scholarly journals Thai Students’ Decision Making in Societal Issue of Surface Area and Concentrated Solutions as a Factor in the Rate of Chemical Reactions

2015 ◽  
Author(s):  
Jeeruwan Chattabud ◽  
Paisan Suwannoi ◽  
Tawee Sranamkam ◽  
Chokchai Yuenyong
Keyword(s):  
Decision Making ◽  
Surface Area ◽  
Chemical Reactions ◽  
Concentrated Solutions ◽  
Societal Issue ◽  
Thai Students

Study of the pozzolanic activity and hydration products of cement pastes with addition of natural zeolites

Clay Minerals ◽  
2011 ◽  
Vol 46 (2) ◽  
pp. 241-250 ◽  
Author(s):  
V. Lilkov ◽  
O. Petrov ◽  
V. Petkova ◽  
N. Petrova ◽  
Y. Tzvetanova
Keyword(s):  
Surface Area ◽  
Cement Paste ◽  
Chemical Reactions ◽  
Natural Zeolite ◽  
Early Stage ◽  
Pozzolanic Activity ◽  
Large Surface Area ◽  
Natural Zeolites ◽  
Hydration Products ◽  
Cement Pastes

AbstractThis paper presents results from comparative thermogravimetric, calorimetric and pozzolanic activity analyses of five natural zeolite samples from Bulgaria, Slovakia, Philippines, USA and North Korea. The zeolites actively participate in the hydration processes of cement. Their activity in the early stage of hydration is based mainly on the large surface area of the particles while, in the later stages of activation, chemical reactions occur between the products of the hydration of cement and the soluble SiO2 that is present in the bulk of the zeolites. It has been shown that in all cement pastes which contain zeolite additives, the quantity of portlandite is lower than that in pure cement paste or is even totally absent. The amounts of hydration products are greater when 30% zeolite is used than when 10% zeolite is added (excluding the sample with chabazite). The lowest pozzolanic activity is shown by chabazite, which possessed the lowest SiO2/Al2O2 ratio.

scholarly journals A hierarchical approach to model decision making: a study in chemotactic behavior ofEscherichia coli

2019 ◽  
Author(s):  
Safar Vafadar ◽  
Kaveh Kavousi ◽  
Hadiseh Safdari ◽  
Ata Kalirad ◽  
Mehdi Sadeghi
Keyword(s):  
Decision Making ◽  
Chemical Reactions ◽  
Experimental Studies ◽  
Hierarchical Approach ◽  
Homogeneous Markov Process ◽  
Detailed Model ◽  
E Coli ◽  
Physical And Chemical ◽  
To Receive ◽  
Chemotactic Behavior

AbstractReducing the complex behavior of living entities to its underlying physical and chemical processes is a formidable task in biology. Complex behaviors can be characterized as decision making: the ability to process the incoming information via an intracellular network and act upon this information to choose appropriate strategies. Motility is one such behavior that has been the focus many modeling efforts in the past. Our aim is to reduce the chemotactic behavior in E. coli to its molecular constituents in order to paint a comprehensive and end-to-end picture of this intricate behavior. We utilize a hierarchical approach, consisting of three layers, to achieve this goal: at the first level, chemical reactions involved in chemotaxis are simulated. In the second level, the chemical reactions give rise to the mechanical movement of six independent flagella. At the last layer, the two lower layers are combined to allow a digital bacterium to receive information from its environment and swim through it with verve. Our results are in concert with the experimental studies concerning the motility of E. coli cells. In addition, we show that our detailed model of chemotaxis is reducible to a non-homogeneous Markov process.

