X-ray absorption near-edge structure (XANES) spectroscopy has been used to characterize the chemistry of antiwear (AW) films generated from mineral base oil containing a zinc dialkyl dithiophosphate additive. These films were formed on rubbed steel surfaces with a reciprocating boundary contact using different sliding frequencies. The phosphorus L-edge XANES spectra show that these films have slightly different chemical natures. Longer chain polyphosphates were present on the steel surface prepared at the higher sliding frequencies. The surface morphology of these films was investigated using atomic force microscopy. These images show that the surface morphology of the AW films changes with the sliding frequency. Round and bigger antiwear pads were formed at a lower frequency while higher frequencies resulted in thinner films and flattened surfaces. Nanomechanical properties of these antiwear films were investigated by nanoindentation measurement and the elastic moduli extracted from force-displacement (f-d) curves are similar for all antiwear films, 100 ± 10 GPa.
X-ray absorption near edge structure (XANES) spectroscopy has been used to characterize the chemistry of thermal films on steel samples, which were generated from a mineral base oil containing a zinc dialkyl dithiophosphate (ZDDP) additive. These films were formed at 150°C by immersing steel coupons in ZDDP oil solutions. The phosphorus L-edge XANES spectra show that these films are composed of polyphosphates, unreacted ZDDP and other thiophosphate intermediates. Phosphorus K-edge FY XANES was used to monitor the thickness of these films, and the data are consistent with thickness derived by focussed ion beam (FIB) milling and SEM imaging. The sulphur K-edge TEY and FY XANES spectra show that these films are composed of different sulphur components, which depend upon the formation times. The surface morphology of these films was investigated using atomic force microscopy (AFM). These images show that the surface morphology of the thermal films changes with the formation time. 31P NMR spectra show that both primary and secondary ZDDP decomposes gradually at 150°C.
Antiwear (AW) films, generated from a mineral base oil containing a zinc dialkyl dithiophosphate (ZDDP) additive, were studied as a function of formation temperature, load and rubbing time. The surface morphology of these films was investigated using atomic force microscopy (AFM), and surface roughness calculated for the observed differing surface morphologies. The morphology of the films is heterogeneous for all the tested conditions, but the surface roughness is dependent on the rubbing condition. X-ray absorption near edge structure (XANES) spectroscopy has been used to characterize the chemistry of these films, and the intensity of the phosphorus K-edge was also used to monitor their thickness. The thickness of these films is in the range of 10-90 nm depending on the running conditions. Phosphorus L-edge spectra show that these films have a similar chemical nature with variable polyphosphate chain-lengths. 31P NMR was used to study the decomposition of ZDDP in the residual oils. The spectra show that the primary and secondary ZDDP react differently under the various conditions. The tribological characteristics of these AW films were probed by measuring the coefficients of friction (l) and the wear scar width (WSW) of the counter faces. l is highly related to the applied load and the results of WSW measurements show that the wear performance is related to all the tested parameters, temperature, load and rubbing time.
We conducted a meta-analysis to evaluate the relationship between erythropoietin (EPO) polymorphisms and diabetic microvascular complications. We searched the PubMed, Embase, Cochrane library, Web of Science, Wanfang, and Chinese National Knowledge Infrastructure databases for appropriate studies. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to evaluate the associations. Ultimately, eight studies consisting of 2,861 cases and 2,136 controls were identified and included in our meta-analysis. Results with our genotype model indicated an association between rs1617640 polymorphisms and diabetic microvascular complications (TT vs. GG: OR = 1.544, 95% CI = 1.089–2.189, P = 0.015). No clear associations between the rs1617640 and rs507392 polymorphisms and diabetic retinopathy were observed. By contrast, rs551238 polymorphisms were associated with increased diabetic retinopathy risk (allele model: OR = 0.774, 95% CI = 0.658–0.911, P = 0.002; genotype model: AC vs. CC: OR = 0.598, 95% CI = 0.402–0.890, P = 0.011; dominant model: OR = 0.561, 95% CI = 0.385–0.817, P = 0.003; recessive model: OR = 0.791, 95% CI = 0.643–0.973, P = 0.026). These results indicate that EPO polymorphisms are a risk factor for diabetic microvascular complications.
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