bluuebunny/crossref_metadata_2025 huggingface dataset:
Endogenous Choice of Strategic Variables in an Asymmetric Duopoly with Respect to the Demand Functions that Firms Face
Authors: Nakamura Yasuhiko
Published: February 2015

This paper examines endogenous choice of firm's strategic variables—i.e. price or quantity contract—in a duopoly in which the demand functions that they face are asymmetric in managerial delegation case with separation between ownership and management. We show that when the degree of asymmetry between the demand functions that the two firms face is low, price and quantity competitions are observed in the equilibrium, whereas when the degree of such asymmetry is high, the two types of market structures in which the strategic variables selected by the two owners are different from each other are observed in the equilibrium.
KdmA, a histone H3 demethylase with bipartite function, differentially regulates primary and secondary metabolism in Aspergillus nidulans
Authors: Gacek‐Matthews Agnieszka , Noble Luke M. , Gruber Clemens , Berger Harald , Sulyok Michael , Marcos Ana T. , Strauss Joseph , Andrianopoulos Alex
Published: February 2015

Aspergillus nidulans kdmA encodes a member of the KDM4 family of jumonji histone demethylase proteins, highly similar to metazoan orthologues both within functional domains and in domain architecture. This family of proteins exhibits demethylase activity towards lysines 9 and 36 of histone H3 and plays a prominent role in gene expression and chromosome structure in many species. Mass spectrometry mapping of A. nidulans histones revealed that around 3% of bulk histone H3 carried trimethylated H3K9 (H3K9me3) but more than 90% of histones carried either H3K36me2 or H3K36me3. KdmA functions as H3K36me3 demethylase and has roles in transcriptional regulation. Genetic manipulation of KdmA levels is tolerated without obvious effect in most conditions, but strong phenotypes are evident under various conditions of stress. Transcriptome analysis revealed that – in submerged early and late cultures – between 25% and 30% of the genome is under KdmA influence respectively. Transcriptional imbalance in the kdmA deletion mutant may contribute to the lethal phenotype observed upon exposure of mutant cells to low‐density visible light on solid medium. Although KdmA acts as transcriptional co‐repressor of primary metabolism genes, it is required for full expression of several genes involved in biosynthesis of secondary metabolites.
Recognizing cross‐ecosystem responses to changing temperatures: soil warming impacts pelagic food webs
Authors: Fey Samuel B. , Mertens Andrew N. , Beversdorf Lucas J. , McMahon Katherine D. , Cottingham Kathryn L.
Published: February 2015

The energy and materials that move across ecosystem boundaries influence food web structure and key ecosystem functions. Despite the acknowledged importance of such ecological subsidies, surprisingly little information is available regarding the role of environmental temperature in influencing subsidy quality and the response of the recipient ecosystem. We evaluated the impacts of temperature‐mediated changes in leaves from deciduous trees, an important subsidy from terrestrial to freshwater ecosystems, on both the producer‐based and detritivore‐based components of a pelagic pond food web in a field mesocosm experiment. We hypothesized that variation in leaf chemistry driven by increased soil temperature would alter both the quality of leaf subsidies and the pond response. We collected red maple Acer rubrum leaves from heated and ambient temperature plots from the long‐term soil warming experiment at the Harvard Experimental Forest and added them to 167‐l field mesocosms containing established plankton communities, creating ‘no leaf’, ‘ambient leaf’ and ‘heated leaf’ treatments during autumn 2012. We then monitored physical, chemical, and biological responses to treatments until the mesocosms froze six weeks later. Experimental soil warming altered the chemical composition of deciduous leaves, the physical and chemical environment of the aquatic ecosystems to which leaves were added, and the pelagic pond food webs as measured by community composition. Compared to leaves from ambient‐temperature soils, leaves from warmed soils initially resulted in lower water column phosphorus and dissolved organic carbon, reducing bacterial densities. However, the diminished carbon and phosphorus resulting from soil warming also increased light availability that ultimately stimulated cladoceran zooplankton relative to ambient‐temperature leaves. Our results suggest that changes in temperature can alter ecological subsidies in unanticipated ways, and suggest that accurately predicting the potential consequences of climate change will require conducting research across ecosystem boundaries.
Late Ordovician brachiopods from Peru and their palaeobiogeographical relationships
Authors: Villas Enrique , Colmenar Jorge , Gutiérrez‐Marco Juan C.
Published: February 2015

