bluuebunny/crossref_metadata_2025 huggingface dataset:
Recombinant human arginase inhibits the in vitro and in vivo proliferation of human melanoma by inducing cell cycle arrest and apoptosis
Authors: Lam Tin‐Lun , Wong Gabriel K. Y. , Chow Ho‐Yin , Chong Hiu‐Chi , Chow Tsz‐Lung , Kwok Sui‐Yi , Cheng Paul N. M. , Wheatley Denys N. , Lo Wai‐Hung , Leung Yun‐Chung
Published: October 2010

Melanoma has been shown to require arginine for growth, thus providing a potential Achilles’ heel for therapeutic exploitation. Our investigations show that arginine depletion, using arecombinant form ofhumanarginase I (rhArg), efficiently inhibits the growth of mammalian melanoma cell lines in vitro. These cell lines are consistently deficient in ornithine transcarbamylase (OTC) expression, correlating with their sensitivity to rhArg. Cell cycle distribution of A375 human melanoma cells treated with rhArg showed a remarkable dual‐phase cell cycle arrest in S and G2/M phases, in contrast to the G2/M single‐phase arrest observed with arginine deiminase (ADI), another arginine‐degrading enzyme. rhArg and ADI both induced substantial apoptosis in A375 cells, accompanied by global modulation of cell cycle‐ and apoptosis‐related transcription. Moreover, PEGylated rhArg dramatically inhibited the growth of A375 and B16 melanoma xenografts in vivo. Our results establish for the first time that (PEGylated) rhArg is a promising candidate for effective melanoma treatment, with fewer safety issues than ADI. Insight into the mechanism behind the antiproliferative activity of rhArg could inform us in designing combination therapies for future clinical trials.
Wnt/β‐catenin signaling is stimulated by α‐melanocyte‐stimulating hormone in melanoma and melanocyte cells: implication in cell differentiation
Authors: Bellei Barbara , Pitisci Angela , Catricalà Caterina , Larue Lionel , Picardo Mauro
Published: October 2010

Wnt/β‐catenin signaling plays important roles in many developmental processes including neural crest‐derived melanocyte development and migration. However, the effective contribution of Wnt/β‐catenin pathway in melanogenesis in adult human melanocytes has not been fully elucidated. Here, we report that in melanoma cells and in normal human melanocytes, melanogenesis stimulation by α‐melanocyte‐stimulating hormone (α‐MSH) induces phosphorylation of β‐catenin‐Ser675 and stabilization of β‐catenin protein. Activation of protein kinase A by α‐MSH attenuates glycogen synthase kinase‐3β, which regulates ubiquitin‐dependent degradation of β‐catenin, suggesting a coordinated mechanism of β‐catenin activity stimulation. Consistent with increased nuclear β‐catenin, cyclic adenosine monophosphate (cAMP) elevation facilitates β‐catenin‐dependent transactivation of many Wnt target genes. Moreover, chromatin immunoprecipitation assays demonstrated an increased association of β‐catenin with the proximal promoter of microphthalmia‐associated transcription factor, the master regulator of pigmentation. These results demonstrate the existence of cross talk between the cAMP and Wnt pathways in melanocytes, suggesting that β‐catenin could play a key role in the physiological regulation of epidermal melanogenesis.
Comparison of chemistry analytes between 2 portable, commercially available analyzers and a conventional laboratory analyzer in reptiles
Authors: McCain Stephanie L. , Flatland Bente , Schumacher Juergen P. , Clarke III Elsburgh O. , Fry Michael M.
Published: October 2010

Background:Advantages of handheld and small bench‐top biochemical analyzers include requirements for smaller sample volume and practicality for use in the field or in practices, but little has been published on the performance of these instruments compared with standard reference methods in analysis of reptilian blood.

Objective:The aim of this study was to compare reptilian blood biochemical values obtained using the Abaxis VetScan Classic bench‐top analyzer and a Heska i‐STAT handheld analyzer with values obtained using a Roche Hitachi 911 chemical analyzer.

Methods:Reptiles, including 14 bearded dragons (Pogona vitticeps), 4 blue‐tongued skinks (Tiliqua gigas), 8 Burmese star tortoises (Geochelone platynota), 10 Indian star tortoises (Geochelone elegans), 5 red‐tailed boas (Boa constrictor), and 5 Northern pine snakes (Pituophis melanoleucus melanoleucus), were manually restrained, and a single blood sample was obtained and divided for analysis. Results for concentrations of albumin, bile acids, calcium, glucose, phosphates, potassium, sodium, total protein, and uric acid and activities of aspartate aminotransferase and creatine kinase obtained from the VetScan Classic and Hitachi 911 were compared. Results for concentrations of chloride, glucose, potassium, and sodium obtained from the i‐STAT and Hitachi 911 were compared.

Results:Compared with results from the Hitachi 911, those from the VetScan Classic and i‐STAT had variable correlations, and constant or proportional bias was found for many analytes. Bile acid data could not be evaluated because results for 44 of 45 samples fell below the lower linearity limit of the VetScan Classic.

