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- 저자 : Norbeck (검색결과 10 건)
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Carbon Source Dependent Dynamics of the Ccr4-Not Complex in Saccharomyces cerevisiae
Joakim Norbeck 한국미생물학회 2008 The journal of microbiology Vol.46 No.6
We have investigated the composition of the conserved Ccr4-Not complex during different physiological states of Saccharomyces cerevisiae. Major changes were found, most notably in the expression of the central scaffold protein Not1p, which was strongly reduced in the absence of glucose. The low expression of Not1p was also evident from the inability of Pop2p to co-purify Not1p in cells from cultures lacking glucose. However, Not1p was still essential under conditions of low expression. The downregulation of Not1p indicates that many of the Ccr4-Not complex components are likely to have roles outside of the complex. We suggest that the use of different carbon sources will be a good starting point to unravel these functions.
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Nina Johansson,Karl O. Persson,Joakim Norbeck,Christer Larsson 한국생물공학회 2017 Biotechnology and Bioprocess Engineering Vol.22 No.2
Ethylene is a major petrochemical for which biotechnological production methods are an attractive alternative. Here we use a system based on a bacterial ethylene forming enzyme (EFE) expressed in Saccharomyces cerevisiae. Metabolic modelling performed in a previous study identified re-oxidation of NADH as a factor limiting ethylene production in S. cerevisiae. In line with this, we here found that strains with multicopy plasmid expression of the heterologous oxidases nox and Aox1 led to significantly increased specific ethylene productivity, up 12 and 36%, respectively, compared to the control strain with empty plasmid. However the productivity and yield was only improved in the AOX expressing strain compared to that of the control strain. Both oxidase expressing strains also exhibited increased respiration rates compared to the reference strain, with specific oxygen consumption rates being roughly doubled in both strains. The AOX strain furthermore exhibited a significant increase in the EFE substrate 2-oxoglutarate formation compared to the reference strain, linking an improvement in ethylene production to both increased respiratory capacity and increased substrate availability, thereby corroborating our previous finding.
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T. HUAI,T. D. DURBIN,S. H. RHEE,J. M. NORBECK 한국자동차공학회 2003 International journal of automotive technology Vol.4 No.1
Exhaust emissions were characterized for a fleet of 10 alternative-fuel vehicles (AFVs) including 5 compressed natural gas (CNG) vehicles, 3 liquefied petroleum gas (LPG) vehicles and 2 85% methano1/15% Califrnia Phase 2 gasoline (M85) vehicles. In addition to the standard regulated emissions and detailed speciation of organic gas compounds. Fourier Transform Infrared Spectroscopy (FTIR) was used to measure ammonia (NH₃) and nitrous oxide (N₂O) emissions. NH₃ emissions averaged 0.124 g/mi for the vehicle fleet with a range from <0.004 to 0.540 g/mi. N₂O emissions averaged 0.022 g/mi over the vehicle fleet with range from <0.002 to 0.077 g/mi. Modal emissions showed that both NH₃ and N₂O emissions began during catalyst light-off and continued as the catalyst reached its operating temperature. N₂O emissions primarily were farmed during the initial stages of catalyst light-off. Detailed speciation measurements showed that the principal component of the fuel was also the primary organic gas species found in the exhaust. In particular, methane. propane and methanol composed on average 93%. 79%. and 75% of the organic gas emissions. respectively. for the CNG. LPG. and M85 vehicles.<br/>
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Huai, T.,Durbin, T.-D.,Rhee, S.-H.,Norbeck, J.-M. The Korean Society of Automotive Engineers 2003 International journal of automotive technology Vol.4 No.1
Exhaust emissions were characterized for a fleet of 10 alternative-fuel vehicles (AFVx) including 5 compressed natural gas (CNG) vehicles. 3 liquefied petroleum gas (LPG) vehicles and 2 85% methanol/15% California Phase 2 gasoline (M85) vehicles. In addition to the standard regulated emissions and detailed speciation of organic gas compounds, Fourier Transform Infrared Spectroscopy (FTIR) was used to measure ammonia (NH$_3$) and nitrous oxide ($N_2$O) emissions. NH$_3$, emissions averaged 0.124 g/mi for the vehicle fleet with a range from <0.004 to 0.540 g/mi. $N_2$O emissions averaged 0.022 g/mi over the vehicle fleet with range from <0.002 to 0.077 g/mi. Modal emissions showed that both NH$_3$, and $N_2$O emissions began during catalyst light-off and continued as the catalyst reached its operating temperature. $N_2$O emissions primarily were formed during the initial stages of catalyst light-off. Detailed speciation measurements showed that the principal component of the fuel was also the primary organic gas species found in the exhaust. In particular, methane, propane and methanol composed on average 93%, 79%, and 75% of the organic gas emissions, respectively, for the CNG, LPG. and M85 vehicles.
