bluuebunny/crossref_metadata_2025 huggingface dataset:
The use of topography‐based parameters for the assessment and prediction of surface wear
Authors: Sherrington I. , Mercer S.
Published: July 2006

This paper examines the use of surface parameters as ‘tools’ for assessing and predicting surface wear. It begins by briefly reviewing other work published on wear assessment based on entirely topography‐based parameters, and concludes that other elements of surface condition are needed, in addition to topography, to assess and characterise the contact if topography‐based parameters are to be employed to predict wear. This paper discusses why areal measurements of bearing area and plasticity index are suitable candidates as a basis for assessing and predicting surface wear, and outlines the potential value of using these parameters in conjunction with a wear equation. The validity of this suggestion is illustrated by some preliminary data from a series of pin‐on‐disc wear experiments involving areal assessments of the bearing area and plasticity index of the rough tip of a brass pin. Predictions of the first stage of a wear simulation are compared to experimental data, and the paper concludes by presenting some general conclusions and suggestions about how the work could be developed.
Modifications to improve the accuracy of a four‐ball test apparatus
Authors: Lacey P. I. , Davenport D. W. , D'spain F. M. , Reed D. J.
Published: July 2006

The four‐ball wear test machine is one of the most widely used tribological tools in both research and industry. In general, the test geometry is self‐aligning and minimises the opportunity for random variation. Nonetheless, accurate control of the test parameters remains vital to repeatability and reproducibility. The present paper details a number of modifications to a commercially available test apparatus that have been found to improve accuracy. The applied load on some apparatus was found to vary from the correct value, probably due to frictional drag in the loading system. A feedback control loop was designed and fitted to the applied load mechanism, which resulted in significantly improved accuracy. Finally, the apparatus was fully automated, with complete computer control of all test parameters. Under this, following cleaning and assembly of the test specimens, the required test procedure could be selected from a menu of standard methods, and the computer program then adjusted the test parameters according to the method selected, greatly reducing the possibility of operator error.
Stick‐slip with the slip phase as the starting point
Authors: van de Velde Frederik , de Baets Patrick , Degrieck Joris
Published: July 2006

In the literature, the stick‐slip phenomenon is always explained and modelled as starting from an initial stick phase. However, stick‐slip can also occur after a decrease in the imposed velocity, commencing above the critical (stick‐slip‐free) velocity. In this paper, it will be shown how stick‐slip can originate from a situation of pure sliding (without stick phases), if the slope of the friction force‐relative sliding velocity relation (F‐vrel gradient) is negative. The F‐vrel gradient used to study stick‐slip must, because of the interaction between the friction force and the dynamic behaviour of the mechanical system, be derived from velocity changes with the same time‐constant as the mechanical system of which the friction interface is part. It will also be shown that steady‐state friction data, and dynamic (non‐stationary) friction results obtained for relatively large (but fast) velocity variations, can lead to completely false conclusions related to stick‐slip.
Wear investigation of spur gear teeth
Authors: Flodin Anders
Published: July 2006

An FZG back‐to‐back gear test machine has been used to investigate the initial wear of spur gears. By making plastic replicas of the tooth surfaces, and measurements of the same using a 3D stylus instrument, the wear pattern has been analysed. The wear tests were run on the machine according to a predefined schedule. During planned stops, negative surface replicas were made. The replicas were measured, and the amount and distribution of wear analysed. SEM pictures were also taken of the tooth surfaces, and several different types of damage were identified. The results were compared with simulated results using identical loading and geometry. It was found that the wear was quite severe at the root of the wheels and also significant at the tip. The wear was also found to form an overloaded wave pattern on the original involute form of the tooth.
A study of electrical pitting of journal bearings with water‐contaminated lubricant
Authors: Prashad Har
Published: July 2006

The investigations reported in this paper concern the effect of the use of a degraded lubricant on bearing life. A diagnosis of the premature failure of the hydrodynamic journal bearings of a synchronous condenser has been carried out. The surface of the failed bearings has been examined and the cause of the failure investigated. A theoretical analysis has also been undertaken to calculate the number of cycles that take place before failure occurs. The number of cycles thus established matched that of the cycles/duration of operation before the premature failure of the bearings. The process leading to the premature failure and the role of the degraded lubricant have been identified. Remedial measures have been successfully implemented to reuse the existing bearings. Measures have been suggested to avoid repeated failures.