Conclusions:Although the 2 portable instruments might provide measurements with clinical utility, there were significant differences compared with the reference analyzer, and development of analyzer‐specific reference intervals is recommended.
Detection of biclonal gammopathy by capillary zone electrophoresis in a cat and a dog with plasma cell neoplasia
Authors: Facchini Roberto Vailati , Bertazzolo Walter , Zuliani Davide , Bonfanti Ugo , Caldin Marco , Avallone Giancarlo , Roccabianca Paola
Published: October 2010

Abstract:Gammopathies associated with plasma cell neoplasms in a 15‐year‐old female spayed domestic shorthaired cat and a 9‐year‐old female spayed Rottweiler dog were evaluated by serum protein electrophoresis. In the cat, the plasma cell neoplasm was found in the liver and spleen, and an evaluable sample of bone marrow was not obtained. Some of the plasma cells had the morphologic appearance of flame cells. The paraprotein was confirmed as IgG based on agar gel immunodiffusion precipitation and both immunocytochemical and immunohistochemical staining. The dog had multiple myeloma with production of IgG and IgA paraproteins. In both cases, serum proteins were evaluated by 2 methods of protein electrophoresis: cellulose acetate electrophoresis (CAE) and capillary zone electrophoresis (CZE). In the cat and the dog, CAE showed a single large oligoclonal‐like peak, which occurred in the γ‐region in the cat and the β‐γ‐region in the dog, whereas CZE showed a biclonal gammopathy with 2 very close narrow spikes in the γ‐ and β‐γ‐regions in the cat and dog, respectively. In selected cases, CZE may be more effective than routine CAE in distinguishing oligoclonal from monoclonal or biclonal paraproteinemia.
Paraneoplastic hypoglycemia in a diabetic dog with an insulin growth factor‐2–producing mammary carcinoma
Authors: Rossi Gabriele , Errico Giorgia , Perez Pierpaolo , Rossi Giacomo , Paltrinieri Saverio
Published: October 2010

Abstract:A 6‐year‐old intact female Labrador Retriever had diabetes mellitus, which had been difficult to control with insulin. The dog also had a solid ductal mammary carcinoma with very rapid growth, which was temporally related to onset of hypoglycemia. Eight months after initial diagnosis of diabetes, the dog had a hypoglycemic crisis. Insulin administration was stopped and serum glucose concentration returned to normal. Three months after discontinuing insulin, another hypoglycemic crisis occurred. During subsequent months, serum glucose concentrations remained at life‐threatening levels (1.64–2.12 mmol/L, reference interval 4.44–6.66 mmol/L) simultaneously with an increase in the size of the mammary tumor, which reached a diameter of about 16 cm. At the time of surgery for removal of the tumor serum glucose concentration was 2.20 mmol/L and was then monitored every 3 hours after excision of the tumor. The glucose concentration continued to rise and reached 9.99 mmol/L 12 hours after the removal of the mammary tumor. Immunohistochemical staining demonstrated expression of insulin growth factor‐2 by tumor cells, which apparently had caused the hypoglycemia during tumor growth even in a diabetic dog. Hyperglycemia associated with diabetes was pronounced after excision of the tumor and had been masked by the paraneoplastic effect of the tumor.
Prevalence of dog erythrocyte antigens in retired racing Greyhounds
Authors: Iazbik Maria Cristina , O'Donnell Margee , Marin Liliana , Zaldivar Sara , Hudson Dawn , Couto C. Guillermo
Published: October 2010

Background:Blood groups in dogs are designated as dog erythrocyte antigen (DEA) 1.1, 1.2, 3, 4, 5, 7, andDal. There is limited information about the frequency of different antigens in Greyhound dogs, despite their frequent use as blood donors.

Objectives:The aims of this study were to determine the frequencies of DEA 1.1, 1.2, 3, 4, 5, and 7 in Greyhounds, to compare the frequencies with those of non‐Greyhound dogs, and to evaluate the presence of naturally occurring anti‐DEA antibodies.

Methods:Blood was collected from 206 Greyhound and 66 non‐Greyhound dogs being screened as potential blood donors. Blood‐typing was performed at Animal Blood Resources International by tube agglutination utilizing polyclonal anti‐DEA antibodies.

Results:Of the Greyhound dogs, 27/206 (13.1%) were positive for DEA 1.1, and this frequency was significantly lower (P<.0001) than for non‐Greyhound dogs of which 40/66 (60.6%) were DEA 1.1‐positive. The frequency of positivity for both DEA 1.1 and 1.2 was also lower in Greyhounds (P<.0001). There were no significant differences between Greyhounds and non‐Greyhounds for DEA 1.2, 3, 4, 5, or 7. All 137 dogs (113 Greyhounds and 24 non‐Greyhounds) that were evaluated for naturally occurring anti‐DEA antibodies in serum were negative. A higher percentage of Greyhound dogs (57.3%, 118/206) were considered “universal donors” (negative for all DEAs except DEA 4) compared with non‐Greyhound dogs (28%, 13/46).

Conclusion:The frequency of positivity for DEA 1.1 in our population of Greyhounds was significantly lower than previously reported for dogs. Furthermore, a large majority of Greyhounds met the criteria for universal donors.
Effects of physical and chemical immobilization on hematologic and biochemical variables in captive brown brocket deer (Mazama gouazoubira)
Authors: Munerato Marina Salles , Duarte José Maurício Barbanti , Pereira Gener Tadeu , Marques José Antônio
Published: October 2010

Background: Alterations in cellular and chemical constituents in blood are indicators of physical or chemical restraint in deer.

Objectives: The aim of this study was to determine the effects of physical and chemical restraint on hematologic and biochemical analytes in captive brown brocket deer (Mazama gouazoubira).

