Application of MEMS technology in automotive sensors and actuators

Sensors and actuators are the critical system components that collect and act on information in the analog environment and link it to the world of digital electronics. The functional groups of sensors, software, controller hardware, and actuators from the backbone of present and future automotive systems. Unit volumes for sensors and actuators in the automotive industry are measured in millions per year and at a unit cost of a few dollars. The design of sensors and actuators has increasingly made use of microelectromechanical systems (MEMS) technology. This technology is well suited to producing a class of micromachined sensors and actuators that combines signal processing and communications on a single silicon chip or contained within the same package. This paper contains a discussion of the issues in producing MEMS sensors and actuators from the concept selection stage to the manufacturing platform. Examples of commercial and emerging automotive sensors and actuators are given, which illustrate the various aspects of device development. Future trends in MEMS technology as applied to automotive components are also discussed     

Synthesis and reactivity of coumarin 3,4-epoxide

Coumarin is used widely as a fragrance constituent and is administered clinically in the treatment of certain lymphedemas and malignancies. Although toxicity occurs only rarely in humans treated clinically with high-dose coumarin, it is well established that coumarin is hepatotoxic in the rat. This species difference in susceptibility to toxicity reflects the disparate metabolic processes occurring in humans and rodents. In humans, coumarin is converted extensively via cytochrome P450 2A6 to the nontoxic 7-hydroxycoumarin metabolite. In contrast, coumarin 3,4-epoxidation is thought to predominate in rodent species, resulting in the formation of several potentially toxic metabolites. Coumarin epoxide is thought to be highly unstable and has not been isolated synthetically or as a microsomal product. To address this issue, coumarin 3,4-epoxide was synthesized, and its stability and fate have been determined. Coumarin 3,4-epoxide was prepared by reacting coumarin with dimethyldioxirane. The epoxide was stable in organic solvents and survived conditions required for analysis by gas chromotography. Its structure was confirmed via 1H-NMR and gas chromatography-mass spectrometry-infrared spectroscopy (GC-MS-IR). In contrast, coumarin 3,4-epoxide was unstable in aqueous solution, converting within 20 sec to a ring-opened compound. Using GC-MS-IR analysis, the single coumarin 3,4-epoxide product was identified as o-hydroxyphenylacetaldehyde (o-HPA). Although other investigators have suggested that 3-hydroxycoumarin is an intermediate in o-HPA formation from coumarin 3,4-epoxide, we have demonstrated that 3-hydroxycoumarin, incubated in an aqueous system or with liver microsomal proteins, does not form o-HPA. Thus, the results of the present work establish that coumarin 3,4-epoxide can be synthesized and that o-HPA, which has previously been shown to be a prominent coumarin metabolite in rat liver microsomal incubations, is formed directly from coumarin 3,4-epoxide. These results suggest that both coumarin 3,4-epoxide and o-HPA may contribute to the hepatotoxicity of coumarin.     

Is Construction Labor Productivity Really Declining?

Macroeconomics data suggest that labor productivity declined significantly in the construction industry during the 1979–1998 period. However, microeconomic studies indicate the contrary. This paper critically examines the construction labor productivity macroeconomic data in the United States from 1979 to 1998 to determine their validity and reliability. Data collection, distribution, manipulation, analysis, and interpretation are reviewed and problems are identified. The paper also presents a comparison of construction and manufacturing labor productivity during this period. The main conclusion of the study is that the raw data used to calculate construction productivity values at the macroeconomic level and their further manipulation and interpretation present so many problems that the results should be deemed unreliable. The uncertainty generated in the process of computing these values is such that it cannot be determined if labor productivity has actually increased, decreased, or remained constant in the construction industry for the 1979–1998 period.     

Characterization of Lunar Dust for Toxicological Studies. II: Texture and Shape Characteristics

The morphology (shape and texture) of dust fractions of five Apollo lunar soils and a lunar dust simulant, JSC-1Avf, was studied using scanning electron microscopy. Shape (aspect ratio and complexity) of particles was described based on the two-dimensional projection images. The distributions of aspect ratio and complexity of particles are reported. It was determined that the Apollo lunar dust particles consist mainly of impact-produced glass, with complicated morphologies, extensive surface areas per grain, and sharp, jagged edges. Importantly, many grains contain elaborate vesicular textures, representing minute agglutinates. Dust simulant JSC-1Avf also has similar shapes as lunar dust, but differs in surface texture and area (smooth and nonvesicular). These data provide information for toxicity studies of lunar dust and for selecting a suitable lunar dust simulant.     

Development of an on-line SPE-LC-ESI-MS method for urinary nucleosides: hyphenation of aprotic boronic acid chromatography with hydrophilic interaction LC-ESI-MS

The development of an on-line automated SPE-HPLC--ESI-MS method is described for targeted metabolomic analysis of urinary modified nucleoside levels. The setup comprises a boronate affinity column as a trapping device, a hydrophilic interaction chromatography (HILIC) separation and information-dependent MS detection modes. The system was optimized using standards and tested on biological samples, detecting a number of modified nucleosides. Other urinary biomarkers could also be analyzed by the system developed: for example, the urinary nucleobases were also available for analysis. A simultaneous creatinine-monitoring experiment was also demonstrated to be viable when utilizing the method, which is of benefit as creatinine is a urinary normalizing factor.     

Regioselective Organocatalytic Formation of Carbamates from Substituted Cyclic Carbonates

A highly regioselective catalytic approach has been developed towards carbamates derived from cyclic organic carbonates by reaction of the latter with amine reagents under organocatalytic control. For various combinations of carbonate and amine substrates, an organocatalyst (TBD: 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene) was used to increase the reaction kinetics while exerting excellent regioselective control. The current method is the first general approach towards the control over the regioselectivity of this reaction using a wide variety of easily accessed substituted organic carbonates.