bluuebunny/crossref_metadata_2025 huggingface dataset:
The regulation of the endosomal compartment by p53 the tumor suppressor gene
Authors: Yu Xin , Riley Todd , Levine Arnold J.
Published: March 2009

The endosomal compartment of the cell is involved in a number of functions including: (a) internalizing membrane proteins to multivesicular bodies and lysosomes; (b) producing vesicles that are secreted from the cell (exosomes); and (c) generating autophagic vesicles that, especially in times of nutrient deprivation, supply cytoplasmic components to the lysosome for degradation and recycling of nutrients. The p53 protein responds to various stress signals by initiating a transcriptional program that restores cellular homeostasis and prevents the accumulation of errors in a cell. As part of this process, p53 regulates the transcription of a set of genes encoding proteins that populate the endosomal compartment and impact upon each of these endosomal functions. Here, we demonstrate that p53 regulates transcription of the genes TSAP6 and CHMP4C, which enhance exosome production, and CAV1 and CHMP4C, which produce a more rapid endosomal clearance of the epidermal growth factor receptor from the plasma membrane. Each of these p53‐regulated endosomal functions results in the slowing of cell growth and division, the utilization of catabolic resources and cell‐to‐cell communication by exosomes after a stress signal is detected by the p53 protein. These processes avoid errors during stress and restore homeostasis once the stress is resolved.
Postdispersal Seed Fate of Tropical Montane Trees in an Agricultural Landscape, Southern Costa Rica
Authors: Cole Rebecca J.
Published: March 2009

Variation in postdispersal seed fate is an important factor driving patterns of forest regeneration. Because most previous studies have not tracked final seed fate and have commonly equated seed removal with predation without considering the possibility of secondary dispersal, little is known about individual seed mortality factors in successional and degraded habitats. This study tracked the postdispersal fate of large‐seeded tropical montane trees in abandoned pasture, young secondary forests, and small forest fragments during two consecutive years in an agricultural landscape in southern Costa Rica. The incidence of secondary dispersal by animals, scatterhoarding in particular, and the effects of seed burial on germination were measured. Overall, seeds survived through germination more often in secondary forests with high levels of mortality occurring in abandoned pastures and forest fragments. The majority of seed mortality was caused by rodent predation in forest fragments, insects and fungal pathogens in secondary forests, and a combination of desiccation, insects, and fungal pathogens in pastures. Seeds were frequently secondarily dispersed in larger forest fragments, whereas they were only rarely moved in pastures and secondary forests. Burial tended to improve germination in pastures and was important for an often scatterhoarded species, Otoba novogranatensis, in all habitats. The results of this study suggest that: (1) seed mortality factors differ in response to the type of habitat degradation; (2) large‐seeded species have high potential for survival when dispersed to young secondary forests; and (3) seed removal is not a reliable proxy for seed predation, particularly in less degraded forest fragments.
Effects of Vegetation Thinning on Above‐ and Belowground Carbon in a Seasonally Dry Tropical Forest in Mexico
Authors: Vargas Rodrigo , Allen Edith B. , Allen Michael F.
Published: March 2009

Mature tropical forests are disappearing and secondary forests are becoming more abundant, thus there is an increasing need to understand the ecology and management of secondary forests. In the Yucatan Peninsula, Mexico, seasonally dry tropical forests are subject to frequent fire, and early‐successional stands are extremely dense. We applied vegetation thinning (removal of all stems < 2 cm in diameter) to hasten secondary succession and open the understory to reduce the fire ladder in an 11‐yr‐old stand. We quantified the effect of vegetation thinning on above‐ and belowground carbon over 5 yr. Aboveground carbon included all standing vegetation and belowground carbon included fine roots and organic carbon in the Oi, Oe, and Oa soil horizons. Trees with diameter of 2–10 cm and > 10 cm had higher carbon accumulation rates in thinned plots than in control plots. Carbon stored in the Oi‐horizon and the Oe > 2 mm fraction remained significantly higher in thinned plots even 5 yr after treatment. Carbon in fine roots was significantly higher in thinned plots, and radiocarbon (14C) data suggest that fine roots in thinned plots were recently produced in comparison with fine roots in control plots. We did not find significant differences in total ecosystem carbon after 5 yr (126 ± 6 and 136 ± 8 Mg C/ha, respectively). These results suggest rapid carbon recovery and support the hypothesis that young tropical forests thinned to hasten succession and reduce the fire hazard may have only a short‐term negative impact on carbon accumulation in vegetation and soils.
The nature of the ASCA/INTEGRAL source AX J183039-1002: A new Compton-thick AGN?
Authors: Bassani L. , Landi R. , Campana R. , McBride V. A. , Dean A. J. , Bird A. J. , Green D. A. , Ubertini P. , De Rosa A.
Published: March 2009