A Sandbian brachiopod association from the Calapuja Formation, in the Peruvian Altiplano, north‐west of Lake Titicaca, has allowed a re‐examination of the palaeobiogeographical relationships between Gondwana and Avalonia during the Late Ordovician, when the palaeocontinents are considered to be already very distant from one another. The brachiopod fauna includes the new species Onnizetina calapujensis sp. nov., Horderleyella chacaltanai sp. nov., Drabovinella minuscula sp. nov. and Tasmanella curtiseptata sp. nov., as well as Caeroplecia sp., Dinorthis cf. flabellulum and Tunariorthis cardocanalis. In addition, Colaptomena expansa expansa and Heterorthis retrorsistria, known from the British Burrellian Stage of the Caradoc Series (late Sandbian) in Wales and the Welsh Borderlands, have also been identified. The brachiopod collection is the most diverse known from a single locality in the whole Central Andean Basin. Within it, forms with clear Gondwanan links occur, such as the new species of Onnizetina, Drabovinella and Horderleyella, and typical representatives of the Avalonian faunas, such as the Welsh Colaptomena expansa expansa and Heterorthis retrorsistria. The brachiopod species exchange between the Proto‐Andean margin of Gondwana and Avalonia, now believed to be possible during the late Sandbian, allows a reconsideration of the global taxonomic affinities of both regions. With this in mind, detrended correspondence analysis (DCA) and cluster analysis have been applied to an updated rhynchonelliformean brachiopod matrix consisting of presence/absence data. The scatter plot resulting from the DCA allows a vivid visualization of the grouping and geographical trends of the South American localities with respect to Avalonia–Baltica and the Mediterranean margin of Gondwana during the Sandbian. Our results agree with previous palaeogeographical reconstructions, depicting Avalonia very close to Baltica and already distant from Gondwana. As a few brachiopod species, with low dispersal potential, would have been able to migrate between those distant palaeocontinents, the existence of intermediate islands in the Rheic Ocean, permitting the transit by island hopping of eurythermal species, must be considered.
Over‐expression of GhUGP1 in upland cotton improves fibre quality and reduces fibre sugar content
Authors: Li Bo , Yang Yang , Hu Wen‐Ran , Li Xiao‐Dong , Cao Jia‐Qiang , Fan Ling
Published: February 2015

GhUGP1 (cotton uridine diphosphate glucose pyrophosphorylase) is one of the most highly expressed genes and proteins in fast elongation cotton fibres. The objective of this study was to determine whether fibre quality and reduced sugar content could be improved in fibres by over‐expressing GhUGP1 in cotton plants under conditions of low autumn temperatures and large diurnal temperature differences. A plant GhUGP1 vector was constructed and introduced into the 3‐6‐7 cotton line using agrobacterium‐mediated transformation. Following selection with kanamycin sulphate and polymerase chain reaction (PCR) and Southern blotting analyses, three independent homozygous transgenic lines were selected for molecular and chemical study. Compared with wild type, the transcriptional activity of GhUGP1 was higher and more long lasting in the transgenic lines. Fibres were longer and stronger, soluble and reduced sugar levels were significantly decreased, and cellulose levels were significantly increased. In addition, plant height also increased by 40.1‐45.1%. These results demonstrate that GhUGP1 expression was considerably increased in the transgenic plants, accelerating the conversion of oligosaccharides to polysaccharides in the developing cotton fibre.
Tsukamurella inchonensis infection in a child with Hodgkin's lymphoma
Authors: Ochi Fumihiro , Tauchi Hisamichi , Moritani Kyoko , Miyamoto Hitoshi , Ohkusu Kiyofumi , Ishii Eiichi
Published: February 2015

Tsukamurella spp. infection is a rare but important cause of bacteremia in immunocompromised patients. The organism is an aerobic, Gram‐positive, weakly acid‐fast bacillus that is difficult to differentiate from other aerobic Actinomycetales by standard laboratory methods. Here, we report on the case of a 14‐year‐old patient with Hodgkin's lymphoma who, after intensive chemotherapy, developed Tsukamurella inchonensis bacteremia, which was identified on the peripherally inserted central venous catheter (PICC) using 16S rRNA sequencing analysis. The bacteremia was successfully controlled with antimicrobial therapy and subsequent removal of the PICC. This is the first report of bacteremia by Tsukamurella inchonensis in immunocompromised children. Careful observation and prompt analysis of opportunistic infection, including Tsukamurella spp., is very important in immunocompromised children.
Collagenous sprue in a 3‐month‐old infant
Authors: Jimbo Keisuke , Aoyagi Yo , Tanaka Masanori , Ohbayashi Naho , Fujii Tohru , Kudo Takahiro , Ohtsuka Yoshikazu , Shimizu Toshiaki
Published: February 2015

Collagenous sprue (CS) is a severe malabsorption disorder, the etiology of which has not been well defined. Herein, we report the case of a 3‐month‐old infant with CS who responded to steroid and immunomodulator treatment and presented a thick subepithelial collagen band. A 3‐month‐old Japanese girl presented with severe watery diarrhea that lasted for 2 weeks. She was admitted to the referring hospital, but symptomatic improvement was not achieved with fasting and rehydration. Gastroduodenal endoscopy showed an edematous duodenal mucosal surface. Duodenal biopsy indicated severe villous atrophy with infiltration of mostly CD8‐positive T cells; and deposition of subepithelial collagen was confirmed. The subepithelial collagen deposits, however, had disappeared after treatment. Historically, child‐onset CS is extremely rare and this case is likely to be the youngest case of infantile CS. The present case suggests that CS should be considered as a differential diagnosis for intractable diarrhea, even in infants.
Familial IPEX syndrome: Different glomerulopathy in two siblings
Authors: Park Eujin , Chang Hye Jin , Shin Jae Il , Lim Beom Jin , Jeong Hyeon Joo , Lee Kyoung Bun , Moon Kyoung Chul , Kang Hee Gyung , Ha Il‐Soo , Cheong Hae Il
Published: February 2015

