bluuebunny/crossref_metadata_2025 huggingface dataset:
Fuel Flexibility Influences on Premixed Combustor Blowout, Flashback, Autoignition and Instability
Authors: Lieuwen Tim , McDonell Vince , Petersen Eric , Santavicca Domenic
Published: September 2008

This paper addresses the impact of fuel composition on the operability of lean premixed gas turbine combustors. This is an issue of current importance due to variability in the composition of natural gas fuel supplies and interest in the use of syngas fuels. Of particular concern is the effect of fuel composition on combustor blowout, flashback, dynamic stability, and autoignition. This paper reviews available results and current understanding of the effects of fuel composition on the operability of lean premixed combustors. It summarizes the underlying processes that must be considered when evaluating how a given combustor’s operability will be affected as fuel composition is varied.
Prediction of Engine Performance Under Compressor Inlet Flow Distortion Using Streamline Curvature
Authors: Pachidis Vassilios , Pilidis Pericles , Templalexis Ioannis , Alexander Theodosios , Kotsiopoulos Petros
Published: September 2008

Traditionally, engine performance has been simulated based on non-dimensional maps for compressors and turbines. Component characteristic maps assume by default a given state of inlet conditions which can not be easily altered in order to simulate two-dimensional or three-dimensional flow phenomena. Inlet flow distortion, for example, is usually simulated by applying empirical correction factors and modifiers to default component characteristics, alternatively, the parallel compressor theory may be applied. The accuracy of the above methods has been rather questionable since they are unable to capture in sufficient fidelity component-level, complex physical processes and analyze them in the context of the whole engine performance. The technique described in this paper integrates a zero-dimensional (non-dimensional) gas turbine modeling and performance simulation system and a two-dimensional, streamline curvature compressor software. The two-dimensional compressor software can fully define the characteristics of a compressor at several operating condition and is subsequently used in the zero-dimensional cycle analysis to provide a more accurate, physics-based estimate of compressor performance under clean and distorted inlet conditions, replacing the default compressor maps. The high-fidelity component communicates with the lower fidelity cycle via a fully automatic and iterative process for the determination of the correct operating point. This study discusses in detail the development, validation and integration of the two-dimensional, streamline curvature compressor software and presents the various loss models used in the code. It also discusses the relative changes in the performance of a two-stage, experimental compressor with different types of radial pressure distortion obtained by running the two-dimensional streamline curvature compressor software independently. Moreover, the performance of a notional engine model, utilizing the coupled, two-dimensional compressor, under distorted conditions is discussed in detail and compared against the engine performance under clean conditions.
Performance Optimization of Advanced H2/Air Cycle Power Plants Based on Natural Gas Partial Oxidation
Authors: Gambini Marco , Vellini Michela
Published: September 2008

In this paper the overall performance of an advanced combined cycle (CC) and of a new advanced mixed cycle (AMC), fed by hydrogen-rich fuel gas, has been evaluated. Obviously, hydrogen must be produced and here we have chosen the partial oxidation of natural gas for its production, quantifying all the thermal and electric requirements. At first, a simple combination between hydrogen production section and power section is performed. In fact, the heat loads of the first section can be satisfied (nearly completely) by using the various raw syngas cooling, but in this case it is not possible to use any part of this heat in the power section. The final result is an overall efficiency of about 44%. Then, by using the Pinch Technology, a more efficient, even if more complex, solution can be conceived; in this case the overall efficiency becomes very interesting especially for the AMC (efficiency is over 50%). This result is very important with the view of a transition toward a “clean energy” economy, based on an energy carrier such as hydrogen.
IR Structured Emission-Based Speciation, Thermometry, and Tomography of CO and H2O in High-Pressure Combustors
Authors: Goldstein Neil , Gregor Brian , Lee Jamine , Kramer Stephen K. , Kozola Stuart , Semega Kenneth J.
Published: September 2008

Passive optical probes and high-resolution emission spectroscopy are used to provide a general-purpose real-time temperature and chemical species sensing capability. Probes can be inserted in the combustor, at the turbine inlet, in the augmenter, or at the engine exit with application as an engine development diagnostic tool that provides spatially resolved measurements of the key combustion parameters: temperature, CO concentration, and H2O concentration. Multiple probes are arrayed to collect the emitted infrared radiation over different views of the hot gas path. Line-of-sight averaged concentrations and temperatures are determined by spectral analysis of the emitted radiation along each line of sight (LOS). Spatial profiles may also be determined by simultaneous analysis of overlapping lines of sight. The collected infrared spectra contain optically thin and optically thick features that reflect the effects of emission and absorption within the combustion region. The known spectral structure of the component spectra can be used for the automated interpretation of the observed radiance spectra in terms of concentrations and temperatures along the line of sight, and in specific volume elements of overlapping lines of sight. In this work, we present measurements of atmospheric-pressure flames and high-pressure combustors and describe the formalism for fitting the observed spectra to a basis of simulated spectra to extract estimates of concentrations and temperatures. The spectral basis is constructed using a multilayer radiation transport model, in which each line-of-sight or measurement volume is divided into segments of uniform concentration and temperature. The observed radiance emanating from each segment is calculated as a function of the local physical variables. The collection of observed data, which contains a highly structured emission spectrum over each line of sight, is fit to the spectral basis to extract line-of-sight averaged physical properties, or in the case of spatial reconstruction, volume-averaged properties for each of the overlap regions.
Experimental Study of a Flameless Gas Turbine Combustor
Authors: Li Guoqiang , Gutmark Ephraim J. , Overman Nick , Cornwell Michael , Stankovic Dragan , Fuchs Laszlo , Milosavljevic Vladimir
Published: September 2008

