Standard Ruggedness Study on Moisture Induced Sensitivity Tester

Moisture damage is one of the major issues causing premature failure of Hot Mix Asphalt (HMA) pavements. However, there are no reliable test methods to determine moisture sensitivity in the laboratory. Moisture Induced Sensitivity Tester (MIST) is a new procedure that replicates moisture conditioning in the laboratory. However, the MIST does not have a standard test method and current testing is performed based on the manufacturer recommended settings. A ruggedness study (ASTM E1169) was performed on the MIST to determine if the tolerances of the test parameters have any impact on test results. The study was performed on only one mix. The manufacturer suggested test conditions are pressure, temperature, air void content (VTM) and height of compacted sample. The effect of the tolerances of these test conditions on indirect tensile strength (ITS) and Volume Change of the MIST conditioned samples were analyzed. The results from this study show that the tolerances on VTM and height of the sample had an effect on ITS of the HMA compacted samples while the VTM alone had an impact on Volume Change. A small experiment was performed to determine if the tolerance of the water bath soak after MIST conditioning had an impact on ITS values of the compacted HMA samples. The results suggest that the recommended 2-3 hour water bath soak had an effect on ITS values.Civil & Environmental Engineerin

Temperature monitoring during cardiopulmonary bypass--do we undercool or overheat the brain?

Objective: Brain cooling is an essential component of aortic surgery requiring circulatory arrest and inadequate cooling may lead to brain injury. Similarly, brain hyperthermia during the rewarming phase of cardiopulmonary bypass may also lead to neurological injury. Conventional temperature monitoring sites may not reflect the core brain temperature ðT8Þ: We compared jugular bulb venous temperatures (JB) during deep hypothermic circulatory arrest and normothermic bypass with Nasopharyngeal (NP), Arterial inflow (AI), Oesophageal (O), Venous return (VR), Bladder (B) and Orbital skin (OS) temperatures. Methods: 18 patients undergoing deep hypothermia (DH) and 8 patients undergoing normothermic bypass (mean bladder T8—36.29 8C) were studied. For DH, cooling was continued to 15 8C NP (mean cooling time—66 min). At pre-determined arterial inflow T8; NP, JB and O T8’s were measured. A 6-channel recorder continuously recorded all T8’s using calibrated thermocouples. Results: During the cooling phase of DH, NP lagged behind AI and JB T8’s. All these equilibrated at 15 8C. During rewarming, JB and NP lagged behind AI and JB was higher than NP at any time point. During normothermic bypass, although NP was reflective of the AI and JB T8 trends, it underestimated peak JB T8 ðP 0:001Þ: Towards the end of bypass, peak JB was greater than the arterial inflow T8 ðP 0:023Þ: Conclusions: If brain venous outflow T8 (JB) accurately reflects brain T8; NP T8 is a safe surrogate indicator of cooling. During rewarming, all peripheral sites underestimate brain temperature and caution is required to avoid hyperthermic arterial inflow, which may inadvertently, result in brain hyperthermia

The Society of Thoracic Surgeons, The Society of Cardiovascular Anesthesiologists, and The American Society of ExtraCorporeal Technology: Clinical Practice Guidelines for Cardiopulmonary Bypass-Temperature Management During Cardiopulmonary Bypass

To improve our understanding of the evidence-based literature supporting temperature management during adult cardiopulmonary bypass, The Society of Thoracic Surgeons, the Society of Cardiovascular Anesthesiology and the American Society of ExtraCorporeal Technology tasked the authors to conduct a review of the peer-reviewed literature, including 1) optimal site for temperature monitoring, 2) avoidance of hyperthermia, 3) peak cooling temperature gradient and cooling rate, and 4) peak warming temperature gradient and rewarming rate. Authors adopted the American College of Cardiology/American Heart Association method for development clinical practice guidelines, and arrived at the following recommendation