bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unsteady Flow Features and Vibration Stresses of an Actual Size Steam Turbine Last Stage in Various Low Load Conditions
Authors: Shibukawa Naoki , Iwasaki Yoshifumi , Watanabe Mitsunori 
Published: November 2013

Experimental investigations with a six stage real scale low pressure steam turbine operated at a very low load conditions are presented in this paper. Although the tested 35 inch last stage blades are circumferentially coupled at both tip and mid span with an intention to reduce the vibration stress, still its increase was observed at extremely low load condition.
The pressure fluctuations were measured by several silicon diaphragm sensors which were mounted on both inner and outer casings of the stator inlet, exit and blade exit position. The measurement of the vibration stress was performed by strain gauges on several blades.
The power spectra of unsteady pressures were precisely investigated considering both their location and steam flow condition. And the results implied that huge reverse flow and re-circulation started in the same location as a blade-to-blade CFD predicted. In terms of the correlation between vibration stress and the flow feature, the pressure fluctuation around the blade tip produces dominant effects on the vibration stress.
The unsteady pressure frequency were also investigated and compared with those of the blade resonance and rotational speed. Basic trends observed in the results are similar to what other researchers reported, and on top of that, the continuous trends of pressure fluctuation and blade vibration stress were systematically investigated. Even the wall pressure, not the pressure on blade surface, showed the effective fluctuations which excited the several nodes of natural frequencies of the last stage blade.
A series of FFT of fluid force by a full annulus quasi-steady CFD simulation seems to predict dominant mode of the excitation which account for the behavior of vibration stresses. The mechanism of the rapid stress increase was examined by considering CFD results and measured unsteady pressure data together.
As the test facility takes a responsibility as an independent power producer, the tests were conducted in real plant operations which include multi stage effects, inlet distortions, Reynolds Number effect and so on. The obtained data and the particular indicator of vibration stress increase can be used as a part of design tool validation with neither aerodynamic nor mechanical corrections.
CFD Investigation of Vane Nozzle and Impeller Design for HPT Blade Cooling Air Delivery System
Authors: Tian Shuqing , Zhang Qin , Liu Hui 
Published: November 2013

In the design of a HPT blade cooling air delivery system, sufficient supply pressure and lower relative total temperature are required to guarantee HPT blades working properly in the high temperature environment. The pre-swirl vane nozzles and the radial impellers are used in the delivery system with lower radial location of pre-swirl nozzle to achieve the requirements.
In this paper, CFD analysis is utilized for designing the vane nozzles and the radial impellers. Two HPT blade cooling air delivery systems were explored. The baseline is a system without impellers, and the alternative is a system with impellers. The results show that the impeller contributes to the delivery system by pumping effectiveness thus decreasing the extracted air pressure. The parity of swirl ratio between the flow and the broach slots is a main factor that decreases the system pressure loss, which can be improved by the radial impellers. The well-designed contoured radial-impeller vane with 30° front angle and 20° trailing angle is recommended in the blade cooling air delivery system design because of its good aerodynamic performance and closely radial outflow. The cascade vane nozzle with more than 70° angle turn is recommended in the pre-swirl nozzle design. It has a good aerodynamic performance with discharge coefficient greater than 0.99 and deviation angle less than 1.3°.
The well-designed radial impeller pays big contributions to the blade cooling air delivery system with 11.4% increase of the thermal effectiveness and 10.2% decrease of the pressure loss versus the system without impellers.
Combustion System Update SGT5-4000F: Design, Testing and Validation
Authors: Kock Boris F. , Prade Bernd , Witzel Benjamin , Streb Holger , Koenig Mike H. 
Published: November 2013