The theoretical analysis has the potential to ascertain the shaft voltage once the severity of the physical damage on the liner surface of the bearing and the duration of its operation have been established.
A study of the measurement of surface temperature at a cam/tappet contact
Authors: Ito Akemi , Yang Lisheng , Negishi Hideo
Published: July 2006

Cam/tappet wear is one of the most difficult reliability and durability problems to predict during the development of a prototype engine valve‐train system. In the present study, the cam/tappet surface temperature was measured and calculated to determine the effect of surface temperature on the lubricating conditions at a cam/tappet contact. The measurement method, sometimes called the dynamic thermocouple technique, was based on the Seebeck effect: by using different materials for the cam and tappet, the cam/tappet contact point becomes the hot junction of a ‘thermocouple’. The cam/tappet contact surface temperature can therefore be measured continuously. The measured temperature results show good agreement with predictions. Temperature spikes, however, were not found in the test using new oil, but were shown by the theoretical model. Such results indicate that the cam/tappet interface operates in effective lubricating conditions, even when the oil temperature is relatively high. Further research with degraded oil supplied at high temperature is needed for a thorough understanding of abnormal cam wear.
Tribological and mechanical investigation of SiO2 and Si3N4 coatings on fused silica and borosilicate glass
Authors: Klaffke D. , Beck U.
Published: July 2006

Amorphous SiO2 and Si3N4 plasma‐enhanced chemical vapour deposited (PECVD) coatings were deposited on two different substrate materials (fused silica and borosilicate glass), with three coating thicknesses (0.1, 0.5, and 1.0 μm). The mechanical properties (hardness and elastic modulus) were determined by depth‐sensing indentation, with loads from 700 mN down to 0.1 mN. Tribological behaviour was studied in instrumented oscillating sliding tests at room temperature with a ball‐on‐flat arrangement, in which the coated disc was tested against an alumina ball, at a load of 1 N. Interpretation of the measurement of hardness and modulus of the coatings has to take into consideration the influence of layer thickness and the effect of the substrate. Tensile film stress and crack generation were only observed for Si3N4 on fused silica above a threshold thickness. Friction and wear measurements show that the coating has an effect on friction, while wear is affected by the thin coatings only for a short running‐in phase. The morphology of the wear scars indicates that the coatings have good adhesion. Despite crack generation, delamination effects were not observed. Indentation patterns similarly showed excellent lateral homogeneity of the mechanical properties over the entire film surface, and indicated that load‐displacement curves may be used to characterise the system.
Recent trends in the total characterization of new‐generation base fluids
Authors: Singh I. D. , Sahoo S. K. , Adhvaryu A.
Published: July 2006

The quality of lubricating base oils used worldwide is changing rapidly as a result of stringent environmental regulation and the pressing need for oils to perform well under severe operating conditions. For example, although the base oil market in India now depends entirely on conventional group I base oils, group II and III base oils will soon be mandatory in lubrication formulation. These oils are generally more stable towards oxidation due to the virtual absence of heteroatom‐containing compounds and to their low aromatic content. The analytical procedures developed over the years for the characterization of new and used group I mineral base oils will not be successful for all the requirements of these new oils. Thus, a systematic study is required to test the universal validity of characterisation methodology for these new‐generation base fluids. This paper focuses on the use of various analytical techniques for base oil characterization and the methodology required for the total characterization of new‐generation base oils.
Inertia and couple‐stress effects on squeeze‐film characteristics with reference to biological bearings
Authors: Walicki Edward , Walicka Anna
Published: July 2006

Couple stresses affect lubrication when additives are used or the lubricant contains long‐chain molecules. Such couple stresses may have a considerable effect on the behaviour of bearings in practice. The influence of couple stresses and lubricant inertia on the mechanical parameters of a curvilinear thrust bearing with a squeeze film is considered in this paper. Simulation of the squeeze‐film behaviour of a human joint modelled as a spherical bearing is discussed as an example.
Friction property study of the surface of ZDDP and MoDTC antiwear additive films using AFM/LFM and force curve methods
Authors: Ye Jiping , Kano Makoto , Yasuda Yoshiteru
Published: July 2006

The friction properties and material differences of the surface of ZDDP and MoDTC antiwear additive films, which give clear evidence of different friction coefficients in a pin‐on‐disc test, have been studied using atomic force microscopy (AFM)/lateral force microscopy (LFM) and force curve methods. The AFM/LFM observations show that the friction force on the surface of MoDTC additive films over the sliding area of a steel disc is lower and the friction force of ZDDP additive films is higher than that of afilmless area. Lateral force scope‐trace evaluations reveal that the ratio of the friction forces on the surface of the ZDDP film, the filmless area, and the MoDTC film under the same normal force is approximately 1.5:1.0:0.7. Force curve measurements indicate that the surface materials of the ZDDP film, thefilmless area, and the MoDTC film differ according to their attractive forces, that is 29 nN for the ZDDP film, 22 nN for the filmless area, and 12 nN for the MoDTC film. These results correspond to the friction behaviour in the pin‐on‐disc test and also agree with the idea of the formation of solid MoS2 lubricant from MoDTC additives on the surface of the antiwear film.
Thermo‐oxidative stability of new‐generation base oils
Authors: Pandey D. C. , Sahoo S. K. , Singh I. D.
Published: July 2006

