salt at 45 ̊C temperature were as optimum treatment, thereby, reducing the salt percentage from 2.5 % to 1.25 % without significant reduction in textural properties such as Hardness (resistance of food at the first bitting of the food), Cohesiveness (maintaining the strength of the food during chewing) and Springiness (ability of foos to recovery of its origin shape and size at the first biting). The increasing of the amount of enzyme also resulted in reduction of WHC, significantly (p<0.05). Moreover, when the enzyme and salt were used at low concentrations, the more whiteness and lightness of surimi gel wre produced. Simultaneous effect of salt increasing and setting temperature reduction, resulted in significant higher redness (a*) (p<0.05). Besides, the effect of enzyme alone on yellow factor (b*) was not significant, whereas the simultaneous effect of increasing in enzyme and temperature resulted higher b* factor (p<0.05).