This paper presents experimental data, performed at atmospheric conditions, on a novel flameless combustor with application to gas turbine engines. Flameless combustion is characterized by distributed flame and even temperature distribution achieved at conditions of high preheat air temperature and sufficiently large amounts of recirculating low oxygen concentration exhaust gases. Extremely low emissions of NOx, CO, and UHC are reported in this paper for flameless combustion in a multiple jets premixed gas turbine combustor. Measurements of the flame chemiluminescence, CO and NOx emissions, acoustic pressure, temperature field, and velocity field reveal the influence of various parameters including: preheat temperature, inlet air mass flow rate, combustor exhaust nozzle contraction ratio, and combustor chamber diameter on emissions and combustion dynamics. The data indicate that greater air mass flow rates, thus larger pressure drop, promotes the formation of flameless combustion and lower NOx emissions for the same flame temperature. This flameless combustor is basically a premixed combustion in which NOx emissions is an exponential function of the flame temperature regardless of different air preheating temperatures. High preheat temperature and flow rates also help in forming stable combustion which is another advantageous feature of flameless combustion. The effects of the combustor exhaust contraction and the combustion chamber diameter on emissions and combustion dynamics are discussed.
3D Flow Prediction and Improvement of Holes Arrangement of a Film-Cooled Turbine Blade Using a Feature-Based Jet Model
Authors: Burdet Andre´ , Abhari Reza S.
Published: September 2008

A feature-based jet model has been proposed for use in 3D CFD prediction of turbine blade film cooling. The goal of the model is to be able to perform computationally efficient flow prediction and optimization of film-cooled turbine blades. The model reproduces in the near hole region the macro flow features of a coolant jet within a Reynolds-Averaged Navier Stokes (RANS) framework. Numerical predictions of the 3D flow through a linear transonic film-cooled turbine cascade are carried out with the model, with a low computational overhead. Different cooling holes arrangement are computed and the prediction accuracy is evaluated versus experimental data. It shown that the present model provides a reasonably good prediction of the adiabatic film-cooling effectiveness and Nusselt number around the blade. A numerical analysis of the interaction of coolant jets issuing from different rows of holes on the blade pressure side is carried out. It is shown that the upward radial migration of the flow due to the passage secondary flow structure has an impact on the spreading of the coolant and the film cooling effectiveness on the blade surface. Based on this result, a new arrangement of the cooling holes for the present case is proposed that leads to a better spanwise covering of the coolant on the blade pressure side surface.
Application of Constructal Theory to Prediction of Boundary Layer Transition Onset
Authors: Walsh E. J. , Hernon D. H. , McEligot D. M. , Davies M. R. D. , Bejan A.
Published: September 2008

Accurate transition onset modeling is a fundamental part of modern turbomachinery designs, where bypass transition is the dominant mechanism of transition to turbulence. Despite this situation a range of transition onset models exist primarily based upon both integral and local parameters within the boundary layer. All such transition models have empirical origins. To date the relationships between such models has not been forthcoming and hence lack of physical understanding of the transition process is evident. This paper details a new approach to transition modeling and provides a theoretically based approach to transition onset prediction by invoking a single principle developed within constructal theory. We not only present a new model but also demonstrate the equivalence between existing models by implementing the same theory. Such understanding of the transition onset problem may provide a new perspective towards more theoretically based transition onset models rather than empirical ones, although much work remains to be done in understanding the receptivity mechanisms within a laminar boundary layer.
Fault Diagnosis and Prognosis of Gas Turbine Engines Based on Qualitative Modeling
Authors: Kim Kyusung , Mylaraswamy Dinkar
Published: September 2008

This paper presents the development of a new fault diagnosis and prognosis algorithm based on qualitative modeling, which provides improved fault isolation. A fault diagnosis and prognosis algorithm is developed to detect and identify faults in the startup components of turbine engines while the faults are still in progress. Such diagnosis and prognosis will make it possible to take proper action before the system breaks down. The evidence associated with startup component failure is based on the aggregation of three dynamic events occurring in different time windows. These events are observable from speed at peak EGT (exhaust gas temperature), peak EGT, and start time. Discrete event modeling observes the unsynchronized occurrence of events. The algorithm was tested with data collected from the field; test results were obtained for twenty-nine engines, including six engines with failed startup components. The developed fault prognosis system successfully predicts failure for all six cases. In the earliest case, alarms triggered sixteen flights before the startup component breakdown and five flights in advance for the latest case.
NDE Technology for Ceramic Composites
Authors: Ellingson William A. , Deemer Christopher M. , Sun Jiangang , Koehl Eugene R.
Published: September 2008

