bluuebunny/crossref_metadata_2025 huggingface dataset:
A Generalized Integral Numerical Solution Method for Lubrication Problems
Authors: Khader M. S.
Published: November 2009

A generalized numerical method for solving Reynolds equation of lubrication is developed. The method is general for the Reynolds equation in its one and two dimensional forms. The present numerical technique is based on converting the differential form of Reynolds equation to an integral form and using there with a universal singular solution of a unit source Poisson type equation. A fast efficient iterative numerical scheme is then employed for solving the integral equation for the pressure distribution. The paper is divided into two parts, the first is devoted to the method development while the second part is confined to the application of the method to different problems related to bearings.
A Boundary Integral Equation Method for the Study of Slow Flow in Bearings With Arbitrary Geometries
Authors: Kelmanson M. A.
Published: November 2009

This paper investigates the steady slow flow of an incompressible viscous fluid in the region between an inner circular cylinder rotating with constant angular velocity and an outer stationary cylinder of arbitrary cross section. The numerical solution technique known as the boundary integral equation method is employed in which the governing partial differential equations of motion are recast into coupled integral equations by repeated applications of the divergence theorem. The method is applied to the two dimensional flow within the eccentric journal bearing, and it is found that certain aspects of previous analytic treatments of this bearing have been in error. An extension of the method is applied to solve for the flow within an elliptical bearing, for which no analytic solution or numerical results are available. This extension is able to solve for the flow within any bearing geometry, however complex. It is found that the present method is particularly suited to the prediction of flow separation within noncircular bearings, and it is hoped that these results and techniques will lead to a better understanding of the conditions causing the phenomenon of cavitation.
Determination of the Load Capacity of a Finite Width Journal Bearing by a Finite-Element Method in the Case of a Non-Newtonian Lubricant
Authors: Bourgin P. , Gay B.
Published: November 2009

Additives are commonly used to improve the performance of lubricating oils. Correlatively, the lubricant viscosity depends on the rate of shear: the fluid becomes non-Newtonian. Assuming that the nonlinear relationship between the rate of strain tensor and the stress tensor is cubic, the film equations are derived within the approximations of lubrication theory. The governing equation, which generalizes the Reynolds’ equation, is a nonlinear partial differential equation, subject to two nonlinear constraints. The particular case of a finite width journal bearing is considered here; this problem is solved by the finite-element method, using a gradient technique. The numerical results are compared with established results for newtonian lubricants. The influence of the non-Newtonian parameter on the pressure field and on the bearing capacity is predicted.
Hybrid Porous Gas Journal Bearings: Steady State Solution Incorporating the Effect of Velocity Slip
Authors: Singh K. C. , Rao N. S. , Majumdar B. C.
Published: November 2009

A theoretical analysis is presented to predict the steady state performance characteristics of externally pressurized rotating gas journal bearings incorporating the effect of velocity slip at the porous interface. The governing equation for flow in the porous media and the modified Reynolds equation derived from the Navier-Stokes equations satisfying the velocity slip boundary condition, are solved simultaneously for film pressure distribution. Due to the nonlinearity of modified Reynolds equation the solution is obtained by perturbation method using finite difference technique. The dimensionless load capacity, attitude angle and mass rate of flow are computed numerically for different operating parameters. The effect of slip on the static characteristic is discussed. Comparison of the results with similar available solution for the no-slip case shows good agreement.
Prediction of Leakage Gap in Nonaxisymmetric Geometry Face Seals
Authors: Lebeck A. O.
Published: November 2009

With the recognition that seal faces are not perfectly flat and/or that nonaxisymmetric seal loading will cause seal faces to distort, there is a need to predict whether or not a leakage gap will result. If a gap does occur, it is then necessary to predict its size and circumferential variation. In this paper, a tool for predicting seal gap is developed. The method is general. Initial face profiles are arbitrary. Ring cross-sections and seal loading may vary circumferentially. The model uses the stiffness properties of a general ring finite element and couples the two rings by a series of springs which represent contact at the face. The entire problem is solved using a finite element method. The seal load is incremented so that as deflection increases, springs representing face contact are included in the problem as required. The final result is seal gap as a function of angular position or contact pressure at points where the faces touch. The model has been verified experimentally using two rings with an eccentric load which causes a gap to develop. Agreement with the experiment is good. The model is also used to predict leakage gap in some magnetically loaded commercial seals. A comparison between predicted leakage and measured leakage is made and the comparison is good. The model should find wide application in providing accurate analysis for seal leakage problems. It can be used to establish flatness guidelines as well as to show the effects of nonaxisymmetric loading on seal leakage.
A New Concept of Zero-Leakage Noncontacting Mechanical Face Seal
Authors: Etsion I.
Published: November 2009

A new concept of zero-leakage noncontacting mechanical face seal is described. Analysis of the seal performance and optimization of the seal ring geometry are presented. The main features of the new seal is a balance between pressure-induced and shear-induced flows and the simplicity of construction and performance prediction. Design charts for optimum seal configuration are given and the potential of the new concept is demonstrated by numerical examples.
Dynamics of Offset Bearings: Parametric Studies
Authors: Booker J. F. , Olikara P.
Published: November 2009

