Thermal processing as a means to prepare durable, submicron thickness ionomer films for study by transmission infrared spectroscopy.

A high temperature solution processing method was adapted to prepare durable, freestanding, submicrometer thickness films for transmission infrared spectroscopy studies of ionomer membrane. The materials retain structural integrity following cleaning and ion-exchange steps in boiling solutions, similar to a commercial fuel cell membrane. Unlike commercial membrane, which typically has thicknesses of >25 µm, the structural properties of the submicrometer thickness materials can be probed in mid-infrared spectral measurements with the use of transmission sampling. Relative to the infrared attenuated total reflection (ATR) technique, transmission measurements can sample ionomer membrane materials more uniformly and suffer less distortion from optical effects. Spectra are reported for thermally processed Nafion and related perfluoroalkyl ionomer materials containing phosphonate and phosphinate moieties substituted for the sulfonate end group on the side chain. Band assignments for complex or unexpected features are aided by density functional theory (DFT) calculations.

Elucidating the ionomer-electrified metal interface.

The competitive adsorption of Nafion functional groups induce complex potential dependencies (Stark tuning) of vibrational modes of CO adsorbed (CO(ads)) on the Pt of operating fuel cell electrodes. Operando infrared (IR) spectroscopy, polarization modulated IR spectroscopy (PM-IRRAS) of Pt-Nafion interfaces, and attenuated total reflectance IR spectroscopy of bulk Nafion were correlated by density functional theory (DFT) calculated spectra to elucidate Nafion functional group coadsorption responsible for the Stark tuning of CO(ads) on high surface area fuel cell electrodes. The DFT calculations and observed spectra suggest that the side-chain CF3, CF2 groups (i.e., of the backbone and side chain) and the SO3(-) are ordered by the platinum surface. A model of the Nafion-Pt interface with appropriate dihedral and native bond angles, consistent with experimental and calculated spectra, suggest direct adsorption of the CF3 and SO3(-) functional groups on Pt. Such adsorption partially orders the Nafion backbone and/or side-chain CF2 groups relative to the Pt surface. The coadsorption of CF3 is further supported by Mulliken partial charge calculations: The CF3 fluorine atoms have the highest average charge among all types of Nafion fluorine atoms and are second only to the sulfonate oxygen atoms.

Table Saw Injuries: Are Our Safety Features Really Keeping Us Safe?

BACKGROUND: Currently, table saws sold in the United States have 3 safety features (riving knife, blade guard, and antikickback device) designed to prevent personal injury; however, these features can hinder the user's movements and are often disabled or removed. Despite the frequency of table saw injuries, there is relatively limited literature regarding them. METHODS: We performed a retrospective, observational study of characteristics associated with injuries incurred while using a table saw. Electronic medical records from Bassett Medical Center were reviewed from 2002 to 2014 to identify patients who sustained table saw injury, and surveys were sent to the patients. Tests of association between survey variables (eg, presence/absence of safety device vs severity of injury) were carried out using chi-square or Fisher exact test. RESULTS: Seventy-three percent of those injured had disabled their safety features or had no safety features present; 27% of those injured had one or more safety features enabled when they sustained the injury. Of those injured, 18% sustained a "mild" injury (skin laceration), 39% sustained a "moderate" injury (nerve or tendon injury), and 43% sustained a "severe" injury (partial or complete amputation). There was no statistically significant association between severity of the injury and presence/absence of safety features. CONCLUSIONS: This study highlights 2 major problems with the current safety features: People are dissatisfied with current safety features, disabling them and sustaining injuries, and even when they are enabled, people are still getting injured-suggesting inadequacy of the current features.