Multiple-input microcantilever sensors

A surface-micromachined micro-electro-mechanical-system (MEMS) process has been used to demonstrate multiple-input chemical sensing using selectively coated cantilever arrays. Cantilever motion due to absorption-induced stress was readout using a custom-designed, eight-channel integrated circuit. Combined hydrogen and mercury vapor detection was achieved with a palm-sized, self-powered module with spread-spectrum telemetry reporting.     

Permeation and diffusion of environmental pollutants through flexible polymers

Permeation and diffusion characteristics of high density polyethylene (HDPE), elasticized polyolefin, and polychloroprene membranes have been determined for various organic pollutants at 22 and 50°C. A standard ASTM permeation cell method was used to measure the permeation rate while an immersion/weight gain method was used to obtain the diffusion coefficient. Thickness-dependent permeation rates were determined for HDPE membranes. An equimolar mixture of various permeants was also used to see the possibility of synergistic effects by combination of permeants. The experimental results are discussed in relation to the suitability of HDPE membranes in severe environments.     

Performance of a gas flow meter calibration system utilizing critical flow venturi standards

A set of Critical Flow Venturis (CFVs) were manufactured by Flow Systems and calibrated by NIST in Gaithersburg, MD. Subsequently these flow standards along with pressure and temperature standards have been integrated into a gas flow meter calibration (GFC) system. Performance data and an uncertainty analysis is discussed here in this paper. Calibration data on these CFV standards will be used to inter-compare the NIST and CEESI primary facilities.     

Single molecule magnets on a gold surface: in situ electrospray deposition, x-ray absorption and photoemission

Single molecule magnets based on the dodecamanganese (III, IV) cluster with two different types of ligand (acetate and benzoate) have been studied on the Au(111) surface. Due to the non-volatile and fragile nature of the molecules, we have used ultra-high vacuum electrospray deposition to produce a series of surface coverages from a fraction of a monolayer to multilayer films in both cases. Synchrotron radiation based electron spectroscopy has been used to study the adsorption of the molecules on the Au(111) surface and the effect that this has on the oxidation states of the manganese atoms in the core. In both cases, reduction of the core is observed due to the interaction with the surface, to essentially the same extent despite substantial differences in the size and nature of the ligand shell.     

The Electrodeposition of Chromium from Tervalent Chromium Salt Solutions. Part I. Chromium Chloride and Chromium Sulphate Baths

The “imponderables” which affect the framework within which the Plating Shop must be planned are listed. The grouping of vats, cleaners and rinses are discussed and alternative methods of hand operation of plating vats described. The importance of depth of plating vats is stressed and various methods of constructing floors, drainage and vat supports are briefly indicated. Layouts for barrel plating shops both with inclined and horizontal barrels are suggested, and the importance of correct housing for electrical and other ancillary plant is emphasised.     

A national meeting for medical students--new pedagogic approach. High tempo visits to different scientific fields]

The methionine analogue 2-amino-5-hexenoic acid (homoallylglycine, Hag) can be utilized by Escherichia coli in the initiation and elongation steps of protein biosynthesis. Use of an E. coli methionine auxotroph and Hag-supplemented medium resulted in replacement of ca. 85% of the methionine residues in mouse dihydrofolate reductase expressed under control of a bacteriophage T5 promoter. N-terminal sequencing indicated 92+/-5% occupancy of the initiator site by Hag. The vinyl function of Hag remains intact in the purified protein and suggests new chemistries for modification of natural and artificial proteins prepared in bacterial hosts.