Novel “offset” designs offer greatly improved durability in applications for which conventional journal bearings are only marginally satisfactory. They are particularly attractive for duty cycles which combine nonreversing loading with limited angular oscillation. Offset designs seem equally promising for steady-state operation with counter-rotation of shaft and sleeve under fixed load, or (equivalently) with load rotating at half shaft speed. Both cases are elucidated through (dimensional) numerical examples and (nondimensional) parametric studies. In both cases performance of full journal bearings is shown to be both significantly improved by small offsets and fairly insensitive to small departures from optimal values.
Cavitation in an Oscillatory Oil Squeeze Film
Authors: Parkins D. W. , May-Miller R.
Published: November 2009

This paper records observed features of cavitation arising in an oscillatory oil squeeze film. In the experimental apparatus, two nondeformable surfaces contained the oil film. The square upper surface oscillated, normally to the oil film, at any frequency between 5 and 50 Hz. A transparent lower surface together with a viewing and synchronising system enabled cavitation bubble patterns in the oil film to be observed and photographed at any point in the oscillatory cycle. Three different behavioral regimes (designated 1, 2, and 3) have been observed, each characterized by the method of forming cavitation bubbles together with particular features in the oil film pressure, thickness and bubble extent-time cycle. Descriptions are given of the salient features of each regime, and the transition from one to another. The paper contains photographs of cavitation bubble patterns at important points in the typical oscillatory cycles together with their location in the oil film pressure and thickness time histories.
Pressure Spikes and Stability Considerations in Elastohydrodynamic Lubrication Models
Authors: Kostreva M. M.
Published: November 2009

Analytical tools useful in mathematical modeling of the elastohydrodynamic lubrication are developed. Stability maps which delimit the applicability of the two parameter EHL model are computed using linearized stability analysis and numerical analytic continuation. An exact solution is derived (for a region of constant film thickness within the lubricant) which explains the nature of a class of pressure spikes which arise under severe conditions. The relationship between stability and pressure spikes is discussed.
Contact Stresses Between Layered Elastic Cylinders
Authors: Solecki R. , Ohgushi Y.
Published: November 2009

Frictionless static contact between two layered elastic cylinders is examined. Local curvature of the the contacting surfaces is taken into account. Green’s function is derived and utilized to reduce the contact problem to Fredholm integral equation of the first kind with unknown contact width, unknown contact pressure distribution and unknown normal approach. Solution of this integral equation is obtained in the form of an infinite system of linear algebraic equations with the aid of Fourier transformation. The resulting equations are solved to give the pressure distribution and the normal approach for assumed contact width. Numerical results of two examples are presented: one in which an elastic layer bonded to a rigid cylinder is indented by another rigid cylinder, and, a second in which a layered elastic cylinder is indented by another layered elastic cylinder. The results obtained in the first example are compared with analytical solutions and with experimental data known from the literature.
Friction and Wear With a Fully Melting Surface
Authors: Stiffler A. K.
Published: November 2009

A theoretical model for melt lubrication is given which depends on the mass melt rate itself to develop load support between parallel surfaces. Expressions are derived for film thickness and temperature, coefficient of friction, and wear. The theory is applied to projectile rotating bands and ice skating.
Dynamically Loaded Journal Bearings: Finite Element Method Analysis
Authors: Goenka P. K.
Published: November 2009

In this paper a finite element formulation for transient analysis of journal bearings is described. The formulation can be used for partial or full-arc bearings with oil-supply hole and oil-feed grooves, with tapered or misaligned journal, and with elliptical or eccentric bearings. An important feature of this analysis is relatively low computing cost. The analysis is followed by an illustrative example in which 17 different cases of a connecting-rod bearing are solved.
The Swing-Pad Bearing: An Experimental Evaluation
Authors: Rightmire Glenn K.
Published: November 2009

The characteristic performance of the swing-pad bearing is evaluated in a parative study with the tilting-pad bearing. Frictional data are presented, together with representative pressure and film thickness distributions under both rigid elastomer shoes.
Squeeze Film Forces in a Magnetic Shaft Suspension System
Authors: Knox L. D.
Published: November 2009

Viscous squeeze film forces were studied as they pertain to a magnetic shaft suspension system (magnetic bearing). A nonrotating magnetically suspended shaft generates hydrodynamic fluid forces as it oscillates radially within a close fitting concentric cylinder. Experimental results from a scaled model verify the theoretical analysis. The study includes the finite and infinite length cases (1/4<L/D<8) for large diameter to clearance ratios (D/c>50). The viscous squeeze film forces increase the phase margin in the magnetic bearing closed-loop control systems used in state-of-the-art cryogenic refrigerators.
Dynamic Characteristics of a Hydrostatic Gas Bearing Driven by Oscillating Exhaust Pressure
Authors: Watkins C. B. , Branch H. D. , Eronini I. E.
Published: November 2009

