bluuebunny/crossref_metadata_2025 huggingface dataset:
A Case Report of Successful Treatment With Plasma Exchange for Hemophagocytic Syndrome Associated With Severe Systemic Juvenile Idiopathic Arthritis in an Infant Girl
Authors: Nakakura Hyogo , Ashida Akira , Matsumura Hideki , Murata Takuji , Nagatoya Katsuyuki , Shibahara Nobuhisa , Inoue Toru , Tamai Hiroshi
Published: March 2009

Abstract:  An infantile case of hemophagocytic syndrome (HPS) with systemic juvenile idiopathic arthritis (s‐JIA), refractory to methylprednisolone pulse therapy and cyclosporine A administration, was successfully treated by plasma exchange. The patient was a one‐year‐old Japanese girl who had developed recurrent steroid‐dependent signs, including fever, skin eruption, and hepatopathy, while in France, where she had been diagnosed as having s‐JIA at eight months of age. As a high fever and rheumatoid rash were evident on arrival at our hospital, she was admitted and given intravenous methylprednisolone pulse therapy and cyclosporine A. She developed pancytopenia with a generalized clonic seizure, high fever, and liver dysfunction after her cytomegalovirus (CMV) titer became positive during the course of treatment; therefore, she was treated with ganciclovir. She was subsequently diagnosed as having HPS complicating s‐JIA from the findings of a bone marrow aspirate. At this time, her blood examination data including a high level of C‐reactive protein and hyperferritinemia, suggested that her s‐JIA was very active, and the pancytopenia continued after her CMV titer became negative. Therefore, CMV infection against a background of active s‐JIA could have triggered the HPS in this case. Because the HPS was resistant to an immunosuppressive regime of methylprednisolone pulse therapy and cyclosporine A, plasma exchange therapy was started. After three sessions of this therapy, the patient's symptoms and laboratory data were markedly improved. Our experience suggests that plasma exchange should be considered as a therapeutic tool for HPS refractory to conventional therapy.
Modelling of Cytotoxicity Data (CC50) of Anti‐HIV 1‐[5‐Chlorophenyl) Sulfonyl]‐1H‐Pyrrole Derivatives Using Calculated Molecular Descriptors and Levenberg–Marquardt Artificial Neural Network
Authors: Arab Chamjangali M.
Published: March 2009

A nonlinear quantitative structure anti‐HIV activity relationship study was presented for modelling and predicting pyrryl aryl sulfones cytotoxicity data. Levenberg‐Marquardt artificial neural network was used to link molecular structures and cytotoxicity data. A data set consisting of 27 derivatives of 1‐[5‐chlorophenyl) sulfonyl]‐1H‐pyrrole was used in this study. Among a large number of calculated descriptors, only eight significant molecular descriptors were obtained by stepwise regression, as the most feasible descriptors, and then they were used as inputs for neural network. The data set was randomly divided into 20 training and 7 validation sets and the neural network architecture and its parameters were optimized. The prediction ability of the model was evaluated using the validation data set, leave‐one‐out cross‐validation and response randomization method. The mean square errors and mean absolute errors for the validation data set were 0.0067 and 0.066, respectively, and for the leave‐one‐out method, they were 0.013 and 0.087, respectively. The results obtained showed the excellent prediction ability and stability of the proposed model in the prediction of cytotoxicity data of the corresponding anti‐HIV analogues.
QSAR Studies of CYP2D6 Inhibitor Aryloxypropanolamines Using 2D and 3D Descriptors
Authors: Roy Partha Pratim , Roy Kunal
Published: March 2009

Thirty six aryloxypropanolamine compounds with cytochrome 2D6 (CYP2D6) inhibitory activity were subjected to molecular shape analysis and molecular field analysis studies to explore the required molecular shape features as well as information on putative interactions with the active site of the enzyme. In addition to the 3D QSAR models, impact of two‐dimensional (2D; thermodynamic, structural and topological including E‐state parameters) descriptors towards the inhibitory activity was also studied. The whole data set was divided into training (n = 26) and test (n = 10) sets byK‐means clustering technique. The chemometric tools used for molecular shape analysis and molecular field analysis were GFA and G/PLS techniques respectively. The G/PLS model derived in molecular field analysis using maximum common subgroup alignment was found to be the best model based on highest external (R2pred = 0.912) predictive power with lowest RMSEP value (0.363). The molecular field analysis‐derived models suggest the requirement of U‐shape conformation for optimum interactions as well as importance of different substituents on the aryloxypropanol fragment like indolylalkyl substituent. The molecular shape analysis models indicate the importance of distribution of positive and negative charges on the surface of the molecules. The QSAR models with 2D descriptors reveal the importance of bulk, branching and presence of different fragments.
Dye Labelling of Nucleosides
Authors: Katritzky Alan R. , Khelashvili Levan , Kovacs Judit , Shanab Karem
Published: March 2009