Thermo‐oxidation of base oils is the primary cause of lubricant degradation and engine failure during use. Degradation is mainly due to high‐temperature oxidation and thermal decomposition near the piston ring zone, forming oxygenated compounds that polymerise to form high‐molecular‐weight insoluble deposits. New‐generation base oils are found to be more stable towards oxidation and deposit formation due to the absence of aromatics and polynaphthenes. However, compatibility with antioxidants and other additives is now of greater concern because of the poor solvency of these oils. With the increase in the purity of the oil, sometimes the oxidation performance is poor in comparison to group I oils, mainly due to the removal of sulphur compounds, which act as natural antioxidants.

Thermal techniques, such as differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), are emerging as fast and accurate methods for determining the thermo‐oxidative stability of base oils and their additive blends, making it possible to measure the oxidation induction time, incipient oxidation temperature, and deposit‐forming tendency. The objective of this work is to evaluate the thermo‐oxidative stability of new‐generation group II/III base oils without antioxidant additives, using DSC and TGA. The kinetics of base oil oxidative degradation are studied using different heating rates. The data obtained from thermal techniques are correlated with the micro‐oxidation data obtained from the Penn State Micro‐Oxidation (PSMO) test. The response of a typical antioxidant additive, zinc dialkyldithiophosphate, towards oxidative degradation of base oils has also been studied.
Assessment of the useful life of current long‐drain and future low‐phosphorus engine oils
Authors: Korcek S. , Jensen R. K. , Johnson M. D.
Published: July 2006

The assessment of engine oil useful life is an important step in the development of future low‐phosphorus, catalyst‐compatible, and long‐drain engine oils. This paper describes the development and application of a new laboratory screening test, the Ford oil ageing test (FOAT), for the assessment of engine oil useful life. FOAT simulates the Sequence IIIE engine dynamometer test and evaluates oils on the basis of viscosity increase. It correlates well with both single‐ and double‐length Sequence IIIE test results. FOAT allows for inexpensive screening of candidate oils prior to engine tests and is currently being used in the evaluation of future low‐phosphorus engine oils. This comparative study has demonstrated that low‐phosphorus, catalyst‐compatible engine oils can be formulated to provide a similar useful life to current commercial long‐drain oils.
A contribution to determining the friction coefficient in hydroforming of tubes
Authors: Plancak M. , Vollertsen F.
Published: July 2006

Hydroforming is a relatively new technology, which enables complex shaped hollow parts to be produced efficiently. Compared to alternative methods, this technology is characterised by significant potential advantages, such as complex shape production, lightweight design, high accuracy, and process integration.

The tribological aspects of hydroforming are very significant, as friction influences all the main process parameters practically in a direct or indirect way. However, there is a paucity of information relating to hydroforming tribology. In most reports on this subject only qualitative data regarding the friction coefficient are given. However, for finite‐element method simulation and optimal process and tool design, quantitative data are indispensable.

This paper describes an attempt to determine the coefficient of friction in both the elastic and plastic states of a workpiece during tube hydroforming processes. Push‐through tests were carried out in order to determine the coefficient of friction in the elastic state, and tube upsetting tests were conducted for the plastic state. Various commercial lubricants were used in the experiments.
Nano‐scratch study of molecular deposition films on silicon wafers using nano‐indentation
Authors: Deguo Wang , Siwei Zhang , Manglai Gao
Published: July 2006

Experiments on molecular deposition (MD) films with and without alkyl terminal groups deposited on silicon wafers were conducted using nano‐indentation. It was found that MD films and alkyl‐terminated MD films exhibit a higher critical load and a lower coefficient of friction than the silicon substrate. The critical load increases with the number of layers, and the coefficients of friction of MD films with alkyl terminal groups are lower than those of the corresponding MD films with the same number of layers but without alkyl terminal groups.
Some considerations concerning lubrication in high‐performance internal combustion engines
Authors: Righes Giuseppe , Garro Attilio , Calderale Pasquale Mario
Published: July 2006

The increasing rotational speeds and the weight reduction of high‐performance internal combustion engines are accompanied by problems of lubrication, heat transfer, and vibration that are mostly negligible in medium‐ and low‐performance engines. To deal with such phenomena under demanding operating conditions necessitates a specific design. The dynamics of the power system between crankshaft and related sub‐components, e. g., bending and torsional vibrations of the connecting rod, ovalisation of the head and eye of the connecting rod, and vibrations of thin cylinder liners, are critical for the lubrication system in general, and for oil film pressure fields in particular. In some cases, no information on these features has existed until now, so no quantification of the variables involved has been possible. Over the last few years a systematic investigation has been performed to take into account the critical points and their fundamental importance in the design of such engines.

