جستجوی مقالات مرتبط با کلیدواژه « کربن » در نشریات گروه « علوم پایه »

The production reaction of iron from iron (III) oxide (hematite, Fe2O3) in industry is carried out by burning a mixture of hematite/carbon at high temperatures. Typically, in schools and student research laboratories, this experiment is conducted using the wood-sulfur method, where sulfur-coated wood sticks are immersed in the Fe2O3/Na2CO3 mixture and then ignited. The wood-sulfur experiment is mentioned as a laboratory experiment in the eleventh-grade experimental science book. The aim of this article is to find other carbon substitutes (such as laboratory carbon and organic materials like wood waste from carpentry and paper waste) for wood-sulfur and compare their performance. The results showed that the paper method (immersing paper in Fe2O3/Na2CO3) is preferred over the wood-sulfur method because the entire process is carried out by a single piece of paper, and depending on the paper dimensions, different amounts of the mixture can be used. In methods using carbon and wood waste (wood powder), the components of the mixture are combined together and form a paste-like consistency, which is then ignited. It is worth mentioning that the product obtained from the carbon method is purer qualitatively compared to other methods and contains less carbon because in the other three methods, a larger portion of carbon burns without participating in the reaction. Furthermore, in the carbon and wood waste method, a desired amount of paste can be made and used in several experiments, eliminating the need to repeat the manufacturing process for each experiment. Qualitative observations indicated that the iron production efficiency of these methods follows the order: wood-sulfur < paper waste < wood waste < laboratory carbon.

In this study, we have evaluated gamma ray and neutron shielding of platinum carbon nanotubes using Geant 4 Monte Carlo simulator in the photon energy range of 15-0.015 (𝑀𝑒𝑉) . We have calculated the mass attenuation coefficient, the half value layer, the tenth value layer, the mean free path and the ratio of the linear attenuation coefficient of Compton scattering to the total linear attenuation coefficient and the remove cross section of fast neutrons, which is necessary to check the performance of a shield for these parameters. XMuDat program was used to validate the data. The Geant4 results are in good agreement with the values obtained from the XMuDat program. We have also analyzed them. Finally, the results obtained for nanomaterials have been depicted in suitable forms. At the end, suggestions for using these nanomaterials in places where there are restrictions on weight, mechanical stability and strength are given .

Today, on the city’s issues Context; recent intellectual orientations are being born. Low carbon city is one of the newest theoretical and practical ideas about how modern sustainable urban management and city and urban life development. In this regard, the study of sources in this field shows that the establishment of low-carbon conceptual structures due to the multiplicity of sides in themselves tended to scatter in their subject areas and this process can be effective during on the related knowledge. The main goal of this research is to develop a conceptual model of low-carbon cities in order to read and recognize its concept and theory.

 In this research, a theoretical and evaluative model of reading low-carbon cities accordance with the available texts with a theoretical orientation has been prepared and compiled by Qualitative approach and Documentary research. The research period is between 1400-1401.

Fidings:

 The low-carbon city is theoretically a multilevel conceptual structure with the possibility of polygonal readings in categories, defining and evaluating procedures. According on the mentioned Gap, formulating one or a set of conceptual and evaluative models; It makes possible the integrated reading of this new mental and objective concept of future urban planning on world scale.

the conceptual structure of low carbon city has special and unique coordinates that has not been theoretically considered and integrated by researchers. it is possible to have a more accurate and complete knowledge of the low carbon city, and at the same time, the development options of this model are possible in future researches in accordance with the advances in knowledge

Herein, a facile, nontoxic, economic and fast green synthesis method was utilized to prepare carbon quantum dotes (CQDs). The CQDs were prepared via microwave-assisted hydrothermal method using Ferula assa-foetida. plant as carbon source. The effects of microwave power and irradiation time on optical and photoluminescence properties of CQDs were investigated. The CQDs prepared under optimum power and irradiation time (100 W, 10 min) have the average diameter of ~ 6 nm and emitted a bright blue light, when they were excited under a UV light with λex = 360 nm. The florescent quantum yield (QY) of the CQDs was 33 % which is higher than other CQDs prepared by bio-source carbons. FTIR and SEM-EDS mapping results confirmed the presence of nitrogen and sulfur elements in the CQDs structure. The CQDs were implemented into polyvinyl alcohol (PVA) matrix to prepare PVA-CQDs films. The prepared films also emitted an intense bule light with CIE index of (0.185, 0.121). The green-synthesized CQDs and PVA-CQDs film via a fast, facile and economic approach, have great potential to be used in various application fields.

