bluuebunny/crossref_metadata_2025 huggingface dataset:
The absence of an identifiable single catalytic base residue in Thermobifida fusca exocellulase Cel6B
Authors: Vuong Thu V. , Wilson David B.
Published: June 2009

Thermobifida fusca exocellulase Cel6B acts by an inverting hydrolysis mechanism; however, the catalytic acid and base residues for this enzyme have not been confirmed. Site‐directed mutagenesis and kinetic studies were used to show that Asp274 is the catalytic acid, which is consistent with what is found for other members of family‐6 glycoside hydrolases; however, a single catalytic base was not identified. Mutation of all putative catalytic base residues, within 6 Å of the −1/+1 glucose subsites, including the highly conserved Asp226, Asp497 and Glu495, as well as Ser232 and Tyr220, did not reveal a catalytic base, although these residues are all important for activity. We propose a novel hydrolysis mechanism for T. fusca Cel6B involving a proton‐transferring network to carry out the catalytic base function.
Investigating pressure bandaging for snakebite in a simulated setting: Bandage type, training and the effect of transport
Authors: Canale Elizabeth , Isbister Geoffrey K , Currie Bart J
Published: June 2009

Background:  The clinical evidence base for the use of pressure bandaging in snakebite is limited. We aimed to investigate if pressure bandages (PB) generated and maintained presumptive optimal pressures in a simulated setting.

Methods:  A total of 96 subjects were recruited, 78 health professionals and 18 from the general public. Participants were asked to apply PB with crepe and with an elasticized bandage without instruction. A paediatric blood pressure cuff attached to a pressure transducer was used to measure the pressure generated. PB application with elasticized bandages was repeated by 36 participants (18 general public and 18 health professionals) with feedback on pressures attained, and reassessment on the sixth subsequent attempt. Pressure was also measured under correctly applied bandages during an ambulance ride.

Results:  The median pressure generated under crepe bandages was 28 mmHg (interquartile range [IQR]: 17–42 mmHg) compared with 47 mmHg (IQR 26–83 mmHg) with elasticized bandages, with most subgroups applying the elasticized bandage closer to the estimated optimal pressure (55–70 mmHg). Following training, the median pressure for the 36 participants was 65 mmHg (IQR 56–71 mmHg), closer to the optimal range than initial attempts. On initial bandaging, 5/36 (14%) participants achieved optimal pressure range with elasticized bandages, compared with 18/36 (50%) after training (P = 0.002). Crepe bandages initially correctly applied did not maintain desired pressure during ambulance transport on urban roads over 30 min. Elasticized bandages maintained pressure.

Conclusions:  PB was poorly done by the general public and health professionals. Crepe bandages rarely generated optimal pressures compared with elasticized bandages, but training did improve participants' ability to apply elasticized bandages. PB recommendations should be modified to specify appropriate bandage types.
Prospective study of 101 patients with suspected drink spiking
Authors: Quigley Paul , Lynch Dania M , Little Mark , Murray Lindsay , Lynch Ann‐Maree , O'Halloran Sean J
Published: June 2009

Objective:  To evaluate cases of suspected drink spiking presenting to the ED by the prospective collection of standardized relevant historical, clinical and laboratory data.

Methods:  A prospective observational study of 101 patients presenting to metropolitan hospital ED with suspected drink spiking within the previous 12 h. Clinical history, including details surrounding the alleged drink spiking incident, and examination. Blood ethanol concentration measurement, together with the analysis of urine and blood samples for illicit and sedative drugs.

Results:  Of the 97 alleged drink spiking cases included, there were only 9 plausible cases. We did not identify a single case where a sedative drug was likely to have been illegally placed in a drink in a pub or nightclub. Illicit drugs were detected in 28% of the study group. Ethanol was commonly detected, with the mean number of standard drinks consumed being 7.7 ± 3.9 SD, and the median blood ethanol concentration at the time of presentation was 0.096% (96 mg/dL). At follow‐up there were no major sequelae and no police prosecutions. Thirty five per cent of patients still believed that they had been a victim of drink spiking irrespective of the results.

Conclusion:  Our study did not reflect the current public perception of drink spiking. Drink spiking with sedative or illicit drugs appears to be rare. If drink spiking does occur, ethanol appears to be the most common agent used. Of greater concern was the frequency of illicit drug use and excessive ethanol consumption within the study population, making it difficult to determine whether a person had truly had a drink spiked.
Childhood Plasmodium falciparum malaria complicated by splenic abscess
Authors: Thapa Rajoo , Ghosh Apurba , Banerjee Tapanjyoti
Published: June 2009

We report on an 8‐year‐old girl with Plasmodium falciparum malaria complicated by splenic abscess during the course of her infection. The diagnosis of malaria was based upon the demonstration of trophozoites of P. falciparum in the peripheral blood smear. The trophozoites of the same organism were visualized on the Giemsa‐stained smear prepared from the percutaneous splenic aspirate specimen. The patient failed to respond to parenteral Artesunate alone, which demanded emergent splenectomy. To our knowledge, this is the first report of splenic abscess complicating the course of childhood P. falciparum malaria in the English literature.
Establishment of a Transgenic Sickle-Cell Mouse Model to Study the Pathophysiology of Priapism
Authors: Bivalacqua Trinity J. , Musicki Biljana , Hsu Lewis L. , Gladwin Mark T. , Burnett Arthur L. , Champion Hunter C.
Published: June 2009

Introduction

Priapism is a poorly understood disease process with little information on the etiology and pathophysiology of this erectile disorder. One group of patients with a high prevalence of priapism is men with sickle-cell disease.

