bluuebunny/crossref_metadata_2025 huggingface dataset:
Dockerin‐containing protease inhibitor protects key cellulosomal cellulases from proteolysis in Clostridium cellulolyticum
Authors: Xu Tao , Li Yongchao , He Zhili , Zhou Jizhong
Published: December 2013

Cellulosomes are key for lignocellulosic biomass degradation in cellulolytic Clostridia. Better understanding of the mechanism of cellulosome regulation would allow us to improve lignocellulose hydrolysis. It is hypothesized that cellulosomal protease inhibitors would regulate cellulosome architecture and then lignocellulose hydrolysis. Here, a dockerin‐containing protease inhibitor gene (dpi) in Clostridium cellulolyticum H10 was characterized by mutagenesis and physiological analyses. The dpi mutant had a decreased cell yield on glucose, cellulose and xylan, lower cellulose utilization efficiency, and a 70% and 52% decrease of the key cellulosomal components, Cel48F and Cel9E respectively. The decreased cellulolysis is caused by the proteolysis of major cellulosomal components, such as Cel48F and Cel9E. Disruption of cel9E severely impaired cell growth on cellulose while loss of cel48F completely abolished cellulolytic activity. These observations are due to the combinational results of gene inactivation and polar effects caused by intron insertion. Purified recombinant Dpi showed inhibitory activity against cysteine protease. Taken together, Dpi protects key cellulosomal cellulases from proteolysis in H10. This study identified the physiological importance of cellulosome‐localized protease inhibitors in Clostridia.
Beyond catalysis: vitamin B12 as a cofactor in gene regulation
Authors: Klug Gabriele
Published: December 2013

Vitamin B12 is well known as an enzyme cofactor in the catalysis of many important biological reactions, and the role of B12 in regulation of bacterial gene expression as a ligand of riboswitches is well established. Only recently evidence has emerged that B12 can also affect bacterial gene expression by acting as a cofactor of regulatory proteins. In 2011 a role of B12 as a cofactor of the transcriptional repressor of carotenogenesis, CarH, in Myxococcus xanthus was reported. B12 is required for light‐dependent DNA binding by CarH, which can therefore be considered to be a new type of photoreceptor. Cheng et al. (2014) report the identification of B12 as a cofactor of the AerR protein in Rhodobacter capsulatus. AerR acts as an antirepressor of the CrtJ protein, which represses photosynthesis genes when binding to its target promoters. As in Myxococcus B12 may have the role of a chromophore in photoreception, but it is suggested that a main function of AerR is the sensing of B12. The co‐regulation of the pathways is beneficial because the syntheses of B12, haem and bacteriochlorophylls share common precursors and the accumulation of the free molecules is toxic.
Vitamin B12 regulates photosystem gene expression via the CrtJ antirepressor AerR in Rhodobacter capsulatus
Authors: Cheng Zhuo , Li Keran , Hammad Loubna A. , Karty Jonathan A. , Bauer Carl E.
Published: December 2013

The tetrapyrroles haem, bacteriochlorophyll and cobalamin (B12) exhibit a complex interrelationship regarding their synthesis. In this study, we demonstrate that AerR functions as an antirepressor of the tetrapyrrole regulator CrtJ. We show that purified AerR contains B12 that is bound to a conserved histidine (His145) in AerR. The interaction of AerR to CrtJ was further demonstrated in vitro by pull down experiments using AerR as bait and quantified using microscale thermophoresis. DNase I DNA footprint assays show that AerR containing B12 inhibits CrtJ binding to the bchC promoter. We further show that bchC expression is greatly repressed in a B12 auxotroph of Rhodobacter capsulatus and that B12 regulation of gene expression is mediated by AerR's ability to function as an antirepressor of CrtJ. This study thus provides a mechanism for how the essential tetrapyrrole, cobalamin controls the synthesis of bacteriochlorophyll, an essential component of the photosystem.
Quantitative trait locus mapping of floral and related traits using an F2 population of Aquilegia
Authors: Zhu Ruirui , Gao Yike , Zhang Qixiang
Published: December 2013

The objective of this study was to determine quantitative trait loci (QTL) underlying ten floral and related traits in Aquilegia. The traits assessed were calyx diameter, corolla diameter, petal length, petal blade length, sepal length, sepal width, spur length, spur width, plant height and flower number. These are important traits for ornamental value and reproductive isolation of Aquilegia. QTL analysis of these traits was conducted using single‐marker analysis and composite interval mapping (CIM). We used an F2 population consisting of 148 individuals derived from a cross between the Chinese wild species Aquilegia oxysepala and the cultivar Aquilegia flabellata ‘pumila’. Resulting CIM analysis identified 39 QTLs associated with these traits, which were mapped on seven linkage groups. These QTLs could explain 1.22–53.28% of the phenotypic variance. Thirty‐one QTLs, which explained more than 10% of the phenotypic variation, were classified as major QTLs. Graphical representations of the QTLs on seven linkage groups were made. Our research provides the potential for future molecular assisted selection breeding programmes and the cloning of target genes through fine mapping.
Potential of genomic selection in rapeseed (Brassica napus L.) breeding
Authors: Würschum Tobias , Abel Stefan , Zhao Yusheng
Published: December 2013