Vibration of a statically loaded, inherently compensated hydrostatic journal bearing due to oscillating exhaust pressure is investigated. Both angular and radial vibration modes are analyzed. The time-dependent Reynolds equation governing the pressure distribution between the oscillating journal and sleeve is solved together with the journal equation of motion to obtain the response characteristics of the bearing. The Reynolds equation and the equation of motion are simplified by applying regular perturbation theory for small displacements. The numerical solutions of the perturbation equations are obtained by discretizing the pressure field using finite-difference approximations with a discrete, nonuniform line-source model which excludes effects due to feeding hole volume. An iterative scheme is used to simultaneously satisfy the equations of motion for the journal. The results presented include Bode plots of bearing-oscillation gain and phase for a particular bearing configuration for various combinations of parameters over a range of frequencies, including the resonant frequency.
Influence of Internal Stresses on the Stressing of Material in Components Subjected to Rolling-Contact Loads
Authors: Broszeit E. , Adelmann J. , Zwirlein O.
Published: November 2009

The stressing of a material in concentrated contacts can be calculated using f.e. the equivalent stress hypothesis by Huber, von Mises, Hencky (distortion energy hypothesis). The stress level can be directly related to the local yield properties of the material. For the calculation of the equivalent stress the influence of friction and internal stresses in the material have to be taken into account. The local stress level in the half space strongly depends on friction and internal stresses. It will be demonstrated, that it is necessary to have a look at a greater part of the full half space to find the maximum stress level.
A Study of the Elastohydrodynamic Problem in Rectangular Elastomeric Seals
Authors: Prati E. , Strozzi A.
Published: November 2009

This paper deals with the study of the elastohydrodynamic lubrication in elastomeric rectangular seals with rounded edges. The photoelastic and the numerical methods are employed in the determination of the dry contact pressure distribution. The existence of two contact pressure peaks near the seal edges is clarified. The influence of the sealed pressure and the sliding velocity on the pressure distribution is examined experimentally. The influence of Poisson’s ratio and constitutive relation on the stress field is studied numerically. The inverse hydrodynamic theory and the numerical method are used in the determination of the fluid film profile. The experimental and numerical fluid film shapes at the inlet are discussed. The influence on the film shape of the sealed pressure is studied experimentally, while the influence of the sliding velocity is examined numerically. The agreement between the experimental and the numerical results for the common cases is satisfactory.
Thermomechanical Cracking in Layered Media From Moving Friction Load
Authors: Ju F. D. , Chen T. Y.
Published: November 2009

This investigation studies a two-dimensional model of a layered medium subjected to the frictional excitation of a high-speed asperity traversing over the surface of the medium. The general analytical solutions of the mechanical stress state, the temperature field and the thermal stress state are obtained and expressed in the Fourier transform expressions. Numerical solutions are carried out for cases of uniform and parabolic pressure distributions. The resulting stress state yields the conditions for the asperity to initiate cracks in the layered medium. This paper studies further the thickness effect of the surface layer, the effect of relative stiffness of the surface layer and the substrate, and the effect of an insulating layer versus a conductive layer.
Blade Tip Geometry—A Factor in Abrading Sintered Seal Material
Authors: Wolak J. , Emery A. F. , Etemad S. , Choi S. R.
Published: November 2009

Experimental results are presented for the case of titanium blade tip specimens of various geometrical configurations rubbing at 100 m/s against specimens of nickel-chromium sintered powder metal seal material, the latter being fed toward the rotating blades at an incursion rate of 0.0254 mm/s. Blade tips in the form of orthogonal cutting tools with about 85° negative rake angles exhibited desirable abrading capabilities as measured by the tear free appearance of the grooves they generated in the seal material, little wear of blade tips, low forces of interaction and low seal densification. Similar results have been obtained for blade specimens with tips of small radius of curvature as well as for square ended and slanted blade tips plasma sprayed with abrasive particles. The relationship between the size of these particles and their abrading effectiveness is considered.
Creation and Maintenance of Cavities Under Horizontal Surfaces in Steady and Gust Flows
Authors: Arndt R. E. A. , Hambleton W. T. , Kawakami E. , Amromin E. L.
Published: November 2009

An experimental study of air supply to bottom cavities stabilized within a recess under a horizontal surface has been carried out in a specially designed water tunnel. The air supply necessary for creating and maintaining an air cavity in steady and gust flows has been determined over a wide range of speed. Flux-free ventilated cavitation at low flow speeds has been observed. Stable multiwave cavity forms at subcritical values of Froude number were also observed. It was found that the cross-sectional area of the air supply ducting has a substantial effect on the air demand. Air supply scaling laws were deduced and verified with the experimental data obtained.
2D Numerical Simulations of Blade-Vortex Interaction in a Darrieus Turbine
Authors: Amet E. , Maître T. , Pellone C. , Achard J.-L.
Published: November 2009

The aim of this work is to provide a detailed two-dimensional numerical analysis of the physical phenomena occurring during dynamic stall of a Darrieus wind turbine. The flow is particularly complex because as the turbine rotates, the incidence angle and the blade Reynolds number vary, causing unsteady effects in the flow field. At low tip speed ratio, a deep dynamic stall occurs on blades, leading to large hysteresis lift and drag loops (primary effects). On the other hand, high tip speed ratio corresponds to attached boundary layers on blades (secondary effects). The optimal efficiency occurs in the middle range of the tip speed ratio where primary and secondary effects cohabit. To prove the capacity of the modeling to handle the physics in the whole range of operating condition, it is chosen to consider two tip speed ratios (λ=2 and λ=7), the first in the primary effect region and the second in the secondary effect region. The numerical analysis is performed with an explicit, compressible RANS k-ω code TURBFLOW, in a multiblock structured mesh configuration. The time step and grid refinement sensitivities are examined. Results are compared qualitatively with the visualization of the vortex shedding of Brochier (1986, “Water channel experiments of dynamic stall on Darrieus wind turbine blades,” J. Propul. Power, 2(5), pp. 445–449). Hysteresis lift and drag curves are compared with the data of Laneville and Vitecoq (1986, “Dynamic stall: the case of the vertical axis wind turbine,” Prog. Aerosp. Sci., 32, pp. 523–573).
Application of MI Simulation Using a Turbulent Model for Unsteady Orifice Flow
Authors: Nakao Mitsuhiro , Kawashima Kenji , Kagawa Toshiharu
Published: November 2009