Methods: Six adult deer were physically restrained and randomly anesthetized in a crossover design using 3 protocols (P). In P1, anesthesia was induced directly with isoflurane using a face mask and was maintained with isoflurane delivered by endotracheal tube. In P2, oral premedication with midazolam was followed 1 hour later by induction and maintenance of anesthesia with isoflurane, as in P1. In P3, intravenous anesthesia with a combination of ketamine, xylazine, and atropine was followed by anesthesia with isoflurane, as in P1. Blood was collected immediately after physical restraint (T0) and during anesthesia at 20‐minute intervals (T15, T35, and T55). Hematologic and biochemical constituents were determined using manual methods or automated analyzers, with cortisol measured by enzyme immunoassay.

Results: During physical restraint, following food and water restriction, significant hemoconcentration, increased WBC count, and lower cortisol concentration were observed compared with results at T15, T35, and T55. During anesthesia, lymphocyte count was lower in P2 than P1, urea concentration was decreased at T15 using P2, and plasma glucose concentration was increased after T0 (P<.01). Among the anesthetic protocols, there was a trend for decreased cortisol concentration using P2.

Conclusions: Physical restraint and anesthesia affect some blood constituents in captive brown brocket deer, and midazolam premedication may modify the intensity of the stress response.
SIMULATIONS TO INVESTIGATE ANIMAL MOVEMENT EFFECTS ON POPULATION DYNAMICS
Authors: DUFFY KEVIN J.
Published: October 2010

Abstract Movement of organisms will influence their ecology and demographics. Animal movements are often characterized by path structures with directional persistence. The extent to which this impacts on population dynamics is investigated in this paper using theoretical simulations. The effects of different movement strategies on variations in visits to individual patches across a forage area are discussed. Variations in resource biomass across patches are shown to persist after long simulations. Consumer resource equations with movement are used to show how heterogeneity in resources caused by these variations can affect global population dynamics. With directional movements (random or persistent), dynamics change from limit cycles to stable equilibrium solutions. It is suggested that this effect has the potential to increase survival because perturbations from unforeseen factors (like drought) are less likely to crash populations.
In vitro study of biofilm formation and effectiveness of antimicrobial treatment on various dental material surfaces
Authors: Li L. , Finnegan M.B. , Özkan S. , Kim Y. , Lillehoj P.B. , Ho C.‐M. , Lux R. , Mito R. , Loewy Z. , Shi W.
Published: October 2010

Elevated proportions of Candida albicans in biofilms formed on dentures are associated with stomatitis whereas Streptococcus mutans accumulation on restorative materials can cause secondary caries. Candida albicans, S. mutans, saliva‐derived and C. albicans/saliva‐derived mixed biofilms were grown on different materials including acrylic denture, porcelain, hydroxyapatite (HA), and polystyrene. The resulting biomass was analysed by three‐dimensional image quantification and assessment of colony‐forming units. The efficacy of biofilm treatment with a dissolved denture cleansing tablet (Polident®) was also evaluated by colony counting. Biofilms formed on HA exhibited the most striking differences in biomass accumulation: biofilms comprising salivary bacteria accrued the highest total biomass whereas C. albicans biofilm formation was greatly reduced on the HA surface compared with other materials, including the acrylic denture surface. These results substantiate clinical findings that acrylic dentures can comprise a reservoir for C. albicans, which renders patients more susceptible to C. albicans infections and stomatitis. Additionally, treatment efficacy of the same type of biofilms varied significantly depending on the surface. Although single‐species biofilms formed on polystyrene surfaces exhibited the highest susceptibility to the treatment, the most surviving cells were recovered from HA surfaces for all types of biofilms tested. This study demonstrates that the nature of a surface influences biofilm characteristics including biomass accumulation and susceptibility to antimicrobial treatments. Such treatments should therefore be evaluated on the surfaces colonized by the target pathogen(s).
Community and gene composition of a human dental plaque microbiota obtained by metagenomic sequencing
Authors: Xie G. , Chain P.S.G. , Lo C.‐C. , Liu K.‐L. , Gans J. , Merritt J. , Qi F.
Published: October 2010

Human dental plaque is a complex microbial community containing an estimated 700 to 19,000 species/phylotypes. Despite numerous studies analysing species richness in healthy and diseased human subjects, the true genomic composition of the human dental plaque microbiota remains unknown. Here we report a metagenomic analysis of a healthy human plaque sample using a combination of second‐generation sequencing platforms. A total of 860 million base pairs of non‐human sequences were generated. Various analysis tools revealed the presence of 12 well‐characterized phyla, members of the TM‐7 and BRC1 clade, and sequences that could not be classified. Both pathogens and opportunistic pathogens were identified, supporting the ecological plaque hypothesis for oral diseases. Mapping the metagenomic reads to sequenced reference genomes demonstrated that 4% of the reads could be assigned to the sequenced species. Preliminary annotation identified genes belonging to all known functional categories. Interestingly, although 73% of the total assembled contig sequences were predicted to code for proteins, only 51% of them could be assigned a functional role. Furthermore, ∼ 2.8% of the total predicted genes coded for proteins involved in resistance to antibiotics and toxic compounds, suggesting that the oral cavity is an important reservoir for antimicrobial resistance.
Deletion of competence‐induced genes over‐expressed in biofilms caused transformation deficiencies in Streptococcus mutans
Authors: Eaton R.E. , Jacques N.A.
Published: October 2010