Installation of gas turbine components made of ceramic matrix composite (CMC) materials, which have limited test bed data bases, can put test engines at risk. Further, changes in properties of the materials of these components have been shown to occur with exposure. Risks to the engine can be mitigated through the application of proper nondestructive inspection methods. Further, while still under development, proper application of certain nondestructive evaluation (NDE) technologies seem likely to be able to provide data that can be correlated to retained strength or other properties of these composite materials. If sufficient data were available informed decisions could be made regarding reuse, repair or replace with appropriate NDE. Over the past fourteen years, Argonne National Laboratory (ANL), has been developing various NDE methods specifically for CMC materials. These NDE technologies include: infrared based thermal imaging, air-coupled ultrasonic approaches, high spatial resolution x-ray computed tomography and more recently optical coherence tomography and guided plate waves. This paper will review the developments of these NDE technologies and will provide results with collaboration from engine and laboratory materials tests.
High Efficiency Hybrid Cycle Engine
Authors: Shkolnik Nikolay , Shkolnik Alexander C.
Published: September 2008

A “High Efficiency Hybrid Cycle” (HEHC) thermodynamic cycle is explored. This four-stroke cycle borrows elements from Otto, Diesel, Atkinson, and Rankine cycles. Air is compressed into an isolated combustion chamber, allowing for true isochoric combustion, and extended duration for combustion to proceed until completion. Combustion products expand into a chamber with greater volume than intake. We provide details of a compact HEHC design implementation using rotary pistons and isolated rotating combustion chambers. Two Pistons simultaneously rotate and reciprocate and are held in position by two roller bearings. One Piston performs intake and compression, while the other performs exhaust and expansion. We predict a reduction of energy losses, moving part counts, weight and size over conventional engines.
Effects of Boost Pressure on Piston Lubrication of Diesel Engine
Authors: Takiguchi Masaaki , Yoshiga Yohei , bin Lukman Mohd Sofwam
Published: September 2008

The state of piston lubrication-has been determined with reference to piston friction force measured by our developed single-cylinder supercharged small bore diesel engine with a boost pressure of up to 150kPa. The result is that the state of lubrication deteriorates markedly immediately before the compression top dead center due to increased boost pressure and immediately after the compression top dead center due to increased engine load. Moreover, the crankshaft offset, piston pin offset and multi-grade oil further deteriorate piston lubrication with a boost pressure.
Experimental Study of Thermal Performance and Pressure Drop in Compact Heat Exchanger Installed in Automotive
Authors: Saidi M. H. , Mozafari A. A. , Esmaeili Sany A. R. , Neyestani J.
Published: September 2008

In this Study, radiator performance for passenger car has been studied experimentally in wide range of operating conditions. Experimental prediction of Nusselt number and heat transfer coefficient for coolant in radiator tubes are also performed with ε–NTU method. The total effectiveness coefficient of radiator and heat transfer coefficient in air side is calculated via try and error method considering experimental data. The Colburn factor and pressure drop are also estimated for this heat exchanger. Examples of application demonstrate the practical usefulness of this method to provide empirical data which can be used during the design stage.
Simulation of Marine Diesel Engine Propulsion System Dynamics During Extreme Maneuvering
Authors: Livanos George A. , Simotas George N. , Dimopoulos George G. , Kyrtatos Nikolaos P.
Published: September 2008

The dynamic behavior of a typical four-stroke, medium-speed, marine diesel engine driving a Controllable Pitch Propeller (CPP) is investigated during ship maneuvering including fast propeller pitch changes. A modular model has been developed in Simulink/Matlab for the simulation of the dynamics of ship propulsion. The developed model considers the ship propulsion system as a set of three main modules: the engine, the propeller and the ship hull. The developed ship propulsion dynamics model has been validated with a wide range of experimental data from a 500 kW test engine (MAN B&W 5L16/24), coupled to a four quadrant electric brake (AEG), installed at the test-bed of the Laboratory of Marine Engineering of the National Technical University of Athens (NTUA/LME). The model was then used for the investigation of marine diesel engine behavior during load changing including some extreme maneuvering case scenarios such as Crash Stop, Full Astern and Full Ahead maneuvers. The resulting ship propulsion model is a reduced order model, which can easily be used for detailed studies such as engine-control during fast transient loadings, with accuracy and small computational cost.
DEVERT®: The DEUTZ Concept to Meet the Emission Level U.S. EPA Tier 3 and EU COM 3A for Non-Road Engines
Authors: Bu¨lte Heiner , Beberdick Wolfgang , Pu¨tz Manfred , Kipke Peter
Published: September 2008

From 2006 to 2008 depending on the power ratings, Deutz has to update its complete engine product portfolio of compact engines to meet the emission legislation U.S. EPA Tier 3 and EU COM 3A for applications of mobile nonroad machinery. This challenge covers air cooled, oil cooled and as well water cooled engines up to 500 kW. To provide the best solution for the customer with respect to engine price, fuel consumption, power rating and torque characteristics. Deutz will introduce a technology concept called DEVERT® — Deutz Variable Emissions Reduction Technology. In the wide range of industrial applications of construction machinery, agriculture, material handling, and others DEVERT® provides an optimised solution for every case. The technology approach of DEVERT® consists of injection systems like the mechanical unit pump system and the Deutz Common Rail (DCR®), 2 and 4 valve cylinder-heads, different solutions for internal and external exhaust gas recirculation, and also variable valve actuation. The focus of this paper is on the water-cooled, in-line engine families 2012 and 2013 with a displacement of 4 to 7 l. Based on the application of DEVERT® to these engine families the different technologies are explained by their functionality and their impact on emissions and performance. A short outlook of the emission legislation on future technologies is given. Here exhaust after-treatment will have a significant impact on the engine package with new challenges for the variety of applications.
Exhaust System Gas-Dynamics in Internal Combustion Engines
Authors: Pearson R. , Bassett M. , Virr P. , Lever S. , Early A.
Published: September 2008

