Electrochemical impedance spectroscopy study of high-palladium dental alloys. Part I: Behavior at open-circuit potential*

Electrochemical impedance spectroscopy (EIS) was used to study the in vitro corrosion of three representative high-palladium alloys and a gold–palladium alloy for comparison. The corrosion resistances (measured as the charge transfer resistance R _CT from an equivalent circuit) of the high-palladium alloys and the gold–palladium alloy were comparable in simulated body fluid and oral environments, and under simulated dental plaque. The great similarity in corrosion behavior for the three high-palladium alloys is largely attributed to their substantial palladium content and passivity in the laboratory test media, and possibly to their similar structure at the submicron level. Differences in composition and microstructure at the micron level and greater, including the effects of heat treatment simulating the firing cycles for dental porcelain, do not have noteworthy effects on the in vitro corrosion of the three high-palladium alloys. Good accuracy and convenience of extracting corrosion characteristics from equivalent circuit modeling, along with the capability of providing intrinsic information about the corrosion mechanism, enable EIS to be an excellent alternative method to conventional potentiodynamic polarization for evaluating the corrosion behavior of noble dental alloys.     

A new paradigm: The investment casting cooperative arrangement

Under the leadership of five collaborating companies, the Investment Casting Cooperative Arrangement (ICCA) is in the first two years of a six-year vision that will contribute to maintaining the U.S. competitive advantage in aerospace and, more specifically, aeropropulsion. Equally important is the new paradigm that is being developed for other technologies and industries; it includes the ability of competitive companies to work together as a team in the development of generic technologies that will enhance overall competitiveness. A critical component in the success of a program such as the ICCA is the team’s ability to network and interact with other consortia operating with the same technologies so that the efforts are aligned, all resources are being leveraged, and frequent lines of communication have been established at all levels. As a result, the ICCA provides a model framework for genuine interaction among industry, federal laboratories, and universities.     

Measurement of serum isopropanol and the acetone metabolite by proton nuclear magnetic resonance: application to pharmacokinetic evaluation in a simulated overdose model

The regional distribution of [11C]d-threo-methylphenidate in mouse brain was very similar to that of [3H]WIN 35,428 ((-)-2 beta-carbomethoxy-3 beta-(4-fluorophenyl)tropane), and the two radioligands were displaced from striatum similarly after administration of the potent cocaine analog RTI-55 ((-)-2 beta-carbomethoxy-3 beta-(4-iodophenyl)tropane). However, while striatal [3H]WIN 35,428 increased between 5 and 30 min, striatal [11C]d-threo-methylphenidate halved. Thus [11C]d-threo-methylphenidate binds similarly to but more reversibly than [3H]WIN 35,428. The methyl ester of L-DOPA (L-3,4-dihydroxyphenylalanine; 200 mg/kg) plus benserazide plus clorgyline, which markedly elevates rat striatal extracellular dopamine (Wachtel and Abercrombie, 1994, J. Neurochem. 63, 108), decreased the mouse striatum-to-cerebellum ratio for [11C]d-threo-methylphenidate at 30 min by 13% (P < 0.05). In positron emission tomographic (PET) baboon studies [11C]d-threo-methylphenidate binding was insensitive to drugs expected to lower endogenous dopamine. These experiments suggest that normal synaptic dopamine does not compete for binding with [11C]d-threo-methylphenidate, and will not affect PET measures of dopamine transporter availability.     

An automatic liquid nitrogen filling system

Spectroscopic measurements at low temperature require liquid nitrogen in some type of research dewar. Often the research dewar must be refilled from a reservoir dewar several times during the course of an experiment. A system is described which automatically refills a research dewar from a reservoir dewar. Two sensors are used for detecting the liquid nitrogen level in the research dewar, and an external nitrogen gas supply is used to provide the pressure to effect the transfer of liquid nitrogen.     

Freeze-substitution without aldehyde or osmium fixatives: ultrastructure and implications for immunocytochemistry

Cryo-fixation followed by freeze-substitution without aldehyde or osmium fixation has been investigated as a method for preparing biological specimens with a view to minimizing antigenic alteration. Samples of both solid tissues (mouse small intestine and human kidney) and a human tumour cell line grown in vitro were rapidly frozen by impact (slammed) onto a copper block cooled with liquid nitrogen. They were freeze-substituted at ?80°C in methanol, and embedded at low temperature in Lowicryl K4M or HM20. Resin blocks were polymerized by ultraviolet light. Well-preserved ultrastructure was observed in the outer 10–15 μm of all samples. Positive immunocytochemical localization of fixation-resistant and fixation-labile antigens was obtained on sections of human kidney and the human breast tumour cell line ZR-75-1 at both light and electron microscope levels.     