Measurement-integrated (MI) simulation is a numerical simulation in which experimental results are fed back to the simulation. The calculated values become closer to the experimental values. In the present paper, MI simulation using a turbulent model is proposed and applied to steady and unsteady oscillatory airflows passing an orifice plate in a pipeline. Velocity and pressure feedbacks are conducted and both feedback methods showed good agreement with the experimental results. Moreover, the calculation times between the MI simulation and ordinary simulation were compared in steady and unsteady conditions. The calculation time was demonstrated to be significantly reduced compared with ordinary simulation.
Flow Patterns and Aerodynamic Performance of Unswept and Swept-Back Wings
Authors: Yen Shun C. , Huang Lung –C.
Published: November 2009

The effects of sweep-back angle (Λ), Reynolds number (Re), and angle of attack (α) on the boundary-layer flow structures and aerodynamic performance of a finite swept-back wing were experimentally investigated. The Reynolds number and sweep-back angle used in this test is 30,000<Re<130,000 and 0 deg≤Λ≤45 deg. The wing model was made of stainless steel, and the wing airfoil is NACA 0012. The chord length is 6 cm, and the semiwing span is 30 cm; and therefore, the semiwing aspect ratio is 5. The boundary-layer flow structures were visualized using the surface oil-flow technique. Seven boundary-layer flow modes were categorized by changing Re and α. A six-component balance is used to determine aerodynamic loadings. The aerodynamic performance is closely related to the boundary-layer flow modes. The stall angle of attack (αstall) is deferred from 9 deg to 10 deg (for an unswept wing), to 30 deg to 35 deg (for a swept-back wings of Λ>30 deg). The deferment of αstall is induced from the increased rotation energy and turbulent intensity generated from the secondary flow. Furthermore, the increased rotation energy and turbulent intensity resisted the reverse pressure generated at high α.
Theoretical Study of the Laminar Flow in a Channel With Moving Bars
Authors: Hu Hai-Ping , Yeh Rong-Hua
Published: November 2009

This paper presents a study of the laminar flow in a channel with longitudinal moving bars arrayed along the channel width. The governing equations describing the fluid, which flows along the direction of the bar’s length, are expressed with double Poisson equations and are solved by eigenfunction-expansion and point-match method. The result shows that when the solid bars move forward, the fluid flow will move in the same direction, and the f Re decreases as the positive velocity of bars increases. However, when the bars move backward, a reverse flow will occur in the channel, and the f Re is higher at larger negative velocity of bars. For a channel flow with moving bars, the f Re value is not a constant, such as a classical one without moving bars, in which the f Re value is a constant. Furthermore, when the area of the cross section of the bar is fixed, both the mean velocities and the f Re values of the fluid can be obtained under different velocities and aspect ratios of the bars.
Control of Vortex Shedding From a Plate at Incidence Angles in the Range of 0–90 Deg
Authors: Shao Chuan Ping , Lin Jian Zhong
Published: November 2009

A thin strip cross-sectional element is used to suppress vortex shedding from a plate with a width to thickness ratio of 4.0 at incidence angles in the range of 0–90 deg and a Reynolds number of 1.1×104. The axes of the element and plate are parallel. The incidence angle of the element is 90 deg and the ratio of strip width to plate thickness is 0.5. Extensive measurements of wake velocities, together with flow visualization, show that vortex shedding from both sides of the plate is suppressed at incidence angles in the range of 0–55 deg if the element is placed at points in effective zones. Unilateral vortex shedding occurs if the element is applied at points in unilateral effective zones. The changes in sizes and locations of the effective and unilateral effective zones with the change in plate incidence are investigated, and the mechanism of the control is discussed. Two patterns of unilateral vortex shedding are observed. Pattern I occurs on the side where there is no element, and oppositely, pattern II occurs on the side where the element resides. A resonance model is proposed to illustrate the occurrence of pattern II unilateral shedding. The phenomenon of unilateral vortex shedding means that the vortex can be generated without strong interaction between the shear layers separated from the bluff body.
Modification of Axial Fan Flow by Trailing Edge Self-Induced Blowing
Authors: Eberlinc Matjaž , Širok Brane , Dular Matevž , Hočevar Marko
Published: November 2009

