bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of Unsteady Flow Field in a Low-Speed One and a Half Stage Axial Compressor: Effects of Tip Gap Size on the Tip Clearance Flow Structure at Near Stall Operation
Authors: Hah Chunill , Hathaway Michael , Katz Joseph 
Published: September 2014

The primary focus of this paper is to investigate the effect of rotor tip gap size on how the rotor unsteady tip clearance flow structure changes in a low speed one and half stage axial compressor at near stall operation (for example, where maximum pressure rise is obtained). A Large Eddy Simulation (LES) is applied to calculate the unsteady flow field at this flow condition with both a small and a large tip gaps. The numerically obtained flow fields at the small clearance matches fairly well with the available initial measurements obtained at the Johns Hopkins University with 3-D unsteady PIV in an index-matched test facility which renders the compressor blades and casing optically transparent. With this setup, the unsteady velocity field in the entire flow domain, including the flow inside the tip gap, can be measured. The numerical results are also compared with previously published measurements in a low speed single stage compressor (Maerz et al. [2002]). The current study shows that, with the smaller rotor tip gap, the tip clearance vortex moves to the leading edge plane at near stall operating condition, creating a nearly circumferentially aligned vortex that persists around the entire rotor. On the other hand, with a large tip gap, the clearance vortex stays inside the blade passage at near stall operation.
With the large tip gap, flow instability and related large pressure fluctuation at the leading edge are observed in this one and a half stage compressor. Detailed examination of the unsteady flow structure in this compressor stage reveals that the flow instability is due to shed vortices near the leading edge, and not due to a three-dimensional separation vortex originating from the suction side of the blade, which is commonly referred to during a spike-type stall inception. The entire tip clearance flow is highly unsteady. Many vortex structures in the tip clearance flow, including the sheet vortex system near the casing, interact with each other. The core tip clearance vortex, which is formed with the rotor tip gap flows near the leading edge, is also highly unsteady or intermittent due to pressure oscillations near the leading edge and varies from passage to passage. For the current compressor stage, the evidence does not seem to support that a classical vortex breakup occurs in any organized way, even with the large tip gap. Although wakes from the IGV influence the tip clearance flow in the rotor, the major characteristics of rotor tip clearance flows in isolated or single stage rotors are observed in this one and a half stage axial compressor.
Automatic Three Dimensional Grid Generation in Turbo Machine Blade Passages
Authors: Zagitov R. A. , Dushko A. N. , Shmotin Yu. N. 
Published: September 2014

Generation of the grid for blade passages with packaging using universal grid generators usually takes much time. The paper is devoted to grid generation in turbo machine blade passages with packaging in automatic mode. The main requirement to the approach is to obtain the grid with minimum engineer participant. In the developed procedure engineer must specify only general input data: number of nodes, cell size near solid bodies and geometrical data.
Multiblock structured grids are considered. All grid blocks have node-to-node attachment between each other; periodicity is also specified from node to node. The grid in blade passage consists of two blocks: “O” grid around blade and “H” grid in blade passage. Additional blocks are used to describe different ZR-effects such us tip clearances, leakage seals and bleed air systems.
A variational method of constructing three dimensional grids composed of hexahedral cells is applied. The combination of the energy density functional and cell size functional is used. The first functional lets us control the shapes and the second functional lets us control the sizes of grid cells. Grid untangling procedure is also developed.
Developed approach was tested using the blades of axial and centrifugal compressors and axial turbines. Results of grid generation are presented.
Dynamic Response of a Metal and a CMC Turbine Blade During a Controlled Rub Event Using a Segmented Shroud
Authors: Langenbrunner Nisrene , Weaver Matt , Dunn Michael G. , Padova Corso , Barton Jeffery 
Published: September 2014