We report on the identification of the X/soft γ-ray source AX J183039–1002 detected with ASCA and INTEGRAL/IBIS. The source, which has an observed 20–100 keV flux of ∼8.6 × 10−11 erg cm−2 s−1, is inside a diffuse radio supernova remnant (SNR) and is spatially coincident with a compact radio source. We analysed archival Chandra and XMM–Newton observations in order to identify the ASCA/INTEGRAL source. A point-like Chandra X-ray object was found to be positionally coincident with the compact radio source and within the error circle of the ASCA and INTEGRAL sources. Although the association of a compact radio/X-ray source with a radio SNR could be indicative of a pulsar wind nebula (PWN), the XMM–Newton X-ray spectrum is compatible with an absorbed, Seyfert-2 like active galactic nucleus, since it provides evidence for an iron emission line of ∼1 keV equivalent width; furthermore the X-ray source spectrum is similar to that of other Compton thick AGN where the ≲2 keV data are associated to a warm reflector and the ≳10 keV one to a cold reflector.
Fast TeV variability in blazars: jets in a jet
Authors: Giannios Dimitrios , Uzdensky Dmitri A. , Begelman Mitchell C.
Published: March 2009

The fast TeV variability of the blazars Mrk 501 and PKS 2155−304 implies a compact emitting region that moves with a bulk Lorentz factor of Γem∼ 100 towards the observer. The Lorentz factor is clearly in excess of the jet Lorentz factors Γj≲ 10 measured on sub-pc scales in these sources. We propose that the TeV emission originates from compact emitting regions that move relativistically within a jet of bulk Γj∼ 10. This can be physically realized in a Poynting flux-dominated jet. We show that if a large fraction of the luminosity of the jet is prone to magnetic dissipation through reconnection, then material outflowing from the reconnection regions can efficiently power the observed TeV flares through synchrotron-self-Compton emission. The model predicts simultaneous far-ultraviolet/soft X-ray flares.
Protective effects of exercise preconditioning on hindlimb unloading‐induced atrophy of rat soleus muscle
Authors: Fujino H. , Ishihara A. , Murakami S. , Yasuhara T. , Kondo H. , Mohri S. , Takeda I. , Roy R. R.
Published: March 2009

Aim:  A chronic decrease in the activation and loading levels of skeletal muscles as occurs with hindlimb unloading (HU) results in a number of detrimental changes. Several proteolytic pathways are involved with an increase in myofibrillar protein degradation associated with HU. Exercise can be used to counter this increase in proteolytic activity and, thus, may be able to protect against some of the detrimental changes associated with chronic decreased use. The purpose of the present study was to determine the potential of a single bout of preconditioning endurance exercise in attenuating the effects of 2 weeks of HU on the mass, phenotype and force‐related properties of the soleus muscle in adult rats.

Methods:  Male Wistar rats were subjected to HU for 2 weeks. One half of the rats performed a single bout of treadmill exercise for 25 min immediately prior to the 2 weeks of HU.

Results:  Soleus mass, maximum tetanic tension, myofibrillar protein content, fatigue resistance and percentage of type I (slow) myosin heavy chain were decreased in HU rats. In addition, markers for the cathepsin, calpain, caspase and ATP‐ubiquitin‐proteasome proteolytic pathways were increased. The preconditioning endurance exercise bout attenuated all of the detrimental changes associated with HU, and increased HSP72 mRNA expression and protein levels.

Conclusion:  These findings indicate that exercise preconditioning may be an effective countermeasure to the detrimental effects of chronic decreases in activation and loading levels on skeletal muscles and that an elevation in HSP72 may be one of the mechanisms associated with these responses.
Avian influenza A H5N1 infections in Bali province, Indonesia: a behavioral, virological and seroepidemiological study
Authors: Santhia Ketut , Ramy Ayu , Jayaningsih Putri , Samaan Gina , Putra Anak Agung Gde , Dibia Nyoman , Sulaimin Cynthia , Joni Gusti , Leung Connie Y. H. , Malik Peiris Joseph Sriyal , Wandra Toni , Kandun Nyoman
Published: March 2009

Background  Bali Province was affected by avian influenza H5N1 outbreaks in birds in October 2003. Despite ongoing circulation of the virus, no human infection had been identified by December 2005.

Objectives  To assess behavioral patterns associated with poultry rearing in Bali, and to identify potential risk factors for H5N1 infection in humans and in household chickens, ducks and pigs.

Methods  A behavioral, virological and seroepidemiologic survey in 38 villages and three live bird markets was completed in December 2005. A multi‐stage cluster design was used to select 291 households with 841 participants from all nine districts in Bali. Specimens were collected from participants as well as a maximum of three pigs, chickens and ducks from each household. Eighty‐seven market vendors participated, where specimens were collected from participants as well as chickens and ducks.

Results  Twenty out of the 38 villages sampled had H5N1 outbreaks. Despite exposure to H5N1 outbreaks, none of the participants from villages or markets were seropositive for H5N1. None of the pigs tested were positive for H5N1. Virus isolation rate in ducks and chicken in markets was higher than in households. Transport of poultry in or out of villages was a risk factor for outbreaks in household chickens and ducks.