The sensitivity of engine performance to gas-dynamic phenomena in the exhaust system has been known for around 100 years but is still relatively poorly understood. The nonlinearity of the wave-propagation behaviour renders simple empirical approaches ineffective, even in a single-cylinder engine. The adoption of analytical tools such as engine-cycle-simulation codes has enabled greater understanding of the tuning mechanisms but for multi-cylinder engines has required the development of accurate models for pipe junctions. The present work examines the propagation of pressure waves through pipe junctions using shock-tube rigs in order to validate a computational model. Following this the effects of exhaust-system gas dynamics on engine performance are discussed using the results from an engine-cycle-simulation program based on the equations of one-dimensional compressible fluid flow.
Synthesis of nanoscale CNx/TiAlN multilayered coatings by ion-beam-assisted deposition
Authors: Cao M. , Li D. J. , Deng X. Y. , Sun X.
Published: September 2008

CN x / TiAlN multilayered coatings with different nanoscale modulation periods and ratio of CNx within each period were prepared by ion-beam-assisted deposition at room temperature. Auger electron spectroscopy (AES), x-ray diffraction (XRD), and nanoindenter and a profiler were used to characterize the microstructure and mechanical properties of the coatings. The low-angle XRD pattern and AES indicated a well-defined multilayered structure of the coating. Although monolithic CNx and TiAlN coatings formed amorphous and nanocrystalline structures, respectively, the CNx/TiAlN multilayers exhibited coherent epitaxial growth due to the mutual growth-promoting effect at small CNx layer thickness (<0.6 nm). At modulation period Λ=2.83 nm and CNx thickness of 10% within each period, the multilayers exhibited strong TiAlN (111) and weak AlN (111) textures and showed the highest hardness (32 GPa), elastic modulus (409 GPa), and critical fracture load (65.7 mN).
Test particle Monte Carlo study of the cryogenic pumping system of the Karlsruhe tritium neutrino experiment
Authors: Luo X. , Day Ch.
Published: September 2008

The cryogenic pumping system (CPS) is the last active tritium pumping system of the Karlsruhe tritium neutrino (KATRIN) experiment, in which the neutrino mass will be directly measured from the tritium beta decay. The spectrometer systems downstream to the CPS are required to be tritium-free. The high pumping speed of the CPS is to be provided by condensed argon frost at 3–3.5K on the surfaces of the beamline tubes. In this unique design the beta particles can be simultaneously guided to the spectrometers by the superconducting magnets around the beamline tubes. In addition, nonevaporable getter (NEG) strips or NEG coated tubes are to be used in the last two sections of the CPS to secure this tritium-free boundary in case of a cryogenic failure event. In this article, the properties of the CPS are studied by the test particle Monte Carlo method, in which the effects of the argon frost sticking coefficient, the geometry of the beamline tube and the bend angle between two beamline sections are addressed. The tritium flow rate reduction factor and the adsorption distribution profile are estimated. The performance of the NEG section at different geometries is also presented.
Study of fluorocarbon plasma in 60 and 100MHz capacitively coupled discharges using mass spectrometry
Authors: Ushakov Andrey , Volynets Vladimir , Jeong Sangmin , Sung Dougyong , Ihm Yongho , Woo Jehun , Han Moonhyeong
Published: September 2008

The signals of positive ions and radicals formed in the fluorocarbon plasma of the capacitively coupled plasma reactor were measured using a quadrupole mass spectrometry and optical emission actinometry. The plasma was produced at 60 and 100MHz frequencies for the same reactor configuration and gas mixtures. Experiments were performed at 25mTorr with a SiO2 wafer on the grounded electrode. Mass spectra of ions were measured in C4F8∕O2∕Ar and C4F6∕O2∕Ar gas mixtures at 500–1500W generator powers. For 60 and 100MHz discharges production of fluorocarbon ions and radicals is discussed. It was found that the production of heavy species increases with frequency. The high mass signals such as C3F3+, C2F4+, C2F5+, C3F5+, C4F7+ decrease when CHF3 is added to the gas mixture. However, the signals of CFx+ (x=1,2,3) do not change significantly. These results are compared to the results of polymer film deposition on the wafer. It was suggested to control the polymerization film formation by adding small amount of CHF3 to the process mixture.
Characteristics of Hf-silicate thin films synthesized by plasma enhanced atomic layer deposition
Authors: Liu Jiurong , Martin Ryan M. , Chang Jane P.
Published: September 2008

Hafnium silicate films were grown by alternating the deposition cycles of hafnium oxide and silicon oxide using a plasma enhanced atomic layer deposition process. The as-deposited and 900 °C annealed hafnium silicate films were determined to be amorphous using grazing incidence x-ray diffraction. This suggested that the formation of hafnium silicate suppressed the crystallization of HfO2 at high temperatures. The dielectric constants increased from ∼5 to ∼17 as the hafnium content increased from 9 to 17 at. % in the hafnium silicate films. The leakage currents through the Hf-rich Hf-silicate films were two to three orders of magnitude lower than that of SiO2 with the same equivalent oxide thickness in the range of 1.6–2.3 nm. The estimated band gap of Hf-silicate films from the O 1s plasma loss spectra increased with the increasing Si content due to the higher band gap of SiO2 than that of HfO2.
Contribution of statistical time delay and formative time to total electrical breakdown time delay in argon for different afterglow periods
Authors: Pejovic Momcilo M. , Pejovic Milic M.
Published: September 2008