Genomic selection employs genome‐wide marker data to predict genomic breeding values. In this study, a population consisting of 391 lines of elite winter oilseed rape derived from nine families was used to evaluate the prospects of genomic selection in rapeseed breeding. All lines have been phenotyped for six morphological, quality‐ and yield‐related traits and genotyped with genome‐wide SNP markers. We used ridge regression best linear unbiased prediction in combination with cross‐validation and obtained medium to high prediction accuracies for the studied traits. Our results illustrate that among‐family variance contributes to the prediction accuracy and can lead to an overestimation of the prospects of genomic selection within single segregating families. We also tested a scenario where estimation of effects was carried out without individuals from the family in which breeding values were predicted, which yielded lower but nevertheless attractive prediction accuracies. Taken together, our results suggest that genomic selection can be a valuable genomic approach for complex agronomic traits towards a knowledge‐based breeding in rapeseed.
Transverse myelitis and acute motor sensory axonal neuropathy due to Legionella pneumophila: A case report
Authors: Canpolat Mehmet , Kumandas Sefer , Yikilmaz Ali , Gumus Hakan , Koseoglu Emel , Poyrazoğlu Hatice Gamze , Kose Mehmet , Per Huseyin
Published: December 2013

Guillain–Barré syndrome is a rapidly progressive symmetrical muscle weakness associated with acute inflammatory disease. Transverse myelitis (TM) is the inflammation of the spinal cord characterized by rapidly evolving muscle weakness in the lower extremities, defects in sensory level and sphincter dysfunction. Guillain–Barré syndrome, and TM association occurs very rarely in childhood. A 7‐year‐old girl presented with complaints of neck pain, spout‐style vomiting, cough, shortness of breath, and acute paraparesis with sensory and sphincter disturbance. The patient was intubated because of increased respiratory distress. A positive direct fluorescein antigen test in bronchoalveolar lavage confirmed Legionella pneumophila infection. Imaging and neurophysiologic studies were diagnostic for TM with acute motor and sensory axonal neuropathy. She was treated with a combination of high‐dose methylprednisolone and intravenous immunoglobulins, and we observed incomplete recovery. The presented case is the first child with concomitant TM and acute motor and sensory axonal neuropathy related to L. pneumophila infection.
Paraovarian cyst torsion in children: Report of two cases
Authors: Yilmaz Yavuz , Ozen Ibrahim Onur , Caliskan Dogus , Dilmen Ugur
Published: December 2013

Paraovarian cysts are assumed to be rare in childhood. This assumption is due to the fact that most patients with paraovarian cyst are asymptomatic unless complicated. Owing to the wide range of pathologies in differential diagnosis, preoperative diagnosis of paraovarian cyst presents a challenge. Herein is reported two cases of complicated paraovarian cyst in children.
Intramuscular anti‐D in chronic immune thrombocytopenia children with severe thrombocytopenia
Authors: Sirachainan Nongnuch , Anurathapan Usanarat , Chuansumrit Ampaiwan , Songdej Duantida , Wongwerawattanakoon Pakawan , Hutspardol Sakara , Kitpoka Pimpun
Published: December 2013

Nine patients with chronic immune thrombocytopenia and platelet counts <20 × 109/L, with a median age of 7.8 (3.8–15.5) years, received three phases of 10 mcg/kg/dose of intramuscular anti‐D. Phase 1 was anti‐D daily for 5 days, followed by phase 2, anti‐D weekly for 12 weeks and withheld when platelet counts ≥20 × 109/L, and then phase 3 was anti‐D once every 2 weeks for 24 weeks. According to the International Working Group criteria, in phase 1, 66.7% of patients responded to the treatment. In phases 2 and 3, 11.1% (0–41.7%) and 7.7% (0–33.3%) of total episodes of follow up, respectively, responded to the treatment. Therefore, intramuscular anti‐D given at a dose of 10 mcg/kg for 5 days is an alternative method to raise platelet counts in chronic immune thrombocytopenia children with severe thrombocytopenia where the intravenous form of anti‐D is not available.
Fulminant form of acute disseminated encephalomyelitis in a child treated with mild hypothermia
Authors: Ichikawa Kazushi , Motoi Hirotaka , Oyama Yoshitaka , Watanabe Yoshihiro , Takeshita Saoko
Published: December 2013

We describe the case of a 3‐year‐old boy diagnosed with the fulminant form of acute disseminated encephalomyelitis (ADEM). He developed general fatigue, fever, drowsiness and difficulty in walking. He had extensive multiple high‐intensity lesions in the white matter of the cerebrum and cerebellum, which are typical findings of ADEM. He became comatose and developed decerebrate rigidity with severe brain edema despite high‐dose methylprednisolone therapy, and then was subjected to mild hypothermia therapy, and given i.v. immunoglobulin. The patient recovered remarkably with the sequela of only mild action tremor. The patient was considered to have acute hemorrhagic leukoencephalitis (AHLE), an extremely severe form of ADEM, in terms of the rapidly deteriorating clinical course and neuroimaging features. It was speculated that AHLE and ADEM might be a continuous disease spectrum. It is considered that the severe brain edema associated with ADEM or AHLE is a suitable indication for mild hypothermia therapy.
Use of non‐invasive total hemoglobin measurement as a screening tool for anemia in children
Authors: Amano Izuki , Murakami Ayako
Published: December 2013