Aim

Establish an in vivo transgenic sickle-cell mouse model to study the pathophysiology of sickle-cell disease-associated priapism.

Methods

Transgenic sickle-cell disease mice, expressing human sickle hemoglobin, were utilized. Three groups of mice were used: (i) wild type (WT), (ii) sickle-cell heterozygotes (Hemi), and (ii) sickle-cell homozygotes (Sickle). Two age groups of each cohort of mice were utilized: young adult (4–6 months) and aged (18–22 months).

Main Outcome Measures

Histological (trichrome stain to measure ratio of collagen to smooth muscle), penile hydroxyproline content (collagen content), and transmission electron microscopic analysis of WT, Hemi, and Sickle mice penes, as well as in vivo erectile responses [change in intracavernous pressure (ICP)] to cavernous nerve stimulation (CNS), were determined. The frequency of erectile responses (erections/hour) pre- and poststimulation was also measured in each of the experimental groups.

Results

Sickle mice had increased (P < 0.05) collagen to smooth muscle ratio and hydroxyproline content in the penis when compared with WT and Hemi mice penes. Transmission electron microscopy demonstrated thickened smooth muscle cell bundles, disruption of the endothelial lining of the corporal sinusoids, and increased (P < 0.05) caveolae number. Sickle mice had significantly (P < 0.05) higher ICP to CNS and increased (P < 0.05) frequency of erections pre- and post-CNS when compared with WT and Hemi mice erectile responses. Sickle mice did develop ED (change in ICP in response to CNS) with increasing age.

Conclusions

The morphometric changes of the penis and exaggerated in vivo erectile responses support the use of this transgenic sickle-cell disease animal model to study the pathophysiological mechanisms involved in sickle-cell disease-associated priapism.
Subjectively Measured Ejaculation Latency Time and Its Association with Different Sexual Activities While Controlling for Age and Relationship Length
Authors: Jern Patrick , Santtila Pekka , Johansson Ada , Varjonen Markus , Witting Katarina , Von Der Pahlen Bettina , Sandnabba Kenneth
Published: June 2009

Introduction

Recently, attempts to formulate valid and suitable definitions for (different subcategories of) premature ejaculation have resulted in substantial progress in the pursuit to gain knowledge about ejaculatory function. However, the association between ejaculatory dysfunction and different types of sexual activities has yet to be thoroughly investigated, and (due to conflicting results between studies) the potential effects of age and relationship length still need to be taken into account.

Aim

The aim of this study is to investigate the associations of age, relationship length, frequency of different sexual activities, and different modes of achieving ejaculation with self-reported ejaculation latency time.

Main Outcome Measures

The main outcome is establishing associations between age, relationship length, self-reported ejaculation latency time, and frequency of different kinds of sexual activities and different modes of achieving ejaculation (such as achieving ejaculation through oral or vaginal sex).

Methods

Statistical analyses of data on age, relationship length, self-reported ejaculation latency time, and frequency of different sexual activities and different modes of achieving ejaculation were conducted on a population-based sample of 3,189 males aged 18–48 years (mean = 29.9 years, standard deviation = 6.94).

Results

Age and relationship length were significantly negatively associated with self-reported ejaculation latency time. Frequency of different kinds of sexual behavior generally had a positive association with self-reported ejaculation latency time, as had different modes of achieving ejaculation.

Conclusions

The findings highlight the need for more extensive studies on and increased knowledge of different aspects of ejaculatory function before a valid and suitable definition for premature ejaculation can be formulated.
Advantages of a Synthetic Peptide Immunogen Over a Protein Immunogen in the Development of an Anti‐Pilus Vaccine for Pseudomonas aeruginosa
Authors: Kao Daniel J. , Hodges Robert S.
Published: June 2009

The type IV pilus is an important adhesin in the establishment of infection by Pseudomonas aeruginosa. We have previously reported on a synthetic peptide vaccine targeting the receptor‐binding domain of the main structural subunit of the pilus, PilA. The receptor‐binding domain is a 14‐residue disulfide loop at the C‐terminal end of the pilin protein. The objective of this study was to compare the immunogenicity of a peptide‐conjugate to a protein subunit immunogen to determine which was superior for use in an anti‐pilus vaccine. BALB/c mice were immunized with the native PAK strain pilin protein and a synthetic peptide of the receptor‐binding domain conjugated to keyhole limpet haemocyanin. A novel pilin protein with a scrambled receptor‐binding domain was used to characterize receptor‐binding domain‐specific antibodies. The titres against the native pilin of the animals immunized with the synthetic peptide‐conjugate were higher than the titres of animals immunized with the pilin protein. In addition, the affinities of anti‐peptide sera for the intact pilin receptor‐binding domain were significantly higher than affinities of anti‐pilin protein sera. These results have significant implications for vaccine design and show that there are significant advantages in using a synthetic peptide‐conjugate over a subunit pilin protein for an anti‐pilus vaccine.
Filtering and Counting of Extended Connectivity Fingerprint Features Maximizes Compound Recall and the Structural Diversity of Hits
Authors: Hu Ye , Lounkine Eugen , Bajorath Jürgen
Published: June 2009