Sintering of Iron Ores in a Millipot in Comparison with Tablet Testing and Industrial Process

To explore the feasibility of small-scale sintering pot testing, a ‘millipot’ facility (diameter of 53 mm and height of 400 mm) was established and used to examine the sintering performance of iron ores and other non-traditional ferrous materials. The sintering performance of a millipot was examined across a range of different operational conditions (coke rate and suction pressure) and compared with an industrial sinter strand operation. Tablet tests were also performed to assist in the design of the millipot experiments and identify conditions for achieving mineral composition similar to the industrial sinter. For the millipot experiments, the materials used need to be compacted to increase the bulk density, and a higher coke rate is required to compensate the high heat loss caused by wall effects. A higher suction pressure is also necessary to maintain an oxidizing atmosphere in the sinter bed. As expected, it was not possible to eliminate the wall effect, which resulted in more primary hematite at edges of the sintered column. However, the sintered material from the center of column simulates industrial sinter reasonably well. As such, millipot provides a practical way to evaluate the sintering process and material performance at laboratory scale, helping to bridge the gap between tablet sintering and large scale pot sintering, or full scale plant trial. The results of millipot testing can be used for designing larger scale experiments or commercial sintering trials.     

Responses of breadmaking quality to sulphur in three wheat varieties

Field experiments were carried out at three sites in England to investigate the effects of S fertilisation on breadmaking quality of three winter wheat varieties (Hereward, Rialto and Spark) in the 1996–1997 season. The soils at the three sites differed in extractable S contents. Depending on site, either 180 and 230 kg ha⁻¹ N or 230 and 280 kg ha⁻¹ N treatments were factorially combined with three S treatments (0, 20 and 100 kg ha⁻¹ S). Addition of S increased loaf volume significantly at two sites where grain S concentration was also significantly increased and grain N:S ratio decreased. Application of the extra 50 kg ha⁻¹ N increased grain protein concentration but did not increase loaf volume at any of the sites. Loaf volume was found to correlate more closely with grain S than with grain protein concentration. Addition of S generally decreased the elastic modulus of gel protein and dough resistance but increased dough extensibility. Despite considerable differences in their dough rheology, the responses in rheology and loaf volume to S were similar in all three varieties. Selected flour samples of Rialto from the Bridgets site were also analysed for the glutenin subunit distribution, showing that S addition increased the relative proportion of low-molecular-weight subunits at the expense of high-molecular-weight subunits of glutenin. This study therefore shows that the beneficial effects of S on breadmaking quality are associated with decreased dough elasticity and increased extensibility resulting from effects on the amount and composition of the glutenin polymers. The results also indicate that S fertilisation is required in some areas of England to maintain breadmaking quality. © 1999 Society of Chemical Industry     

Improving food security through agricultural research and development in Timor-Leste: a country emerging from conflict

Timor-Leste is a small, poor and predominantly-agricultural nation of less than 1 million people. Most families suffer from chronic food insecurity practising food rationing 1–6 months of the year. The small size of Timor-Leste, its recent birth as a nation and conflict history, together with little previous research on staple crops make it a unique crucible to test the effect of a major post-conflict initiative of agriculture research on national food security. Research started in 2000 with the introduction of germplasm of staple crops (maize, peanut, rice, cassava and sweet potato). Replicated trials confirmed by extensive evaluation in farmer-managed trials revealed significant yield advantages over the local cultivar in maize of 53%, in peanut of 31%, in rice of 23% and in sweet potato of 80%, accompanied by improvements in size and eating quality. Cultivars of maize (2), peanut (1), rice (1) and sweet potato (3) were released in 2007. One year later an early adoption study of 544 farmers involved in on-farm trials showed that 73% had re-grown new cultivars. Cultivar adoption not only increased household food security but often produced surpluses for sale in the market—sometimes for the first time. The project is planning to increase seed production and dissemination to move from a highly positive pilot-scale impact in six Districts to impact food security nationally.