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1
Umehara, K. "HC reduction system for cold start and warm-up phases — Improvement of catalyst warm-up by retarded ignition". JSAE Review 18, n.º 1 (enero de 1997): 67–68. http://dx.doi.org/10.1016/s0389-4304(96)00056-2.
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Khalilikhah, O. y M. Shalchian. "Modelling and Fuzzy-Threshold Control of SI Engine for Emission Reduction during Cold Start Phase". International Journal of Automotive and Mechanical Engineering 16, n.º 4 (30 de diciembre de 2019): 7225–42. http://dx.doi.org/10.15282/ijame.16.4.2019.05.0539.
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We present a controllable model of an internal combustion engine that captures the overlapping of the cylinder valves as a controllable parameter and its effect on engine efficiency and EGR rates. The model parameters have been calibrated for the EF7 engine and validated with experimental data. This model successfully estimates the performance and HC and NOx emissions concentration of the engine under cold start operating condition. A model-based fuzzy-threshold control strategy has been proposed in cold start operating condition. This strategy uses the overlapping angle of the cylinder inlet and outlet valves as an extra degree of freedom in comparison to the regular PID strategy in order to accelerate the warm-up duration the catalyst converter while reduces the exhaust harmful emissions during the warm-up phase. The proposed controller model has been verified in MATLAB Simulink environment and simulation results indicates 8.6% reduction of the start-up time of the catalyst converter and reduction of 3.5%, 8.5% and 7% of HC, NO and fuel consumption respectively during the catalyst warm-up phase.
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Benjamin, S. F. y C. A. Roberts. "Automotive catalyst warm-up to light-off by pulsating engine exhaust". International Journal of Engine Research 5, n.º 2 (abril de 2004): 125–47. http://dx.doi.org/10.1243/146808704773564541.
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Benjamin, S. F. y C. A. Roberts. "Warm up of automotive catalyst substrates: Comparison of measurements with predictions". International Communications in Heat and Mass Transfer 25, n.º 1 (enero de 1998): 19–32. http://dx.doi.org/10.1016/s0735-1933(97)00134-6.
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Jeong, S.-J. y W.-S. Kim. "A new strategy for improving the warm-up performance of a light-off auto-catalyst for reducing cold-start emissions". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 215, n.º 11 (1 de noviembre de 2001): 1179–96. http://dx.doi.org/10.1243/0954407011528725.
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Light-off catalysts are often used to minimize cold-start emissions. The improved coldstart performance of light-off catalysts (LOCs) needs the optimal design in terms of flow distribution, geometric surface areas (GSA), precious metal (PM) loading, cell density and space velocity (SV). In this study, these influential factors are numerically investigated using an integrated numerical technique by considering not only the three-dimensional fluid flow but also the heat and mass transfer with chemical reactions. The present results indicate that uneven catalyst loading by depositing highly active catalyst materials upstream of the monolith is beneficial during the warm-up period, but its effect is severely deteriorated when the SV is above 100 000 h-1. To maximize light-off performance, this study suggests that: (a) the LOC be designed as a double-substrate type; (b) a substrate with high GSA and high PM loading at the face be placed at the front; (c) the cell density of the rear monolith be lower to reduce the pressure drop. In this paper, some initial results towards a new strategy of dual substrates are also reported to shorten the light-off time and improve conversion efficiency during warm-up. The proposed approach was very effective in reducing back pressure and cold-start emissions during the early seconds of engine operation.
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Benjamin, S. F. y C. A. Roberts. "Catalyst warm-up to light-off by pulsating engine exhaust: Two-dimensional studies". International Journal of Engine Research 5, n.º 3 (junio de 2004): 257–80. http://dx.doi.org/10.1243/1468087041549607.
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Benjamin, S. F. y C. A. Roberts. "Modelling warm-up of an automotive catalyst substrate using the equivalent continuum approach". International Journal of Vehicle Design 22, n.º 3/4 (1999): 253. http://dx.doi.org/10.1504/ijvd.1999.001868.
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JungKim, Chan, Sank Wook-Han, Ki Hyun Kim, Moo Yeon Lee y Gee Soo Lee. "Effects of the exhaust gas heat recovery system with a plate heat exchanger on the warm-up performance characteristics of the gasoline engine". International Journal of Engineering & Technology 7, n.º 2.12 (3 de abril de 2018): 136. http://dx.doi.org/10.14419/ijet.v7i2.12.11110.
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Background/Objectives: To meet the regulations for the fuel economy, an EHRS (Exhaust gas Heat Recovery System, which was installed within the vehicle exhaust system and recovered the heat from the exhaust gas, were needed. The EHRS enabled the engine to achieve the fast warm-up performance for reducing friction loss during the cold start.The objective of this paper was to investigate the effects of the design parameters of the EHRS with a plate heat exchanger on the warm-up performance of a gasoline engine.Methods/Statistical analysis: The EHRS with the plate heat exchanger was manufactured and installed behind the catalyst in the exhaust system of the gasoline direct injection engine. The experimental study and multi-disciplinary analysis were carried out to investigate the effects of the EHRS on the warm-up performance of the engine, such as the coolant temperature, the exhaust gas temperature and the recovery heat at idle condition and the step-load condition.Findings: Because the recovery of heat was about 1. 7 kW at idle condition, the effect of the EHRS on the warm-up performance was negligible. However, due to 17.2 kW of the recovery of heat at the stepload condition of T=140 Nm at N=2,400 rpm, the EHRS enabled to shorten the warm-up time by 548 s comparison that of the base engine.Improvements/Applications: The fuel economy will be expected to be improved through an EHRS, which provides the improved combustion in the warm-up phase and a decrease in friction loss.
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Benjamin, S. F. y C. A. Roberts. "Warm up of an automotive catalyst substrate by pulsating flow: a single channel modelling approach". International Journal of Heat and Fluid Flow 21, n.º 6 (diciembre de 2000): 717–26. http://dx.doi.org/10.1016/s0142-727x(00)00025-4.
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Merkisz, Jerzy, Jacek Pielecha y Monika Andrych-Zalewska. "Influence of the Length of a Catalyst-Coated Glow Plug on Exhaust Emissions". Energies 13, n.º 24 (11 de diciembre de 2020): 6557. http://dx.doi.org/10.3390/en13246557.
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This paper discusses the application of an in-cylinder catalyst in reducing the exhaust emissions from a diesel engine. This is an additional method of exhaust gas aftertreatment; yet the placement of a catalyst in the combustion chamber (i.e., the closest location to the process of combustion) allows a reduction of the emissions ‘at source’ (the catalyst applied on the glow plugs). For the investigations, we used an engine dynamometer to reproduce the traffic conditions of a homologation test carried out on a chassis dynamometer. We carried out the investigations on a Euro 4 1.3 JTD MultiJet diesel engine. The selection of the research object was followed by an analysis of the number of engines used in the EU meeting individual emission standards. We present results (measurement of carbon monoxide, hydrocarbons, nitrogen oxides, particle number, and carbon dioxide) related to the assessment of the applicability of the in-cylinder catalyst for three types of glow plugs: standard, catalyst-covered, and a prototype plug with an elongated catalyst-covered heating part. Prototype catalytic glow plugs ensure a few percent reduction in the emission of carbon monoxide, hydrocarbons, carbon dioxide, and particle number. The use of such a solution (glow plug replacement) in most diesel engines (easy to retrofit) would improve the environmental performance of combustion engines. It is of particular importance that in-cylinder catalysts are most efficient during cold start and warm-up, which is often the case in urban driving.
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Boam, D. J., I. C. Finlay, T. W. Biddulph, T. A. Ma, R. Lee, S. H. Richardson, J. Bloomfleld et al. "The Sources of Unburnt Hydrocarbon Emissions from Spark Ignition Engines during Cold Starts and Warm-Up". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 208, n.º 1 (enero de 1994): 1–11. http://dx.doi.org/10.1243/pime_proc_1994_208_152_02.
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The results of a three-year collaborative research study into the sources of unburnt hydrocarbon (uHC) emissions are reported. The study sought to extend existing knowledge of the sources in an engine to the crucial period following a cold start and before the exhaust catalyst becomes fully effective. The study, carried out on a range of engines but centred on the Rover M 16 four-valve engine, identified a number of sources, all of which are equally important in the warm-up period. The paper concludes with some recommendations for the control of uHC emissions
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Armbruster, H., S. Stucki, E. Olsson y S. Gjirja. "On-board conversion of alcohols to ethers for fumigation in compression ignition engines". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 217, n.º 3 (1 de marzo de 2003): 155–64. http://dx.doi.org/10.1243/09544070360550444.
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Fumigation of dimethyl ether (DME) is an interesting option for using methanol as a fuel in compression ignition engines. In this concept, a fraction of the methanol used as a fuel is catalytically converted on-board to DME and water, and the products of the conversion are introduced into the engine via the combustion air. With an optimized engine the performance as well as emissions are comparable with those obtained when running the engine on alcohol with polyethylene glycol as ignition improver. The methanol conversion has been tested with different catalysts under various conditions. Because of its superior thermal stability and the low costs, γ-Al2O3 has been selected as the most promising catalyst for converting methanol to DME in suffcient rates for an on-board application. The chemical kinetics and the mass transfer limitations of the γ-Al2O3 catalyst used for the methanol dehydration were evaluated. The rate-determining step of the catalytic reaction is found to be the reaction of adsorbed intermediates (the Langmuir-Hinshelwood mechanism); mass transfer is limited by Knudsen diffusivity. The kinetic data were used to design a catalytic converter for fuel processing on-board. Providing DME for fumigation in a 180 kW engine will require approximately 0.7 kg of catalyst. The compact catalyst is necessary for an effcient and fast start-up of the process. The transient behaviour (cold/warm start-up; load changes) of a fixed-bed reactor with γ-Al2O3 has been estimated using simplified models, which show that the cold start problem should be manageable in less than 1 min. With the hot gas of a methanol burner in front of the fixed bed or a bifunctional catalyst, the catalyst bed can be heated to 250 °C and the reaction of methanol to DME started within 25 s. This is an acceptable time for cold-starting an engine in heavy-duty vehicles.