Dye‐labelled nucleosides were obtained in 30–79% (average 45%) yields by treating N‐(4‐arylazobenzoyl)‐1H‐benzotriazoles 3a–b with appropriate nucleosides. Similarly, 3a–b afforded dye‐labelled threoninol conjugates in 55–89% (average 67%) yields. All novel products were characterized by NMR and elemental analysis.
Normalization of Previously Shortened Telomere Length under Treatment with Imatinib Argues against a Preexisting Telomere Length Deficit in Normal Hematopoietic Stem Cells from Patients with Chronic Myeloid Leukemia
Authors: BRÜMMENDORF TIM H. , ERSÖZ INCI , HARTMANN ULRIKE , BALABANOV STEFAN , WOLKE HOLGER , PASCHKA PETER , LAHAYE TANJA , BERNER BIRGIT , BARTOLOVIC KEROL , KREIL SEBASTIAN , BERGER UTE , GSCHAIDMEIER HARALD , BOKEMEYER CARSTEN , HEHLMANN RÜDIGER , DIETZ KLAUS , LANSDORP PETER M. , KANZ LOTHAR , HOCHHAUS ANDREAS
Published: March 2009

Abstract: Telomeres are composed of TTAGGG repeats and associated proteins. In somatic cells, telomere repeats are lost with each cell division, eventually leading to genetic instability and cellular senescence. In previous studies, we described substantial and disease stage‐specific telomere shortening in peripheral blood (PB) leukocytes from patients with chronic myeloid leukemia (CML). Here, we sought to determine whether age‐adjusted telomere length in PB granulocytes (deltaTELgran) is associated with response to treatment with the selective tyrosine kinase inhibitor imatinib. A total of 517 samples from 206 patients in chronic phase (CP), accelerated phase (AP), and blast crisis (BC) before and up to 706 days after initiation of imatinib therapy (median: 144 days) were analyzed by quantitative fluorescence in situ hybridization of interphase cells in suspension (Flow‐FISH); telomere fluorescence was expressed in molecular equivalents of soluble fluorochrome units (MESF). Telomere length in samples from start of treatment up to day 144 was significantly shorter (mean ± SE; −1.5 ± 0.3 kMESF) compared to samples from patients treated for more than 144 days (−0.8 ± 0.3 kMESF, p= 0.035). In patients with repeated measurements, a significant increase in telomere length under treatment was observed. Median telomere length in major remission was found to be significantly longer compared to patients without response to treatment measured either by cytogenetics (n= 246, p < 0.05), interphase FISH (n= 204, p= 0.002), or quantitative RT‐PCR (n= 371, p < 0.05). In conclusion, the increase in telomere length under treatment with imatinib reflects a shift from Ph+ to Ph− cells in the PB of patients with CML.
Characterization of Cord Blood Hematopoietic Stem Cells
Authors: MAZURIER FRÉDÉRIC , DOEDENS MONICA , GAN OLGA I. , DICK JOHN E.
Published: March 2009

Abstract:A major problem hampering the development of effective stem cell‐based therapies is the absence of a clear understanding of the composition of the hematopoietic stem cell (HSC) pool in humans and howex vivomanipulation can differentially affect the various HSC classes. This paper will review recent advances in the use of the NOD/SCID xenotransplant assay to characterize the human stem cell compartment and to determine howex vivoculture affects stem cells. Using lentivector‐mediated clonal tracking we found that only 4 days of culture can significantly reduce the number of SCID‐repopulating cells (SRCs) contributing to the human graft. Similar results were seen with a competitive assay strategy where non‐cultured cells marked with the RFP‐lentivector markedly outcompete cultured cells marked with a EGFP‐lentivector both transplanted into the same NOD/SCID mouse. A novel intrafemoral (IF) assay was developed to permit the transplantation of human stem cells that might be difficult to detect using the traditional IV injection method. With the IF assay we identified a novel class of human stem cell with the ability to rapidly generate a large graft of human myeloid and erythroid cells within 2 weeks post transplant.
Efficient Characterization of Retro‐, Lenti‐, and Foamyvector‐Transduced Cell Populations by High‐Accuracy Insertion Site Sequencing
Authors: SCHMIDT MANFRED , GLIMM HANNO , WISSLER MANUELA , HOFFMANN GESA , OLSSON KARIN , SELLERS STEPHANIE , CARBONARO DENISE , TISDALE JOHN F. , LEURS CORDULA , HANENBERG HELMUT , DUNBAR CYNTHIA E. , KIEM HANS‐PETER , KARLSSON STEFAN , KOHN DONALD B. , WILLIAMS DAVID , VON KALLE CHRISTOF
Published: March 2009

Abstract: The identification of unknown genomic flanking DNA sequences can be used for the molecular monitoring of retro‐, lenti‐ and foamyviral integration, transgenes in early embryogenesis, insertional mutagenesis, cell fate, and stem cell plasticity. Most existing methods reflect shortcomings in sensitivity and or specificity, thus limiting genomic sequencing of unknown flanking DNA to clonal preparations. The application of linear amplification‐mediated PCR (LAM‐PCR), a recently developed direct sequencing technique for flanking DNA, should circumvent current limitations in different research fields. This technique combines preamplification of target DNA with a unique succession of enzymatic reactions on solid‐phase. Using LAM‐PCR, we show the previously unfeasible in vivo retro‐, lenti‐ and foamyvirus integration site analysis in primate peripheral blood hematopoietic cells and human xenograft hematopoiesis. In light of two severe adverse events that occurred in a clinical SCID‐X1 gene therapy trial, in vivo monitoring of the reinfused transduced cell pool by integration site analysis will be an important component of each gene transfer and therapy study aimed at clinical use.
Adult Bone Marrow Stem Cells Regenerate Myocardium in Ischemic Heart Disease
Authors: ORLIC DONALD
Published: March 2009

