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Test Duration (test + duration)
Selected AbstractsChromate reduction in wastewater at different pH levels using thin iron wires,A laboratory studyENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2005Li-Yang Chang Abstract The effectiveness of using thin zero-valent iron (Fe0) wires in the treatment of wastewater generated from a metal cleaning facility and with a pH in the range of 2 to 10 was examined. It was found that (1) when the sample containing low levels of total chromium (,14 mg/L) was mixed with iron wires at a pH of 3 to 8, 50 to 90% of the total chromium could be reduced in 4 h; (2) the initial reduction efficiency was pH-dependent: the lower the pH, the higher the reduction rate; (3) variations of solution pH, redox electrical potential, and electrical conductivity (EC) in samples were also pH-dependent; (4) the adsorption/reduction efficiency was limited by the diffusion of Cr(VI) from wastewater to the iron surface when the test duration was long; (5) when the initial pH = 3, iron corrosion and redox reaction dominated the reduction process; however, with pH = 8 or 10, corrosion, surface passivation, or metal precipitation could compete with reduction; (6) the used iron wires were still effective in chromium removal in new samples at pH = 3; and (7) some desorption of adsorbed chromium was observed in acidic samples when the test duration was long. Scanning electron microscope images and energy-dispersive X-ray spectra collected from iron samples also indicate that the efficiency of chromium adsorption/reduction is pH-dependent. Our results suggest that using zero-valent iron to polish acidic wastewater containing low contents of chromium and other heavy metals is feasible. © 2005 American Institute of Chemical Engineers Environ Prog, 2005 [source] Ecdysteroid synthesis and imaginal disc development in the midge Chironomus riparius as biomarkers for endocrine effects of tributyltinENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2002Torsten Hahn Abstract Acute effects of the endocrine disruptor bis (tri- n -butyltin) oxide (TBTO) on molting-hormone biosynthesis and imaginaldisc development were investigated in larvae of the midge Chironomus riparius (Meigen). Ecdysteroid synthesis was measured by 24-h incubation of molting-hormone-synthesizing tissues (prothoracic glands) in vitro with or without the addition of TBTO. The amount of ecdysteroids produced was analyzed by radioimmunoassay. Developmental effects in vivo were investigated by determining the developmental phase of the genital imaginal discs before and after a 48-h exposure to TBTO in water. Sex-specific effects were found with both endpoints. Ecdysteroid synthesis was significantly reduced (analysis of variance [ANOVA], p , 0.005) in female larvae at all concentrations (TBTO-Sn at 50, 500, and 5,000 ng/L), whereas a significant elevation of the biosynthesis rate occurred in male larvae in the 500-ng/L treatment (ANOVA, p , 0.05). In vivo experiments with development of the genital imaginal disc within a 48-h exposure period revealed a significantly slower development in female larvae and a significantly faster development in male larvae (contingency tables, p , 0.001) at all concentrations tested (TBTO-Sn at 10, 50, 200, and 1,000 ng/L). These results partly coincided with the in vitro effects on molting-hormone synthesis. The 48-h median lethal concentration (LC50) was 25 ,g/L (20,30 ,g/L 95% confidence intervals). The combination of in vitro and in vivo methods has proven to be a useful approach for the detection of endocrine effects of TBTO in C. riparius at levels 2,000-fold below the LC50 value. High sensitivity and short test duration suggest that chironomids may have potential as freshwater sentinel organisms for endocrine-disrupting chemicals. [source] A universal alternating immersion simulator for accelerated cyclic corrosion tests,MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 2 2008A. W. Hassel A new device for performing accelerated cyclic immersion tests is described. The main achievement is to realise a high cycling rate without a proportional increase in the test duration. The device is also capable of performing tests according to EU ISO 11130 specification. A minimal invasive drying system is used that neither heats air nor sample and the flow rate is still low as to prevent a mechanical delamination of paints or loose corrosion products. A multiple sample set-up is realised that provides individual reference electrodes. The random access through a multiplexer allows individual investigation of the samples even by electrochemical impedance spectroscopy under immersion conditions. The device and its test principle are applicable in both industrial and laboratorial scale applications. Two application examples are given to demonstrate the versatility of the alternating immersion tester. One addresses the corrosion protection performance of different zinc-coated steel sheets; the other quantifies the patina formation kinetics of low-alloyed steels with weathering properties. [source] Zum Korrosionsverhalten von Nicrofer 3033 in hochkonzentrierter SchwefelsäureMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2002H. Werner Untersuchungen zum Korrosionsverhalten von Nicrofer 3033 (1.4591) erfolgten in 93%iger und 95,99%iger technischer Schwefelsäure bei Temperaturen von 70,200°C. 6-h-Versuche mit gravimetrischer Auswertung und Messung des Freien Korrosionspotentials und 48-h-Versuche mit gravimetrischer Auswertung dienten zur Ermittlung des Einflusses von Schwefelsäurekonzentration und Temperatur bei An- und Abwesenheit von SO2 auf die Beständigkeit von Blechproben. Der Einfluss der Strömungsgeschwindigkeit wurde in 6-h-Versuchen durch Rotation von Rohrproben bei Umfangsgeschwindigkeiten bis 2 m/s untersucht. Aus den Potential- und gravimetrischen Messungen folgt für Temperaturen ab 100°C eine