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Sparis, P. D., P. Botsaris, A. Karkanis y J. Tatsios. "Three-way catalyst assessment via outlet—inlet temperature measurements: Driving tests". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 211, n.º 6 (1 de junio de 1997): 445–54. http://dx.doi.org/10.1243/0954407971526579.
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This paper presents and discusses experimental data obtained during driving tests simulating the test cycle, ECE 15, and relates exhaust gas levels of hydrocarbon (HC) and carbon monoxide (CO) to catalyst outlet—inlet temperature differences. It also presents the preliminary results from the operation of a microcontrolled on-board diagnostics (OBD) II catalyst efficiency assessment system based on a statistical analysis of the catalyst outlet—inlet temperature difference thermocouple signal. There are indications that this system performs satisfactorily after an adequate warm-up period, if a sampling period in the order of 300—400 s is allowed. Although this operating principle is supported by considerable experimental evidence, there are several technical problems that must be overcome before it can comply to the OBD II requirements. Firstly, as engine loads increase, the efficiency of all catalysts tested is improved considerably by the high exhaust gas temperatures. Furthermore, as the catalyst outlet—inlet temperature difference tends to decrease, so does the sensitivity of the measurements. During driving, catalyst outlet—inlet temperature differences could also be affected by other external factors such as the car speed, rain or snow etc., or long-term temperature sensor drift. Present results indicate that catalyst outlet—inlet temperature difference is also influenced by the ambient temperature. A preliminary analysis of the data indicates that a linear relationship may exist between these two quantities, however, more tests are required for a statistical proof of this assertion. In spite of these problems, the results presented here tend to support the idea that a catalyst performance assessment system using temperature probes is technically feasible. However, further tests are required under various engine operating conditions and environments before a final conclusion can be drawn.
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Mondt, J. R. "Adapting the Heat and Mass Transfer Analogy to Model Performance of Automotive Catalytic Converters". Journal of Engineering for Gas Turbines and Power 109, n.º 2 (1 de abril de 1987): 200–206. http://dx.doi.org/10.1115/1.3240025.
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Using theory for mass transfer of a diffusing specie with very low concentration, rate equations and a mass-balance equation can be combined to derive a differential equation for mass transfer in an automotive catalytic converter. A closed-form solution to this equation shows conversion efficiency to be a function of the dimensionless size of the converter, or the number of transfer units, Ntum. This mass-transfer-limited analysis does not include catalyst kinetics; hence it is limited to fully warm, fresh catalyst performance. However, a technique is developed to model lightoff of a catalytic converter by combining convective heat transfer when warming up with mass-transfer-limited conversion when fully warm. Realistic assessment of the merit of a catalytic converter must also include the influence of size and shape on flow pressure drop. Accordingly the size and shape of square-cell monoliths and packed-sphere bead beds are correlated with both conversion performance and pressure drop. Applications of these correlations are shown to compare realistically the size versus performance characteristic of monoliths with that for bead beds, in spite of drastically different flow patterns for the two converters. Model predictions are confirmed by engine-dynamometer and vehicle test results.
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Li, Huiling, Yuqi Wang, Yikui Zhu, Xujian Xu, Aimin Wu y Xiaomei Deng. "Bamboo-derived magnetic carbonaceous solid acid catalyst for the conversion of corncob into furfural promoted by warm water immersion". BioResources 13, n.º 3 (25 de junio de 2018): 6221–37. http://dx.doi.org/10.15376/biores.13.3.6221-6237.
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In this study, a bamboo-derived magnetic carbonaceous solid acid catalyst (BC@Fe3O4@SO3H) was synthesized by FeCl3 impregnation, which was followed by incomplete carbonization and -SO3H group functionalization. FT-IR, XRD, and TGA results showed that the prepared catalyst contained -SO3H, -COOH, and phenolic -OH groups. It exhibited poor adsorption ability for the dominating sugars released during the catalytic conversion process. The prepared bamboo-derived magnetic carbonaceous solid acid presented high catalytic activity for depolymerization and conversion of corncob hemicellulose. Warm water immersion under 60 °C was able to destroy the complex corncob cell wall structure and accelerated the dissolution of carbohydrates. The highest furfural yield of 54.1 mg/g was obtained from 40 °C water-immersed corncob after reacting at 180 °C for 30 min. Up to 96.1% of the corncob hemicellulosic backbone sugars were depolymerized to monosaccharides and oligosaccharides in the hydrolysates. The prepared catalyst exhibited a simple magnetic recovery process and high stability. This work provides promising strategies for biomass utilization via renewable materials.
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Jeong, Soo-Jin y Woo-Seung Kim. "A study on the optimal monolith combination for improving flow uniformity and warm-up performance of an auto-catalyst". Chemical Engineering and Processing: Process Intensification 42, n.º 11 (noviembre de 2003): 879–95. http://dx.doi.org/10.1016/s0255-2701(02)00140-x.
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Galindo, José, Vicente Dolz, Javier Monsalve-Serrano, Miguel Angel Bernal Maldonado y Laurent Odillard. "EGR cylinder deactivation strategy to accelerate the warm-up and restart processes in a Diesel engine operating at cold conditions". International Journal of Engine Research 23, n.º 4 (28 de septiembre de 2021): 614–23. http://dx.doi.org/10.1177/14680874211039587.
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The aftertreatment systems used in internal combustion engines need high temperatures for reaching its maximum efficiency. By this reason, during the engine cold start period or engine restart operation, excessive pollutant emissions levels are emitted to the atmosphere. This paper evaluates the impact of using a new cylinder deactivation strategy on a Euro 6 turbocharged diesel engine running under cold conditions (−7°C) with the aim of improving the engine warm-up process. This strategy is evaluated in two parts. First, an experimental study is performed at 20°C to analyze the effect of the cylinder deactivation strategy at steady-state and during an engine cold start at 1500 rpm and constant load. In particular, the pumping losses, pollutant emissions levels and engine thermal efficiency are analyzed. In the second part, the engine behavior is analyzed at steady-state and transient conditions under very low ambient temperatures (−7°C). In these conditions, the results show an increase of the exhaust temperatures of around 100°C, which allows to reduce the diesel oxidation catalyst light-off by 250 s besides of reducing the engine warm-up process in approximately 120 s. This allows to reduce the CO and HC emissions by 70% and 50%, respectively, at the end of the test.
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Serrano, José R., Francisco J. Arnau, Jaime Martín y Ángel Auñón. "Development of a Variable Valve Actuation Control to Improve Diesel Oxidation Catalyst Efficiency and Emissions in a Light Duty Diesel Engine". Energies 13, n.º 17 (3 de septiembre de 2020): 4561. http://dx.doi.org/10.3390/en13174561.
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Growing interest has arisen to adopt Variable Valve Timing (VVT) technology for automotive engines due to the need to fulfill the pollutant emission regulations. Several VVT strategies, such as the exhaust re-opening and the late exhaust closing, can be used to achieve an increment in the after-treatment upstream temperature by increasing the residual gas amount. In this study, a one-dimensional gas dynamics engine model has been used to simulate several VVT strategies and develop a control system to actuate over the valves timing in order to increase diesel oxidation catalyst efficiency and reduce the exhaust pollutant emissions. A transient operating conditions comparison, taking the Worldwide Harmonized Light-Duty Vehicles Test Cycle (WLTC) as a reference, has been done by analyzing fuel economy, HC and CO pollutant emissions levels. The results conclude that the combination of an early exhaust and a late intake valve events leads to a 20% reduction in CO emissions with a fuel penalty of 6% over the low speed stage of the WLTC, during the warm-up of the oxidation catalyst. The same set-up is able to reduce HC emissions down to 16% and NOx emission by 13%.
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Umezawa, Yuka, Hiroki Seto, Toshiro Imamura y Toru Namerikawa. "Reducing Air Pollutant Emissions and Optimizing Fuel Economy by Controlling Torque and Catalyst warm-up in mild HEV via Cascaded MPC". IFAC-PapersOnLine 56, n.º 2 (2023): 670–75. http://dx.doi.org/10.1016/j.ifacol.2023.10.1644.
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Sorokin, V. V. "Calculation of Start-Up Time of Passive Catalytic Hydrogen Recombiner of Localization Safety System of a Nuclear Power Plant Equipped with VVER". ENERGETIKA. Proceedings of CIS higher education institutions and power engineering associations 65, n.º 1 (2 de febrero de 2022): 67–75. http://dx.doi.org/10.21122/1029-7448-2022-65-1-67-75.