Abstract: Recent studies have demonstrated the existence of several populations of primitive cells in mouse and human bone marrow that have the capacity, both in vitro and in vivo, to give rise to cells of all three germ layers. Mesenchymal/stromal stem cells and hematopoietic stem cells are the leading candidates for this activity that some believe may recapitulate the potential of embryonic stem cells. Very little is known about the molecular controls for this adult stem cell activity commonly referred to as transdifferentiation or plasticity. Regeneration of a large number of cell types and tissues has been investigated with one of the most extensively studied being the myocardium. These studies involved ligation of the left coronary artery in adult mice and the direct injection or mobilization of bone marrow stem cells. Using this protocol we, and others, have observed the generation of new cardiomyocytes and endothelial cells in the zone of ischemic myocardium. This approach has progressed to clinical trials at several academic institutions. Although the preliminary findings from these trials do not permit unequivocal conclusions, they do suggest that safety and feasibility are not significant problems that would argue against extending these trials in a large, randomized, double‐blinded study. When considerations such as these are addressed, cell therapy may become a new modality in the treatment of heart patients.
Microsatellite markers for the ectomycorrhizal basidiomycete Lactarius mammosus
Authors: HÖGBERG N. , GUIDOT A. , JONSSON M. , DAHLBERG A.
Published: March 2009

We report the characterization of polymorphic microsatellite markers in the ectomycorrhizal fungus Lactarius mammosus Fr. Two enrichment protocols were used to isolate microsatellite loci and polymorphism was explored within 31 sporocarps originating from a forest site in northern Sweden. We found nine variable microsatellite loci with the number of alleles per locus varying between 2 and 5, and expected heterozygosities ranging from 0 to 0.84. These loci are available for the analysis of genetic structure and gene flow in L. mammosus populations.
Polymerase chain reaction primers for polymorphic microsatellite loci in the ant Pseudomyrmex gracilis (Formicidae: Pseudomyrmecinae)
Authors: SCHMID VOLKER S. , KAUTZ STEFANIE , TRINDL ANDREAS , HEINZE JÜRGEN
Published: March 2009

The elongate twig ant Pseudomyrmex gracilis is widely distributed in the New World ranging from southern USA to Brazil and northern Argentina. To investigate its within‐colony relatedness, we developed primers for nine polymorphic microsatellite loci. High levels of within‐population variation were observed, with number of alleles ranging from two to 13, and heterozygosity from 0.28 to 0.90. The loci showed no deviations from Hardy–Weinberg equilibrium and no linkage disequilibrium.
Isolation and characterization of microsatellite loci from rock shell, Thais clavigera
Authors: HWANG G. , MYUNG C. S. , PARK S. I. , SONG S. J. , MACLEAN N.
Published: March 2009

Imposex (superimposition of male genital organs on female phenotype) of the rock shell or whelk, Thais clavigera, shows typical evidence of endocrine disruption by organotin compounds within inter‐tidal zones polluted by such compounds. It will be informative to see how low fertility caused by imposex of this species finally affects the genetic diversity of polluted populations. For future use in population genetic research of the rock shell, we report the isolation and characteristics of 11 highly polymorphic microsatellite markers with a mean of 11.7 alleles per locus. We observed heterozygosities of these sequences ranging from 0.43 to 0.95. These markers will be useful for future ecological genetic studies of rock shell.
Isolation and characterization of 11 tetranucleotide microsatellite loci in the Egyptian mongoose (Herpestes ichneumon)
Authors: RODRIGUES MÓNICA , FERNANDES CARLOS A. , PALOMARES FRANCISCO , AMORIM ISABEL R. , BRUFORD MICHAEL W. , SANTOS‐REIS MARGARIDA
Published: March 2009

We report the isolation of 11 polymorphic tetranucleotide microsatellite loci in the Egyptian mongoose (Herpestes ichneumon). In a sample of 27 individuals, we observed between 4 and 7 alleles per locus and their observed and expected heterozygosities ranged from 0.37 to 0.85 and from 0.44 to 0.79, respectively. All genotypic frequencies conformed to Hardy–Weinberg equilibrium expectations and there were no instances of linkage disequilibrium detected between pairs of loci.
Manglietia lawii sp. nov. (Magnoliaceae) from Yunnan, China
Authors: Liao Wen‐Fang , Xia Nian‐He
Published: March 2009

Manglietia lawii N. H. Xia & W. F. Liao, a new species of Manglietia from Yunnan, China, is described and illustrated. It is closely related to M. forrestii W. W. Smith, but differs by having villous gynoecium and glabrous tepals.
Evaluating the global ‘Evidence Footprint’: how can evidence better serve the needs of global public health?
Authors: Pang Tikki , Tharyan Prathap
Published: March 2009

