Influence of MAX-Phase Deformability on Coating Formation by Cold Spraying

As solid-state deposition technique avoiding oxidation, cold gas spraying is capable of retaining feedstock material properties in the coatings, but typically fails to build up coatings of brittle materials. Ceramic MAX phases show partial deformability in particular lattice directions and may thus successfully deposit in cold spraying. However, deformation mechanisms under high strain rate, as necessary for cohesion and adhesion, are not fully clear yet. A MAX-phase deposit only builds up, if the specific mechanical properties of the MAX phase allow for, and if suitable spray parameter sets get realized. To investigate the influence of material properties and deposition conditions on coating microstructure and quality, three MAX phases, Ti3SiC2, Ti2AlC and Cr2AlC, were selected. Up to ten passes under different spray parameters yielded Ti2AlC and Cr2AlC coatings with thicknesses of about 200-500 \ub5m. In contrast, Ti3SiC2 only forms a monolayer, exhibiting brittle laminar failure of the impacting particles. In all cases, the crystallographic structure of the MAX-phase powders was retained in the coatings. Thicker coatings show rather low porosities (< 2%), but some laminar cracks. The deposition behavior is correlated with individual mechanical properties of the different MAX-phase compositions and is discussed regarding the particular, highly anisotropic deformation mechanisms

Increased platelet reactivity is associated with circulating platelet-monocyte complexes and macrophages in human atherosclerotic plaques

Objective: Platelet reactivity, platelet binding to monocytes and monocyte infiltration play a detrimental role in atherosclerotic plaque progression. We investigated whether platelet reactivity was associated with levels of circulating platelet-monocyte complexes (PMCs) and macrophages in human atherosclerotic carotid plaques. Methods: Platelet reactivity was determined by measuring platelet P-selectin expression after platelet stimulation with increasing concentrations of adenosine diphosphate (ADP), in two independent cohorts: the Circulating Cells cohort (n = 244) and the Athero-Express cohort (n = 91). Levels of PMCs were assessed by flow cytometry in blood samples of patients who were scheduled for percutaneous coronary intervention (Circulating Cells cohort). Monocyte infiltration was semi-quantitatively determined by histological examination of atherosclerotic carotid plaques collected during carotid endarterectomy (Athero-Express cohort). Results: We found increased platelet reactivity in patients with high PMCs as compared to patients with low PMCs (median (interquartile range): 4153 (1585-11267) area under the curve (AUC) vs. 9633 (3580-21565) AUC, P<0.001). Also, we observed increased pl

Standardization of automated 25-hydroxyvitamin D assays: How successful is it?

Objectives Multiple 25(OH)D assays have recently been aligned to improve comparibility. In this study we investigated the performance of these assays using both native single-donor sera with target values certified by a reference method as well as single donor sera from a heterogeneous patient population. Design & methods 25(OH)D levels were measured in twenty reference samples (Ref!25OHD; Labquality, Finland) using five automated methods (Lumipulse, Liaison, Cobas, iSYS and Access) and one aligned ID-XLC-MS/MS method (slope: 1,00; intercept: 0,00; R = 0,996). Furthermore, 25(OH)D concentrations measured in 50 pregnant women and 52 random patients using the 5 automated assays were compared to the ID-XLC-MS/MS. In addition, Vitamin D binding protein (DBP) was measured. Results Most automated assays showed significant differences in 25(OH)D levels measured in reference samples. Slopes varied from 1,00 to 1,33, intercepts from − 5.48 to − 15,81 nmol/L and the R from 0,971 to 0,997. This inaccuracy was even more prominent in a heterogeneous patient population. Slopes varied from 0,75 to 1,35, intercepts from − 9.02 to 11,51 nmol/L and the R from 0,840 to 0,949. For most assays the deviation in 25(OH)D concentration increased with elevating DBP concentrations suggesting that DBP might be one of the factors contributing to the inaccuracy in currently used automated 25(OH)D methods. Conclusions Despite the use of standardized assays, we observed significant differences in 25(OH)D concentrations in some automated methods using reference material obtained from healthy single donor sera. In sera of a patient population this inaccuracy was even worse which is highly concerning as patient samples are being investigated in clinical laboratories

