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ABSTRACT: The neuroprotective effect of hypothermia has long been recognized. The aim of this work was to compare the neuroprotective effect of systemic, head and local vascular cooling hypothermia procedures in ischemic rats.
Stroke in Sprague-Dawley rats (n=64) was induced by a 3 hour right middle cerebral artery occlusion using an intraluminal filament. Before reperfusion, ischemic animals (n=16 in each group) received hypothermia (systemic, head or local vascular) or no treatment. Brain temperature, infarction volume (n=8 in each group) and functional outcome (n=8 in each group) were compared.
Regarding brain temperature, vascular cooling significantly reduced the temperature of ischemic territory in cortex from 37.2 +/- 0.1 to 33.4 +/- 0.4 degrees C and in striatum from 37.5 +/- 0.2 to 33.9 +/- 0.4 degrees C within 5 minutes. This hypothermic condition remained for up to 60 minutes after reperfusion. However, systemic cooling reduced brain temperature at a similar level for six times longer. In the head cooling group, the target temperature was reached in 15 minutes, but returned to normal within 5 minutes. Although all hypothermia procedures induced neuroprotection, ischemic rats with vascular cooling showed significantly (p<0.001) better neuroprotection with 10.7 +/- 2.6% infarction, compared to 54.2 +/- 1.9% (no treatment), 37.1 +/- 1.0% (head cooling) and 29.1 +/- 3.4% (systemic cooling). Significantly (p<0.001) better effects on motor function were also detected in vascular cooling groups at 14 and 28 days.
Vascular cooling appears to be the most effective in reducing infarct volume and improving functional outcome than the other two hypothermia methods in a rat ischemia/reperfusion model.
Neurological Research 05/2010; 32(4):378-83. · 1.52 Impact Factor
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ABSTRACT: Purpose – This paper seeks to study the tribological properties, corrosion inhibition properties and action mechanism of two triazine-containing disulfides, TOSS and TOMA, as additives in combustion engine base oil (5CST); those properties of an alkyl disulfide dodecyl disulfide and zinc dialkyldithiophosphate (ZDDP) were also evaluated for comparison to discover whether these additives could be used as potential substitute candidates for ZDDP. Design/methodology/approach – Their tribological performances were evaluated using a four-ball machine. The worn surfaces were investigated by scanning electron microscopy and X-ray photoelectron spectroscopy (XPS) Findings – The three additives have good load-carrying capacity and corrosion inhibition properties comparable with those of ZDDP. The anti-wear properties of the triazine-containing disulfides TOSS and TOMA are good but a little inferior to those of ZDDP. The friction-reducing performances of the additives are better than those of ZDDP. The XPS results show that absorption and tribochemical reactions occur to generate a complex boundary lubrication films comprising inorganic sulfate, sulfide, iron oxide and organic nitrogen, and sulfur-containing compounds. Research limitations/implications – The anti-oxidation properties are still to be estimated, and the synergistic effectiveness with other additives could be demonstrated. Practical implications – These additives are good extreme pressure and anti-wear additives in combustion engine base oil and, through further modification of molecular structure or combination with other additives, they may be a potential replacement for ZDDP. Originality/value – To reduce the cost, the products synthesized were not finely separated. Their tribological properties as additives in the widely used combustion engine base oil were first investigated and results indicate that they show excellent performances.
Industrial Lubrication and Tribology 03/2008; 60(2):86-92. · 0.35 Impact Factor
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ABSTRACT: Three alkyloxy-s-triazine derivatives were synthesized and their tribological properties as lubricants for steel–steel contact were evaluated using an Optimol SRV tester at 20°C and 100°C. Their thermal stabilities were also investigated by thermogravimetric analysis. The results show that the three alkyloxy-s-triazine lubricants have good thermal stability. Moreover, 2,4,6-tris(1,1,5-tri-H-octafluoropentyloxy)-1,3,5-s-triazine (FPOT) possesses the best anti-wear property and good load-carrying capacity both at 20°C and 100°C. At 20°C the anti-wear effectiveness of 2,4,6-tris(n-pentyloxy)-1,3,5-s-triazine (POT) is the worst, while at 100°C that of the 1,1,5-tri-H-octafluoropentyloxy and/or 1,1,7-tri-H-dodecafluoroheptyloxy tri-substituted s-triazine mixture (FMOT) is the worst. In addition, the friction-reducing properties of the two fluoroalkyloxy-s-triazines, FPOT and FMOT, are not as good as those of the non-fluorine-containing alkyloxy-s-triazine POT. Scanning electron spectroscopy with an energy dispersive analyzer of X-ray and X-ray photoelectron spectroscopy analyses of the worn surface indicate that during the rubbing process, tribochemical reactions occur between the lubricants and the metal surface to generate a complex boundary lubrication film comprised of FeF2, Fe(OH)2, organofluorine and organonitrogen compounds. Copyright © 2006 John Wiley & Sons, Ltd.
Journal of Synthetic Lubrication 02/2006; 23(1):1 - 10.
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ABSTRACT: Nitrogen-containing heterocyclic compounds are used more widely because they have been proven to possess excellent antioxidant, anticorrosion and anti-wear properties and high thermal stabilities. With the development of modern machines and to meet the requirement of environment protection, nitrogen-containing heterocyclic derivatives are also regarded as novel potentially excellent ashless multifunctional lubricating oil additives. Therefore we carried out a series of investigations about the tribochemistry of nitrogen-containing heterocyclic compounds. To promote the development, some valuable and representative conclusions (such as the relationship between the molecular structures and their tribological properties, the influence of different active elements and their mechanism) are introduced in this paper.
Tribology Letters 01/2002; 13(2):87-93. · 1.58 Impact Factor
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ABSTRACT: A series of S, P-containing triazine derivatives, 2,4-bis-(diethylamino)-6-(O,O′-dialkyl dithiophosphate)-s-1,3,5-triazine, which are potential environmentally friendly lubricating oil additives, were synthesized. The tribological properties as lubricating oil additives in vegetable oil were evaluated using a four-ball tester. The results show that the series of triazine derivatives possess good antiwear performance, excellent load-carrying capacity. These compounds also show good friction-reducing properties. The action mechanism was estimated through analysis of the worn surface with X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM).
Wear. 257:389-394.