The present paper considers some of the phenomena related to lubrication in high‐performance engines. The need is highlighted for further investigations using computational and experimental methodologies.
Adhesion of cleaned nanoscopic metal contacts
Authors: Santner E. , Spaltmann D.
Published: July 2006

Nanoscopic metal contact in the context used in this paper means atomic force microscope (AFM) tips in contact with cleaned, flat, smooth surfaces in ultrahigh vacuum. Such idealised contact conditions are of more and more relevance for technical friction systems despite the fact that for the latter the loads and the velocities are usually higher, the materials used are impure (e. g. alloys) and contaminants or lubricants are present between the sliding surfaces. Sliding contacts in micro‐system technology, which is unequivocally a key technology of the future, will presumably be compared with such idealised conditions. Another important reason for the investigation of nanoscopic contacts is the strong interest in the understanding of the elementary processes and mechanisms causing friction. The investigation of friction systems with a reduced number of influencing parameters offers a chance to gain insight into elementary processes and to compare the results with theoretical models based on physical principles, such as molecular dynamics simulation.
Investigation of antiwear coatings deposited by the pvd process
Authors: Tuszynski W. , Szczerek M. , Michalczewski R.
Published: July 2006

The tribological properties of various PVD‐deposited coatings (vacuum arc method) have been tested, both single‐layer coatings (TiN, CrN, Ti(C,N), and Cr(C,N)) and multilayer coatings (Cr(C,N)/CrN/Cr and CR(C,N)/(CrN+Cr2N)/CrN/Cr). An unlubricated ball‐on‐disc tribosystem was used in which an Al2O3 ball is pressed against a coated steel disc rotating in the horizontal plane. A novelty of the method is the removal of wear debris from the contact zone using a draught of dry argon. This improves the repeatability of the test results and the stability of the tribological characteristics.

It is shown that CrN coatings exhibit the best antiwear properties and Ti(C,N) the worst. Multilayer coatings have better antiwear properties than single‐layer ones. The friction coefficients for CrN and Cr(C,N) coatings are much smaller than for the commonly used TiN.

A correlation has also been found between the physical properties of the coatings tested (adhesion of the coating to the substrate assessed in scratch tests, and coating hardness) and their antiwear properties. An improvement in coating‐substrate adhesion results in wear reduction, while greater hardness (causing a coating embrittlement increase and a change in the wear mechanism) brings about greater wear. There is no correlation between the physical properties and the friction coefficients of the coatings tested.
Influence of test parameters on friction and wear results obtained in oscillating sliding tests with 100cr6 steel against sic‐based materials
Authors: Klaffke D.
Published: July 2006

In order to characterise materials for tribological applications, model tests with simple contact geometry are in widespread use. Friction and wear behaviour can be determined with high accuracy from this type of test. Tests with oscillating sliding motion have the advantage that only small‐sized specimens are required. However, the fact that the results of model tests are affected considerably by the choice of test parameters is often overlooked. In order to check the influence of test parameters on friction and wear results, tests were performed in which the relevant parameters (stroke, frequency, load, relative humidity of the surrounding air) were varied. Comparative studies with different SiC‐based materials (SiC, SiSiC, and SiC‐TiC) against steel (100Cr6) under unlubricated conditions at room temperature show that in all cases the relative humidity is an important parameter, influencing the friction and wear results substantially. Additionally, several parameters can modify friction and wear behaviour more or less significantly. The effects of test parameters on friction and wear are discussed here on the basis of the wear mechanism. Some of the consequences of this for planning test series and for the practical use of test results are noted.
Mechanism of ploughing wear of martensite nodular cast iron
Authors: Jingpei Xie , Eigin Wang , Wenyan Wang , Yanpei Shong , Luoli Li
Published: July 2006

The mechanism of ploughing wear of martensite nodular cast iron has been investigated by means of elastic contact theory, stress interferometry, and scanning electron microscopy. Stress distributions in the contact area are plotted through numerical quadrature. The results show that the formation of cracks is between 0.2a and 0.5a (a is the radius of the contact curve). The driving force to produce crack extension along the Y axis is τyzmax and the extension direction is 45° to the horizontal. The driving force to produce crack extension along the X axis is either τx or τxzmax and the direction of crack extension is 37° to the horizontal.
Water‐Lubricated and Dry‐Running Properties of Ceramic Journal Bearings
Authors: Andersson Peter
Published: July 2006

Journal bearings and other well‐defined sliding surfaces are important for numerous moving mechanical assemblies. Quite often sliding surfaces are produced on particular components during fabrication, for which reason the manufacturer needs to know the properties of the materials in order to optimise production processes and the running‐in characteristics of the sliding surfaces. This paper describes application‐orientated tests to support the selection of ceramic materials for water‐lubricated and unlubricated journal bearings and similar sliding surfaces. The ceramics studied were different grades of alumina, sialon, silicon carbide, and zirconia. The most promising results were obtained with a dense, sintered silicon carbide.
Comparison of Empirical Methods and Measurements for the Determination of Wear of Worm Gears
Authors: Kral P. , Pausch S.
Published: July 2006

