bluuebunny/crossref_metadata_2025 huggingface dataset:
Turbine Generator Expert System Development
Authors: Xu Shuzhen , Cooper Terry , Doerr William
Published: March 2012

This paper presents the methodology adopted for developing an expert system tool to assist in evaluating the condition of a turbine generator. Fuzzy logic is used to represent the reasoning process of an experienced engineer as well as the incomplete information inherent in this type of evaluation. The results of the evaluation inform engineers of: (a) whether the inspected unit is in good condition, (b) if not, the damage mechanisms or failure modes present, and (c) the non statistical but weighted confidence level of the evaluation.
Case Study of the Effect of Generator Retaining Ring Shrink Fit on Rotor Tooth Top Cracking
Authors: Peters Daniel T. , Haley Kevin M.
Published: March 2012

A significant concern in generator operation is cracking in the tops of the rotor teeth due to cyclic fatigue. The shrink fit of a retaining ring over the rotor end induces compressive stresses in the rotor to contain the entire assembly and reduce shear stresses in the rotor teeth during operation. This paper is a case study of the effect of this shrink fit on fatigue life using three dimensional finite element analysis with nonlinear contact to simulate the interaction between the rotor, wedges and retaining ring. For the analysis, consideration was made for both operational and shut down loading to determine the stress state in both conditions for application in fatigue analysis. Overspeed conditions were not considered for this analysis.
Development and Verification of Ultra-Long-Blade for Next Generation Steam Turbine
Authors: Ooyama Hiroharu , Miyawaki Toshihiro , Mori Kazushi , Watanabe Toshio , Hirakawa Yuichi , Maruyama Takashi
Published: March 2012

Mitsubishi Heavy Industries, Ltd. (MHI) has developed “LP-End Blades Series” by employing the ISB (Integral Shroud Blade) structure and has lead high efficiency and reliability of the steam turbine. The latest technology has been integrated into Ultra-Long-Blades design for the next generation’s steam turbine. This paper describes the design summary of 3600rpm-50inch/3000rpm-60inches and 1800/1500rpm-74/62inches Blades and results of the verification tests.
Technical Challenges of Retubing the E´lectricite´ de France (EDF) Belleville Unit 2
Authors: Jones Merwin W. , Massey Kim M. , Voisin David
Published: March 2012

This paper describes the numerous challenges involved in the partial retubing of the Belleville Nuclear Station Unit 2 steam surface condenser using 64,242 tubes. Specific challenges of the project included retubing with both duplex stainless steel tubes and with brass alloy tubes, analyzing the risk of flow induced tube vibration and designing a staking system to prevent such vibration, and, replacement of six tubesheets. The tubesheet stresses were analyzed using a beam strip analysis and ANSYS, and new tubesheets were reverse engineered from original drawings. Tubesheets were aligned to the support plate holes using a newly developed laser alignment system. Prior to the retubing, extensive mockup tests were performed to optimize the rolling torque, and to determine rolling parameters that limit the work-hardening of the brass tubes. Testing also included leak testing the mockup joints with a small pressure vessel and then performing a helium leak test of the pressurized tube joints. Tests were performed with both smooth and serrated holes.
Reliability and Availability Modeling of Mechanical Systems Using Stochastic Petri Net
Authors: Kumar Girish , Jain Vipul , Gandhi O. P.
Published: March 2012

Reliability and availability modeling of complex mechanical systems such as power plants in a single model, considering binary/tertiary states of individual components, using Markov approach is difficult due to state space explosion problem. Inclusion of various types of dependencies in the model further aggravates it. Moreover, the Markov approach is applicable when failure and repair time distributions are exponential. As the time to failure of mechanical components in most of the cases follows Weibull distribution, the Markov approach cannot be realistically applied for such systems. To overcome this, Stochastic Petri net (SPN) hierarchical modeling is proposed in this paper. The model is based on three aspects of the system: hierarchical level, basic structure and dependency. The three hierarchical levels are considered in the model. Individual component (level ‘3’) SPN model is developed assuming Weibull failure distribution, while the individual subsystem (level ‘2’) SPN model is developed considering the arrangement of components within the subsystem. The individual model at level ‘2’ is reduced to an equivalent single net model and its equivalent transition rate is derived from its basic structure assuming the independence of components. The assumption of independence is relaxed for the system model (level ‘1’) and the dependencies (e.g. repair, standby redundancy, load sharing) are incorporated. The repair distribution in the system model is assumed exponential and repairs are considered at the subsystem level. Reachable markings are generated for the system model to obtain the reduced state space model. The proposed methodology provides realistic assessment of reliability and availability values. The suggested methodology is demonstrated for the ‘Cooling Tower System’.
Technical and Engineering Decisions That Drive Choices for Predictive Analytics of Plant Data
Authors: Nieman William
Published: March 2012

