bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Study on a Compact Methanol-Fueled Reformer With Heat Regeneration Using Ceramic Honeycomb (2nd Report: Reaction Region Detection by a Positive Ion Current Probe)
Authors: Rai Yasuhiro , Kogame Hideyuki , Tatsumi Kazuya , Nakabe Kazuyoshi
Published: March 2012

A compact tubular-type fuel reformer was fabricated and operated under fuel-rich combustion conditions of methanol, focusing on the partial oxidation reaction (POR). Ceramic honeycomb strainer blocks were inserted in the reactor. In the authors’ previous study, Case-1 of only one honeycomb block insertion showed that the reaction region formed in the downstream of the block. This block worked as a reaction stabilizer. The other condition, Case-2, was operated with the secondary honeycomb block inserted in the downstream of the reaction region in addition to the first block. This geometrical structure sandwiched the reaction region between the two blocks, and the thermal energy possessed by the exhaust gas could be regenerated to the reaction region by radiation exchange between these two blocks, which resulted in enhancing the preheating of the premixed gas. By this effect, the methanol-conversion and hydrogen-production in Case-2 were enhanced by about 10% compared to Case-1. In the present study, the reaction characteristics of the fuel reformer were investigated in detail, by detecting the location of the reaction region. Detailed temperature profiles in the streamwise direction were measured with traversable thermocouples, and positive ion current distributions corresponding to the reaction region were measured with a Langmuir probe. It was confirmed by the both measurements that there exists a reaction region right after the first honeycomb block which accompanies with sharp temperature gradients. The estimated thickness of the reaction region, however, was as wide as several millimeters to a centimeter, which is believed to be a ‘mild reaction’ stabilized by the first honeycomb block. In Case-2, the high-temperature region became broader compared to Case-1, which indicates that the enhancement of preheating of premixed gas was achieved by the heat regenerated from the secondary honeycomb block.
Advanced Gas Turbine Technology for Sendai Thermal Power Station, Unit No. 4
Authors: Ohno Sadahiro , Yamazaki Hiroyuki , Hagi Naoki , Nishimura Hidehiko
Published: March 2012

Worldwide environmental concerns are placing center focus on effective utilization of energy and carbon dioxide emission reductions. The power generation industry has engaged in the replacement of existing aged thermal power plants with state-of-the-art natural gas fired power plants capable of achieving considerable reductions in energy consumption and emissions of green house gases. The replacement of three exiting 175MW heavy oil and coal-firing power plants with a highly effective 446MW gas-firing combined cycle power plant owned and operated by Tohoku Electric Power Company is one example of this effort. The construction of the new Sendai thermal power station, Unit No.4 started in November, 2007 achieving commercial operation in July, 2010. Mitsubishi Heavy Industries most recent 50Hz F class gas turbine upgrade, the M701F4 was adopted for this project. This engine is based on the successful M701F3 gas turbine with a 6% air flow increase and a slight bump of the turbine inlet temperature in order to achieve better thermal efficiency and more power output. The application of these advanced technologies resulted in a plant thermal efficiency of approximately 58% LHV of the new unit from the original 43% of the previous coal-firing units. The application of these advanced technologies and the use of natural gas resulted in a 2/3 carbon-dioxide emissions reduction.
Wind Direction Characteristics of a Vertical Axis Wind Turbine Using the Mechanism of a Bird’s Wing With a Wind Collector
Authors: Tanzawa Yoshiaki , Sato Takao , Hashizume Takumi
Published: March 2012

This paper describes the wind direction characteristics of the wind collector used for our 8th model of the vertical axis wind turbine using the mechanism of a bird’s wing. The 8th model is divided into two sections top and bottom. Each section looks like a Savonius wind turbine. The blade is divided into seven rows of plates. Each 0.18mm stainless plate has only one side attached to the frame. Wind from the outside enlarges the space between the blades, and passes through. However, wind from the inside closes the space. In the wind collector, four wind collection boards are located every 90 degrees around this wind turbine. In an earlier paper, it was confirmed that these collection boards collected 1.6 times the wind and resulted in twice the output. In this paper, the variations in the wind collector characteristics due to the wind direction are clarified experimentally. A wind tunnel experiment using six different wind directions shows that the output increases for four wind directions and decreases for one wind direction. Additionally, the computer simulation confirms the wind direction and the wind speed distribution around the wind turbine when the wind collection boards are in place.
Study Results of Combustion Characteristics in Oxy-Fuel Combustion Process
Authors: Gotou Takahiro , Yamada Toshihiko , Kiga Takashi , Misawa Nobuhiro , Hashimoto Keiichiro
Published: March 2012