Immune dysregulation, polyendocrinopathy, enteropathy, X‐linked (IPEX) syndrome (OMIM 304790) is a rare hereditary disorder of the immune regulatory system caused by FOXP3 mutations. The clinical features of this syndrome include a wide spectrum of severe autoimmune diseases and renal involvement, mostly due to tubulointerstitial diseases, in some patients. Glomerulopathy of membranous nephropathy (MN) and minimal change nephrotic syndrome (MCNS), however, have also been reported. We encountered two children with IPEX syndrome from the same family. Interestingly, they had different glomerular lesions: one had MN and the other had MCNS. Herein we describe the cases of these siblings and review the possible mechanisms for the development of two different renal lesions.
Buffering effect of parental engagement on the relationship between corporal punishment and children's emotional/behavioral problems
Authors: Tong Lian , Shinohara Ryoji , Sugisawa Yuka , Tanaka Emiko , Watanabe Taeko , Koeda Tatsuya , Anme Tokie
Published: February 2015

Background

Previous research has established links between corporal punishment and children's developmental problems, but few studies have investigated the moderating effect of positive parenting between corporal punishment and children's developmental difficulties in detail. This study investigated the buffering effect of parental engagement on the association between corporal punishment and children's emotional/behavioral problems.

Methods

The main caregivers completed the Evaluation of Environmental Stimulation Scale (EES), which is an evaluation of daily parenting behaviors, and the Strengths and Difficulties Questionnaire (SDQ), which evaluates children's developmental problems.

Results

Corporal punishment was associated with worse emotional and behavioral problems in children, whereas parental engagement in games or sports was associated with fewer emotional symptoms. Similarly, parental engagement in homework or housework significantly moderated the association between corporal punishment and children's behavioral problems.

Conclusions

Parental engagement positively moderated the association between parental corporal punishment and children's developmental difficulties. This association varied with child gender.
Intravenous pentamidine for Pneumocystis carinii/jiroveci pneumonia prophylaxis in pediatric transplant patients
Authors: Clark Abigail , Hemmelgarn Trina , Danziger‐Isakov Lara , Teusink Ashley
Published: February 2015

SMX/TMP is the current gold standard for prophylaxis against PCP in immunocompromised pediatric patients. Currently, there are several second‐line options for prophylaxis but many, including intravenous (IV) pentamidine, have not been reported to be as effective or as safe as SMX/TMP in the pediatric transplant population. This study is to determine the efficacy and safety of IV pentamidine in preventing PCP in pediatric transplant patients. A retrospective chart review was conducted to evaluate all transplant patients that received at least one dose of IV pentamidine from January 2010 to July 2013. The primary outcome, IV pentamidine efficacy, was evaluated by the incidence of PCP diagnosis for 28 days after the last dose of IV pentamidine if patient was transitioned to another agent for PCP prophylaxis. Patients on IV pentamidine for entire course of PCP prophylaxis were followed at least six months after discontinuation of IV pentamidine. The safety of IV pentamidine was assessed by the incidence of adverse events leading to pentamidine discontinuation. All data were analyzed using descriptive statistics. All transplant patients at CCHMC who had received IV pentamidine were reviewed, and 333 patients met inclusion criteria. The overall incidence of PCP was found to be 0.3% for pediatric transplant patients on pentamidine. Pentamidine was found to be safe, and the incidence of adverse events leading to discontinuation was 6% with the most common reason being tachycardia 2.1%. IV pentamidine is safe and effective as PCP prophylaxis in pediatric transplant patients with a PCP breakthrough rate of 0.3% (1 of 333 patients), and only 20 adverse events led to discontinuation. We recommend that IV pentamidine be considered as a second‐line option in pediatric transplant patients who cannot tolerate SMX/TMP.
Phylogeny and origin of Fusarium oxysporum f. sp. vanillae in Indonesia
Authors: Pinaria A. G. , Laurence M. H. , Burgess L. W. , Liew E. C. Y.
Published: February 2015

Vanilla stem rot, caused by Fusarium oxysporum f. sp. vanillae (Fov), is the main constraint to increasing vanilla production in the major vanilla‐producing countries, including Indonesia. The current study investigated the origin of Fov in Indonesia using a multigene phylogenetic approach. Nineteen Fov isolates were selected to represent Indonesia, the Comoros, Mexico and Réunion Island. The translation elongation factor 1 alpha gene and the mitochondrial small subunit ribosomal RNA gene phylogenies resolved the Fov isolates into three distinct clades in both phylogenetic species of the F. oxysporum species complex, indicating a polyphyletic pattern of evolution. In addition, Fov isolates from Indonesia were also polyphyletic. These results suggest that the vanilla stem rot pathogen in Indonesia has a complex origin. The implications for disease management are discussed.
Task switching mediates direct interference of intertarget distractors in the attentional blink: An event‐related potential study
Authors: Brisson Benoit
Published: February 2015