Ceramic Matrix Composites, CMCs, provide several benefits over metal blades including weight and increased temperature capability, and have the potential for increased engine performance by reduction of the cooling flow bled from the compressor and by allowing engines to run at higher turbine inlet temperatures. These CMC blades must be capable of surviving fatigue (high cycle and low cycle), creep, impact, and any tip rub events due to the engine missions or maneuvers that temporarily close blade tip/shroud clearances.
As part of a co-operative research program between GE Aviation and the Ohio State University Gas Turbine Laboratory, OSU GTL, the response of a CMC stage 1 low-pressure turbine blade has been compared with the response of an equivalent metal turbine blade using the OSU GTL large spin-pit facility (LSPF) as the test vehicle. Load cells mounted on the casing wall, strain gages mounted on the airfoils, and other instrumentation are used to assess blade tip rub interactions with a 120-degree sector of a representative turbine stationary casing. The intent of this paper is to present the dynamic response of both the CMC and the metal blades with the turbine disk operating at design speed and with representative incursion rates and depths. Casing wear and blade tip wear are both characterized for several types of rub conditions including a light, medium, and heavy rub at room temperature. For each condition, the rub primary dynamic modes have been evaluated, and the corresponding blade tip loads have been calculated. The preliminary results suggest that a CMC blade has similar abilities to a metal blade during a rub event.
Gas Turbine Fault Classification Using Probability Density Estimation
Authors: Loboda Igor 
Published: September 2014

Diagnostics is an important aspect of a condition based maintenance program. To develop an effective gas turbine monitoring system in short time, the recommendations on how to optimally design every system algorithm are required. This paper deals with choosing a proper fault classification technique for gas turbine monitoring systems.
To classify gas path faults, different artificial neural networks are typically employed. Among them the Multilayer Perceptron (MLP) is the mostly used. Some comparative studies referred to in the introduction show that the MLP and some other techniques yield practically the same classification accuracy on average for all faults. That is why in addition to the average accuracy, more criteria to choose the best technique are required. Since techniques like Probabilistic Neural Network (PNN), Parzen Window (PW) and k-Nearest Neighbor (K-NN) provide a confidence probability for every diagnostic decision, the presence of this important property can be such a criterion. The confidence probability in these techniques is computed through estimating a probability density for patterns of each concerned fault class.
The present study compares all mentioned techniques and their variations using as criteria both the average accuracy and availability of the confidence probability. To compute them for each technique, a special testing procedure simulates numerous diagnosis cycles corresponding to different fault classes and fault severities. In addition to the criteria themselves, criteria imprecision due to a finite number of the diagnosis cycles is computed and involved into selecting the best technique.
Improving x‐ray fluorescence signal for benchtop polychromatic cone‐beam x‐ray fluorescence computed tomography by incident x‐ray spectrum optimization: A Monte Carlo study
Authors: Manohar Nivedh , Jones Bernard L. , Cho Sang Hyun 
Published: September 2014

Purpose:To develop an accurate and comprehensive Monte Carlo (MC) model of an experimental benchtop polychromatic cone‐beam x‐ray fluorescence computed tomography (XFCT) setup and apply this MC model to optimize incident x‐ray spectrum for improving production/detection of x‐ray fluorescence photons from gold nanoparticles (GNPs).Methods:A detailed MC model, based on an experimental XFCT system, was created using the Monte Carlo N‐Particle (MCNP) transport code. The model was validated by comparing MC results including x‐ray fluorescence (XRF) and scatter photon spectra with measured data obtained under identical conditions using 105 kVp cone‐beam x‐rays filtered by either 1 mm of lead (Pb) or 0.9 mm of tin (Sn). After validation, the model was used to investigate the effects of additional filtration of the incident beam with Pb and Sn. Supplementary incident x‐ray spectra, representing heavier filtration (Pb: 2 and 3 mm; Sn: 1, 2, and 3 mm) were computationally generated and used with the model to obtain XRF/scatter spectra. Quasimonochromatic incident x‐ray spectra (81, 85, 90, 95, and 100 keV with 10 keV full width at half maximum) were also investigated to determine the ideal energy for distinguishing gold XRF signal from the scatter background. Fluorescence signal‐to‐dose ratio (FSDR) and fluorescence‐normalized scan time (FNST) were used as metrics to assess results.Results:Calculated XRF/scatter spectra for 1‐mm Pb and 0.9‐mm Sn filters matched (r ≥ 0.996) experimental measurements. Calculated spectra representing additional filtration for both filter materials showed that the spectral hardening improved the FSDR at the expense of requiring a much longer FNST. In general, using Sn instead of Pb, at a given filter thickness, allowed an increase of up to 20% in FSDR, more prominent gold XRF peaks, and up to an order of magnitude decrease in FNST. Simulations using quasimonochromatic spectra suggested that increasing source x‐ray energy, in the investigated range of 81–100 keV, increased the FSDR up to a factor of 20, compared to 1 mm Pb, and further facilitated separation of gold XRF peaks from the scatter background.Conclusions:A detailed MC model of an experimental benchtop XFCT system has been developed and validated. In exemplary calculations to illustrate the usefulness of this model, it was shown that potential use of quasimonochromatic spectra or judicious choice of filter material/thickness to tailor the spectrum of a polychromatic x‐ray source can significantly improve the performance of benchtop XFCT, while considering trade‐offs between FSDR and FNST. As demonstrated, the current MC model is a reliable and powerful computational tool that can greatly expedite the further development of a benchtop XFCT system for routine preclinical molecular imaging with GNPs and other metal probes.
Association between Serotype-Specific Antibody Response and Serotype Characteristics in Patients with Pneumococcal Pneumonia, with Special Reference to Degree of Encapsulation and Invasive Potential
Authors: Athlin Simon , Kaltoft Margit , Slotved Hans-Christian , Herrmann Björn , Holmberg Hans , Konradsen Helle Bossen , Strålin Kristoffer 
Published: September 2014

