bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of citrullination on the function and conformation of antithrombin
Authors: Ordóñez A. , Martínez‐Martínez I. , Corrales F. J. , Miqueo C. , Miñano A. , Vicente V. , Corral J.
Published: October 2009

Antithrombin is an anticoagulant serpin with conformational sensitivity. Mutations and environmental factors may induce its polymerization by a mechanism involving domain swapping, which still requires verification. We have evaluated the functional and conformational effects on antithrombin of citrullination, a post‐translational modification catalyzed by peptidylarginine deiminase (PAD), which changes arginine to citrulline. Purified antithrombin (native and latent forms) and plasma were incubated with PAD in the presence and absence of heparin. Citrullines were identified by proteomic analysis. Anti‐activated factor X activity determination, IEF, SDS/PAGE and native PAGE were performed. The cleavage pattern with the metalloprotease AspN was studied, and its target residues were identified by Edman sequencing. We confirmed that citrullination of antithrombin abolished its activity; this abolition of activity was accelerated by heparin, which facilitated the early citrullination of Arg393 (P1 residue). Proteomic analyses revealed nine additional citrullines that caused a significant decrease in its electrostatic potential (from 5.95 to 5.06). It was demonstrated that citrullination of antithrombin caused its polymerization. The observation that these polymers, like heat‐generated polymers, are cleaved by AspN in helix I is compatible with their linkage by domain swapping from strand 5 to strand 4 of β‐sheet A.
Dermaseptin DA4, although closely related to dermaseptin B2, presents chemotactic and Gram‐negative selective bactericidal activities
Authors: Auvynet Constance , Joanne Pierre , Bourdais Julie , Nicolas Pierre , Lacombe Claire , Rosenstein Yvonne
Published: October 2009

Antimicrobial peptides participate in innate host defense by directly eliminating pathogens as a result of their ability to damage the microbial membrane and by providing danger signals that will recruit innate immune cells to the site of infection. Dermaseptin DA4 (DRS‐DA4), a new antimicrobial peptide of the dermaseptin superfamily, was identified based on its chemotactic properties, contrasting with the currently used microbicidal properties assessment. The peptide was isolated and purified by size exclusion HPLC and RP‐HPLC from the skin of the Mexican frog, Pachymedusa dacnicolor. MS and amino acid sequence analyses were consistent with the structure GMWSKIKNAGKAAKAAAKAAGKAALGAVSEAM. CD experiments showed that, unlike most antimicrobial peptides of the dermaseptin superfamily, DRS‐DA4 is not structured in the presence of zwitterionic lipids. DRS‐DA4 is a potent chemoattractant for human leukocytes and is devoid of hemolytic activity; in addition, bactericidal tests and membrane perturbation assays on model membranes and on Escherichia coli and Staphylococcus aureus strains have shown that the antibacterial effects of DRS‐DA4 and permeabilization of the inner membrane are exclusively selective for Gram‐negative bacteria. Interestingly, despite high sequence homology with dermaseptin S4, dermaseptin B2 was not able to induce directional migration of leukocytes, and displayed a broader bactericidal spectrum. A detailed structure–function analysis of closely related peptides with different capabilities, such as DRS‐DA4 and dermaseptin B2, is critical for the design of new molecules with specific attributes to modulate immunity and/or act as microbicidal agents.
Towards a platform for the metabonomic profiling of different strains of Drosophila melanogaster using liquid chromatography–Fourier transform mass spectrometry
Authors: Kamleh Muhammad A. , Hobani Yahya , Dow Julian A. T. , Zheng Liang , Watson David G.
Published: October 2009

A platform based on hydrophilic interaction chromatography in combination with Fourier transform mass spectrometry was developed in order to carry out metabonomics of Drosophila melanogaster strains. The method was able to detect ∼ 230 metabolites, mainly in the positive ion mode, after checking to eliminate false positives caused by isotope peaks, adducts and fragment ions. Two wild‐type strains, Canton S and Oregon R, were studied, plus two mutant strains, Maroon Like and Chocolate. In order to observe the differential expression of metabolites, liquid chromatography‐mass spectrometry analyses of the different strains were compared using sieve 1.2 software to extract metabolic differences. The output from sieve was searched against a metabolite database using an Excel‐based macro written in‐house. Metabolic differences were observed between the wild‐type strains, and also between both Chocolate and Maroon Like compared with Oregon R. It was established that a metabonomic approach could produce results leading to the generation of new hypotheses. In addition, the structure of a new class of lipid with a histidine head group, found in all of the strains of flies, but lower in Maroon Like, was elucidated.
Efficacy of an esfenvalerate plus methoprene aerosol for the control of eggs and fifth instars of Plodia interpunctella (Lepidoptera: Pyralidae)
Authors: Jenson Emily A. , Arthur Frank H. , Nechols James R.
Published: October 2009

