Decline in perfluorooctanesulfonate and other polyfluoroalkyl chemicals in American Red Cross adult blood donors, 2000-2006

In 2000, 3M Company, the primary global manufacturer, announced a phase-out of perfluorooctanesulfonyl fluoride (POSF, C8F17SO2F)-based materials after perfluorooctanesulfonate (PFOS, C8F17SO3-) was reported in human populations and wildlife. The purpose of this study was to determine whether PFOS and other polyfluoroalkyl concentrations in plasma samples, collected in 2006 from six American Red Cross adult blood donor centers, have declined compared to nonpaired serum samples from the same locations in 2000-2001. For each location, 100 samples were obtained evenly distributed by age (20-69 years) and sex. Analytes measured, using tandem mass spectrometry, were PFOS, perfluorooctanoate (PFOA), perfluorohexanesulfonate (PFHxS), perfluorobutanesulfonate (PFBS), N-methyl perfluorooctanesulfonamidoacetate (Me-PFOSA-AcOH), and N-ethyl perfluorooctanesulfonamidoacetate (Et-PFOSA-AcOH). The geometric mean plasma concentrations were for PFOS 14.5 ng/mL (95% CI 13.9-15.2), PFOA 3.4 ng/ mL (95% CI 3.3-3.6), and PFHxS 1.5 ng/mL (95% CI 1.4-1.6). The majority of PFBS, Me-PFOSA-AcOH, and Et-PFOSA-AcOH concentrations were less than the lower limit of quantitation. Age- and sex-adjusted geometric means were lower in 2006 (approximately 60% for PFOS, 25% for PFOA, and 30% for PFHxS) than those in 2000-2001. The declines for PFOS and PFHxS are consistent with their serum elimination half-lives and the time since the phase-out of POSF-based materials. The shorter serum elimination half-life for PFOA and its smaller percentage decline than PFOS suggests PFOA concentrations measured in the general population are unlikely to be solely attributed to POSF-based materials. Direct and indirect exposure sources of PFOA could include historic and ongoing electrochemical cell fluorination (ECF) of PFOA, telomer production of PFOA, fluorotelomer-based precursors, and other fluoropoly-mer production.     

Seismic analysis incorporating detailed structure–abutment–foundation interaction for quasi-isolated highway bridges

The Illinois Department of Transportation has adopted an economical and pragmatic methodology for designing earthquake-resistant highway bridges in the Midwestern United States. These so-called quasi-isolated bridges employ low-cost non-seismically designed bearing components as sacrificial structural fuses. During seismic events, fusing actions of these components and subsequent sliding of superstructures on substructures are intended to achieve response characteristics similar to those of conventionally isolated bridges that employ specially designed isolators. This study explores seismic structure-abutment-foundation interaction for quasi-isolated bridges in Illinois, employing a detailed yet efficient non-linear finite-element model for seat-type bridge abutments. The abutment model incorporates many structural components and geotechnical mechanisms that are critical to seismic response of the structure-abutment-foundation (SAF) system. Through non-linear static analyses performed on a complete bridge model, the force-transfer mechanisms, component fusing performance, and potential failure modes of the SAF system were explored. Using earthquake ground motions, non-linear dynamic analyses were conducted to evaluate seismic characteristics of the quasi-isolated bridge, sequences of critical limit state occurrences, and effects of abutment attributes on bridge seismic performance. The influence of abutment model sophistication on simulated bridge response was also highlighted by direct comparison of simulation results obtained from different models.     

The utility of placing recollection in opposition to familiarity in early discrimination of healthy aging and very mild dementia of the Alzheimer’s type.

This study explored the ability to control familiarity-based information in a memory exclusion paradigm in healthy young, older adults, and early stage DAT individuals. We compared the predictive power of memory exclusion performance to standard psychometric performance in discriminating between aging and the earliest stage of DAT and between APOe4-present and APOe4-absent genotype in healthy control individuals. Participants responded “yes” to words that were previously semantically encoded, and “no” to words that were previously read aloud and to new words. The number of targets and distractors on the read “distractor” list was manipulated to investigate the degree to which aging and DAT influence the ability to recollect in the face of distractor familiarity due to repetition. Memory exclusion performance was better for healthy older adults than very mild DAT individuals and better for healthy control individuals with APOe4 allele than those without APOe4 allele even after controlling for standard psychometric performance. Discussion focuses on the importance of attentional control systems in memory retrieval and the utility of the opposition paradigm for discriminating healthy versus pathological aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modeling and in-situ observation of mechanical resonances in single, vertically-oriented carbon nanofibers

In this paper, we have analyzed mechanical resonances in carbon nanotubes (CNTs) based on single, vertically-oriented tubes for their potential application in high-frequency, high-Q, miniaturized resonators. The nano-electro-mechanical (NEM) resonators were modeled using a commercially available finite-element-simulator, where the electro-mechanical coupling of the CNT to an incoming AC signal on a probe in close proximity was examined. The modeling results confirmed that the mechanical resonance was maximized when the frequency of the input signal was equal to the first order harmonic of the CNT. An investigation of the resonance frequency was also performed for various geometrical parameters of our unique three-dimensional (3D) NEMS architecture. Finally, in-situ observations of mechanical resonance in single, vertically oriented tubes is also reported, where such measurements were conducted inside a scanning-electron-microscope. This work suggests that our vertically oriented tubes are potentially well-suited for resonator applications, such as filter banks in communication systems or for mass sensing applications.     