Power generation has the goal of maximizing power output while minimizing operations and maintenance cost. The challenge for plant manager is to move closer to reliability limits while being confident the risks of any decision are understood. To attain their goals and meet this challenge they are coming to realize that they must have frequent, accurate assessment of equipment operating conditions, and a path to continued innovation-. At a typical plant, making this assessment involves the collection and effective analysis of reams of complex, interrelated production system data, including demand requirements, load, ambient temperature, as well as the dependent equipment data. Wind turbine health and performance data is available from periodic and real-time systems. To obtain the timeliest understanding of equipment health for all the key resources in a large plant or fleet, engineers increasingly turn to real-time, model-based solutions. Real-time systems are capable of creating actionable intelligence from large amounts and diverse sources of current data. They can automatically detect problems and provide the basis for diagnosis and prioritization effectively for many problems, and they can make periodic inspection methods much more efficient. Technology exists to facilitate prediction of when assets will fail, allowing engineers to target maintenance costs more effectively. But, it is critical to select the best predictive analytics for your plant. How do you make that choice correctly? Real-time condition monitoring and analysis tools need to be matched to engineering process capability. Tools are employed at the plant in lean, hectic environments; others are deployed from central monitoring centers charged with concentrating scarce resources to efficiently support plants. Applications must be flexible and simple to implement and use. Choices made in selection of new tools can be very important to future success of plant operations. So, these choices require solid understanding of the problems to be solved and the advantages and trade-offs of potential solutions. This choice of the best Predictive Analytic solution will be discussed in terms of key technology elements and key engineering elements.
Performance of a Self-Circulating Thermosyphon
Authors: Hagino Naoto , Yoshida Hiro
Published: March 2012

A series of laboratory experiments on self-circulating thermosyphon (SCT) was carried out. The thermosyphon system consists of heating section, condenser, reservoir, and heat exchanging section. The basic performance was elucidated. The present thermosyphon system works by itself under certain conditions of tilting angle of the condenser, the water filling rate, and the input power. The startup time of the present system is remarkably improved. The effect of the buoyancy on the driving force is indicated through the tilting angle of the condenser.
A Demonstration Study on a High Performance Vertical Roller Mill for a Pulverized Coal Firing Boiler
Authors: Takeno Yutaka , Kanemoto Hiroaki , Mitsui Hideo
Published: March 2012

We have developed new technologies to improve particle classification performance of vertical roller mills using a rotary nozzle ring with reverse swirling flow and a louver separator. A rotary nozzle and a louver are installed in primary and secondary classification sections of the mill, respectively. A series of tests using a pilot scale mill showed that these technologies reduce the fraction of coarse particles, power consumption of the mill and mill differential pressure. For an industrial scale-up, we conducted a demonstration test using a vertical roller mill equipped in a 700MW thermal power plant consisting of a pulverized coal firing boiler and six mills with approx. 70t/h nominal grinding capacity in each. In this paper, we discuss demonstration test results on the viewpoint of decreasing coarse particle fractions, power consumption and mill differential pressure. Under normal operating conditions, the coarse particle fraction in pulverized coal was reduced more than 50%, power consumption was reduced 7% and differential pressure was reduced approx. 50%. Additionally, power consumption was reduced approx. 15% under high coal feed conditions. We confirmed that these new technologies effectively improved performance in higher mill loading rates. These results provide a prospect of upgrading the plant performance, especially in reducing unburned carbon in fly ash and power consumption of auxiliary equipment.
Enthalpy and Exergy Analysis of Domestic Desiccant Air Conditioner With Cooling Dehumidification and Heating Humidification Using Process Simulator
Authors: Hirano Shun , Hisazumi Yoshinori , Hori Tsukasa , Wakabayashi Tsutomu , Kishimoto Akira , Enomoto Hakaru , Ueda Kentaro
Published: March 2012

To popularize the use of desiccant air conditioners in residences, a system that can supply cooled and dried air in summer as well as heated and humidified air in winter is proposed. An evaporative cooler that affords an increase in cooling capacity and the amount of humidification is used in this system. The results of the enthalpy and exergy analyses, performed using a process simulator, showed that significant exergy losses occurred at the blower, heater, and desiccant rotor. In addition, exergy loss occurred at the direct evaporative cooler in heating humidification. Furthermore, it was found that there exists an optimal water temperature that yields peak exergy efficiency from the desiccant rotor.
Development of Plant Performance Analysis System for Geothermal Power Plant
Authors: Nakao Yoshinobu , Takahashi Toru , Watanabe Yutaka
Published: March 2012

Geothermal energy is considered a comparatively abundant renewable energy resource. The geothermal power generation system has negligible environmental impact (approximately 0.015kg-CO2/kWh), and it is expected to help prevent carbon dioxide emissions to the atmosphere. On the other hand, in our institute, we have developed general purpose software (EnergyWin™) to analyze the thermal efficiencies of power generation systems easily and rapidly. Such software can not only analyze the plant performance but also investigate the effect of the performance-deteriorated equipment or air condition change on power output quantitatively. Using this software, we have developed a new plant performance analysis system based on actual operation data for geothermal power plants. Then, applying the system to existing facilities, we have analyzed the plant performance and evaluated the effectiveness of the plant maintenance strategy during periodic inspection for consistency.
Development of Mitsubishi 1600°C Class J-Type Gas Turbine
Authors: Araki M. , Masada J. , Hada S. , Ito E. , Tsukagoshi K.
Published: March 2012