The contribution of statistical time delay and formative time to total electrical breakdown time delay in an argon-filled tube at 4mbar pressure for afterglow periods from 3msto300s has been analyzed. This contribution was analyzed on the basis of total electrical breakdown time-delay experimental data and their standard deviation. It was shown that for values of afterglow period from 3to70ms, the contribution of statistical time delay to total electrical breakdown time delay can be neglected. For afterglow periods higher then 70ms the experimental results of total electrical breakdown time delay can be described by Laue’s distribution, which was developed for statistical time delay. It shows that in this case the formative time is much smaller than the statistical time delay, so the total electrical breakdown time delay is approximately equal to the statistical time delay.
Comment on "A Global Map of Human Impact on Marine Ecosystems"
Authors: Heath Michael R.
Published: September 2008

Halpern
et al
. (Reports, 15 February 2008, p. 948) integrated spatial data on 17 drivers of change in the oceans to map the global distribution of human impact. Although fishery catches are a dominant driver, the data reflect activity while impacts occur at different space and time scales. Failure to account for this spatial disconnection could lead to potentially misleading conclusions.
The Magnetic Memory of Titan's Ionized Atmosphere
Authors: Bertucci C. , Achilleos N. , Dougherty M. K. , Modolo R. , Coates A. J. , Szego K. , Masters A. , Ma Y. , Neubauer F. M. , Garnier P. , Wahlund J.-E. , Young D. T.
Published: September 2008

After 3 years and 31 close flybys of Titan by the Cassini Orbiter, Titan was finally observed in the shocked solar wind, outside of Saturn's magnetosphere. These observations revealed that Titan's flow-induced magnetosphere was populated by “fossil” fields originating from Saturn, to which the satellite was exposed before its excursion through the magnetopause. In addition, strong magnetic shear observed at the edge of Titan's induced magnetosphere suggests that reconnection may have been involved in the replacement of the fossil fields by the interplanetary magnetic field.
FBXW7 Targets mTOR for Degradation and Cooperates with PTEN in Tumor Suppression
Authors: Mao Jian-Hua , Kim Il-Jin , Wu Di , Climent Joan , Kang Hio Chung , DelRosario Reyno , Balmain Allan
Published: September 2008

The enzyme mTOR (mammalian target of rapamycin) is a major target for therapeutic intervention to treat many human diseases, including cancer, but very little is known about the processes that control levels of mTOR protein. Here, we show that mTOR is targeted for ubiquitination and consequent degradation by binding to the tumor suppressor protein FBXW7. Human breast cancer cell lines and primary tumors showed a reciprocal relation between loss of FBXW7 and deletion or mutation of PTEN (phosphatase and tensin homolog), which also activates mTOR. Tumor cell lines harboring deletions or mutations in
FBXW7
are particularly sensitive to rapamycin treatment, which suggests that loss of
FBXW7
may be a biomarker for human cancers susceptible to treatment with inhibitors of the mTOR pathway.
Characterization of the Community Structure of a Dechlorinating Mixed Culture and Comparisons of Gene Expression in Planktonic and Biofloc-Associated “Dehalococcoides” andMethanospirillumSpecies
Authors: Rowe Annette R. , Lazar Brendan J. , Morris Robert M. , Richardson Ruth E.
Published: September 2008

This study sought to characterize bacterial and archaeal populations in a perchloroethene- and butyrate-fed enrichment culture containing hydrogen-consuming “Dehalococcoides ethenogenes” strain 195 and aMethanospirillum hungateistrain. Phylogenetic characterization of this microbial community was done via 16S rRNA gene clone library and gradient gel electrophoresis analyses. Fluorescence in situ hybridization was used to quantify populations of “Dehalococcoides” andArchaeaand to examine the colocalization of these two groups within culture bioflocs. A technique for enrichment of planktonic and biofloc-associated biomass was developed and used to assess differences in population distribution and gene expression patterns following provision of substrate. On a per-milliliter-of-culture basis, mostD. ethenogenesgenes (the hydrogenase genehupL; the highly expressed gene for an oxidoreductase of unknown function,fdhA; the RNA polymerase subunit generpoB; and the 16S rRNA gene) showed no statistical difference in expression between planktonic and biofloc enrichments at either time point studied (1 to 2 and 6 h postfeeding). Normalization of transcripts to ribosome (16S rRNA) levels supported that planktonic and biofloc-associatedD. ethenogeneshad similar gene expression profiles, with one notable exception; planktonicD. ethenogenesshowed higher expression oftceArelative to biofloc-associated cells at 6 h postfeeding. These trends were compared to those for the hydrogen-consuming methanogen in the culture,M. hungatei. The vast majority ofM. hungateicells, ribosomes (16S rRNA), and transcripts of the hydrogenase genemvrDand the housekeeping generpoEwere observed in the biofloc enrichments. This suggests that, unlike the comparable activity ofD. ethenogenesfrom both enrichments, planktonicM. hungateiis responsible for only a small fraction of the hydrogenotrophic methanogenesis in this culture.
Novel Carotenoid-Based Biosensor for Simple Visual Detection of Arsenite: Characterization and Preliminary Evaluation for Environmental Application
Authors: Yoshida Kazuyuki , Inoue Koichi , Takahashi Yuko , Ueda Shunsaku , Isoda Katsuhiro , Yagi Kiyohito , Maeda Isamu
Published: September 2008