Conclusions  The study highlighted that the market chain and associated behaviors may play a role in maintaining the virus in household flocks. The study adds evidence that transmission of H5N1 to humans remains a rare event despite high level handling of both healthy and sick birds.
Detecting methylation patterns of p16, MGMT, DAPK and E‐cadherin genes in multiple myeloma patients
Authors: YUREGIR O. OZALP , YURTCU E. , KIZILKILIC E. , KOCER N. E. , OZDOGU H. , SAHIN F. I.
Published: March 2009

Multiple myeloma (MM) is a B‐cell neoplasia characterized by the clonal proliferation of plasma cells. Besides known genetic abnormalities, epigenetic changes are also known to effect MM pathogenesis. DNA methylation is an epigenetic mechanism that silences genes by adding methyl groups to cytosine‐guanine dinucleotides at the promoter regions. In this study, the methylation status of four genes; p16, O6‐methyl guanine DNA methyl transferase (MGMT), death‐associated protein kinase (DAPK) and E‐cadherin (ECAD); at the time of diagnosis was investigated using methylation‐specific polymerase chain reaction (MS‐PCR). In the 20 cases studied; methylation of the promoter regions of p16, MGMT, DAPK and ECAD genes was detected in 10%, 40%, 10% and 45% of the cases, respectively. In 65% (13/20) of cases, at least one of the genes studied had promoter methylation; while 35% of cases (7/20) had methylated promoters of more than one gene. There was a significant correlation between promoter hypermethylation of MGMT and the presence of extramedullary involvement; but for the other genes no correlation was found regarding disease properties like age, disease stage, clinical course and the presence of lytic bone lesions. Determining the methylation profiles of genes in MM, could lead to a new understanding of the disease pathogenesis and guide the assessment of treatment options.
Microsatellites from the charcoal rot fungus (Macrophomina phaseolina)
Authors: BAIRD RICHARD E. , WADL PHILLIP A. , WANG XINWANG , JOHNSON DENITA H. , RINEHART TIMOTHY A. , ABBAS HAMED K. , SHIER THOMAS , TRIGIANO ROBERT N.
Published: March 2009

Microsatellite loci were identified from the charcoal rot fungus (Macrophomina phaseolina). Primer pairs for 46 loci were developed, and of these, 13 were optimized and screened using genomic DNA from 55 fungal isolates collected predominantly from two soybean fields in Mississippi. Twelve of the optimized loci were polymorphic and the number of alleles per locus ranged from 6 to 22. These microsatellites will be useful in population and pathogenicity studies to correspond with development of potential disease‐resistant soybean and other susceptible crops.
Isolation and characterization of microsatellite loci in Symbiodinium B1/B184, the dinoflagellate symbiont of the Caribbean sea fan coral, Gorgonia ventalina
Authors: ANDRAS JASON P. , KIRK NATHAN L. , COFFROTH MARY ALICE , HARVELL C. DREW
Published: March 2009

Here we report primers targeting 10 microsatellite loci of dinoflagellates in the genus Symbiodinium (clade B1/B184) symbiotic with the Caribbean sea fan coral, Gorgonia ventalina. Primers were tested on 12 Symbiodinium B1/B184 cultures, as well as 40 genomic DNA extracts of G. ventalina tissue samples. All loci were polymorphic with allelic richness ranging from 4–16. Gene diversity ranged from 0.15 to 0.91. These primers provide powerful tools for examining the fine‐scale population structure and dynamics of Symbiodinium within a single host species.
Isolation and characterization of eight microsatellite loci from the longheaded eagle ray, Aetobatus flagellum (Elasmobranchii, Myliobatidae)
Authors: YAGISHITA N. , YAMAGUCHI A.
Published: March 2009

The longheaded eagle ray, Aetobatus flagellum feeds mainly on bivalves, and there have been some indications that the current reduction in the bivalve population in southern Japan may be due to an increase in the number of longheaded eagle rays. Consequently, the ‘predator control programme’ for reducing the longheaded eagle ray population was established in 2001 in Japan. For studying the population genetics of the longheaded eagle ray, we isolated eight polymorphic microsatellite loci (two to six alleles per locus; expected heterozygosity, 0.172–0.700) from this species.
New Holland honeyeater (Phylidonyris novaehollandiae) microsatellites: isolation and characterization of 15 novel markers using an enrichment method
Authors: MYERS STEVEN A. , GARDNER MICHAEL G. , DONNELLAN STEPHEN , KLEINDORFER SONIA
Published: March 2009

The New Holland honeyeater (Phylidonyris novaehollandiae) plays a significant role in the pollination and sustainability of Australia's endemic flora, and hence fauna. Despite this key ecosystem function, knowledge of P. novaehollandiae life‐history traits and population dynamics remain poorly understood. We describe the development of primers amplifying 22 P. novaehollandiae microsatellite loci. Fifteen of the loci were found to be polymorphic, with observed heterozygosity between 0.500 and 1.000, and from four to 17 alleles per locus in adult birds from the study site.
Highly polymorphic microsatellite markers for Radix balthica (Linnaeus 1758)
Authors: SALINGER M. , PFENNINGER M.
Published: March 2009

We present data for eight polymorphic microsatellite markers isolated from a microsatellite‐enriched DNA library for the freshwater snail Radix balthica. Three of them were specific for R. balthica while five also amplified polymorphic products in two congeneric species. Test application on populations from all over the species range has shown that these loci are highly informative for analysing population structure and estimating migration rates. Observed deviations from Hardy–Weinberg equilibrium are attributed to a mixed mating system.
New polymorphic microsatellite markers and development of mitotyping primers for West Mediterranean green toad species (Bufo viridis subgroup)
Authors: COLLIARD CAROLINE , SICILIA ALESSANDRA , MORITZ CRAIG , PERRIN NICOLAS , STÖCK MATTHIAS
Published: March 2009