Oxy-fuel combustion is expected to be one of the promising systems on CO2 capture from pulverized-coal fired power plant, and enable the CO2 to be captured in a more cost-effective manner compared to other CO2 capture process with the power generation from the results of previous study. Some studies in this area are implemented under Australia-Japan consortium established in 2004 and joint venture for Callide Oxy-fuel Project under Australia-Japan consortium is established in March 2008. The project is now under way for the retrofit oxy-fuel combustion to an existing power plant by way of demonstration and is implemented in Callide-A power plant No.4 unit owned by CS Energy with a capacity of 30MWe in Australia. This project aims at capturing CO2 from an actual power plant for CO2 storage. The demonstration operation will start in 2011. One of the key issues to achieve the reliable and stable operation is countermeasure against corrosion. Recently, we studied the behaviors of corrosive substances in combustion gas and trace elements in flue gas, which is mainly sulfur compounds and Hg respectively. Sulfur compounds causes corrosion of boiler tubes, and Hg causes corrosion of aluminum base heat exchangers in the CO2 processing unit. Knowledge of their behaviors in oxyfuel is insufficient, and obtaining their knowledge is important for suitable material selection, countermeasure against corrosion, and optimal process design. In order to confirm the behaviors of corrosion components and Hg, the pilot-scale combustion test in IHI is performed at the combustion test facilities; the capacity of the furnace is 1.2MWt. The combustion test is conducted under oxy-fuel and air combustion conditions because of confirmation of the difference in both conditions. In this paper, the behaviors of corrosion components and Hg in the oxy-fuel combustion process are introduced. These results obtained in this study can significantly contribute to the design and the improvement of the oxyfuel combustion process towards the commercialization.
Effects of Copper Ions and Chelate Agent on Output of Ascorbic Acid Fuel Cell
Authors: Furugori Ryota , Ikeda Seiki , Tanaka Makoto
Published: March 2012

A catalyst plays an important role in fuel cell because of promotion of chemical reaction for room temperature type fuel cell. In general, platinum is adopted as a catalyst even though it is very expensive. An ascorbic acid aqueous solution is able to react without catalyst for the oxidation reaction. At first, authors made sure of generation of the electric output using ascorbic acid for fuel without the catalyst. Next, we were able to increase the electric output with adding to metal ions to ascorbic acid aqueous solution. Finally, high and stable electric output was obtained by using the chelating agent.
A Liquid-Piston Steam Engine
Authors: Yatsuzuka Shinichi , Niiyama Yasunori , Fukuda Kentarou , Hagiwara Yasumasa , Nishizawa Kazutoshi , Shikazono Naoki
Published: March 2012

Reduction of global carbon dioxide emissions is one of the most critical challenges for realizing sustainable society. In order to reduce carbon dioxide emissions, energy efficiency must be improved. Waste heat recovery with external combustion engine is expected to be one of the promising technologies for efficient energy utilization. However, the temperature of waste heat is getting lower with the progress of energy technologies. For example, in Japan which is known as one of the most energy-efficient countries in the world with advanced technologies such as cogeneration and hybrid automobiles, total amount of disposed heat below 300 °C is as much as 10% of the total amount of primary energy supply. Conventional external combustion engines, such as Stirling, thermoacoustic1 and steam engines2 show significant decrease in their efficiency at low temperatures below 300 °C. Utilization of high-temperature heat sources, however, requires relatively expensive materials and advanced processing technologies to achieve high reliability. In order to overcome these issues, a novel liquid-piston steam engine is developed, which achieves high efficiency as well as high reliability and low cost using low temperature heat below 300 °C. Present liquid-piston steam engine demonstrated a thermal efficiency of 12.7% at a heating temperature of 270 °C and a cooling temperature of 80 °C, which was about 40% of the Carnot efficiency operating at same temperatures. The liquid-piston steam engine operated even with wet steam, without requiring steam to be superheated. This low temperature operation yielded relatively little deformation of components, which leads to high reliability of the engine. In addition, present liquid piston engine can achieve both high efficiency and low cost compared to conventional external combustion engines, because it has only one moving part whereas both Stirling and Rankin engines have at least two moving parts. The developed liquid piston engine is thus expected to possess large possibility of recovering energy from waste heat.
Effects of Oxygenated Treatment on Exfoliation of Duplex Scale in Steam Path
Authors: Xu Hong
Published: March 2012

Oxygenated treatment (OT) is an excellent choice for supercritical (SC) and ultrasupercritical (USC) fossil units to alleviate flow accelerated corrosion (FAC). Unfortunately, many large utility boilers had suffered series bursts caused by exfoliation of duplex scale in steam path after adopting OT measures. It has been hopeful always about that OT should be independent of scale exfoliation, but many tube failures in fossil power plants go by contraries. Ecocide hypothesis which has been verified reveals the secret of the causal relationship between OT and exfoliation. Ecocide is the abbreviation of “Evaporating Consumption of Chromium Induced Disastrous Exfoliation” and that’s the essence of our hypothesis. We can explain the mechanism of exfoliation of duplex scale in oxygenated steam path with the help of ecocide hypothesis, and furthermore we can predict the risk of OT. Concerned with operating utility boilers which intend to apply OT, the longer the operating history, the greater the risk; the higher the concentration of oxygen in steam, the greater the risk; the higher the parameters of steam, the greater the risk. To avoid the risk of exfoliation, OT should be synchronously scheduled in commissioning.
Energy Efficiency Analysis on a Farm Biogas CHP Plant
Authors: Shi Huixian , Pei Xiaomei , Zhu Hongguang , Li Yongming
Published: March 2012

Based on the mode of off-grid and supplying power for a 10,000 Chicken Farm, there is a experimental study and energy efficiency analysis on a biogas CHP. The results indicate that, the biogas CHP system can satisfy the demand on heating of biogas digester and electricity of farm’s. Reusing the gas-fired remaining heating powered in the internal engine to heat the digester, it can guarantee the temperature in the biogas digester between 32°C and 34°C, even if the climate is very cold. The power load vary obviously in 24 hours, power efficiency and energy efficiency of the biogas CHP plant increase with increasing of the power load of the farm. In low power load operation, the power generation efficiency and energy efficiency of entire system is very low, respectively 4.3%–19%, with the increasing of the load, the measured power efficiency is up to 19.2% when energy efficiency up to 47%, which is lower than that of the fossil CHP. By analyzing the main reason, it is found that the off-grid mode restricts the power load to vary with that of the farm passively, the heat efficiency exchanging is low between the cylinder water and the flue gas heat exchanger of the system, need to be reconstructed and installed gear change iso-frequency mechanism for decreasing the in-gas-fired quantity.
Study of Humid Air Gas Turbine System by Experiment and Analysis
Authors: Takahashi Toru , Watanabe Yutaka , Araki Hidefumi , Eta Takashi
Published: March 2012