Mitsubishi Heavy Industries, Ltd. (MHI) developed a 1100°C class D-type gas turbine in the 1980s and constructed the world’s first successful large-scale combined cycle power plant. Since then, MHI has developed the F and G-type gas turbines with higher turbine inlet temperature and has delivered these units worldwide accumulating successful commercial operations. MHI is currently participating in a Japanese National Project to promote the development of component technology for the next generation 1700°C class gas turbine. MHI recently developed a 1600°C class J-type gas turbine utilizing some of the technologies developed in the National Project. This paper discusses the history and evolution of MHI large frame gas turbine for power generation and the 1600°C class J-type gas turbine update, including the engine specification, verification and trial operation status.
Development and Application of the Intelligent Decision System for Entire Process of Coal Blending
Authors: Chen Gang , Xia Ji , Peng Peng , Yang Tao , Gao Wei , Yan Zhuming , Jiang Jian
Published: March 2012

Blended-coal-firing is an effective method to reduce pollutant emissions and increase boiler efficiency when lack of designed coals. In order to improve the technical level of coal blending, a intelligent decision system of whole coal-utilizing process was developed in this work. For the entire life course of coals in power plant, this system could provide automated decisions for coal stacking, coal blending, taking coal, pulverizing and combustion optimization, and built a platform for information management and coal dispatching.The database and expert system theories were bases of the system, while the optimize blending theory and intelligent multi-objective optimization were the core algorithm. To make the boiler operation safety, economic and environmental was the ultimate goal. During the development of system, a technique of dynamic monitoring of coal bunker and a two-level coal blending optimization method were proposed, which could provide feasible solutions for accurate blending and the entire process tracking of coals. After the completion of system, in December 2009, it was installed and running in the Guangdong Red Bay power plant which equipped 600MW boiler. The software can help improving the efficiency and decision-making level of coal blending work, enhancing the boiler’s full load capacity of stable combustion, and reducing emissions. It has achieved good economic and social benefits until now.
Technology for Straightening the Bent GT Rotor
Authors: Zhu Yongxiang , Leng Jinming , Tang Shidong
Published: March 2012

The GT rotor is composed of a plurality of discs and two shafts. The GT gas turbine rotor may be bent after assembled because of each part has its geometric tolerance.The scheme must be carry out to straight the bend rotor. In oder to get well high speed balance, the surface of each disc excircle, torque tube and disc adaptor can’t be remachine on lath after assemble. We can machine the journal of the shaft on horizontal lathe to straight the slightly bended rotor. For the serious bended rotor, we must disassemble the rotor and change the parallelism of two side of the disc flange on vertical lathe to get a straight rotor. This attic detailed analysis these two schemes and proposed specific actions measures, then the problem of how to straight a bent GT rotor get well solution.
Time Delay Estimator for Boiler Tube Leakage Localization
Authors: An Liansuo , Wang Peng , Shen Guoqing , Shi Jie
Published: March 2012

The inference of strong background noise and reflected by the wall and tube rows surface makes it impossible that justify accurately leakage position employing the characteristic received by multi-channel sensors. It is the ‘bottleneck’ for promoting the accuracy of boiler tube leakage location. The 600MW supercritical boiler model was established, the leakage source propagation process of reflection and attenuation in boiler furnace was simulated by EASE. The approximate signal to noise ratio (SNR) was obtained and the reverberation time was calculated with the squared impulse response integration method on the foundation of simulation. The time delay estimation algorithm PTN, SWITCH derived from PHAT and ML, respectively, are proposed and experiments results revealed the superiority over the classical generalized cross correlation (GCC) method in reverberant and noisy boiler background. Although SWITCH is outperformed by PTN slightly, but the prior knowledge of reverberant energy to direct energy ratio may be hard to obtain in practice and frequencies onset detection is required in PTN method, so the implementation of SWITCH is much easier.
Laser-Induced Emission of Ultrafine Particulates Evolved by Pulverized Coal Pyrolysis
Authors: Chen Linghong , Pan Zhenyan , Cen Kefa , Qiu Kunzan , Grehan Gerard
Published: March 2012

The importance of on line measurement of ultrafine particulates in pulverized coal flames is mainly due to the detection of ultrafine particulate in the effluent for pollution control, and the quantification of fuel burnout in real time within a boiler for improved understanding of the flame heat transfer soot modeling as well. A method has been investigated using laser-heated emission within an O2-free flame which provides a continuous in situ measurement of ultrafine particles during high-temperature pulverized coal pyrolysis. Bituminous coal particles are entrained by nitrogen along the centerline of a laminar flow flat flame burner, where a hydrogen-air flame under fuel-rich condition is used as a heat source. The temperatures of the hydrogen flame were measured by a finite-wire silica-coated Platinum-Rhodium type B Thermocouple. Volatiles released during the coal pyrolysis form a cloud of ultrafine particles at high temperature. A pulse laser sheet introduced to the flame heats the ultrafine particles to incandescent temperatures. The time-resolved laser-induced emission signals with different incident laser-pulse fluences were evaluated. The volume faction of ultrafine particles was associated with the peak value of the signals, and the mean particle size characterized by a time constant of the exponential signal decay. A strong dependence of the characteristic peak value and emission time constant during laser-heated particle cooling from the measured coal particle class could be determined. Specialties in signal evaluation due to residence time in the hydrogen flame for two sizes of coal particles are discussed.
Clarification of Measurement Error of Orifice Flow Meter in Wet Steam Flow
Authors: Morita Ryo , Umezawa Shuichi , Funaki Tatsuya , Inada Fumio , Sakai Masayuki , Ishibashi Masahiro , Uchiyama Yuta , Amari Haruo , Takamoto Masaki , Shimada Hiroyuki
Published: March 2012