Previous studies identified nine genes with increased expression in Streptococcus mutans biofilms of which six possessed putative ComX promoter sequences and were homologous to competence‐induced genes in Streptococcus pneumoniae, Streptococcus gordonii and Bacillus subtilis. As competence increases in biofilms, a study was undertaken into the roles that these biofilm‐induced genes might play in transformation. Only five of the nine gene deletions had a significant effect on transformation efficiency. Deletion of the genes for recombinase A, recA, DNA processing protein, dprA and single‐stranded DNA‐binding protein, ssbA, produced results comparable with those from other bacteria, supporting the contention that these proteins have similar functions in S. mutans competence. The uncharacterized genes SMU.769 and SMU.836 produced results in variance to deletion mutants of putative homologues in S. pneumoniae. Deletion of SMU.769 reduced chromosomal transformation 2.3‐fold. SMU.769 belongs to a family of conserved genes induced by the competence‐stimulating peptide and which have no established function. In contrast, deletion of SMU.836 reduced transformation of both plasmid and chromosomal DNA to <3%. Homology searches suggested that Smu.836 belongs to a family of competence‐induced peptidoglycan hydrolases with a conserved enzyme domain and a species‐variable cell‐binding domain for which the best characterized member is the choline‐binding protein D, CbpD, of S. pneumoniae.
Activity of antimicrobial peptide mimetics in the oral cavity: I. Activity against biofilms of Candida albicans
Authors: Hua J. , Yamarthy R. , Felsenstein S. , Scott R.W. , Markowitz K. , Diamond G.
Published: October 2010

Naturally occurring antimicrobial peptides hold promise as therapeutic agents against oral pathogens such as Candida albicans but numerous difficulties have slowed their development. Synthetic, non‐peptidic analogs that mimic the properties of these peptides have many advantages and exhibit potent, selective antimicrobial activity. Several series of mimetics (with molecular weight < 1000) were developed and screened against oral Candida strains as a proof‐of‐principle for their antifungal properties. One phenylalkyne and several arylamide compounds with reduced mammalian cytotoxicities were found to be active against C. albicans. These compounds demonstrated rapid fungicidal activity in liquid culture even in the presence of saliva, and demonstrated synergy with standard antifungal agents. When assayed against biofilms grown on denture acrylic, the compounds exhibited potent fungicidal activity as measured by metabolic and fluorescent viability assays. Repeated passages in sub‐minimum inhibitory concentration levels did not lead to resistant Candida, in contrast to fluconazole. Our results demonstrate the proof‐of principle for the use of these compounds as anti‐Candida agents, and their further testing is warranted as novel anti‐Candida therapies.
Activity of antimicrobial peptide mimetics in the oral cavity: II. Activity against periopathogenic biofilms and anti‐inflammatory activity
Authors: Hua J. , Scott R.W. , Diamond G.
Published: October 2010

Whereas periodontal disease is ultimately of bacterial etiology, from multispecies biofilms of gram‐negative anaerobic microorganisms, much of the deleterious effects are caused by the resultant epithelial inflammatory response. Hence, development of a treatment that combines anti‐biofilm antibiotic activity with anti‐inflammatory activity would be of great utility. Antimicrobial peptides (AMPs) such as defensins are naturally occurring peptides that exhibit broad‐spectrum activity as well as a variety of immunomodulatory activities. Furthermore, bacteria do not readily develop resistance to these agents. However, clinical studies have suggested that they do not represent optimal candidates for exogenous therapeutic agents. Small‐molecule mimetics of these AMPs exhibit similar activities to the parent peptides, in addition to having low toxicity, high stability and low cost. To determine whether AMP mimetics have the potential for treatment of periodontal disease, we examined the activity of one mimetic, mPE, against biofilm cultures of Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis. Metabolic assays as well as culture and biomass measurement assays demonstrated that mPE exhibits potent activity against biofilm cultures of both species. Furthermore, as little as 2 μg ml−1 mPE was sufficient to inhibit interleukin‐1β‐induced secretion of interleukin‐8 in both gingival epithelial cells and THP‐1 cells. This anti‐inflammatory activity is associated with a reduction in activation of nuclear factor‐κB, suggesting that mPE can act both as an anti‐biofilm agent in an anaerobic environment and as an anti‐inflammatory agent in infected tissues.
Green and Red Er3+ Photoluminescence Behavior in Various Fluoride Glasses
Authors: Herrmann Andreas , Ehrt Doris
Published: October 2010

Two pure fluoride and three fluoride phosphate glasses with known properties and global structure have been doped with Er3+ (4f11) in a concentration range between 1019 and 1021 Er3+ cm−3. A typical fluorozirconate (ZBLAN) and a typical fluoroaluminate glass (FP00) were compared. The effect of P2O5 addition in fluoroaluminate glasses was investigated with varying phosphate content between 0 and 20 mol% (FPx). Important physical properties were determined to characterize the glass samples. The static and dynamic luminescence behavior of the green (4S3/2→4I15/2) and red (4F9/2→4I15/2) emission have been studied by ultraviolet and visible excitation. The pure fluoroaluminate and fluorozirconate glass samples provide very high green luminescence emission intensity and long lifetime (about 600 μs) due to surrounding fluorine ligands. It is known that adding phosphate to the fluoroaluminate glass increases the glass‐forming ability but it decreases the luminescence intensity and lifetime drastically due to more oxygen ligands and higher electron–phonon coupling. The red emission has much lower intensity. Strong luminescence quenching could be found for all types of glass samples with an increasing Er3+ concentration. The glass samples investigated are very useful for applications as special photonic equipments.
Laser‐Induced Periodic Surface Crystalline Patterns on SrO–0.5Li2O–4.5B2O3 and BaO–0.5Na2O–4.5B2O3 Glasses and Optical Second Harmonic Generation
Authors: Vaish Rahul , Rodriguez Vincent , Maglione Mario , Etourneau Jean , Varma Kalidhindi B. R.
Published: October 2010