Humid air gas turbine systems that are regenerative cycle using humidified air can achieve higher thermal efficiency than gas turbine combined cycle power plant (GTCC) even though they do not require a steam turbine, a high combustion temperature, or a high pressure ratio. In particular, the advanced humid air gas turbine (AHAT) system appears to be highly suitable for practical use because its composition is simpler than that of other systems. Moreover, the difference in thermal efficiency between AHAT and GTCC is greater for small and medium-size gas turbines. To verify the system concept and the cycle performance of the AHAT system, a 3MW-class pilot plant was constructed that consists of a gas turbine with a two-stage centrifugal compressor, a two-stage axial turbine, a reverse-flow-type single-can combustor, a recuperator, a humidification tower, a water recovery tower, and other components. As a result of an operation test, the planned power output of 3.6MW was achieved, so that it has been confirmed the feasibility of the AHAT as a power-generating system. In this study, running tests on the AHAT pilot plant is carried out over one year, and various characteristics such as the effect of changes in ambient temperature, part-load characteristics, and start-up characteristics were clarified by analyzing the data obtained from the running tests.
Practice of Deep Desulphurization in a 300MW CFB Boiler
Authors: Zeng Tinghua , Zhan Zhigang , Fang Jian , Liu Yi
Published: March 2012

Design of the first “300MW Circulating Fluidized Bed (CFB) boiler+limestone/gypsum wet Flue Gas Desulphurization (FGD) system” in the world is introduced, operating parameters of the boiler and FGD system are analyzed. The operating bed temperature is higher than 940°C, efficiency of the boiler is more than 93.5%. In the mean time, SO2 remove efficiency is higher than 95%, and 65% dust remove efficiency is gotten in the FGD system. Practice showed that deep desulphurization and deNOx of CFB boiler has higher SO2 remove efficiency at lower Ca/S ratio compared with traditional inner desulphurization mode, it can meet more and more rigid environmental protection emission standard, and is suitable to more fuels. Deep desulphurization and deNOx of CFB boiler can also realize high temperature CFB boiler which doesn’t aim to inner desulphurization and low NOx emission, and benefits to low-grade, high sulfur content fuels. Research of deep desulphurization and deNOx should be a developing direction for large capacity CFB boiler.
Reliability and Availability Prediction of Main Stop Valve and Control Valve Systems of Steam Turbines
Authors: Shi Jinyuan , Wang Yong , Zhong Xiaoping , Deng Zhicheng
Published: March 2012

A method for the reliability and the availability prediction of main stop valve and control valve systems of steam turbines is presented. The calculation models for the reliability and the availability of series, parallel and series-parallel systems of main stop valves and control valves are introduced. The reliability block diagrams, the availability block diagrams, formulas for the reliability prediction and the availability prediction of systems with 2 main stop valves and 2 control valves, 2 main stop valves and 4 control valves, 2 main stop valves and 6 control valves, 4 main stop valves and 4 control valves are given together with some examples. The mathematical model for the reliability and the availability prediction method of main stop valve and control valve systems of steam turbine is simple and the physical meaning is definite. The reliability and availability of main stop valve and control valve systems can be quantitatively already calculated and improved during the design stage. A basis is thus provided for the reliability and the availability design of main stop valve and control valve systems of steam turbines.
Influencing Parameters Analysis on Dynamics Characteristic of a Double-Span Rotor System
Authors: Li Wei , Che Yongqiang , Sheng Deren , Chen Jianhong
Published: March 2012

Based on the Hamilton Principle, a model of the double-disk and double-span rotor system is established by three journal bearings supported. Due to Hamilton Principle from the energy angle, the rotor system equation of motion form is simple and easy to solve using the Fourth order Runge-Kutta method in MATLAB. The dynamic characteristic of the double-span rotor system are studied with the coupled effect of the nonlinear oil-film force, the nonlinear seal force and the mass eccentric force of disk. The numerical calculation results show that the bifurcation motion of the rotor system is easier to occur at lower rotation speed with the increasing of the seal pressure drop, seal length, disk eccentricity and the reduction of the seal clearance. This modeling and analysis method can be further applied for the multi-span rotor system.
Energy Saving and Optimization Research on the Condensation-Steam System of a Supercritical Thermal Power Plant
Authors: Zhao Yunyun , Zhang Yanping , Huang Shuhong , Li Jianlan , Li Yueqin
Published: March 2012