Extended connectivity fingerprints produce variable numbers of structural features for molecules and quantitative comparison of feature ensembles is typically carried out as a measure of molecular similarity. As an alternative way to utilize the information content of extended connectivity fingerprint features, we have introduced a compound class‐directed feature filtering technique. In combination with a simple feature counting protocol, feature filtering significantly improves the performance of extended connectivity fingerprint similarity searching compared with state‐of‐the‐art fingerprint search methods. Subsets of extended connectivity fingerprint features that are unique to active compounds are found to be responsible for high compound recall. Moreover, feature filtering and counting is shown to result in significantly higher scaffold hopping potential than data fusion or fingerprint averaging methods. Extended connectivity fingerprint feature filtering and counting represents one of the simplest similarity search methods introduced to date, yet it produces top compound recall and maximizes the scaffold diversity of hits, which is a longstanding goal of similarity searching.
On the Origins of Enzyme Inhibitor Selectivity and Promiscuity: A Case Study of Protein Kinase Binding to Staurosporine
Authors: Tanramluk Duangrudee , Schreyer Adrian , Pitt William R. , Blundell Tom L.
Published: June 2009

Relationships between ligand binding and the shapes of the binding sites in families of homologous enzymes are investigated by comparing matrices of distances between key binding site atoms. Multiple linear regression is used to help identify key distances that influence ligand binding affinity. In order to illustrate the utility of this generic approach, we study protein kinase binding sites for ATP and the promiscuous competitive inhibitor, staurosporine. We show that the size of the gatekeeper residue and the closure between the first glycine of the GXGXXG motif and the aspartate of the DFG loop act together to promote tight binding. Our web‐based tool, ‘mapping analogous hetero‐atoms onto residue interactions’ (MAHORI), indicates that the greater the number of hydrogen bonds made by the kinase around the methylamine group of staurosporine, the tighter the binding. The conservation of surrounding atoms identified using our novel grid‐based method clearly demonstrates that the most structurally conserved part of the binding site for staurosporine is the main chain of the hinge region. The critical role of interactions that are not dependent on side‐chain identities is consistent with the promiscuous nature of this inhibitor.
Potent Triazolothione Inhibitor of Heat‐Shock Protein‐90
Authors: Feldman Richard I. , Mintzer Bob , Zhu Daguang , Wu James M. , Biroc Sandra L. , Yuan Shendong , Emayan Kumar , Chang Zheng , Chen Deborah , Arnaiz Damian O. , Bryant Judi , Ge Xue Snow , Whitlow Marc , Adler Marc , Polokoff Mark A. , Li Wei‐Wei , Ferrer Mike , Sato Takashi , Gu Jian‐Ming , Shen Jun , Tseng Jih‐Lie , Dinter Harald , Buckman Brad
Published: June 2009

Heat‐shock protein‐90 is an attractive target for anticancer drugs, as heat‐shock protein‐90 blockers such as the ansamycin 17‐(allylamino)‐17‐demethoxygeldanamycin greatly reduce the expression of many signaling molecules that are disregulated in cancer cells and are key drivers of tumor growth and metastasis. While 17‐(allylamino)‐17‐demethoxygeldanamycin has shown promise in clinical trials, this compound class has significant template‐related drawbacks. In this paper, we describe a new, potent non‐ansamycin small‐molecule inhibitor of heat‐shock protein‐90, BX‐2819, containing resorcinol and triazolothione rings. Structural studies demonstrate binding of BX‐2819 to the ADP/ATP‐binding pocket of heat‐shock protein‐90. The compound blocked expression of heat‐shock protein‐90 client proteins in cancer cell lines and inhibited cell growth with a potency similar to 17‐(allylamino)‐17‐demethoxygeldanamycin. In a panel of four cancer cell lines, BX‐2819 blocked growth with an average IC50 value of 32 nm (range of 7–72 nm). Efficacy studies demonstrated that treatment with BX‐2819 significantly inhibited the growth of NCI‐N87 and HT‐29 tumors in nude mice, consistent with pharmacodynamic studies showing inhibition of heat‐shock protein‐90 client protein expression in tumors for greater than 16 h after dosing. These data support further studies to assess the potential of BX‐2819 and related analogs for the treatment of cancer.
DHEA improves impaired activation of Akt and PKC ζ/λ‐GLUT4 pathway in skeletal muscle and improves hyperglycaemia in streptozotocin‐induced diabetes rats
Authors: Sato K. , Iemitsu M. , Aizawa K. , Ajisaka R.
Published: June 2009

Aim:  Addition of dehydroepiandrosterone (DHEA) to a cultured skeletal muscle locally synthesizes 5α‐dihydrotestosterone (DHT). It induced activation of glucose metabolism‐related signalling pathway via protein kinase B (Akt) and protein kinase C zeta/lambda (PKC ζ/λ)‐glucose transporter‐4 (GLUT4) proteins. However, such an effect of DHEA in vivo remains unclear.