Nitrogen as an essential nutrient element for organisms has many different oxidation numbers. Nitrogen cycling is sum of the changes and transformations of these oxidation numbers of nitrogen. One of the important nitrogen cycling process is mineralization that has important role in soil fertility. Mineralization has two stages that accomplishes by Nitrosomonas and Nitrobacter respectively. The environmental conditions and type of nitrogen containing material affect the activity of these microorganisms and consequently affect the rate and amount of mineralization. Generally, inappropriate ventilation and anaerobic conditions, drought, salinity and soil compaction decrease the amount of mineralization. Plowing the soil and plant residual management has positive effects on mineralization. The decomposition of Organic residues degradation is related to the ratio of soil C/N. Nitrogen-rich compounds, like legumes, vegetables and weeds, and animal fertilizers that have low C/N, decompose at a higher rate, and, by decomposition, more nitrogen is released. Lignine-rich and rough residues such as palm, sugarcane bagasse, cereals and wood remnants with high C/N have a slower decomposition. The number C/N=24 is considered as an indicator in organic matter decomposition and nitrogen mineralization. If residues such as wheat straw with C/N=80 are added to the soil, the microorganisms use soil nitrogen storage to adjust their C/N and thus to supply their nitrogen, causing a shortage of nitrogen.  Conversely, if residues such as young hay with C/N=13 are added to the soil, the excess nitrogen will reach to plant. Therefore, plant residues management and crop rotation is very important. In practice, in order to prevent of nitrogen deficiency in plant, organic residues with low nitrogen contents should add nitrogen to the as soil as chemical fertilizer. In some areas, residues of previous crops are burned which reduces the storage of organic matter and soil fertility, air pollution and increase greenhouse gases. This is while these residues can have many useful uses. Due to low contents of organic matter in most of country’s soils and dry climates, it is necessary to apply of managing practices in order to maintain and increase soil organic matter.

Many economic tools have been proposed and used to reduce climate change. Carbon trading is one of these market-based tools that is recognized as a cost-effective way to change climate and environmental issues. Today, the issue of carbon sequestration and bioenergy production versus fossil fuels is great concern of governments, and many efforts have been made to reduce or control carbon dioxide emissions. The aim of this study is to investigate carbon price fluctuations and predict price trends based on historical carbon price data in the time series 2005-2020. Data were analyzed by regression analysis based on Fuller augmented Dicky after eliminating inflation. The results show that the trend of carbon prices has fluctuated during this period. The average expected price of carbon is 3,303,589 Iranian Rials.Many economic tools have been proposed and used to reduce climate change. Carbon trading is one of these market-based tools that is recognized as a cost-effective way to change climate and environmental issues. Today, the issue of carbon sequestration and bioenergy production versus fossil fuels is great concern of governments, and many efforts have been made to reduce or control carbon dioxide emissions. The aim of this study is to investigate carbon price fluctuations and predict price trends based on historical carbon price data in the time series 2005-2020. Data were analyzed by regression analysis based on Fuller augmented Dicky after eliminating inflation. the trend of carbon prices has ش fluctuated during this period. The average expected price of carbon is 3,303,589 Iranian Rials.

The study of biomass and carbon in mangrove forests is often performed by allometry methods. The allometry models in Mangrove trees are influenced by factors such as species, ecological conditions, and tree age. To study the allometry equation of hara shrub (Avicennia marina) in the Nayband Bay, a complete shrub of Hara from the mentioned area was picked up at 6 stations, and biometry, biomass, and carbon content of the samples were measured. According to the results, the best model for estimating the biomass in mangrove shrubs in Nayband is the power equation using a stem diameter at 30 cm height (ABG = 139.3d301.263). The ratio of the root to the top part (leaf and trunk) is 24%. According to the content of carbon in the biomass samples, the amount of carbon was 42% of the upper part biomass and 39% of the root biomass. The obtained allometry equation in this study is different from mature Avicennia marina in different parts of the world and Iran.

Iran's beech forests are one of the most important vegetation communities in the country which are highly ecologically important due to their dynamic and diverse vegetation and fertile soils, as well as the large area of ​​arid and semi-arid lands in the country. But there is little information about the carbon stocks of these forests.

In this research, the aboveground carbon of trees and carbon stock in three sites in selected forestry plans in three northern provinces (Gilan, Mazandaran, Golestan) were selected and sampled from trees in random plots and from soil at depths of 0-30 and 30 to 60 centimeter was done. Ponce-Hernanadez method was used to estimate the aboveground carbon of trees and the Valky Block method was used for soil carbon sequestration and all calculations were made in terms of tons per hectare.