Abstract  Aerosol insecticides may provide an alternative to fumigants for control of the Indianmeal moth, Plodia interpunctella (Hübner), the Indianmeal moth, a major insect pest of stored processed food. In this study, eggs and larvae (5th instars) of P. interpunctella were exposed to aerosol applications of the pyrethroid esfenvalerate and insect growth regulator methoprene, alone and in combination, in open and obstructed positions inside small sheds. When larvae were exposed to methoprene alone, adult emergence from those exposed larvae was 7.1%± 1.5%. In contrast, adult emergence was 92.5%± 3.5% when larvae were exposed to esfenvalerate alone. When eggs were exposed to methoprene, adult emergence of those exposed eggs was approximately 75%; however, when eggs were exposed to esfenvalerate, adult emergence was approximately 35%. In the combination treatment of methoprene plus esfenvalerate at their respective label rates, adult emergence following larval exposure was 0.91%± 0.61% compared to 16.3%± 9.6% when eggs were exposed. Based on our results, methoprene alone is highly effective in reducing adult emergence after larval exposure. However, it is not as effective on eggs as esfenvalerate. A combination treatment of esfenvalerate plus methoprene could be used to control eggs and the wandering‐phase larval stages of P. interpunctella. An economic risk analysis also supports a strategy of combining methoprene and esfenvalerate.
An Agent‐Based Model of Entrepreneurial Behavior in Agri‐Food Markets
Authors: Ross R. Brent , Westgren Randall E.
Published: October 2009

Rapid technological innovation and globalization have led to increasingly complex agri‐food supply chains and networks, and uncertain agri‐food markets. Given this type of competitive environment, management scholars have argued that agri‐food firms that adopt capabilities for entrepreneurship will outperform firms that do not. We use agent‐based simulation methods to explore this hypothesis. Agent‐based models are particularly relevant in this study as they allow for the explicit simulation of the entrepreneurial behaviors and firm interactions that lead to wealth creation. In our analysis, we find that entrepreneurial capabilities of alertness, risk‐taking, and efficiency vary in their effect on firm performance given alternative agri‐food strategic landscape configurations.

L'innovation technologique rapide et la mondialisation ont donné lieu à des chaînes d'approvisionnement agroalimentaire et à des réseaux de plus en plus complexes ainsi qu'à des marchés agroalimentaires incertains. Compte tenu de ce type d'environnement concurrentiel, les spécialistes en gestion soutiennent que les entreprises agroalimentaires qui possèdent des capacités entrepreneuriales surclasseront celles qui n'en possèdent pas. Nous avons utilisé des modèles de simulation multi‐agent pour étudier cette hypothèse. Les modèles multi‐agent sont particulièrement pertinents dans la présente étude puisqu'ils permettent la simulation explicite de comportements entrepreneuriaux et d'interactions entre firmes qui engendrent la création de richesse. Les résultats de notre analyse ont montré que les capacités entrepreneuriales, telles que la vigilance, la prise de risque et l'efficacité, ont des répercussions variées sur la performance d'une firme en raison de différentes configurations stratégiques du paysage agroalimentaire.
Precision cosmology from X-ray AGN clustering
Authors: Basilakos Spyros , Plionis Manolis
Published: October 2009

We place tight constraints on the main cosmological parameters of spatially flat cosmological models by using the recent angular clustering results of XMM–Newton soft (0.5–2 keV) X-ray sources, which have a redshift distribution with a median of z∼ 1. Performing a standard likelihood procedure, assuming a constant in comoving coordinates active galactic nuclei (AGN) clustering evolution, the AGN bias evolution model of Basilakos, Plionis & Ragone-Figueroa and the Wilkinson Microwave Anisotropy Probe5 value of σ8, we find stringent simultaneous constraints in the (Ωm, w) plane, with Ωm= 0.26 ± 0.05, w=−0.93+0.11−0.19.
Hypoxia Selectively Inhibits KCNA5 Channels in Pulmonary Artery Smooth Muscle Cells
Authors: Firth Amy L. , Platoshyn Oleksandr , Brevnova Elena E. , Burg Elyssa D. , Powell Frank , Haddad Gabriel H. , Yuan Jason X.‐J.
Published: October 2009

Acute hypoxia induces pulmonary vasoconstriction and chronic hypoxia causes pulmonary vascular remodeling characterized by significant vascular medial hypertrophy. Electromechanical and pharmacomechanical mechanisms are involved in regulating pulmonary vasomotor tone, while changes in cytosolic Ca2+ concentration ([Ca2+]cyt) are an important signal in regulating contraction and proliferation of pulmonary artery smooth muscle cells (PASMC). Hypoxia‐induced increases in [Ca2+]cyt are, in part, mediated by selective inhibition of voltage‐gated K+ (Kv) channels in PASMC. Kv1.5, encoded by the KCNA5 gene, is a Kv channel α subunit that forms functional homotetrameric and heterotetrameric Kv channels in PASMC. Activity of Kv channels contributes to the regulation of resting membrane potential. Overexpression of the human KCNA5 gene in rat PASMC and other cell types increases whole‐cell Kv currents and causes membrane hyperpolarization. However, acute hypoxia only reduced Kv currents in KCNA5‐transfected PASMC. These results provide compelling evidence that Kv1.5 is an important hypoxia‐sensitive Kv channel in PASMC, contributing to regulation of membrane potential and intracellular Ca2+ homeostasis during hypoxia. This hypoxia‐sensitive mechanism essential for inhibiting Kv1.5 channel activity is exclusively present in PASMC.
2BAD: an application to estimate the parental contributions during two independent admixture events
Authors: BRAY T. C. , SOUSA V. C. , PARREIRA B. , BRUFORD M. W. , CHIKHI L.
Published: October 2009