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The hydrogen removal system ensures hydrogen safety. At a VVER nuclear power plant, it consists of passive catalytic hydrogen recombiners. The calculation of devices is of great importance for safety justification, since the complex conditions of an accident at a power unit are not reproducible in experiments. The recombiner consists of a casing and a cassette with catalytic elements, the design of which ensures the passage of a gaseous medium through the device. Upon contact with the catalyst, a chemical reaction of hydrogen and oxygen compounds occurs, accompanied by the release of heat; as a result, the concentration of hydrogen under the shell decreases. The problem is starting from a cold state since the activity of the cold catalyst is low, and the thrust is not observed until the catalyst is heated and a column of warm gas is formed inside the device. The transition from the cold state to the working state takes a certain time, during which the recombiner performance is below nominal. The start-up time is a parameter that is important in terms of safety. The article calculates the start-up time of a hydrogen recombiner with a catalytic block in the form of equidistant parallel catalytic plates. Local cross-sectional averages and transmission coefficients are used, the latter taking into account the influence of free convection and chemical reaction. The gas velocity is determined by the balance of buoyant and resistance forces. The calculated data and the data known from the scientific and technical literature coincide satisfactorily. As a conservative estimate of the start-up time of the recombiner, it is recommended to use the value of 300 s. An increase in temperature practically does not affect the start of the recombiner with an active catalyst, an increase in the concentration of hydrogen accelerates the start, and a decrease in pressure slows it down. The results obtained in the study can be used in the justification of the safety of VVER nuclear power plants and the examination of reports on the justification of the safety of power units.
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Yoshida, Y., K. Oyakawa, Y. Aizawa y H. Kaya. "A High-Temperature Catalytic Combustor With Starting Burner". Journal of Engineering for Gas Turbines and Power 123, n.º 3 (1 de octubre de 2000): 543–49. http://dx.doi.org/10.1115/1.1373397.
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A catalytic combustion system has high potential to achieve low NOx emission level. When this combustion system is applied to a gas turbine, the required combustor performance must be maintained over a wide range of operating conditions. These conditions range from cold starting to steady-state operation. Particularly during the initial stage of cold starting when the catalyst is not yet activated, the catalyst must be heated by some means. This study proposes a new concept of a catalytic combustor with a direct heating system using vaporizing tube for starting burner in order to downsize the combustor and reduce the warm-up time during cold starts. The effectiveness of this concept is experimentally verified. Furthermore, NOx, CO, and HC emissions during startup can be reduced to a low level so as to achieve ultra-low pollution of the catalytic combustion over a wide range of operating conditions from cold start to steady-state operation. This paper outlines the operation concept covering cold start, verification of the concept through the experiments with flame visualization in the combustor, spray characteristics, construction of the combustor, and combustion characteristics that show low pollution in various operating conditions of the catalytic combustor.
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Jeong, Soo-Jin, Woo-Seung Kim y Taehun Kim. "An application of CFD to improve warm-up performance of the 3-way auto-catalyst by high surface area and low thermal mass". International Journal of Vehicle Design 29, n.º 3 (2002): 243. http://dx.doi.org/10.1504/ijvd.2002.002012.
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Oluwadare, Benjamin Segun, Samson Adedayo Adeleye y Taiwo Oluwasesan Oni. "Performance Analysis of Hydroxyl (HHO) Gas Addition on a Gasoline Generator". European Journal of Applied Science, Engineering and Technology 2, n.º 2 (1 de marzo de 2024): 334–54. http://dx.doi.org/10.59324/ejaset.2024.2(2).25.
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The research explores the use of hydroxyl (HHO) gas as a renewable energy source due to the over-reliance on fossil fuels in conventional engines. An HHO cell is designed to produce hydrogen gas used in conventional generators. The cell uses electrolysis of water and potassium hydroxide as a catalyst. The HHO gas is generated with ordinary water without any catalyst and the detailed results of the reaction and analysis are presented. The goal is to develop and test-run an electrolytic cell on a gasoline engine (spark ignition engine) and measure the variation of its parameters in comparison to that of a gasoline engine. The efficiency, performance, power output, and emission are tested under load. This study comprises detailed work on the performance analysis of the HHO cell on the conventional generator, establishes the relationship between the variation of the KOH catalyst against time to produce the HHO gas, the relationship between the variation in voltage and how it directly influences the rate of gas production. Warm water, which is raised above room temperature, is used to verify the above-stated relationships, check if it holds and check the more efficient means of operating the electrolyte based on the temperature of the water used. An increase in the temperature of the water above room temperature leads to more gas production, thereby increasing the efficiency of the HHO cell in gas production. When HHO cell is operated with ordinary water without a catalyst at room temperature, it is observed that the reaction forms a cloudy around the plates of the cell, but the reaction is not turbulent with no significant amount of gas produced, as compared to that of the presence of potassium hydroxide (KOH), which serves as a catalyst to speed up the rate of the reaction and enhance the production of the HHO gas. This clearly shows the need and importance of the presence of a catalyst in the reaction. HHO cell is operated with salt (NaCl) as a catalyst in replacement for potassium hydroxide (KOH) to check the reaction and the rate of gas production. The reaction observed is metal rusting, though it is turbulent a bit more than that of the presence of KOH solution.
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Ramesh, Aswin K., Gregory M. Shaver, Cody M. Allen, Soumya Nayyar, Dheeraj B. Gosala, Dina Caicedo Parra, Edward Koeberlein, James McCarthy y Doug Nielsen. "Utilizing low airflow strategies, including cylinder deactivation, to improve fuel efficiency and aftertreatment thermal management". International Journal of Engine Research 18, n.º 10 (14 de marzo de 2017): 1005–16. http://dx.doi.org/10.1177/1468087417695897.
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Approximately 30% of the fuel consumed during typical heavy-duty vehicle operation occurs at elevated speeds with low-to-moderate loads below 6.5 bar brake mean effective pressure. The fuel economy and aftertreatment thermal management of the engine at these conditions can be improved using conventional means as well as cylinder deactivation and intake valve closure modulation. Airflow reductions result in higher exhaust gas temperatures, which are beneficial for aftertreatment thermal management, and reduced pumping work, which improves fuel efficiency. Airflow reductions can be achieved through a reduction of displaced cylinder volume by using cylinder deactivation and through reduction of volumetric efficiency by using intake valve closure modulation. This paper shows that, depending on load, cylinder deactivation and intake valve closure modulation can be used to reduce the fuel consumption between 5% and 25%, increase the rate of warm-up of aftertreatment, maintain higher temperatures, or achieve active diesel particulate filter regeneration without requiring dosing of the diesel oxidation catalyst.
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Andrych-Zalewska, Monika, Zdzislaw Chlopek, Jacek Pielecha y Jerzy Merkisz. "Influence of the In-Cylinder Catalyst on the Aftertreatment Efficiency of a Diesel Engine". Energies 16, n.º 6 (18 de marzo de 2023): 2826. http://dx.doi.org/10.3390/en16062826.
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The article discusses the use of a catalyst inside the cylinder, the task of which is to reduce exhaust emissions from a diesel engine. The catalyst (platinum) applied to the glow plugs provided an additional method of exhaust aftertreatment. Due to their usage, especially in urban driving, passenger cars are characterized by small mileage between individual trips, so they often operate from a cold engine start and work at a low engine temperature, which leads to reduced catalytic reactor efficiency. For this reason, the efficiency of the internal catalyst was tested in relation to the efficiency of the external reactor. This efficiency was determined based on exhaust emission measurements (before and after the catalytic reactor) in two stages: stage 1: idling of a hot engine, and stage 2: simulation of the NEDC test (valid for the selected test object). The tests were carried out on an engine dynamometer, where the traffic conditions from the type-approval test carried out on a chassis dynamometer could be replicated. The tests were carried out on a Euro 4 1.3 JTD MultiJet diesel engine. The results (measurement of carbon monoxide, hydrocarbons, and the number of particles) related to the assessment of the effect the catalyst in the cylinder were discussed. The obtained catalytic reactor efficiency results, regardless of the type of research, indicated that it achieved the highest efficiency in reducing the concentration of hydrocarbons, and the lowest—in relation to the number of solid particles (as that is not its primary function). It is particularly significant that the in-cylinder catalytic converter was most efficient during the cold engine start, which happens frequently in urban driving. The efficiency of the diesel oxidation catalytic reactor (DOC) during the engine start-up and warm-up phases with the use of standard glow plugs reached values of 31.3%, 34.1% and 14.3%, respectively, for carbon monoxide, hydrocarbons and the particle number. On the other hand, the determined efficiency of the DOC in a setup with the modified glow plugs was 28.9%, 35.7% and 12.5%, respectively. The proposed solution can be used to improve the combustion quality in internal combustion engines used in hybrid vehicles, which are characterized by frequent engine starts and stops. In addition, it is possible to use such a solution retroactively in traditional vehicles powered by an internal combustion engine, which could result in an improvement in their emission class through what is called retrofitting.
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Boehman, A. L., J. W. Simons, S. J. Niksa y J. G. McCarty. "Dynamic Stress Behavior in Catalytic Combustors". Journal of Energy Resources Technology 119, n.º 3 (1 de septiembre de 1997): 164–70. http://dx.doi.org/10.1115/1.2794985.