Axial fans often show adverse flow conditions at the fan hub and at the tip of the blade. The modification of conventional axial fan blade is presented. Hollow blade was manufactured from the hub to the tip. It enables the formation of self-induced internal flow through internal passages. The internal flow enters the passage of the hollow blade through the opening near the fan hub and exits through the trailing edge slots at the tip of the hollow blade. The study of the influence of internal flow on the flow field of axial fan and modifications of axial fan aerodynamic characteristics is presented. The characteristics of the axial fan with the internal flow were compared to characteristics of a geometrically equivalent fan without internal flow. The results show integral measurements of performance testing using standardized test rig and the measurements of local characteristics. The measurements of local characteristics were performed with a hot-wire anemometry and a five-hole probe. Reduction in adverse flow conditions near the trailing edge at the tip of the hollow blade, boundary-layer reduction in the hollow blade suction side, and reduction in flow separation were attained. The introduction of the self-induced blowing led to the preservation of external flow direction defined by the blade geometry, which enabled maximal local energy conversion. The integral characteristic reached a higher degree of efficiency.
Assessment of DES Models for Separated Flow From a Hump in a Turbulent Boundary Layer
Authors: Lyons Daniel C. , Peltier Leonard J. , Zajaczkowski Frank J. , Paterson Eric G.
Published: November 2009

Separated flow past a hump in a turbulent boundary layer is studied numerically using detached-eddy simulation (DES), zonal detached-eddy simulation (ZDES), delayed detached-eddy simulation (DDES), and Reynolds-averaged Navier–Stokes (RANS) modeling. The geometry is smooth so the separation point is a function of the flow solution. Comparisons to experimental data show that RANS with the Spalart–Allmaras turbulence model predicts the mean-field statistics well. The ZDES and DDES methods perform better than the DES formulation and are comparable to RANS in most statistics. Analyses motivate that modeled-stress depletion near the separation point contributes to differences observed in the DES variants. The order of accuracy of the flow solver ACUSOLVE is also documented.
Cavitation Inception in the Wake of a Jet-Driven Body
Authors: Arndt Roger E. A. , Amromin Eduard L. , Hambleton William
Published: November 2009

Although cavitation inception in jets has been studied extensively, little is known about the more complex problem of a jet flow interacting with an outer flow behind a moving body. This problem is studied experimentally by considering inception behind an axisymmetric body driven by a waterjet. Tests were carried out for various water tunnel velocities and jet speeds such that jet velocity ratio UJ/U could be varied in the range of 0–2. Distinctly different cavitation patterns were observed at zero jet velocity (when cavitation appeared in spiral vortices in such flows) and at various jet velocity ratios (when cavitation appeared around the jet in such flows). A simple superposition analysis, utilizing particle imaging velocimetry (PIV) measurements, is able to qualitatively predict the experimental result. On the basis of these observations, a numerical prediction of cavitation inception number based on viscous-inviscid interaction concept is suggested.
New insights on the genetic basis of Portuguese grapevine and on grapevine domestication
Authors: Lopes M. S. , Mendonça D. , Rodrigues dos Santos M. , Eiras-Dias J. E. , da Câmara Machado A.
Published: November 2009

As the ancestor of cultivated grape, Vitis vinifera subsp. sylvestris represents a unique, invaluable genetic resource for the improvement of cultivated grapevines. Recently, five populations of wild grapevines were identified in Portugal. Sixty vines were characterized with 11 nuclear SSR markers and further compared with 70 genotypes of Portuguese Vitis vinifera subsp. sativa. The obtained data demonstrate moderate genetic differentiation between wild grapevine populations and moderate to high genetic differentiation between wild and cultivated grapevines. However, the identification of high degrees of similarity between wild and cultivated grapes (up to 87%) and a putative parent–progeny relationship between wild and cultivated grapes with 17 additional SSR markers is indicative of gene flow between local wild grapevine populations and Portuguese domesticated vines. Also, the ancestry of some Azorean cultivars was ascertained. The obtained data further support the hypothesis of several domestication centres, with Portugal, Spain, and Italy playing a particular role after the last glaciation, giving rise to many of the Western European cultivars.
Fine mapping of the epistatic suppressor gene (esp) of a recessive genic male sterility in rapeseed (Brassica napus L.)
Authors: Xu Zhenghua , Xie Yanzhou , Hong Dengfeng , Liu Pingwu , Yang Guangsheng
Published: November 2009

9012AB, a recessive genic male sterility (RGMS) line derived from spontaneous mutation in Brassica napus , has been playing an important role in rapeseed hybrid production in China. The male sterility of 9012AB is controlled by two recessive genes (ms3 and ms4) interacting with one recessive epistatic suppressor gene (esp). The objective of this study was to develop PCR-based markers tightly linked to the esp gene and construct a high-resolution map surrounding the esp gene. From the survey of 512 AFLP primer combinations, 3 tightly linked AFLP markers were obtained and successfully converted to codominant or dominant SCAR markers. Furthermore, a codominant SSR marker (Ra2G08) associated with the esp gene was identified through genetic map integration. For fine mapping of the esp gene, these PCR-based markers were analyzed in a large BC1 population of 2545 plants. The esp gene was then genetically restricted to a region of 1.03 cM, 0.35 cM from SSR marker Ra2G08 and 0.68 cM from SCAR marker WSC6. The SCAR marker WSC5 co-segregated with the target gene. These results lay a solid foundation for map-based cloning of esp and will facilitate the selection of RGMS lines and their temporary maintainers.
Genetic linkage mapping for molecular dissection of chilling requirement and budbreak in apricot (Prunus armeniacaL.)
Authors: Olukolu Bode A. , Trainin Taly , Fan Shenghua , Kole Chittaranjan , Bielenberg Douglas G. , Reighard Gregory L. , Abbott Albert G. , Holland Doron
Published: November 2009