The results showed that, both carbon tree and soil carbon stocks were increased in both depths from East to West, but the amount of soil carbon stocks was decreased with increasing depth. Estimates have shown that the carbon stock potential of the country's beech forests was an average of 227.475 t / ha in aboveground section and 205.190 t / ha in the underground (soil) section.

These results demonstrate the further need for urgent conservation operations for this valuable heritage of our country by emphasizing the prevention of further destruction.

Biochar is a carbon rich product which created under low Oxygen conditions. In this study the effect of Biochar in three levels 0, 0.5 and 1 weight percentage on morphological traits like height, SLA, aboveground and underground biomass, length and volume of root and physiological characteristics such as chlorophylls, gas exchange and electrolyte leakage for two Bromus tomentellus and Medicago sativa species were investigated. Results showed that biochar increased the height of both B. tomentellus and M. sativa which was higher in 0.5 level than 1 percent. However, there were no differences between control and 1 percent of M. sativa. In both species biochar has no effect on SLA. Biochar had no effects on aboveground and below ground biomass for B. tomentellus and significantly increased below ground biomass and no effect on above ground biomass. Both root length and volume increased by biochar. Biochar had no effect on chlorophylls of B. tomentellus but in level 0.5 lead to increasing of chlorophylls for M. sativa. Gas exchange increased by biochar and electrolyte leakage had no significant effect. In general, increasing biochar level reduced morphological traits and increased physiological traits.

In this work, the damage produced in Carbon and Silicon by fast neutrons in the energy range of 0.15 to 10 MeV was calculated using TRIM code. In this range of energy, the dominant interaction is the elastic scattering. The information about recoil, nuclei energy, scattering angle and the depth in which the interaction was occurred is necessary to run TRIM code. For calculating the energy and scattering angle of recoil nuclei, the spectrum of scattered nuclei should be known. The spectrum of scattered Silicon and Carbon was calculated by using an analytical method to relate the statistical distributions to each other. Comparison of the calculated scattered spectrum with experimental one confirmed the validity of the calculation method. Calculations revealed that the damage produced in silicon is higher than the one produced in the Carbon. This is because the displacement energy threshold in Carbon is higher than the Silicon. So, using of Carbon in neutron exposure is recommended.

In this study, the synthesis of adapalene as an active pharmaceutical ingredient on a laboratory scale is examined. Our effort was focused on catalyzing C-C coupling as a difficult step in the adapalene total synthesis, using the zinc nanoparticles as well as eliminating the magnesium reagent. The use of zinc nanoparticles in C-C coupling is associated with increased yields compared with its bulk powder form. The best results were obtained using 1- (5-bromo-2-methoxy phenyl) adamantane and methyl 6-bromo-2-naphthoate in the presence of zinc nanoparticles in dry tetrahydrofuran followed by adding NiCl2 (DPPE) as the catalyst. Replacing the magnesium with zinc nanoparticles, this reaction can scale up to higher scales.

This paper presents optical properties of colloidal carbon quantum dots C-QDs in distilled water produced by using a method of alkali-assisted surfactant-free oxidation of cellulose acetate. The formation of colloidal carbon nanocrystals with the size range of ~ 4-5 nm was confirmed by using high-resolution transmission electron microscopy. The photoluminescence PL properties of the colloid were investigated at different applied excitation wavelengths and we observed a wide range of tunable visible to near-infrared NIR emissions with good stability from the C-QD colloid. A detailed analysis of the results shows that the visible and NIR luminescent properties of the colloidal C-QDs can be attributed to the mechanisms of quantum confinement and surface effects, respectively.

