We have spectroscopically determined breath ammonia levels in seven patients with end-stage renal disease while they were undergoing hemodialysis at the University of California, Los Angeles, dialysis center. We correlated these measurements against simultaneously taken blood samples that were analyzed for blood urea nitrogen (BUN) and creatinine, which are the accepted standards indicating the level of nitrogenous waste loading in a patient's bloodstream. Initial levels of breath ammonia, i.e., at the beginning of dialysis, are between 1,500 ppb and 2,000 ppb (parts per billion). These levels drop very sharply in the first 15-30 min as the dialysis proceeds. We found the reduction in breath ammonia concentration to be relatively slow from this point on to the end of dialysis treatment, at which point the levels tapered off at 150 to 200 ppb. For each breath ammonia measurement, taken at 15-30 min intervals during the dialysis, we also sampled the patient's blood for BUN and creatinine. The breath ammonia data were available in real time, whereas the BUN and creatinine data were available generally 24 h later from the laboratory. We found a good correlation between breath ammonia concentration and BUN and creatinine. For one of the patients, the correlation gave an R 2 of 0.95 for breath ammonia and BUN correlation and an R 2 of 0.83 for breath ammonia and creatinine correlation. These preliminary data indicate the possibility of using the real-time breath ammonia measurements for determining efficacy and endpoint of hemodialysis.end-stage renal disease ͉ breath analysis E xpired human breath has been analyzed extensively by mass spectrometric techniques for the existence of a variety of trace amounts of volatile organic compounds and several small inorganic molecules such as ammonia, nitric oxide, carbon disulfide, and carbon dioxide (1). Of these, several gases exhaled in human breath, e.g., ammonia, nitric oxide, aldehydes, and ketones, have been linked to kidney and liver malfunction, asthma, diabetes, cancer, and ulcers (2-4). Others, such as carbon disulfide, ethane, butane, and pentane have been linked to neurological disorders, including schizophrenia (5, 6). A few nascent technologies promise the ability to detect some of these compounds at the required parts-per-million (ppm) or parts-per-billion (ppb) concentration levels while in the presence of other interfering species. Recently, a chemiluminescence detector is being deployed for quantifying nitric oxide in human breath (7-9). Of the above aff lictions, endstage renal failure forces over 197,000 patients who require hemodialysis in the United States to undergo lengthy, threetimes-per-week, often painful, in-clinic treatment (paid by Medicare) to compensate for the loss of their kidney functions. Another 28,000 patients undergo peritoneal-or hemodialysis in their homes. Improper, insufficient, and͞or delayed treatment leads quickly to secondary organ failures and a rapid death.Our study indicates that a breath ammonia measurement may be capable of p...

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Industrial ecology is a new approach to the industrial design of products and processes and the implementation of sustainable manufacturing strategies. It is a concept in which an industrial system is viewed not in isolation from its surrounding systems but in concert with them. Industrial ecology seeks to optimize the total materials cycle from virgn material to finished material, to component, to product, to waste product, and to ultimate disposal. To better characterize the topic, the National Academy of Sciences convened a colloquium from which were derived a number of salient contributions. This paper sets the stage for the contributions that follow and discusses how each fits into the framework of industrial ecology.

A strain-balanced, InP-based quantum cascade laser structure designed for light emission at 4.6μm was grown by metal-organic chemical vapor deposition. A maximum total optical power of 1.6W was obtained in continuous-wave mode at 300K for uncoated devices processed in buried heterostructure geometry with stripe dimensions of 5mm by 9.5μm. Corresponding maximum wall plug efficiency and threshold current density were measured to be 8.8% and 1.05kA∕cm2, respectively. Fully hermetically packaged laser of identical dimensions produced in excess of 1.5W under the same conditions.