Methods:  Using streptozotocin (STZ)‐induced rats with type 1 diabetes mellitus, we tested the hypothesis that a single bout of DHEA injection in the rats improves hyperglycaemia and muscle GLUT4‐regulated signalling pathway. After 1 week of STZ injection (55 mg kg−1) with male Wistar rats, fasting glucose concentrations were determined in a blood sample taken from the tail vein. Blood glucose levels were then monitored for 180 min after DHEA or sesame oil (control) was injected (n = 10 for each group).

Results:  Blood glucose levels decreased significantly for 30–150 min after 2 mg DHEA injection in the STZ rats. In the skeletal muscle, expression and translocation of GLUT4 protein, phosphorylation of Akt and PKC ζ/λ, and phosphofructokinase and hexokinase enzyme activities increased significantly by DHEA injection. However, DHEA‐induced improvements in Akt and PKC ζ/λ‐GLUT4 pathways were blocked by a DHT inhibitor.

Conclusion:  These results suggest that a single bout of DHEA injection can improve hyperglycaemia and activate the glucose metabolism‐related signalling pathway via Akt and PKC ζ/λ‐GLUT4 proteins of skeletal muscles in rats. Moreover, these results show that a DHEA‐induced increase in muscle glucose uptake and utilization might contribute to improvement in hyperglycaemia in type 1 diabetes mellitus.
Not again! Public perception, regulation, and nanotechnology
Authors: Sylvester Douglas J. , Abbott Kenneth W. , Marchant Gary E.
Published: June 2009

It is often argued that immediate government action regarding nanotechnology is needed to ensure that public opinion does not mistakenly view nanotechnology as dangerous, to restore public trust in government, and to increase the legitimacy of government action through increased public participation. This article questions whether governments can achieve these goals. As the world lurches toward regulation of nanotechnology, we should ask Why the rush? Can anticipatory action, perceived as the government doing something, fulfill the competing hopes to “restore trust,”“pave the way” for nanotechnology, “increase awareness,” and “satisfy democratic notions of accountability”? Or is government action more likely to increase existing divisions over nanotechnology's future?
Divided government and US federal rulemaking
Authors: Yackee Jason Webb , Yackee Susan Webb
Published: June 2009

Despite paying a great deal of attention to the effects of divided government on legislative outputs, scholars of American politics have surprisingly ignored the potential impact of divided government on bureaucratic regulatory outputs. In this article we argue that divided government should reduce the volume of federal agency rulemaking. We test this hypothesis against a data set covering 21,000 rules from 1983 to 2005. Our study is one of the first to analyze the determinants of federal bureaucratic rulemaking activity across such a long period of time. Our results demonstrate that during periods of divided government, agencies issue fewer rules and fewer substantively significant rules than they do during periods of unified government. These findings suggest that divided government impedes agency rulemaking.
Quantitation of whole blood Epstein‐Barr virus DNA is useful for assessing treatment response in patients with non‐Hodgkin’s lymphoma
Authors: JO S. A. , HWANG S.‐H. , KIM S. Y. , SHIN H.‐J. , CHUNG J. S. , SOL M. Y. , CHANG C. L. , LEE E. Y.
Published: June 2009

Introduction.  Epstein‐Barr virus (EBV) is a well‐known tumorigenic virus and is associated with lymphoproliferative disorders. Quantitations of EBV viral loads in plasma and peripheral blood mononuclear cells have been reported to be useful biomarkers for monitoring Hodgkin’s lymphoma and EBV‐associated non‐Hodgkin lymphoma (NHL).

Methods.  In the present study, whole blood specimens were used to determine quantitatively EBV viral loads, which were then compared with clinical data. Using real‐time quantitative polymerase chain reaction (RQ‐PCR), EBV‐DNA was monitored in whole blood samples from patients with NHL (n = 61) at the time of diagnosis, relapse, and follow‐up.

Results.  A statistically significant correlation was observed between positive EBV viral load and extranodal involvement in diffuse large B‐cell lymphoma at the time of diagnosis or relapse (n = 29, P = 0.009). In patients who were serially checked for EBV‐DNA levels (n = 16), viral load was found to fall to undetectable levels during complete remission. On the contrary, progressive disease and relapse were found to be associated with sustained or elevated EBV‐DNA levels.

Conclusion.  These results suggest that whole blood EBV‐DNA quantitation might be of value as a convenient biomarker for therapeutic responsiveness of NHL.
introgress: a software package for mapping components of isolation in hybrids
Authors: GOMPERT ZACHARIAH , ALEX BUERKLE C.
Published: June 2009

A new software package (introgress) provides functions for analysing introgression of genotypes between divergent, hybridizing lineages, including estimating genomic clines from multi‐locus genotype data and testing for deviations from neutral expectations. The software works with co‐dominant, dominant and haploid marker data, and does not require fixed allelic differences between parental populations for the sampled genetic markers. Permutation and parametric procedures generate neutral expectations for introgression and provide a basis for significance tests of observed genomic clines. The software also implements maximum likelihood estimates of hybrid index from genotypic data and a number of graphical analyses. The package is an extension of the R statistical software, is written in the R language and is freely available through the Comprehensive R Archive Network (CRAN; http://cran.r‐project.org/). In this study, we describe introgress and demonstrate its use with a sample data set.
Web‐Based Experiments for the Study of Collective Social Dynamics in Cultural Markets
Authors: Salganik Matthew J. , Watts Duncan J.
Published: June 2009