The efficiency and reliability of thermal power plant directly depends on conditions of the condensation-steam system. The key of energy-saving and optimal operation in condensation-steam system is to adjust the circulating cooling water flow with different operation conditions to get the optimal vacuum. This paper presents the optimal mathematical model of circulating water flow of a 600MW supercritical thermal power plant using Matlab/Simulink. And this model has comprehensively considered the coupling influence of many parameters on the optimal vacuum, including circulating cooling water temperature, cooling water flow, vacuum pump output, condenser cleanness, and makeup water. This model can not only simulate the thermodynamic parameters of the condensation-steam system on operation conditions, but also simulate the influence of the health status of condensation-steam equipments on the operating performance. The accuracy of this model is validated by comparing the simulation results with design parameters under different conditions. We studied the optimal vacuum on off-design conditions using the model. The research shows that the change of the vacuum pump output will affect the results of the optimum circulating water flow, so the net power of the unit should be calculated with consideration of the change of the vacuum pump output in order to get the more practical optimal circulating water flow. The cleanliness of heat transfer surface has a great influence on the optimum circulating water flow. When the cleanliness is poor, the unit needs larger circulating flow to maintain the optimal vacuum. We should estimate the cleanliness of heat transfer surface to arrange suitable cleaning interval time according to the operation conditions of the unit.
Parameter Identification of Steam Turbine Speed Governor System
Authors: Yang Tao , Tang Lei , Li Yanghai , Gao Wei , Wang Kun , Zhang Pinting , Zhang Yanping , Huang Shuhong
Published: March 2012

The dynamic characteristics of the steam turbine speed governor system is one of the major factor that influence the security of the power system. It has important practical significance for the security of the power system to establish the detailed dynamic model of the steam turbine speed governor system through parameter identification. This paper starts from the actual needs of the modeling of steam turbine speed governor system, several key issues such as field test of the speed control system, data preprocessing, parameter identification and simulation verification are researched, the solution of the key problems in the field static test and dynamic disturbance test is summarized, a variety of data preprocessing algorithms and parameter identification algorithms are achieved, and a new method for the simulation verification is proposed. On this basis, software based on MATLAB for the parameter identification of the steam turbine governor system is developed, which can perform the data preprocessing, parameter identification and simulation verification. The software offers a variety of parameter identification method to identify the linear and nonlinear part of the system model quickly and efficiently, and provides detailed qualitative and quantitative method for the evaluation of the simulation verification. The parameter identification results of steam turbine governor system of a power plant show that the software is user friendly and feature rich, and also show that it can complete parameter identification of steam turbine speed governor system intelligently and precisely.
Study on Natural Vibration Characteristics of Large Scale Composite Wind Turbine Blades
Authors: Yang Yi , Tan Chengcheng , Xie Danmei , Xiong Yangheng , Shi Yang , Li Wangfan
Published: March 2012

As the single unit capacity has been increased, the length of wind turbine blade is becoming longer, and the blade vibration fatigue damage caused by impact of wind turbines has become an important issue of wind turbine security. Therefore, modal analysis and study on the impact of crack on the natural frequency of the wind turbine blade are of great significance. The finite element software ANSYS was used to establish a finite element model of a 1.5MW composite wind turbine blade, with a structure of twisted variable cross-section and hollow core in the first place of this paper. Modal analysis of the model established in this paper showed that the blade vibrates in 3 different forms, they are flap within the rotating plane, flutter vibration perpendicularity to the rotating plane and torsional vibration around the blade shaft. Among all the orders, flap and flutter vibration are predominent in low modes, while torsional vibration appears only in high modes (above the fifth order). Then blade models with cracks in the root were established to analyze the regularity of the blade natural frequencies with the crack location, depth and the variation of the angle. The results showed that: as the location of the crack changed in wingspan direction, the change of frequencies showed two basic trends: one was declining gradually; the other was decreasing and then increasing before decreasing again, and the minimum the maximum value appeared at location around 32.5% and 87.5% of the blade root respectively. As crack depth increased gradually, the frequencies reduced continuously, and compared to crack location, influence of crack depth was more prominent. For slant crack, when the crack angle, that is the angle between the crack section chord line and the foliosine plane, increased, all orders of frequencies gradually increased, indicating that the influence of the crack on the blade stiffness decreases as the angle increases.
Experimental Study on the Effects of Declivitous Angle of Secondary Air on the Flow Characteristics and Coal Combustion of a Down-Fired
Authors: Shi Jian , Chen Yuzhong , Hou Yubo , Yao Bin
Published: March 2012

Aiming at Foster Wheeler (FW) technology down-fired boiler with horizontal F layer secondary air, in which the strong horizontal momentum of the secondary air seriously pounds the down flowing coal gas flame, making the problems of short trip of coal flame and low flame fullness of the furnace, and this leads to higher carbon content of fly ash and so on. A designed adjusting device making the declivitous angle of secondary air is erected in the F layer wind box of a FW down-fired furnace, so the declivitous angle of secondary air can be regulated freely. By this means, the declivitous angle of the F layer secondary air is able to be refined depending on the real combustion situation to achieve the best configuration of the momentum radio by downward momentum from the arch and horizontal momentum from the front/rear wall. As a result, it is able to adapt the change of the furnace combustion situation, extending the flame travel, and improving the combustion process and efficiency. This method was applied to a 300MW grade FW down-fired boiler, and the cold flow field results by fireworks showed the down flow depth of the primary air increasing with the declivitous angle. The best flow field was achieved as the declivitous angle was set to 45°. Based on the cold flow field experiments, combustion experiment was accomplished to compare with the coal combustion performance before the declivitous refinement of the F layer secondary air. It was shown that the carbon content of the fly ash was greatly decreased after the refinement, and the combustion efficiency was increased by 3.3%.
Energy Performance of PV Windows Used in Different Cities of China
Authors: Li Peng , Guo Wen-Wen , Qiu Zhong-Zhu
Published: March 2012