Several approaches have been developed to calculate the relative contributions of parental populations in single admixture event scenarios, including Bayesian methods. In many breeds and populations, it may be more realistic to consider multiple admixture events. However, no approach has been developed to date to estimate admixture in such cases. This report describes a program application, 2BAD (for 2‐event Bayesian ADmixture), which allows the consideration of up to two independent admixture events involving two or three parental populations and a single admixed population, depending on the number of populations sampled. For each of these models, it is possible to estimate several parameters (admixture, effective sizes, etc.) using an approximate Bayesian computation approach. In addition, the program allows comparing pairs of admixture models, determining which is the most likely given data. The application was tested through simulations and was found to provide good estimates for the contribution of the populations at the two admixture events. We were also able to determine whether an admixture model was more likely than a simple split model.
Novel set of multiplex assays (SalPrint15) for efficient analysis of 15 microsatellite loci of contemporary samples of the Atlantic salmon (Salmo salar)
Authors: OLAFSSON KRISTINN , HJORLEIFSDOTTIR SIGRIDUR , PAMPOULIE CHRISTOPHE , HREGGVIDSSON GUDMUNDUR OLI , GUDJONSSON SIGURDUR
Published: October 2009

We report the development of new PCR assays and loading panels for the Atlantic salmon using 15 microsatellite loci. A total of 8, 3 and 4 loci were coamplified in three separate PCRs using labelled primers and loaded on the ABI DNA analyzer in two separate panels. Amplified alleles were clearly typed, and easily interpretable results were obtained. The method was successfully applied in different laboratories, even when different types of DNA polymerase were employed. The method is useful for analysing paternity, population genetics and conservation as well as for selective breeding programmes.
Methods for MHC genotyping in non‐model vertebrates
Authors: BABIK W.
Published: October 2009

Genes of the major histocompatibility complex (MHC) are considered a paradigm of adaptive evolution at the molecular level and as such are frequently investigated by evolutionary biologists and ecologists. Accurate genotyping is essential for understanding of the role that MHC variation plays in natural populations, but may be extremely challenging. Here, I discuss the DNA‐based methods currently used for genotyping MHC in non‐model vertebrates, as well as techniques likely to find widespread use in the future. I also highlight the aspects of MHC structure that are relevant for genotyping, and detail the challenges posed by the complex genomic organization and high sequence variation of MHC loci. Special emphasis is placed on designing appropriate PCR primers, accounting for artefacts and the problem of genotyping alleles from multiple, co‐amplifying loci, a strategy which is frequently necessary due to the structure of the MHC. The suitability of typing techniques is compared in various research situations, strategies for efficient genotyping are discussed and areas of likely progress in future are identified. This review addresses the well established typing methods such as the Single Strand Conformation Polymorphism (SSCP), Denaturing Gradient Gel Electrophoresis (DGGE), Reference Strand Conformational Analysis (RSCA) and cloning of PCR products. In addition, it includes the intriguing possibility of direct amplicon sequencing followed by the computational inference of alleles and also next generation sequencing (NGS) technologies; the latter technique may, in the future, find widespread use in typing complex multilocus MHC systems.
Reactivity of white blood cell flux to hyperoxia in patients infected with human immunodeficiency virus
Authors: Resch Hemma , Garhöfer Gerhard , Dejaco‐Ruhswurm Irene , Kiss Barbara , Wedrich Andreas , Schmetterer Leopold , Rainer Georg
Published: October 2009

Purpose:  The aetiology of the apparently vasoocclusive phenomena in human immunodeficiency virus (HIV)‐related retinopathy is not well understood. Several hypotheses, including infectious damage of the retinal vasculature and altered retinal haemodynamics, have been postulated. Direct measurement of oxygen tension in the retina is not possible in vivo and indirect methods have to be employed. The objective of this study was to investigate the retinal vascular response to 100% oxygen breathing in patients with HIV.

Methods:  Twelve patients infected with HIV and 12 healthy individuals, matched for age, sex and smoking habits, were studied in an open study using the blue‐field entoptic technique for the measurement of retinal white blood cell (WBC) flux. Reactivity in retinal blood flow during 100% O2 breathing over 15 min was measured and expressed as percentage change over baseline.

Results:  WBC velocity during oxygen inhalation decreased over baseline by 9.0 ± 5.8% in HIV‐infected patients and by 18.6 ± 5.4% in healthy participants (p < 0.04 between groups, anova). The decrease in WBC velocity was paralleled by a decrease in WBC density. This decrease tended to be more pronounced in healthy participants (13.6 ± 7.9%) than in HIV‐infected patients (8.0 ± 10.8%), but the difference was not statistically significant (p = 0.1 between groups, anova). WBC flux decrease was 16.2 ± 11.4% in HIV‐infected patients and 29.5 ± 9.5% in the control group and was significant between groups (p = 0.007 between groups, anova).