Social scientists are often interested in understanding how the dynamics of social systems are driven by the behavior of individuals that make up those systems. However, this process is hindered by the difficulty of experimentally studying how individual behavioral tendencies lead to collective social dynamics in large groups of people interacting over time. In this study, we investigate the role of social influence, a process well studied at the individual level, on the puzzling nature of success for cultural products such as books, movies, and music. Using a “multiple‐worlds” experimental design, we are able to isolate the causal effect of an individual‐level mechanism on collective social outcomes. We employ this design in a Web‐based experiment in which 2,930 participants listened to, rated, and downloaded 48 songs by up‐and‐coming bands. Surprisingly, despite relatively large differences in the demographics, behavior, and preferences of participants, the experimental results at both the individual and collective levels were similar to those found in Salganik, Dodds, and Watts (2006). Further, by comparing results from two distinct pools of participants, we are able to gain new insights into the role of individual behavior on collective outcomes. We conclude with a discussion of the strengths and weaknesses of Web‐based experiments to address questions of collective social dynamics.
How Do Engineering Scientists Think? Model‐Based Simulation in Biomedical Engineering Research Laboratories
Authors: Nersessian Nancy J.
Published: June 2009

Designing, building, and experimenting with physical simulation models are central problem‐solving practices in the engineering sciences. Model‐based simulation is an epistemic activity that includes exploration, generation and testing of hypotheses, explanation, and inference. This paper argues that to interpret and understand how these simulation models function in creating knowledge and technologies requires construing problem solving as accomplished by a researcher–artifact system. It draws on and further develops the framework of “distributed cognition” to interpret data collected in ethnographic and cognitive‐historical studies of two biomedical engineering research laboratories, and articulates the notion of distributed model‐based cognition to answer the question posed in the title.
Use of suppression subtractive hybridization to identify genetic differences between differentially virulent genotypes of Paenibacillus larvae, the etiological agent of American Foulbrood of honeybees
Authors: Fünfhaus Anne , Ashiralieva Ainura , Borriss Rainer , Genersch Elke
Published: June 2009

Paenibacillus larvae is the causative agent of American Foulbrood of honeybees, a fatal brood disease not only killing infected larvae but also lethal to infected colonies. Recently four different genotypes of P. larvae (enterobacterial repetitive intergenic consensus I–IV) have been described and it was shown that these genotypes also differ in phenotype, especially in virulence. To unravel the genetic differences between these four genotypes, suppression subtractive hybridization was used. From 106 analysed clones, 92 represented genotype‐specific sequences, whereas 14 sequences turned out to be specific only for the particular strain used as tester in the subtraction. Nearly half of the sequences (46%) could only be annotated based on poorly characterized sequences. The remaining sequences corresponded to categories related to metabolism, especially secondary metabolite biosynthesis, transport and catabolism, to information storage and processing, and to cellular processes. In particular, we could show that the P. larvae genome contains genes and/or giant gene clusters coding for antibiotics, and we identified the first P. larvae toxin, a member of the family of adenosine diphosphate‐ribosyltransferases.
Implications of Turbine Erosion for an Aero-Engine’s
High-Pressure-Turbine Blade’s Low-Cycle-Fatigue Life-Consumption
Authors: Naeem Muhammad
Published: June 2009

Some in-service deterioration in any mechanical device, such as a military aero-engine, is inevitable. As a result of experiencing any deterioration, an aero-engine will seek a different steady operating point thereby resulting in a variation in the high-pressure spool speeds in order to provide the same thrust to keep aircraft’s performance invariant. Any increase in the high-pressure spool speed results in greater low-cycle fatigue damage for the hot-end components and thereby higher engine’s life-cycle costs. Possessing better knowledge (of the impacts of high-pressure turbine’s erosion upon the low-cycle fatigue life-consumption of aero-engine’s hot-end components) helps the users to take wiser management decisions. For a military aircraft’s mission profile, using bespoke computer simulations, the impacts of turbine erosion for high-pressure turbine-blade’s low-cycle fatigue life-consumption have been predicted.
Characteristics of Flow and Flame Behavior Behind Rifled/Unrifled Nozzles
Authors: San Kuo C. , Hsu Hung J.
Published: June 2009

A novel rifled nozzle was installed behind a conventional combustion exhauster to improve combustion efficiency. The rifled nozzles improve the momentum transmission, turbulent strength, and mixing efficiency between the central jet and annular jet. The flow characteristics behind the nozzles (rifled and unrifled) were visualized and detected using the smoke-wire flow visualization, particle image velocimetry, and hot-wire anemometry. The cold flow structures were categorized into four modes—jet flow, single bubble, dual bubble, and turbulent flow. The topological scheme was adopted to analyze and verify these flow modes. The flame structures behind the nozzles (rifled and unrifled) are classified into three modes—jet flame, flickering flame, and turbulent flame—using the direct-photo visualization. The flame height of a 12-rifled nozzle is decreased by about 50% under that of an unrifled nozzle. The flame shedding frequency declines rapidly in the flickering flame mode and the relationship between the Strouhal number (Sr) and annular velocity (ua) is Sr=0.0238+0.13/ua.
A Computational Model of the Mark-IV Electrorefiner: Phase I—Fuel Basket/Salt Interface
Authors: Hoover Robert , Phongikaroon Supathorn , Li Shelly , Simpson Michael , Yoo Tae-Sic
Published: June 2009