We report new polymorphic microsatellites for three species of Palearctic green toads (Bufo viridis subgroup): 10 in B. balearicus and seven each in B. siculus and B. boulengeri. Diversity at these loci, measured for 27 B. balearicus, 23 B. siculus and 11 B. boulengeri, ranged from low to high (two to 10 alleles). Mitotyping primers, specific to the control region, which allow fast screening of parapatric Sicilian endemic B. siculus and Italian mainland‐origin B. balearicus, were developed.
Muscular and pulmonary O2 uptake kinetics during moderate‐ and high‐intensity sub‐maximal knee‐extensor exercise in humans
Authors: Krustrup P. , Jones A. M. , Wilkerson D. P. , Calbet J. A. L. , Bangsbo J.
Published: March 2009

The purpose of this investigation was to determine the contribution of muscle O2 consumption () to pulmonary O2 uptake () during both low‐intensity (LI) and high‐intensity (HI) knee‐extension exercise, and during subsequent recovery, in humans. Seven healthy male subjects (age 20–25 years) completed a series of LI and HI square‐wave exercise tests in which (direct Fick technique) and (indirect calorimetry) were measured simultaneously. The mean blood transit time from the muscle capillaries to the lung (MTTc‐l) was also estimated (based on measured blood transit times from femoral artery to vein and vein to artery). The kinetics of and were modelled using non‐linear regression. The time constant (τ) describing the phase II kinetics following the onset of exercise was not significantly different from the mean response time (initial time delay +τ) for kinetics for LI (30 ± 3 vs 30 ± 3 s) but was slightly higher (P < 0.05) for HI (32 ± 3 vs 29 ± 4 s); the responses were closely correlated (r= 0.95 and r= 0.95; P < 0.01) for both intensities. In recovery, agreement between the responses was more limited both for LI (36 ± 4 vs 18 ± 4 s, P < 0.05; r=−0.01) and HI (33 ± 3 vs 27 ± 3 s, P > 0.05; r=−0.40). MTTc‐l was ∼17 s just before exercise and decreased to 12 and 10 s after 5 s of exercise for LI and HI, respectively. These data indicate that the phase II kinetics reflect kinetics during exercise but not during recovery where caution in data interpretation is advised. Increased probably makes a small contribution to during the first 15–20 s of exercise.
Acid‐sensing ion channels in neurones of the rat suprachiasmatic nucleus
Authors: Chen Chun‐Hao , Hsu Yi‐Ting , Chen Chih‐Cheng , Huang Rong‐Chi
Published: March 2009

We used reduced slice reparations to study ASIC‐like currents in the rat central clock suprachiasmatic nucleus (SCN). In reduced SCN preparations, a drop of extracellular pH evoked a desensitizing inward current to excite SCN neurones to fire at higher rates. Under voltage‐clamped conditions, all SCN neurones responded to a 5 s pH step to 6.4 with an inward current that decayed with an average time constant of 1.2 s to 10% of the peak at the end of step. The current was blocked by amiloride with an IC50 of 14 μm and was carried mainly by Na+, suggesting an origin of ASIC‐like channels. The SCN neurones were sensitive to neutral pH, with 94% of cells responding to pH 7.0 with an inward current. The study of sensitivity to pH between 7.0 and 4.4 revealed a two‐component dose‐dependent H+ activation in most SCN neurones, with the first component (85% in amplitude) having a pH50 of 6.6, and the second (15%) a pH50 of 5. The ASIC‐like currents were potentiated by lactate and low Ca2+, but were inhibited by Zn2+. RT‐PCR analysis demonstrated the presence of mRNA for ASIC1a, 2a, 2b, and 3 in SCN. Compared to other central neurones, the unique presence of ASIC3 along with ASIC1a in SCN neurones may contribute to the high pH sensitivity and unusual inhibition by Zn2+. The high pH sensitivity suggests that the SCN neurones are susceptive to extracellular acidification of physiological origins and that the ASIC current might play a role in regulating SCN excitability.
Some Problems of Boundary Conditions in the Cavitation
Authors: Terentiev Alexey G.
Published: March 2009

Most of cavitation problems are considered by standard conditions i.e. Neumann’s condition on the boundary, constant pressure on the cavity boundary and undisturbed flow in infinty. In this paper cavitating flow problems are considered by following conditions: a) evaporation from free boundary into the cavity, b) capillary surface tension on the boundary of the cavity, c) simulated gravity field in a flow, d) compressibility of the fluid. All these problems have been investigated analytically and obtained a number of calculated data.
Transonic and Supersonic Inviscid Flow Equations in 3-D Eccentric Nozzles
Authors: Mazaheri Ali Reza , Emdad Homayoon , Ahmadi Goodarz
Published: March 2009

Three dimensional unsteady inviscid flows in convergent-divergent nozzles is of importance in understanding the stability of rockets and jet propulsion. A computer program for evaluating unsteady inviscid flow conditions in three-dimensional eccentric as well as concentric nozzles is developed. The program uses the cell-centered finite-volume method based on Roe’s approximate Riemann solver scheme. The flow simulation results in concentric circular nozzles are compared with the one-dimensional analytic solutions and the accuracy of the computation model is verified. The results for steady and unsteady flows through eccentric and concentric convergent-divergent nozzles are then presented. A range of exit to throat areas, pressure ratios, and inlet Mach number are considered.
New Abilities of the Multiapplication elsA Software in the Field of Turbomachinery Flow Computation
Authors: Castillon L. , Billonnet G. , Plot S.
Published: March 2009