Conclusion:  Our results indicate a reduced reactivity of WBC flux to systemic hyperoxia in patients with HIV. Whether abnormal retinal haemodynamics in HIV‐infected persons contributes to the pathogenesis of HIV‐related microvascular diseases or is a consequence of the structural changes associated with the disease is unknown.
Oncocytic lesions of the ophthalmic region: a clinicopathological study with emphasis on cytokeratin expression
Authors: Østergaard Jens , Prause Jan U. , Heegaard Steffen
Published: October 2009

Purpose:  This study aimed to make a nationwide clinicopathological study of oncocytic lesions in the ophthalmic region and to characterize their cytokeratin (CK) expression.

Methods:  All histologically diagnosed oncocytic lesions in the ophthalmic region registered in Denmark over a 25‐year period were collected and re‐evaluated using a monoclonal antimitochondrial antibody (MU213‐UC). Clinical data were registered. Immunohistochemical characterization was performed with a panel of anti‐CK antibodies.

Results:  A total of 34 oncocytic lesions were identified and reviewed. The incidence that required surgical intervention in the Danish population could be approximated to 0.3 lesions per million capita per year. Patient ages ranged from 45 years to 89 years, with a peak incidence in the eighth decade. Female patients were twice as common as male. Lesions were typically described as red–brown, cystic and slow‐growing. The antimitochondrial antibody MU213‐UC produced a distinct and intense immunostaining of all oncocytic lesions and was found to be useful in substantiating oncocytic differentiation. Twenty‐six of the lesions originated in the caruncle, three in the conjunctiva, two in the lacrimal sac, one at the semilunar plica, one on the eyelid margin and one peripunctally. Lesions were histologically classified as adenoma (oncocytoma) (26), hyperplasia (4) and metaplasia (4). Fourteen oncocytic lesions representing different locations and differentiation were further evaluated for CK expression. Basal‐type oncocytic cells reacted with antibodies against CK 5/6, CK 7, CK 8, CK 13, CK 14, CK 17, CK 18 and CK 19, and suprabasal cells with CK 4, CK 7, CK 8, CK 18 and CK 19. Antibodies against CK 1+10 and CK 20 showed no reaction.

Conclusions:  Oncocytic lesions of the ophthalmic region most frequently present as caruncular oncocytomas. The CK profile is similar to the lacrimal‐ and accessory lacrimal gland duct elements and supports the theory that these lesions originate in the lacrimal‐ and accessory lacrimal glands.
Erythropoietin and iron therapy in patients with renal failure
Authors: DEL VECCHIO LUCIA , LOCATELLI FRANCESCO
Published: October 2009

Anemia, which is a common complication of chronic kidney disease (CKD), may significantly impair quality of life, increase cardiovascular risk and reduce long‐term survival if left untreated. Today, erythropoiesis‐stimulating agents (ESAs) are the main tool for anemia correction; they can be differentiated on the basis of mean serum half life on short‐ and long‐acting molecules, the latter requiring longer administration intervals. According to international guidelines, the target hemoglobin to be obtained by treatment is between 11 and 12 g/dL. In general, the intravenous route is more convenient for hemodialysis patients, whereas the subcutaneous one is preferable in all other CKD patients. ESA dose requirements are rarely predictable in the individual patient and thus need to be titrated according to hemoglobin increases. In order to achieve ESA effectiveness, patients often need iron supplementation, either orally or intravenously. The intravenous route is the most widely used, especially in hemodialysis patients.
Beam-Down Mirror: Thermal and Stress Analyses
Authors: Ben-Zvi Rami , Segal Akiba , Epstein Michael
Published: October 2009

The “beam-down” optics or solar tower reflector, developed and demonstrated at the Weizmann Institute of Science during the past 9 years, could be a useful modification of the classic solar tower technology, especially for solar applications where reacting solids are involved or heavy equipment has to be placed on top of a conventional tower. The theory of this optics has been thoroughly studied and reported elsewhere. This paper details the development and experience gained with the mirror facets of the tower reflector. Thermal and stress analyses are presented here, validated by temperature measurements and calculated incident flux map. The projection for a large scale solar plant of about 100 MW at the aperture of the receiver is illustrated. The current basic design of the facet made of a sandwich of mirrors glued back-to-back seems to be a feasible solution for future applications. Aluminum-glass facets failed, and cracks in the glass were observed in the course of time. Years of experience proved that using only natural cooling to the surrounding, for the glass/glass facets, which can reach 130–140°C during operation under average incident solar flux of about 30 kW/m2, is a viable design. Maximum working temperatures of 160°C were experienced without any degradation of the reflectivity and the performance of these facets after several hundreds of operation hours.
Predicted Efficiency of a Low-Temperature Nanofluid-Based Direct Absorption Solar Collector
Authors: Tyagi Himanshu , Phelan Patrick , Prasher Ravi
Published: October 2009