It is well known that the wetness of steam flow sometimes causes measurement errors of the steam flow meter. However, it is difficult to clarify a particular error quantitatively in actual plants and factories, and thus far, there has been no established method for estimating the error caused by the wetness of steam flow. Therefore, wet steam flow rate measurement experiments were conducted to clarify the measurement error caused by the wetness of steam flow in a plant and a factory. In this study, as the first step, the orifice flow meter was applied because it is the main flow meter in actual plants. Experiments were conducted with the steam flow apparatus by changing the flow rate, pressure and wetness. As a result, the correlation between the measurement error and the flow condition was clarified. Moreover, for the correction of the error, a new correction method was applied and was confirmed to be better than existing methods now being used.
Evaluation of Crack Growth Behavior of Alloy 625 Under Cyclic Loading in a Steam Environment at 750°C
Authors: Takeda Yoichi , Sato Hirofumi , Yamamoto Shuhei , Tokunaga Takamichi , Ohji Akio
Published: March 2012

Advanced ultra supercritical (A-USC) steam power generation, in which high-pressure steam is raised to beyond 700°C, is being studied internationally. The creep strength of Ni-based super alloys evaluated at these high temperatures in an air environment makes these materials promising candidates for the material to be used for the structural components of these generators. Since they are exposed to high temperature steam, it is important that the effect of the environment on the degradation of these materials is investigated. In this investigation, the crack growth rate under cyclic loading in a 750°C steam environment using a compact tension specimen was evaluated. Crack length monitoring using the direct current potential drop technique was applied to the growing crack in a high temperature environment in order to evaluate the time-dependent behavior of the crack growth. The dependence of the loading rate and amplitude in terms of the stress intensity factor was obtained. The crack growth rate increased with decreasing loading rate and increasing amplitude. Multiple loading patterns were applied to a single specimen during crack length monitoring. When the loading pattern was changed to a different pattern, in most of the cases, the crack growth rate started to change and then became stable aftera transition period. The influence of intermetallics and different phases on the crack growth behavior is discussed based on the oxidation rate of these phases.
A craft-project loudspeaker to serve as an educational demonstration
Authors: Porter Scott P. , Domme Daniel J. , Sell Alexander W. , Whalen Jeffrey S.
Published: March 2012

Moving-coil loudspeakers typify the interdisciplinary nature of acoustics: in order to reproduce sound, these devices employ principles of electricity, magnetism, mechanics, and acoustics. The widespread use of loudspeakers has made them a familiar and valuable opportunity to introduce students to acoustics. A low-cost loudspeaker project/demonstration is presented here that is built from scratch using common household items and craft supplies. A variety of educational topics may be illustrated with this device, making it appropriate for a wide range of academic levels.
Modular system for studying tonal sound excitation in resonators with heat addition and mean flow
Authors: Matveev Konstantin I. , Hernandez Rafael
Published: March 2012

An educational experimental system has been developed for studying tonal sound generation in acoustic resonators. Tones are excited by either heat addition or vortex shedding in the presence of mean flow. The system construction is straightforward and inexpensive. Several test arrangements and experimental data are described in this paper. The experimental setups include a modified Rijke tube, a standing-wave thermoacoustic engine, a baffled tube with mean flow, and an acoustic energy harvester with a piezoelement. Simplified mathematical models for interpreting data are discussed, and references are provided to literature with more advanced analyses. The developed system can assist both graduate and undergraduate students in understanding acoustic instabilities via conducting and analyzing interesting experiments.
A numerical approach to sound levels in near-surface refractive shadows
Authors: Cheinet Sylvain
Published: March 2012

The present study formulates a consistent method to simulate the outdoor, near-surface sound propagation through realistic refractive conditions. The correlated atmospheric stratification and turbulence properties are derived from standard meteorological quantities through flux-profile similarity relationships. The propagation of a monochromatic sound field is simulated in presence of the turbulence and stratification effects and an impedance ground. The propagation model uses a numerical solution of a second-order moment parabolic equation, which is introduced and evaluated. The so-formed coupled atmospheric-acoustic model is used to systematically investigate the sound levels in near-surface refractive shadows. In an illustrative propagation scenario, the shadow zone sound levels are predicted to show significant variations with the meteorological conditions. Specifically, the sound levels decrease with the adverse wind, as a consequence of enhanced mean upward refraction. Conversely, they increase with the absolute value of the surface heat flux, as a consequence of enhanced turbulence scattering. Implications for the assessment of the sound levels in shadow zones are discussed.
HIV Interplay with SAMHD1
Authors: Schaller Torsten , Goujon Caroline , Malim Michael H.
Published: March 2012

A protein that controls nucleic acid metabolism affects the balance between HIV infection and immune responses.
Who Needs Psychiatrists?
Authors: Miller Greg
Published: March 2012

Mental health care is desperately needed throughout the developing world. An Indonesian province is testing an unconventional approach.
Central Role of Dynamic Tidal Biofilms Dominated by Aerobic Hydrocarbonoclastic Bacteria and Diatoms in the Biodegradation of Hydrocarbons in Coastal Mudflats
Authors: Coulon Frédéric , Chronopoulou Panagiota-Myrsini , Fahy Anne , Païssé Sandrine , Goñi-Urriza Marisol , Peperzak Louis , Acuña Alvarez Laura , McKew Boyd A. , Brussaard Corina P. D. , Underwood Graham J. C. , Timmis Kenneth N. , Duran Robert , McGenity Terry J.
Published: March 2012