Commercial production of apricot is severely affected by sensitivity to climatic conditions, an adaptive feature essential for cycling between vegetative or floral growth and dormancy. Yield losses are due to late winter or early spring frosts and inhibited vegetative or floral growth caused by unfulfilled chilling requirement (CR). Two apricot cultivars, Perfection and A.1740, were selected for high and low CR, respectively, to develop a mapping population of F1individuals using a two-way pseudo-testcross mapping strategy. High-density male and female maps were constructed using, respectively, 655 and 592 markers (SSR and AFLP) spanning 550.6 and 454.9 cM with average marker intervals of 0.84 and 0.77 cM. CR was evaluated in two seasons on potted trees forced to break buds after cold treatments ranging from 100 to 900 h. A total of 12 putative CR quantitative trait loci (QTLs) were detected on six linkage groups using composite interval mapping and a simultaneous multiple regression fit. QTL main effects of additive and additive × additive interactions accounted for 58.5% ± 6.7% and 66.1% ± 5.8% of the total phenotypic variance in the Perfection and A.1740 maps, respectively. We report two apricot high-density maps and QTLs corresponding to map positions of differentially expressed transcripts and suggested candidate genes controlling CR.
Development of microsatellite markers for common bean (Phaseolus vulgarisL.) based on screening of non-enriched, small-insert genomic libraries
Authors: Blair Matthew W. , Torres Monica Muñoz , Pedraza Fabio , Giraldo Martha C. , Buendía Hector F. , Hurtado Natalia
Published: November 2009

Microsatellite markers are useful genetic tools for a wide array of genomic analyses although their development is time-consuming and requires the identification of simple sequence repeats (SSRs) from genomic sequences. Screening of non-enriched, small-insert libraries is an effective method of SSR isolation that can give an unbiased picture of motif frequency. Here we adapt high-throughput protocols for the screening of plasmid-based libraries using robotic colony picking and filter preparation. Seven non-enriched genomic libraries from common bean genomic DNA were made by digestion with four frequently cutting restriction enzymes, double digestion with a frequently cutting restriction enzyme and a less frequently cutting restriction enzyme, or sonication. Library quality was compared and three of the small-insert libraries were selected for further analysis. Each library was plated and picked into 384-well plates that were used to create high-density filter arrays of over 18 000 clones each, which were screened with oligonucleotide probes for various SSR motifs. Positive clones were found to have low redundancy. One hundred SSR markers were developed and 80 were tested for polymorphism in a standard parental survey. These microsatellite markers derived from non-SSR-enriched libraries should be useful additions to previous markers developed from enriched libraries.
Identification of genes for resistance to a Digitaria isolate of Magnaporthe grisea in common wheat cultivars
Authors: Nga N. T.T. , Hau V. T.B. , Tosa Y.
Published: November 2009

Common wheat cultivars are resistant to Magnaporthe grisea , a crabgrass ( Digitaria sanguinalis )-specific species of the blast fungus. To dissect the genetic basis of this “nonhost” type of resistance, we need an exceptional cultivar that is susceptible to M. grisea. A screening under various conditions revealed that Triticum aestivum ‘Chinese Spring’ (CS) was susceptible to M. grisea isolate Dig41 when incubated at high temperature (26 °C) after inoculation. By contrast, T. aestivum ‘P168’, ‘Shin-chunaga’ (Sch), ‘Norin 4’ (N4), ‘Norin 26’ (N26), ‘Norin 29’ (N29), ‘Red Egyptian’ (RE), and ‘Salmon’ (Slm) and Triticum compactum ‘No. 44’ (Cmp) were highly resistant even at the high temperature. When F2 seedlings derived from crosses between the resistant cultivars and CS were inoculated with Dig41, they segregated in a 3:1 ratio of resistant to susceptible, suggesting that the resistance of each cultivar is controlled by one major gene. Crosses of N4 with P168, Sch, N26, N29, and Cmp yielded no susceptible F2 seedlings, suggesting that these six cultivars share the same gene. Similarly, a cross between RE and Slm yielded no susceptible F2 seedlings, suggesting that these two cultivars share the same gene. On the other hand, crosses between the N4 group and the RE group produced resistant and susceptible seedlings in a 15:1 ratio, indicating that these two groups carry different genes inherited independently. The gene in N4 was located on chromosome 4A by a monosomic analysis and designated Rmg4, while the gene in RE was located on chromosome 6D using a series of chromosome substitution lines and designated Rmg5. These results suggest that the resistance of common wheat to M. grisea, an inappropriate species of the blast fungus, is under a simple genetic control.
The complete mitogenome sequences of the palaeopteran insectsEphemera orientalis(Ephemeroptera: Ephemeridae) andDavidius lunatus(Odonata: Gomphidae)
Authors: Lee Eun Mee , Hong Mee Yeon , Kim Man Il , Kim Min Jee , Park Hae Chul , Kim Kee Young , Lee In Hee , Bae Chang Hwan , Jin Byung Rae , Kim Iksoo
Published: November 2009