Transparent SrO–0.5Li2O–4.5B2O3 (SLBO) and BaO–0.5Na2O–4.5B2O3 (BNBO) glasses were fabricated via the conventional melt‐quenching technique. The amorphous and glassy characteristics of the as‐quenched samples were respectively confirmed by X‐ray powder diffraction and differential thermal analysis studies. Optically clear SLBO and BNBO glass nano/microcrystal composites were obtained by heat treating the as‐quenched glasses slightly above their respective glass transition temperatures. These glass nano/microcrystal composites exhibited second harmonic signals in transmission mode when exposed to infrared laser beam at λ=1064 nm. Interestingly, second harmonic waves were found to undergo optical diffraction and was attributed to the presence of self‐organized microcrystalline patterns associated with 0.5–2 μm periodicities.
Effect of Creep on the Residual Stresses in Tube-to-Tubesheet Joints
Authors: Laghzale Nor Eddine , Bouzid Abdel-Hakim
Published: October 2010

Steam generators are the subject of major concern in nuclear power plant safety. Within these generators, the tightness barrier, which separates the primary and secondary circuits, is ensured by the existence of a residual contact pressure at the tube-to-tubesheet joint interface. Any leakage is unacceptable, and its consequences are very heavy in terms of the human and environmental safety as well as maintenance cost. Some studies have been conducted to understand the main reasons for such failure. However, no analytical model able to predict the attenuation of the residual contact pressure under the effect of material creep relaxation behavior. The development of a simple analytical model able to predict the change in the residual contact pressure as a function of time is laid out in this paper. The results from the analytical model are checked and compared with those of finite elements. A simulation conducted on a high temperature tube-to-tubesheet joint has shown that relaxation of the contact stress due to creep can be significant and should be considered in the design.
Thermal Aspects of Uranium Carbide and Uranium Dicarbide Fuels in Supercritical Water-Cooled Nuclear Reactors
Authors: Grande Lisa , Villamere Bryan , Allison Leyland , Mikhael Sally , Rodriguez-Prado Adrianexy , Pioro Igor
Published: October 2010

Supercritical water-cooled nuclear reactors (SCWRs) are a Generation IV reactor concept. SCWRs will use a light-water coolant at operating parameters set above the critical point of water (22.1 MPa and 374°C). One reason for moving from current Nuclear Power Plant (NPP) designs to SCW NPP designs is to increase the thermal efficiency. The thermal efficiency of existing NPPs is between 30% and 35% compared with 45% and 50% of supercritical water (SCW) NPPs. Another benefit of SCWRs is the use of a simplified flow circuit, in which steam generators, steam dryers, steam separators, etc. can be eliminated. Canada is in the process of conceptualizing a pressure tube (PT) type SCWR. This concept refers to a 1200-MWel PT-type reactor. Coolant operating parameters are as follows: a pressure of 25 MPa, a channel inlet temperature of 350°C, and an outlet temperature of 625°C. The sheath material and nuclear fuel must be able to withstand these extreme conditions. In general, the primary choice for the sheath is a zirconium alloy and the fuel is an enriched uranium dioxide (UO2). The sheath-temperature design limit is 850°C, and the industry accepted limit for the fuel centerline temperature is 1850°C. Previous studies have shown that the maximum fuel centerline temperature of a UO2 pellet might exceed this industry accepted limit at SCWR conditions. Therefore, alternative fuels with higher thermal conductivities need to be investigated for SCWR use. Uranium carbide (UC), uranium nitride (UN), and uranium dicarbide (UC2) are excellent fuel choices as they all have higher thermal conductivities compared with conventional nuclear fuels such as UO2, mixed oxides (MOX), and thoria (ThO2). Inconel-600 has been selected as the sheath material due its high corrosion resistance and high yield strength in aggressive supercritical water (SCW) at high-temperatures. This paper presents the thermalhydraulics calculations of a generic PT-type SCWR fuel channel with a 43-element Inconel-600 bundle with UC and UC2 fuels. The bulk-fluid, sheath and fuel centerline temperature profiles, together with a heat transfer coefficient profile, were calculated for a generic PT-type SCWR fuel-bundle string. Fuel bundles with UC and UC2 fuels with various axial heat flux profiles (AHFPs) are acceptable since they do not exceed the sheath-temperature design limit of 850°C, and the industry accepted limit for the fuel centerline temperature of 1850°C. The most desirable case in terms of the lowest fuel centerline temperature is the UC fuel with the upstream-skewed cosine AHFP. In this case, the fuel centerline temperature does not exceed even the sheath-temperature design limit of 850°C.
Heavy-Section Steel Technology and Irradiation Programs—Retrospective and Prospective Views
Authors: Nanstad Randy K. , Bass B. Richard , Merkle John G. , Pugh Claud E. , Rosseel Thomas M. , Sokolov Mikhail A.
Published: October 2010