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Dynamic stress behavior during catalytic combustion of methane has been simulated under transient warm-up, cool-down, and cyclic conditions. The numerical model combines a two-dimensional solution to the transport equations, solution of an energy balance on the monolith wall, and the NIKE3D structural analysis code to predict thermal stresses. The model also includes a detailed heterogeneous kinetics model for a proprietary palladium oxide (PdO) catalyst, but the model ignores gas-phase reactions. Results illustrate that thermal stresses as high as 630 MPa can form during transient operating modes, which risks structural failure of the ceramic monolith. The maximum computed thermal stress concentrations occur near the inlet of the monolith. Peak transverse stresses (which act to form axial cracks) typically form near the inlet and centerline of the monolith structure, while peak axial stresses form near the edges of the flat plate that represents the monolith structure. Increasing the preheat temperature of the incoming fuel and air mixture lessens the peak thermal stress. To a first approximation, the magnitude of the peak transverse stress during any transient cycle considered with our model can be estimated from the maximum value of the gradient in the computed temperature profiles.
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Chen, Longfei, Richard Stone y Dave Richardson. "Effect of the valve timing and the coolant temperature on particulate emissions from a gasoline direct-injection engine fuelled with gasoline and with a gasoline–ethanol blend". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 226, n.º 10 (23 de mayo de 2012): 1419–30. http://dx.doi.org/10.1177/0954407012444966.
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Variable-valve-timing technology and ethanol addition to gasoline are both considered to be effective strategies for better performance and potential improvement in the fuel economy in gasoline engines. In this study, a Jaguar V8, naturally aspirated spray-guided direct-injection engine was operated with four different valve-timing combinations using an unleaded gasoline and a gasoline–10 vol % ethanol blend. The internal exhaust gas recirculation rate and the in-cylinder gas temperature were modelled for different valve-timing strategies. The results showed that a high valve overlap led to high internal exhaust gas recirculation and a high charge temperature, which evidently improved the fuel spray atomization and reduced the particulate matter emissions. Adding 10 vol % ethanol led to a rise in the total particle number and the total particle mass in emissions by a factor of up to 2 under warm-engine conditions (with a coolant temperature of 90 °C) but led to a reduction in the total particle number and the total particle mass in emissions by up to two-thirds under cold conditions (with a coolant temperature of 20 °C). Thermogravimetric analysis tests were conducted to analyse the compositions of filter-borne particulate matter emissions, and more than 75 mass % organic material was always present. All measurements are reported for both pre- and post-three-way-catalyst samples, the latter always showing a significant reduction (a factor of about 2) in the particulate matter emissions.
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Guo, Dongdong, Yunshan Ge, Xin Wang, Haixu Liu, Sheng Su, Chunbo Li y Tinghong Tao. "Sub-23 nm Particle Emissions from China-6 GDI Vehicle: Impacts of Drive Cycle and Ambient Temperature". Atmosphere 13, n.º 8 (1 de agosto de 2022): 1216. http://dx.doi.org/10.3390/atmos13081216.
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Both the EU and China are evaluating the feasibility of lowering the detection limit of particle number (PN) measurement to 10 nm in future legislations, making it necessary to better understand the sub-23 nm particle emission characteristics from state-of-the-art vehicles. In this study, solid PN emissions with a diameter larger than 10 nm and 23 nm (known as SPN10 and SPN23) were compared over the WLTC, RTS95, and a so-called “worst-case” real driving emission (RDE) cycle (highly dynamic/0 °C) using two certification-level particle number counters (PNCs) employing evaporation tube (ET) and catalytic stripper (CS) as volatile particle remover (VPR). The results show that SPN10 emissions were 31.7%, 27.8%, and 15.2% higher than SPN23 over the WLTC, RTS95, and laboratory RDE cycles. Sub-23 nm particles were almost not identified within the engine cold-start phase and tended to be a hot-running pollutant favored by aggressive driving styles (frequent accelerations and high engine loads), fuel-cut during decelerations, and long idles. Lower testing temperature delayed the light-off of catalyst and, therefore, significantly reduced the formation of sub-23 nm particles within the engine warm-up stage. Lowering the detection limit to 10 nm is deemed to provide more public health protection since it will guide manufacturers to pay more attention to vehicle hot-running emissions.
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Tulaphol, Sarttrawut, Nurak Grisdanurak, Franklin Anariba, Chantra Tongcumpou y Pummarin Khamdahsag. "Batch and Continuous Flow Treatment Studies of Trichloroethylene Contaminated in Water by Silver and Cerium Doped Zinc Oxide Adsorption and Photocatalysis". Sains Malaysiana 52, n.º 2 (28 de febrero de 2023): 533–45. http://dx.doi.org/10.17576/jsm-2023-5202-16.
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The development of photocatalytic treatment in continuous flow systems to be more practical is challenging. This research aimed to study batch and continuous flow treatment of trichloroethylene (TCE) contaminated in water by silver and cerium doped zinc oxide (0.005Ag-0.005Ce-ZnO) visible light driven photocatalyst. This catalyst was selected to represent the green route synthesis with simplicity and ease of upscaling. The 0.005Ag-0.005Ce-ZnO powder was synthesized using sticky rice flour as a template. Mechanical coating of the 0.005Ag-0.005Ce-ZnO powder on activated alumina (Al2O3) beads was done to improve the appropriate packing in the fixed bed columns. Characterization of 0.005Ag-0.005Ce-ZnO showed a higher response to visible light and smaller crystallite size compared to zinc oxide synthesized with the same method. Using sticky rice starch as a template increased the uniform distribution of the elements. The photocatalytic batch test over 0.005Ag-0.005Ce-ZnO powder, 0.30 g/100 mL, could remove TCE up to 80% in 180 min. The decrease of TCE via photocatalysis compared to volatilization, adsorption, and photolysis presented the predominance of photocatalysis. Langmuir-Hinshelwood kinetics described that the decrease of TCE more depended on the reaction than adsorption. In addition, the TCE degradation steadily remained at 80-90% along the run of 0.005Ag-0.005Ce-ZnO@Al2O3 photocatalysis under visible light from both warm white lamps and sunlight in the continuous flow system. Besides photocatalysis, TCE adsorption on 0.005Ag-0.005Ce-ZnO@Al2O3 packed in the columns showed significant results. Our findings presented the possibility of applying the photocatalytic continuous flow system to remove TCE in industrial wastewater.
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Lapuerta, Magín, Ángel Ramos, David Fernández-Rodríguez y Inmaculada González-García. "High-pressure versus low-pressure exhaust gas recirculation in a Euro 6 diesel engine with lean-NOx trap: Effectiveness to reduce NOx emissions". International Journal of Engine Research 20, n.º 1 (16 de diciembre de 2018): 155–63. http://dx.doi.org/10.1177/1468087418817447.
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Exhaust gas recirculation can be achieved by means of two different routes: the high-pressure route (high-pressure exhaust gas recirculation), where exhaust gas is conducted from upstream of the turbine to downstream of the compressor, and the low-pressure one (low-pressure exhaust gas recirculation), where exhaust gas is recirculated from downstream of the turbine and of the aftertreatment system to upstream of the compressor. In this study, the effectiveness of both exhaust gas recirculation systems on the improvement of the NOx-particulate matter emission trade-off has been compared on a Euro 6 turbocharged diesel engine equipped with a diesel oxidation catalyst, a lean-NOx trap, and a diesel particulate filter. Emissions were measured both upstream and downstream of the aftertreatment system, at different combinations of engine speed and torque (corresponding to different vehicle speeds), at transient and steady conditions, and at different coolant temperatures as switch points to change from high-pressure exhaust gas recirculation to low-pressure exhaust gas recirculation. It was shown that low-pressure exhaust gas recirculation was more efficient than high-pressure exhaust gas recirculation to reduce NOx emissions, mainly due to the higher recirculation potential and the lower temperature of the recirculated gas. However, such a differential benefit decreased as the coolant temperature decreased, which suggests the use of high-pressure exhaust gas recirculation during the engine warm-up. It was also shown that the lean-NOx trap storage efficiency decreased more rapidly at high engine load than at medium load and that such reduction in efficiency was much faster when high-pressure exhaust gas recirculation was used than when low-pressure exhaust gas recirculation was used.
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Gordon, T. D., A. A. Presto, A. A. May, N. T. Nguyen, E. M. Lipsky, N. M. Donahue, A. Gutierrez et al. "Secondary organic aerosol formation exceeds primary particulate matter emissions for light-duty gasoline vehicles". Atmospheric Chemistry and Physics Discussions 13, n.º 9 (4 de septiembre de 2013): 23173–216. http://dx.doi.org/10.5194/acpd-13-23173-2013.
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Abstract. The effects of photochemical aging on emissions from 15 light-duty gasoline vehicles were investigated using a smog chamber to probe the critical link between the tailpipe and ambient atmosphere. The vehicles were recruited from the California in-use fleet; they represent a wide range of model years (1987 to 2011), vehicle types and emission control technologies. Each vehicle was tested on a chassis dynamometer using the unified cycle. Dilute emissions were sampled into a portable smog chamber and then photochemically aged under urban-like conditions. For every vehicle, substantial secondary organic aerosol (SOA) formation occurred during cold-start tests, with the emissions from some vehicles generating as much as 6 times the amount of SOA as primary particulate matter after three hours of oxidation inside the chamber at typical atmospheric oxidant levels. Therefore, the contribution of light duty gasoline vehicle exhaust to ambient PM levels is likely dominated by secondary PM production (SOA and nitrate). Emissions from hot-start tests formed about a factor of 3–7 less SOA than cold-start tests. Therefore, catalyst warm-up appears to be an important factor in controlling SOA precursor emissions. The mass of SOA generated by photo-oxidizing exhaust from newer (LEV1 and LEV2) vehicles was only modestly lower (38%) than that formed from exhaust emitted by older (pre-LEV) vehicles, despite much larger reductions in non-methane organic gas emissions. These data suggest that a complex and non-linear relationship exists between organic gas emissions and SOA formation, which is not surprising since SOA precursors are only one component of the exhaust. Except for the oldest (pre-LEV) vehicles, the SOA production could not be fully explained by the measured oxidation of speciated (traditional) SOA precursors. Over the time scale of these experiments, the mixture of organic vapors emitted by newer vehicles appear to be more efficient (higher yielding) in producing SOA than the emissions from older vehicles. About 30% of the non-methane organic gas emissions from the newer (LEV1 and LEV2) vehicles could not be speciated, and the majority of the SOA formed from these vehicles appears to be associated with these unspeciated organics. These results for light-duty gasoline vehicles contrast with the results from a companion study of on-road heavy-duty diesel trucks; in that study late model (2007 and later) diesel trucks equipped with catalyzed diesel particulate filters emitted very little primary PM, and the photo-oxidized emissions produced negligible amounts of SOA.