Due to its renewable and nonpolluting nature, solar energy is often used in applications such as electricity generation, thermal heating, and chemical processing. The most cost-effective solar heaters are of the “flat-plate” type, but these suffer from relatively low efficiency and outlet temperatures. The present study theoretically investigates the feasibility of using a nonconcentrating direct absorption solar collector (DAC) and compares its performance with that of a typical flat-plate collector. Here a nanofluid—a mixture of water and aluminum nanoparticles—is used as the absorbing medium. A two-dimensional heat transfer analysis was developed in which direct sunlight was incident on a thin flowing film of nanofluid. The effects of absorption and scattering within the nanofluid were accounted for. In order to evaluate the temperature profile and intensity distribution within the nanofluid, the energy balance equation and heat transport equation were solved numerically. It was observed that the presence of nanoparticles increases the absorption of incident radiation by more than nine times over that of pure water. According to the results obtained from this study, under similar operating conditions, the efficiency of a DAC using nanofluid as the working fluid is found to be up to 10% higher (on an absolute basis) than that of a flat-plate collector. Generally a DAC using nanofluids as the working fluid performs better than a flat-plate collector, however, much better designed flat-plate collectors might be able to match or outperform a nanofluids based DAC under certain conditions.
Optimal Design of a Molten Salt Thermal Storage Tank for Parabolic Trough Solar Power Plants
Authors: Gabbrielli R. , Zamparelli C.
Published: October 2009

This paper presents an optimal design procedure for internally insulated, carbon steel, molten salt thermal storage tanks for parabolic trough solar power plants. The exact size of the vessel and insulation layers and the shape of the roof are optimized by minimizing the total investment cost of the storage system under three technical constraints: remaining within the maximum allowable values of both temperature and stress in the steel structure, and avoiding excessive cooling and consequent solidification of the molten salt during long periods of no solar input. The thermal, mechanical and economic aspects have been integrated into an iterative step-by-step optimization procedure, which is shown to be effective through application to the case study of a 600MWh thermal storage system. The optimal design turns out to be an internally insulated, carbon steel storage tank characterized by a maximum allowable height of 11m and a diameter of 22.4m. The total investment cost is about 20% lower than that of a corresponding AISI 321H stainless steel storage tank without internal protection or insulation.
A Simple Experimental Method for Thermal Characterization of Shape-Stabilized Phase Change Materials
Authors: Palomo Del Barrio E. , Dauvergne J. L. , Morisson V.
Published: October 2009

A new method for characterization of shape-stabilized phase change materials (PCMs) based on one single sample and one single experimental device has been proposed. The simplicity of the experimental device is comparable to that of the T-history method: a cylinder of PCM, which is heated/cooled in a furnace following specific temperature patterns (steps, isotherms, and ramps). Instead of simple energy balances as in the T-history method, a numerical heat transfer model is used to retrieve the whole set of parameters/functions characterizing the PCM from temperature measurements at one single point within the PCM. A powerful inversion technique has been proposed for that. Its most striking feature is that it allows identification of enthalpy-temperature functions in an easy way. They are retrieved by solving a problem of time-dependent source estimation by inversion of a linear heat conduction model. It is shown that unknown sources are the output of a linear and invariant state model whose inputs are measured temperatures within the PCM. Enthalpy-temperature functions, as well as parameters derived from heat capacities, transition temperatures, and latent heat, are thus calculated in a simple way. An experimental test for characterization of graphite/salt composites has been carried out to illustrate the appropriateness of our developments.
Molten-Salt Tubular Absorber/Reformer (MoSTAR) Project: The Thermal Storage Media of Na2CO3–MgO Composite Materials
Authors: Kodama Tatsuya , Gokon Nobuyuki , Inuta Shin-ichi , Yamashita Shingo , Seo Taebeom
Published: October 2009

The molten-salt tubular absorber/reformer (MoSTAR) project aims to develop a novel type of “double-walled” tubular absorber/reformer with molten-salt thermal storage at high temperature for use in solar natural-gas reforming and solar air receiver, and to demonstrate its performances on the sun with a 5 kWt dish-type solar concentrator. The new concept of double-walled reactor tubes is proposed for use in a solar reformer by Niigata University, Japan, and involves packing a molten/ceramic composite material in the annular region between the internal catalyst tube and the exterior solar absorber wall. This solar tubular absorber concept may be also applied to solar air receiver for solar thermal power generation. The MoSTAR project includes the development of molten-salt thermal storage media, the new design and the fabrication of absorber/reformer with the double-walled absorber tubes, and finally the solar demonstration on the 5 kWt dish concentrator of Inha University in Korea. In this paper, thermal storage media of the series of Na2CO3–MgO composite materials were tested in a double-walled reformer tube with a thermal storage capacity of about 0.3 kWh. The chemical reaction performances for dry reforming of methane during cooling or heat-discharge mode of the reactor tube were investigated using an electric furnace. The experimental results obtained under feed gas mixture of CH4/CO2=1:3 at a residence time of 0.3 s and at 1 atm showed that the single reactor tube with 90 wt % Na2CO3/10 wt % MgO composite material successfully maintained a high methane conversion above 90% with about 0.9 kW reforming scale based on high heating value during 45 min of the heat-discharge mode. The chemical reaction performances of the reactor tube were investigated also for the solar-simulating operation mode. The application of the new reactor tubes to solar tubular reformers is expected to help realize stable operation of the solar reforming process under fluctuating insolation during a cloud passage.
Performance of Large-Scale Seasonal Thermal Energy Stores
Authors: Ochs F. , Heidemann W. , Müller-Steinhagen H.
Published: October 2009

