Brominated flame retardants in seawater and atmosphere of the Atlantic and the Southern Ocean

Seawater and air samples were collected aboard the FS Polarstern during the cruises ANT-XXV/1 + 2 in the Atlantic and Southern Ocean in 2008. The particulate and dissolved phase in water and particulate and gaseous phase in air were analyzed separately for nine polybrominated diphenyl ethers (PBDEs) and six non-PBDE brominated flame retardants (BFRs). Air concentrations of 2,3-dibromopropyl-2,4,6-tribromophenyl ether (DPTE) and hexabromobenzene (HBB) in the gaseous and particulate phase (median = 0.56 pg m(-3) for DPTE and 0.92 pg m(-3) for HBB) were comparable to ∑(9)PBDEs (1.0 pg m(-3)). Pentabromotoluene (PBT) was detectable in ～30% of the gaseous phase samples, whereas concentration of 2,4,6-tribromophenyl allylether (ATE), hexachlorocyclopentenyl-dibromocyclooctane (HCDBCO) and 2-ethyl-1-hexyl 2,3,4,5-tetrabromobenzoate (EHTBB) were below their method detection limits. DPTE, and PBDEs were also found in seawater at low pg per liter levels. Elevated seawater concentrations of PBDEs and DPTE were measured in the English Channel and close to South African coast. Concentrations of DPTE, BDE-47, and BDE-99 in the atmosphere generally decreased from Europe toward the Southern Ocean, whereas no latitudinal trend was observed in seawater. Air-water exchange gradients suggested net deposition dominates for all selected substances. The medians of net deposition fluxes for the air-water gas exchange were 83, 21, 69, 20, and 781 pg m(-2) day(-1) for BDE-47, BDE-100, BDE-99, DPTE, and HBB, whereas medians of dry deposition fluxes were 2.0, 0.3, 1.2, 1.0, and 0.5 pg m(-2) day(-1) for BDE-47, BDE-100, BDE-99, DPTE, and HBB. Overall, these results highlight the important role of the long-range atmospheric transport of PBDE and non-PBDE BFRs to remote regions.     

A −40-dB EVM 20-MHz subsampling multistandard receiver architecture with dynamic carrier detection,bandwidth estimation,and EVM optimization

In this work, a reconfigurable multistandard subsampling receiver with dynamic carrier frequency detection and system-level EVM optimizations is proposed. Ideal software defined radio (SDR) receivers promise complete flexibility at the expense of high-performance analog-to-digital converters (ADCs) that are challenging to implement in current technologies for low-power applications. This scenario leads to the research of digital intensive sampling receivers with discrete-time signal processing (DTSP) implemented in analog domain. This approach makes it feasible to move channel selection filtering and dynamic gain adaptability from analog to digital domain. The proposed receiver employs subsampling down-conversion along with subband filters to dynamically detect the carrier frequency of the incoming signal, estimate its bandwidth, and identify if the signal is present in one of the target standard bands. This carrier detection provides a unique capability to reconfigure the receiver dynamically. Additionally, in this work, system-level EVM optimization is proposed considering frequency synthesizer phase noise, IQ mismatch, sampling frequency selection and block-level gain, noise, and nonlinearity. The RF front end of the proposed receiver is modeled in Verilog-AMS whereas the digital signal processing is implemented in Simulink-Matlab. The complete receiver has been verified to detect and process three different bands belonging to three different standards (GSM, UMTS, and WLAN) with the carrier frequency ranging from 0.9 to 2.5 GHz. Test signals with 4-QAM modulation, maximum bandwidth of 20 MHz, and input-dynamic range from –109 to –20 dBm is utilized to demonstrate the receiver performance including an EVM of –40 dB.     

Characterization of high-boiling petroleum distillate fractions by proton and 13C nuclear magnetic resonance spectrometry

High-boiling (535–675 °C) distillate fractions of Wilmington (Calif. USA) and Gach Saran (Iran) crude oils were separated into saturate, monoaromatic, diaromatic and polyaromatic-polar fractions by passage through a silica-gel—alumina dual packed chromatography column. These fractions were further separated on the basis of molecular volume by gel-permeation chromatography (g.p.c.). Select g.p.c. fractions were then analyzed by ¹H and ¹³C n.m.r. spectroscopy. The fraction of aromatic carbons (Ar-C) of the total carbon content of a given series of g.p.c. fractions, obtained directly from the ¹³C n.m.r. spectra, showed a significant range of values (e.g. 13.2% to 29.2%) within each series. Furthermore, the values of %Ar-C within a series of g.p.c. fractions showed a maximum in each case. No such maximum was observed in the ¹H n.m.r. spectra for the fraction of aromatic proton (%Ar-H) content compared to the total proton content of any of the g.p.c. fraction series. Signals observed in the ¹³C n.m.r. spectra confirmed the presence of aliphatic chains attached to aromatic structures in the monoaromatic, diaromatic and polyaromatic-polar g.p.c. series of each distillate fraction. Well-defined signals, not attributable to straight-chain aliphatic material, were also observed in the ¹³C n.m.r. spectra. Comparison of the chemical shifts of these ¹³C n.m.r. signals with those spectra of model compounds obtained experimentally, and with appropriate systems in the literature, strongly suggested the presence of saturated terpenoid-like structures as well as the presence of methyl groups in sterically hindered positions on an aromatic ring system. Gated decoupling techniques and the use of a relaxation agent were used to overcome the deleterious effects of slow relaxation times and Nuclear Overhauser Enhancement (NOE) on the analytical quality of the ¹³C n.m.r. spectra.     

Methanol Adsorption on V2O3(0001)

Well ordered V₂O₃(0001) layers may be grown on Au(111) surfaces. These films are terminated by a layer of vanadyl groups which may be removed by irradiation with electrons, leading to a surface terminated by vanadium atoms. We present a study of methanol adsorption on vanadyl terminated and vanadium terminated surfaces as well as on weakly reduced surfaces with a limited density of vanadyl oxygen vacancies produced by electron irradiation. Different experimental methods and density functional theory are employed. For vanadyl terminated V₂O₃(0001) only molecular methanol adsorption was found to occur whereas methanol reacts to form formaldehyde, methane, and water on vanadium terminated and on weakly reduced V₂O₃(0001). In both cases a methoxy intermediate was detected on the surface. For weakly reduced surfaces it could be shown that the density of methoxy groups formed after methanol adsorption at low temperature is twice as high as the density of electron induced vanadyl oxygen vacancies on the surface which we attribute to the formation of additional vacancies via the reaction of hydroxy groups to form water which desorbs below room temperature. Density functional theory confirms this picture and identifies a methanol mediated hydrogen transfer path as being responsible for the formation of surface hydroxy groups and water. At higher temperature the methoxy groups react to form methane, formaldehyde, and some more water. The methane formation reaction consumes hydrogen atoms split off from methoxy groups in the course of the formaldehyde production process as well as hydrogen atoms still being on the surface after being produced at low temperature in the course of the methanol ?? methoxy + H reaction.