The first Siemens AG SGT5-4000F engine with hybrid burner ring combustor (HBR) was introduced in 1996. Since then, frequent evolutionary design improvements of the combustion system were introduced to fulfill the continuously changing market requirements. The improvements particularly focused on increased thermodynamic performance, reduced emissions, and increasing operational flexibility in terms of load gradients, fuel flexibility, and turndown capability.
According to the Siemens product development process, every design evolution had to pass several validation steps to ensure high reliability and best performance. The single steps included cold flow and mixing tests at atmospheric pressure, high-pressure combustion tests in full-scale sector combustion test rigs, and full engine tests at the Berlin test facility (BTF).
After successful validation, the design improvements were gradually released for commercial operation. In a first step, cooling air reduction features have been implemented in 2005, followed by the introduction of a premixed pilot as second step in 2006. Both together resulted in a significant reduction of the NOx emissions of the system. In a third step, an aerodynamic burner modification was introduced in 2007, which improved the thermo-acoustic stability of the system towards higher turbine inlet temperatures and adapted to fuel preheating to allow for increased cycle efficiency. All three features together have been released as package in 2010 and to date accumulated more than 50,000 operating hours (fleet leader 24,000).
This paper reports upon the steps towards this latest design status of the SGT5-4000F and presents results from typical focus areas of lean premixed combustion systems in gas turbines including aero-dynamical optimization, fuel/air mixing improvements and cooling air management in the combustor.
Aerodynamic Interactions Between a High Pressure Turbine and the First Low Pressure Stator
Authors: Gougeon Pierre , Ngo Boum Ghislaine , Lebœuf Francis 
Published: November 2013

This paper presents a numerical study on the interaction between a single-stage high-pressure turbine and the first vane row of a low-pressure turbine at aerodesign conditions. It focuses on the simulation of the flow within the inter-turbine duct and the loss generated in the downstream low-pressure vane.
Former experiments provided steady and unsteady measurements in the duct between the high and the low-pressure turbines and after the low-pressure nozzle. A 3D unsteady RANS approach with phase-lagged boundary conditions is used to characterize the unsteady periodic effects developing in the inter-turbine channel and downstream in the low-pressure vane.
For the numerical study, two different configurations were considered: a single stage high-pressure turbine configuration and a high-pressure rotor coupled with a low-pressure vane. For the second one, two inlet boundary conditions are considered upstream of the rotor: a circumferentially uniform boundary condition and a circumferentially non uniform rotating boundary condition. The resulting flow fields are compared within the intermediate duct.
A harmonic Fourier analysis is carried out to underline the effects of upstream and downstream stator and the interaction with the high-pressure rotor. An unsteady Adamczyk decomposition within a plane located in the duct showed the influence of the different components and the levels of unsteadiness. Comparisons with experimental data show a reasonable good agreement.
A Skeletal Mechanism for the Reactive Flow Simulation of Methane Combustion
Authors: Karalus Megan F. , Fackler K. Boyd , Novosselov Igor V. , Kramlich John C. , Malte Philip C. 
Published: November 2013

A skeletal mechanism for the prediction of NOx emissions from methane combustion at gas turbine conditions is developed in the present work. The goal is a mechanism that can be used in computational fluid dynamic modeling of lean premixed (LPM) combustors. A database of solutions from 0-D, adiabatic, homogeneous reactors (PSRs) is computed using CHEMKINPRO [1] over a parameter space chosen to include pressures from 1 to 30 atm, equivalence ratios from 0.4 to 1.0, and mean PSR residence times from slightly greater than blowout to 3ms. A resisidence time of 3 ms represents a useful maximum for the super-equilibrium flame zone where most of the NOx forms in LPM combustors. Fuel oxidation and NOx formation are treated separately in the reduction process. The method of Directed Relation Graph (DRG) is applied for methane oxidation and its extension, DRG-aided sensitivity analysis (DRGASA), is used to determine the skeletal NOx mechanism to append to the methane mechanism. Post-processing of the PSR solution database and implementation of the reduction algorithm are accomplished in SAGE [2], a Python based, open-source mathematics software package. The skeletal oxidation and NOx mechanisms are validated against full GRI 3.0 [3] in both PSR and laminar flame speed calculations. When compared with the detailed GRI 3.0 mechanism, NOx emissions are predicted within 7% near blowout and 3% at 3ms, and laminar flame speeds are predicted within 20% over the range of equivalence ratios and pressures. The skeletal mechanism is presented here and it should be noted that all reactions of the H2/CO submechanism are retained.
The skeletal mechanism consists of 22 species and 122 reactions for methane oxidation and an additional 8 species and 55 reactions to describe NOx formation (30 species, 177 reactions total). The final skeletal mechanism with NOx chemistry is available for download here [4]. To demonstrate the predictive capability of the validated mechanism in a reactive flow system, it is implemented in an ANSYS Fluent model of a single jet stirred reactor, the results of which are compared to experimental reactor data presented in [5] and [6]. Predicted and measured profiles of temperature and NOx emissions are shown. Temperature and NOx emissions compare well in the recirculation zone of the JSR, although both NOx emissions and temperature are under-predicted in the jet region. Finally, the contribution of each chemical pathway for NOx formation is evaluated.
Increased Proportions of Bifidobacterium and the Lactobacillus Group and Loss of Butyrate-Producing Bacteria in Inflammatory Bowel Disease
Authors: Wang Wei , Chen Liping , Zhou Rui , Wang Xiaobing , Song Lu , Huang Sha , Wang Ge , Xia Bing 
Published: November 2013