In this paper, building simulation software Energy Plus was used to simulate thermal performance, and PV electricity generation of five kinds of glazing system install on the office building in four cities of China, Harbin, Beijing, Shanghai, and Shenzhen, which represent severe cold zone, cold zone, hot summer and cold winter zone, hot summer and warm winter zone respectively. According to the simulation results, the best glazing system for the severe cold zone Harbin and the cold zone Beijing is double PV system, while natural ventilated PV system for the hot summer and cold winter zone Shanghai, the hot summer and warm winter zone Shenzhen. The energy saving rates of the optimal PV glazing system compared to the local SC at Harbin, Beijing, Shanghai, and Shenzhen are 12.3%, 4.9%, 4.8%, 10% respectively.
CO Concentration Measurement in the High Temperature Flame With Tunable Diode Laser Absorption Spectroscopy
Authors: Xu Ting , Wang Fei , Jiang Zhishen , Yan Jianhua , Cen Kefa , Yuan Ke , Xiao Huiping
Published: March 2012

CO concentration real-time monitoring in combustion process has great significance in improving combustion efficiency and controlling combustion emissions. No CO-spectroscopy solid state sensors are available at the high temperature of 1600K–2000K in the flames. Gas sensing based on tunable diode laser absorption spectroscopy (TDLAS) with the advantages of high sensitivity, high selectivity, quick response and non-intrusiveness offers the possibility for on-line measurement in combustion environment. CO absorption line located at 2302.12nm is selected for measurement by direct absorption method in premixed C3H8/Air flat flame. Experiment results show that, when equivalence ratio is larger than one, the concentration of CO in the flame is increased with the increase of equivalence ratio. It proves that this method can be used on combustion environment.
Multistage Model for Short Term Wind Power Forecasting
Authors: Shi J. , Liu Y. Q. , Yang Y. P. , Han S. , Lee W. J.
Published: March 2012

The increased integration of wind power into the electric grid poses new challenges due to its fluctuation and volatility. Short term wind power forecasting is one of the most effective ways to deal with it. Various individual non-linear models are proposed to meet the data requirement to forecast short term wind power. However, as every model has its advantage and weakness, when these models are applied to different wind farms, the forecasting accuracy of every model varies because of distinct data character. This paper analyzes individual forecast models like Wavelet Transform and Support Vector Machine (SVM), and then puts forward a complex-valued forecasting model which is based on Artificial Natural Network in accordance with forecasting data provided by National Climatic Data Center in U.S. The existing individual models are matched and trained according to certain means by Natural Network to propose a multistage model. For variable data from different wind farms, the model can adjust and optimize portion of individual models. Compared with each single model, the multistage model has more robust adaptation and faster calculation speed, which can improve the forecasting precision and have more engineering value.
The Large Capacity Pulverized Coal Fired Utility Boiler and the Low NOx Combustion Technology Developments in China in Response to Environmental Challenges
Authors: Zhou Hao , Mo Guiyuan , Cen Kefa
Published: March 2012

Large capacity pulverized coal fired utility boiler technology is in quick developments in China, hundreds of super critical boilers have been constructed in the last several years which can achieve high efficiency and low pollutants emissions. The different types of super critical boilers are introduced in this paper, they include the single-furnace with double fireball corner fired furnace, the wall fired furnace and the tower-type furnace. The low NOx combustion technologies have been widely used to face the environmental challenges. The low NOx technologies employed in pulverized-coal boilers consist of the combustion modification and post-combustion technology. The low NOx combustion modification technology includes the low NOx burner, close coupled over fire air (CCOFA) and separated over fire air (SOFA). The post-combustion technology consists of selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR) technologies. Zhejiang University develops integrated low NOx technology, including the low NOx combustion system, SNCR system and SCR system. This integrated technology can reduce the NOx emissions to be lower than 50 mg/Nm3.
Intraradical Dynamics of Two Coexisting Isolates of the Arbuscular Mycorrhizal Fungus Glomus intraradices Sensu Lato as Estimated by Real-Time PCR of Mitochondrial DNA
Authors: Krak Karol , Janoušková Martina , Caklová Petra , Vosátka Miroslav , Štorchová Helena
Published: March 2012

Real-time PCR in nuclear ribosomal DNA (nrDNA) is becoming a well-established tool for the quantification of arbuscular mycorrhizal (AM) fungi, but this genomic region does not allow the specific amplification of closely related genotypes. The large subunit of mitochondrial DNA (mtDNA) has a higher-resolution power, but mtDNA-based quantification has not been previously explored in AM fungi. We applied real-time PCR assays targeting the large subunit of mtDNA to monitor the DNA dynamics of two isolates of
Glomus intraradices
sensu lato coexisting in the roots of medic (
Medicago sativa
). The mtDNA-based quantification was compared to quantification in nrDNA. The ratio of copy numbers determined by the nrDNA- and mtDNA-based assays consistently differed between the two isolates. Within an isolate, copy numbers of the nuclear and the mitochondrial genes were closely correlated. The two quantification approaches revealed similar trends in the dynamics of both isolates, depending on whether they were inoculated alone or together. After 12 weeks of cultivation, competition between the two isolates was observed as a decrease in the mtDNA copy numbers of one of them. The coexistence of two closely related isolates, which cannot be discriminated by nrDNA-based assays, was thus identified as a factor influencing the dynamics of AM fungal DNA in roots. Taken together, the results of this study show that real-time PCR assays targeted to the large subunit of mtDNA may become useful tools for the study of coexisting AM fungi.
Psychrotolerant Paenibacillus tundrae Isolates from Barley Grains Produce New Cereulide-Like Depsipeptides (Paenilide and Homopaenilide) That Are Highly Toxic to Mammalian Cells
Authors: Rasimus Stiina , Mikkola Raimo , Andersson Maria A. , Teplova Vera V. , Venediktova Natalia , Ek-Kommonen Christine , Salkinoja-Salonen Mirja
Published: March 2012

