Effect of Thickener Particle Geometry and Concentration on the Grease EHL Film Thickness at Medium Speeds

The aim of this paper was to understand the parameters influencing the grease film thickness in a rolling elastohydrodynamically lubricated contact under fully flooded conditions at medium speeds. Film thickness measurements were taken under pure rolling for six commercial greases and their bled oils. The grease film thickness was found to be higher than corresponding bled oil, suggesting the presence of thickener in the contact. No rheological properties (characterized by steady and dynamic shear) showed any direct relation to the film thickness of the studied greases. AFM measurements of the thickener microstructure, from which the dimensional properties of the thickener particles (fibers/platelets/spheres) were estimated, showed that the relative increase in the film thickness due to entrainment of the thickener was proportional to the ratio of thickener volume fraction to the size of the fibers/platelets/spheres. Hence, with the same concentration, smaller thickener particles lead to the generation of thicker films than larger thickener particles. Next, this relation was used to establish the percentage of the thickener particles passing through the contact. Depending on the grease type, between about 1 and 70 % of the thickener particles were found to travel through the contact

Transient elastohydrodynamic lubrication analysis of a novel metal-on-metal hip prosthesis with a non-spherical femoral bearing surface

Effective lubrication performance of metal-on-metal hip implants only requires optimum conformity within the main loaded area, while it is advantageous to increase the clearance in the equatorial region. Such a varying clearance can be achieved by using non-spherical bearing surfaces for either acetabular or femoral components. An elastohydrodynamic lubrication model of a novel metal-on-metal hip prosthesis using a non-spherical femoral bearing surface against a spherical cup was solved under loading and motion conditions specified by ISO standard. A full numerical methodology of considering the geometric variation in the rotating non-spherical head in elastohydrodynamic lubrication solution was presented, which is applicable to all non-spherical head designs. The lubrication performance of a hip prosthesis using a specific non-spherical femoral head, Alpharabola, was analysed and compared with those of spherical bearing surfaces and a non-spherical Alpharabola cup investigated in previous studies. The sensitivity of the lubrication performance to the anteversion angle of the Alpharabola head was also investigated. Results showed that the non-spherical head introduced a large squeeze-film action and also led to a large variation in clearance within the loaded area. With the same equatorial clearance, the lubrication performance of the metal-on-metal hip prosthesis using an Alpharabola head was better than that of the conventional spherical bearings but worse than that of the metal-on-metal hip prosthesis using an Alpharabola cup. The reduction in the lubrication performance caused by the initial anteversion angle of the non-spherical head was small, compared with the improvement resulted from the non-spherical geometry

The behaviour of lubricated EHD contacts subjected to vibrations

Machine components containing contacts working in elastohydrodynamic (EHD) conditions are often subjected to vibrations. These may be originated from the mechanism or machine the contact is part of, the surrounding environment and within the contact itself. The influence of vibrations upon the behaviour of elastohydrodynamic films has been studied experimentally in a number of papers, but a comprehensive study of the effect of the parameters of the oscillatory motion upon the film thickness has not been carried out yet. In this study the authors evaluate the effect of the frequency of the oscillatory motion upon the EHD film thickness. Optical interferometry is used to measure lubricant film thickness in a ball-on-flat disc arrangement. A high – speed camera records the interferometric images for later analysis and conversion into film thickness maps. The disc runs at a constant angular velocity while the ball is driven by the traction forces developed in the EHD film. In steady state conditions, this would ensure pure rolling conditions, however in the present investigation the ball is subjected to harmonic vibrations in a direction perpendicular to the plane of the film. The contact under study is lubricated by basic oils and the temperature is kept at a constant value of 60°C. The aim of this paper is to understand how vibrations influence the lubricant film formation

LTR retrotransposon dynamics in the evolution of the olive (Olea europaea) genome.

Improved knowledge of genome composition, especially of its repetitive component, generates important information for both theoretical and applied research. The olive repetitive component is made up of two main classes of sequences: tandem repeats and retrotransposons (REs). In this study, we provide characterization of a sample of 254 unique full-length long terminal repeat (LTR) REs. In the sample, Ty1-Copia elements were more numerous than Ty3-Gypsy elements. Mapping a large set of Illumina whole-genome shotgun reads onto the identified retroelement set revealed that Gypsy elements are more redundant than Copia elements. The insertion time of intact retroelements was estimated based on sister LTR's divergence. Although some elements inserted relatively recently, the mean insertion age of the isolated retroelements is around 18 million yrs. Gypsy and Copia retroelements showed different waves of transposition, with Gypsy elements especially active between 10 and 25 million yrs ago and nearly inactive in the last 7 million yrs. The occurrence of numerous solo-LTRs related to isolated full-length retroelements was ascertained for two Gypsy elements and one Copia element. Overall, the results reported in this study show that RE activity (both retrotransposition and DNA loss) has impacted the olive genome structure in more ancient times than in other angiosperms

Boundary Conditions for Elastohydrodynamics of Circular Point Contacts

The paper presents the solution of an elastohydrodynamic point contact condition using inlet and outlet lubricant entrainment with partial counter-flow. The inlet and outlet boundaries are determined using potential flow analysis for the pure rolling of contiguous surfaces. This shows that Swift–Stieber boundary conditions best conform to the observed partial counter-flow at the inlet conjunction, satisfying the compatibility condition. For the outlet region, the same is true when Prandtl–Hopkins boundary conditions are employed. Using these boundary conditions, the predictions conform closely to the measured pressure distribution using a deposited pressure-sensitive micro-transducer in a ball-to-flat race contact. Furthermore, the predicted conjunctional shape closely conforms to the often observed characteristic keyhole conjunction through optical interferometry. The combined numerical–experimental analysis with realistic boundary conditions described here has not hitherto been reported in the literature

Daratumumab-Based Treatment for Immunoglobulin Light-Chain Amyloidosis

Background Systemic immunoglobulin light-chain (AL) amyloidosis is characterized by deposition of amyloid fibrils of light chains produced by clonal CD38+ plasma cells. Daratumumab, a human CD38-targeting antibody, may improve outcomes for this disease. Methods We randomly assigned patients with newly diagnosed AL amyloidosis to receive six cycles of bortezomib, cyclophosphamide, and dexamethasone either alone (control group) or with subcutaneous daratumumab followed by single-agent daratumumab every 4 weeks for up to 24 cycles (daratumumab group). The primary end point was a hematologic complete response. Results A total of 388 patients underwent randomization. The median follow-up was 11.4 months. The percentage of patients who had a hematologic complete response was significantly higher in the daratumumab group than in the control group (53.3% vs. 18.1%) (relative risk ratio, 2.9; 95% confidence interval [CI], 2.1 to 4.1; P Daratumumab in Light-Chain Amyloidosis In a randomized trial of bortezomib, cyclophosphamide, and dexamethasone as compared with the same therapy plus daratumumab, patients with light-chain amyloidosis who received daratumumab had a higher frequency of hematologic complete response than those who did not (53.3% vs. 18.1%). Deaths were most commonly due to cardiac failure