Nowadays climate changes as one of the major environmental issues have been put forward the most important challenge in sustainable development and poverty elimination. Carbon sequestration is a process in which carbon dioxide absorbs from the atmosphere and accumulates in carbohydrates form in plant tissues, litter, and soil. Rangelands ecosystems have a great potential in carbon sequestration because of including half of the lands on the earth. In addition, their carbon storage is about 10 percent of total biomass carbon storage in terrestrial ecosystems and 30 percent of organic carbon. In a global scale, about 500 billion tons of carbon sequestrate in the rangelands annually. To reduce atmospheric carbon dioxide and greenhouse gas balance, atmospheric carbon should be captured and sequestrated. Carbon as one of the main greenhouse gases element sequesters by photosynthesis in plant biomass. Carbon sequestration by the rangelands plants is the most simple and the cheapest way to decrease this gas. Therefore identifying the species that have high ability to carbon sequestration can help us in the rangelands rehabilitation and reclamation. Materials and methods The study area was 2598 ha including the exclosures and grazed rangelands in the mountainous region of Behshahr. This region is located on 53°54'01- 53 52' 06" longitudes and 36° 38' 24"- 36° 36' 16" latitude. The maximum and minimum elevations are 1707 meters and 1043 meters above sea level, respectively. The area annual precipitation is 409 mm and the temperature is between -15 °C to 37 °C that its maximum occurs in the May. The climate is semi-arid cold based on Emberger technique.In this study, the effects of exclosure and grazed on the carbon sequestration was studied in two plant species in the Vezvar rangelands of Hezarjarib in Behshahr. Vegetation and soil sampling was done by random-systematic method with two 100 m transects and 40 plots. The plot numbers were obtained based on the plant distribution pattern in the area. The soil sampling was done in two depths of 0-15 and 15-30 cm with a total 80 soil samples. Organic carbon determined by the Walkley-Black method. The species biomass measurement was done in above-ground and under-ground completely by weight and cutting method.Shooting and rooting organs of the species Astragalus gossypinus F. and Dactylis glomerata L. were separated from each other after transfer to the laboratory. The carbon sequestration coefficient of the plant organs was determined with combustion method.The carbon sequestration coefficient of the different species, organs, and the soils under these species were then analyzed in the Lab. In this study, Comparison of the carbon sequestration in two species was done by t-Test method. This investigation was done by SPSS v.19 and EXCEL software. Results and discussion The statistical results presented in Table 1 showed that the mean of canopy percent in enclosure area is higher than that of the grazed region. Table 1. t-Test analysis of canopy percent in the exclosure and grazed area

Arghash gold district includes five gold-bearing vein systems, (Au-I to Au-V) and one antimony-rich vein hosted by intermediate to silicic volcanic rocks, tuffs, granite, and diorite. Pyrite is the main sulfide mineral consisting of four generations (Py-I to Py-IV). Py-I to III are intimately associated with gold; however, Py-IV is barren. The δ34S values of pyrites in conventional bulk analyses fall into two groups, one highly enriched in 34S (δ34S= +9.3 to +21.8‰), and the other less enriched to slightly depleted in 34S (δ34S= +5.1 to -4.3‰). In-situ laser probe experiments were carried out to characterize various generations of pyrite. The results indicate a relatively narrow range for Py-I to Py-III (δ34S= -5.8 to +0.1‰) consistent with a magmatic source for sulfur. Py-IV is highly enriched (δ34S= +8.9 to +23.7‰), implying contributions of sulfur from sources enriched in 34S, like evaporites. The high δ34S values in the enriched group can be attributed to a significant occurrence of Py-IV in this group. The δ34S values of two stibnites from Sb ore (-18.8 and -14.4‰) suggest a different sulfur, and possibly metal source, and/or radical changes in the physicochemical conditions of the fluid during deposition of stibnite. Metasedimentary basement rocks could contribute sulfur and metal to the circulating fluids. δ13CPDB values of vein calcites are near 1 per mil suggesting a sedimentary source for carbon. Carbonate units and interlayers in the area are a suitable source for CO2 in the ore fluids. The stable isotope data suggest that hydrothermal fluids experienced a complex history of water/rock interaction and that ore components, were derived, at least partly, from country rocks.

In this study, the method of radiocarbon dating was applied to determine the age of fossil shell samples, obtained from southern shores of Iran. The radiocarbon (14C) dating method has been applied in many fields, including oceanography, geology, and archaeology. In this method the sample is pretreated in physical and chemical procedures, then using a Benzene Synthesis System, benzene (C6H6) is synthesized from the sample. One gram of the synthesized benzene is added into a teflon counting vial containing 12ml scintillator Hisafe3. In order to count and determine the radioactivity concentration of beta particles emitted from radiocarbon, the liquid scintillation counting method is applied. The age determination of fossil samples has been carried out by using count per minute (cpm) values from beta counting of 14C in synthesized samples comparing to the obtained results from Oxalic Acid Modern Standard. For 8 shell samples studied, the determined ages are in the range of 210-3890 years, according to Before Present (BP; before 1950). The efficiency of Liquid Scintillation Counting system for 14C is calculated to be about 92% and the calculation error for the low age samples was ±40 years and for the high age samples was ±100 years, respectively.