Empirical methods use the results of test bench measurements with varying gear running conditions (such as output torque, type of lubricating oil, and material of worm and worm wheel) to allow one to derive mathematical relations for more easily calculating the wear that occurs. In this paper the empirical methods of Neupert and Steingröver are applied to two worm gears and the results described. Also, test bench measurements on two different test gears (of different worm flank shapes and slightly differing material and geometrical dimensions) were carried out. For these measurements, two types of lubricating oils, mineral and synthetic, were used. The advantages and disadvantages of the empirical methods compared to the test bench measurements and computer simulations to determine the wear of worm gears (empirical calculations, measurements, and mathematical modelling and simulations) are presented and discussed in detail. These results should help to select the best method for each case of wear evaluation.
A Theoretical Approach to Evaluating the Performance Characteristics of Double‐Decker High‐Precision Bearings
Authors: Prashad Har
Published: July 2006

This paper presents a theoretical approach to evaluating the deflection and indentation of the track surface of the inner race, the stiffness, and the life of double‐decker high‐precision bearings (DDHPBs). The deflection, indentation, and stiffness of DDH‐PBs have been compared with those of conventional bearings of the same bore under identical operating conditions. The analysis, in general, indicates that the deflection of the DDHPB is less and the stiffness is greater than in conventional bearings. Computation of the data under various loads indicates that the indentation on the ball tracks of the DDHPB is comparable to or less than that of conventional bearings of the same bore. The better performance characteristics of the DDHPB make it useful in various industrial applications.
Investigation of the Thermal Behaviour of Non‐metallic Curved‐Face‐Width Spur Gears
Authors: Andrei L. , Epureanu A. , Andrei G. , Walton D.
Published: July 2006

This paper describes a curved‐face‐width spur gear, specially designed for manufacture from non‐metallic materials. The benefits of this gear are the higher contact ratio, bending and Hertzian contact resistance, and greater tooth stiffness compared to standard spur gears. A modified geometry is proposed for the gear tooth, the height of which varies along the gear face width. Due to the reduction in tooth height, in sections away from the gear centre, lower sliding friction is expected, with consequences for the gear's thermal behaviour. The complex gear geometry makes the design of a die difficult; therefore the gears were cut on a milling machine, using a special kinematic generation process and related equipment. The tooth flank profile, an involute or near involute in sections away from the gear half‐width plane, as well as the flank surface quality determined by the single‐cutter tool used for gear manufacture, influence the meshing condition, and can be detrimental to the thermal behaviour of the gear. Experimental tests were carried out to examine the influence of load and speed on the temperature of the curved‐face‐width spur gears with modified geometry. The measured temperature of the non‐standard gear is further compared with the predicted temperature of plastic standard spur gears of the same specification.
The influence of oxygen on the friction and wear behaviour of a copper—steel couple under electric current
Authors: Bouchoucha A. , Chekroud S. , Paulmier D.
Published: July 2006

The tribological behaviour of a copper—steel couple similar to those in electrified railways has been studied as a function of mechanical, electrical, and environmental parameters. The experimental results obtained in an oxygen atmosphere show that this factor has a major influence on the wear behaviour. While there was a reduction in the average coefficient of friction compared to in argon, under oxygen there was twice the wear found under air, and six times that found under argon. In the absence of an electric current, the nature of the wear was essentially mild adhesive. However, with an electric current at the interface, fluctuations, particularly at high intensities, were recorded in both the coefficient of friction and the electrical contact resistance, and there was severe wear. Discussion of the results is based on examination of the wear surfaces and analysis of the phenomena observed during sliding contact.
Study of grey relational grade identification for ferrography based on characteristic analysis of wear debris
Authors: Hu Xianguo , Zhan Song , Zheng Shousen
Published: July 2006

Attention has been focused on how to achieve intelligent automation in ferrographic diagnosis in order to overcome the subjectivity of the diagnosis process. The present paper reports on a technique of characteristic measurement developed on the basis of the VC++ 6.0 programming platform, with characteristic parameters such as area, roundness, and aspect ratio being extracted from images of wear debris based on digital image analysis. However, the extraction of characteristic parameters from a ferrographic image is not the ultimate purpose of ferrographic diagnosis. The wear particles should be classified into several pre‐decision categories and their statistical distribution should also be calculated. The grey relational grade theory is introduced in this paper as a way to recognise wear debris and a new software system has been developed to deal with the problems occurring in the automation of ferrographic diagnosis. It is shown that the identification rules can be used to treat some real wear debris images with generally satisfactory results.
Study of the formation of gouging pits in Mn7Cr2 steel under impact abrasive wear conditions
Authors: Xie J. P. , Wang A. Q. , Yuan H. L. , Wang W. Y. , Li L. L.
Published: July 2006