The attentional blink (AB) refers to the difficulty in reporting a second target (T2) presented shortly after a first target (T1) in a stream of distractors. The goal of the present study was to investigate distractor‐based interference in the AB by recording the P3 component of the event‐related potential to both targets. An intertarget distractor was presented at lag 1 (T1+1), at lag 2 (T1+2), or at neither of these two lags (no distractor). T2 was always presented at lag 3, as the last item in the stream. In two experiments, the P3 from T1 was attenuated in the T1+1 condition compared to the two other distractor conditions. In absence of a task switch (Experiment 1), the P3 from T2 was delayed in both the T1+1 and T1+2 conditions. In the presence of a task switch (Experiment 2), the P3 from T2 was delayed only in the T1+1 condition. Results demonstrate that intertarget distractors can modulate the AB directly but only in absence of a task switch.
T cell subsets in human airways prior to and following endobronchial administration of endotoxin
Authors: Ronit Andreas , Plovsing Ronni R. , Gaardbo Julie C. , Berg Ronan M.G. , Hartling Hans J. , Konge Lars , Iversen Martin , Ullum Henrik , Møller Kirsten , Nielsen Susanne Dam
Published: February 2015

Background and objectives

Bronchial instillation of lipopolysaccharide (LPS) provides a reversible model of lung inflammation that may resemble early stages of acute respiratory distress syndrome (ARDS). We investigated the distributions of T‐cell subsets in the human airways and sought to determine whether pro‐ and anti‐inflammatory T cells are involved in the local immune response to lung inflammation.

Methods

Bronchoalveolar lavage (BAL) was performed in 15 healthy volunteers, after which Escherichia coli LPS (4 ng/kg) was administered. BAL was repeated at 2, 4, 6, 8 or 24 h after instillation of LPS.

Results

BALF CD4+ and CD8+ T cells were characterized by expression of activation markers (HLA‐DR+CD38+), the proportion of cells expressing naïve markers (CD45RA+CD27+CCR7+) was lower, and that of cells expressing effector memory markers (CD45RA‐CD27+CCR7‐) was higher, compared with peripheral blood. Bronchial LPS induced a local inflammatory response with recruitment of CD4+ (P = 0.014), CD8+ T cells (P = 0.034), an increase in the proportion of CD4+CD25+CD127lowFoxp3+ regulatory T cells (Tregs) (P = 0.045) and a tendency towards an increase in CD4+CD161+ cells (P = 0.071) were observed.

Conclusions

A unique distribution of T cells with little day‐to‐day variation was found in human airways. An increase in Tregs after endobronchial LPS suggests a role for Tregs during early stages of pulmonary inflammation.
Be Careful What You Wish For: The Ironic Connection Between the Civil Rights Struggle and Today's Divided America
Authors: McAdam Doug
Published: February 2015

The deep political and economic divisions that characterize the contemporary United States have been the subject of much discussion and analysis. However, most of the accounts of these divisions have tended to emphasize relatively recent events or trends, such as the Tea Party movement or the extreme partisanship that has marked the last three presidential administrations (e.g., Obama, George Bush Jr., Clinton). The origins of today's divisions, however, have much older roots. They date to the heyday of the Civil Rights struggle and ironically to the seminal achievements of the movement. More accurately, it is the story of not one, but two parallel movements, the revitalized civil rights movement of the early to mid‐1960s and the powerful segregationist countermovement, that quickly developed in response to the African‐American freedom struggle. The argument is that over the course of the decade of the 1960s, these two linked struggles decisively altered the partisan geography of the United States, and in the process pushed the national Democratic and Republican parties sharply to the left and right, respectively, undermining the centrist policy convergence of the postwar period and setting the parties on the divisive course they remain on today.
The Constitution of Trust: Function, Configuration and Generation of Trust in Alternative Food Networks
Authors: Thorsøe Martin , Kjeldsen Chris
Published: February 2015

Alternative Food Networks (AFNs) are often mentioned as a way to reconfigure the link between producers and consumers and build trust in the food system. This article explores the function, configuration and generation of trust in AFNs. The structure is twofold. First we discuss the theoretical underpinnings of trust, in both recent AFN literature and in sociology, and develop a conceptual framework for analysing trust in AFNs. Second, we explore the function, configuration and generation of trust in the Food Communities of Copenhagen and Aarhus (in Danish: ‘Fødevarefællesskaberne’). The Food Communities are a network of urban consumers sourcing organic products from regional producers. Empirically, the article demonstrates how trust functions as a mechanism that creates coherency and which facilitates co‐operation in the food network. Furthermore, the Food Communities are characterised by high levels of systemic and personal trust. Several mechanisms, such as managing expectations, establishing trustworthiness, and developing a common normative basis, are employed and contribute to the generation and maintenance of trust.
Upper‐extremity deep venous thrombosis after whole blood donation: report of three cases from a single blood center
Authors: Newman Bruce , Rajpurkar Madhvi , Ozgonenel Bulent , Lal Anup , Kuriakose Philip
Published: February 2015

BACKGROUND

There are two upper‐extremity deep venous thrombosis (UEDVT) cases after whole blood donation reported in the English medical literature. Three additional UEDVT cases after whole blood donation were reported to our blood center within a 13‐month period.

STUDY DESIGN AND METHODS

A case study was done for each case in collaboration with a clinical physician. A description of the donation event, donor demographics, risk factors for thrombosis, treatment, and outcome were described.