ABSTRACTWe studied the immunoglobulin (Ig) response to causative serotype-specific capsular polysaccharides in adult pneumococcal pneumonia patients. The serotypes were grouped according to their degree of encapsulation and invasive potential. Seventy patients with pneumococcal pneumonia, 20 of whom were bacteremic, were prospectively studied. All pneumococcal isolates from the patients were serotyped, and the Ig titers to the homologous serotype were determined in acute- and convalescent-phase sera using a serotype-specific enzyme-linked immunosorbent assay. The Ig titers were lower in bacteremic cases than in nonbacteremic cases (P< 0.042). The Ig titer ratio (convalescent/acute titer) was ≥2 in 33 patients, 1 to 1.99 in 20 patients, and <1 in 17 patients. Patients ≥65 years old had a lower median Ig titer ratio than did younger patients (P< 0.031). The patients with serotypes with a thin capsule (1, 4, 7F, 9N, 9V, and 14) and medium/high invasive potential (1, 4, 7F, 9N, 9V, 14, and 18C) had higher Ig titer ratios than did patients with serotypes with a thick capsule (3, 6B, 11A, 18C, 19A, 19F, and 23F) and low invasive potential (3, 6B, 19A, 19F, and 23F) (P< 0.05 for both comparisons after adjustment for age). Ig titer ratios of <1 were predominantly noted in patients with serotypes with a thick capsule. In 8 patients with pneumococcal DNA detected in plasma, the three patients with the highest DNA load had the lowest Ig titer ratios. In conclusion, a high antibody response was associated with serotypes with a thin capsule and medium/high invasive potential, although a low antibody response was associated with serotypes with a thick capsule and a high pneumococcal plasma load.
Determination of Specific Antibody Responses to the Six Species of Ebola and Marburg Viruses by Multiplexed Protein Microarrays
Authors: Kamata Teddy , Natesan Mohan , Warfield Kelly , Aman M. Javad , Ulrich Robert G. 
Published: September 2014