A study of the formation of gouging pits in Mn7Cr2 steel under impact abrasive wear conditions was conducted using theories of elastic impact and contact, analysis of photo‐elasticity, and scanning electron microscopy (SEM). The results show that the maximum shear stress occurs at z = 0. 48a, and this initiates a crack; the crack propagates at an angle of 45° from the horizontal; and the gouging pit is conical. The SEM observations are in agreement with the theoretical calculations.
Two energy efficient algorithms for tracking objects in a sensor network
Authors: Rapaka Arvind , Madria Sanjay
Published: July 2006

We propose two energy efficient algorithms for locating a target object moving in an area covered by a wireless ad hoc network. The first algorithm developed conserve energy by efficiently identifying sensor nodes, asHome Nodes, and use only local messages between neighboring nodes to follow the trail of the object. Since we avoid the long‐range transmission and maximize the localization, the algorithms reduce the communication cost. The dynamic nature of the second algorithm exploits the predefined parameters such as the object velocity. Our algorithm represents query shipping against the conventional data shipping as a means to reduce the amount of data being shipped across the network. Hence, it locates the objects over the network with minimal energy conservation using short‐range message transmissions. The performance analysis (both experimental and theoretical) shows the effectiveness of the two algorithms in comparison to another tracking algorithm. Copyright © 2006 John Wiley & Sons, Ltd.
Estimating nest locations of bumblebee Bombus ardens from flower quality and distribution
Authors: Suzuki Yukari , Kawaguchi Lina G. , Toquenaga Yukihiko
Published: July 2006

The central‐place forager in a social‐insect colony, e.g., the bumblebee, has been expected to maximize its net rate of energy gain to increase the success of its colony. In addition to foraging behavior, the nest location is an important factor for the success of the colony. The bumblebee's nest location would be affected by the spatial distribution of flowers and their food quality. In this study, we constructed a model to estimate bumblebee nest sites, using the net energy intake rate at available food sites for workers foraging from the nest site. We hypothesized that the probability of colony establishment at a site in coordinates (x, y) was high as the sum of the net energy intake rate I(x, y) increased. To obtain I(x, y), nectar standing crop, sugar concentration, and foraging time were measured for ten plant species in the study site covering 6.25 km2. As available flowers changed seasonally, I(x, y) was calculated for three periods: the end of April, the beginning of May, and the middle of May. To verify our hypothesis, we compared the estimations in our model with the actual nest sites of Bombus ardens found in the beginning of May and June by means of tracking bumblebees. From the results, we considered that the net energy intake rate at mid‐May might represent the probability of colony establishment, because it could affect colony persistence and reproductive success.
Unadapted behaviour of native, dominant ant species during the colonization of an aggressive, invasive ant
Authors: Le Breton Julien , Orivel Jérôme , Chazeau Jean , Dejean Alain
Published: July 2006

Among the factors driving the invasive success of non‐indigenous species, the “escape opportunity” or “enemy release” hypothesis argues that an invader's success may result partly from less resistance from the new competitors found in its introduced range. In this study, we examined competitive interactions between the little fire ant Wasmannia auropunctata (Roger) and ant species of the genus Pheidole in places where both are native (French Guiana) and in places where only species of Pheidole are native (New Caledonia). The experimental introduction of W. auropunctata at food resources monopolized by the Pheidole species induced the recruitment of major workers only for the Guianian Pheidole species, which were very effective at killing Wasmannia competitors. In contrast, an overall decrease in the number of Pheidole workers and no recruitment of major workers were observed for the New Caledonian species, although the latter were the only ones able to kill the Wasmannia workers. These results emphasize the inappropriate response of native dominant New Caledonian species to W. auropunctata and, thus, the importance of enemy recognition and specification in the organization of ant communities. This factor could explain how invasive animal species, particularly ants, may be able to successfully invade species‐rich communities.
Plasticity and ontogenetic drift of biomass allocation in response to above‐ and below‐ground resource availabilities in perennial herbs: a case study of Alternanthera philoxeroides
Authors: Geng Yu‐Peng , Pan Xiao‐Yun , Xu Cheng‐Yuan , Zhang Wen‐Ju , Li Bo , Chen Jia‐Kuan
Published: July 2006