ABSTRACT

Dysbiosis in the intestinal microbiota of persons with inflammatory bowel disease (IBD) has been described, but there are still varied reports on changes in the abundance of
Bifidobacterium
and
Lactobacillus
organisms in patients with IBD. The aim of this investigation was to compare the compositions of mucosa-associated and fecal bacteria in patients with IBD and in healthy controls (HCs). Fecal and biopsy samples from 21 HCs, 21 and 15 Crohn's disease (CD) patients, and 34 and 29 ulcerative colitis (UC) patients, respectively, were analyzed by quantitative real-time PCR targeting the 16S rRNA gene. The bacterial numbers were transformed into relative percentages for statistical analysis. The proportions of bacteria were uniformly distributed along the colon regardless of the disease state.
Bifidobacterium
was significantly increased in the biopsy specimens of active UC patients compared to those in the HCs (4.6% versus 2.1%,
P
= 0.001), and the proportion of
Bifidobacterium
was significantly higher in the biopsy specimens than in the fecal samples in active CD patients (2.7% versus 2.0%,
P
= 0.012). The
Lactobacillus
group was significantly increased in the biopsy specimens of active CD patients compared to those in the HCs (3.4% versus 2.3%,
P
= 0.036). Compared to the HCs,
Faecalibacterium prausnitzii
was sharply decreased in both the fecal and biopsy specimens of the active CD patients (0.3% versus 14.0%,
P
< 0.0001 for fecal samples; 0.8% versus 11.4%,
P
< 0.0001 for biopsy specimens) and the active UC patients (4.3% versus 14.0%,
P
= 0.001 for fecal samples; 2.8% versus 11.4%,
P
< 0.0001 for biopsy specimens). In conclusion,
Bifidobacterium
and the
Lactobacillus
group were increased in active IBD patients and should be used more cautiously as probiotics during the active phase of IBD. Butyrate-producing bacteria might be important to gut homeostasis.
Pretreatment of Urine Samples with SDS Improves Direct Identification of Urinary Tract Pathogens with Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry
Authors: Sánchez-Juanes F. , Siller Ruiz M. , Moreno Obregón F. , Criado González M. , Hernández Egido S. , de Frutos Serna M. , González-Buitrago J. M. , Muñoz-Bellido J. L. 
Published: November 2013

ABSTRACT

We pretreated with SDS 71 urine samples with bacterial counts of >10
5
CFU/ml and matrix-assisted laser desorption ionization–time of flight (MALDI-TOF) identification scores of <2, in order to minimize failure rates. Identification improved in 46.5% of samples, remained unchanged in 49.3%, and worsened in 4.2%. The improvement was more evident for Gram-negative (54.3%) than for Gram-positive (32%) bacteria.
Copy Numbers of Telomeric Repeat Sequences of Human Herpesvirus 6B in Clinical Isolates: Possibility of Mixed Infections
Authors: Kato Yuri , Ihira Masaru , Umeda Mami , Higashimoto Yuki , Kawamura Yoshiki , Ohashi Masahiro , Ishi Junichi , Yoshikawa Tetsushi 
Published: November 2013