A novel whole-cell arsenite biosensor was developed using the photosynthetic bacterium
Rhodopseudomonas palustris
no. 7 and characterized. A sensor plasmid containing the operator-promoter region of the
ars
operon and
arsR
gene from
Escherichia coli
and the
crtI
gene from
R. palustris
no. 7 was introduced into a blue-green mutant with
crtI
deleted,
R. palustris
no. 711. The biosensor changed color in response to arsenite, and the change was obvious to the naked eye after 24 h without further manipulation. Real-time reverse transcription-PCR showed that the
crtI
mRNA was induced 3-fold at 3 h and 2.5-fold at 6 h after addition of 50 μg/liter arsenite compared with the no-arsenite control, and consistent with this, the relative levels of lycopene and rhodopin also increased compared with the control. Colorimetric analysis of the bacteria showed that the hue angle had clearly shifted from green-yellow toward red in an arsenic dose-dependent manner at 24 h after arsenite addition. This obvious shift occurred irrespective of the culture conditions before arsenite was added, indicating that the color change of the biosensor is stable in water samples containing various concentrations of dissolved oxygen. Finally, assays using samples prepared in various types of mineral water indicated that this biosensor could be used to screen groundwater samples for the presence of arsenite in a variety of locations, even where electricity is not available.
Phylogenetic Comparison of the Methanogenic Communities from an Acidic, Oligotrophic Fen and an Anaerobic Digester Treating Municipal Wastewater Sludge
Authors: Steinberg Lisa M. , Regan John M.
Published: September 2008

Methanogens play a critical role in the decomposition of organics under anaerobic conditions. The methanogenic consortia in saturated wetland soils are often subjected to large temperature fluctuations and acidic conditions, imposing a selective pressure for psychro- and acidotolerant community members; however, methanogenic communities in engineered digesters are frequently maintained within a narrow range of mesophilic and circumneutral conditions to retain system stability. To investigate the hypothesis that these two disparate environments have distinct methanogenic communities, the methanogens in an oligotrophic acidic fen and a mesophilic anaerobic digester treating municipal wastewater sludge were characterized by creating clone libraries for the 16S rRNA and methyl coenzyme M reductase alpha subunit (
mcrA
) genes. A quantitative framework was developed to assess the differences between these two communities by calculating the average sequence similarity for 16S rRNA genes and
mcrA
within a genus and family using sequences of isolated and characterized methanogens within the approved methanogen taxonomy. The average sequence similarities for 16S rRNA genes within a genus and family were 96.0 and 93.5%, respectively, and the average sequence similarities for
mcrA
within a genus and family were 88.9 and 79%, respectively. The clone libraries of the bog and digester environments showed no overlap at the species level and almost no overlap at the family level. Both libraries were dominated by clones related to uncultured methanogen groups within the
Methanomicrobiales
, although members of the
Methanosarcinales
and
Methanobacteriales
were also found in both libraries. Diversity indices for the 16S rRNA gene library of the bog and both
mcrA
libraries were similar, but these indices indicated much lower diversity in the 16S digester library than in the other three libraries.
AbiV, a Novel Antiphage Abortive Infection Mechanism on the Chromosome of
Lactococcus lactis
subsp.
cremoris
MG1363
Authors: Haaber Jakob , Moineau Sylvain , Fortier Louis-Charles , Hammer Karin
Published: September 2008

Insertional mutagenesis with pGhost9::IS
S1
resulted in independent insertions in a 350-bp region of the chromosome of
Lactococcus lactis
subsp.
cremoris
MG1363 that conferred phage resistance to the integrants. The orientation and location of the insertions suggested that the phage resistance phenotype was caused by a chromosomal gene turned on by a promoter from the inserted construct. Reverse transcription-PCR analysis confirmed that there were higher levels of transcription of a downstream open reading frame (ORF) in the phage-resistant integrants than in the phage-sensitive strain
L. lactis
MG1363. This gene was also found to confer phage resistance to
L. lactis
MG1363 when it was cloned into an expression vector. A subsequent frameshift mutation in the ORF completely eliminated the phage resistance phenotype, confirming that the ORF was necessary for phage resistance. This ORF provided resistance against virulent lactococcal phages belonging to the 936 and c2 species with an efficiency of plaquing of 10
−4
, but it did not protect against members of the P335 species. A high level of expression of the ORF did not affect the cellular growth rate. Assays for phage adsorption, DNA ejection, restriction/modification activity, plaque size, phage DNA replication, and cell survival showed that the ORF encoded an abortive infection (Abi) mechanism. Sequence analysis revealed a deduced protein consisting of 201 amino acids which, in its native state, probably forms a dimer in the cytosol. Similarity searches revealed no homology to other phage resistance mechanisms, and thus, this novel Abi mechanism was designated AbiV. The mode of action of AbiV is unknown, but the activity of AbiV prevented cleavage of the replicated phage DNA of 936-like phages.
In Situ Detection of Freshwater Fungi in an Alpine Stream by New Taxon-Specific Fluorescence In Situ Hybridization Probes
Authors: Baschien Christiane , Manz Werner , Neu Thomas R. , Marvanová Ludmila , Szewzyk Ulrich
Published: September 2008