Changes in plant biomass allocation in response to varying resource availabilities may result from ontogenetic drift caused by allometric growth (i.e., apparent plasticity), a true adjustment of ontogenetic trajectories (true plasticity) or both (complex plasticity). Given that the root allocation of annual species usually decreases during the growth, the developmentally explicit model predicts that annual herbs will exhibit true plasticity in root allocation under above‐ground resource limitation and apparent plasticity for moderate stress of below‐ground resource. For perennial species, the root allocation of which increases during growth, the reverse patterns would be expected. In this study, we tested the developmentally explicit model with a perennial weed, Alternanthera philoxeroides (Mart.) Griseb. We report its adaptive changes and ontogenetic drift of root allocation in response to different resource levels (i.e., light, water and nutrient availability) by comparing root allocation on both an age and a size basis. The root allocation of A. philoxeroides increased with the size (i.e., ontogenetic drift) during the growth, and exhibited significant changes in response to different resource availabilities. Furthermore, the root allocation in response to water or nutrient availability exhibited typical complex plasticity, while the light stress only slowed down the growth, with the ontogenetic trajectory unchanged (apparent plasticity). The contrasting responses to above‐ground and below‐ground stresses were consistent with the prediction of the developmentally explicit model.
Chronic musculoskeletal pain in patients with the chronic fatigue syndrome: A systematic review
Authors: Meeus Mira , Nijs Jo , De Meirleir Kenny
Published: July 2006

Background: In addition to debilitating fatigue the majority of patients with chronic fatigue syndrome (CFS) experience chronic widespread pain.

Aims: Conducting a systematic review to critically assess the existing knowledge on chronic pain in CFS. We focussed on the definition, the prevalence and incidence, the aetiology, the relevance and the therapy strategy for chronic musculoskeletal pain and post‐exertional pain in CFS.

Methods: To identify relevant articles, we searched eight medical search engines. The search terms “chronic fatigue syndrome” AND “pain”, “nociception”, “arthralgia” and “myalgia”, were used to identify articles concerning pain in CFS. Included articles were reviewed by two blinded researchers.

Results: Twenty‐five articles and two abstract were identified and selected for further appraisal. Only 11 search results focussed on musculoskeletal pain in CFS patients. Regarding the standardized review of the articles, a 96% agreement between the researchers was observed. There is no consensus in defining chronic widespread pain in CFS, and although there is little or no strong proof for the exact prevalence, chronic pain is strongly disabling in CFS. Aetiological theories are proposed (sleep abnormalities, tryptophan, parovirus‐B, hormonal and brain abnormalities and central sensitisation) and a reduction of pain threshold after exercise has been shown. Furthermore depression seemed not related to pain in CFS and a staphylococcus toxoid vaccine caused no significant pain reduction.

Conclusions: The results from the systematic review highlight the clinical importance of chronic pain in CFS, but only few studies addressing the aetiology or treatment of chronic pain in CFS are currently available.
Detection of European ancestry in escaped farmed Atlantic salmon, Salmo salar L., in the Magaguadavic River and Chamcook Stream, New Brunswick, Canada
Authors: O'Reilly Patrick T. , Carr Jonathan W. , Whoriskey Frederick G. , Verspoor Eric
Published: July 2006

The use of European Atlantic salmon strains for commercial culture by the salmon farming industry has never been permitted in Nova Scotia or New Brunswick, Canada. Despite this, varying levels of European ancestry were detected in escaped farmed salmon in the Magaguadavic River (in 1999 and 2000) and in Chamcook Stream (in 2003), New Brunswick. Of the 53 escaped farmed salmon smolts from the Magaguadavic River and 17 escaped farmed parr from Chamcook Stream analysed, a single European “type” allele was observed at a single locus in two escaped farmed salmon smolts from the Magaguadavic River and in two escaped farmed parr from the Chamcook Stream. Of the 35 escaped farmed salmon adults analysed, two captured at the Magaguadavic fishway had European “type” microsatellite alleles at multiple loci and one also exhibited European “type” mitochondrial DNA. These results highlight the need for better containment strategies for freshwater hatcheries and genetic screening programmes for farmed salmon broodstock to minimize the likelihood of the introgression of non-local genetic material into severely depressed wild Atlantic salmon populations in the Bay of Fundy region.
A review of the impacts of salmonid farming on marine coastal ecosystems in the southeast Pacific
Authors: Buschmann Alejandro H. , Riquelme Verónica A. , Hernández-González María C. , Varela Daniel , Jiménez Jaime E. , Henríquez Luis A. , Vergara Pedro A. , Guíñez Ricardo , Filún Luis
Published: July 2006