In 1965, the Atomic Energy Commission, at the advice of the Advisory Committee on Reactor Safeguards, initiated the process that resulted in the establishment of the Heavy Section Steel Technology (HSST) program at Oak Ridge National Laboratory. In 1989, the Heavy-Section Steel Irradiation (HSSI) program, formerly the HSST task on irradiation effects, was formed as a separate program, and in 2007, the HSST/HSSI programs, sponsored by the U.S. Nuclear Regulatory Commission (USNRC), celebrated 40 years of continuous research oriented toward the safety of light-water nuclear reactor pressure vessels (RPVs). This paper presents a summary of results from those programs with a view to future activities. The HSST program was established in 1967 and initially included extensive investigations of heavy-section low-alloy steel plates, forgings, and welds, including metallurgical studies, mechanical properties, fracture toughness (quasi-static and dynamic), fatigue crack-growth, and crack-arrest toughness. Also included were irradiation effects studies, thermal shock analyses, testing of thick-section tensile and fracture specimens, and nondestructive testing. In the subsequent decades, the HSST Program conducted extensive large-scale experiments with intermediate-size vessels (with varying size flaws) pressurized to failure, similar experiments under conditions of thermal shock and even pressurized thermal shock (PTS), wide-plate crack-arrest tests, and biaxial tests with cruciform-shaped specimens. Extensive analytical and numerical studies accompanied these experiments, including the development of computer codes such as the recent Fracture Analysis of Vessels Oak Ridge code currently being used for PTS evaluations. In the absence of radiation damage to the RPVs, fracture of the vessel is improbable. However, it was recognized that exposure to high energy neutrons can result in embrittlement of radiation-sensitive RPV materials. The HSSI Program conducted a series of experiments to assess the effects of neutron irradiation on RPV material behavior, especially fracture toughness. These studies included RPV plates and welds, varying chemical compositions, and fracture toughness specimens up to 101.6 mm (4 in.) thickness. The results of these investigations, in conjunction with results from commercial reactor surveillance programs, are used to develop a methodology for the prediction of radiation effects on RPV materials. Results from the HSST and HSSI programs are used by the USNRC in the evaluation of RPV integrity and regulation of overall nuclear plant safety.
A New Method for Stress Categorization on Planes
Authors: Godbole P. B. , Pore Supak
Published: October 2010

A new method employing the fitting of a least squares plane to stress distribution obtained from a finite element analysis for evaluating categorized values is presented. The property of a least squares fit, i.e., the preservation of volume under stress distribution and the plane of consideration, is used in evaluating various numerical integrals. The procedure is demonstrated through application to a typical shell nozzle junction.
Analytical Modeling of Flat Face Flanges With Metal-to-Metal Contact Beyond the Bolt Circle
Authors: Galai Hichem , Bouzid Abdel-Hakim
Published: October 2010

Design rules for flat face flanges with metal-to-metal contact beyond the bolt circle are covered by Appendix Y of the American Society of Mechanical Engineers Code. These design rules are based on Schneider’s work (1968, “Flat Faces Flanges With Metal-to-Metal Contact Beyond the Bolt Circle,” ASME J. Eng. Power, 90(1), pp. 82–88). The prediction of tightness of these bolted joints relies very much on the level of precision of the self-sealing gasket compression during operation. The evaluation of this compression requires a rigorous flexibility analysis of the joint including bolt-flange elastic interaction. This paper analyses flange separation and the bolt load change in flat face bolted joints. It proposes two different analytical approaches capable of predicting flange rotation and bolt load change during operation. The first method is based on the beam theory applied to a continuous flange sector. This approach is an improvement of the discrete beam theory used in the Schneider model. The second method is based on the circular plate theory and is developed for the purpose of a more accurate assessment of the load changes. As in the Taylor Forge method, this approach is, in general, better suited than the beam theory for flat face flanges, in particular when the flange width is small. The proposed models are compared with the discrete beam theory and validated using numerical finite element analysis on different flange sizes.
Prediction of Collapse Stress for Pipes With Arbitrary Multiple Circumferential Surface Flaws
Authors: Li Yinsheng , Hasegawa Kunio , Onizawa Kunio , Cofie Nathaniel G.
Published: October 2010

When a flaw is detected in a stainless steel piping system of a nuclear power plant during in-service inspection, the limit load estimation method provided in codes such as ASME Section XI or JSME S NA-1-2008 can be applied to evaluate the integrity of the pipe. However, in the current editions of these codes, a limit load estimation method is only provided for pipes containing a single flaw. Independent multiple flaws, such as stress corrosion cracks, have actually been detected in the same plane of stainless steel piping systems. In this paper, a failure estimation method by formula is proposed for any number and arbitrary distribution of multiple independent circumferential flaws in the same plane of a pipe. Using the proposed method, numerical solutions are compared with experimental results to validate the model, and several numerical examples are provided to show its effectiveness.
A Novel Scheme for Computing Gun Barrel Temperature History and Its Experimental Validation
Authors: Mishra Avanish , Hameed Amer , Lawton Bryan
Published: October 2010

