bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Vortex Behaviour of the Rotating-Stall Cell of a Centrifugal Compressor With Vaned Diffuser
Authors: Chen Y. N. , Seidel U. , Haupt U. , Rautenberg M. 
Published: March 2015

The aerodynamic behaviour of the rotating-stall cell of a centrifugal compressor with radial blading and vaned diffuser is investigated experimentally using two stagnation pressure transducers located parallel to each other on the opposing walls of the semi-vaneless annular space between the impeller and the diffuser. The transducers are turned simultaneously step by step through an angle of 360° during the measurement, so that the flow field of both the forward and reverse flows and the swirl flow components can be detected in the stalled and the unstalled regions.
It was shown in the previous papers of the authors (1991 b) that the jet and wake in the flow of the blade channel in the normal operating range are cores of longitudinal vortices with opposite rotational sense. During rotating stall, the jet of a blade channel bends over the outlet edge of the blade and is converted into the wake of the neighbouring one to form a vortex loop around the blade in question. The swirling speed of this vortex loop (the vorticity) is measured to be about twice impeller speed for the present case. The vortex loops of the adjacent blades then join together to form a bubble, the stall cell, embodying the region of the stalled blades.
The outer reach of the vortex bubble forms the border of the outer lobe of the Rossby waves associated with the vortex pair “high” (H) and “low” (L) guiding the stall cell. The longitudinal-vortex-nature of the jet stream along the flank of the Rossby wave, as determined recently in a vaneless diffuser by the authors (1991a), is confirmed in the present investigation. Its intensity reaches a velocity of about 20% u2 when measured in the absolute frame, or 120% u2 when measured in the rotating impeller frame, superimposed by a swirling component of (1 to 4) x ωimp (u2 = tangential velocity of the impeller outlet. ωimp = angular velocity of the impeller).
Liquid Sheet Disintegration and Atomization Process on a Simplified Airblast Atomizer
Authors: LaVergne G. , Trichet P. , Hebrard P. , Biscos Y. 
Published: March 2015

Liquid sheet break-up in co flowing shear flow is the mean by which liquids are atomized in practical injectors for gas turbine combustors. The present study explores experimentally the mechanisms of liquid sheet instabilities and spray formation. Experiments are conducted on four airblast geometries.
A high speed video camera associated to an image processing unit was used to study the liquid sheet instabilities. A microphone and a frequency analyzer were used to track the disintegration frequency. Instability amplitude and disintegration lenght of the liquid sheet were measured.
A two component Phase Doppler Particle Analyzer was used to characterize the resultant spray. The spatial distribution of the particle size is influenced by the swirling flow field.
These experimental results will be used to assess models of fuel sheet instabilities and disintegration.
Heat Transfer to a Rotating Drum in an Annulus With a Stator Blade Row and Axial Throughflow
Authors: Childs P. R. N. , Turner A. B. , Vaughan C. M. , Rayner D. , Bayley F. J. 
Published: March 2015

This paper describes an experimental and numerical investigation of heat transfer to a rotor drum rotating in an annulus with an axial throughflow of air. The application of the work is principally to the transient heating of axial compressor rotor drums, and the results obtained extend the range of previously published correlations by an order of magnitude. Rotational Reynolds numbers (Reω = ωri2/ν) up to 1.5 × 106 and axial Reynolds numbers (ReD = uaDh/ν, Dh = 2(ro – ri)) up to 3.7 × 105 have been achieved experimentally.
A new experimental facility is described in which a 400mm diameter rotor drum, instrumented with miniature thermopile type heat flux meters and thermocouples, can be air turbine driven at up to 10000rpm. The drum rotates in an annulus with a gap of 30mm in which complete rows of stator vanes can be mounted to enable the effect of vane/rotor drum clearance to be examined. A correlation for the heat transfer between the rotor drum and a stator blade row is presented for varying axial and rotational Reynolds numbers and blade/rotor drum radial clearance.
Numerical Generator Protection Offers New Benefits of Gas Turbines
Authors: Ilar M. , Wittwer M. 
Published: March 2015

