Strategies for Information Development and Utilization for Toxic Chemicals

In the last five years, several countries have expanded and strengthened their arrangements for regulating existing chemicals, and for controlling the introduction into commerce of new chemicals. One simple, uncontroversial fact has led many to believe that those controls are necessary: the natural environment is now contaminated with many synthetic organic chemicals, some of which are believed to be carcinogens, mutagens, teratogens, or several of the above. Technological progress in organic analysis over the last three decades has been so rapid that relatively quick and inexpensive identification of such contaminants at parts per billion concentrations is now possible. A one cubic centimeter sample of drinking water can be processed, essentially instantaneously, into a computer listing of synthetic organic contaminants. So much is now uncontroversial, but controversy begins with interpretation, and with the subsequent policy proposals

Valuing Potential Groundwater Protection Benefits

This paper explores the implications of endogenous risk for the economic value of preventing groundwater contamination. We consider the analytical implications of endogenous risk for five key building blocks frequently used to structure studies of groundwater valuation: The probability and the location of contamination, the exposed population, risk perceptions, and Intertemporal issues

Comparison of flow characteristics and vascular reactivity of radial artery and long saphenous vein grafts [NCT00139399]

BACKGROUND: The morphological and functional differences between arteries and veins may have implications on coronary artery bypass graft (CABG) survival. Although subjective differences have been observed between radial artery (RA) and long saphenous venous (LSV) grafts, these have not been quantified. This study assessed and compared the flow characteristics and in-vivo graft flow responses of RA and LSV aorto-coronary grafts. METHODS: Angiograms from 52 males taken 3.7 ± 1.0 months after CABG surgery were analyzed using adjusted Thrombolysis in Myocardial Infarction (TIMI) frame count. Graft and target coronary artery dimensions were measured using quantitative coronary angiography. Estimated TIMI velocity (V(E)) and volume flow (F(E)) were then calculated. A further 7 patients underwent in-vivo graft flow responses assessments to adenosine, acetylcholine and isosorbide dinitrate (ISDN) using intravascular Doppler. RESULTS: The V(E )for RA grafts was significantly greater than LSV grafts (P = 0.002), however there was no difference in volume F(E )(P = 0.20). RA grafts showed positive endothelium-dependent and -independent vasodilatation, and LSV grafts showed no statistically significant response to adenosine and acetylcholine. There was no difference in flow velocity or volume responses. Seven RA grafts (11%) had compromised patency (4 (6%) ≥ 50% stenosis in the proximal/distal anastomoses, and 3 (5%) diffuse narrowing). Thirty-seven (95%) LSV grafts achieved perfect patency and 2 (5%) were occluded. CONCLUSION: The flow characteristics and flow responses of the RA graft suggest that it is a more physiological conduit than the LSV graft. The clinical relevance of the balance between imperfect patency versus the more physiological vascular function in the RA graft may be revealed by the 5-year angiographic follow-up of this trial

Endothelial Linings in Prosthetic Vascular Grafts

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73894/1/j.1749-6632.1987.tb33036.x.pd

Flow-Dependent Mass Transfer May Trigger Endothelial Signaling Cascades

It is well known that fluid mechanical forces directly impact endothelial signaling pathways. But while this general observation is clear, less apparent are the underlying mechanisms that initiate these critical signaling processes. This is because fluid mechanical forces can offer a direct mechanical input to possible mechanotransducers as well as alter critical mass transport characteristics (i.e., concentration gradients) of a host of chemical stimuli present in the blood stream. However, it has recently been accepted that mechanotransduction (direct mechanical force input), and not mass transfer, is the fundamental mechanism for many hemodynamic force-modulated endothelial signaling pathways and their downstream gene products. This conclusion has been largely based, indirectly, on accepted criteria that correlate signaling behavior and shear rate and shear stress, relative to changes in viscosity. However, in this work, we investigate the negative control for these criteria. Here we computationally and experimentally subject mass-transfer limited systems, independent of mechanotransduction, to the purported criteria. The results showed that the negative control (mass-transfer limited system) produced the same trends that have been used to identify mechanotransduction-dominant systems. Thus, the widely used viscosity-related shear stress and shear rate criteria are insufficient in determining mechanotransduction-dominant systems. Thus, research should continue to consider the importance of mass transfer in triggering signaling cascades