Primary Cement Debris After Total Knee Arthroplasty

Polyethylene wear is accelerated by third body cement debris and contributes to aseptic loosening after knee arthroplasty. Saline irrigation with pulse lavage is expected to render the joint free of such particles. The purpose of this study is to qualitatively characterize such primary cement debris remaining in the knee joint after cemented total knee arthroplasty and briefly discuss ways to decrease it further.

First investigation of eclipsing binary KIC 9026766: analysis of light curve and periodic changes

We investigate a short-period W UMa binary KIC 9026766 with an orbital period of 0.2721278d in the Kepler field of view. By applying an automated q-search for the folded light curve and producing a synthetic light curve for this object based on the PHOEBE code, we calculate the fundamental stellar parameters. We also analyze the O − C curve of the primary minima. The orbital period changes can be attributed to the combination of an upward quadratic function and light-travel time effect (LTTE) due to a possible third body with a minimum mass of 0.029 M ⊙ and an orbital period of 972.5866 ±0.0041d. The relative luminosity of the primary and secondary eclipses (Min I − Min II) is calculated. The periodogram of the residuals of the LTTE and Min I − Min II show peaks with the same period of 0.8566d. The background effect of two nearby stars on our target is the possible reason for this signal. By considering the amplitudes and periods of the remaining signals in the O − C curve of minima, spot motion is possible.

Tribological Behavior of Ionic Liquid with Nanoparticles

This research aims to formulate a new lubricant containing oxide nanoparticles for enhancing anti-wear ability and reducing friction. Different concentrations of copper oxide (CuO) and zinc oxide (ZnO) nanoparticles were separately added to an ionic liquid, methyltrioctylammonium bis(trifluoromethylsulfonyl)imide [N1888] [NTf2], to formulate the tested lubricants. The tribological properties of the lubricants were tested by performing ball-on-disc wear tests on a tribotester (MTM, PCS Instruments). The results show that both the CuO and ZnO nanoparticles can increase the friction reduction ability of the ionic liquid when used as a neat lubricant. The anti-wear characteristic of the ionic liquid is increased by adding ZnO nanoparticles but decreased by adding CuO nanoparticles. The best tribological performance observed for the concentration of 0.2 wt% ZnO, with the wear scar diameter is reduced by 32% compared to the pure ionic liquid. The results of SEM/EDX analysis on the worm morphologies show different lubrication mechanisms of the nanoparticles in the [N1888] [NTf2], which are tribo-sintering for CuO nanoparticles, and third body with pure rolling effect for ZnO nanoparticles.

Orbital Design and Control for Jupiter-Observation Spacecraft

This paper investigates the evolution of orbits around Jupiter and designs a sun-synchronous repeating ground track orbit. In the dynamical models, the leading terms of the Jupiter’s oblateness are J2 and J4 terms. A reasonable range of ground track repetition parameter Q is given and the best observation orbit elements are selected. Meanwhile, the disturbing function acting on the navigation spacecraft is the atmospheric drag and the third body. The law of altitude decay of the spacecraft’s semimajor orbit axis caused by the atmospheric drag is studied, and the inclination perturbation caused by the sun’s gravity is analyzed. This paper designs a semimajor axis compensation strategy to maintain the orbit’s repeatability and proposes an initial inclination prebiased strategy to limit the local time at the descending node in a permitted range. In particular, these two methods are combined in the context of sun-synchronous repeating ground track orbit for better observation of the surface of Jupiter.

Differences in Wear and Material Integrity of NAO and Low-Steel Brake Pads under Severe Conditions

In this study, through severe reduced-scale braking tests, we investigate the wear and integrity of organic matrix brake pads against gray cast iron (GCI) discs. Two prototype pad materials are designed with the aim of representing a typical non-metal NAO and a low-steel (LS) formulation. The worn surfaces are observed with SEM. The toughness of the pad materials is tested at the raw state and after a heat treatment. During braking, the LS-GCI disc configuration produces heavy wear. The friction parts both keep their macroscopic integrity and wear appears to be homogeneous. The LS pad is mostly covered by a layer of solid oxidized steel. The NAO-GCI disc configuration wears dramatically and cannot reach the end of the test program. The NAO pad suffers many deep cracks. Compacted third body plateaus are scarce and the corresponding disc surface appears to be very heterogeneous. The pad materials both show similar strength at the raw state and similar weakening after heat treatment. However, the NAO material is much more brittle than the LS material in both states, which seems to favor the growth of cracks. The observations of crack faces suggest that long steel fibers in the LS material palliate the brittleness of the matrix, even after heat damage.