Sorption of Perfluorochemicals to Granular Activated Carbon in the Presence of Ultrasound

Perfluorochemicals (PFCs) are emerging pollutants of increasing public health and environmental concern due to their worldwide distribution, environmental persistence, and bioaccumulation potential. Activated carbon adsorption is an effective method to remove PFCs from water. Herein, we report on the sorption of four PFCs: perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), perfluorobutane sulfonate (PFBS), and perfluorobutanoate (PFBA), from deionized water (MQ) and landfill groundwater (GW) by granular activated carbon (GAC) in the absence and presence of 20 kHz ultrasound. In all cases, the adsorption kinetics were found to be well-represented by a pseudosecond-order model, with maximum monolayer sorption capacity and initial sorption rate values following the orders q_(e)^(PFOS) > q_(e)^(PFOA) > q_(e)^(PFBS) > q_(e)^(PFBA) and v_(0)^(PFOS) > v_(0)^(PFBS) > v_(0)^(PFOA) > v_(0)^(PFBA), respectively. The equilibrium adsorption was quantified by the BET multilayer absorption isotherm, and the monolayer sorption capacity increased with increasing PFC chain length: q_(m)^(PFOS) > q_(m)^(PFOA) > q_(m)^(PFBS) > q_(m)^(PFBA). The equilibrium PFC sorption constants, q_e and q_m, and the sorption kinetic constants, v_0 and k_2, were greater in Milli-Q water than in landfill groundwater with or without pretreatment, indicating competition for sorption sites by natural and cocontaminant groundwater organics. Ultrasonic irradiation significantly increased the PFC−GAC sorption kinetics, 250−900%, and slightly increased the extent of PFC equilibrium adsorption, 5−50%. The ultrasonic PFC−GAC sorption kinetics enhancement increased with increasing PFC chain length, suggesting ultrasound acts to increase the PFC diffusion rate into GAC nanopores

Ground-based detections of thermal emission from CoRoT-1b and WASP-12b

We report a new detection of the H-band thermal emission of CoRoT-1b and two confirmation detections of the Ks-band thermal emission of WASP-12b at secondary eclipses. The H-band measurement of CoRoT-1b shows an eclipse depth of 0.145%\pm0.049% with a 3-{\sigma} percentile between 0.033% - 0.235%. This depth is consistent with the previous conclusions that the planet has an isother- mal region with inefficient heat transport from dayside to nightside, and has a dayside thermal inversion layer at high altitude. The two Ks band detections of WASP-12b show a joint eclipse depth of 0.299%\pm0.065%. This result agrees with the measurement of Croll & collaborators, providing independent confirmation of their measurement. The repeatability of the WASP-12b measurements also validates our data analysis method. Our measurements, in addition to a number of previous results made with other telescopes, demonstrate that ground-based observations are becoming widely available for characterization of atmospheres of hot Jupiters.Comment: 20 pages, including 8 figures and 1 table. Accepted for publication in Ap

Intra and Inter-PON ONU to ONU Virtual Private Networking using OFDMA in a Ring Topology

Abstract—In this paper, we propose a novel WDM-PON architecture to support efficient and bandwidth-scalable virtual private network (VPN) emulation over both inter-PON and intra- PON. The virtual ring link for the VPN communications among ONUs is realized by using additionally low-cost optical passive components and OFDMA technology. Moreover, the downstream traffic wavelength is reused for the upstream traffic signal by using re-modulation technology. We report on a successful transmission of 10.7 Gbps OOK upstream and 10.7 Gbps DPSK downstream, together with 1.25 Gbps 16-QAM OFDM VPN traffic, over 20 km no-zero dispersion shifted fiber (NZDSF). In this paper, we propose a novel WDM-PON architecture to support efficient and bandwidth-scalable virtual private network (VPN) emulation over both inter-PON and intra-PON. The virtual ring link for the VPN communications among ONUs is realized by using additionally low-cost optical passive components and OFDMA technology. Moreover, the downstream traffic wavelength is reused for the upstream traffic signal by using re-modulation technology. We report on a successful transmission of 10.7 Gbps OOK upstream and 10.7 Gbps DPSK downstream, together with 1.25 Gbps 16-QAM OFDM VPN traffic, over 20 km no-zero dispersion shifted fiber (NZDSF)

Infrared Eclipses of the Strongly Irradiated Planet WASP-33b, and Oscillations of its Host Star