Universal screening for anemia is important in children, but invasive blood sampling is required. A new device (Radical‐7® Pulse CO‐Oximeter™, Masimo, Irvine, CA, USA) now enables non‐invasive hemoglobin concentration (SpHb) measurement to be done, but the usefulness of this device for anemia screening in children is unclear. The objective of this study was to compare SpHb with complete blood count (CBC) using a hematology analyzer (Microsemi® LC‐667CRP; Fukuda Denshi, Tokyo, Japan). SpHb measurement with Radical‐7® was done as part of a medical check‐up in 3‐year‐old children (n = 110). Another 43 pediatric patients were checked for CBC using Microsemi® and monitored with Radical‐7®. The mean SpHb level of the 3‐year‐old children was 12.1 ± 0.64 g/dL (range, 10.8–13.7 g/dL). The correlation of Radical‐7® and Microsemi® was 0.602 (P < 0.0001). On Bland–Altman comparison, bias was −0.6 ± 1.1 g/dL. Even though further improvement is required, Radical‐7® offers many possibilities in the context of primary screening.
Microclimate next to the skin: influence on percutaneous absorption of caffeine (ex‐vivo study)
Authors: Lboutounne Y. , Silva J. , Pazart L. , Bérard M. , Muret P. , Humbert P.
Published: December 2013

Background/purpose

Contact between skin surface and external environment induces a microclimate at the skin surface. That microclimate affects skin interaction with xenobiotics substances. We have developed a new device to explore the influence of environmental parameters, on percutaneous absorption. The aim of this study was to study the influence of external humidity and temperature on percutaneous absorption of caffeine.

Methods

Six exposure conditions were tested: four by combining two temperatures (27°C and 42°C) with two relative humidities (28% and 70%), performed by our device and two others by using Franz diffusion cell (unoccluded conditions, with skin surface in contact with ambient laboratory environment (27°C/33%) and in occluded conditions with skin surface covering by impermeable membrane).

Results

Kinetic curve profile of percutaneous absorption of caffeine revealed different shapes characteristics depending on environmental exposure conditions. These profiles were related to evaporative process, of deposited preparation on skin surface combined with water uptake resulting from water flux through skin.

Conclusion

Our results highlight a preponderant role of microclimate above the skin on percutaneous absorption of caffeine. The device used in this study will be a useful tool to investigate ex vivo, the influence of microclimate on percutaneous absorption.
China and the Trans‐Pacific Partnership: A Numerical Simulation Assessment of the Effects Involved
Authors: Li Chunding , Whalley John
Published: December 2013

The Trans‐Pacific Partnership (TPP) is a new negotiation on cross‐border liberalisation of goods and service flows going beyond WTO disciplines and focused on issues such as regulation and border controls. This paper uses numerical simulation methods to assess the potential effects of a TPP agreement on China and also China's inclusion or exclusion on other countries. We use a numerical 11‐country global general equilibrium model with trade costs and inside money. Trade costs are calculated using a method based on gravity equations. TPP barriers potentially removable are trade costs less tariffs. Simulation results reveal that China will be slightly hurt by TPP initiatives in welfare when China is out, but the total production and export will be increased. Other non‐TPP countries will be mostly hurt in welfare, but member countries will mostly gain. If China takes part in TPP, she will significantly gain and increase other TPP countries' gain as well. The comparison of TPP effects and global free trade effects show that the positive effects of global free trade are stronger than TPP effects. Japan's joining TPP would be beneficial to both herself and most of other TPP countries, but which negative effects on China's welfare when out of TPP will increase further.
EU‐China Collaboration in the Reform of the International Monetary System: Much Ado About Nothing?
Authors: Otero‐Iglesias Miguel , Zhang Ming
Published: December 2013

The global financial crisis has shown that the current international monetary system (IMS) suffers from an inherent flaw: it depends on US current account deficits for the provision of global liquidity. Under this arrangement, peripheral countries have to accept periodically the debasement of the US dollar. Thus, there are some mutual incentives for the EU and China to reform the current IMS through cooperation. Both are in favour of stable exchange rates, and both are keen to constrain US macroeconomic profligacy. There have been some efforts towards these objectives in the past, especially during the French presidency of the G20 in 2011. However, there has been no significant progress. On the European side, there is not a united and independent Europe which could act as the primary agent of reform. On the Chinese side, Beijing does not see Europe as a reliable partner because the latter is deemed to have a major vested interest in the current regime. As a result, the French government failed to focus the world's attention on the reform of the IMS during G20 Cannes Summit, and the Chinese government has chosen a more unilateral way to internationalise its own currency.
JK null alleles identified from Japanese individuals with Jk(a−b−) phenotype
Authors: Onodera T. , Sasaki K. , Tsuneyama H. , Isa K. , Ogasawara K. , Satake M. , Tadokoro K. , Uchikawa M.
Published: December 2013