A novel approach to improve operation and performance in flow field-flow fractionation

A new system design and setup are proposed for the combined use of asymmetrical flow field-flow fractionation (AF4) and hollow-fiber flow field-flow fractionation (HF5) within the same instrumentation. To this purpose, three innovations are presented: (a) a new flow control scheme where focusing flow rates are measured in real time allowing to adjust the flow rate ratio as desired; (b) a new HF5 channel design consisting of two sets of ferrule, gasket and cap nut used to mount the fiber inside a tube. This design provides a mechanism for effective and straightforward sealing of the fiber; (c) a new AF4 channel design with only two fluid connections on the upper plate. Only one pump is needed to deliver the necessary flow rates. In the focusing/relaxation step the two parts of the focusing flow and a bypass flow flushing the detectors are created with two splits of the flow from the pump. In the elution mode the cross-flow is measured and controlled with a flow controller device. This leads to reduced pressure pulsations in the channel and improves signal to noise ratio in the detectors. Experimental results of the separation of bovine serum albumin (BSA) and of a mix of four proteins demonstrate a significant improvement in the HF5 separation performance, in terms of efficiency, resolution, and run-to-run reproducibility compared to what has been reported in the literature. Separation performance in HF5 mode is shown to be comparable to the performance in AF4 mode using a channel with two connections in the upper plate. (C) 2010 Elsevier B.V. All rights reserved

Asymmetric borane reduction using mixtures of homochiral amino alcohol ligands

The asymmetric borane reduction of acetophenone is investigated using mixtures of homochiral β-amino alcohol ligands. With stoichiometric amounts of a mixture of two- or three-amino alcohols, the e.e. remains at the level of the best amino alcohol for a wide composition range. A small but statistically significant enhancement in e.e. is observed when 10 mol% of an amino alcohol mixture of (1S,2R)-1-amino-2-indanol and (S)-phenylglycinol is used as chiral ligand.

Fractional flow reserve is not associated with inflammatory markers in patients with stable coronary artery disease.

BACKGROUND: Atherosclerosis is an inflammatory condition and increased blood levels of inflammatory biomarkers have been observed in acute coronary syndromes. In addition, high expression of inflammatory markers is associated with worse prognosis of coronary artery disease. The presence and extent of inducible ischemia in patients with stable angina has previously been shown to have strong prognostic value. We hypothesized that evidence of inducible myocardial ischemia by local lesions, as measured by fractional flow reserve (FFR), is associated with increased levels of blood based inflammatory biomarkers. METHODS: Whole blood samples of 89 patients with stable angina pectoris and 16 healthy controls were analyzed. The patients with stable angina pectoris underwent coronary angiography and FFR of all coronary lesions. We analyzed plasma levels of cytokines IL-6, IL-8 and TNF-α and membrane expression of Toll-like receptor 2 and 4, CD11b, CD62L and CD14 on monocytes and granulocytes as markers of inflammation. Furthermore, we quantified the severity of hemodynamically significant coronary artery disease by calculating Functional Syntax Score (FSS), an extension of the Syntax Score. RESULTS: For the majority of biomarkers, we observed lower levels in the healthy control group compared with patients with stable angina who underwent coronary catheterization. We found no difference for any of the selected biomarkers between patients with a positive FFR (≤ 0.75) and negative FFR (>0.80). We observed no relationship between the investigated biomarkers and FSS. CONCLUSION: The presence of local atherosclerotic lesions that result in inducible myocardial ischemia as measured by FFR in patients with stable coronary artery disease is not associated with increased plasma levels of IL-6, IL-8 and TNF-α or increased expression of TLR2 and TLR4, CD11b, CD62L and CD14 on circulating leukocytes