24 research outputs found

    The Compatibility of Refrigerants and Lubricants with Engineering Plastics

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    Seven oil immersion studies were completed at both 20 and 60C. Test bars used in this study fall within the manufacturer specification limits of physical consistency and integrity. Refrigerant Immersion studies at ambient and 60C are also complete. Equilibrium refrigerant gas solubilities of the 32 ISO VG branched acid polyolester with all ten refrigerants have been determined and completed at 20C. Finally, the thermal aging of plastics at constant refrigerant pressure exposure with seventeen refrigerant lubricant combinations have been completed

    The rationale and design of the antihypertensives and vascular, endothelial, and cognitive function (AVEC) trial in elderly hypertensives with early cognitive impairment: Role of the renin angiotensin system inhibition

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    <p>Abstract</p> <p>Background</p> <p>Prior evidence suggests that the renin angiotensin system and antihypertensives that inhibit this system play a role in cognitive, central vascular, and endothelial function. Our objective is to conduct a double-blind randomized controlled clinical trial, the antihypertensives and vascular, endothelial, and cognitive function (AVEC), to compare 1 year treatment of 3 antihypertensives (lisinopril, candesartan, or hydrochlorothiazide) in their effect on memory and executive function, cerebral blood flow, and central endothelial function of seniors with hypertension and early objective evidence of executive or memory impairments.</p> <p>Methods/Design</p> <p>The overall experimental design of the AVEC trial is a 3-arm double blind randomized controlled clinical trial. A total of 100 community eligible individuals (60 years or older) with hypertension and early cognitive impairment are being recruited from the greater Boston area and randomized to lisinopril, candesartan, or hydrochlorothiazide ("active control") for 12 months. The goal of the intervention is to achieve blood pressure control defined as SBP < 140 mm Hg and DBP < 90 mm Hg. Additional antihypertensives are added to achieve this goal if needed. Eligible participants are those with hypertension, defined as a blood pressure 140/90 mm Hg or greater, early cognitive impairment without dementia defined (10 or less out of 15 on the executive clock draw test or 1 standard deviation below the mean on the immediate memory subtest of the repeatable battery for the assessment of neuropsychological status and Mini-Mental-Status-exam >20 and without clinical diagnosis of dementia or Alzheimer's disease). Individuals who are currently receiving antihypertensives are eligible to participate if the participants and the primary care providers are willing to taper their antihypertensives. Participants undergo cognitive assessment, measurements of cerebral blood flow using Transcranial Doppler, and central endothelial function by measuring changes in cerebral blood flow in response to changes in end tidal carbon dioxide at baseline (off antihypertensives), 6, and 12 months. Our outcomes are change in cognitive function score (executive and memory), cerebral blood flow, and carbon dioxide cerebral vasoreactivity.</p> <p>Discussion</p> <p>The AVEC trial is the first study to explore impact of antihypertensives in those who are showing early evidence of cognitive difficulties that did not reach the threshold of dementia. Success of this trial will offer new therapeutic application of antihypertensives that inhibit the renin angiotensin system and new insights in the role of this system in aging.</p> <p>Trial Registration</p> <p>Clinicaltrials.gov NCT00605072</p

    Potentially Useful Polyolester Lubricant Additives: An Overview of Antioxidants, Antiwear and Antiseize Compounds

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    Reliable service lubrication of compressors with polyolesters that do not contain additives is the optimal goal for hermetic compressor use. Chlorine derived from CFC and HCFC refrigerants is reported to have effective antiwear properties and negates the widespread use of additives in mineral oil lubricated systems. The use of antioxidants for mineral oil and polyolesters have been reported; antioxidant additive activity seems essential for polyolesters.- Antiwear and antiseize additives seem to be a short term goal for use with polyolesters. High silicone aluminum to steel wear seems to be a primary target for additive use. The interaction of specific heteroatom organic compounds with highly polar surface active synthetic polyolester lubricants is complex. Results of an extensive literature search describe results from a service base determined at ambient conditions. Known lubricant additives used in the hermetic compressor industry, the. mode of action of several types of additives and some lubricant additive chemistry that demonstrates selective thermal stability in conjunction with the chemical structure are examined
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