Currently, the palaeopteran lineages (insect orders Ephemeroptera and Odonata) that have a problematic relationship with neopteran lineages are poorly represented by mitogenome sequences. In this study, we have determined the complete mitogenome of the oriental mayfly, Ephemera orientalis (Ephemeroptera: Ephemeridae), and the dragonfly Davidius lunatus (Odonata: Gomphidae). The 16 463 bp mitogenome of E. orientalis and the 15 912 bp mitogenome of D. lunatus have many of the features typically detected in insect mitogenomes. Although the initiation codon for the D. lunatus COI gene is the typical ATA, E. orientalis is unusual in that no typical start codon was detected in the start region of the COI gene. The A+T-rich regions of both mitogenomes have some unusual features. The E. orientalis A+T-rich region harbors two identical 55 bp sequences separated by 158 bp, and the D. lunatus A+T-rich region harbors a tandem repeat comprising two identical 261 bp copies and one partial copy of the repeat. Additionally, the A+T-rich regions of both mitogenomes harbor the stem-and-loop structures flanked by the conserved sequences “TA(A)TA” at the 5′ end and “G(A)nT” at the 3′ end, which have been suggested to be the signals involved in minor strand replication initiation. Furthermore, the D. lunatus A+T-rich region contains two tRNA-like structures with proper anticodon and cloverleaf structures.
Comparative analysis of genetic diversity between Qinghai-Tibetan wild and Chinese landrace barley
Authors: Gong Xue , Westcott Sharon , Li Chengdao , Yan Guijun , Lance Reg , Sun Dongfa
Published: November 2009

Fifty-two SSR markers were used to evaluate the genetic diversity of 33 Qinghai-Tibetan wild barley accessions, 56 landraces collected primarily from other parts of China, and 1 Israeli wild barley accession. At the 52 SSR loci, 206 alleles were detected for the 90 accessions, among which 111 were common alleles. The number of alleles per locus ranged from 1 to 9, with an average of 4.0. Polymorphism information content (PIC) values ranged from 0 to 0.856 among all the markers, with an average of 0.547. The PIC value of Qinghai-Tibetan wild barley varied from 0 to 0.813 with an average of 0.543, while in landraces, the markers showed a range of 0 to 0.790 with an average of 0.490. The SSR markers could clearly differentiate the Qinghai-Tibetan wild barley from the landraces. Twenty-four unique alleles were observed in Qinghai-Tibetan wild barley, and the frequency of unique alleles in Qinghai-Tibetan wild barley was about 2.1 times higher than that in the landraces, on average. Five of the 7 chromosomes had more unique alleles in the Qinghai-Tibetan wild barley, but chromosome 2H had more unique alleles in the landraces. The presence of many unique alleles may reflect the adaptation of this barley germplasm to diverse environments and production systems.
Genome variation in the symbiotic nitrogen-fixing bacteriumSinorhizobium meliloti
Authors: Guo Hong , Sun Sheng , Eardly Bertrand , Finan Turlough , Xu Jianping
Published: November 2009

Differences in genome size and gene content are among the most important signatures of microbial adaptation and genome evolution. Here, we investigated the patterns of genome variation among 10 natural strains of the symbiotic nitrogen-fixing bacterium Sinorhizobium meliloti , using pulse field gel electrophoresis (PFGE) and whole-genome microarray hybridizations. Our PFGE analysis showed a genome size range of 6.45–7.01 Mbp, with the greatest variation arising from the pSymA replicon, followed by pSymB; no size difference was evident among the chromosomes. Consistent with this pattern of size differences, 41.2% of open reading frames (ORFs) on pSymA were variably absent/present, followed by 12.7% on pSymB and 3.7% on the chromosome. However, the ORFs that were variably duplicated were more evenly distributed among the three replicons: 11.0%, 16.5%, and 15.3% of ORFs on pSymA, pSymB, and the chromosome, respectively. Among the 10 strains, the percentage of ORFs that were absent ranged from 1.51% to 6.35%, and the percentage of ORFs that were duplicated ranged from 0.27% to 8.56%. Our analyses showed that host plants, geographic origins, multilocus enzyme electrophoretic types, and replicon sizes had little influence on the distribution patterns of absent or duplicated ORFs. The proportions of ORFs that were either variably absent/present or variably duplicated differed greatly among the functional categories, for each of the three replicons as well as for the whole genome. Interestingly, we observed positive correlations among the three replicons in the number of absent ORFs as well as the number of duplicated ORFs, consistent with coordinated gene gains and losses in this important bacterium in nature.
Prediction of novel isoforms of the mouse Mpv17l protein
Authors: Magoulas Charalambos , Jasim Avin , Lopez de Heredia Luis
Published: November 2009