Navier-Stokes solvers are now common tools in current design and analysis of turbomachinery bladings, and their validation is therefore essential. In this context, ONERA is working on the validation of the elsA software, which is a multi application CFD solver using an object-oriented architecture. This paper presents a review of 3D steady computations performed at ONERA on turbomachinery applications with the elsA software. The aim is to show and to present the numeric tools available in the elsA software for such applications. Three turbomachinery applications are presented : the NASA 37 transonic rotor, Vega2’s transonic turbine stage and the experimental ISO cascade.
Compression of Barotropic Turbulence Simulation Data Using Wavelet-Based Lossy Coding
Authors: Wilson John P.
Published: March 2009

Single-precision floating point data from a simulation of barotropic turbulence is compressed with a wavelet-based method. The quantity being compressed is vorticity. The compression error is evaluated both in terms of error in the vorticity and the error in various quantities derived from the vorticity. Numerical error is evaluated in all quantities and visualizations of the vorticity and correlation of the error with the uncompressed data are evaluated. It is found that depending on the quantities of interest and the evaluation criteria, compression ratios of 4:1 to 256:1 are achievable. Under a conservative definition of acceptable error, it is possible to recover quantities of interest from data compressed 4:1 (8bpp), the data rate that in existing practice is used for visualization.
The Effect of Bubbles on Vortical Flows
Authors: Lu Jiacai , Ferna´ndez Auturo , Tryggvason Gretar
Published: March 2009

The effect of bubbles on vortical flows near walls is examined by direct numerical simulations. A simple model problem, consisting of two slightly perturbed counter rotating vortex tubes plus a parabolic pressure driven velocity profiles is used. Initially, the flow is seeded with several bubbles near the wall. As the flow evolves, the bubbles are entrained into the vortices, where they accelerate the breakdown of the vortices. The flow rate and the wall shear is monitored and the result show that the presence of bubbles leads to a slight decrease in drag and thus an increase in flow rate.
A Three-Dimensional Numerical Study of Tin Droplets Landing Sequentially on a Solid Surface
Authors: Ghafouri-Azar R. , Mostaghimi J. , Chandra S.
Published: March 2009

A three-dimensional (3-D) model of spreading and solidification was used to investigate the sequential deposition of two tin droplets for different offset landing. Numerical simulations predicted the shape and size of the landing tin droplet as it spread over a previously landed splat. The model applies a fixed-grid Eulerian control volume to solve the fluid dynamics and energy equations. The Volume of Fluid (VOF) algorithm is used to track the free surface deformation. The comparison of the simulated images and experimental photographs validated the prediction of the model.
The Static Pressure Field on the Casing of the Turbine Rotor in an Automotive Torque Converter Based on High Frequency-Response Rotating Probe Measurement
Authors: Liu Y. F. , Lakshminarayana B.
Published: March 2009

The static pressure on the rotating turbine casing wall of an automotive torque converter was measured using high frequency-response probe at different speed ratios. The static pressure drop on the turbine rotor casing is the highest compared to the data near the casing wall and the mass averaged value at both the design condition (SR = 0.6) and the peak efficiency condition (SR = 0.8) due to higher centrifugal force effect. The static pressure distributions along the camber line indicate that the blade loading is highest near the turbine mid-chord region at all speed ratios, which can be attributed mainly to the strong Coriolis force due to the strong flow turning both in the meridional direction and on the blade-to-blade surface along the camber line. The normalized static pressure contours indicate that the flow does not separate near the turbine casing (shell). A substantial pressure gradient exists across the passage, which indicates that flow turning and Coriolis force have significant influences. The total unsteadiness is relatively high near the turbine leading edge and low near the turbine trailing edge. The low unsteady level may indicate that the highly viscous fluid employed in the torque converter may have a strong influence on damping the unsteadiness caused by rotor/rotor and rotor/stator interactions.
An Experimental Characterization of the Flow Past an Airfoil in the Wake of a Circular Rod
Authors: Michard M. , Jacob M. C. , Grosjean N.
Published: March 2009

An experimental study of the flow past an airfoil in the wake of a rod shows that, at high Reynolds numbers, the vortices shed by the rod are strongly stretched and split near the leading edge and affected by small scale turbulence structures. These are shown to enhance three-dimensional effects, and to broaden the spectrum around the shedding frequency. The airfoil leading edge is the dominant acoustic source region. Post-processing tools combining Proper Orthogonal Decomposition and new vortex identification algorithms are applied to PIV measurements in order to extract the main vortical structures from snapshots, and study their variability.
Unsteady Propulsor Force Prediction for Spatially and Temporally Varying Inflow
Authors: Huyer Stephen A. , Snarski Stephen R.
Published: March 2009