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Gordon, T. D., A. A. Presto, A. A. May, N. T. Nguyen, E. M. Lipsky, N. M. Donahue, A. Gutierrez et al. "Secondary organic aerosol formation exceeds primary particulate matter emissions for light-duty gasoline vehicles". Atmospheric Chemistry and Physics 14, n.º 9 (13 de mayo de 2014): 4661–78. http://dx.doi.org/10.5194/acp-14-4661-2014.
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Abstract. The effects of photochemical aging on emissions from 15 light-duty gasoline vehicles were investigated using a smog chamber to probe the critical link between the tailpipe and ambient atmosphere. The vehicles were recruited from the California in-use fleet; they represent a wide range of model years (1987 to 2011), vehicle types and emission control technologies. Each vehicle was tested on a chassis dynamometer using the unified cycle. Dilute emissions were sampled into a portable smog chamber and then photochemically aged under urban-like conditions. For every vehicle, substantial secondary organic aerosol (SOA) formation occurred during cold-start tests, with the emissions from some vehicles generating as much as 6 times the amount of SOA as primary particulate matter (PM) after 3 h of oxidation inside the chamber at typical atmospheric oxidant levels (and 5 times the amount of SOA as primary PM after 5 × 106 molecules cm−3 h of OH exposure). Therefore, the contribution of light-duty gasoline vehicle exhaust to ambient PM levels is likely dominated by secondary PM production (SOA and nitrate). Emissions from hot-start tests formed about a factor of 3–7 less SOA than cold-start tests. Therefore, catalyst warm-up appears to be an important factor in controlling SOA precursor emissions. The mass of SOA generated by photooxidizing exhaust from newer (LEV2) vehicles was a factor of 3 lower than that formed from exhaust emitted by older (pre-LEV) vehicles, despite much larger reductions (a factor of 11–15) in nonmethane organic gas emissions. These data suggest that a complex and nonlinear relationship exists between organic gas emissions and SOA formation, which is not surprising since SOA precursors are only one component of the exhaust. Except for the oldest (pre-LEV) vehicles, the SOA production could not be fully explained by the measured oxidation of speciated (traditional) SOA precursors. Over the timescale of these experiments, the mixture of organic vapors emitted by newer vehicles appears to be more efficient (higher yielding) in producing SOA than the emissions from older vehicles. About 30% of the nonmethane organic gas emissions from the newer (LEV1 and LEV2) vehicles could not be speciated, and the majority of the SOA formed from these vehicles appears to be associated with these unspeciated organics. By comparing this study with a companion study of diesel trucks, we conclude that both primary PM emissions and SOA production for light-duty gasoline vehicles are much greater than for late-model (2007 and later) on-road heavy-duty diesel trucks.
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Isaksen, Geir Villy, Johan Åqvist y Bjørn Olav Brandsdal. "Enzyme surface rigidity tunes the temperature dependence of catalytic rates". Proceedings of the National Academy of Sciences 113, n.º 28 (27 de junio de 2016): 7822–27. http://dx.doi.org/10.1073/pnas.1605237113.
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The structural origin of enzyme adaptation to low temperature, allowing efficient catalysis of chemical reactions even near the freezing point of water, remains a fundamental puzzle in biocatalysis. A remarkable universal fingerprint shared by all cold-active enzymes is a reduction of the activation enthalpy accompanied by a more negative entropy, which alleviates the exponential decrease in chemical reaction rates caused by lowering of the temperature. Herein, we explore the role of protein surface mobility in determining this enthalpy–entropy balance. The effects of modifying surface rigidity in cold- and warm-active trypsins are demonstrated here by calculation of high-precision Arrhenius plots and thermodynamic activation parameters for the peptide hydrolysis reaction, using extensive computer simulations. The protein surface flexibility is systematically varied by applying positional restraints, causing the remarkable effect of turning the cold-active trypsin into a variant with mesophilic characteristics without changing the amino acid sequence. Furthermore, we show that just restraining a key surface loop causes the same effect as a point mutation in that loop between the cold- and warm-active trypsin. Importantly, changes in the activation enthalpy–entropy balance of up to 10 kcal/mol are almost perfectly balanced at room temperature, whereas they yield significantly higher rates at low temperatures for the cold-adapted enzyme.
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Skupnevskii, S. V., Elena G. Pukhaeva, A. K. Badtiev, F. K. Rurua, F. E. Batagova y Zh G. Farnieva. "Improving safety of oil adjuvant-based vaccines". Russian Journal of Infection and Immunity 12, n.º 5 (16 de noviembre de 2022): 953–62. http://dx.doi.org/10.15789/2220-7619-iso-1897.
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High adjuvant reactogenicity is the main limitation for increasing the effectiveness of vaccine therapy. The aim was to reduce the immunotoxicity effects of complete Freunds adjuvant (CFA) in warm-blooded animals. Materials and methods. The study examined Wistar rats by dividing animals into negative control (solvents); positive control (single subcutaneous CFA injection of 0.1 ml/200 g body weight (b.w.)); the minimum and maximum (per os administration of 1:4 citric and succinic acids in ratio of 17 and 88 mg/kg b.w. during 4 weeks after immunization of CFA) experiment. Body weight, hematological (complete blood count) and biochemical (hydroperoxides, malondialdehyde, catalase activity, mitochondrial dehydrogenase activity) parameters were dynamically investigated. At the end of the experiment, necropsy was performed and the relative internal organ mass coefficients were calculated. The spleen and connective tissue (knee joint) were examined histologically. The median, C25C75 quartiles, MannWhitney U-test were calculated. Results and discussion. it was found that parameters examined were within normal range in animals of negative control group. Immunization of warm-blooded animals with CFA was accompanied by transition of acute-to- chronic inflammatory reaction (week 3 and week 7, respectively). The total leukocyte count increased from 12.5 109 (negative control) up to 26.6 109/L (P = 0.01) on week 3 followed by its decline down to 19.2 109/L (P = 0.01) by week 7. Platelet count also increased significantly: from 506 109 (negative control) up to 656 109/L (P = 0.01, week 3) followed by decrease down to 610 109/L by week 7 (P = 0.01). Activation of lipid peroxidation was manifested by malondialdehyde (MDA) level elevated by 55.861.8% (P = 0.01); the general CFA-related toxic effect resulted in 11.7% weight loss (P = 0.01), spleen swelling and thymus reduction. Administration of antioxidant acids led to a dose-dependent decline in inflammation (leukocyte count at the minimum dosage 19.6 10920.9 109/L; at the maximum 16.6 10916.0 109/L), as well as normalized the platelet/leukocyte index up to 29.536.3 (positive control 24.6, negative control 40.5). The acid-related protective effect was also manifested as maintained body weight, activated catalase and inhibited lipid peroxidation. The therapeutic effect in alleviated degenerative changes in the spleen and connective tissue were revealed: reduced hemorrhagic focuses and swelling as well as preserved histoarchitectonics. Conclusion. The use of citric and succinic acids contributes to profoundly lowered CFA toxicity due to increased total antioxidant status, inhibited lipid peroxidation, improved mitochondrial metabolic activity, which ultimately lead to a decline in general systemic inflammation and allows to recommend such acids as immunoprotectors from oil adjuvant-coupled effects.
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Allay, Sanjita, Rohini Lama, Usha Chakraborty y Biswanath Chakraborty. "Antioxidative responses of mandarin plants to water stress". NBU Journal of Plant Sciences 7, n.º 1 (2013): 21–28. http://dx.doi.org/10.55734/nbujps.2013.v07i01.003.
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Citrus reticulata grows in warm climatic conditions. Stresses such as water logging, drought, soil acidity, unbalanced nutrition and pathogenic infestation lead to root injury resulting in citrus tree decline and therefore huge economic losses. In order to determine the effect of flooding and drought on mandarin plants, mandarin plants were subjected to water logging condition in the field and in pots for drought condition. Biochemical and morphological changes induced by water logging and drought conditions were determined. The plants showed slight wilting and leaf dropping by the third day of flooding whereas in drought the leaves curled up, became crisp and later dried out. Marked changes in antioxidative enzymes such as peroxidase, catalase and ascorbate peroxidase was observed during stress in comparison to control plants. Antioxidative activity was seen to be more in the leaves than in the roots. Among the antioxidants carotenoid content showed a significant decrease during the flood stress but increased in drought stress. An increase in ascorbate content was observed during stress in comparison to the control. From this study, we can conclude that water stress causes adjustment of antioxidant balance in mandarin plants.