The Cochrane Collaboration must strive to become a more global organization and help facilitate the use of evidence to improve public health, especially in the developing world. It can do so by improving the scope and relevance of its sytematic reviews, by building capacity in countries to synthesize and use evidence for health policy development, and by addressing the challenge of developing methodologies for dealing with different types of evidence commonly used by health decision‐makers in resource‐ and evidence‐challenged settings.
Brauer–Manin obstruction for integral points of homogeneous spaces and representation by integral quadratic forms
Authors: Colliot-Thélène Jean-Louis , Xu Fei
Published: March 2009

An integer may be represented by a quadratic form over each ring ofp-adic integers and over the reals without being represented by this quadratic form over the integers. More generally, such failure of a local-global principle may occur for the representation of one integral quadratic form by another integral quadratic form. We show that many such examples may be accounted for by a Brauer–Manin obstruction for the existence of integral points on schemes defined over the integers. For several types of homogeneous spaces of linear algebraic groups, this obstruction is shown to be the only obstruction to the existence of integral points.
Antagonism of orexin receptor‐1 in the retrotrapezoid nucleus inhibits the ventilatory response to hypercapnia predominantly in wakefulness
Authors: Dias Mirela Barros , Li Aihua , Nattie Eugene E.
Published: March 2009

Recent data from transgenic mice suggest that orexin plays an important role in the ventilatory response to CO2 during wakefulness. We hypothesized that orexin receptor‐1 (OX1R) in the retrotrapezoid nucleus (RTN) contributes to chemoreception. In unanaesthetized rats, we measured ventilation using a whole‐body plethysmograph, together with EEG and EMG. We dialysed the vehicle and then SB‐334867 (OX1R antagonist) into the RTN to focally inhibit OX1R and studied the effects of both treatments on breathing in air and in 7% CO2. During wakefulness, SB‐334867 caused a 30% reduction of the hyperventilation induced by 7% CO2 (mean ± S.E.M., 135 ± 10 ml (100 g)−1 min−1) compared with vehicle (182 ± 10 ml (100 g)−1 min−1) (P < 0.01). This effect was due to both decreased tidal volume and breathing frequency. There was a much smaller, though significant, effect in sleep (9% reduction). Neither basal ventilation nor oxygen consumption was affected. The number and duration of apnoeas were similar between control and treatment periods. No effect was observed in a separate group of animals who had the microdialysis probe misplaced (peri‐RTN). We conclude that projections of orexin‐containing neurons to the RTN contribute, via OX1Rs in the region, to the hypercapnic chemoreflex control during wakefulness and to a lesser extent, non‐rapid eye movement sleep.
Age‐ and fitness‐related alterations in vascular sympathetic control
Authors: Studinger Péter , Goldstein Richard , Taylor J. Andrew
Published: March 2009

In the current study we explored (1) if there were differences in sympathetic activity and baroreflex function by age, sex, or physical activity status, (2) if any aspect of baroreflex function related to differences in resting sympathetic activity, and (3) if mechanical and/or neural baroreflex components related to differences in integrated baroreflex gain. Electrocardiogram, blood pressure, carotid diameter and muscle sympathetic nerve activity were recorded continuously at rest and during sequential bolus injections of sodium nitroprusside and phenylephrine in 22 young, 21 older sedentary and 10 older trained individuals. Analyses of co‐variance were used to examine age, sex and training status differences and to explore the explanatory power of integrated baroreflex gain and its mechanical and neural components. Training status and sex influenced neither resting sympathetic outflow nor sympathetic baroreflex gain components. Older subjects had a smaller mechanical component and a strong tendency towards a greater neural component of the sympathetic baroreflex during both pressure falls and pressure rises. Opposing age‐related changes in mechanical and neural components resulted in a smaller integrated gain during pressure falls, but a greater integrated gain during pressure rises in older subjects. Thus, in older individuals, compromised sympathetic activation to pressure falls was owing to the stiffening of barosensory vessels, whereas the more sensitive sympathoinhibition to pressure rise was due to an increased neural control. Enhanced neural control with age, however, did not contribute the increased resting sympathetic outflow, which indicates that these two changes are probably driven by distinct neural mechanisms.
Coupled Deformation Modes in the Large Deformation Finite Element Analysis: Generalization
Authors: Dmitrochenko Oleg N. , Hussein Bassam A. , Shabana Ahmed A.
Published: March 2009

The effect of the absolute nodal coordinate formulation (ANCF)–coupled deformation modes on the accuracy and efficiency when higher order three-dimensional beam and plate finite elements are used is investigated in this study. It is shown that while computational efficiency can be achieved in some applications by neglecting the effect of some of the ANCF-coupled deformation modes, such modes introduce geometric stiffening/softening effects that can be significant in the case of very flexible structures. As shown in previous publications, for stiff structures, the effect of the ANCF-coupled deformation modes can be neglected. For such stiff structures, the solution does not strongly depend on some of the ANCF-coupled deformation modes, and formulations that include these modes lead to numerical results that are in good agreement with formulations that exclude them. In the case of a very flexible structure, on the other hand, the inclusion of the ANCF-coupled deformation modes becomes necessary in order to obtain an accurate solution. In this case of very flexible structures, the use of the general continuum mechanics approach leads to an efficient solution algorithm and to more accurate numerical results. In order to examine the effect of the elastic force formulation on the efficiency and the coupling between different modes of deformation, three different models are used again to formulate the elastic forces in the absolute nodal coordinate formulation. These three methods are the general continuum mechanics approach, the elastic line (midsurface) approach, and the elastic line (midsurface) approach with the Hellinger–Reissner principle. Three-dimensional absolute nodal coordinate formulation beam and plate elements are used in this study. In the general continuum mechanics approach, the coupling between the cross section deformation and the beam centerline or plate midsurface displacement is considered, while in the approaches based on the elastic line and the Hellinger–Reissner principle, this coupling is neglected. In addition to the fully parametrized beam element used in this study, three different plate elements, two fully parametrized and one reduced order thin plate elements, are used. The numerical results obtained using different finite elements and elastic force formulations are compared in this study.
Thermal Management of Downhole Oil and Gas Logging Sensors for HTHP Applications Using Nanoporous Materials
Authors: Rafie Saeed
Published: March 2009