This article describes the benefits offered by a new type of numerical protection system, applied to gas turbine generators.
World-wide more than 100 different generators with a total rating of about 6000 MW are equipped with this type of protection system.
This protection system is completely independent of other power plant equipment, with its own DC power supplies, input isolating auxiliary current and voltage transformers and optocoupler or relay type binary input/output devices as well as serial communication links. The heart of the system is a multiprocessor high speed bus capable of handling the communication between the measuring inputs, the protection algorithm processor (s) and the output units.
The system makes use of a large library of modular, pretested protective functions.
Continuous self-monitoring enhances the availability of the complete protective system.
Modern, well coordinated protection and turbine control systems offer new advantages to the user such as faster handling of emergency situations through the availability of more and better information together with the possibility of faster and more detailed fault analysis. In addition, a reduction in the time required for commissioning, e.g. for cables and instrument transformers, can be realized.
This paper is presented to provide some understanding of the application of the protection system introduced here, in particular in connection with the ABB gas turbine generator unit type GT11N. Also introduced are the main components involved, such as numerical protective functions, self-monitoring of protection systems, and data exchange.
1/4 Scale Hot Flow Model Test of a GE LM2500 Exhaust System
Authors: Vandam D. , Birk A. M. 
Published: March 2015

A facility has been constructed to test exhaust systems for the GE LM2500 Gas Turbine. The facility is capable of simulating the hot flow exhaust conditions for the LM2500 in 1/4 scale.
The facility was constructed to study LM2500 exhaust system performance including the effects of small changes in the geometry of the LM2500 exhaust collector and also to study the effects of devices such as infrared signature suppressors on the overall exhaust system performance. The facility is currently instrumented to measure local static and total pressures, local swirl angles, exit plane total and static pressure distribution, and primary (engine exhaust) and secondary (enclosure cooling air) mass flow rates. The facility has been constructed to accommodate a variety of exhaust uptake geometries. Tests were recently conducted to study certain aspects of exhaust system performance. Sample data is presented and comparisons are made with other available data.
Metatranscriptomic Analysis of Diminutive Thiomargarita-Like Bacteria (“Candidatus Thiopilula” spp.) from Abyssal Cold Seeps of the Barbados Accretionary Prism
Authors: Jones Daniel S. , Flood Beverly E. , Bailey Jake V. 
Published: February 2015

ABSTRACT

Large sulfur-oxidizing bacteria in the family
Beggiatoaceae
are important players in the global sulfur cycle. This group contains members of the well-known genera
Beggiatoa
,
Thioploca
, and
Thiomargarita
but also recently identified and relatively unknown candidate taxa, including “
Candidatus
Thiopilula” spp. and “
Ca
. Thiophysa” spp. We discovered a population of “
Ca
. Thiopilula” spp. colonizing cold seeps near Barbados at a ∼4.7-km water depth. The Barbados population consists of spherical cells that are morphologically similar to
Thiomargarita
spp., with elemental sulfur inclusions and a central vacuole, but have much smaller cell diameters (5 to 40 μm). Metatranscriptomic analysis revealed that when exposed to anoxic sulfidic conditions, Barbados “
Ca
. Thiopilula” organisms expressed genes for the oxidation of elemental sulfur and the reduction of nitrogenous compounds, consistent with their vacuolated morphology and intracellular sulfur storage capability. Metatranscriptomic analysis further revealed that anaerobic methane-oxidizing and sulfate-reducing organisms were active in the sediment, which likely provided reduced sulfur substrates for “
Ca
. Thiopilula” and other sulfur-oxidizing microorganisms in the community. The novel observations of “
Ca
. Thiopilula” and associated organisms reported here expand our knowledge of the globally distributed and ecologically successful
Beggiatoaceae
group and thus offer insight into the composition and ecology of deep cold seep microbial communities.
A Replicative Plasmid Vector Allows Efficient Complementation of Pathogenic Leptospira Strains
Authors: Pappas Christopher J. , Benaroudj Nadia , Picardeau Mathieu 
Published: February 2015

ABSTRACT

Leptospirosis, an emerging zoonotic disease, remains poorly understood because of a lack of genetic manipulation tools available for pathogenic leptospires. Current genetic manipulation techniques include insertion of DNA by random transposon mutagenesis and homologous recombination via suicide vectors. This study describes the construction of a shuttle vector, pMaORI, that replicates within saprophytic, intermediate, and pathogenic leptospires. The shuttle vector was constructed by the insertion of a 2.9-kb DNA segment including the
parA
,
parB
, and
rep
genes into pMAT, a plasmid that cannot replicate in
Leptospira
spp. and contains a backbone consisting of an
aadA
cassette,
ori
R6K, and
oriT
RK2/RP4. The inserted DNA segment was isolated from a 52-kb region within
Leptospira
mayottensis
strain 200901116 that is not found in the closely related strain
L. mayottensis
200901122. Because of the size of this region and the presence of bacteriophage-like proteins, it is possible that this region is a result of a phage-related genomic island. The stability of the pMaORI plasmid within pathogenic strains was tested by passaging cultures 10 times without selection and confirming the presence of pMaORI. Concordantly, we report the use of
trans
complementation in the pathogen
Leptospira interrogans
. Transformation of a pMaORI vector carrying a functional copy of the
perR
gene in a null mutant background restores the expression of PerR and susceptibility to hydrogen peroxide comparable to that of wild-type cells. In conclusion, we demonstrate the replication of a stable plasmid vector in a large panel of
Leptospira
strains, including pathogens. The shuttle vector described will expand our ability to perform genetic manipulation of
Leptospira
spp.
Site-Directed Mutagenesis of HgcA and HgcB Reveals Amino Acid Residues Important for Mercury Methylation
Authors: Smith Steven D. , Bridou Romain , Johs Alexander , Parks Jerry M. , Elias Dwayne A. , Hurt Richard A. , Brown Steven D. , Podar Mircea , Wall Judy D. 
Published: February 2015