The Kidd blood group system consists of three common phenotypes: Jk(a+b−), Jk(a−b+) and Jk(a+b+), and one rare phenotype, Jk(a−b−). Jka/Jkb polymorphism is associated with c.838G>A (p.Asp280Asn) in exon 9 of the JK (SLC14A1) gene, and the corresponding alleles are named JK*01 and JK*02. The rare phenotype Jk(a−b−) was first found in a Filipina of Spanish and Chinese ancestry, and to date, several JK null alleles responsible for the Jk(a−b−) phenotype have been reported. We report seven novel JK null alleles, 4 with a JK*01 background and 3 with a JK*02 background, identified from Jk(a−b−) Japanese.
Phylogenetic relationships among populations of the Nacobbus aberrans (Nematoda, Pratylenchidae) complex reveal the existence of cryptic species
Authors: Lax Paola , Rondan Dueñas Juan C. , Gardenal Cristina N. , Doucet Marcelo E.
Published: December 2013

The plant‐parasitic nematode Nacobbus aberrans sensu lato is an agricultural pest of quarantine importance. Due to the morphometric, physiological and genetic variability observed within the species, there is no agreement on the taxonomy of this nematode. The objective of this study was to analyse the ITS rDNA region and the D2–D3 expansion segments of 28S rDNA in 10 Argentine populations and one from Ecuador and to establish their phylogenetic relationship with other known sequences from South and North America. Phylogenetic trees of the ITS gene showed seven statistically well‐supported clades; the high and significant Fst values obtained among these groups confirmed this partitioning. The Argentine populations here considered were separated into three clades: one comprising a population from the Andean region and two grouping nematodes from lower altitudes. Three other clades were distinguished for South American populations, which included known sequences of individuals from Peru, Bolivia and north of Argentina. The other clade included sequences from Mexico, Ecuador and two Argentine populations of unknown origin. The important degree of genetic divergence observed among Andean populations suggests that the Andes may have played a crucial role in speciation of Nacobbus, which would have originated in this region. Although D2–D3 segments exhibited lower variation, they were useful for establishing phylogenetic relationships among the Argentine populations considered in this work. As there are no other GenBank sequences available for these segments, it was not possible to make comparisons with other populations from South and North America. The considerable genetic differentiation observed in ITS rDNA region among Nacobbus populations showed evidence of cryptic species within the N. aberrans s.l. complex. Integration of morphological and morphometric studies and molecular analyses considering other genes may aid in the identification of species and their phylogenetic relationships within this genus.
Effect of Cold Storage and Freezing on the Biomechanical Properties of Swine Growth Plate Explants
Authors: Ménard Anne-Laure , Soulisse Candice , Raymond Pascale , Londono Irène , Villemure Isabelle
Published: December 2013

Ex vivo biomechanical testing of growth plate samples provides essential information about its structural and physiological characteristics. Experimental limitations include the preservation of the samples since working with fresh tissues involves significant time and transportation costs. Little information is available on the storage of growth plate explants. The aim of this study was to determine storage conditions that could preserve growth plate biomechanical properties. Porcine ulnar growth plate explants (n = 5 per condition) were stored at either 4 °C for periods of 1, 2, 3, and 6 days or frozen at −20 °C with slow or rapid sample thawing. Samples were tested using stress relaxation tests under unconfined compression to assess five biomechanical parameters. The maximum compressive stress (σmax) and the equilibrium stress (σeq) were directly extracted from the experimental curves, while the fibril-network reinforced biphasic model was used to obtain the matrix modulus (Em), the fibril modulus (Ef), and the permeability (k). No significant changes were observed in σeq and Em in any of the tested storage conditions. Significant decreases and increases, respectively, were observed in σmax and k in the growth plate samples refrigerated for more than 48 h and in the frozen samples, when compared with the fresh samples. The fibril modulus Ef of all stored samples was significantly reduced compared to the fresh samples. These results indicate that the storage of growth plates in a humid chamber at 4 °C for a maximum of 48 h is the condition that minimizes the effects on the measured biomechanical parameters, with only Ef significantly reduced. Refrigerating growth plate explants for less than 48 h maintains their maximal stress, equilibrium stress, matrix modulus, and permeability. However, cold storage at 4 °C for more than 48 h and freezing storage at −20 °C significantly alter the biomechanical response of growth plate samples. Appropriate growth plate sample storage will be beneficial to save time and reduce transportation costs to pick up fresh samples.
Experimental Investigation of Liquid Jet Breakup in a Cross Flow of a Swirling Air Stream
Authors: Sikroria Tushar , Kushari Abhijit , Syed Saadat , Lovett Jeffery A.
Published: December 2013

This paper presents the results of an experimental investigation of liquid jet breakup in a cross flow of air under the influence of swirl (swirl numbers 0 and 0.2) at a fixed air flow Mach number 0.12 (typical gas turbine conditions). The experiments have been conducted for various liquid to air momentum flux ratios (q) in the range of 1 to 25. High speed (@ 500 fps) images of the jet breakup process are captured and those images are processed using matlab to obtain the variation of breakup length and penetration height with momentum flux ratio. Using the high speed images, an attempt has been made to understand the physics of the jet breakup process by identification of breakup modes—bag breakup, column breakup, shear breakup, and surface breakup. The results show unique breakup and penetration behavior which departs from the continuous correlations typically used. Furthermore, the images show a substantial spatial fluctuation of the emerging jet resulting in a wavy nature related to effects of instability waves. The results with 15 deg swirl show reduced breakup length and penetration related to the nonuniform distribution of velocity that offers enhanced fuel atomization in swirling fuel nozzles.
H2 Optimization of Damped-Vibration Absorbers for Suppressing Vibrations in Beams With Constrained Minimization
Authors: Tursun Murat , Eşkinat Eşref
Published: December 2013