An accurate modeling of gun barrel temperature variation over time is important to assess wear and the number of shot fires needed to reach cook-off. Using lumped parameter methods, an internal ballistics code was developed to compute heat transfer to the gun barrel for given ammunition parameters. Subsequently the finite element method was employed to model gun barrel temperature history (temperature variation over time). Simulations were performed for a burst of nine shots and the results were found to match satisfactorily to the corresponding experimental measurements. Wear or erosion of the barrel during a gun fire is very sensitive toward the maximum bore surface temperature. The proposed scheme can accurately simulate gun barrel temperature history; hence improved wear calculations can be made with it. An important and unique advantage of the developed scheme is that it easily couples internal ballistics simulations with the finite element methods.
Microstructure and Mechanical Properties of G17CrMoV5-10 Cast Steel After Regenerative Heat Treatment
Authors: Golański Grzegorz
Published: October 2010

This paper presents the results of a research on the influence of regenerative heat treatment on microstructure and properties of a cast steel after long-term operation at the elevated temperature. The material under investigation was G17CrMoV5-10 cast steel taken out (in the form of a section) from an internal frame of steam turbine serviced for about 250,000 h. Performed research has proven that through the microstructure degradation long-term service contributes to an embrittlement and decrease in yield strength and tensile strength. The heat treatment, however, contributes to an impact energy increase regardless of the applied parameters (cooling rate). It has also been established that the optimum combination of strength properties and impact energy is ensured by the microstructure of high tempered bainite, whereas low strength properties and impact energy were obtained for the microstructure, which was slowly cooled from the austenitizing temperature, i.e., the ferritic-bainitic-ferritic microstructure.
Vibration Diagnosis Featuring Blade-Shaft Coupling Effect of Turbine Rotor Models
Authors: Anegawa Norihisa , Fujiwara Hiroyuki , Matsushita Osami
Published: October 2010

As is well known, zero and one nodal diameter (k=0 and k=1) modes of a blade system interact with the shaft system. The former couples with torsional and/or axial shaft vibrations, and the latter with bending shaft vibrations. This paper addresses the latter. With respect to k=1 modes, we discuss, from experimental and theoretical viewpoints, in-plane blades and out-of-plane blades attached radially to a rotating shaft. We found that when we excited the shaft at the rotational speed of Ω=|ωb−ωs| (where ωb is the blade natural frequency, ωs the shaft natural frequency, and Ω is the rotational speed), the exciting frequency ν=ωs induced shaft-blade coupling resonance. In addition, in the case of the in-plane blade system, we encountered an additional resonance attributed to deformation caused by gravity. In the case of the out-of-plane blade system, we experienced two types of abnormal vibrations. One is the additional resonance generated at Ω=ωb/2 due to the unbalanced shaft and the anisotropy of bearing stiffness. The other is a flow-induced, self-excited vibration caused by galloping due to the cross-sectional shape of the blade tip because this instability disappeared in the rotation test inside a vacuum chamber. The two types of abnormal vibrations occurred at the same time, and both led to the entrainment phenomenon, as identified by our own frequency analysis technique.
A New Analysis Tool Assessment for Rotordynamic Modeling of Gas Foil Bearings
Authors: Howard Samuel A. , San Andrés Luis
Published: October 2010

Gas foil bearings offer several advantages over traditional bearing types that make them attractive for use in high-speed turbomachinery. They can operate at very high temperatures, require no lubrication supply (oil pumps, seals, etc.), exhibit very long life with no maintenance, and once operating airborne, have very low power loss. The use of gas foil bearings in high-speed turbomachinery has been accelerating in recent years although the pace has been slow. One of the contributing factors to the slow growth has been a lack of analysis tools, benchmarked to measurements, to predict gas foil bearing behavior in rotating machinery. To address this shortcoming, NASA Glenn Research Center (GRC) has supported the development of analytical tools to predict gas foil bearing performance. One of the codes has the capability to predict rotordynamic coefficients, power loss, film thickness, structural deformation, and more. The current paper presents an assessment of the predictive capability of the code named XLGFBTH©. A test rig at GRC is used as a simulated case study to compare rotordynamic analysis using output from the code to actual rotor response as measured in the test rig. The test rig rotor is supported on two gas foil journal bearings manufactured at GRC with all pertinent geometry disclosed. The resulting comparison shows that the rotordynamic coefficients calculated using XLGFBTH© represent the dynamics of the system reasonably well especially as they pertain to predicting critical speeds.
Experimental Investigation of the Nonlinear Response of Swirl-Stabilized Flames to Equivalence Ratio Oscillations
Authors: Kim Kyu Tae , Lee Jong Guen , Quay Bryan D. , Santavicca Domenic
Published: October 2010

The nonlinear response of a swirl-stabilized flame to equivalence ratio oscillations was experimentally investigated in an atmospheric-pressure, high-temperature, lean-premixed model gas turbine combustor. To generate high-amplitude equivalence ratio oscillations, fuel was modulated using a siren-type modulating device. The mixture ratio oscillations at the inlet of the combustion chamber were measured by the infrared absorption technique, and the flame’s response, i.e., the fluctuation in the flame’s rate of heat release, was estimated by CH∗ chemiluminescence emission intensity. Phase-resolved CH∗ chemiluminescence images were taken to characterize the dynamic response of the flame. Results show that the amplitude and frequency dependence of the flame’s response to equivalence ratio oscillations is qualitatively consistent with the flame’s response to inlet velocity oscillations. The underlying physics of the nonlinear response of the flame to equivalence ratio oscillations, however, is associated with the intrinsically nonlinear dependence of the heat of reaction and burning velocity on the equivalence ratio. It was found that combustion cannot be sustained under conditions of high-amplitude equivalence ratio oscillations. Lean blowoff occurs when the normalized amplitude of the equivalence ratio oscillation exceeds a threshold value. The threshold value is dependent on the mean equivalence ratio and modulation frequency.
Investigation of Auto-Ignition of a Pulsed Methane Jet in Vitiated Air Using High-Speed Imaging Techniques
Authors: Meier W. , Boxx I. , Arndt C. , Gamba M. , Clemens N.
Published: October 2010