DAVE: A Comprehensive Software Suite for the Reduction,Visualization, and Analysis of Low Energy Neutron Spectroscopic Data

National user facilities such as the NIST Center for Neutron Research (NCNR) require a significant base of software to treat the data produced by their specialized measurement instruments. There is no universally accepted and used data treatment package for the reduction, visualization, and analysis of inelastic neutron scattering data. However, we believe that the software development approach adopted at the NCNR has some key characteristics that have resulted in a successful software package called DAVE (the Data Analysis and Visualization Environment). It is developed using a high level scientific programming language, and it has been widely adopted in the United States and abroad. In this paper we describe the development approach, elements of the DAVE software suite, its usage and impact, and future directions and opportunities for development.     

Serum concentrations of 11 polyfluoroalkyl compounds in the u.s. population: data from the national health and nutrition examination survey (NHANES)

We measured the concentrations of 11 polyfluoroalkyl compounds (PFCs), including perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and perfluorohexane sulfonic acid (PFHxS) in 1562 serum samples collected from a representative U.S. population 12 years of age and older in the 1999-2000 National Health and Nutrition Examination Survey. Participants represented both sexes, three race/ethnicities (non-Hispanic blacks, non-Hispanic whites, and Mexican-Americans), and four age categories (12-19 years, 20-39 years, 40-59 years, and 60 years and older). PFCs were extracted from 100 microL of serum using on-line solid-phase extraction coupled to isotope dilution-high performance liquid chromatography-tandem mass spectrometry; limits of detection ranged from 0.05 to 0.2 ng/ mL. PFOS, PFOA, PFHxS, and perfluorooctane sulfonamide were detected in all samples analyzed; 2-(N-ethyl-perfluorooctane sulfonamido) acetic acid, 2-(N-methyl-perfluorooctane sulfonamido) acetic acid, and perfluorononanoic acid were detected in more than 90% of samples, which suggests prevalent exposures to several PFCs in the U.S. population. The concentrations of most PFCs were similar regardless of the participants' ages but were higher in males than in females. Mexican Americans had lower concentrations than non-Hispanic blacks and non-Hispanic whites, whose concentrations were similar. Higher education was associated with higher concentrations of PFOS and PFOA. These data will serve as a nationally representative baseline of the U.S. population's exposure to PFCs to which other populations can be compared, and will play an important role in public health by helping set research priorities, ranging from health effects studies to defining sources and pathways of exposure.     

High-Speed Visualization of Two-Phase Flow in a Micro-Scale Pin-Fin Heat Exchanger

Flow regimes and bubble growth are observed in a pin-fin micro-scale heat exchanger with R-11 as the working fluid. The heat exchanger is machined in silicon and derived from a DNA micro-array consisting of 150 μm-square fins separated by 50 μm-square passages. The fins are staggered and oriented 45 degrees to the flow direction such that approximately 750 channel intersections occur within the volume of the exchanger. The purpose of the study is to determine if this multiply-connected geometry produces the flow blockage, reversal, and other instabilities observed in single and parallel micro-channel configurations. The upper surface of the exchanger is a glass plate that provides optical access. High-speed digital photography and microscope optics are used to obtain real-time images of the flow at a framing rate of 5 kHz. The lower surface is electrically heated and instrumented with a heat flux gage. Inlet and outlet temperatures and pressures, heater and wall temperatures, and volumetric flow rate are monitored. Nucleation is observed near the entrance of the heat exchanger. In the central section, developed vapor regions are composed of broad slug-like vapor fronts immediately followed by a slowly growing bubbly flow. An annular regime dominates the downstream section of the exchanger with drop-like liquid structures appearing at the downstream edge of fins. The heat transfer coefficient decreases with exit quality as in other micro-scale exchangers; however, the flow instability present in parallel channel exchangers is not observed in this configuration.     

Metabiotic associations of molds and Salmonella Poona on intact and wounded cantaloupe rind

Salmonella Poona, a serotype rarely implicated in human infections, has recently caused several cantaloupe-associated outbreaks of salmonellosis. Metabiotic associations of molds and foodborne pathogens on produce have been reported. We tested proteolytic activity and measured changes in the pH of cantaloupe rind caused by growth of Alternaria alternata, Cladosporium cladosporioides, Epicoccum nigrum, Geotrichum candidum, and Penicillium expansum. Survival and growth characteristics of Salmonella Poona co-infected with each mold on the surface rind and in wounded rind tissue as affected by temperature were determined. C. cladosporioides, G. candidum, and P. expansum, but not A. alternata and E. nigrum, showed proteolytic activity on agar media containing gelatin and/or casein, with concurrent increases in pH, thus favoring survival and growth of salmonellae. Intact and mechanically wounded tissue of cantaloupe rinds were inoculated with a five-strain mixture of S. Poona and/or test mold. Five inoculation schemes were used: mold only, S. Poona only, mold and S. Poona simultaneously, mold then S. Poona 3 days later, and S. Poona then mold 3 days later. The pH of cantaloupe rinds inoculated with molds and stored at 20 degrees C for 14 days was significantly higher (P < or =0.05) than on day 0. Only the pH of rinds inoculated with C. cladosporioides or G. candidum was significantly higher (P < or =0.05) on day 21 than on day 0, when cantaloupes were stored at 4 degrees C. An initial population of S. Poona increased from 3.3 log(10) cfu/sample (ca. 7 cm(2)) of cantaloupe rind to populations as high as 9.5 log(10) cfu/sample during storage at 20 degrees C for up 14 days, regardless of co-inoculation with molds. Populations of S. Poona decreased or remained constant at 4 degrees C for up to 21 days. Results demonstrate that persistence and growth of S. Poona on intact, wounded, and decaying cantaloupe rind are not markedly affected by the presence of molds.