Vibration absorbers are efficient and robust tools for reducing vibration and noise. Researchers use various alternative approaches and validate their methods with examples consisting of mass-spring-damper systems. Focusing on the minimization of the vibration amplitudes via passive absorber approach, a new and efficient method for calculating the optimum parameters of N absorbers attached to a uniform beam with M mode shapes (where N and M are any positive integers) has been developed. First, for the most general case, dissipation due to damping, kinetic, and potential energy and the effects of external forces are analyzed. The Lagrange's equation is used to provide the state space representation of the system. State space representation of a system with N absorbers and M mode shapes is composed. On the basis of the state space representation and the Lyapunov function, the H2 norm of the transfer function of the system is utilized in the newly developed optimization package. The system output is minimized by the optimization algorithm and displayed with a comparison between cases without an absorber and with randomly selected absorber parameters. As a conclusion, with the help of this method for calculation of optimal absorber parameters, one can easily design a mechanical system according to design criteria.
Particle Image Velocimetry Measurements in a Representative Gas-Cooled Prismatic Reactor Core Model: Distribution of Flow From the Upper Plenum to the Fuel Block Arrangement
Authors: Conder Thomas E. , Budwig Ralph S. , Skifton Richard S.
Published: December 2013

An experiment was conducted at Idaho National Laboratory to investigate the bypass flow associated with a Gas Turbine-Modular Helium Reactor in direct support of Computational Fluid Dynamic validation [1]. Velocity fields within a representative quartz model, consisting of an upper plenum, upper block, and lower block, were measured using Particle Image Velocimetry; after which, flow rates were calculated in each section. The present study was carried out to determine flow distribution from the upper plenum to the fuel block assembly. It was found that the flow rates in the lower six coolant channels varied from their average only by 2.4, 4.6, and 2.5% for the low, medium, and high flow cases, respectively. Consequently, it was concluded that the non-uniform inlet velocity condition in the upper plenum had insignificant effect on flow distribution to the coolant channels and interstitial gap.
Effects of Operating Frequency of a Synthetic Jet and Cross Flow Velocity on the Heat Transfer Enhancement in a Micro-Channel
Authors: Zschirnt Mark E. , Lee Ann , Yeoh Guan H.
Published: December 2013

Current devices have been reported to approach 1 MW/m2 so that current heat dissipation devices will not be able to cope with increasing heat flux. It has therefore been proposed that in order to manage the ever-increasing heat rejection demands, it will be necessary to have cooling fluid flowing through micro-channels in the microchip itself. Since laminar flow is likely to result for reasonable pressure drops in these micro-channels, the heat transfer rate will need to be enhanced if this approach is to be successfully used. Synthetic jets, which are the main focus of this research, generate vortex structures which disrupt the flow. They have, therefore, been proposed as a means of providing mixing, thereby augmenting the heat transfer potential of the fluid in the micro-channel.

A two-dimensional computational model has been developed to investigate the cooling effect of a synthetic jet interacting with a turbulent cross-flow in a micro-channel. Validation of the hydrodynamics feature of the flow was done by comparing numerical results against existing experimental results.

A parametric study was performed on a fixed geometry by using a constant wall temperature to investigate the effect of operating frequency of the synthetic jet actuator coupling with different flow rates in the micro-channel. The operating frequencies of the jet were simulated at 1000 Hz, 1500 Hz and 2000 Hz while the cross flows vary from 0 to 10 m/s. In general, the flow structures in the micro-channel were shown to be greatly disrupted when the synthetic jet actuator was turned on. However, the heat transfer enhancement due to the operation of the synthetic jet reduces as the cross flow increases. The frequency of the diaphragm oscillation has a large influence on the distance between the adjacent vortices and therefore on the average flow rate in the micro-channel. The near wall Nusselt Number was calculated in order to compare the effects of operating frequency of the jet and flow rate in the micro-channel. The jet Reynolds number was increased by 50% when the actuator frequency was increased from 1000 Hz to 1500 Hz while the heat transfer enhancement was increased by 21%. Further increment of actuator frequency from 1000 Hz to 2000 Hz resulted in a doubled jet Reynolds number while the heat transfer enhancement was improved by 66%. The heat transfer enhancement showed greater improvement when the actuator operating at 2000 Hz.
Temporal Gas Volume Fraction and Bubble Velocity Measurement Using an Impedance Needle Probe
Authors: Pirouzpanah Sahand , Morrison Gerald L.
Published: December 2013

Impedance probes are used by the oil and gas industry to investigate multiphase flow behavior. In this study, an impedance needle probe has been developed to measure the local and temporal gas volume fraction in conductive and non-conductive process fluid. Measuring both resistance and capacitance enables this probe to be functional in both types of fluids and facilitates the measurement of local bubble velocity. Two 1/32″ insulated brass (alloy 260) rods with bare tips protrude into the flow. The gap between the electrodes is designed to be 0.085″. The probe can measure directional bubble velocity by measuring duration of signal gradient from liquid to gas transition. For a known distance between electrodes and by the measured time, directional bubble velocity in the direction of the connecting line between electrodes can be measured. The ratio between the time interval when signal is non-zero to the total time represents the temporal gas volume fraction.
Evaluation of a Close Coupled Slotted Orifice, Electric Impedance, and Swirl Flow Meters for Multiphase Flow
Authors: Morrison Gerald , Pirouzpanah Sahand , Cevik Muhammet , Patil Abhay
Published: December 2013