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Carriker, Colin R., Paige Rombach, Brooke M. Stevens, Roger A. Vaughan y Ann L. Gibson. "Acute dietary nitrate supplementation does not attenuate oxidative stress or the hemodynamic response during submaximal exercise in hypobaric hypoxia". Applied Physiology, Nutrition, and Metabolism 43, n.º 12 (diciembre de 2018): 1268–74. http://dx.doi.org/10.1139/apnm-2017-0813.
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The purpose of this study was to investigate changes in oxidative stress, arterial oxygen saturation (SaO2), blood pressure (BP), and heart rate (HR) during exercise in hypobaric hypoxia following acute dietary nitrate supplementation. Nine well-trained (maximal oxygen consumption, 60.8 ± 7.8 mL·kg−1·min−1) males (age, 29 ± 7 years) visited the laboratory on 3 occasions, each separated by 1 week. Visit 1 included a maximal aerobic cycling test and five 5-min increasing-intensity exercise bouts in a normobaric environment (1600 m). A single dose of either a nitrate-depleted placebo (PL) or a nitrate-rich beverage (NR; 12.8 mmol nitrate) was consumed 2.5 h prior to exercise during visits 2 and 3 (3500 m) in a double-blind, placebo-controlled, crossover study consisting of a 5-min cycling warm-up and 4 bouts, each 5 min in duration, separated by 4-min periods of passive rest. Exercise wattages were determined during visit 1 and corresponded to 25%, 40%, 50%, 60%, and 70% of normobaric maximal oxygen consumption. Catalase and 8-isoprostane were measured before and after exercise (immediately before and 1 h postexercise, respectively). NR increased plasma nitrite (1.53 ± 0.83 μmol·L−1) compared with PL (0.88 ± 0.56 μmol·L−1) (p < 0.05). In both conditions, postexercise (3500 m) 8-isoprostane (PL, 23.49 ± 3.38 to 60.90 ± 14.95 pg·mL−1; NR, 23.23 ± 4.12 to 52.11 ± 19.76 pg·mL−1) and catalase (PL, 63.89 ± 25.69 to 128.15 ± 41.80 mmol·min−1·mL−1; NR, 78.89 ± 30.95 to 109.96 ± 35.05 mmol·min−1·mL−1) were elevated compared with baseline resting values (p < 0.05). However, both 8-isoprostane and catalase were similar in the 2 groups (PL and NR) (p = 0.217 and p = 0.080, respectively). We concluded that an acute, pre-exercise dose of dietary nitrate yielded no beneficial changes in oxidative stress, SaO2, BP, or HR in healthy, aerobically fit men exercising at 3500 m.
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Djordjevic, Dusica Z., Dejan G. Cubrilo, Vladimir S. Puzovic, Milena S. Vuletic, Vladimir I. Zivkovic, Nevena S. Barudzic, Dragan S. Radovanovic, Dragan M. Djuric y Vladimir Lj Jakovljevic. "Changes in Athlete’s Redox State Induced by Habitual and Unaccustomed Exercise". Oxidative Medicine and Cellular Longevity 2012 (2012): 1–7. http://dx.doi.org/10.1155/2012/805850.
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The purpose of this study was to assess the influence of sport-specific and nonspecific bouts of exercise on athletes’ redox state. Blood samples were collected from 14 handball players immediately before and after graded exercise test on the cycle ergometer and handball training. Levels of superoxide anion radical (O2-), hydrogen peroxide (H2O2), nitrites (NO2-) as markers of nitric oxide, index of lipid peroxidation (TBARs), glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT) activity were determined. Exercise intensity was assessed by a system for heart rate (HR) monitoring. Average athletes’ HR was not significantly different between protocols, but protocols differed in total time and time and percentage of time that athletes spent in every HR zone. The laboratory exercise test induced a significant increase of H2O2and TBARs as well as the decrease of the SOD and CAT activity, while after specific handball training, levels ofNO2-were increased and SOD activity decreased. It seems that unaccustomed short intensive physical activity may induce oxidative stress in trained athletes, while sport-specific activity of longer duration and proper warm-up period may not. Further research should show whether the change of protocol testing and the implementation of various supplementations and manual methods can affect the redox equilibrium.
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Yatsenko, V., O. Ulianych y Y. Yanowskiy. "Effect of iron, zinc and boron on the growth, physiological state, productivity and storability of Allium Sativum L." Ukrainian Journal of Ecology 10, n.º 4 (10 de agosto de 2020): 18–22. http://dx.doi.org/10.15421/2020_164.
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The importance of studying in agriculture the impact of individual micronutrients on the course of production processes and their impact on the quality of garlic is an important issue. The influence of iron, zinc and boron in different norms against the background of the recommended norm NPK. The research results showed significant increasing of chlorophyll content by the application of Iron 10 and 20 kg/ha – 12.0 and 16.4%; by the application zinc increasing of chlorophyll was significant on all variants – 15.1; 48.0 and 30.4% in respectively with the norms. By the application of boron content of chlorophyll was the least significant – 10.9% at the maximum norm – 6 kg/ha. The dynamic activity of antioxidant enzymes was similar before the dynamics of growth processes. The activity of the enzyme was highest for the optimal norms of micronutrients. Among the studied complex of the enzymes most significantly increases actityes catalase (CAT) and glutathione S-transferase (GST). Zinc has the greatest effect on the formation of bulb mass. The increase in bulb weight by the application of zinc fertilizer was significant in all variants – + 14.3–20.0% to control. Fertilization with microelements in the minimum and optimal norms contributed to a significant increase in yield, the application of maximum norms led to a decrease in productivity in general, except boron, where plant productivity increased with increasing norms, from which it can be concluded that garlic needs were insufficient 6 kg/ha is not the maximum. With fertilization of iron in the norms of 10 and 20 kg/ha the yield increase was 4.26 and 4.85 t/ha and was significant, by the application of 30 kg/ha of iron the yield of garlic was higher than the control by 3.70 t/ha. Zinc fertilization had the best effect on yield increase (+ 4.25–5.12 t/ha). A significant increase in yield for boron fertilization was observed at the maximum rate (+3.26 t/ha). By the application of zinc and boron contributed to the extension of the marketability of garlic bulbs to 210 and 220 days for warm storage and up to 240 and 260 days for cold. During warm storage, after 210 and 260 days – during cold storage there was a mass germination of the cloves. Bulbs of the control variant and y the application of iron germinated after 120 and 180 and 190–210 days according to the variant and storage regime. Further research is to study the combinations of the studied micronutrients on physiological processes and biochemical parameters and to optimize their norms for local fertilization.
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McLaughlin, Jay P., Ramanjaneyulu Rayala, Ashley J. Bunnell, Mukund P. Tantak, Shainnel O. Eans, Khadija Nefzi, Michelle L. Ganno, Colette T. Dooley y Adel Nefzi. "Bis-Cyclic Guanidine Heterocyclic Peptidomimetics as Opioid Ligands with Mixed μ-, κ- and δ-Opioid Receptor Interactions: A Potential Approach to Novel Analgesics". International Journal of Molecular Sciences 23, n.º 17 (25 de agosto de 2022): 9623. http://dx.doi.org/10.3390/ijms23179623.
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The design and development of analgesics with mixed-opioid receptor interactions has been reported to decrease side effects, minimizing respiratory depression and reinforcing properties to generate safer analgesic therapeutics. We synthesized bis-cyclic guanidine heterocyclic peptidomimetics from reduced tripeptides. In vitro screening with radioligand competition binding assays demonstrated variable affinity for the mu-opioid receptor (MOR), delta-opioid receptor (DOR), and kappa-opioid receptor (KOR) across the series, with compound 1968-22 displaying good affinity for all three receptors. Central intracerebroventricular (i.c.v.) administration of 1968-22 produced dose-dependent, opioid receptor-mediated antinociception in the mouse 55 °C warm-water tail-withdrawal assay, and 1968-22 also produced significant antinociception up to 80 min after oral administration (10 mg/kg, p.o.). Compound 1968-22 was detected in the brain 5 min after intravenous administration and was shown to be stable in the blood for at least 30 min. Central administration of 1968-22 did not produce significant respiratory depression, locomotor effects or conditioned place preference or aversion. The data suggest these bis-cyclic guanidine heterocyclic peptidomimetics with multifunctional opioid receptor activity may hold potential as new analgesics with fewer liabilities of use.
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Wei, Wei, Jian-ye Chen, Ze-xiang Zeng, Jian-fei Kuang, Wang-jin Lu y Wei Shan. "The Ubiquitin E3 Ligase MaLUL2 Is Involved in High Temperature-Induced Green Ripening in Banana Fruit". International Journal of Molecular Sciences 21, n.º 24 (9 de diciembre de 2020): 9386. http://dx.doi.org/10.3390/ijms21249386.
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Harvested banana fruit ripened under warm temperatures above 24 °C remain green peel, leading to severe economic loss. E3 ubiquitin-ligases, as the major components in the ubiquitination pathway, have been implicated to play important roles in temperature-stress responses. However, the molecular mechanism underlying high temperature-triggered stay-green ripening bananas in association with E3 ubiquitin-ligases, remains largely unknown. In this study, a RING-type E3 ubiquitin ligase termed MaLUL2, was isolated and characterized from banana fruit. The MaLUL2 gene contains 1095 nucleotides and encodes a protein with 365 amino acids. The MaLUL2 protein contains a domain associated with RING2 (DAR2) and a RING domain, which are the typical characteristics of RING-type E3 ligases. MaLUL2 expression was up-regulated during high temperature-induced green ripening. Subcellular localization showed that MaLUL2 localized in the nucleus, cytoplasm, and plasma membrane. MaLUL2 displayed E3 ubiquitin ligase activity in vitro. More importantly, transient overexpression of MaLUL2 in banana fruit peel increased the level of ubiquitination in vivo and led to a stay-green phenotype, accompanying with decreased expression of chlorophyll catabolic genes. Collectively, these findings suggest that MaLUL2 might act as a negative regulator of chlorophyll degradation and provide novel insights into the regulatory mechanism of high temperature-induced green ripening bananas.