RESULTS

A 33‐year‐old woman and two 17‐year‐old, first‐time‐donating men presented with arm pain, swelling, and bruising within hours to 3 days after donation. Two had distal UEDVTs in the basilic or brachial veins, and one had a proximal UEDVT in the subclavian and axillary veins extending into the basilic vein. One donor (woman) had known risk factors for DVT and the other two did not. Anticoagulant therapy was initiated on all patients and was continued for 3, 4, and 9 months. Two donors with the distal UEDVTs recovered completely while the donor with the proximal UEDVT was treated with anticoagulation for 9 months and continued to have a slight residual, nonobstructive thrombosis. The donor was switched to low‐dose aspirin prevention. The two donors reported in the literature had complete resolution of thrombosis.

CONCLUSIONS

Four of five donors recovered completely after anticoagulation treatment for UEDVT, including two of three donors in this study. A review of all cases in the medical literature, including 20 recent Australian cases described in an abstract, provides a more complete description of this adverse donation injury.
Interleukin‐10 limits intense acute swimming‐induced muscle mechanical hyperalgesia in mice
Authors: Borghi Sergio M. , Pinho‐Ribeiro Felipe A. , Zarpelon Ana C. , Cunha Thiago M. , Alves‐Filho Jose C. , Ferreira Sergio H. , Cunha Fernando Q. , Casagrande Rubia , Verri Waldiceu A.
Published: February 2015

New Findings

What is the central question of this study?

This study investigated the role of the endogenous anti‐inflammatory cytokine interleukin‐10 in intense acute swimming‐induced muscle mechanical hyperalgesia in mice.

What is the main finding and its importance?

Endogenous interleukin‐10 has a key role in limiting exercise‐induced muscle pain in a model presenting similarities to delayed‐onset muscle soreness in mice. Interleukin‐10 reduced muscle pain by diminishing leucocyte recruitment, hyperalgesic cytokine production, oxidative stress and myocyte damage.

Interleukin‐10 (IL‐10) is an antihyperalgesic cytokine. In this study, IL‐10‐deficient (IL‐10−/−) mice were used to investigate the role of endogenous IL‐10 in intense acute swimming‐induced muscle mechanical hyperalgesia, which presents similarities with delayed‐onset muscle soreness. An intense acute swimming session of 1 or 2 h induced significant muscle mechanical hyperalgesia in a time‐dependent manner in wild‐type mice compared with the sham group 24 h after the session, which was further increased in IL‐10−/− mice (P ˂ 0.05). Intraperitoneal treatment of wild‐type mice with IL‐10 (1–10 ng) reduced muscle mechanical hyperalgesia in a dose‐dependent manner and reversed the enhanced muscle hyperalgesia in IL‐10−/− mice (P ˂ 0.05). The 2 h swimming session induced increases in tumour necrosis factor‐α, interleukin‐1β and IL‐10 production in the soleus muscle. However, tumour necrosis factor‐α and interleukin‐1β production in the soleus muscle were even higher in IL‐10−/− mice between 2 and 6 h after the stimulus (P ˂ 0.05). There was no statistical difference in the levels of the antihyperalgesic cytokines interleukin‐4, interleukin‐5, interleukin‐13 and transforming growth factor‐β between wild‐type and IL‐10−/− mice (P ˃ 0.05). Interleukin‐10 deficiency also resulted in increased myeloperoxidase activity, greater depletion of reduced glutathione levels, increased superoxide anion production and the maintenance of high plasma concentrations of creatine kinase (until 24 h after the swimming session) in soleus muscle (P ˂ 0.05). These results demonstrate that endogenous IL‐10 controls intense acute swimming‐induced muscle mechanical hyperalgesia by limiting oxidative stress and cytokine production.
Vibration of a Rotor With Extremely Nonlinear Stiffness Passing Through Critical Speeds
Authors: Liu Baojiang , Yan Litang , Li Qihan , Zhu Zigen
Published: February 2015

Soft spring nonlinearity refers to supporting stiffness becomes smaller with increase of vibratory displacements. In this paper, transient response and subharmonic vibration of a rotor with extremely soft nonlinear spring characteristics are investigated. A simple but exact computer model of the phenomena has been evolved based on the numerical integration of a finite difference formulation. Response curves and wave forms of the rotor vibration passing through critical speeds are computed. The subharmonic vibration of the rotor with soft nonlinear spring characteristics has been observed by spectral analysis of vibratory response. It is shown that the rotor will tend to bounce when its vibratory displacements exceed the offset distance of the system with stiffness K1 when it is accelerated for passing through critical speeds and the vibratory motion after bouncing is predominantly at the forcing frequency. Maximum amplitude of transient response is affected mainly by damping ratio ξ, the degree of nonlinearity β and the offset distance h. A series of subharmonic pseudo critical peaks will appear in the acceleration of a rotor with soft nonlinear spring characteristics. But the general nature of the subharmonic vibration is much different from that with hard ones. Finally some computational results are demonstrated by an experiment.
Rotor Instability Induced by Radial Clearance in Ball Bearing Supports
Authors: Lin Yao-Qun
Published: February 2015

