The Adsorption of Synovene on ZDDP Wear Tracks: A Sum Frequency Generation (SFG) Vibrational Spectroscopy Study

The adsorption of the lubricant additive Synovene on steel and on ZDDP/steel wear tracks from base oil has been investigated by sum frequency generation (SFG) vibrational spectroscopy, an interface specific technique. SFG spectra (resonances) were investigated in the C-H stretching region and arise from the aliphatic chains of the palm oil constituent of Synovene. The observation of SFG spectra means that Synovene is adsorbed at the oil/metal and at the oil/ZDDP/metal interfaces and that the aliphatic chains of Synovene have a net polarisation order with respect to the surface. The intense spectrum observed when the film is first formed decreases in intensity with increasing temperature. It is proposed that this is due to a decrease in film thickness as the film tends towards monolayer thickness. A dependence of the intensity and shape of SFG resonances on film thickness due to a thickness-dependent interference effect has been observed in other thin film systems, most notably lipid films on gold. Supporting evidence for the film thickness hypothesis comes from examining the spectra of different thickness films of palmitic acid on steel, one of the constituents of Synovene. The spectra on the wear track are less intense and less reproducible than on the bare metal. After periods of several days at room temperature the spectra on both surfaces gain in intensity implying a return to thicker layers of Synovene under cold conditions.BP Castro

Thermal Behaviour of Synovene and Oleamide in Oil Adsorbed on Steel

AbstractOleamide and Synovene lubricant additives when mixed together show a clear co-operative effect leading to friction and wear reduction. Sum Frequency Generation vibrational spectroscopy has been used to record in situ spectra of these additives with the aim of understanding the behaviour of these molecules when adsorbed on steel immersed in a model base oil at pre-selected temperatures. The spectra of the individual components and of mixtures have been recorded up to 130 °C. Individual spectra from both molecules have been distinguished using per-deuterated oleamide. The temperature at which maximum ordered adsorption of pure Synovene molecules occurs drops from ~ 130 to ~ 70 °C in the mixture with oleamide. Our results show that co-adsorption occurs, which causes a change in net polar orientation of the oleamide component suggesting the hydrocarbon chains of the oleamide molecules reverse their polar orientation when Synovene is present. The net effect of co-adsorption and change in orientation as well as conformation of the two molecules could explain the reduction of friction and wear observed at the metal–metal interface.</jats:p

The safety of over-the-counter niacin. A randomized placebo-controlled trial [ISRCTN18054903]

BACKGROUND: Niacin is widely available over the counter (OTC). We sought to determine the safety of 500 mg immediate release niacin, when healthy individuals use them as directed. METHODS: 51 female and 17 male healthy volunteers (mean age 27 years SD 4.4) participated in a randomized placebo-controlled blinded trial of a single dose of an OTC, immediate-release niacin 500 mg (n = 33), or a single dose of placebo (n = 35) on an empty stomach. The outcomes measured were self-reported incidence of flushing and other adverse effects. RESULTS: 33 volunteers on niacin (100%) and 1 volunteer on placebo (3%) flushed (relative risk 35, 95% confidence interval (CI) 6.8–194.7). Mean time to flushing on niacin was 18.2 min (95% CI: 12.7–23.6); mean duration of flushing was 75.4 min (95% CI: 62.5–88.2). Other adverse effects occurred commonly in the niacin group: chills (51.5% vs. 0%, P < .0001), generalized pruritus (75% vs. 0%, P = <.001), gastrointestinal upset (30% vs. 3%, P = .005), and cutaneous tingling (30% vs. 0%, P = <.001). Six participants did not tolerate the adverse effects of niacin and 3 required medical attention. CONCLUSION: Clinicians counseling patients about niacin should alert patients not only about flushing but also about gastrointestinal symptoms, the most severe in this study. They should not trust that patients would receive information about these side effects or their prevention (with aspirin) from the OTC packet insert

Effects of different membranes and dialysis technologies on patient treatment tolerance and nutritional parameters

There is increasing evidence that the biochemical and cellular phenomena induced by blood/membrane/dialysate interactions contribute to dialysis-related intradialytic and long-term complications. However, there is a lack of large, prospective, randomized trials comparing biocompatible and bioincompatible membranes, and convective and diffusive treatment modalities. The primary aim of this prospective, randomized trial was to evaluate whether the use of polysulfone membrane with bicarbonate dialysate offers any advantages (in terms of treatment tolerance, nutritional parameters and pre-treatment beta(2)-microglobulin levels) over a traditional membrane (Cu-prophan(R)). A secondary aim was to assess whether the use of more sophisticated methods consisting of a biocompatible synthetic membrane with different hydraulic permeability at different ultrafiltration rate (high-flux hemodialysis and hemodiafiltration) offers any further advantages. Seventy-one Centers were involved and stratified according to the availability of only the first two or all four of the following techniques: Cuprophan(R) hemodialysis (Cu-HD), low flux polysulfone hemodialysis (LfPS-HD), high-flux polysulfone high-flux hemodialysis (HfPS-HD), and high-flux polysulfone hemodiafiltration (HfPS-HDF). The 380 eligible patients were randomized to one of the two or four treatments (132 to Cu-HD, 147 to LfPS-HD, 51 to HfPS-HD and 50 to HfPS-HDF). The follow-up was 24 months. No statistical difference was observed in the algebraic sum of the end points between bicarbonate dialysis with Cuprophan(R) or with low-flux polysulfone, or among the four dialysis methods under evaluation. There was a significant decrease in pre-dialysis plasma beta(2)-microglobulin levels in high-flux dialysis of 9.04+/-10.46 mg/liter (23%) and in hemodiafiltration of 6.35+/-12.28 mg/liter (16%), both using high-flux polysulfone membrane in comparison with Cuprophan(R) and low-flux polysulfone membranes (P=0.032). The significant decrease in pre-dialysis plasma beta(2)-microglobulin levels could have a clinical impact when one considers that beta(2)-microglobulin accumulation and amyloidosis are important long-term dialysis-related complications