The Mpv17l protein has two isoforms, M-LPL and M-LPS, which both regulate the production of reactive oxygen species (ROS) and protect against mitochondrial oxidative stress and apoptosis. M-LPL is ubiquitously expressed, while M-LPS is expressed mostly in the kidney of aged animals. We identified a variety of transcripts of the Mpv17l gene that could encode novel isoforms by mapping expressed sequence tags on the mouse M-LP genomic locus. We analysed the expression and evolutionary conservation of a novel Mpv17l transcript (mpv17l-002) that is predicted to encode a new protein, termed M-LP2. The isoform M-LP2 has the full length of M-LPS plus six amino acids at the end of its amino terminus, which could be encoded by an alternative 5′-flanking sequence. We show that the mRNA of M-LP2 has a different pattern of expression than the mRNA of M-LPS, and sequences of both transcripts are conserved in the rodent genome; however, neither of these isoforms is detected in the human genome. These observations suggest that the functions of certain M-LP isoforms are tissue- and species-specific, implying that their potential involvement in ROS metabolism may be redundant or may be complemented by other members of the Mpv17 family.
Molecular, morphological, and cytological analysis of diverseBrachypodium distachyoninbred lines
Authors: Filiz E. , Ozdemir B. S. , Budak F. , Vogel J. P. , Tuna M. , Budak H.
Published: November 2009

Brachypodium distachyon (brachypodium) is a small grass with the biological and genomic attributes necessary to serve as a model system for all grasses including small grains and grasses being developed as energy crops (e.g., switchgrass and Miscanthus ). To add natural variation to the toolkit available to plant biologists using brachypodium as a model system, it is imperative to establish extensive, well-characterized germplasm collections. The objectives of this study were to collect brachypodium accessions from throughout Turkey and then characterize the molecular (nuclear and organelle genome), morphological, and cytological variation within the collection. We collected 164 lines from 45 diverse geographic regions of Turkey and created 146 inbred lines. The majority of this material (116 of 146 inbred lines) was diploid. The similarity matrix for the diploid lines based on AFLP analysis indicated extensive diversity, with genetic distances ranging from 0.05 to 0.78. Organelle genome diversity, on the other hand, was low both among and within the lines used in this study. The geographic distribution of genotypes was not significantly correlated with either nuclear or organelle genome variation for the genotypes studied. Phenotypic characterization of the lines showed extensive variation in flowering time (7–22 weeks), seed production (4–193 seeds/plant), and biomass (15–77 g). Chromosome morphology of the collected brachypodium accessions varied from submetacentric to metacentric, except for chromosome 5, which was acrocentric. The diverse brachypodium lines developed in this study will allow experimental approaches dependent upon natural variation to be applied to this new model grass. These results will also help efforts to have a better understanding of complex large genomes (i.e., wheat, barley, and switchgrass).
Telomere analysis of platyhelminths and acanthocephalans by FISH and Southern hybridization
Authors: Bombarová Marta , Vítková Magda , Špakulová Marta , Koubková Božena
Published: November 2009

We examined the composition of telomeres in chromosomes of parasitic worms, representatives of the flatworm groups Monogenea and Cestoda (Platyhelminthes), and thorny-headed worms (Syndermata: Acanthocephala) by fluorescence in situ hybridization (FISH) with different telomeric repeat probes. Our results show that the (TTAGGG)n sequence, supposed to be the ancestral telomeric repeat motif of Metazoa, is conserved in Monogenea ( Paradiplozoon homoion ) and Cestoda ( Caryophyllaeus laticeps , Caryophyllaeides fennica , and Nippotaenia mogurndae ) but not in Acanthocephala ( Pomphorhynchus laevis and Pomphorhynchus tereticollis ). In the Pomphorhynchus species, no hybridization signals were obtained with the “nematode” (TTAGGC)n, “arthropod” (TTAGG)n, and bdelloid (TGTGGG)n telomeric probes using FISH with their chromosomes and Southern hybridization with P. laevis DNA. Therefore, we suggest that parasitic Acanthocephala have evolved yet unknown telomeric repeat motifs or different mechanisms of telomere maintenance.
HACRE1, a recently inserted copia-like retrotransposon of sunflower (Helianthus annuus L.)
Authors: Buti M. , Giordani T. , Vukich M. , Gentzbittel L. , Pistelli L. , Cattonaro F. , Morgante M. , Cavallini A. , Natali L.
Published: November 2009

In this paper we report on the isolation and characterization, for the first time, of a complete 6511 bp retrotransposon of sunflower. Considering its protein domain order and sequence similarity to other copia elements of dicotyledons, this retrotransposon was assigned to the copia retrotransposon superfamily and named HACRE1 ( Helianthus annuus copia-like retroelement 1). HACRE1 carries 5′ and 3′ long terminal repeats (LTRs) flanking an internal region of 4661 bp. The LTRs are identical in their sequence except for two deletions of 7 and 5 nucleotides in the 5′ LTR. Based on the sequence identity of the LTRs, HACRE1 was estimated to have inserted within the last ∼84 000 years. The isolated sequence contains a complete open reading frame with only one complete reading frame. The absence of nonsense mutations agrees with the very high sequence identity between LTRs, confirming that HACRE1 insertion is recent. The haploid genome of sunflower (inbred line HCM) contains about 160 copies of HACRE1. This retrotransposon is expressed in leaflets from 7-day-old plantlets under different light conditions, probably in relation to the occurrence of many putative light-related regulatory cis-elements in the LTRs. However, sequenced cDNAs show less variability than HACRE1 genomic sequences, indicating that only a subset of this family is expressed under these conditions.