ABSTRACT

Methylmercury is a potent neurotoxin that is produced by anaerobic microorganisms from inorganic mercury by a recently discovered pathway. A two-gene cluster, consisting of
hgcA
and
hgcB
, encodes two of the proteins essential for this activity.
hgcA
encodes a corrinoid protein with a strictly conserved cysteine proposed to be the ligand for cobalt in the corrinoid cofactor, whereas
hgcB
encodes a ferredoxin-like protein thought to be an electron donor to HgcA. Deletion of either gene eliminates mercury methylation by the methylator
Desulfovibrio desulfuricans
ND132. Here, site-directed mutants of HgcA and HgcB were constructed to determine amino acid residues essential for mercury methylation. Mutations of the strictly conserved residue Cys93 in HgcA, the proposed ligand for the corrinoid cobalt, to Ala or Thr completely abolished the methylation capacity, but a His substitution produced measurable methylmercury. Mutations of conserved amino acids near Cys93 had various impacts on the methylation capacity but showed that the structure of the putative “cap helix” region harboring Cys93 is crucial for methylation function. In the ferredoxin-like protein HgcB, only one of two conserved cysteines found at the C terminus was necessary for methylation, but either cysteine sufficed. An additional, strictly conserved cysteine, Cys73, was also determined to be essential for methylation. This study supports the previously predicted importance of Cys93 in HgcA for methylation of mercury and reveals additional residues in HgcA and HgcB that facilitate the production of this neurotoxin.
Extended-Spectrum-β-Lactamase-Producing Enterobacteriaceae Isolated from Vegetables Imported from the Dominican Republic, India, Thailand, and Vietnam
Authors: Zurfluh Katrin , Nüesch-Inderbinen Magdalena , Morach Marina , Zihler Berner Annina , Hächler Herbert , Stephan Roger 
Published: February 2015

ABSTRACT

To examine to what extent fresh vegetables imported into Switzerland represent carriers of extended-spectrum-β-lactamase (ESBL)-producing
Enterobacteriaceae
, 169 samples of different types of fresh vegetables imported into Switzerland from the Dominican Republic, India, Thailand, and Vietnam were analyzed. Overall, 25.4% of the vegetable samples yielded one or more ESBL-producing
Enterobacteriaceae
, 78.3% of which were multidrug resistant. Sixty isolates were obtained:
Escherichia coli
, 26;
Klebsiella pneumoniae
, 26;
Enterobacter cloacae
, 6;
Enterobacter aerogenes
, 1; and
Cronobacter sakazakii
, 1. We found 29 isolates producing CTX-M-15, 8 producing CTX-M-14, 7 producing CTX-M-55, 3 producing CTX-M-65, 1 each producing CTX-M-1, CTX-M-3, CTX-M-27, and CTX-M-63, 5 producing SHV-2, 3 producing SHV-12, and 1 producing SHV-2a. Four of the
E. coli
isolates belonged to epidemiologically important clones: CTX-M-15-producing B2:ST131 (1 isolate), D:ST405 (1 isolate), and D:ST38 (2 isolates). One of the D:ST38 isolates belonged to the extraintestinal enteroaggregative
E. coli
(EAEC) D:ST38 lineage. Two of the
K. pneumoniae
isolates belonged to the epidemic clones sequence type 15 (ST15) and ST147. The occurrence of antibiotic-resistant pathogenic and commensal
Enterobacteriaceae
in imported agricultural foodstuffs constitutes a source of ESBL genes and a concern for food safety.
Extensive Genetic Variability Linked to IS
26
Insertions in the
fljB
Promoter Region of Atypical Monophasic Variants of Salmonella enterica Serovar Typhimurium
Authors: Boland Cécile , Bertrand Sophie , Mattheus Wesley , Dierick Katelijne , Jasson Vicky , Rosseel Toon , Van Borm Steven , Mahillon Jacques , Wattiau Pierre 
Published: February 2015