ABSTRACTInfectious hemorrhagic fevers caused by the Marburg and Ebola filoviruses result in human mortality rates of up to 90%, and there are no effective vaccines or therapeutics available for clinical use. The highly infectious and lethal nature of these viruses highlights the need for reliable and sensitive diagnostic methods. We assembled a protein microarray displaying nucleoprotein (NP), virion protein 40 (VP40), and glycoprotein (GP) antigens from isolates representing the six species of filoviruses for use as a surveillance and diagnostic platform. Using the microarrays, we examined serum antibody responses of rhesus macaques vaccinated with trivalent (GP, NP, and VP40) virus-like particles (VLP) prior to infection with the Marburg virus (MARV) (i.e.,Marburg marburgvirus) or the Zaire virus (ZEBOV) (i.e.,Zaire ebolavirus). The microarray-based assay detected a significant increase in antigen-specific IgG resulting from immunization, while a greater level of antibody responses resulted from challenge of the vaccinated animals with ZEBOV or MARV. Further, while antibody cross-reactivities were observed among NPs and VP40s of Ebola viruses, antibody recognition of GPs was very specific. The performance of mucin-like domain fragments of GP (GP mucin) expressed inEscherichia coliwas compared to that of GP ectodomains produced in eukaryotic cells. Based on results with ZEBOV and MARV proteins, antibody recognition of GP mucins that were deficient in posttranslational modifications was comparable to that of the eukaryotic cell-expressed GP ectodomains in assay performance. We conclude that the described protein microarray may translate into a sensitive assay for diagnosis and serological surveillance of infections caused by multiple species of filoviruses.
Characterization of T-Cell Responses to Conserved Regions of the HIV-1 Proteome in BALB/c Mice
Authors: Ondondo Beatrice , Abdul-Jawad Sultan , Bridgeman Anne , Hanke Tomáš 
Published: September 2014

ABSTRACTA likely requirement for a protective vaccine against human immunodeficiency virus type 1 (HIV-1)/AIDS is, in addition to eliciting antibody responses, induction of effective T cells. To tackle HIV-1 diversity by T-cell vaccines, we designed an immunogen, HIVconsv, derived from the most functionally conserved regions of the HIV-1 proteome and demonstrated its high immunogenicity in humans and rhesus macaques when delivered by regimens combining plasmid DNA, nonreplicating simian (chimpanzee) adenovirus ChAdV-63, and nonreplicating modified vaccinia virus Ankara (MVA) as vectors. Here, we aimed to increase the decision power for iterative improvements of this vaccine strategy in the BALB/c mouse model. First, we found that prolonging the period after the ChAdV63.HIVconsv prime up to 6 weeks increased the frequencies of HIV-1-specific, gamma interferon (IFN-γ)-producing T cells induced by the MVA.HIVconsv boost. Induction of strong responses allowed us to map comprehensively the H-2d-restricted T-cell responses to these regions and identified 8 HIVconsv peptides, of which three did not contain a previously described epitope and were therefore considered novel. Induced effector T cells were oligofunctional and lysed sensitized targetsin vitro. Our study therefore provides additional tools for studying and optimizing vaccine regimens in this commonly used small animal model, which will in turn guide vaccine improvements in more expensive nonhuman primate and human clinical trials.
Identification of a Novel RNA Virus Lethal to Tilapia
Authors: Eyngor Marina , Zamostiano Rachel , Kembou Tsofack Japhette Esther , Berkowitz Asaf , Bercovier Hillel , Tinman Simon , Lev Menachem , Hurvitz Avshalom , Galeotti Marco , Bacharach Eran , Eldar Avi 
Published: September 2014

ABSTRACT
Tilapines are important for the sustainability of ecological systems and serve as the second most important group of farmed fish worldwide. Significant mortality of wild and cultured tilapia has been observed recently in Israel. The etiological agent of this disease, a novel RNA virus, is described here, and procedures allowing its isolation and detection are revealed. The virus, denominated tilapia lake virus (TiLV), was propagated in primary tilapia brain cells or in an E-11 cell line, and it induced a cytopathic effect at 5 to 10 days postinfection. Electron microscopy revealed enveloped icosahedral particles of 55 to 75 nm. Low-passage TiLV, injected intraperitoneally in tilapia, induced a disease resembling the natural disease, which typically presents with lethargy, ocular alterations, and skin erosions, with >80% mortality. Histological changes included congestion of the internal organs (kidneys and brain) with foci of gliosis and perivascular cuffing of lymphocytes in the brain cortex; ocular inflammation included endophthalmitis and cataractous changes of the lens. The cohabitation of healthy and diseased fish demonstrated that the disease is contagious and that mortalities (80 to 100%) occur within a few days. Fish surviving the initial mortality were immune to further TiLV infections, suggesting the mounting of a protective immune response. Screening cDNA libraries identified a TiLV-specific sequence, allowing the design of a PCR-based diagnostic test. This test enables the specific identification of TiLV in tilapines and should help control the spread of this virus worldwide.
Characteristics of Patients Recently Infected with HIV-1 Non-B Subtypes in France: a Nested Study within the Mandatory Notification System for New HIV Diagnoses
Authors: Brand Denys , Moreau Alain , Cazein Françoise , Lot Florence , Pillonel Josiane , Brunet Sylvie , Thierry Damien , Le Vu Stéphane , Plantier Jean-Christophe , Semaille Caroline , Barin Francis 
Published: September 2014