Paenilide is a novel, heat-stable peptide toxin from
Paenibacillus tundrae
, which colonizes barley.
P. tundrae
produced 20 to 50 ng of the toxin mg
−1
of cells (wet weight) throughout a range of growth temperatures from +5°C to +28°C. Paenilide consisted of two substances of 1,152 Da and 1,166 Da, with masses and tandem mass spectra identical to those of cereulide and a cereulide homolog, respectively, produced by
Bacillus cereus
NS-58. The two components of paenilide were separated from those of cereulide by high-performance liquid chromatography (HPLC), showing a structural difference suggesting the replacement of
O
-Leu (cereulide) by
O
-Ile (paenilide). The exposure of porcine spermatozoa and kidney tubular epithelial (PK-15) cells to subnanomolar concentrations of paenilide resulted in inhibited motility, the depolarization of mitochondria, excessive glucose consumption, and metabolic acidosis. Paenilide was similar to cereulide in eight different toxicity endpoints with porcine and murine cells. In isolated rat liver mitochondria, nanomolar concentrations of paenilide collapsed respiratory control, zeroed the mitochondrial membrane potential, and induced swelling. The toxic effect of paenilide depended on its high lipophilicity and activity as a high-affinity potassium ion carrier. Similar to cereulide, paenilide formed lipocations, i.e., lipophilic cationic compounds, with K
+
ions already at 4 mM [K
+
], rendering lipid membranes electroconductive. Paenilide-producing
P. tundrae
was negative in a PCR assay with primers specific for the
cesB
gene, indicating that paenilide was not a product of plasmid pCER270, encoding the biosynthesis of cereulide in
B. cereus
. Paenilide represents the first potassium ionophoric compound described for
Paenibacillus
. The findings in this paper indicate that paenilide from
P. tundrae
is a potential food-poisoning agent.
Characterization of the Intracellular Glutamate Decarboxylase System: Analysis of Its Function, Transcription, and Role in the Acid Resistance of Various Strains of Listeria monocytogenes
Authors: Karatzas Kimon-Andreas G. , Suur Laura , O'Byrne Conor P.
Published: March 2012

The glutamate decarboxylase (GAD) system is important for the acid resistance of
Listeria monocytogenes
. We previously showed that under acidic conditions, glutamate (Glt)/γ-aminobutyrate (GABA) antiport is impaired in minimal media but not in rich ones, like brain heart infusion. Here we demonstrate that this behavior is more complex and it is subject to strain and medium variation. Despite the impaired Glt/GABA antiport, cells accumulate intracellular GABA (GABA
i
) as a standard response against acid in any medium, and this occurs in all strains tested. Since these systems can occur independently of one another, we refer to them as the extracellular (GAD
e
) and intracellular (GAD
i
) systems. We show here that GAD
i
contributes to acid resistance since in a Δ
gadD1D2
mutant, reduced GABA
i
accumulation coincided with a 3.2-log-unit reduction in survival at pH 3.0 compared to that of wild-type strain LO28. Among 20 different strains, the GAD
i
system was found to remove 23.11% ± 18.87% of the protons removed by the overall GAD system. Furthermore, the GAD
i
system is activated at milder pH values (4.5 to 5.0) than the GAD
e
system (pH 4.0 to 4.5), suggesting that GAD
i
is the more responsive of the two and the first line of defense against acid. Through functional genomics, we found a major role for GadD2 in the function of GAD
i
, while that of GadD1 was minor. Furthermore, the transcription of the
gad
genes in three common reference strains (10403S, LO28, and EGD-e) during an acid challenge correlated well with their relative acid sensitivity. No transcriptional upregulation of the
gadT2D2
operon, which is the most important component of the GAD system, was observed, while
gadD3
transcription was the highest among all
gad
genes in all strains. In this study, we present a revised model for the function of the GAD system and highlight the important role of GAD
i
in the acid resistance of
L. monocytogenes
.
Cloning, Overexpression in Escherichia coli, and Characterization of a Thermostable Fungal Acetylxylan Esterase from Talaromyces emersonii
Authors: Waters Deborah M. , Murray Patrick G. , Miki Yuta , Martínez Angel T. , Tuohy Maria G. , Faulds Craig B.
Published: March 2012

The gene encoding an acetylxylan esterase (AXE1) from the thermophilic ascomycete
Talaromyces emersonii
was cloned, expressed in
Escherichia coli
, and characterized. This form of AXE1, rTeAXE1, exhibits increased thermostability and activity at a higher temperature than other known fungal acetyl esterases, thus having huge potential application in biomass bioconversion to high value chemicals or biofuels.
Characterization of Extended-Spectrum β-Lactamase Genes Found among Escherichia coli Isolates from Duck and Environmental Samples Obtained on a Duck Farm
Authors: Ma Junying , Liu Jian-Hua , Lv Luchao , Zong Zhiyong , Sun Yan , Zheng Hongqing , Chen ZhangLiu , Zeng Zhen-Ling
Published: March 2012

