Dip Pen Nanolithography (DPN) is a lithographic technique that allows direct deposition of chemicals, metals, biological macromolecules, and other molecular “inks” with nanometer dimensions and precision. This paper addresses recent developments in the design and demonstration of high-density multiprobe DPN arrays. High-density arrays increase the process throughput over individual atomic force microscope (AFM) probes and are easier to use than arrays of undiced commercial probes. We have demonstrated passive arrays made of silicon (8 probes, 310 μm tip-to-tip spacing) and silicon nitride (32 probes, 100 μm tip-to-tip spacing). We have also demonstrated silicon nitride “active” arrays (10 probes, 100 μm tip-to-tip spacing) that have embedded thermal actuators for individual probe control. An optimization model for these devices, based on a generalized multilayer thermal actuator, is also described.

Current field experience with microbiological influenced corrosion (MIC) has now extended into the medium-grade stainless steels containing 4% molybdenum and in excess of 20% chromium. These may indeed be special cases where a combination of synergistic effects, temperature, and wet-dry cycles have aggravated a situation that is already subject to a mild form of MIC. Data are presented from a fresh water field site, comparing the relative performance of several welded coupons, including AISI 304L, 316L, and higher alloyed grades, 622, C276, C-22, 25-6Mo exposed to principally iron-oxidizing bacteria. Specific data is also presented from a saltwater laboratory study of AISI 316/E308 welds where sulfate-reducing bacteria were included. Normally this weld configuration is considered “mismatched” however has nevertheless been employed at several inland power stations. Data is presented which suggests that under “freshwater” conditions (ie. < 150 ppm Cl−) excluding deposits originating from other sources, for example, calcareous scales, an increase in chromium content may significantly reduce the problem. The laboratory study showed that severe generalized rusting of 316/E308 welds may be expected in the presence of fermentative and sulfate-reducing bacteria in chloride environments. The relationship of these data, and of those available in the literature, to the problem of long-term radioactive waste disposal, is discussed with respect to materials selection.

A newly discovered worked mammoth bone is described. It exhibits butchering marks and demonstrates man's contemporaneity in Florida with a late Pleistocene fauna.