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MEASUREMENT OF OPERATIONAL ACTIVITY FOR NONROAD DIESEL CONSTRUCTION EQUIPMENT
HUAI T.,SHAH S. D.,DURBIN T. D.,NORBECK J. M. The Korean Society of Automotive Engineers 2005 International journal of automotive technology Vol.6 No.4
In order to better quantify the contribution from nonroad sources to emission inventories, it is important to understand not only the emissions rates of these engines but also activity patterns that can be used to accurately portray their in-use operation. To date, however, very little information is available on the actual activity patterns of nonroad equipment. In this study, a total of 18 pieces of nonroad equipment were instrumented with collected data including intake manifold air pressure (MAP), exhaust temperature and, on a subset of vehicles, engine rpm and throttle position. The equipment included backhoes, compactors, dozers, motor graders, loaders and scrappers used in applications such as landfilling, street maintenance and general roadwork. The activity patterns varied considerably depending on the type of equipment and the application. Daily equipment operating time ranged from less than 30 minutes to more than 8 hours, with landfill equipment having the highest daily use. The number of engine starts per day ranged from 3-11 lover the fleet with an average of 5 starts per day. The average percent idle time for the fleet was approximately $25\%$ with a range from 11 to $65\%$ for individual pieces of equipment. Duty cycles based on exhaust temperature/throttle position profiles were also developed for two graders and one dozer.
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MEASUREMENT OF OPERATIONAL ACTIVITY FOR NONROAD DIESEL CONSTRUCTION EQUIPMENT
T. HUAI,S.D. SHAH,T.D. DURBIN J.M. NORBECK 한국자동차공학회 2005 International journal of automotive technology Vol.6 No.4
In order to better quantify the contribution from nonroad sources to emission inventories, it is important to understand not only the emissions rates of these engines but also activity patterns that can be used to accurately portray their in-use operation. To date, however, very little information is available on the actual activity patterns of nonroad equipment. In this study, a total of 18 pieces of nonroad equipment were instrumented with collected data including intake manifold air pressure (MAP), exhaust temperature and, on a subset of vehicles, engine rpm and throttle position. The equipment included backhoes, compactors, dozers, motor graders, loaders and scrappers used in applications such as landfilling, street maintenance and general roadwork. The activity patterns varied considerably depending on the type of equipment and the application. Daily equipment operating time ranged from less than 30 minutes to more than 8 hours, with landfill equipment having the highest daily use. The number of engine starts per day ranged from 3?11 over the fleet with an average of 5 starts per day. The average percent idle time for the fleet was approximately 25% with a range from 11 to 65% for individual pieces of equipment. Duty cycles based on exhaust temperature/throttle position profiles were also developed for two graders and one dozer.
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Methane steam reforming for synthetic diesel fuel production from steam-hydrogasifier product gases
Seok Ku Jeon,Chan Seung Park,Sang Done Kim,송병호,Joseph M. Norbeck 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.6
Steam-methane reforming (SMR) reaction was studied using a tubular reactor packed with NiO/ γ-Al2O3 catalyst to obtain synthesis gases with H2/CO ratios optimal for the production of synthetic diesel fuel from steamhydrogasification of carbonaceous materials. Pure CH4 and CH4-CO2 mixtures were used as reactants in the presence of steam. SMR runs were conducted at various operation parameters. Increasing temperature from 873 to 1,023 K decreased H2/CO ratio from 20 to 12. H2/CO ratio decreased from 16 to 12 with pressure decreasing from 12.8 to 1.7 bars. H2/CO ratio also decreased from about 11 to 7 with steam/CH4 ratio of feed decreasing from 5 to 2, the lowest limit to avoid severe coking. With pure CH4 as the feed, H2/CO ratio of synthesis gas could not be lowered to the optimal range of 4-5 by adjusting the operation parameters; however, the limitation in optimizing the H2/CO ratio for synthetic diesel fuel production could be removed by introducing CO2 to CH4 feed to make CH4-CO2 mixtures. This effect can be primarily attributed to the contributions by CO2 reforming of CH4 as well as reverse water-gas shift reaction, which led to lower H2/CO ratio for the synthesis gas. A simulation technique, ASPEN Plus, was applied to verify the consistency between experimental data and simulation results. The model satisfactorily simulated changes of H2/CO ratio versus the operation parameters as well as the effect of CO2 addition to CH4 feed.
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Hydrodynamics of a hybrid circulating fluidized bed reactor with a partitioned loop seal system
배달희,Minyoung Yun,문종호,진경태,선도원,Chan Seung Park,Joseph M. Norbeck 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.7
A circulating fluidized bed (CFB) with a hybrid design has been developed and optimized for steam hydrogasification. The hybrid CFB is composed of a bubbling fluidized bed (BFB) type combustor and a fast fluidized bed (FB) type gasifier. Char is burnt in the combustor and the generated heat is supplied to the gasifier along with the bed materials. Two different types of fluidized beds are connected to each other with a newly developed partitioned loop seal to avoid direct contact between two separate gas streams flowing in each fluidized bed. Gas mixing tests were carried out with Air and Argon in a cold model hybrid CFB to test the loop seal efficiency. Increase in solid inventory in the loop seal can improve the gas separation efficiency. It can be realized at higher gas velocity in fast bed and with higher solid inventory in the loop seal system. In addition, bed hydrodynamics was investigated with varying gas flow conditions and particle sizes in order to obtain a full understanding of changes of solid holdup in the FB. The solid holdup in the FB increased with increasing gas velocity in the BFB. Conversely, increase in gas velocity in the FB contributed to reducing the solid holdup in the FB. It was observed that changing the particle size of bed material does not have a big impact on hydrodynamic parameters.
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