More than 30 international research and pilot seasonal thermal energy stores (TESs) were realized within the past 30 years. Experiences with operation of these systems show that TES are technically feasible and work well. Seasonal storage of solar thermal energy or of waste heat from heat and power cogeneration plants can significantly contribute to substitute fossil fuels in future energy systems. However, performance with respect to thermal losses and lifetime has to be enhanced, while construction costs have to be further reduced. This paper gives an overview about the state-of-the-art of seasonal thermal energy storage with the focus on tank and pit TES construction. Aspects of TES modeling are given. Based on modeled and measured data, the influence of construction type, system configuration, and boundary conditions on thermal losses of large-scale TES is identified. The focus is on large-scale applications with tank and pit thermal energy stores and on recent investigations on suitable materials and constructions. Furthermore, experiences with the operation of these systems with respect to storage performance are discussed.
Experimental Study of PCM Inclusion in Different Building Envelopes
Authors: Castellón C. , Castell A. , Medrano M. , Martorell I. , Cabeza L. F.
Published: October 2009

The main objective of this paper is to demonstrate experimentally that it is possible to improve the thermal comfort and reduce the energy consumption of a building without substantial increase in the weight of the construction materials with the inclusion of phase change materials (PCM). PCM are a suitable and promising technology for this application. This paper presents an experimental setup to test PCM with various typical insulation and construction materials in real conditions in Puigverd de Lleida (Lleida, Spain). Nine small house-sized cubicles were constructed: two with concrete, five with conventional brick, and two with alveolar brick. PCM was added in one cubicle of each typology. For each type of construction specific experiments were done. In all cubicles, free-floating temperature experiments were performed to determine the benefits of using PCM. A Trombe wall was added in both concrete cubicles and its influence was investigated. All brick cubicles were equipped with domestic heat pumps as Heating, Ventilation, and Air Conditioning (HVAC) system; therefore, the energy consumption was registered, providing real information about the energy savings. Results were very good for the concrete cubicles, since temperature oscillation were reduced by up to 4°C through the use of PCM and also peak temperatures in the PCM cubicle were shifted in later hours. In the brick cubicles, the energy consumption of the HVAC system in summer was reduced by using PCM for set points higher than 20°C. During winter an insulation effect of the PCM is observed, keeping the temperatures of the cubicles warmer, especially during the cold hours of the day.
Simulation study on a Domestic Solar/Heat Pump Heating System Incorporating Latent and Stratified Thermal Storage
Authors: Trinkl Christoph , Zörner Wilfried , Hanby Vic
Published: October 2009

Both solar and heat pump heating systems are innovative technologies for sustaining ecological heat generation. They are gaining more and more importance due to the accelerating pace of climate change and the rising cost of limited fossil resources. Against this background, a heating system combining solar thermal collectors, heat pump, stratified thermal storage, and water/ice latent heat storage has been investigated. The major advantages of the proposed solar/heat pump heating system are considered to be its flexible application (suitable for new and existing buildings because of acceptable space demand), as well as the improvement of solar fraction (extended solar collector utilization time, enhanced collector efficiency), i.e., the reduction of electric energy demand for the heat pump by management of the source and sink temperatures. In order to investigate and optimize the heating system, a dynamic system simulation model was developed. On this basis, a fundamental control strategy was derived for the overall co-ordination of the heating system with particular regard to the performance of the two storage tanks. In a simulation study, a fundamental investigation of the heating system configuration was carried out and an optimization was derived for the system control, as well as the selection of components and their dimensioning. The influence of different parameters on the system performance was identified, where the collector area and the latent heat storage volume were found to be the predominant parameters for system dimensioning. For a modern one-family house of 120 m2 living area with a specific annual heat demand of 60 kWh/(m2 a) for both heating and domestic hot water, a solar collector area of 30 m2, and a latent heat store volume of 12.5 m3 are proposed for the location of Wuerzburg (Germany). In this configuration, the heating system reaches a seasonal performance factor of 4.6, meaning that 78% of the building’s and users’ heat demand are delivered by solar energy. The results show that the solar/heat pump heating system can give an acceptable performance using up-to-date components in a state-of-the-art building.
Rapid Boiling of a Two-Phase Droplet in an Immiscible Liquid at High Superheat
Authors: Haustein Herman D. , Gany Alon , Elias Ezra
Published: October 2009

This work studies experimentally the rapid boiling of a droplet rising in a host liquid environment, within a range of superheats (0.2<Ja∗<0.5) not previously investigated. The direct-contact rapid-boiling process has many advantages in the fields of heat exchange and multiphase flow. By taking into account the superheat, heat transfer, and hydrodynamics of the multiphase-droplet the aim of this study is to create greater insight into the character of this transient-boiling process, for the first time. The sudden depressurization of a water column led to the rapid boiling of liquid propane droplets rising by buoyancy. During this millisecond boiling distinct stages were identified. Appropriate critical times for the transition between stages were defined by a simplified model, among these a novel criterion for the sudden pause in boiling caused by the engulfing liquid-film's collapse. Good agreement was found between these predicted time-points and measured changes in the boiling profile. This form of boiling, though being very rapid and sustaining high heat transfer rates, is still calm in nature, therefore, more predictable and widely applicable. Understanding this form of boiling suggests that the “design” of the boiling curve may be possible by setting the initial parameters.
The Effect of Hydrocarbon Structure Upon Fuel Sooting Tendency in a Turbulent Spray Diffusion Flame
Authors: Bowden T. T. , Pearson J. H.
Published: October 2009