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Ernst, Lisa, Zoltan Czigany, Pascal Paschenda, Mareike Schulz, Lukas Breuer, Janosch Kunczik, Michael Czaplik et al. "A Proof-of-Concept Preclinical Study Using a Novel Thermal Insulation Device in a Porcine Kidney Auto-Transplantation Model". International Journal of Molecular Sciences 23, n.º 22 (9 de noviembre de 2022): 13806. http://dx.doi.org/10.3390/ijms232213806.
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Ischemia-reperfusion injury remains a fundamental problem during organ transplantation logistics. One key technical factor is the rapid allograft rewarming during the time of vascular reconstruction in the recipient. In this pilot study, a new thermal insulation bag (TIB) for organ transplantation was used. Insulation capacity, tissue compatibility, and usability were tested initially ex vivo on porcine kidneys (n = 24) followed by the first in vivo usage. Fourteen female German landrace pigs underwent kidney auto-transplantation after 24 h cold storage (4 °C). During the implantation process the kidney was either insulated with the new TIB, or it was not thermo-protected at all, which represents the clinical standard. In this proof-of-concept study, the usability (knife-to-skin-time) and the general thermal capacity (30 min warm storage at 38 °C ex vivo p < 0.001) was shown. The clinical outcome showed significant differences in the determination of CRP and pi-GST levels. Syndecan-1 Antibody staining showed clear significant higher counts in the control group (p < 0.01) indicating epithelial damage. However, the effect on renal outcomes in not severely pre-damaged kidneys does not appear to be conclusively significant. A close follow-up study is warranted, especially in the context of marginal organs or in cases where anastomosis-times are prolonged due to surgical complexity (e.g., multiple vessels and complex reconstructions).
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Gál, Robert, Pavel Mokrejš, Jana Pavlačková y Dagmar Janáčová. "Cyprinus carpio Skeleton Byproduct as a Source of Collagen for Gelatin Preparation". International Journal of Molecular Sciences 23, n.º 6 (15 de marzo de 2022): 3164. http://dx.doi.org/10.3390/ijms23063164.
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Byproducts obtained from fish processing account for up to 70% of their live weight and represent a large amount of unused raw materials rich in proteins, fats, minerals, and vitamins. Recently, the management of the use of predominantly cold-water fish byproducts has become a priority for many processing companies. This paper describes the biotechnological processing of byproducts of warm-water Cyprinus carpio skeletons into gelatins. A Taguchi experimental design with two process factors (HCl concentration during demineralization of the starting material and the amount of enzyme during enzyme conditioning of the collagen) examined at three levels (0.5, 1.0 and 2.0 wt%; 0.0, 0.1 and 0.2 wt% respectively) was used to optimize the processing of fish tissue into gelatin. Depending on the preparation conditions, four gelatin fractions were prepared by multi-stage extraction from the starting material with a total yield of 18.7–55.7%. Extensive characterization of the gel-forming and surface properties of the prepared gelatins was performed. Gelatins belong to the group of zero–low-medium Bloom value (0–170 Bloom) and low–medium viscosity (1.1–4.9 mPa·s) gelatins and are suitable for some food, pharmaceutical, and cosmetic applications. During processing, the pigment can be isolated; the remaining solid product can then be used in agriculture, and H3PO4Ca can be precipitated from the liquid byproduct after demineralization. The carp byproduct processing technology is environmentally friendly and meets the requirements of zero-waste technology.
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Pranneshraj, Velumani, Manjeet Kaur Sangha, Ivica Djalovic, Jegor Miladinovic y Maduraimuthu Djanaguiraman. "Lipidomics-Assisted GWAS (lGWAS) Approach for Improving High-Temperature Stress Tolerance of Crops". International Journal of Molecular Sciences 23, n.º 16 (20 de agosto de 2022): 9389. http://dx.doi.org/10.3390/ijms23169389.
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High-temperature stress (HT) over crop productivity is an important environmental factor demanding more attention as recent global warming trends are alarming and pose a potential threat to crop production. According to the Sixth IPCC report, future years will have longer warm seasons and frequent heat waves. Thus, the need arises to develop HT-tolerant genotypes that can be used to breed high-yielding crops. Several physiological, biochemical, and molecular alterations are orchestrated in providing HT tolerance to a genotype. One mechanism to counter HT is overcoming high-temperature-induced membrane superfluidity and structural disorganizations. Several HT lipidomic studies on different genotypes have indicated the potential involvement of membrane lipid remodelling in providing HT tolerance. Advances in high-throughput analytical techniques such as tandem mass spectrometry have paved the way for large-scale identification and quantification of the enormously diverse lipid molecules in a single run. Physiological trait-based breeding has been employed so far to identify and select HT tolerant genotypes but has several disadvantages, such as the genotype-phenotype gap affecting the efficiency of identifying the underlying genetic association. Tolerant genotypes maintain a high photosynthetic rate, stable membranes, and membrane-associated mechanisms. In this context, studying the HT-induced membrane lipid remodelling, resultant of several up-/down-regulations of genes and post-translational modifications, will aid in identifying potential lipid biomarkers for HT tolerance/susceptibility. The identified lipid biomarkers (LIPIDOTYPE) can thus be considered an intermediate phenotype, bridging the gap between genotype–phenotype (genotype–LIPIDOTYPE–phenotype). Recent works integrating metabolomics with quantitative genetic studies such as GWAS (mGWAS) have provided close associations between genotype, metabolites, and stress-tolerant phenotypes. This review has been sculpted to provide a potential workflow that combines MS-based lipidomics and the robust GWAS (lipidomics assisted GWAS-lGWAS) to identify membrane lipid remodelling related genes and associations which can be used to develop HS tolerant genotypes with enhanced membrane thermostability (MTS) and heat stable photosynthesis (HP).
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Tordai, Dóra Zsuszanna, Noémi Hajdú, Ramóna Rácz, Ildikó Istenes, Magdolna Békeffy, Orsolya Erzsébet Vági, Miklós Kempler et al. "Genetic Factors Associated with the Development of Neuropathy in Type 2 Diabetes". International Journal of Molecular Sciences 25, n.º 3 (2 de febrero de 2024): 1815. http://dx.doi.org/10.3390/ijms25031815.
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Neuropathy is a serious and frequent complication of type 2 diabetes (T2DM). This study was carried out to search for genetic factors associated with the development of diabetic neuropathy by whole exome sequencing. For this study, 24 patients with long-term type 2 diabetes with neuropathy and 24 without underwent detailed neurological assessment and whole exome sequencing. Cardiovascular autonomic function was evaluated by cardiovascular reflex tests. Heart rate variability was measured by the triangle index. Sensory nerve function was estimated by Neurometer and Medoc devices. Neuropathic symptoms were characterized by the neuropathy total symptom score (NTSS). Whole exome sequencing (WES) was performed on a Thermo Ion GeneStudio S5 system determining the coding sequences of approximately 32,000 genes comprising 50 million base pairs. Variants were detected by Ion Reporter software and annotated using ANNOVAR, integrating database information from dbSNP, ClinVar, gnomAD, and OMIM. Integrative genomics viewer (IGV) was used for visualization of the mapped reads. We have identified genetic variants that were significantly associated with increased (22–49-fold) risk of neuropathy (rs2032930 and rs2032931 of recQ-mediated genome instability protein 2 (RMI2) gene), rs604349 of myosin binding protein H like (MYBPHL) gene and with reduced (0.07–0.08-fold) risk (rs917778 of multivesicular body subunit 12B (MVB12B) and rs2234753 of retinoic acid X receptor alpha (RXRA) genes). The rs2032930 showed a significant correlation with current perception thresholds measured at 5 Hz and 250 Hz for n. medianus (p = 0.042 and p = 0.003, respectively) and at 5 Hz for n. peroneus (p = 0.037), as well as the deep breath test (p = 0.022) and the NTSS (p = 0.023). The rs2032931 was associated with current perception thresholds (p = 0.003 and p = 0.037, respectively), deep breath test (p = 0.022), and NTSS (p = 0.023). The rs604349 correlated with values measured at 2000 (p = 0.049), 250 (p = 0.018), and 5 Hz (p = 0.005) for n. medianus, as well as warm perception threshold measured by Medoc device (p = 0.042). The rs2234753 showed correlations with a current perception threshold measured at 2000 Hz for n. medianus (p = 0.020), deep breath test (p = 0.040), and NTSS (p = 0.003). There was a significant relationship between rs91778 and cold perception threshold (p = 0.013). In our study, genetic variants have been identified that may have an impact on the risk of neuropathy developing in type 2 diabetic patients. These results could open up new opportunities for early preventive measures and might provide targets for new drug developments in the future.
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Mondal, K. K., C. Mani, J. Singh, S. R. Dave, D. R. Tipre, A. Kumar y B. M. Trivedi. "Fruit Rot of Tinda Caused by Pseudomonas aeruginosa–A New Report from India". Plant Disease 96, n.º 1 (enero de 2012): 141. http://dx.doi.org/10.1094/pdis-05-11-0404.
