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Barthel, A.J.,Luo, J.,Hwang, K.S.,Lee, J.Y.,Kim, S.H. Elsevier Sequoia [etc.] 2016 Wear: An international journal on the science and Vol.350 No.-
<P>Although samples are visibly clean, organic deposits could have tremendous impacts on tribological measurements and interpretation of friction and wear behaviors. This paper discusses the boundary lubrication effects of invisible residues from organic solvents that have been widely used in tribological studies in ambient conditions. Stainless steel, soda lime glass, and copper substrates were cleaned using UV/ozone treatment or organic solvents such as alcohols where the solvent was allowed to evaporate from the surface. In ball-on-flat tribo-tests, all UV/ozone cleaned samples showed high friction and catastrophic wear immediately upon sliding due to the absence of lubricants at the sliding interface, while samples cleaned by organic solvent experienced low friction and minimal wear for hundreds of reciprocating cycles. Analyses of the surface by atomic force microscopy and vibrational spectroscopy indicated that the solvent cleaning deposits hydrocarbon residue on metal and oxide substrates. This residue is due to trace impurities with low vapor pressures inevitably present in the bulk liquid, regardless of solvent purity, which become concentrated upon vaporization of the high vapor pressure solvent. These results demonstrated that drying after cleaning with organic solvents is equivalent to a dip-coating of low vapor pressure organics onto the sample surface. This dip-coating effect can be avoided if surfaces are cleaned using UV/ozone or if the surface is immediately rinsed with DI water and blow-dried after cleaning with organic solvent. These results indicate that the friction coefficients of the samples with organic residues should not be interpreted with the shear strength model of friction. (C) 2016 Elsevier B.V. All rights reserved.</P>
Peter Barthel 한국천문학회 2017 天文學論叢 Vol.32 No.1
AKARI and the subsequent Herschel Space Observatory have yieldedtremendous advancement in our knowledge of the infrared-submillimeterproperties of active galaxies and active galactic nuclei, AGN. Thisshort review describes some highlights. Active galaxies are found to dowhat they are supposed to do: build up their stellar bodies whilebuilding up their central black holes.
( Patrick Prager ),( Manuela Kunz ),( Regina Ebert ),( Ludger Klein-hitpass ),( Jakob Sieker ),( Thomas Barthel ),( Franz Jakob ),( Christian Konrads ),( Andre Steinert ) 대한슬관절학회 2018 대한슬관절학회지 Vol.30 No.3
Purpose: Mesenchymal stem cells (MSCs) isolated from the anterior cruciate ligament (ACL) share multiple characteristics of bone marrow-derived mesenchymal stem cells (BMSCs), allowing their use for regenerative therapies. Injuries to the ACL can affect people of all ages. This study assesses whether the regenerative potential of ACL-derived MSCs (ACL-MSCs) from old donors is as high as the potential of ACL-MSCs from young donors. Materials and Methods: ACL-MSCs were isolated from ACL tissues obtained from young and old donors at the time of ACL reconstruction or arthroplasty. Proliferative capacity, multilineage differentiation potential (chondrogenic, osteogenic, and adipogenic lineages), and transcriptome-wide gene expression were assessed and compared between young and old donors. BMSCs of middle-aged donors served as an additional comparator. Results: No substantial differences between ACL-MSCs from young and old donors were observed in their proliferative capacity and multilineage differentiation potential. The latter did not substantially differ between both ACL-MSC groups and BMSCs. Differential expression of genes related to the cytoskeleton and to protein dephosphorylation amongst other pathways was detected between ACL-MSCs from young and old donors. Conclusions: Regenerative potential of ACL-MSCs from old donors was not substantially lower than that from young donors, suggesting that regenerative therapies of ACL tears are feasible in both age groups. In vivo studies of the effect of age on the efficacy of such therapies are needed.