The sooting tendencies of various hydrocarbon structures have been studied in a model gas turbine combustor at a pressure of 0.35 MPa and a preheated air temperature of 530 K. The results of this study have indicated that the sooting tendencies of fuels containing only single ring aromatics, fused bicyclic saturates, and unsaturated nonaromatics will be related to the overall hydrogen content of the fuel. However, experimental fuel blends with high concentrations (> 20 percent wt) of naphthalenes or tetralins exhibit sooting properties that are dependent upon the presence of such components. It is suggested that a kinetic scheme utilizing aromatic rings as nuclei upon which reactive fragments may stabilize can explain the present results.
Statistical Characteristics of Velocity, Concentration, Mass Transport, and Momentum Transport for Coaxial Jet Mixing in a Confined Duct
Authors: Johnson B. V. , Bennett J. C.
Published: October 2009

An experimental study of mixing downstream of coaxial jets discharging into an expanded circular duct was conducted to obtain data for the evaluation and improvement of turbulent transport models currently used for combustor flow modeling. A combination of turbulent momentum transport rate and two velocity component data were obtained from simultaneous measurements with a two-color LV system. A combination of turbulent mass transport rate, concentration and velocity data were obtained from simultaneous measurements with laser velocimeter (LV) and laser induced fluorescence (LIF) systems. These measurements were used to obtain mean, second central moment, skewness and kurtosis values for three velocity components and the concentration. These measurements showed the existence of countergradient turbulent axial mass transport where the annular jet fluid was accelerating the inner jet fluid. Results from the study are related to the assumptions employed in the current mass and momentum turbulent transport models.
Temperature Profile Development in Turbulent Mixing of Coolant Jets With a Confined Hot Crossflow
Authors: Wittig S. L. K. , Elbahar O. M. F. , Noll B. E.
Published: October 2009

The mixing of coolant air jets with the hot gas exiting the primary zone is of major importance to the combustor exit temperature profile. Geometry and momentum flux ratios are the dominant parameters. A theoretical and experimental study of single as well as opposite-wall jet injection into a hot crossflow reveals the applicability and limitations of existing correlations. Modified correlations are presented for opposite-wall injection with jets of different momentum flux ratios. The advantages in applying field methods for describing the flow are discussed.
Redesign and Performance Analysis of a Transonic Axial Compressor Stator and Equivalent Plane Cascades With Subsonic Controlled Diffusion Blades
Authors: Dunker R. , Rechter H. , Starken H. , Weyer H.
Published: October 2009

In order to verify a new controlled diffusion blade design concept, the stator of an existing transonic axial compressor stage was redesigned. Stator and equivalent cascade tests revealed the potential of such blades for a considerably higher aerodynamic loading than it has been applied up to now. The design procedure is described, and the results of plane cascade and stage testing are submitted, including performance analysis of both cascade and stator blade sections, at design and off-design operating conditions. The blade profile shapes and cascade geometries were calculated by means of an inverse, two-dimensional method taking also into account the axial velocity density ratio (AVDR). This design concept is essentially based on prescribed blade pressure distributions, which are optimized with respect to the blade boundary layer development. The flow phenomena are illustrated by means of loss and flow turning investigations, blade pressure distributions, and laser velocimetry data. The test results reveal that the two-dimensional approach applied is quite promising for the three-dimensional blade design. Finally, overall and blade element performance comparisons between the original NACA 65 profiled stator and the redesigned one demonstrate the favorable flow behavior of the new stator, as well as the great potential of the controlled diffusion blade concept.
Measurements of the Flow From a High-Speed Compressor Rotor Using a Dual Probe Digital Sampling (DPDS) Technique
Authors: Shreeve R. P. , Neuhoff F.
Published: October 2009

The flow from a high-speed rotor in a rotor-first arrangement has been measured using a “dual-probe, digital sampling (DPDS)” technique. The flow field was found to be steady in rotor coordinates (periodic in machine coordinates) outside the rotor wake, and three components of velocity and the pressure field were determined in this area. The wake regions were unsteady. In these regions the measurements based on ensemble averages of multiple samples did not follow the behavior established during calibration in steady uniform free-jet flow, except near the wake center. The broadening of the wake and three-dimensional effects in the flow field were measured at reduced throttle and increased speeds. The results serve to illustrate the potential of the measurement technique, on which the emphasis of the presentation is placed.
Performance Evaluation of Centrifugal Compressor Impellers Using Three-Dimensional Viscous Flow Calculations
Authors: Moore J. , Moore J. G. , Timmis P. H.
Published: October 2009