In rotor dynamics, the rotor nonsynchronous natural frequency vibration, or rotor instability, has been mainly ascribed to two mechanisms, i.e., internal friction effects and fluid actions. It is shown, however, in this paper that the radial clearance in ball bearing supports can also induce rotor instability through an internal-impacts mechanism. The behavior of the rotor with radial clearance in its ball bearing supports is simulated numerically. The computer simulations show that there is a speed range in which the rotor will vibrate at both the synchronous frequency and the natural frequency. Below or above this speed range, the rotor has only the synchronous response and its harmonics. An experimental investigation was conducted to verify this analysis. The experimental results agree well with the theoretical predictions.
Estimation of Vibration at Critical Locations Using Available Measurements and Machine Configuration Data
Authors: Franklin Wesley , Muszynska Agnes , Bently Donald E.
Published: February 2015

This paper discusses one of the problems associated with establishing acceptable vibration levels for rotating machinery related to non collocation of critical vibration and available measurement locations. A critical vibration location is any point along the rotor which has a reduced clearance or a high potential for rubbing, such as seal locations. Non collocation occurs because the physical and/or environmental conditions at the critical locations prohibit the installation of suitable measurement transducers at those points. This leads to the dilemma of correlating the critical and measured vibration responses so the machine can be protected at the critical locations using the known responses at the measurement positions. This paper presents a method for estimating the vibration amplitudes and phases, either synchronous or nonsynchronous, at the critical locations using the known vibration responses at the measurement points, the current operating speed, the machine configuration data, and optimization techniques. A computer program has been developed for a personal computer running Windows 3.1 under DOS 5.0 which uses finite element modeling of the rotor to create a calculated rotor response and a data acquisition system to get the actual measured responses. A local convergence algorithm is then implemented to minimize the error between the calculated and measured vibration responses at the measured locations. The calculated responses at the critical locations then become the estimated vibration response for these points. To evaluate the accuracy of the technique, experiments were conducted using a rotor rig in which the vibration responses at both the critical and measurement locations were measured.

The computer program was then used to estimate the vibration responses at the critical locations. The estimated vibration responses were then compared with the measured responses at the same location to evaluate the effectiveness of the technique.

The results of these experiments are also included in this paper.
Use of Local X-Ray Computerized Tomography for High-Resolution, Region-of-Interest Inspection of Large Ceramic Components for Engines
Authors: Sivers E. A. , Holloway D. A. , Ellingson W. A.
Published: February 2015

Reliability continues to be an issue in the development of ceramic components for high-temperature, high-wear applications in advanced engine designs. Recently, high-resolution, three-dimensional, X-ray computerized tomography (XRCT) has been shown to be invaluable for inspecting relatively small components. However, the time and system capacity required to collect complete high-resolution data for large ceramic objects is often prohibitive. When only the critical regions of a large component need be inspected with high resolution, region-of-interest XRCT is a viable alternative. By using local XRCT methods on data taken through only the critical area, it is possible to reconstruct flat, “edge-enhanced” images in which density differences are clearly delineated. We present XRCT results from local scans of critical regions in a large, pressure-slip-cast, Si3N4 turbine rotor and two Si3N4 test phantoms. We also illustrate how the method can be extended to larger assemblies of ceramic components.
Development of 300 kW Class Ceramic Gas Turbine (CGT 301)
Authors: Saito Masayasu , Sasa Tadashi , Sakakida Masaru , Kurata Kimio
Published: February 2015

CGT 301 is a recuperated single shaft ceramic gas turbine for cogeneration use, which has characteristics suited for continuous full load application. The ceramic parts are designed according to the axisymmetric structure design–concept to reduce size, thermal stress and deformations. One of the leading features of this constructive design is that it does not have a large scroll and combustor is located on the shaft axis.

The primary type ceramic gas turbine of turbine inlet temperature (TIT) 1200 °C was designed. The configuration and structure of the ceramic turbine were improved on the basis of the data obtained in the fundamental experiments as well as the results of the numerical analysis. Ceramic combustor liners were designed and the NOx emission tests were also successfully carried out. Tests and flow performance evaluations of ceramic heat exchanger tubes were carried out. The combination of axial and centrifugal stages of compressor was evaluated by a compressor test facility. These results were described in this paper.
Development of a Low Emission Combustor for a 100kW Automotive Ceramic Gas Turbine: I
Authors: Sasaki Masafumi , Kumakura Hirotaka , Suzuki Daishi , Sugiyama Katsuhiko , Ohkubo Youichirou
Published: February 2015

A low emission combustor for a 100kW ceramic gas turbine, which is intended to meet Japanese emission standards for gasoline passenger cars, has been designed and subjected to initial performance tests. A prevaporization-premixing combustion system was chosen as the most suitable system for the combustor. The detailed combustor design, including the use of ceramic components and fuel injectors, was pursued taking into account the allowable engine dimensions for vehicle installation. In the initial performance tests conducted at a combustor inlet temperature of 773K, a low NOx level was obtained that satisfied the steady state target at this temperature level.
Acquisition of Operational Knowledge of an Industrial Gas Turbine Cogeneration Plant by Optimization
Authors: Yokoyama R. , Ito K.
Published: February 2015