A method to compute unsteady propulsor forces for spatially and temporally varying inflows is presented. A propulsor flow prediction code, previously developed by the Massachusetts Institute of Technology, was modified and upgraded to account for time varying inflow and multiple blade rotations. The original code utilizes lifting surface theory and discretizes the propulsor surface as boundary elements to compute the unsteady potential flow. Experimental data characterizing the full unsteady, three-dimensional turbulent inflow to a Swirl-Induced Stator Upstream of Propulsor (SISUP) propulsor, were used as inflow boundary conditions. Experimental data recorded the periodic velocity fluctuations due to the stator wakes as well as the broadband turbulent characteristics of the inflow. Blade force, integrated shaft force, and blade pressure are computed based on the experimental inflow. The effect of periodic variations in the inflow was examined to determine the effect on unsteady blade forces. For these cases, the time mean experimental effective inflow is used and a fluctuating component is added for flow in the axial direction. This may be viewed as an effectively fluctuating freestream. Comparisons of unsteady force and radiated noise are then made with the baseline mean flow case to gauge the time-varying effects. Fluctuating velocity dramatically altered the force spectra even at frequencies different from the velocity fluctuation frequency. This modified algorithm can now be utilized to examine a wider set of time-dependent propulsor flow problems and to calculate the associated performance due to these unsteady flows.
A Non-Overlapping Domain Decomposition Method for the Stokes Problem
Authors: Zsaki Attila , Paraschivoiu Marius
Published: March 2009

A domain decomposition method for the Stokes problem using Lagrange multipliers is described. The dual system associated with the Lagrange multipliers is solved based on an iterative procedure using the two-level finite element tearing and interconnecting (FETI) method. Numerical tests are performed by solving the driven cavity problem. An analysis of the number of outer iterations and an evaluation of the cost of the inner iterations are reported. Comparison with the well-known Uzawa algorithm shows a reduction in the floating point operations count of the inner iterations while achieving the same number of outer iterations.
Design of Flexible Containers for Sloshing Control
Authors: Gradinscak M. , Semercigil S. E. , Turan O¨. F.
Published: March 2009

Sloshing is the low frequency oscillation of a liquid in a partially full container. Only a limited number of attempts is reported in the literature to control sloshing. Amongst these limited attempts, no effort can be found to employ the flexibility of liquid containers to suppress sloshing. Here, progress is reported of an ongoing research program at Victoria University to determine the critical design parameters of flexible containers to achieve effective control. Numerical predictions as well as experimental observations are presented.
Influence of Instabilities on the Trajectory of a Light Sphere
Authors: Jenny Mathieu , Bouchet Gilles , Dusˇek Jan
Published: March 2009

Recent numerical simulations of the wake of a fixed sphere have confirmed that hydrodynamic forces are likely to have a significant impact on the trajectory of a freely falling (or ascending) sphere. An ideally spherical body ceases to follow a straight vertical trajectory at the Reynolds number (based on its velocity U and diameter d) corresponding to the onset of the primary instability responsible for the breaking of axisymmetry in a fixed sphere wake, i.e. at Re = 212. This instability has been shown to generate a steady non axisymmetric flow with a symmetry plane containing the asymptotic flow velocity, the orientation of which is arbitrary, i.e. selected by any small perturbation at the instability onset. In this communication, we present further work focussed on the experimental investigation of the effect of instabilities on the trajectory of a free sphere. The axisymmetry breaking results in a lift and torque, the vector of lift lying in the symmetry plane and the torque being normal to this plane. This leads to the conclusion that a free-falling (ascending) sphere will be deviated from its vertical trajectory as soon as its Reynolds number reaches the threshold of 212. Moreover, the trajectory will be deflected in an arbitrarily selected vertical plane. An experimental setup has been implemented to investigate this effect. It consists of a 2.5 m high water tank with a .5 times .5 m cross section placed in an air-conditioned chamber allowing to control finely the asymptotic Reynolds number of small spheres (on the order of a mm in diameter) by varying the water temperature. Spheres of densities close to that of water, both lighter and heavier, are considered. The trajectories are investigated fully in three dimensions by processing of images of two cameras following the sphere movement. The preliminary results, presented here for polypropylene spheres lighter than water, confirm the numerically and theoretically predicted effect. After a short acceleration phase roughly in vertical direction the primary instability deflects the trajectories each time in a different vertical plane. The investigation of the fixed sphere wake showed the onset of a secondary Hopf-type instability at Re ≈ 275. The same type of instability develops clearly for free spheres. Unlike for the fixed sphere, the secondary instability is observed to dominate and to yield a wavy trajectory with a vertical mean direction.
Simplified Two-Fluid Models for Dilute Turbulent Multiphase Flows Using Equilibrium Closure
Authors: Balachandar S. , Ferry J. , Rani S.
Published: March 2009

In two-fluid models of multiphase flow the dispersed phase is treated as a continuum and here we explore the consequences of the dispersed phase being in equilibrium with the surrounding flow. Under equilibrium the particle velocity field can be expressed as an explicit expansion in the surrounding fluid velocity. To the leading order the particle velocity is the same as the local fluid velocity and the first order correction will be shown to capture important physics such as preferential accumulation of particles and turbuphoretic particle migration. To verify the equilibrium expansion, we have performed direct numerical simulations of particles and bubbles in the canonical problems of isotropic turbulence and a turbulent channel flow, where “true” particles moved according to their Lagrangian equations of motion are compared with “test” particles moved according to the equilibrium particle velocity. For small particles the equilibrium expansion is shown to converge rapidly. The equilibrium concept will be extended to the rotational motion and thermal field of the particle. The equilibrium approximation for the particle provides a clean mechanism for two-way coupling and a rigorous set of equations for the description of multi-phase flow turbulence, in the limit of a dilute dispersion of small particles.
A Bridge Between Science and Practical Engineering
Authors: Yedidiah S.
Published: March 2009