One of the main challenges in designing oil & gas downhole wireline logging tools for high temperature and high pressure (HTHP) environments is to put together the most efficient thermal packaging to enhance the tool’s temperature survival time. In general, not all electronic components and sensors can withstand severe downhole temperature (max 500 degrees Fahrenheit). For those heat sensitive components, their electrical response and performance either decay or in some cases they completely fail when their temperature exceeds 300° F. In oil & gas wireline logging applications, the heat sensitive components can be thermally protected inside a Dewar vacuum flask that includes one or two thermal isolators and heat sinks. Cooler electronic components results in longer logging times that lead to a much higher performance and profitability. This paper first discusses the development of a one-dimensional analytical model to determine the transient temperature of heat sensitive sensors and electronic components in wireline logging tools. Second, it introduces a new and improved thermal packaging scheme based on a newly developed and commercially available nanoporous material. This material has a very low thermal conductivity and is used as a thermal shield between the outside environment and the electronics inside the flask. The new packaging scheme also includes a new design for the heat sink which is made of several solid disks separated by this nanoporous material. Results from this new design have shown roughly a 30% improvement compared with the conventional design. Results from both analytical and laboratory tests are discussed in this paper.
The Science and Technology of Al-Ga Alloys as a Material for Energy Storage, Transport and Splitting Water
Authors: Woodall Jerry M. , Ziebarth Jeffrey , Allen Charles R.
Published: March 2009

Currently, there is much public discussion about the realization of a hydrogen economy as a viable alternative for future large-scale energy sources. Hydrogen as an energy source has several compelling features. For example, its gravimetric energy density is three times that of oil, its combustion and fuel cell product is usually water and, hence, does not leave a carbon footprint, and its abundance, as water is plentiful.
Metal/Semiconductor Nanocomposites for Direct Thermal to Electric Energy Conversion
Authors: Shakouri Ali
Published: March 2009

Thermoelectric effects can be used for direct conversion of heat into electricity using a solid-state device. We describe novel metal/semiconductor nanostructured materials where the heat and charge transport are modified at the atomic level. Hot electron filtering using heterostructure barriers is used to break the trade off between high Seebeck coefficient and high electrical conductivity. Embedded ErAs nanoparticles are used to reduce the lattice thermal conductivity without significant effect on electrical conductivity. The thermal conductivity, electrical conductivity, and Seebeck coefficient of ErAs:InGaAlAs alloys are characterized. The measured ZT is ∼1 at high temperatures 650 K. Integrated circuit fabrication techniques are used to transfer the n- and p-type thin films onto AlN plates and power generation modules are made with hundreds of thin film elements. An output power density >1W/cm2 is demonstrated at an external temperature difference of 120K across the module. Finally, the prospect of other metal semiconductor multilayer structures based on TiN/GaN for high temperature operation will be briefly reviewed.
Local Cooling Effectiveness Distribution of an Integrated Impingement and Pin Fin Cooling Configuration
Authors: Nakamata Chiyuki , Mimura Fujio , Matsushita Masahiro , Yamane Takashi , Fukuyama Yoshitaka , Yoshida Toyoaki
Published: March 2009

An integrated impingement and pin-fin cooling configuration is investigated experimentally. Temperature measurements have been performed for several test pieces with various pin/hole arrangements to clarify an influence of pin/hole arrangements on cooling effectiveness. The experiment has been conducted with 673K combustion gas flow and room temperature cooling air. Reynolds number of combustion gas flow is 380000 and Reynolds number of cooling air flow is in the range from 5000 to 30000. An infrared camera is used to measure a temperature distribution on a specimen surface. The area-averaged cooling effectiveness and the local cooling effectiveness are evaluated for each specimen and compared each other. There are evidences of the existence of pins on the local cooling effectiveness at the exact location of those. But the local cooling effectiveness are independent of the hole arrangement.
Energy Production From Biomass: Development of a General Model and Application to Anaerobic Digestion
Authors: Bettocchi R. , Pinelli M. , Spina P. R. , Venturini M. , Cenci G. , Morini M.
Published: March 2009

The process which includes production, gathering and transformation of biomass into renewable fuels and then into energy (both electrical and thermal) involves a large number of decisions to select the most efficient plant layout. The aim of the paper is to develop a general model for the simulation of the entire process from biomass to energy production in order to identify optimal plant solutions with respect to the current scenario. First, the hypotheses which can be adopted for the development of a physics-based model are outlined and discussed. Then, the model is implemented in Matlab environment, by adopting a modular structure in order to reproduce different plant configurations. Secondly, a general objective function is identified. Finally, an early-stage application of the model for methane production from biomass through anaerobic digestion is reported.
Efficiency Definition and Load Management for Reciprocating and Centrifugal Compressors
Authors: Kurz Rainer , Brun Klaus
Published: March 2009