A computer-aided advisory system is proposed which assists operators in operating an industrial gas turbine cogeneration plant rationally from the economic viewpoint. An optimization approach is adopted to acquire knowledge of the plant’s operational strategy. The on/off and rated/part load status for each piece of constituent equipment is determined so as to minimize the hourly operational cost subject to the energy demand requirement. Various restrictions which must be satisfied in a real operation are incorporated simultaneously. The operational strategy by optimization is compared with that by a real operation, using real data measured on several representative days. The operational status obtained for combinations of electricity and steam demands is illustrated by operational maps.
Investigation of Failures in Gas Turbines: Part 1 — Techniques and Principles of Failure Investigation
Authors: Dundas Robert E.
Published: February 2015

This paper is Part 1 of a two-part paper on the principles and methods of failure investigation in gas turbines. The qualities of a successful failure investigator are presented, and the most efficacious approaches to an investigation are discussed. An example of an aircraft accident that might have been avoided is used to support the necessity for thorough and conclusive investigations into failures.

Two case histories involving heavy-duty industrial gas turbines are described to demonstrate different aspects of the logical approach to construction of hypotheses and the determination of the essential cause of a failure — the one event without which the failure would not have occurred.
Investigation of Failure in Gas Turbines: Part 2 — Engineering and Metallographic Aspects of Failure Investigation
Authors: Dundas Robert E.
Published: February 2015

This paper opens with a discussion of the various mechanisms of cracking and fracture encountered in gas turbine failures, and discusses the use of metallographic examination of crack and fracture surfaces. The various types of materials used in the major components of heavy-duty industrial and aeroderivative gas turbines are tabulated. A collection of macroscopic and microscopic fractographs of the various mechanisms of failure in gas turbine components is then presented for reference in failure investigation. A discussion of compressor damage due to surge, as well as some overall observations on component failures, follows. Finally, a listing of the most likely types of failure of the various major components is given.
An Analytical Model of Axial Compressor Off-Design Performance
Authors: Camp T. R. , Horlock J. H.
Published: February 2015

An analysis is presented of the off-design performance of multistage axial-flow compressors. It is based on an analytical solution, valid for small perturbations in operating conditions from the design point, and provides an insight into the effects of choices made during the compressor design process on performance and off-design stage matching.

It is shown that the mean design value of stage loading coefficient (ψ = Δho/U2) has a dominant effect on off-design performance, whereas the stage-wise distribution of stage loading coefficient and the design value of flow coefficient have little influence. The powerful effects of variable stator vanes on stage-matching are also demonstrated and these results are shown to agree well with previous work.

The slope of the working line of a gas turbine engine, overlaid on overall compressor characteristics, is shown to have a strong effect on the off-design stage-matching through the compressor. The model is also used to analyse design changes to the compressor geometry and to show how errors in estimates of annulus blockage, decided during the design process, have less effect of compressor performance than has previously been thought.
Blading Design Procedure for Centrifugal Impellers
Authors: Al-Zubaidy Sarim N.
Published: February 2015

The paper proposes a direct method for the aerothermodynamic design of centrifugal flow impellers (based on a prescribed space rate of diffusion) that can be used to aid the design methodology of radial impellers. The design procedure employs the basic laws of fluid motion to determine the required flow path and thus the detailed passage coordinates. Numerical optimization techniques were used to control the manner by which the relative velocity components were allowed to vary so that a simple loss criteria (entropy generation) was kept minimum throghout the solution.

The development of the method was undertaken with the idea of obtaining a self sufficient design method which would be influenced as little as possible by the preconceived notions of what the optimum impeller blading should look like.
Numerical Investigations of Centrifugal Compressor Flows With Tip Leakage Using a Pressure Correction Method
Authors: Tourlidakis A. , Elder R. L.
Published: February 2015

In this paper, a three-dimensional computational model for the solution of the time-averaged Navier-Stokes equations, based on a pressure correction method and the k-ε turbulence model, is presented and implemented for the viscous flow modelling through a series of centrifugal compressors. Theoretical calculations with the current fully elliptic method are carried out and the results are compared critically with available experimental data and with results from other computational models. A radial and two backswept high-speed subsonic compressors with different geometrical and operating characteristics are analysed at design and off-design conditions. In all cases, a wake flow pattern is evident and strong secondary flows are discerned. The tip clearance effects on the relative flow pattern are found to be important and are appropriately simulated. The predictive capability of the current flow model is judged to be encouraging taking into consideration the limitations of the physical models and the numerical schemes involved in the computations.
An Assessment of Weighted-Least-Squares Based Gas Path Analysis
Authors: Doel David L.
Published: February 2015

Manufacturers of gas turbines have searched for three decades for a reliable way to use gas path measurements to determine the health of jet engine components. They have been hindered in this pursuit by the quality of the measurements used to carry out the analysis. Engine manufacturers have chosen weighted-least-squares techniques to reduce the inaccuracy caused by sensor error. While these algorithms are clearly an improvement over the previous generation of gas path analysis programs, they still fail in many situations. This paper describes some of the failures and explores their relationship to the underlying analysis technique. It also describes difficulties in implementing a gas path analysis program. The paper concludes with an appraisal of weighted-least-squares based gas path analysis.
Effect of Pressure on Combustion Characteristics in LBG–Fueled 1300°C–Class Gas Turbine
Authors: Nakata Toshihiko , Sato Mikio , Ninomiya Toru , Yoshine Toshiyuki , Yamada Masahiko
Published: February 2015

Developing integrated coal gasification combined cycle systems ensures that Japan will have cost–effective and environmentally sound options for supplying future power generation needs. The reduction of NOx emissions and increasing the inlet temperature of gas turbines are the most significant issues in gas turbine development in IGCC. The coal gasified fuel, which is produced in a coal gasifier of air–blown entrained–flow type has calorific value as low as 1/10 of natural gas. Furthermore the fuel gas contains ammonia when a gas cleaning system is a hot type, and ammonia will be converted to nitrogen oxides in the combustion process of a gas turbine.