This paper discusses the causes and effects of the ever-growing gap between academia and the practicing engineer. Also, it suggest a possible means which might be capable to bring both approaches closer together. Recent advances in science have opened up new horizons before the practicing engineers. However, these new developments require to make use of so much information, that it makes it impossible for a single person to master simultaneously both: The scientific and the practical aspects of a given problem. It is very difficult for scientists to follow and to become intimately familiar with all the innovations which are continuously occurring in their own field. The less can a scientist afford to be distracted by attempts to master all the intricacies of the practical aspects of problems, which a practicing engineer has to take care of. The same is also true in relation to the possibility, that an engineer will master all the new developments which are occurring in science. To alleviate this problem, the academic community in Japan has recently adopted new criteria for the accreditation of institutions which are teaching engineering [4]. To become accredited, an engineering educational institution has to include, into its curriculum, also courses of a practical nature. The steps adopted in Japan will undoubtedly bring some relief to the problem. However, their effectiveness could be significantly enhanced by introducing a course which would teach how to translate a mathematical expression into its physical meaning. The capability to execute such a translation could bring science much closer to practical engineering. This paper presents a case history which illustrates the negative effects of the existing gap [1,2,3]. Also, it illustrates, how the existing gap between academia and the practicing engineer could be narrowed: By a course which would teach, how to translate a mathematical equation into its relevant physical meaning. Finally, it presents a case-history, which demonstrates the enormous potentials of a proper translation of a mathematical equation into its relevant physical meaning.
Fluid Flow Separation in Down Comer During a Safety Injection Scenario: Quantitative Experimental Results
Authors: Bichet Th. , Martin A. , Beaud F.
Published: March 2009

Within the framework of the nuclear power plant lifetime issue, the assessment of the French 900 MWe (3-loops) series Reactor Pressure Vessel (RPV) integrity was performed. A simplified analysis has shown that one of the most severe loading condition is given by the small break loss of coolant accidents (SBLOCA) due to the pressurized injection of cold water (9°C) into the cold leg and down comer of the RPV. Two main physical phenomena, considered important for the RPV cooling transient, were identified during numerical application obtained with EDF CFD tools. These phenomena are the fluid flow separation and the plume oscillations in the down comer. In order to consolidate these numerical results with the EDF home code, called Code_Saturne, an experimental study has been carried out with the new EDF R&D facility. This transparent experimental model is based on the representation at 1/2 scale of a cold leg and a third of down comer including a thermal shield. The experiments were realized by injecting of salt water flow (density effects) in the cold leg according to a similitude study based on Froude number conservation between experiments and reactor scenarios. Firstly, this paper presents the main qualitative experimental results, based essentially on visualizations of different injections of dyed salt water in the cold leg and in the down comer. The physical phenomena observed showed a qualitative good agreement between visualizations and numerical results. Secondly, this paper presents the first experimental results of the assessment of the fluid flow separation in the experimental model obtained with temperature probes inserted in the down comer. We showed, in the experiments analysis, the fluid flow separation and the jet oscillations were detected. The next step will consist to compare these quantitative experiments with numerical study which will be carry out with Code_Saturne.
Parallelized Domain Decomposition Techniques for Multiphase Flow
Authors: Uzgoren Eray , Shyy Wei , Garbey Marc
Published: March 2009

Direct simulation of multiphase flows is a challenging task due to the moving interface and property variations between phases. In this study, a parallel domain decomposition method is implemented for such flows to lower the computing cost. Specifically, the approach consists of the additive Schwarz method for domain decomposition, the projection method for the Navier-Stokes equations, the immersed boundary method for treating the interfacial dynamics, and the multigrid method to expedite the solution of the pressure Poisson equation. The issues related to load balancing, communication and computation, scalability in regard to grid size and the number of processors, and interface shape deformation, are studied using both SGI Altix and Linux-based Beowulf systems. As the number of processors increases, as expected, the domain decomposition technique results in modest decrease in convergence rate, while the multigrid technique is effective in reducing the computational cost. The additional computational cost incurred by the immersed boundary method for tracking the interface is not significant.
Numerical Determination of Rock-Mass Thermal Conductivity
Authors: Case John , Wagner Ralph A.
Published: March 2009

Temperature distributions from the Single Heater Test of the Yucca Mountain Project were used to determine rock-mass thermal conductivity. The Single Heater Test, located in a densely welded tuff in Alcove 5 of the Exploratory Studies Facility at Yucca Mountain, is nominally 13-m wide, 10-m deep and 5.5-m high. A centrally located, 5-m long, 4 kW electrical heater was activated for 9 months. During the heating phase and subsequent cooling phase of a similar duration, temperatures were measured hourly from more than 300 thermocouples emplaced in boreholes strategically drilled into the test block. An inverse method, that assumes a linearized system, was applied. This method minimized the sum of residuals between temperature measurements and simulations. The simulations were based on temporal and spatial superposition of a series of point sources that represented a linear heat source akin to the line-source heater in the Single Heater Test. Also the method accounted for fluctuations in the power of the central heater through the use of convolution methods. Subsequently, the derived value for rock-mass thermal conductivity was compared to values determined from several laboratory and field techniques that accounted for both matrix and lithophysal porosity. In general, agreement between the various methods was good.
Measurement and Calculation of Heat Exchanger Performance Using Film Method
Authors: Bougriou Che´rif , Bessai¨h Rachid , Eckert Kerstin , Kadja Mahfoud
Published: March 2009