Mudflats and salt marshes are habitats at the interface of aquatic and terrestrial systems that provide valuable services to ecosystems. Therefore, it is important to determine how catastrophic incidents, such as oil spills, influence the microbial communities in sediment that are pivotal to the function of the ecosystem and to identify the oil-degrading microbes that mitigate damage to the ecosystem. In this study, an oil spill was simulated by use of a tidal chamber containing intact diatom-dominated sediment cores from a temperate mudflat. Changes in the composition of bacteria and diatoms from both the sediment and tidal biofilms that had detached from the sediment surface were monitored as a function of hydrocarbon removal. The hydrocarbon concentration in the upper 1.5 cm of sediments decreased by 78% over 21 days, with at least 60% being attributed to biodegradation. Most phylotypes were minimally perturbed by the addition of oil, but at day 21, there was a 10-fold increase in the amount of cyanobacteria in the oiled sediment. Throughout the experiment, phylotypes associated with the aerobic degradation of hydrocarbons, including polycyclic aromatic hydrocarbons (PAHs) (
Cycloclasticus
) and alkanes (
Alcanivorax
,
Oleibacter
, and
Oceanospirillales
strain ME113), substantively increased in oiled mesocosms, collectively representing 2% of the pyrosequences in the oiled sediments at day 21. Tidal biofilms from oiled cores at day 22, however, consisted mostly of phylotypes related to
Alcanivorax borkumensis
(49% of clones),
Oceanospirillales
strain ME113 (11% of clones), and diatoms (14% of clones). Thus, aerobic hydrocarbon biodegradation is most likely to be the main mechanism of attenuation of crude oil in the early weeks of an oil spill, with tidal biofilms representing zones of high hydrocarbon-degrading activity.
Properties and Biological Role of Streptococcal Fratricins
Authors: Berg Kari Helene , Biørnstad Truls Johan , Johnsborg Ola , Håvarstein Leiv Sigve
Published: March 2012

Competence for natural genetic transformation is widespread in the genus
Streptococcus
. The current view is that all streptococcal species possess this property. In addition to the proteins required for DNA uptake and recombination, competent streptococci secrete muralytic enzymes termed fratricins. Since the synthesis and secretion of these cell wall-degrading enzymes are always coupled to competence development in streptococci, fratricins are believed to carry out an important function associated with natural transformation. This minireview summarizes what is known about the properties of fratricins and discusses their possible biological roles in streptococcal transformation.
Transcriptional Response of the Cellobiose Dehydrogenase Gene to Cello- and Xylooligosaccharides in the Basidiomycete Phanerochaete chrysosporium
Authors: Hori Chiaki , Suzuki Hitoshi , Igarashi Kiyohiko , Samejima Masahiro
Published: March 2012

Cellobiose dehydrogenase (CDH) gene transcripts were quantified by reverse transcription-PCR (RT-PCR) in cultures of
Phanerochaete chrysosporium
supplemented with various cello- and xylooligosaccharides in order to elucidate the mechanism of enhanced CDH production in xylan/cellulose culture. Cellotriose and cellotetraose induced
cdh
expression, while xylobiose and xylotriose induced expression of cellobiohydrolase genes, especially
cel7C
.
A Pseudomonas viridiflava-Related Bacterium Causes a Dark-Reddish Spot Disease in Glycine max
Authors: González Ana J. , Fernández Ana M. , San José Mateo , González-Varela Germán , Rodicio M. Rosario
Published: March 2012

A virulentPseudomonas viridiflava-related bacterium has been identified as a new pathogen of soybean, one of the most important crops worldwide. The bacterium was recovered from forage soybean leaves with dark-reddish spots, and damage on petioles and pods was also observed. In contrast, common bean was not affected.
Electrical Phenotypes of Calcium Transport Mutant Strains of a Filamentous Fungus, Neurospora crassa
Authors: Hamam Ahmed , Lew Roger R.
Published: March 2012

We characterized the electrical phenotypes of mutants with mutations in genes encoding calcium transporters—a mechanosensitive channel homolog (
MscS
), a Ca
2+
/H
+
exchange protein (
cax
), and Ca
2+
-ATPases (
nca-1
,
nca-2
,
nca-3
)—as well as those of double mutants (the
nca-2 cax
,
nca-2 nca-3
, and
nca-3 cax
mutants). The electrical characterization used dual impalements to obtain cable-corrected current-voltage measurements. Only two types of mutants (the
MscS
mutant; the
nca-2
mutant and
nca-2
-containing double mutants) exhibited lower resting potentials. For the
nca-2
mutant, on the basis of unchanged conductance and cyanide-induced depolarization of the potential, the cause is attenuated H
+
-ATPase activity. The growth of the
nca-2
mutant-containing strains was inhibited by elevated extracellular Ca
2+
levels, indicative of lesions in Ca
2+
homeostasis. However, the net Ca
2+
effluxes of the
nca-2
mutant, measured noninvasively with a self-referencing Ca
2+
-selective microelectrode, were similar to those of the wild type. All of the mutants exhibited osmosensitivity similar to that of the wild type (the turgor of the
nca-2
mutant was also similar to that of the wild type), suggesting that Ca
2+
signaling does not play a role in osmoregulation. The hyphal tip morphology and tip-localized mitochondria of the
nca-2
mutant were similar to those of the wild type, even when the external [Ca
2+
] was elevated. Thus, although Ca
2+
homeostasis is perturbed in the
nca-2
mutant (B. J. Bowman et al., Eukaryot. Cell 10:654–661, 2011), the phenotype does not extend to tip growth or to osmoregulation but is revealed by lower H
+
-ATPase activity.
Molecular Subtyping of Treponema pallidum during a Local Syphilis Epidemic in Men Who Have Sex with Men in Melbourne, Australia
Authors: Azzato Francesca , Ryan Norbert , Fyfe Janet , Leslie David E.
Published: March 2012