The Role of Surface Area of ZnO Nanoparticles as an Agent for some Chemical Reactions

2014 ◽  
Vol 354 ◽  
pp. 201-213 ◽  
Author(s):  
Mohamad Sahban Alnarabiji ◽  
Noorhana Yahya ◽  
Sharifah Bee Abdul Hamid ◽  
Khairun Azizi Azizli ◽  
Muhammad Kashif ◽  
...  
Keyword(s):  
Band Structure ◽  
Surface Area ◽  
Chemical Reactions ◽  
Oil Recovery ◽  
Adsorption Energy ◽  
Zno Nanoparticles ◽  
High Surface ◽  
Sol Gel ◽  
Nitrate Hexahydrate ◽  
Zno Nps

Synthesising zinc oxide nanoparticles (ZnO-NPs) to get certain characteristics to be applied in Enhanced Oil Recovery (EOR) is still challenging to date. In this work, the importance of high surface area of ZnO nanoparticles as EOR agent was highlighted. A simulation on density of state (DOS), band structure and adsorption energy of hydrogen and nitrogen gases on the surface of ZnO was carried out; it is observed that from the band structure of the band gap value for ZnO is 0.808ev. For the ZnO, Zn 4s states contribute to conduction band and O 2p states contribute to valence band. ZnO-NPs were synthesised using the sol-gel method by dissolving zinc nitrate hexahydrate in nitric acid and varying the stirring time (1 and 24h) and sintering time (30 and 40 min). A microwave oven was used for annealing ZnO without insulating the samples in any casket. The results show that 30 and 40 min of annealing and stirring for 1 & 24 h influenced the morphology and size of ZnO-NPs. These parameters could be tailored to generate a range of nanoparticle morphology (flask and/with agglomerated nanoparticles in a corn shape) obtained by Field Emission Scanning Electron Microscope (FESEM) and hexagonal crystal, determined by X-ray diffractometer (XRD), with the mean size of 70.5 & 74.9 nm and a main growth at the peak (101). The prepared sample via stirring for 24h and sintering for 40 min was chosen to prepare ZnO nanofluid because it has the highest surface area (BET) among the rest of samples, 0.23 m2/g. 10% of Original Oil In Place (OOIP) was recovered successfully to prove that ZnO is a good candidate to be applied in some chemical reactions. Moreover, it was found that ZnO is a promising catalyst for ammonia synthesis based on the adsorption energy of hydrogen and nitrogen gases (-1.05 and-1.60 kcal/mol respectively).

scholarly journals Numerical analysis of the chemical kinetic mechanisms of ozone depletion and halogen release in the polar troposphere

2014 ◽  
Vol 14 (7) ◽  
pp. 3771-3787 ◽  
Author(s):  
L. Cao ◽  
H. Sihler ◽  
U. Platt ◽  
E. Gutheil
Keyword(s):  
Boundary Layer ◽  
Surface Area ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Ozone Depletion ◽  
Polar Regions ◽  
Reaction Cycle ◽  
Reactive Surface ◽  
Halogen Species

Abstract. The role of halogen species (e.g., Br, Cl) in the troposphere of polar regions has been investigated since the discovery of their importance for boundary layer ozone destruction in the polar spring about 25 years ago. Halogen species take part in an auto-catalytic chemical reaction cycle, which releases Br2 and BrCl from the sea salt aerosols, fresh sea ice or snowpack, leading to ozone depletion. In this study, three different chemical reaction schemes are investigated: a bromine-only reaction scheme, which then is subsequently extended to include nitrogen-containing compounds and chlorine species and corresponding chemical reactions. The importance of specific reactions and their rate constants is identified by a sensitivity analysis. The heterogeneous reaction rates are parameterized by considering the aerodynamic resistance, a reactive surface ratio, β, i.e., the ratio of reactive surface area to total ground surface area, and the boundary layer height, Lmix. It is found that for β = 1, a substantial ozone decrease occurs after five days and ozone depletion lasts for 40 h for Lmix = 200 m. For about β ≥ 20, the time required for major ozone depletion ([O3] < 4 ppb) to occur becomes independent of the height of the boundary layer, and for β = 100 it approaches two days, 28 h of which are attributable to the induction and 20 h to the depletion time. In polar regions, a small amount of NOx may exist, which stems from nitrate contained in the snow, and may have a strong impact on the ozone depletion. Therefore, the role of nitrogen-containing species on the ozone depletion rate is studied. The results show that the NOx concentrations are influenced by different chemical reactions over different time periods. During ozone depletion, the reaction cycle involving the BrONO2 hydrolysis is dominant. A critical value of 0.0004 of the uptake coefficient of the BrONO2 hydrolysis reaction at the aerosol and saline surfaces is identified, beyond which the existence of NOx species accelerates the ozone depletion event, whereas for lower values, deceleration occurs.

