We have carried out a near-infrared, narrow-band imaging survey of the Crab Nebula, in the H 2 2.12 µm and Br 2.17 µm lines, using the Spartan Infrared camera on the SOAR Telescope. Over a 2.8'  5.1' area that encompasses about 2/3 of the full visible extent of the Crab, we detect 55 knots that emit strongly in the H 2 line. We catalog the observed properties of these knots. We show that they are in or next to the filaments that are seen in optical-passband emission lines. Comparison to HST [S II] and [O III] images shows that the H 2 knots are strongly associated with compact regions of low-ionization gas. We also find evidence of many additional, fainter H 2 features, both discrete knots and long streamers following gas that emits strongly in [S II]. A pixel-by-pixel analysis shows that about 6 percent of the Crab's projected surface area has significant H 2 emission that correlates with [S II] emission. We measured radial velocities of the [S II] 6716 emission lines from 47 of the cataloged knots and find that most are on the far (receding) side of the nebula. We also detect Br emission. It is right at the limit of our survey, and our Br filter cuts off part of the expected velocity range. But clearly the Br emission has a quite different morphology than the H 2 knots, following the long linear filaments that are seen in Hα and in [O III] optical emission lines.

We used K-band spectra to measure the H 2 excitation temperatures in six molecular knots associated with the filaments in the Crab Nebula. The temperatures are quite high -in the range T ∼ 2000-3000 K, just below the H 2 dissociation temperature. This is the temperature range over which the H 2 1-0 S(1) line at λ2.121 μm has its maximum emissivity per unit mass, so there may be many additional H 2 cores with lower temperatures that are too faint to detect. We also measured the electron density in adjacent ionized gas, which on the assumption of gas pressure balance indicates densities in the molecular region n mol ∼ 20 000 H baryons cm −3 , although this really is just a lower limit since the H 2 gas may be confined by other means. The excited region may be just a thin skin on a much more extensive blob of molecular gas that does not have the correct temperature and density to be as easily detectable. At the opposite extreme, the observed knots could consist of a fine mist of molecular gas in which we are detecting essentially all of the H 2 . Future CO observations could distinguish between these two cases. The Crab filaments serve as the nearby laboratories for understanding the very much larger filamentary structures that have formed in the intracluster medium of cool-core galaxy clusters.

A new experiment for use in introductory nanotechnology courses is described. This experiment allows students to fabricate metallic wires with microscale lateral dimensions and nanoscale vertical dimensions. Fabrication occurs in the capillaries of polydimethylsiloxane (PDMS) stamps modified with hydrophilic polymers. This experiment provides students with an opportunity to conduct templateassisted electrodeposition of micro-and nanomaterials, utilizing a reusable template instead of the commonly used porous, anodic alumina oxide (AAO) membranes that require dissolution to examine the wires. Fabrication of the metal wires is accomplished via the reduction of metal cations in the channels of modified PDMS stamps. In addition, this experiment introduces students to characterization using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and atomic-force microscopy (AFM). The microscale dimensions of the silver wires accommodate imaging with optical microscopy for institutions possessing limited characterization capabilities.

Recent trends of assimilating water well records into statewide databases provide a new opportunity for evaluating spatial dynamics of groundwater quality and quantity. However, these datasets are scarcely rigorously analyzed to address larger scientific problems because they are of lower quality and massive. We develop an approach for utilizing well databases to analyze physical and geochemical aspects of groundwater systems, and apply it to a multiscale investigation of the sources and dynamics of chloride (Cl ) in the near-surface groundwater of the Lower Peninsula of Michigan. Nearly 500,000 static water levels (SWLs) were critically evaluated, extracted, and analyzed to delineate long-term, average groundwater flow patterns using a nonstationary kriging technique at the basin-scale (i.e., across the entire peninsula). Two regions identified as major basin-scale discharge zones-the Michigan and Saginaw Lowlands-were further analyzed with regional- and local-scale SWL models. Groundwater valleys ("discharge" zones) and mounds ("recharge" zones) were identified for all models, and the proportions of wells with elevated Cl concentrations in each zone were calculated, visualized, and compared. Concentrations in discharge zones, where groundwater is expected to flow primarily upwards, are consistently and significantly higher than those in recharge zones. A synoptic sampling campaign in the Michigan Lowlands revealed concentrations generally increase with depth, a trend noted in previous studies of the Saginaw Lowlands. These strong, consistent SWL and Cl distribution patterns across multiple scales suggest that a deep source (i.e., Michigan brines) is the primary cause for the elevated chloride concentrations observed in discharge areas across the peninsula.

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