We observe two secondary eclipses of the strongly irradiated transiting planet WASP-33b in the Ks band, and one secondary eclipse each at 3.6- and 4.5 microns using Warm Spitzer. This planet orbits an A5V delta-Scuti star that is known to exhibit low amplitude non-radial p-mode oscillations at about 0.1-percent semi-amplitude. We detect stellar oscillations in all of our infrared eclipse data, and also in one night of observations at J-band out of eclipse. The oscillation amplitude, in all infrared bands except Ks, is about the same as in the optical. However, the stellar oscillations in Ks band have about twice the amplitude as seen in the optical, possibly because the Brackett-gamma line falls in this bandpass. We use our best-fit values for the eclipse depth, as well as the 0.9 micron eclipse observed by Smith et al., to explore possible states of the exoplanetary atmosphere, based on the method of Madhusudhan and Seager. On this basis we find two possible states for the atmospheric structure of WASP-33b. One possibility is a non-inverted temperature structure in spite of the strong irradiance, but this model requires an enhanced carbon abundance (C/O>1). The alternative model has solar composition, but an inverted temperature structure. Spectroscopy of the planet at secondary eclipse, using a spectral resolution that can resolve the water vapor band structure, should be able to break the degeneracy between these very different possible states of the exoplanetary atmosphere. However, both of those model atmospheres absorb nearly all of the stellar irradiance with minimal longitudinal re-distribution of energy, strengthening the hypothesis of Cowan et al. that the most strongly irradiated planets circulate energy poorly. Our measurement of the central phase of the eclipse yields e*cos(omega)=0.0003 +/-0.00013, which we regard as being consistent with a circular orbit.Comment: 23 pages, 9 figures, 3 tables, accepted for the Astrophysical Journa

z'-band Ground-Based Detection of the Secondary Eclipse of WASP-19b

We present the ground-based detection of the secondary eclipse of the transiting exoplanet WASP-19b. The observations were made in the Sloan z'-band using the ULTRACAM triple-beam CCD camera mounted on the NTT. The measurement shows a 0.088\pm0.019% eclipse depth, matching previous predictions based on H- and K-band measurements. We discuss in detail our approach to the removal of errors arising due to systematics in the data set, in addition to fitting a model transit to our data. This fit returns an eclipse centre, T0, of 2455578.7676 HJD, consistent with a circular orbit. Our measurement of the secondary eclipse depth is also compared to model atmospheres of WASP-19b, and is found to be consistent with previous measurements at longer wavelengths for the model atmospheres we investigated.Comment: 20 pages, 10 figures. Published in the ApJ Supplement serie

Self-assembly of a model amphiphilic oligopeptide incorporating an arginine headgroup

The self-assembly in aqueous solution of the alanine-rich peptide A12R2 containing twelve alanine residues and two arginine residues has been investigated. This oligomeric peptide was synthesized via NCA-polymerization methods. The surfactant-like peptide is found via FTIR to form antiparallel dimers which aggregate into twisted fibrils, as revealed by cryogenic-transmission electron microscopy. The fibril substructure is probed via detailed X-ray scattering experiments, and are uniquely comprised of twisted tapes only 5 nm wide, set by the width of the antiparallel A12R2 dimers. The packing of the alanine residues leads to distinct “b-sheet” spacings compared to those for amyloid-forming peptides. For this peptide, b-sheet structure coexists with some a-helical content. These ultrafine amyloid fibrils present arginine at high density on their surfaces, and this may lead to applications in nanobiotechnology

Illusion and Reality in the Atmospheres of Exoplanets

The atmospheres of exoplanets reveal all their properties beyond mass, radius, and orbit. Based on bulk densities, we know that exoplanets larger than 1.5 Earth radii must have gaseous envelopes, hence atmospheres. We discuss contemporary techniques for characterization of exoplanetary atmospheres. The measurements are difficult, because - even in current favorable cases - the signals can be as small as 0.001-percent of the host star's flux. Consequently, some early results have been illusory, and not confirmed by subsequent investigations. Prominent illusions to date include polarized scattered light, temperature inversions, and the existence of carbon planets. The field moves from the first tentative and often incorrect conclusions, converging to the reality of exoplanetary atmospheres. That reality is revealed using transits for close-in exoplanets, and direct imaging for young or massive exoplanets in distant orbits. Several atomic and molecular constituents have now been robustly detected in exoplanets as small as Neptune. In our current observations, the effects of clouds and haze appear ubiquitous. Topics at the current frontier include the measurement of heavy element abundances in giant planets, detection of carbon-based molecules, measurement of atmospheric temperature profiles, definition of heat circulation efficiencies for tidally locked planets, and the push to detect and characterize the atmospheres of super-Earths. Future observatories for this quest include the James Webb Space Telescope, and the new generation of Extremely Large Telescopes on the ground. On a more distant horizon, NASA's concepts for the HabEx and LUVOIR missions could extend the study of exoplanetary atmospheres to true twins of Earth.Comment: Invited Review for the 25th Anniversary issue of JGR Planets, in pres