Reciprocating compressors and centrifugal compressors use different definition of compressor efficiency. This paper will provide guidelines for a true comparison, as well as a universal efficiency definition for both types of machines, based on the requirements the ultimate user is really interested in. Further, the impact of actual pipeline conditions on the change of efficiency at different loads, using different means of control, is evaluated.
A Conceptual Flutter Analysis of a Packet of Vanes Using a Mass-Spring Model
Authors: Corral Roque , Gallardo Juan Manuel , Martel Carlos
Published: March 2009

The linear aeroelastic stability of a simplified mass-spring model representing the basic dynamics of a sector of Na airfoils is analyzed. The degree of multiplicity of the eigenvalues of the simplified structural model is Na−1 and hence its mode-shapes are not determined in a unique way. The aerodynamic damping strongly depends on the mode shape and hence its accurate determination is essential in order to obtain realistic values of damping. This in-determination is removed when the aerodynamic forces associated to the motion of the airfoils are added or a platform with finite stiffness is considered. In both cases the problem is not degenerated anymore and the mode-shapes of the system are uniquely determined. It is shown that the expected stabilizing effect due to the packets may be negligible, depending on the relative strength of the aerodynamic forces and the stiffness of the lower platform. It is also shown that, for the most unstable situation, the aeroelastic behaviour of the problem may be, in first approximation, very similar to that of a continuous ring.
NOx Suppression From a Micro-Gas Turbine Approaching the Mild-Combustion Regime
Authors: Cameretti Maria Cristina , Reale Fabrizio , Tuccillo Raffaele
Published: March 2009

The authors present in this paper a refined methodology, already introduced in a recent paper, aiming to find the best compromises between the need of reducing the NOx emission from a micro-gas turbine and the preservation of satisfactory efficiency and energy saving levels. The method founds on an integrated approach consisting of an advanced cycle analysis, which includes the component matching study, and the CFD based validation of the most interesting cases. The latter refer to the activation of the exhaust recirculation to the compressor inlet, in order to generate conditions close to those characterized by a mild combustion.
Experimental Study on Velocity Characteristic Distribution in Non-Premixed Circular-Disc Stabilized Flames
Authors: Ge Bing , Zang Shu-Sheng , Gu Xin
Published: March 2009

Experiments have been performed to investigate the characteristic modes and structures of non-premixed circular-disc stabilized flames under different operation conditions, and a combustion regime diagram between recirculation zone flame and central-jet dominated flame was presented. By PIV technique, the experiment measured the velocity distributions of the non-premixed circular-disc stabilized flames with different fuel jet to annular air flow velocity ratios, and the characteristic modes and structures were observed. The results show the fuel jet to airflow velocity ratio is a controlling parameter to the velocity distributions and characteristic modes of the non-premixed circular-disc stabilized flames: with the increase of the fuel jet to air flow velocity ratio, minimum mean axial velocity on centerline adds; the distance from bluffbody to the position of minimum axial velocity on centerline increases at first, then reduces a little, finally increases rapidly. The experiment also shows there is a function relationship between the velocity ratio and the distance from bluff-body surface to the position of the minimum mean axial velocity on centerline. The combustion regime diagram between recirculation zone flame and central-jet dominated flame can also be plotted precisely according to the relationship curves of the velocity ratio and the minimum mean axial velocity of centerline.
Detection of Gas Turbines Malfunctions From Emission Concentration Distributions
Authors: Romessis C. , Mathioudakis K.
Published: March 2009

A method for detecting gas turbines malfunctions through engine emissions concentration plots is presented. The method is materialized through the use of a bank of Probabilistic Neural Networks (PNNs). The main idea comes from the fact that specific operating and health conditions of an engine lead to specific concentrations of emissions on the exhaust area. By comparison of an emission concentration plot with emission plots of known engine health conditions, diagnostic conclusions can be extracted. The stochastic nature of emission concentrations can be handled by PNNs, a specific type of Artificial Neural Networks which are known to be efficient probabilistic classifiers. The diagnostic problem and the overall diagnostic procedure are first described. A detailed description of the way the diagnostic procedure is set-up, with focus on building the PNNs, follows. The case of an operating family of turbofan engines is used to evaluate the effectiveness of the method. The examined case demonstrates that the proposed method can act as an additional tool on the existing methods for better and safer fault diagnosis.
Analysis of Shrink Fit Interface Stresses for Rotating Circular Disks
Authors: Jafri Syed Muhammad Mohsin
Published: March 2009

This paper presents an analysis of the stresses and radial deformations in three elastic disks shrink fitted together to form a rotating assembly. The analytical results derived from this paper assume the three disks to be perfectly circular. The stress distribution as well as the displacement is assumed to be functions of radial coordinate and rotational speed. The thickness of disks is also assumed to be small as compared to their diameters. The results include the radial and tangential stress distribution at the interface for both static disks and for rotating motion of the assembly. The interference fit between the disks is also seen to be a function of rotational speed.
Time Characterisation of the Anodic Loop of a Pressurized Solid Oxide Fuel Cell System
Authors: Traverso A. , Trasino F. , Magistri L. , Massardo A. F.
Published: March 2009