Calculations of three-dimensional viscous flow in the impeller of a centrifugal compressor are used as the basis of a study of the thermodynamics of the compression process. Flow in a high hub-tip ratio low specific speed impeller of approximately 3.4:1 pressure ratio is considered. Results are presented showing the work and loss production processes in the impeller. A strong influence of tip-leakage flow on the performance of this unshrouded wheel is found.
Combustion Research Related to Utilization of Coal as a Gas Turbine Fuel
Authors: Davis-Waltermire D. M. , Anderson R. J.
Published: October 2009

A nominal 293 kw (1 MBtu/hr) atmospheric pressure, refractory-lined combustor has been used to investigate the effects of a number of combustor and fuel dependent variables on combustion efficiency and flue gas characteristics for minimally cleaned, coal-derived gas (MCG) and coal water mixtures. The variables which have been evaluted include: percent excess air, air distribution, combustion air preheat temperature, swirl number, fuel feedrate, coal particle size, coal loading in slurry, and slurry viscosity. Characterization of the flue gas included major/minor gas species, alkali levels, and particulate loading, size, and composition. These atmospheric pressure combustion studies accompanied by data from planned pressurized studies on coal-water slurries and hot, minimally cleaned, coal-derived gas will aid in the determination of the potential of these fuels for use in gas turbines.
Medium-Speed Diesel Engines: Part I—Design Trends and the Use of Residual/Blended Fuels
Authors: Thomas F. J. , Ahluwalia J. S. , Shamah E. , van der Horst G. W.
Published: October 2009

Fuel costs can exceed 50 percent of the total diesel plant’s operational expenditures. To reduce fuel costs, medium-speed engines are now available with improved fuel consumption and ability to burn residual fuels. Part I of this paper reviews these engine and design changes needed for both improved fuel consumption and the ability to burn poorer quality fuels. Characteristics of these fuels and international fuel specifications are discussed. Ignition quality of residual fuels by a modified ASTM D 613 procedure are presented and correlation shown to calculated diesel index and calculated carbon aromaticity index (CCAI). Residual fuel ignition delay effects on combustion pressure rise, fuel consumption, and piston temperature in a laboratory single-cylinder diesel engine are shown.
A Simplified Method for Elastic-Plastic-Creep Structural Analysis
Authors: Kaufman A.
Published: October 2009

A simplified inelastic analysis computer program (ANSYMP) was developed for predicting the stress-strain history at the critical location of a thermomechanically cycled structure from an elastic solution. The program uses an iterative and incremental procedure to estimate the plastic strains from the material stress-strain properties and a plasticity hardening model. Creep effects can be calculated on the basis of stress relaxation at constant strain, creep at constant stress or a combination of stress relaxation and creep accumulation. The simplified method was exercised on a number of problems involving uniaxial and multiaxial loading, isothermal and nonisothermal conditions, dwell times at various points in the cycles, different materials, and kinematic hardening. Good agreement was found between these analytical results and nonlinear finite element solutions for these problems. The simplified analysis program used less than 1 percent of the CPU time required for a nonlinear finite element analysis.
SEM Investigations of Fatigue Crack Propagation in RR 58 Aluminum Alloy
Authors: Cameron D. W. , Jeal R. H. , Hoeppner D. W.
Published: October 2009

Aluminum alloy RR 58 (AA 2618) has been viewed during exposure to cyclic loading, which is applied using a load frame inserted into a scanning electron microscope. Thus observation of surface interactions of the material microstructure with a propagating crack is feasible. Photomicrographs and (for the purposes of analysis and presentation) dynamic, real-time video-recordings used to document the processes will be displayed and the nature of the observations presented in relation to existing physical understanding of fatigue. Some additional ideas will be included based on the results presented herein.
Computation of Nitric Oxide and Soot Emissions From Turbulent Diffusion Flames
Authors: Ahmad T. , Plee S. L. , Myers J. P.
Published: October 2009

An existing steady-state, locally homogeneous flow model of turbulent spray combustion was modified to predict NO emission from a spray flame and soot emission from a gas-jet flame. The effect of turbulent fluctuations on the reaction rates was accounted for. The predicted NO emission from an n-pentane spray with a changing injection velocity could be correlated with the convective time scale of the flow. Calculation of soot emission from a burning turbulent gas jet indicated that the centerline soot concentration reaches a peak upstream of the maximum temperature location and then decreases due to soot oxidation and dilution by air entrainment.
Airfoil Heat Transfer Calculation Using a Low Reynolds Number Version of a Two-Equation Turbulence Model
Authors: Wang J. H. , Jen H. F. , Hartel E. O.
Published: October 2009

A two-dimensional, boundary-layer program, STAN5, was modified to incorporate a low-Reynolds number version of the K-ε, two-equation turbulence model for the predictions of flow and heat transfer around turbine airfoils. The K-ε, two-equation model with optimized empirical correlations was used to account for the effects of free-stream turbulence and transitional flow. The model was compared with experimental flat plate data and then applied to turbine airfoil heat transfer prediction. A two-zone model was proposed for handling the turbulent kinetic energy and dissipation rate empirically at the airfoil leading edge region. The result showed that the predicted heat transfer coefficient on the airfoil agreed favorably with experimental data, especially for the pressure side. The discrepancy between predictions and experimental data of the suction surface normally occurred at transitional and fully turbulent flow regions.