In this study, we focused on evaluating the occurrence of extended-spectrum β-lactamase (ESBL)-producing
Escherichia coli
in fecal samples of healthy ducks and environmental samples from a duck farm in South China. Duck cloacal swabs and pond water samples were cultivated on MacConkey agar plates supplemented with ceftiofur. Individual colonies were examined for ESBL production. Bacteria identified as
E. coli
were screened for the presence of ESBL and plasmid-borne AmpC genes. The genetic relatedness, plasmid replicon type, and genetic background were determined. Of 245 samples analyzed, 123 had
E. coli
isolates with ceftiofur MICs higher than 8 μg/ml (116 [50.4%] from 230 duck samples and 7 [46.7%] from 15 water samples).
bla
CTX-M
,
bla
SHV-12
,
bla
CMY-2
, and
bla
DHA-1
were identified in 108, 5, 9, and 1 isolates, respectively. The most common
bla
CTX-M
genes were
bla
CTX-M-27
(
n
= 34),
bla
CTX-M-55
(
n
= 27),
bla
CTX-M-24e
(
n
= 22), and
bla
CTX-M-105
(
n
= 20), followed by
bla
CTX-M-14a
,
bla
CTX-M-14b
,
bla
CTX-M-24a
, and
bla
CTX-M-24b
. Although most of the CTX-M producers had distinct pulsotypes, clonal transmission between duck and water isolates was observed.
bla
CTX-M
genes were carried by transferable IncN, IncF, and untypeable plasmids. The novel CTX-M gene
bla
CTX-M-105
was flanked by two hypothetical protein sequences, partial IS
Ecp1
upstream and truncated IS
903D
,
iroN
,
orf1
, and a Tn
1721
-like element downstream. It is suggested that the horizontal transfer of
bla
CTX-M
genes mediated by mobile elements and the clonal spread of CTX-M-producing
E. coli
isolates contributed to the dissemination of
bla
CTX-M
in the duck farm. Our findings highlight the importance of ducks for the dissemination of transferable antibiotic resistance genes into the environment.
Isolation of Potentially Novel Brucella spp. from Frogs
Authors: Eisenberg Tobias , Hamann Hans-Peter , Kaim Ute , Schlez Karen , Seeger Helga , Schauerte Nicole , Melzer Falk , Tomaso Herbert , Scholz Holger C. , Koylass Mark S. , Whatmore Adrian M. , Zschöck Michael
Published: March 2012

Bacterial isolates from frogs were phenotypically identified as
Ochrobactrum anthropi
, but 16S rRNA sequencing showed up to 100% identity with
Brucella inopinata
. Further analysis of
recA
,
omp2a
,
omp2b
,
bcsp31
, and IS
711
and multilocus sequence analysis (MLSA) verified a close relationship with
Brucella
, suggesting the isolates may actually represent novel members of this growing genus of zoonotic pathogens.
Genetic Analysis of the Upper Phenylacetate Catabolic Pathway in the Production of Tropodithietic Acid by Phaeobacter gallaeciensis
Authors: Berger Martine , Brock Nelson L. , Liesegang Heiko , Dogs Marco , Preuth Ines , Simon Meinhard , Dickschat Jeroen S. , Brinkhoff Thorsten
Published: March 2012

Production of the antibiotic tropodithietic acid (TDA) depends on the central phenylacetate catabolic pathway, specifically on the oxygenase PaaABCDE, which catalyzes epoxidation of phenylacetyl-coenzyme A (CoA). Our study was focused on genes of the upper part of this pathway leading to phenylacetyl-CoA as precursor for TDA.Phaeobacter gallaeciensisDSM 17395 encodes two genes with homology to phenylacetyl-CoA ligases (paaK1andpaaK2), which were shown to be essential for phenylacetate catabolism but not for TDA biosynthesis and phenylalanine degradation. Thus, inP. gallaeciensisanother enzyme must produce phenylacetyl-CoA from phenylalanine. Using random transposon insertion mutagenesis of apaaK1-paaK2double mutant we identified a gene (ior1) with similarity toiorAandiorBin archaea, encoding an indolepyruvate:ferredoxin oxidoreductase (IOR). Theior1mutant was unable to grow on phenylalanine, and production of TDA was significantly reduced compared to the wild-type level (60%). Nuclear magnetic resonance (NMR) spectroscopic investigations using13C-labeled phenylalanine isotopomers demonstrated that phenylalanine is transformed into phenylacetyl-CoA by Ior1. Using quantitative real-time PCR, we could show that expression ofior1depends on the adjacent regulator IorR. Growth on phenylalanine promotes production of TDA, induces expression ofior1(27-fold) andpaaK1(61-fold), and regulates the production of TDA. Phylogenetic analysis showed that the aerobic type of IOR as found in many roseobacters is common within a number of different phylogenetic groups of aerobic bacteria such asBurkholderia,Cupriavidis, andRhizobia, where it may also contribute to the degradation of phenylalanine.
Influence of Seasonality on the Genetic Diversity of Vibrio parahaemolyticus in New Hampshire Shellfish Waters as Determined by Multilocus Sequence Analysis
Authors: Ellis Crystal N. , Schuster Brian M. , Striplin Megan J. , Jones Stephen H. , Whistler Cheryl A. , Cooper Vaughn S.
Published: March 2012