A dynamic Solid Oxide Fuel Cell (SOFC) model was integrated with other system components (i.e.: reformer, anodic off-gas burner, anodic ejector) to build a system model that can simulate the time response of the anode side of an integrated 250 kW pressurized SOFC hybrid system. After model description and data on previous validation work, this paper describes the results obtained for the dynamic analysis of the anodic loop, taking into account two different conditions for the fuel flow input: in the first Case (I), the fuel flow follows with no delay the value provided by the control system, while in the second Case (II) the flow is delayed by a volume between the regulating valve and the anode ejector, this being a more realistic case. The step analysis was used to obtain information about the time scales of the investigated phenomena: such characteristic times were successfully correlated to the results of the subsequent frequency analysis. This is expected to provide useful indications for designing robust anodic loop controllers. In the frequency analysis, most phase values remained in the 0–180° range, thus showing the expected delay-dominated behavior in the anodic loop response to the input variations in the fuel and current. In Case I, a threshold frequency of 5Hz for the pressure and STCR, and a threshold frequency of 31Hz for the anodic flow were obtained. In the more realistic Case II, natural gas pipe delay dominates, and a threshold frequency of 1.2Hz was identified, after which property oscillations start to decrease towards null values.
Accelerated Oxidation of Type 347 Stainless Steel Primary Surface Recuperators Operating Above 600°C
Authors: Matthews Wendy J. , More Karren L. , Walker Larry R.
Published: March 2009

Type 347 stainless steel has traditionally been used in the manufacture of microturbine primary surface recuperators. It has been established during the past few years that the water vapor present in the microturbine exhaust gas causes accelerated oxidation of austenitic stainless steels at operating temperatures above ∼600°C (∼1110°F), which has resulted in the replacement of austenitic stainless steels with more highly alloyed Fe-based alloys and Ni-based alloys in microturbine recuperators. The effect of water vapor on type 347 stainless steel primary surface recuperators has been studied extensively by Capstone Turbine Corporation in collaboration with Oak Ridge National Laboratory. Several recuperators exposed in a Capstone C60 MicroTurbine™ under different steady-state and cyclic operating conditions, have been microstructurally characterized. Evaluation of surface oxide scale formation and associated compositional changes has been carried out on representative sections from recuperators with operating lives ranging from ∼2,000–15,000 hours. Results from the microstructural and compositional analyses of the engine-tested recuperators illustrate the progression of accelerated oxidation of type 347 stainless steel at recuperator operating temperatures above 600°C.
A Simple Sub-Idle Component Map Extrapolation Method
Authors: Gaudet Shaun R. , Gauthier J. E. Donald
Published: March 2009

This paper describes a simple sub-idle component map extrapolation method. Used in conjunction with gas turbine performance models, it enables designers to estimate sub-idle gas turbine performance during engine start-up. The lack of information available regarding component maps in the sub-idle regime creates major challenges for starting system designers or control system designers as the numerical convergence of performance models decreases rapidly below idle speed. The proposed component map extrapolation method alleviates this problem by extrapolating given component map data well below idle speed. The underlying equations of the method are based on the principles of incompressible similarity laws. Also known as pump laws, these equations are modified to account for compressibility effects by varying the similarity law exponents. To estimate the integrity of the extrapolated component maps and to build confidence in the sub-idle extrapolation method, extrapolate speed lines were compared to speed lines found in the original component map. Even though the extrapolation method is yet to be experimentally validated, preliminary estimates showed that the extrapolation method did produce adequate component maps. To demonstrate the potential of the component extrapolation method when used in conjunction with gas turbine performance models, a virtual test case engine was modeled and used to produce start-up performance data.
PM and Mercury Continuous Measurement Systems: Responding to an Emerging Challenge
Authors: Carr Peter
Published: March 2009

USEPA’s recent promulgation of the Clean Air Interstate Rule (CAIR) and Clean Air Mercury Rule (CAMR), and the designation of domestic fine particulate non-attainment areas, has spurred interest in adding particulate matter (PM) and mercury continuous emission monitoring systems (CEMS) to US power plants. While much of this interest has centered at least initially on pulverized coal-fired boiler units, the burgeoning integrated gasification combined cycle (IGCC) power market will likely also face the challenge of applying these new air emission measurement technologies. This paper will address the regulatory drivers which will encourage application of the PM and mercury CEMS on IGCC facilities, and it will discuss and evaluate the various measurement technologies/equipment available to comply with the new continuous emission measurement requirements. It will also summarize how various monitoring equipment suppliers have responded to this regulatory initiative. Finally, it will offer strategies to reduce the attendant risks and uncertainties associated with applying what are essentially emerging measurement technologies — technologies that will be tasked with demonstrating compliance with well-defined, strict air emission limitations.
Spiral Heat Exchanger Utilizing Dimpled Primary Surface
Authors: Glezer B. , Borisov I. , Khalatov A. , Kobsar S.
Published: March 2009