Spent driver fuel from the Experimental Breeder Reactor-II is currently being treated in the Mark-IV electrorefiner in the Fuel Conditioning Facility at Idaho National Laboratory. The modeling approach to be presented here has been developed to help understand the effect of different parameters on the dynamics of this system. The first phase of this new modeling approach focuses on the fuel basket/salt interface involving the transport of various species found in the driver fuels (e.g., uranium and zirconium). This approach minimizes the guessed parameters to only one, the exchange current density (i0). U3+ and Zr4+ were the only species used for the current study. The result reveals that most of the total cell current is used for the oxidation of uranium, with little being used by zirconium. The dimensionless approach shows that the total potential is a strong function of i0 and a weak function of wt % of uranium in the salt system for initiation processes.
Gas Turbine Aero-Engine First Stage Turbine Blade Failure Investigation
Authors: Mustafa Alaaeldin H. , Badairy Hameed H. , Mehta Sudhir
Published: June 2009

Plugging material in some of the film cooling channels of a failed aero-gas turbine engine first stage turbine blade is analyzed using the energy dispersive X-ray spectroscopy in an environmental scanning electron microscope. The objective of the analysis was to identify the nature and source of the plugging material that appears to have caused overheating and eventual failure of some of the blades. The results of the analysis indicate that the plugging material, which occurs as a dense aggregate of 0.1 m diameter fibers, is mainly composed of Zr, Y, and O. In addition, the material shows presence of micron size particles dispersed between the fibers. The analysis of the particles indicates they are fluoride-rich compounds, possibly of yttrium or calcium. Small or trace amounts of Ca, Na, and Mg are also observed in the plugging material. The analysis of the areas surrounding the plugged cooling channels shows presence of Cr–Co–Ni–aluminide bond coat and a discontinuous platinum coat over the bond coat. In contrast, the areas surrounding the fractured surface and melted edge show significant presence of calcium fluoride and Mg–Al–silicate. The analysis of melted edge shows presence of all the elements representing various coating layers as well as the impurities; however, Zr and Y were not detected in the melted areas.
Enhanced Fault Localization Using Probabilistic Fusion With Gas Path Analysis Algorithms
Authors: Kyriazis A. , Mathioudakis K.
Published: June 2009

A method for gas turbine fault identification from gas path data, in situations with a limited number of measurements, is presented. The method consists of a two stage process: (a) localization of the component or group of components with a fault and (b) fault identification by determining the precise location and magnitude of component performance deviations. The paper focuses on methods that allow improved localization of the faulty components. Gas path analysis (GPA) algorithms are applied to diagnostic sets comprising different combinations of engine components. The results are used to derive fault probabilities, which are then fused to derive a conclusion as to the location of a fault. Once the set of possible faulty components is determined, a well defined diagnostic problem is formulated and the faulty parameters are determined by means of a suitable algorithm. It is demonstrated that the method has an improved effectiveness when compared with previous GPA based methods.
A Method to Evaluate Fission Gas Release During Irradiation Testing of Spherical Fuel
Authors: van der Merwe Hanno , Venter Johan
Published: June 2009

The evaluation of fission gas release from spherical fuel during irradiation testing is critical to understand expected fuel performance under real reactor conditions. Online measurements of krypton and xenon fission products explain coated particle performance and contributions from graphitic matrix materials used in fuel manufacture and irradiation rig materials. Methods that are being developed to accurately evaluate fission gas release are described here together with examples of evaluations performed on irradiation tests HFR-K5, -K6, and EU1bis.
Results of Tests to Demonstrate a 6-in.-Diameter Coater for Production of TRISO-Coated Particles for Advanced Gas Reactor Experiments
Authors: Barnes Charles M. , Marshall Douglas W. , Keeley Joe T. , Hunn John D.
Published: June 2009

The next generation nuclear plant (NGNP)/advanced gas reactor (AGR) fuel development and qualification program includes a series of irradiation experiments in Idaho National Laboratory’s advanced test reactor. Tristructural isotropic (TRISO)-coated particles for the first AGR experiment, AGR-1, were produced at Oak Ridge National Laboratory (ORNL) in a 2-in.(5-cm)-diameter coater. A requirement of the NGNP/AGR program is to produce coated particles for later experiments in coaters more representative of industrial scale. Toward this end, tests have been performed by Babcock and Wilcox (Lynchburg, VA) in a 6-in.(15-cm)-diameter coater. These tests have led to successful fabrication of particles for the second AGR experiment, AGR-2. While a thorough study of how coating parameters affect particle properties was not the goal of these tests, the test data obtained provide insight into process parameter/coated particle property relationships. Most relationships for the 6-in.-diameter coater followed trends found with the ORNL 2-in. coater, in spite of differences in coater design and bed hydrodynamics. For example, the key coating parameters affecting pyrocarbon anisotropy were coater temperature, coating gas fraction, total gas flow rate, and kernel charge size. Anisotropy of the outer pyrolytic carbon layer also strongly correlates with coater differential pressure. In an effort to reduce the total particle fabrication run time, silicon carbide (SiC) was deposited with methyltrichlorosilane (MTS) concentrations up to 3 mol %. Using only hydrogen as the fluidizing gas, the high concentration MTS tests resulted in particles with lower than desired SiC densities. However, when hydrogen was partially replaced with argon, high SiC densities were achieved with the high MTS gas fraction.
TRU-Fueled Very High Temperature Reactors for Applications Requiring an Extended Operation With Minimized Control and No Refueling
Authors: Tsvetkov Pavel V. , Lewis Tom G. , Alajo Ayodeji B.
Published: June 2009