The feasibility of a multiphase flow meter utilizing closely coupled slotted orifice and swirl flow meters along with an impedance sensor is investigated. The slotted flow meter has been shown to exhibit well behaved response curves to two phase flow mixtures with the pressure difference monotonically increasing with mixture density and flow rate. It has been determined to have less than 1% uncertainty in determining the flow rate if the density of the fluid is known. Flow visualizations have shown that the slotted orifice is a very good mixing device as well producing a homogenous mixture for several pipe diameters downstream of the plate. This characteristic is utilized to provide a homogeneous mixture at the inlet to the swirl meter. This is possible since the slotted orifice is relatively insensitive to upstream and downstream flow disturbances. The swirl meter has been shown to indicate decreased flow rate as the mixture density increases which is opposite to the slotted orifice making the solution of the two meter outputs to obtain density and flow rate feasible. Additional instrumentation is included. Between the slotted orifice and swirl meter where the flow is homogenous a custom manufactured electrical impedance sensor is installed and monitored. This array of instrumentation will provide three independent measurements which are evaluated to determine which system of equations are robust enough to provide accurate density and flow rate measurement over a wide range of gas volume fractions using a very compact system.
A Numerical Investigation of High Lift Coefficient Airfoils Near Regions of Stall
Authors: Venters Ravon , Helenbrook Brian
Published: December 2013

The cross-sectional geometry of a diffuser-augmented wind turbine (DAWT) is often that of a cambered airfoil oriented at an angle of attack such that the lift coefficient of the airfoil is maximal. Beyond this angle separation occurs, and the performance decreases. Thus, predicting this transition is important for creating an optimally designed diffuser. The focus of this work is to validate two numerical methods for predicting the onset of separation for highly cambered airfoils. The numerical models investigated are a Reynolds-averaged-Navier-Stokes (RANS) k–ε model and XFOIL. The results were compared to each other and to experimental data. Overall the most accurate model was the k–ε model. Using this model, an optimization of a 2D DAWT was performed which determined the optimal placement of the diffuser. This optimization showed that the optimal angle of attack for the diffuser is much greater than what one would expect based on the maximum lift angle of an airfoil in a free-stream.
Application of Molecular Tagging Velocimetry to Two-Phase (Gas/Liquid) Flows
Authors: Bohl Douglas , Green Adam , Kuzmich Kayla
Published: December 2013

The application of Molecular Tagging Velocimetry (MTV) to two-phase flows is investigated in this paper. The two phase flows under investigation were gas/liquid flows where the two phase region was composed of “clouds” of very fine bubbles with variable bubble densities (i.e. void fractions). MTV was applied to two different flows, a turbulent fully developed channel flow and a cavitating diffuser. The presence of the bubbles was found to degrade the image contrast. The amount the contrast was degraded depended on the bubble density of the two-phase region. Specifically, as the bubble density increased the image contrast within the two-phase region dropped. Measurements were found to be possible with contrast levels as low as 20 counts. While this contrast level was below the minimum contrast level recommended for measurements in prior studies, measurements were possible with elevated noise levels.
Performance and Internal Flow of Contra-Rotating Small Hydro Turbine
Authors: Shigemitsu Toru , Fukutomi Junichiro , Sonohata Ryosuke
Published: December 2013

Small hydropower generation is one of important alternative energy, and potential of small hydropower is great. Efficiency of small hydro turbines is lower than that of large one, and these small hydro turbine’s common problems are out of operation by foreign materials. Then, there are demands for small hydro turbines to keep high performance and wide flow passage. Therefore, we adopted contra-rotating rotors, which can be expected to achieve high performance and enable to use low-solidity rotors with wide flow passage, in order to accomplish high performance and stable operation. Final goal of this study is development of a small hydro turbine like electrical goods, which has high portability and makes an effective use of unused small hydro power energy source. In this research, experimental apparatus of the contra-rotating small hydro turbine with 60mm casing diameter was manufactured and performance of it was investigated by an experiment. Efficiency of the contra-rotating small hydro turbine was high in pico-hydro turbine and high efficiency could be kept in wide flow rate range. Internal flow condition, which was difficult to measure experimentally, was shown by the numerical flow analysis. Further, influence of spokes to support the rotor was clarified. Then, a relation between the performance and internal flow condition was considered by the experimental and numerical analysis results.
The Unsteady Flow in a Centrifugal Pump With Special Slope Volute
Authors: Gao Bo , Zhang Ning , Li Zhong , Yang Minguan
Published: December 2013

Conventional single stage centrifugal pumps are mostly designed with a spiral volute. Due to relative movement between impeller and the asymmetric volute the flow at the outlet of the impeller is strongly interacting with the volute flow. The unsteady phenomenon leads to unbalanced radial dynamic forces as well, especially at off-design points, giving rise to pump vibration and hydraulic noises.