Paper presents a small demonstrator of the heat exchanger technology based on spiral counter-flow arrangement of dimpled primary surfaces. The heat exchanger has been developed as result of collaborative effort between Ukrainian and US scientists, authors of the paper. The heat transfer surfaces were fabricated out of stainless steel foil with arrays of spherical dimples augmenting heat transfer on the hot (gas) sides and corresponding spherical protrusions enhancing heat transfer on the cold (air) sides of the heat exchanger passages. About thirty primary surface geometries have been studied prior to selection of the presented configuration. Protruding diagonal ribs were introduced between lines of dimples on each side of the low-pressure passages, which were sandwiched between high-pressure passages, to prevent collapsing of the heat transfer surfaces under the pressure difference of 3.5 Bar. The counter-flow heat exchanger was assembled out of 24 (12 pairs) spiral rectangular cross-section channels, which were formed between dimpled surfaces. Development work was focused on optimizing thermal effectiveness and pressure losses within the heat exchanger core with little attention devoted to the entry and exit sections of the heat exchanger. The paper provides details of the experimental rig that was build for testing of the heat exchanger simulating operational parameters, which were representative for microturbine application. The overall recuperator effectiveness of 80–82% at total pressure loss of 10% was measured, including entry and exit losses. Excessive pressure losses in the entry-exit sections and headers were found to be main contributors to these losses. It was revealed that losses in the headers were related to inadequate structural support of the foil surfaces in the lower pressure passages, causing these passages to be partially closed. Design improvement measures addressing this issue are being evaluated with a goal of achieving 90% effectiveness with total pressure losses of less than 5% of the air inlet pressure.
Periodical Unsteady Flow Within a Rotor Blade Row of an Axial Compressor: Part I — Flow Field at Midspan
Authors: Mailach Ronald , Lehmann Ingolf , Vogeler Konrad
Published: March 2009

In this two-part paper results of the periodical unsteady flow field within the third rotor blade row of the four-stage Dresden Low-Speed Research Compressor are presented. The main part of the experimental investigations was performed using Laser-Doppler-Anemometry. Results of the flow field at several spanwise positions between midspan and rotor blade tip will be discussed. In addition time-resolving pressure sensors at midspan of the rotor blades provide information about the unsteady profile pressure distribution. In part I of the paper the flow field at midspan of the rotor blade row will be discussed. Different aspects of the blade row interaction process are considered for the design point and an operating point near the stability limit. The periodical unsteady blade-to-blade velocity field is dominated by the incoming stator wakes, while the potential effect of the stator blades is of minor influence. The inherent vortex structures and the negative jet effect, which is coupled to the wake appearance, are clearly resolved. Furthermore the time-resolved profile pressure distribution of the rotor blades is discussed. Although the negative jet effect within the rotor blade passage is very pronounced the rotor blade pressure distribution is nearly independent from the convectively propagating chopped stator wakes.
Regenerator Design Using Lumped Parameters and More-Exact Forms
Authors: Wilson David Gordon , Ballou Jon
Published: March 2009

Regenerators that transfer heat from one gas flow to another produce temperature changes in both flows. Design calculations are normally based on the approximation that the gas properties are those at the mean temperatures of each flow. The present study examines the errors in results that come from that approximation, and offers two alternative methods of arriving at improved accuracy.
A Preliminary Parametric Study for Geared, Intercooled and/or Recuperated Turbofan for Short Range Civil Aircrafts
Authors: Colmenares Fernando , Pascovici Daniele , Ogaji Stephen , Pilidis Pericles
Published: March 2009

Aviation plays a key role in economic prosperity and quality of lifestyle. However there is an increasing concern that current trends of consumption of natural resources cannot continue. It is imperative that major targeted investments are made into economical and reliable environment friendly propulsion and power solutions. A significant amount of this investment will be in the aerospace sector. A well utilised civil aircraft may burn more than 2000 times its weight in fuel during its life, so the examination of the propulsion system is essential from an environmental point of view. A preliminary parametric study for geared, intercooled and/or recuperated turbofan for short range commercial transport applications has been performed with regard to fuel consumption and emissions. A high by-pass ratio turbofan engine with performance characteristics and technology from the year 2000 was set up as a baseline. The results offer interesting qualitative comparisons showing that, for instance, a recuperated engine will yield a lower fuel burn for lower OPR values. An engine with a mid-compressor intercooler may give significant reduction of NOx emissions whilst increasing the amount of CO2. The intercooled and recuperated cycle offers higher thermal efficiencies (i.e. higher fuel consumption benefit) in comparison to other cycles at medium OPR values; therefore NOx formation may be reduced as well as the engine core weight. Additionally, the inherent advantage of high BPR against low BPR turbofans in terms of SFC is evident (GTF). Clearly, therefore, an increase of BPR is an inevitable solution for the reduction of both fuel consumption and the level of noise produced, however this may involve NOx and integration penalties, hence innovative cycles (e.g.: ICR) and state of the art combustor technology (e.g.: PERM and LDI combustors) must be considered. This is first on the series of work that would be carried out on the cycles being proposed in this paper. Further work on the issues of weight, noise, aircraft performance, other emissions, economics, etc, so-called a multidisciplinary objective assessment, would be published when completed. Also, at this time the design has been limited to take-off being the point of maximum aerodynamic performance. An extension to full mission is currently under investigation.