This paper presents an analysis of transuranium nuclide (TRU)-fueled very high temperature reactor (VHTR) systems focusing on applications requiring an extended operation with minimized control and no refueling (single-batch mode). As an example of such applications, international deployment opportunities for grid-appropriate VHTR systems could be mentioned addressing demands for electricity, industrial heat, and co-generation in those regions where minimized servicing is desirable for various reasons. The study is performed for the hexagonal block core concept within the framework of the ongoing U.S. DOE Nuclear Energy Research Initiative project on utilization of higher actinides (TRUs and partitioned minor actinides (MAs)) as a fuel component for extended-life VHTRs. The up-to-date analysis has shown reasonable reactivity swings, core life limits with respect to fast fluences, and criticality.
Analysis of Ultrafiltration and Mass Transfer in a Bioartificial Pancreas
Authors: Jaffrin M. Y. , Reach G. , Notelet D.
Published: June 2009

A bioartificial pancreas is an implantable device which contains insulin secreting cells (Langerhans islets), separated from the circulating blood by a semi-permeable membrane to avoid rejection. This paper describes the operation of such a device and evaluates the respective contributions of diffusion and ultrafiltration to the glucose and insulin mass transfer. It is shown that the pressure drop along the blood channel produces across the first half of the channel an ultrafiltration flux toward the islet compartment followed in the second half by an equal flux in reverse direction from islets to blood. The mass transfer analysis is carried out for an optimal geometry in which a U-shaped blood channel surrounds closely a very thin islet compartment formed by a folded flat membrane. A complete model of insulin release by this device is developed and is compared with in vitro data obtained with rats islets. Satisfactory kinetics is achieved with a polyacrylonitrile membrane used in hemodialysis. But the model shows that the membrane hydraulic permeability should be increased by a factor of 10 to significantly improve the performance.
A Theory of Blood Flow in Skeletal Muscle
Authors: Schmid-Scho¨nbein G. W.
Published: June 2009

A theoretical analysis of blood flow in the microcirculation of skeletal muscle is provided. The flow in the microvessels of this organ is quasi steady and has a very low Reynolds number. The blood is non-Newtonian and the blood vessels are distensible with viscoelastic properties. A formulation of the problem is provided using a viscoelastic model for the vessel wall which was recently derived from measurements in the rat spinotrapezius muscle (Skalak and Schmid-Scho¨nbein, 1986b). Closed form solutions are derived for several physiologically important cases, such as perfusion at steady state, transient and oscillatory flows. The results show that resting skeletal muscle has, over a wide range of perfusion pressures an almost linear pressure-flow curve. At low flow it exhibits nonlinearities. Vessel distensibility and the non-Newtonian properties of blood both have a strong influence on the shape of the pressure-flow curve. During oscillatory flow the muscle exhibits hysteresis. The theoretical results are in qualitative agreement with experimental observations.
A Hypothesis on the Mechanism of Trauma of Lung Tissue Subjected to Impact Load
Authors: Fung Y. C. , Yen R. T. , Tao Z. L. , Liu S. Q.
Published: June 2009

When a compressive impact load is applied on the chest, as in automobile crash or bomb explosion, the lung may be injured and show evidences of edema and hemorrhage. Since soft tissues have good strength in compression, why does a compression wave cause edema? Our hypothesis is that tensile and shear stresses are induced in the alveolar wall on rebound from compression, and that the maximum principal stress (tensile) may exceed critical values for increased permeability of the epithelium to small solutes, or even fracture. Furthermore, small airways may collapse and trap gas in alveoli at a critical strain, causing traumatic atelectasis. The collapsed airways reopen at a higher strain after the wave passes, during which the expansion of the trapped gas will induce additional tension in the alveolar wall. To test this hypothesis, we made three new experiments: (1), measuring the effect of transient overstretch of the alveolar membrane on the rate of lung weight increase; (2) determining the critical pressure for reopening collapsed airways of rabbit lung subjected to cyclic compression and expansion; (3) cyclic compression of lung with trachea closed. We found that in isolated rabbit lung overstretching increases the rate of edema fluid formation, that the critical strain for airway reopening is higher than that for closing, and that these critical strains are strain-rate dependent, but independent of the state of the trachea, whether it is open or closed. Furthermore, a theoretical analysis is presented to show that the maximum principal (tensile) stress is of the same order of magnitude as the maximum initial compressive stress at certain localities of the lung. All these support the hypothesis. But the experiments were done at too low a strain rate, and further work is needed.
An Experimental Approach to Evaluate the Dynamic Behavior of the Human Knee
Authors: Jans H. W. J. , Dortmans L. J. M. G. , Sauren A. A. H. J. , Huson A.
Published: June 2009