ABSTRACT

The presence of HIV-1 non-B subtypes in Western Europe is commonly attributed to migration of individuals from non-European countries, but the possible role of domestic infections with non-B subtypes is not well investigated. The French mandatory anonymous reporting system for HIV is linked to a virological surveillance using assays for recent infection (<6 months) and serotyping. During the first semester of years 2007 to 2010, any sample corresponding to a non-B recent infection was analyzed by sequencing a 415-bp
env
region, followed by phylogenetic analysis and search for transmission clusters. Two hundred thirty-three recent HIV-1 infections with non-B variants were identified. They involved 5 subtypes and 7 circulating recombinant forms (CRFs). Ninety-two cases (39.5%) were due to heterosexual transmissions, of which 39 occurred in patients born in France. Eighty-five cases (36.5%) were identified in men having sex with men (MSM). Forty-three recent non-B infections (18.5%) segregated into 14 clusters, MSM being involved in 11 of them. Clustered transmission events included 2 to 7 cases per cluster. The largest cluster involved MSM infected by a CRF02_AG variant. In conclusion, we found that the spread of non-B subtypes in France occurs in individuals of French origin and that MSM are particularly involved in this dynamic.
Rapid Diagnosis of Cryptococcal Meningitis by Use of Lateral Flow Assay on Cerebrospinal Fluid Samples: Influence of the High-Dose “Hook” Effect
Authors: Lourens Adré , Jarvis Joseph N. , Meintjes Graeme , Samuel Catherine M. 
Published: September 2014

ABSTRACT
Cryptococcal meningitis is the most frequent cause of meningitis and a major cause of mortality in HIV-infected adults in Africa. This study evaluated the performance of the lateral flow assay (LFA) on cerebrospinal fluid (CSF) samples for the diagnosis of cryptococcal meningitis against that of existing diagnostic tests. LFA performed on 465 undiluted CSF samples had a sensitivity of 91%. When the LFA was paired with Gram staining, a sensitivity of 100% was achieved after implementation of a dilution step for samples with negative LFA results and the presence of yeasts on microscopy. Microscopy is essential for preventing the reporting of false-negative results due to the high-dose “hook” effect.
Inconsistency of Phenotypic and Genomic Characteristics of Campylobacter fetus Subspecies Requires Reevaluation of Current Diagnostics
Authors: van der Graaf-van Bloois Linda , Miller William G. , Yee Emma , Rijnsburger Martine , Wagenaar Jaap A. , Duim Birgitta 
Published: September 2014

ABSTRACT

Classifications of the
Campylobacter fetus
subspecies
fetus
and
venerealis
were first described in 1959 and were based on the source of isolation (intestinal versus genital) and the ability of the strains to proliferate in the genital tract of cows. Two phenotypic assays (1% glycine tolerance and H
2
S production) were described to differentiate the subspecies. Multiple molecular assays have been applied to differentiate the
C. fetus
subspecies, but none of these tests is consistent with the phenotypic identification methods. In this study, we defined the core genome and accessory genes of
C. fetus
, which are based on the closed genomes of five
C. fetus
strains. Phylogenetic analysis of the core genomes of 23
C. fetus
strains of the two subspecies showed a division into two clusters. The phylogenetic core genome clusters were not consistent with the phenotypic classifications of the
C. fetus
subspecies. However, they were consistent with the molecular characteristics of the strains, which were determined by multilocus sequence typing,
sap
typing, and the presence/absence of insertion sequences and a type I restriction modification system. The similarity of the genome characteristics of three of the phenotypically defined
C. fetus
subsp.
fetus
strains to
C. fetus
subsp.
venerealis
strains, when considering the core genome and accessory genes, requires a critical evaluation of the clinical relevance of
C. fetus
subspecies identification by phenotypic assays.