Beständigkeit mit , 0,1 mm/a für Nicrofer 3033 (1.4591) ab etwa 98,5%. Um 125°C scheint jedoch ein Gebiet zu existieren, wo zumindest bei längerer Versuchsdauer die Beständigkeit bis herab zu etwa 97,5% erhalten bleibt. Untersuchungen zum Strömungseinfluss weisen darauf hin, dass in dem genannten Gebiet mit zunehmender Strömungsgeschwindigkeit wieder eine Aktivierung erfolgt. Bei den anderen Temperaturen ist dagegen der Strömungseinfluss gering. Diese Ausweitung des Beständigkeitsbereiches um 125°C belegt, dass die Temperaturabhängigkeit von Nicrofer 3033 (1.4591) in hochkonzentrierter Schwefelsäure nicht monoton ist. Es treten in Abhängigkeit von der Schwefelsäurekonzentration bei unterschiedlichen Temperaturen Korrosionsmaxima und -minima auf. Bei Anwesenheit von SO2 erfolgt nur bei niedrigen Versuchstemperaturen, 80°C, 100°C im 6-h-Versuch und 70°C, 80°C im 48-h-Versuch, eine Einengung des Beständigkeitsbereiches. Contribution to corrosion behaviour of Alloy 33 in high concentrated sulfuric acid Investigations on the corrosive behaviour of Alloy 33 were conducted in 93% and 95,99% technical sulfuric acid at temperatures of 70,200°C. 6-h-tests with gravimetric evaluation and measurement of the free corrosion potential and 48-h-tests with gravimetric evaluation served to determine the influence of the sulfuric acid concentration and the temperature on the resistance of sheet samples at presence and absence of SO2. The influence of the flow rate was examined in 6-h-tests via rotation of pipe samples at circumferential speeds up to 2 m/s. The potential and gravimetric measurements showed that there is a resistance with , 0.1 mm/a for Alloy 33 as from about 98.5% at temperatures from 100°C. However, about 125°C there seems to be a zone at which the resistance down to about 97.5% is kept at least for a long test duration. Examinations on the flow influence indicate that there is a reactivation in the said zone with increasing flow speed. However, the flow influence is low at the other temperatures. This extension of the resistance zone about 125°C proves that the temperature sensitivity of Alloy 33 is not monotonous in highly concentrated sulfuric acid. There are corrosion maxima and minima as a function of the sulfuric acid concentration at different temperatures. If SO2 is present, there is only a limitation of the resistance zone at low test temperatures, 80°C, 100°C in the 6-h-test and 70°C, 80°C in the 48-h-test. [source] Living related small bowel transplantation in children: 3-dimensional computed tomography donor evaluationPEDIATRIC TRANSPLANTATION, Issue 1 2004Fabrizio Panaro Abstract:, The evaluation of the small bowel vascular anatomy of living small bowel donors (LSBD) is usually performed with conventional angiography (CA). Recently, angio computed tomography (CT) has become a valid study of the vascular anatomy for kidney and liver living donors. We studied the applicability of angio CT with 3-D reconstruction (3-D-ACT) in the evaluation of LSBD. Potential LSBDs for pediatric transplant underwent both CA and 3-D-ACT to evaluate the anatomy of the distal branches of the superior mesenteric artery and vein. Angio-CT was performed with General Electric Lightspeed Scanner. The 3-D reconstruction was performed on the TeraRecon workstation. Adverse reactions, contrast dosage, test duration, invasiveness, hospital-stay, patient discomforts and accuracy were evaluated. Four potential donors (four female; mean age: 30.5 yr; mean BMI: 28.4) underwent both tests. Adverse reactions correlated to contrast agent used (90 mL CA, 150 mL 3-D-ACT) were not reported. CA required a hospitalization of 6 h as opposed to immediate discharge after the 3-D-ACT. The CA required the placement of transfemoral catheter and therefore greater patient discomfort than with 3-D-ACT. The 3-D-ACT arterial images were rated as equivalent to CA, however, 3-D-ACT venous images were rated better than the CA in all cases. CT-angiography with 3-D reconstruction is an acceptable method for vascular evaluation. When compared with routine angiography, it is less invasive, better tolerated and faster, but does require a significantly greater volume of venous contrast. 3-D-ACT also offers a better evaluation of the venous phase, and thus may become the test of choice to evaluate the vascular anatomies of LSBD candidates. [source] Long-term Reliability Prediction of 935 nm LEDs Using Failure Laws and Low Acceleration Factor Ageing TestsQUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 6 2005Y. Deshayes Abstract Numerous papers have already reported various results on electrical and optical performances of GaAs-based materials for optoelectronic applications. Other papers have proposed some methodologies for a classical estimation of reliability of GaAs compounds using life testing methods on a few thousand samples over 10,000 hours of testing. In contrast, fewer papers have studied the complete relation between degradation laws in relation to failure mechanisms and the estimation of lifetime distribution using accelerated ageing tests considering a short test duration, low acceleration factor and analytical extrapolation. In this paper, we report the results for commercial InGaAs/GaAs 935 nm packaged light emitting diodes (LEDs) using electrical and optical measurements versus ageing time. Cumulative failure distributions are calculated using degradation laws and process distribution data of optical power. A complete methodology is described proposing an accurate reliability model from experimental determination of the failure mechanisms (defect diffusion) for this technology. Electrical and optical characterizations are used with temperature dependence, short-duration accelerated tests (less than 1500 h) with an increase in bias current (up to 50%), a small number of samples (less than 20) and weak acceleration factors (up to 240). Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||