The production of farmed salmonids in Chile reached 550 000 t in 2004. The industry is considered to be consolidated, but with potential for further expansion to the south into pristine coastal areas. The environmental impacts of the salmonid farming industry in Chile were reviewed in 1996, and evidence at that time did not suggest significant adverse effects. However, after almost ten years of sustained growth, current evidence indicates that significant loss of benthic biodiversity and localized changes in the physico-chemical properties of sediments have occurred in areas with salmonid farms. Furthermore, the presence of these farms significantly increases in pulses the density of dinoflagellates. Data suggest that escaped farmed fish may have an impact on native species, although their survival in the wild appears low. The abundance of omnivorous diving and carrion-feeding marine birds increased from twofold to fivefold in areas with salmon farms compared with control areas without them. It is urgent that an ecosystem approach be implemented to assess all impacts of salmonid farming on coastal ecosystems in southern Chile.
Cervico-thoracic teratoma masquerading as lymphatic malformation
Authors: Bhutta M F , Ching H-Y , Hartley B E J
Published: July 2006

A case is presented of a nine-month-old male infant who presented acutely with an anterior neck and mediastinum mass compressing the trachea. Radiological assessment by ultrasound, magnetic resonance imaging and computed tomography suggested the nature of the mass to be a lymphatic malformation (cystic hygroma). The excised specimen was revealed as a mature teratoma. The inability to distinguish between lymphatic malformation and teratoma on multi-imaging modalities confers a risk of mismanaging these lesions with the use of sclerotherapy; surgical excision is the necessary treatment. The potential consequences are discussed.
In99, an In100-related integron, its occurrence and prevalence in clinical Pseudomonas aeruginosa strains from a central region of Portugal
Authors: CAETANO T. , FERREIRA S. , MONDEGO A. P. , CORREIA A. , MENDO S.
Published: July 2006

In99, a possible ancestor of In100, is a class 1 integron associated with carbenicillinase (blaPSE) and aminoglycoside resistance genes [aac(6′)-Ib and aadA2]. In99 was present in 8 of 81 clinical isolates of Pseudomonas aeruginosa from unrelated patients collected in different years. The strains fell into two clonal groups and exhibited resistance to β-lactams and aminoglycosides.
Heat flow variations on a slowly accreting ridge: Constraints on the hydrothermal and conductive cooling for the Lucky Strike segment (Mid‐Atlantic Ridge, 37°N)
Authors: Lucazeau Francis , Bonneville Alain , Escartin Javier , Von Herzen Richard P. , Gouze Philippe , Carton Hélène , Cannat Mathilde , Vidal Valérie , Adam Claudia
Published: July 2006

We report 157 closely spaced heat flow measurements along the Lucky Strike segment in the Mid‐Atlantic Ridge (MAR) for ages of the ocean floor between 0 and 11 Ma. On the eastern flank of a volcanic plateau delimiting off‐axis and axial domains, the magnitude of heat flow either conforms to the predictions of conductive lithospheric cooling models or is affected by localized anomalies. On the western flank it is uniformly lower than conductive model predictions. We interpret the observed patterns of heat flow by lateral fluid circulation in a highly permeable oceanic basement. The circulation geometries are probably 3‐D rather than 2‐D and are determined by the configuration of the basement/sediment interface and the distribution of effectively unsedimented seamounts where water recharge can occur. Two major hydrothermal circulation systems can possibly explain the observations off‐axis: the first would involve lateral pore water flow from west to east, and the second would have a reverse flow direction. The wavelengths and magnitudes of heat flow anomalies require Darcy velocities of the order of 1–4 m/year, which are similar to those proposed for fast‐accreted crust elsewhere. However, a large proportion of this MAR domain remains unaffected by hydrothermal cooling, which is a relatively unusual observation but confirms the validity of conductive thermal models for seafloor ages between 5 and 10 Ma. Closer to the ridge axis (<5 Myr old crust), water circulation affects the overall axial domain, as larger proportions of basement are exposed. As much as 80–90% of the heat flux from the axial domain may be transferred to the Lucky Strike vent field, in agreement with the estimated discharge.
Astronomic calibration of the late Eocene/early Oligocene Massignano section (central Italy)
Authors: Jovane Luigi , Florindo Fabio , Sprovieri Mario , Pälike Heiko
Published: July 2006

We present an astronomically tuned polarity timescale for the late Eocene/early Oligocene based on a cyclic limestone/marls sedimentary succession exposed at Massignano, Italy (GSSP for the Eocene‐Oligocene boundary). Here we applied spectral analysis techniques to the high‐resolution magnetic susceptibility record. The results provide clear evidence of a regular and cyclic signal that allows us to discard a stochastic mechanism as controlling these fluctuations. Conversely, these outcomes reveal the presence of stable and notable periodicities that are in tune with those associated with orbital forcing. Through a cyclostratigraphic analysis of the rhythmic sedimentary alternations and combination with the results of time series analysis of the proxy record, we refine the late Eocene portion of the GPTS. Through astronomical tuning of the rhythmic sedimentary alternations to recent astronomically calculated variations of Earth's orbit we recalibrated the polarity boundaries ages and the main stratigraphic events recognized throughout the sedimentary record. Among these, an age of 33.714 Ma is proposed for the E/O boundary.