Treponema pallidum
is the causative agent of syphilis, a sexually transmitted infection of significant public health importance. Since 2000 there has been a marked increase in the number of cases of syphilis infections notified in Victoria, Australia, with the majority of cases occurring in men who have sex with men (MSM) and the highest incidence being in HIV-infected MSM. The molecular subtyping method described by Pillay et al. (A. Pillay et al., Sex. Transm. Dis. 25:408–414, 1998) has been used in this study to determine the diversity of
T. pallidum
subtypes circulating locally and to look for any relationship between
T. pallidum
subtypes and HIV status over a 6-year period (2004 to 2009).
Treponema pallidum
DNA was detected in 303 patient specimens (
n
= 3,652), and full subtyping profiles were obtained from 90 of these (from 88 patients). A total of 11
T. pallidum
subtypes were identified: types 14e (28, 31.1%), 14d (15, 16.7%), 14k (13, 14.4%), 14p (12, 13.3%), 14i (7, 7.8%) 14b (6, 6.7%), 14l (5, 5.6%), and 12i, 13b, 13i, and 13e (1 each, 1.1%). This study showed a similar level of variation among circulating
T. pallidum
strains compared with that in other studies using the same methodology. A different mix of strains and different predominating strains have been found at each geographical study location, with type 14e emerging as the predominant local strain in Victoria. There was no detectable trend between
T. pallidum
subtypes and the specimen collection site or stage of syphilis (where known), nor was there any relationship between particular strains and HIV status.
The Observables of a Dissipative Quantum System
Authors: Chruściński Dariusz , Facchi Paolo , Marmo Giuseppe , Pascazio Saverio
Published: March 2012

A time-dependent product is introduced between the observables of a dissipative quantum system, that accounts for the effects of dissipation on observables and commutators. In the t → ∞ limit this yields a contracted algebra. This product can be transported back by duality on the space of states. The general ideas are corroborated by a few explicit examples.
Specific inhibition of mitochondrial oxidative stress suppresses inflammation and improves cardiac function in a rat pneumonia-related sepsis model
Authors: Zang Qun S. , Sadek Hesham , Maass David L. , Martinez Bobbie , Ma Lisha , Kilgore Jessica A. , Williams Noelle S. , Frantz Doug E. , Wigginton Jane G. , Nwariaku Fiemu E. , Wolf Steven E. , Minei Joseph P.
Published: March 2012

Using a mitochondria-targeted vitamin E (Mito-Vit-E) in a rat pneumonia-related sepsis model, we examined the role of mitochondrial reactive oxygen species in sepsis-mediated myocardial inflammation and subsequent cardiac contractile dysfunction. Sepsis was produced in adult male Sprague-Dawley rats via intratracheal injection of S. pneumonia (4 × 106colony formation units per rat). A single dose of Mito-Vit-E, vitamin E, or control vehicle, at 21.5 μmol/kg, was administered 30 min postinoculation. Blood was collected, and heart tissue was harvested at various time points. Mito-Vit-E in vivo distribution was confirmed by mass spectrometry. In cardiac mitochondria, Mito-Vit-E improved total antioxidant capacity and suppressed H2O2generation, whereas vitamin E offered little effect. In cytosol, both antioxidants decreased H2O2levels, but only vitamin E strengthened antioxidant capacity. Mito-Vit-E protected mitochondrial structure and function in the heart during sepsis, demonstrated by reduction in lipid and protein oxidation, preservation of mitochondrial membrane integrity, and recovery of respiratory function. While both Mito-Vit-E and vitamin E suppressed sepsis-induced peripheral and myocardial production of proinflammatory cytokines (tumor necrosis factor-α, interleukin-1β, and interleukin-6), Mito-Vit-E exhibited significantly higher efficacy ( P < 0.05). Stronger anti-inflammatory action of Mito-Vit-E was further shown by its near-complete inhibition of sepsis-induced myeloperoxidase accumulation in myocardium, suggesting its effect on neutrophil infiltration. Echocardiography analysis indicated that Mito-Vit-E ameliorated cardiac contractility of sepsis animals, shown by improved fractional shortening and ejection fraction. Together, our data suggest that targeted scavenging of mitochondrial reactive oxygen species protects mitochondrial function, attenuates tissue-level inflammation, and improves whole organ activities in the heart during sepsis.
Cardiac hypertrophy in the newborn delays the maturation of fatty acid β-oxidation and compromises postischemic functional recovery
Authors: Oka Tatsujiro , Lam Victoria H. , Zhang Liyan , Keung Wendy , Cadete Virgilio J. J. , Samokhvalov Victor , Tanner Brandon A. , Beker Donna L. , Ussher John R. , Huqi Alda , Jaswal Jagdip S. , Rebeyka Ivan M. , Lopaschuk Gary D.
Published: March 2012