The study is performed in 1300°C–class gas turbine combustor firing coal–gasified fuel in IGCC power generation systems. In the previous study the advanced rich–lean combustor of 150–MW class gas turbine was designed to hold stable combustion burning low–Btu gas fuel and to reduce fuel NOx emission that is produced from the ammonia in the fuel. By testing it under atmospheric pressure conditions, we have studied the effects of fuel parameters on combustor performances and listed the basic data for development applications. In this study, by testing it under pressurized conditions, we have obtained a very significant result through investigating the effect of pressure on combustion characteristics and wish to provide herein a summary of our findings.
Measurement of Turbine Blade-Tip Rotordynamic Excitation Forces
Authors: Martinez-Sanchez Manuel , Jaroux Belgacem , Song Seung Jin , Yoo Soomyung
Published: February 2015

This paper presents results of a program to investigate the magnitude, origin and parametric variations of destabilizing forces which arise in high power turbines due to blade-tip leakage effects.

Five different unshrouded turbine configurations and one configuration shrouded with a labyrinth seal were tested with static offsets of the turbine shaft. The forces along and perpendicular to the offset were measured directly with a dynamometer, and were also inferred from velocity triangles and pressure distributions obtained from detailed flow surveys. These two routes yielded values in fair agreement in all cases. For unshrouded turbines, the cross-forces are seen to originate mainly (∼2/3) from the classical Alford mechanism (nonuniform work extraction due to varying blade efficiency with tip gap) and about 1/3 from a slightly skewed hub pressure pattern. The direct forces arise mainly (3/4) from this pressure pattern, with the rest due to a slight skewness of the Alford mechanism. The pressure nonuniformity (lower pressures near the widest gap) is seen to arise from a large-scale redistribution of the flow as it approaches the eccentric turbine.

The cross-forces are found to increase substantially when the gap is reduced from 3.0% to 1.9% of blade height, probably due to viscous blade-tip effects. The forces also increase when the hub gap between stator and rotor decreases. The force coefficient decreases with operating flow coefficient.

In the case of the shrouded turbine, most of the forces arise from nonuniform seal pressures. This includes about 80% of the transverse forces. The rest appears to come from uneven work extraction (Alford mechanism). Their level is about 50% higher than in the unshrouded cases.
Numerical Investigation of Enhanced Dilution Zone Mixing in a Reverse Flow Gas Turbine Combustor
Authors: Crocker D. Scott , Smith Clifford E.
Published: February 2015

An advanced method for dilution zone mixing in a reverse flow gas turbine combustor was numerically investigated. For long mixing lengths associated with reverse flow combustors (X/H > 2.0), pattern factor was found to be mainly driven by nozzle-to-nozzle fuel flow and/or circumferential airflow variations; conventional radially injected dilution jets could not effectively mix out circumferential non-uniformities.

To enhance circumferential mixing, dilution jets were angled to produce a high circumferential (swirl) velocity component. The jets on the outer liner were angled in one direction while the jets on the inner liner were angled in the opposite direction, thus enhancing turbulent shear at the expense of jet penetration. 3-D CFD calculations were performed on a three-nozzle (90°) sector, with different fuel flow from each nozzle (90%, 100% and 110% of design fuel flow). The computations showed that the optimum configuration of angled jets reduced the pattern factor by 60% compared to an existing conventional dilution hole configuration. The radial average temperature profile was adequately controlled by the inner-to-outer liner dilution flow split.
Prediction of the Transient Thermodynamic Response of a Closed-Cycle Regenerative Gas Turbine
Authors: Korakianitis T. , Hochstein J. I. , Zou D.
Published: February 2015

This paper presents instantaneous-response and transient-flow component models for the prediction of the transient response of gas turbine cycles. The component models are based on applications of the principles of conservation of mass, energy, and momentum. The models are coupled to simulate the system transient thermodynamic behavior, and used to predict the transient response of a closed-cycle regenerative Brayton cycle. Various system transients are simulated using: the instantaneous-response turbomachinery models coupled with transient-flow heat-exchanger models; and transient-flow turbomachinery models coupled with transient-flow heat-exchanger models. The component sizes are comparable to those under consideration for the solar-powered Space Station (radial turbomachinery), but the models can easily be expanded to other applications with axial turbomachinery. An iterative scheme based on the principle of conservation of working-fluid mass in the system is used to compute the mass-flow rate at the solar-receiver inlet during the transients. In the process the mass-flow rate of every component at every time step is also computed. Representative results of different system models are compared and discussed.