In this paper, we present a method of calculation by partial or total condensation of the water vapor contained in the humid air, over the smooth or finned tubes-heat recupurators. This study presents an implantation of the film method in a computer code developed here. The mathematical model used is validated by our experimental approach, using tubes bundles in staggered and aligned arrangements. The heat transfer coefficient by convection around the fin is supposed too be constant. The computer code predicts the heat flux exchanged in a range of 20% and 5%, in wet and dry regime, respectively. The apparent heat transfer coefficient by condensation can exceed 10 times the value of the heat transfer coefficient. The mathematical model used is validated with the experimental data obtained in this study.
Computational Studies of Turbulent Flow in an Isothermal Suddenly Enlarged Combustion Chamber
Authors: Mishra D. P. , Vishak T.
Published: March 2009

The present work is concerned with computational studies of turbulent flow under isothermal condition in a suddenly enlarged combustion chamber using time averaged Navier-Stokes equations with an eddy-viscosity turbulence closure model. Results were compared well with that of experimental data available in open literature. The effect of inlet turbulence intensity is found to be the dominant parameter determining the flow field. However this effect is found to be decreasing with the increase in the expansion ratio. The increase of turbulence level decreases the reattachment length due to the energy supply to the separating shear layer, which is a major factor determining the reattachment length. It has been found out that for same expansion ratio, the reattachment length attains a minimum value for low turbulence Reynolds number, increases with increase in Reynolds number, and attains a maximum limit. Both the turbulent kinetic energy and the turbulent dissipation rate are found to be maximum in the shear layer and also keep increasing with the increase in turbulence intensity.
Accurate Prediction of Friction Factor for Laminar Flow in Irregular Annuli
Authors: Haddad O. M. , Al-Odat M. Q.
Published: March 2009

Steady fully-developed laminar flows of an incompressible fluid in an annulus of different irregular cross-sectional geometry are investigated numerically. Accurate prediction of the friction factor of these flows is obtained using the high-order finite element method. This study is focused on the annular flow between rectangular and triangular ducts under all possible arrangements. Our results showed excellent agreement with the corresponding results available in the literature. It is found that for all cases considered, the increase in the hydraulic radius of the annular area would lead to a decrease in the value of (fRe). In addition, for a fixed hydraulic radius: it is found that the square in triangle case (TS-case) has the lowest value of (fRe) whereas the square in square case (SS-case) has the largest value of (fRe).
Large Eddy Simulations of High Speed Flows
Authors: Kannepalli C. , Arunajatesan S. , Calhoon W. H. , Dash S. M.
Published: March 2009

RANS models are required for the prediction of scalar fluctuations and turbulent transport in the high speed flow regime. These models will have application, for example, in missile exhaust plume signature analyses, scramjet combustors and other important areas. However, experimentally derived scalar fluctuation data needed to develop these models for the high speed flow regime is not readily available due to the inability of relevant experimental measurement techniques (e.g. hot wires) to cope with this flowfield environment. This issue poses significant difficulties for model development in this flow regime. Researchers have used different values for the turbulent Prandtl and Schmidt numbers but no consensus has been reached as to what these values have to be for high speed flows. To address this difficulty, a two part program has been initiated to fill the data gap and thus facilitate model development. Part I of this program involves the collection of LES data over a wide range of conditions. Part II involves the use of these data to evaluate and develop RANS tools to improve predictive capabilities. This paper presents results and findings of Part I of this program. Several flow fields of relevance to the problems mentioned above are studied. These include classical unit problems such as high and low Mach number shear layers, boundary layers and separated flows such as compression corner flows. In the process we are gradually extending the applicability of LES to more complex flows and at the same time enabling RANS model development by facilitating flow databases in the high speed flight regime. The findings of this study elucidate the effects of compressibility on the character of mean scalar profiles, variations in turbulent Prandtl number, and on scalar rms fluctuations.
Experimental and Numerical Modeling Studies of Laser Chemical Vapor Deposition on Moving Optical Fibers
Authors: Kwok Kinghong , Chiu Wilson K. S.
Published: March 2009

An atmospheric-pressure laser-induced chemical vapor deposition (CVD) reactor has been developed that is capable of continuously depositing carbon protective films on moving optical fibers from several hydrocarbon precursors. The relationship between operating parameters and the carbon deposition temperature was investigated experimentally and the results indicate that they are highly dependent on the laser power density and the fiber’s drawing velocity. A computational heat transfer model was developed to calculate the fiber surface temperature during deposition and to provide a deeper understanding of the fundamental principles that govern laser heating and the carbon CVD processes. The surface temperatures obtained from experiments are compared with the calculated temperature in order to validate the numerical model.