An experimental arrangement for the investigation of auto-ignition of a pulsed CH4 jet in a coflow of hot exhaust gas from a laminar lean premixed H2/air flame at atmospheric pressure is presented. The ignition events were captured by high-speed imaging of the OH∗ chemiluminescence associated with the igniting flame kernels at a frame rate of 5 kHz. The flow-field characteristics were determined by high-speed particle image velocimetry and Schlieren images. Furthermore, high-speed imaging of laser-induced fluorescence of OH was applied to visualize the exhaust gas flow and the ignition events. Auto-ignition was observed to occur at the periphery of the CH4 jet with high reproducibility in different runs concerning time and location. In each measurement run, several hundred consecutive single shot images were recorded from which sample images are presented. The main goals of the study are the presentation of the experimental arrangement and the high-speed measuring systems and a characterization of the auto-ignition events occurring in this system.
Computational Modeling of Turbulent Mixing of a Transverse Jet
Authors: Ivanova Elizaveta M. , Noll Berthold E. , Aigner Manfred
Published: October 2010

This paper presents numerical simulations of turbulent mixing of a jet in crossflow. The test case is chosen to resemble scalar mixing processes in the premixing zones of gas turbine combustion chambers. Steady and unsteady simulations employing three different computational approaches are presented: steady Reynolds-averaged Navier–Stokes, unsteady Reynolds-averaged Navier–Stokes, and scale-adaptive simulations. Presented results comprise the (time-averaged) profiles of flow velocities, turbulent kinetic energy of the flow, Reynolds stresses, passive scalar distribution, turbulent scalar fluxes, and the turbulent variance of the passive scalar. All presented results are directly validated against experimental data. Additionally, two parameter studies are presented. Both studies are related to the accuracy of the turbulent scalar mixing predictions for all used simulation methods. In the first study, the dependence of the scalar mixing predictions on the value of the turbulent Schmidt number is considered. In the second study, the dependence of the predicted turbulent scalar variance on the used modeling approach is analyzed.
Numerical and Experimental Analysis of the Temperature Distribution in a Hydrogen Fuelled Combustor for a 10 MW Gas Turbine
Authors: Masi Massimo , Gobbato Paolo , Toffolo Andrea , Lazzaretto Andrea , Cocchi Stefano
Published: October 2010

Proper cooling of the hot components and an optimal temperature distribution at the turbine inlet are fundamental targets for gas turbine combustors. In particular, the temperature distribution at the combustor discharge is a critical issue for the durability of the turbine blades and the high performance of the engine. At present, CFD is a widely used tool to simulate the reacting flow inside gas turbine combustors. This paper presents a numerical analysis of a single can type combustor designed to be fed both with hydrogen and natural gas. The combustor also features a steam injection system to restrain the NOx pollutants. The simulations were carried out to quantify the effect of fuel type and steam injection on the temperature field. The CFD model employs a computationally low cost approach, thus the physical domain is meshed with a coarse grid. A full-scale test campaign was performed on the combustor: temperatures at the liner wall and the combustor outlet were acquired at different operating conditions. These experimental data, which are discussed, were used to evaluate the capability of the present CFD model to predict temperature values for combustor operation with different fuels and steam to fuel ratios.
Numerical Study of Aerodynamic Losses of Effusion Cooling Holes in Aero-Engine Combustor Liners
Authors: Andreini A. , Bonini A. , Caciolli G. , Facchini B. , Taddei S.
Published: October 2010

Due to the stringent cooling requirements of novel aero-engines combustor liners, a comprehensive understanding of the phenomena concerning the interaction of hot gases with typical coolant jets plays a major role in the design of efficient cooling systems. In this work, an aerodynamic analysis of the effusion cooling system of an aero-engine combustor liner was performed; the aim was the definition of a correlation for the discharge coefficient (CD) of the single effusion hole. The data were taken from a set of CFD RANS (Reynolds-averaged Navier-Stokes) simulations, in which the behavior of the effusion cooling system was investigated over a wide range of thermo/fluid-dynamics conditions. In some of these tests, the influence on the effusion flow of an additional air bleeding port was taken into account, making it possible to analyze its effects on effusion holes CD. An in depth analysis of the numerical data set has pointed out the opportunity of an efficient reduction through the ratio of the annulus and the hole Reynolds numbers: The dependence of the discharge coefficients from this parameter is roughly linear. The correlation was included in an in-house one-dimensional thermo/fluid network solver, and its results were compared with CFD data. An overall good agreement of pressure and mass flow rate distributions was observed. The main source of inaccuracy was observed in the case of relevant air bleed mass flow rates due to the inherent three-dimensional behavior of the flow close to bleed opening. An additional comparison with experimental data was performed in order to improve the confidence in the accuracy of the correlation: Within the validity range of pressure ratios in which the correlation is defined (>1.02), this comparison pointed out a good reliability in the prediction of discharge coefficients. An approach to model air bleeding was then proposed, with the assessment of its impact on liner wall temperature prediction.