In order to weaken the unsteady phenomenon, a special kind of slope volute is designed. Different from the spiral one, it keeps the radial size of the volute casing unchanged, but increasing the axial size to make sure the sectional area changing regularly from the tongue to pump outlet. CFD analysis has used to solve the unsteady 3D viscous flow in both conventional and special designed centrifugal pumps with the same impeller for several flow rates.

Compared to the spiral volute pump, there’s secondary flow with only one vortex existing in the slope volute. The average pressure and amplitudes of pressure fluctuations keep nearly unchanged along the slope volute wall due to the symmetrical shape in the radial direction. The pressure distributions for both pumps at fBPF are also very different. Interaction of the impeller flow with the tongue is weaken due to the different kind of tongue shape. It has little influence on the interaction flow field in the pump with slope volute. The radial load component always reaches a minimun magnitude at nominal conditions for both pumps. But the traces calculated for the pump with slope vloute are less stretched in the radial direction than those computed for the pump with spiral volute. Results indicate that a lower pulsation of the radial force is expected, and hardly affected by the flow rate for the pump with slope volute.
Use of the POD and the Coherent Structure Detection Criteria to Study the Flow Dynamics Downstream a Confined Square Obstacle
Authors: Abassi Wafik , Aloui Fethi , Ben Nasrallah Sassi , Legrand Jack , Labraga Larbi
Published: December 2013

Studying the concept of the vortex is an essential tool in the comprehension of fluid dynamics. Despite this, it is still very difficult to find a universal definition of a vortex. Several methods of detection and characterization of vortex structures has been developed and performed. Specifically tailored for PIV data, they present an important topic in modern experimental fluid mechanics.

In fact, the performance of the method is related to its effectiveness in the velocity data analysis and to successfully detect and locate the vortices as well as calculate the characteristic vortex parameters.

In the present study, we explore the efficiency of different vortex detection algorithms such as the vorticity ω, Γ2 and Q criteria by studying the vortices structures in the wake of a confined square obstacle.

Proper orthogonal decomposition (POD) of the velocity fields was used to extract the energetic contribution of the different instabilities modes.

These methods were firstly applied to an experimentally two-dimensional instantaneous velocity fields obtained by Particle Image Velocimetry (PIV) technique. Then, in a second step, we tested these criterions on a numerical velocity fields determined from Lattice Boltzmann simulations and compared to experimental results.
Influence of Vane Number on the Performance of Axial-Flow Pump Under Low-Flow-Rate Conditions
Authors: Kang Can , Huang Qifeng , Li Yunxiao
Published: December 2013

In order to further probe the relations between hydraulic features and instantaneous vibration of impeller pump, an axial flow pump designed with different combination schemes of rotor and stator is numerically investigated. Vane numbers of 5, 7 and 9 are separately adopted to match the same impeller with 4 blades. Attentions are paid on the pump’s performance under low flow rates. Saddle-shaped performance curves are proved during the three pumps’ operation with the variation of flow rate. With pre-defined non-dimensional parameters, distributions of axial velocity near the impeller and vane are described. Pressure waves and wake in the region between impeller and vane influence significantly the turbulent flow patterns and energy dissipation. Typical frequencies achieved through fast Fourier transformation of fluctuating pressures also indicate that the emergence of low-frequency components and energy dissipation in the rotor-stator interaction (RSI) region arouse more non-deterministic factors of hydraulic excitation.
Flow Patterns of an Annular Viscoplastic Jet
Authors: Hammad Khaled J.
Published: December 2013

The global flow field characteristics of a submerged annular viscoplastic jet were investigated within the steady laminar flow regime. The governing mass and momentum conservation equations, along with the Bingham rheological model, were numerically solved using a finite-difference scheme. Central and outer recirculation zones typically characterize the flow of a Newtonian annular jet. However, the performed parametric study revealed new and unique-to-viscoplastic-fluids flow features. The following flow patterns were observed and classified according to the characteristics of the central and outer recirculation zones: 1) for small yield numbers, central and outer recirculation zones exist. The extent of the outer zone and recirculation intensity of both zones were found to substantially diminish with the yield number; 2) at a high enough yield number, a stagnant, attached-to-the-wall region replaces the outer recirculation zone while a central, yet weaker one, still exists; 3) a further increase in the yield number results in the replacement of the weak central recirculation zone with a stagnant one and the elimination of flow recirculation throughout the whole flow field. The annular jet was found to decay faster and dissipate more rapidly when increasing the inner-to-outer annular nozzle diameter ratio.
Numerical Simulation of the Interaction Between Fluid Flow and Elastic Flaps Oscillations
Authors: Habchi Charbel , Russeil Serge , Bougeard Daniel , Harion Jean-Luc , Menanteau Sebastien , El Hage Hisham , El Marakbi Ahmed , Peerhossaini Hassan
Published: December 2013