ABSTRACT

Fifty-nine monophasic
Salmonella enterica
serovar Typhimurium isolates, collected in Belgium during the period from 2008 to 2011, have been serotyped as 4,[5]:i:− and shown to harbor an
fljB
coding sequence. The genetic differences between these strains and phenotypically biphasic
Salmonella
Typhimurium were analyzed through PCR and DNA sequencing. Genetic alterations in the
fljB
promoter region affecting expression of the phase 2 flagellin were observed in 53 isolates. Other genetic events in the invertible region carrying the
fljB
promoter were observed in 2 isolates. For the remaining 4 isolates, no molecular differences with a reference biphasic
Salmonella
Typhimurium strain could be observed. Next-generation sequencing of one representative isolate affected in the
fljB
promoter region revealed a 26-kb IS
26
composite transposon insertion along with a local genomic rearrangement. Several other IS
26
element-mediated alterations of this genomic region were observed. This group of monophasic
Salmonella
Typhimurium isolates was genetically heterogeneous, as revealed by multilocus variable-number tandem-repeat analysis (MLVA), PCR, and sequencing. Pigs and pork represented a major source of such monophasic isolates in Belgium, as reported in other countries. Three out of 5 isolates of human origin presented genetic profiles identical to those of food isolates, demonstrating the pathogenic potential of the newly characterized variants and potential dissemination along the food chain. This study highlighted the key role played by IS
26
insertions in the loss of phase 2 flagellin expression and the subsequent generation of multiple monophasic variant lineages from biphasic
Salmonella
Typhimurium ancestors.
Phylogenetically Distinct Phylotypes Modulate Nitrification in a Paddy Soil
Authors: Zhao Jun , Wang Baozhan , Jia Zhongjun 
Published: February 2015

ABSTRACT

Paddy fields represent a unique ecosystem in which regular flooding occurs, allowing for rice cultivation. However, the taxonomic identity of the microbial functional guilds that catalyze soil nitrification remains poorly understood. In this study, we provide molecular evidence for distinctly different phylotypes of nitrifying communities in a neutral paddy soil using high-throughput pyrosequencing and DNA-based stable isotope probing (SIP). Following urea addition, the levels of soil nitrate increased significantly, accompanied by an increase in the abundance of the bacterial and archaeal
amoA
gene in microcosms subjected to SIP (SIP microcosms) during a 56-day incubation period. High-throughput fingerprints of the total 16S rRNA genes in SIP microcosms indicated that nitrification activity positively correlated with the abundance of
Nitrosospira
-like ammonia-oxidizing bacteria (AOB), soil group 1.1b-like ammonia-oxidizing archaea (AOA), and
Nitrospira
-like nitrite-oxidizing bacteria (NOB). Pyrosequencing of
13
C-labeled DNA further revealed that
13
CO
2
was assimilated by these functional groups to a much greater extent than by marine group 1.1a-associated AOA and
Nitrobacter
-like NOB. Phylogenetic analysis demonstrated that active AOB communities were closely affiliated with
Nitrosospira
sp. strain L115 and the
Nitrosospira multiformis
lineage and that the
13
C-labeled AOA were related to phylogenetically distinct groups, including the moderately thermophilic “
Candidatus
Nitrososphaera gargensis,” uncultured fosmid 29i4, and acidophilic “
Candidatus
Nitrosotalea devanaterra” lineages. These results suggest that a wide variety of microorganisms were involved in soil nitrification, implying physiological diversification of soil nitrifying communities that are constantly exposed to environmental fluctuations in paddy fields.
Sialic Acid-Mediated Gene Expression in Streptococcus pneumoniae and Role of NanR as a Transcriptional Activator of the
nan
Gene Cluster
Authors: Afzal Muhammad , Shafeeq Sulman , Ahmed Hifza , Kuipers Oscar P. 
Published: February 2015