ABSTRACT
In order to determine whether mixed infections of human herpesvirus 6B (HHV-6B) occur in immunocompetent and immunocompromised individuals, we examined the copy numbers of telomeric repeat sequences (TRS) of clinical isolates. In clinical isolates obtained from patients with exanthem subitum caused by primary HHV-6B infection, PCR products with HHV-6B TRS ranging between 400 and 800 bp were amplified. PCR products of various sizes were amplified in four clinical isolates from drug-induced hypersensitivity syndrome (DIHS) patients and 15 isolates from hematopoietic stem cell transplant (HSCT) recipients with HHV-6B reactivation. Based on the sequence analysis of the PCR products, the copy numbers of TRS in DIHS and HSCT patients were between 42 and 82 and 22 and >90, respectively. For two of the HSCT recipients, HHV-6B TRS PCR products of different sizes were detected in several isolates from each patient, which suggests mixed HHV-6B infections. In two of the posttransplant HHV-6B encephalitis patients, the sizes of the TRS nested PCR products amplified from the reactivated virus detected in the central nervous system differed from those of the virus detected in initial isolates from peripheral blood mononuclear cells. Taken together, these results suggest that PCR analysis of TRS copy number is a reliable tool for the discrimination of HHV-6B clinical isolates. Additionally, mixed HHV-6B infections occurred in HSCT recipients, and in some cases, compartmentalization of the HHV-6B strains to the central nervous system versus the blood compartment occurred in posttransplant HHV-6B encephalitis patients.
Incorporation of a Proteotyping Approach Using Mass Spectrometry for Surveillance of Influenza Virus in Cell-Cultured Strains
Authors: Fernandes Neil D. , Downard Kevin M. 
Published: November 2013

ABSTRACT
The reemergence of deadly pandemic influenza virus strains has necessitated the development of improved methods for rapid detection and subtyping of influenza viruses that will enable more strains to be characterized at the molecular level. Representative circulating strains of human influenza viruses from primary clinical specimens were grown in cell culture, purified through polyethylene glycol precipitation, proteolytically digested with an endoproteinase, and analyzed and identified by high-resolution mass spectrometry using unique signature peptides that are characteristic of type A H1N1 and H3N2 and type B influenza viruses. This proteotyping approach enabled circulating strains of type A influenza virus to be typed and subtyped, cocirculating seasonal and pandemic H1N1 viruses to be differentiated, and the lineage of type B viruses to be determined through single-ion detection by high-resolution mass spectrometry. Results were obtained using virus titers comparable to those used in reverse transcription (RT)-PCR assays with clinical specimens grown in cell cultures. The methodology represents a more rapid and direct approach than RT-PCR and can be integrated into existing procedures currently used for the surveillance of emerging pandemic and seasonal influenza viruses.
Risk Assessment of H2N2 Influenza Viruses from the Avian Reservoir
Authors: Jones Jeremy C. , Baranovich Tatiana , Marathe Bindumadhav M. , Danner Angela F. , Seiler Jon P. , Franks John , Govorkova Elena A. , Krauss Scott , Webster Robert G. 
Published: November 2013

ABSTRACT
H2N2 influenza A viruses were the cause of the 1957-1958 pandemic. Historical evidence demonstrates they arose from avian virus ancestors, and while the H2N2 subtype has disappeared from humans, it persists in wild and domestic birds. Reemergence of H2N2 in humans is a significant threat due to the absence of humoral immunity in individuals under the age of 50. Thus, examination of these viruses, particularly those from the avian reservoir, must be addressed through surveillance, characterization, and antiviral testing. The data presented here are a risk assessment of 22 avian H2N2 viruses isolated from wild and domestic birds over 6 decades. Our data show that they have a low rate of genetic and antigenic evolution and remained similar to isolates circulating near the time of the pandemic. Most isolates replicated in mice and human bronchial epithelial cells, but replication in swine tissues was low or absent. Multiple isolates replicated in ferrets, and 3 viruses were transmitted to direct-contact cage mates. Markers of mammalian adaptation in hemagglutinin (HA) and PB2 proteins were absent from all isolates, and they retained a preference for avian-like α2,3-linked sialic acid receptors. Most isolates remained antigenically similar to pandemic A/Singapore/1/57 (H2N2) virus, suggesting they could be controlled by the pandemic vaccine candidate. All viruses were susceptible to neuraminidase inhibitors and adamantanes. Nonetheless, the sustained pathogenicity of avian H2N2 viruses in multiple mammalian models elevates their risk potential for human infections and stresses the need for continual surveillance as a component of prepandemic planning.
Immunoprevalence and Immunodominance of HLA-Cw∗0801-Restricted T Cell Response Targeting the Hepatitis B Virus Envelope Transmembrane Region
Authors: Tan Anthony T. , Sodsai Pimpayao , Chia Adeline , Moreau Eglantine , Chng Melissa H. Y. , Tham Christine Y. L. , Ho Zi Zong , Banu Nasirah , Hirankarn Nattiya , Bertoletti Antonio 
Published: November 2013

