The ability of grease to generate elastohydrodynamic (EHD) films has
been studied and interpreted in terms of the response of grease structure to
contact conditions. For most liquid lubricants, EHD film thickness depends upon
the rheological properties of the fluid in the contact inlet. This mechanism is
reasonably well understood for fluids that are Newtonian in behaviour. However,
greases have complex bulk structures, the scale of which is larger than the
dimensions of a contact inlet. The EHD performance of grease must therefore
depend upon the response of grease structure to the high-shear inlet conditions.
In this study, EHD film thickness has been measured for a range of greases
using optical interferometry. In parallel work, grease structural changes have
been monitored directly in the inlet of EHD contacts using reflection-absorption
infrared spectroscopy. By using these two approaches in combination, changes
in composition and loss of bulk grease structure have been observed and
correlated with the ability of greases to form films under EHD conditions.
Hydrophobic interaction chromatography (HIC) is a classic purification tool applied in protein and antibody, laboratory and industrial production process. It has been mainly used for the removal of both product-related impurities such as aggregates, as well as process contaminants such as host cell proteins. This review will focus on the recent development of HIC in its applications in the industrial purification processes. The process economy and requirements of high product purity and quality have driven much of the recent advancement in HIC chromatography in terms of increased throughput and enhanced selectivity or resolution. Meanwhile, high throughput screening (HTS), design of experiments (DoE) and platform approach for process development have been applied to shorten the development time. The throughput improvement has been achieved through new resins with increased binding capacity, using dual salts for load conditioning, and operating in the flow-through mode. In addition, hydrophobic interaction membrane filter chromatography technology reduces bed volumes and buffer usage and potentially improves process throughput by reducing cycle time. Selectivity and/or resolution enhancements have been achieved through optimization of operation parameters such as temperature and efforts such as application of solvent additives.
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