Risk of gastric infection with
Vibrio parahaemolyticus
increases with favorable environmental conditions and population shifts that increase prevalence of infective strains. Genetic analysis of New Hampshire strains revealed a unique population with some isolates similar to outbreak-causing strains and high-level diversity that increased as waters warmed.
Functional Robustness of a Polycyclic Aromatic Hydrocarbon Metabolic Network Examined in a
nidA
Aromatic Ring-Hydroxylating Oxygenase Mutant of Mycobacterium vanbaalenii PYR-1
Authors: Kim Seong-Jae , Song Jaekyeong , Kweon Ohgew , Holland Ricky D. , Kim Dae-Wi , Kim Jongnam , Yu Li-Rong , Cerniglia Carl E.
Published: March 2012

In this study, we obtained over 4,000 transposon mutants of
Mycobacterium vanbaalenii
PYR-1 and analyzed one of the mutants, 8F7, which appeared to lose its ability to degrade pyrene while still being able to degrade fluoranthene. This mutant was identified to be defective in
nidA
, encoding an aromatic ring-hydroxylating oxygenase (RHO), known to be involved in the initial oxidation step of pyrene degradation. When cultured with pyrene as a sole source of polycyclic aromatic hydrocarbon (PAH), high-pressure liquid chromatography analysis revealed that the
nidA
mutant showed a significant decrease in the rate of pyrene degradation compared to the wild-type PYR-1, although pyrene was still being degraded. However, when incubated with PAH mixtures including pyrene, phenanthrene, and fluoranthene, the pyrene degradation rate of the mutant was higher than that of the mutant previously incubated with pyrene as a sole source of PAH. There was no significant difference between wild-type PYR-1 and the mutant in the rates of phenanthrene and fluoranthene degradation. From the whole-cell proteome analysis of mutant 8F7 induced by pyrene, we identified expression of a number of RHO enzymes which are suspected to be responsible for pyrene degradation in the
nidA
mutant, which had no expression of NidA. Taken together, results in this study provide direct evidence for the
in vivo
functional role of
nidA
in pyrene degradation at the level of the ring-cleavage-process (RCP) functional module but also for the robustness of the PAH metabolic network (MN) to such a genetic perturbation.
Density of the Waterborne Parasite Ceratomyxa shasta and Its Biological Effects on Salmon
Authors: Hallett Sascha L. , Ray R. Adam , Hurst Charlene N. , Holt Richard A. , Buckles Gerri R. , Atkinson Stephen D. , Bartholomew Jerri L.
Published: March 2012

The myxozoan parasite
Ceratomyxa shasta
is a significant pathogen of juvenile salmonids in the Pacific Northwest of North America and is limiting recovery of Chinook (
Oncorhynchus tshawytscha
) and coho (
O. kisutch
) salmon populations in the Klamath River. We conducted a 5-year monitoring program that comprised concurrent sentinel fish exposures and water sampling across 212 river kilometers of the Klamath River. We used percent mortality and degree-days to death to measure disease severity in fish. We analyzed water samples using quantitative PCR and Sanger sequencing, to determine total parasite density and relative abundance of
C. shasta
genotypes, which differ in their pathogenicity to salmonids. We detected the parasite throughout the study zone, but parasite density and genetic composition fluctuated spatially and temporally. Chinook and coho mortality increased with density of their specific parasite genotype, but mortality-density thresholds and time to death differed. A lethality threshold of 40% mortality was reached with 10 spores liter
−1
for Chinook but only 5 spores liter
−1
for coho. Parasite density did not affect degree-days to death for Chinook but was negatively correlated for coho, and there was wider variation among coho individuals. These differences likely reflect the different life histories and genetic heterogeneity of the salmon populations. Direct quantification of the density of host-specific parasite genotypes in water samples offers a management tool for predicting host population-level impacts.
Metabolome and Transcriptome of the Interaction between Ustilago maydis and Fusarium verticillioides
In Vitro
Authors: Jonkers Wilfried , Rodriguez Estrada Alma E. , Lee Keunsub , Breakspear Andrew , May Georgiana , Kistler H. Corby
Published: March 2012

The metabolome and transcriptome of the maize-infecting fungi
Ustilago maydis
and
Fusarium verticillioides
were analyzed as the two fungi interact. Both fungi were grown for 7 days in liquid medium alone or together in order to study how this interaction changes their metabolomic and transcriptomic profiles. When grown together, decreased biomass accumulation occurs for both fungi after an initial acceleration of growth compared to the biomass changes that occur when grown alone. The biomass of
U. maydis
declined most severely over time and may be attributed to the action of
F. verticillioides
, which secretes toxic secondary metabolites and expresses genes encoding adhesive and cell wall-degrading proteins at higher levels than when grown alone.
U. maydis
responds to cocultivation by expressing siderophore biosynthetic genes and more highly expresses genes potentially involved in toxin biosynthesis. Also, higher expression was noted for clustered genes encoding secreted proteins that are unique to
U. maydis
and that may play a role during colonization of maize. Conversely, decreased gene expression was seen for
U. maydis
genes encoding the synthesis of ustilagic acid, mannosylerythritol D, and another uncharacterized metabolite. Ultimately,
U. maydis
is unable to react efficiently to the toxic response of
F. verticillioides
and proportionally loses more biomass. This
in vitro
study clarifies potential mechanisms of antagonism between these two fungi that also may occur in the soil or in maize, niches for both fungi where they likely interact in nature.