During the neonatal period, cardiac energy metabolism progresses from a fetal glycolytic profile towards one more dependent on mitochondrial oxidative metabolism. In this study, we identified the effects of cardiac hypertrophy on neonatal cardiac metabolic maturation and its impact on neonatal postischemic functional recovery. Seven-day-old rabbits were subjected to either a sham or a surgical procedure to induce a left-to-right shunt via an aortocaval fistula to cause RV volume-overload. At 3 wk of age, hearts were isolated from both groups and perfused as isolated, biventricular preparations to assess cardiac energy metabolism. Volume-overload resulted in cardiac hypertrophy (16% increase in cardiac mass, P < 0.05) without evidence of cardiac dysfunction in vivo or in vitro. Fatty acid oxidation rates were 60% lower ( P < 0.05) in hypertrophied hearts than controls, whereas glycolysis increased 246% ( P < 0.05). In contrast, glucose and lactate oxidation rates were unchanged. Overall ATP production rates were significantly lower in hypertrophied hearts, resulting in increased AMP-to-ATP ratios in both aerobic hearts and ischemia-reperfused hearts. The lowered energy generation of hypertrophied hearts depressed functional recovery from ischemia. Decreased fatty acid oxidation rates were accompanied by increased malonyl-CoA levels due to decreased malonyl-CoA decarboxylase activity/expression. Increased glycolysis in hypertrophied hearts was accompanied by a significant increase in hypoxia-inducible factor-1α expression, a key transcriptional regulator of glycolysis. Cardiac hypertrophy in the neonatal heart results in a reemergence of the fetal metabolic profile, which compromises ATP production in the rapidly maturing heart and impairs recovery of function following ischemia.
Theoretical comparison of wall-derived and erythrocyte-derived mechanisms for metabolic flow regulation in heterogeneous microvascular networks
Authors: Roy Tuhin K. , Pries Axel R. , Secomb Timothy W.
Published: March 2012

The objective of this study is to compare the effectiveness of metabolic signals derived from erythrocytes and derived from the vessel wall for regulating blood flow in heterogeneous microvascular networks. A theoretical model is used to simulate blood flow, mass transport, and vascular responses. The model accounts for myogenic, shear-dependent, and metabolic flow regulation. Metabolic signals are assumed to be propagated upstream along vessel walls via a conducted response. Arteriolar tone is assumed to depend on the conducted metabolic signal as well as local wall shear stress and wall tension, and arteriolar diameters are calculated based on vascular smooth muscle mechanics. The model shows that under certain conditions metabolic regulation based on wall-derived signals can be more effective in matching perfusion to local oxygen demand relative to regulation based on erythrocyte-derived signals, resulting in higher extraction and lower oxygen deficit. The lower effectiveness of the erythrocyte-derived signal is shown to result in part from the unequal partition of hematocrit at diverging bifurcations, such that low-flow vessels tend to receive a reduced hematocrit and thereby experience a reduced erythrocyte-derived metabolic signal. The model simulations predict that metabolic signals independent of erythrocytes may play an important role in local metabolic regulation of vascular tone and flow distribution in heterogeneous microvessel networks.
Slackness between vessel and myocardium is necessary for coronary flow reserve
Authors: Young Jonathan M. , Choy Jenny S. , Kassab Ghassan S. , Lanir Yoram
Published: March 2012

Tone regulation in coronary microvessels has largely been studied in isolated vessels in the absence of myocardial tethering. Here, the potential effect of radial tethering and interstitial space connective tissue (ISCT) between coronary microvessels and the surrounding myocardium was studied. We hypothesized that rigid tethering between microvessels and the myocardium would constrain the active contraction of arterioles and is not compatible with the observed tone regulation. The ISCT between coronary microvessels and myocardium in five swine was found to increase exponentially from 0.22 ± 0.02 μm in capillaries (modified Strahler order 0) of the endocardium to 34.9 ± 7.1 μm in epicardial vessels ( order 10). Microvessels with both soft tethering and ISCT gap were capable of significant changes in vessel resistance (up to an ∼1,600% increase), consistent with experimental measurements of high coronary flow reserve. Additionally, the mechanical energy required for myogenic contraction was estimated. The results indicate that rigid tethering requires up to four times more mechanical energy than soft tethering in the absence of a gap. Hence, the experimental measurements and model predictions suggest that effectiveness and efficiency in tone regulation can be achieved only if the vessel is both softly tethered to and separated from the myocardium in accordance with the experimental findings of ISCT gap. These results have fundamental implications on future simulations of coronary circulation.
Diet-induced obesity severely impairs myelinated aortic baroreceptor reflex responses
Authors: McCully Belinda H. , Brooks Virginia L. , Andresen Michael C.
Published: March 2012