ABSTRACT

HLA-C-restricted T cells have been shown to play an important role in HIV control, but their impact on protection or pathogenesis in other viral infections remains elusive. Here, we characterized the hierarchy of HLA class I-restricted hepatitis B virus (HBV) epitopes targeted by CD8 T cells in HBV-infected subjects. The frequency of CD8 T cells specific for a panel of 18 HBV epitopes (restricted by HLA-A∗0201/03/07 [hereinafter HLA-A0201/03/07], -A1101, -A2402/07, -B5801, -B4001, -B1301, and -Cw0801) was quantified in a total of 59 subjects who resolved HBV infection. We found that the HLA-Cw0801-restricted epitope comprised of Env residues 171 to 180 (Env
171–180
) is immunoprevalent in the Southeast Asian subjects (10/17 HLA-Cw0801-positive subjects) and immunodominant in the majority of HLA-Cw0801-positive subjects able to control HBV infection. HLA-Cw0801-restricted Env
171–180
-specific CD8 T cells recognized endogenously produced HBV surface antigen (HBsAg) and tolerated amino acid variations within the epitope detected in HBV genotypes B and C. In conclusion, we demonstrate that the HLA-Cw0801-restricted Env
171–180
T cell response is an important component of the HBV-specific adaptive T cell immunity in Asians infected with HBV. Thus, HLA-C restricted T cells might play an important role in various viral infections.
Human Cytomegalovirus Major Immediate Early 1 Protein Targets Host Chromosomes by Docking to the Acidic Pocket on the Nucleosome Surface
Authors: Mücke Katrin , Paulus Christina , Bernhardt Katharina , Gerrer Katrin , Schön Kathrin , Fink Alina , Sauer Eva-Maria , Asbach-Nitzsche Alexandra , Harwardt Thomas , Kieninger Bärbel , Kremer Werner , Kalbitzer Hans Robert , Nevels Michael 
Published: November 2013

ABSTRACT
The 72-kDa immediate early 1 (IE1) protein encoded by human cytomegalovirus (hCMV) is a nuclearly localized promiscuous regulator of viral and cellular transcription. IE1 has long been known to associate with host mitotic chromatin, yet the mechanisms underlying this interaction have not been specified. In this study, we identify the cellular chromosome receptor for IE1. We demonstrate that the viral protein targets human nucleosomes by directly binding to core histones in a nucleic acid-independent manner. IE1 exhibits two separable histone-interacting regions with differential binding specificities for H2A-H2B and H3-H4. The H2A-H2B binding region was mapped to an evolutionarily conserved 10-amino-acid motif within the chromatin-tethering domain (CTD) of IE1. Results from experimental approaches combined with molecular modeling indicate that the IE1 CTD adopts a β-hairpin structure, docking with the acidic pocket formed by H2A-H2B on the nucleosome surface. IE1 binds to the acidic pocket in a way similar to that of the latency-associated nuclear antigen (LANA) of the Kaposi's sarcoma-associated herpesvirus. Consequently, the IE1 and LANA CTDs compete for binding to nucleosome cores and chromatin. Our work elucidates in detail how a key viral regulator is anchored to human chromosomes and identifies the nucleosomal acidic pocket as a joint target of proteins from distantly related viruses. Based on the striking similarities between the IE1 and LANA CTDs and the fact that nucleosome targeting by IE1 is dispensable for productive replication even in “clinical” strains of hCMV, we speculate that the two viral proteins may serve analogous functions during latency of their respective viruses.
Expression Profile of MicroRNAs in Epstein-Barr Virus-Infected AGS Gastric Carcinoma Cells
Authors: Marquitz Aron R. , Mathur Anuja , Chugh Pauline E. , Dittmer Dirk P. , Raab-Traub Nancy 
Published: November 2013

ABSTRACT
Latent infection with Epstein-Barr virus (EBV) is responsible for multiple types of malignancies, including 10% of all gastric carcinomas. The microRNA (miRNA) expression in several EBV-infected AGS gastric carcinoma cell lines was determined. Infected cells expressed the viral BamHI A rightward transcript (BART) miRNAs at high levels and had consistently decreased expression of a small fraction of cellular miRNAs with specific downregulation of tumor suppressor miRNAs. These changes likely reflect expression of the viral noncoding RNAs and not latent protein expression.