New rRNA-targeting oligonucleotide probes permitted the fluorescence in situ hybridization (FISH) identification of freshwater fungi in an Austrian second-order alpine stream. Based on computer-assisted comparative sequence analysis, nine taxon-specific probes were designed and evaluated by whole-fungus hybridizations. Oligonucleotide probe MY1574, specific for a wide range of
Eumycota
, and the genus (
Tetracladium
)-specific probe TCLAD1395, as well as the species-specific probes ALacumi1698 (
Alatospora acuminata
), TRIang322 (
Tricladium angulatum
), and Alongi340 (
Anguillospora longissima
), are targeted against 18S rRNA, whereas probes TmarchB10, TmarchC1_1, TmarchC1_2, and AlongiB16 are targeted against the 28S rRNA of
Tetracladium marchalianum
and
Anguillospora longissima
, respectively. After 2 weeks and 3 months of exposure of polyethylene slides in the stream, attached germinating conidia and growing hyphae of freshwater fungi were accessible for FISH. Growing hyphae and germinating conidia on leaves and in membrane cages were also visualized by the new FISH probes.
Hydrogenomics of the Extremely Thermophilic Bacterium
Caldicellulosiruptor saccharolyticus
Authors: van de Werken Harmen J. G. , Verhaart Marcel R. A. , VanFossen Amy L. , Willquist Karin , Lewis Derrick L. , Nichols Jason D. , Goorissen Heleen P. , Mongodin Emmanuel F. , Nelson Karen E. , van Niel Ed W. J. , Stams Alfons J. M. , Ward Donald E. , de Vos Willem M. , van der Oost John , Kelly Robert M. , Kengen Servé W. M.
Published: September 2008

Caldicellulosiruptor saccharolyticus
is an extremely thermophilic, gram-positive anaerobe which ferments cellulose-, hemicellulose- and pectin-containing biomass to acetate, CO
2
, and hydrogen. Its broad substrate range, high hydrogen-producing capacity, and ability to coutilize glucose and xylose make this bacterium an attractive candidate for microbial bioenergy production. Here, the complete genome sequence of
C. saccharolyticus
, consisting of a 2,970,275-bp circular chromosome encoding 2,679 predicted proteins, is described. Analysis of the genome revealed that
C. saccharolyticus
has an extensive polysaccharide-hydrolyzing capacity for cellulose, hemicellulose, pectin, and starch, coupled to a large number of ABC transporters for monomeric and oligomeric sugar uptake. The components of the Embden-Meyerhof and nonoxidative pentose phosphate pathways are all present; however, there is no evidence that an Entner-Doudoroff pathway is present. Catabolic pathways for a range of sugars, including rhamnose, fucose, arabinose, glucuronate, fructose, and galactose, were identified. These pathways lead to the production of NADH and reduced ferredoxin. NADH and reduced ferredoxin are subsequently used by two distinct hydrogenases to generate hydrogen. Whole-genome transcriptome analysis revealed that there is significant upregulation of the glycolytic pathway and an ABC-type sugar transporter during growth on glucose and xylose, indicating that
C. saccharolyticus
coferments these sugars unimpeded by glucose-based catabolite repression. The capacity to simultaneously process and utilize a range of carbohydrates associated with biomass feedstocks is a highly desirable feature of this lignocellulose-utilizing, biofuel-producing bacterium.
Formulation of a Defined V8 Medium for Induction of Sexual Development of
Cryptococcus neoformans
Authors: Kent Cory R. , Ortiz-Bermúdez Patricia , Giles Steven S. , Hull Christina M.
Published: September 2008

For over 3 decades, sexual development in the human fungal pathogen
Cryptococcus neoformans
and other fungi has been initiated by growing compatible mating partners on V8 juice medium. Although this medium is an efficient inducer of sexual development, the mechanism by which it promotes the process is unknown. To understand how V8 juice medium induces sexual development, we attempted to purify inducing factors from V8 juice, and we carried out a complete compositional analysis of V8 juice. We discovered that no single factor is responsible for the effects of V8 juice medium. Rather, the unique composition of V8 juice medium provides the proper nutrient composition for inducing and sustaining complete sexual development. Utilizing these findings, we developed a defined V8 (DV8) medium that mimics V8 juice medium in sexual development assays. Then, using DV8 as a tool, we explored the roles that specific molecules play in enhancing sexual development. Surprisingly, we discovered that copper is a key factor, leading to an upregulation of the mating pheromone genes
MF

a

and
MF
α, both required for the initial steps in sexual development. The utilization of DV8 to investigate the effects of copper on sexual development presented here is an example of how defining the conditions that induce sexual development will advance the study of
C. neoformans
.
Occurrence of Free-Living Amoebae in Communities of Low and High Endemicity for Buruli Ulcer in Southern Benin
Authors: Eddyani Miriam , De Jonckheere Johan F. , Durnez Lies , Suykerbuyk Patrick , Leirs Herwig , Portaels Françoise
Published: September 2008