Diet-induced obesity (DIO) attenuates the arterial cardiac baroreceptor reflex, but the mechanisms and sites of action are unknown. This study tested the hypothesis that DIO impairs central aortic baroreceptor pathways. Normal chow control (CON) and high-fat-chow obesity-resistant (OR) and obesity-prone (OP) rats were anesthetized (inactin, 120 mg/kg) and underwent sinoaortic denervation. The central end of the aortic depressor nerve (ADN) was electrically stimulated to generate frequency-dependent baroreflex curves (5–100 Hz) during selective activation of myelinated (A-fiber) or combined (A- and C-fiber) ADN baroreceptors. A mild stimulus (1 V) that activates only A-fiber ADN baroreceptors induced robust, frequency-dependent depressor and bradycardic responses in CON and OR rats, but these responses were completely abolished in OP rats. Maximal activation of A fibers (3 V) elicited frequency-dependent reflexes in all groups, but a dramatic deficit was still present in OP rats. Activation of all ADN baroreceptors (20 V) evoked even larger reflex responses. Depressor responses were nearly identical among groups, but OP rats still exhibited attenuated bradycardia. In separate groups of rats, the reduced heart rate (HR) response to maximal activation of ADN A fibers (3 V) persisted in OP rats following pharmacological blockade of β1-adrenergic or muscarinic receptors, suggesting deficits in both parasympathetic nervous system (PNS) and sympathetic nervous system (SNS) reflex pathways. However, the bradycardic responses to direct efferent vagal stimulation were similar among groups. Taken together, our data suggest that DIO severely impairs the central processing of myelinated aortic baroreceptor control of HR, including both PNS and SNS components.
Two weeks of muscle immobilization impairs functional sympatholysis but increases exercise hyperemia and the vasodilatory responsiveness to infused ATP
Authors: Mortensen S. P. , Mørkeberg J. , Thaning P. , Hellsten Y. , Saltin B.
Published: March 2012

During exercise, contracting muscles can override sympathetic vasoconstrictor activity (functional sympatholysis). ATP and adenosine have been proposed to play a role in skeletal muscle blood flow regulation. However, little is known about the role of muscle training status on functional sympatholysis and ATP- and adenosine-induced vasodilation. Eight male subjects (22 ± 2 yr, V̇o2max: 49 ± 2 ml O2·min−1·kg−1) were studied before and after 5 wk of one-legged knee-extensor training (3–4 times/wk) and 2 wk of immobilization of the other leg. Leg hemodynamics were measured at rest, during exercise (24 ± 4 watts), and during arterial ATP (0.94 ± 0.03 μmol/min) and adenosine (5.61 ± 0.03 μmol/min) infusion with and without coinfusion of tyramine (11.11 μmol/min). During exercise, leg blood flow (LBF) was lower in the trained leg (2.5 ± 0.1 l/min) compared with the control leg (2.6 ± 0.2 l/min; P < 0.05), and it was higher in the immobilized leg (2.9 ± 0.2 l/min; P < 0.05). Tyramine infusion lowers LBF similarly at rest, but, when tyramine was infused during exercise, LBF was blunted in the immobilized leg (2.5 ± 0.2 l/min; P < 0.05), whereas it was unchanged in the control and trained leg. Mean arterial pressure was lower during exercise with the trained leg compared with the immobilized leg ( P < 0.05), and leg vascular conductance was similar. During ATP infusion, the LBF response was higher after immobilization (3.9 ± 0.3 and 4.5 ± 0.6 l/min in the control and immobilized leg, respectively; P < 0.05), whereas it did not change after training. When tyramine was coinfused with ATP, LBF was reduced in the immobilized leg ( P < 0.05) but remained similar in the control and trained leg. Training increased skeletal muscle P2Y2 receptor content ( P < 0.05), whereas it did not change with immobilization. These results suggest that muscle inactivity impairs functional sympatholysis and that the magnitude of hyperemia and blood pressure response to exercise is dependent on the training status of the muscle. Immobilization also increases the vasodilatory response to infused ATP.
Lung development and the host response to influenza A virus are altered by different doses of neonatal oxygen in mice
Authors: Buczynski Bradley W. , Yee Min , Paige Lawrence B. , O'Reilly Michael A.
Published: March 2012

Oxygen exposure in preterm infants has been associated with altered lung development and increased risk for respiratory viral infections later in life. Although the dose of oxygen sufficient to exert these changes in humans remains unknown, adult mice exposed to 100% oxygen between postnatal days 1– 4 exhibit alveolar simplification and increased sensitivity to influenza virus infection. Additionally, two nonlinear thresholds of neonatal oxygen exposures were previously identified that promote modest (between 40% and 60% oxygen) and severe (between 80% and 100% oxygen) changes in lung development. Here, we investigate whether these two thresholds correlate with the severity of lung disease following respiratory viral infection. Adult mice exposed to 100% oxygen at birth, and to a lesser extent 80% oxygen, demonstrated enhanced body weight loss, persistent inflammation, and fibrosis following infection compared with infected siblings exposed to room air at birth. In contrast, the host response to infection was indistinguishable between mice exposed to room air and 40% or 60% oxygen. Interestingly, levels of monocyte chemoattractant protein (MCP)-1 were equivalently elevated in infected mice that had been exposed to 80% or 100% oxygen as neonates. However, reducing levels of MCP-1 using heterozygous Mcp-1 mice did not affect oxygen-dependent changes in the response to infection. Thus lung development and the host response to respiratory viral infection are disrupted by different doses of oxygen. Our findings suggest that measuring lung function alone may not be sufficient to identify individuals born prematurely who have increased risk for respiratory viral infection.