Nanoencapsulation of Food Ingredients

2017 ◽  
pp. 132-152
Author(s):  
Manzoor Ahmad Shah ◽  
Shabir Ahmad Mir ◽  
Mudasir Bashir
Keyword(s):  
Gastrointestinal Tract ◽  
Surface Area ◽  
Chemical Reactions ◽  
Food Item ◽  
Food System ◽  
Wall Material ◽  
Food Ingredients ◽  
Nanosized Materials ◽  
Food Nanotechnology ◽  
Biological Substrates

Nanoencapsulation of food ingredients is one of the important applications of food nanotechnology. Nanoencapsulation is a technique used to produce nanocapsules from core materials packed within a wall material. Food manufacturers need to incorporate food ingredients with specific functional properties into food products. However, these ingredients may slowly degrade and lose their activity, or become hazardous due to various chemical reactions. They can also react with other components in the food system, which may lower their bioavailability, or change the color or taste of a product, allowing the food item to become prone to spoilage and deterioration. The protection of food ingredients against degradation and interaction with other food components may be done using the nanoencapsulation technique. It also, helps to enhance the bioavailability of food ingredients by protecting them during the digestive processes, improved uptake in the gastrointestinal tract and enhanced transport to the target sites. Nanosized materials provide a larger surface area for interaction with the biological substrates than microsized materials. Various techniques such as emulsification, coacervation, nanoprecipitation, solvent evaporation, spray drying and freeze drying are widely used techniques for nanoencapsulation of food ingredients.

scholarly journals Development of Covalent Triazine Frameworks as Heterogeneous Catalytic Supports

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1326 ◽  
Author(s):  
Norini Tahir ◽  
Chidharth Krishnaraj ◽  
Karen Leus ◽  
Pascal Van Der Voort
Keyword(s):  
Heterogeneous Catalysis ◽  
Surface Area ◽  
Chemical Reactions ◽  
Chemical Stability ◽  
Structural Design ◽  
Heterogeneous Catalysts ◽  
Molecular Complexes ◽  
Heterogeneous Catalytic ◽  
Catalytic Supports ◽  
Thermal And Chemical Stability

Covalent triazine frameworks (CTFs) are established as an emerging class of porous organic polymers with remarkable features such as large surface area and permanent porosity, high thermal and chemical stability, and convenient functionalization that promotes great potential in heterogeneous catalysis. In this article, we systematically present the structural design of CTFs as a versatile scaffold to develop heterogeneous catalysts for a variety of chemical reactions. We mainly focus on the functionalization of CTFs, including their use for incorporating and stabilization of nanoparticles and immobilization of molecular complexes onto the frameworks.

Mastication of Rubber. I. Mechanism of Plasticizing by Cold Mastication

1953 ◽  
Vol 26 (2) ◽  
pp. 386-405 ◽  
Author(s):  
M. Pike ◽  
W. F. Watson
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Physical Properties ◽  
Surface Area ◽  
Chemical Reactions ◽  
General Scheme ◽  
Basic Function ◽  
Large Surface Area ◽  
Essential Difference ◽  
High Shearing

Abstract The process of cold mastication has been rationalized in terms of recognized chemical reactions, and its essential difference from the hot mastication process has been demonstrated. Many apparently unrelated phenomena occurring on cold mastication, as, for example, are collected in a recent survey, can be interpreted as specific manifestations of the general scheme now presented. A clearer understanding of the basic function of the masticator is relevant to the design of such machines, i.e., the provision of high shearing forces for low-temperature chain rupture and the exposure of large surface area for high-temperature autoxidative breakdown. No acceleration of cold plasticization by added compounds is normally obtainable under the shear conditions of the Banbury mixer, but may be encountered under more efficient shear and in oxygen-deficient conditions. Cold mastication is revealed as a versatile method for producing rubbers of a wide variety of physical properties, i.e., softer (linear degraded) rubbers, harder and soluble (branched or cross-linked) rubbers, and insoluble (cross-linked) rubbers.

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