Buruli ulcer or
Mycobacterium ulcerans
disease occurs mainly in areas in proximity to standing or slowly running freshwater, habitats in which free-living amoebae occur. For this reason, a possible link between the habitat of
M. ulcerans
and free-living amoebae was investigated. Free-living amoebae and mycobacteria were isolated from water and biofilm specimens taken from protected and unprotected sources of water in villages known to have either high or low endemicity for Buruli ulcer in Benin. Amoebae were isolated from 78.8% of samples. A greater proportion of water bodies in areas of high endemicity had amoebae than in areas of low endemicity (83.3% versus 66.7%). Protected sources of water were significantly more likely to contain amoebae in areas of high endemicity than in areas of low endemicity (88.0% versus 11.1%). Several pathogenic free-living amoebae and mycobacteria were isolated. However, no
M. ulcerans
was isolated and no specimen was positive for IS
2404
PCR. Our results show that the study area has a water hygiene problem, which is greater in areas of high Buruli ulcer endemicity than in areas of low endemicity. Our observations indicate that additional studies are required to explore the possible link between free-living amoebae and mycobacteria.
Salmonella enterica
Serovar Enteritidis Genes Induced during Oviduct Colonization and Egg Contamination in Laying Hens
Authors: Gantois I. , Ducatelle R. , Pasmans F. , Haesebrouck F. , Van Immerseel F.
Published: September 2008

Salmonella enterica
serovar Enteritidis is the predominant serovar associated with salmonellosis worldwide, which is in part due to its ability to contaminate the internal contents of the hen's egg. It has been shown that
S. enterica
serovar Enteritidis has an unusual tropism for the avian reproductive tract and an ability to persist in the oviduct and ovary. Factors allowing
S. enterica
serovar Enteritidis strains to contaminate eggs could be a specific interaction with the oviduct tissue, leading to persisting oviduct colonization. In vivo expression technology, a promoter-trap strategy, was used to identify genes expressed during oviduct colonization and egg contamination with
S. enterica
serovar Enteritidis. A total of 25 clones with in vivo-induced promoters were isolated from the oviduct tissue and from laid eggs. Among the 25 clones, 7 were isolated from both the oviducts and the eggs. DNA sequencing of the cloned promoters revealed that genes involved in amino acid and nucleic acid metabolism, motility, cell wall integrity, and stress responses were highly expressed in the reproductive tract tissues of laying hens.
Histo-Blood Group Antigen Assay for Detecting Noroviruses in Water
Authors: Cannon Jennifer L. , Vinjé Jan
Published: September 2008

We evaluated a novel, magnetic-bead-based histo-blood group antigen assay for the recovery of low numbers of norovirus particles. Using this assay, with Norwalk virus seeded in environmental waters as a model, we were able to recover 30 to 300 genomic copies of the virus.
Cryptosporidium
Source Tracking in the Potomac River Watershed
Authors: Yang Wenli , Chen Plato , Villegas Eric N. , Landy Ronald B. , Kanetsky Charles , Cama Vitaliano , Dearen Theresa , Schultz Cherie L. , Orndorff Kenneth G. , Prelewicz Gregory J. , Brown Miranda H. , Young Kim Roy , Xiao Lihua
Published: September 2008

To better characterize
Cryptosporidium
in the Potomac River watershed, a PCR-based genotyping tool was used to analyze 64 base flow and 28 storm flow samples from five sites in the watershed. These sites included two water treatment plant intakes, as well as three upstream sites, each associated with a different type of land use. The uses, including urban wastewater, agricultural (cattle) wastewater, and wildlife, posed different risks in terms of the potential contribution of
Cryptosporidium
oocysts to the source water.
Cryptosporidium
was detected in 27 base flow water samples and 23 storm flow water samples. The most frequently detected species was
C. andersoni
(detected in 41 samples), while 14 other species or genotypes, almost all wildlife associated, were occasionally detected. The two common human-pathogenic species,
C. hominis
and
C. parvum
, were not detected. Although
C. andersoni
was common at all four sites influenced by agriculture, it was largely absent at the urban wastewater site. There were very few positive samples as determined by Environmental Protection Agency method 1623 at any site; only 8 of 90 samples analyzed (9%) were positive for
Cryptosporidium
as determined by microscopy. The genotyping results suggest that many of the
Cryptosporidium
oocysts in the water treatment plant source waters were from old calves and adult cattle and might not pose a significant risk to human health.
First Cultivation and Ecological Investigation of a Bacterium Affiliated with the Candidate Phylum OP5 from Hot Springs
Authors: Mori Koji , Sunamura Michinari , Yanagawa Katsunori , Ishibashi Jun-ichiro , Miyoshi Youko , Iino Takao , Suzuki Ken-ichiro , Urabe Tetsuro
Published: September 2008

The phylogenetic group termed OP5 was originally discovered in the Yellowstone National Park hot spring and proposed as an uncultured phylum; the group was afterwards analyzed by applying culture-independent approaches. Recently, a novel thermophilic chemoheterotrophic filamentous bacterium was obtained from a hot spring in Japan that was enriched through various isolation procedures. Phylogenetic analyses of the isolate have revealed that it is closely related to the OP5 phylum that has mainly been constructed with the environmental clones retrieved from thermophilic and mesophilic anaerobic environments. It appears that the lineage is independent at the phylum level in the domain
Bacteria
. Therefore, we designed a primer set for the 16S rRNA gene to specifically target the OP5 phylum and performed quantitative field analysis by using the real-time PCR method. Thus, the 16S rRNA gene of the OP5 phylum was detected in some hot-spring samples with the relative abundance ranging from 0.2% to 1.4% of the prokaryotic organisms detected. The physiology of the above-mentioned isolate and the related environmental clones indicated that they are scavengers contributing to the sulfur cycle in nature.