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Fruit rot disease (FRD), an emerging problem of tinda (Praecitrullus fistulosus) in India. FRD epidemics begin during rainy and warm weather and often spoil marketable produce. Symptoms appear as numerous, pale brown-to-dark brown, deeply penetrating circular soft rot lesions on fleshy fruit tissues. Noneffervescent bacterial exudates occasionally form on lesions. Repeated isolations from FRD-affected tinda fruits consistently yielded the same bacterial species. Inoculation of the isolated bacterium into asymptomatic tinda fruits produced identical soft rot symptoms. Fruits were inoculated with the isolate ITCC B0030 (0.1 OD) by removing a 2.0-cm deep tissue plug with a sterile cork borer (5 mm in diameter) and injecting the inoculum with a syringe in the cylindrical cavity. After inoculation, the plug (upper 5 mm) was reinserted, sealed with sterile paraffin, and covered with a small piece of wet absorbent cotton to prevent dehydration. High humidity (>90%) and 30 to 33°C temperature was maintained after inoculation in a glasshouse. After 4 to 10 days, fruits showed FRD symptoms. The reisolated bacterium from artificially inoculated symptomatic fruits was identical with the original inoculated bacterium. Identity of the bacterial pathogen for FRD was confirmed by phenotypic and genotypic methods. The causal bacterium was a gram-negative, non-sporing motile rod with a single polar flagellum. The bacterium produced yellowish green and blue-green diffusible pigments on King's B (KB) medium. On yeast dextrose calcium carbonate agar at 30°C, the colonies produced abundant, blue, diffusible pigment within 48 h. The bacterium grew at temperatures up to 42°C but not at 4°C. Excellent growth occurred on Salmonella-Shigella agar and MaConkey's medium, as reported also for Pseudomonas aeruginosa strain P8. The bacterium produced ammonia, hydrogen sulfide, arginine dihydrolase, urease, lipase, catalase, gelatinase, and casinase but not amylase, indole, or acetyl methyl carbinol. The bacterium was identified as P. aeruginosa using Biolog based Bacterial Identification System version 4.2 (Biolog Inc., Hayward, CA). The bacterium did not utilize cellobiose, dulcitol, maltose, sorbitol, sucrose, arabinose, and starch. Upon infiltration on tobacco leaves (Nicotiana tabacum cv. Xanthi) at 107 or more cells ml–1, the bacterium gave a strong hypersensitive reaction within 24 h. Transmission electron micrographs (TEM, KYKY 1000B, Japan) of the causal bacterium revealed a single, polar flagellum. Identity was further confirmed as P. aeruginosa based on 16S rRNA sequence (1,491 nt) analysis with universal primers F1 (5′-GAGTTTGATCCTGGCTCAG-3′) and R13 (5′-AGAAAGGAGGTGATCCAGCC-3′). A blastN search of GenBank revealed a >99% nt identity with P. aeruginosa strain TAUC 7 (HQ914782). The 16S rRNA gene sequence (1,491 nt) was deposited in Bankit GenBank (JF797204). To our knowledge, this is the first report of fruit rot of tinda caused by P. aeruginosa in India (ITCC B0030) and a new record of bacterial rot of Praecitrullus fistulosus induced by a fluorescent and blue-green pigment producing P. aeruginosa. To date, P. syringae pv. lachrymans and a nonfluorescent P. pseudoalcaligenes subsp. citrulli were reported to infect Citrullus lanata (1) and Praecitrullus fistulosus (2), respectively. References: (1) D. L. Hopkins and N. C. Schenck. Phytopathology 62:542, 1972. (2) N. W. Schaad et al. Int. J. Syst. Bacteriol. 28:117, 1978.
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Foster, John L., Kalen Vos, Mrunal C. Joshi, Gregory M. Shaver, James McCarthy, Eric Holloway y Lisa Farrell. "Diesel Engine 2-Stroke Breathing for Aftertreatment Warm-Up". International Journal of Engine Research, 22 de octubre de 2021, 146808742110523. http://dx.doi.org/10.1177/14680874211052381.
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Since the introduction of diesel urea SCR technology, aftertreatment thermal management has become critical for maintaining SCR catalyst light-off and thereby low cumulative cycle NOx emissions. A novel diesel engine aftertreatment thermal management strategy is proposed which utilizes a 2-stroke breathing variable value actuation strategy to increase the mass flow rate of exhaust gas. Experiments showed that when emissions are constrained to the same level as a state-of-the-art thermal management strategy, 2SB does not increase heat transfer to aftertreatment. However, if constraints are allowed to flex, temperatures comparable to a state-of-the-art thermal management calibration could be achieved with a 1.75× exhaust mass flow rate, potentially helping heat the SCR catalyst in a cold-start scenario.
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"Methanol reformer with quick shifting to reforming after catalyst warm-up". Fuel Cells Bulletin 2002, n.º 1 (enero de 2002): 16. http://dx.doi.org/10.1016/s1464-2859(02)80077-3.
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Mohapatra, Priyabrata y Mayank Mittal. "A Simplified One-Dimensional Mathematical Model to Study the Transient Thermal Behavior of an Oxidation Catalyst with Both Low and High Levels of CO Concentration at the Inlet". Chemical Product and Process Modeling 14, n.º 3 (27 de febrero de 2019). http://dx.doi.org/10.1515/cppm-2018-0049.
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Abstract In recent years, the permissible limits of engine exhaust emissions are reduced considerably. Hence a quick warm-up and high conversion efficiency of the catalyst system is essential to meet upcoming stringent emission regulations. In the present work, the transient thermal behavior of an oxidation catalyst is studied using a one-dimension mathematical modeling approach with the focus on CO oxidation for dual-fuel engine application. At first, the heat generation due to chemical reactions is considered negligible for studying the warm-up behavior. Upon obtaining a good agreement between predicted warm-up temperature profiles with available literature data, the effect of an electrical heater on the warm-up behavior is investigated. The model is then extended by incorporating heat generation due to CO oxidation. A simplified reaction rate model is considered in order to reduce the computational complexity. It is observed that the simplified model agrees well with the experimental data for both low and high levels of CO concentration at the inlet, typical in dual-fuel technology when an engine is operated under diesel and dual-fuel modes, respectively.
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Chauhan, Sanchita y V. K. Srivastava. "Modeling the Effect of Temperature on Propylene Conversion during Warm-Up in a Monolithic Converter". Chemical Product and Process Modeling 3, n.º 1 (25 de septiembre de 2008). http://dx.doi.org/10.2202/1934-2659.1232.
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In order to improve air quality, catalytic converters have been extensively employed throughout the world. These monolithic catalytic converters are very effective in reducing pollution only after they have heated up. The catalyst warming-up process takes some time and during this period a considerable amount of pollutants, especially hydrocarbons, is released into the atmosphere. In this paper, a one-dimensional model for the hydrocarbon propylene was developed, taking into account heat and mass transfer between the exhaust gas and the catalyst surface and the catalytic reaction. The equations so formed are a set of ordinary differential equations (ODEs) and a partial differential equation (PDE). The ODEs are solved using the Runge-Kutta method of fourth order and the PDE by backward implicit scheme. The effect of varying the inlet gas temperature and initial catalyst solid temperatures on conversion of propylene was analysed.
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Falcão Weissinger, Frederico, Caio Henrique Rufino, Alexander Peñaranda Mendoza, André Luiz Martelli, Eugênio Coelho, Vincent Bigliardi y Pedro Teixeira Lacava. "Electrically heated catalyst enabling pollutants reduction in hybrid vehicles fueled with ethanol". International Journal of Engine Research, 14 de diciembre de 2023. http://dx.doi.org/10.1177/14680874231214010.
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Plug-in hybrid electric vehicles (PHEV) have the potential of combining the benefits of a renewable electric mix with biofuels. More recently, PHEV have been designed to be equipped with a small combustion engine known as range extender (RE), thus allowing an improvement in vehicle’s range while converting fuel energy through a highly efficient path. Despite being a convenient strategy for decarbonizing light vehicles, the intermittent operation of the engine may create issues regarding the catalytic conversion of pollutants, yielding an increase in local harmful emissions. This drawback may be intensified depending on the used fuel. Hydrous ethanol is a promising alternative for gasoline and is already available in some countries, such as Brazil. However, ethanol has a great enthalpy of vaporization and it results in a charge cooling, affecting the catalyst warm-up and making the intermittent operation with ethanol more challenging. Hence, this study was motivated by the need of improving the catalytic efficiency of flexfuel RE operating with both gasoline and hydrous ethanol. Thus, a calibration was firstly performed to shorten the warm-up phase with ethanol. Then, an electrical heater was employed for accelerated catalyst heating, further improving emissions from ethanol operation, aiming at attaining future emissions regulations. Experimental tests were conducted in a vehicle under FTP72 cycle using a chassis dynamometer. The calibration adjustments resulted in a warm-up phase for ethanol <10 s longer than that for gasoline. The stable operation phase resulted in similar emissions for both fuels. On the cycle average, a reduction in CO for ethanol was observed, and although the methane and NOx emissions were slightly increased due to colder catalyst operation, significant improvements were obtained on a well-to-wheel (WTW) analysis. The use of an electrically heated catalyst (EHC) improved the emissions during the warm-up phase, significantly reducing the emission of NOx and non-methane organic compounds.