An experimental approach for an in vitro investigation of some aspects of dynamic force transmission through the human knee joint is presented. Essentially, the behavior of the joint was analyzed by measuring the responses to low level random excitation of the tibia while the femur was clamped. A global equilibrium position of the joint was attained by exerting static forces on the tibia via three tendinous muscle attachments. The responses to the applied dynamic loads were measured using a multi-channel dynamic measuring system and quantified by means of transfer function analysis techniques. Some preliminary experimental results are presented to illustrate the effects of variation of the direction and the magnitude of the applied dynamic and static loads.
On the Generalization of the Weinbaum-Jiji Bioheat Equation to Microvessels of Unequal Size; The Relation Between the Near Field and Local Average Tissue Temperatures
Authors: Zhu M. , Weinbaum S. , Jiji L. M. , Lemons D. E.
Published: June 2009

The extensive series of experiments reported in Lemons et al. [1] show that measureable local tissue temperature fluctuations are observed primarily in the vicinity of the 100–500 μm countercurrent vessels of the microcirculation and thus strongly support the basic hypothesis in the new bioheat equation of Weinbaum and Jiji [2] that these countercurrent microvessels are the principal determinants of local blood-tissue heat transfer. However, the detailed temperature profiles in the vicinity of these vessels indicate that large asymmetries in the local temperature field can result from the significant differences in size between the countercurrent artery and vein. Using the superposition techniques of Baish et al. [9], the paper first presents a solution to the classic problem of an unequal countercurrent heat exchanger with heat loss to the far field. This solution is then used to generalize the Weinbaum-Jiji bioheat equation and the conductivity tensor that appears in this equation to vessels of unequal size. An asymptotic analysis has also been developed to elucidate the relationship between the near field temperature of the artery-vein pair and the local average tissue temperature. This analysis is used to rigorously prove the closure approximation relating the local arterial-venous temperature difference and the mean tissue temperature gradient which had been derived in [2] using a more heuristic approach.
Numerical Study on the Flow of a Non-Newtonian Fluid Through an Axisymmetric Stenosis
Authors: Nakamura Masahide , Sawada Tadashi
Published: June 2009

The laminar steady flow of non-Newtonian fluid (biviscosity fluid) through an axisymmetric stenosis is calculated using the finite element methods. The flow pattern, the separation and reattachment points, and the distributions of pressure and shear stress at the wall are obtained. Then, the axial force acting on the stenosis is evaluated. It is suggested by the authors that this force can become one of the causes of post-stenotic dilatation. Calculated results show that the non-Newtonian property of blood weakens the distortion of flow pattern, pressure and shear stress at the wall associated with the stenosis and that the non-Newtonian property of blood decreases the axial force acting on the stenosis.
Epicardial Coronary Blood Flow Including the Presence of Stenoses and Aorto-Coronary Bypasses—II: Experimental Comparison and Parametric Investigations
Authors: Wiesner T. F. , Levesque M. J. , Rooz E. , Nerem R. M.
Published: June 2009

This article is the second in a series which presents a computer model of the left coronary arteries. The first article discussed the geometry, the governing equations, and the numerical method employed. This paper details an acute canine experiment used to validate the approach as well as the systematic investigation of several important parameters governing the left coronary circulation. These parameters include peripheral resistance, wall properties, and altered geometric properties through various stenosis/bypass configurations. With appropriate selection of parameters, the model reproduces an in vivo waveform very closely. The model also predicts many clinical phenomena, such as the “critical” value of stenosis, the dramatic reduction in flow through a stenosis when bypassed, and the restorative effect of the bypass upon flow to the distal bed. The model also is used to show that the autonomic state of the animal profoundly affects the influence of various factors, e.g., the critical value of a stenosis is much higher under resting conditions than under hyperemic conditions.
Vortex Generation in Pulsatile Flow Through Arterial Bifurcation Models Including the Human Carotid Artery
Authors: Fukushima Takayoshi , Homma Tatsuji , Harakawa Kiyohito , Sakata Noriyuki , Azuma Takehiko
Published: June 2009

Visualization experiments were performed to elucidate the complicated flow pattern in pulsatile flow through arterial bifurcations. Human common carotid arteries, which were made transparent, and glass-models simulating Y- and T-shaped bifurcations were used. Pulsatile flow with wave forms similar to those of arterial flow was generated with a piston pump, elastic tube, airchamber, and valves controlling the outflow resistance. Helically recirculating flow with a pattern similar to that of the horseshoe vortex produced around wall-based protuberances in circular tubes was observed in pulsatile flow through all the bifurcations used in the present study. This flow type, which we shall refer to as the horseshoe vortex, has also been demonstrated to occur at the human common carotid bifurcation in steady flow with Reynolds numbers above 100. Time-varying flows also produced the horseshoe vortex mostly during the decelerating phase. Fluid particles of dye solution approaching the bifurcation apex diverged, divided into two directions perpendicularly, and then showed helical motion representing the horseshoe vortex formation. While this helical flow was produced, the stagnation points appeared on the wall upstream of the apex. Their position was dependent upon the flow distribution ratio between the branches in the individual arteries. The region affected by the horseshoe vortex was smaller during pulsatile flow than during steady flow. Lowering the Reynolds number together with the Womersley number weakened the intensity of helical flow. A separation bubble, resulting from the divergence or wall roughness, was observed at the outer or inner wall of the branch vessels and made the flow more complicated.