Lubricant rheology applied to elastohydrodynamic lubrication

Viscosity measurements in a high pressure rheometer, elastohydrodynamic simulator studies (including the development of a temperature measuring technique), and analytical fluid modeling for elastohydrodynamic contacts are described. The more recent research which is described concerns infrared temperature measurements in elastohydrodynamic contacts and the exploration of the glassy state of lubricants. A correlation, of engineering significance, was made between transient surface temperature measurements and surface roughness profiles. Measurements of glass transitions of lubricants and the study of the effect of rate processes on materials lead to the conclusion that typical lubricants go into the glassy state as they pass through the contact region of typical elastohydrodynamic contacts

Pressure-viscosity measurements for several lubricants to 5.5 x 10 to the 8th power Newtons per square meter (8 x 10 to the 4th psi) and 149 C (300 F)

A capillary viscometer was used to measure viscosity as a function of pressure, temperature, and shear stress for a number of lubricants. The conditions under which the measurements were made are specified. The results obtained for each material are analyzed. It was determined that all pressure-viscosity coefficients decreased with increasing temperature. Data from other techniques such as optical elastohydrodynamics, oscillating crystal, and low shear capillary viscometry were compared with the results obtained

Investigations of lubricant rheology as applied to elastohydrodynamic lubrication

The pressure viscometer was modified to permit the measurement of viscosity at elevated pressures and shear stresses up to 5 x 10 to the 6th power N/sq m (720 psi). This shear stress is within a factor of three of the shear stress occurring in a sliding ehd point contact such as occurs in the ehd simulator. Viscosity data were taken on five lubricant samples, and it was found that viscous heating effects on the viscosity were predominant and not non-Newtonian behavior at the high shear stresses. The development of the infrared temperature measuring technique for the ehd simulator was completed, and temperature data for a set of operating conditions and one lubricant are reported. The numerical analysis of the behavior of nonlinear lubricants in the lubrication of rollers is reported

Emil Zuckerkandl, M.D. (1849-1910): Bridging Anatomic Study and the Operating Room Table.

In the mid-19th century, the Vienna School of Anatomy was at the epicenter of the rapidly growing field of anatomy. One of the school’s most distinguished professors, Hungarian-born anatomist Emil Zuckerkandl was instrumental in transforming anatomy from a descriptive science to one of practical and clinical value. A prolific researcher interested in nearly all areas of morphology and most famously, the chromaffin system, Zuckerkandl’s discoveries from more than a century ago still provide a foundation for surgeons to this day

Substantial Doubt Remains about the Efficacy of Anti-Amyloid Antibodies

Alzheimer's disease (AD) is a prevalent, progressive, and ultimately fatal neurodegenerative disorder that is defined pathologically by the accumulation of amyloid plaques and tau neurofibrillary tangles in the brain. There remains an unmet need for therapies that can halt or slow the course of AD. To address this need, the FDA has provided a mechanism, under its Accelerated Approval pathway, for potential therapeutics to be approved based in part on their ability to reduce brain amyloid. Through this pathway, two monoclonal anti-amyloid antibodies, aducanumab and lecanemab, have been approved for clinical use. More recently, another amyloid-lowering antibody, donanemab, generated a statistically significant outcome in a phase 3 clinical trial and will shortly come under FDA review. While these monoclonal antibodies are not yet routinely used in clinical practice, the series of recent positive clinical trials has fostered enthusiasm amongst some AD experts. Here, we discuss three key limitations regarding recent anti-amyloid clinical trials: (1) there is little to no evidence that amyloid reduction correlates with clinical outcome, (2) the reported efficacy of anti-amyloid therapies may be partly, or wholly, explained by functional unblinding, and (3) donanemab in its phase 3 trial had no effect on tau burden, the pathological hallmark more closely related to cognition. Taken together, these observations call into question the efficacy of anti-amyloid therapies.Comment: 11 pages, 2 figures; Update 11/18/2023: Added subheadings to manuscript to improve readability, added a new data point to Figure 1A and Figure 2 for the recently published A4 clinical tria

Investigations of lubricant rheology as applied to elastohydrodynamic lubrication

Traction prediction in sliding elastohydrodynamic (EHD) contacts was examined along with an elastohydrodynamic lubrication simulation of the effects of load and speed on temperatures in the EHD contact. An existing shear stress theory and lubricant rheological model were studied and evaluated by applying them to traction prediction. Results obtained using measured film thickness and surface temperature data, were compared with measured traction values. The infrared technique for measuring temperatures in an EHD contact was further developed and ball surface and fluid temperatures are reported for sliding speeds of 0.35 to 5.08 m/s at 0.52 to 2.03 GN/sq m maximum pressure and surface roughnesses of .011 to .381 micrometers c.1.a. The relationship between asperity interaction, as measured by relocation surface profilimetry and high frequency temperature measurements, and the ratio of film thickness to surface roughness was also studied

Determination of Transgene Copy Number by Real-Time Quantitative PCR

Efficient methods to characterize transgenic plants are important to quickly understand the state of the transformant. Determining transgene copy number is an important step in transformant characterization and can differentiate between complex and simple transformation events. This knowledge can be extremely useful when determining what future experiments and uses the transgenic lines can be utilized for. The method described here uses real-time quantitative PCR to determine the transgene copy number present in the genome of the transformant. Specifically, this method measures the relative transgene copy number by comparing it with an endogenous gene with a known copy number. This method is a quick alternative to the Southern blot, a method that is commonly used to determine gene copy number, and is effective when screening large numbers of transformants