ABSTRACT

In this study, we investigated the transcriptomic response of
Streptococcus pneumoniae
D39 to sialic acid (
N
-acetylneuraminic acid [Neu5Ac]). Transcriptome comparison of wild-type D39 grown in M17 medium with and without sialic acid revealed the elevated expression of various genes and operons, including the
nan
gene cluster (
nan
operon I and
nanA
gene). Our microarray analysis and promoter-
lacZ
fusion studies showed that the transcriptional regulator NanR acts as a transcriptional activator of
nan
operon I and the
nanA
gene in the presence of sialic acid. The putative regulatory site of NanR in the promoter region of
nan
operon I is predicted and confirmed by promoter truncation experiments. Furthermore, the role of CcpA in the regulation of the
nan
gene cluster is demonstrated through microarray analysis and promoter-
lacZ
fusion studies, suggesting that in the presence of sialic acid and glucose, CcpA represses the expression of
nan
operon I while the expression of the
nanA
gene is CcpA independent.
A Novel Triplex Quantitative PCR Strategy for Quantification of Toxigenic and Nontoxigenic Vibrio cholerae in Aquatic Environments
Authors: Bliem Rupert , Schauer Sonja , Plicka Helga , Obwaller Adelheid , Sommer Regina , Steinrigl Adolf , Alam Munirul , Reischer Georg H. , Farnleitner Andreas H. , Kirschner Alexander 
Published: February 2015

ABSTRACT

Vibrio cholerae
is a severe human pathogen and a frequent member of aquatic ecosystems. Quantification of
V. cholerae
in environmental water samples is therefore fundamental for ecological studies and health risk assessment. Beside time-consuming cultivation techniques, quantitative PCR (qPCR) has the potential to provide reliable quantitative data and offers the opportunity to quantify multiple targets simultaneously. A novel triplex qPCR strategy was developed in order to simultaneously quantify toxigenic and nontoxigenic
V. cholerae
in environmental water samples. To obtain quality-controlled PCR results, an internal amplification control was included. The qPCR assay was specific, highly sensitive, and quantitative across the tested 5-log dynamic range down to a method detection limit of 5 copies per reaction. Repeatability and reproducibility were high for all three tested target genes. For environmental application, global DNA recovery (GR) rates were assessed for drinking water, river water, and water from different lakes. GR rates ranged from 1.6% to 76.4% and were dependent on the environmental background. Uncorrected and GR-corrected
V. cholerae
abundances were determined in two lakes with extremely high turbidity. Uncorrected abundances ranged from 4.6 × 10
2
to 2.3 × 10
4
cell equivalents liter
−1
, whereas GR-corrected abundances ranged from 4.7 × 10
3
to 1.6 × 10
6
cell equivalents liter
−1
. GR-corrected qPCR results were in good agreement with an independent cell-based direct detection method but were up to 1.6 log higher than cultivation-based abundances. We recommend the newly developed triplex qPCR strategy as a powerful tool to simultaneously quantify toxigenic and nontoxigenic
V. cholerae
in various aquatic environments for ecological studies as well as for risk assessment programs.
Constitutive Cylindrospermopsin Pool Size in Cylindrospermopsis raciborskii under Different Light and CO
2
Partial Pressure Conditions
Authors: Pierangelini Mattia , Sinha Rati , Willis Anusuya , Burford Michele A. , Orr Philip T. , Beardall John , Neilan Brett A. 
Published: February 2015

ABSTRACT

Cylindrospermopsin (CYN) and 7-deoxy-cylindrospermopsin (dCYN) are potent hepatotoxic alkaloids produced by numerous species of cyanobacteria, including the freshwater
Cylindrospermopsis raciborskii
.
C. raciborskii
is an invasive cyanobacterium, and the study of how environmental parameters drive CYN production has received significant interest from water managers and health authorities. Light and CO
2
affect cell growth and physiology in photoautotrophs, and these are potential regulators of cyanotoxin biosynthesis. In this study, we investigated how light and CO
2
affect CYN and dCYN pool size as well as the expression of the key genes,
cyrA
and
cyrK
, involved in CYN biosynthesis in a toxic
C. raciborskii
strain. For cells growing at different light intensities (10 and 100 μmol photons m
−2
s
−1
), we observed that the rate of CYN pool size production (μ
CYN
) was coupled to the cell division rate (μ
c
) during batch culture. This indicated that CYN pool size under our experimental conditions is constant and cell quotas of CYN (Q
CYN
) and dCYN (Q
dCYN
) are fixed. Moreover, a lack of correlation between expression of
cyrA
and total CYN cell quotas (Q
CYNs
) suggests that the CYN biosynthesis is regulated posttranscriptionally. Under elevated CO
2
(1,300 ppm), we observed minor effects on Q
CYN
and no effects on expression of
cyrA
and
cyrK
. We conclude that the CYN pool size is constitutive and not affected by light and CO
2
conditions. Thus,
C. raciborskii
bloom toxicity is determined by the absolute abundance of
C. raciborskii
cells within the water column and the relative abundance of toxic and nontoxic strains.