Several numerical methods have been developed recently to solve problems including the interaction between viscous fluid flow and elastic solid structures. In this work, an in-house partitioned numerical solver is developed by using the open source C++ library OpenFOAM. Finite volume method is used to discretize the fluid flow problem on a moving mesh in an Arbitrary Lagrangian-Eulerian formulation and by using an adaptive time step. The structural elastic deformation is analyzed in a Lagrangian formulation using the St. Venant-Kirchhoff constitutive law. The solid structure is discretized by the finite volume method in an iterative segregated approach. The automatic mesh motion solver is based on Laplace smoothing equation with variable mesh diffusion. The strong coupling between the segregated solvers and the equilibrium on the fluid-structure interface are achieved by using an iterative implicit fixed-point algorithm with dynamic Aitken’s relaxation method. The solver is first validated on a benchmark largely used in the open literature. Then, a more complex case is studied including two elastic flaps immersed in a pulsatile fluid flow. The present solver predicts accurately the interaction between the complex flow structures generated by the flaps and the effect of the flaps oscillations on each other.
Characteristics of Dynamic Forces Generated by a Flapping Butterfly
Authors: Kuroki Taichi , Fuchiwaki Masaki , Tanaka Kazuhiro , Tabata Takahide
Published: December 2013

Many studies on the mechanism of butterfly flight have been carried out. A number of recent studies have examined the flow field around insect wings. Moreover, Micro-air-vehicles and micro-flight robots that mimic the flight mechanisms of insects have attracted significant attention, and a number of MAVs and micro-flight robots that use various devices have been reported. However, these robots were not practical. One of the reasons for this is that the flying mechanism of insects has not yet been clarified sufficiently. The present authors developed a flapping-wing robot without tail wings and focused on the flow field around the wings created by the flapping motion and its elastic deformation. In the present study, we attempt to clarify the relationship between the vortex ring over the wing and the dynamic lift generated by the flapping wing. The dynamic lift becomes large rapidly in the downward flapping and reaches a maximum at a flapping angle of −30 deg. After the maximum, the dynamic lift decreases gradually and the dynamic lift in upward flapping is approximately constant. The growth of the vortex ring formed by the flapping wing was clarified to contribute significantly to the dynamic lift acting on the butterfly. We should consider the interaction of both vortex ring both in downward flapping and in upward flapping in order to estimate the dynamic lift exactly using the circulation of the vortex ring.
Large-Eddy Simulations of Owl-Like Wing Under Low Reynolds Number Conditions
Authors: Kondo Katsutoshi , Aono Hikaru , Nonomura Taku , Oyama Akira , Fujii Kozo , Yamamoto Makoto
Published: December 2013

Flow fields around an owl-like wing and aerodynamic characteristics at a chord Reynolds number of 23,000 are investigated using three-dimensional implicit large-eddy simulation. The cross sectional profile of the owl wing model named “owl-like wing” is constructed based on the owl wing at 40% of the span length from the root. It consists of flat upper surface, large camber, and thin geometry. Results show that at low angles of attack (α), separation, transition, and reattachment are observed in the instantaneous flow fields on the pressure side. The laminar separation bubbles can be seen in time- and span-averaged flow fields. It is likely that lift and drag generation is correlated with the location of separation points on the suction side. However, it has little influence on behavior of CL-α curve. On the other hand, at high angles of attack, the flow on the pressure side is fully attached. The flow on the suction side is similar to that of the pressure side at low angles of attack. It is found that unlike the case of the flow at the low angles of attack, the laminar separation bubble on the suction side affects the response of CL to variation of α. Furthermore, it is possible to decrease the drag and to increase the lift when the location of the laminar separation bubble is well organized by an appropriate airfoil surface geometry. Also, the deeply concaved lower surface contributes to lift enhancement. From those factors mentioned above, the owl-like wing gains higher lift-to-drag ratio comparing with conventional thin and thick symmetrical airfoils such as NACA0002 and NACA0012. Indeed, maximum lift-to-drag ratio of the owl-like wing is approximately 23 at the angle of attack of 6.0 degrees at Reynolds number of 23,000.
Implications of Using Dual Number Derivatives With a Numerical Solution
Authors: Pakalapati Suryanarayana R. , Sezer Hayri , Celik Ismail B.
Published: December 2013

Dual number arithmetic is a well-known strategy for automatic differentiation of computer codes which gives exact derivatives, to the machine accuracy, of the computed quantities with respect to any of the involved variables. A common application of this concept in Computational Fluid Dynamics, or numerical modeling in general, is to assess the sensitivity of mathematical models to the model parameters. However, dual number arithmetic, in theory, finds the derivatives of the actual mathematical expressions evaluated by the computer code. Thus the sensitivity to a model parameter found by dual number automatic differentiation is essentially that of the combination of the actual mathematical equations, the numerical scheme and the grid used to solve the equations not just that of the model equations alone as implied by some studies. This aspect of the sensitivity analysis of numerical simulations using dual number auto derivation is explored in the current study. A simple one-dimensional advection diffusion equation is discretized using different schemes of finite volume method and the resulting systems of equations are solved numerically. Derivatives of the numerical solutions with respect to parameters are evaluated automatically using dual number automatic differentiation. In addition the derivatives are also estimated using finite differencing for comparison. The analytical solution was also found for the original PDE and derivatives of this solution are also computed analytically. It is shown that a mathematical model could potentially show different sensitivity to a model parameter depending on the numerical method employed to solve the equations and the grid resolution used. This distinction is important since such inter-dependence needs to be carefully addressed to avoid confusion when reporting the sensitivity of predictions to a model parameter using a computer code. A systematic assessment of numerical uncertainty in the sensitivities computed using automatic differentiation is presented.